Добірка наукової літератури з теми "Turbo engine lubricant"

Along with the increasing progress of gasoline type of fuel led to many types of gasoline fuel sold in Indonesia to meet consumer demand required for fuel energy motor fuel. Includes Premium fuel types, Pertalite, Pertamax, Pertamax Turbo, and Pertamax Racing. Therefore, with the number of options are conducted research on the use of 3 different types of fuel are: Premium, Pertalite, and Pertamax tested on a 125cc motor fuel engine for 7 hours nonstop at 4000 rpm speed to know the effect on the difference in decrease in value of Viscosity and TBN SAE10W-30 lubricating oil used on the combustion engine. Given the function Lubricant oil is also very important in maintaining the durability and performance of the engine. The results show that the use of Pertamax fuel has the highest decrease in Viscosity and TBN value compared to Pertalite and Premium fuels. Where each value of Viscosity and TBN on the sample of Pertamax lubricant 9.7 cSt and 6.9 mg KOH / g. Pertalite 9.8 cSt and 7.1 mg KOH / g. Premium 7.2 cSt and 10 mg KOH / g.

The problem of increasing the unit power of the engine without making changes to its design is solve by using a turbo supercharger. However, due to the intensity of the turbochargers operating mode, which are characterized by engine speed variability due to changing load indicators during operation (the number of rotor revolutions varies from 30000 min-1 to 120000 min-1, engine exhaust gases have a temperature of about 7500C), there is a need to improve the efficiency of the turbocharger bearing lubrication system. The purpose of the research is to ensure the operability and increase the reliability of turbochargers of diesel engines. To achieve this goal, a constructive solution for the lubrication system of the bearing assembly was propose, i.e., a membrane-type hydraulic accumulator was structurally provided in the lubrication system of the bearing assembly. Experimental studies were conduct to identify the operability and effectiveness of this constructive solution. The experiment was carried out on the KAMAZ-740 engine, the turbocharger shaft drive was carried out in normal mode, that is, from exhaust gases. L-02-40 fuel was use, SAE 10W–40 API was use as a lubricant. The turbocharger shaft speed varied from minimum to maximum by changing the engine speed and then stopping it. During the experiments, the following parameters of the turbocharger operation were measure: the duration of inertial rotation of the turbocharger rotor; the duration of pressure reduction in the turbocharger lubrication system. The dependences of the influence of the duration of the pressure drop in the turbocharger lubrication system and the duration of rotation of the turbocharger shaft by inertia with parallel inclusion of the accumulator in its lubrication system and in the normal mode of lubrication of the bearing are reveal. It is established that the installation of a device for feeding the turbocharger bearing during a sharp reduction in engine speed will increase the run-out of the turbocharger rotor from 30 to 65 s while maintaining the normal operating mode of the turbocharger lubrication system

Post fuel injection in the expansion stroke is used for diesel particulate filter regeneration; however, fuel spray impinges on the cylinder liner due to the low temperature and pressure conditions. Fuel adhesion and fuel flowing down across the cylinder liner, the so-called “wall-flow,” was observed by high-speed video images, and this adhesion is a cause of diesel engine lubricant oil dilution and the deterioration of fuel consumption in diesel engines. In this article, the fuel adhesion and the wall-flow of post diesel fuel injections were investigated with a high pressure-temperature constant volume optical chamber. The in-cylinder temperatures and pressures at 30, 60, and 90 °CA ATDCs, conditions commonly employed in post fuel injection timings, were measured by an actual engine, and similar conditions were created in the constant volume chamber by the combustion of a pre-mixed gas of ethylene, oxygen, and nitrogen. Fuel masses of 0.6, 1.1, and 1.7 mg per hole were injected at each ATDC setting. The weight of the adhered fuel on the wall and the fuel in the piston-cylinder crevice were measured by precision balance, and the liquid–vapor phases in the spray were observed by Mie scattering and shadowgraph methods. To measure the thickness of the adhered fuel on the cylinder wall, the laser-induced fluorescence method was employed. The results show that the fuel spray penetration and adhesion on the cylinder wall were different in the test conditions investigated here. With the early post injection, most of the injected fuel vaporizes without penetrating to the cylinder liner and gaseous diesel fuel is condensed on the cylinder wall. A thin and widely spread out fuel film is formed on the cylinder wall; however, no wall-flow could be confirmed by the high-speed video images. With late post fuel injections, the strong penetration of liquid fuel reaches the cylinder wall, and a thick and widely spread out fuel film was formed on the cylinder wall and the wall-flow phenomenon was observed here. However, the quantity of fuel involved in the wall-flow was smaller than that of the fuel adhering to the cylinder wall. The effects of in-cylinder pressure and temperature on the fuel adhesion on the cylinder wall were investigated. With the increase in pressure and temperature, the quantity of adhering fuel was reduced, suggesting that the boost pressure increase by turbo charging and a higher engine load is effective to reduce fuel adhesion. Furthermore, the effects of multiple post fuel injections on fuel adhesion to the cylinder wall were investigated, maintaining the total fuel injection amounts. With increases in the number of fuel injections, the total percentage of adhering post fuel on the cylinder wall was reduced. In the multiple fuel injections, it was observed that fuel motion takes place during the spray pass after the first and second fuel injections and that the penetration length of the second and third fuel sprays increases.

