Download or read book Measurement Versus Predictions of Rotordynamic Coefficients and Leakage Rates for a Hole pattern Gas Seal with Negative Preswirl written by Philip David Brown and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results of high supply (up to 84 bar) pressure testing of hole-pattern annular gas seals performed at the Texas A & M Turbomachinery Laboratory in College Station, TX. The test variables were chosen to determine the influence of pressure ratio, rotor speed, and negative preswirl on seal performance. Preswirl signifies the circumferential fluid flow entering a seal, and negative preswirl indicates a fluid swirl in the direction opposite of rotor rotation. Changes in pressure ratio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the mid-range of excitation frequencies. Pressure ratio showed some influence on direct and cross-coupled damping at low excitation frequencies. Rotor speed significantly affected both cross-coupled stiffness and cross-coupled damping. As rotor speed increased, the magnitude of cross-coupled rotordynamic coefficients increased due to the positive fluid swirl induced by rotor rotation. For the low rotor speed, negative inlet preswirl was able to overpower the positive rotor induced fluid rotation, producing a negative cross-coupled stiffness. This outcome showed that, for hole-pattern seals, positive fluid swirl does indeed produce positive cross-coupled stiffness coefficients and negative fluid swirl produces negative cross-coupled stiffness coefficients. The addition of negative preswirl greatly reduced cross-coupled rotordynamic coefficients, while direct rotordynamic terms were unaffected. Cross-over frequency signifies the excitation frequency where effective damping transitions from a negative value to a positive value with increasing excitation frequency. Peak effective damping was increased by 50% and cross-over frequency reduced by 50% for high-negative preswirl versus zero preswirl results. This led to the conclusion that a reverse swirl could greatly enhance the stability of hole-pattern balance piston seals. A two-control-volume model that uses the ideal gas law at constant temperature (ISOT) was used to predict rotordynamic coefficients and leakage. This model predicted direct rotordynamic coefficients well, but greatly under predicted cross-coupled rotordynamic coefficients especially at high negative preswirls. The model predicted seal leakage well at low pressure ratios, but showed increasing error as the pressure ratio was increased. These results showed that the prediction model could not adequately estimate cross-coupled rotordynamic coefficients for a hole-pattern seal with negative inlet preswirl and requires modification to do so.

Download or read book Measurements Versus Predictions for Rotordynamic Coefficients and Leakage Rates for a Novel Hole pattern Gas Seal written by Brent Alan Seifert and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented for measured and predicted rotordynamic coefficients and leakage for hole-pattern seals with a hole depth that varies axially along the seal. Testing was done to discover how pressure ratio, inlet preswirl, and rotor speed affect the seals' rotordynamic characteristics and leakage. The results were compared to a constant hole depth hole-pattern seal. Experimental results show that the seals' rotordynamic characteristics are not strongly influenced by pressure ratio. There were three preswirl conditions tested, each separated by a 6.9 bar (100psi) difference in inlet pressure. Therefore, normalized preswirl results were compared. The normalized results indicate that introducing inlet fluid preswirl affects the cross coupled stiffness and effective damping coefficients. Inlet preswirl increases the magnitude of cross-coupled stiffness. Effective damping decreases with inlet preswirl, as well as the effective damping cross-over frequency increasing. These results indicate that swirl brakes would be of great value. Rotor speed had a significant effect on the cross-coupled coefficients; both increased with speed. Experimental results were compared to results for a constant hole depth hole pattern seal. The variable hole-depth seal has higher direct damping. The cross-coupled stiffness and cross-coupled damping coefficients were very similar. The direct stiffness was always lower at lower frequencies and higher at higher frequencies for the variable hole depth hole-pattern seal. This was also the case for effective stiffness. The effective damping of the variable hole-depth seal was not only larger than for the constant hole depth seal, it also had a drastically lower cross-over frequency. The difference in cross-over frequency was 40 percent on average. Experimental results for rotordynamic characteristics and leakage were compared to theoretical predictions by ISOTSEAL 2, a modified version of ISOTSEAL. Both cross-coupled stiffness and damping are reasonably predicted. Direct damping is always under-predicted. ISOTSEAL 2 does a poor job of predicting direct stiffness. Direct stiffness is over-predicted at lower frequencies and under-predicted at higherfrequencies. This is also the case for effective stiffness. ISOTSEAL 2 under-predicts the direct damping, but does an excellent job of predicting the direct damping crossover frequency. Seal leakage is well predicted by ISOTSEAL 2.

