Study On Principle Of Quasi Gas Power Cycle Engine For Power MEMS

Power MEMS is micro electromechanical system based power sources, which has extensive prospect in fields of airspace, communication, biomedicine, national defense and so on, and which will bring profound significance to the society. At present, there are many investigates into Power MEMS and many conceptual model machines have been manufactured. However, most of them were essentially generated by scaling the corresponding macro heat engines down to meso scale. The thermodynamic processes of these micro-scaled heat engines are totally the same as that of those corresponding macro engines but the geometrical similarity generated in the process of scaling down can hardly ensure the accuracy of the mechanical similarity and the thermal similarity, which results in no appearance of successful Power MEMS model machine with ultra-high power density and extremely restricts the development of international Power MEMS research.Based on this, the theory of quasi gas power cycle with ultra-high power density for Power MEMS is proposed exploringly in this paper. The theoretical design and analyze of Power MEMS micro engine, which adopts this cycle, are also carried out. Meanwhile, taking micro pipeline and annular combustor as example, the chemical reaction dynamic soft CHEMKIN is applied to simulate the micro-combustion of hydrogen-oxygen mixture. Finally, the design and manufacturing of a prototype and its test-rig is performed, together with corresponding experimental research.Firstly, the principle of quasi gas power cycle for Power MEMS is detailedly presented in this paper. And based on this, the theoretical design of micro engine with quasi gas power cycle for Power MEMS is discussed, including conceptual design and corresponding structural design. Meanwhile, simple dynamic analysis and thermodynamic analysis of the engine designed are also performed. The results indicate that the strength of the prototype whose outer diameter is 43mm meets the challenge with a speed of 5000rpm and the thermal efficiency and the engine output tend upwards as the increase of premix gas pressure.Secondly, the micro-combustion of H₂/air and H₂/O₂ mixture in the line type and the Power MEMS annular micro-scaled combustor is simulated and the impact of pressure, equivalence ratio and catalytic agent on chemical reaction rate, the distribution and variation of gas temperature and component in the combustion chamber is emphasized. The result indicates that in the micro pipeline combustor, higher pressure is good for increasing the combustion efficiency of micro combustor while too high pressure will limit the specific combustion intensity; the burning of H2/O2 will be more sufficient if a proper equivalence ratio is chosen; the catalytic combustion needs a smaller heat flux or temperature to complete ignition. However, the impact of pressure on annular combustor is similar to that on pipeline combustor. And its ignition also needs catalysis or outside heat because of the scale effect.Finally, the trial manufacture and experimental research of the prototype of quasi gas power cycle for Power MEMS is performed, which focuses on the manufacturing process of the prototype, the designing of the micro test-rig and the dynamometric test. The successful test-running of the prototype in reverse-drag test proves the feasibility of the mechanical structure but for some reasons, the max speed of the prototype stays only around 2000r/min. However, within the range of speed tested, the output power of the prototype increases along with its speed and the max output power is 16W.