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 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 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 Master s Theses Directories written by and published by . This book was released on 2004 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Education, arts and social sciences, natural and technical sciences in the United States and Canada".
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 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 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 A Comparison of Rotordynamic coefficient Predictions for Annular Honeycomb Gas Seals Using Different Friction factor Models written by Rohan Joseph D'Sousa and published by . This book was released on 2000 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Rotordynamic Analysis of Annular Honeycomb stator Turbulent Gas Seals Using a New Friction factor Model Based on Flat Plate Tests written by Tae Woong Ha and published by . This book was released on 1992 with total page 348 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 Experimental Rotordynamic Coefficient Results for Honeycomb Seals written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Test results (leakage and rotordynamic coefficients) are presented for seven honeycomb-stator smooth-rotor seals. Tests were carried out with air at rotor speeds up to 16,000 cpm and supply pressures up to 8.2 bars. Test results for the seven seals are compared, and the most stable configuration is identified based on the whirl frequency ratio. Results from tests of a smooth-rotor/smooth-stator seal, a teeth-on-stator labyrinth seal, and the most stable honeycomb seal are compared. Elrod, David A. and Childs, Dara W. Unspecified Center AERODYNAMIC COEFFICIENTS; HONEYCOMB STRUCTURES; LABYRINTH SEALS; LEAKAGE; ROTOR AERODYNAMICS; STATORS; COMPARISON; TABLES (DATA); TEST EQUIPMENT...
Download or read book Analysis of Two phase Flow in Damper Seals for Cryogenic Turbopumps written by Grigory L. Arauz and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Cryogenic damper seals operating close to the liquid-vapor region (near the critical point or slightly sub-cooled) are likely to present two-phase flow conditions. Under single phase flow conditions the mechanical energy conveyed to the fluid increases its temperature and causes a phase change when the fluid temperature reaches the saturation value. A bulk-flow analysis for the prediction of the dynamic force response of damper seals operating under two-phase flow conditions is presented as: all-liquid, liquid-vapor, and all-vapor, i.e. a "continuous vaporization" model. The two-phase region is considered as a homogeneous saturated mixture in thermodynamic equilibrium. The flow in each region is described by continuity, momentum and energy transport equations. The interdependency of fluid temperature and pressure in the two-phase region (saturated mixture) does not allow the use of an energy equation in terms of fluid temperature. Instead the energy transport is expressed in terms of fluid enthalpy. Temperature in the single-phase regions, or mixture composition in the two-phase region are determined based on the fluid enthalpy. The flow is also regarded as adiabatic since the large axial velocities typical of the seal application determine small levels of heat conduction to the walls as compared to the heat carried by fluid advection. Static and dynamic force characteristics for the seal are obtained from a perturbation analysis of the governing equations. The solution expressed in terms of zeroth and first order fields provide the static (leakage, torque, velocity, pressure, temperature and mixture composition fields) and dynamic (rotordynamic force coefficients) seal parameters. Theoretical predictions show good agreement with experimental leakage and pressure profiles available from a Nitrogen at cryogenic temperatures. Force coefficients predictions for two-phase flow conditions show significant fluid compressibility effects, particularly for mixtures with low mass content of vapor. Under these conditions, an increase on direct stiffness and reduction of whirl frequency ratio are shown to occur. Prediction of such important effects will motivate experimental studies as well as a more judicious selection of the operation conditions for the seals used in cryogenic turbomachinery."--Page ii.
Download or read book Testing of Turbulent Seals for Rotordynamic Coefficients written by Dara W. Childs and published by . This book was released on 1982 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: A facility has been developed for dynamic testing of straight and convergent-tapered seals with the capability of measuring the radial and tangential force components which result from a circular centered orbit. The test apparatus causes the seal journal to execute small-eccentricity centered circular orbits within its clearance circle. Dynamic measurements are made and recorded of the seal-displacement-vector components, and of the pressure field. The pressure field is integrated to yield seal tangential and radial reaction-force components. Representative test data are provided and discussed for straight seals.
Download or read book Proceedings of the National Aerospace Propulsion Conference written by Gullapalli Sivaramakrishna and published by Springer Nature. This book was released on 2022-07-23 with total page 633 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the select proceedings of the 3rd National Aerospace Propulsion Conference (NAPC 2020). It discusses the recent trends in the area of aerospace propulsion technologies covering both air-breathing and non-air-breathing propulsion. The topics covered include state-of-the-art design, analysis and developmental testing of gas turbine engine modules and sub-systems like compressor, combustor, turbine and alternator; advances in spray injection and atomization; aspects of combustion pertinent to all types of propulsion systems and nuances of space, missile and alternative propulsion systems. The book will be a valuable reference for beginners, researchers and professionals interested in aerospace propulsion and allied fields.
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:
Download or read book An Annular Gas Seal Analysis Using Empirical Entrance and Exit Region Friction Factors written by David Alan Elrod and published by . This book was released on 1989 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wall shear stress results from stationary-rotor flow tests of five annular gas seals are used to develop entrance and exit region friction factor models. The friction factor models are used in a bulk-flow seal analysis which predicts leakage and rotor-dynamic coefficients. The predictions of the analysis are compared to experimental results and to the predictions of Nelson's analysis (1985). The comparisons are for smooth-rotor seals with smooth and honeycomb-stators. The present analysis predicts the destabilizing cross-coupled stiffness of a seal better than Nelson's analysis. Both analyses predict direct damping well and direct stiffness poorly.