Download or read book Test Versus Predictions for Rotordynamic Coefficients and Leakage Rates of Hole pattern Gas Seals at Two Clearances in Choked and Unchoked Conditions written by Jonathan Leigh Wade and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis documents the results of high pressure testing of hole-pattern annular gas seals conducted at the Texas A & M University's Turbomachinery Laboratory. The testing conditions were aimed at determining the test seals sensitivity to pressure ratio, inlet fluid preswirl, rotor speed, and rotor to seal clearance. The rotordynamic coefficients showed only small changes resulting from the different pressure ratios tested. Only the damping terms at the lower frequencies showed some influence. One other notable result from the testing of different pressure ratios is that the seals were tested in a choked flow condition, and there was not a significant change in the seal behavior when the seals transitioned to the choked condition. The inlet fluid preswirl only had a notable effect on the cross-coupled stiffness in the larger clearance tests. These results lead to the conclusion that a swirl brake could have some rotordynamic value, but only if the seals have sufficiently large clearance. Conversely this also means that if hole-pattern seals are being implemented with a small clearance, then a swirl brake would not be an effective way to improve the rotordynamic stability of the system. The only significant effect that the rotor speeds had on the rotordynamic coefficients were that the cross-coupled coefficients increased as the rotor speed increased. This is the expected result because as the rotor speed increases there is a greater shear force on the gas as it passes through the seal resulting in more fluid circumferential velocity, which results in stronger cross-coupled coefficients. The changes in clearance resulted in drastic changes in the magnitude of the coefficients. The smaller clearance yielded much higher coefficients than the larger clearance. All of the rotordynamic coefficients were predicted well by ISOTSEAL. The code was found to do a good job predicting the seal leakage as well. This gives more credence to the coefficients and leakage that ISOTSEAL predicts.

Download or read book Journal of Engineering for Gas Turbines and Power written by and published by . This book was released on 2008 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measured Results for a New Hole pattern Annular Gas Seal Incorporating Larger Diameter Holes Comparisons to Results for a Traditional Hole pattern Seal and Predictions written by Michael Lloyd Vannarsdall and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: To reduce manufacturing cost and time, a hole-pattern seal incorporating holes of larger diameter (12.19 mm (0.48 inches)) has been proposed. Experimental leakage and rotordynamic coefficients for this new seal design are presented. This experimental data was compared to theoretical results generated by ISOTSEAL a program developed by Kleynhans and Childs. Finally, the performance of this new hole-pattern seal was compared to a hole-pattern seal tested by Wade. The experiments are configured to investigate the influence of changes in pressure ratio, preswirl, rotor speed, and clearances on seal characteristics. Due to stator stability issues, the peak inlet pressures had to be varied to allow for testing. Consequently, to study the effect of inlet preswirl and clearance, data were non-dimensionalized or normalized. Cross-coupled coefficients were relatively frequency-independent while direct coefficients were functions of excitation frequency. For all test cases, the seal developed negative direct stiffness at low frequencies. Tests showed that pressure ratio had minimal effect on rotordynamic coefficients. Non-dimensional cross-coupled stiffness increased with increasing preswirl causing the seal to become less stable with increasing preswirl. Cross coupled stiffness increased with increasing running speed. Two clearances: 0.1 mm (4 mils) and 0.2 mm (8 mils) were tested. The results demonstrated that non-dimensionalized stiffness is greater for the smaller clearance. The larger clearance develops larger normalized direct damping values, and has enhanced stability. Rotordynamic predictions are poor for cross-coupled coefficients. Generally, ISOTSEAL over-predicts direct stiffness and under-predicts direct damping. Negative stiffness was not predicted by ISOTSEAL. Predictions do improve for the smaller clearance. ISOTSEAL does a good job of predicting non-dimensional leakage. Non-dimensionalized direct and effective stiffness were greater for the "old" hole-pattern seal tested by Wade. However, the "new" seal generally developed greater normalized direct damping and exhibited a lower cross-over frequency. Non-dimensionalized leakage was greater for the seal tested here. Production of this new seal proved to be more difficult than originally thought. The price of the new seal cost approximately the same as an original hole-pattern seal.

Download or read book A Comparison of Experimental Rotordynamic Coefficients and Leakage Characteristics Between Hole pattern Gas Damper Seals and a Honeycomb Seal written by Zeping Yu and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Orlando, FL, Jun 2-Jun 5, 1997.

