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1026 Stirling Engines

The Stirling engine so named because it is based on the Stirling thermo-dynamic cycle was conceived more than a century ago. Stirling engines produce power not by explosive internal combustion, but by an external heat source usually a continuous-combustion burner. Until recently, reliability problems have limited their use to hobbyists. It is only in the past generation that a viable free-piston Stirling was developed. All Stirling engines can be operated with a wide variety of fuels, including fossil fuels, biomass,* solar, geothermal, and nuclear energy. When used with fossil and biomass fuel, the continuous-combustion heater head avoids temperature spikes, which makes emissions very low and easy to control. The Stirling engine is a heat recovery device, like the steam turbine. Several European utilities are demonstrating this technology for residential micro-CHP applications. Even at these very small sizes, electric efficiencies of more than 30 have been achieved.

498 Stirling Engine Burnerpreheater Cross Section

Cross-section of Philips-Ford 4 98 Stirling engine hurner preheater. Regenerative exchangers are used in the Philips Ford multicylinder engines with swashplate drive which are under development for automotive use. Fig. 7.16 is a cross-section of the hot parts assembly of a Philips Ford automotive Stirling engine showing the regenerative heat exchanger (called on the drawing the preheater core). Similar units are incorporated in Stirling engines for automotive use being developed by United Stirling of Sweden. The 'thermal-wheel' regenerative heat exchanger has been studied extensively tu connection with the development of gas-turbine engines for vehicular applications, and the technology is directly applicable to ihe Stirling-engine air preheater. The disc may be fabricated from any

Heat Exchangers In Stirling Engines

The diagrams given in Fig. 7.5 are somewhat complicated but worthy of close attention to appreciate a fundamental aspect of Stirling engine operation. Each diagram contains two curves, superimposed. One curve represents the mass-flow rates into and out of the expansion space the other represents mass-flow rates into and out of the compression space. Curves above the zero datum line represent flow into the expansion space and oia of the compression space. Curves below the zero datum line represent tlow on of the expansion space and into the compression space. When these are superimposed as in Fig. 7.5 the areas where the curves overlap represent the period of net flow through the dead space, that is through the heat exchangers. Referring to Fig. 7.5, the period A -B represents the flow of fluid through the heal exchangers towards the expansion space with fluid flowing from the compression space into the dead space and from the dead space into the expansion space- It is evident from the...

10 Control Systems For Stirling Engines

Control systems are necessary to regulate the power output (torque) and speed of a Stirling engine. Sometimes the engine speed is held constant whatever the load, i.e. stationary constant-speed fixed-frequency electric-power generators. Sometimes, as in automotive applications, wide ranges of both speed and load are encountered. liy way of example, consider the hypothetical load speed characteristics shown in Fig. 10.1. Diagram (a), representative of an electric-power generator, a pump, or a fan. shows the input power requirements as a function of speed for different levels of voltage or pressure. Diagram (b). representative of a Stirling engine, shows the power output as a function of speed at different levels of the mean pressure in the engine. If the engine be coupled directly to the load the characteristics will be superimposed as in diagram (c).

19 Stirling Engines For Heat Pumps Stationary Power And Totalenergy Systems

Stirling engines are under study or development for a variety of non-automotive applications that can be broadly classified into three groups heat pumps, stationary power generation and total energy or co-generation systems. Stationary power generation embraces a wide range of energy conversion activity but is usually interpreted to mean the production of electric power. The same term can also be applied to pneumatic (air compression) or hydraulic power systems operating in a fixed location or as the auxiliary power systems on board an automotive, flight, or marine vehicle. Power levels can range from the few watts of an unmanned navigation signal generator to the gigawatts of a base-load electric-power utility-system. Current interest in Stirling engines for stationary power is concentrated in modular engines of 500 to 2000 horsepower utilizing municipal, agricultural and industrial wastes and small low-power engines.

12 Philips Stirling Engines

Stirling Wobble Plate

Work on Stirling engines has been in progress since 1937 al the Research Laboratories of N. V. Philips Gloeilampenfabricken, Eindhoven, Netherlands, the large international company well known for electrical and electronic products. The work on Stirling engines, extending over 40 years, can be broken into distinct phases The cryogenic phase, from 1945 to the present (1978) was concerned with the development and production of Stirling engines working as cryogenic cooling engines. Interest in Stirling engines at Philips sprang from the need to provide a simple lightweight electric-power generator for their radio receivers and transmitters in areas with no electric-power supply. Various thermally-activated systems were considered, including steam engines and thermoelectric generators. Stirling engines were chosen for development because the actual thermal efficiency of the hot-air engines available or known about at the time was so very low compared with the ideal value. Professor Hoist,...

15 United Stirling Engines

Philips Stirling Engine Cooler

The declared aim of United Stirling is to commercialize the Stirling engine. Following a decade of development they appear to be well on the way to achieving this aim with both the technology and the will to do it. United Stirling will not manufacture engines on a production basis, but rather, will serve as design and development consultants for established engine manufacturers. An important development announced in 1977 by the U.S. Department of Energy was the formation ol' a second major Stirling engine development group for automotive engines including United Stirling, of Malmo, Sweden, Mechanical Technology Inc of Latham, New York, and American Motors Inc., of Detroit, Michigan. Since inception of United Stirling a decade ago, the vehicular application of Stirling engines has dominated their papers in the open literature. Principal emphasis has been given to the engines' advantageous characteristics from the aspect of atmospheric pollution, noise, and more recently, omnivorous...

7 Heat Exchangers In Stirling Engines

American Combustion Technology Handbook

Heat exchangers arc key components in Stirling engines their significance cannot he overemphasized. No engine can work properly with poor heat exchangers although, conversely, the best heat exchangers will not, of themselves, make good an otherwise poor engine. There may be four separate heat exchangers in a Stirling engine system. These are illustrated in Fig. 7.1 and include, for the prime mover converting heat to work (a) heater fb) regenerator (c) cooler For a Stirling engine operating as a heat pump, a yet dilferent terminology is appropriate. The heat pump utilizes work to elevate the temperature of heat supplied at near-atmosphere temperatures. In this application the heater of the prime mover becomes the 'absorber' of the heat pump and the cooler of the prime mover becomes the 'heater' of the heat pump. In principle, therefore, the primary considerations for the heat exchangers are similar for all applications of Stirling engines. With this preamble we shall hereafter confine...

29 trunk piston engines

Trunk Piston Engine

The marine diesel propulsion market is dominated by direct-coupled low speed two-stroke crosshead engines and geared high medium speed four-stroke trunk piston engines but some Japanese and east Asian regional operators of coastal shortsea, fishing and small oceangoing vessels appreciate the merits of a 'hybrid' alternative the low speed four-stroke trunk piston engine. Akasaka Diesels' low speed trunk piston engine equivalent to the Hanshin EL programme, the A series, is produced in six-cylinder 280 mm, 310 mm, 340 mm, 370 mm, 380 mm, 410 mm and 450 mm bore versions with a stroke bore ratio of around 1.95 1. The A45S model develops 3309 kW at 220 rev min. The overall Akasaka portfolio embraces designs with bore sizes ranging from 220 mm to 500 mm and offering outputs from 375 kW to 6066 kW. The 500 mm bore 620 mm stroke U50 model is available in six, eight and nine-cylinder forms developing 674 kW cylinder at 380 rev min.

