m /F .....30 ...... DOE/NASN0032-34 NASA CR-190780 MTI Report 91TR15 Automotive Stirling Engine Development Project William D. Ernst Mechanical Technology Incorporated Latham, New York and Richard K. Shaltens Lewis Research Center Cleveland, Ohio February 1997 Prepared for NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Lewis Research Center Under Contract DEN3-32 for U.S. DEPARTMENT OF ENERGY Conservation and Renewable Energy Office of Vehicle and Engine R&D DOE/NASA/0032-34 NASA CR-190780 MTI Report 91TR15 Automotive Stirling Engine Development Project William D. Ernst Mechanical Technology Incorporated Latham, New York Richard K. Shaltens Lewis Research Center Cleveland, Ohio February 1997 Prepared for National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio 44135 Under Contract DEN3-32 for U.S. DEPARTMENT OF ENERGY Conservation and Renewable Energy Office of Vehicle and Engine R&D Washington, DC 20545 Under Interagency Agreement DE-AI01-85CE50112 Page intentionally left blank Mechanical Technology Inc. SUMMARY The objectives of the Automotive Stifling Engine (ASE) Development project were to transfer European Stirling engine technology to the United States and develop an ASE that would demonstrate a 30% improvement in combined metro-highway fuel economy over a comparable spark ignition (SI) engine in the same production vehicle. In addi- tion, the ASE should demonstrate the potential for reduced emissions levels while maintaining the performance characteristics of SI engines. Mechanical Technology Incorporated (MTI) developed the ASE in an evolutionary manner, starting with the test and evaluation of an existing stationary Stirling engine and proceeding through two experimental engine designs: the Mod I and the Mod II. Engine technology development resulted in elimination of strategic materials, increased power density, higher temperature and efficiency operation, reduced system complexity, long-life seals, and low-cost manufacturing designs. Mod Ii engine dynamometer tests demonstrated that the engine system configuration had accomplished its performance goals for power (60 kW) and efficiency (38.5%) to within a few percent. Tests with the Mod II installed in a delivery van demonstrated a combined fuel economy improvement consistent with engine performance goals and the potential for low emissions levels. A modified version of the Mod II was identified as a manufacturable ASE design for commercial production. In conjunction with engine technology development, technology transfer proceeded through two ancillary efforts: the Industry Test and Evaluation Program (ITEP) and the NASA Technology Utilization (TU) project. The ITEP served to introduce Stirling tech- nology to industry, and the TU project provided vehicle field demonstrations for third- party evaluation in everyday use and accomplished more than 3100 hr and 8,000 miles of field operation. To extend technology transfer beyond the ASE project, a Space Act Agreement between MTI and NASA-Lewis Research Center allowed utilization of pro- ject resources for additional development work and emissions testing as part of an industry-funded Stirling Natural Gas Engine program. iii Page intentionally left blank MechanicalTechnologyInc. TABLE OF CONTENTS PAGE SECTION iii SUMMARY ............................................................. LIST OF FIGURES ........................................................ vii LIST OF TABLES ......................................................... ix 1.0 INTRODUCTION AND BACKGROUND ................................... 1-1 1.1 ASE Project Summary ............................................. 1-1 1.2 Report Content .................................................. 1-12 2-1 2.0 MOD I ENGINE SUMMARY ............................................ 2-4 2.1 Mod I Engine Operation and Performance ............................. 2.2 Industry Test and Evaluation Program ................................ 2-5 2.3 Endurance Testing ............................................... 2-7 3.0 MOD II ENGINE DEVELOPMENT ....................................... 3-1 3.1 Original Design Description ........................................ 3-1 3.1.1 External Heat System ....................................... 3-2 3.1.2 Hot Engine System ......................................... 3-7 3.1.3 Cold Engine/Drive System .................................... 3-13 3.1.4 Control Systems and Auxiliaries ............................... 3-28 3.2 Hardware Development ........................................... 3-41 3.2.1 Design Changes from the Original Hardware Design ............... 3-41 3.2.2 Test and Development Efforts ................................. 3-46 3.2.3 Engine Test History Summary ................................. 