High-speed Flight Vehicles Research Articles

An experimental and computational study of hydrogen–air combustion in the LAPCAT II supersonic combustor

Dual-mode ramjet/scramjet engines are considered a promising propulsion system for the next generation commercial high-speed transport flight vehicles. In this study we combine experimental measurements of high-speed (subsonic and supersonic) combustion at different operating conditions in the LAPCAT-II dual-mode ramjet/scramjet combustor with Large Eddy Simulations (LES) using finite rate chemistry models and skeletal H2–air combustion chemistry. The combustor geometrically consists of four sections, and experiments have been realized for wall injection of H2 in a Mach = 2 vitiated air-flow for total pressures and temperatures of p0 = 0.40 MPa, 1414 K < T0 < 1707 K, and a fixed equivalence ratio of ϕ=0.15. For this p0 the combustor is over-expanded, and the transition from supersonic to subsonic flow occurs at the beginning of the fourth combustor section. The flow and combustion diagnostics include measurements of p0 and T0 upstream of the combustor, wall-pressure profiles and Schlieren as well as OH* chemiluminescence imaging. The computational set-up consists of the full combustor, from the nozzle into the dump-tank. The computational model is composed of a compressible finite rate chemistry LES model, using the mixed subgrid flow model and the Partially Stirred Reactor (PaSR) combustion model, together with a novel skeletal 22 step H2–air reaction mechanism. Qualitative as well as quantitative comparisons between experiments and simulations show reasonably good agreement, but most importantly reveal a high sensitivity of both the LES predictions and the experiments to T0. The LES results are further used to describe the underlying mechanisms of flow, wall-injection, mixing, self-ignition and turbulent combustion, and how these interrelated processes are modified by increasing the total temperature under otherwise identical conditions.

Simulation analysis study on the flutter characteristics of control rudder in high speed flight vehicle

This paper dedicates to study on the flutter characteristics of control rudder of high speed flight vehicle, and proposes a novel parameter-tuning method for the flutter characteristics optimization of control rudder at the beginning design stage of flight vehicle by combining parametrized dynamic modeling technology, aerodynamic and aeroelastic flutter analysis methodology. Effects of typical parameters, including leading edge sweep angle, tip chord length, root chord length and span, on flutter characteristics of the control rudder in a high speed flight vehicle are studied. Research results have considerable significance for the design adjustment of the rudder configuration, and can be used to avoid the design reiteration and reduce design cycle.

Research on Thermal Insulation Performance of Lightweight Thermal Protection Materials for High Speed Aircraft under Different Boundary Conditions

The determination of thermal insulation performance of thermal protection materials or structures is an indispensable and important step in the safety design of high speed flight vehicles. To obtain the temperature difference of the radiating surface for plate specimens under three different boundary conditions in heat insulation experiments (the specimens were placed either vertically or horizontally with the radiating surface facing down or horizontally with the radiating surface facing up), three thermal test setups were established to test the thermal insulation performance of light-weight ceramic specimens at different temperatures. The results show that the radiating surface temperature was the highest when the specimen was placed horizontally with the radiating surface facing down, while it was the lowest when the specimen was placed horizontally with the radiating surface facing up.The numerical calculation results agreed very well with the experimental ones, confirming the credibility and accuracy of the experimental results. The different thermal insulation performances of the plate specimens obtained under three different boundary conditions will provide important guidance for designers in the design of thermal protection systems for large cabins of high speed flight vehicles.

