Theoretical And Experimental Study On Liquid Nitrogen Engine

Technology of vehicle is challenged by two serious problems, shortage of energy and pollution. So people make great effort to realize the Green Vehicle, which means high efficiency and low emission pollution. Liquid nitrogen car is one of the Green Vehicles. The energy density of liquid nitrogen is higher than other energy storage mediums. Liquid nitrogen engine runs without heavy metal pollution. It is so much clean as an atmosphere cleaner. In some sense, liquid nitrogen is regard as waste byproduct, so it is not expensive.Funded by the Natural Science of Foundation of China-Ford Fund-"Research on air powered vehicle engine" (No.50122115), by Division of Science and Technologies of Zhejiang provincial government under a key project-"The Research of Compressed Air Engine" (No.021101759), and also funded by the National Research Foundation for the Doctoral Program of Higher Education of China-"The Theoretical and Experimental Research for The Liquid Nitrogen Engine" (No.20020335079), the research project aim at liquid nitrogen engine. The work had been carried out can be summarized as follows: 1. Thermal cycle analysisBased on the classical thermodynamics, influence of isobaric reheat and isovolumetric reheat on cycle output is discussed. Based on the finite time thermodynamic theory, the thesis discusses the optimization of Rankine cycle, Brayton cycle and Stirling cycle between constant temperature heat source and constant temperature heat sink or between variable temperature heat source and constant temperature. The thesis focus on the influence of ratio between work medium heat conductivity and heat conductivity of heat exchanger on the cycle performance, and the influence of ratio between heat conductivity of high temperature heat exchanger and heat conductivity of low temperature heat exchanger on the cycle performance. The results can be use to direct the optimization of real engineering cycle and engine design.2. The platform for efficiency analysis evaluationThe platform for efficiency analysis is established. The work focuses on the efficiency of liquid nitrogen engine operating on open Rankin cycle. The influences of heat exchanger and engine on system efficiency are distinguished. The thesis also analysis the efficiency of the compound cycle of liquid nitrogen engine operating on open Rankin cycle together with the liquid nitrogen refrigeration cycle and economy in detail. The exergic efficiency of liquid nitrogen engine operating on ideal cycle and the exergic loss of real engineering cycle are studied.3. Models and optimization of Work process in cylinderOn the basis of experimental datum and the principle of variable mass thermodynamics, the models of intake, expansion and exhaust processes are presented. According to this model, feasibility analysis of realizing the Quasi-Isothermal expansion by control residual temperature in cylinder and intake temperature is focused. The thesis presents the analysis of liquid nitrogen engine open cycle with pressure drop irreversibility on the basis of principles of finite time thermodynamics. The simulation results proof the supersonic flow exist in inlet, the feasibility to stabilize the flow mass and to maintain high pressure in cylinder using shock wave is theoretically proved.4. Experimental studyIn thesis, speed characteristic curves and load characteristic curves are presented. The thesis forcuses on the influence of match between intake angle and exhaust angle on liquid nitrogen engine performances. The experimental datum proofs the design of circumrotating valve and the variable mass thermodynamic model of process in cylinder.Compared to previous studies, the present researches are innovative in:1. The platform for efficiency analysis of liquid nitrogen engine.2. The variable mass thermodynamic models of process in cylinder are established and proofed.3. Theoretically, feasibility to stabilize the flow mass and to maintain high pressure in cylinder using shock wave in inlet is proved.4. On the basis of principles of finite time ther...