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Artykuły w czasopismach na temat "Transient friction measurement"
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Li, Yufeng, i Aric Kumaran Menon. "A Theoretical Analysis of Breakaway Friction Measurement". Journal of Tribology 116, nr 2 (1.04.1994): 280–86. http://dx.doi.org/10.1115/1.2927210.
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The transient response of an I-beam friction measurement system to a constant disk acceleration is theoretically analyzed. The friction measurement system is modeled as a single-degree-of-freedom system. It is found that the true breakaway friction is different from the measured breakaway friction, and that the true breakaway time is also different from the measured breakaway time. The system measurement error is evaluated as a function of the acceleration, the effective mass, the spring stiffness, as well as the static and kinetic coefficients of friction. A closed-form dimensionless solution is derived for the system measurement error. If the dynamic effect of the measurement system can be neglected by selecting an appropriate effective mass and acceleration, the maximum possible discretization error can be estimated as a dimensionless function of the discretization frequency, the breakaway friction, the spring stiffness, and the acceleration.
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Prölß, Maximilian, Hubert Schwarze, Thomas Hagemann, Philipp Zemella i Philipp Winking. "Theoretical and Experimental Investigations on Transient Run-Up Procedures of Journal Bearings Including Mixed Friction Conditions". Lubricants 6, nr 4 (1.12.2018): 105. http://dx.doi.org/10.3390/lubricants6040105.
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This paper focuses on the operating behavior of journal bearings for industrial machinery application during run-ups. For this purpose, a numerical simulation code that is based on a two-dimensional extended and generalized Reynolds equation and a full three-dimensional energy equation, was advanced by a theoretical model considering the effects of mixed friction and warming of journal components during start-up. The mixed friction routine contained the elastic half-spaces model proposed by Boussinesq, which considers the influence of rough surfaces by implementing flow factors and calculates additional stiffness and dissipation in areas with solid interactions. Furthermore, a transient term was added in the energy equation to consider the thermal inertia of journal, and bearing to ensure a realistic heating during run-ups. Results of the prediction were compared to experimental data taken from a special test rig built up for validation procedures. Besides the conventional sensors for temperature, oil flow, and relative motion between shaft and stator, a contact voltage measurement was installed to determine the intensity of mixed friction. The evaluation of experimental data by Stribeck curves, based on a shaft torsion measurement, indicated a significant influence of run-up time on frictional moment. The friction coefficient of the rotor bearing system was strongly influenced by the run-up time. A short run-up time reduced the frictional coefficient in the mixed lubrication regime while the opposite behavior was observed in the hydrodynamic lubrication regime. The numerical code predicted these tendencies in good agreement with experimental data, however, only if the transient energy model was applied.
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Hoić, Matija, Alen Miklik, Milan Kostelac, Joško Deur i Andreas Tissot. "Analysis of the Accuracy of Mass Difference-Based Measurement of Dry Clutch Friction Material Wear". Materials 14, nr 18 (16.09.2021): 5356. http://dx.doi.org/10.3390/ma14185356.
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The paper demonstrates that the dry clutch friction plate wear rate, measured based on the plate mass difference method, exhibits a transient behavior after each change of friction interface temperature level. The effect is hypothesized to be caused by a temperature-dependent change in the moisture content/mass level in the friction material. To test this hypothesis, a series of synchronized characterization experiments have been conducted by using two friction plates, one for wear tests and the other for drying in an oven under the same temperature conditions. Based on the analysis of test results, a moisture content compensation procedure, which reduces the transient wear rate from being 100% to being 50% higher compared to stabilized wear rate, is proposed and verified. The gained insights are used to set recommendations on the organization of routine wear characterization experiments aimed at avoiding the effect of moisture content influence on the accuracy of wear measurement. The main recommendations are to minimize the number of temperature target level changes through proper design of the experiment, insert a run-in test after every long test pause, and execute a pre-heat, blind wear test at the beginning of each test day.
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Hwang, J. J., G. J. Hwang, R. H. Yeh i C. H. Chao. "Measurement of Interstitial Convective Heat Transfer and Frictional Drag for Flow Across Metal Foams". Journal of Heat Transfer 124, nr 1 (15.05.2001): 120–29. http://dx.doi.org/10.1115/1.1416690.
