Effects of split and single injection strategies on particle number emission and combustion of a GDI engine

Abstract

Influence of fuel injection parameters of the single and split injection strategies on combustion, performance and particle number emission had been investigated on a gasoline direct injection engine with stoichiometric mixture combustion under medium and low engine operating conditions. The test results showed that the optimal injection timing for single injection strategy was about 290–280 °CA BTDC, and an earlier or a later injection timing could lead to a deterioration of particle number emission. For split injection strategy, the injected parameters also needed to be optimized subtly in order to improve particle number emission. When the inappropriate injected parameters were adopted, particle number emission increased rather than decrease when compared with single injection strategy. Similar to single injection strategy, when the second injection timing of split injection strategy further retarded from 280 °CA BTDC, the particle number emission and brake-specific fuel consumption also started to deteriorate, and the in-cylinder combustion process was delayed and slowed. The optimal first injection timing was about 300 °CA BTDC. When the first injection timing was delayed to 280 °CA BTDC with the second injection timing being 260 °CA BTDC, the particle number emission increased and the shortened interval time between first and second fuel injection might have had a negative effect. The smaller difference of the fuel quantity between the first and the second injection was not good for the improvement of particle number emission and brake-specific fuel consumption, and the best injection proportion was 2:8. Overall, the engine particle number emission could be decreased to some extent, which could reach about 10–30%, by split injection strategy with optimal control parameters at medium and low engine loads.

Numerical investigation of the effect of injection timing on the in-cylinder activity of a gasoline direct injection engine

“…Moreover, Zhuang et al 27 found that a significant oil-rich zone would appear in the center of the cylinder at delayed injection timing, which made nitrogen oxides (NO x ) emissions increase. Xie et al 28 found experimentally that the presence of optimal injection timing resulted in the best emissions performance. Further, Firat 29 indicated that compared to single-injection strategy, multistage injection strategies reduce the direct injection spark ignition (DISI) engine emissions such as NO x , carbon monoxide (CO), and unburned hydrocarbon (UHC).…”

Visualization of soot formation in load transients during GDI engine warm-up

“…6,7 Particulate emissions are highly sensitive to the start of combustion timing as well as the properties of the engine, its speed, and the spark advance. 8,9 For example, Xie et al 10 showed that delaying the spark advance from 25 CAD to 5 CAD can reduce particulate emissions from GDI engines by 50%. In a typical GDI engine drive cycle, particulate emissions peak during cold starts and transients, when there is an abrupt change in engine load or both load and speed together.…”