Investigation of Spark-Ignited
Combustion in
Very High Speed, Four-Stroke Engines, 03-9280
Principal Investigators
Rudolf H. Stanglmaier
Charles E. Roberts
Darius Mehta
Christopher J. Chadwell
J. Corwin Snyder
Inclusive Dates: 10/01/01 - 01/01/03
Background - Modern race engines operate at speeds approaching 20,000 revolutions per minute (rpm), yet much of SwRI's understanding of spark-ignited combustion was developed from experimental data obtained below 3,000 rpm.
Approach - The goal of this project is to develop a fundamental understanding of the combustion process in very high-speed, spark-ignition engines and to correlate the laminar burning velocity of the fuel-air mixture to engine performance. The approach involves three distinct tasks: 1) characterizing high-performance fuels by measuring relevant properties, 2) measuring combustion performance of these fuels in an engine operating at very high speeds, and 3) using experimental results to extend and validate in-house combustion models. More specifically, a procedure was developed for measuring the laminar burning velocity of fuel-air mixtures. This fundamental property, which is of great interest for high-speed combustion, is not generally available. These fuels are being tested in a production motorcycle engine capable of operating at engine speeds up to 13,000 rpm, under carefully controlled conditions. Finally, the experimental results will be used to validate in-house combustion models. It is expected that the submodels for turbulence intensity and decay will require tuning or modification, as they were developed from experimental results obtained at much lower engine speeds.
Accomplishments - A technique for measuring the laminar burning velocity of air/fuel mixtures was developed and validated. This technique involves the use of a centrally ignited spherical combustion chamber (top illustration), and a complementary analysis code. More than 40 different fuel samples have been tested to date. A high-speed motorcycle engine has been used successfully to measure the relative performance of several fuels (second illustration). A procedure for measuring the fuel's sensitivity to equivalence ratio and spark timing has been developed and employed. The team has obtained excellent agreement between the measured spark timing for best power and the expected spark advance based on the measured laminar burning velocity of the fuels. During the final stage of the project, an in-house combustion model will be calibrated with the use of the experimental engine and burning velocity data.
 |
|
|
Apparatus and data acquisition equipment for the measurement of laminar burning velocity of fuel-oxidizer mixtures under elevated pressures and temperatures |
|
  |
|
|
Front (left) and back (right) views of the engine, showing instrumentation for cylinder pressure, exhaust oxygen content, and various temperatures |
|
