Characteristics of the Effective Cross-Sectional Area Reduction of the Turbine Nozzle Throat and Engine Performance of KSLV-II

The engines for the Korea Space Launch Vehicle-II (KSLV-II) are liquid oxygen/kerosene gas generator cycle engine. The turbine is driven by fuel rich gas of the gas generator. The turbine gas in kerosene-fueled engines contains a large amount of soot, which leads to a decrease in the turbine nozzle throat area as it burns. Understanding this characteristic is essential as it affects the performance of the engine during flight. In this paper, the authors observed the changes in the turbine nozzle throat area of the KSLV-II engines as a function of burning time to determine the performance characteristics of the engine. Since the turbine nozzle throat area cannot be directly measured during flight or firing tests on the ground, the effective cross-sectional area of the turbine was estimated using pressure and temperature ratios across the turbine rotor. The discharge coefficient variations of KSLV-II 1st and 3rd stage engine’s turbine nozzle throat in the development firing tests were analyzed. Although it is evident that carbon accumulates on the turbine nozzle over time, the detachment of this carbon and the restoration of the turbine's effective area occur in a seemingly random manner.