916 Opposedpiston engine

The Lucas and Trojan engines, with parallel cylinder barrels, may be described as uniflow opposed-piston engines since the scavenge air flows continuously from the inlet ports uncovered by one piston to the exhaust ports uncovered by the other, the two pistons moving towards each other for compression and away from each other for expansion. Fig. 9.16 Sultzer opposed-piston engine Fig. 9.16 Sultzer opposed-piston engine

17 Stirling Engines For Artificial Hearts

The U.S. artificial heart program was extraordinarily broad in scope. At the First Artificial Heart Conference, held in 1969. ninety-two technical papers were presented by the sixty-three separate contractors on a very wide range of topics. Of this total, sixteen papers were concerned with implantable energy sources and, within this group, only two were devoted to Stirling engines. A third paper discussed a fiuidic control device for coupling Stirling engine gas compressors to the blood pump. It is clear, therefore, that work on Stirling engines was but a small part of a large program. However, because of the specific nature of this book the discussion here will be confined to matters related to Stirling engines. Two research and development programs on Stirling engines have been sponsored by the Artificial Heart Program of the National Institute of Health from ils beginning in the mid-1960s to the present time. The two research contractors have been the Aerojet Liquid Rocket Company...

Freepiston Stirling Engines

Tin- following chapter was contributed by William Bcalc, President, Sunpower Inc., Athens, Ohio, Heale invented the frcc-piston Stirling engine in the late 1950s while a professor of mechanical engineering at the University of Ohio. Over the next dccadc. with remarkably single-minded dedication, he developed the concept to an operational stage. In the university environment he was unable to secure adequate funds to develop the frcc-piston engine commercially and so lie founded the company he now leads. Sunpower is unique as the only company in the world in commercial production of Stirling engines. Their best known machine is the small free-piston engine demonstrator available as a water pump, electric power generator, or a refrigeration pump. Sunpower's principal business is research and development work in advanced free-piston Stirling engine developments, some of which are discussed below.

Stirling Engines For Space Power

Given the elementary but irrefutable logic above it is difficult to understand the virtual total neglect of Stirling engines by NASA during the 1960s. This was the era of prodigious expenditures on hydrogen-oxygen fuel cells for the Apollo missions. 011 the Rankine cycle SNAP8 reactor power-plant, and on various Bray ton turbines. So are as is known, no NASA funds atid only minor Air Force funds were expended on Stirling engines. One possible explanation for NASA neglect of Stirling engines is that the confidentiality clauses in the Philips licence agreement foredad full-hearted participation by General Motors in Government contracts which required full disclosure. Other companies known to have been interested in the possibilities of the Stirling engine were daunted and discouraged by the impressive thorn-fence of patents that Philips built around the new technology and the exclusive licence with General Motors. At any event only one program of substance on Stirling engines for space...

9 Operating Characteristics Of Stirling Engines

A Stirling engine consists essentially of two spaces of variable volume and different temperatures connected by a duct. The spaces arc (illed with the working fluid and the duct is provided with apparatus for adding heat (heater), abstracting heat (cooler) or storing heat (regenerator). The system can be arranged in any number of ways, in single or multiple combinations, with the volume variations caused by reciprocating or rotary motion. Whatever form of mechanical arrangement is adopted certain common factors and considerations prevail which affect the system performance. These are discussed below. For any Stirling-engine system the maximum power and efficiency would be achieved if the ideal Stirling cycle described in Chapter 2 could be followed. This requires that all the working fluid in the system is. at any instant, in the same condition (thermodynamic equilibrium) and all the heat added to the cycle or rejected from it is transferred at constant temperature. Similarly, at any...

The Literature Of Stirling Engines

The following bibliography of Stirling engines includes books, papers, patents, and other material generally available from a good technical library. The material is arranged in alphabetical order of the prime author. The list is by no means complete. Additions arc being entered constantly as new papers are written, and as others, previously unknown, are found. Many of these contribute further new references. All the material has been through the author's hand at one time or another and most is. euphemistically speaking, on file at the University of Calgary. The literature of Stirling engines is surprisingly extensive. Some measure of the interest in a subject can be gained by the number of papers written about it. Fig. 22.1 shows the annual number of publications about Stirling engines in the forty-year period. 1940-80. These numbers were gleaned from Martini (1978a) who gives an extensive bibliography arranged chronologically, by subject and by author. The present situation is...

2122 Stirling engine

Stirling Engine Diagram

The Stirling engine, invented by Robert Stirling, first built in 1816 and subsequently produced on a small scale, is not an internal combustion power unit. Its working gas is cycled in a closed circuit, passing through a heat exchanger on the way round. Gases such as hydrogen, helium and freon have been used in the closed circuit. Originally, it was a viable alternative to the steam engine, for example in marine propulsion, but it has yet to be proved competitive with the internal combustion engine for road vehicle applications. However, it could become attractive owing to its virtually zero oil consumption and long intervals between oil changes, long service life, relative silence, a thermal efficiency potentially of about 40 to 45 at part load, acceptance of a wide variety of fuels in a continuously burning heater, and a very clean exhaust. Its disadvantages are complexity, bulk and weight. The specific weight of a 10 kW engine is about 10 kW kW, but becomes lower as the power...

9 Operating Characteristics Of

STIRLING ENGINES 203 Emission characteristics of Stirling engines 216 Free-piston Stirling engines 233 II FREE-PISTON STIRLING ENGINES 254 Description of free-piston engine dynamics 254 The two-piston free-piston engine 259 The piston-displacer free-piston engine 261 Double-acting free-piston engines 263 Computer simulation of free-piston dynamics 266 Design problems in free-piston engines 270 12 PHILIPS STIRLING ENGINES 288

Robert St I Rung And His Family

Robert Stirling Engine

Robert Stirling (uncle) Robert Stirling Robert Stirling was born in Cloag on October 25, 1790. He studied at the University of Glasgow, as is mentioned in the Pastie, but also at Edinburgh University (1805-6 and 1808). In 1805 he took classes in Latin and Greek, and in 1806 he studied advanced Latin and Greek, logic and mathematics, metaphysics and rhetoric. There is no record of his classes in 1808 and it is possible that it is not the same Robert Stirling who attended in that year, as owing to a change in the system of keeping records at that time his place of origin is not given. Robert Stirling was 15 years old when he went to Edinburgh. This age. or even younger, was quite normal for entering the university in those days. Robert Stirling was licensed to preach by the Presbytery of Dunbarton on July 4. 1815. He was presented to the second charge at Kilmarnock, Ayrshire, by the Commissioner of the Duke and Duchess of Portland, and was ordained to the Ministry on September 19. 1816....

6 Mechanical Arrangements

Tun. elements of a Stirling engine include two spaces at different temperatures having volumes lhat can he varied cyclically and which arc connected through a regenerative heal exchanger and auxiliary heat exchangers. These simple elements can be combined in a surprisingly wide range of mechanical arrangements. Some have been identified (Finkelstein 1.959) by the name of the inventor or original user. Many variations were used in the nineteenth century and have been adopted or re-invented for application to modern engines. In other cases novel mechanisms or embodiments previously unknown are used. New arrangements are still being devised, some are good, some bad only time will tell which will attain commercial application. In this work the name Stirling engine is limited to regenerative engntes where the flow is controlled by volume changes. Machines where the llow is controlled by valves are called F.riesson engines. These names are chosen somewhat arbitrarily in an attempt to...

