This master thesis deals with design of compression part of Braysson engine which is instrumental to energy producing. The first part addresses generally the problem of Braysson cycle and briefly sums the knowledge about compressors. The next part focuses on the projection of design itself. It contains proposals of various possibilities of solutions, choice of optimal variants. Individual parts of the machine are described and design and control computations are provided. The final part contains evaluation.

Diploma thesis focus on the design of turbocharger in SW MS Excel. For required flow and pressure ratio, the thermodynamics parameters were calculated for the turbocharger. From these, geometry was designed and the condition of mediums was calculated for each part of the turbine and compressor. At last basic characteristics of the turbine and compressor on varying the regime of engine operation the rotation was made and offered an idea about the working point position.

This article describes the first development phase of a centrifugal compressor with variable geometry which is designed to match the needs of future heavy-duty engines. Requirements of truck engines are analyzed, and their impact on the properties of the compressor map is evaluated in order to identify the most suitable kind of variable geometry. Our approach utilizes the transformation of engine data into pressure ratio and mass flow coordinates that can be displayed and interpreted using compressor maps. One-dimensional and three-dimensional computational fluid dynamics fluid flow calculations are used to identify loss mechanisms and constraints of fixed geometry compressors. Linking engine goals and aerodynamic objectives yields specific recommendations on the implementation of the variable geometry compressor.

The thesis presents a method of evaluation for blade damage in Combustion Turbine Compressor Section. This method involves use of multiple domains within a single Finite Element Model to predict the effect of damage on the blade properties. This approach offers significant time and effort savings when compared to traditional evaluation methods of similar problems. It is demonstrated via examples that the multi-domain modeling approach yields acceptable accuracy results. The economical implications of described method are readily applicable to both the industrial and the aerospace Combustion Turbine fields. It is economically impractical to replace the blade at each damage occurrence. However, the evaluation time involved in making associated decisions can be extensive if traditional methods of evaluation are used. The specific contributions of this study are twofold: 1. Time savings during evaluation 2. Compressor Blades may be returned to service which are otherwise replaced

An experimental investigation of the wake of a low-speed axial-flow compressor rotor was conducted with and without the presence of steady inlet total pressure distortions. The steady three-dimensional rotor inlet flow was obtained by a five-hole pneumatic pressure probe, while the one-dimensional rotor exit data were obtained using a piggyback steady/unsteady total pressure probe in non-nulling mode. Both inlet and exit flow conditions were measured in the stationary frame of reference. Results indicate increases in wake thickness and magnitude of total pressure defect as blade loading increased into the distortion cycle. The wake suction side jet increased in width and magnitude as blade loading increased, which appears to be a response to flow blockage caused by the growing boundary layer on the blades. Based on one-dimensional exit total pressure conditions with respect to the distortion screen, the dynamic response of the intra-blade passage flow does not appear to be a function of blade loading, measurement span, or distortion intensity within the ranges tested. Unsteady one-dimensional rotor exit suction side jet width and magnitude varied a great deal within and outside of the distorted region, and were only moderately correlated to inlet flow conditions. Changes in the unsteady one-dimensional rotor wake width and magnitude were usually in phase with and strongly correlated to changes in the inlet flow conditions. / Master of Science

No description available.

Experiments were carried out to investigate the effect of ambient air temperatures on the heat pump performance using a variable speed compressor. Ambient air temperatures were varied from 40 to 60 °F to simulate different seasons. The compressor frequencies of 45 Hz, 50 Hz, 55 Hz, and 60 Hz were studied to determine the optimal frequency under various heating loads. The investigation was carried out by showing the compressor power input, heating output, and coefficient of performance for each case. Thermal cycle analysis along with the heat exchanger theory was used to analyze the system energy balance, heat transfer rates, p-h diagrams, and coefficient of performance. The overall heat transfer coefficients were also determined for both the evaporator and the condenser. Only the capillary tube was used to regulate the refrigerant flow rate. The variable speed compressor system used in this study will help save energy when compared with the traditional steady speed system. The variable speed compressor system will hopefully provide a more comfortable and steady indoor temperature than the traditional system, which is controlled by only an on-off switch. The speed controlled compressor system proposed we believe will help saving more energy than traditional steady speed system. The variable speed compressor system will hopefully provide a more comfort and steady indoor temperature than the traditional system which is controlled by one switch. It is believed that the variable speed compressor system may allow the indoor temperature air to be steady-going and prevent the switch working frequently. / Mechanical Engineering

