Transient Three-Dimensional Side-Load Analysis of a Film-Cooled Nozzle

Abstract

Transient three-dimensional numerical investigations on the side load physics for an engine encompassing a film cooled nozzle extension and a regeneratively cooled thrust chamber, were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructuredgrid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Ultimately, the computational results will be provided to the nozzle designers for estimating of effect of the peak side load on the nozzle structure.Computations simulating engine startup at ambient pressures corresponding to sea level and three high altitudes were performed. In addition, computations for both engine startup and shutdown transients were also performed for a stub nozzle, operating at sea level. For engine with the full nozzle extension, computational result shows starting up at sea level, the peak side load occurs when the lambda shock steps into the turbine exhaust flow, while the side load caused by the transition from free-shock separation to restricted-shock separation comes at second; and the side loads decreasing rapidly and progressively as the ambient pressure decreases. For the stub nozzle operating at sea level, the computed side loads during both startup and shutdown becomes very small due to the much reduced flow area.

Transient Side-Load Analysis of Out-of-Round Film-Cooled Nozzle Extensions

“…The general layout of the outer boundaries and the wall boundaries of the MCC, nozzle, TEM, and nozzle extension are similar to those of a previous J-2X side load study and are, described in detail in Ref. [8].…”

“…Simply put, the ramp rates, or histories, of the inlet pressure, fluid temperature and species concentrations play an important role in determining the type of side load physics, magnitude and duration of the side loads during the transient operations. In terms of the type of side load physics, it was demonstrated that a combustion wave occurred during a transient startup of the SSME due to the excess fuel dump [7]; On the other hand, it was also demonstrated that the combustion wave disappeared when the excess fuel dump was replaced with helium purge in the J-2X startup transient [8]. In terms of the magnitude and duration of the side loads, it was demonstrated that the peak side load dropped to about half after the total ramp time decreased from 5 s to 1 s [7], for the SSME startup simulation.…”

“…The thermodynamic properties of the individual species are functions of temperature. The multiphysics pertinent to this study have been anchored in earlier efforts, e.g., SSME axial force and wall heat transfer [20], SSME startup side load and dominant shock breathing frequency [7], J-2X startup and shutdown side loads for a nozzlette configuration [8], nozzle film cooling applications [26], and conjugate heat transfer [27].…”

“…For film-cooled engines such as the Japanese LE-7A engine and the U.S. J-2X engine, the major side load generating physics have been associated with the jump of the separation line [3,8]. Other side load physics such as the Free-Shock Separation (FSS)-to-Restricted-Shock Separation (RSS) transition have been mentioned as the critical one for the European Vulcain engine [9].…”

“…Therefore, transient nozzle side load is considered a high risk item and a critical design issue during any new engine development. For that reason, many research efforts [5][6][7][8][9][10][11][12][13][14][15][16][17][18] have been devoted to understanding the side load physics and their impact on the magnitude of side loads. For regeneratively-cooled engines such as the Space Shuttle…”