车用甲醇裂解器的换热器设计研究
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摘要
利用发动机尾气余热对甲醇进行加热,使其裂解为氢气和一氧化碳等的混合气,裂解后将这种混合气体导入发动机燃烧室进行燃烧。这种燃用形式将可以克服甲醇的毒性、腐蚀性和低温冷启动等不良性质的影响,并可以实现甲醇的高比例使用,具有广阔的市场前景。车载甲醇裂解器的换热器是整个裂解器中非常关键的组成部分,它关系到尾气余热利用率进而影响甲醇的裂解效率,即催化剂必须在特定的温度内工作,温度过低则甲醇裂解率低,温度高则催化剂失效,所以换热器的设计就十分关键,必须保证把甲醇蒸汽加热到260-390℃之间,催化剂才能起到真正的作用。作为一种换热装置,换热器的种类较多,但针对甲醇裂解器的换热器,需要考虑生产成本,清洗方便,选材和使用范围,工作安全,经久耐用等情况,因此需要为甲醇裂解器设计一款能达到上述目的的换热器。
本文以该换热器为研究对象,以其性能符合甲醇裂解的条件为研究目标,对换热器做了热力分析、结构设计及仿真,具有一定的工程实用价值和理论意义。本文主要研究内容如下:
1)本文深入研究了换热器的结构形式,确定固定管板式管壳换热器为本文要设计的换热器。以BN492汽油机为配套发动机设计了换热器相关零部件的结构尺寸,并利用经验公式等对甲醇裂解器换热器进行了强度校核和热力分析;对换热器的平均温度、换热系数、甲醇消耗量、对流传热膜系数、总传热面积、总传热系数等参数进行了计算,计算结果表明上述结构尺寸都满足换热器国家标准和设计要求。
2)利用GAMBIT软件建立了换热器及相关零部件(管板、法兰等)的三维模型,为使之后的对流传热性能仿真分析能够顺利进行,对零部件的结构细节进行了适当的简化;采用GAMBIT软件对换热器及其相关零部件进行网格划分和边界条件设定;介绍了自然对流换热模型,同时对布斯尼斯克假设(J.Bous sinesq hypothesis model)进行了说明,并根据布斯尼斯克假设推导出自然对流边界层的基本方程组。对换热器壳程建立湍流模型,选择了标准k～?湍流模型;压力～速度耦合方程采用SIMPLEC方法;流动方程与换热方程组均采用二阶迎风差分格式,流体进、出口采用压力进、出口边界条件;换热器的整个外壁面采用绝热边界条件。
3)基于流体动力学计算分析软件FLUENT6.0对换热器的温度场、内部流场进行了模拟分析,并对换热器截面上的压力场进行了分析,最后利用FLUENT6.0软件对换热器进行了热效率仿真。仿真分析结果显示:对换热器热效率仿真表明该换热器能够满足车载裂解器对热量的需求,即经过换热器以后,壳程内从八个大气压下降到四个大气压,管程内尾气温度从入口时的600℃左右下降到200～250℃,尾气释放的热量主要被用于裂解甲醇,基本满足了换热器的设计要求。
Methanol using engine exhaust heat to heat, it cracked into hydrogen and carbon monoxide mixture, cracking after this mixture into the engine combustion chamber for combustion.This form can be overcome by burning methanol toxicity, corrosion and low temperature properties of cold start and other adverse effects and can be used to achieve a high percentage of methanol, it has broad market prospects. Automotive heat exchanger methanol cracker in the whole critical components, It is thus related to the exhaust heat utilization efficiency of the decomposition of methanol, the catalyst must work within a specific temperature, ambient temperature is too low then the low rate of methanol decomposition, the catalyst for high temperature failure,must ensure that the methanol steam heated to between 260-390℃, the catalyst can play a real role. As a heat transfer device, more types of heat exchangers, but for the heat exchanger methanol cracker, need to consider the cost of production, easy to clean, the selection and use of the range, work safety, durability, etc., so the need for methanol Cracker designed to achieve the above purpose a heat exchanger.
In this paper, the heat exchanger as the research object, with its performance in line with the conditions for the study of methanol cracking goal, made of heat exchanger thermal analysis, structural design and simulation, has some practical value and theoretical significance.This mainly includes the following:
1) This article studies the structure of the heat exchanger to determine the fixed tube shell and tube heat exchanger plate of this paper to design the heat exchanger. To BN492 gasoline engine designed for supporting the related parts of the structure of heat exchanger size, and use empirical formula for the methanol cracker and other heat exchanger and thermal analysis of the strength check; the average temperature of the heat exchanger, heat transfer coefficient , Methanol consumption, heat transfer film coefficient, total heat transfer area, overall heat transfer coefficient and other parameters were computed and the results show that the size of the structure of the national standards are met and the heat exchanger design requirements.