Nonlinear Random Response Analyses of Panels Considering Transverse Shear Deformations under Combined Thermal and Acoustic Loads

The panel structures of flight vehicles at supersonic or hypersonic speeds are subjected to combined thermal, acoustic, and aerodynamic loads. Because of the combined thermal and acoustic loads, the panel structure may exhibit nonlinear random vibration responses, such as the snap‐through phenomenon and random vibrations. These unique dynamic behaviors of the panel structure under combined thermal and acoustic loads can result in serious damage or fatigue failure of the panel structures of high‐speed flight vehicles. This study investigates the nonlinear random responses of thin and thick panels under combined thermal and acoustic loads. The panels are modeled based on the first‐order shear deformation theory (FSDT) to account for transverse shear deformations. The von‐Karman nonlinear strain–displacement relationship is used for geometric nonlinearity in the out‐of‐plane direction of the panel. The thermal load distribution is assumed to be constant in the thickness direction of the panel. The random acoustic load is represented as stationary White–Gaussian random pressure with zero mean and uniform magnitude over the panels. Static and dynamic equations are derived using the principle of virtual work and the nonlinear finite element method. A thermal postbuckling analysis is conducted using the Newton–Raphson method, and the dynamic nonlinear equations are solved using the Newmark‐β time integration method. In the present numerical analyses, the snap‐through responses for both the thin and thick panels are investigated, and the results indicate that the loading conditions that cause snap‐through are different for thin and thick panels.

Interplay of Surface Deformation and Shock-Induced Separation in Shock/Boundary-Layer Interactions

Shock wave/boundary-layer interactions represent an extreme loading condition in the structural design of high-speed flight vehicles. However, the complexity of this problem has primarily restricted study to rigid, undeformed surfaces. As such, little is known regarding the impact surface deformation, due to structural compliance, has on the induced loads. The current study focuses on this problem by comparing changes in the shock-induced separation bubble length, as well as the resulting changes in the surface pressure distribution and integrated structural loads, for both static and unsteady surface deformation using a Reynolds-averaged Navier–Stokes flow solution. Results examine the differences due to the frequency of deformation, relative length between the separation bubble and deformation, and the deformation mode. Surprisingly, unsteady surface deformation is found to result in only marginal changes to the separation bubble length, whereas static surface deformation can result in both significant increases and decreases. This is linked, through analytical and numerical studies, to dependency of separation onset on both surface curvature and the spatial gradient of surface velocity, which have competing effects for harmonic motion. These findings provide important insight into the potential impact of surface compliance on shock-induced structural loads and guide the development of model reduction strategies for shock-dominated flows.

Effects of nozzle arrangement on uniformity of multiple impinging jets heat transfer in a fast cooling simulation device

A cooling simulation device utilizing multiple impinging jets is built for ground cooling simulation tests of high speed flight vehicles. To help the design of the device and supply a relatively uniform heat flux on the test piece surface, a three-dimensional numerical study is performed in this paper to investigate the effects of nozzle arrangement on the convective heat transfer uniformity of the impinging jets. A simplified physical model with the size of 200mm×200mm×50mm is built and the shear-stress transport (SST) k-ω turbulence model is used in the calculation. The nozzle quantity is varied from 8 × 8 to 32 × 32 for uniform nozzle arrays with a fixed total area of the nozzles. The corresponding numerical results of uniform nozzle arrangements are analyzed in details. Based on the 16 × 16 uniform arrangement results, the effects of diameter varying nozzle arrangements on heat transfer uniformity are further examined. Finally, an overall performance evaluation indicator named QU ratio is used in the optimization of nozzle arrangement, which proves to be effective and convenient in practice.

Vibratory loads and response prediction for a high-speed flight vehicle during launch events

High-speed flight vehicles (HSFVs) such as space launch vehicles and missiles undergo severe dynamic loads which are generated during the launch and in in-flight environments. A typical vehicle is composed of thin plate skin structures with high-performance electronic units sensitive to such vibratory loads. Such lightweight structures are then exposed to external dynamic loads which consist of random vibration, shock, and acoustic loads created under the operating environment. Three types of dynamic loads (acoustic loads, rocket motor self-induced excitation loads and aerodynamic fluctuating pressure loads) are considered as major components in this study. The estimation results are compared to the design specification (MIL-STD-810) to check the appropriateness. The objective of this paper is to study an estimation methodology which helps to establish design specification for the dynamic loads acting on both vehicle and electronic units at arbitrary locations inside the vehicle.

