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The energy supply mode of a micro-cathodic arc thruster (μ-CAT) was adjusted based on the charge and discharge characteristics of the energy storage element, and the cathode discharge characteristics of μ-CAT were studied under different energy supply modes. We applied an electrical method to measure the discharge characteristics of μ-CAT, with an enhanced intensified charge coupled device spectrum detector to measure the plasma parameters of μ-CAT, allowing analysis of the internal logic among thruster plasma parameters, arc discharge characteristics, and thruster energy supply mode. The mechanisms of μ-CAT were analyzed and characteristics of accumulated discharge, energy distribution, and ion velocity distribution of thruster were compared under different energy supply modes to obtain the effect of the energy supply mode on the discharge characteristics of the interelectrode of μ-CAT. The results show that the energy supply mode of μ-CAT affected the ionization characteristics and ionization stability of the micro-cathodic arc thruster, causing a multistage ionization difference in the cathode metal target. This would not only affect the propulsion performance of the thruster, but also affect the change of the number of particles in the cathode region in a single discharge cycle. [ABSTRACT FROM AUTHOR]

Purpose: The geometric parameters of the compressor blade have a noteworthy influence on compressor stability, which should be meticulously designed. However, machining inaccuracies cause the blade geometric parameters to deviate from the ideal design, and the geometric deviation exhibits high randomness. Therefore, the purpose of this study is to quantify the uncertainty and analyze the sensitivity of the impact of blade geometric deviation on compressor stability. Design/methodology/approach: In this work, the influence of blade geometric deviation is analyzed based on a subsonic compressor rotor stage, and three-dimensional numerical simulations are used to compute samples with different geometric features. A method of combining Halton sequence and non-intrusive polynomial chaos is adopted to carry out uncertainty quantitative analysis. Sobol' index and Spearman correlation coefficient are used to analysis the sensitivity and correlation between compressor stability and blade geometric deviation, respectively. Findings: The results show that the compressor stability is most sensitive to the tip clearance deviation, whereas deviations in the leading edge radius, trailing edge radius and chord length have minimal impact on the compressor stability. And, the effects of various blade geometric deviations on the compressor stability are basically independent and linearly superimposed. Originality/value: This work provided a new approach for uncertainty quantification in compressor stability analysis. The conclusions obtained in this work provide some reference value for the manufacturing and maintenance of rotor blades. [ABSTRACT FROM AUTHOR]

In this paper, the relationship between the morphology of the cathode crater and plasma ionization between thrusters is studied by adjusting the input energy of the micro-cathode arc thruster (μ CAT). We monitor the morphology of the cathode crater of the μ CAT using scanning electron microscopy and explore the relationship between the crater morphology and the internal energy loss of the cathode crater. This relationship, combined with the numerical simulation results, is used to monitor the ionization between the electrodes of the μ CAT using an enhanced intensified charge coupled device spectrum detector. The effect of cathode crater morphology on the ionization of the propellant during the operation of the μ CAT is determined. The results show that with a change in the input power processing unit voltage, the external profile and depth-to-diameter ratio of the cathode crater change, resulting in a change in the internal energy loss of the thruster cathode crater and then affecting the ionization efficiency of the cathode working fluid in the μ CAT. Under the condition of basically unchanged cathode feed energy flow density, reasonable adjustment of the depth-to-diameter ratio of the cathode crater can effectively improve the ionization efficiency of the cathode working fluid in the μ CAT. [ABSTRACT FROM AUTHOR]

