What is the Injection Advance Angle?

[ElliotRose]

The injection advance angle refers to the crankshaft rotation angle from when the fuel injector starts injecting fuel to when the piston reaches the top dead center. The size of the injection advance angle greatly affects the operating condition of a diesel engine. If the injection advance angle is too large, it will result in a longer pre-combustion period, causing rough engine operation. Conversely, if the injection advance angle is too small, it will lead to excessive delay in the combustion process, reducing the maximum pressure value and significantly decreasing the thermal efficiency of the diesel engine. The impact of the injection advance angle on pressure is as follows: 1. The maximum average pressure in the cylinder increases as the injection timing advances; 2. With the advance of injection timing, the ignition delay period lengthens, increasing the amount of fuel evaporation during this period, forming more fuel-air mixture at the moment of ignition. These combustible mixtures burn almost simultaneously during the rapid combustion phase, significantly raising the peak combustion pressure.