2) The use of GAMBIT software to establish a heat exchanger and related parts (tube sheets, flanges, etc.) of the three-dimensional model for the thermal convection after the simulation can proceed smoothly, the structural details of the components were properly Simplification; using GAMBIT software and related components for heat exchangers mesh and boundary conditions; describes the natural convection heat transfer model, while J. Bous sinesq hypothesis model assumptions are described And assumptions derived according J. Bous sinesq hypothesis model assumptions the basic natural convection boundary layer equations. Of the heat exchanger shell Distance established turbulence model, choose the standard k ~ ? turbulence model; pressure-velocity coupling equation ~ SIMPLEC methods used; flow equations and heat transfer equations are second-order upwind difference scheme, the fluid inlet and outlet by pressure into , outlet boundary conditions; heat the entire outer wall adiabatic boundary conditions.3) Based on computational fluid dynamics analysis software FLUENT6.0 temperature of heat exchanger, the internal flow field simulation, and the heat exchanger section of the pressure field analysis, the final software for use FLUENT6.0 Thermal efficiency of thermal simulation were carried out. In this paper, FLUENT6.0 software simulation results show: the thermal efficiency of the heat exchanger simulation shows that the heat exchanger can meet the vehicle needs of cracker on the heat, ie, after the heat exchanger after the shell fell within the atmosphere from eight to four Atmospheric pressure, exhaust gas temperature inside the tube pass the time from the entrance down to about 600℃200 ~ 250℃, exhaust heat released is mainly used for methanol
本文以该换热器为研究对象,以其性能符合甲醇裂解的条件为研究目标,对换热器做了热力分析、结构设计及仿真,具有一定的工程实用价值和理论意义。本文主要研究内容如下:
1)本文深入研究了换热器的结构形式,确定固定管板式管壳换热器为本文要设计的换热器。以BN492汽油机为配套发动机设计了换热器相关零部件的结构尺寸,并利用经验公式等对甲醇裂解器换热器进行了强度校核和热力分析;对换热器的平均温度、换热系数、甲醇消耗量、对流传热膜系数、总传热面积、总传热系数等参数进行了计算,计算结果表明上述结构尺寸都满足换热器国家标准和设计要求。
2)利用GAMBIT软件建立了换热器及相关零部件(管板、法兰等)的三维模型,为使之后的对流传热性能仿真分析能够顺利进行,对零部件的结构细节进行了适当的简化;采用GAMBIT软件对换热器及其相关零部件进行网格划分和边界条件设定;介绍了自然对流换热模型,同时对布斯尼斯克假设(J.Bous sinesq hypothesis model)进行了说明,并根据布斯尼斯克假设推导出自然对流边界层的基本方程组。对换热器壳程建立湍流模型,选择了标准k～?湍流模型;压力～速度耦合方程采用SIMPLEC方法;流动方程与换热方程组均采用二阶迎风差分格式,流体进、出口采用压力进、出口边界条件;换热器的整个外壁面采用绝热边界条件。
3)基于流体动力学计算分析软件FLUENT6.0对换热器的温度场、内部流场进行了模拟分析,并对换热器截面上的压力场进行了分析,最后利用FLUENT6.0软件对换热器进行了热效率仿真。仿真分析结果显示:对换热器热效率仿真表明该换热器能够满足车载裂解器对热量的需求,即经过换热器以后,壳程内从八个大气压下降到四个大气压,管程内尾气温度从入口时的600℃左右下降到200～250℃,尾气释放的热量主要被用于裂解甲醇,基本满足了换热器的设计要求。
Methanol using engine exhaust heat to heat, it cracked into hydrogen and carbon monoxide mixture, cracking after this mixture into the engine combustion chamber for combustion.This form can be overcome by burning methanol toxicity, corrosion and low temperature properties of cold start and other adverse effects and can be used to achieve a high percentage of methanol, it has broad market prospects. Automotive heat exchanger methanol cracker in the whole critical components, It is thus related to the exhaust heat utilization efficiency of the decomposition of methanol, the catalyst must work within a specific temperature, ambient temperature is too low then the low rate of methanol decomposition, the catalyst for high temperature failure,must ensure that the methanol steam heated to between 260-390℃, the catalyst can play a real role. As a heat transfer device, more types of heat exchangers, but for the heat exchanger methanol cracker, need to consider the cost of production, easy to clean, the selection and use of the range, work safety, durability, etc., so the need for methanol Cracker designed to achieve the above purpose a heat exchanger.
