稀混合气火花辅助压燃中着火温度影响及其控制参数研究

doi:10.3969/j.issn.1674-8484.2021.02.012

摘要/Abstract

摘要：

为了实现对着火时刻的调控,解耦关键控制参数对压燃程度和压燃时刻的影响,采用小升程凸轮轴,在负气门重叠角下, 过量空气系数为1.2时,通过实验和计算,进行了火花辅助压燃着火温度影响及其关键控制参数研究。结果表明：以循环压燃部分放热量相对循环放热量占比定义压燃率,可以反映压燃程度;压燃率可以回归为以有效压缩比、废气再循环（EGR）率、点火提前角等关键控制参数为自变量的解析关系;提取压燃时刻未燃部分混合气的温度958.13 (±15） K作为压燃着火温度。总之,可以将压燃率的影响因素分解到操作参数和结构参数,在某一具体参数下,通过压燃率与关键控制参数解析关系,对着火时刻进行预判和调控。

关键词: 汽油机, 辅助压燃, 有效压缩比, 废气再循环(EGR)率, 压燃率

Abstract:

The ignition conditions and influencing factors of auxiliary compression ignition were studied to realize the control towards the moment of fire and to decouple the influence of key control parameters on the degree of compression combustion and the moment of compression combustion. Under the condition of negative valve overlap angle by using small lift camshaft and the air excess coefficient was 1.2, the experiments and calculations were carried out. The results show that the compression burning rate can be defined by the proportion of the heat released in the circulation compression burning part relative to that of the circulation emission, which can reflect the degree of compression burning. The compression burning rate can be reflected by the key control parameters such as the effective compression ratio, exhaust gas recirculation (EGR) rate and ignition advanced angle, which are the analytic relationship of independent variables. The temperature 958.13(±15) K of the unburned part of mixed gas at the moment of compression combustion is given as the ignition temperature. In a word, the influencing factors of the compression combustion rate can be decomposed into operation parameters and structural parameters. For a specific parameter, through the analytic formulation of the relationship between the compression combustion rate and key control parameters, the fire-timing can be predicted and controlled.

Key words: gasoline engine, auxiliary compression ignition, effective compression ratio, exhaust gas recirculation (EGR), compression ignition rate

中图分类号:

TK411.2

孙剑, 耿路, 赖海鹏, 高定伟, 于书海. 稀混合气火花辅助压燃中着火温度影响及其控制参数研究[J]. 汽车安全与节能学报, 2021, 12(2): 232-242.

SUN Jian, GENG Lu, LAI Haipeng, GAO Dingwei, YU Shuhai. Study on ignition temperature conditions and influencing factors of lean burn spark assisted compression ignition[J]. Journal of Automotive Safety and Energy, 2021, 12(2): 232-242.

图/表 22

气缸数	4
排量	1.998 L
缸径×行程	82 mm × 94.6 mm
几何压缩比	14
燃油喷射形式	中置直喷
喷射压力	35 MPa
点火能量	90 mJ
最大爆发压力	12 MPa
气道滚流比/流量系数	2.337 / 0.349
进气凸轮包角,CA	175°
排气凸轮包角,CA	145°
进气门升程	6 mm
排气门升程	4 mm

表1 发动机基本参数

图1 计算模型

图2 着火时刻随曲轴转角的变化

图3 缸内温度随曲轴转角的变化

图4 压燃率定义示意图

图5 缸内温度随曲轴转角的变化

图6 不同压燃率拐点时刻未燃部分温度

图7 不同压燃率下的燃烧放热曲线及其对应燃烧模式

图8 不同曲柄转角(CA)下各参数对压燃温度贡献

图9 不同压缩比下各关键因素对缸内温度的作用

图10 不同点火提前角和压燃率下各因素对缸内温度作用

图11 n = 2 000 r/min, BMEP = 200 kPa压燃率(η)随内部EGR和有效压缩比变化的分布图

图12 进、排气相位对压燃率( η )分布的影响

图13 压燃比预测公式性能评估

图14 不同水温下50%压燃率区域对应的有效压缩比和EGR率范围

图15 不同λ下50%压燃率区域对应的有效压缩比和EGR率范围

图16 n = 2 000 r/min, BMEP = 200 kPa工况下λ拓展压燃率

图17 n = 2 000 r/min, BMEP = 200 kPa 工况下λ拓展放热率

图18 n = 2 000 r/min,不同负荷下的λ拓展压燃率

图19 n = 2 000 r/min, BMEP = 400 kPa,不同λ下的循环爆震最大值（KP_PK）

图20 n = 2 000r/min, BMEP = 200 kPa最佳油耗点油耗对比

图21 n = 2 000 r/min, BMEP = 200 kPa最佳油耗点瞬时放热率对比

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