基于微观场的重型增压柴油机工作循环能量流及流仿真
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摘要
为了探索重型增压柴油机工作循环中能量流、?流变化和损耗的规律并从缸内微观层面分析其原因,该文以CA6DL重型车用增压柴油机为研究对象,基于热力学基本原理、试验数据及仿真结果计算并分析了不同工况下工作循环中能量流、?流变化和损耗的规律。以B50工况为例,从缸内速度、当量比、温度分布的角度出发,对引起燃烧过程中能量流、?流变化和损耗的原因进行了分析。结果表明:增压柴油机工作循环中能量流、?流变化主要发生在燃烧过程;传热?、燃料累计?、排气损失、CA90、?效率等参数正相关于负荷,而内部?损失及传热?所占燃料?比例负相关于负荷,B25、B50、B75工况下内部?损失占燃料?比例分别为31.3%、29.9%、28.3%;理论当量比区域多集中在中等流速区;燃烧过程中期,缸内流场与高温区在缸壁附近的叠加作用加剧了缸壁的传热损失;当量比分布越不均匀,燃油氧化速率越快,高低温区体积占比差距越大,温升越缓慢,内部?损失率越大。
In order to investigate the energy, exergy loss, exergy change rules and to explain the change reasons from the perspective of micro-field in cylinder, the experiments, simulation, thermodynamics basic principles and theoretical calculation under various steady working conditions were carried out by taking a heavy-duty turbocharged diesel engine as the research object. In the working process of heavy-duty turbocharged diesel engine, there must be internal factors in working process which causing energy and exergy changes, especially in combustion process, such as diffusion and oxidation, mixing, heat transfer of different temperature layers, while these factors are closely related to the movement of mixture gas, the mixing uniformity of fuel and air, temperature distribution. The causes of energy, exergy and loss in turbocharged diesel engine working process were discussed from the aspects of velocity, equivalent ratio and temperature distribution in cylinder. Since the variation trend of the parameters were basically same under different working conditions, taking the B50 working condition as an example, the change causes and rules of energy flow, exergy flow and its loss in combustion process were analyzed from distribution of flow velocity, equivalent ratio and temperature distribution. The results indicated that, Firstly, the change of energy and exergy flow mainly occured in combustion process, the degree of change in other processes was not obvious. Second, parameters such as heat transfer exergy, accumulation burn fuel exergy, exhaust loss energy, CA90, exergy efficiency were positively correlated with engine load, the corresponding exergy efficiency were 34.7%, 38.9%, 40.8% at B25, B50, B75 working condition. Third, the proportion of internal exergy loss and heat transfer exergy to fuel exergy were negative correlated with engine load, the former were 31.3%、29.9%、28.3% at B25、B50、B75 working condition respectively, the thermal efficiency of diesel engine could be effectively improved by avoiding running at the low load, with the increasing of speed, the proportions of cumulative heat transfer and internal exergy losses to fuel exergy slightly increasing, while the proportions of exhaust exergy to fuel exergy increased more. Fourth, in the middle of the combustion process, the superposition of the flow motion and the high temperature zone near the cylinder wall aggravated the heat transfer loss. Fifth, the theoretical equivalent ratio region mostly concentrated in the medium velocity zone, the nonuniform distribution of fuel and air, rapid fuel oxidation rate contribute to a greater exergy loss rate caused by diffusion and oxidation, the theoretical equivalent ratio was closer to the cylinder wall caused the greater heat transfer loss, at B50 working condition, the maximum heat transfer ratio was about 11 J/°CA after top dead center 15 °CA when there was the maximum contact area between combustion chamber wall and in-cylinder gas. Sixth, the volume size of high and low temperature region and the temperature rise of low temperature region determined the exergy loss rate resulted from temperature difference in cylinder, the volume fraction of the low temperature region at the late stage of combustion process was about 15% at B50 working condition, the exergy loss caused by temperature difference was larger than other time. In the combustion process of a turbocharged diesel engine, the volume of high and low temperatures region in cylinder was closer, the slower the temperature raising in the low temperature region were, the greater the loss rate was caused by the heat transfer in the cylinder. Finally, the flow velocity distribution, homogeneity of equivalent ratio distribution, high and low temperature region volume and temperature raising in cylinder had certain effects on the internal exergy loss rate.