The impact of geometric deviation due to manufacturing on compressor performance is considerable in engineering practice. To investigate the impact of blade thickness deviation on compressor performance and flow loss at various rotational speeds, a three-dimensional steady numerical simulation on Rotor 37 was conducted. The quantification of uncertainty was accomplished using a non-intrusive polynomial chaos method. The viscous dissipation coefficient was introduced to analyze the uncertain influence of blade thickness deviation on flow loss. Based on the type of loss source, the flow field was divided into six regions, including the blade tip region, blade root region, leading edge region, trailing edge region, blade surface region, and mainstream region. The results indicate that the sensitivity of total pressure ratio to thickness deviation increases significantly with an increase in the rotational speed. Under peak efficiency conditions, the effect of blade thickness deviation on flow dissipation in leading edge region decreases initially and then increases with an increase in the rotational speed. Meanwhile, the impact on flow loss in other regions increases with the increase in the rotational speed. Under near stall conditions, the blade thickness deviation has a great impact on the flow losses in the blade tip region, leading edge region, and mainstream region at 60% design rotational speed. However, the blade tip region and trailing edge region are more noticeably affected at 100% design rotational speed. Furthermore, the quantification of standard deviation of flow losses in various regions under different rotational speeds and conditions reveals that the flow loss fluctuation in the leading edge region and mainstream region varies with changes in operating conditions and rotational speeds, but the fluctuation of flow loss in other regions is independent of the rotational speed. [ABSTRACT FROM AUTHOR]

In this study, the material loss relationship between the electrodes of a micro-cathodic arc thruster was investigated by adjusting the input voltage. The crater morphology of the micro-cathodic arc thruster was observed with a scanning electron microscope. The internal crater material was analyzed with an energy spectrum analyzer. On this basis, the arc path is obtained and the material loss of the structure between the electrodes of the micro-cathodic arc thruster was studied through further numerical simulation. The experimental and simulation results show that with a change in the Power processing unit (PPU) input voltage of the micro-cathodic arc thruster, the material distribution in the cathode crater and the discharge channel between the electrodes changed, affecting the bombardment of ions between the electrodes of the thruster on the insulating structure and conductive coating. In engineering applications, regulation of the arc breakdown path can effectively reduce the total energy of ion bombardment on the wall. • Study on micro-morphology and composition distribution characteristics of arc crater of micro-cathode arc thruster. • Study on the distribution characteristics of PPU input voltage and discharge channel between thrusters. • The ion bombardment on the wall under different discharge channels is simulated. • With the increase of PPU input voltage, the dominant factor of inter-electrode structure loss changes. [ABSTRACT FROM AUTHOR]

Micro-cathode arc thrusters have been widely used in micro-nanosatellites owing to their high specific impact, long lifetime, repeatable startup, low thrust and high control precision. Micro-cathode arc thrusters and their derivatives are currently being developed and optimized. The micro-cathode arc thruster can generate plasma stably and efficiently, and form a thrust force under a magnetic field with very low power in pulsed operation mode. This paper reviews the last 20 years of literature on micro-cathode arc thrusters, with a focus on papers published in this field in the last 5 years. In light of the development of the micro-cathode arc thruster and the latest research, the direction of future development and the application of key technologies are reviewed. Future micro-cathode arc propulsion systems are expected to exhibit higher reliability, longer lifetimes, higher specific impact, greater integration and higher thrust and to be operated in various modes. [ABSTRACT FROM AUTHOR]

To explore the effect of energy input on the discharge characteristics of a micro cathode arc thruster, the relationships between the different input PPU voltages of the micro cathode arc thruster and the plume shape, arc characteristics, thruster propulsion performance, and working fluid ionization are characterized in this research. The results obtained using a high-speed camera indicate that the change in the thruster's energy input affects the plume contraction. Further, the results of spectroscopy and electrical testing analyses show that an increase in the thruster input voltage prolongates the arc duration, ionization rate of the arc, and degree of plume contraction. When the thruster is in a low input voltage state, the arc ionization rate primarily affects thrust-to-power ratio. However, when the thruster is in a high input voltage state, the degree of plume contraction primarily affects propulsion efficiency. • The effect of Energy Input on the Discharge Characteristics of the Thruster is studied. • The electrical and spectroscopic diagnosis results of the micro-cathode arc thruster are given. • Changes in energy input will affect the proportion of high-energy ions, thereby affecting the ion velocity in the plume. • The increase in ion velocity leads to an increase in the radial loss of plume energy. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the effect of pulse frequency on the discharge characteristics of a micro-cathode arc thruster. We used an intensified charge-coupled device (ICCD) and high-resolution spectrometer to capture the plasma emission process of a micro-cathode arc thruster. The change in the valence ion ratio under different discharge frequencies of the thruster is studied with respect to the change in light intensity. The relationship between the pulse frequency and Ti + ion ratio, cathode emission plasma bunch velocity, and normalized thrust are studied. The spectral and electrical test results demonstrate that the proportion of high-energy ions emitted from the cathode increases with the increase in interpole discharge frequency, and the ion bunch velocity and normalized thrust of the thruster are both improved. • The effect of pulse frequency on the discharge characteristics of the thruster is studied. • The electrical and spectroscopic diagnosis results of the micro-cathode arc thruster are given. • The change of pulse frequency will affect the arc background pressure and thus affect the arc concentration. • The increase in arc concentration leads to an increase in the proportion of high-energy ions emitted by the cathode. [ABSTRACT FROM AUTHOR]