The deflections of screw rotors under machining forces cause mismatch between the male and female rotors and, consequently, accelerated wear and suboptimal efficiency in their performance. Optimizing the machining process to minimize the generated forces and accounting for the resulting mismatch in the design of the rotor profile requires accurately computing the machining forces in computer simulations. Virtual machining systems combine graphics-based computation of the Cutter-Workpiece Engagement (CWE) with the physics-based models of machining mechanics to simulate the forces during complex machining processes. However, because of the high computational load of graphical simulations, virtual machining is not suitable for the repetitive force simulations that are required for optimizing the design and manufacturing of rotors. In this work, we present a new method that simulates screw milling forces based on the process kinematics instead of graphical simulations. Utilizing mathematical equations that describe the process kinematics, the theoretical rotor profile is determined for feasible combinations of cutting tool profile, setup angle, and centre distance. Subsequently, to find the milling forces, the cutting edge is discretized into multiple small edge segments and a mechanistic cutting force model is used to determine the local cutting forces at each segment. After geometric and kinematic transformations of these local forces, the screw milling forces are obtained for each roughing and finishing pass. Instead of graphics-based methods, the engagement conditions between the cutter and workpiece are determined by the ensemble of 2D rotor and tool profiles; as a result, the computational efficiency is increased substantially. The semi-analytical nature of the presented method allows for computing the forces with arbitrary resolution within a reasonable time. The accuracy and efficiency of the presented method is verified by comparing the simulated forces against a dexel-based virtual machining system. / Graduate

A numerical case study of a multistage compressor with relative supersonic rotors is presented. The purpose of the investigation was to determine the flow instability mechanism of the UEET compressor and its relation to the rotor shock structure in the relative velocity reference frame. The computational study was conducted with the NASA code ADPAC , utilizing the mixing-plane assumption for the boundary condition between adjacent, relatively-rotating blade rows. A steady, five-blade-row, numerical simulation using the Baldwin-Lomax turbulence model was performed, creating several constant speed lines. The results are presented, highlighting the role shock structure plays in the stability of the compressor. The shock structure in the downstream rotor isolates the upstream rotor from the exit conditions until the shock detaches from the leading edge. At this point the shock structure in the upstream rotor moves, changing the conditions for the downstream rotor. This continues with increasing pressure at the exit until the shock in the upstream rotor detaches from the leading edge. This event causes an instantaneous drop in the mass flow rate, initiating positive incident separation on the suction side of stator-two. / Master of Science

An 8 blade, 7 passage linear compressor cascade with tip leakage was built. The flowfield downstream of the cascade was measured using four sensor hot-wire anemometers, from which the mean velocity field , the turbulence stress field and velocity spectra were obtained. Oil flow visualizations were done on the endwall underneath the blade row. Also studied were the effects of tip gap height, and blade boundary layer trip variations. The results revealed the presence of two distinct vortical structures in the flow. The tip leakage vortex is formed due to the roll up the tip flow as it exits the tip gap region. A second vortex, counter-rotating when compared to the tip leakage vortex, is formed due to the separation of the flow leaving the tip gap from the endwall. Increasing the tip gap height increases the strength of the tip leakage vortex, and vice versa. Changing the boundary layer trip had no effect on the flowfield due the fact that boundary layers on the blade surface had separated. As the vortices develop downstream, the tip leakage vortex convects into the passage "pushing" the counter rotating vortex with it. As it does so, the tip leakage vortex dominates the endwall flow region, and is responsible for most of the turbulence present in the downstream flow field. This turbulence production is primarily due to axial velocity gradients in the flow, and not due to the circulatory motion of the vortex. Velocity spectra taken in the core of the vortex show the broadband characteristics typical of such turbulent flows. The results also revealed that the wakes of the blades exhibit characteristics of two-dimensional plane wakes. The wake decays much faster than the vortex. Velocity spectra taken in the wake region show the broadband characteristics of such turbulent flows, and also suggest that there might be some coherent motion in the wake as a result of vortex shedding from the trailing edge of the blades. The present study reveals the complex nature of such flows, and should provide valuable information in helping to understand them. This study was made possible with support from NASA Langley through grant number NAG-1-1801 under the supervision of Dr. Joe Posey / Master of Science