柴油机缸内辐射换热.doc
约59页DOC格式手机打开展开
柴油机缸内辐射换热,摘要燃烧过程是研究柴油机缸内工作过程的关键，而燃烧过程与传热是相互耦合的，其中的传热主要为热对流和热辐射。柴油机缸内热对流的研究已有较为成熟的理论和经验公式，可以较合理地预测对流换热量的大小。而对柴油机缸内的热辐射的研究，由于辐射传热的复杂性，目前一般资料还没有详细的介绍，但是实验研究的结果表明，对于大中型柴油机，其缸...
内容介绍
此文档由会员 违规屏蔽12 发布
摘要
燃烧过程是研究柴油机缸内工作过程的关键，而燃烧过程与传热是相互耦合的，其中的传热主要为热对流和热辐射。柴油机缸内热对流的研究已有较为成熟的理论和经验公式，可以较合理地预测对流换热量的大小。而对柴油机缸内的热辐射的研究，由于辐射传热的复杂性，目前一般资料还没有详细的介绍，但是实验研究的结果表明，对于大中型柴油机，其缸内辐射传热量占总传热量的10％～45％。随着计算机技术和测试技术的发展，使柴油机缸内热辐射问题的深入研究成为可能。本文对可用于缸内辐射换热计算的各种模型进行比较，以寻找能够准确合理地模拟柴油机缸内辐射传热情况的模型方法。
本文的研究对象为G4135直喷式柴油机，首先用前处理软件GAMBIT建立燃烧室模型，燃烧室的网格采用分块网络划分法，划分网格后导入FLUENT软件生成动网格，然后分别用离散传递模型（DTRM）、Rosseland辐射模型、离散坐标辐射模型（DO）以及P-1近似辐射模型对柴油机缸内的辐射物性参量进行模拟。
首先对辐射吸收系数、辐射热流密度进行模拟，结果表明其随曲轴转角的变化规律符合燃烧的一般规律；随后对碳烟浓度进行模拟，结果表明DO模型模拟出的碳烟浓度与实验数据吻合最好，P-1模型次之，其它辐射模型的模拟结果与实验值差距很大；接着分别用DO模型和P-1模型对燃烧室内的辐射温度和平均气体温度进行模拟，计算出该情况下的火焰温度，将计算得到的火焰温度与实验测得的火焰温度进行比较，结果表明DO模型模拟出的结果与实验值两者差距仅8％，而P-1模型与实验值相差31％，验证了DO模型在模拟柴油机缸内的辐射传热过程方面具有一定的可靠性。随后运用模拟效果较好的DO模型，对构成柴油机燃烧室的不同零部件的辐射传热情况进行模拟分析，并研究了不同转速和负荷对辐射温度、碳烟浓度和辐射热流密度的影响，结果表明辐射温度、碳烟浓度和辐射热流密度随着负荷的增加而增大，随着转速的下降而上升，且辐射传热量占总传热量的份额为26％～48％。
本文的研究方法和结果可以对同类型柴油机的辐射传热研究起到抛砖引玉的作用。
关键词 辐射传热；柴油机；辐射模型；FLUENT；燃烧
Abstract
To study the working process of the diesel engine, the combustion process is the key, and the combustion process is coupled with the heat transfer. The main heat transfer of combustion process is convection heat transfer and thermal radiation. The study on convection heat transfer in cylinder has got mature theory and empirical formula, so the size of convective heat transfer can be predicted reasonably. Due to its complexity of the study of thermal radiation, general information has not described in details yet, but experiment studies have concluded that, for large diesel engines, the radiation heat transfer medium of its total radiation heat transfer from 10% to 45%. With the development of computer technology and testing technology, the depth study of heat radiation in diesel engine cylinder turns possible. This article is intended to find a radiation model which can accurately simulate the radiation heat transfer in cylinder.
In this paper, the G4135 diesel engine model was taken as an example. First, GAMBIT was used to build the model of the combustion chamber, and grid of combustion chamber is divided by block network, then import into FLUENT software after meshing. And then use the model such as Discrete transfer radiation model (DTRM), Rosseland radiation model, discrete ordinates radiation model (DO) and the P-1 radiation model provided by FLUENT software, to analyze the physical parameters of radiation in cylinder.
First, the radiation absorption coefficient and radiation heat flux was simulated, and the results showed that their variation with crank angle agreed with the general rules of combustion; Then the soot density was simulate, the results showed that the soot density simulated by DO radiation model in the best agreement with experimental data, followed by P-1 radiation model, but simulation results of the other radiation models was different from experimental data greatly; Then DO radiation model and P-1 radiation model were used to simulate radiation temperature and the average gas temperature in combustion chamber, and calculate the flame temperature under these conditions, compared the calculated flame temperature with the experimental flame temperature, the results simulated by the DO radiation model differ from the experimental data with t only 8%, while the P-1 radiation model with 31%, which verified that the DO radiation model has some reliability in simulating the radiation heat transfer in diesel engine cylinder. Then use the DO radiation model which was a better simulation model, to simulate and analyze the radiation heat transfer of different parts of the combustion chamber, and study the different speed and load how to impact the radiation temperature, soot density and the radiation heat flux, the results show that the radiation temperature, soot density and radiation heat flux is proportional with the load, and inversely with the speed, and radiation heat transfer shared from 26% to 48% of total heat transfer.
