Search Results

Hypersonic flight vehicles have potential applications in strategic defence, space missions, and future civilian high-speed transportation systems. ...Scramjet-powered air-breathing hypersonic vehicles experience extreme heat loads induced by combustion, shock waves and viscous heat dissipation.

Abstract At hypersonic speed, severe aerodynamic heating is observed, and temperatures are too high to cool by radiation cooling; active cooling such as ablative cooling is helpful in this situation. ...A Computational Fluid Dynamics (CFD) simulation of a two-dimensional (2D) lifting body against thermally perfect air in a hypersonic region (Mach number, M > 5) is carried out for M = 5–9 to obtain a heat-transfer-minimized sweepback angle (ΛHT-min), at which heat transfer to the vehicle is minimum.

Abstract At supersonic aircraft speeds, aerodynamically heated surfaces, e.g., nose, wing leading edges, are infrared (IR) signature sources from the tactically crucial frontal aspect. This study numerically predicts and then illustrates the minimization of IR contrast between the nose and background sky radiance by the emissivity optimization (εw,opt) technique, which has the least performance penalties. The IR contrast between the aircraft nose and its replaced background in 1.9-2.9 μm short-wave IR (SW-IR), 3-5 μm medium-wave IR (MW-IR), and 8-12 μm long-wave IR (LW-IR) bands are obtained. The IR contrast especially in LW-IR (i) increases with flight Mach number (M ∞) for a given flight altitude (H) and εw (ii) decreases with increasing H for a given M ∞ and εw. The εw,opt for a flight altitude of 5 km is found to decrease from 0.99 at M ∞ = 0.001 (low subsonic) in all three bands to 2 × 10−4 in MW-IR and 0.0213 in LW-IR bands at M ∞ = 3 (high supersonic).

This section presents the basic equations for computing ice protection requirements for nontransparent and transparent surfaces and for fog and frost protection of windshields. Simplified graphical presentations suitable for preliminary design and a description of various types of ice, fog, frost, and rain protection systems are also presented.

This section presents methods and examples of computing the steady-state heating and cooling loads of aircraft compartments. In a steady-state process the flows of heat throughout the system are stabilized and thus do not change with time. In an aircraft compartment, several elements compose the steady-state air conditioning load.

The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible. With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2.

This section presents the basic equations for computing ice protection requirements for nontransparent and transparent surfaces and for fog and frost protection of windshields. Simplified graphical presentations suitable for preliminary design and a description of various types of ice, fog, frost, and rain protection systems are also presented.

This section presents the basic equations for computing ice protection requirements for nontransparent and transparent surfaces and for fog and frost protection of windshields. Simplified graphical presentations suitable for preliminary design and a description of various types of ice, fog, frost, and rain protection systems are also presented.

This document summarizes types of heat sinks and considerations in relation to the general requirements of aircraft heat sources, and it provides information to achieve efficient utilization and management of these heat sinks. In this document, a heat sink is defined as a body or substance used for removal of the heat generated by hydrodynamic or thermodynamic processes. This document provides general data about airborne heat sources, heat sinks, and modes of heat transfer. The document also discusses approaches to control the use of heat sinks and techniques for analysis and verification of heat sink management. The heat sinks are for aircraft operating at subsonic and supersonic speeds.

The purpose of this section is to provide methods and a set of convenient working charts to estimate penalty values in terms of take-off fuel weight for any given airplane mission. The curves are for a range of specific fuel consumption (SFC) and lift/drag ratio (L/D) compatible with the jet engines and supersonic aircraft currently being developed. A typical example showing use of the charts for an air conditioning system is given. Evaluation of the penalty imposed on aircraft performance characteristics by the installation of an air conditioning system is important for two reasons: 1 It provides a common denominator for comparing systems in the preliminary design stage, thus aiding in the choice of system to be used. 2 It aids in pinpointing portions of existing systems where design improvements can be most readily achieved.