In order to investigate the energy, exergy loss, exergy change rules and to explain the change reasons from the perspective of micro-field in cylinder, the experiments, simulation, thermodynamics basic principles and theoretical calculation under various steady working conditions were carried out by taking a heavy-duty turbocharged diesel engine as the research object. In the working process of heavy-duty turbocharged diesel engine, there must be internal factors in working process which causing energy and exergy changes, especially in combustion process, such as diffusion and oxidation, mixing, heat transfer of different temperature layers, while these factors are closely related to the movement of mixture gas, the mixing uniformity of fuel and air, temperature distribution. The causes of energy, exergy and loss in turbocharged diesel engine working process were discussed from the aspects of velocity, equivalent ratio and temperature distribution in cylinder. Since the variation trend of the parameters were basically same under different working conditions, taking the B50 working condition as an example, the change causes and rules of energy flow, exergy flow and its loss in combustion process were analyzed from distribution of flow velocity, equivalent ratio and temperature distribution. The results indicated that, Firstly, the change of energy and exergy flow mainly occured in combustion process, the degree of change in other processes was not obvious. Second, parameters such as heat transfer exergy, accumulation burn fuel exergy, exhaust loss energy, CA90, exergy efficiency were positively correlated with engine load, the corresponding exergy efficiency were 34.7%, 38.9%, 40.8% at B25, B50, B75 working condition. Third, the proportion of internal exergy loss and heat transfer exergy to fuel exergy were negative correlated with engine load, the former were 31.3%、29.9%、28.3% at B25、B50、B75 working condition respectively, the thermal efficiency of diesel engine could be effectively improved by avoiding running at the low load, with the increasing of speed, the proportions of cumulative heat transfer and internal exergy losses to fuel exergy slightly increasing, while the proportions of exhaust exergy to fuel exergy increased more. Fourth, in the middle of the combustion process, the superposition of the flow motion and the high temperature zone near the cylinder wall aggravated the heat transfer loss. Fifth, the theoretical equivalent ratio region mostly concentrated in the medium velocity zone, the nonuniform distribution of fuel and air, rapid fuel oxidation rate contribute to a greater exergy loss rate caused by diffusion and oxidation, the theoretical equivalent ratio was closer to the cylinder wall caused the greater heat transfer loss, at B50 working condition, the maximum heat transfer ratio was about 11 J/°CA after top dead center 15 °CA when there was the maximum contact area between combustion chamber wall and in-cylinder gas. Sixth, the volume size of high and low temperature region and the temperature rise of low temperature region determined the exergy loss rate resulted from temperature difference in cylinder, the volume fraction of the low temperature region at the late stage of combustion process was about 15% at B50 working condition, the exergy loss caused by temperature difference was larger than other time. In the combustion process of a turbocharged diesel engine, the volume of high and low temperatures region in cylinder was closer, the slower the temperature raising in the low temperature region were, the greater the loss rate was caused by the heat transfer in the cylinder. Finally, the flow velocity distribution, homogeneity of equivalent ratio distribution, high and low temperature region volume and temperature raising in cylinder had certain effects on the internal exergy loss rate.
引文
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[14]王建昕,帅石金.汽车发动机原理[M].北京:清华大学出版社,2011.
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[18]向拉.船用天然气发动机建模仿真与燃烧放热率研究[D].哈尔滨:哈尔滨工程大学,2015.Xiang La.Working-process Simulation and Heat Release Research of Marine Natural Gas Engine[D].Harbin:Harbin Engineering University,2015.(in Chinese with English abstract)
[19]李伟峰.高稀释-预混合天然气发动机燃烧过程分析与优化[D].长春:吉林大学,2016.Li Weifeng.Anaylsis and Optimization of Combustion Process of High Dilution Premixed Natural Gas Engines[D].Changchun:Jilin University,2016.(in Chinese with English abstract)
[20]王永珍,陈贵堂.高等工程热力学[M].北京:清华大学出版社,2013.
[21]王迟宇.柴油机热平衡数值仿真与试验研究[D].杭州:浙江大学,2007.Wang Chiyu.Study on Heat Balance of Diesel Engine Based on Numerical Simulation and Experiment[D].Hangzhou:Zhejiang University,2007.(in Chinese with English abstract)
[22]C D Rakopoulos,E G Giakoumis.Second-law analysis applied to internal combustion engines operation[J].Progress in Energy and Combustion Science,2006,32(1):2-47.
