Download or read book Experimental Dynamic Forced Performance of a Centrally Grooved End Sealed Squeeze Film Damper written by Lady Paola Mahecha Mojica and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze film dampers (SFDs) provide viscous damping to attenuate excessive vibrations and enhance system stability in turbomachinery. SFDs are of special importance in aircraft engines which use rolling element support bearings that, by themselves, do not provide enough damping to ensure safe operation. A modular test rig capable of simulating actual operating conditions in aircraft jet engines is used to test two centrally grooved, end sealed, SFDs. Both SFDs have diameter D and nominal radial clearance c and consist of two parallel squeeze film lands separated by a deep circumferential groove of length LG and depth dG. A short length damper with film land lengths L and a long damper with land lengths 2L are tested. Piston rings seal the damper lands. An ISO VG2 lubricant is supplied to the SFD via three radial holes that discharge lubricant into the central groove. The lubricant passes through the damper lands and across the piston ring seals to finally exit the damper at ambient pressure. Circular orbit tests of amplitude ~0.5c and for static eccentricities varying from 0 to ~0.36c are conducted on the two sealed dampers. The instrumental variable filter method (IVFM) serves to identify the SFD dynamic force coefficients. The parameter identification range is 50Hz to 210Hz for the short damper and 110Hz to 250Hz for the long damper. Large amplitude dynamic pressures measured in the central groove demonstrate that the central groove does not divide the damper in two separate film lands, but the lubricant in the groove interacts with the squeeze film lands, hence contributing significantly to the SFD forced response. Dynamic pressures in the film lands and in the central groove reveal that both dampers operate free of air ingestion or cavitation for the tested static eccentricities and amplitudes of motion. Comparisons to test results for the same SFD configurations but with open ends demonstrate the effectiveness of the end seals on increasing the direct damping coefficients. For the sealed ends short length damper, the added mass coefficients are ~2 times larger and the damping coefficients are ~3.8 times larger than the respective coefficients of the open ends long damper. For the sealed ends long damper, the damping coefficients are ~2.8 times, and the added mass coefficients are ~3.1 times larger than coefficients from the open ends configuration. The identified SFD direct stiffness coefficients are nearly zero except at the maximum static eccentricity for the long damper. Predictions from a novel computational model that include the effects of the central groove, the lubricant feed holes and the end seals are in excellent agreement with results from the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the test results, while the added mass coefficients are under predicted by ~25 percent. Experimental results from the two sealed SFD configurations lead to a better understanding of the effects of end seals as well as central feed groves on the SFD forced performance. The results presented in this thesis will help improve the effectiveness of SFDs aircraft jet engines.

Download or read book Performance of a Short Open End Squeeze Film Damper With Feed Holes written by Gary Daniel Bradley and published by . This book was released on 2013 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: With increasing rotor flexibility and shaft speeds, turbomachinery undergoes large dynamic loads and displacements. Squeeze film dampers (SFDs) are a type of fluid film bearing used in rotating machinery to attenuate rotor vibration, provide mechanical isolation, and/or to tune the placement of system critical speeds. Industry has a keen interest in designing SFDs that are small, lightweight, and mechanically simple. To achieve this, one must have a full understanding of how various design features affect the SFD forced performance. This thesis presents a comprehensive analysis, experimental and theoretical, of a short (L=25.4 mm) open ends SFD design incorporating three lubricant feed holes (without a circumferential feed groove). The damper radial clearance (c=127 [mu]m), L/D ratio (0.2), and lubricant (ISO VG2) have similar dimensions and properties as in actual SFDs for aircraft engine applications. The work presents the identification of experimental force coefficients (K, C, M) from a 2-DOF system model for circular and elliptical orbit tests over the frequency range [omega]=10-250Hz. The whirl amplitudes range from r=0.05c-0.6c, while the static eccentricity ranges from eS=0-0.5c. Analysis of the measured film land pressures evidence that the deep end grooves (provisions for installation of end seals) contribute to the generation of dynamic pressures in an almost purely inertial fashion. Film land dynamic pressures show both viscous and inertial effects. Experimental pressure traces show the occurrence of significant air ingestion for orbits with amplitudes r>0.4c, and lubricant vapor cavitation when pressures drop to the lubricant saturation pressure (PSAT~0 bar). Identified force coefficients show the damper configuration offers direct damping coefficients that are more sensitive to increases in static eccentricity (eS) than to increases in amplitude of whirl (r). On the other hand, SFD inertia coefficients are more sensitive to increases in the amplitude of whirl than to increases in static eccentricity. For small amplitude motions, the added or virtual mass of the damper is as large as 27% of the bearing cartridge mass (MBC=15.15 kg). The identified force coefficients are shown to be insensitive to the orbit type (circular or elliptical) and the number of open feed holes (3, 2, or 1). Comparisons of damping coefficients between a damper employing a circumferential feed groove1 and the current damper employing feed holes (no groove), show that both dampers offer similar damping coefficients, irrespective of the orbit amplitude or static eccentricity. On the other hand, the grooved damper shows much larger inertia force coefficients, at least ~60% more. Predictions from a physics based model agree well with the experimental damping coefficients, however for large orbit motion, over predict inertia coefficients due to the model neglecting convective inertia effects. Credence is given to the validity of the linearized force coefficients by comparing the actual dissipated energy to the estimated dissipated energy derived from the identified force coefficients. The percent difference is below 25% for all test conditions, and in fact is shown to be less than 5% for certain combinations of orbit amplitude (r), static eccentricity (eS), and whirl frequency ([omega]). The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151179

