Thermal cycle design of liquid nitrogen engine

To resolve the frost build-up on the surface of the main heat exchanger and the low efficiency problem encountered in building test bench of liquid nitrogen powered engine, a 4-stage liquid nitrogen- methane-ethylene-R134a isentropic Rankine power cycle was presented. Thermodynamic computation results showed that the specific work output of liquid nitrogen in the new cycle was 129% more than that in the single Rankine cycle. After adequately considering the irreversibility, the energy density of liquid nitrogen was still higher than that of current chemical battery. The new propulsion system can operate in a variety of environmental conditions while not being hampered by the frost build-up, and the solar energy can also be included to extend the vehicle's driving range. Comparison of the presented propulsion system with the system based on Brayton cycle showed that they owned similar specific work output under ideal operation condition, and the isentropic Rankine cycle was better when practical factors like pressure drop and temperature difference were considered.