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 Numerical Simulation of Flow Field Inside a Squeeze Film Damper and the Study of the Effect of Cavitation on the Pressure Distribution written by Milind Nandkumar Khandare and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Squeeze Film Dampers (SFDs) are employed in high-speed Turbomachinery, particularly aircraft jet engines, to provide external damping. Despite numerous successful applications, it is widely acknowledged that the theoretical models used for SFD design are either overly simplified or incapable of taking into account all the features such as cavitation, air entrainment etc., affecting the performance of a SFD. On the other hand, experimental investigation of flow field and dynamic performance of SFDs can be expensive and time consuming. The current work simulates the flow field inside the dynamically deforming annular gap of a SFD using the commercial computational fluid dynamics (CFD) code Fluent and compares the results to the experimental data of San Andrés and Delgado. The dynamic mesh capability of Fluent and a User Defined Function (UDF) was used to replicate the deforming gap and motion of the rotor respectively. Two dimensional simulations were first performed with different combinations of rotor whirl speed, operating pressures and with and without incorporating the cavitation model. The fluid used in the simulations was ISO VG 2 Mobil Velocite no. 3. After the successful use of the cavitation model in the 2D case, a 3D model with the same dimensions as the experimental setup was built and meshed. The simulations were run for a whirl speed of 50 Hz and an orbit amplitude of 74 um with no through flow and an inlet pressure of 31kPa (gauge). The resulting pressures at the mid-span of the SFD land were obtained. They closely agreed with those obtained experimentally by San Andrés and Delgado.

Download or read book Analysis of the Characteristics of a Squeeze Film Damper by Three dimensional Navier Stokes Equations written by Changhu Xing and published by . This book was released on 2009 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The squeeze film damper is widely used in turbomachinery due to its ability to reduce vibration, help transition through the critical speed (resonance) and diminish the force transmitted to the support frame. Instead of the commonly used Reynolds equation modeling technique, this dissertation employed the three-dimensional Navier-Stokes equations. These equations are coupled with a homogeneous cavitation model, Gumbel ([pi]-film) or full Sommerfeld (2[pi]-film) cavitation strategies in dealing with the flow field and pressure development in a squeeze film damper. The characteristics of the pressure distribution, velocity field, dynamic force and the associated damping and inertia coefficients were investigated by the parametric studies using either lubricant properties such as the gas concentration, viscosity and density or damper geometry. The equation of motion for a rigid or flexible rotor model was employed in the stability analysis for the rotor-damper operating system. The dynamic coefficients were introduced into the equations to determine the rotor trajectory and stability through the source term. By analyzing the eccentricity, rotor deflection and transmissibility response, this dissertation has pointed to a methodology of finding the 'preferred range' of both one- and two-phase squeeze dampers. Further parametric studies on the rotor-damper system evaluate the effects of the lubricant dynamic viscosity, density, gaseous or vaporous cavitation, gas concentration, static eccentricity, whirling speed, rotor flexibility, retainer spring stiffness, the lumped mass distribution and the amount of imbalance. These parameters are necessary in optimizing the design of a damper. Except for the analysis based on the equations of motion, the direct numerical simulation for the determination of the journal orbit was performed by the coupling of flow, grid deformation and stress module in CFD-ACE+. The close match of the two sets of results strengthened the confidence of the simulation results. The experimental portion of this study was designed to validate qualitatively and quantitatively the numerical simulations in pressure distribution, cavitation visualization and the damper vibration. The damper vibration was measured by means of proximity sensors located circumferentially around the supporting frame; the pressure evolution was measured by pressure transducers and the gaseous and vaporous cavitation was visualized by both a digital camera with strobotac lighting and a high speed (5000fps) camera. The experimental results corroborated the theoretical analysis."--Abstract.

