spaces were almost the same temperature as the hot end of the regenerator. Both sets decreased slightly as the phase angle (engine speed) was increased. The 2.0 MPa case dropped even more for high speeds. This is due mainly to the large mixing loss in hot spaces, and depends almost completely on the mass transfer rate [16], The working gas temperatures at the cold end of the regenerator were about the same for any pressure and decreased linearly with engine speed. It also turned out that for constant heater temperature operations, the temperature gradients (Trh—Trc) were almost constant, independent of charge pressure. Compression space temperatures, on the other hand, did tend to elevate with increased engine speed, with the higher pressures tending to bring about higher temperatures and a deterioration of cooler efficiency. One possible reason for this is a choking action of the transfer port orifice during the upwards motion of the power piston. Concluding Remarks Preliminary testing of a small NALSEM-125 engine generator model has been done to provide a better understanding of the thermodynamic and dynamic engine performance. Significant findings and problems of operation are summarized below: (1) A transfer port in this type of engine has a large influence on pressure variations in high power operations, and will probably turn out to be quite important in the final engine design. The effect of the magnet on the motion of the piston/magnet plunger coupling should also be considered a key factor over the low speed range. One way to solve these problems is to modify the transfer port configuration and to modify the magnetic behavior of the linear alternator. (2) Except for the above operational problems, the NALSEM-125 engine’s power output and thermal efficiency depends on operating parameters very much like
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