The passage shock wave end wall boundary layer interaction in a transonic compressor was investigated with a laser transit anemometer. A two stage transonic compressor designed without inlet guide vanes was used in this flow field investigation. Measurements of the flow velocity were made within the first stage rotor passage of this transonic compressor. Laser measurements were made in two blade passages at six axial locations from 10% of the axial blade chord in front of the leading edge to 30% of the axial blade chord into the blade passage. At three of these axial locations, laser traverses were taken at different radial immersions to investigate the flow behavior near the tip end wall. Twenty-six different locations were traversed circumferentially. The measurements reveal that the end wall boundary layer in this region is separated from the core flow by what appears to be a shear layer where the passage shock wave and all ordered flow seem to end abruptly. / Ph. D. / incomplete_metadata

The objective of this research is the computer simulation of the vibrations of the suspension system of a two-cylinder reciprocating compressor. A theoretical model is developed to describe the various steps undertaken to calculate the response of this six-degree-of-freedom rigid system. The response, which is in the form of a displacement vector, serves as the input to a computer animation of the motion of the orbit of the compressor with respect to the four suspension system springs. The theoretical model is developed by calculating (1) the System Mass and Inertial Matrix, (2) the Gyroscopic Matrix, (3) the Total Assembly Stiffness Matrix, and (4) the Shaking Forces and Moments Matrix. Experimental and finite element methods used to evaluate the parameters required to calculate these matrices are also discussed. An eigenanalysis is performed to calculate the eigenvalue frequencies and eigenvectors for the system. The force analysis is performed to calculate the forcing function in the time domain for the first 40 harmonics. The Fast Fourier Transform method is used to transform the forcing function from the time domain to the frequency domain. The validity of the results are checked by simultaneously developing another model using IMP (Integrated Mechanisms Program). The response is then calculated in original coordinates, after performing a modal transformation. Finally, the response, which is a displacement vector, is utilized by an animation program in PHIGS (Programmer's Hierarchical Interactive Graphics Standard) to animate the motion of the orbit of the compressor. / Master of Science

The objectives of this research are the prediction of the thermodynamic behavior of a multi-stage intercooled reciprocating compressor and its progressive loss of performance due to leakage. A theoretical model is developed to simulate the thermodynamics of the compressor system and the lubricating condition and wear of the piston ring pack for a multi-stage intercooled reciprocating compressor. A first law of thermodynamics approach is used to determine the thermodynamic properties of the gas inside the cylinders, the intercoolers and the inlet and discharge manifold. The compressor valves are modeled as single degree-of-freedom, spring-mass=damper systems. The flows through the valves are calculated based on the steady flow equations for equivalent orifices. The lubricating condition of the piston ring pack are determined on the basis of hydrodynamic lubrication theory. The wear of the piston rings is assumed to occur when the hydrodynamic oil film between the piston ring and cylinder bore breaks down. Based on the theoretical model, a computer program is developed. This program is tested on an Ingersoll-Rand Model 242, two stage aircooled reciprocating air compressor. The comparison of the experimental values of the pressure variations in the first cylinder with the value predicted by the computer program shows a reasonable match. The computer program predicts the pressure, temperature and mass flow rates for each cylinder and the intercooler. Also predicted is the wear rate of each piston ring. The progressive loss in the compressor mass discharge, and hence the loss in its performance, is determined by calculating the leakage losses several times, updating the leakage area each time based on the wear rate of the piston rings. The result shows a drop of about 15 percent in the discharge rate of the Model 242 compressor after 8000 hours of running time. / Master of Science

An experimental investigation of the performance characteristics of a solid wall linear compressor cascade was conducted. The purpose of the experiments was to determine the effects of the blade row configuration parameters stagger and solidity on the pre-and post-stall behavior of the flow in the cascade. Tests were conducted at a solidity of 1.5, and for two stagger angles, 36.4 degrees and 25 degrees. The investigation included the use of high speed motion pictures with smoke flow visualization in the cascade, measurements of the total pressure and velocity of the flow upstream and downstream of the cascade, and measurements of the blade surface pressures. The experiments were conducted for a range of angle of attack from 0 degrees to 45 degrees. To determine the effects of solidity on the pre- and post-stall behavior of the flow in the cascade, the results obtained for the present 1.5 solidity cascade were compared to previous results from the same cascade tested at a solidity of 1.0. The flow in the two cascades was observed to be similar in nature, but the influence of the reduced blade loading in the high solidity cascade was apparent. For the higher solidity cascade, flow losses at low angle of attack were found to be larger, but stalling behavior was delayed. / Master of Science

No description available.

This thesis introduces the application of computer-aided engineering techniques to the dynamic analysis of reciprocating compressor designs. The analysis process is detailed in three steps. The first step, an interactive pre-processor, develops the shaking forces and torques acting on the machine. The second step is a batch processed program that performs a dynamic simulation of the compressor in operation. The compressor and mounting are simulated as a rigid body with six degrees-of-freedom (X, Y, and Z translations and roll, pitch, and yaw) mounted to the ground with up to 25 arbitrarily oriented springs and dampers. Additionally, an eigenanalysis is performed that returns the natural frequencies and modes for the machine. The final step is an interactive postprocessor where the user may examine the results of the eigenanalysis as well as the operating orbit of the machine. A series of programs that implement the analysis process was developed. The specialized formulations for the six coupled, non-linear equations of motion are presented. Color computer graphics and animation are used for visual output displays. The dynamic simulation program is designed to function on many computer systems, from low-cost personal computers to large mainframes, while the pre- and post-processing programs are designed for the personal computer. The programs were tested by comparing the predicted results with those of an Ingersoll-Rand model 242 two piston, two stage, 3 hp compressor. The correlation between the experimental and predicted results show that the programs can accurately simulate the dynamics of a reciprocating compressor operating at steady-state. Typically, the acceleration results agree for the six degrees-of-freedom in both the time and frequency domain to within 8%. / Master of Science