Due to the increasing fuel cost and environmental targets, the demand for more efficient gas turbines has risen considerably in the last decade. One of the most important systems in a gas turbine is the secondary air system, which provides cooling air to the disks and to the blades. It also provides air for sealing of the bearing chambers. The amount of secondary air that is extracted from the compressor is a performance penalty for the engine. In aero engines, bearing chambers are in most cases sealed by the most traditional type of seal, the labyrinth seal. Bearing chambers contain the oil lubricated components like bearings and gears. In order to avoid oil migration from the bearing chamber into the turbomachinery, the seals are pressurized by secondary air; thus, a pressure difference is setup across the seal, which retains the lubricant into the bearing chamber. Oil loss can lead to a number of problems like oil fire or coking with the probability of an uncontained destruction of the aero engine. Oil fumes can also cause contamination of the air conditioning system of the aircraft thus cause discomfort to the passengers. Beside labyrinth seals, other types of seals such as brush seals and carbon seals are used. Both the latter are contact type seals, that is, they may be installed with zero gap and lift during operation when they get pressurized. Brush seals particularly may be installed having an overlap with the rotating part. An original aero engine bearing chamber was modified by MTU Aero Engines to run with brush seals in a simulating rig in Munich. Two types of brush seals were used for testing: (a) a brush seal with bristles made of Kevlar fibers and (b) a brush seal with bristles made of steel. Both types were installed with an overlap to the rotor. The targets set were twofold: (a) to measure the transient temperatures in the rotor and particularly in the contact zone between the bristles and the rotor and (b) to calculate the heat generation by the seals which could enable predictions of the heat generation in future applications (i.e., scaling to bigger rotor diameters). For the heat transfer calculations, numerical models using ansys cfx were created. Additionally, a coupled computational fluid dynamics (CFD) and finite element analysis (FEA) approach was applied to simulate flow and bristle's behavior. In order to obtain the transient temperature measurements with high fidelity, a new pyrometric technique was developed and was applied for the first time in brush seals as reported by Flouros et al. (2013, “Transient Temperature Measurements in the Contact Zone Between Brush Seals of Kevlar and Metallic Type for Bearing Chamber Sealing Using a Pyrometric Technique,” ASME J. Gas Turbines Power, 135(8), p. 081603) and Flouros et al. (2012, “Transient Temperature Measurements in the Contact Zone Between Brush Seals of Kevlar and Metallic Type for Bearing Chamber Sealing Using a Pyrometric Technique,” ASME Turbo Expo 2012, Copenhagen, Paper No. GT2012-68354). This technique has enabled positioning of the pyrometer (SensorthermGmbH, www.sensortherm.com) into the bristles pack of the seal adjacent to the rotating surface. The pyrometer could record the frictional temperature evolution in the bristles/rotor contact zone during accelerations or decelerations of the rotor. The sealing air demand can be reduced up to 97% with brush seals compared to traditional three fin labyrinth. It has been estimated that this can result in a reduction in fuel burned up to 1%. Further, the reduction in air flow has additional potential benefits such as a possible simplification of the bearing chamber architecture (vent less chamber). Even though the rotor was accelerated up to 19,500 rpm, the temperature induced overshoots in the seal/rotor contact zone have caused no deterioration in either the materials or the oil.

