{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T16:02:58Z","timestamp":1791302578746,"version":"4.1.0"},"reference-count":36,"publisher":"American Chemical Society (ACS)","issue":"39","license":[{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"Special Key Project of Chongqing Technology Innovation and Application Development","award":["cstc2021jscx-dxwtBX0024"],"award-info":[{"award-number":["cstc2021jscx-dxwtBX0024"]}]},{"name":"Yunnan Precious Metals Laboratory Science and Technology Program Project","award":["YPML-20240502086"],"award-info":[{"award-number":["YPML-20240502086"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,10,6]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>This study uses numerical simulation methods to explore the knock mechanism of hydrogen engines and proposes a knocking classification basis based on pressure wave characteristics and the flame propagation state. Based on the location of the pressure wave, whether the flame propagation speed reaches the theoretical Chapman\u2013Jouguet (CJ) detonation velocity, and whether the pressure wavefront is coupled with the flame front, hydrogen engine knock is divided into three categories: deflagration-knock, detonation-knock, and superknock. Analysis shows that deflagration-knock is caused by the interaction between flames and pressure waves, and its intensity is relatively weak. Both detonation-knock and superknock are caused by the coupling of the flame front and pressure wavefront to form detonation waves. The core difference between the two is that the pressure waves appear in different positions. The pressure wave of detonation-knock appears near the cylinder wall, while the pressure wave of superknock appears at the flame front, and the latter has significantly higher knock intensity than the former. Additionally, this study simulated preignition events by setting up dual ignition sources to explore the knock mechanism induced by preignition.<\/jats:p>","DOI":"10.1021\/acsomega.6c06931","type":"journal-article","created":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T03:02:18Z","timestamp":1790218938000},"page":"59840-59860","source":"Crossref","is-referenced-by-count":0,"title":["Classification\nand Mechanism Analysis of Knock Modes\nin Hydrogen Engines"],"prefix":"10.1021","volume":"11","author":[{"given":"Junqi","family":"Wu","sequence":"first","affiliation":[{"name":"Chongqing University , , ,","place":["Chongqing, China, 400044"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zekai","family":"Zhao","sequence":"additional","affiliation":[{"name":"Chongqing University , , ,","place":["Chongqing, China, 400044"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2905-0549","authenticated-orcid":true,"given":"Zhaolei","family":"Zheng","sequence":"additional","affiliation":[{"name":"Chongqing University , , ,","place":["Chongqing, China, 400044"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,9,23]]},"reference":[{"issue":"1","key":"2026100610492909800_cit1","doi-asserted-by":"publisher","first-page":"774","DOI":"10.1016\/j.ijhydene.2011.04.062","article-title":"Research on optimal control to resolve\nthe contradictions between restricting abnormal combustion and improving\npower output in hydrogen fueled engines","volume":"37","author":"Yang","year":"2012","journal-title":"Int.