Feasibility study of different cooling techniques in a ground fast cooling simulation device

In this paper, a ground fast cooling simulation device is designed for the thermal testing of the materials and parts on high speed flight vehicles. Experimental investigation is performed to validate the effectiveness of the design and feasibilities of 4 different cooling techniques with both Ti alloy and C/SiC test pieces. The results show that air impingement cooling is the most feasible cooling method because it offers high cooling rates and it’s compatible with Ti alloy and C/SiC. LN and water jet impingement cooling prove to be unfeasible mainly due to the uncontrollability and destruction of thermocouples, respectively. Water spray cooling, however, is found to be feasible only for Ti alloy test pieces and destructions of C/SiC test pieces are observed after the experiment. Based on SEM images of the microstructure, oxidation effects of water spray cooling on C/SiC are briefly analyzed.

Numerical study of impinging jets heat transfer with different nozzle geometries and arrangements for a ground fast cooling simulation device

In this paper, a comparative study is performed to check the nozzle geometry and arrangement effects on impinging jets heat transfer performance to help the design of a ground fast cooling simulation device which is used for the thermal tests of high speed flight vehicles. Based on the simplified physical model, the impinging jets heat transfer is modeled using the shear-stress transport (SST) k-ω turbulence model. A total of 21 different nozzle configurations including 7 geometries are considered in the numerical simulation. Heat transfer performances concerning heat transfer intensity and heat flux uniformity in different cases are compared with each other. Analysis is given on the corresponding flow fields and surface heat flux distributions. To help the optimization of nozzle geometry and arrangement in designing the device, an indicator named QU ratio is proposed for the overall performance evaluation of the nozzle configurations. The effectiveness of the QU ratio is validated based on the numerical results and it can be used to help determine the best design for certain given conditions of the ground fast cooling device.

Experimental Research on Thermal-Vibration for Composite Trilaminated Wing Structure

The wing structures of long-range, high-speed flight vehicles bear vibration during the flying time. The high temperatures caused by aerodynamic heating can greatly change the elasticity properties of the materials in a high-speed flight vehicle, leading to an alteration in the vibration characteristics of high-speed flight vehicle structures. In this paper, the high-temperature environment test system and vibration test system were combined to conduct a thermal-vibration test for the composite trilaminated wing structure that comprised composite materials and metallic materials. The vibration characteristics of the composite trilaminated wing structure, such as natural frequency and vibration mode, were obtained in 200°C, 300 oC and 400 oC environments. The results provide an important basis for the dynamic characteristics analysis and safety and reliablity design of wing structures comprised composite materials and metallic materials under a thermal-vibration environment.

Experimental and Numerical Study on Heat Transfer Characteristics of Metallic Honeycomb Core Structure in Transient Thermal Shock Environments

The metallic honeycomb core structure has important engineering applications in the aerospace and aviation fields due to several advantages, such as being lightweight, its strong resistance to deformation in high-temperature environments, and its excellent energy absorption characteristics. In the present study, a transient heating experimental system for high-speed flight vehicles was developed to study the thermal insulation characteristics of a superalloy honeycomb core structure at different thermal shock rates $$(5\,^{\circ }\mathrm{C}{\cdot }\mathrm{s}^{-1}\, \mathrm{to}\,30\,^{\circ }\mathrm{C}{\cdot }\mathrm{s}^{-1})$$ . The highest instantaneous temperature tested was $$950\,^{\circ }\mathrm{C}$$ . The three-dimensional finite element method was used to numerically calculate the thermal insulation characteristics of the metallic honeycomb core structure in a high-speed thermal shock environment. The calculated results agree well with the experimental results; this agreement demonstrates that to an extent, numerical calculations are a better alternative than expensive experiments. The results of this study provide an important reference for the thermal protection design of metallic honeycomb core structures of high-speed flight vehicles.

