Method for Measurement of Single-Injector Heat Transfer Characteristics and Its Application in Studying Gas-Gas Injector Combustion Chamber

Abstract

In the development of a Liquid Propellant Rocket Engine (LPRE), injector is always the element which requires the longest development period. An injector always especially in the initial design phase needs hundreds and thousands of tests to get a choice. These numerous tests, in turn, require reliable and accurate measurement method to give the basic support. The strength, the life cycle, and the cooling system effectiveness are highly dependent on heat transfer into and out of the system (Tramecourt et al., 2005). Heat transfer characteristics, combined with combustion efficiency, and combustion instability, are the three key parameters needed to be investigated in developing a new injector in a combustion chamber. The heat transfer characteristics generally contain the temperature and heat flux on the hot-gas-wall in the combustion chamber. The combustion efficiency and combustion instability can be observed easily by measuring the chamber pressure. However, it is always very hard to measure the temperature and heat flux on hot-gas-wall of the chamber in the hot-tests due to the extreme environment in LPRE chambers (temperature > 3000K, pressure > 10atm). Additionally, considerable efforts have been dedicated to model combustion in combustion chambers to understand and predict the heat transfer to the chamber walls (Zurbach, 2006), whereas the validation of computational fluid dynamics (CFD) design tools requires reliable experimental data assessment. This acquires a comprehensive set of data in the same facility, including wall heat fluxes along with inflow measurements (Tucker et al., 2005). To obtain the exact wall heat flux data, a reliable measurement method, in turn, is also required. Though a number of efforts had contributed to design new injectors and study on heat transfer of injectors, studies focusing on the measurement method are less well documented. In recent years, Pennsylvania State University, University of Florida and NASA MSFC etc. made many attempts on studying the heat transfer characteristics of some injectors in heat sink chambers (Conley et al., 2007; Jones et al., 2006; Marshall et al., 2005; Santoro & Pal, 2005; Vaidyanathan et al., 2007, 2010b). They applied coaxial thermocouple to measure two point temperatures at the same axial location and difference radial locations in a heat-sink copper combustion chamber, and then used the temperatures to calculate the local heat flux