1992-07-01

Thermal Analysis of a Shower-Head Burner 921226

The NASA Langley Research Center plans to cany out realistic full-scale tests of supersonic combustion ramjet engines at its 8-Foot High Temperature Tunnel (HTT). Consisting mainly of a shower-head type fuel injector (spray bar), the burner and combustion chamber of the tunnel provides the energy needed to attain high-temperature air flows ranging from 1300 to 3000 K and Mach numbers of 4 to 7 at the test section. Required high-temperature fields are generated during the combustion process in a Liquid Oxygen (Lox) Mode environment where air is enriched to about 47 percent by mass in oxygen concentration. The main objectives of this paper are to determine the most important parameters to enable computation of thermal stresses, heat-transfer coefficients, and convective temperatures on the spray bar. In order to compute heattransfer coefficients, NASA will utilize the FLUENT computer code along with well-known empirical methods such as Churchill, Bernstein and Petukhov. For determining convective temperatures around the spray bar, FLUENT Version 3.0 along with experimental data will be used. Two-dimensional, three-dimensional, steady-state and transient, two and three-step reaction, as well as low and high fuel velocity cases, were run using FLUENT. While the combination of computer codes and empirical equations has proved to be an excellent means of obtaining solution to complex engineering problems, conclusions derived from this project are that utilization of the FLUENT code allows for prediction of higher convective temperatures than experimental data at shutdown conditions. On the other hand, empirical equations are acceptable for calculation of heat-transfer coefficients.
The structural analyst assigned to the project will be provided with the temperature fields and heat transfer coefficients obtained in this project, and he will decide upon their use for computing thermal stresses in the spray bar. It is suggested that experimental test conditions and FLUENT code runs should have the same initial and boundary conditions.

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