Session: 06-02 Pressure Gain Combustion I

Paper Number: 129204

129204 - Numerical Analysis and Design of New Exhaust Section Downstream of Constant Volume Combustor 

During the last 30 years, the increasing power demand and the evidence of climate change led the scientific community to turn its research interest towards more sustainable energy systems. For more than 60 years, remarkable advancements were applied in the field of Gas Turbines (GT) for the enhancement of their performance. However, the feasibility region for further efficiency improvements is likely fully explored in the case of conventional GTs, in which the burner is based on the constant-pressure process. Consequently, innovative solutions should be employed. Within this framework, Pressure Gain Combustors (PGC) could offer a breakthrough solution exploiting either their isochoric or detonative heat release process. These unconventional machines can increase the stagnation pressure along the combustion process resulting in higher temperature levels at the entrance of the High-Pressure Turbine (HPT) vane. Nevertheless, the resulting increment of the cycle's thermal efficiency should not be accompanied by the counteract of the harsh oscillating exhaust flow by the PGC. A key milestone for these technologies is to appropriately couple the PGC with the HPT, focusing on the alleviation of the strong unsteadiness of the flow. On this basis, Pprime Institute operates a prototype Constant-Volume Combustor (CVC) with rotary valves fed by a mixture of air and liquid iso-octane. The current exhaust plenum consists of a rectangular plenum coupled with a converging-diverging nozzle. The present work describes the design methodology of a new exhaust section which can suppress the fluctuating behaviour of the outflow and properly guide the high enthalpy burned gases inside of the HPT to allow for an efficient expansion. The components of the new outlet section are the existing rectangular plenum, a transition duct, and a transonic Inlet Guide Vane (IGV) series. The current work explores the flow dynamics of these elements by numerical means using the commercial 3-D solver ANSYS Fluent. This activity is split into two parts. In the first part of the paper the design of the transition duct is introduced and the parametrization of the upper and lower endwalls are described. A Design of Experiments (DOE) of 81 samples is presented. The flow domain includes the spacer and the transition duct followed by a large artificial plenum to attenuate the oscillating pressure waves before reaching the outlet boundary. Every case is tested for two periods of the CVC by solving the Unsteady Reynolds-Averaged Navier-Stoke (URANS) equations under the appropriately scaled down periodic transient inlet boundary conditions. Due to the absence of the IGVs, there is a need to scale down the varying inlet boundary conditions to analyse the pulsating behaviour of the samples in their actual subsonic flow regime. The election of the best duct is based on the pressure losses and on their oscillating behaviour during the last analysed period. Afterwards, the flow analysis results of the baseline, worst and best case are highlighted. The second part of the paper refers to the study of the ensemble exhaust system. The flow domain consists of the spacer, the best given transition duct by the DOE, the IGVs, and a large artificial plenum. The total throat area of the four IGV channels per CVC is equal to the throat area of the existing circular nozzle. The LS89 vane by von Karman Institute for Fluid Dynamics (VKI) is chosen as an appropriate airfoil profile. Its presence allows for applying the real time-resolved periodic inlet boundary conditions. After satisfying the unsteady convergence criteria, one period of CVC is analysed. Every component is evaluated in terms of pressure losses and oscillations. Finally, the performance of the IGV is investigated, where the transonic flow regime alternates with the subsonic flow during one CVC operating period. Present activity is performed in the frame of the INSPIRE project (Grant Agreement 956803) funded by the European Commission through a Marie Sklodowska-Curie action.

 

Presenting Author: Panagiotis Gallis Politecnico di Torino

Presenting Author Biography: Gallis Panagiotis holds a MEng in Mechanical Engineering and specializes in Fluid Dynamics. During his academic studies at the department of Energy of the Aristotle University of Thessaloniki, he developed expertise in the area of Aeronautics and Powertrains. His thesis was concerned with the experimental visualization of compressible flow phenomena in an ORC supersonic turbine rotor, utilizing a water table. Following his undergraduate studies, he completed a research master program, offered by the Von Karman Institute in Belgium. Within the context of the aforementioned course of study, he conducted a research project focusing on the stall inception investigation of the LEMCOTEC H25 test section. He is currently performing Doctoral Studies in the Politecnico di Torino at the Department of Energy (DENERG). His work is focused on the numerical analysis for the investigation of the integration of High Pressure Turbine Stage with the Pressure Gain Combustors. In particular, he explores the interaction between the Constant Volume Combustor (CVC) and Rotating Detonation Engine (RDE) with the first stage of a subsequent turbine. He participates to the EU funded Marie - Curie Activity INSPIRE which is consisted of 15 Early Stage Researchers (ESRS) in 8 insitutions in Europe.

His research interests revolve around CFD analysis, Turbomachinery Optimization and Secondary Flow structures.

Authors:

Panagiotis Gallis Politecnico di Torino
Daniela Anna Misul Politecnico di Torino
Bastien Boust Pprime Institute, CNRS-ENSMA–University of Poitiers
Marc Bellenoue Pprime Institute, CNRS-ENSMA–University of Poitiers
Simone Salvadori Politecnico di Torino