液氮发动机试验及效率分析

为了解液氮储能气动发动机的工作特点，实现液氮可用能的高效利用，搭建了液氮动力系统试验台架，测试了发动机在进气压力为0.1～1 MPa和转速为300～1 500 r/min区间内的动力性能和经济性能.分析了试验结果所展现的液氮发动机的动力性能和经济性能随进气压力和转速的变化规律.试验发现,发动机的输出功率与进气压力成正比关系；气阻现象使得发动机效率不随系统压力的增加而增加.系统的不可逆损失归结为内部不可逆损失和外部不可逆损失两部分并建立了相应的数学模型，结合试验数据，计算了液氮的单位质量可用能在系统中的分配.结果说明漏气损失与系统输出具有相同的量级，应该杜绝系统的漏气；换热损失消耗了大部分的液氮可用能，构建高效的液氮动力系统，必须采用多级循环.

Experimental study on liquid nitrogen powered engine and its efficiency analysis

An experimental bench was built to test working characters of liquid nitrogen powered engine and used to find out methods to make full use of the liquid nitrogeffs working potentials. Dynamic behaw iors and economy of the engine including power, air consuming rate and thermal efficiency were tested on the pressure range from 0.1 to 1 MPa and speed range from 300 to 1500 r/min. Effects of inlet pressure and engine speeds on engine performance were analyzed basing on experimental results. Engine power was in direct rate to inlet pressure, and air stock phenomenon hampered energy efficiency increasing with inlet pressure. Losses of work potentials were categorized into internal irreversibility part and external irreversibility part to articulate the quantities and locations of these losses clearly. Mathematics modules were given corresponding to each part of loses. Associating with test results, the allocation of exergy of liquid nitrogen in the system was given. Results showed that leakage had the same order of magnitude. Fluid leakage should be abandoned and multistage cycle should be adopted were proposed to achieve high efficiency of liquid nitrogen propulsion system.