Injection Strategies for Isobaric Combustion

Abstract

In a previous study, we demonstrated that the isobaric combustion cycle, achieved with a split injection strategy, can be more suitable for the double compression expansion engine concept than the conventional diesel combustion cycle. The present work is focused on understanding the effect of different injection strategies on the heat release, efficiency, and emissions of isobaric combustion at the peak cylinder pressure of 150 bar. In situ injection rate measurements are performed to improve our understanding of the heat release rate shape and pollutant formation. A variation of load is performed to demonstrate the feasibility of the isobaric combustion cycle at higher loads, and the means of achieving them. The thermal efficiency reduces at lower loads because of heat losses. It peaks at a medium load point before reducing again at higher loads because of exhaust losses. The effect of altering the injection strategy on the isobaric combustion cycle is also studied at a constant equivalence ratio. The alteration of injection strategy is proven to have minimal effect on efficiency, loss mechanisms, and emissions when more than one injection is used.

In Situ Injection Rate Measurement to Study Single and Split Injections in a Heavy-Duty Diesel Engine

“…Figure 5. Estimation of the delay between the measured signal and the actual injection due to a finite distance between the sensing element and the injector nozzle [4].…”

“…In addition, Nehmer and Reitz [3] studied the effect of injection strategy on soot and NOx formation in a diesel engine and demonstrated significant reductions of these emissions. Babayev et al [4][5] also studied different injection strategies and their effects on the combustion characteristics. In particular, constant-pressure combustion, which was proven superior to the conventional diesel combustion, required complex injection strategies with multiple main injection events.…”

“…In our previous studies [4,21] injection rate measurements were conducted for various injection strategies including single and multiple (up to five) main injections events, required to achieve constantpressure combustion. The measurements were performed using the same experimental configuration presented in this paper.…”

A numerical investigation of isobaric combustion strategy in a compression ignition engine

“…Owing to the excessive pressure (up to 300 bar) in the HP unit, it is desirable for the DCEE concept to adopt an isobaric combustion strategy instead of a typically preferred isochoric combustion strategy [18,19]. Okamoto and Uchida's work [20] has shown that it is possible to realize isobaric combustion using three injectors.…”

“…The previous studies related to the isobaric combustion strategy are mostly focused on experimental or 1D simulation research [5,18]. Therefore, this work intends to further enhance our understanding of the isobaric combustion strategy using the three-dimensional (3D) computational dynamics fluid (CFD) approach.…”