Download or read book Performance of an Open Ends Squeeze Film Damper Operating with Large Amplitude Orbital Motions written by Sung Hwa Jeung and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze Film Dampers (SFDs) aid to suppress rotor vibrations and enhance the stability of high-speed rotor-bearing systems. A SFD is a simple oil lubricated film between a stationary housing and a precessing (whirling) journal. Aircraft engines use SFDs as the only means to provide damping to otherwise rigid ball bearing supports. This thesis presents experimental results for the dynamic forced performance of a test open ends SFD operating with large amplitude whirl motions, centered and off centered within the bearing clearance. The test rig comprises of an elastically supported bearing with a damper section having two parallel film lands separated by a feed groove. A film land is 25.4 mm long, with diameter 127 mm and nominal radial clearance c=0.251 mm. Two orthogonally placed shakers apply dynamic loads on the bearing to induce circular orbit motions at prescribed whirl frequencies. A static loader, 45° away from each shaker, pulls the bearing to a static eccentric position. Circular orbit tests were performed (10-100 Hz frequency range) for eight increasing orbit amplitudes (r=0.08c to ~0.71c) and under four static eccentricities (e[subscript s]=0.0c to ~0.76c). An identification method estimates the test damper force coefficients from transfer functions in the frequency domain. The analysis shows that the SFD damping force coefficients increase with the static eccentricity (e[subscript s]) increase. On the other hand, the damper inertia coefficients decrease as the orbit amplitude (r) becomes large and also increase modestly with the static eccentricity (e[subscript s]). Predictions from a physical model show good agreement with the test dynamic force coefficients. The accuracy of the linearized SFD force coefficients (K, C, M)[subscript SFD] is evaluated from comparing the differences in mechanical work performed by actual and linear SFD reaction forces. The difference in mechanical work (E[subscript diff]) increases with increasing static eccentricity (e[subscript s]) and orbit amplitude (r). However, for most test conditions (r/c≤0.4,e[subscript s]/c≤0.25), E[subscript diff] is less than ~5%, thus showing the linearized SFD force coefficients represent well the forced response of the actual test SFD system. The test and predicted force coefficients as well as the analysis of the pressure fields contribute to a better understanding of the kinetics of SFDs operating with moderate tolarge amplitude size whirl motions, centered and off-centered. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151648

Download or read book Proceedings of the 9th IFToMM International Conference on Rotor Dynamics written by Paolo Pennacchi and published by Springer. This book was released on 2015-05-26 with total page 2214 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of the 9th IFToMM International Conference on Rotor Dynamics. This conference is a premier global event that brings together specialists from the university and industry sectors worldwide in order to promote the exchange of knowledge, ideas, and information on the latest developments and applied technologies in the dynamics of rotating machinery. The coverage is wide ranging, including, for example, new ideas and trends in various aspects of bearing technologies, issues in the analysis of blade dynamic behavior, condition monitoring of different rotating machines, vibration control, electromechanical and fluid-structure interactions in rotating machinery, rotor dynamics of micro, nano and cryogenic machines, and applications of rotor dynamics in transportation engineering. Since its inception 32 years ago, the IFToMM International Conference on Rotor Dynamics has become an irreplaceable point of reference for those working in the field and this book reflects the high quality and diversity of content that the conference continues to guarantee.

