Session: 06-02 Pressure Gain Combustion I

Paper Number: 126791

126791 - Numerical Analysis of a Flow Control System for High-Pressure Turbine Vanes Subject to Highly Oscillating Inflow Conditions 

Under the prism of introducing pioneering technologies in the propulsive field, the Rotating Detonation Engine (RDE) continuously attracts the Gas-Turbine (GT) research community. This type of engine is part of a large group of unconventional machines which employs Pressure Gain Combustion (PGC) as their main mechanism. Their advantageous performance against the conventional quasi iso-baric burners emerges from the stagnation pressure rise during a fast, either iso-choric deflagrative or denotative combustion mode. On the other hand, this distinctive feature should not be counteracted by the produced unsteadiness if someone considers the integration of RDE with a turbine. The present numerical work aims both at analysing a pulsating inflow to HPT vane and at designing a capable flow control system to weaken the oscillations of the vane. First, an HPT vane capable to ingest high enthalpy flow is designed, aiming at an inlet Mach number around 0.6. The hub and tip end-walls of the vane of CT-3 turbine facility of von Karman Institute for Fluid Dynamics are parametrised using two identical splines symmetrical to the midspan. Furthermore, the airfoil profile is parametrised with the help of two splines for the suction and pressure side. With the help of Latin Hypercube sampling method, 312 samples are generated by varying the 18 geometrical parameters. The 3-D CFX solver of ANSYS is used to solve the Reynolds-Averaged Navier-Stokes (RANS) equations for the nominal steady inlet boundary conditions of the CT-3 facility. The objective functions of the optimization procedure are the total to static efficiency and the deviation in respect to the outlet metal angle of the vane. Thus, a response surface is created by the performance evaluation of the samples. Different optimization algorithms offered the best geometry. The presence of the diffusive endwalls intensively enlarges the secondary flows and their occupied area at the outlet of the vane is extended. Constant inlet conditions of the vane do not deteriorate vane’s operation, whereas pulsating conditions from a RDC generate an uncontrolled motion of the vane’s secondary flows that impacts its performance and ultimately stage efficiency. To cope with this problem that could neglect any cycle efficiency improvement associated to the pressure gain cycle, a flow control device for the weakening of the secondary flow’s motion is proposed. The flow control system comprises a series of five circular ducts connected to the diffusive end-walls and scattered equally in the pitch-wise direction. A series is placed on the hub while another series on the tip, symmetrically to the mid-span. These pipes are supplied with a constant inlet stagnation pressure and temperature. First, RDE's representative periodic boundary conditions are inserted (in a reduced magnitude scale) at the inlet of the redesigned HPT vane without flow control. After solving the Unsteady RANS (URANS) equations by using the ANSYS Fluent 3-D solver, vane performance is evaluated in terms of efficiency and oscillations using the stagnation pressure transient signals of various locations. Secondly, the inlet of the vane equipped with the flow control system is subject to the periodic transient inlet stagnation properties. By solving the URANS for enough periods, the vane with the flow control system is similarly evaluated in terms of efficiency and attenuation of the pulse with the help of the transient total pressure signals. A straight comparison of the performance, damping factors, flow field and efficiency is conducted between the two cases for one period for various frequencies of the inlet transient boundary conditions, ensuring that the flow control system is superior regardless the period of the pulse. In conclusion, by blowing air of low temperature upstream of leading edge the secondary flows motion is weakened, the average temperature of the vane's walls is decreased, the oscillations are reduced, and the quality of stator’s outflow for the subsequent rotor’s expansion is increased. Present activity is performed in the frame of the INSPIRE project (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
Simone Salvadori Politecnico di Torino
Daniela Anna Misul Politecnico di Torino