Non-Reactive Experimental Analysis of an Exhaust Section downstream of a CVC

The overall architecture of gas turbines has been recently re-evaluated by investigating innovative cycles aimed at substantially increasing the thermal efficiency. One attractive solution is the pressure gain combustion cycle and in particular the Constant Volume Combustor (CVC) technology. The aim of this paper is to present the experimental results obtained analyzing an exhaust system designed to integrate a CVC with a high-pressure turbine vane. In particular, the geometry of the CVC tested at the PPrime Institute has been considered for the design of the new device. That CVC uses a mixture of air and liquid iso-octane, while an isochoric, exothermic process is ensured by using two pairs of rotary valves. The newly-designed transition duct aims at greatly reducing the flow fluctuations generated by the valves, and is positioned between the CVC and an existing converging-diverging nozzle. Two windows are placed at the top and at the side of the duct to allow for performing particle image velocimetry analysis. The current experimental campaign is inert as fuel injection does not take place. Two different test runs have been performed by varying the inlet stagnation pressure of the combustion chamber. Obtained results demonstrate the ability of the duct to both accelerate the flow field and reduce the time-dependent distortions generated by the exhaust valves. The presented results also pave the way for a following reactive campaign, which is expected to prove the overall concept and to provide fundamental information about the coupling between the CVC and the turbine.