3-52 3.3 Fuel Economy ................................................... 3-55 3.3.1 Initial Mod II/Vehicle Design ................................... 3-59 3.3.2 Mod II Fuel Economy ........................................ 3-61 3.3.3 Engine and System Hardware Effects on Fuel Economy ............ 3-65 3.3.4 Vehicle Effects on Fuel Economy .............................. 3-66 3.4 Deere & Co. Manufacturing Cost Study ................................ 3-67 4.0 TECHNOLOGY TRANSFER ............................................ 4-1 4.1 NASA TU Project ................................................. 4-1 4.1.1 Phase I................................................... 4-3 4.1.2 Phase II .................................................. 4-8 4.1.3 Phase III .................................................. 4-12 4.2 Stirling Natural Gas Engine Program ................................. 4-15 5.0 TECHNOLOGY STATUS AND DEVELOPMENT NEEDS ..................... 5-1 5.1 Performance Improvement ......................................... 5-1 5.2 Emissions Reduction ............................................. 5-5 5.3 Manufacturing Cost Reduction ...................................... 5-6 5.4 Reliability/Operational Improvements ................................. 5-7 V Mechanical Technology Inc. TABLE OF CONTENTS (continued) SECTION PAGE 5.5 Adaptation to Nonautomotive Applications ............................. 5-8 5.6 Other Technology Needs .......................................... 5-9 5.7 Summary ....................................................... 5-9 6.0 CONCLUSIONS ..................................................... 6,1 7.0 REFERENCES ...................................................... 7-1 APPENDIX A: BIBLIOGRAPHY OF RELEVANT ASE PROJECT PUBLICATIONS ...... A-1 APPENDIX B: ASE PROJECT DOCUMENTATION CATEGORIZED BY ENGINE NUMBER ......................................... B-1 vi MechanicalTechnologyInc. LIST OF FIGURES NUMBER PAGE 1-1 ASE Project Summary Schedule .................................... 1-4 1-2 Engine Technology Progression ..................................... 1-5 1-3 Engine Pedormance-lmprovement Trends ............................. 1-7 1-4 Summary of Emission Testing with Mod II-Powered LLV ................... 1-10 1-5 Mod II Net Shaft Power ............................................ 1-11 1-6 Mod II Net Shaft Efficiency . ........... .................. 1-11 2-1 Comparison of Mod I and Upgraded Mod I Engines ...................... 2-2 2-2 Upgraded Mod I Engine Performance ................................ 2-5 2-3 ITEP Schedule .................................................. 2-6 2-4 Accelerated Duty Cycle ............................................ 2-8 2-5 Federal Urban Driving Cycle ........................... ............. 2-8 3-1 Mod II BSE Cross Section ......................................... 3-1 3-2 External Heat System ............................................. 3-2 3-3 CGR Combustor Assembly ......................................... 3-4 3-4 Fuel Nozzle and Ignitor ..................................... ....... 3-6 3-5 Typical Annular Heater Head ....................................... 3-8 3-6 Typical Annular Hot Engine System .................................. 3-9 3-7 Heater Head Tube ............................................... 3-10 3-8 Fins on Rear Row Tubes .......................................... 3-10 3-9 Heater Head Assemblies .......................................... 3-11 3-10 Hot Engine System ............................................... 3-12 3-11 Regenerator Assembly ............................................ 3-12 3-12 Cold Engine/Drive System ......................................... 3-13 3-13 Pistons Protruding Through Coolers .................................. 3-15 3-14 Water Passages ................................................. 3-15 3-15 Cooler Assembly ................................................. 3-17 3-16 Seal Housing Assembly ........................................... 3-18 3-17 Piston and Connecting Rod Assembly ................................ 3-19 3-18 Crankshaft Assembly ............................................. 3-21 3-19 Crankpin Offset .................................................. 3-22 3-20 Lubrication System ............................................... 3-25 3-21 Cooling System .................................................. 3-26 3-22 Balance System Schematic ........................................ 3-28 3-23 Engine Control Systems ........................................... 3-29 3-24 Combustion Control System ........................................ 3-31 3-25 Heater Head Temperature Control ................................... 3-33 3-26 Air-to-Fuel Ratio Control ........................................... 3-34 3-27 Combustion Air Supply ...........................................