DOE/NASA/0032-28 NASA CR-175106 MT186ASE58SRI . Automotive Stirling Engine Mod II Design Report Noel P. Nightingale Mechanical Technology Incorporated Latham, New York 12110 October 1986 Prepared for National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio 441 35 Under Contract DEN 3-32 for s U.S. DEPARTMENT OF ENERGY Conservation and Renewable Energy Office of Vehicle and Engine R&D Washington, D.C. 20545 Under Interagency Agreement DE-AI01 -85CE50112 PREFACE This report presents the culmination of years of work Many people helped in the preparation of this by many dedicated individuals. It describes an report. With great injustice. there is no space here to engine that places the United States at the forefront thank each person individually. My acknowledg- of a new, dynamic technology The need for this ment, though, would be incomplete without thanking engine was recowzed by Congress in the mid- 1970s Dr. Beno Sternlicht,whose vision gave the Automotive when it sought to protect our nation from the Stirling Engine program an identity, I also wish to vulnerability of a dependency on a sole type of thank those who made it possible for the work to be fuel. An alternative power plant -one with superior performed, including congressional leaders, mem- efficiency and multifuel capability over existing bers of the Department of Energy, and the very engines-was envisioned. competent staff of NASA particularly at the Lewis The Stirling engine is this alternative. Research Center. The engineers and staff at United Stirling AB in Malmo, Sweden, receive my most Invented in the early nineteenth century, the Stirling engine was regarded as a laboratory curiosity and grateful praise for their patience and guidance in the engine design. Similarly, credit must be gwen to was not taken seriously by the engineering com- the Mechanical munity What hampered its development? Two engineers at Technology Incor- porated who devoted endless hours and a great reasons are evident. a heat engine, the Stirling As deal of their personal time to this effort. In particular, must operate at high temperature, e.g.,7OOOC the engine described herein was conceived mainly ( 1292OF). and the long-life, high-temperature materials necessary were not available. Second, by John Corey to whom we are all indebted for his early Stirling engines were slow-running machines keen understanding of the Stirling cycle and his practical design talents. that produced low power and therefore could not compete with the more versatile spark ignition and Special mention must be extended to Sharon diesel engines. These reasons are no longer valid, Valiquette for visualizing the format of this report. as evidenced by the work described in this report. Without her unique talents as editor, this report In fact, I maintain that Stirling engine technology would be just another technical document rambling for hundreds of pages. Finally, the unique graphics now contains advancements as rapid and siccant as those in microchip technology and that this leap are the result of the special talents of Dean Rueckert whom express my thanks. forward will invalidate any existing misconceptions to I of Stirling in the general technical community Although designed for an automotive application, the basic concept of this engine can be used across Noel P. Nightingale a broad range of applications. It represents, there- Assistant General Manager fore, not a subtle change in the technology but a Stirling Engine Systems Division watershed achievement. Mechanical Technology Incorporated There will be those who will read this document and smugly whisper that the Stirling engine will never be a practical power plant and that the need for such an engine has disappeared forever. In reply to those readers, I offer the following quote from the US.Gas Turbine Committee of the National Aca- demy of Science in 1940: "Even considering the improvement possible . the gas turbine could hardly be considered a feasible application to airplanes because of the difficulty in complying with the stringent weight requirements." iii CONTENTS PREFACE iii AUTOMOTIVE STIRLING ENGINE 1 ENGINE DESIGN SUMMARY 5 MOD I1 STIRLING ENGINE -A SYNOPSIS EXTERNAL HEAT SYSTEM HOT ENGINE SYSTEM COLD ENGINE/DRIVE SYSTEM CONTROL SYSTEMS AND AUXILIARIES CONCLUSIONS 37 APPENDIX A 38 CHEVROLET CELEBRITY SPECIFICXION APPENDIX B 40 MOD I1 ENGINE SPECIFICATION APPENDIX C 41 FUEL ECONOMY AND PERFORMANCE CALCULATIONS APPENDIX D 42 THE AUTOMOTIVE STIRLING ENGINE DEVELOPMENT PROGRAM BIBLIOGRAPHY 50 V AWOMOTIVE STIRLING ENGINE As established in 1978, Title I11 of public Law 95-238, Other engine development efforts addressed the Automotive Propulsion Research and Develop- emission levels, power train reliability and life, com- ment Act directed the Secretary of Energy to create petitive initial and life-cycle costs, and noise and new programs and to accelerate existing ones within safety characteristics to