A three-color, three-component Laser Doppler Anemometer (LOA) capable of making simultaneous measurements of three components of velocity is described, and the use of this LOA to measure three non-orthogonal velocity components in the rotor blade passage of a single-stage axial-flow compressor is reported. Measurements were made at four radial locations from 50% span out to the blade tip, and at seven different axial locations from -0.55 axial chord 1.40 axial chord. Measurements were made at only one throttle setting. The measured velocities are used to determine the flow in the orthogonal axial - tangential - radial, x - t - r, coordinate system of the compressor. Although the mean velocities and entire Reynolds stress tensor are obtained with this system, only the mean velocities are reported. Results are presented in the form of a series of vector plots showing: 1.) the primary flow as projected on the x - t plane and 2.) the secondary flow in the t - r plane. The LOA measurements are shown to agree with pitot probe measurements in the stationary frame and basic secondary flow theory. A detailed error analysis is presented, taking into account both measurement uncertainties and statistical biasing. An analysis is also made of particle lag in the rotating flow of the compressor blade passage. A discussion of the difficulties encountered in making three dimensional velocity measurements in turbomachinery blade passages is presented. Suggestions are made for improving the present system for this task. / Master of Science

This thesis presents the results from measurements taken during the transient unstable operation of an axial-flow transonic core-compressor rotor. The measurements were taken to better understand the unstable flow physics of transonic rotors. The rotor, commonly referred to as Rotor 37, was designed by NASA Lewis to be the first stage of an advanced, eight-stage, core-compressor having a high pressure ratio (about 20:1), good efficiency and sufficient stall margin. The rotor was tested without the presence of a stator (or any of the following seven stages) at the NASA Lewis single-stage, high-speed, core-compressor test-rig. The measurements were obtained with a single circumferential, high-response, total pressure and total temperature probe. The measurements were taken immediately after the machine was ’tripped’ into unstable operation by slowly closing the downstream throttle valve. Measurements were obtained at several different span-wise locations and at two different operating speeds. The rotor was shown to exhibit many of the same characteristics typical of low-speed axial-flow machines. Both rotating stall cells and surge cycles were present during unstable operation. The surge cycles present immediately after the inception of unstable operation involved a large-extent single-cell type rotating stall that was present only during the first half of the surge cycles (the second half of these surge cycles involved operation in the stable operating region). However, as the unstable operation progressed (approximately three to five surge cycles later), surge cycles were present that contained a multiple-cell smaller-extent type rotating stall that existed throughout the entire surge cycle with no partial operation in the stable operating region. Thus, compressor system recovery from single-cell large-extent rotating stall (partial operation in stable operating range during the surge cycle) is more probable than recovery from multiple-cell small-extent rotating stall (no operation in stable operating range during the surge cycle). Rotor wheel speed was shown to be an important variable in influencing the form of unstable operation. Surge and rotating stall were shown to be coupled during the unstable operation. Furthermore, the surge/stall coupling was shown to be related more by pressure interactions than by temperature or efficiency interactions. Also, this high hub-tip ratio transonic rotor was shown to exhibit instantaneous stalling across the entire blade span (typical of low-speed, high hub-tip ratio machines). Attempts to fit the data to Greitzer’s one-dimensional lumped-parameter model are presented and the reasons for poor agreement are discussed. / Master of Science

The rigid-body rotational vibration of a resiliently mounted air compressor about an axis parallel to the axis of the rotor is investigated. An analysis of the motion of the compressor base is conducted using empirical acceleration data. The effect on roll vibration of changing various compressor design parameters is studied using a computer simulation program, PABEWE. This digital simulation incorporating slider-crank linkage analysis employs the strict equations of motion. Control theory is used to control the roll vibration. The control theory is applied to simplified equations of motion and incorporates various feedbacks. Recommendations are offered for the reduction of roll vibration levels. / Master of Science

The study involves the development of a finite element model of a hermetic reciprocating compressor for noise prediction applications. Inherent difficulties in developing the finite element model of a complicated structure are discussed and appropriate modeling strategies are evolved. The development of the complete compressor finite element model is carried out in two stages - modeling of the compressor housing and the assembly of components into the compressor assembly. The compressor housing is isolated for detailed modeling. Geometry complexity, secondary masses, spring mounts, lap-joint and manufacturing variations pose challenges in developing a reliable model. Frequent comparisons are made with experimental mobility scans to obtain insights into the actual behavior of the modeled structure. When possible, weaknesses are located in the finite element model and corrected. After sufficient revisions, 23 natural frequencies (excluding the rigid body modes) are found for the compressor housing in the low frequency range (below 2000 Hz) of analysis. Forced response calculations are also used to correlate the analytical model and test data, with a maximum of 5% disagreement for the 14 natural frequencies that could be correlated. Compressor assembly modeling involves detailed solid modeling of internal components for inertia properties, developing reduced-degrees-of-freedom models of mounting springs and modeling of the shockloop. The dynamic behavior of the crankcase is investigated separate from the compressor assembly model. Finally, the components are assembled and the compressor assembly is solved for its natural frequencies by the component mode synthesis method. Eighty seven natural frequencies below 2000 Hz (excluding the rigid body modes) are found for the compressor assembly model. This model can be used to predict velocity responses on the surface of the housing, with the internally generated forces as excitations. Velocity response data are directly used in sound prediction. / Master of Science