大缸径天然气发动机进气道结构对气体流动影响的研究

发布时间：2018-05-26 02:18

本文选题：天然气发动机 + 进气道　；参考：《中国舰船研究院》2015年硕士论文

【摘要】：天然气发动机的开发、应用能有效促进我国能源结构调整,实现节能减排。提高功率密度、提高热效率、降低排放,是天然气发动机开发过程中的研究热点。合理的气流组织对天然气发动机实现清洁、高效燃烧有着重要的影响,而进气道结构是决定缸内空气量及涡流强度的关键因素,直接对气流组织和燃烧过程产生影响。天然气发动机在进气道上布置有燃气喷嘴和节气门,其结构同样会对缸内气体流动产生影响。因此,以某中速大缸径天然气发动机串联式切向气道为研究对象,采用CFD模拟和气道稳流试验相结合的方法,研究了进气道结构,燃气喷嘴及节气门结构对缸内气体流动的影响规律。具体研究内容如下:首先,应用CFD仿真研究,提出了天然气发动机进气道结构主特征参数:气道导向角Av,气道喉口直径dv,气阀锥角An和弯曲半径R,并研究了其对气体流动的影响规律。模拟结果表明:当Av减小7%时,气道平均流量系数降低约2%,平均涡流比提高约25%;当dv减小4%时,气道平均流量系数降低约3%,平均涡流比提高约10%;当An减小17%时,气道平均流量系数降低约2%,平均涡流比降低约15%;当R减小7%时,气道平均流量系数降低0.2约%,平均涡流比降低约2%。同时可将各主特征参数对气体流动的影响规律应用在相似机型进气道的设计开发,若考虑增大进气道的流通性,可优先增大喉口直径dv;若考虑增大进气道的涡流强度,可优先减小气道导向角Av。然后,应用CFD仿真研究,确定了燃气喷嘴和节气门结构对气体流动的的影响规律。模拟结果表明:加装燃气喷嘴和节气门后气道性能稍有变差,平均流量系数降低约4%,平均涡流比降低约2%,实际上这种影响主要来自于燃气喷嘴结构。最后,应用3D打印快速成型技术加工试验件,该方法具有精度高,加工周期短的特点,大大减小了试验件铸造偏差对试验结果的影响,并极大的缩短了加工周期。同时开展气道稳流试验验证了CFD仿真计算的准确性,分析表明:仿真计算与稳流试验结果有很高的一致性,可将两者平均流量系数的偏差控制在3%以内,平均涡流比的偏差控制在10%以内。本课题的研究实现了应用CFD仿真技术对气道性能的定性判断和定量分析,提高了试验验证的效率和水平。CFD仿真技术与气道稳流试验的有机结合,可作为气道设计开发的重要手段之一。
[Abstract]:The development and application of natural gas engine can effectively promote the adjustment of energy structure and realize energy saving and emission reduction. Increasing power density, increasing thermal efficiency and reducing emissions are the hot spots in the development of natural gas engine. Reasonable airflow distribution plays an important role in the clean and efficient combustion of natural gas engine. The structure of intake port is the key factor to determine the air volume and swirl intensity in the cylinder and has a direct impact on the airflow organization and combustion process. The gas nozzle and throttle are arranged on the intake port of the natural gas engine, and its structure will also affect the gas flow in the cylinder. Therefore, a series tangential port of a medium speed and large cylinder diameter natural gas engine is used as the research object. The structure of the inlet is studied by using the method of CFD simulation and steady flow test of the port. The influence of nozzle and throttle structure on gas flow in cylinder. The specific research contents are as follows: first, the application of CFD simulation research, The main characteristic parameters of intake port structure of natural gas engine are presented: Port guide angle Av, throat diameter DVD, air valve cone angle an and bending radius R, and its influence on gas flow is studied. The simulation results show that when AV decreases by 7, the mean flow coefficient of the airway decreases by about 2 and the mean eddy current ratio increases by about 25 percent; when DV decreases by 4, the average flow coefficient of the airway decreases by about 3 and the average eddy current ratio increases by about 10 percent; when an decreases by 17 percent, the flow coefficient increases by about 10 percent; and when an decreases by 17 percent, the flow coefficient increases by about 10 percent. The mean flow coefficient of the airway is reduced by about 2 and the mean eddy current ratio is reduced by about 15. When R is reduced by 7, the average flow coefficient of the airway is reduced by about 0.2 and the average eddy current ratio by about 2. At the same time, the influence of main characteristic parameters on gas flow can be applied to the design and development of the similar type of inlet. If the flow of the inlet is increased, the diameter of the throat can be increased first, and if the eddy current intensity of the inlet is increased, The airway guide angle Av can be reduced preferentially. Then, the influence of gas nozzle and throttle structure on gas flow is determined by CFD simulation. The simulation results show that the performance of the gas nozzle and throttle is slightly worse, the average flow coefficient is reduced by about 4 percent and the average eddy current ratio is reduced by about 2 percent. In fact, this effect is mainly due to the structure of the gas nozzle. Finally, the 3D printing rapid prototyping technology is used to process the test piece. The method has the characteristics of high precision and short processing cycle, which greatly reduces the influence of casting deviation on the test results and greatly shortens the processing period. At the same time, the accuracy of CFD simulation is verified by the steady flow test. The analysis shows that there is a high consistency between the simulation calculation and the steady flow test result, and the deviation of the average flow coefficient between the two can be controlled within 3%. The deviation of the average eddy current ratio is controlled within 10%. In this paper, the qualitative judgment and quantitative analysis of the airway performance are realized by using the CFD simulation technology, and the efficiency of the test verification is improved, and the level of the simulation technology is combined with the steady flow test. It can be used as one of the important means of airway design and development.
【学位授予单位】：中国舰船研究院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK403

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