配气相位对增压PFI汽油机性能的影响规律研究

发布时间：2018-04-16 09:31

本文选题：增压汽油机 + 配气相位　；参考：《吉林大学》2016年硕士论文

【摘要】：增压进气道喷射汽油机在低转速、大负荷工况下存在扭矩输出偏低,加速响应迟钝等缺陷;在部分负荷工况下,传统汽油机存在热效率低,燃料能量利用率低,发动机泵气损失高等缺陷。针对上述问题,本文在增压PFI汽油机模型基础上,调整配气相位,分析其低速、大负荷工况下动力输出特性、部分负荷工况下燃油经济性提升的潜在能力,研究结论如下:第一,低转速、全负荷工况。调整配气相位,利用气门重叠期的进气道、排气道压差,实现扫气,提高充气效率。本文研究转速1200rpm、全负荷工况,结果表明:在进气门早开角(IVO)为30°CA、排气门晚关角(EVC)为20°CA时,发动机输出最大扭矩。如气门重叠角过大,会有部分燃油空气混合气流出气缸外,造成燃油损失,影响发动机的热效率以及动力输出。当气门重叠角超过50°CA时,发动机扭矩急剧下降。第二,部分负荷工况。基于Atkinson循环发动机原理,探索配气相位影响燃油经济性的规律。研究转速1600rpm、中小负荷工况,在平均有效压力相同的情况下,随着进气晚关角度的增加,发动机的比油耗逐渐降低,尤其是在平均有效压力小于6bar时,随着进气晚关角的增加,比油耗有降低趋势。当平均有效压力超过6bar工况时,比油耗随着进气晚关角度的增加并没有很大的降低,反而降低发动机的扭矩输出。中等负荷工况下,仅调节进气门相位不能实现全负荷控制,应用节气门与进气门配合工作,实现发动机的全负荷控制。在转速2400rpm、2800rpm、3200rpm、3600rpm下,中等负荷增压状态下,进气晚关角在原机55°CA的基础上分别延迟至70°CA、85°CA、100°CA,节气门开度在20%、40%、60%、80%负荷下,发动机的扭矩输出分别降低约3%、8.6%、16.2%,比油耗分别降低了0.3%、0.5%、1.6%。在高转速工况下,当平均有效压力超过10bar时,随着进气晚关角度的增加,比油耗不再发生变化。即在高转速大负荷状态下,进气晚关角度的变化并不能有效改善发动机的经济性。当平均有效压力由4bar变化到10bar过程中,虽然进气晚关角度增加,但是比油耗的变化只在1.3%以内,比油耗并没有明显降低。因此在大负荷工况下,进气晚关角度的增加并不能提高燃油经济性,而动力输出却有所下降。
[Abstract]:The turbocharged intake port injection gasoline engine has some defects such as low speed, low torque output and slow acceleration under heavy load condition, while under partial load condition, the traditional gasoline engine has low thermal efficiency and low fuel energy utilization ratio.Engine pump gas loss high defects.In order to solve the above problems, based on the model of turbocharged PFI gasoline engine, this paper adjusts the phase of valve distribution, analyzes the characteristics of power output at low speed and high load, and the potential ability of improving fuel economy under partial load.The conclusions are as follows: first, low speed, full load condition.Adjust the phase of valve distribution, use the inlet of valve overlap period, exhaust port pressure difference, realize scavenging, improve the efficiency of inflation.In this paper, the rotating speed of 1200rpm is studied. The results show that the maximum torque of the engine is obtained when the inlet valve with an early opening angle of 30 掳CAand the exhaust valve with a late closing angle of 20 掳CA.If the valve overlap angle is too large, part of the fuel air mixture will flow out of the cylinder, resulting in fuel loss, which will affect the engine thermal efficiency and power output.When the valve overlap angle exceeds 50 掳CA, the engine torque drops sharply.Second, partial load condition.Based on the principle of Atkinson cycle engine, the effect of valve phase on fuel economy is explored.In the case of the same average effective pressure, the specific fuel consumption of the engine decreases gradually with the increase of the intake late closing angle, especially when the average effective pressure is less than 6bar, and with the increase of the inlet air late closing angle.There is a tendency to lower fuel consumption than oil consumption.When the average effective pressure exceeds the 6bar working condition, the specific fuel consumption does not decrease greatly with the increase of the intake late closing angle, but the torque output of the engine is reduced.Under the medium load condition, only adjusting the intake valve phase can not realize the full load control. The throttle and the intake valve are used to work together to realize the full load control of the engine.Under the condition of 2400rpmMN 2800rpmng 3200rpmng 3600rpm, under the condition of medium load supercharging, the intake late closing angle was delayed to 70 掳CA-85 掳CA-100 掳CA on the basis of 55 掳CA, respectively, and the throttle opening degree was 200.6080%, the torque output of the engine was reduced by about 38.6U 16.2and the fuel consumption was reduced by 0.3U 0.51.6.At high speed, when the average effective pressure exceeds 10bar, the specific fuel consumption will not change with the increase of the angle of late closing of inlet air.That is, under the condition of high speed and high load, the change of intake late closing angle can not effectively improve the engine economy.When the average effective pressure changes from 4bar to 10bar, the specific fuel consumption is only within 1.3%, although the inlet air closing angle increases, and the specific oil consumption does not decrease obviously.Therefore, under the heavy load condition, the increase of the intake late closing angle can not improve the fuel economy, but the power output is decreased.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK411

【参考文献】