Process fluid-lubricated thrust bearings (TBs) in a turbomachine control rotor placement due to axial loads arising from pressure fields on the front shroud and back surface of impellers. To date, prediction of aerodynamic-induced thrust loads is still largely empirical. Thus, needs persist to design and operate proven TBs and to validate predictions of performance derived from often too restrictive computational tools. This paper describes a test rig for measurement of the load performance of water-lubricated hydrostatic/hydrodynamic TBs operating under conditions typical of cryogenic turbo pumps (TPs). The test rig comprises of a rigid rotor composed of a thick shaft and two end collars. A pair of flexure-pivot hydrostatic journal bearings (38 mm in diameter) supports the rotor and quill shaft connected to a drive motor. The test rig hosts two TBs (eight pockets with inner diameter equal to 41 mm and outer diameter equal to 76 mm); one is a test bearing and the other is a slave bearing, both facing the outer side of the thrust collars on the rotor. The slave TB is affixed rigidly to a bearing support. A load system delivers an axial load to the test TB through a nonrotating shaft floating on two aerostatic radial bearings. The test TB displaces to impose a load on the rotor thrust collar, and the slave TB reacts to the applied axial load. The paper presents measurements of the TB operating axial clearance, flow rate, and pocket pressure for conditions of increasing static load (max. 3600 N) and shaft speed to 17.5 krpm (tip speed 69.8 m/s) and for an increasing water supply pressure into the TBs, max. 17.2 bar (250 psig). Predictions from a bulk flow model that accounts for both fluid inertia and turbulence flow effects agree well with recorded bearing flow rates (supply and exiting through the inner diameter), pocket pressure, and ensuing film clearance due to the imposed external load. The measurements and predictions show a film clearance decreasing exponentially as the applied load increases. The bearing flow rate also decreases, and at the highest rotor speed and lowest supply pressure, the bearing is starved of lubricant on its inner diameter side, as predicted. The measured bearing flow rate and pocket pressure aid to the empirical estimation of the orifice discharge coefficient for use in the predictive tool. The test data and validation of a predictive tool give confidence to the integration of fluid film TBs in cryogenic TPs as well as in other more conventional (commercial) machinery. The USAF Upper Stage Engine Technology (USET) program funded the work during the first decade of the 21st century.