Costs And Applications

No specific data on the costs of United Stirling engines have been published. Comparative estimates for total operating costs have been given by Rosenqvist ef al. (1977), and by Carlqvist et al. (1977) for 150 kW (204 hp) Stirling and diescl engines for the typical 13 000 kg (28 665 lbm) city-suburban delivery truck shown in Fig. 15.19. Initial cost for the Stirling engine was assumed to be 50 per cent higher than the diesel engine. The radiator eost was assumed to be twice that for the cost of the diesel engine radiator. A variety of other assumptions, some credible, some questionable, were made with Ihe result that the Stirling engine

Gaseous Working Fluids

TheoreticaI comparisons The first numerical comparison of different working fluids was given by Meijer (1970a) with the presentation of the characteristics reproduced in Fig. 8.1. I bis figure was a summary of extensive computer optimization studies carried out by Philips using their Stirling engine simulation computer program. All the results referred to large engines of 165 kW (225 brake hp) per cylinder having a heater temperature of 700 C (1295CF). cooler temperature of 25 C (77 F) and maximum gas pressure of 1 lOMN nr (15 954 lbs per sq in). The overall efficiency of the

Automotive Applications In Mining

Hallare and Rosenqvist (1977) indicated that the first commercial applications for United Stirling engines will be for underground mine vehicles. The use of diesel engines in underground minework is a subject of increasing concern to those involved with industrial health and safety. Stirling engines for underground mine vehicles have advantages in terms of reduced vehicle emissions, quiet operation, and low-temperature exhausts. Moreover, it is possible to foresee the next step for combination of the engine with thermal storage so as completely to eliminate exhaust emission when operating underground. Electric power is always available for recharging during shift changes or when loading and unloading. For mine locomotives used above and below ground, a combustion-heating system may be turned on when operating on the surface. It would provide the energy for both surface propulsion and to replenish the thermal battery for underground operation.

Liquid Working Fluids

Stirling Malone Engine

Closcd-cycle regenerative engines with liquid working fluids were described by John Malone (1931). They conform in every way to the definition for a Stirling engine given in Chapter 1. However, liquid cycle regenerative engines are sufficiently different to be classified separately, perhaps as Malone-cycle engines. The mechanical arrangement used by Malone to describe his engine operation was similar to that shown in Fig. 8.18. Two parallel cylinders contained reciprocating elements. One was a displacer including a regenerator and the other was a piston equipped with pressure seals. The arrangement corresponded in every way to the Heinrici Stirling engine arrangement for a piston-displacer system in separate cylinders. The upper end of the displacer cylinder was heated and the lower end was cooled. The compression cylinder was cooled. work diagrams for the system based on arbitrary volume units and the pressures quoted by Malone are shown in Fig. 8.19. The system is clearly capable of...

Charles Louis Franchot

Single-acting Stirling engines were invented early in the nineteenth century, and the application in IS I 5 by Robert Stirling for his lirst engine patent may perhaps be reckoned an appropriate date. Other variations and arrangements of single-acting Stirling engines have been conceived at intervals since. Double-acting Stirling engines were also invented in the nineteenth century. Babcock (1885) ascribes the invention of the two-cylinder, twin-system, double-acting engine to the French engineer, Charles Louis Franchot in 1853. This was subsequently re-invented a century later by Finkelslcin and Polanski (1959) and was later incorporated in a multiple-cylinder, free-piston arrangement by Finkelstein (1963b). The general form of double-acting engines with three or more cylinders is ascribed by Babcock to the celebrated British scientist engineer Sir William Siemens, better known for his work in steel making. Siemens designed the double-acting Stirling engine shown in Fig. 6.2, having...

Regenerative Displacer Engines

Malta Stationary Engines

Another model engineer interested in the Stirling engine is W. D. Urwick, of Malta, who has undertaken an extensive program of testing the regenerative displacer. In the Urwick design, the conventional displacer is replaced by a series of screen discs mounted on the displacer shaft, which act as a regenerator. Urwick (1975) reported various experiments in which the engine tested performed as well or better with this regenerative displacer than with a conventional displacer, despite the greatly reduced compression ratio accompanying the change. Discolora- Etc 20.4. Model Stirling engine with regenerative displacer by W. D. Urwick (I975).

Stationary Power Generation

Stationary Engines Malta Scrap

Stirling engines have attractive characteristics for stationary power applications. They have a wide multifucl capability, operate without noise, have excellent part-load performance, and respond fast to sudden changes in load. They have the potential to operate for very long periods with minimal maintenance and low lubricant-oil consumption. In the closing years of the twentieth century, the multifuel capability of the Stirling engine will most likely become important. The engine can operate on any source of heat, and so as oil and gas become increasingly valuable, more and more use will be made in power generation of solid fuel like coal, industrial wastes such as wood bark, forestry trimmings, agricultural wastes, and municipal wastes. Anything that is combustible can be consumed in high-efliciency tluidi .ed beds, or other advanced combustors to producc the hot gases for heating Stirling-engine systems. Similarly the combination of a free-piston Stirling-engine linear alternator...

Power Control Systems

Stirling Engine Philips

Variation in the mean pressure level of the working fluid is the most widely used and best-known control system for power regulation in Stirling engines. It was used to some extent on the more sophisticated air FiO. 10.8. Work diagrams lor Philips I'ype 4-235 four cylinder rhombic-drive Stirling engine illustrating the control achieved by the loss-regulation short-circuit feature. FiO. 10.8. Work diagrams lor Philips I'ype 4-235 four cylinder rhombic-drive Stirling engine illustrating the control achieved by the loss-regulation short-circuit feature. A schematic diagram of the power control system used on United Stirling engines is reproduced in Fig. 10.9. It can be recognized as virtually identical to the above system. To increase power, the control valve is moved to the right so that gas (lows directly from the reservoir to the engine. Hallare and Rosenqvist (1977). in a discussion of the control system, have revealed that a timed supply system is used which admits additional...

Hotair Engine Competitions

The 5 cm3 (0.3 in3) engines of Urwick and Collins were built for the first hot-air engine competition, held at the 1977 Model Engineer Exhibition in London. This competition was sponsored by A. N. Clark and promoted by Model Engineer magazine. In light of the increasing interest in model Stirling engines, it was correctly believed that the time was right for an international competition (Chaddock 1976). Seventeen people entered the competition, and the winner. F F. Clapham of Bristol, produced an engine beyond the sponsors' wildest expectations. It was pressurized with air at over 6.7 MN nr (1000 lb per sq in), and it produced 39.4 watts at 900 rpm. This machine was designed and built in 600 hours, and it was the first Stirling engine Clapham had ever built. Fig. 20.6. Model Stirling engine by Clapham (1977). This high-pressure high-performance engine won the first hot-air engine competition for engines with 5 cm1 piston displacement. Output was 95 watts at 2000 revolutions per minute...

5 Preliminary Engine Design

Wn i.jam rhai.fi. observed several years ago (hat the power output of many Stirling engines conformed approximately to the simple equation This can be rearranged as P (pfVt> ) constant. The equation was found by Beale to be approximately true for all types and sizes of Stirling engines for which data were available including free-piston machines and those with crank mechanisms. In most instances the engines operated with heater temperatures of 650 V and cooler temperatures of 65 C. Many have an overly sanguine view of the capability of Stirling engines. One frequently hears proposals to convert small internal combustion engines to Stirling engines operating on low pressure air and using furnace heat or solar energy to produce several kilowatts of power. The Beale number is useful for dispelling such high hopes. For example, consider a small internal combustion engine having two cylinders with l to. 5.1. The Fictile numliei as a function o( heater temperature. A design guideline for...

4 Theoretical Analysis Of Stirling Engi

Tiieouhticai. analyses of Stirling engines have been developed with varying degrees of sophistication. The most simple analysis is that for the ideal Stirling cycle, where the thermodynamic cycle comprises two isothermal and two constant-volume regenerative processes. However this involves such gross idealization of the process occurring in an actual Stirling engine as to be suitable only for the most elementary, preliminary design calculations. program now installed on a commercial computer network and available for general use on payment of a royalty fee. Later in the closing years of the 1970s substantial efforts were devoted to Stirling engine simulation by other workers and a variety of advanced engine simulation programs have become available. (d) to compare and comment briefly on the advanced level analyses for Stirling engines making reference to the source documents for those who wish to investigate further.