Download or read book Test Versus Predictions for Rotordynamic and Leakage Characteristics of a Convergent tapered Honeycomb stator smooth rotor Annular Gas Seal written by Daniel Eduardo Van Der Velde Alvarez and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents the results for measured and predicted rotordynamic coefficients and leakage for a convergent-tapered honeycomb seal (CTHC). The test seals had a diameter of 114.968 mm (4.5263 in) at the entrance, and a diameter of 114.709 mm (4.5161 in) at the exit. The honeycomb cell depth was 3.175 mm (0.125 in), and the cell width was 0.79 mm (0.0311 in). Measurements are reported with air as the test fluid at three different speeds: 10,200, 15,200, and 20,200 rpm; with a supply pressure of 69 bar (1,000 psi), with exit-to-inlet pressure ratios from 20% to 50%, and using two rotors that are 114.3 mm (4.500 in) and 114.5 mm (4.508 in) respectively; this enables the same seals to be tested under two different conditions. The q factor, which is just a simple way to quantify taper is defined as the taperangle seal parameter and is calculated using the inlet and exit radial clearance. Two taper-angles parameters were calculated; q = 0.24 for the 114.3 mm (4.500 in) rotor, and q = 0.386 for the 114.5 mm (4.508 in) rotor. The q = 0.24 condition was compared to a constant clearance honeycomb seal (CCHC q = 0) because both sets of data were taken with the same rotor diameter. The direct stiffness, effective stiffness, and direct damping coefficients were larger for q = 0.24. The CTHC q = 0.24 eliminates the direct negative static stiffness obtained with CCHC (q = 0). The cross-coupled stiffness and damping also were larger for q = 0.24, especially at low frequencies. Effective damping is one of the best indicators in determining the stability of a roughened stator annular gas seal. The frequency at which it changes sign is called the cross-over frequency. In applications, this frequency needs to be lower than the rotorsystem0́9s first natural frequency. Otherwise, the seal will be highly destabilizing instead of highly stabilizing. The magnitude of effective damping and the cross-over frequency also increases with q for all frequencies. Constant clearance honeycomb seals have less leakage than convergenttapered honeycomb seals. CTHC (q = 0.24), has approximately 20 percent more leakage than CCHC (q = 0). The experimental results for rotordynamic characteristics and leakage were compared to theoretical predictions by the two-control-volume developed by Kleynhans and Childs. All rotordynamic coefficients were reasonably predicted for all cases. The model does a better job predicting the cross-coupled stiffness and damping coefficients rather than the direct stiffness and damping coefficients. Also, the two-control-volume model predicts the dynamic characteristics of CCHC (q = 0) better, and does not predict well the effective stiffness and damping for CTHC q = 0.386.

Download or read book Analysis for Leakage and Rotordynamic Coefficients of Surface roughened Tapered Annular Gas Seals written by C. C. Nelson and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Comparison of Experimental and Theoretical Results for Leakage Pressure Gradient and Rotordynamic Coefficients for Tapered Annular Gas Seals written by David Alan Elrod and published by . This book was released on 1986 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study of the Effects of Inlet Preswirl on the Dynamic Coefficients of a Straight bore Honeycomb Gas Damper Seal written by Tony Brandon Sprowl and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In high-pressure centrifugal compressors, honeycomb seals are often used as replacements for labyrinth seals to enhance dynamic stability. A concern exists with the loss of this enhanced stability if the honeycomb cavities become clogged with debris over time. So, as a first objective, static and dynamic tests were conducted on a constant-clearance honeycomb and a constant-clearance smooth-bore seal under three inlet preswirl conditions to determine the effects of inlet preswirl. The resulting leakage flowrate and dynamic parameters, effective stiffness and damping of the seal, were measured for each seal and then compared, with the smooth-bore seal representing the honeycomb seal with completely clogged cells. The second objective was to evaluate a two-control volume theory by Kleynhans and Childs with the measured data under the influence of preswirl. Both seals have a 114.7mm bore with a radial clearance of 0.2mm from the test rotor. The honeycomb seal has a cell width of 0.79mm and cell depth of 3.2mm. The target test matrix for each preswirl setting consisted of three exit-to-inlet pressure ratios of 15%, 35%, and 50%, and three rotor speeds out to 20,200 rpm. The target inlet air pressure was 70 bar-a. Experimental results show that, for a clean honeycomb seal, preswirl has little effect on effective stiffness, Keff*, and decreases effective damping, Ceff*, by about 20% at the high inlet preswirl ratio (%7E0.6). However, comparing smooth and honeycomb seal results at higher inlet preswirl shows a potential reduction in Keff* by up to 68%, and a large drop and shift in positive Ceff* values, which could cause an instability in the lower frequency range. Measured leakage shows a potential increase of about 80%, regardless of test conditions. A swirl brake at the seal entrance would fix this loss in stability by significantly reducing inlet preswirl. The two-control-volume theory model by Kleynhans and Childs seems to follow the frequency-dependent experimental data well for the honeycomb seal. Theory predicts conservatively (under-predicts) for stability parameters such as k* and Ceff* and for leakage. Predictions for K and Keff may possibly be improved with better measured friction factor coefficients for each seal.