Des températures de fonctionnement plus élevées et une diminution de la consommation en huile dans les turboréacteurs de future génération risquent d’entraîner une dégradation de l’huile plus importante que sur les moteurs actuels. Il est donc nécessaire de suivre l’évolution de cette dégradation. Ce travail de thèse a pour objectif de comprendre les mécanismes réactionnels d’oxydation de l’huile dans un turboréacteur en s’intéressant plus particulièrement à l'influence et au comportement des deux additifs antioxydants (PAN, DODPA). Dans un premier temps, des essais d’oxydation accélérée ont été réalisés sur le PetroOxy afin d’identifier les produits de réaction, de hiérarchiser le rôle des additifs antioxydants dans ces conditions d’essai et d’optimiser les techniques de caractérisation (HPLC et FTIR) utilisées au cours de cette thèse. Dans un second temps, la décomposition en plusieurs mélanges représentatifs de l’huile de lubrification a permis de démontrer que la consommation du PAN était plus élevée que celle du DODPA. En effet, les produits formés par le PAN sont des produits finaux (dont la quantité ne cesse d’augmenter avec le temps) tandis que le DODPA est capable de produire des composés ayant également un effet antioxydant. Ces derniers vont se former puis réagir avec les radicaux libres, ce qui permet de ralentir la consommation de l’antioxydant d’origine (le DODPA). Les études menées sur le vieillissement d’un film d’huile sur une plaque plane ont permis de mieux appréhender les mécanismes dans un environnement plus proche de celui du moteur. L’efficacité du DODPA vis à vis du PAN a été mise en évidence. De plus, l’effet synergique dû à la combinaison de ces deux antioxydants dans l’huile a été démontré. Par ailleurs, l’étude sur l’influence des paramètres a permis de déterminer les constantes cinétiques nécessaires pour construire le modèle cinétique de prévision de la consommation des antioxydants sur une plaque inclinée. Un banc d’oxydation permettant de reproduire les conditions de fonctionnement d’un système huile présent dans un turboréacteur a été conçu au cours de cette thèse. Le but de ce montage est de distinguer les 3 modes de vieillissement de l’huile qui sont : liquide (dans le réservoir et les canalisations), brouillard (à la sortie des roulements) et film (s’écoulant sur les parois des enceintes) afin d’être capable d’étudier les mécanismes d’oxydation régissant les 3 états. Enfin, la comparaison des résultats obtenus pour chaque mode de vieillissement étudié a permis de déterminer une teneur minimum en antioxydant nécessaire dans l’huile (soit 30 %) pour que l’ester de néopolyol ne soit pas affecté par l’oxydation, autrement dit, pour que l’huile garderait une qualité suffisante pour assurer son fonctionnement dans le turboréacteur
Higher operating temperatures and lower oil consumption in future-generation of turbo engines may result in greater oil degradation than current engines. It is therefore necessary to follow the evolution of this degradation. This thesis aims to understand the oxidation by free radical chain reactions of a neopolyol ester lubricant in a turbo engine, focusing more particularly on the influence and behaviour of the two antioxidants additives (PAN, DODPA). Accelerated oxidation tests were carried out on the PetroOxy device in order to identify the degradation products, to prioritize the role of the antioxidant additives under these test conditions and to optimize the characterization techniques (HPLC and FTIR) used during this thesis. The decomposition into several representative mixtures of the lubricating oil made it possible to demonstrate that the consumption of the PAN was higher than that of DODPA. In fact, the products formed by the PAN are final products (the quantity of which keeps increasing over time) while the DODPA is able to produce compounds that also have an antioxidant effect. These will form and react with free radicals, which will slow down the consumption of the original antioxidant (DODPA). Studies conducted on the ageing of thin film oil on a flat plate have helped to better understand the mechanisms in an environment closer to that of the engine. The effectiveness of DODPA regarding PAN has been highlighted. In addition, the synergistic effect due to the combination of these two antioxidants in the oil has been demonstrated. Finally, the study on the influence of the parameters made it possible to calculate the kinetic constants useful for the formulation of the kinetic model, which provides the prediction of the consumption rate of the antioxidants on an inclined plate. A test bench reproducing the operating conditions of an oil system present in a turbo engine was designed and built during this thesis. The purpose of this assembly is to distinguish the 3 modes of ageing of the lubricant, which are : bulk oil (in the tank and the pipes), mist (at the exit of the bearings) and thin film (flowing on the walls of the enclosures) in order to study the oxidation mechanisms governing the 3 states. Finally, the comparison of the results obtained for each mode of ageing studied made it possible to determine a minimum antioxidant content required in the lubricant (i.e. 30 %) so that the neopolyol ester is not affected by the oxidation, in others words, the lubricant will keep a sufficient quality to ensure its operation in the turbo engine

An oil-free, 150 Hp turbocharger was successfully operated to 100% speed (95,000 rpm), with turbine inlet temperatures to 650°C on a turbocharger gas test stand. Development of this high speed turbomachine included bearing and lubricant component development tests, rotor-bearing dynamic simulator qualification and gas stand tests of the assembled turbocharger. Self acting, compliant foil hydrodynamic air bearings capable of sustained operation at 650°C and maximum loads to 750 N were used in conjunction with a newly designed shaft and system center housing. Gas stand and simulator test results revealed stable bearing temperatures, low rotor vibrations, good shock tolerance and the ability of the rotor bearing system to sustain overspeed conditions to 121,500 rpm. Bearing component development tests demonstrated 100,000 start stop cycles at 650°C with a newly developed solid film lubricant coating. In a separate demonstration of a 100 mm compliant foil bearing, loads approaching 4,500 N were supported by a compliant foil bearing. This combination of component and integrated rotor-bearing system technology demonstrations addresses many of the issues associated with application of compliant foil bearings to gas turbine engines.