Electromotive Division Engines

Cleveland Diesel Engine Division Work on Stirling engines at the Electromotive Division was not well documented but useful information about this activity can be compiled from the various references listed above, principally Heffner (1966), Percival (1967), Mattavi el al. (1969) and Percival (1974). Work on heavy, high-power Stirling engines apparently started at the Cleveland Diesel Engine Division of General Motors about 1958. Cleveland Diesel had supplied the majority of submarine engines during the Second World War and had strong connections with the U.S. Navy. In addition, they were builders of heavy diesel engines for locomotives and surface vessels. Their interest in Stirling engines was for use as an alternative to diesel engines for submarines, river and harbour work boats, and for locomotive propulsion. The Cleveland Diesel Engine-Division was dissolved in 1962 and the Stirling engine project was transferred to the Electromotive Division at LaGrange, Illinois. 'extreme...

Bibliography And References

B (1977). Demonstration of a free-piston Stirling linear alternator power conversion svstem. Proc. 12th E.C.E.C pp. 1488-1495. Washington, D.C Aug. 28-Sept. 2. p is ton Stirling engine driven linear alternator. Phase 1 Report No. 77TR40. Mech. 'fech. Inc. Goo dale. T. C. and Walter, D. (1976). Hydrogen safety tests of the Stirling engine. Stanford Research Institute Report, No. S.R.I., Project PYC-2696, to the Ford Motor Co (included as Appendix A in Kitzcr 1977b). Goranson. R. B. (1968). Application of the raioisotope-fuellcd Stirling engine to circulatory support systems. MDAC Final Report. No. DAC-60742, June. -et al. (1968). Development of a simplified Stirling engine to power circulatory assist devices. Proc. 3rd l.E.C.E.C., Boulder. Colorado. Aug. Grashop, F. (1890). Tlteorie der Kraftmaschinen. Hamburg. Ghatch, S. (1976). Advanced Automotive Propulsion. AIChE, New York, Vol. 1, pp. 2-5. Hui-'m r, F. E. (1966). Highlights from 6500 hours of...

Tempiuature Control Systems

The temperature control systems used in Stirling engines are all basically similar. The principle is that the temperature of the heater tubes (or other critical part) is to be maintained constant at all operating condi- 'The Stirling engine fuel control is designed so that the engine heater tubes arc operated at n constant temperature of 1470 F (799 C). A temperature sensor mounted on one of the heater tubes' is the primary control devicc in the air and fuel control circuit. The combustion blower is driven directly from the engine. The amount of air supplied is regulated by the temperature sensor through a throttle valve which is interconnected with (he fuel air control to maintain a constant A F ratio (30 per cent excess air)'.

Stirling Finkelstein 1959

Civil Engineering Engines

The original .Stirling engine. Reproduction of a drawing showing the first Stirling engine, from the original patent specifications of 1816. Such an engine was used in 18IK for pumping water from a quarry (after Finkelstein 1959). 1-IG. 6.5. The original .Stirling engine. Reproduction of a drawing showing the first Stirling engine, from the original patent specifications of 1816. Such an engine was used in 18IK for pumping water from a quarry (after Finkelstein 1959). configuration it was lirst used by Robert Stirling, in IS 16. for the engine shown in Fig. 6.5. Ii has been used, also, for most of the machines developed by Philips, both prime movers and cooling engines. Crank-driven engines can be of the type used by Stirling, with a regenerative displacer, or may have a separate external regenerator of the Rankine-Napier type. The possibility exists for the necessary volume variations to be gained by an oscillating-cvlindei mechanism, but, so lar as is known, machines of...

General Aspects Of Design

The best compilation of design daia for the heat exchangers in Stirling engines is undoubtedly the classic work by Kays and London (1964) entitled Compact Heat Exchangers. The book is. quite simply, required reading for anyone wishing to undertake the design or analysis of the heat nature and wide availability of the book no effort will be made to reproduce the straightforward design procedures for compact tubular, finned and regenerative heat exchangers that are so well treated therein. Rather, the space available will be devoted to brief discussion of some of the aspects of design peculiar to Stirling engines that are not found or not stressed in Compact Heat Exchangers. The principal consideration particular to Stirling engines is the compelling need to make effective use of the internal void volume of the heat exchangers and connecting ports. We have seen earlier how an increase in the dead volume results in a reduced volume compression ratio Vmux Vmln and in a reduced pressure...

Transientflow Effects

Difficulties in the design of heal exchangers for Stirling engines arise from the cyclic transient-flow elTects. Most industrial heat exchangers are subject to steady constant-flow conditions with relatively slow rates of change in the flow conditions. This is by no means the case for the heat exchangers used in Stirling engines where the flow conditions change continuously and experience wide variations in pressure, density, and velocity, to the extent of reversing the flow direction twice per cycle. All this complicates the situation considerably and makes the design of the regenerator and other heat exchangers a difficult art. Initial contemplation of Stirling engines leads one to believe that when the engine is operating, the working fluid flows from the expansion space through the heater, regenera.or, and cooler to the compression space, and then retraces its step in returning to the expansion space. Such a view is oversimplified and applicable only to the ideal Stirling engine....

Temperature And Energy Di St Ri Hut

Fig. 7.2 shows a typical temperature distribution in a Stirling engine of advanced design. Inlet-air enters the engine at the atmosphere temperature and is heated in the preheater before passing to the combustion space. Fuel is added and combustion occurs, heating the products of combustion to a very high temperature. The combustion products then pass through the heater, where heat is transferred to the working fluid, and through the preheater. where heat is transferred to the inlet-air. The cooled products finally leave the engine. In many applications where air pollution is an important consideration, a fraction (up to one half) of the exhaust products arc recirculated back through the combustion chamber. This increased mass flow of relatively inert fluid moderates the maximum temperature attained in combustion and so reduces the amount of oxides of nitrogen (NOJ produced. Some extra work is then required to cause the air to flow through the system and therefore a fan will be...

So Mr Elementary Considerations

Tin- first and second Laws of Thermodynamics appear to apply to all thermal power machines, including Stirling engines. Unfortunately no way to demonstrate the first and second laws in some simple but irrefutable fashion has been devised. Equally, of course, it is completely outside human experience for a machine to behave in contravention of these fundamental laws, despite the aspirations ol many inventors. Proposals for perpetual motion machines always contravene the fust or second law.

Definition

A Stirling engine is a mechanical device which operates on a closed regenerative thermodynamic cycle, with cyclic compression and expansion of the working fluid at different temperature levels. The flow is controlled by volume changes, and there is a net conversion of heat to work or vice versa. Other machines exist which operate on an open regenerative cycle, where the flow of working fluid is controlled by valves. For convenience, these may be called Ericsson engines. Unfortunately the distinction is not widely established in practice and the name 'Stirling engine' is frequently indiscriminately applied to all types of regenerative machines.

138148

J. 11977). Design considerations of i thermal storage Stirling engine automobile. S.A.E. Paper No. 770080, pp 1 12. Detroit. Mich. Auxtm, W L. < 1977). Development of a Stirling engine powered heat activated heat pump. Proc. I2ih I.E.C.E.C., pp. 397-401, Washington. D.C., Aug. 28-Scpt. 2.