Numerical Study on Transient Heat Transfer of a Quartz Lamp Heating System

Thermal ground testing is an accepted and frequently used method for simulating the aerodynamic heating of high speed flight vehicles. A numerical method based on a finite volume method for a quartz lamp heating system, used in thermal testing, is proposed. In this study, the unstructured finite-volume method (UFVM) for radiation has been formulated and implemented in a fluid flow solver GTEA on unstructured grids. For comparison and validation of the proposed method, a 2D furnace with cooling pipes was chosen. The results obtained from the proposed FVM agreed well with the exact solutions. Numerical results show that the quartz lamp can be simplified as a slat with the same temperature radiation source, and a simplified 2D thermal testing case was then simulated with the coupling effects of radiation, convection, and conduction heat transfer. Different temperature loading curves and ratios of intervals between the lamps and lamp length (l/s) were studied using the proposed method. The radiation heat flux on the metal surface was a wave-shaped curve. Comparing the different interval ratios, we found that the smaller the interval ratio, the larger the maximum value and the smaller the difference between the maximum and minimum heat flux.

Integrated Aerodynamic Thermal Structure Design Optimization Method of Lifting Surfaces

A ERODYNAMIC heating of lifting surfaces of high-speed flight vehicles should be seriously considered. A high-temperature field may cause the characteristics of materials to change, and an inhomogeneous temperature with inhomogeneous temperature gradients may induce thermal stress. As a result, resultant structural stiffness and stiffness distribution probably change, which will lead to the changes of structural normalmodes and unsteady aerodynamic loads. Furthermore, these changes will influence performances of aeroelasticity for lifting surfaces, such as the critical flutter velocity, a crucial parameter for high-speed flight vehicles. The structural design of lifting surfaces in high-speed flow is highly complicated, which involves serious coupling among aerodynamic, thermal, and structural disciplines. Aeroelasticity and aerothermoelasticity in hypersonic conditions were first researched in the late 1950s and during the 1960s [1–3]. Because of the development of computational technologies and relevant modeling methods, since about 2000, studies of aeroelasticity and aerothermoelasticity in hypersonic flow have drawn more and more attention [4–6]. Bisplinghoff [7] summarized the important aspects of aerothermoelasticity and pointed out that aerothermoelasticity can be considered as the expansion of Collar’s aeroelastic triangle including the coupling of aerodynamic heating. Ericsson et al. [8] studied the aerothermoelastic features of an aluminum finned missile. Spain et al. [9] presented an overview of selected National Aero-Space Plane (NASP) aeroelastic studies at the NASA Langley Research Center. Rodgers [10] performed the aerothermoelastic analysis of a NASP vertical fin. Thornton and Dechaumphai [11] investigated an integrated code using the finite element method (FEM) including flow and thermal and structural coupling. Recently, Friedmann [12] pointed out that modern aeroelasticity encompasses a much broader set of problems by the aeroservothermoelastic hexahedron. Tran and Farhat [13] accomplished the aerothermoelastic analysis of a flat panel using an integrated fluid-structural-thermal solver. McNamara et al. [14] studied the aeroelastic and aerothermoelastic behaviors in hypersonic flow using NASA Langley Research Center code CFL3D. All the works above only considered one-way thermal coupling. In addition, McNamara and Friedmann [15] conducted a comprehensive survey of the past, the state of art, and the future on aeroelasticity and aerothermoelasticity in hypersonic flow. With the existing level of knowledge and the computational capability of the current computers, to solve this fully coupled aerodynamic-thermal-structural problem is rather difficult in engineering design. A hierarchical solution approach from [14] is feasible in engineering design,which decomposes the original highly coupled problem into a series of separated simple problems. In this solution, the aerodynamic heating and the internal transient heat transfer analysis of structures are not calculated simultaneously, that is, the transient heat transfer analysis follows the computation of the aerodynamic heating. Afterwards all the temperature fields resulting from the transient heat transfer analysis are considered as the thermal boundaries for the thermal structure analysis and the thermal mode analysis, respectively. The first six orders of thermal modes of each temperature field are chosen as the input data of flutter analysis. This solution is also a one-way coupled process. Because of the high performance requirement of high-speed flight vehicles, structural design only considering strength criterion is not sufficient in applications. Aeroelastic characteristics should be used as constraints in structural design optimization, especially for aerothermoelastic design problems. Therefore, in this paper, an integrated aerodynamic-thermal-structural analysis and design optimization method is presented, and the entire integrated analysis will be computationally expensive. For the purpose of decreasing computational cost and reducing optimization time, a novel global optimization strategy using adaptive radial basis functions based on fuzzy clustering developed by the authors [16] is used to optimize the lifting surfaces consideringmultidisciplinary coupling. Based on this integrated analysis and design optimization method, a design optimization of lifting surfaces in high-speed flow is carried out. Under the constraints of the displacement and the flutter velocity, the structural mass of the lifting surface is minimized through adjusting the distributions of the structural stiffness and the mass, simultaneously.