This work details an analytical assessment of heat generation in a turbine aero-engine main-shaft bearing and the development of a model to predict that heat generation. The new model is based on an empirical model, previously developed by the Air Force Research Laboratory (AFRL), which features physics based terms multiplied by empirical regression coefficients. That model proved to be limited in that portions of the terms were essentially an extension of the regression coefficients due to the fact that the experimental data was limited to that of one bearing. Additionally, there were separate models for each rolling element material. To develop the new model, the validated bearing analysis code ADORE was used to generate power loss data for angular contact ball bearings of various sizes. The effects of speed, thrust load, pitch diameter, element diameter, number of rolling elements, lubricant inlet temperature, lubricant flow rate, and rolling element material (AISI M50 bearing steel and silicon nitride) are examined. Speed and thrust load are addressed at four levels each. Number of elements, bore diameter, and element diameter as well as lubricant temperature and flow rate are each addressed at three levels. These effects are captured in the model through traction (friction), churning (drag), and shearing (viscous) terms and their respective regression coefficients. The material effect is address through the use of an effective elastic modulus within an estimate of raceway to rolling element contact area. The performance of the model was then compared with experimental data collected in the AFRL High Mach Engine (HME) Bearing Rig. The model created in this work provides designers with an effective tool to examine bearing heat generation during the early engine design phases, avoiding the significant computational and front end expense of other, more detailed methods.

Turbochargers (TCs) aid to produce smaller and more fuel-efficient passenger vehicle engines with power outputs comparable to those of large displacement engines. This paper presents further progress on the nonlinear dynamic behavior modeling of rotor-radial bearing system (RBS) by including engine-induced (TC casing) excitations. The application concerns to a semi-floating bearing design commonly used in high speed turbochargers. Predictions from the model are validated against test data collected in an engine-mounted TC unit operating to a top speed of 160 krpm (engine speed = 3600 rpm). The bearing model includes non-cylindrical lubricant films as in a semi-floating ring bearing with an anti-rotation button. The nonlinear rotor transient response model presently includes input base motions for the measured TC casing accelerations for increasing engine load conditions. Engines induce TC casing accelerations rich in multiple harmonic frequencies; amplitudes being significant at 2 and 4 times the main engine speed. FFT post-processing of predicted nonlinear TC shaft motions reveals a subsynchronous whirl frequency content in good agreement with test data, in particular for operation at the highest engine speeds. Predicted total shaft motion is also in good agreement with test data for all engine loads and over the operating TC shaft speed range. The comparisons validate the rotor-bearing model and will aid in reducing product development time and expenditures.

The constant development of aero engines towards lighter but yet more compact designs, without decreasing their efficiency, has led to gradually increased demands of the lubrication systems, such as the bearing chambers of the aero engine. For this reason, it is of particular importance to increase our level of understanding of the flow field inside the bearing chambers in order to optimize its design and performance. The flow field in such cases is of a complicated nature since there is a strong interaction between air-flow and lubricant oil together with the geometrical configurations and the shaft rotational speed inside the bearing chamber. The behavior of this interaction must be investigated in order to understand the flow field development inside the aero engine bearing and, at a next step, optimize its performance in relation to the lubrication and heat transfer capabilities. Such an effort is presented in this work where an investigation of the air-flow field development inside the front bearing chamber of an aero engine is attempted. The front bearing chamber is divided in two separate smaller sections where the flow passes from the first section partially through the bearing and the holding structure, to the second one where the vent and the scavenge are placed. The investigation was performed with the combined use of experimental measurements and Computational Fluid Dynamics (CFD) modeling. The experimental measurements were carried out with the use of a Laser Doppler Anemometry (LDA) system in an experimental rig modeling the front bearing chamber of an aero engine for real operating conditions taking into account both air-flow and lubricant oil-flow and for a varying number of shaft rotating speeds. The CFD modeling was performed with the use of a commercial CFD package. The air-flow inside the bearing was modeled with the adoption of a porous medium assumption. The experimental measurements and the CFD computations presented similar flow patterns and satisfactory quantitative agreement. At the same time the effect of the important parameters such as the air and oil mass flow together with the shaft rotation speed and the effect of the chamber inside geometry were identified. These conclusions can be exploited in future attempts in combination with the developed CFD model, in order to optimize the efficiency of the lubricant and cooling system. The latter forms the main target of this work which is the development of a useful engineering tool capable of predicting the flow field inside the aero engine bearing so as to be used for optimization efforts.

