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Arcjet thruster has been a widely used electrical propulsion technology on GEO satellites since 1993. In its long history of technical development and commercial application, lifetime verification of an arcjet thruster is always one of the most important and expensive tasks. Considering that the main life limitation of an arcjet thruster is electrode ablation and a significant share of the total ablation happens in its starting-up process, the starting-up process is studied with arc voltage signals. Through interpretation of arc voltage signals, the transfer process of the arc root on the anode surface is identified, and ΔT (the duration of the arc root transfer process) is suggested to be a characteristic parameter for fast evaluation of lifetime assessment and design optimization for an arcjet thruster. With this criterion, the influences of typical parameters on the starting-up process are established through comparison with a benchmark parameter. According to experimental results, an increase of the gas flow will obviously reduce ΔT, while a smaller swirl aperture and a longer throat channel do not have a remarkable correlation with ΔT. Moreover, with a sample of a smaller throat diameter to increase the flow velocity, a reduction of ΔT is achieved. Meanwhile, the modifications also affect the stability of arcjet thruster operation, which is also discussed.

During the operation of ADN (ammonium dinitramide, (NH4+N(NO2)2−))-based thrusters, the ADN-based liquid propellant, a non-toxic green energetic material, tends to flow boil in the capillary tube due to heat transfer from the wall. A three-dimensional transient numerical simulation of the flow boiling of ADN-based liquid propellant in the capillary tube was carried out using the VOF (Volume of Fluid) coupled Lee model. The flow-solid temperature and the gas–liquid two-phase distribution and the wall heat flux at different heat reflux temperatures were analyzed. The results show that the magnitude of the mass transfer coefficient of the Lee model significantly influences the gas–liquid distribution in the capillary tube. The total bubble volume increased from 0 mm3 to 957.4 mm3 when the heat reflux temperature was increased from 400 K to 800 K. The bubble formation position moves upwards along the inner wall surface of the capillary tube. Increasing the heat reflux temperature intensifies the boiling phenomenon. When the outlet temperature exceeded 700 K, the transient liquid mass flow rate in the capillary tube was already reduced by more than 50%. The results of the study can be used as a reference for the design of ADN-based thruster.

In this paper, the flame structure of a liquid propellant ammonium dinitramide–methanol aqueous solution in a small model thruster is investigated. The thruster is composed of an injector and a com...

In this paper, the combustion process of liquid propellant ammonium dinitramide (ADN)-methanol aqueous solution in a small space thruster is investigated experimentally and numerically. The phase Doppler anemometer measurement is used to investigate the injection process and the results are used as the liquid boundary condition in the simulation to minimize uncertainties. Hot fire tests have also been operated to estimate the performance of the thruster. To simulate the complicated processes in the thruster, a modified multi-component droplet model is employed to simulate the evaporation process considering the interaction between the liquid droplet and the porous media. A non-equilibrium model for the porous media is used to describe the heat transfer in the catalyst bed. A reduced chemical mechanism containing 18 species and 40 reactions is used to simulate the reactions of gas-phase ADN and methanol. The results show that the decomposition of ADN and the oxidization of methanol do not happen synchronously in the chamber. The decomposition of ADN takes place near the inlet while methanol is oxidized downstream of the porous media. The establishment of pressure in the thruster depends on the evaporation and reaction processes and the temperature changes relatively slowly because the porous media increases the thermal inertia of the whole system.

In this work, the evaporation and combustion processes of liquid propellant ammonium dinitramide–methanol aqueous solution were investigated by a thermogravimetric analyzer and a Curie-point pyrolysis unit, respectively, and the gas-phase products were measured by a Fourier transform infrared spectroscopy. The results showed that methanol and water evaporated first, followed by the decomposition of ammonium dinitramide at heating rates of 5–15°C/min. When a catalyst was added, ammonium dinitramide decomposed much faster and released heat that let methanol evaporate immediately as the propellant solution was in contact with the catalyst particles. To explore how the decomposition of ammonium dinitramide is coupled with the oxidation of methanol, the propellant solution was heated by a Curie-point pyrolysis unit at a rate of 3000°C/s to temperatures ranging from 160 to 670°C. Large amounts of nitrous oxide and ammonia were detected at all temperatures, suggesting that most of the decomposition of ammonium d...

With the increasing of space activities and people’s awareness of environmental protection, it is necessary to develop a new non-toxic space propulsion system with high performance. Hydroxylammonium nitrate (HAN)/1-ethyl-3-methyl-imidazolium ethylsulfate([Emim][EtSO4]) blend ionic liquid propellant is a potential replacement with non-toxic and high-performance characteristics for hydrazine type liquid propellants, which can be used in both chemical and electrical propulsion system. This paper introduced the thermogravimetric experimental analysis (TGA-DSC) results of HAN/[Emim][EtSO4] ionic liquid propellant with the thermal decomposition and catalytic decomposition process. Its mass-loss process and exothermic process under different reaction conditions at a heating rate of 5K/min~15K/min were studied. Generally, the mass-loss results showed that there were four characteristic stages during the decomposition process of the HAN/[Emim][EtSO4] ionic liquids, which were the evaporation of the water solvent, decomposition of the HAN component, further decomposition of the [Emim][EtSO4], and slow loss of the residual substances. At the same time, two exothermic peaks were observed, which respectively corresponded to the decomposition of HAN and the further decomposition of [Emim][EtSO4]. Using catalyst can significantly reduce the decomposition temperature of the propellant and the residual mass. The contents in this paper proved that this propellant had a good application prospect within the catalytic ignition aerospace thruster.

