CRANFIELD UNIVERSITY A.G. VARELIS TECHNOECONOMIC STUDY OF ENGINE DETERIORATION AND COMPRESSOR WASHING FOR MILITARY GAS TURBINE ENGINES SCHOOL OF ENGINEERING Master of Science by Research THESIS SCHOOL OF ENGINEERING DEPARTMENT OF POWER AND PROPULSION MSc by Research Thesis Academic Year 2007-2008 Angelos G. Varelis Technoeconomic Study of Engine Deterioration and Compressor Washing for Military Gas Turbine Engines Supervisor: Prof. P. Pilidis September 2008 © Cranfield University 2008. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner. ABSTRACT Despite spending much of their operating life in clear air, aircraft gas turbine engines are naturally prone to deterioration as they are generally not fitted with air filters. Engines are particularly at risk during takeoff and landing, and whilst operating in areas of pollution, sand, dust storms, etc. The build-up of contaminants, especially on the compressor surfaces, leads to a dramatic reduction in compressor efficiency, which gives rise to a loss of available power, increased fuel consumption and increased exhaust gas temperature. These conditions can lead to flight delays, inspection failures, withdrawal from service, increased operating costs and safety compromises.With the growing interest in life cycle costs for gas turbine engines, both engine manufacturers and operators are investigating the tradeoffs between performance improvements and associated maintenance costs. This report introduces the problem of output and efficiency degradation in two aero gas turbine engines (the T56–A–15 and the F110–GE–129) caused by various deterioration factors. Their causes are broadly discussed and the effects on powerplant performance are simulated and analyzed. One of the key factors leading to performance losses during operation of these engines is compressor fouling. The fouling can come from a wide variety of sources; hydrocarbons from fuel and lubricating oils; volcanic ash; pollen; marine aerosols; dust; smoke; pollution, etc. The presence of these fouling sources acts as a bonding agent for the solid contaminants, ‘gluing’ them to the compressor surfaces. Thus, the aggravation in terms of power output, fuel consumption and additional time to carry out a typical mission will be assessed and an economic analysis will be attempted in order to quantify the effects of compressor fouling on the additional costs which arise, because of this specific deterioration. The effect of compressor fouling can be maintained by frequent cleaning to improve efficiency, resulting, hence, in improved power output, fuel savings and prolonged engine life. Compressor cleaning is thoroughly presented, and the implementation of on-wing off-line cleaning on the performance of the F110 engine was investigated from a technical and economical standpoint. Finally, according to the results obtained, the optimal frequency of compressor washing for the F110 engine is estimated, in order to eliminate safety compromises, improve performance and reduce the engine’s life cycle cost. AKNOWLEDGEMENTS I would like to express my gratitude to my supervisor Professor Pericles Pilidis, for his help, guidance and understanding, necessary to drive me along the project throughout this year, and the Department of Power Engineering and Propulsion of Cranfield University, for providing me with all the necessary tools and support to complete this Master. In addition, I would like to thank Mr. Paul Lambart, Projects Director of R-MC Power Recovery Ltd, with whom I had the opportunity to have a fruitful conversation, which helped me acquire a broader view of the technoeconomic aspects of compressor cleaning. I would also like to extend my sincere thanks to all the friends from Cranfield University and especially to Elias Tsoutsanis, who, despite his PhD studies, was always available for discussion and willing to support me in many aspects of my University life, including, of course, the broader understanding of anything related to the operation of a gas turbine engine. Moreover, I would like to express my appreciation to the Hellenic Air Force for providing me with the opportunity to study in Cranfield University, in a Department that was and still remains of my greatest interest, and to my colleagues from the 111 Combat Wing Engine Maintenance Department for all the things we shared in our everyday work in the last 10 years. My passion for gas turbine engines comes from working with such capable, professional and enthusiastic people. Finally, and most important, I would like to dedicate this work to my wife Anna and my sons Yioryo and Anastasio for their patience, unceasing support and sacrifices during my studies in Cranfield University. "True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us." Socrates LIST OF CONTENTS LIST OF FIGURES…………………………………………………………............ i LIST OF TABLES…………………………………………………………............... iv NOTATION……...……………………………………………………………........... vi ACRONYMS…………………………………………………………………............ x 1.0. INTRODUCTION……….....…………………………………….............. 1 1.1. Background........………………………………………………………… 1 1.2. Aim of the Thesis......................…………………………………........... 3 1.3. Thesis Scope................................................................………........... 4 1.5. Thesis Layout…………………………………………………………….. 4 2.0. LITERATURE REVIEW......................…………………...................... 6 2.1. Performance Degradation....……………………………………............ 6 2.1.1. Degradation Rate...………………………………………………........... 6 2.1.2. Causes of Degradation………………………………………………….. 7 2.1.2.1 Fouling…………………………………………………………………….. 10 2.1.2.2 Erosion………………………………………………………………......... 14 2.1.2.3 Corrosion……………………………………………………………......... 16 2.1.2.4 Thermal Distortion……………………………………………………….. 18 2.1.2.5 Foreign Object Damage and Domestic Object Damage…………….. 19 2.1.2.6 Rubbing Wear.................................................................................... 20 2.1.2.7 Engine Operating Conditions and Maintenance Practices................. 20 2.2. Compressor Cleaning......................................................................... 21 2.2.1. Manual Cleaning................................................................................ 23 2.2.2. Abrasive Cleaning.............................................................................. 24 2.2.3. Wet Cleaning...................................................................................... 24 2.2.3.1 Offline Washing.................................................................................. 24 2.2.3.2 Online Washing.................................................................................. 27 2.3. On-wing Off-line Cleaning of Aero Engines………….……………….. 33 2.3.1. Risks and Benefits of On-wing Off-line Cleaning…………………….. 39 2.4. Performance Simulation Software...................................................... 40 3.0. GENERAL ENGINE DESCRIPTION AND MODELING.................... 42 3.1. The T56-A-15 Engine..........................……………..……………......... 42 3.2. The F110-GE-129 Engine...................……………..……………......... 45 4.0. ANALYSIS OF ENGINE’S DETERIORATION....................………… 47 4.1. Simulation of the Engine’s Deterioration............................................ 47 4.2. Simulated Faults Representation....……………………………………. 48 4.3. The T56-A-15 engine……………………………….............................. 52 4.3.1. Compressor Fouling.....................................……………………......... 52 4.3.2. Turbine Fouling............................................……………………......... 54 4.3.3. Turbine Erosion...........................................…………………………... 56 4.4. The F110-GE-129 Engine...................……………..……………......... 58 4.4.1. Compressor Fouling.....................................……………………......... 58 4.4.2. Turbine Fouling............................................…………………….......... 64 4.4.3. Turbine Erosion...........................................…………………………... 66 5.0. OPERATIONAL EFFECTIVENESS ANALYSIS…………………….. 70 5.1. Mission Profiles………………………………………………………….. 70 5.2. Mission Analysis……………………………………………………........ 71 5.3 Mission A……………………………………………………………......... 72 5.4 Mission B…………...……………………………………………….......... 74 5.5. Operational Effectiveness Evaluation…………………………………. 76 5.6. Discussion of the Results……………………………………………….. 78 6.0. TECHNOECONOMIC STUDY OF COMPRESSOR WASHING……. 82 6.1. Effects of Compressor Washing on Fuel Savings...………………….. 82 6.2. Effects of Compressor Deterioration on Creep Life……………….…. 84 6.3. Compressor Washing Frequency Optimization ……………………… 86 7.0. CONCLUSIONS & RECOMMENDATIONS FOR FUTURE WORK.. 88 7.1. Conclusions........................……………………………………………. 88 7.2. Recommendations for Future Work…...................………………....... 94 REFERENCES………………………………………………………………............ 95 APPENDICES……………………………………………………………………….. 102 LIST OF FIGURES Figure 2.1 Compressor characteristics – Engine degradation……… 9 Figure 2.2 Fouling caused by severe carbonaceous oily type of deposits, because of oil leaks in the bearing system……. 10 Figure 2.3 Industrial gas turbine compressor fouling…………………. 12 Figure 2.4 Gas turbine fouling…………………………………………... 14 Figure 2.5 Compressor blade erosion………………………………….. 15 Figure 2.6 Compressor blade corrosion……………………………….. 17 Figure 2.7 FOD of Industrial Gas Turbine Blades..…………………… 19 Figure 2.8 Compressor blades before and after cleaning…………… 22 Figure 2.9 Cleaning fluid spraying