Passenger vehicle turbochargers (TCs) offer increased engine power and efficiency in an ever-competitive marketplace. Turbochargers operate at high rotational speeds and use engine oil to lubricate fluid film bearing supports (radial and axial). However, TCs are prone to large amplitudes of sub-synchronous shaft motion over wide ranges of their operating speed. Linear rotordynamic tools cannot predict the amplitudes and multiple frequency shaft motions. A comprehensive nonlinear rotordynamics model coupled to a complete fluid-film-bearing model solves in real time the dynamics of automotive turbochargers. The computational design tool predicts the limit cycle response for several inner and outer film clearances and operating conditions including rotor speed and lubricant feed pressure. Substantial savings in product development and prototype testing are the benefits of the present development. The paper presents predictions of the linear and nonlinear shaft motion of an automotive turbocharger supported on a semi-floating ring bearing. The shaft motion predictions are compared to measurements of shaft motion at the compressor nose for speeds up to 240 krpm, and for lubricant inlet pressure of 4 bar at 150°C. Linear and nonlinear rotordynamic models reproduce very well the test data for synchronous response to imbalance. The nonlinear results show two sub-synchronous whirl frequencies whose large magnitudes agree well with the measurements. A large side load predicted for this turbocharger must be considered for accurate prediction of the rotordynamic response.

Abstract In the present work, a wetting and drying model is coupled with Eulerian Thin-Film model (ETFM) to analyze the wetting and drying behavior inside the bearing chamber. In the enhanced model, an additional source term is included to account for the contact angle effect. These models were coupled with volume-of-fluid (VOF) such that the core region is resolved by VOF and region close to the chamber walls, where a thin film is expected is resolved by either ETFM or enhanced ETFM model. Numerical studies are conducted for a shaft speed of 5,000 rpm, lubricant and air flow rates of 100 1/hr and 10 g/s respectively, at a scavenging ratio of 4. In the case of enhanced ETFM model lubricant to surface contact angle was varied from 10° to 45°. The performance of enhanced ETFM model is evaluated to capture drying and wetting behavior on a flat plate and found to be satisfactory. Film thickness prediction of enhanced ETFM model is found to be comparable with the VOF predictions reported in the literature. The effect of contact angle on the spreading of oil and film thickness is found to be small for the investigated conditions on an aero-engine bearing chamber.

The continuous increase of the temperature and pressure levels in modern aeroengines has significantly increased the demands on the design of the lubrication system. Among other things the oil/air system of a gas turbine engine has to ensure that engine operation does not permit oil coking or oil fires in order to guarantee high reliability and safety of the engine. To improve existing and develop new design rules, a fundamental study of the conditions leading to oil firing within an oil contaminated environment has been initiated. Three ignition mechanisms relevant for the triggering of an oil fire in the bearing chamber or in the secondary air system are investigated in detail: the spontaneous ignition of the lubricant (autoignition), the ignition of the lubricant near a hot surface (hot surface ignition) and the propagation of a flame within a vent pipe into the bearing chamber (vent pipe flashback). The present paper focusses on the experimental approach and procedure. The different test rigs are presented and their functioning is demonstrated by means of initial results.

Abstract In the present work, a coupled volume-of-fluid (VOF) model with Eulerian thin-film model (ETFM) approach is used to predict the film thickness in an aero-engine bearing chamber. Numerical studies are conducted for a wide range of shaft speeds with lubricant and air flow rates of 100 1/hr and 10 g/s respectively, at a scavenge ratio of 4 on a simplified bearing chamber test rig. Air-flow analysis inside the bearing chamber is also assessed. Primary and secondary airflow predictions are found to be in good agreement with the experimental results. The coupled ETFM+VOF approach is found to be sensitive enough to capture the qualitative trend of oil film formation and distribution over the chamber wall. Oil collection near the sump at a low shaft speed and a rotating oil film at a higher shaft speed are well captured.

