Abstract:

A three-dimensional model and a one-dimensional kinematics model for a direct injection gasoline engine were established and validated through engine experiments. The combustion characteristics in the first firing cylinder and the kinematics characteristics of the engine under the conditions of forward and reverse rotation were simulated when different fuel injection methods and spark ignition timings were employed at direct start. The results show that the peak cylinder pressure in the first firing cylinder after combustion in the cases of split injection is higher than that at single injection. But its magnitude is affected by spark ignition timing. Higher peak cylinder pressure increases the crank angles, which the engine can move in the reverse rotation direction. The engine speed in the forward rotation direction is the largest when the sequent cylinder is ignited at about 2° before the biggest reverse crank angles in both single injection and split injection, which is helpful to a successful direct start.

Key words: gasoline engine, direct start, kinematics, simulation

摘要：

建立了直喷汽油机的三维数值模型和运动学模型，并进行了试验验证。模拟了直喷汽油机在直接起动过程中不同喷油策略和点火时刻下的燃烧特性、反转和正转过程的运动特性。结果表明：与单次喷油相比，采用两次喷油策略时，首个着火气缸内混合气燃烧后的最大气缸压力较大，而且其大小受到点火时刻的影响；首个着火气缸内混合气燃烧后的最大气缸压力较大，则直喷汽油机反转过程中转过的最大角度较大；在各种喷油条件下，第2个着火气缸在反转到其最大转角前2°左右点火，正转过程转速较高，有利于直喷汽油机的直接起动。

关键词: 汽油机, 直接起动, 运动学, 模拟