Effects of the injection timing on knock and combustion characteristics in dual-fuel dual-injection engines

Abstract

To utilize ethanol fuel in spark ignition engines more efficiently and flexibly, a new ethanol/gasoline dual-direct injection concept in gasoline engine is proposed. Therefore, based on the dual-fuel dual-direct injection system, the effects of different injection timings and two injector positions on the characteristics of combustion were studied comprehensively, and the effects of different octane numbers and temperature stratifications on knock and combustion were explored. The results show that as for Position A (ethanol injecting toward spark plug), with the delay of injection timing, knock tendency and its intensity increase initially and then decrease due to the comprehensive effect of ethanol evaporation and fuel stratification; on the contrary, for Position B (ethanol injecting toward end-gas region), retarding the injection timing of ethanol can effectively reduce the knock propensity. As for the engine performance, a dual-direct injection performs best, especially the retarded injection timing of ethanol for Position A. It can be found that with the delay of the fuel injection timing, the torque first increases and then decreases. The brake-specific fuel consumption decreases initially and then increases at maximum brake torque spark timing.

Dual injection: An effective and efficient technology to use renewable fuels in spark ignition engines

“…This paper aims to review the recent progress in dual injection of gasoline and renewable fuels in SI engines. The dual injection concept here specifically refers to the combination of DI and PFI which has attracted the most research attention, although there are a few studies on dual PFI [43][44][45][46][47][48][49] and dual DI [50,51]. This paper is organised as follows.…”

A comparative study of PODE/gasoline and n-heptane/gasoline in a spark-assisted homogeneous charge compression ignition engine with dual-injection strategies and EGR

“…Compared with direct injection, dual injection enhanced the mixing of fuel and air and flame propagation. [20][21][22][23] The knock resistance and fuel economy are significantly improved by controlling the injection timing. Meanwhile, a dualinjection system can control over mixture stratification in the cylinder so the fuel can be ignited easily.…”

Combined experimental and numerical study on fuel deposition characteristics of an impinging PFI spray with different impingement geometries

“…Despite the leading share of the gasoline direct injection (GDI) system in current spark ignition (SI) engines, the old fashioned port fuel injection (PFI) system regains some attention in recent years, primarily due to the popularity of the dual-injection technology. 1,2 The SI engine adopting dual-injection technology combines the PFI and GDI systems together, thereby shows the potential to integrate advantages of the both. 3 Compared to the GDI engine, the dual-injection engine can not only significantly mitigate the particulate number (PN) emission, 4,5 but also achieve more flexible blending ratios when using renewable fuels.…”