Transient Plasma Ignition for Clean, Fuel-Efficient, Transportation Vehicle Engines. Final Report

摘要

The use of non-thermal transient plasma ignition (TPI) as an alternative to spark ignition (SI) for internal combustion engines was investigated. A 2.5 liter 4-cylinder test engine was used that has two spark plug ports per cylinder to enable direct, instantaneous and valid comparisons of spark and corona ignition at the same time under identical engine operating conditions. A ceramic corona electrode was designed that fits in the new test engine and is capable of withstanding the pressures and temperatures encountered inside the combustion chamber. The corona ignition system was tested on the engine and an increase (compared to spark ignition) in both peak pressures and indicated mean effective pressure (IMEP) were observed. Testing showed typically 15 - 20% increases in IMEP and much shorter burn durations at identical operating conditions. Moreover, the tradeoff between thermal efficiency and brake specific NOx emissions was found to improve with TPI. It is proposed that these advantages of corona ignition may be exploited by either (1) the use of leaner fuel-air ratios or (2) by designing engines with lower turbulence levels, thereby reducing heat loss to cylinder walls and increasing thermal efficiency, and employing corona ignition to obtain sufficiently rapid burning.