气动发动机工作过程理论与实验研究

【作者】 蔡金雷；

【导师】 俞小莉；

【作者基本信息】 浙江大学 ， 动力机械及工程， 2004， 硕士

【摘要】 日益严重的环境问题和紧张的石油资源使汽车工业的发展面临着严重的挑战。为此世界各国相继出台了有关政策法规，一方面用以严格限制发动机的有害排放，另一方面积极鼓励清洁汽车的研究开发。 气动汽车是清洁汽车的一种，采用气动发动机作为动力装置。气动发动机是采用高压空气储存能量，通过高压气体在发动机气缸内膨胀实现机械能输出的动力装置。它不仅能使交通能源多元化，而且可以实现尾气污染零排放。 本文以气动发动机为研究对象，主要完成以下工作： 1．从理论上建立了气动发动机理想的工作过程，从可用能量分析的角度探讨合理的膨胀初始压力和膨胀方式。对于30MPa压缩气体，提出分级膨胀更有利于提高发动机的经济性能，并通过计算得到最优的膨胀级数。 2．设计了新型的旋转阀配气机构，基于采用此配气机构的发动机，建立理论的缸内压力曲线数学模型，较好地预测了缸内的压力变化趋势，但与实验结果相比，在量值上存在较大的差异。 3．选择RNGκ—ε湍流模型，基于CFD软件Fluent平台，对进气道流场进行数值模拟。 4．模拟结果进行分析，得出气体在气缸内的能量以流动动能和静压力能的形式存在，由于流入气缸的气体动能不能完全转化为静压力，致使实验所得的压力曲线没有理论计算结果饱满。同时发现，旋转阀的流量系数主要随着其开度增加而增大，受进出口压力比的影响较小。 5．搭建气动发动机的实验台架，分析缸内压力的变化规律，探讨进气时刻对发动机性能的影响，发现最佳的进气时刻为上止点。 6．在上止点进气的情况下，对气动发动机进行动力性能和经济性能实验。研究发现，实验用发动机在转速为1000r／min时，输出功率最大，在低速(＜1200r／min)的工况下运行具有较好的经济性能。当发动机工作在高负荷区时，发动机也具有较好的经济性能。 7．根据理论和实验分析结果，提出一种有利于提高发动机经济性能的配气机构设计方案。更多还原

【Abstract】 The development of auto is challenged by the more serious pollution and the shortage of petroleum. Many countries make many rules and policies for its further development, which are strict with the deleterious exhaust and encourage the research of clean auto.The air-powered car is one of the clean autos, which is driven by the air-powered engine, which is the power mechanism through changing the energy stored in compressed air into mechanical energy. It not only makes autos have more resources, but also makes autos no pollution.The air-powered engine was studied in this paper and all of the following were completed during this course.1. The ideal work process was established on theory. The reasonable initial pressure and the mode of expand were discussed by the analysis of available energy. Multi stages of expand was put forward for the compressed air with the pressure 30MPa and the optimal stages of expand was reached.2. The circumrotating valve was designed and the theoretical model was established for the pressure in the cylinder. The model can forecast the trend of the pressure, but there is some difference in the quantity.3. Based on the characters of intake flow, the flow field was simulated with theRNGk- turbulence model.4. As the results, the energy of the air in the cylinder includes the energy of flow and the static pressure energy. This is the one of the most important reason for the difference between the theoretical and experimental indicated diagram. The jaw opening influenced the coefficient of flow mostly.5. The experimental bench was established. The optimal time of inlet was obtained by analyzing the influence of inlet open time on the performance of engine.6. When the intake process begins at TDP, many experiments were done. As the results, the output power is most at the speed of 1 OOOr/min. When the speed is lower than 1200r/min, the engine has better economical performance. When the engine operates with high load, it also has better economical performance.7. Based on these results, a design scheme of valve with high efficiency was put forward.更多还原