Doubleacting Engines

Cross-section of four-cylinder double-acting Stirling engine Type V4X (cylinder bore 50 mm, stroke 46 mm after Carlqvist cf til. 1975). Fit . 15.6. Cross-section of four-cylinder double-acting Stirling engine Type V4X (cylinder bore 50 mm, stroke 46 mm after Carlqvist cf til. 1975).

Gm Research Engines

Percival (1974) has indicated that in the first five years of research and development work on Stirling engines cITort was concentrated on component development, specifically (j) numerous studies and demonstrations of thermal energy storage systems in combination with Stirling engines. In twelve years between the start of the program in 1958 and its abrupt termination in 19711 over 30 000 hours operating experience on Stirling engines had been gained. The accelerating pace of the project was such that over 50 per cent of the operating experience was gained over the final three years and 75 per cent in the last five. In addition many thousands of hours of operation were accumulated on seal, bearing, combustion, regenerator, and heat transfer rigs. Ground power unit The principal visible achievement of the G.M. Research program was the Ground Power Unit Stirling engine generator. These units sustained a decade of development. The final model, a GPU3, is shown in I-ig. 13.1. The engine...

Totalenergy Systems

Solar Stirling Ensine Parts

Stirling engines appear to be well suited for use in total energy systems as prime movers, heat pumps, or refrigerating engines. The particular characteristics of the Stirling engine which are advantageous in total energy applications arc, primarily, the multifuel capability, quiet operation, minimal exhaust emissions, excellent part-load efficiency, and good starting, control, and torque characteristics. Walker (1967) appears to have been the lirst to consider Stirling engines for total-energy systems in a survey carried out for the Institute of Gas Technology. loiter Jaspers and du Pre (1973) assessed the prospects of the Stirling engine in total energy systems to be highly favourable. Lehrfeld (1977a) analysed, very comprehensively, the use of Philips Stirling engines in total energy systems in a variety of applications, commercial and hospital buildings, residential apartment buildings, and offices. This study was summarized (Lehrfeld (1977b) and further referred to in a survey of...

702 132

J. < 1974). An investigation of the effect of an exhaust gas recuperator on the performance of a Stirling engine. Project Report No. 278. Sch. Engineering. Univ. of Bath. U.K. Pillar, S. (1978). Free-piston Stirling systems for power generation and heat pumps. Inst, of Gas Tech. Seminar, Stirling Cycle Prome Movers, Chicago, HI June. ----- (1976). Stirling engine program. Highway Vehicle System Contractors -(1978). Ford Stirling engine powertrain development. DOE Hwy. Veil. Syst. -van Gn-ssEL, R. and Reinink, F. (1973). The Stirling Engine for Passenger - and on Jonoe, A. K. (1978). A free piston Stirling engine for small solar (1975). Stirling heat pump for healing. German Patent 2 400 256. Ragsdale, R. G. (1977). Stirling engine project status. Proc. ERDA Adv. Auto Power Syst. Com. Coord. Mfg Dearborn. Mich., Oct. NT1S. Springfield, Va. (1978). Stirling engine project status. DOE Hwy. Veh. Syst. Com. Coord. Mtg Troy. Mich May. Rai i,is, C. J. and...

Qsqa197

Summer Civil Pump

This reversal of the role of the heat exchanger between winter and summer operation may be effected by simply reversing the direction of rotation of the Stirling engine. This would be a simple matter indeed, if the Stirling engine were driven by an electric motor. In the Stirling-Stirling arrangement a reversal in the direction of rotation might he more difficult to achieve. An early attempt to develop a duplex Stirling engine cooling unit was made by Walker (1968a) under contract to the British Ministry of F10. 19.4 Stirling-engine heat pump for summer cooling or winter heating. F10. 19.4 Stirling-engine heat pump for summer cooling or winter heating. One of the principal advantages of the duplex Stirling arrangement is the use of a common fluid for the combined Stirling engines. This can be most attractive in free-piston engines where the use of a common fluid greatly relaxes the sealing arrangements. Furthermore, in free-piston engines the use of gas bearings employing the working...

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Ford Torino Stirling

Basic designs of displacer-type Stirling engines with rhombic-drive mechanisms and using rolling diaphragm seals are shown in Fig. 12.12 (Rietdijk ci al 1965). The single-cylinder machine required four seals The invention of the rhombic drive and the rolling seal provided an apparently invincible combination for the development of successful Stirling engines. The pace of development at Philips was greatly stimulated and was no doubt enhanced by the association with General Motors in the United States following the licence agreement in 1958. Single cylinder prototype engines of 7.4 kW (III hp the Philips Type I-9S engine) and of 65 kW (90 hp designated GM Type 1-51050) were developed in addition to the original 30 kW (40 hp) engine. The photograph shown in Fig. 12.13 of this trio of prototype engines was given by Mcijer in a review paper (Meijer 1969c). lite four-cylinder 265 kW (360 hp) engine (designated GM Type 4-S12I0) shown in Fig. 12.14 A 1-98 engine was used in the remarkable...

Iarly History

Robert Stirling, a minister of the Church of Scotland and originator of the regenerative heat exchanger, invented the closed-cycle regenerative engine in 1816 and remained actively involved with his brother. James, in its development for many years. As with all engineering developments they were beset by limitations of materials and at the end of his life, in 1876, Robert was led to write The internal combustion engine, in the form of the hot bulb gas engine was invented about the middle of the nineteenth century. Subsequently it was developed in the form of the gasoline, spark-ignition engine and the oil, compression-ignition engine. Later, at the turn of the century, the electric motor was invented and developed. Together, the internal combustion engine and electric motor gradually superseded both steam and Stirling engines in small sizes. However, a glance at the Sears-Roebuck catalogue for the early 1900s shows that in the United States, hot-air engines could be bought...

Specific Output

Sears Roebuck Steam Engine

The size and weight of Stirling engines for a given power output is important in many applications, particularly in the automotive, locomotive, space, and under-watcr power fields. It is still important, bul rather less critical in the stationary generator, heal pump and total energy, and surface marine fields. Savings in size and weight result from elevation of the pressure of the working fluid and from ingenious design. The rhombic-drive single-action. piston-displacer engines of the 1960s were relatively big, heavy machines. However, the conversion lo double-acting Siemens type Stirling engines (see Chapter 13) permitted the construction of machines thai were half the size and weight id' the rhombic-drive units. This brought Stirling engines to sizes and weights comparable with diesel and gasoline motors. Mcijer (1970b) presented the data reproduced in Fig. 9.16 which shows the specific weight as a function of power output for Stirling, diesel, and gasoline engines. Fig. 9.16....

Friction Effects

There arc two important friction effects to consider in Stirling engines. The first is the mechanical-friction effect arising from the action of piston rings, rubbing seals, bearings, oil pumping, and the like. With the engine idling and producing no useful output power there will still be considerable mechanical friction. This will increase as the engine speed and pressure increase. Inclusion of mechanical friction reduces engine output and efficiency as represented by the line lG-G' in Fig. 9.4.

Heat Pumps

Stirling Engine Heat Pump

A Stirling engine may be used in relation to a heat pump in two ways When the Stirling engine is used as the heat pump it accepts heat at a low (probably) ambient temperature and rejects the heat at a higher temperature to a heating system. Such an arrangement is shown diagrammatically in Fig. 19.1. The system is illustrated by reference to the ideal Stirling cycle P-V diagram and a single-cylinder, piston-displacer. single-acting, Stirling engine. Heat is absorbed during the expansion process at ambient temperature (TH) from an external source (shown as a lake or river). The heat is rejected from the engine during the compression process and is carried off to perform a useful heating function in the building. Of course work must be supplied (equal to the shaded area on the ' V diagram) to allow the Stirling engine to work in this way. This external work may be supplied from any power source, including an electric motor or a heat engine, perhaps another Stirling engine. The...