Aeroelastic stability analysis of heated panel with aerodynamic loading on both surfaces

Focusing on the aeroelastic stability of thin panel structure of airframe component such as engine nozzle of high-speed flight vehicles, a nonlinear aeroelastic model for a two-dimensional heated panel exposing both surfaces to the airflow with different aerodynamic pressures is established. The von Karman large deflection plate theory and the first-order piston theory are used in the formulation of aeroelastic motion. The critical conditions for aeroelastic stability and the stability boundaries are obtained using theoretical analysis and numerical computations, respectively. The results show that the panel is more prone to become unstable when its two surfaces are subject to aerodynamic loading simultaneously; only if the sum of the aerodynamic pressures on both surfaces of the panel satisfies flutter stability condition, can the panel be likely aeroelastically stable; compared with the general panel flutter problem that only one surface is exposed to the airflows, the present condition makes the panel become aeroelastically unstable at relatively small flight aerodynamic pressure.

Experimental research on the ultimate strength of hard aluminium alloy 2017 subjected to short-time radioactive heating

Alloy 2017 (Al–Cu–Mg) is a hard aluminium alloy strengthened by heat treatment. Because of its higher strength, finer weldability and ductility, hard aluminium alloy 2017 has been widely used in the field of aeronautics and astronautics. However, the ultimate strength and other characteristic mechanical parameters of aluminium alloy 2017 in a transient heating environment are still unclear, as these key mechanical parameters are lacking in the existing strength design handbook. The experimental characterisation of these critical parameters of aluminium alloy 2017 is undoubtedly meaningful for reliably estimating life span of and improving safety in designing high-speed flight vehicles. In this paper, the high-temperature ultimate strength, loading time and other mechanical properties of hard aluminium alloy 2017 under different transient heating temperatures and loading conditions are investigated by combining a transient aerodynamic heating simulation system and a material testing machine. The experimental results reveal that the ultimate strength and loading capability of aluminium alloy 2017 subjected to transient thermal heating are much higher than those tested in a long-time stable high-temperature environment. The research of this work not only provides a substantial basis for the loading capability improvement and optimal design of aerospace materials and structures subject to transient heating but also presents a new research direction with a practical application value.

Shock wave diffraction about a wedge in a gas-microdroplet mixture

Shock wave interacts with the droplets as a high-speed flight vehicle penetrates cloud or rain storm in the earth’s atmosphere. Interaction of the shock with the gas-droplet two-phase medium significantly affects the aerodynamic performance of the flight vehicle. In the present paper, we investigate the aerodynamic field and wall variables as the moving shock wave diffracts over a wedge in the droplet-gas mixture. We used the compressible two-fluid model equations that have been solved by the HLL-based weighted average flux (WAF) method. The viscous drag force and the heat transfer terms have been included in the model to let the gas and the droplet phases interact. We investigate the effects of the three parameters associated with the microdroplets: the void fraction, the size and the material. We elaborate how the relaxation zone created by the shock wave diffraction is structured and changed in the droplet-gas mixture.

