Super-knock suppression for highly turbocharged gasoline engines using lean mixture control strategy with the same energy density

Abstract

Super-knock has been the main obstacle to improve power density and engine efficiency of modern gasoline engines. Previous researches show that the key points of super-knock are composed of pre-ignition and detonation. The former is the inducement and the latter is the root reason why super-knock could damage engines dramatically. Lots of studies have been conducted to suppress super-knock by eliminating pre-ignition. Using a rapid compression machine, this work explores the lean mixture control strategy to eliminate detonation and thus suppressing super-knock. Furthermore, a one-dimensional simulation model was set up to investigate the mechanism of how lean mixture could suppress detonation and super-knock. The experimental and simulation results show that based on detonation and super-knock operating condition, adding 80% additional air while keeping the same fuel energy density could transfer combustion from detonation mode to super-sonic auto-ignitive deflagration mode. The peak pressure and pressure oscillation could be reduced significantly. This indicates that boosted lean burn could suppress detonation and thus suppress super-knock effectively, even if pre-ignition occurs. It could be an effective and practical control strategy to protect modern highly turbocharged gasoline engines.

Numerical simulation research on the influence of the parameters of water injection on the GDI engine

“…With the deepening of the understanding of the knock phenomenon, researchers have proposed various methods, such as reducing the CR, delaying the IT, enriching the mixture, increasing the turbulence and combustion speed, reducing the intake temperature, adopting antiknock alternative fuels, and water injection, to suppress knock. [18][19][20][21][22] Abdellatief et al 23 pointed out that adding certain additives (bioethanol, isooctane, etc.) to gasoline can improve the antiknock resistance of the engine.…”

Experimental assessment of ignition characteristics of lubricating oil sprays related to low-speed pre-ignition (LSPI)

“…27,28 Lean mixture control strategies can also help reducing this problem. 29 Some authors correlated the flame speed variations by fuel type with LSPI. 26 Composition of the lubricant oil also plays an important role.…”