Mixture preparation strategies in an optical four-valve port-injected gasoline engine

Abstract

The mixture formation in a single-cylinder, optical port-injected gasoline engine was investigated for both closed- and open-valve injection strategies with a combination of phase Doppler anemometry, laser-induced fluorescence and Mie scattering and correlated with combustion development and exhaust emissions. Detailed crank angle resolved data of the flow and mixture distribution during induction and compression have revealed the advantages of early open-valve injection, in terms of extending the lean limit and maintaining satisfactory engine performance and HC/NOx emissions, achieved through charge stratification in the vicinity of the spark plug at the time of ignition.

Modelling of mixture preparation in a small engine with port fuel injection

“…In all cases, the final charge inside the cylinder is lean, with the baseline case having the highest combustible charge close to the spark plug location at spark timing. Charge stratification is also observed from the simulation results when the spray is directed at the back of the intake valve, in agreement with earlier findings (Gold et al, 2000). The exact location of the rich region varies from case to case, and further studies may be required to ensure a rich mixture at the spark location under all operating conditions.…”

“…Unlike in small engines where the lack of space makes in situ visualisation and characterisation of the spray extremely difficult, large engines lend themselves easier for diagnostic studies. Arcoumanis et al (1998) and Gold et al (2000) experimentally studied flow under closed-valve and open-valve injection in a low speed 4-valve optical engine using laser-based techniques, and concluded that open-valve injection with a high tumble in the cylinder could lead to stable and efficient operation of the engine even at an air/fuel ratio of 24, through stratification. High speed visualisation of the fuelling process in the port of a 4-valve firing PFI engine under closed-valve injections were performed by Shin et al (1995) who found the wall film flow to play an important role in fuel transport.…”

Optical investigation of the fuel injector influence in a PFI spark ignition engine for two-wheel vehicles

“…After reaching the combustion chamber, the fuel droplets stuck on the piston surfaces created fuel-rich zones that developed dynamically under the effect of the gas flow influencing the composition of the mixture and hence the combustion process. Analogous effects involved the fuel droplets stripped by the fuel film deposited onto the port wall or the back side of the inlet valve [6][7][8][18][19][20]. To better understand the influences of these phenomena on the combustion process, cycle resolved imaging was performed.…”

Optical investigations of fuel deposition burning in ported fuel injection (PFI) spark-ignition (SI) engine

“…Liquid fuel film forms in gasoline engines near the valves due to the impingement of the injected fuel spray on the intake manifold and on the ports' surfaces [1][2][3][4][5]. Once formed, the film develops dynamically under the influence of the gas flow and of the valve movement [1,2].…”

“…Once formed, the film develops dynamically under the influence of the gas flow and of the valve movement [1,2]. The heat exchange with port walls and with the surrounding gas leads to the fuel evaporation, affecting the composition of the mixture and hence the complexity of the flow and the combustion process [3][4][5]. In particular, liquid fuel vaporization and fire near the valves can reduce the flame speed and the complete flame propagation creating locally rich-zones.…”