Effects of Port Injection Specifications on Emission Behavior of THC and Engine Maximum Power 2017-32-0059
In this paper, it is also elucidated that the influence of the downstream injection, which caused different fuel behavior in contrast with upstream injection, on the THC after warm-up and at the maximum power, as well as its mechanism. The mechanism is clarified by use of the intake port visualization system. First, at each injection position, the effect of injection timing on THC emission after warm-up was evaluated. In the downstream injection, THC emission increases during the injection timing, in which the fuel spray directly flows in-cylinder during the intake process (hereinafter defined as the intake valve opening injection timing), and the amount of THC emission is reduced at the other injection timing (hereinafter defined as the intake valve closing injection timing). Based on the results of visualizing the intake port, injected fuel phase near the intake valve is spray in the downstream injection. Furthermore, the high temperature intake valve immediately caused the fuel spray to evaporate at the intake valve closing injection timing and then flown in-cylinder. Next, the influences of the injection pressure and the injection timing on the maximum power are evaluated at each injection position. In the downstream injection, the intake air mass flow and the maximum power at the intake valve opening injection timing are increased. Furthermore, the tendency in downstream injection becomes more prominent in high injection pressure. In the downstream injection, intake air mass flow and the maximum power increased due to the fuel cooling effect by the direct spray flow in-cylinder.