Integrated Heat Exchange For Recuperation In Gas Turbine Engines
Naval Postgraduate School 93943 United States
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While the use of recuperators in gas turbine engines is quite favorable for increasing cycle efficiency, it is currently only feasible to apply this technology to land-based engines. Transferring this technology toaviation or ship gas turbines is difficult due the size and weight of the heat exchanger components required. An alternate approach would be to embed a heat exchange system within the engine using existing bladesurfaces to extract and insert heat. Due to the highly turbulent and transient flow, heat transfer coefficients in turbomachinery are extremely high, making this possible. Heat transfer between the turbine and compressor blade surfaces could be accomplished using evaporative heat pipes. This study explores the feasibility of embedding this heat exchange system within engines using athermodynamic approach to quantify cycle improvements and compare them to those of other modified cycles. The real performance effects are taken into account based on the heat transfer coefficients within turbomachinery obtained from experimental studies. The effectiveness of an integrated heat exchange system was found to be 4.5. Using this integrated heat exchange system for recuperation in gas turbine cycles improves efficiency at pressure ratios less than 22. Using this heat exchange system for intercooling improves efficiency from 1 to 2 and increases engine power output by 1 to 7, depending on pressure ratio. Cycle improvements of over 1 inefficiency can lead to significant fuel savings for both the USN and USMC.