| In this paper,the burners in partially premixed gas water heaters are studied.Analyze the influence of the structural parameters of the burner on the combustion uniformity and stability,optimize the size of the burner structure,and obtain a new burner structure that is superior to the prototype.In the operation process of the prototype burner,the variable-load combustion has problems such as inner flame dimming,flame vibration,floating of the flame root,intermittent flameout of ultra-low load operation,etc.,without changing the parameters of the outer support frame and the air supply system of the burner.On the basis of this,the burner is modified by changing the structural parameters,and the optimal structure is found by the combination of numerical simulation and experimental verification,so that it can be safer and more stable under the high load regulation ratio.The main contents of this paper are as follows:Firstly,the main factors affecting the combustion stability of the burner are theoretically analyzed.Take single burner as the object,the parameters include the premixing degree of methane and air flow in the chamber,and the mixed flow state at the outlet.The numerical model,flow model and component transport model are established.Numerical simulation of the burner was carried out using CFD software.Secondly,the gas-fired water heater combustion experimental platform was built to test the thermal efficiency,hot water yield,flame state and smoke exhaustion of the water heater under high and low load,and the minimum combustion heat load of the burner was determined.The experimental results are compared with the simulation results to verify the reliability of the numerical simulation method.Next,for the main structural parameters of the single burner,the influence of the structural size change on the performance of the burner is compared and analyzed to obtain the optimal structure size.Finally,the optimized burner and the prototype are simultaneously tested and verified by combustion experiments,and the conclusion is obtained.The research results show that the parameters affecting the burner's performance(airflow combination and distribution)mainly include the distribution chamber arc,the ejector's throatwidth,the gradient size of the manifold,and the gas tube and outer wall gap.The arc ofthe distribution chamber is reduced,the flow deviation and mean deviation of fire hole from 1to 8 decreased from 15.9% to 13.3%,a decrease of 2.6%,solve the problem of too low front end distribution,and the air flow speed of the entire burner holes is more uniform;the throat width of the ejector is increased by 1.5 mm.Conducive to the formation of a uniform and small gradient pressure field at the bottom of the distribution chamber;the difference between the exit velocity and the average flow velocity of several groups of fire holes at the back end is reduced by 5.6%,improving the stability of the entire flame;the gradient size of the manifold is x=10,d = 2.9,Under the high and low load,the main burner's flow and mean deviation are reduced by 22.5% and 19.8% compared with the prototype.The main fire hole methane concentration and mean deviation are reduced by 2.3% and 1.9% compared with the prototype;gas pipe and outer wall There is a gap between them,which can weaken the deviation of the main jet and help the methane and air to be premixed sufficiently;the jet flow is not concentrated behind the burner,which is conducive to the uniform flow velocity of the burner.Through the experimentally optimized burner,it is found that the combustion stability under small load is greatly improved compared with the prototype,which shows that the height of the fire flame is uniform and Consistent,the inner flame is clear and there is no obvious vibration,which proves that the simulation results are real and reliable... |
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