STUDY ON SYSTEM PERFORMANCE OF LIQUIEFIED AIR CYCLE ENGINE

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Based on the experimental results, an analytical method of estimating a liquefaction (mass of liquefied air cooled by 1 kg of liquid hydrogen), and an outlet temperature of liquid hydrogen of the heat exchanger was established, by which we easily evaluate the performance of the heat exchanger cooled by liquid hydrogen. Using this analytical method, we will be able to easily improve the performance of heat exchanger. The specific impulse of LACE was estimated using the above -mentioned method. More than 1,000 second of the specific impulse was calculated even in a simple LACE system. The higher specific impulse will be able to obtain by improvement of the heat exchanger, selection of the optimum LACE system, the selection of the optimum delivery pressure of liquid hydrogen pump, etc. Judging from the mentioned above performance of the present LACE engine, it will be considered that the LACE engine would be a one of the candidates of a rocket based combined cycle engine for a future reusable launch vehicle. The effect of the flight trajectory on the LACE engine was numerically investigated. The numerical results showed that the specific impulse of the present LACE system was smaller than that expected in the low flight Mach number. Therefore, some means, for instance the use of subcooled liquid hydrogen, will be required which enhance the performance of the LACE engine in the low flight Mach number.