Study On The Characteristics Of Exergy In The Process Of Piloted Methane Turbulent Combustion

Exergy analysis method of thermodynamic systems is widely used in power station boiler, heat exchanger, engine and other equipment, which provides the theoretic foundation for improving availability of system and reducing the loss of fuel. The traditional exergy analysis method can only reveal the total characteristic of exergy in macroscopic thermodynamic process. Howerver, it can not show the law of local loss nor the distribution characteristics, and then optimize thermodynamic processes based on the characteristics of exergy.This study based on the theory of non-equilibrium thermodynamics and numerical simulation method, concludes the local exergy and local exergy loss calculation theory, which can analyze the characteristics of exergy in the process of piloted methane turbulent combustion from micro to macro and study on the influences of the characteristics of exergy for the changes of the flame parameters. So as to reduce the loss of combustion process and improve the efficiency of combustion. The study contents are as follows:Numerical simulation of Flame D experiment of methane turbulent combustion based on Sydney piloted flame burner is carried out. The results show that the simulated values of the flame are roughly the same as the experimental values, which basically meet the study needs.The local exergy and local exergy loss calculation theory in combuston are concluded. According to the basic hypothesis, the different physical meaning and physical process, local exergy and loacl exergy loss are classified. Moreover, the the transport and transformation laws of local exergy which change with the time are revealed.Combined with the theories of local exergy and exegy loss and data by numerical simulation, the characteristics of exergy of Flame D is analysised and calculated. It shows that the area between chemical exergy control zone and thermal exergy control zone, appears combustion, heat transfer and mass transfer process obviously. The heat transfer exergy loss control zone is on both sides of the chemical reaction exergy loss control zone. From the computational domain inlet to the outlet, chemical exergy, mechanical exergy and total exergy decreases gradually, however, thermal exergy and chemical reaction exergy loss increases first and then decreases. From the viewpoint of the quantity of exergy loss, heat transfer is the main factor of exergy loss and chemical reaction is the second, theviscous dissipation and diffusion mass transfer can be ignored in the processes of exergy transport and transformation. The general trend of transformation of exergy is that chemical exergy and mechanical exergy transform into heat exergy.The influence of exergy of characteristics with the changes of Reynolds number and equivalence ratio is revealed in section and the overall of the flame. It shows that, with the increase of Reynolds number, each of exergy and exergy loss increased along the flow direction in the same section. Efficiency of thermal exergy, efficiency of total exergy, heat transfer and chemical reaction exergy loss change weakly and the heat transfer exergy loss play the dominant role in all. With the increase of the equivalence ratio, thermal exergy, chemical exergy, total exergy, efficiency of thermal exergy and efficiency of total exergy improve along the flow direction in the same section. the heat transfer exergy loss also play the dominant role in all.All results of characteristic of exergy analysis show that reasonable spatial distribution of chemical reaction can adjust the spatial distribution of local heat transfer exergy loss, which makes total heat transfer exergy loss decreased and lead to increase of efficiency of thermal exergy and total exergy.For the complex thermal system, exergy loss which is weak in some processes have an significant effect on efficiency of thermal exergy and efficiency of total exergy. So the optimiztation of efficiency also need to be considered in other aspects such as the spatial organization structure in the transportation and transformation process, the time scale of the process and so on.