Aerospace Engineering Commons^™

Vehicle Performance Optimization Utilizing The Air Turbo-Ramjet Propulsion System; Methodology Development And Applications, Kirk Christensen

Doctoral Dissertations

"The ATR (Air TurboRocket) is an air breathing propulsion system in which the turbocompressor turbine is powered by a hot drive gas which is generated independently of the air flow through the compressor. The ATR has a lower specific impulse (Isp) and higher thrust compared to a similar size turbojet but a lower thrust and higher Isp compared to similar size solid rocket motor (SRM). This work defines the benefits of ATR propulsion for tactical vehicles.

ATR simulation codes were developed to support analysis of hypothetical ATR powered vehicles. Both turbojet powered and SRM powered vehicles were also evaluated against …

A Dual Neural Network Architecture For Linear And Nonlinear Control Of Inverted Pendulum On A Cart, S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The use of a self-contained dual neural network architecture for the solution of nonlinear optimal control problems is investigated in this study. The network structure solves the dynamic programming equations in stages and at the convergence, one network provides the optimal control and the second network provides a fault tolerance to the control system. We detail the steps in design and solve a linearized and a nonlinear, unstable, four-dimensional inverted pendulum on a cart problem. Numerical results are presented and compared with linearized optimal control. Unlike the previously published neural network solutions, this methodology does not need any external training, …

Target Profile Estimation Using Haar Functions, William R. Bockman, S. N. Balakrishnan, Christopher D'Souza, James Cloutier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An approach to estimating the target acceleration in a maneuvering target model using Haar function partial summations to model the target acceleration is developed. A kinematic constraint is applied to the maneuvering target model and the effects of the use of this constraint are reviewed.

Gas And Liquid Phase Transport In Pulsed Fuel Sprays, Pete D. Jennings, James A. Drallmeier

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An infrared extinction technique was used to characterize spatially and temporally the vapor phase of a transient fuel spray. Optical extinction data were taken at two laser wavelengths and compared to obtain fuel vapor partial pressure values averaged over the line-of-sight through the spray. A transient fuel injector spray was characterized at several axial positions with a spatial resolution of 0.125 cm and a temporal resolution of 0.2 ms. With the knowledge of an axisymmetric spray pulse, the line-of-sight averaged results were deconvoluted to obtain spatially resolved vapor pressure data. The same spray was also characterized using phase/doppler interferometry to …

Effect Of Inflow Pressure And Wall Heat Transfer On Shock-Induced Combustion/Detonation, B. S. Green, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Oblique detonation waves are possible ignition mechanisms for scramjet engines. Results from a numerical study of the effects of changing the inflow pressure on oblique detonation wave structure for supersonic flow of a stoichiometric hydrogen-air mixture over a flat plate followed by a ramp are presented. Viscous effects and finite-rate chemistry are considered. Inflow pressure is varied from 0.1 to 1 atmosphere for Mach 4 inflow over a 30-degree ramp. Also, the effect of wall heat transfer rate is examined by comparing adiabatic wall, and constant temperature wall solutions. A separation bubble forms at the intersection of the flat plate …

Optimization For Maximum Performance High-Speed Engines, David W. Riggins

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Fuel-air combustion and the generation of irreversibility in high-speed flows are described in terms of the fundamental principles of nonequilibrium, work availability, and entropy increases. Engine thrust is analytically related to the overall engine irreversibility and the degree of combustion: Issues involving mixing enhancement assessment and engine optimization are then formalized and clarified. The concept of thrust-potential, as used in engine design and optimization, is shown to be a consistent application of the principles and findings of this and related investigations. This work was supported through NASA Grant NAG 1-1189. Special thanks are due to Charles McClinton at NASA Langley …

A Class Of Modified Hopfield Networks For Aircraft Identification And Control, Jie Shen, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper presents a class of modified Hopfield neural networks and their use in solving aircraft optimal control and identification problems. This class of networks consists of parallel recurrent networks which have variable dimensions that can be changed to fit the problems under consideration. It has a structure to implement an inverse transformation that is essential for embedding optimal control gain sequences. Equilibrium solutions are discussed. Energy minimization of the networks leads to identification of the system parameters. Numerical results are provided to identify the dynamics of an aircraft, and the corresponding optimal control is calculated online. Comparison of the …