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Convective heat transfer and friction drag in a duct inserted with aluminum foams have been studied experimentally. The combined effects of foam porosity (ε=0.7, 0.8, and 0.95) and flow Reynolds number (1900⩽Re⩽7800) are examined. Frictional drags for flow across the aluminum foam are measured by pressure taps, while interstitial heat transfer coefficients in the aluminum foam are determined using a transient single-blow technique with a thermal non-equilibrium two-equation model. Solid material temperature distribution is further measured for double check of the heat transfer results. To understand the frictional drag mechanisms, smoke-wire flow visualization is conducted in the aluminum-foam ducts. Results show that both the friction factor and the volumetric heat transfer coefficient increase with decreasing the foam porosity at a fixed Reynolds number. In addition, the aluminum foam of ε=0.8 has the best thermal performance under the same pumping power constraint among the three aluminum foams investigated. Finally, empirical correlations for pore Nusselt number are developed in terms of pore Reynolds number under various foam porosities.
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Wei, Wei, Jian Wei Yu, Tao You, Xiao Fen Yu i Yong Hong Wang. "Evaluation of the Transient Temperature Distribution of End-Face Sliding Friction Pair Using Infrared Thermometry". Key Engineering Materials 613 (maj 2014): 213–18. http://dx.doi.org/10.4028/www.scientific.net/kem.613.213.
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A real-time temperature measurement system was designed for end-face sliding friction pairs with an infrared (IR) probe and IR thermography installed on it. The approximate temperature of contact surface was measured by the probe while non-contact surface’s temperature distribution was determined with the IR thermography. Two experiments with constant load but varied rotational speeds were carried out, and a preliminary study was made to analyze the variation of temperature in the friction process. Furthermore, the probe data was used as thermal load to calculate the temperature field by the FEM model and the result was verified using IR images. The experimental results showed that the infrared measurement system can detect and record the interface-temperature variation accurately. The probe data showed a good dynamic performance with the variation of friction coefficient. In addition, the calculated temperature field showed good accordance with the IR thermography data.
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Gulino, R., S. Bair, W. O. Winer i B. Bhushan. "Temperature Measurement of Microscopic Areas Within a Simulated Head/Tape Interface Using Infrared Radiometric Technique". Journal of Tribology 108, nr 1 (1.01.1986): 29–34. http://dx.doi.org/10.1115/1.3261139.
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This study concerns the infrared measurement of steady-state and transient temperatures of microscopic areas within the contact region formed by a magnetic tape passing over a simulated recording head. This research demonstrates that the tape surface temperature can be measured within specific limits of response time and sensitivity. Due to its high tranmissivity in the relevant infrared band, sapphire was chosen as the material to be used in the fabrication of a simulated recording head. A Barnes RM2A infrared microscope was the principle radiometer used, while a best effort was made in scanning with an AGA Thermovision 750. The friction force versus load characteristics of the head-magnetic tape interface were also observed. The high speed measurements were divided into two regimes; non-contact hydrodynamic film region, and tape-head contact regime. The temperature measurements displayed a strong correlation with the measured friction force versus load curve. Almost no temperature rise was found in the noncontact hydrodynamic film region while a temperature rise of a few degrees Celsius was found when there was tape-head contact. The results with the AGA Thermovision 750 were consistent with the measurements obtained with the Barnes RM2A.
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Meng, Fei, i Junqiang Xi. "Numerical and Experimental Investigation of Temperature Distribution for Dry-Clutches". Machines 9, nr 9 (3.09.2021): 185. http://dx.doi.org/10.3390/machines9090185.
