Performance Of Hypersonic Vehicle Research Articles

RBFNN-Based Anti-Input Saturation Control for Hypersonic Vehicles

In hypersonic flight control, characterized by challenges posed by input saturation, model parameter uncertainties, and external disturbances, this paper introduces a pioneering anti-input saturation control method based on RBFNN adaptivity. We have developed adaptive laws to enhance control system adaptability and robustness by integrating mission profiles, actuator saturation failure modes, and self-evolving neural network design. Furthermore, our approach introduces a novel anti-input saturation auxiliary system, effectively addressing input saturation constraints. This innovation ensures system stability and precise tracking, even in severe input saturation constraints. The results reveal that the system’s steady-state tracking error remains under 2% under input saturation constraints, and the convergence speed demonstrates an impressive 20% improvement. These findings underscore this research’s substantial advancement in hypersonic flight control. It may significantly enhance the controllability and performance of hypersonic vehicles in real-world scenarios.

Thermal cracking performance of Al-nanoparticle-containing nanofluids

Endothermic hydrocarbon fuels containing energetic nanoparticles, which combine high-energy–density and endothermic capability, are promising for improving the flight performance of hypersonic vehicles. Here, the feasibility of nanofluid fuels as energetic endothermic fuel is studied. Aluminum nanoparticles (Al NPs)-containing nanofluid fuels were prepared by dispersing 0.1 wt% and 0.5 wt% Al NPs into JP-10, decahydronaphthalene (DHN) and methylcyclohexane (MCH), respectively. Characterizations of nanofluid fuels confirm the addition of Al NPs improves the density and combustion performance of the hydrocarbon fuels. The cracking performance of three fuels with Al NPs added is slightly inhibited in the order of DHN > MCH > JP-10. Cracking conversion (and heat sink) of JP-10, DHN and MCH containing 0.5 wt% Al NPs decrease by 3.0 %, 18.8 % and 14.1 % (and 0.04, 0.09 and 0.05 MJ/kg), respectively. JP-10 is the least affected by Al NPs. Meanwhile, Al NPs are observed to slightly increase the amount of coking during cracking, and the non-uniformly dispersed Al can be found in the coke deposition. This work indicates the potential application of energetic nanofluids to serve as endothermic fuels, and provides the method for the further development of high-energy–density endothermic fuels.

Numerical investigation of unsteady aerodynamic characteristics induced by the interaction of oblique/bow shock waves during rotation

The interactions between oblique and bow shock waves are significant problems related to the aerodynamic force and thermal performance of hypersonic vehicles, but few studies have considered the dynamic effect of the body's motion on the phenomena. In this work, a numerical study on the oblique and bow shock waves ahead of an elliptic cylinder rotating with a forced-oscillation approach was conducted at Mach 5 by solving the unsteady, two-dimensional Navier–Stokes equations in a non-inertial coordinate system. The hysteresis loops of aerodynamic coefficients were analyzed first, and it was found that the moment is sensitive to rotation. Then, two different hysteresis forms were found at positive and negative angles of rotation (AOR), corresponding to cases with the interference point above or below the wall, respectively. When AOR is positive, the rate-dependent transition hysteresis among various shock interaction types causes the movement of strong flow structures (reflected shock wave, Mach stem, and jet) to always lag behind the body's motion. When AOR is negative, besides the evolution hysteresis of flow structures, two unusual patterns between Edney Types III and VI were observed on different transition paths, which led to very different peak pressures. Also discussed are the driving mechanisms associated with the effect of the subsonic region and the downstream boundary of the interaction zone, as well as the modulating action of the formed virtual Laval flow channel. Additional simulations were performed to study the effect of rotation speed on the transition boundary and the transition structures between Types III and VI.

Noise level effect on the hypersonic boundary layer

The boundary layer state has a critical effect on hypersonic vehicle performance and the noise level is the main factor causing the differences between the boundary layer transition in a wind tunnel test and that in a real flight. The second mode wave frequency of the 7° half-angle cone models as measured in four hypersonic wind tunnels is collected. The effects of the noise level on the boundary layer are determined by comparing dimensionless parameters, which are nondimensionalized based on computed values. The results indicate that the noise level could affect the second mode wave frequency and the boundary layer thickness, where the second mode wave frequency decreases and the boundary layer thickness increases with increasing noise level. However, the mechanism by which the noise level influences the second mode wave frequency and the boundary layer thickness requires further study.