\nJ. Hydrogen Energy"},{"issue":"3","key":"2026100610492909800_cit2","doi-asserted-by":"publisher","first-page":"327","DOI":"10.1016\/S0016-2361(03)00245-X","article-title":"Knock rating of gaseous\nfuels in a single cylinder spark ignition engine","volume":"83","author":"Rahmouni","year":"2004","journal-title":"Fuel"},{"issue":"2","key":"2026100610492909800_cit3","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2022.126532","article-title":"The effect of the acoustically\nabsorbing wall on the knocking phenomenon of hydrogen engines","volume":"333","author":"Xu","year":"2023","journal-title":"Fuel"},{"key":"2026100610492909800_cit4","volume-title":"Combustion: Physical and Chemical\nFundamentals, Modeling and Simulation, Experiments, Pollutant Formation","author":"Warnatz","year":"2006"},{"key":"2026100610492909800_cit5","doi-asserted-by":"publisher","DOI":"10.1016\/j.energy.2019.116244","article-title":"Quantitative\nevaluation of n-butane\nconcentration on knock severity of a natural gas heavy-duty SI engine","volume":"189","author":"Chen","year":"2019","journal-title":"Energy"},{"key":"2026100610492909800_cit6","doi-asserted-by":"publisher","DOI":"10.1016\/j.applthermaleng.2026.131897","article-title":"A novel\nknock assessment method for spark-ignition\nmethanol engines integrating multi-cycle knock occurrence frequency\nand single-cycle knock intensity","volume":"302","author":"Wang","year":"2026","journal-title":"Appl. Therm.\nEng."},{"issue":"7","key":"2026100610492909800_cit7","doi-asserted-by":"publisher","first-page":"3156","DOI":"10.1016\/j.ijhydene.2009.01.091","article-title":"Visualization of auto-ignition\nand pressure wave during\nknocking in a hydrogen spark-ignition engine","volume":"34","author":"Kawahara","year":"2009","journal-title":"Int. J. Hydrogen Energy"},{"key":"2026100610492909800_cit8","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2026.138347","article-title":"Experimental study on\ncombustion characteristics in a low-pressure direct-injection hydrogen\nengine","volume":"415","author":"Ge","year":"2026","journal-title":"Fuel"},{"key":"2026100610492909800_cit9","doi-asserted-by":"publisher","first-page":"63","DOI":"10.1016\/j.combustflame.2017.07.004","article-title":"Effect of pressure\nwave disturbance on auto-ignition mode transition and knocking intensity\nunder enclosed conditions","volume":"185","author":"Pan","year":"2017","journal-title":"Combust. Flame"},{"issue":"35","key":"2026100610492909800_cit10","doi-asserted-by":"publisher","first-page":"15510","DOI":"10.1016\/j.ijhydene.2013.09.078","article-title":"Interaction of pressure\nwave and propagating flame during knock","volume":"38","author":"Yang","year":"2013","journal-title":"Int.\nJ. Hydrogen Energy"},{"issue":"51","key":"2026100610492909800_cit11","doi-asserted-by":"publisher","first-page":"27904","DOI":"10.1016\/j.ijhydene.2020.07.117","article-title":"Numerical study of the effect of injection\ntiming on the knock combustion in a direct-injection hydrogen engine","volume":"45","author":"Ye","year":"2020","journal-title":"Int. J. Hydrogen Energy"},{"key":"2026100610492909800_cit12","doi-asserted-by":"publisher","DOI":"10.1016\/j.apenergy.2020.114854","article-title":"The effect of energy\nintensification on the formation of severe knock in internal combustion\nengines","volume":"266","author":"Xu","year":"2020","journal-title":"Appl. Energy"},{"key":"2026100610492909800_cit13","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2022.123302","article-title":"Numerical investigation on combustion and knock\nformation mechanism of hydrogen direct injection engine","volume":"316","author":"Li","year":"2022","journal-title":"Fuel"},{"key":"2026100610492909800_cit14","doi-asserted-by":"crossref","unstructured":"Li, Y.