Numerical investigation of the effect of injection strategy on a high-pressure isobaric combustion engine

Abstract

High-pressure isobaric combustion adopted in the double compression expansion engine (DCEE) has the prospect to achieve higher thermal efficiency compared to conventional diesel combustion. This work numerically explored the effects of various injection strategies on the combustion and emission characteristics of isobaric combustion. The study developed a mathematical model to predict the injection rate profile. After validations, extensive simulations were conducted with a peak pressure of up to 300 bar – mimicking the high-pressure unit of DCEE. Several major engine design parameters such as the exhaust recirculation gas (EGR) rate, engine speed, injection strategy, and intake pressure were varied and evaluated. The results demonstrated that a higher EGR rate resulted in a higher exhaust loss but a lower heat transfer loss owing to the lower combustion temperature, so the thermal efficiency exhibited a firstly growing and then declining trend. Besides, a higher engine speed generated a higher thermal efficiency due to the shorter combustion duration and thus lower heat transfer loss. Consequently, a peak thermal efficiency of 47.5% was achieved at EGR = 50% and 1800 rpm. The high-pressure cylinder performance can also be improved with an appropriate introduction of the isochoric combustion, but its impact on the whole DCEE setup needs further investigation.

Study of the Variation of Fuel Pressure to Improve Spraying and the Range of the Injection Jet

“…The injector is the most important component in this analysis test, as it will allow us to evaluate its spent fuel supply efficiency and how it evolves quantitatively at different operating pressures [17] as well as the different options it will present in the fuel consumption simulation [18]. The efficiency and speed of combustion depend on the process of mixing and fuel injection [19], for which the behavior of combustion must also be analyzed according to the characteristics of the mixture and dosing of fuel in its reaction processes, altering the parameters of spraying and pressure as performed by Liu X. et al [20].…”

“…According to a lot of the investigations, when injecting fuel into the engine, various problems will occur that hinder its power and development due to insufficient pressure and injection distance [16,26]. The work guide made by Schrödinger et al [27] examines the effect of fuel injection time on the flame shape and stability position and also shows parameters of variability in combustion in the process of ignition of the mixture as performed by Liu X. et al [20]. However, the main objective of the synthesis study will be to change the injection pressure to increase the jet range for better range at the intake valve inlet of the engine and the atomization of the fuel to generate better dosing of the air-fuel mixture.…”