Predictions of NALSEM-125 Engine Performance Prediction of output power produced by this early NALSEM engine design was made using second-order isothermal Schmidt cycle theory [13] and based on the engine configuration as given in Fig. 2. In any gamma-type machine, the compression space is split between two cylinders (displacer piston space and power piston space) with an interconnecting transfer port. For simple analysis, the volume of the transfer port was assumed to be included in the dead space. Power was calculated assuming the power piston always operates at resonance with a phase lag of 90° relative to the working pressure. This arises since the NALSEM free piston machine operates similarly to a simple harmonic oscillator. The efficiency of the Carnot cycle was assumed to be 70% in view of various power losses experienced in actual engines, while the generator efficiency ( = t/G) was assumed to be 80%. This is because the linear alternator is still also currently under development and cannot be considered to have reached final efficiency. Estimated results for electrical power and overall thermal efficiency are shown in Figs. 3(a) and (b), respectively. It is seen from these analytical data that the NALSEM engine can deliver an electric power output of about 180 We at an allowable maximum pressure of 2.5 MPa, which is better than the nominal specifica-
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