Download or read book Identification of Force Coefficients in Two Squeeze Film Dampers with a Central Groove written by Sanjeev Seshagiri and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze Film Dampers (SFD) provide viscous damping in rotor bearing systems to reduce lateral vibration amplitudes and to isolate mechanical components. Aircraft engine shafts, often supported on roller bearings, operate at high rotational speeds and are susceptible to large amplitude shaft whirl due to rotor imbalance. SFDs aid to reduce such large whirl amplitudes while also eliminating rotor instabilities. The current work quantifies experimentally the forced performance of two parallel squeeze SFDs separated by a central groove. Force coefficients are identified in a specialized SFD test rig constructed to undergo similar operating and loading conditions as in jet engines. Of interest is to quantify the effect of a central feed groove on the forced performance of SFDs and to validate predictions from a computational tool. The test rig comprises of an elastically supported bearing structure and one of two journals. Tests are conducted on two open ends SFDs, both with diameter D and nominal radial clearance c; each damper with two parallel film land lengths L= 1/5 D and 2L, separated by a feed groove of width L and depth 3/4 L. ISO VG 2 grade lubricant oil flows into the central groove via 3 orifices, 120 degrees apart, and then through the film lands to finally exit to ambient. In operation, a static loader pulls the bearing to various static off center positions with respect to the stationary journal, and electromagnetic shakers (2,200 N) excite the test system with single frequency loads over a frequency range to generate rectilinear, circular and elliptical orbits with specified motion amplitudes. A frequency domain method identifies the SFD mechanical parameters, viz., stiffness, damping, and added mass coefficients. The long damper generates 7 times more direct damping and 2 times more added mass compared to the short length damper. The damping coefficients are sensitive to the static eccentricity (up to 50 percent c) while showing lesser dependency on the amplitude of whirl motion (up to 20 percent c). On the other hand, added mass coefficients are nearly constant with static eccentricity and decrease with higher amplitudes of motion. The magnitudes of identified cross-coupled coefficients are insignificant for all imposed operating conditions for either damper. Large dynamic pressures recorded in the central groove demonstrate the groove does not isolate the film lands by merely acting as a source of lubricant, but contributes to the generation of large added mass coefficients. The recorded dynamic pressures in the film lands and central groove do not evidence lubricant vapor or gas cavitation for the tested static eccentricities and amplitudes of motion. The direct damping coefficients for both dampers are independent of excitation frequency over the frequency range of the tests. Predictions derived from a novel SFD computational tool that includes flow interactions in the central groove and oil supply orifices agree well with the experimental force coefficients for both dampers. The current work advances the state of the art in SFDs for jet engines.

Download or read book An Investigation Into Squeeze film Dampers written by and published by . This book was released on 1981 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of an Aero engine Squeeze film Damper written by Muzaffer Doğan and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Study of Hydrodynamic Force Coefficients for a Grooved Squeeze Film Damper written by Jia Xin Zhang and published by . This book was released on 1994 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Squeeze Film Damper Technology written by J. Walton and published by . This book was released on 1986 with total page 145 pages. Available in PDF, EPUB and Kindle. Book excerpt: A test rig was constructed and proper instrumentation provided for measuring the performance of squeeze film dampers. The tests provided both conceptual understanding of the mechanism of damper operation by providing data on the viscous and inertia components of the fluid film, and on the modalities of oil delivery via the feeding holes and grooves, for both sealed and unsealed dampers. Quantitative data were then provided for the entire gamut of variables attending the design of squeeze film dampers and these were then compared with theoretical predictions. A particularly important part of the test was the visual documentation via both still and motion pictures of cavitation which is still not a fully understood phenomenon under dynamic conditions. Failure tests were conducted to simulate damper response to extreme loadings such as resulting form loss of a turbine blade. While the correlation with theory was shown to be generally valid up to the upper ranges of speeds, the quality of correlation was much affected by the encountered variation of boundary conditions in the feed grooves. The latter thus emerges as an aspect of squeeze film damper mechanics which needs further study.

