Design Of Fuel Wide Adaptability Stove And Structure Optimization Based On CFD

Decentralized heating is one of the important ways of heating in winter.The way of using bulk coal as fuel and direct-fired exhaust in decentralized heating causes serious air pollution.In view of the problem of pollutant emission from decentralized heating,clean heating methods such as "coal-to-electricity" and"coal-to-gasn have been put forward in China.However,due to resource,economy,habits and other factors,solid fuel heating still has a large market.Based on this,clean heating stoves have become an important development direction.Considering the reality of rural fuel diversification,stoves with wide fuel adaptability have a larger market demand.For this reason,a stove model which can burn high volatile fuel and low volatile fuel was established and simulated by CFD.The stove model designed can be switched between over-fire heating and under-fire heating modes.In this paper,straw pellet fuel is used as the representative of high volatile fuel to simulate the performance of the stove in under-fire heating condition.The results show that the maximum temperature is 1271°C and the average temperature is 421℃ in the combustion chamber,and the calculated thermal efficiency is 89%with 24 kW design power.In addition,Fujian anthracite is used as the representative of low volatile fuel to simulate the performance of the stove in over-fire heating conditions.The results show that the calculated thermal efficiency is 41%while the designed power of the stove remains unchanged.The results of calculating thermal efficiency by simulating over-fire heating and under-fire heating on the stove are quite different.In this paper,the influence of flue gas recirculation on the combustion of pellet fuel and the emission of NOx from stove under the condition of under-fire heating is studied.When 10%of the flue gas returns to the primary air intake,the maximum temperature in the combustion chamber decreases by 44℃ and NO emission decreases by 27%.However,when the same amount of flue gas returns to the secondary air intake,there is no emission reduction effect.When the flue gas enters the combustor by the primary air inlet,the temperature in the combustor decreases with the increase of the flue gas volume.The recirculation ratio increases from 0 to 30%,the maximum temperature decreases 266℃,the average temperature of the flue gas outlet decreases by 40 C,and the emission of NO decreases with the increase of the flue gas recirculation.When the recirculation ratio is less than 15%,the reduction rate is faster.When the recirculation ratio is more than 15%,the reduction rate slows down The effect of flue gas recirculation on the thermal efficiency of stove is not obvious,only reduces by 1%.Flue gas recirculation can effectively reduce NOx emission without affecting thermal efficiency.