周 磊,刘宗宽,江枭枭,卫海桥
AuthorsHTML:周 磊，刘宗宽，江枭枭，卫海桥
AuthorsListE:Zhou Lei,Liu Zongkuan,Jiang Xiaoxiao,Wei Haiqiao
AuthorsHTMLE:Zhou Lei，Liu Zongkuan，Jiang Xiaoxiao，Wei Haiqiao
Unit:天津大学内燃机燃烧学国家重点实验室，天津 300072
Unit_EngLish:State Key Laboratory of Engines，Tianjin University，Tianjin 300072，China
Abstract_Chinese:针对天然气高压喷射(high pressure direct injection，HPDI)模式双燃料船用低速机缸内的压力振荡现象，基 于计算流体动力学软件 CONVERGE 耦合化学反应动力学机理，采用三维数值模拟方法，研究天然气及引燃柴油喷 射时刻对缸内压力振荡和燃烧粗暴的影响．结果表明：天然气喷射提前或引燃油喷射推迟均会增大天然气预混燃烧 比例，燃烧剧烈程度增加，导致燃烧粗暴恶化，缸内压力峰值升高，压力升高率增大，但后者会推迟天然气被引燃 的时刻，造成燃烧相位推迟．天然气喷射时刻提前至－4° CA ATDC 时，缸内出现压力振荡．对于天然气燃烧粗暴 且出现压力振荡的工况，提前喷射引燃油，两种燃料可能会同时发生燃烧粗暴，造成燃烧进一步恶化．天然气压燃 有利于缓解引燃导致的燃烧初期较强的压力振荡，然而随着燃烧进程的发展，会造成更加剧烈的燃烧粗暴，但可通 过引入引燃油缓解此现象．实际应用中，可以考虑在引燃天然气之前实现部分压燃以降低整体压力振荡强度．分析 甲烷氧化反应路径中关键中间产物发现，HCO(醛基)可用于表征双燃料发动机燃烧粗暴及压力振荡的剧烈程度及持 续期长短；CH3(甲基)可作为燃烧粗暴及压力振荡的指示物质，其短时大量积累预示着燃烧粗暴的发生；同时， CH3 可以作为甲烷开始从低温反应过渡到高温反应的表征物质．
Abstract_English:To investigate the in-cylinder pressure oscillation of a low-speed dual-fuel marine engine under high pressure direct injection(HPDI)operation mode，we conducted a three-dimensional numerical study to analyze the effects of dual-fuel injection timing on pressure oscillation and combustion roughness. To perform the simulation，we used a computational fluid dynamics software CONVERGE coupled with chemical reaction kinetics. Results show that either the advanced injection of gas fuel or deferred injection of pilot fuel can increase the premixed combustion ratio and enhance the intensity of the combustion process，leading to rough combustion. Both the in-cylinder pressure and rate of pressure rise increase. However，the combustion phase is delayed in the cases with the postponed injection of pilot fuel due to the retarded ignition timing of the gas fuel. In-cylinder pressure oscillation occurs with advances in the natural-gas injection timing to -4° CA ATDC. For cases characterized by pressure oscillation and rough combustion of natural gas，advancing pilot fuel injection timing can enhance the rough combustion of dual fuel. In the initial stage of combustion，pressure oscillation can be reduced by the auto-ignition of the natural gas，but even rougher combustion may result with the process of combustion. However，this outcome can be reduced by the injection of pilot fuel. In production engines，the partial compression ignition of natural gas can be used to reduce the in-cylinderpressure oscillation before the ignition of the natural gas. The research of intermediate products based on the CH4 chemical reaction pathways shows that HCO can be used to indicate the intensity and duration of the in-cylinder pressure oscillation and rough combustion of the dual-fuel engine. CH3 can indicate rough combustion of the dual fuel， with the rapid accumulation of CH3 indicating its occurrence. Moreover，CH3 can also indicate transformation from a low-temperature to high-temperature reaction of CH4.
Keyword_Chinese:低速机；天然气；柴油；喷射时刻；压力振荡
Keywords_English:low-speed engine；natural gas；diesel；injection timing；pressure oscillation

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