Download or read book Turbomachinery Rotordynamics written by Dara Childs and published by John Wiley & Sons. This book was released on 1993-04-16 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: Imparts the theory and analysis regarding the dynamics of rotating machinery in order to design such rotating devices as turbines, jet engines, pumps and power-transmission shafts. Takes into account the forces acting upon machine structures, bearings and related components. Provides numerical techniques for analyzing and understanding rotor systems with examples of actual designs. Features an excellent treatment of numerical methods available to obtain computer solutions for authentic design problems.

Download or read book A Comparison of Experimental and Theoretical Results for Leakage Pressure Distribution and Rotordynamic Coefficients for Annular Gas Seals written by Colby Oran Nicks and published by . This book was released on 1984 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Leakage Predictions for Rayleigh step Helium purge Seals written by and published by . This book was released on 1988 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Centrifugal Pumps written by Johann Friedrich Gülich and published by Springer. This book was released on 2014-10-24 with total page 1146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gives an unparalleled, up-to-date, in-depth treatment of all kinds of flow phenomena encountered in centrifugal pumps including the complex interactions of fluid flow with vibrations and wear of materials. The scope includes all aspects of hydraulic design, 3D-flow phenomena and partload operation, cavitation, numerical flow calculations, hydraulic forces, pressure pulsations, noise, pump vibrations (notably bearing housing vibration diagnostics and remedies), pipe vibrations, pump characteristics and pump operation, design of intake structures, the effects of highly viscous flows, pumping of gas-liquid mixtures, hydraulic transport of solids, fatigue damage to impellers or diffusers, material selection under the aspects of fatigue, corrosion, erosion-corrosion or hydro-abrasive wear, pump selection, and hydraulic quality criteria. As a novelty, the 3rd ed. brings a fully analytical design method for radial impellers, which eliminates the arbitrary choices inherent to former design procedures. The discussions of vibrations, noise, unsteady flow phenomena, stability, hydraulic excitation forces and cavitation have been significantly enhanced. To ease the use of the information, the methods and procedures for the various calculations and failure diagnostics discussed in the text are gathered in about 150 pages of tables which may be considered as almost unique in the open literature. The text focuses on practical application in the industry and is free of mathematical or theoretical ballast. In order to find viable solutions in practice, the physical mechanisms involved should be thoroughly understood. The book is focused on fostering this understanding which will benefit the pump engineer in industry as well as academia and students.

Download or read book Rotordynamics of Turbomachinery written by John M. Vance and published by John Wiley & Sons. This book was released on 1991-01-16 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describes the rotordynamic considerations that are important to the successful design or troubleshooting of a turbomachine. Shows how bearing design, fluid seals, and rotor geometry affect rotordynamic behavior (vibration, shaft whirling, bearing loads, and critical speeds), and describes two successful computational methods for rotordynamic analysis in terms that can be understood by practicing engineers. Gives descriptive accounts of the state of the art in several areas of the field and presents important mathematical or computational concepts, describing equations and formulas in physical terms for better understanding. Also offers tips for troubleshooting unstable machines and provides practical interpretations of vibration measurements.

Download or read book Hydrodynamics of Pumps written by Christopher E. Brennen and published by Cambridge University Press. This book was released on 2011-03-28 with total page 287 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrodynamics of Pumps is a reference for pump experts and a textbook for advanced students. It examines the fluid dynamics of liquid turbomachines, particularly pumps, focusing on special problems and design issues associated with the flow of liquid through a rotating machine. There are two characteristics of a liquid that lead to problems and cause a significantly different set of concerns than those in gas turbines. These are the potential for cavitation and the high density of liquids, which enhances the possibility of damaging, unsteady flows and forces. The book begins with an introduction to the subject, including cavitation, unsteady flows and turbomachinery, basic pump design and performance principles. Chapter topics include flow features, cavitation parameters and inception, bubble dynamics, cavitation effects on pump performance, and unsteady flows and vibration in pumps - discussed in the three final chapters. The book is richly illustrated and includes many practical examples.

Download or read book A Comparison of Experimental Rotordynamic Coefficient and Static Characteristic Results for Hole pattern Damper Seals and a Honeycomb Seal written by Zeping Yu and published by . This book was released on 1996 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: