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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]

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]

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]

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]