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The temperature rise of the engaging clutch during shifting depends heavily on the transmitted torque. Precisely estimating the clutch temperature not only improves clutch control but also the optimal design of the clutch. However, the contact surface of the friction lining is closed, and the surface temperature is often difficult to measure accurately. In this study, a theoretical model of a two-dimensional transient temperature field for the friction disc has been established. In the radial and axial directions under different launching conditions, the temperature field of a friction disc is investigated. Four stages of clutch engagement have been determined, and finite-element analysis has been used to study the temperature field of a single clutch and to determine its duration.Then, the latest internationally developed distributed optical fiber sensing technology is used to perform measurement tests on the designed dry clutch friction characteristic test rig. The distributed fiber-optic temperature measurement technology can accomplish accurate temperature measurement with fast response speed and can acquire temperature value on different radii of friction discs with high spatial resolution. Such temperature sensing technology is very suitable for clutch working conditions. By analyzing the simulation and experimental results of temperature variation of different radii, different working conditions and different components, an important reference is provided for the establishment of the clutch temperature model and the optimization of the clutch heat dissipation structure design.
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Hu, Yusheng, Rongting Zhang, Jinquan Zhang, Qifeng Song i Guangxiong Chen. "Friction-Excited Oscillation of Air Conditioner Rotary Compressors: Measurements and Numerical Simulations". Lubricants 10, nr 4 (25.03.2022): 50. http://dx.doi.org/10.3390/lubricants10040050.
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The oscillation of a rotary compressor was measured and analyzed in the frequency and time domains. The harmonic wavelet transform was used to dissolve the oscillation signal into a series of single-frequency components. A power spectrum analysis of the single-frequency components shows that there are many vibration components whose frequencies are one, double, triple, quadruple, and even tens of times the rotating frequency. An envelope spectrum analysis shows that some single-frequency components originate from the friction-excited oscillation of the compressor. A full-size mode-coupling model of the rotary compressor was established to forecast the friction-excited oscillation of the compressor using the transient dynamics method and the complex eigenvalue method. The measurement results are consistent with the predictive results. A sensitivity analysis of the main parameters shows that the coefficient of friction has a major impact on the development tendency of the friction-excited oscillation of rotary compressors.
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Irawan, Yudy Surya, Moch Agus Choiron i Wahyono Suprapto. "Tensile strength and thermal cycle analysis of AA6061 friction weld joints with different diameters and various friction times". Eastern-European Journal of Enterprise Technologies 2, nr 12 (110) (30.04.2021): 15–21. http://dx.doi.org/10.15587/1729-4061.2021.227224.
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The paper reports measurement of tensile strength and the thermal cycle of AA6061 aluminum alloy circular bar friction weld with different diameters and various friction times. A continuous drive friction welding (CDFW) of AA6061 was conducted to weld the AA6061 circular bar with different diameters of 30 mm for the rotating part and 15 mm for the stationary part. The CDFW process was carried out with the revolution speed of 1,600 rpm, the initial compressive force of 2.8 kN during the friction stage for various friction times of 10, 12, and 14 seconds, and an upset force of 28 kN for 60 seconds. The flash temperature was measured using a digital infrared thermometer gun. Computer simulation using the finite element method was also done by coupling transient thermal and static structural methods. The flash temperature becomes higher along with increasing friction time based on the digital infrared thermometer gun measurement and finite element analysis. The results of tensile strength testing show that the specimen with a friction time of 12 seconds has the highest tensile strength. Based on the hardness testing result, it is found that the specimen with a friction time of 10 seconds has higher hardness, but it has an incomplete joint flash so that the tensile strength is lower than that of the specimen with a friction time of 12 seconds. Besides, the hardness of the specimen with a friction time of 12 seconds is higher than that of the specimen with a friction time of 14 seconds. The flash size becomes bigger along with the increase of the friction time based on the macrostructure observation on the longitudinal section of the CDFW specimen. It is confirmed by the temperature measurement and finite element analysis that the specimen with a friction time of 12 seconds has heat input to form the CDFW joint that has a maximum tensile strength in the range of this study
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Chen, Chao, i Chongmin She. "Creep Effect Analysis at the Friction Interface of a Rotary Ultrasonic Motor". International Journal of Applied Mechanics 07, nr 02 (kwiecień 2015): 1550031. http://dx.doi.org/10.1142/s1758825115500313.
