Showing papers on "Scramjet published in 1979"

Criteria for self-ignition of supersonic hydrogen-air mixtures

Abstract: A correlation of available self ignition data for supersonic hydrogen-air mixtures in configurations representative of scramjet combustors was made. The correlation was examined in light of simplified ignition-limit models. The data and model included cases of injection from transverse fuel jets on walls, transverse jets behind swept and unswept steps, and transverse injection ahead of swept and unswept steps and strut bases. The results provide useful guidance for predicting self ignition in a variety of applications. The likely regions for self ignition in a combustor are given in order of merit.

Initial wind tunnel tests at Mach 4 and 7 of a hydrogen-burning, airframe-integrated scramjet

Abstract: A research investigation of a new, fixed-geometry, hydrogen-burning scramjet engine concept, designed for total airframe integration, is currently in progress. Two heavily instrumented engine models incorporate inlet and combustor designs developed previously in component tests. Initial tests of these subscale engine models are being conducted in ground facilities at conditions simulating flight at Mach numbers 4 and 7. The scramjet test results which are presented include inlet performance, ignition/reaction aids, inlet-combustor interactions, and engine performance in terms of thrust balance measurements and internal pressure and heating rate distributions. The relationship of these results to flight engine performance is discussed.

Thermal-structural Design Study of an Airframe-integrated Scramjet

Abstract: Design concepts for the cooled structures assembly for the Langley Scramjet engine, for engine subsystems, and for the aircraft/engine interface were developed and evaluated. Results show that the objectives for the Scramjet engine can be met. A thermal protection system was defined that makes it possible to attain a life of 100 hours and 1000 cycles, which is the specified goal. With stoichiometric combustion, the fuel provides an adequate heat sink for cooling the engine at Mach numbers up to 9 at the minimum fuel flow condition. The mechanical design is feasible for manufacture using conventional materials. For the cooled structures in a six-module engine, the mass per unit capture area is 1328 kg/sq m (259 lb/sq ft). The total mass of a six-module engine assembly including the fuel system is 1577 kg (3477 lb).

Numerical investigation of the perpendicular injector flow field in a hydrogen fueled scramjet

Abstract: A computer program has been developed which numerically solves the full (elliptic) two-dimensional Navier-Stokes and specie equations near a slotted perpendicular hydrogen fuel injector in a scramjet engine. The program currently predicts the turbulent mixing of injected hydrogen fuel and air without reaction, and allows the study of separated regions of flow immediately preceding and following the injector as well as the complex shock-expansion structure produced by the injector in this region of the engine. Results are presented that describe the size of the separated regions near the injector as well as locations where ignition is likely to occur.

Validation of scramjet exhaust simulation technique at Mach 6

Abstract: Current design philosophy for hydrogen-fueled, scramjet-powered hypersonic aircraft results in configurations with strong couplings between the engine plume and vehicle aerodynamics. The experimental verification of the scramjet exhaust simulation is described. The scramjet exhaust was reproduced for the Mach 6 flight condition by the detonation tube simulator. The exhaust flow pressure profiles, and to a large extent the heat transfer rate profiles, were then duplicated by cool gas mixtures of Argon and Freon 13B1 or Freon 12. The results of these experiments indicate that a cool gas simulation of the hot scramjet exhaust is a viable simulation technique except for phenomena which are dependent on the wall temperature relative to flow temperature.

Combustor modelling for scramjet engines

Abstract: A system of computer programs is being developed to analyse and predict the complex flow fields found in hydrogen-fueled scramjet combustors. Each program is designed to solve the governing equation system for the type of flow present in a particular combustor region. A two-dimensional parabolic program has been found to be valuable in the development and experimental evaluation of turbulence and chemistry models for supersonic flow, and in the development of a program to model supersonic flow downstream of the fuel injection struts by means of solutions to the three-dimensional parabolic Navier-Stokes equations and species equations. A partially elliptic code has been derived to account for local subsonic flow regions, and fully elliptic programs have been developed by the consideration of streamwise diffusion effects for the recirculating flow fields near transverse fuel injectors. The programs are currently being applied to problems of scramjet engine development.

