Development Of Gas Water Heater Based On Porous Media Combustion

At present,the annual consumption of coal in China is close to 2/3 of the primary energy consumption in China.Environmental pressure is intensified by increasing pollution.In this case,the energy industry tends to use cleaner energy and improve the efficiency of energy utilization.Natural gas application has the advantage that exhaust gas after natural gas combustion is cleaner than coal and oil combustion,therefore natural gas applied extensively.Gas water heater is the main gas equipment for civil use.Improving the efficiency and reducing pollutant emissions will have a positive impact on urban environment.Porous media combustion is a new type of combustion technology,with advantages of extended load range,low pollutant emission,which is consistent with the trend of gas water heater improvement.Therefore,the application of the porous media combustion in gas water heater will be likely to enhance performance of gas water heater.In this thesis,the flame propagation and temperature characteristics of porous medium burner was studied first.In the same firing rate of combustion,with the increase of excess air ratio,the flame will become stable from flashback,and then lift-off finally.Flame stability can be maintained in a certain range of excess air ratio.The overall temperature of the combustor decreases with the decrease of the firing rate.Secondly,the pollutant emission of the porous medium burner was studied.With the decrease of the firing rate,CO emission increases,while the NOx emission decreases.In the minimum firing rate conditions,CO emission is even beyond the regulation limit of gas water heater.Therefore,the effect of material composition and the thickness of the porous medium on the emission of pollutants at low combustion intensity are studied.In order to further oxidize the CO emission at low firing rate condition,catalytic enhancement is introduced according to large specific surface area of porous media.Copper manganese oxides catalyst was supported by impregnation.Effect of impregnation zone and copper manganese proportion on pollutant emission characteristics is studied.Based on previous experiment,porous medium gas water heater prototype platform is built with great help of Vanward Co.Ltd.,Guangdong.The experimental results showthat the porous medium gas water heater enlarges load range and reduces pollutant emission compared to original gas water heater,which means the performance of gas water heater has improved.The experimental results bode bright prospects for further improvement and prototype mass-production.