Influence of injection strategies on knock resistance and combustion characteristics in a DISI engine

Abstract

The combustion of a direct injection spark ignition engine is significantly affected by the fuel injection strategy due to the impact this strategy has on the gas-mixture formation and the turbulence flow. However, comprehensive assessments on both knock and engine performances for different injection strategies are generally lacking. Therefore, the main objective of the present study is to provide an experimental evidence of how a single injection strategy and a split injection strategy compare in terms of both knock tendency and engine performances like thermal efficiency, torque and combustion stability. Starting from the optimization of a single injection strategy, a split injection strategy is then evaluated. Under the present operating conditions, an optimum secondary injection timing of 100 CAD BTDC is found to have significant improvements on both the knock resistance and the overall engine performances. It should be noted that the present results indicate that the relationship between double injection and anti-knock performance is not monotonous. In addition, the double injection shows superior potential in improving fuel economy and power performance in contrast with the single injection thanks to a more stable combustion when a late injection timing is applied.

Lean Burn Flame Kernel Characterization for Different Spark Plug Designs and Orientations in an Optical GDI Engine

“…Nevertheless, several studies [5][6][7] forecast that internal combustion engines (ICEs) will continue to play an important role among vehicular propulsion systems for the next decade (also foreseeing their application in hybrid powertrains or thanks to the use of synthetic fuels) and for distributed energy generation solutions. In this context, gasoline direct injection (DI) in spark ignition (SI) engines has been widely adopted in recent years, often in combination with engine downsizing and turbocharging, due to its capability to significantly reduce knock tendency [8][9][10]. The possibility of implementing lean burn combustion systems and reducing fuel consumption is a further advantage of DISI engines [11][12][13], even if this operating regime requires specific aftertreatment systems [14] and features lower combustion stability [15].…”

Split Injection Strategy Optimization to Achieve Ideal Stratified‐Charge Mixture and Reinforce Ultralean Burn in a High Compression Ratio Direct Injection Spark Ignition Engine

“…[ 16 ] Recent research indicated that compared to single injection (SI), split injection could expand the knock limit and increase the indicated thermal efficiency through charge cooling effect and advancing combustion phase. [ 17,18 ] LBC and high compression ratio (CR) are the two main technologies to improve thermal efficiency [ 19–21 ] but the fact that the CR of spark ignition engine is constrained by the knock combustion. Ning et al [ 20 ] investigated the LBC characteristics in a high CR DISI methanol engine and discovered that under λ = 1.4, greater brake thermal efficiency was obtained.…”