Theoretical And Experimental Study On Pulsating Combustion Characteristics

The pattern of China's energy structure which is given priority to coal will not change for a long time in the future,pollution from coal combustion has a great harm to human health and the environment.Thus improving the combustion efficiency of fuel and controlling the emissions of pollutants are problems to be solved.As a kind of combustion method which is different from the conventional steady combustion,the pulsating combustion has the advantages of high combustion efficiency and high combustion intensity,high heat transfer efficiency and small pollutant discharge,etc.It not only can improve the energy efficiency,save energy and reduce the industrial producion and operation costs,but also can reduce pollutant emissions and protect the environment.In this paper,a pulsating combustion thermoacoustic experiment bench is first set up,the thermoacoustic characteristics of a Rijke tube pulsating burner with vertical placement and horizontal placement were experimentally investigated,the influences of the parameters such as length-diameter ratio,heat source power,heat source temperature,heat source position and wind speed on the start-up power,sound area,frequency and sound pressure level were discussed.The experimental results show that:(1)with the increase of the length-diameter ratio,the power required for the thermoacoustic oscillation is first reduced and then increased,and reaches the minimum value at L/D=20;the ratio of the sound area to the total length increases first and then decreases,and reaches the maximum value at L/D=25;the overall trend of the sound frequency is gradually reduced;sound pressure level as a whole showes that the trend is first increased and then decreased,and the maximum value is reached at L/D=25.(2)with the increase of heat source power,the sound area remains almost unchanged;the overall trend of sound frequency and sound pressure level are increased.(3)with the heat source temperature increasing,the overall trend of sound frequency increases.(4)as the position of the heat source moving from the bottom to the top,the frequency tends to decreasing gradually;the sound pressure level generally increases first and then decreases,and reaches the maximum at the distance L/4.(5)as the wind speed increasing,the frequency decreases and the sound pressure level increases.Secondly,on the basis of the thermoacoustic experiment,the best Rijke tube placement and the best length-diameter ratio are selected for the heat transfer experiment.Two types of heat transfer tubes named water-cooled jacket and serpentine tube are designed.The experimental results show that: under the condition of the same heat source power and the cooling water flow,in the presence of pulsation,the heat transfer coefficient is increased and the heat transfer effect is enhanced.The lowest and the highest heat transfer efficiency of the heat transfer tube named water-cooled jacket is increased by 10.59% and 113.3%;the lowest and the highest heat transfer efficiency of the heat transfer tube named serpentine tube is increased by 37.43% and 368.75%.