Doubleacting Engines

Subsequent development effort was switched from single-acting to double-acting engines. In the paper by Aim or al. (1973) both United Stirling and MAN/MWM announced their abandonment of the rhombic-drive engine in favour of double-acting engines with crank and connecting-rod drive mechanisms. It is likely that both companies were influenced in their decisions by the experience of the other licensee. General Motors, who had been actively developing double-acting engines since 1965.

The new engine developed by United Stirling, designated the Type V4X, is shown in cut-away form in Fig. 15.5, and in cross-section in Fig. 15.6. A schematic view of the connections for the four-cylinder double-acting engine is shown in Fig. 15.7. The new arrangement allowed the use

H enter tubes



Cooler tubes



Fiston Piston rod Hydrogen seal unit

Tower cunttol dead volumes

Crosshead Connecting rod Balance shaft Crankshaft Staner

Oil sump

Stirling Engine Technology

Oil sump

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).

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).

of a single burner supplying heat to all four cylinders and a single recuperator for the preheated air. The cylinders, arranged in a narrow vee, allowed ior a favourable cold connecting-duct arrangement and for the use of a conventional single crank/connecting-rod/crosshead drive mechanism.

Prototype engines of the new form were operating by 1973 and it was possible to project specific weights of 4.3-5.0 kg/kW (7-8 lb per hp), half the values attained with rhombic-drive machines and accompanied by concomitant savings in cost. Development of the V4 engine has been vigorously pursued, with progress reported fr c:r. tim c to time in the literature.

Carlqvist et al. (1975) disclosed that the experimental engines had four cylinders arranged at a centre-line angle of tt/6 radians (30') with cylinder bores of 50 mm (1.97 in) and a stroke of 46 mm (1.81 in). Engine power was in the range of 30-40 k\V with efficiencies up to 30 per cent and speeds up to 4500 rpm using hydrogen as the working fluid. The engine was designed to use established engine technology where possible, particularly in the area of bearings, crankshafts, and other components.

Hie shape and size of the engine were such that it could be accommodated in the engine compartment of vehicles with little modification. Rosenqvist et al. (1977) described the first vehicle installation undertaken in 1972/74 in a joint U.S. Ford/United Stirling program. The engine, designated V4X31. was installed in a 1972 Ford Pinto car which ran for the first time in March 1974. Tests were terminated in December 1974 with total test distance of about 643.7 km (400 miles). This vehicle was equipped with a power train including a torque convertor and automatic transmission. The power control system of the engine was a United Stirling development utilizing a variable dead volume to control the amplitude of pressure variations and hence power output.

A second vehicle installation was undertaken with engine V4X35 in a 197-1 Ford Taunus estate car.The engine and transmission are shown in Fig. 15.8 and the vehicle engine compartment in Fig. 15.9. This machine utilized a single dry-plate clutch and an all-synchronized four-speed manual gearbox. The control system for this engine was of the conventional type where power variation was obtained by adjustment of the mean pressure level in the engine.

production engines

Despite these interesting and practical demonstrations the V4X engine was basically intended as a workhorse for component and system development. Much was accomplished and now three different production series engines have been defined (Hallare and Rosenqvist 1977) to

Pic. 15.8. United Stirling doublc-acting engine Type V4X35 with clutch and four-speed manual transmission (after Rosenqvist ef at. 1977).
Marine Stirling Engine
Fig. 15.9. Engine compartment of Ford Taunus cur with United Stirling V4X engine installed (after Rosenqvist el <it. 1977).

encompass a range of vehicular and other applications. The main performance criteria for these production engines are:

Type Designation

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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