Experimental Research And Numerical Simulation Of Porous Media Gas-fired Hot Water Boiler

Porous media combustion has the advantages of high combustion intensity,high combustion efficiency and low pollutant emission.Compared with traditional free space combustion,the combustion of the porous inert media can realize the immersion combustion and form the steady combustion flame.Porous media has good radiation and heat conduction,but the research on the combustion heat transfer of porous media is still in the stage of theoretical research.In this thesis,we design a porous media gas-fired hot water boiler in a 80.6kW,by the combined method of experiment and numerical simulation,the working performance of the gas-fired hot water boiler are studied deeply.In this thesis,the experiment gas is natural gas and air,and the premixed combustion is organized in the condition of equivalent ratio 0.90.Firstly,the working performance of the porous media gas-fired hot water boiler is studied under constant water flow condition.The results showed that:under the test conditions the porous media gas-fired hot water boiler combustion chamber temperature distribution,the exhaust gas temperature is low,and the boiler can effectively recover the latent heat of condensation of water vapor in flue gas,The heat efficiency of the low calorific value is up to 106.8%,and the thermal efficiency of the high calorific value is up to 96.6%.The maximum pressure difference of inlet and outlet of combustion chamber is 937Pa,with the increase of the intensity of combustion,CO emissions decreased,while the NO_x emissions increased gradually,but the maximum value is only 44.6mg/Nm~3,far below the GB13271-2014 for the key areas of the gas boiler NO_x emission limits of 150mg/Nm~3.Based on the practical application of gas fired hot water boiler needs to meet the constant temperature water demand,in this thesis,the characteristics of heat transfer and pollutant emission of porous media gas-fired hot water boiler under different combustion intensity were studied when it provide 60?,70?,80?and 90?four different temperature hot water.The test results show that:the temperature distribution of the combustion chamber and the heat efficiency of the porous media gas-fired hot water boiler are mainly influenced by the combustion intensity,while the change of the water flow rate has little effect on the two;The heat transfer coefficient of the two part of the combustion chamber and the rear part of the heat exchanger increases with the increase of the combustion intensity,but the former is less affected by the change of water flow rate and the latter is affected by changes in water flow is obvious;CO and NO_x emissions are mainly influenced by the intensity of combustion,and the greater the intensity of combustion,the smaller the effect of water flow on the two.Based on the FLUENT software to establish a three-dimensional model of combustion chamber part of the porous media gas-fired hot water boiler,combustion chamber structure on different cooling boundary coefficient were studied,analyzed the temperature distribution of combustion chamber,the combustion reaction rate and pollutant emissions,the results show that the combustion and pollutant emission characteristics of combustion chamber with cooling boundary coefficient is 6.0 are the best.