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Academic literature on the topic 'Equivalent piston model'
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Journal articles on the topic "Equivalent piston model"
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Нгуен, Ван Зионг, and Александр Витальевич Белогуб. "ОПРЕДЕЛЕНИЕ ГРАНИЧНЫХ УСЛОВИЙ ДЛЯ РАСЧЁТА ТЕРМОНАПРЯЖЕННОГО СОСТОЯНИЯ ПОРШНЯ." Aerospace technic and technology, no. 1 (March 7, 2019): 39–47. http://dx.doi.org/10.32620/aktt.2019.1.04.
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The paper deals with the study of the influence of the working process parameters of the two-stroke opposed piston engine like D100 (20.7/2×25.4), especially the heat exchange between the working substance and the wall of the combustion chamber (CC) – cylinder and pistons on temperature and stress-strain state of the piston. To make an estimation of the effect of a working process on the boundary condition we considered the internal heat balance and specific features of gas dynamic loading of main parts of the cylinder-piston group. To calculate the temperature fields, the actual boundary conditions of non-stationary thermal loading were replaced with the equivalent steady-state ones, obtained from the condition that the amount of heat perceived by the piston surface in real and conditionally equivalent processes are equal. Equivalent parameters of heat transfer are calculated by the condition of conservation of the amount of heat passing through the walls of the CS. It was performed the validation of the calculation of equivalent heat exchange parameters. It is shown that in case of an error in specifying the initial conditions, for example, temperature per 100K, the temperature of the piston CC surface may change by 5K in the first 5 operating cycles. It is shown that the developed model of the workflow can be adjusted according to the available experimental data and used to model the boundary conditions. The authors made corrections to the dependence obtained by prof. Rosenblit, to determine the current heat transfer coefficient from the working fluid to the walls of the CC by the total heat removal for the cycle, equal to 20%. It was obtained the average coefficient of heat transfers from the working fluid to the piston and the temperature of the cycle for the nominal mode, which are 3500 W/(m2•K) and 835 K respectively. It was carried out the simulation of the thermal properties of the gap between the piston ring and the groove filled with combustion products. It is shown that the conditions of heat transfer through annular grooves and rings require clarification in modeling, which is associated with the conditions of heat transfer in the gaps, and the gap can be replaced by a gasket with appropriate thermal properties.
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Xu, Zhao Ping, and Si Qin Chang. "Simulation of an Opposed-Piston Four-Stroke Free-Piston Generator." Applied Mechanics and Materials 336-338 (July 2013): 585–89. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.585.
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In order to achieve efficient conversion of the chemical energy of fuel into the electrical energy, a novel opposed-piston four-stroke free-piston generator is developed in this paper by equipping one free-piston engine with two linear generators. Mathematical models of the opposed-piston four-stroke free-piston generator are created based on the kinetic equation of the free-piston motion, the state equation of the ideal gas, and an equivalent heat release function of the combustion process. Dynamical properties of the system are simulated and analyzed by using the created model, and results from the simulation are presented. According to the simulation, the new four-stroke free-piston generator can realize running without vibrations.
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Quan, Lingxiao, Haihai Gao, Changhong Guo, and Shichao Che. "Assessment of the Dynamics Flow Field of Port Plate Pair of an Axial Piston Pump." Processes 8, no. 1 (January 8, 2020): 86. http://dx.doi.org/10.3390/pr8010086.
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This paper aims at studying the dynamic fluid evolution process of port plate pair of an axial piston pump. First of all, The Renormalization Group k-ε model (RNG k-ε model) is implemented to simulate the dynamic flow distribution and forecast the evolution of the internal vortex structure inside the valve plate chamber with different speeds of pistons and velocities of inlet fluid by using computational fluid dynamics software. Then, an equivalent amplification test model of a piston-valve plate is built up based on Reynolds similarity theory; the flow state of the piston-valve plate flow field is observed applied the particle image velocimetry (PIV) measuring technique. The resulting uniformity of numerical simulation and PIV measurement verifies that the RNG k-ε model can achieve high-precision prediction for the vortex structure inside the valve plate chamber. Through analysis of velocity contours and streamlines of the flow field, it can be found that vortices with different scales, strengths and positions will occur during the process of fluid distribution, and the scale and strength of the vortex inside the valve plate chamber will be reduced with the increase of the piston’s moving speed, so the energy loss is also reduced and the efficiency is improved.
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Guan, Dong, Li Jing, Harry H. Hilton, and Junjie Gong. "Dynamic lubrication analysis for a spherical pump." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 233, no. 1 (February 28, 2018): 18–29. http://dx.doi.org/10.1177/1350650118762603.
