Atmospheric pressure pulsed modulated arc discharge plasma

Direct-current(DC)arc plasma has great application values in the field of the chemical industry,but it has the problem of low energy efficiency.Facing the requirement for improving the energy efficiency of the arc,this paper proposes a unique method of pulsed modulated arc(PMA).This method uses high-frequency pulses and reduces the arc current to improve the control of electron temperature.The electrical characteristics,optical characteristics and products are tested.The test results show that during the PMA process,all of the experimental results which include voltage,current and light will significantly increase.These results are analyzed from the perspective of functionality,repeatability and energy conversion.The analysis results show that although the PMA method does not show good parameter consistency,it has potential application prospects because it increases the energy conversion rate by 4.5%and 8%from the perspective of light and products,respectively.

Numerical simulation of the start-up process of a miniature ion thruster

A particle-in-cell Monte Carlo collision model of a discharge chamber is established to investigate the start-up process of a miniature ion thruster.We present the discharge characteristics at different stages(the initial stage,development stage,and stable stage)according to the trend of the discharge current with time.The discharge current is the sum of the sidewall current and the backplate current.During the start-up process,the sidewall current lags behind the backplate current.The variation and distribution characteristics of the discharge current over time are determined by the electron density distribution and electric potential distribution.

基于数据驱动的扭转度偏差对压气机性能的影响

为研究引入扭转度偏差维数变化以及相关性变化对压气机性能量化结果的影响,以某压气机转子叶片扭转度偏差测量结果为基础,采用基于数据驱动的非嵌入式多项式混沌方法,量化研究了叶片扭转度偏差对单级轴流亚声速压气机气动性能的不确定性影响,并进行了敏感性分析。研究结果表明:各工况点处压气机性能标准差均随着引入扭转度偏差维数的增加而减小。通过量化对比发现,考虑叶顶和叶根2个截面上的扭转度偏差,足以保证压气机性能标准差以及性能概率分布形式的收敛性。而在敏感性分析中发现,引入的扭转度偏差维数越多,可以更准确的判别压气机性能最敏感的扭转度偏差区域。随着各截面上扭转度偏差之间相关性逐渐增强,各工况下压气机性能的波动程度也逐渐增强,压气机性能对各扭转度偏差的一阶敏感性指标的差距也逐渐减小,但压气机性能对各截面上扭转度偏差敏感程度的排序并没有改变。

Novel data-driven sparse polynomial chaos and analysis of covariance for aerodynamics of compressor cascades with dependent geometric uncertainties

Polynomial Chaos Expansion(PCE)has gained significant popularity among engineers across various engineering disciplines for uncertainty analysis.However,traditional PCE suffers from two major drawbacks.First,the orthogonality of polynomial basis functions holds only for independent input variables,limiting the model’s ability to propagate uncertainty in dependent variables.Second,PCE encounters the"curse of dimensionality"due to the high computational cost of training the model with numerous polynomial coefficients.In practical manufacturing,compressor blades are subject to machining precision limitations,leading to deviations from their ideal geometric shapes.These deviations require a large number of geometric parameters to describe,and exhibit significant correlations.To efficiently quantify the impact of high-dimensional dependent geometric deviations on the aerodynamic performance of compressor blades,this paper firstly introduces a novel approach called Data-driven Sparse PCE(DSPCE).The proposed method addresses the aforementioned challenges by employing a decorrelation algorithm to directly create multivariate basis functions,accommodating both independent and dependent random variables.Furthermore,the method utilizes an iterative Diffeomorphic Modulation under Observable Response Preserving Homotopy regression algorithm to solve the unknown coefficients,achieving model sparsity while maintaining fitting accuracy.Then,the study investigates the simultaneous effects of seven dependent geometric deviations on the aerodynamics of a high subsonic compressor cascade by using the DSPCE method proposed and sensitivity analysis of covariance.The joint distribution of the dependent geometric deviations is determined using Quantile-Quantile plots and normal copula functions based on finite measurement data.The results demonstrate that the correlations between geometric deviations significantly impact the variance of aerodynamic performance and the flow field.Therefore,it is crucial to consider these correlations for accurately assessing the aerodynamic uncertainty.

Investigation of non-uniform leading-edge tubercles in compressor cascade:Based on multi-objective optimization and data mining

Corner stall receives noticeable attention in the aeroengine field as an important phenomenon in highly-load compressors.Non-uniform leading-edge tubercles,as an effective method to delay stall,are introduced into the compressor.In this paper,the shape of leading-edge tubercles was controlled by a third-order Fourier function.To judge corner stall,a more precise stall indicator for compressor cascade with flow control methods was defined.Besides,the total kinetic energy of the secondary flow at large incidence was adopted as a parameter for stall evaluation to save computing resources.The results of multiobjective optimization reveal that the loss coefficient exhibited negligible variation at design incidence,while the total kinetic energy of secondary flow showed a significant reduction at large incidence,resulting in a substantial increase in stall incidence.In the optimal profiling cases,the stall incidencewas delayed from 7.9°to 11.6°.The major purpose of the research is to provide proper design guidelines for nonuniformleading-edge tubercles and uncover the flow controlmechanisms of leading-edge profiling.Hence,the geometric features that meet different optimization objectives were extracted through geometric analysis near the Pareto Front and through Self-OrganizingMap(SOM)dataminingmethods in the optimization database.Besides,flow field analysis reveals the flow control mechanism of leading-edge tubercles.The convex-concave-convex structure at the 0%-70%blade height region can form two branches of leading-edge vortex pairs that are opposite in the rotation direction to the passage vortex.The two branches of leading-edge vortex pairs mixed with the leading-edge separation vortex to form two stronger mixed vortices,which can effectively suppress the development of passage vortex and delay stall incidence.

Energy regulation of impulse current generator modulated DC arc discharge

This paper proposes a method of impulse current generator modulated DC arc by combining the advantages of pulse and the RF to solve the low electron energy problem of direct current arc.Through experimental analyzing the electrical,spectral,and optical characteristics of the arc,the effect of impulse current generator(ICG)on improving electron energy is discussed.The results show that the ICG consumes more energy to enhance the strength of arc discharge,and therefore electron energy is increased in a microsecond scale.In addition,it is found that the electron energy of the arc discharge can be adjusted by varying inductance,capacitance,and discharge tube:increasing the inductance or capacitance can increase the electron energy firstly and then decrease it.In adjusting the three adjustable components,adjusting the inductor is the most effective method,followed by adjusting the capacitor,and adjusting the repetition frequency has the least effect.The reason is discussed,and it is believed that the results are related to leakage inductance and distributed capacitance.