[23]C D Rakopoulos,C N Michos.Generation of combustion irreversibility in a spark ignition engine under biogashydrogen mixtures fueling[J].International Journal of Hydrogen Energy,2009,34(10):4422-4437.
[24]Samveg Saxena,Nihar Shah,Ivan Bedoya,et al.Understanding optimal engine operating strategies for gasoline-fueled HCCI engines using crank-angle resolved exergy analysis[J].Applied Energy,2014,114(2):155-163.
[25]M.Razmara,M.Bidarvatan,M.Shahbakhti,et al.Optimal exergy-based control of internal combustion engines[J].Applied Energy,2016,183:1389-1403.
[26]刘长铖.基于Modelica语言的柴油机建模仿真研究[D].哈尔滨:哈尔滨工程大学,2017.Liu Changcheng.Study of Diesel Engine Modeling and Simulation Based Modelica[D].Harbin:Harbin Engineering University,2017.(in Chinese with English abstract)
[27]Jonathan M S Mattson,Christopher Depcik.First and second law heat release analysis in a single cylinder engine[J].SAETechnical Paper 2016:DOI:https://doi.org/10.4271/2016-01-0559.
[28]杨秀奇.柴油机工作过程的?分析研究[D].昆明:昆明理工大学,2004.Yang Xiuqi.Exergy Analysis of Working Process Diesel Engine[D].Kunming:Kunming University of Science and Technology,2004.(in Chinese with English abstract)
[29]Liu Jingping,Fu Jianqin,Feng Renhua,et al.Effects of working parameters on gasoline engine exergy balance[J].Journal of Central South University,2013,20(7):1938-1946.
[30]刘敬平,付建勤,任承钦,等.增压直喷汽油机热平衡和?平衡试验对比[J].内燃机学报,2013,31(1):65-71.Liu Jingping,Fu Jianqin,Ren Chengqin,et al.Experimental comparison of heat and exergy balance in a turbocharged direct-Injected gasoline engine[J].Transactions of CSICE,2013,31(1):65-71.(in Chinese with English abstract)
[2]倪计民,刘越,石秀勇,等.可变喷嘴涡轮增压及废气再循环系统改善柴油机排放性能[J].农业工程学报,2016,32(16):82-88.Ni Jimin,Liu Yue,Shi Xiuyong,et al.Variable nozzle turbine combined with venture exhaust gas recirculation system improving emission performance of diesel engines[J].Transactions of the Chinese Society of Agricultural Engineering(Transactions of the CSAE),2016,32(16):82-88.(in Chinese with English abstract)
[3]刘敬平,付建勤,唐琦军,等.自然吸气式汽油机热功转换效率影响因素的共性规律[J].燃烧科学与技术,2014,20(3):208-215.Liu Jingping,Fu Jianqin,Tang Qijun,et al.General relationships among the influencing factors of heat-work conversion process in naturally aspirated gasoline engines[J].Journal of Combustion Science and Technology,2014,20(3):208-215.(in Chinese with English abstract)
[4]周龙保,刘忠长,高宗英.内燃机学[M].北京:机械工业出版社,2010.
[5]Gokalp B,Soyhan H S,Sarac H I,et al.Biodiesel addition to standard diesel fuels and marine fuels used in a diesel engine:Effects on emission characteristics and first-and second-law efficiencies[J].Energy&Fuels,2009,23(4):1849-1857.
[6]Li Yaopeng,Jia Ming,Chang Yachao,et al.Thermodynamic energy and exergy analysis of three different engine combustion regimes[J].Applied Energy,2016,180:849-858.
[7]Li Yaopeng,Jia Ming,Sage L Kokjohn,et al.Comprehensive analysis of exergy destruction sources in different engine combustion regimes[J].Energy,2018,149:697-708.
[8]Romero C,Torregrosa A,Olmeda P,et al.Energy balance during the warm-up of a diesel engine[J].SAE Technical Paper 2014:DOI:https://doi.org/10.4271/2014-01-0676.
[9]Zheng Junnian,Jerald A Caton.Second law analysis of a low temperature combustion diesel engine:Effect of injection timing and exhaust gas recirculation[J].Energy,2012,38(1):78-84.
[10]Samad Jafarnada,Peyman Nemati.Analysis of exhaust gas recirculation(EGR)effects on exergy terms in an engine operation with diesel oil and hydrogen[J].Energy,2017,126:746-755.
