Research Of Theory And Experiment About The Combustion Characteristic Of Solid Fuel Ramjet

In recent years, solid fuel ramjet (SFRJ) has attacted many attentions of researchers in the world due to the high special impulse and simple structure, it has a broad application prospect on supersonic missile and extended-range projectile. The application background of this paper was SFRJ of missile. Combined with theoretical analysis, numerical simulation and experimental investigation, the working state of SFRJ and the regression rate of solid fuel under the different operation conditions were studied detailedly and systematically. It had laid a foundation of theory and experiment for the developing of SFRJ. The main work of this paper was as follows.(1) Based on enthalpy balance method, this paper established fast prediction model of solid fuel regression rate of inner hole burning SFRJ, after completed analysis of the flow field in the solid fuel channel. And the prediction program was compiled. The factors which could effect the regression rate of solid fuel were considered in the model, such as, the combustion chamber inlet diameter, the channel diameter and length of solid fuel and the mass flow rate and total temperature of air. Aimed at SFRJ fueled by polyethylene (PE) and polymethlymetharylate (PMMA),34 calculations were carried out, the conclusions were as follows. The values of errors of the mean regression rate were between-14.4% and 13.5%, and average of absolute value of errors was 5.87%. The instantaneous volume of solid fuel channel changes linearly with time in the working process, this phenomenon was first found in theoretical calculation, and the analysis about this phenomenon was given. Under the operation conditions of calculation, the solid fuel mean regression rate is proportional to the power of -0.21 of solid fuel length.(2) To accurate calculate the heat transfer between flow field and solid fuel surface, the coefficients of viscosity and heat conduction of 6 species in two-step reaction of ethylene and air. Then, through adding source, the numerical simulation method about quasi steady flow field of SFRJ combustor was eatablished in Fluent software platform by using user defined function (UDF). Aimed at SFRJ fueled by PE, the quasi steady flow field of inner hole burning SFRJ combustor was numerically simulated. The influence of parameters such as the mass flow rate and total temperature of air, the dimessionless height of sudden enlargement step, the size of SFRJ and the length of solid fuel was analyzed. The main conclusions were as follows. With the increased of mass flow rate of air, the regression rate of solid fuel increased, air-fuel ratio and pressure in aft-mixing combustion chamber (AFT) increased, the temperature in AFT decreased, the thrust of SFRJ and specific impulse of fuel both increased. When the total temperature of air rised, the regression rate of solid fuel, the temperature and pressure in AFT and the thrust of SFRJ all increased, but the specific impulse of fuel decreased. With the increased of the dimessionless height of sudden enlargement step, the regression rates of solid fuel, the temperature and pressure of AFT, the speed of reaction and the flame-holding ability of SFRJ all increased. When the mass flux and total temperature of air both were same. With the decreased of dimession of SFRJs which were similar on geometric, the regression rates of solid fuel, the temperature and pressure in AFT all increased, however, the flame-holding ability of SFRJ decreased. On other parameters were equal, increased the length of the fuel, did not change the temperature or species distribution of the flow field, or the local regression rate of solid fuel, at same axial location. But, it can decreased the mean regression rate of solid fuel and increased the temperature and pressure in AFT.(3) The configuration of outboard burning SFRJ was presented. The quasi steady flow field of two different diameters (40 millimeter,60 millimeter) outboard burning SFRJ was numerically simulated. Also, to compare, the quasi steady flow field of inner hole burning SFRJ which had same ventilation area with outboard burning was numerically simulated. The conclusions were as follows. Compared with the inner hole burning, before reattachment point, the surface temperature and regression rates of solid fuel increased faster, and the values of them were larger. In the outboard burning SFRJ with 40 millimeter diameter, when the total temperature of air was lower, the regression rates near the end of solid fuel increased along the axis. The point that the regression rates started to increase was moved forward, and the increasing rate decreased when the mass flow rate of air increased. Under the operation conditions of calculation, the mean regression rates were smaller than inner hole burning as a result of the small regression rates in the most region of redevelopment zone. The thrust of outboard burning was lower then of inner hole burning, but the specific impulse were similar.(4) Based on fluid-solid coupling heat transfer and dynamic mesh method, the numerical simulation method about unsteady flow field of SFRJ combustor was eatablished in Fluent software platform by using UDF. They were numerically simulated which were the unsteady flow field of inner hole burning and outboard burning SFRJ combustor. The results showed that. In the inner hole burnging SFRJ, the distribution of temperature and pressure of flow field and the axial vecolity on axis all unchanged essentially. However, in the outboard buring SFRJ, the temperature and pressure of AFT decreased during working precess. To inner hole burning SFRJ, the instantaneous volume of solid fuel channel changes linearly with time in the working process, and instantaneous mean regression rates were inversely proportional to equivalent diameters. In the outboard burning SFRJ with 40 millimeter diameter, the rate decreased, which was the increased rate of the regression rates in the region near the end of solid fuel. Even, it didn’t increase.(5) Completed the polyethylene combustion experiment in SFRJ with inner hole buring and outboard burning. Experiment analyzed the influence of burning surface diameter of fuel, the mass flow rate and total temperature of air, and working time. The results showed that. The flame-holding ability of outboard buring SFRJ. In the outboard burning SFRJ with 40 millimeter diameter, the regression rates near the end of solid fuel increased along the axis. With the increased of mass flow rate of air,, the mean regression rates, the pressure in AFT both increased, but, the temperature in AFT both decreased in inner hole burning SFRJ and outboard SFRJ. With the increased of total temperature of air, the mean regression rates, the pressure and temperature in AFT all increased, in inner hole burning SFRJ and outboard SFRJ. With the increased of working time, the regression rates of inner hole burning SFRJ and outboard burning SFRJ decreased, howerver, the mean mass flow rate of inner hole burning SFRJ unchanged essentially. In the working process of inner hole burning SFRJ, the pressure of AFT unchanged essentially. Theoretical results consistent with the experimental. The location of reattachment points were accurate. The maximum values of errors of the mean regression rates, the temperature and pressure of AFT were 14.42%,13.96% and 6%, respectively. And, the trends of the mean regression rates, the temperature and pressure of AFT changing with the influence factors were the same as experimental.