N O T I C E THIS DOCUMENT HAS BEEN REPRODUCED FROM MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS MUCH INFORMATION AS POSSIBLE 1 J Ultralean Combustion in General Aviation Piston Engines J. E. Chirivella (NASA-CB-163001) QLZPALEAN CCMBU5IION IN 2180-22430 GENEBAL AVIATICN FISTCN ENGIVfS (Jet Propulsion Lab.) 246 p HC A11/dF A01 CSCL 21B Unclas G3/2` 16041 ' December, lr 1979 f• x,12 S a •i J ^ v "y National Aeronautics and Space Administration a ^' Jet Propulsion Laboratory California Institute of Technology '. f Pasadena,California 419.• ,w • r JPL PUBLICATION 79-75 Ultralean Combustion in General Aviation Piston Engines J. E. Chirivella December 1, 1979 National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California The research described in this publication was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under NASA Contract No. NAS7.100. Here is the ultimate in lightness of weight and power - two hundred and twenty-three horses compressed into nine delicate, fin-covered cylinders of aluminum and steel. On this intricate perfection I'm to trust my life across the Atlantic Ocean. The inner organs of this engine - its connecting rods, cams, gears and bearings - will be turning over many hundred times each minute - sparks jumping, teeth meshing, pistons stopping and reversing at incomprehensible speeds. And I'm demanding that this procedure continue for forty hours if need be, for all the 3610 miles between New York and Paris. It seems beyond the ability of any mechanism to stand such a strain..... Charles A. Lindbergh, The Spirit of St. Louis Courtesy of Charles Scribner's Sons Copyright 1953 iii PREFACE The report presented herein formalizes the final episode of the NASA/OAST-sponsored "Hydrogen Enrichment for Aircraft Piston Engines Program." This program was undertaken as a part of the effort that the Office of Aeronautical Propulsion of OAST had devoted to improving the efficiency of aircraft piston engines in general aviation. It was found during the course of the program that the original concept of using hydrogen enrichment to operate engines ultralean, and thus improve their efficiency, had important limitations. The original scope was therefore modified to encompass other successful techniques discovered earlier in the program, and in doing so it was also realized that there was a need for a coherent document which, while summarizing the potentials for fuel economy improvement, would also provide the reader with the minimum background for an in-depth understanding of the st?bject when present technical- , practical and economic issues are taken into account. The major reason for this need was found to be related to the fa --, c that the most important research in aircraft piston engines was conducted during the pre-World War II period and had not been translated into terms used nowadays by the General Aviation community. As part of the program and in an effort to assemble and organize the existing body of knowledge as it affects fuel economy, the open literature was critically reviewed. It is the opinion of this author that an important need of the general aviation technical community will be fulfilled if a document containing the reviewed material with the gaps closed could be made available to the workers in the field. It was deemed that the presentation of the results of the Hydrogen Enrichment for Aircraft Piston Engines Program was an unusual opportunity for such an attempt in spite of the constraints imposed by the scope o f the program. This document contains then a summary of the body of knowledge in aircraft-engine ultralean operation for fuel economy improvement as well as the results of the technical phases of the program. The material has been presented in a somewhat tutorial. form with the intention of making the subject more useful to those in need of data and who lack specialization in the field. Section II contains a historical background illustrating the struggle of aviation for range improvement with a particular emphasis on engine design parameter development, particularly fuel economy and weight. Section III presents a quick review of the general characteristics of a modern aircraft piston engine in general aviation as well as a functional and anatomic description.. Section IV reviews those factors which affect the fuel economy of an engine. Section V elaborates on the procedures and the technical background related to fuel economy improvement by leanout, iden- tifying ultralean operation as the most promising and unexploited technique to achieve fuel economy. Section VI penetrates into the heart of the program iv and fully describes the original hydrogen enrichment technique for ultralean operation as well as the modified procedure for gasoline only which was successfully tested during the program and which proved to be most gratifying to the aircraft industry. Section VII conducts an assess- ment of the applicability of advanced ultralean techniques for the engines presently manufactured and in service but from which no