Experimental Investigation of Combustion Characteristics on Opposed Piston Two-Stroke Gasoline Direct Injection Engine

Abstract

The combustion characteristics of an opposed-piston two-stroke gasoline engine are investigated with experiment. The energy conversion and exergy destruction are analyzed and the organization method of the combustion process is summarized. The effects of phase difference, scavenging pressure, injection timing, ignition timing, and dual spark plug ignition scheme on the combustion process and engine performance are discussed, respectively. The heat release rate of the opposed-piston two-stroke gasoline engine is consistent with the conventional gasoline engine. With the increase of opposed-piston motion phase difference, the scavenging efficiency decreases and overmuch residual exhaust gas is not beneficial to the combustion process. Meanwhile, the faster relative velocity of the opposed-piston near the inner dead center enhances the cylinder working volume change rate, which leads to the rapid decline of in-cylinder pressure and temperature. The 15 °CA of opposed-piston motion phase difference improves the scavenging and combustion process effectively. When scavenging pressure is 0.12 MPa, the scavenging efficiency and heat release rate are improved at medium-high speed conditions. With the delay of injection timing, the flame developing period decreases gradually, and the rapid burning period decreases and then increases. The rapid burning period may reach the minimum value when the injection advance angle is 100 °CA. With the delay of ignition timing, the flame developing period increases gradually, and the rapid combustion period decreases and then increases. The rapid combustion period may reach the minimum value when the ignition advance angle is 20 °CA. Notably, the flat-top piston structure should be matched with the dual spark plug, which the ignition advance angle is 20 °CA at medium-high load conditions.

Experimental research on scavenging process of opposed-piston two-stroke gasoline engine based on tracer gas method

“…The scavenging duration remained constant for different piston motion phase difference. As described in the Ma, 29,30 smaller intake and exhaust piston phase difference shortens free exhaust process leading to a possible burnt gas backflow after intake port opening while overlarge phase difference prolongs post intake period producing fresh charge backflows before intake port closing which reduce trapping rate and scavenging efficiency.…”

“…Relevant simulation and experimental studies have been carried out on the OP2S-GDI engine. Ma 29 shows that the combustion temperature during the whole main combustion period is greater than 817 K, the ignition temperature of methane, when the speed is at 2000 rpm and the load is low. In addition, in order to fully burn the fuel and methane injected into the cylinder, it is necessary to ensure that the trapped air-fuel ratio is greater than 15 and the injected methane concentration does not exceed 3000 ppm.…”

“…After injection, the methane is mixed with high speed intake flow. As shown in Figure 5(b), the distance between the intake collection point and the injection point is about 4.2 m. 29 It can be shown that the tracer gas and intake air have been completely mixed, and the exhaust extraction collection distance is about 0.8 m. The influence of intake collection point location on the intake mole fraction is mainly reflected in the mixing degree of methane and intake gas. While the influence of exhaust collection position on exhaust mole fraction is mainly the consumption and combustion of tracer gas.…”

Knock combustion characteristics of an opposed‐piston two‐stroke gasoline engine

“…The Huh-Gosman fragmentation model, the k-zeta-f turbulence model, the Frolov evaporation model, and the Mundo Sommerfeld wall colliding model are chosen. 37,38 Spray experiment conditions from Ma. 37 are used in a nitrogen atmosphere at a temperature of 293 K and pressure of 0.1 MPa, and 93# gasoline is injected at 13 MPa.…”

“…37,38 Spray experiment conditions from Ma. 37 are used in a nitrogen atmosphere at a temperature of 293 K and pressure of 0.1 MPa, and 93# gasoline is injected at 13 MPa. The spray model is verified in a constant volume test chamber.…”