\n          \n          Research on the\nCombustion and Knock Formation Mechanism of Hydrogen Internal Combustion\nEngines with Direct Injection, Thesis; Tianjin University: China, 2022.","DOI":"10.1016\/j.fuel.2022.123302"},{"issue":"14","key":"2026100610492909800_cit15","doi-asserted-by":"publisher","first-page":"4874","DOI":"10.1016\/j.ijhydene.2015.02.034","article-title":"One-dimensional numerical\nstudy on pressure wave flame interaction and flame acceleration under\nengine-relevant conditions","volume":"40","author":"Wei","year":"2015","journal-title":"Int. J. Hydrogen\nEnergy"},{"issue":"28","key":"2026100610492909800_cit16","doi-asserted-by":"publisher","first-page":"12489","DOI":"10.1016\/j.ijhydene.2013.07.036","article-title":"Dual nature of hydrogen\ncombustion knock","volume":"38","author":"Szwaja","year":"2013","journal-title":"Int. J. Hydrogen Energy"},{"issue":"21","key":"2026100610492909800_cit17","doi-asserted-by":"publisher","first-page":"7927","DOI":"10.1016\/j.ijhydene.2022.11.259","article-title":"Statistically discussing\nimpacts of knock type on the heat release process in hydrogen-fueled\nWankel rotary engine","volume":"48","author":"Meng","year":"2023","journal-title":"Int. J. Hydrogen Energy"},{"issue":"4","key":"2026100610492909800_cit18","doi-asserted-by":"publisher","first-page":"4901","DOI":"10.1016\/j.proci.2018.07.061","article-title":"Investigation of lubricant\ninduced pre-ignition and knocking combustion in an optical spark ignition\nengine","volume":"37","author":"Feng","year":"2019","journal-title":"Proc. Combust. Inst."},{"issue":"2","key":"2026100610492909800_cit19","doi-asserted-by":"publisher","first-page":"166","DOI":"10.1177\/1468087414530388","article-title":"Relationship between super-knock and pre-ignition","volume":"16","author":"Wang","year":"2015","journal-title":"Int. J. Engine Res."},{"issue":"7","key":"2026100610492909800_cit20","doi-asserted-by":"publisher","first-page":"2788","DOI":"10.1016\/j.combustflame.2015.04.010","article-title":"LES study of deflagration\nto detonation mechanisms in a downsized spark ignition engine","volume":"162","author":"Robert","year":"2015","journal-title":"Combust. Flame"},{"issue":"52","key":"2026100610492909800_cit21","doi-asserted-by":"publisher","first-page":"26631","DOI":"10.1016\/j.ijhydene.2021.05.154","article-title":"Experimental and numerical\ninvestigation on effects of pre-ignition positions on knock intensity\nof hydrogen fuel","volume":"46","author":"Xu","year":"2021","journal-title":"Int. J. Hydrogen Energy"},{"key":"2026100610492909800_cit22","doi-asserted-by":"publisher","DOI":"10.1016\/j.applthermaleng.2026.130092","article-title":"Study on multi-cylinder\npre-ignition characteristics and pre-ignition induced super knock\nmechanism of direct injected hydrogen engines","volume":"290","author":"Duan","year":"2026","journal-title":"Appl. Therm. Eng."},{"key":"2026100610492909800_cit23","doi-asserted-by":"publisher","DOI":"10.1016\/j.energy.2025.138041","article-title":"Investigation of knock\ncombustion mechanism and injection angle optimization in a heavy-duty\ndirect-injection hydrogen engine","volume":"335","author":"Liang","year":"2025","journal-title":"Energy"},{"key":"2026100610492909800_cit24","doi-asserted-by":"publisher","DOI":"10.1016\/j.energy.2024.133453","article-title":"Investigations of combustion\ncharacteristics and mechanism of backfire-induced super-knock in a\nturbocharged hydrogen engine","volume":"312","author":"Li","year":"2024","journal-title":"Energy"},{"key":"2026100610492909800_cit25","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2020.119563","article-title":"Effect of hydrogen\nblending on the high temperature auto-ignition of ammonia at elevated\npressure","volume":"287","author":"Chen","year":"2021","journal-title":"Fuel"},{"key":"2026100610492909800_cit26","doi-asserted-by":"publisher","first-page":"31","DOI":"10.1016\/j.pecs.2018.01.002","article-title":"Modeling\nnitrogen chemistry in combustion","volume":"67","author":"Glarborg","year":"2018","journal-title":"Prog. Energy\nCombust. Sci."},{"issue":"5","key":"2026100610492909800_cit27","doi-asserted-by":"publisher","first-page":"3004","DOI":"10.1016\/j.ijhydene.2017.12.066","article-title":"Chemical kinetic modeling\nof ammonia oxidation with improved reaction mechanism for ammonia\/air\nand ammonia\/hydrogen\/air combustion","volume":"43","author":"Otomo","year":"2018","journal-title":"Int. J.