TRANSIENT MODEL OF CRYOGENIC BEARING THERMO-MECHANICAL OPERATING CHARACTERISTICS

CRYOGENIC, LIQUID-PROPULSION SYSTEMS FOR MANNED SPACECRAFT USE HIGH-PERFORMANCE TURBOPUMPS WITH ROLLING-ELEMENT BEARINGS TO SUPPORT THE TURBINE AND PUMP SHAFT. THESE BEARINGS OPERATE AT HIGH SPEED IN THE CRYOGEN BEING PUMPED; THEY ARE HIGHLY LOADED AND POORLY LUBRICATED. THE RESULTINGSENSITIVITY TO THERMO-MECHANICAL INTERACTIONS CAN CAUSE RAPID LOSS OF OPERATING CLEARANCE, INCREASES IN HEAT GENERATION AND COMPONENT TEMPERATURES, AND RAPID BUILD-UP OF CONTACT STRESSES. THE RESULT CAN BE PREMATURE BEARING DETERIORATION OR FAILURE. ALTHOUGH SOME CODES SIMULATE STEADY-STATE CONDITIONS FOR THESE SYSTEMS, THE START, SHUT-DOWN, AND POWER TRANSIENTS ARE BEYOND THEIR SCOPE. THIS PROJECT WILL INVESTIGATE AND DEFINE MODELING TECHNIQUESTO SIMULATE THE THERMO-MECHANICAL, TRANSIENT CHARACTERISTICSOF TURBOPUMP, BEARING SYSTEMS OPERATING IN CRYOGENICS. THE FEASIBILITY OF DEVELOPING AND INSTALLING THE SIMULATION ON APERSONAL WORKSTATION WILL BE INVESTIGATED. THE SOFTWARE PACKAGE WILL BE DESIGNED TO AUGMENT CURRENT MODELS OF TURBOPUMP, SHAFT-BEARING SYSTEMS. GIVEN THE INITIAL CONDITIONS, A DESCRIPTION OF THE SPEED TRANSIENT (INCLUDING LOADS AND COOLANT FLOW), AND THE GEOMETRICAL CHARACTERISTICS, THE MODEL WILL PREDICT THE TRANSIENT COMPONENT TEMPERATURES AND OPERATING CHARACTERISTICS SUCH AS OPERATING CLEARANCES, CONTACT ANGLES, STRESSES, AND LOAD DISTRIBUTIONS. THIS INFORMATION IS VERY USEFUL IN DESIGN EVALUATIONS, LIFE ASSESSMENTS, AND INVESTIGATIONS OF FAILURE SCENARIOS. CRYOGENIC, LIQUID-PROPULSION SYSTEMS FOR MANNED SPACECRAFT USE HIGH-PERFORMANCE TURBOPUMPS WITH ROLLING-ELEMENT BEARINGS TO SUPPORT THE TURBINE AND PUMP SHAFT. THESE BEARINGS OPERATE AT HIGH SPEED IN THE CRYOGEN BEING PUMPED; THEY ARE HIGHLY LOADED AND POORLY LUBRICATED. THE RESULTINGSENSITIVITY TO THERMO-MECHANICAL INTERACTIONS CAN CAUSE RAPID LOSS OF OPERATING CLEARANCE, INCREASES IN HEAT GENERATION AND COMPONENT TEMPERATURES, AND RAPID BUILD-UP OF CONTACT STRESSES. THE RESULT CAN BE PREMATURE BEARING DETERIORATION OR FAILURE. ALTHOUGH SOME CODES SIMULATE STEADY-STATE CONDITIONS FOR THESE SYSTEMS, THE START, SHUT-DOWN, AND POWER TRANSIENTS ARE BEYOND THEIR SCOPE. THIS PROJECT WILL INVESTIGATE AND DEFINE MODELING TECHNIQUESTO SIMULATE THE THERMO-MECHANICAL, TRANSIENT CHARACTERISTICSOF TURBOPUMP, BEARING SYSTEMS OPERATING IN CRYOGENICS. THE FEASIBILITY OF DEVELOPING AND INSTALLING THE SIMULATION ON APERSONAL WORKSTATION WILL BE INVESTIGATED. THE SOFTWARE PACKAGE WILL BE DESIGNED TO AUGMENT CURRENT MODELS OF TURBOPUMP, SHAFT-BEARING SYSTEMS. GIVEN THE INITIAL CONDITIONS, A DESCRIPTION OF THE SPEED TRANSIENT (INCLUDING LOADS AND COOLANT FLOW), AND THE GEOMETRICAL CHARACTERISTICS, THE MODEL WILL PREDICT THE TRANSIENT COMPONENT TEMPERATURES AND OPERATING CHARACTERISTICS SUCH AS OPERATING CLEARANCES, CONTACT ANGLES, STRESSES, AND LOAD DISTRIBUTIONS. THIS INFORMATION IS VERY USEFUL IN DESIGN EVALUATIONS, LIFE ASSESSMENTS, AND INVESTIGATIONS OF FAILURE SCENARIOS.