Experimental And Control Study On Thermoacoustic Instability Of Rijke-Type Swirl Burner

The gas turbine has a wide range of output power,high reliability and compact structure,so it is widely used in the field of power.However,it brings the problem of nitrogen oxide emission,which threatens the social environment gradually.In order to reduce pollution,the technology of lean combustion premixed combustion is popularized.However,the problem of thermal instability is caused by the problem of thermal instability.In order to solve the technical problems in this field.In this paper,the main research object is thermoacoustic instability.The test is based on the traditional Rijke burner,and the hydrocyclone is added.By changing the chemical equivalent ratio,the fuel intake rate,the air intake rate and other system parameters,the temperature characteristics of the combustion process in the swirling burner and its effect on the thermal instability are investigated.The effects of flue gas emission characteristics and thermoacoustic instability on combustion efficiency are studied.First,the temperature characteristics of swirling burner combustion process are studied.The variation trend of temperature in the burner with variable chemical equivalence ratio under different fuel flow rates is given.With the increase of fuel intake,the temperature in the cavity is rising.When the methane intake is 2.0L/min,the temperature value of the bottom of the burner cavity fluctuates near 550K,but when the methane intake is 5.0L/min,the maximum temperature is close to 850K.The temperature span of methane intake is larger between 2.5L/min and 3.0L/min,and the chemical equivalent ratio of lean burn is 0.8.The corresponding temperature is 595K when the methane intake is 2.5L/min,and the corresponding temperature is 696K when the methane intake is 3.0L/min.The temperature of the cavity has a strong regularity with the change of the chemical equivalent ratio.When the chemical equivalent ratio is between 0.8 and 1.1,the temperature in the cavity increases slightly with the increase of the chemical equivalent ratio,and the increase of the chemical equivalent ratio between 1 and 1.1 is very small,and is close to the same.When the chemical equivalence ratio changes from 1.1 to 1.2,the temperature inside the burner decreases to varying degrees.Then,the thermoacoustic instability of Rijke swirl burner is studied.The pressure signal in the Rijke type swirl burner when the thermal acoustic instability reaches the limit cycle oscillation is a time invariant signal,similar to the sine wave.After a summary of the experimental data,it is concluded that when the chemical equivalent ratio is 1.1,the peak amplitude of the thermoacoustic instability reaches the maximum.When the chemical equivalent ratio is less than 1.1,the amplitude of the main peak of the thermal instability increases with the increase of the chemical equivalent ratio;when the chemical equivalent ratio is greater than 1.1,the amplitude of the main peak decreases with the chemical equivalent ratio.In addition,the amplitude of the main peak of the thermal acoustic instability increases rapidly with the increase of the intake rate.When the methane intake is 5.0L/min and the chemical equivalent ratio is 1.1,the amplitude of the main peak of the thermoacoustic instability reaches the maximum,but the change rule is greatly influenced by the chemical equivalent ratio.Finally,the smoke emission characteristics under the condition of thermoacoustic instability are analyzed,including residual O₂,CO and NO_x.The residual concentration of O₂ is very high in most of the working conditions.Only the O₂ concentration in a few working conditions is less than 2%,and the O₂ concentration in all the working conditions decreases with the increase of the chemical equivalent ratio.In addition,some of the measured values vary significantly and vary widely.Strong accident flameout results in very incomplete combustion and the concentration of O₂ also fluctuates.According to the oxygen concentration measured in the flue gas,the O₂ content in the flue gas and the methane not participating in the reaction can be calculated,and the combustion efficiency can be calculated.With the increase of chemical equivalence ratio,the combustion efficiency of the system decreases.When the chemical equivalent ratio is 1,the combustion efficiency is 81.9%,which shows that reducing the chemical equivalent ratio can improve the combustion efficiency of the system and the intense heat acoustic instability significantly reduces the current combustion efficiency of the system.NO_X is one of the main pollutants in the atmosphere.Lean premixed combustion is used to reduce the amount of NO_X.With the increase of chemical equivalent ratio,the concentration of NO_X is getting higher and higher.When the chemical equivalent ratio is 0.8,the concentration of NO_X is less than 5 ppm.When the chemical equivalent ratio is 1,the concentration of NO_X is between 10-30 ppm.Therefore,in the lean burning region,the NO_X emission level of the swirling burner is mainly controlled by the chemical equivalent ratio,with the chemical equivalent.The increase in ratio increases rapidly.When the chemical equivalent ratio is more than the lean burn,the CO emission concentration varies greatly.When the fuel rate is greater than 4.0L/min,the CO concentration is less than 40 ppm.When the fuel rate is less than3L/min,the emission concentration of CO is greatly increased,at most close to 1000 ppm.When the chemical equivalence ratio is 1,the CO content in the flue gas is very low,less than 10ppm.Therefore,although the system can improve the combustion efficiency under the low chemical equivalent ratio,a large number of CO will be produced.This situation should be taken into account in the design of the burner.To sum up,based on the Rijke swirl burner,the research of thermoacoustic instability is carried out,and the information of the platform collection is set up and analyzed,which provides important basic research data for the design,development and safe operation of gas turbine.