[11]Venkateswarlu Chintala,Subramanian K.A.Assessment of maximum available work of a hydrogen fueled compression ignition engine using exergy analysis[J].Energy,2014,67:162-175.
[12]A Hosseinzadeh,R Khoshbakhti Saray,S M Seyed Mahmoudi.Comparison of thermal,radical and chemical effects of EGR gases using availability analysis in dual-fuel engines at part loads[J].Energy Conversion and Management,2010,51(11):2321-2329.
[13]周松,王银燕,明平剑.内燃机工作过程仿真技术[M].北京:北京航空航天大学出版社,2012.
[14]王建昕,帅石金.汽车发动机原理[M].北京:清华大学出版社,2011.
[15]刘永长.内燃机原理[M].武汉:华中科技大学出版社,2001.
[16]沈维道.工程热力学[M].北京:高等教育出版社,2007.
[17]Samad Jafarmadar,Peyman Nemati.Multidimensional modeling of the effect of exhaust gas recirculation on exergy terms in a homogenous charge compression ignition engine fueled by diesel/biodiesel[J].Journal of Cleaner Production,2017,161:720-734.
[18]向拉.船用天然气发动机建模仿真与燃烧放热率研究[D].哈尔滨:哈尔滨工程大学,2015.Xiang La.Working-process Simulation and Heat Release Research of Marine Natural Gas Engine[D].Harbin:Harbin Engineering University,2015.(in Chinese with English abstract)
[19]李伟峰.高稀释-预混合天然气发动机燃烧过程分析与优化[D].长春:吉林大学,2016.Li Weifeng.Anaylsis and Optimization of Combustion Process of High Dilution Premixed Natural Gas Engines[D].Changchun:Jilin University,2016.(in Chinese with English abstract)
[20]王永珍,陈贵堂.高等工程热力学[M].北京:清华大学出版社,2013.
[21]王迟宇.柴油机热平衡数值仿真与试验研究[D].杭州:浙江大学,2007.Wang Chiyu.Study on Heat Balance of Diesel Engine Based on Numerical Simulation and Experiment[D].Hangzhou:Zhejiang University,2007.(in Chinese with English abstract)
[22]C D Rakopoulos,E G Giakoumis.Second-law analysis applied to internal combustion engines operation[J].Progress in Energy and Combustion Science,2006,32(1):2-47.
[23]C D Rakopoulos,C N Michos.Generation of combustion irreversibility in a spark ignition engine under biogashydrogen mixtures fueling[J].International Journal of Hydrogen Energy,2009,34(10):4422-4437.
[24]Samveg Saxena,Nihar Shah,Ivan Bedoya,et al.Understanding optimal engine operating strategies for gasoline-fueled HCCI engines using crank-angle resolved exergy analysis[J].Applied Energy,2014,114(2):155-163.
[25]M.Razmara,M.Bidarvatan,M.Shahbakhti,et al.Optimal exergy-based control of internal combustion engines[J].Applied Energy,2016,183:1389-1403.
[26]刘长铖.基于Modelica语言的柴油机建模仿真研究[D].哈尔滨:哈尔滨工程大学,2017.Liu Changcheng.Study of Diesel Engine Modeling and Simulation Based Modelica[D].Harbin:Harbin Engineering University,2017.(in Chinese with English abstract)
[27]Jonathan M S Mattson,Christopher Depcik.First and second law heat release analysis in a single cylinder engine[J].SAETechnical Paper 2016:DOI:https://doi.org/10.4271/2016-01-0559.
[28]杨秀奇.柴油机工作过程的?分析研究[D].昆明:昆明理工大学,2004.Yang Xiuqi.Exergy Analysis of Working Process Diesel Engine[D].Kunming:Kunming University of Science and Technology,2004.(in Chinese with English abstract)
[29]Liu Jingping,Fu Jianqin,Feng Renhua,et al.Effects of working parameters on gasoline engine exergy balance[J].Journal of Central South University,2013,20(7):1938-1946.
[30]刘敬平,付建勤,任承钦,等.增压直喷汽油机热平衡和?平衡试验对比[J].内燃机学报,2013,31(1):65-71.Liu Jingping,Fu Jianqin,Ren Chengqin,et al.Experimental comparison of heat and exergy balance in a turbocharged direct-Injected gasoline engine[J].Transactions of CSICE,2013,31(1):65-71.(in Chinese with English abstract)