scholarly journals Vibration Characteristics of the HPOTP (High-Pressure Oxygen Turbopump) of the SSME (Space Shuttle Main Engine)

1985 ◽  
Vol 107 (1) ◽  
pp. 152-159 ◽  
Author(s):  
D. W. Childs ◽  
D. S. Moyer
Keyword(s):  
Nonlinear Model ◽  
Space Shuttle ◽  
Power Level ◽  
Structural Dynamic ◽  
Basic Model ◽  
Synchronous Motion ◽  
High Pressure Oxygen ◽  
Bearing Loads ◽  
Gas Seals ◽  
Main Engine

A review is presented of various rotordynamic problems which have been encountered and eliminated in developing the current flight engines and of continuing subsynchronous problems which are being encountered in developing a 109 percent power level engine. The basic model for the HPOTP, including the structural dynamic model for the rotor and housing and component models for the liquid and gas seals, turbine-clearance excitation forces, and impeller-diffuser forces, are discussed. Results from a linear model are used to examine the synchronous response and stability characteristics of the HPOTP, examining bearing load and stability problems associated with the second critical speed. Various seal modifications are examined and shown to have favorable consequences with respect to bearing reactions and stability. Differences between linear and nonlinear model results are discussed and explained in terms of simple models. The transient nonlinear model is used to demonstrate forced subsynchronous motion similar to that observed in test data for models which are lightly damped but stable. The subsynchronous motion results from bearing clearance nonlinearities. Simulation results indicates that synchronous bearing loads can be reduced but that sub-synchronous motion is not eliminated by seal modifications.

Improved Rotor Response of the Uprated High Pressure Oxygen Turbopump for the Space Shuttle Main Engine

1989 ◽  
Vol 111 (2) ◽  
pp. 163-169 ◽  
Author(s):  
R. F. Beatty ◽  
M. J. Hine
Keyword(s):  
High Pressure ◽  
Critical Speed ◽  
Space Shuttle ◽  
Pressure Oxygen ◽  
Bearing Life ◽  
Bending Mode ◽  
Bearing Stiffness ◽  
High Pressure Oxygen ◽  
Bearing Loads ◽  
Main Engine

During development testing of the High Pressure Oxygen Turbopump (HPOTP) of the Space Shuttle Main Engine (SSME) to produce 109 percent of the rated thrust level, subsynchronous rotor whirl was encountered. This whirl was attributed to bearing wear reducing the radial bearing stiffness that caused the rotor second bending mode critical speed to enter the operating speed range. To eliminate this whirl, the pump end bearing loads were reduced to increase bearing life and damping added between the rotor and housing. This was achieved by converting impeller annular seals into “damping” seals that react part of the applied load and also damp the rotor response. Furthermore, the second rotor critical speed was increased by the added stiffness of the seal conversion and stiffening the rotor shaft. The bearing load reduction was verified by strain gaging the pump end bearing support into a load cell. These strain gages also were used to directly measure bearing ball wear during engine tests.

scholarly journals Steady-State Analysis of a Nonlinear Rotor-Housing System

1990 ◽  
Author(s):  
Y. B. Kim ◽  
S. T. Noah
Keyword(s):  
Steady State ◽  
Degrees Of Freedom ◽  
Space Shuttle ◽  
Harmonic Balance Method ◽  
Housing System ◽  
Impedance Method ◽  
Computational Technique ◽  
Housing Systems ◽  
High Pressure Oxygen ◽  
Main Engine

The periodic steady state response of a high pressure oxygen turbopump (HPOTP) of a space shuttle main engine (SSME), involving a clearance between the bearing and housing carrier, is sought. A harmonic balance method utilizing Fast Fourier Transform (FFT) algorithm is developed for the analysis. An impedance method is used to reduce the number of degrees of freedom to the displacements at the bearing clearance. Harmonic and subharmonic responses to imbalance for various system parameters are studied. The results show that the computational technique developed in this study is an effective and flexible method for determining the stable and unstable periodic response of complex rotor-housing systems with clearance type nonlinearity.

Residual-Flexibility Corrections for Transient Modal Rotordynamic Models

1978 ◽  
Vol 100 (2) ◽  
pp. 251-256 ◽  
Author(s):  
D. W. Childs ◽  
J. B. Bates
Keyword(s):  
Space Shuttle ◽  
Power Level ◽  
Computer Time ◽  
Operating Speed ◽  
Flexible Rotors ◽  
Modes Of Vibration ◽  
Time Requirements ◽  
Reaction Forces ◽  
Bearing Stiffness ◽  
High Pressure Oxygen

An extension is presented to a modal formulation for the dynamics of flexible rotors. To date, rotordynamic modal formulations have retained for integration those modes of vibration whose natural frequencies are within or slightly above the operating speed range of the rotor, with higher-order modes simply discarded. In this study, the residual-flexibility technique is employed to account for the “static” contribution of these higher-frequency modes without requiring their integration. The residual-flexibility technique accounts directly for the static contribution of higher frequency modes due to imbalance and external transient loading, and has been adapted to account for reaction forces which are not accounted for by the nominal rotor/bearing stiffness matrix, e.g., bearing damping forces or speed-dependent bearing stiffnesses. The High-Pressure-Oxygen Turbopump of the Space Shuttle Main Engine (SSME) is analyzed. The maximum operating speed of this turbopump lies between its first and second critical speeds. Comparisons are made without residual-flexibility corrections for two through six modes retained for integration. Simulation runs are made for (a) a deceleration through the first critical speed and (b) a constant speed run at FPL (full power level). The results demonstrate that the residual-flexibility approach yields a significant improvement in accuracy for a comparatively modest increase in computer-time requirements.

scholarly journals Steady-State Analysis of a Nonlinear Rotor-Housing System

1991 ◽  
Vol 113 (4) ◽  
pp. 550-556 ◽  
Author(s):  
Y. B. Kim ◽  
S. T. Noah
Keyword(s):  
Steady State ◽  
Degrees Of Freedom ◽  
Space Shuttle ◽  
Harmonic Balance Method ◽  
Housing System ◽  
Impedance Method ◽  
Computational Technique ◽  
Housing Systems ◽  
High Pressure Oxygen ◽  
Main Engine

The periodic steady-state response of a high-pressure oxygen turbopump (HPOTP) of a space shuttle main engine (SSME), involving a clearance between the bearing and housing carrier, is sought. A harmonic balance method utilizing Fast Fourier Transform (FFT) algorithm is developed for the analysis. An impedance method is used to reduce the number of degrees of freedom to the displacements at the bearing clearance. Harmonic and subharmonic responses to imbalance for various system parameters are studied. The results show that the computational technique developed in this study is an effective and flexible method for determining the stable and unstable periodic response of complex rotor-housing systems with clearance-type nonlinearity.

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