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Theoretical and experimental studies for the creep mechanism at the friction interface between rotor and stator of traveling wave type rotary ultrasonic motors (TRUM) are performed in this work. A modeling method is developed to investigate the creep and the distributed contact pressure in the friction interface for the piezoelectric composite stator with complex geometries. The annular laminated structure of the stator is discretized into a semi-analytical plate element in the radial direction, and the teeth on top of the stator are modeled by the finite element (FE) method. Then a coupled approach for the continuous plate and FE discretized teeth is proposed to investigate the interface contact mechanism. Finally, the accelerated aging tests for TRUM are conducted to study the creep effect in the friction layer during the long-term storage, the startup state is investigated experimentally by the transient characteristics measurement system. It is shown that transient characteristics of TRUM are strongly affected by the creep effect at the friction interface. The vibration response of the stator is weakened by the creep of the contact layer, and the amplitude of the piezoelectric composite plate decreases with increasing creep percentage. It is theoretically and experimentally proved that the creep percentage of over 20% can lead to the startup failure of TRUM.
Rozprawy doktorskie na temat "Transient friction measurement"
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Costa, BÃrbara Cristina Alves da. "Load measurement error influence on friction factor calibration of pipe water distribution networks through do reverse transient method and genetic algorithm". Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=13621.
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O estudo de redes hidrÃulicas para fins de operaÃÃo ou anÃlise de viabilidade para ampliaÃÃo ou recuperaÃÃo das mesmas à iniciado pela calibraÃÃo, neste contexto, entendida como identificaÃÃo de parÃmetros tais como: fator de atrito, rugosidade e diÃmetro. O MÃtodo Transiente Inverso em conjunto com Algoritmo genÃtico se mostra eficiente nessa tarefa. O referido mÃtodo emprega o MÃtodo das CaracterÃsticas na soluÃÃo das equaÃÃes de movimento para escoamento transiente em tubos de redes e a otimizaÃÃo das soluÃÃes à baseada na Teoria Evolutiva e avaliada por uma funÃÃo objetivo, que neste estudo à o somatÃrio do mÃdulo da diferenÃa entre as cargas medidas e calculadas pelo modelo para cada conjunto de soluÃÃes. Considerando que o objetivo do desenvolvimento de modelos matemÃticos para a calibraÃÃo de redes hipotÃticas à a utilizaÃÃo dos mesmos em redes reais, e que nessas, a coleta de dados de carga està sujeita a erros de mediÃÃo, seja devido a defeitos nos equipamentos seja por condiÃÃes ambiente desfavorÃveis ou outros efeitos aleatÃrios e tendo em vista a relevÃncia dos fatores de atrito nas tubulaÃÃes, pela sua relaÃÃo com perdas de carga que devem ser controladas para um Ãtimo funcionamento de redes, garantindo um abastecimento contÃnuo em quantidade e condiÃÃes de funcionamento adequados, este trabalho propÃe-se a verificar a interferÃncia da presenÃa de erros de mediÃÃo de carga transiente na identificaÃÃo dos fatores de atrito em duas redes hidrÃulicas hipotÃticas. As mesmas sÃo de portes diferentes com relaÃÃo ao nÃmero de anÃis, nÃs e tubos. Ambas sÃo alimentadas por um reservatÃrio cada. As condiÃÃes transientes sÃo atribuÃdas a uma manobra de vÃlvula instalada em um dos nÃs de cada rede. A coleta de dados de carga à restrita a 20% dos nÃs de cada rede, sendo que um deles à o nà onde se encontra a vÃlvula. O tempo de observaÃÃo do transiente hidrÃulico à restrito ao tempo da manobra de vÃlvula, 20s, e ocorre em intervalos de 0,1s, resultando em 200 registros de carga. A condiÃÃo permanente das redes à inicialmente desconhecida o conhecimento acerca da mesma à restrito a carga nos reservatÃrios e demandas nos nÃs, bem como diÃmetros dos tubos, os fatores de atrito sÃo inicialmente estipulados. A determinaÃÃo das condiÃÃes permanente e transiente bem como a identificaÃÃo dos fatores de atrito à realizada com a utilizaÃÃo de um modelo hidrÃulico e geram cargas transientes que sÃo consideradas convencionalmente verdadeiras, essas entÃo recebem incrementos de diversos erros sistemÃticos e aleatÃrios, que geram novas cargas e essas sÃo consideradas coletadas com erros de mediÃÃo. A partir dessas novas cargas sÃo realizadas identificaÃÃes de fatores de atrito, os quais sÃo comparados com os que foram obtidos considerando um caso ideal de cargas sem erros de mediÃÃo. A referida comparaÃÃo à realizada atravÃs do Erro MÃdio Relativo e da FunÃÃo Objetivo Ãtima. Os resultados encontrados