Development and Validation of a 0-D/1-D Model to Evaluate Pulsating Conditions from a Constant Volume Combustor

The growing demand in electrical power, the increased number of flight passengers, and the constantly increasing mean global temperature level push towards a remarkable performance improvement of Gas Turbines (GTs), which are yet probably close to their technological limit. Hence, research community in turbomachinery is trying to adopt a different GT cycle based on the Pressure Gain Combustion (PGC) concept. That innovative technology exploits a pressure rise within the combustion process (e.g., Constant Volume Combustor, Rotating Detonation Combustor, etc.), thus theoretically leading to higher thermal efficiency (+15 per cent for small/medium GT size) and conversely to lower specific fuel consumption. Institute Pprime operates a Constant Volume Combustor (CVC) with rotary valves fed by a mixture of air and liquid iso-octane. A rectangular duct coupled with a converging-diverging nozzle is placed downstream from the combustion chamber. An experimental campaign by Pprime offers time-resolved pressure measurements of the test rig that serve as boundary condition and validation data for numerical simulations. The present paper aims at performing 0-D / 1-D modelling of CVC using the GT-Power software, which is an Internal Combustion Engine (ICE) modelling tool that involves piston s motion. The latter is here modified in accordance to the peculiar motionless case of CVC. By considering a parametrization of discharge coefficients, a modified non-dimensional burning rate, and an appropriate heat transfer model the simulation is able to match the experimental pressure fluctuation with acceptable accuracy. The main outcome of the present activity relies on the definition of credible CVC exit conditions, otherwise unavailable. The obtained total pressure and total temperature pulsating conditions are necessary to study the existing nozzle, and will be used to design a designed transition duct able to weaken flow pulsation and to properly feed the turbine, thus counteracting the cycle s efficiency reduction associated to the unsteady CVC outflow.