Nonlinear Predictive Control with Sliding Mode for Hypersonic Vehicle

Hypersonic vehicles are difficult to control due to their rapid time variation, dynamic nonlinearity, strong coupling, and model uncertainty. This paper proposes a new nonlinear predictive controller to solve the problem. An improved model predictive controller is used to improve the dynamic control performance of hypersonic vehicles by converting nonlinear dynamics into a state-dependent linear model. The sliding surface can significantly increase the speed of convergence. The radial basis function is used to reduce the influence of system uncertainty. The stability of the proposed controller is analyzed based on the Lyapunov approach. The comparison of simulation results verifies the excellent control performance of the proposed method both in convergence speed and antidisturbance ability.

Investigating the Effects of H, CH3, and C2H5 Radicals on the Kinetics of Ignition for Methane/Air Mixtures

Abstract A comprehensive understanding of the effects of free radicals on the ignition properties of practical fuel is critical for the performance of hypersonic vehicles. In this study, the free radical effects of H, CH3, and C2H5 on the ignition delay times of methane/air mixtures at dosages of 10−7–10−2 (mole fraction) were systemically analyzed via kinetic analysis with two detailed mechanisms (i.e., AramcoMech 2.0 and USC MECH II). Results showed that the addition of free radicals mainly promoted the ignition process at low temperature (800 K), while the addition of molecule H2 mainly improved the ignition process at high temperature (1250 K). When the additional fractions of free radicals were less than 10−3, promoting effects of the three kinds of free radicals were the same. Differences appeared only when the contents were higher than 10−2. Further kinetic analyses indicated that the addition of free radicals could change the critical reactions during the ignition process of methane/air mixtures. The ignition delay times were reduced by increasing the generation rate of OH radical and heat release rate with the addition of free radicals, while the overall output of OH and flame temperature were not affected by the free radicals.

Machine Learning Strategy for Wall Heat Flux Prediction in Aerodynamic Heating

The efficient and accurate prediction of the aeroheating performance of hypersonic vehicles is a challenging task in the thermal protection system structure design process, which is greatly affected by grid distribution, numerical schemes, and iterative steps. From the inspiration of the theoretical analysis and machine learning strategy, a new wall heat flux prediction framework is proposed first by establishing the relationship between the wall heat flux and the flow variables at an extreme temperature point (ETP) in the normal direction of the corresponding wall grid cell, which is named the machine learning (ML)-ETP method. In the training phase, the flow properties and their gradients at the ETP and the distance from the ETP normal to the wall are employed as feature values, and the accurate wall heat flux predicted by the converged fine grid is regarded as the tag value. With the assistance of the trained regression model, the heat flux of the same configuration with a coarse grid in the wall-normal direction could be predicted accurately and efficiently. Moreover, test cases of different configurations and inflow conditions with a coarse grid are also carried out to assess the model’s generalization performance. All comparison results demonstrate that the ML-ETP strategy could predict wall heat flux more rapidly and accurately than the traditional numerical method due to its nonstrict grid distribution requirements. The improvement of the predictive capability of the coarse-graining model could make the ML-ETP method an effective tool in hypersonic engineering applications, especially for unsteady ablation simulations or aerothermal optimizations.

Numerical simulation of hypersonic thermochemical nonequilibrium flows using nonlinear coupled constitutive relations

To predict aeroheating performance of hypersonic vehicles accurately in thermochemical nonequilibrium flows accompanied by rarefaction effect, a Nonlinear Coupled Constitutive Relations (NCCR) model coupled with Gupta’s chemical models and Park’s two-temperature model is firstly proposed in this paper. Three typical cases are intensively investigated for further validation, including hypersonic flows over a two-dimensional cylinder, a RAM-C II flight vehicle and a type HTV-2 flight vehicle. The results predicted by NCCR solution, such as heat flux coefficient and electron number densities, are in better agreement with those of direct simulation Monte Carlo or flight data than Navier-Stokes equations, especially in the extremely nonequilibrium regions, which indicates the potential of the newly-developed solution to capture both thermochemical and rarefied nonequilibrium effects. The comparisons between the present solver and NCCR model without a two-temperature model are also conducted to demonstrate the significance of vibrational energy source term in the accurate simulation of high-Mach flows.

