Seminar - Starting and Design of Axisymmetric Scramjet Intakes for Hypersonic Airbreathing Propulsion By Dr. Hideaki Ogawa
Date: 29 September 2014 (Monday)
Time: 2:00 pm – 3:00 pm
Venue: EF305, The Hong Kong Polytechnic University
Hypersonic airbreathing propulsion offers great potential for reliable and economical access to-space as well as atmospheric flight. In particular, scramjets (Supersonic Combustion Ramjets) are a promising technology that can enable efficient and flexible transport systems by removing the need to carry oxidisers and other propulsion limitations of conventional rocket engines. Following the world’s first in-flight demonstration of supersonic combustion in the HyShot II Program of The University of Queensland in July 2002, the last decade has seen remarkable milestones achieved by various flight experiments including the NASA X-43 vehicles in the Hyper-X program in March and November 2004, and the Boeing X-51A WaveRider in May 2010. A simple axisymmetric scramjet configuration has been explored in the SCRAMSPACE Program as an international collaboration led by Australia, with promising performance demonstrated in shock tunnel testing. It operates in a sequential process: hypersonic inflow is compressed to a desired higher pressure (and consequently high temperature) at the exit of the inlet, which induces combustion in the downstream chamber. The reacted gas expands in the nozzle to produce thrust. Combined with innovative concepts such as upstream fuel injection in the inlet and radical-farming shock-induced combustion, this simple geometry can bring numerous advantages in aerodynamic and combustion efficiency, aerothermal and structural management as well as manufacture. In spite of these merits, however, high internal compression axisymmetric inlets are inherently difficult to start spontaneously during flight. The flow inside the scramjet engine must be supersonic throughout in normal operation in the started’ case. However, high contraction inlets can also operate in an ‘unstarted’ mode, where the flow choke at the exit of the inlet leads to a subsonic inlet and a strong bow shock formed upstream of the inlet, resulting in dramatic reduction in inlet mass capture and thus engine thrust. Reliable intake starting is thus a subject of crucial importance, intrinsic to internal compression axisymmetric geometries, where the structure does not allow surplus mass flow to spill overboard. This seminar presents the results of numerical studies undertaken to examine the capability of various methods to achieve in-flight inlet starting based on two principles: unsteady flow effects and variable geometries. Examples include instantaneous rupture of conical diaphragms and addition of bleed slots for the former class, and opening doors and sliding doors (or diaphragm erosion) for the latter. It also briefly presents the physical insight obtained into the flow phenomena inside axisymmetric engine intakes shortened by various techniques such as leading-edge truncation and stunting (axial contraction) as well as design insights gained via multi-objective optimisation based on evolutionary algorithms assisted by surrogate modelling.
Dr. Hideaki Ogawa completed Master’s courses at the Department of Aerodynamics and Astronautics at Stanford University and The University of Tokyo. He obtained a PhD degree at The University of Cambridge in high-speed aerodynamics, focusing on flow control of shock wave / boundary layer interactions for transonic aerofoils and supersonic engine intakes in experimental and analytical approaches. He worked for the Mitsubishi Heavy Industries in Japan and Cenaero in Belgium for the research and development of various aerospace applications such as supersonic aircraft, rockets and jet engines. He joined the Centre for Hypersonics at The University of Queensland as a research fellow in 2009, followed by the current appointment as a senior research fellow at RMIT University since 2013. He has been conducting research in various international projects with collaborators in Australia, Canada, Hong Kong, Japan, Russia, and USA. His primary research interests and specialities at present include intake flow physics and starting of axisymmetric scramjet engines, multiobjective design optimisation of various scramjet components and fuel injection, and trajectory optimisation of space transport systems powered by rocket-based combined cycle engines.