experimental data is available to judge their eligibility. Section VIII is in essence a study of the strategy required as well as the logistics involved should ultralean burning be attempted now, and takes into account the existing confusion in the fuel situation, aircraft engine evaluation, and introduction of advanced systems in general aviation. The study also includes highlights of trends in the automobile industry as they may affect further developments in general aviation. A summarized list of conclusions and recommendations is offered in Section IX for convenience. This document will without a doubt awake controversy and disagreement among some of the engine specialists active in industry and government agencies. It hrs been the honest attempt of the author to present the findings of the program and his views as principal investigator. It is hoped that other more detailed studies and developments will follow which may verify, clarify, disprove or contradict the claims presented herein, but it is judged that the main objective of the program has been accomplished if the attention of the aircraft industry and government agencies is focused on ultralean combustion as a potential for improving fuel economy in aviation during the transition scenario to alternate fuels. J. E. Chirivella Principal Investigator Hydrogen Enrichment for Aircraft Piston Engines f f i p v :i ACKNOWLEDGMENTS The Hydrogen Enrichment for Aircraft Piston Engines Program was initiated and carried on under the direction of the NASA/OAST Office of Aeronautical Propulsion. AVCO-Lycoming Division s..d Beech Aircraft Corporation were under contract and fully participated during the different program phases. The author is grateful for support given the program by many individuals and organizations. Key roles were played by the following people: From the Jet Propulsion Laboratory: Wesley A. Menard, Supervisor of the Combustion Research Group and former principal investigator of this program, who was instrumental in starting the program and who provided technical direction during Phase I. He was also responsible for the planning of Phase II and later continued to provide technical and administrative guidance. A major portion of the success of the program is credited to him. Donald J. Cerini, Task Leader for Development of the Hydrogen Generator, who advanced the hydrogen generator technology to the point of making it airworthy for the flight test phase. He operated the hydrogen generator in flight, an arduous task. Glen H. Haskins, who conducted the integration and installation of the hydrogen generator systems on the engine. His indefatigable dedication to the program is here especially acknowledged. Jack Rupe, developer of the hydrogen enrichment concept, who was deeply involved in organizing and starting the program. Philip I. Moynihan, Member of Technical Staff and task leader for the systems analysis conducted in Phase I, who provided the initial evaluation of the merits of the ultralean burn approach. Jerry L. Brown, from the Procurement Division, who conducted the contractual effort. Doug Maple, who was responsible for editing the report and whose valuable suggestions have substantially enhanced it. Richard M. Clayton, who reviewed the final report and provided important suggestions in the organization of the presented material. From AVCO-Lycoming Division: Frank Riddell, Vice President of Engineering, for sharing his remarkable engine experience and for the enthusiastic support he gave to the program. vi Larry C. Duke, Assistant Chief Engineer, who headed the Lycoming technical team that had responsibility for the test cell phase. Dr. Duke's numerous suggestions contributed to the success of the program. Roy Meyer, test engineer who conducted the tests and collected the data. From Beech Aircraft Corporation: Robert C. Umscheid, who headed the Beech Technical team and was responsible for the flight test phase of the program. Mr. Umscheid contributed very effectively in all phases of the program, providing technical assistance and support as a formidable organizer. 0. W. Scott, Chief, R&D Systems, who enthusiastically supported the program, providing a valuable interface. Van D. Gregg, project pilot, who skillfully implemented, in flight, the ultralean techniques through a wide range of operating conditions. L. Johannsen, flight test engineer, who collected and reported the flight test data. The author wishes in particular to express his gratitude to H. W. Johnson and D. J. Miller of the NASA/OAST Office of Aeronautical Propulsion for their direction, guidance, interest and support. Finally, but not least, the author expresses his appreciation to his wife, Margaret Chirivella, who assembled and typed the rough draft of this report with no motivation but love. vii ABSTRACT The role of ultralean combustion in achieving fuel economy in general aviation piston engines is investigated. The aircraft internal combustion engine is reviewed with regard to general aviation require- ments, engine thermodynamics and systems.