Aircraft engine rotors, invariably supported on rolling element bearings with little damping, are particularly sensitive to rotor imbalance and sudden maneuver loads. Most engines incorporate Squeeze Film Dampers (SFDs) as means to dissipate mechanical energy from rotor motions and to ensure system stability. The paper quantifies experimentally the dynamic forced performance of two end sealed SFDs with dimensions and operating envelope akin to those in actual jet engine applications. The current experimental results complement and extend prior research conducted with open ends SFDs [21]. In the tests, two journals make for two SFD configurations, both with diameter D = 127 mm and nominal radial film clearance c = 0.127 mm. One short length damper has film lands with extent L = 12.7 mm, while the other has 25.4 mm (= 2L) land lengths. A central groove with length LG = L and depth at ¾ L separates the film lands. A light viscosity lubricant is supplied into the central groove via 3 orifices, 120° apart, and then flows through the film lands whose ends are sealed with tight piston rings. The oil pushes through the piston rings to discharge at ambient pressure. In the tests, a static load device pulls the damper structure to increasing eccentricities (max. 0.38c) and external shakers exert single-frequency loads, 50 Hz–250 Hz, inducing circular orbits with amplitudes equaling ∼5% of the film clearance. The lubricant feed and groove pressures and flow rates through the top and bottom film lands are recorded to determine the flow resistances through the film lands and the end seals. Measured dynamic pressures in the central groove are as large as those in the film lands thus demonstrating a strong flow interaction, further intensified by the piston ring end seals which are effective in preventing side leakage. Dynamic pressures and reaction loads are substantially higher than those recorded with the open ends dampers. Comparisons to test results for two identical damper configurations but open ended [21] demonstrate at least a thrice increase in direct damping coefficients and no less than a twice increment in added mass coefficients. Predictions from a physics based model that includes the central groove, the lubricant feed holes and the end seals’ flow conductances are in agreement with the test results for the short length damper. For the long damper, the predicted damping coefficients are in good agreement with the measurements while the added masses are under predicted by ∼25%.

Gas turbine aircraft engine manufacturers push for simple squeeze film damper (SFD) designs, short in length, yet able to provide enough damping to ameliorate rotor vibrations. SFDs employ orifices to feed lubricant directly into the film land or into a deep groove. The holes, acting as pressure sources (or sinks), both disrupt the film land continuity and reduce the generation of squeeze film dynamic pressure. Overly simple predictive formulations disregard the feedholes and deliver damping (C) and inertia (M) force coefficients not in agreement with experimental findings. Presently, to bridge the gap between simple theory and practice, the paper presents measurements of the dynamic forced response of an idealized SFD that disposes of the feedholes altogether. The short-length SFD, whose diameter D = 125 mm, has one end submerged (flooded) within a lubricant bath and the other end exposed to ambient. ISO VG 2 lubricant flows by gravity through the film land of length L = 25.4 mm and clearance c = 0.122 mm. From dynamic load tests over excitation frequency range 10–250 Hz, experimental damping coefficients (CXX, CYY) from the flooded damper agree well with predictions from the classical open ends model with a full film for small amplitude whirl motions (r/c << 1), centered and off-centered. Air ingestion inevitably occurs for large amplitude motions (r/c > 0.4) thus exacerbating the difference between predictions and tests results. For reference, identical tests were conducted with a practical SFD supplied with lubricant (Pin = 0.4 bar) via three orifice feedholes, 120° apart at the film land mid plane. A comparison of test results shows as expected, that for small amplitude (r/c ∼ 0.05) orbits, the flooded damper generates on average 30% more damping than the practical configuration as the latter’s feedholes distort the generation of pressure. For large amplitude motions (r/c > 0.4), however, the flooded damper provides slightly lesser damping and inertia coefficients than the SFD with feedholes whose pressurized lubricant delivery alleviates air ingestion in the film land. The often invoked open ends SFD classical model is not accurate for the practical engineered design of an apparently simple mechanical element.