This study method and results can give better ideas to be the study of the radiation heat transfer of the same type of engine.
Keywords radiation heat transfer；Diesel engine；radi..
燃烧过程是研究柴油机缸内工作过程的关键，而燃烧过程与传热是相互耦合的，其中的传热主要为热对流和热辐射。柴油机缸内热对流的研究已有较为成熟的理论和经验公式，可以较合理地预测对流换热量的大小。而对柴油机缸内的热辐射的研究，由于辐射传热的复杂性，目前一般资料还没有详细的介绍，但是实验研究的结果表明，对于大中型柴油机，其缸内辐射传热量占总传热量的10％～45％。随着计算机技术和测试技术的发展，使柴油机缸内热辐射问题的深入研究成为可能。本文对可用于缸内辐射换热计算的各种模型进行比较，以寻找能够准确合理地模拟柴油机缸内辐射传热情况的模型方法。
本文的研究对象为G4135直喷式柴油机，首先用前处理软件GAMBIT建立燃烧室模型，燃烧室的网格采用分块网络划分法，划分网格后导入FLUENT软件生成动网格，然后分别用离散传递模型（DTRM）、Rosseland辐射模型、离散坐标辐射模型（DO）以及P-1近似辐射模型对柴油机缸内的辐射物性参量进行模拟。
首先对辐射吸收系数、辐射热流密度进行模拟，结果表明其随曲轴转角的变化规律符合燃烧的一般规律；随后对碳烟浓度进行模拟，结果表明DO模型模拟出的碳烟浓度与实验数据吻合最好，P-1模型次之，其它辐射模型的模拟结果与实验值差距很大；接着分别用DO模型和P-1模型对燃烧室内的辐射温度和平均气体温度进行模拟，计算出该情况下的火焰温度，将计算得到的火焰温度与实验测得的火焰温度进行比较，结果表明DO模型模拟出的结果与实验值两者差距仅8％，而P-1模型与实验值相差31％，验证了DO模型在模拟柴油机缸内的辐射传热过程方面具有一定的可靠性。随后运用模拟效果较好的DO模型，对构成柴油机燃烧室的不同零部件的辐射传热情况进行模拟分析，并研究了不同转速和负荷对辐射温度、碳烟浓度和辐射热流密度的影响，结果表明辐射温度、碳烟浓度和辐射热流密度随着负荷的增加而增大，随着转速的下降而上升，且辐射传热量占总传热量的份额为26％～48％。
本文的研究方法和结果可以对同类型柴油机的辐射传热研究起到抛砖引玉的作用。
关键词 辐射传热；柴油机；辐射模型；FLUENT；燃烧
Abstract
To study the working process of the diesel engine, the combustion process is the key, and the combustion process is coupled with the heat transfer. The main heat transfer of combustion process is convection heat transfer and thermal radiation. The study on convection heat transfer in cylinder has got mature theory and empirical formula, so the size of convective heat transfer can be predicted reasonably. Due to its complexity of the study of thermal radiation, general information has not described in details yet, but experiment studies have concluded that, for large diesel engines, the radiation heat transfer medium of its total radiation heat transfer from 10% to 45%. With the development of computer technology and testing technology, the depth study of heat radiation in diesel engine cylinder turns possible. This article is intended to find a radiation model which can accurately simulate the radiation heat transfer in cylinder.
In this paper, the G4135 diesel engine model was taken as an example. First, GAMBIT was used to build the model of the combustion chamber, and grid of combustion chamber is divided by block network, then import into FLUENT software after meshing. And then use the model such as Discrete transfer radiation model (DTRM), Rosseland radiation model, discrete ordinates radiation model (DO) and the P-1 radiation model provided by FLUENT software, to analyze the physical parameters of radiation in cylinder.
First, the radiation absorption coefficient and radiation heat flux was simulated, and the results showed that their variation with crank angle agreed with the general rules of combustion; Then the soot density was simulate, the results showed that the soot density simulated by DO radiation model in the best agreement with experimental data, followed by P-1 radiation model, but simulation results of the other radiation models was different from experimental data greatly; Then DO radiation model and P-1 radiation model were used to simulate radiation temperature and the average gas temperature in combustion chamber, and calculate the flame temperature under these conditions, compared the calculated flame temperature with the experimental flame temperature, the results simulated by the DO radiation model differ from the experimental data with t only 8%, while the P-1 radiation model with 31%, which verified that the DO radiation model has some reliability in simulating the radiation heat transfer in diesel engine cylinder. Then use the DO radiation model which was a better simulation model, to simulate and analyze the radiation heat transfer of different parts of the combustion chamber, and study the different speed and load how to impact the radiation temperature, soot density and the radiation heat flux, the results show that the radiation temperature, soot density and radiation heat flux is proportional with the load, and inversely with the speed, and radiation heat transfer shared from 26% to 48% of total heat transfer.
This study method and results can give better ideas to be the study of the radiation heat transfer of the same type of engine.
Keywords radiation heat transfer；Diesel engine；radi..
