Development and Application of Laser Techniques for Studying Fuel Dynamics and NO Formation in Engines

Abstract: Development and application of some laser techniques for the study of engine combustion are presented. The investigations mainly cover two aspects: fuel dynamics and formation of NO. Fuel dynamics is one of the most central problems in engine design since many performance parameters are affected by it; emission formation, efficiency, drivability etc. The studies include cycle-resolved measurements of short-circuiting losses in two-stroke engines, mixture stratification in a direct-injection gasoline engine, and mixture formation in DI diesel engines. NO is one of the most harmful pollutants from combustion and is subject to tightening emission regulations. Absolute NO concentrations were determined in a near-production spark ignition engine, and a two-photon detection scheme was evaluated for use in practical applications. Furthermore, an alternative fuel for diesel engines, DME, was investigated with respect to optical properties and fuel properties when used in DI diesel engines. One of the major advantages of using laser diagnostics in this context is their unique capability of providing simultaneous multi-point information in two dimensions, e.g. on species concentrations. They also feature superior spatial and temporal resolution and are, almost always, non-intrusive. The use of probe sampling to determine species concentrations yields lower resolution in space and time and inevitably disturbs flows and temperature fields.