demonstram que os erros de mediÃÃo interferem na identificaÃÃo dos fatores de atrito apesar de nÃo ser possÃvel delinear uma relaÃÃo entre os mesmos.The study of hydraulic networks for operation purposes or viability analysis for extension or renovation of the same is started the calibration in this context understood as identification parameters, such as friction coefficient, surface roughness and diameter. The Transient Inverse Method in conjunction with genetic algorithm is efficient in this task shows. This method employs the method of characteristics in the solution of the equations of motion for transient flow in networks of pipes and the optimization of solutions is based on Evolutionary Theory and evaluated by an objective function, which in this study is the sum of the difference between the module loads measured and calculated by the model for each set of solutions. Whereas the objective of the development of mathematical models for calibration hypothetical networks is their use in real networks, and that these, the collection of payload data is subject to measurement errors, is due to defects in the equipment or by conditions unfavorable environment or other random effects and taking into account the relevance of friction factors in pipelines, by their relationship to head losses that must be controlled to a great operation of networks, ensuring a continuous supply in quantity and appropriate operating conditions, this work is proposed to verify the influence of the presence of transient load measurement errors in the identification of friction factors in two hypothetical hydraulic networks. They are of different sizes with the number of rings, knots and tubes. Both are each fed by a reservoir. The transient conditions are assigned to a valve maneuver installed in one of the nodes of each network. The load data collection is restricted to 20% of the nodes in each network, one of which is the node where the valve is located. The hydraulic transient observation time is restricted to the valve maneuver time, 20s, and occurs at intervals of 0.1s, resulting in 200 charge records. The permanent condition of networks is initially unknown knowledge about the same is restricted to load in the reservoirs and demands on us as well as pipe diameter, the friction factors are initially stipulated. The determination of the permanent and transient conditions and the identification of the friction factors is performed using a hydraulic model and generate transient loads which are conventionally considered true, then these various steps of receiving systematic and random errors, which generate new burdens and these are considered collected with measurement errors. From these new loads are carried IDs friction factors, which are compared with those obtained considering an ideal case with no measurement errors loads. This comparison is performed using the mean relative error and function great goal. The results show that measurement errors in the identification of interfering friction factors although not possible to draw a relationship between them.
Części książek na temat "Transient friction measurement"
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Filippi, S., M. Citelli i A. Akay. "Measurement of transient friction hysteresis". W Tribology Series, 495–506. Elsevier, 2003. http://dx.doi.org/10.1016/s0167-8922(03)80077-9.
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Kumar, Ashwani. "Low to High Speed Transient Structural and Thermal Temperature Measurement of Oil-Lubricated Multi-Speed Heavy Vehicle Transmission Gearbox System Based on FEA". W Advanced Numerical Simulations in Mechanical Engineering, 1–21. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3722-9.ch001.
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The main objective of this chapter is dynamic structural and thermal analysis of multi speed transmission gearbox (medium duty truck) using Finite Element Analysis (FEA). To evaluate the dynamic strength of transmission gearbox assembly transient structural analysis was performed. Dynamic varying loads at different rotational speed were applied to perform the transient analysis. In gear meshing operation at high rotational speed and loading condition, frictional heat is generated inside gearbox assembly. To reduce the effect of frictional heat, gear oil is used. In this research study gear oil SAE 85W140 was used for cooling and performance enhancement. Steady state thermal analysis was performed to evaluate the thermal effect of frictional heat, rotational speed of shafts (pinion, gear) and load with gear oil lubrication. In thermal effect gearbox surface temperature was measured at different points. FEA simulation results have been validated using experimental results available in literature.
