Presentation on theme: "-Final Project Report- 12/04/01 Madeline Close and Christopher Johnson"— Presentation transcript:
1 The Effects of Nozzle Geometry on the Specific Impulse of a Pulse Detonation Engine -Final Project Report-12/04/01Madeline Close and Christopher JohnsonProf. Edward Greitzer, Advisor
2 Overview Background and Motivation Objective Technical Approach Experimental ResultsConclusionsAcknowledgementsQuestions
3 Background-Motivation Interest in pulse detonation engines (PDEs) has renewed in the past decade.PDEs are a structurally lightweight form of propulsion with high specific impulse (Isp)CFD calculations have been done to estimate the effects of varying nozzle geometries; however, few experimental results exist to substantiate the theoretical conclusions
4 ObjectiveTo determine the effects of nozzle geometry on the specific impulse of pulse detonation engines
5 Technical ApproachSix nozzles were designed and manufactured for testing conditions at Air Force Research Laboratory (AFRL)
6 Nozzle Geometry Matrix Nozzle DesignationTube to Throat Area RatioExit to Throat Area RatioStraight1Converging 13Converging 210Converging-Diverging 12Converging-Diverging 2PlugAll nozzles were manufactured on-campus in the Gelb Laboratory with the exception of the plug (Central Machine Shop).
7 Nozzle DesignConverging contour derived from the MIT supersonic wind tunnel design and scaled for specific area ratiosDiverging contours calculated using Method of CharacteristicsPlug nozzle contour based on a previous geometry
12 PDE TermsStart/endCycle: 3-part process Frequency: engine cycles per second (Hz)Ignition delay time: time between engine fill and ignition (ms)Fill fraction: fraction of tube the gases would fill at STPFillPurgeFire
21 Summary of Nozzle Performance Straight nozzle gave slight improvement in performance over baseline at same dimensional frequencies[predicted by Eidelmann and Yang in AIAA paper ]Smaller converging nozzle (C10) and small converging-diverging nozzle (CD10) backfired at higher frequencies.
22 Summary of Nozzle Performance Larger converging nozzle (C3) performed well: maximum Isp of 4500 sec. at 40HzLarger converging-diverging nozzle (CD3) was consistently below baseline performance.Plug nozzle (PG) was consistently 10%-20% above baseline performance
23 ConclusionsShock reflections should be considered in choosing the Atube/A*.Converging nozzles and plug nozzle performed best relative to baseline.Converging-diverging nozzles performed poorly in the test conditions.
24 Future workMore families of nozzles need to be tested. CFD analysis of diverging nozzles shows they improve Isp.Higher frequency tests should be performed.Develop design method for making nozzles to maximize Isp.
25 Acknowledgements Professor Ed Greitzer, Project Advisor Don Weiner, Carl Dietrich, and Jerry Wentworth for machine shop helpDr. Fred Schauer and Dr. Royce Bradley for help at WPAFB-APRLProfessors Ian Waitz and Mark Drela for technical assistance in nozzle designDr. David Tew (UTRC) and Dr. Doug Talley (AFRL) for project advice