Performance Study Of The Compressed-air Power System Based On Single-screw Expanders

Energy crisis and environmental problems have become a focus of attention of all mankind, the traditional car not only consume oil resources but also pollute the environment because of exhaust emissions, so the new types of car have been developed to alleviate the two problems by countries in the world.Air-powered car use air-powered engine to convert pressure energy contained by high pressure gas into mechanical energy to drive the car. Air-powered engine compared with the traditional internal combustion engine has the following advantages:(1) No combustion process, simple equipment requirement and low cost.(2) The working medium come from air and exhaust pure air or nitrogen, no any pollution to the environment.(3) The temperature of exhaust gas can be used as the cold source of air conditioning of air-powered car without additional energy consumption, and emissions into the atmosphere helps to lower the temperature of the surrounding environment, reduce the urban heat island effect. Due to these advantages of air-powered car, which can relieve the energy crisis and environmental pollution at the same time, and major attention will be paid in the auto industry.In view of the current situation of simple air-powered engine, a new kind power system of air-powered car, using single-screw expander as air-powered engine, is proposed. To explore operating characteristics of new air-powered engine and the performance of power system, a experimental study on this system is carried out.According to two single-screw expanders with rotor diameter of195mm and155mm independent researched by our laboratory, experiment platforms of compressed air power systems are designed and set up using air compressor and compressed air bottle as gas source respectively. Experimental researches on working performance of single screw expanders are carried out. The preliminary results show that single-screw expander running smoothly and no obvious resonance phenomenon when using air compressor as gas source. A better power performance, refrigeration performance, economic performance and working efficiencies can be obtained in high inlet pressure, high inlet temperature and high rotational speed. In the experiment, expander can reach maximum torque of169.6N-m, maximum power output of51.08kW, maximum temperature drop of88.28℃, minimum gas consuming ratio of44.07kg/kW·h, and maximum total efficiency of60%. Single-screw engine has unique gas properties with compressed air bottle taken when using compressed air bottle as gas source, which is dependent on the working characteristics of pressure reducer. In the conditions of experimental maximum inlet pressure at10bar and the maximum operating speed at3000r/min, expander can obtain the best performance. Expander can reach maximum power output of9.94kW, maximum total efficiency of58.32%,and minimum gas consuming ratio of59.57kg/kW·h. In a word, they show good working performance.