\nHydrogen Energy"},{"key":"2026100610492909800_cit28","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2024.133500","article-title":"Effect of combustion\nchamber geometry on performance and emissions of direct injection\nhydrogen engines","volume":"382","author":"Li","year":"2025","journal-title":"Fuel"},{"issue":"12","key":"2026100610492909800_cit29","first-page":"1230","article-title":"Experimental Study on\nCombustion and Knock Characteristics of an Intake Manifold Hydrogen-Injected\nEngine","volume":"55","author":"Wei","year":"2022","journal-title":"J. Tianjin Univ. (Sci. Technol.)"},{"key":"2026100610492909800_cit30","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2026.138347","article-title":"Experimental study on\ncombustion characteristics in a low-pressure direct-injection hydrogen\nengine","volume":"415","author":"Ge","year":"2026","journal-title":"Fuel"},{"key":"2026100610492909800_cit31","doi-asserted-by":"publisher","first-page":"98","DOI":"10.1016\/j.applthermaleng.2018.09.001","article-title":"Effects of applying\nEGR with split injection strategy on combustion performance and knock\nresistance in a spark assisted compression ignition (SACI) engine","volume":"145","author":"Zhou","year":"2018","journal-title":"Appl. Therm. Eng."},{"key":"2026100610492909800_cit32","doi-asserted-by":"publisher","first-page":"164","DOI":"10.1016\/j.fuel.2012.03.033","article-title":"UV\u2013visible\nlight absorption\nby hydroxyl and formaldehyde and knocking combustion in a DME-HCCI\nengine","volume":"98","author":"Azimov","year":"2012","journal-title":"Fuel"},{"issue":"3","key":"2026100610492909800_cit33","doi-asserted-by":"publisher","first-page":"1","DOI":"10.13949\/j.cnki.nrjgc.2026.03.001","article-title":"Effect of intake port\nwater injection on knock in hydrogen internal combustion engines","volume":"47","author":"Han","year":"2026","journal-title":"Internal Combust. Engine Eng."},{"key":"2026100610492909800_cit34","unstructured":"Xu, H.\n          \n          Study on the Induction\nand Destruction Mechanism of Detonation Waves in Enclosed Spaces under\nSevere Knock in Internal Combustion Engines, Thesis; Tianjin University: China, 2018."},{"key":"2026100610492909800_cit35","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2023.129009","article-title":"Toward highly-efficient\ncombustion of ammonia-hydrogen engine: Prechamber turbulent jet ignition","volume":"352","author":"Zhou","year":"2023","journal-title":"Fuel"},{"key":"2026100610492909800_cit36","doi-asserted-by":"publisher","DOI":"10.1016\/j.fuel.2024.131090","article-title":"Towards sustainable hydrogen and\nammonia internal combustion engines: Challenges and opportunities","volume":"364","author":"El-Adawy","year":"2024","journal-title":"Fuel"}],"container-title":["ACS Omega"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acsomega.6c06931","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/acsodf\/article-pdf\/11\/39\/59840\/68631049\/acsomega.6c06931.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/acsodf\/article-pdf\/11\/39\/59840\/68631049\/acsomega.6c06931.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T15:49:09Z","timestamp":1791301749000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/acsodf\/article\/11\/39\/59840\/5437219\/Classification-and-Mechanism-Analysis-of-Knock"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,23]]},"references-count":36,"journal-issue":{"issue":"39","published-online":{"date-parts":[[2026,9,23]]},"published-print":{"date-parts":[[2026,10,6]]}},"URL":"https:\/\/doi.org\/10.1021\/acsomega.6c06931","relation":{},"ISSN":["2470-1343"],"issn-type":[{"value":"2470-1343","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,23]]}}}