Knowledge Bank

The experimental determination of temperature and pressure distributions in the high-velocity gas stream encountered in a rocket engine exhaust plume is of value in gaining greater insight into the actual combustion processes occurring in the engine. The study of injector and nozzle processes is also aided by such measurements. In addition, knowledge of the temperature and pressure distributions is essential for the calculation of the radiation emanating from the exhaust plume. In the technique described herein the spectral radiance and transmittance of infrared active exhaust species are measured along a series of coplanar, chordal lines of sight spanning the exhaust. The data thus obtained allow equations describing the radiant energy transfer through the exhaust to be solved for the radial distributions of spectral radiance and emissivity. From these latter two quantities, the radial distributions of temperature and partial pressure are calculated. A recently completed program using this technique to map the exhaust plume of a 1000-pound-thrust rocket motor firing the propellants liquid oxygen/kerosene and liquid oxygen/alcohol is described. Instruments being developed to study exhaust plumes produced during short duration tests (20 millisecond) and also to study large liquid propellant engine exhausts are also described.