Numerical and experimental study of the vaporization cooling in gasoline direct injection sprays

The spray of a high-pressure gasoline direct injection (GDI) injector has been studied experimentally at engine-like conditions and by numerical simulations. The high-pressure injection of isooctane fuel into a chamber leads to an evaporation of the injected liquid and to the formation of an ignitable fuel–air mixture at particular locations in the spray. The energy needed for this evaporation is provided by the background gas which in turn experiences a temperature drop. Experiments were conducted using the pure rotational coherent anti-Stokes Raman scattering (RCARS) technique in order to measure the temperature of the gas phase. The numerical simulation were done with a mixed Eulerian–Lagrangian approach. For varying injection pressures, a clear influence on the vaporization cooling has been found in the numerical results which is in contrast to the experiments. However, the experimental results for varying fuel temperatures are well reproduced.