Ramjet Nozzle Analysis for Transport Aircraft Configuration for Sustained Hypersonic Flight

Abstract

For the past several decades, research dealing with hypersonic flight regimes has been restricted mainly to military applications. Hypersonic transportation could be a possible and affordable solution to travel in the medium term and there is renewed interest from several private organisations for commercial exploitation in this direction. Various combined cycle propulsion configurations have been proposed and the present paper deals with implications for the nozzle component of a ramjet configuration as part of one such combined cycle propulsion configuration. An investigation was undertaken for a method of turbine-based propulsion which enables the hypersonic vehicle to take off under its own power and propel the aircraft under different mission profiles into ramjet operational Mach regimes. The present study details an optimal method of ramjet exhaust expansion to produce sufficient thrust to propel the vehicle into altitudes and Mach regimes where scramjet operation can be initiated. This aspect includes a Computational Fluid Dynamics (CFD)-based geometric study to determine the optimal configuration to provide the best thrust values. The CFD parametric analysis investigated three candidate nozzles and indicated that the dual bell nozzle design produced the highest thrust values when compared to other nozzle geometries. The altitude adaptation study also validated the effectiveness of the nozzle thrust at various altitudes without compromising its thrust-producing capabilities. Computational data were validated against published experimental data, which indicated that the computed values correlated well with the experimental data.

A Scramjet Compression System for Hypersonic Air Transportation Vehicle Combined Cycle Engines

“…The use of 190,000 elements was justified by mesh convergence study illustrated below in Figure 12b, which shows that after 190,000 elements, there were no significant change to the results. The results in Figure 12b are indicative and derived from the original simulations for the ramjet system, published by Baidya et al [17], while similar convergence effects were obtained at the higher Mach numbers tested in scramjet-suitable conditions. At Mach 5 the boundary layer is thicker at the flat surface underneath the vehicle's forebody and at the ramp, whereas at Mach 8 the boundary layer is thinner at both forebody and at the ramps.…”

“…The requirement from this aircraft was for sustained Mach 8 cruise flight for a substantial part of the flight envelope with the ramjets assisting during phases 2 and 3 of the flight envelope ( Table 1). The concept paper as well as it combustion characteristics have been detailed in a previous publications [16,17]. …”

“…Before the inlet and isolator of the scramjet were even designed, potential layouts of the engines and integration with the vehicle were investigated, because almost all hypersonic air-breathing ramjet and scramjet engines use the forebody of the vehicle as the external compression surfaces and the vehicle's aft body as the expansion surface. Furthermore, the position of the engines and the sizing limits that the vehicle would be able to accommodate had to be decided [16,17]. It was established that the scramjet would be set in the middle and a pair of ramjets would be attached on either side.…”

“…Furthermore, the position of the engines and the sizing limits that the vehicle would be able to accommodate had to be decided [16,17]. It was established that the scramjet would be set in the middle and a pair of ramjets would be attached on either side.…”

Ramjet Compression System for a Hypersonic Air Transportation Vehicle Combined Cycle Engine

“…An example outline of the desired profile is given in Table 1 [6]. In order to remain feasible, the profile is attained by the combined operation of a turbojet, ramjet, and scramjet propulsion system.…”