Allison Division And The Solar Engine Project

So far as is known, the Allison Division was actively engaged in only one Stirling-engine development: a 3 kW (4 hp) solar space power plant. The work was done for Ihe U.S. Air Force and has been excellently documented in a series of ten technical reports (Parker and Malik 1962) of which Volume I on engine design, and Volume 10 on engine experimental evaluation, are most relevant. The remaining reports are concerned with other aspects of the system. The engine was also reported by Parker and Smith (1960), by Welsh el ai. (1959), and by Welsh and Monson (1962). The engine designated the Type PD46, shown in Fig. 1.3.10. was a single-cylinder rhombic-drive machine having a cylinder bore of 6.03 cm (2.375 in), a stroke of 2.84 cm (1.118 in) with helium as the working fluid at a mean cycle pressure of 10.3 MN/m* (1500 lb per sq in). The rated electrical output of the generator driven by the engine was 3 kW at a speed of 3000 revolutions per minute. The design overall thermal efficiency was 30 per cent.

The engine was noteworthy principally because the cylinder head and heater lubes were heated by liquid metal (NaK) al a temperature of 677 °C' (1250 °F). This represents an historic First in view of the subsequent developments that have been made and are yet to come with thermal energy storage, solar power, and nuclear energy systems.

Fib. 13.10. Allison Type PD46 Stirling engine for solar-heated space power-plant.

The engine was also noteworthy as the only significant expenditure of U.S. government funds on Stirling engines for space power plants during the era of high space expenditures in the 1960s. For reasons that have never been explained the National Aeronautics and Space Administration (NASA) resolutely neglected to consider the Stirling engine for space applications and the Air Force invested only relatively minor expenditures in the Allison program.

The PD46 engine generator operated a total of 76 hours on test. The design objective of 3 kW (4 hp) electrical output at 30.5 per cent was not achieved. The actual maximum output was 2565 watts (3.5 hp) at an efficiency of 23 per cent. Such a near-miss of objective is typical of initial efforts and there is little doubt that subsequent development would have seen significant improvement in performance. Regrettably, funding for an advanced flight-qualified engine was not forthcoming and the development was abandoned. Volume 10 of the report referred to contains detailed test results of the engine operation with descriptions of the various difficulties encountered. It is a prime repository of practical operational experience and is recommended for close study.

Following the termination of the PD46 engine work, no further Stirling engine development is known to have occurred at the Allison Division. Pcrcival (1974) has disclosed that various conceptual design studies were made for solar, chemically fuelled, and isotope-heated space power plants, foi torpedo engines and for residential air conditioners.

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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