Knock is an abnormal and stochastic combustion phenomenon which limits the efficiency of spark ignition engines. It occurs because of autoignition initiated locally in hot spots in the fuel/air mixture ahead of the advancing flame front. The onset of knock is governed by chemical kinetics and is determined by the pressure and temperature history of the hot spot and the anti-knock quality of the fuel. Knock intensity is governed by the evolution of the pressure wave set off by the initial autoignition. As engine designers seek higher efficiency through downsizing and turbocharging, occasional extremely intense knock, ‘superknock’, is found to occur, even though operating conditions are chosen to avoid knock. Superknock is a manifestation of developing detonation which can be triggered by autoignition of the fuel/air mixture at high pressures and temperatures. Another stochastic phenomenon, preignition, is necessary but not sufficient to enable the pressures and temperatures that could cause superknock. These phenomena are discussed in this review.
BradleyD. Autoignitions and detonations in engines and ducts. Philos T Roy Soc A2012; 370: 689–714.
7.
KalghatgiGTBradleyD. Pre-ignition and ‘super-knock’ in turbo-charged spark ignition (SI) engines. Int J Engine Res2012; 13(4): 399–414.
8.
KalghatgiG. Developments in internal combustion engines and implications for combustion science and future transport fuels. P Combust Inst2015; 35: 101–115.
YoungM. Cyclic dispersion in the homogeneous-charge spark-ignition engine – a literature survey. SAE paper 810020, 1981.
11.
OzdorNDulgerMSherE. Cyclic variability in spark ignition engines a literature survey. SAE paper 940987, 1994.
12.
KalghatgiG. Spark ignition, early flame development and cyclic variation in I.C. engines. SAE paper 870163, 1987.
13.
McKenzieJChengW. The anatomy of knock. SAE paper 2016-01-0704, 2016.
14.
KalghatgiG. Fuel anti-knock quality – part I. Engine studies. SAE paper 2001-01-3584, 2001.
15.
KalghatgiG. Fuel anti-knock quality – part II. Vehicle studies – how relevant is motor octane number (MON) in modern engines? SAE paper 2001-01-3585, 2001.
16.
BellA. Modern SI engine control parameter responses and altitude effects with fuels of varying octane sensitivity. SAE paper 2010-01-1454, 2010.
17.
Coordinating Research Council (CRC), Inc. Vehicle performance effect of octane on knock sensor equipped vehicles. CRC report no. 597, 1995. Alpharetta, GA: CRC.
18.
WhelanDSchmidtGHischierM. An acceleration based method to determine the octane number requirement of knock sensor equipped vehicles. SAE paper 982721, 1998.
19.
SugawaraYAkasakaYKagamiM. Effects of gasoline properties on acceleration performance of commercial vehicles. SAE paper 971725, 1997.
20.
StradlingRRickeardDHamjeHWilliamsJZemrochP. Effect of octane on the performance of two gasoline direct injection passenger cars. SAE paper 2015-01-0767, 2015.
21.
LeoneTGAndersonJEDavisRSIqbalAReeseRAShelbyMHet al. The effect of compression ratio, fuel octane rating, and ethanol content on spark-ignition engine efficiency. Environ Sci Technol2015; 49: 10778–10789.
22.
KalghatgiGNakataKMogiK. Octane appetite studies in direct injection spark ignition (DISI) engines. SAE paper 2005-01-0244, 2005.
23.
KalghatgiG. Auto-ignition quality of practical fuels and implications for fuel requirements of future SI and HCCI engines. SAE paper 2005-01-0239, 2005.
MittalVHeywoodJ. The shift in relevance of fuel RON and MON to knock onset in modern SI engines over the last 70 years. SAE Int J Engine2009; 2(2): 1–10.
26.
MittalVHeywoodJ. The relevance of fuel RON and MON to knock onset in modern SI engines. SAE paper 2008-01-2414, 2008.
27.
AmerABabikerHChangJKalghatgiGAdomeitPBrassatAGüntherM. Fuel effects on knock in a highly boosted direct injection spark ignition engine. SAE Int J Fuel Lubr2012; 5(3): 1048–1065.
28.
DaviesTCracknellRLovettGCruffLFowlerJ. Fuel effects in a boosted DISI engine. SAE paper 2011-01-1985, 2011.
29.
KalghatgiGHeadRChangJViolletYBabikerHAmerA. An alternative method based on toluene/n-heptane surrogate fuels for rating the anti-knock quality of practical gasolines. SAE Int J Fuel Lubr2014; 7(3): 663–672 (SAE paper 2014-01-2609).
30.
KalghatgiGBabikerHBadraJ. A simple method to predict knock using toluene, N-heptane and iso-octane blends (TPRF) as gasoline surrogates. SAE Int J Engine2015; 8(2): 505–519 (SAE paper 2015-01-0757).
31.
KalghatgiGMorgantiKAlgunaibetISarathyMDibbleR. Knock prediction using a simple model for ignition delay. SAE paper 2016-01-0702, 2016.
32.
