Influences of the fuel injection parameters on the first-cycle firing and the combustion characteristics during the direct-start process for a gasoline direct-injection engine

Abstract

The direct-start method without requiring a starter is a viable and cost-effective solution for generating a frequent and efficient restarting process when start–stop technology is used on a gasoline direct-injection engine. During the direct-start process, the first-cycle combustion characteristics play a key role in determining whether the start mode is successful or not, because the start energy is wholly derived from the in-cylinder combustion without the support of a starter motor on the gasoline direct-injection engine. However, the first-cycle fuel–air mixing and combustion characteristics during the direct-start process of a gasoline direct-injection engine are not fully understood. In this work, the influences of the injection parameters, including the delay between the injection and ignition, the excess air ratio for the single-injection strategy, the delay between the first injection and the second injection for the dual-injection strategy and the ratio of the fuel mass in the first injection to the fuel mass in the second injection for the dual-injection strategy, on the combustion pressure, the heat release rate, the accumulated heat release and the indicated work were investigated experimentally by cycle-by-cycle analysis. The results show that the optimal delay between the injection and ignition of the single-injection strategy was 200 ms as a longer delay or a shorter delay can result in a reduction in the heat released rate, the indicated work and the firing boundary. A shorter delay with the optimal injected fuel mass tended to be more beneficial to the accumulated heat released, the indicated work and the crankshaft speed. Furthermore, with increasing delay and increasing fuel ratio of the fuel mass in the first injection to the fuel mass in the second injection for the dual-injection strategy, the heat release rate, the accumulated heat release and the indicated work first increased and then decreased. The optimum delay was 10 ms and the ratios of the fuel mass in the first injection to the fuel mass in the second injection were 4/1 and 5/1 respectively under the test conditions. Additionally, the dual-injection strategy with an optimized control parameter produced a higher heat release and higher indicated work than the single-injection strategy did.

Correlation analysis of road load fuel economy variations by energy difference for gasoline direct injection and diesel-powered vehicles

“…5 Thus, a gasoline particulate filter may be applied in GDI vehicles in the future to reduce the particulate mass (PM) and PN. 6,7 Reducing the nitrogen oxide (NO x ) emissions is also a very important challenge in passenger cars.…”

“…The first step is calculating the TA RL values for the two cycles. After calculating the RL cycle energy losses individually, the summation of the results was calculated by taking 55% of the RL energy loss from FTP-75 and 45% from HWFET, as shown in equation(6).…”

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

“…On the whole, many engine workers have researched the influence of fuel injection parameters on the engine combustion and emission, [26][27][28][29] and a lot of deep and valuable results have been revealed. But there is relatively little research about the particle emission characteristics of GDI engines.…”