Influence of coaxial air jet on mass diffusion of hydrogen jet injected through lobe-injector at supersonic flow

The technique of fuel injection in the combustion chamber is crucial for increasing the performance of hypersonic vehicles. This study tries to investigate the mechanism of fuel injection and distribution when fuel and air are injected through coaxial lobe injectors. The main attention of this work is to present the mechanism of fuel mixing of transverse jet injected from various lobe injectors. Comparison of coaxial gets (air and fuel jet) with equivalent simple jet (fuel without air jet) is done to achieve an efficient model for the combustion chamber. In this work, finite-volume is used to simulate and study of fuel injection performance of a transverse hydrogen jet in different lobe injectors. 3-D flow visualizations are done to reveal the mechanism of the fuel penetration and streamline pattern for introduced models. Strength of circulation and fuel mixing efficiency are also investigated in the present work for 2-, 3-, and 4-lobe nozzles. Our outcomes indicate that the mixing performance of coaxial air and fuel jet injected through the 3-lobe nozzle is about 25% better than other nozzle types. Our findings confirm that injection of air jet through the core of the lobe nozzle increases fuel mixing up to 200% at the combustion chamber.

Enhancing the take-off performance of hypersonic vehicles using the improved chimp optimisation algorithm

AbstractThe performance of hypersonic vehicles in the take-off stage considerably influences their capability of accomplishing the flight tasks. This study is aimed at enhancing the take-off performance of a cruise aircraft using the improved chimp optimisation algorithm. The proposed algorithm, which uses the Sobol sequence for initial population generation and a function of the weight factors, can effectively overcome the problems of premature convergence and low accuracy of the original algorithm. In particular, the Sobol sequence aims to obtain a better fitness value in the first iteration, and the weight factor aims to accelerate the convergence speed and avoid the local optimal solution. The take-off mass model of the hypersonic vehicle is constructed considering the flight data obtained using the pseudo-spectral method in the climb phase. Simulations are performed to evaluate the algorithm performance, and the results show that the algorithm can rapidly and stably optimise the benchmark function. Compared to the original algorithm, the proposed algorithm requires 28.89% less optimisation time and yields an optimised take-off mass that is 1.72kg smaller.

Multi-objective aerodynamic optimization of two-dimensional hypersonic forebody-inlet based on the heuristic algorithm

Nowadays, the forebody-inlet integrated design optimization becomes more and more important in improving the performance of hypersonic vehicles. And several achievements have been made to improve the performance of the two-dimensional hypersonic forebody-inlet integrated vehicle. However, all these works are faced with many defects. For example, the work adopting the gradient algorithm is easy to be trapped in the local optimum solution. The data-driven optimization method is with a low level of accuracy. Moreover, the geometry parameterization methods adopted in those optimization procedures are hardly implemented to complex configurations. In this study, a global-searching multi-objective optimization framework is proposed to overcome these limitations and to carry out multi-objective optimization of the two-dimensional hypersonic forebody-inlet shape. The framework includes the Free-Form Deformation (FFD) method, the mesh deformation method, the high-accuracy Reynolds Averaged Navier-Stokes (RANS) solver, and the global-searching heuristic algorithm. Results obtained by this framework indicate that the total pressure recovery coefficient, the pressure rising ratio, and the mass flow coefficient are increased by 3.97%, 9% and 7.35%, respectively, which suggests that the optimization framework proposed in this study is promising to be widely used in practical engineering applications.

Effects of chemical energy accommodation on nonequilibrium flow and heat transfer to a catalytic wall

The accurate prediction of the aeroheating performance of hypersonic vehicles requires more detailed modeling of the catalysis process, rather than merely employing a catalytic coefficient. In this paper, the theoretical modeling, as well as the direct simulation Monte Carlo method, is used to preliminarily study the incomplete chemical energy accommodation effects, that is, only a part of the potential energy released in the heterogenous recombination reaction is transferred to the surface, while the remaining is retained as the vibrational energy of the desorbed molecule. An integrated model is proposed to describe the contribution of each energy mode in the rarefied nonequilibrium heat and mass transfer process. Based on the model and several Damköhler numbers, an analytical formula is derived, and is also shown to compare well with the numerical results. On account of the incomplete accommodations of the chemical and vibrational energy on the wall, a variation up to 20% is observed in predicting the stagnation point heat flux under typical nonequilibrium flow conditions. This study could enrich our understanding of the nonequilibrium heat transfer phenomenon and also shows a potential practical value.

