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DT-3 is a high performance low-freezing monopropellant developed in the 1980s in China, DT-3 is also the world's first practical use of low freezing point propellant. As a monopropellant for pose control, it is necessary to precisely control the thrust output. In this paper, a three-dimensional simulation is conducted, mass flow rate, preheating temperature and the size of the catalytic bed are studied for the controlling of thrust and start-up process. The results indicate that: When the mass flow is around 92.8 g/s, the thrust force reaches the designed thrust. Increasing mass flow, will lead to the temperature rise in the catalytic bed, and thus slightly accelerate the reaction process, eventually obtaining a relatively small propellant remaining at the catalytic bed exit position. Secondly, the increase in the preheat temperature facilitates faster entry of the thruster into the desired output state, while the impact on the final thrust is limited. Thirdly, the length of the posterior catalytic bed has an optimal value, the short catalytic bed causes the components to not react completely, excessive catalytic bed will affect the thrust output, and the best length is around 32 mm. [ABSTRACT FROM AUTHOR]

The combustion processes of Ammonium perchlorate/Hydroxyl-terminated polybutadiene (AP/HTPB) aerospace propellant are analytically studied to determine the effect of wall materials and thickness on the heat transfer characteristics within a solid micro thruster. In this study, the flow and combustion characteristic of the propellant are described in terms of a combustion rate equation associated with a chemical reaction kinetics model. The profiles describing changes in the combustion surface by the user-defined function (UDF) are used to obtain the distribution of temperature and content of propellant using a numerical method. The combustion time and thrust are simulated to validate the results by comparing them with the results from the literature. Moreover, we demonstrate that a smaller thermal conductivity and a larger heat capacity of the wall material can lead to improvement in the thruster performance. Finally, analyzing the significant effects of wall thickness the heat transfer characteristics within the thruster allowed us to determine an optimal wall thickness value. [ABSTRACT FROM AUTHOR]

In the paper, the influences of cross-sectional area of iron core and ampere turn on the static electromagnetic characteristics have been studied through numerical simulation method. The iron core’s structure was redesigned in order to achieve the strong electromagnetic force. The ampere turn has greatly effects on the electromagnetic force for the magnetic saturation phenomenon; the oversize ampere turn would weak the electromagnetic conversation owing to the energy losses. Besides that, in order to quantitatively find out the effects of solenoid valve parameters on the dynamic response characteristics, the dynamic process of solenoid valve has been simulated. After the simulation method is validated by the experiment, the influences of four parameters (i.e. firing current, holding current, spring pre-tightening force and spring stiffness) on the whole process of the solenoid valve have been studied. The results show that the four parameters have great effects on the dynamic response characteristics of solenoid valve. The firing current impacts the opening process and holding current impacts the closing process, respectively. The spring pre-tightening force has influence on both the opening process and closing process. The spring stiffness almost has no effect on the dynamic characteristics of solenoid valve. [ABSTRACT FROM AUTHOR]

Cavitation is a common phenomenon in diesel injector and has a strong influence on the internal flow. However, studies so far have focused on cavitation characteristics inside the nozzle. Its influence on the flow during control valve opening remains still unclear. In the paper, a computational study focused on the flow and cavitation phenomena within control valve has been reported and the effects of control valve’s structure parameters (including rounded edge, seal cone angle and outflowing control-orifice structure) on the flow and cavitation characteristics have been investigated in detail. Firstly the 3D model has been validated in terms of single injection quantity and fuel injection duration, showing a good consistency. And then, the development from sheet cavitation to cloud cavitation and the relationship between cavitation, pressure and velocity has been discussed. Based on the numerical results obtained, it is shown that not only the variation of pressure but also the velocity is the important factor which affects cavitation. The increase of the flow velocity reduces the pressure within the flow field which can aggravate the development of cavitation. As cavitation region increases, the fuel flow is hindered and the flow velocity decreases. However, the decrease of flow velocity has suppressed the development of cavitation. All of those variations form a cyclical process. [ABSTRACT FROM AUTHOR]