Download or read book Proceedings of the 6th National Symposium on Rotor Dynamics written by J. S. Rao and published by Springer Nature. This book was released on 2020-10-13 with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents select papers presented during the 6th National Symposium on Rotor Dynamics, held at CSIR-NAL, Bangalore, and focuses on the latest trends in rotor dynamics and various challenges encountered in the design of rotating machinery. The book is of interest to researchers from mechanical, aerospace, tribology and power industries, engineering service providers and academics.

Download or read book Numerical Simulation of Squeeze Film Dampers and Study of the Effect of Central Groove on the Dynamic Pressure Distribution written by Praneetha Boppa and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze film dampers are used in the high speed turbo machinery industry and aerospace industries as a means to reduce vibration amplitude, to provide damping, to improve dynamic stability of the rotor bearing system and to isolate structural components. The effects of cavitation included in previous studies were not effective. The effect of different design parameters were not studied thoroughly as experimental investigation of squeeze film dampers is very expensive. Few of them used numerical investigation but the methods they used are either time consuming or complicated. The present study investigated the feasibility of applying a steady state solver, which is computationally less expensive, for analyzing flow field inside the squeeze film dampers. The behavior of dynamic pressure profiles at different operating conditions, and the effect of a central groove on dynamic pressure profiles were also studied. Simulation results of a 3D case which is similar to the one experimentally studied by Delgado were used to establish if the moving reference frame (MRF) model in Fluent 12.1 can be used. A steady state solver in an absolute frame of reference was used to produce whirling motion of the rotor in this study. The inlet pressure of 31kpa and the whirling speed of 50 and 100Hz were used as boundary conditions. The mixture model with three percent dissolved air in lubricant is used to model multiphase flow. Singhal cavitation model is used to model cavitation. The simulations (50,000 iterations) were run until steady state solutions were reached. The results closely agreed with those obtained experimentally by San André́s and Delgado. Numerical simulations of three-dimensional cases with an additional central groove on the squeeze film land were also performed to predict the effect of central groove on dynamic pressure profiles. Addition central groove reduces the pressures and forces generated by squeeze film damper.

Download or read book Preliminary Investigation of the Dynamic Force Response Coefficients for Squeeze Film Bearing Dampers written by and published by . This book was released on 1974 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of the hydrodynamic force response of a squeeze film bearing damper with end seals was carried out. Measurements of the pressure distribution about a journal constrained to more in a circular orbit were made for the journal orbit centered in the annular clearance and offset from the center of the annular clearance. The effects of cyclic flow in a radial inlet were studied for the case of the journal orbit centered in the annular clearance.

Download or read book Experimental Study of a Grooved Squeeze Film Damper written by Grigory Luis Arauz and published by . This book was released on 1993 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Study of Uncentralized Squeeze Film Dampers written by Roger D. Quinn and published by . This book was released on 1983 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Identification of Force Coefficients in a Squeeze Film Damper with a Mechanical Seal written by Adolfo Delgado-Marquez and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze film dampers (SFDs) with low levels of external pressurization and poor end sealing are prone to air entrapment, thus reducing the damping capability. Furthermore, existing predictive models are too restrictive. Single frequency, unidirectional load and centered circular orbit experiments were conducted on a revamped SFD test rig. The damper journal is 1" in length and 5" in diameter, with nominal clearance of 5 mils (0.127 mm). The SFD feed end is flooded with oil, while the discharge end contains a recirculation groove and four orifice discharge ports to prevent air ingestion. The discharge end is fully sealed with a wave-spring that pushes a seal ring into contact with the SFD journal. The measurements conducted without and with lubricant in the squeeze film lands, along with a frequency domain identification procedure, render the mechanical seal dry-friction force and viscous damping force coefficients as functions of frequency and motion amplitude. The end seal arrangement is quite effective in eliminating side leakage and preventing air entrainment into the film lands. Importantly enough, the dry friction force, arising from the contact forces in relative motion, increases significantly the test element equivalent viscous damping coefficients. The identified system damping coefficients are thus frequency and amplitude of motion dependent, albeit decreasing rapidly as the motion parameters increase. Identified force coefficients, damping and added mass, for the squeeze film damper alone agree very well with predictions based on the full film, short length SFD model.

Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1985 with total page 1052 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimentally Determined Stiffness and Damping of an Inherently Compensated Air Squeeze film Damper written by Robert Ernest Cunningham and published by . This book was released on 1975 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: