The near-wall jet in crossflow (JICF) is a configuration applied for different purposes. In gas turbine combustion chambers, the injection of dilution air and the injection of fuel into a crossflow for mixing and subsequent reacting are examples of reacting JICF. In the field of film cooling, air injections help to isolate a component's surface from aggressive flows and cool it. Active cooling is necessary and even inevitable to protect the combustor as well as turbine vanes and blades from the high thermal loads, which exceed the material capability limits. Obviously, non-reacting and slow mixing processes and interaction with the mainstream are intended in this case. However, the injected air for film cooling may mix and ignite near the surface due to the presence of reactive elements and residual fuel within the turbulent main flow in combination with high temperature conditions. The desired cooling of the component changes to heat release to the surface. This phenomenon was already demonstrated in literature. Thus, the accurate thermal design of components and the JICF investigation are essential processes. To study the appearance and structure of reacting JICF together with the heat release to the wall, a test bench was designed and operated for the injection of cold gaseous fuels into a hot oxygen-rich mainstream of 1600 K. The focus was on hydrogen, methane and propane, as the interest in these fuels has increased lately. Optical measurement techniques were applied to give insight into the reaction zone. Additionally, installed thermocouples within the surface provided temperature data, which were used in a post-processing step to determine the wall heat fluxes by means of the inverse heat conduction method. Hydrogen showed highest reactivity and led to the highest heat flux augmentation even at low fuel mass flow rates. The stable flames were directly anchored to the injection locations. From two-line laser-induced thermometry, reaction temperatures around 1800 K were determined, which were higher than that of the hydrocarbons. The reaction zone of methane on the other hand was least stable and highly turbulent. A significant ignition delay was found for methane. In addition, lowest heat fluxes were detected. In general, the ignition location of the hydrocarbons shifted upstream with increasing momentum ratio, but moved away from the surface, such that the heat release to the surface declined. Compared to angled injection, the normal injection reduced the ignition delay, as enhanced mixing occurred. Even though lower fuel mass flows were injected in the angled configuration, the heat fluxes were comparable to those of normal injection. The structure of the reaction zone was validated by numerical results. RANS simulations with the Eddy Dissipation Concept combustion model were performed. The shape of the simulated reaction was in good agreement with the experimental findings and also an ignition delay length could be predicted by the simulation. However, the combustion model overestimated the reaction temperature.    «

The near-wall jet in crossflow (JICF) is a configuration applied for different purposes. In gas turbine combustion chambers, the injection of dilution air and the injection of fuel into a crossflow for mixing and subsequent reacting are examples of reacting JICF. In the field of film cooling, air injections help to isolate a component's surface from aggressive flows and cool it. Active cooling is necessary and even inevitable to protect the combustor as well as turbine vanes and blades from the...    »