Mdc G2025 19689

Developments in Stirling engines. ASME Paper No. 72-WA Encr-9, - (1975a). The frce-displaccr. free-piston Stirling engine Potential Energy (1977a). Stirling Engine Research Institute Newsletter. No. 1. Feb. Subsequently issued at Irregular Intervals, Publ. Joint Centre Tor Grad. Studies. Richland, Wash.

Summary

The contributions to Stirling engine technology made by General Motors in the period 1958-1970 were summarized by Percival (1974) as follows 3. Their program developed the first precision-control constant-speed governor for Stirling engines, which embodied entirely new-concepts to the field of governing and which accomplished the following 4. Their program developed the first automatic fuel controls for starting a Stirling engine over a wide ambient temperature range, without smoke emissions. (c) The idea of swash-plate-type axial Stirling engines (the program provided analytical and experimental verification of the low-friction characteristics of properly designed swash-plate mechanisms with hydrodynamic type bearings). (g) The first 90 k V (120 hp), four-cylinder, in-line double acting Stirling engine for a proposed bus installation. The General Motors program was cancelled as testing just started. (b) The concept of thermal energy (heat) storage with the Stirling engine. (Initial...

Preheaters

A preheater is not necessary to the operation of a Stirling engine. It is a desirable accessory for all but small orimitive enuines and it is virtually Therefore, complying with customary engineering usage, a Stirling engine equipped with a preheater may also be said to be operating on a regenerative cycle. Thus in the Stirling engine there are two regenerators to consider (a) the interna regenerator interposed between the cooler and the heater through which flows the working fluid at high pressure and (b) the external regenerator which is the exhaust-gas inlet-air preheat heat exchanger operating at, substantially, atmospheric pressure. To add yet further confusion the Stirling engine external regenerator, or the exhaust-gas inlet-air preheater. may be a heat exchanger that is of the regenerative or alternatively of the recuperative type. Both recuperative and regenerative preheaters have been applied to Stirling engines. Early Philips engines all used recuperative preheaters, one of...

Safety

Despite its many attractions as the best working fluid for Stirling engines, hydrogen has the disadvantage of extremely wide flanimability limits in air ranging from 5 to 75 per cent mixtures of hydrogen and air. Other gases, methane, for example, have much closer flanimability limits of 6 to 14 per cent methane in air by volume. Moreover, hydrogen has a high affinity to oxygen and the enthalpy of reaction (heat released in burning) 129000kJ kg (30 960 Btu lbJ of hydrogen, compares with 50 143 kJ kg (12 034 Biu lbJ for methane. Percival < 1974) cited hydrogen permeation of materials as one of the principal unresolved problems in Stirling engines. He indicated that one avenue of approach adopted by Philips was to provide an impermeable ceramic liner in the heater tubes but provided no details and the matter has never been mentioned in any of the several papers published by Philips. These important matters have noi been sufficiently addressed in the public literature. They are...

Nomenclature

Stirling engines are frequently called by other names, including hot-air or hot-gas engines, or one of a number of designations reserved for particular arrangements of engine, i.e. I leinrici. Robinson, or Rankine-Napier. The result is a general lack of clarity in the nomenclature. It may be argued, convincingly, that the designation 'Stirling cycle' should be reserved for a particular idealized thermodynamic cycle, and the name 'Stirling engine' for a particular form of machine (which, incidentally, does not work on the Stilling cycle, a situation that does nothing to improve clarity). A preierred generic title would be 'regenerative thermal machine'. It is almost certainly too late for logic to prevail, and the name 'Stirling engine' will continue to be widely and indiscriminately used. 1 Iowcver, a clear distinction should always be made between machines where the flow is controlled by (a) volume changes (Stirling engines) and (b) valves (Ericsson engines), because they have...

Cooler Design

In principle Stirling engines may be air-cooled or water-cooled just as internal combustion engines are. However we have seen earlier that because the exhaust stack loss must be low. the cooling system of a Stirling engine must handle up to twice the load imposed on the cooling system of an internal combustion engine of similar power output. In addition to this, the efficiency of a Stirling engine falls markedly as the cooler temperature increases and is accompanied by deterioration in the mechanical properties of the polymer materials commonly used for sliding seals. Therefore it is desirable to have the cooler temperature at the minimum possible value. This combination of factors makes direct air cooling of Stirling engines virtually impossible except in small model engines or larger but unpres-surized low power, slow-running engines intended for long unattended operation.

5wx lTQm427

Finkelstein (1960a) devised a generalized thermodynamic analysis of Stirling engines in which the processes of compression and expansion were not confined to isothermal conditions. In this generalized analysis the processes of compression anil expansion in it- engine cylinders could be specified to occur anywhere between the two limiting cases fn his presentation. Finkelstein included only > rie Set of numerical results. This referred to a heat pump with the temperature ratio r 'f 7'c 2. The coefficient of performance of 1.0 with isothermal processes was reduced to 0.543 with adiabatic processes. Similarly Stoddart (I960) found that a Stirling engine prime mover having a Schmidt cycle (Carnot) efficiency of 50 per cent with isothermal compression and expansion THEORETICAL ANALYSIS OF STIRLING ENGINES 59

25 Stirling External Combustion Engines

A Stirling engine is an external combustion heat engine and, therefore, does not require a specific fuel a Stirling engine-generator can convert any sufficient heat source into useful electrical power. These generator sets are also physically small and very efficient even below 100 W (e). With the added advantages of high reliability, long life, very low noise, and maintenance-free operation, Stirling engines are ideal for distributed generation applications where the generator must be located within a residence or business office, and for cogeneration as shown in Figure 2.10.

212Essential processes in ic power units

The piston engine can accomplish the first two processes with high efficiency and reliability, but is less successful with the third owing to its unsuitability for handling the large volumes at the low pressure end of the expansion, this being incomplete unless continued in a turbine, which is admirably suited to deal with large volumes at low pressure. Hence, as explained in Chapter 16, the exhaust turbo supercharger forms a mechanically independent but not thermodynamically self-contained high-speed unit which increases the power of the main engine but does not require to be geared to the low-speed power shaft. Moreover, since the gases reach the turbine blades at a manageable temperature, no insoluble temperature-stress-time factor arises with the material of the blading.

542 Moving componentspistons

Very much higher heat transfer rates are obtained with water cooling than with oil cooling. There would therefore be much to be said for employing water colling of the pistons in highly rated engines. Unfortunaely the problems of obtaining a completely liquid-tight system are such that it is not possible to do this in a trunk type piston engine since water leaks into the lubricating oil are inadmissible. For trunk piston engines, oil cooling of the piston has to be used. Two basic types of cooling are employed, although the actual design of piston may incorporate both types.

254 Controls and Communications Dispatchability

Being connected to the grid is an excellent way to operate Stirling generators. The grid controls the generator frequency and voltage, so very little is needed for the connection other than the requisite safety equipment. Connecting a free-piston Stirling generator to the grid is a fairly simple operation and requires minimal hardware for the European grid. Utilities in the U.S. are only now becoming exposed to numerous consumer level, grid-coupled generators, and must evaluate implementing them with the U.S. grid.

255Utility Interfacing

As previously noted, Stirling generators can be used for both on- and off-grid applications. It is left to the utility companies and their customers to decide what is most appropriate. Stirling generators are reliable enough that a utility company may consider leasing a unit to a remote off-grid customer, thus avoiding the costs of building power lines or larger generators on site. An off-grid Stirling micro-cogeneration system is a very reliable and cost-effective solution for providing heat and power in a remote location. Stirling engines require no maintenance, so there is basically nothing the end user has to do to it once the system is installed. The utility can also choose the fuel used by the generator and make certain it is available to the customer. Reliable, maintenance-free, silent operation and a long operating life are some important advantages Stirling generators offer the utility that cannot be found in conventional small-scale generators. Utility companies in areas...

Fuel oils lubricating oils and their treatment

Trunk piston engine lubricating oil must lubricate the cylinders as well as the crankcase some contamination from the products of combustion will therefore occur, resulting in acidity and carbon deposits. The oil must, in addition to lubricating, neutralise the acids and absorb the deposits.

14 The Distributed Generation Technologies

Distributed generation is any small-scale electrical power generation technology that provides electric power at or near the load site it is either interconnected to the distribution system, directly to the customer's facilities, or both. According to the Distributed Power Coalition of America (DPCA), research indicates that distributed power has the potential to capture up to 20 of all new generating capacity, or 35 Gigawatts (GW), over the next two decades. The Electric Power Research Institute estimates that the DG market could amount to 2.5 to 5 GW year by 2010. DG technologies include small combustion turbine generators (including microturbines), internal combustion reciprocating engines and generators, photovoltaic panels, and fuel cells. Other technologies including solar thermal conversion, Stirling engines, and biomass conversion are considered DG. In this book, the term DG is limited to units below 10 MW electrical output.

Operational Differences

In the non-lube or oil-free piston and piston ring assembly there is no oil film to support the piston, so the metallic piston must be kept off the cylinder bore by other means or serious damage will result. Note that this is the difference between lube and non-lube principle.

426 Singletube damper

The Woodhead Manufacturing Company has produced a single-tube damper without a floating piston. In it the inert gas is free in the cylinder and therefore tends to emulsify the fluid. Although the gas and oil separate while the vehicle is stationary, re-emulsification occurs rapidly owing to the large flow rates inherent in the design, the performance of the unit therefore becomes normal equally rapidly. An advantage of this type of damper is the impossibility of jacking up and subsequent bending of the piston rod, in the event of leakage of fluid past a free piston. Also, again because of the absence of the free piston, the dead length of the damper is small. Moreover, the performance of these emulsion-type dampers is affected less than that of the fluid type by variations in working temperature. Single-tube dampers in general have the advantage that, for a given overall diameter, the piston area is greater, but they have the disadvantage of a higher built-in pressure.

Raymond Farnell and Duncan Riding

Roger Richards is Principal Engineer with Ricardo Consulting Engineers. He has worked on various engine areas, from Stirling engines through alternative fuels and artificial intelligence applied to condition monitoring. He is responsible for the development of novel techniques for improving efficiencies and emissions of large engines.

02 Design theory and practice

The price premium necessary for electric-drive vehicles is not an intrinsic one, merely the price one has to pay for goods of relatively low volume manufacture. However, the torque characteristics of electric motors potentially allow for less complex vehicles to be built, probably without change-speed gearboxes and possibly even without differential gearing, drive-shafting, clutch and finaldrive gears, pending the availability of cheaper materials with the appropriate electromagnetic properties. Complex ignition and fuel-injection systems disappear with the conventional IC engine, together with the balancing problems of converting reciprocating motion to rotary motion within the piston engine. The exhaust system, with its complex pollution controllers, also disappears along with the difficult mounting problems of a fire-hazardous petrol tank.

49 The PNGV programme impetus for change

The US OTA considers that the most likely configuration of a PNGV prototype would be a hybrid vehicle, powered in the near term by a piston engine, and in the longer term perhaps by a fuel cell. It notes that there is no battery technology that can presently achieve the equivalent of 80 mpg. Thus, the proton exchange membrane (PEM) fuel cell is seen as the more likely candidate. The DOE further stresses that meeting the fuel economy goal will require new technologies for energy conversion, energy storage, hybrid propulsion, and lightweight materials.

Frequencyresponse curve

Free-piston engine mech eng A prime mover utilizing free-piston motion controlled by gas pressure in the cylinders. 'frei .pis-tsn 'en-jsn free-piston gage eng An instrument for measuring high fluid pressures in which the pressure is applied to the face of a small piston that can move in a cylinder and the force needed to keep the piston stationary is determined. Also known as piston gage. frei pis-tsn 'gaij free port civ eng An isolated, enclosed, and policed port in or adjacent to a port of entry, without a resident population. 'fri .port free slack See free float. frei 'slak free-swelling index eng A test for measuring the free-swelling properties of coal consists of heating 1 gram of pulverized coal in a silica crucible over a gas flame under prescribed conditions to form a coke button, the size and shape of which are then compared with a series of standard profiles numbered 1 to 9 in increasing order of swelling. 'fri .swel-ig 'in.deks free turbine mech eng In a turbine engine, a...

253 Technical Developments and Outstanding Barriers

Stirling cycle engines have developed considerably in recent years. The free-piston configuration has served as an enabling technology for a great deal of energy conversion development. Stirling Technology Company (STC) and Sun Power Inc. are the leading developers of free-piston Stirling cycle engine generators with capacities ranging from 10 W to 5 kW. These generators have demonstrated maintenance-free operating lives far beyond that of gasoline or diesel engine generators. Ongoing endurance testing has proven so far that these generators can run continuously without maintenance for over six years, about 55,000 hours, with no observable degradation in performance. The potential operating life of these generators is well over twenty years. Similar prototype engines are currently available to utilities and other interests for evaluation, while the designs are being refined to lower costs and prepare for mass production. Development work is also under way to produce more reliable and...

1041 CHP Technology Cost and Performance Characteristics

Operating costs include both fuel and nonfuel expenses (such as replacement of spark plugs for engines, and replacement of stacks for fuel cells). As discussed above, many of the most efficient technologies can operate on only very pure (expensive) fuels. Per Btu, the cheapest fuel is coal, which can be used only with boiler steam turbine and Stirling engine CHP applications. The primary economic driver for CHP is production of power at rates that are lower than the utility's delivered price. Figure 10.5 demonstrates graphically how CHP compares with traditional central station generation combined with the necessary transmission and distribution (T& D) to move the power to the load. Figure 10.6 shows the convergence of first cost of many CHP technologies. While it is true that the costs of all the technologies have fallen steadily, Figure 10.6 (which shows the average capital cost of each technology) reveals that some have declined more quickly than others. Technologies just...

47 Prospects for EV package design

But the 'writing on the wall' for the first generation of electric cars appeared in the World War I period with the development of electric starters for thermal engines. This was followed by unprecedented improvement, by development, of the piston engine and the success of the Ford Model T generation vehicles in the 1920s which substantially outperformed early electric cars. From then on until 1960 when high-power solid-state switching devices were developed and EVs were basically used for delivery and other secondary applications. Between 1960-1980, a new generation of EVs was developed, of which mechanical-handling trucks and golf-carts were the

Thermal Barrier Coatings for Diesel Engine Components

An additional set of problems will be associated with the transfer of aerospace TBCs to diesel engines. This is partly because thicker coatings will be required to meet the insulation needs for most of the more advanced applications, and higher stresses are generally associated with thicker coatings. Currently NASA-Lewis is managing two DOE-sponsored contracts which are designed to develop thermal barrier coatings for truck diesel engines. (This program has been discussed at this conference). This work is building, in part, on earlier programs which led to the development of the thick plasma sprayed turbine blade tip-clearance seals which are now flying in certain commercial gas turbine engines (ref.24). These seals, like coatings for diesel engine piston heads and valves, operate at temperatures too low for bond coat oxidation to be a concern. As a result, it possible to use intermediate layers of mixed,ceramic and metal to alleviate thermal expansion mismatch strains. Possibly,the...

