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Automotive Stirling Engine Development Project

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The final report for this project is:

Ernst, William D. and Shaltens, Richard K. (1993), "Automotive Stirling Engine Development Project", Final Report, NASA Contractor Report 190780, MTI Report 91TR15

The Abstract, part of the Summary, the main headings from the Table of Contents and the Conclusions from this report are reproduced below.

 

ABSTRACT

The development and verification of automotive Stirling engine (ASE) component and system technology is described as it evolved through two experimental engine designs: the Mod I and the Mod II.

Engine operation and performance and endurance test results for the Mod I are summarized. Mod II engine and component development progress is traced from the original design through hardware development, laboratory test, and vehicle installation. More than 21,000 hr. of testing were accomplished, including 4800 hr. with vehicles that were driven more than 59,000 miles. 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 engine installed in a delivery van demonstrated combined metro-highway fuel economy improvements consistent with engine performance goals and the potential for low emission levels. A modified version of the Mod II has been identified as a manufacturable design for an ASE.

As part of the ASE project, the Industry Test and Evaluation Program (ITEP), NASA Technology Utilization (TU) project, and the industry-funded Stirling Natural Gas Engine program were undertaken to transfer ASE technology to end users. The results of these technology transfer efforts are also summarized.

 

SUMMARY (partial)

The objectives of the Automotive Stirling Engine (ASE) Development project were to transfer European Stirling engine technology to the United States and develop an ASE that would demonstrate 30% improvement in combined metro-highway fuel economy over a comparable spark ignition (SI) engine in the same production vehicle. In addition, 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. ..........................

(The remaining part of the summary contains essentially the same material that is contained in the abstract)

 

MAIN HEADINGS FROM TABLE OF CONTENTS

  • SUMMARY
  • LIST OF FIGURES
  • LIST OF TABLES
  • 1.0 INTRODUCTION AND BACKGROUND
  • 2.0 MOD I ENGINE SUMMARY
  • 3.0 MOD II ENGINE DEVELOPMENT
  • 4.0 TECHNOLOGY TRANSFER
  • 5.0 TECHNOLOGY STATUS AND DEVELOPMENT NEEDS
  • 6.0 CONCLUSIONS
  • 7.0 REFERENCES
  • APPENDIX A: BIBLIOGRAPHY OF RELEVANT ASE PROJECT PUBLICATIONS
  • APPENDIX B: ASE PROJECT DOCUMENTATION CATEGORIZED BY ENGINE NUMBER

 

CONCLUSIONS

This final report has summarized work performed in the ASE project. The project's success can be determined by comparing accomplishments to the defined project goals and contract requirements. In so doing, the following conclusions can be made:

 

  1. The potential for improvement in fuel economy for Stirling engines over SI engines has been demonstrated. A 10 to 13% improvement in fuel economy for the Mod II over the SI engine has been demonstrated for the USPS LLV in the EPA driving cycle. Based on test data obtained with the LLV, if the original Mod II Celebrity vehicle had been retained for fuel economy demonstration, the project goal of a 30% improvement could have been achieved. The Mod II engine had been sized and optimized for the Celebrity. Component optimization would also provide further improvements for USPS LLV fuel economy.
  2. The potential for low emissions has been demonstrated in the Mod II engine: CO=<2.2 g/mi, NOx=<0.9 g/mi, and HC=<0.4 g/mi with gasoline. The 1985 Federal emission limits were easily met without using a catalyst.
  3. The ability to operate on a broad range of liquid fuels was demonstrated. This evaluation was achieved not only in an engine test cell but also in vehicle operation.
  4. Measured Mod II SES [Stirling Engine System] power and efficiency performance was in excellent agreement with analytical projections, i.e., the differences were less than 4% in power and less than 1% in efficiency.
  5. Vehicle performance of a Stirling engine can be predicted from engine dynamometer test results. The Mod II-powered USPS LLV prediction of a 10% fuel economy improvement in the EPA driving cycle over the comparable SI-powered vehicle was verified by experiment.
  6. A manufacturable Stirling engine automotive design has been identified under the project. The engine is the Mod II (V-block design with annular heater head) concept modified per the Deere & Co. VA/VE study. Manufacturing costs of $3500 to $4000 were projected by Deere & Co. for commercial production of 15,000 units per year.
  7. In accomplishing the objective of transferring European Stirling engine technology to the United States, the ASE project succeeded in establishing an extensive U.S. technology and vendor base capable of designing, developing, and commmercializing Stirling engines. As a further indication of successful technology transfer, MTI, along with a gas industry consortium (GRI, NYGAS, and others) and Hercules Engines, Inc. of Canton, Ohio, is developing a commercial Stirling engine based on ASE technology developed in the Stirling Natural Gas Engine Program.
  8. The NASA TU project demonstrated the ability of a Stirling-powered vehicle to be operated over the road by non-Stirling personnel; it demonstrated adequate availability and drivability.

     

The above report is for sale by the National Technical Information Service, Springfield, Virginia 22161

Last updated: Wednesday, May 3, 1995

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