meet 1984 federal standards. the Department of Energy (DOE) to ensure the The design and demonstration of an automotive development of advanced automotive engines. The Stirling engine, designated the Mod 11, represent the act was based on congressional findings that existing realization of these ASE program goals. The Mod I1 automotive engines failed to meet the nation’s long- reflects the advancements made in Stirling tech- term goals for energy conservation and environ- nology and specifically addresses those problems mental protection. Similar congressional findings that heretofore had prevented the Stirling from established that advanced, alternative automotive achieving widespread acceptance. The Mod I1 not engines could, given sufficient research and de- only fulfills the promise of superior fuel economy velopment, meet these goals and offer potential for but nullifies arguments that Stirling engmes are mass production at a reasonable cost. heavy, expensive, unreliable, and demonstrate To this end, Congress authorized an expanded poor performance. research and development effort to advance auto- motive engine technologies such as the Stirling cycle. The intent was to complement and stimulate corre- AUTOMOTIVE STIRLING ENGINE sponding efforts in the private sector and, in turn, TECHNOLOGY PROGRESSION encourage automotive manufacturers to seriously consider incorporating such technology into their -1978 -1986 products. The Automotive Stirling Engine (ASE) WeighVPower 8.52 kg/kW 3.35 kg/kW Development Program evolved from this legislation. (14 Ib/hp) (5.5 Ib/hp) The program began at Mechanical Technology Manufacturing Cost* $5000+ $1200 Incorporated (MTI) in Latham, New York, in March 1978. Funding was provided by DOE and adminis- Acceleration 36 s 12.4 s** tration by the National Aeronautics and Space 0-97 km/h (0-60 mi/h) Administration Lewis Research Center (NASA-LeRC), Combined Fuel 8.1 km/L 17.5 km/L Cleveland, Ohio, under Contract DEN3-32. Economy (19 mi/gal) (41 mi/gal) The ASE program set out to meet a substantial Rare Metals Cobalt None challenge -the successful integration of a Stirling Seal Life 100 h 2000+ h + engine into an automobile with acceptable driv- *Based on 300,000 units per year ability. At the outset of the program, the main **1417-kg (3125-Ib) car objectives were to develop an automotive Stirling engine and to transfer European Stirling engine tech- nology to the United States. These generic goals have The 1985 Chevrolet Celebrity was chosen as the remained constant, as did a program approach baseline vehicle. This General Motors A-body car focusing on concurrent engine and component has a manual four-speed transmission, a 2.66 drive development efforts. axle gear ratio, and an EPA inertia test weight of The detailed program objectives addressed various 136 1 kg (3000 lb).A front-wheel-drive car, the facets of engine development. First, the automotive Celebrity is representative of the mqority of cars sold Stirling engine must demonstrate at least a 30% in the United States; the A-body line accounted for improvement in EPA combined urban/highway fuel 20% of all GM sales in 1984: Appendix A includes economy over a comparable spark ignition engine. the vehicle specification and Appendix B includes Second, the engine must be installed in an American- the engine specification. manufactured car representative of a reasonable portion of the US. automotive market. Further, to ensure the most meaningful fuel economy com- ‘Selection of the manual transmission purposely deviated from parison, the acceleration rate of the Stirling-powered the popular configumtion. The stock gear mtios am better suited vehicle must match that of the spark ignition-powered to the Stirling application,and the shift schedule could be vehicle, as must the Stirling’s drivability in terms of changed easily and optimized for Stirling engine opem-bon. braking, smooth acceleration with no noticeable peaks or lows, and quick accelerator response. 1 h- m m The Mod 11-powered Celebrity has a predicted com- .-1 E bined fuel economy on unleaded gasoline of 17.5 v km/L (4 1 mi/gal) versus 13.2 h/L(3 1 mi/gal) for the i spark ignition-powered Celebrity E Y The comparison for the highway and urban mile- ages is equally impressive. Highway mileage is s 0 predicted to be 24.7 km/L (58 mi/gal) for the Mod I1 z versus 17.1km/L (40 mi/gal) for the spark ignition engine; urban mileage is 14.1km/L (33 mi/gal) W versus 1 1.1 km/L (26 mi/gal). Confidence for these -I W Mod I1 predictions is based on experience to date 3 with the earlier ganeration Stirling engines used in u. 0 the program. W -z The Celebrity is a highly eff icient vehicle, with a rn fuel economy well above the fleet average for U.S. 907 1361 1814 2268 2 (2000) (3000) (4000) (5000) automobiles. Thus, the Mod I1 predicted fuel economy 0 0 is not only 32% above that of the Celebrity but also TEST WEIGHT, kg (Ib) 50% fleet above the average.