Expenditures For Gasoline

With NASA Lewis Research Center to provide contracting and technical management of the major heat engine projects-the Automotive Gas Turbine, the Automotive Stirling Engine and the Heavy Duty Advanced Diesel and with the Oak Ridge National Laboratory to provide technical management for materials and fuels research and development programs. Automotive Stirling Engine Program goals for the Automotive Stirling Engine (ASE) Program are similar to those for the Gas Turbine with fuel economy improvements on the order of 30 percent, expanded alternative fuel capability and improved emissions being the primary targets of the program. The project began with early proof-of-concept testing of a stationary Stirling engine adapted for automotive installation. Successive engine models were developed to improve fuel economy, vehicle acceleration and engine weight volume. The first generation MOD I and the upgraded MOD IA engines advanced Stirling Technology to a verified 15 percent improvement in...

424 Dampers in practice

Another effect of the intrusion of the piston rod into the cylinder is that the volumes available for accommodation of the fluid on the two sides of the piston differ. Compensation for this can be provided by the incorporation of a flexible element in the cylinder, so that the total volume within it can adjust automatically, as required. This flexible element can be an elastic sphere containing an inert gas, or a free piston with an inert gas between it and the closed end of the cylinder. An alternative is the use of the double-tube design.

Constructional details of the engine

From the outline of the general principles in Chapter 1, and the requirements as regards balance in Chapter 2, we now turn to the details of construction, leaving engines having six or more cylinders to Chapter 4. Sleeve valve, rotary valve, and rotary piston engine constructions will then be dealt with in Chapter 5. The conventional layout described in Section 1.10 has become firmly established, despite attempts to develop for automotive applications others such as the swash-plate motor, widely used for hydraulic power, and the Stirling engine, the relatively large size and weight of which virtually rules it out. The gas turbine, while well established for large power units operating mainly at constant speeds, has so far defied attempts to develop it in sizes small enough and of adequate flexibility for quantity production for automotive applications.

Horsepower

Note that in an opposed-piston engine 'l ' totals the sum of the strokes of the two pistons in each cylinder. To apply the formulae to double-acting engines is somewhat more complex since, for instance, allowance must be made for the piston rod diameter. Where double-acting engines are used it would be advisable to seek the builder's advice about the constants to be used.

256Costs

Free-piston Stirling cycle engines and generators are currently available on a prototype basis for development and technology evaluation programs. Work is under way to have several sizes of generators mass produced. Full scale production of STC's 1 kW generator is planned for the year 2002, with limited production of the 3 kW generator to follow. efficiency of the Stirling engine and lack of significant maintenance requirements bring the operating costs down to levels below most other distributed generation technologies.

10314 Footprint

Three technologies in particular offer compact packaging and have an appeal to end users seeking an unobtrusive CHP system. Stirling engines are the smallest, followed by fuel cells and microturbines. Larger steam turbines, gas turbines, and reciprocating engines are generally isolated in either a factory enclosure or a separate building along with ancillary equipment. Table 10.2 shows equivalent footprint size for several different CHP types. Stirling engine Oven (3)

21Introduction

Piston engine induction system icing, commonly, but not completely accurately, referred to as 'carburettor icing' may occur even on warm days, particularly if they are humid, IT CAN BE SO SEVERE THAT, UNLESS CORRECT ACTION IS TAKEN, THE ENGINE MAY STOP. Induction system icing is more likely at low power setting such as those used during descent, holding, on the approach to a landing or during auto-rotation on a helicopter.

81 Propellers

A propeller or airscrew converts the torque of an engine (piston engine or turboprop) into thrust. Propeller blades have an airfoil section which becomes more 'circular' towards the hub. The torque of a rotating propeller imparts a rotational motion to the air flowing through it. Pressure is reduced in front of the blades and increased behind them, creating a rotating slipstream. Large masses of air pass through the propeller, but the velocity rise is small compared to that in turbojet and turbofan engines.

10313 Noise

Although fuel cells are relatively expensive to install, they are being tested in a number of sites, typically where the cost of a power outage is significant to lost revenues or lost productivity and uninterrupted power is mandatory. Stirling engines should also do well in these markets. Their relatively quiet operation has appeal and, thus, these units are being installed in congested commercial areas. Locating a turbine or engine in a residential area usually requires special consideration and design modifications.

252 Fuels

One of the singular advantages Stirling engines have over internal combustion engines is that they are truly multi-fuel capable. The Stirling cycle requires only a sufficient heat source to operate and does not rely on carefully timed fuel injection and combustion processes as do internal combustion engines. Practical Stirling cycle engines may be operated using propane, natural gas, gasoline, diesel, radioisotopes, solar energy, and even wood or other biomass. The only limitation on fuel source imposed by the engine is that a sufficient amount of heat must be transferred to the cycle at a controllable temperature. There are often minimal changes to fuel systems needed to accommodate different fuel types, but the engine itself requires no new hardware.

Cantilever

Of the cam follower. 'kam ak-sel-s'ra-shsn camber des eng Deviation from a straight line the term is applied to a convex, edgewise sweep or curve, or to the increase in diameter at the center of rolled materials. 'kam-bsr camber angle mech eng The inclination from the vertical of the steerable wheels of an automobile. 'kam-bsr .ag-gsl cam cutter mecheng Asemiautomaticorau-tomatic machine that produces the cam contour by swinging the work as it revolves uses a master cam in contact with a roller. 'kam .ksd-sr cam dwell deseng That part of a cam surface between the opening and closing acceleration sections. 'kam .dwel cam engine mech eng A piston engine in which a cam-and-roller mechanism seems to convert reciprocating motion into rotary motion. 'kam .en-jsn camera study See memomotion study. 'kam-rs . stsd-ei

Compression coupling

kampresh-an ig ish-an 'en-jan compression member eng A beam or other structural member which is subject to compres-sive stress. kam'presh-an .mem-bar compression modulus See bulk modulus of elasticity. kam'presh-an .maj-a-las compression mold eng A mold for plastics which is open when the material is introduced and which shapes the material by heat and by the pressure of closing. kam'presh-an .mold compression pressure mech eng That pressure developed in a reciprocating piston engine at the end of the compression stroke without combustion of fuel. kam'presh-an .presh-ar compression process chem eng The recovery of natural gasoline from gas containing a high proportion of hydrocarbons. kam'presh-an .pra-sas

251 Design

Stirling engines operate on a closed thermodynamic cycle where a temperature differential is converted into mechanical and or electrical power. External heat is supplied at a high temperature to the engine heater head, and thermodynamic waste heat is rejected to ambient temperature. An internal displacer piston physically shuttles the helium working fluid between the hot and cold regions, creating a varying pressure value. That pressure wave causes the power piston to reciprocate. The reciprocating motion can be used to produce shaft power similar to an IC engine or may be used to generate electricity directly using a linear alternator. At no time during the cycle does the working fluid enter or leave the engine, which is hermetically sealed. Therefore, the cycle is defined as closed. Several varieties of Stirling engines have been developed by both private and government organizations. The varieties may be grouped into two fundamental categories kinematic and free-piston. Kinematic...

Lubricating Oils

Significantly improved thermal efficiency, fuel economy and ability to burn poor quality bunkers have resulted from the intensive development of low speed crosshead and high medium speed trunk piston engine designs in the past 20 years. Further progress in performance and enhanced lifetimes can be expected from the exploitation of higher firing pressures and better combustion characteristics.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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