Uncertainty Analysis of Parameters in SST Turbulence Model for Shock Wave-Boundary Layer Interaction

Shock wave-boundary layer interactions (SWBLIs) have a tremendous influence on the performance of hypersonic vehicles. For the numerical simulation of such engineering flows, Reynolds averaged Navier-Stokes (RANS) still occupies an irreplaceable role. However, parameters of turbulence models in RANS have substantial uncertainties, which impact the reliability of simulation results. Thus, the aim of the present study is to conduct an uncertainty analysis on parameters in the shear-stress transport (SST) turbulence model for the simulation of SWBLIs. In the current work, uncertainty quantification was performed first. A surrogate model was constructed by the non-intrusive polynomial chaos (NIPC) method to propagate uncertainties from model parameters to the quantities of interests (QoIs) and quantify them. In the subsequent sensitivity analysis, the key parameters were identified for such flow by calculating the Sobol index of each parameter for various QoIs. The results indicate that uncertainties of model parameters led to non-negligible uncertainties in those QoIs, particularly in skin friction and wall heat flux. The parameters α1, σω1, β1 were identified as primary contributors through the sensitivity analysis. Moreover, the specific effects of the three parameters on the flow prediction were analyzed by changing the parameters’ values separately.

Finite-time nonsingular terminal sliding mode control-based fuzzy smooth-switching coordinate strategy for AHV-VGI

This paper presents a fuzzy smooth-switching coordinate strategy for air-breathing hypersonic vehicle with variable geometry scramjet inlet (AHV-VGI), which can improve the aerodynamic performance of hypersonic vehicle by moving the movable lip to capture more airflow. The longitudinal model of AHV-VGI is firstly formulated, followed by a strict feedback form model. Wherein, the multiple nonlinear aerodynamic models are established with different elongation distance of translating cowl. Secondly, a finite-time nonsingular terminal sliding mode control (NTSMC) method is introduced to develop velocity and altitude subsystem controllers for each model. After that, an interval type-2 fuzzy logic system technique is employed to guarantee the smoothness during switching process between the adjacent NTSMC controllers. Furthermore, the Lyapunov function combined with adaptive laws are constructed to prove the finite-time stability of the closed-looped switching system. Finally, simulation results are provided to validate the effectiveness of these theoretical results.

Hypersonic drag reduction mechanism of a novel combinational spike and multi-opposing jets aerodynamic configuration

The shock wave drag significantly affects the aerodynamic performance of hypersonic vehicles, a novel combinational configuration is proposed to reduce the drag in this paper. The basic configurations are the spike, nose cone, front and rear jets, respectively. The numerical method is used to study the drag reduction performance. The combinational configuration has weaker reattachment shock wave than the other configurations, and both the peak pressure of nose cone and drag coefficient are decreased by more than 45%, which verifies the excellent drag reduction performance of combinational configuration. The influencing factors are analyzed in this paper. Lengthening the spike and increasing the total pressures of two jets can make the reattachment shock wave away from wall, weaken its intensity and increase the drag reduction performance. Furthermore, the change rates of wall pressure distribution of the nose cone and drag coefficient gradually decrease. When the sizes of two nozzles are small, the rear jet appears as the long penetration mode. When the sizes of two nozzles are larger than corresponding critical sizes, respectively, the rear jet will convert to the short penetration mode. Increasing the sizes of two nozzles makes the reattachment shock wave away from wall and increases drag reduction performance with the rear jet being SPM as well. The size and total pressure of front jet has greater influence on the drag coefficient. The influence of above factors on the flow characteristics and mass flow rate of nozzle is also studied in this paper.

Preface

This proceeding contains the scholarly papers presented in the 3rd International Conference on Aeronautical, Aerospace and Mechanical Engineering (AAME 2020) held in February, 2020 in Bangkok, Thailand.Submissions to the conference have been reviewed by members of the Technical Committee consisted of professors and senior academics from reputable international universities in Australia, Asia, Europe and South Africa. The papers in this proceeding have passed the vigorous review process and amended to the satisfaction of reviewers. The face-to-face presentations have also undergone critiques by expert audience in the conference. It is on this basis that the published papers in this proceeding are good references to future research investigations and analyses.Papers in the conference can be categorised according to the themes of the conference: aeronautical, aerospace and mechanical engineering. It is worth to note that the purpose of categorisation with these themes is only to help readers to search for papers. The proceeding as a whole presents a consistent focus on aerodynamics, aerostructures, mechanical strength and space exploration technologies. The distribution of papers among these themes is close to balanced, i.e. 9 papers in aeronautical, 6 papers in aerospace and 8 papers in mechanical engineering.Among the 9 papers in aeronautical engineering, structural integrity of aerostructures such as airframe and wing are the most common topics. Another common topic is aerodynamics on aeronautical components which extends into analysis of forces and loading. The novel analyses exhibit in these papers push the boundary of knowledge and enable better aircraft design and manufacture.The 6 papers in aerospace engineering are mostly concerning satellite design, operations and communication. Of particular interest is a paper on aerodynamics performance of hypersonic vehicle and another paper on digital twins. Both papers present innovative concepts in the objective of space exploration. As the technological ability of the world increases, there is evidence that many countries are increasing their research activities in space. The number of papers in this conference is encouraging.The remaining 8 papers are grouped under mechanical engineering theme. Typical mechanical papers such as the lifting mechanism and tie rod of landing gears involve analysis of vibration or shock to mechanisms. It is also nice to see more fundamental mechanical engineering problems such as the research on flatness of large deployable antenna are investigated. Likewise, the research investigating flow-induced vibration of prisms has good potential to develop into more accurate prediction of mechanism interaction with fluid flow.The research rigour and strong theoretical fundamentals demonstrated in the publications in this conference make this proceeding a valuable repository of research topics in aeronautical, aerospace and mechanical engineering. I would like to thank the conference committee, the conference secretariat, keynote speakers and all participants for their hard work making this conference a success.Professor John P.T. MoConference Chair, AAME 2020BSc(Engg), MSc(Engg), PhD(Loughborough), FIEAust CPEng NER APEC Engineer IntPE(Aus), CEng, FIMechE, MHKIE, MFIESchool of EngineeringRMIT UniversityFebruary 2020