Streszczenia konferencji na temat "Transient friction measurement"
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Gore, M., S. J. Howell-Smith, P. D. King i H. Rahnejat. "Measurement of In-Cylinder Friction Using the Floating Liner Principle". W ASME 2012 Internal Combustion Engine Division Spring Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ices2012-81028.
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The regime of lubrication changes in a transient manner in many load bearing conjunctions. This is particularly true of any conjunction which is subjected to changes in contact kinematics as the result of stop-start or motion reversals and loading. One such conjunction in the IC engine is the piston-bore contact. A repercussion of these transient events under otherwise perceived steady operating condition is the underlying changes in the mechanisms giving rise to engine efficiency, such as parasitic losses, mainly due to friction. Understanding the nature of these losses is the prelude to any form of palliation. A single cylinder motocross motorbike engine’s cylinder barrel is redesigned to accept wet liners with various incorporated instrumentation. The paper describes one such barrel which incorporates an instrumented floating liner for the purpose of measurement of in-cylinder friction. The principle and design of the floating liner is described. A series of tests are carried out in order to ensure the operational integrity and repeatability of the device. The basic test includes motorised running of the engine without the cylinder head installed. This renders simplified motion of the liner, subject to resistance by friction only. In a sense, under this type of motion, the liner should undergo a form of simple harmonic motion, which is verified using a number of suitably positioned accelerometers. Some more representative tests are reported under motorised conditions with the cylinder head installed. Thus, the effect of chamber pressure is introduced. However, with no combustion pressure, heat output and resulting side forces, a better understanding of tribological conditions is accrued owing to the reduced physical interactions. The results show the dominance of a mixed regime of lubrication at the dead centre reversals.
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Ciocan, Gabriel Dan, Franc¸ois Avellan i Elena Lavinia Berca. "Wall Friction Measurements: Application in a Francis Turbine Cone". W ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31333.
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The boundary layers at a turbine runner outlet and their evolution with the operating points are unknown and represent an important factor for the pressure recovery of the elbow diffuser. To characterize the boundary layer, a hot film probe is used. The measurement accuracy is an important aspect of this study and the measurement procedure is exposed. An experimental campaign is realized in a turbine cone in order to characterize the wall friction evolution for 4 operating points. Both steady and transient analysis of the experimental results are presented.
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So¨derberg, Anders, i Christer Spiegelberg. "Modelling Transient Behavior of a Mechanical System Including a Rolling and Sliding Contact". W ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80906.
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The friction and wear of rolling and sliding contacts are critical factors for the operation of machine elements such as bearings, gears, and cam mechanisms. In precision machines, for example, the main concern is to compensate for frictional losses, so as to improve control accuracy. In other applications it is often desirable to minimize friction losses to improve efficiency, though sometimes high friction is desired to prevent sliding and wear. The aim of this study is to simulate the behavior of a test equipment and show that simulations can be used to study and optimize mechanical systems that include rolling and sliding contact. Simulations can be used to study the system as a whole, as well as the contact conditions. The test equipment and the measurement procedure used are described. In the simulations, a contact model designed to handle transient contact conditions is integrated into a system model. The results show that the contact strongly influences the system. The simulations show that the use of a contact model allows the simulation of systems that contain contacts with different amounts of slip, and that such simulations can be used to study the contact as well as the system. Surface roughness influences the contact stiffness and is included in the simulations.
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Atkins, Nicholas R., i Roger W. Ainsworth. "The Measurement of Shaft Power in a Fully Scaled Transient Turbine Test Facility". W ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68998.
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Transient test facilities offer the potential for the simultaneous study of turbine aerodynamic performance, unsteady flow phenomena and the heat transfer characteristics of a turbine stage. This paper describes the accurate measurement of the shaft power generated by the turbine in the Oxford Rotor Facility (ORF), one of the key requirements for aerodynamic performance testing. A high resolution encoder system has been developed for the accurate measurement of the turbine speed and acceleration. The desired accuracy and frequency response specifications of the system are outlined. The method that has been developed to characterise the error signature of the encoder disc and the signal processing used to remove it are also outlined. The measurement of the losses due to disc windage and bearing friction are also described.
