Flame Temperature Distribution Measurement of Solid Propellants

摘要

All results in this paper are given based on the following assumptions: 1) combustion of the flame is steady; 2) the flame is optically thin for its small size; and 3) the flame is in local thermal equilibrium state. The temperature distributions in the axes for the SQ-2 propellant at different pressures are shown in Fig. 2. There are three areas, the climbing-temperature area, the high-temperature area and the fall-temperature area, in the temperature distribution. The temperature in the high-temperature area is unstable because of the turbulence of the flame and the unsteady of combustion. And also, this instability can be found in the line intensity data without Abel's inversion. The maximum flame temperatures are compared with the results from thermocouple method and equilibrium calculation (shown in Table 1). The data of thermocouple method and equilibrium calculation are provided by the Beijing Institute of Technology. The data in Table 1 show that the maximum flame temperature increases along with the rising of the pressure. The results from the spectroscopy method are about 100 K higher than those from the thermocouple method and much nearer to the temperature from equilibrium calculation with the rising of the pressure. As a reference, Dong Yang has reported that the maximum temperatures of SQ-2 propellant exhaust plumes are 2234 and 2202 K for 240 and 500 mm apart from the motor nozzle when the work pressure of the chamber is about 13.0 MPa. The results from the spectroscopic diagnostic system are reasonable in comparison with the preceding results from other methods. The relative standard deviations of maximum temperature of the SQ-2 propellent's flame at different pressures are less than 5% for all measurements. The temperature distribution of the solid-propellant nitrate-ester-plasticized polyethane (NEPE) is also measured by the spectroscopic diagnostic system. The result is not satisfactory because there are metal particles in the NEPE propellant, which will absorb and scatter the radiation, and emit their own spectrum. Figure 3 shows one of the measurement results. In fact, the temperature measurements for the NEPE propellant at different pressures are made for many times. The relative standard deviations of the maximum flame temperature are about 15% in our measurements, which are a little bit larger. This will be studied in the later work.