The fluid flow treated in this section is isothermal, subsonic, and incompressible. The effects of heat addition, work on the fluid, variation in sonic velocity, and changes in elevation are neglected. An incompressible fluid is one in which a change in pressure causes no resulting change in fluid density. The assumption that liquids are incompressible introduces no appreciable error in calculations, but the assumption that a gas is incompressible introduces an error of a magnitude that is dependent on the fluid velocity and on the loss coefficient of the particular duct section or piece of equipment. Fig. 1A-1 shows the error in pressure drop resulting from assuming that air is incompressible. With reasonably small loss coefficients and the accuracy that is usually required in most calculations, compressible fluids may be treated as incompressible for velocities less than Mach 0.2.

This section presents methods and examples of computing the steady-state heating and cooling loads of aircraft compartments. In a steady-state process the flows of heat throughout the system are stabilized and thus do not change with time. In an aircraft compartment, several elements compose the steady-state air conditioning load.

It is found that control of heat transfer on a wing at hypersonic wing can act as a control device, comparable to that due a moderate flap deflection.

The purpose of this section is to provide methods and a set of convenient working charts to estimate penalty values in terms of take-off fuel weight for any given airplane mission. The curves are for a range of specific fuel consumption (SFC) and lift/drag ratio (L/D) compatible with the jet engines and supersonic aircraft currently being developed. A typical example showing use of the charts for an air conditioning system is given. Evaluation of the penalty imposed on aircraft performance characteristics by the installation of an air conditioning system is important for two reasons: 1 It provides a common denominator for comparing systems in the preliminary design stage, thus aiding in the choice of system to be used. 2 It aids in pinpointing portions of existing systems where design improvements can be most readily achieved.

This section presents the basic equations for computing ice protection requirements for nontransparent and transparent surfaces and for fog and frost protection of windshields. Simplified graphical presentations suitable for preliminary design, and a description of various types of ice, fog, frost, and rain protection systems are also presented.

A supersonic channel airfoil (SCA) concept that can be applied to the leading edges of wings, tails, fins, struts, and other appendages of aircraft, atmospheric entry vehicles and missiles in supersonic flight for drag reduction is described. It is designed to be beneficial at conditions in which the leading edge is significantly blunted and the Mach number normal to the leading edge is supersonic. The concept is found to result in significantly reduced wave drag and total drag (including skin friction drag) and significantly increased L/D. While this reduction over varying flight conditions has been quantified, some leading edge geometries result in adverse increases in peak heat transfer rates. To evaluate the effectiveness of SCAs in reducing drag without paying any penalties in other areas like lifting capacity, heating rates or enclosed volume, the design space was studied in greater detail using MDO methods.

The comparison of CFD predictions with aerodynamic heating data must be preceded by a careful analysis of the experimental data. Of primary interest is the location of transition since boundary layer state is still a user input for most CFD codes and an error here can result in large variations between the numerical and experimental results. Transition can usually be located by observing the associated sharp rise in surface heating rate with increasing Reynolds number. However, on complex vehicles the distributions of laminar, transitional, and turbulent flow will also be complex, and a rise in heating rate may be produced by flow phenomena other than transition. This paper reviews the method used to determine boundary layer state using experimental surface pressure and heat transfer data.

Heat transfer on hemisphere forebody domes at hypersonic velocities can be reduced and/or diffused at selected conditions with an upstream flow separation aerospike.

Supercritical cryogenic hydrogen is being considered as a coolant for certain high heat flux thermal management applications, including hypersonic vehicles such as the National Aero-Space Plane and high power spacecraft systems for the Strategic Defense Initiative.

For the fundamental study of aerodynamic heating of winged vehicle and space planes in hypersonic flow the detailed structure of three-dimensional shock wave/turbulent boundary layer interaction region induced by sweptback sharp fins are investigated carefully by oil flow technique and pressure distribution.