In this study, a high-speed camera was used to capture the ionization process of a Hall thruster with slits on the side of its discharge channel, and the change in light intensity was used to study ionization variations in the thruster channel. The light intensity was distributed along the axis, following a normal distribution. The peak position of the ionization intensity, ionization width fluctuation, and low-frequency oscillation of the Hall thruster was investigated. Experiments and simulations show that the oscillation frequency of the peak position of ionization intensity and the width of the main ionization zone are the same as the frequency of low-frequency oscillations. When discharge current increases, the peak position of ionization intensity moves towards the channel exit and the ionization width narrows during the decay of discharge current oscillations. Moreover, theoretical analyses show that the characteristics of the ionization distribution in the channel under a low-frequency-oscillation time scale are primarily governed by the ionization and supplementation of the mass flow rate. • The plasma distribution image in the inner channel of the Hall thruster is studied. • The discharge situation of the Hall thruster under low frequency oscillation is given. • The channel ionization parameters in the Hall thruster change periodically. • There is a coupling relationship between channel ionization in Hall thruster and low frequency oscillation. [ABSTRACT FROM AUTHOR]

• On-orbit non-intrusive perturbation measurement of Hall effect thrusters. • 10 kHz to 100 kHz analysis better than full frequency domain. • Perturbation signal amplified by scatter numbers in the far-zero region. • The physical core represented by the scatter numbers is the dwell time. • Dwell time is mainly related to breathing oscillations. The failure of Hall effect thruster (HET) is usually the result of the accumulation of several tiny abnormal disturbances during operation. Timely and accurate early warning of perturbations is an important guarantee for the normal operation of thrusters. In this study, when the perturbation rate of HET signal (anode voltage or anode flow rate) is −4% to 4%, the time scale signal of breathing oscillation (BO) in the frequency range of 10 kHz to 100 kHz is statistically analyzed. Experiments show that when the signal is perturbed, the balance between ionization and acceleration of plasma in the discharge channel is destroyed, resulting in the dwell time of the wave peaks and valleys of BO in the far-zero region with the perturbation law, which visually shows that the number of scattered points at the corresponding current value changes regularly. According to the above statistical characteristics, this paper proposes a new condition monitoring index, namely the number of scattered points in the wave peaks side of the far-zero point area, and designs a perturbation indicator for the operating condition of the HET. Compared with direct monitoring of discharge current in engineering, this indicator can amplify the influence of the perturbation signal on BO, and has better identification and accuracy. Meanwhile, the indicator does not use invasive measurement and complex equipment, and is promising to be applied to the monitoring and diagnosis of the perturbation operation state of the on-orbit thruster. [ABSTRACT FROM AUTHOR]

Round combustors as a very desirable kind of supersonic combustor, face the difficulty of combustion organization. The typical cone-strut structure can accomplish some combustion organization, but it has a very high congestion ratio and is hence inefficient. To solve this problem, a method of combining cone-strut configuration and plasma/oxygen addition is proposed in this paper, and its scheme, experiment and combustion mechanism are studied. In the scheme of combustion organization, the fuel injection scheme and plasma arrangement scheme of the approach are projected, accomplished with the advantages of reducing congestion ratio from 20%-26%–13%. In the experiments of combustion organization, the effect of realizing combustion organization of such approach is proved, and three typical combustion organization states, which may be due to low congestion ratio, are displayed one by one, and its transformation speeds between three typical combustion organization states are investigated. In the speculations of mechanism, a set of simplified equations are provided for the first time, and these equations indicate that why the approach is effective and why the three kinds of combustion organization states display one by one. This research has theoretical and technical implications for the development of cone-strut configuration in round combustors. • Provide a combustion organization method of cone-strut/plasma torch with oxygen feedstock for round supersonic combustor. • Experiments confirm feasibility of this method and point out the key stage that affect combustion organization. • The wakeflow equations including combustion reaction is used to explain the feasibility and particularity of the method. [ABSTRACT FROM AUTHOR]

This study proposes a newly designed ignition circuit that does not change the ignition starting parameters of a Hall thruster, reduces the critical ignition voltage, and improves ignition reliability. The complexity and weight of the Hall thruster power supply system are reduced by multiplexing the ignition and discharge power supplies. Under the condition that the design parameters are satisfied, that is, R 3 + R E C 2 is much larger than RCC1, the residual energy in the circuit after the cathode breakdown can be fed into the thruster discharge channel to improve the ignition energy supply. The experimental results show that when the anode voltage is 98 V, only nine of the 100 ignition tests are successful using the traditional ignition circuit, whereas the number of successes using the newly designed ignition circuit is as high as 99, which provides a simple solution method for improving the ignition reliability. [ABSTRACT FROM AUTHOR]

A new method of dual-frequency excited plasma (DFEP) is proposed to enhance ignition for supersonic combustion chamber. It is demonstrated experimentally that this method successfully achieves the acceleration of flame establishment and achieves the purpose of intensified ignition for supersonic flame in a real axisymmetric supersonic combustion chamber. The differences between the DFEP method and the traditional DC excited plasma (DCEP) method in the stage of local-flame establishment, the state of local-flame holding, the state of global-flame backpropagation, and the state of global-flame downstream transport are compared. It is found that the DFEP method can not only shorten the time of the state of the local-flame holding from 292.2 ms to 49.3 ms, but also prevent the suspension of the global-flame when the global-flame is in backpropagation, but this method cannot increase the local-flame propagation velocity and the global-flame backpropagation velocity. Detailed analysis and speculate together indicate that the effect of DFEP on flame comes from its ability to reduce the suspension time of the flame. The reason why DFEP has such a ability is discussed, and a new view never projected before is speculated: ➀ The flame (and shockwave) itself is in an unstable equilibrium between the positive feedback of backpropagation, the negative feedback of flow and the constraint of the expanding section, and the suspension time of flame (as well as shockwave) is positively related to the probability of the shockwave leaving the expanding section by self-excited oscillation. ➁ The extra active O radicals generated by the DFEP can increase the combustion heat release rate and the shockwave intensity, thereby providing a new path to help heat accumulation and making the flame easier to escape from the expanding section under the action of self-excited oscillation. [ABSTRACT FROM AUTHOR]

Facing the requirement of flameholding in a supersonic combustion chamber, a flameholding experiment under dual frequency excited plasma (DF excited plasma) was carried out in an axisymmetric supersonic combustion chamber. The flame establishment process was observed by using a high-speed-camera, and the flameholding characteristics with or without DF excited plasma were analyzed under different equivalence ratio(ER). The experimental results show that the flame will be enhanced by using dual-frequency excitation plasma in the supersonic combustion chamber: the flameholding mode was transformed from a global flame to a local flame, as well as the pressure of the combustion chamber was decreased significantly, when the DF excited plasma is switched off. In the ER range of 0.51 (0.18+0.33)∼0.60 (0.18+0.42), the DF excited plasma could induce a transformation from a local to a global flame, while if the ER is too high (ER>0.69 (0.18+0.51)) or too low (ER<0.18), the action of the DF excited plasma always couldn't. A basic feedback mechanism of the flameholding was proposed, with the consideration of the experimental results. The O radicals generated by the DF excited plasma was one important factors for flame reverse propagation, and the existence of the global flame was another necessary factor. Under the combined action of the O radicals of DF excited plasma and the global flame, the positive feedback process in the combustion chamber will be intensified, and the flame will propagate reversely. [ABSTRACT FROM AUTHOR]