A Finite Element Model Of Thermoacoustic Oscillations In Rayleigh Flow, Carlos A. Gutierrez, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The work reported here describes a portion of the development of a finite element model of thermoacoustic oscillations in ducted flows, including three dimensional geometries and nonuniform mean flows with steady heat addition. The thermoacoustic problem is not modeled by a form of the convected wave equation but instead by the conservation equations in primitive form. In this paper the three-dimensional model is reduced to one dimension, applicable to a uniform geometry, but allowing an axially nonuniform flow with sharp gradients in temperature, density, and Mach number. The steady mean flow is computed as a Rayleigh flow. Calculations are shown …

Hamiltonian Based Adaptive Critics For Missile Guidance, S. N. Balakrishnan, Jie Shen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A Hamiltonian based adaptive critic structure is proposed for solving missile guidance problems. This structure consists of a supervisor neural network called 'critic' and a controller network called 'action'. Together they are used to solve model-based guidance problems. The advantage of this approach is that: i) the training data for each network is created by the other network, ii) the converged solutions yield near optimal guidance over the entire span of the training range, and iii) they can be used as feedback controllers though trained off-line. A main contribution is that we establish a direct link between traditional optimal control …

Radiative Heating In Scramjet Combustors, Harlan F. Nelson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Currently, there is considerable interest in scramjet engines for hypersonic aircraft and missiles. This paper presents preliminary calculations of the radiative heating of the walls of scramjet combustion chambers. The analysis assumes isothermal, constant property flow fields which are representative of actual combustor flow fields. The fuel is H2 and N2 is taken as inert. Temperature in the combustor is on the order of 2000 to 3000 K and pressure is of the order of 5 atm. The combustion products consist mainly of H2O and OH. These gases are strong radiators in the infrared. Radiation heating can be significant because …

Heat Transfer In Two-Phase Solid-Rocket Plumes, Harlan F. Nelson, John C. Fields

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Results of a direct simulation Monte Carlo (DSMC) and free molecule (FM) analysis of convective heat transfer to Al2O3 particles in solid-rocket plume environments are presented. The particle diameters are assumed to be 4μm, and the plume gases are CO2, H2O, CO, and N2. The plume gas temperature is 2000 K. Particle temperatures of 1500, 2000, and 2500 K are investigated for Knudsen numbers from 1/2 to 1000 (from slip flow to FM flow). The Nusselt number is presented in terms of Knudsen number and Reynolds number (or relative velocity). Both the Kavanau and the Kashmarov and Svirshevskii correlations generally …

Global Characteristics And Structure Of Hydrogen-Air Counterflow Diffusion Flames, J. Zhao, Kakkattukuzhy M. Isaac, G. L. Pellett

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A model based on similarity transformation, for the nitrogen-diluted, H2-air opposed-jet laminar counterflow diffusion flame (CFDF), was developed independently of earlier models, and numerically solved to study flame location and flame structure and extinction limits. Numerical stiffness is handled by a special treatment of the species production term. Flame location with respect to the stagnation plane is identified as an important parameter that governs H2-air diffusion flames, and physical explanations are given to show how flame location is affected by fuel dilution, strain rate, and Lewis number. Results show very good agreement with experimental extinction conditions. The effect of thermal …

Non-Axisymmetric Matrix Cracking And Interface Debonding With Friction In Ceramic Composites, F. S. Ji, Lokeswarappa R. Dharani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An three-dimensional analytical model based on the principle of minimum potential energy is developed and applied to determine the stress state in a discrete fiber/matrix composite cylinder subjected to axial tensile loading in the fiber direction and containing a non-symmetric transverse matrix crack and an interface debond. The friction over the debonded interface is incorporated into the analysis. The strain energy release rates associated with the matrix crack and the interface debonding under the combination of the applied load and the interface frictional force are computed. The strain energy release rate criterion has been employed to evaluate the critical applied …

Static And Dynamic Characteristics Of Spot Welded Sheet Metal Beams, K. Pal, Don L. Cronin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Although widely employed as structural components in the auto industry, spot welded sheet metal beams manifest static and dynamic behavior that is not well characterized. For the present study, sample beams of three representative cross-sections—hat, box and box with partition—were fabricated of sheet steel. The spacing between the spot welds that hold these sections together was varied from 25.4 mm (1 in.) to 203.2 mm (8 in.) using a 25.4 mm (1 in.) increment. The beams were subjected to static bending and static torsion tests, and bending and torsional stiffnesses were determined as functions of spot weld spacing. The beams …

On A Method For Obtaining Approximate Solutions To Sturm-Liouville Problems, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A method presented recently to find approximate solutions to a Sturm-Liouville problem is shown to be a special case of a classical weighted residual method. The choice of approximation functions and convergence of the method are also examined. © 1995 American Mathematical Society.