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 12th International Conference on Vibrations in Rotating Machinery written by Institute of Mechanical Engineers and published by CRC Press. This book was released on 2020-10-22 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since 1976, the Vibrations in Rotating Machinery conferences have successfully brought industry and academia together to advance state-of-the-art research in dynamics of rotating machinery. 12th International Conference on Vibrations in Rotating Machinery contains contributions presented at the 12th edition of the conference, from industrial and academic experts from different countries. The book discusses the challenges in rotor-dynamics, rub, whirl, instability and more. The topics addressed include: - Active, smart vibration control - Rotor balancing, dynamics, and smart rotors - Bearings and seals - Noise vibration and harshness - Active and passive damping - Applications: wind turbines, steam turbines, gas turbines, compressors - Joints and couplings - Challenging performance boundaries of rotating machines - High power density machines - Electrical machines for aerospace - Management of extreme events - Active machines - Electric supercharging - Blades and bladed assemblies (forced response, flutter, mistuning) - Fault detection and condition monitoring - Rub, whirl and instability - Torsional vibration Providing the latest research and useful guidance, 12th International Conference on Vibrations in Rotating Machinery aims at those from industry or academia that are involved in transport, power, process, medical engineering, manufacturing or construction.

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 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 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 The Shock and Vibration Digest written by and published by . This book was released on 1989 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Modeling and Experimentation of Squeeze Film Dampers Considering Fluid Inertia Film Cavitation and Design Features in Aircraft Engine written by Tieshu Fan and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unbalance-induced vibration in aircraft engines is the major source of cabin noise and discomfort for passengers. One key component in attenuating the vibration level in an engine rotor is the squeeze film damper (SFD). The implementation of SFDs in high-speed turbomachinery increases the rotor stability and reduces the vibration amplitude at critical speeds. Despite the successful operation of SFDs in aero engines for decades, currently applied SFD models are not sophisticated enough to recognize unique features that affect damping performance. Development of an accurate and computationally efficient model has been an ongoing challenge. The object of this thesis is to develop SFD models that incorporate the fluid inertia, film cavitation, lubricant seals, and supply mechanism to provide a precise prediction of damper behavior at high operating speeds. To be specific, the fluid inertia is resolved by the momentum approximation method and perturbation method; film cavitation is formulated by the Elrod cavitation algorithm [1] and the linear complementarity problem method [2]; the effect of lubricant seals is addressed by the leakage flow at the seal groove for piston ring seals [3]; the supply mechanism is modeled by the flow interaction at the central groove. Moreover, the developed models are integrated into a rotordynamic system to estimate the critical speeds and vibration amplitudes. To accelerate the simulation time, a polynomial interpolation technique for SFD models is introduced to solve for the SFD forces under different operating conditions. Both the steady-state response and the frequency response are presented for an open SFD application. To validate the developed SFD models, an experiment for a single flexible rotor supported with two identical SFDs is executed. Displacements of both the central disk and support SFDs are measured to correlate the theoretical prediction. Some design and operation parameters including the film clearance and supply pressure are examined in the test to evaluate their effect. Results have shown excellent agreement in terms of the critical speed and vibration amplitude. In addition, several other design parameters such as the film length and bearing stiffness are discussed in the model sensitivity to demonstrate the significance of their impact.

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 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 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 Numerical and Experimental Study of a Finite Submerged Squeeze Film Damper written by Ian C. Kinsale and published by . This book was released on 1989 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cities and Their Vital Systems written by Advisory Committee on Technology and Society and published by National Academies Press. This book was released on 1989 with total page 1298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cities and Their Vital Systems asks basic questions about the longevity, utility, and nature of urban infrastructures; analyzes how they grow, interact, and change; and asks how, when, and at what cost they should be replaced. Among the topics discussed are problems arising from increasing air travel and airport congestion; the adequacy of water supplies and waste treatment; the impact of new technologies on construction; urban real estate values; and the field of "telematics," the combination of computers and telecommunications that makes money machines and national newspapers possible.