High-temperature deformation field measurement by combining transient aerodynamic heating simulation system and reliability-guided digital image correlation

To determine the full-field high-temperature thermal deformation of the structural materials used in high-speed aerospace flight vehicles, a novel non-contact high-temperature deformation measurement system is established by combining transient aerodynamic heating simulation device with the reliability-guided digital image correlation (RG-DIC). The test planar sample with size varying from several mm 2 to several hundreds mm 2 can be heated from room temperature to 1100 °C rapidly and accurately using the infrared radiator of the transient aerodynamic heating simulation system. The digital images of the test sample surface at various temperatures are recorded using an ordinary optical imaging system. To cope with the possible local decorrelated regions caused by black-body radiation within the deformed images at the temperatures over 450 °C, the RG-DIC technique is used to extract full-field in-plane thermal deformation from the recorded images. In validation test, the thermal deformation fields and the values of coefficient of thermal expansion (CTEs) of a chromiumnickel austenite stainless steel sample from room temperature to 550 °C is measured and compared with the well-established handbook value, confirming the effectiveness and accuracy of the proposed technique. The experimental results reveal that the present system using an ordinary optical imaging system, is able to accurately measure full-field thermal deformation of metals and alloys at temperatures not exceeding 600 °C.

Distinctive features of the flow past high-speed flight vehicles with air-breathing engines on subsonic, transonic, and low supersonic velocity ranges

The aerodynamic characteristics and distinctive features of the flow past hypersonic integral-layout flight vehicles with air-breathing engines intended for cruise flight in the atmosphere are experimentally investigated. The experiments were conducted on a simplified model designed with regard for the general principles of integration of vehicles of the class considered. The tests were performed in a wind tunnel over the Mach and Reynolds number ranges 0.6 ≤ M ≤ 4 and 6.3 × 106 ≤ Re ≤ 16 × 106, respectively. Balance testing was carried out, the pressure distributions over the vehicle surface were measured, and the flowfields on the model surface were photographed. The effects of mounting a nacelle and contouring the internal duct are considered. The effect of the corrections on the duct flow in the absence of jet modeling is estimated. The results obtained can be used as a basis for developing the aerodynamic configurations of integral-layout flight vehicles, for forming their thrust and aerodynamic parameters under full-scale flight conditions, and for testing computation methods.

Nonlinear Random Response of Panels in an Elevated Thermal-Acoustic Environment

Sonic fatigue is generally considered as being one of the major design areas for the newest generation of high-speed flight vehicles. Efficient analysis methods for predicting nonlinear random response and fatigue life are urgently needed. This paper presents a finite element formulation for the prediction of nonlinear random response of thin isotropic/composite panels subjected simultaneously to high acoustic loads and elevated temperatures. Laminated plate theory and von Karman large displacement relations are used to derive the nonlinear equations of motion for an arbitrarily laminated composite panel subjected to combined acoustic and thermal loads. The nonlinear equations of motion in physical degrees of freedom are transformed to a set of coupled nonlinear equations in truncated modal coordinates, retaining fewer degrees of freedom. Numerical integration is employed to obtain the panel response to simulated Gaussian band-limited white noise. To validate the formulation, results are compared with existing linear and nonlinear solutions to assess the accuracy of nonlinear modal stiffness matrices and simulated random loads. Examples are given for an isotropic panel at various combinations of sound pressure levels and temperatures. Numerical results include rms values of maximum deflection and strain, time histories of deflection and strain response, probability distribution functions, power spectrum densities, and higher statistical moments. Numerical results predicted all three types of panel motions for a thermal buckled simply supported isotropic plate: linear random vibration about one of the buckled equilibrium position, snap-through motions between the two buckled positions, and nonlinear random response over both buckled positions.

Thermal structures - Four decades of progress

Since the first supersonic flight in October 1947, the United States has designed, developed and flown flight vehicles within increasingly severe aerothermal environments. Over this period, major advances in engineering capabilities have occurred that will enable the design of thermal structures for high speed flight vehicles in the twenty-first century. Progress in thermal-structures is surveyed for the last four decades to provide a historical perspective for future efforts.