Hydraulic Simulation of a Ramjet Combustion Chamber: An Optical Method for Local Equivalence Ratios Measurements and Comparison With a CFD Code

Hydraulic simulation is a very useful tool to predict global performances of ramjet combustion chambers and optical techniques can give a lot of information concerning the structure of the flow. Until recently, in the special case of combustion chambers, an optical method, called “global colorimetry” was used in order to obtain a global repartition of equivalence ratios and to predict combustion efficiency. Even if this method is powerful and predictive, it only gives global results. On the other hand, CFD codes give local results on a mesh and need local measurements to be validated. That is the reason why a new optical method, called “local colorimetry” has been developed with a two lateral inlet ramjet research chamber specifically designed for being installed on a hydraulic test rig in order to obtain an experimental database to validate numerical codes. Visualizations are shown and the optical method using laser tomography, LIF and digital acquisition and processing is explained. Experimental procedures are detailed and results concerning local air and fuel flow rates, and local equivalence ratios or mixture fuel/air ratios are analyzed. In addition, an ONERA CFED code is presented and the calculated results are compared with experimental data. Then, recent developments and prospects of the method are presented.