Session: 01-08 Whole Engine Performance and Novel Concepts II

Paper Number: 101005

101005 - Propulsion Aerodynamics for a Novel High-Speed Exhaust System 

One of the key requirements to achieve sustainable high-speed flight, as well as major efficiency improvements in space access, lies in the advanced performance of future propulsive architectures. Such propulsion concepts often feature high-speed nozzles, similar to rocket engines, but are expected to operate at different conditions for longer time periods. Additionally, these concepts usually exhibit complex interaction phenomena between high-speed flows and separated recirculating regions at the base, which are yet not well understood, but are critical both in terms of pressure drag and dynamic loading. This paper presents a numerical investigation of a representative novel propulsive configuration, which employs a high-speed truncated ideal contoured nozzle and a cavity region at the base. Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics calculations are performed to investigate the behaviour of the flow in the near-wake region as well as inside the nozzle for a number of Nozzle Pressure Ratios (NPR) and free stream Mach numbers in the range 2.73 < NPR < 31.4 and 0.7 < M_∞ < 1.4 respectively. The corresponding Reynolds number lies within the range 1.06·10⁶ < Re_d < 1.27·10⁶  based on the maximum diameter of the configuration. Axisymmetric flow separation inside the nozzle is examined and compared to several well-established and widely used empirical separation criteria. Salient characteristics of the flow are identified, and nozzle operation and performance are evaluated. Additionally, Unsteady Reynolds-Averaged Navier-Stokes computations are carried out for the same configuration for a number of selected operating conditions of interest in terms of both Nozzle Pressure Ratios and free stream Mach numbers. The spectral content of the flow at critical positions is extracted and analysed by means of unsteady pressure measurements to identify unsteady flow effects. Both steady and dynamic characterization of the flow features facilitate the proper design of an ongoing experimental campaign for the configuration under investigation. Additionally, a decomposition technique is applied on the results to examine the modal content of the flow and investigate its energy content. Therefore, dominant spatiotemporal coherent structures are identified for this specific flow. Finally, this work provides an in-depth investigation of the steady and unsteady near-wake flow characteristics for a novel propulsive configuration which has not been examined in the open literature and serves as a potential representative baseline case for modern high-speed propulsion concepts.

Presenting Author: Spyros Tsentis Cranfield University

Presenting Author Biography: Spyros holds a 5-year diploma (M.Eng) in Mechanical Engineering from the Aristotle University of Thessaloniki. He is currently undertaking his doctoral studies at Cranfield University, focusing on the base flow aerodynamics of novel propulsive architectures.

Authors:

Spyros Tsentis Cranfield University
Ioannis Goulos Cranfield University
Simon Prince Cranfield University
Vassilios Pachidis Cranfield University
Vladeta Zmijanovic Reaction Engines Ltd