Thermal Contact Conductance Of Ceramic Substrate Junctions, K. C. Chung, H. K. Benson, John W. Sheffield

Mechanical and Aerospace Engineering Faculty Research & Creative Works

No abstract provided.

Improved Finite Element Modeling Of The Turbofan Engine Inlet Radiation Problem, I. Danda Roy, Walter Eversman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Improvements have been made in the finite element model of the acoustic radiated field from a turbofan engine inlet in the presence of a mean flow. The problem of acoustic radiation from a turbofan engine inlet is difficult to model numerically because of the large domain and high frequencies involved. A numerical model with conventional finite elements in the near field and wave envelope elements in the far field has been constructed. By employing an irrotational mean flow assumption, both the mean flow and the acoustic perturbation problem have been posed in an axisymmetric formulation in terms of the velocity …

Vibration Of Point-Supported Rectangular Composite Plates, Serge Abrate

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A general approach is presented to study the free vibrations of rectangular symmetrically laminated composite plates with point supports by using the Rayleigh-Ritz method and the Lagrange multiplier technique for enforcing the zero displacement constraints at the support locations. Polynomial approximation functions are used, and the constitutive relationships are written in terms of four lamination parameters. With these lamination parameters, the number of design variables is reduced to a minimum, which is useful for design optimization purposes, while all symmetric lay-ups are considered. This paper illustrates how the lamination parameters can be used for optimal design of vibrating plates. Results …

A New Neural Architecture For Homing Missile Guidance, S. N. Balakrishnan, Victor Biega

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We present a new neural architecture which imbeds dynamic programming solutions to solve optimal target-intercept problems. They provide feedback guidance solutions, which are optimal with any initial conditions and time-to-go, for a 2D scenario. The method discussed in this study determines an optimal control law for a system by successively adapting two networks - an action and a critic network. This method determines the control law for an entire range of initial conditions; it simultaneously determines and adapts the neural networks to the optimal control policy for both linear and nonlinear systems. In addition, it is important to know that …

Hamiltonian Based Adaptive Critics For Aircraft Control, S. N. Balakrishnan, Jie Shen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aircraft designs are becoming more complex in order to either operate more efficiently as in the commercial sector or to push the performance envelopes as in the military sector. An interesting outcome of this scenario is that `control'' has come to play an important role in helping realize these objectives. Increasingly, control is becoming an integral part of an aircraft design rather than an afterthought. More effective and efficient control of an aircraft is certain to lead to improved performance at a lower cost

Fuzzy Logic In Restructurable Flight Control Systems, S. N. Balakrishnan, H. S. Ho

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a fuzzy logic controller (FLC) is proposed for restructurable flight control systems. The role of the FLC is to stabilize the aircraft upon a fault occurrence. The FLC derives pitch/roll/yaw controls from a generic knowledge base characterized by 49 if-then rules. A linearized model representative of a modern jet fighter provides the basis for the numerical simulation. Simulated faults include various degrees of surface loss at the right stabilator, combined with reduced ailerons and rudder control power. The FLC accomplishes the stabilization task under test conditions without any knowledge of the system parameters. The numerical results demonstrate …

On The Use Of Students For Developing Engineering Laboratories, Bopaya Bidanda, Richard E. Billo

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes a unique and innovative approach that solved the dual problem of starting up a new engineering instructional laboratory in a timely manner, and for teaching engineering students advanced skills in Automatic Data Collection. Students enrolled in a special pilot course were used to develop and startup an Automatic Data Collection laboratory. These students were assigned individual Automatic Data Collection technologies of interest and given total responsibility for the successful startup of the laboratory. The organization and structure of the course modeled the typical team oriented project development efforts in industry. Feedback from students showed the course to …

Intercomparison Between Commercial Condensation Nucleus Counters And An Alternating Temperature Gradient Cloud Chamber, Darryl J. Alofs, C. K. Lutrus, Donald E. Hagen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Three Commercial CNC Counters (TSI Models 3010, 3022A, and 3025A) Are Compared with an Alternating Temperature Gradient Cloud Chamber (ALGR). Electrically Size Classified Aerosols of Sodium Chloride and Silver Are Used. Diffusional Losses within the ALGR Are Much Larger Than for the TSI Instruments: Therefore the ALGR Concentrations Are Corrected for Internal Diffusional Losses, But the TSI Instruments Are Not. the Particle Size Range Tested is 4–90 Nm. for Sodium Chloride, the TSI Concentrations Agreed Fairly Well with the Corrected ALGR at Larger Sizes, and Were Below the Corrected ALGR at Smaller Sizes. the Electrical Aerosol Classifier (EAC) Setting at …