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Lüscher, Patrick, Marin Deflorin, Manuel Voggesser, Peter Stuber, Vincent Galoul i Minseok Ko. "Internal Heat Transfer Measurement on Metal-Based Additively Manufactured Channels Using a Transient Technique". W ASME Turbo Expo 2022: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-79547.
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Abstract The advancements in additive manufacturing (AM) of metals open new possibilities in the design of gas turbine parts. Especially the cooling efficiency of internal channels can be improved with more complex geometries. Naturally, AM channels have a higher surface roughness than conventionally manufactured parts, which influences the cooling air pressure loss as well as the heat transfer. Implementing novel cooling designs using AM can be possible only if the effect of increased surface roughness on the flow and on the heat transfer can be predicted with an appropriate accuracy. The objective of the current study was to measure these parameters experimentally in simple AM channels to build a database for designing complex and efficient cooling designs using the AM technique. A test rig and post-processing method was elaborated to derive the local internal heat transfer distribution of metal-based AM channels. Six circular single channel coupons made by selective laser melting (SLM) were tested for Reynolds numbers ranging from 20000 to 50000. The coupon with the lowest relative roughness shows good agreement with the Dittus-Boelter correlation. All the other coupons show a consistent increase of internal heat transfer and flow friction with the increase of the internal surface roughness.
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Laborenz, Jacob, Malte Krack, Lars Panning, Jo¨rg Wallaschek, Markus Denk i Pierre-Alain Masserey. "Eddy Current Damper for Turbine Blading: Electromagnetic Finite Element Analysis and Measurement Results". W ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45242.
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In the dynamics of turbomachinery the mechanical damping of the blading is in the focus of research for the last decades to improve the dynamic performance in terms of high cycle fatigue issues. Besides that an increased mechanical damping can produce a higher flutter safety margin such that stable operation conditions are achievable in a bigger range. Hence, novel damping techniques are considered besides the well known friction based damping devices. In this paper an extended analysis of the eddy current based damping device for a last stage steam turbine blading presented in GT2009-59593 is conducted. A transient electromagnetic finite element analysis of the eddy current damper is performed and the resulting damping forces are compared to their analytical solution. Parameter studies are carried out and equivalent damping factors are calculated. Furthermore, for the validation of the finite element model a test rig was built which allows for the direct measurement of damping forces when forcing a sinusoidal relative motion. Forced response measurements and simulations are used to demonstrate its dynamic performance and predictability.
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Patel, Himanshu, i Alok Sinha. "Identification of Slip Load, Friction Force and External Force Using Unscented Kalman Filter for Frictionally Damped Turbine Blades". W ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59863.
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Abstract An Unscented Kalman Filter (UKF) based technique has been developed for parameter estimation of turbine blades with friction dampers. The technique is based on integration of Newmark method, an iterative numerical integration method for structural dynamics, with UKF. The technique has been implemented on a single mode model of a turbine blade with a friction damper. Two approaches are developed. First, both steady state vibration and known forcing data are used to estimate parameters such as friction force and slip load. These parameters are treated as additional states of the system and the augmented state space model is used with UKF to estimate parameters. In the second approach, transient vibration response of the system is used to estimate slip load, friction force and unknown sinusoidal forcing function as well. The frequency of sinusoidal external excitation is assumed to be known. The unknown magnitude and phase of the external excitation are represented as a solution of a second order differential equation, which leads to two additional states in the model. Numerical results are presented for both the cases of known and unknown forcing functions in the presence of modeling and measurement errors. A discussion of these results is presented and the validity of the new approach is corroborated.
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Raben, M., J. Friedrichs i J. Flegler. "Brush Seal Frictional Heat Generation: Test Rig Design and Validation Under Steam Environment". W ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-56951.