In this study, a high specific impulse Hall thruster, HEP-140MF, having a high discharge voltage, was used to accelerate ions. We aimed to obtain a high specific impulse and an acceleration zone moving downstream toward the channel exit to reduce wall sputtering erosion of the walls of the discharge channel, hence ensuring an enhanced lifetime. To study the lifetime characteristics of the high specific impulse Hall thruster, a life test was performed on the HEP-140MF thruster for the first time, and performance parameters, such as thrust, specific impulse, and efficiency, were measured. Changes in the performance parameters and evolutions in the surface profiles of the discharge channel wall were summarized. The reasons contributing to these changes during the life test were analyzed. Moreover, the accelerated life test method was validated on the HEP-140MF.

The working processes of the ADN-based liquid thruster are complex, utilizing catalytic decomposition in a catalyst bed and high-pressure combustion in the combustion chamber. The present study examines the experimental performance of high-pressure combustion in an ADN-based liquid thruster. Using the Tunable Diode Laser Absorption Spectroscopy (TDLAS) method, flow parameters such as gas temperature and the characteristic species concentration of CO in the combustion chamber were measured instantaneously under the atmospheric environment. The effects of propellant inlet pressure and the catalyst bed preheated temperature on the combustion process were evaluated. It was found that both an increase in the propellant inlet pressure and an increase in the catalyst bed preheated temperature led to an increase in the gas temperature and a decrease of the CO mole fraction in the combustion chamber. In a hot fire test in the vacuum chamber, the performance of the model thruster under steady operation was tested. The results showed that with the increase of propellant inlet pressure, the combustion chamber pressure and the combustion chamber wall temperature also increase. However, although the increase of the catalyst bed preheated temperature also led to the increase of the combustion chamber wall temperature, the combustion chamber pressure remained nearly constant. These results provide a better understanding of the mechanisms of high-pressure combustion with ADN-based liquid propellants, which is beneficial to the development of green aerospace propulsion techniques. (C) 2015 Elsevier Masson SAS. All rights reserved.

Ammonium Dinitramide (ADN) is a chemical propellant with high-performing, green, and storable characteristics. It has been used as solid propellant and liquid propellant which represents a new trend in chemical propulsion technology. The present study discussed the experimental investigations of a model aerospace thruster with ADN-based liquid propellant. The catalytic decomposition and combustion processes of the ADN-based thruster is significantly complicated. And only few literatures are focused on this topic. In this paper, based on quantum cascade laser (QCL), the combustion process in the ADN-based thruster was investigated. Carbon monoxide(CO) is a characteristic species produced during the chemical reaction of ADN-based liquid propellant. Through the measurement of CO concentration, the complicated catalytic decomposition and combustion processes was described quantitatively. These results are valuable for a better understanding of the mechanisms of the catalytic decomposition and combustion with ADN-based liquid propellant, which is beneficial to the development of green aerospace propulsion techniques.

The pressure oscillation within combustion chambers of aeroengines and industrial gas turbines is a major technical challenge to the development of high-performance and low-emission propulsion systems. In this paper, an approach integrating computational fluid dynamics and one-dimensional linear stability analysis is developed to predict the modes of oscillation in a combustor and their frequencies and growth rates. Linear acoustic theory was used to describe the acoustic waves propagating upstream and downstream of the combustion zone, which enables the computational fluid dynamics calculation to be efficiently concentrated on the combustion zone. A combustion oscillation was found to occur with its predicted frequency in agreement with experimental measurements. Furthermore, results from the computational fluid dynamics calculation provide the flame transfer function to describe unsteady heat release rate. Departures from ideal one-dimensional flows are described by shape factors. Combined with this information, low-order models can work out the possible oscillation modes and their initial growth rates. The approach developed here can be used in more general situations for the analysis of combustion oscillations. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

The present study discusses a general distributed transfer function for non-premixed flames based on conservation equations. Also, a distributed transfer function for idealized, two-dimensional, flat, non-premixed flames is calculated using Green's function method. The unsteady heat release can be represented in terms of thermodynamic relationships based on energy conservation equations. By this method, the distributed flame response in physical domain for both combustion zone and its further downstream is intensively investigated. The lumped unsteady heat release can be obtained by the integration along the axial coordination. For distributed heat release transfer function in frequency domain, a dual-peak response of magnitudes is observed in the fuel-rich zone and the fuel-lean zone, respectively. The processes of the generation and the evolution of hot spots in non-premixed flames are also investigated. Analysis of multiple related parameters is conducted to evaluate the effects of the Strouhal number,...