The effectiveness of perforated liner with bias flow on the control of combustion instability is investigated. Combustion instabilities result from the coupling between acoustic waves and unsteady combustion heat rele...The effectiveness of perforated liner with bias flow on the control of combustion instability is investigated. Combustion instabilities result from the coupling between acoustic waves and unsteady combustion heat release. Sometimes the phenomenon happens in afterburners of aeroengine and rocket engine, and it always causes damage to flame holders, liner seetions and other engine components. Passive methods, such as perforated liner, are often used to suppress such instabilities in application. In this article, first, a burner testbed is built in order to study the characteristic of this phenomenon. The unstable frequencies and unsta- ble area are investigated experimentally. Then an analytical model, based on "transfer element method", is developed and the numerical results are compared with those from experiments. At last the perforated liner is applied to the burner to suppress the instabilities. The results show that the sound pressure can be greatly reduced by the perforated liner.展开更多
In order to weaken the bias flow in the submerged entry nozzle （SEN） with slide- gate, the rotating magnetic field was imposed. The numerical method was employed to investigate the effect of rotating magnetic field ...In order to weaken the bias flow in the submerged entry nozzle （SEN） with slide- gate, the rotating magnetic field was imposed. The numerical method was employed to investigate the effect of rotating magnetic field on the flow field in the SEN and the mold under different slide-gate opening ratios. Numerical results showed that when the slide-gate opening ratio is smaller than 100%, the flow field in the SEN and the mold become asymmetry and there is an obvious circulation under the slide- gate in the SEN. With increasing exciting current, the divergent angle of liquid steel at the SEN outlet increases, the impact depth of liquid steel in the mold decreases. With increasing slide-gate opening ratio, the impact depth of liquid steel in the mold increases and the required exciting current to weaken the bias flow should increase.展开更多
在真空环境下,用采集板模拟离子作用将电子束从ECR中和器中引出,实验研究ECR中和器结构以及工作参数对引出电子束流和中和器性能的影响,从而确定最佳的ECR中和器结构和工作参数。实验结果表明:在最佳的ECR中和器结构组合条件下,气体流量...在真空环境下,用采集板模拟离子作用将电子束从ECR中和器中引出,实验研究ECR中和器结构以及工作参数对引出电子束流和中和器性能的影响,从而确定最佳的ECR中和器结构和工作参数。实验结果表明:在最佳的ECR中和器结构组合条件下,气体流量0.8 m L·min-1、电子束引出偏压88.6 V时,可以引出103.8 m A的束流,推进剂利用效率和电子损耗分别为1.278 9和194.573 W·A-1,能满足ECR离子源离子引出束流的需要。展开更多
Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error...Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.展开更多
基金National Natural Science Foundation of China (50890181)Aeronautical Science Foundation of China (2009ZB51)
文摘The effectiveness of perforated liner with bias flow on the control of combustion instability is investigated. Combustion instabilities result from the coupling between acoustic waves and unsteady combustion heat release. Sometimes the phenomenon happens in afterburners of aeroengine and rocket engine, and it always causes damage to flame holders, liner seetions and other engine components. Passive methods, such as perforated liner, are often used to suppress such instabilities in application. In this article, first, a burner testbed is built in order to study the characteristic of this phenomenon. The unstable frequencies and unsta- ble area are investigated experimentally. Then an analytical model, based on "transfer element method", is developed and the numerical results are compared with those from experiments. At last the perforated liner is applied to the burner to suppress the instabilities. The results show that the sound pressure can be greatly reduced by the perforated liner.
基金financially supported by the National High Technical Research and Development Programme of China (No. 2009AA03Z530)the National Natural Science Foundation of China and Shanghai Baosteel (No. 50834010)+3 种基金the National Natural Science Foundation of China (Nos. 51174058, 51104047 and 51004035)111 Project (No. B07015)the Fundamental Research Funds for the Central Universities(No. N100409007)the Doctor Startup Foundation of Liaoning Province (No.20111009)
文摘In order to weaken the bias flow in the submerged entry nozzle （SEN） with slide- gate, the rotating magnetic field was imposed. The numerical method was employed to investigate the effect of rotating magnetic field on the flow field in the SEN and the mold under different slide-gate opening ratios. Numerical results showed that when the slide-gate opening ratio is smaller than 100%, the flow field in the SEN and the mold become asymmetry and there is an obvious circulation under the slide- gate in the SEN. With increasing exciting current, the divergent angle of liquid steel at the SEN outlet increases, the impact depth of liquid steel in the mold decreases. With increasing slide-gate opening ratio, the impact depth of liquid steel in the mold increases and the required exciting current to weaken the bias flow should increase.
文摘在真空环境下,用采集板模拟离子作用将电子束从ECR中和器中引出,实验研究ECR中和器结构以及工作参数对引出电子束流和中和器性能的影响,从而确定最佳的ECR中和器结构和工作参数。实验结果表明:在最佳的ECR中和器结构组合条件下,气体流量0.8 m L·min-1、电子束引出偏压88.6 V时,可以引出103.8 m A的束流,推进剂利用效率和电子损耗分别为1.278 9和194.573 W·A-1,能满足ECR离子源离子引出束流的需要。
文摘Quasi-longitudinal waves are one type of structural waves, which are important at high frequencies. This paper studies the estimate theory and measurement technique of quasi-longitudinal waves, analyzes the bias error due to the effect of bending waves. In a two-dimensional quasi-longitudinal wave held, the intensity vector is the sum of the effective intensity vector and the intensity variation vector. Its axial component is proportional to two imaginary parts of cross spectral densities and in the measurement, it is measured by a pair of two-transducer arrays. In a one-dimensional quasi-longitudinal wave field, the intensity variation is zero, the intensity is proportional to only one imaginary part of a cross spectral density and it can be measured using a two-transducer array. If bending and quasi-longitudinal waves coexist and the contribution from bending waves cannot be eliminated or reduced to a certain extent, the measured quasi-longitudinal wave intensity will contain a large error. The results measured on the three-beam structure show that quasi-longitudinal wave intensity can be accurately measured using the intensity technique when bending waves are negligible in comparison with quasi-longitudinal waves.