An Engineering Method for Computing the Aerodynamics Performance of Hypersonic Vehicle

For fast and automatic calculation of aerodynamic in conceptual design of hypersonic vehicles, an aerodynamic fast calculation program based on C/C++ is compiled in this paper. In this paper, the HL-20 lift body and the double radial ball model are selected for the example verification, and the calculation results are compared with the wind tunnel experimental data, it is shown the calculation results is highly consistent with the experiment. The program not only can accurately predict the aerodynamic characteristics of hypersonic vehicles, but also be linked to the optimization program as a C++ library file to realize the shape optimization design.

Integrated Guidance and Control for Hypersonic Morphing Missile Based on Variable Span Auxiliary Control

The morphing aircraft can improve the flight performance of hypersonic vehicles by satisfying the flight requirements of large airspace and large velocity field. In this paper, for the hypersonic variable span missile, the dynamic model and aerodynamic model are established on the variable span characteristic. The adaptive dynamic surface control back-stepping method is used to establish the integrated guidance and control (IGC) with terminal angular constraint in the dive phase of the hypersonic variable span missile. The span variety is used to assist the lift control to achieve fast and stable control for the centroid motion. The simulation results demonstrate that the feasibility and robustness of the IGC method of the hypersonic variable span missile is better than the invariable span.

Heat Transfer in Nonequilibrium Flows with Homogeneous and Heterogeneous Recombination Reactions

The aeroheating performance of hypersonic vehicles is usually significantly influenced by the chemical reaction processes. For the new-generation hypersonic cruise vehicles, the boundary-layer flow is shown to be in chemical nonequilibrium due to rarefied gas effects. As a result, there will be a competition between the homogeneous recombination of atoms in the near-wall flowfield and the heterogeneous recombination on the catalytic wall surface, which, leading to a coupling of the heat diffusion and conduction, is beyond the application scope of the classical theories developed originally for the traditional blunt reentry vehicles. In this paper, the theoretical modeling and the direct simulation Monte Carlo method are employed to study the corresponding rarefied nonequilibrium flow and heat transfer phenomena near the sharp leading edges. A generalized model is proposed to evaluate the deviation of the actual aeroheating performance from the classical description. Based on this model, an integrated nonequilibrium criterion and a simple but effective bridging function are introduced to predict the stagnation-point heat transfer under the competitive effects between the homogeneous and heterogeneous recombination of atoms. The analytical formula is validated by the numerical results under various flow conditions.

High-Pressure Capturing Wing Configurations

This paper proposes a family of high-pressure capturing wing configurations that aim to improve the aerodynamic performance of hypersonic vehicles with large volumes. The predominant visual feature of such configurations is a thin wing called a high-pressure capturing wing attached to the top of an upwarp airframe. When flying in the hypersonic regime, high-pressure airflow compressed by the upper surface of the vehicle acts on the high-pressure capturing wing and significantly augments lift on the vehicle with only a small increase in drag, producing a correspondingly high increase in its lift-to-drag ratio. A series of numerical validations were carried out on the basis of both inviscid and viscous computational models in which ideal cones with different cone angles and combined cone–waverider bodies with different volumes were used as airframes. The results clearly demonstrate that a configuration using a high-pressure capturing wing has a significantly higher lift (with a correspondingly high value of lift-to-drag ratio) than one without a high-pressure capturing wing, especially for vehicles with large volumes. This paper contains a preliminary, results-based report of the conditions under which high-pressure capturing wing configurations were tested.