System Modeling And Control Of Smart Structures, Frank J. Kern, Leslie Robert Koval, K. Chandrashekhara, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents multidisciplinary research and curriculum efforts at the University of Missouri-Rolla in the smart structures area. The primary objective of our project is to integrate research results with curriculum development for the benefit of students in electrical, and mechanical and aerospace engineering and engineering mechanics. The approach to the accomplishment of curriculum objectives is the development of a two-course sequence in the smart structures area with an integrated laboratory. The research portion of the project addresses structural identification and robust control methods for smart structures. A brief summary of the research results and a description of curriculum development …

A New Approach To Automatic Target Recognition Using Wavelet Transforms, Anitha Panapakkam, S. N. Balakrishnan, Daniel St. Clair

Computer Science Technical Reports

Automatic Target Recognition (ATR) systems have significant impact in defense applications. There is a continuing need to develop new and robust techniques to handle the increasingly complex ATR problem. The objectives of this thesis are two-fold. First a new technique to be used for ATR is developed and secondly an integrated ATR system to investigate and combine all subsystems is developed. In this thesis, we have developed a new technique for the feature extraction stage of ATR problem using wavelet transforms. Wavelet transforms have been one of the widely investigated areas of research in the past few years. The promising …

The Feasibility Of Using Piezoelectric Flap Actuation In The Active Control Of Flutter, Aaron Laws

Opportunities for Undergraduate Research Experience Program (OURE)

Wing flutter is one of the most important and dangerous phenomenon faced by aircraft structural design engineers. Flutter is a self exciting aeroelastic phenomenon in which portions of an aircraft structure begin to oscillate with exponentially growing amplitudes, produced by the changing aerodynamic forces and moments brought about by the deformation of the structure. There exists a characteristic flight speed, known as the flutter speed, where the structure exhibits sustained harmonic motion, ie. zero damping. Below this velocity, the vibration of the structure due to a perturbation will decrease exponentially, while above this velocity, the vibration will increase exponentially, eventually …

Preliminary Efforts Towards The Analysis Of Unsteady Pressure Measurements Around Wing Models In Transonic Flow, Stephen Witherspoon

Opportunities for Undergraduate Research Experience Program (OURE)

A computer code was developed to implement methods of analyzing unsteady pressure measurements acquired from a wing model immersed in transonic flow. The code uses the fast Fourier Transform to identify phase changes and magnitudes of dominant frequencies over time in the unsteady pressure coefficients. The transformed data, as well as the raw data, are graphed and the results explained in detail identifying features depicted in the graphs. Also, the code performs some simple statistical calculations and smoothes the data to remove insignificant noise in the signal, if desired.

Determination Of Flow Quality And Boundary Layer Thickness In Variable Density Wind Tunnel, Marshall Philips

Opportunities for Undergraduate Research Experience Program (OURE)

The purpose of this paper is to measure the velocity profile in the test section of the Variable Density Wind Tunnel (VDWT). The hot wire anemometer is chosen to measure the velocity profile because of its accuracy and its ability to be moved relatively close to the upper and lower surfaces of the wind tunnel. Special attention is paid to the uniformity of flow velocity in the free stream and whether it varies with position in the tunnel. The measurements were taken at two different stations, two different temperatures, and three different speeds.

Results indicate that the velocity profiles are …

Development Of A Launch System For Performance Studies Of Small Aircraft Models, James J. Schneider

Opportunities for Undergraduate Research Experience Program (OURE)

This paper presents a design of a launching system that can be employed for performance studies on small aircraft models. Further the article describes a design and development of an aircraft model for use with the system. initial analysis and testing of the system using the designed aircraft model will be presented.

The Effect Of Spatial Variation Of The Turbulent Prandtl Number And Calculation Methods For Heat Transfer In High Mach Number Flows, Thomas W. Scott

Opportunities for Undergraduate Research Experience Program (OURE)

The effect of using various spatial distributions of the turbulent Prandtl number on the predicted surface heat transfer in the numerical simulation of Mach 4 flat plate flow is studied. The spatial distribution of the turbulent Prandtl number is shown to have a small effect on surface heat transfer, hence suggesting that the standard assumption of a constant turbulent Prandtl number is acceptable for high Mach number boundary layer type flows. In addition, a wall-cell control volume technique for computing heat transfer shows superior predictive capacity across the Reynolds number range when compared to the conventional calculation of surface heat …