In this paper, the heat exchanger as the research object, with its performance in line with the conditions for the study of methanol cracking goal, made of heat exchanger thermal analysis, structural design and simulation, has some practical value and theoretical significance.This mainly includes the following:
1) This article studies the structure of the heat exchanger to determine the fixed tube shell and tube heat exchanger plate of this paper to design the heat exchanger. To BN492 gasoline engine designed for supporting the related parts of the structure of heat exchanger size, and use empirical formula for the methanol cracker and other heat exchanger and thermal analysis of the strength check; the average temperature of the heat exchanger, heat transfer coefficient , Methanol consumption, heat transfer film coefficient, total heat transfer area, overall heat transfer coefficient and other parameters were computed and the results show that the size of the structure of the national standards are met and the heat exchanger design requirements.
2) The use of GAMBIT software to establish a heat exchanger and related parts (tube sheets, flanges, etc.) of the three-dimensional model for the thermal convection after the simulation can proceed smoothly, the structural details of the components were properly Simplification; using GAMBIT software and related components for heat exchangers mesh and boundary conditions; describes the natural convection heat transfer model, while J. Bous sinesq hypothesis model assumptions are described And assumptions derived according J. Bous sinesq hypothesis model assumptions the basic natural convection boundary layer equations. Of the heat exchanger shell Distance established turbulence model, choose the standard k ~ ? turbulence model; pressure-velocity coupling equation ~ SIMPLEC methods used; flow equations and heat transfer equations are second-order upwind difference scheme, the fluid inlet and outlet by pressure into , outlet boundary conditions; heat the entire outer wall adiabatic boundary conditions.3) Based on computational fluid dynamics analysis software FLUENT6.0 temperature of heat exchanger, the internal flow field simulation, and the heat exchanger section of the pressure field analysis, the final software for use FLUENT6.0 Thermal efficiency of thermal simulation were carried out. In this paper, FLUENT6.0 software simulation results show: the thermal efficiency of the heat exchanger simulation shows that the heat exchanger can meet the vehicle needs of cracker on the heat, ie, after the heat exchanger after the shell fell within the atmosphere from eight to four Atmospheric pressure, exhaust gas temperature inside the tube pass the time from the entrance down to about 600℃200 ~ 250℃, exhaust heat released is mainly used for methanol
引文
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[4]边耀章等.汽车新能源技术[M].北京:机械工业出版社,2003.
[5]谢克昌,李忠.甲醇及其衍生物[M].北京:化学工业出版社.2002,6.
[6]张仲荣,范国梁,宋崇林等.火花点火式电控甲醇发动机非常规污染物的排放特性[J].燃烧科学与技术.2006,12.1:86-89.
[7]汪洋,王雪雁,蒋宁涛等.甲醇发动机的性能研究[J].燃烧科学与技术.2006,12.5:390-393.
[8]郭新宇,刘志远.中国醇醚燃料产业发展的思路及对策[J].煤化工. 2008,6.3:1-4
[9]吴冠京.车用清洁燃料[M].北京:石油工业出版社. 2004: 335.
[10]杨庆佛.关于甲醇燃料应用中的几个问题[C].西安:甲醇燃料发展研讨会论文集,2003.4:17～18.
[11]秦有方,陈士尧,王文波.车辆内燃机原理[M].北京:北京理工大学出版, 1997:18.
[12]冯春晃,高孝洪.甲醇裂解燃料点燃式发动机的研究[J].内燃机学报.1989,7.2: 151-152.
[13]钟洪权,王亚明,张松.甲醇汽油的技术进展及应用前景[J].云南化工.2006,33.5:51-54.
[14] Lu,G.Q.Wang, C.Y.Development of High Performance Micro DMFCS and a DMFC Stack[J]. Journal of Fuel Cell Science and Technology,2006,3:131-135.
[15] Rice, R. W.Sanyal, A. K.Elrod, A. C.Exhaust Gas Emissions of Butanol, Ethanol, and Methanol-Gasoline Blends[J]. Journal of Engineering for Gas Turbines andPower,1991,113:377-381.
[16] Gandhidasan, P.Ertas, A.Anderson, E. E.Review of Methanol and Compressed Natural Gas (CNG) as Alternative for Transportation Fuels[J].Journal of Energy Resources Technology,1991,113:101-106.
[17] Finegold, J.G..Dissociated. methanol vehicle test results[C].Nonpetroleum Vehicular Fuels IV. Arlington,VA,USA,1984:213-228.
[18] Finegold, J.G..Mckinnon, J.T.Dissociated methanol test results[J].Alternate Fuel. Columbus,OH,USA,1986:75-79.
[19] Adelman, H.G.Browning, L.H.Pefley, R.K.Predicted Exhaust Emissions from a Methanol and Jet Fueled Gas Turbine Combustor[J].AIAA JOURNAL ,1986,14:793.
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