混合气分布特性对汽油压燃影响的数值模拟
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摘要
利用三维计算流体力学软件CONVERGE,通过数值模拟的方法,对比研究了缸内单次喷射、缸内多次喷射、气道加缸内喷射的混合气分布及不同混合气分布特性对汽油压燃的影响.结果表明:随气道预混比例的增加,着火时刻的当量比离散度先降低后升高,放热率峰值先升高后降低,最大压力升高率先增大后下降.随预喷时刻的推迟,指示热效率先增大后降低,最大压力升高率的变化较小.在爆发压力(18 MPa)和最大压力升高率(1.5 MPa/°CA)的限制下,相比于缸内单次喷射,气道加直喷策略和缸内两次喷射策略的指示热效率分别从45.6%增加到48.3%、48.2%;碳烟排放分别从0.041 g/(kW·h)减小到0.016 g/(kW·h)、0.015 g/(kW·h).
Computational fluid dynamics software CONVERGE is used to compare the mixed gas distributions under the single-injection strategy,multi-injection strategy and combined strategy of port-injection and directinjection through numerical simulations.In addition,the effects of different mixture distribution characteristics on gasoline compression ignition are studied.With the increase in premixed ratio,the dispersion of equivalence ratio at the moment of ignition initially decreases and then increases,whereas both the peak heat release rate and the maximum pressure rise rate increase first and then decrease.With the delay of pre-injection timing,the indicated thermal efficiency increases first and then decreases,and the change in the maximum pressure rise rate is relatively small.Under the limits of maximum in-cylinder pressure of 18 MPa and maximum pressure rise rate of1.5 MPa/° CA,in comparison with the single-injection strategy,the indicated thermal efficiencies of portinjection combined with direct injection and double injection strategies increase from 45.6% to 48.3% and 48.2%,respectively,and soot emissions are reduced from 0.041 g/(kW·h) to 0.016 g/(kW·h) and 0.015 g/(kW·h),respectively.
Computational fluid dynamics software CONVERGE is used to compare the mixed gas distributions under the single-injection strategy,multi-injection strategy and combined strategy of port-injection and directinjection through numerical simulations.In addition,the effects of different mixture distribution characteristics on gasoline compression ignition are studied.With the increase in premixed ratio,the dispersion of equivalence ratio at the moment of ignition initially decreases and then increases,whereas both the peak heat release rate and the maximum pressure rise rate increase first and then decrease.With the delay of pre-injection timing,the indicated thermal efficiency increases first and then decreases,and the change in the maximum pressure rise rate is relatively small.Under the limits of maximum in-cylinder pressure of 18 MPa and maximum pressure rise rate of1.5 MPa/° CA,in comparison with the single-injection strategy,the indicated thermal efficiencies of portinjection combined with direct injection and double injection strategies increase from 45.6% to 48.3% and 48.2%,respectively,and soot emissions are reduced from 0.041 g/(kW·h) to 0.016 g/(kW·h) and 0.015 g/(kW·h),respectively.
引文
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[2]Reitz R D.An experimental and numerical study on the effects of fuel properties on the combustion and emissions of low-temperature combustion diesel engines[J].Combustion Science and Technology,2014,186(12):1795-1815.
[3]祝宇轩,王浒,张翔宇,等.汽油压燃小负荷燃烧过程优化[J].内燃机学报,2016,34(5):415-422.Zhu Yuxuan,Wang Hu,Zhang Xiangyu,et al.Gasoline compression ignition low-load combustion optimization based on double exhaust valve opening and injection strategy[J].Transactions of CSICE,2016,34(5):415-422(in Chinese).
[4]张波,马桂香,刘海峰,等.汽油压燃低温燃烧技术研究进展与展望[J].小型内燃机与车辆技术,2017,46(4):77-85.Zhang Bo,Ma Guixiang,Liu Haifeng,et al.Review and prospect of the combustion technology of gasoline compression ignition of low temperature combustion[J].Small Internal Combustion Engine and Vehicle Technology,2017,46(4):77-85(in Chinese).
[5]Kalghatgi G T,Risberg P,?ngstr?m H-E.Partially pre-mixed auto-ignition of gasoline to attain low smoke and low NOx at high load in a compression ignition engine and comparison with a diesel fuel[C]//SAE Technical Papers.Detroit,Michigan,USA,2007,2007-01-0006.
[6]Kalghatgi G,Hildingsson L,Johansson B.Low NOx and low smoke operation of a diesel engine using gasoline-like fuels[J].Journal of Engineering for Gas Turbines&Power,2009,132(9):259-271.
[7]Kalghatgi G,Hildingsson L,Harrison A,et al.Autoignition quality of gasoline fuels in partially premixed combustion in diesel engines[J].Proceedings of the Combustion Institute,2011,33(2):3015-3021.
[8]Tuner M,Johansson T,Aulin H,et al.Multi cylinder partially premixed combustion performance using commercial light-duty engine hardware[C]//SAE Technical Papers.Detroit,Michigan,USA,2014,2014-01-2680.
[9]Reitz R D,Diwakar R.Structure of high-pressure fuel sprays[C]//SAE Technical Papers.Detroit,Michigan,USA,1987:870598.
[10]Senecal P K,Richards K J,Pomraning E,et al.A new parallel cut-cell Cartesian CFD code for rapid grid generation applied to in-cylinder diesel engine simulations[C]//SAE Technical Papers.Detroit,Michigan,USA,2007,2007-01-0159.
[11]O'Rourke P J.Collective drop effects on vaporizing liquid sprays[J].Engineering,1981,107(5):2459-2471.
[12]Liu A B,Mather D,Reitz R D.Modeling the effects of drop drag and breakup on fuel sprays[C]//SAE Technical Papers.Detroit,Michigan,USA,1993,930072.
[13]Senecal P K,Pomraning E,Richards K J,et al.Multidimensional modeling of direct-injection diesel spray liquid length and flame lift-off length using CFD and parallel detailed chemistry[C]//SAE Technical Papers.Detroit,Michigan,USA,2003,2003-01-1043.
[14]Wang Hu,Yao Mingfa,Reitz R D.Development of a reduced primary reference fuel mechanism for internal combustion engine combustion simulations[J].Energy&Fuels,2013,27(12):7843-7853.
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