Knock: A Century of Research

Abstract

Knock is one of the main limitations on increasing spark-ignition (SI) engine efficiency. This has been known for at least 100 years, and it is still the case today. Knock occurs when conditions ahead of the flame front in an SI engine result in one or more autoignition events in the end gas. The autoignition reaction rate is typically much higher than that of the flame-front propagation. This may lead to the creation of pressure waves in the combustion chamber and, hence, an undesirable noise that gives knock its name. The resulting increased mechanical and thermal loading on engine components may eventually lead to engine failure. Reducing the compression ratio lowers end-gas temperatures and pressures, reducing end-gas reactivity and, hence, mitigating knock. However, this has a detrimental effect on engine efficiency.Automotive companies must significantly reduce their fleet carbon dioxide (CO 2 ) values in the coming years to meet targets resulting from the 2015 Paris Agreement. One path towards meeting these is through partial or full electrification of the powertrain. However, the vast majority of automobiles in the near future will still feature a gasoline-fueled SI engine; hence, improvements in combustion engine efficiency remain fundamental.As knock has been a key limitation for so long, there is a huge amount of literature on the subject. A number of reviews on knock have already been published, including in recent years. These generally concentrate on current understanding and status. The present work, in contrast, aims to track the progress of research on knock from the 1920s right through to the present day. It is hoped that this can be a useful reference for new and existing researchers of the subject and give further weight to occasionally neglected historical activity, which can still provide important insights today.

Combustion Characteristics of a Hydrogen-Fueled TJI Engine under Knocking Conditions

“…This phenomenon has been analyzed since the beginning of the internal combustion engine's development. The first works on knock combustion were published in 1921 [2] and 1922 [3], as well as the first history of the mentioned topic [4]. Diagnostics of engine operating conditions in terms of knock combustion concerns not only light vehicle engines [5,6], but also marine applications [7,8].…”

Variation of Particles in the Exhaust Plume of Gasoline Direct Injection Vehicles Based on a Multipoint Sampling System: Concentrations, Components, and Numbers

“…To combat global climate change, China has announced the ambitious goal of carbon peak and carbon neutralization . Although electrification is considered the best way to achieve decarbonization in the transport sector, conventional internal combustion engine-powered vehicles will continue to dominate the market in the short term . The most direct route to reduce CO 2 emissions is introducing vehicles with improved fuel efficiency.…”

“…1 Although electrification is considered the best way to achieve decarbonization in the transport sector, conventional internal combustion engine-powered vehicles will continue to dominate the market in the short term. 2 The most direct route to reduce CO 2 emissions is introducing vehicles with improved fuel efficiency. Gasoline direct injection (GDI) vehicles could help reach a fuel consumption reduction of 15% compared with traditional port fuel injection (PFI) vehicles.…”

Numerical investigation for optimization of spark-ignition internal combustion engine knock by Taguchi-Grey method

“…It has been shown that several operating parameters influence the knocking tendency of an internal combustion engine. [5][6][7][8] With the development of CFD (Computational Fluid Dynamics) technology, more and more scholars use simulation methods to investigate the knock of spark-ignition engines. Li et al developed a SAGE model with chemical reaction kinetics to explore the influence of EGR (Exhaust Gas Recirculation) on a high compression ratio engine knock.…”

“…13 Based on the existing literature, previously published research mainly focused on exploring the independent influence of each factor of compression ratio, inlet temperature, spark timing, and EGR rate on knock. [5][6][7] However, few studies highlight the contribution rate and importance ranking of compression ratio, inlet temperature, spark timing, and the EGR rate to knock tendency, which brings difficulties to the control and suppression of spark ignition engine knock. Therefore, this article aims to determine the order of multiple parameters to the influence of knock tendency and peak in-cylinder pressure.…”