Theory And Numerical Simulation Of Spray Combustion Process In Regenerative Liquid Propellant Gun

In order to better understand the spray combustion process and the phenomenon of pressure oscillation in regenerative liquid propellant guns (RLPGs), this dissertation studies the jets spray combustion theory and pressure oscillation mechanism. It is compused of following aspects: the modeling and simulation of one dimensional particle trajectory model in the combustion chamber, the high-speed annular jets atomization mechanism, and the modeling and simulation of multiphase multidimensional flow in chamber. The main content of this paper can be summarized as follows:Firstly, a particle trajectory model of the combustion chamber of an RLPG is established, the gas field is described by unsteady Euler system while the liquid phase is described by the Lagrangian approach. The interaction of the two phases is expressed in the source terms of the equations. The numerical methods for the Euler and Lagrangian coupling euqations is studies. The spray combustion process is simulated by the code written by the author and the high-frequency oscillations are generated naturally. The time-space distributions of main physical parameters are analyzed. The low frequency signal of experimental data is extracted by the technique of wavelet method which is analysed by FFT and the mechanism of pressure oscillations simulated is analyzed. The effects of main structure parameters on the pressure oscillations are discussed.The numerical method of an axially symmetric two-dimensional multiphase reaction flow is established. The form of gas phase governing equations in arbitrary curve coordinate system is derived. Due to the flow field is irregular in RLPG, the combustion chamber is transformed to the rectangular field in computational plane under boundary-fitted coordinate system. Two ways of boundary-fitted grids generation are applied to generate grids in the combustion chamber. The calculation is conducted with MacCormack's two steps of predicted-correction scheme. The stability condition and artifical viscosity are presented. The difference scheme for the two movement boundaries of piston and projectile are deduced, which ensure the physical conservation at these boundaries. The analytic method is used for calculating the liquid phase. The numerical method of source terms is analyzed and the calculating equations are presented in detail.A high-speed liquid sheet spray model is presented for the annular jets in RLPG based on the linear stability analysis and surface wave breakup theory. In addition to the jets atomization, the drops breakup (secondary breakup) is considered. According to the above spray model, the spray structure and spray characteristic parameters are calculated and the influence of main spray factor on the spray characteristic parameters is studied simultaneously. The result indicates that the interior cavity of the annular jet keeps constriction, and gather like column ones finally while the annular jet moving down the injector orifice. There are mostly large droplets at the head of the spray field. The mean droplet diameter decreases with increase of time at a given cross section. The mean diameter decreases with increase of axial distance firstly, and increases later. It is distributed in valley form. The atomization effect can be improved by increasing injection pressure or decreasing the injector orifice size. The spray model is an important part of the interior ballistic multiphase multidimensional model of RLPG and will be used for the interior ballistic simulation.The experimental research of RLPG spray combustion process is carried out and the signal of pressure oscillations in combustion chamber is obtained. The signal process method of wavelet analysis is applied to analyze the experimental data. To better understand and reduce pressure oscillations, a multiphase multidimentional model named SACFIG has been written for the spray combution process in the chamber. The annular jet spray model has been used for the two-dimentional code. The hot spray structure and time-space distributions of main physical parameters under two-dimentional condition are gained. The high-frequency combustion instability is generated in the combustion chamber. The dominant mode of computational pressure oscillation is the second radial mode which coincides with the experiment data well. The mechanisms of the pressure oscillations are studied by two aspects: acoustic process in the chamber and combustion instability. The suppression measures of pressure oscillations are discussed finally.