Performance Potential and Research Needs of a Hypersonic, Airbreathing, Lifting Missile Concept

Abstract: This paper reports the results of a conceptual study to define the performance potential, scaling relationships, and research needs of a hypersonic missile concept formulated about an airframe-integrated propulsion system. A baseline missile design is developed and the rationale for selecting a heat-sink structural approach is described. Modifications to a NASA-Langley-developed fixed-geometry, modular scramjet are presented that may be required to achieve the dual-mode, "hydrocarbon-fueled" engine operational characteristics utilized in predicting missile performance potential. A heat-sink structure is shown to be a viable concept for Mach 6 missiles for ranges of up to 200 n.mi. A heat-sink structure protected by multiwall heat shields is suggested as a potentially attractive system for long-range cruise missiles. Airframe-integrated propulsion systems are shown to offer potentially large benefits for missiles that require high maneuverability. The use of the missile forebody for generating inlet precompression as well as lift and use of the afterbody as a high-expansion ratio, low-drag nozzle also offer improved missile cruise performance. It is concluded that technologies being developed for hypersonic aircraft, with appropriate modifications, also can be useful for hypersonic, airbreathing, lifting missiles.

Numerical Solution for Perpendicular Sonic Hydrogen Injection into a Ducted Supersonic Airstream

Abstract: This note discusses a computer program being developed to study the flow field near opposing perpendicular fuel injectors in scramjets. The MacCormack time-split, finite difference relaxation technique was used to solve the full two-dimensional compressible Navier-Stokes equations along with energy and species equations. By using this technique, a program was developed to consider the turbulent nonreacting flow of hydrogen and air in a rectangular duct. A damping term, proportional to the second derivative of pressure and temperature, was used to produce a stable solution behind the hydrogen jet in the neighborhood of the recompression shock. A case using actual conditions encountered in current scramjet design was analyzed, with results agreeing qualitatively with experimental observations.

Investigation of the feasibility of CARS measurements in scramjet combustion

Abstract: Results are presented of analytical and experimental investigations to determine the feasibility of using coherent anti-Stokes Raman spectroscopy (CARS) to measure temperature and species concentrations in supersonic combustion experiments. Experimental CARS spectra of O2 and H2 in a laboratory flat H2 - air diffusion flame are presented. Temperatures deduced from both species generally agree with radiation corrected thermocouple measurements. Oxygen concentrations were determined from the shape of the experimental spectra. Measured H2 CARS signal magnitudes are in good agreement with analytical predictions based on H2 concentration profiles determined from spontaneous Raman scattering. Based on these results, CARS diagnostics appear to be feasible if problems associated with the supersonic flow are not too severe.

Hypersonic cruise aircraft propulsion integration study, volume 1

Abstract: A hypersonic cruise transport conceptual design is described. The integration of the subsonic, supersonic, and hypersonic propulsion systems with the aerodynamic design of the airframe is emphasized. An evaluation of various configurations of aircraft and propulsion integration concepts, and selection and refinement of a final design are given. This configuration was used as a baseline to compare two propulsion concepts - one using a fixed geometry dual combustion mode scramjet and the other a variable geometry ramjet engine. Both concepts used turbojet engines for takeoff, landing and acceleration to supersonic speed.

Design, Tests, and Verification of a Diffuser System for a Mach 4 Scramjet Test Facility

Abstract: R directed toward developing the technology for an airframe-integrated modular scramjet engine concept currently being conducted at NASA Langley Research Center, involves experimental investigations of hydrogen-burning scramjet models at simulated Mach 4 and 7 flight conditions. The present concept of the airframeintegrated scramjet engine has modules of rectangular cross section with swept leading edges that produce an asymmetric downward flow that sharply increases locally near the cowl when the scramjet inlet unstarts. Tests on a heat-sink, hydrogen-burning model representing one module of this concept have been conducted at Langley in a facility which duplicates Mach 7 flight conditions. For Mach 4 tests, an engine test cell is being modified to contain a freejet, blowdown tunnel that will exhaust to the atmosphere. To provide shock-free tunnel flow to the modular scramjet engine and to meet the atmospheric exhaust condition, a diffuser system is required. The available mass flow rates and the size of existing tunnel hardware dictated that the scramjet model block up to 33% of the tunnel nozzle exit area. A diffuser preliminary design was defined based on published experimental results. However, most of the literature results are not directly applicable to conditions where the model blockage is as high as 33%, and where the model design produces asymmetry by creating a downstream flow that increases when the model inlet unstarts. An experimental investigation was, therefore, undertaken using unheated air and a subscale model of the tunnel-scramjetdiffuser system. A description of the subscale system and some data results obtained during tests with this system are presented. These results were subsequently verified, as a data comparison will show, by "full-scale" engine combustion tests in a Mach 4 facility utilizing a diffuser system based upon the "best arrangement" of the subscale tunnel scramjetdiffuser system.