WestbrookCK. Chemical kinetics of hydrocarbon ignition in practical combustion systems. P Combust Inst2000; 28: 1563–1577.
33.
WestbrookCKDryerFL. Chemical kinetic modeling of hydrocarbon combustion. Prog Energ Combust1984; 10: 1–57.
34.
WarnatzJ. Chemistry of high temperature combustion of alkanes up to octane. In: Proceedings of the 20th symposium (international) on combustion, Ann Arbor, MI, 12–17 August 1984, p.845. Pittsburgh, PA: The Combustion Institute.
35.
SimmieJM. Detailed chemical kinetic models for the combustion of hydrocarbon fuels. Prog Energ Combust2003; 29: 599–634.
36.
GriffithsJF. Reduced kinetic models and their application to practical combustion systems. Prog Energ Combust1995; 21: 25–107.
37.
BradleyDMorleyC. Chapter 7: autoignition in spark-ignition engines. In: PillingMJ (ed.) Low-temperature combustion and autoignition, vol. 35 (Comprehensive chemical kinetics, edited by ComptonRGHancockG). Amsterdam: Elsevier Science B.V, 1997, pp.661–760.
38.
PitzWJCernanskyNPDryerFLEgolfopoulosFFarrellJTFriendDGPitschH. Development of an experimental database and chemical kinetic models for surrogate gasoline fuels. SAE paper 2007-01-0175, 2007.
39.
NaikCPitzWWestbrookCSjöbergMDecJEOrmeJet al. Detailed chemical kinetic modeling of surrogate fuels for gasoline and application to an HCCI engine. SAE paper 2005-01-3741, 2005.
40.
AndraeJBrinckTKalghatgiGT. HCCI experiments with toluene reference fuels modeled by a semidetailed chemical kinetic model. Combust Flame2008; 155: 696–712.
41.
MehlMChenJYPitzWJSarathySMSarathyCK. An approach for formulating surrogates for gasoline with application toward a reduced surrogate mechanism for CFD engine modeling. Energ Fuel2011; 25(11): 5215–5223.
42.
LeppardW. The chemical origin of fuel octane sensitivity. SAE paper 902137, 1990.
43.
KönigGMalyRBradleyDLauAKCSheppardCGW. Role of exothermic centres on knock initiation and knock damage. SAE paper 902136, 1990.
44.
PanJSheppardCTindallABerzinsMPenningtonSVWareJM. End gas inhomogeneity, autoignition and knock. SAE paper 982616, 1998.
45.
BradleyDMorleyCGuXEmersonD. Amplified pressure waves during autoignition: relevance to CAI engines. SAE paper 2002-01-2868, 2002.
46.
ZeldovichYB. Regime classification of an exothermic reaction with nonuniform initial conditions. Combust Flame1980; 39: 211–214.
47.
OppenheimAK. Dynamic features of combustion. Philos T Roy Soc A1985; 315: 471–508.
48.
BradleyDKalghatgiGT. Influence of autoignition delay time characteristics of different fuels on pressure waves and knock in reciprocating engines. Combust Flame2009; 156: 2307–2318.
49.
GhandhiJKimK. A statistical description of knock intensity and its prediction. SAE paper 2017-01-0659, 2017.
50.
ChunKHeywoodJ. Characterization of knock in a spark-ignition engine. SAE paper 890156, 1989.
51.
KalghatgiGMorgantiKAlgunaibetI. Some insights on the stochastic nature of knock and the evolution of hot spots in the end-gas during the engine cycle from experimental measurements of knock onset and knock intensity. SAE paper 2017-01-2233, 2017.
52.
KalghatgiGTBradleyDAndraeJHarrisonAJ. The nature of ‘superknock’ and its origins in SI engines. In: Proceedings of the IMechE conference on internal combustion engines: performance, fuel economy and emissions, London, 8–9 December 2009. Oxford: Chandos Publishing.
53.
GuXJEmersonDRBradleyD. Modes of reaction front propagation from hot spots. Combust Flame2003; 133: 63–74.
54.
RudloffJZaccardiJ-MRichardSAnderlohrJM. Analysis of pre-ignition in highly charged SI engines: Emphasis on the auto-ignition mode. P Combust Inst2013; 34(2): 2959–2967.
55.
WangZLiuHSongTQiYHeXShuaiSWangJX. Relationship between super-knock and pre-ignition. Int J Engine Res2015; 16: 166–180.
56.
PetersNKerschgensBPaczkoG. Super-knock prediction using a refined theory of turbulence. SAE Int J Engine2013; 6(2): 953–967.
FarrellJJohnstonRAndroulakisI. Molecular structure effects on laminar burning velocities at elevated temperature and pressure. SAE paper 2004-01-2936, 2004.
59.
VerhelstSVerstraetenSSierensR. A comprehensive overview of hydrogen engine design features. Proc IMechE, Part D: J Automobile Engineering2007; 221(8): 911–920.
60.
AmannMAlgerTMehtaD. The effect of EGR on low-speed pre-ignition in boosted SI engines. SAE Int J Engine2011; 4(1): 235–245.
