A large-scale high pressure and temperature compressed air feed system for two gas turbine test facilities to enable heat transfer studies

Authors

John Goodenough - Department Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
Andrew Messenger - Department Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK
Paul Beard* - Department Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, UK

Abstract

This paper details the design of the 1 MW compressed air system supplying heated air at 327°C (600 K), 50 barg infrastructure upgrade to two world-leading gas turbine test rigs: the Oxford Turbine Research Facility (OTRF) and the Engine Component AeroThermal (ECAT) facility. These are two established, high TRL facilities for HP turbine research and have been constantly developed over 40 years - this high temperature air supply system the latest such development programme. The motivation for this is to reduce the development time for novel gas turbine cooling technology, by providing complimentary test facilities with a high degree of engine similarity that can evaluate component performance before committing to expensive full-scale engine testing. The new air supply system enables both facilities to match engine mainstream-to-coolant temperature ratio with run times over 60 seconds, in addition to previously matched Reynolds number, Mach number, combustor temperature, swirl and turbulence profile. The new air supply system consists of four air storage tanks with a total volume of 136m3, three of which are electrically trace heated across 23 individually PID controlled zones. The system heat-up time is 29 hours from ambient and the final temperature stability is better than 5 °C/hour. Up to three liquid-cooled multistage reciprocating compressors deliver 2400 sm3/hr at 50 barg. Dessicant dryers then remove water vapour to -30 °C and oil content is reduced to less than 0,01 mg/m³ at 20°C. A single 300 kW inline electric heater raises the air temperature from 35 °C to 327 °C before entering the storage tanks. All the connecting 3”, 6” and 8 (nominal pipe size) pipework is designed to accommodate nozzle loadings imposed during 8 different operating configurations depending whether individual tanks are heated or operated at ambient temperature. The discharge from the tanks feeds one rig at a time, through 8” flanged pipework that is also trace heated and maintained at the setpoint. The 3.5” throat critical flow venturi nozzle provides flow rate measurements up to 30 kg/s dry air (at 327°C) with an accuracy better than 0.5 % actual reading. Details are provided on the overall system design, the commissioning tests and performance measurements of the flow metering system.