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Sealing technology is a key feature to improve efficiency of steam turbines for both new power stations and modernization projects. One of the most powerful sealing alternatives for reducing parasitic leakages in the blade path of a turbine as well as in shaft sealing areas is the use of brush seals, which are also widely used in gas turbines and turbo compressors. The advantage of brush seals over other sealing concepts is based on the narrow gap that is formed between the brush seal bristle tips and the mating rotor surface together with its radial adaptivity. While the narrow gap between the bristle tips and the rotor leads to a strongly decreased flow through the seal compared with conventional turbomachinery seals, it is important to be aware of the tight gap that can be bridged by relative motion between the rotor and the brush seal, leading to a contact of the bristles and the rotor surface. Besides abrasive wear occurrence, the friction between the bristles and the rotor leads to heat generation which can be detrimental to turbine operation due to thermal effects, leading to rotor bending connected to increasing shaft vibrations. In order to investigate the frictional heat generation of brush seals, different investigation concepts have been introduced through the past years. To broaden the knowledge about frictional heat generation and to make it applicable for steam turbine applications, a new testing setup was designed for the steam test rig of the Institute of Jet Propulsion and Turbomachinery - TU Braunschweig, Germany, enabling temperature measurements in the rotor body under stationary and transient operation in steam by using rotor-integrated thermocouples. Within this paper, the development of the instrumented new rotor design and all relevant parts of the new testing setup is shown along with the testing ability by means of the validation of the test rig concept and the achieved measurement accuracy. First results prove that the new system can be used to investigate frictional heat generation of brush seals under conditions relevant for steam turbine shaft seals.
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Chen, Gang, Guangjun Cao, Weihua Zhang, Suhong Fu, Shuhong Liu, Yulin Wu i Deming Liu. "Prediction Meter Factor of Turbine Meter Considering the Effects of Cavitation". W ASME 2009 Fluids Engineering Division Summer Meeting. ASMEDC, 2009. http://dx.doi.org/10.1115/fedsm2009-78476.
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Turbine meters are wildly used in many fields for flow measurement with high accuracy and good repeatability, but the curve between meter factor and flow rates is affected by cavitation flow inside the meter. Cavitation is the main physical phenomenon which will have great effects on meter factor of turbine meters, especially at large flow rate. The meter factor will change at different cavitation number and will increase when the cavitation number decreases. In order to study its effects on meter factor, transient unsteady numerical simulation is carried out with RNG turbulence model and UDFs (User Defined Functions) based on torque balance equation in FLUENT software. The condensation/evaporation Cavitation Model is included at the simulation process. The results showed that the meter factor increased with the decrease of the cavitation number, and the meter factor is larger than at non-cavitation condition. Also the dynamic characteristics of the turbine flow meter impeller are obtained for the prediction of its meter factor and pressure distributions are obtained by the unsteady numerical simulation. The bearing friction drag is included in the torque balance equation, which is deduced from the theory of bearing.
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Price, Glenn R., Robert K. McBrien, Sandy N. Rizopoulos i Hossein Golshan. "Evaluating the Effective Friction Factor and Overall Heat Transfer Coefficient During Unsteady Pipeline Operation". W 1996 1st International Pipeline Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/ipc1996-1929.
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This paper presents a method to determine the effective friction factor and overall heat transfer coefficient for a high pressure, natural gas pipeline during fully transient flow conditions. Time varying SCADA (Supervisory Control And Data Acquisition) measurements at the pipeline boundaries (i.e., inlet and outlet) provide boundary conditions for a transient flow model as well as additional information that is utilized to determine these parameters. The resulting friction factor and overall heat transfer coefficient minimize the least-squared difference between the additional SCADA measurements at the pipeline outlet and the corresponding values predicted from the transient flow model. This concept is referred to as parameter estimation. The transient flow model is based on a numerical solution of the one-dimensional, unsteady flow equations (i.e., continuity, momentum and energy) which are discretized using a highly accurate compact finite-difference scheme. The transient flow model and parameter estimation are incorporated into a computer program that is initially tested on a simple pipeline with steady flow conditions. Here, the predicted outlet pressure and temperature, using the estimated friction factor and overall heat transfer coefficient, exactly matches the corresponding prescribed values. Subsequently, a portion of the Foothills Pipe Line Ltd. transmission system in Alberta is considered using time varying SCADA flow measurements. The resulting outlet pressure and temperature from the transient flow model are in good agreement with SCADA measurements at this location.