In the present paper, the effects of driving current and solenoid valve’s structure parameters (including iron-core’s length, magnetic pole’s cross-sectional area, coil turn, coil’s position, armature’s thickness, damping hole’s position, damping hole’s size, and width of working air–gap) on the static electromagnetic characteristics have been numerically investigated. From the results, it can be known that the electromagnetic energy conversion will be seriously influenced by driving current for its effects on magnetic field strength and magnetic saturation phenomenon, an excessive increase of current will weak electromagnetic energy conversion for the accelerating power losses. The capacity of electromagnetic energy conversion is also relative to each solenoid valve’s parameter albeit it is not very sensitive to each parameters. The generated electromagnetic force will be enhanced by rising iron-core’s length, equalizing the cross-sectional areas of major and vice poles, increasing coil turn within a moderate range, closing the coil’s position towards armature’s centre, enlarging armature’s thickness, pushing the damping holes’ positions away from armature’s centre, reducing the sizes of damping holes, and reducing the width of working air–gap; but such enhancements won’t be realized once the driving current is excessively higher. [ABSTRACT FROM AUTHOR]

The present investigation numerically studies the evolutions of decomposition and combustion within an ADN-based thruster, and the effects of the catalyst-bed’s three structure parameters (length, diameter, and wall thickness) on the general performance of ADN-based thruster have been systematically investigated. Based upon the calculated results, it can be known that the distribution of temperature gives a Gaussian manner at the exits of the catalyst-bed and the combustion chamber, and the temperature can be obviously effected by each the three structure parameters of the catalyst-bed. With the rise of each the three structure parameter, the temperature will first increases and decreases, and there exists an optimal design value making the temperature be the highest. Via the comparison on the maximal temperature at combustion chamber’s exit and the specific impulse, it can be obtained that the wall thickness plays an important role in the influences on the general performance of ADN-based thruster while the catalyst-bed’s length has the weak effects on the general performance among the three structure parameters. [ABSTRACT FROM AUTHOR]

The influence of four typical injection rate-shapes on direct injection highly-intensified diesel engine combustion process is studied by using three-dimensional CFD software. Through the analysis of ignition delay, heat release rate shape, ratio of premixed combustion and diffusion combustion heat release, the gravity of the combustion process, it shows that; the ignition delay of rectangular injection rate is the shortest, and it gets fired first. The ignition delay of slope-shaped injection rate is the longest. Heat release accounts of the premixed combustion stage of rectangular and trapezoidal injection rate have a larger proportion, and the gravity of combustion process is closer to the top dead center (TDC), combustion capacity is higher, thermal efficiency is higher. Heat release accounts of slope and wedge-shaped premixed combustion stage takes relatively small proportion. [ABSTRACT FROM AUTHOR]

Hydroxylamine nitrate (HAN) is widely considered as a green, non-toxic liquid propellant. Here, given the complex chemical and physical processes occurring in a HAN-based thruster, the steady-state working of such a thruster was studied using a numerical simulation approach. The catalytic decomposition and combustion processes of a HAN/methanol propellant were simulated as a chemical reaction model consisting of 15 species and 11 elementary reactions. By establishing a three-dimensional model of the HAN-based thruster validated by the experiment. In addition, the effects on the performance of the HAN-based thruster of varying fore-catalytic bed porosity, after-catalytic bed porosity and the inlet mass flow rate were investigated. The results showed that the porosity of the fore-catalytic bed had the significant effect on the catalytic decomposition and combustion reaction of the propellant, and the combustion characteristics of the fuel were improved with the change of the porosity of the after-catalytic bed. In addition, the most obvious finding to emerge from this study was that the performance of thruster was improved with the increase of inlet mass flow rate. The results from this paper were expected to provide a reference for the future design and performance evaluation of HAN-based thrusters. • The catalytic decomposition and combustion characteristics of HAN-based thruster were studied by numerical simulation. • Effect of the porosity of fore-catalytic bed on the working process of HAN-based thruster was studied. • Effect of the porosity of after-catalytic bed on the working process of HAN-based thruster was studied. • Effect of inlet mass flow rate on the working process of HAN-based thruster was studied. [ABSTRACT FROM AUTHOR]