Abstract
The reduction of fuel consumption and pollutant emission is the main objective in development of modern IC-engines. A promising method to achieve this is the use of DI-SI engines with a spray-guided mixture formation. One advantage in efficiency of direct injection is the evaporation cooling of the fuel, which allows a higher compression. Although the compression temperature inside the engine can be calculated easily from the boundary conditions, the resulting mixture is not homogeneous through the combustion chamber. Thus, a spatial and temporal resolved measurement of the temperature and fuel concentration during injection is required to locally resolve evaporation rate, mixing and cooling in the spray. An approved method to measure temperature and concentration with a high temporal and spatial resolution under engine relevant conditions is planar laser-induced fluorescence (PLIF). For measurements in the spray, 3-pentanone as fluorescence tracer is added to a non-fluorescent surrogate fuel. The spray of a multi-hole injector is excited quasi-simultaneously by two different excimer lasers (2-line LIF), the temperature and the vapor mass fraction of the fuel can then be calculated from the two signals. The measurements are conducted in a high temperature/pressure cell, where engine relevant conditions can be simulated. To quantify temperature and concentration correctly, a precise fluorescence calibration of the tracer in a flow cell as well as an optimized post processing strategy of the raw images is presented. The results of the measurement are compared to a CFD-simulation under same conditions.