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Dynamic lubrication analyses for a spherical pump, consisting of a piston and cylinder, are presented. Contact forces between piston and cylinder are modeled first using an equivalent ball-on-plane model. Both the effects of external loads and operating conditions are considered in a dynamic elastohydrodynamic lubrication model, which is derived from Reynolds equation. Two assumed time-dependent sine-wave and square-wave loads are applied to the model. Fluid film thicknesses are estimated using the model and assumed loads, effects of different structural, and operational parameters, such as piston diameter, radial clearance, applied load, piston speed, lubricant viscosity, and surface roughness, on fluid film thickness are investigated. Fluid film thickness reactions of more realistic smooth and continuous sine wave loads are compared to discontinuous ones in order to verify whether or not assumed ideal loads are acceptable and reliable. Results indicate that piston diameter, speed, lubricant viscosity have positive relations on the dynamic lubrication performance, and increasing these values can improve the dynamic lubrication regime. While the parameters such as radial clearance, applied load, and surface roughness have the verse effects. Furthermore, the impacts of all the above parameters on fluid film are different either. These obtained results can be used to effectively optimize spherical pump lubrication performance.
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Ding, Fa Jun. "Piston Engine Connecting Rod Transient Dynamic Finite Element Analysis and Maintenance Strategy." Applied Mechanics and Materials 484-485 (January 2014): 272–76. http://dx.doi.org/10.4028/www.scientific.net/amm.484-485.272.
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Connecting rod is the very important connection and force bearing parts of piston engine crank mechanism; work in the role of various kinds of alternating stress. Taking a general rod from Lycoming IO-360-A1B6 aero-piston engine as the analysis object, first, a 3-D finite element model of the rod is established in ANSYS Workbench. And then, considering the influence of gas pressure in cylinder after ignition acting on the connecting rod under engines rated speed conditions, through the transient dynamic analysis, find in all load steps, the maximum equivalent stress occurred at the transition zone between the shaft and little head, and received the maximum equivalent stress versus time curve, to provide numerical basis for improving high-cycle fatigue reliability of the rod. Finally, according to equivalent stress contours of the rod when gas in cylinder peak pressure occurs, initially identified rods hazardous areas,to provide foundation for the development of standard repair process.
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Zhang, Ziwei, Huihua Feng, and Zhengxing Zuo. "Numerical Investigation of a Free-Piston Hydrogen-Gasoline Engine Linear Generator." Energies 13, no. 18 (September 9, 2020): 4685. http://dx.doi.org/10.3390/en13184685.
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The free-piston engine linear generator (FPELG) is being investigated by many researchers because of its high thermal efficiency and its variable compression ratio. However, all researchers focused on the FPELG characteristics with mono-fuel. Therefore, in this paper, the performance of the FPELG that has adopted gasoline with hydrogen as fuel is investigated. The method of coupling the zero-dimensional dynamics model with the multi-dimensional CFD (Computational Fluid Dynamics) combustion model was applied during the simulation process. According to the results, the piston TDC (Top Dead Center), the piston peak piston velocity, and the system operation frequency show a negative correlation with the increase of hydrogen fractions. However, the peak in-cylinder pressure was increased with the hydrogen volume fraction increase, due to the fast flame speed and short combustion duration characteristics of hydrogen. Meanwhile, the indicated efficiency of the free-piston engine was increased from 32.3% to 35.3% with the hydrogen volume fraction change from 0% to 4.5%, when the free-piston engine operates at stoichiometric conditions with fixed ignition timing. In addition, with the ignition timing advance increase, the piston TDC was decreased. The peak piston velocity and the peak in-cylinder pressure were in negative correlation with the ignition timing advance. While the engine indicated that the efficiency was increased with the equivalent degree of ignition timing from 20° to 16°. Therefore, the ignition timing of the FPELG under the spark-ignition combustion mode is supposed to be an effective and practical control variable.
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Nakai, H., N. Ino, and H. Hashimoto. "Effects of Film Temperature on Piston-Ring Lubrication for Refrigeration Compressors Considering Surface Roughness." Journal of Tribology 120, no. 2 (April 1, 1998): 252–58. http://dx.doi.org/10.1115/1.2834419.
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This paper describes a theoretical model for piston-ring lubrication considering the combined effects of surface roughness and oil film temperature variation for refrigeration compressors. In the model, the piston-ring is treated as a one-dimensional dynamically loaded bearing with combined sliding and squeezing motion. The one-dimensional modified Reynolds equation, based on the average flow model by Patir and Cheng, is used to determine the pressure distribution, and the one-dimensional energy equation, considering the heat generated due to contact of asperities, is applied to calculate the oil film temperature distribution. In the analysis of the modified Reynolds equation, the flooded condition and Reynolds condition are employed at the leading edge and trailing edge of piston-ring, respectively. On the other hand, in the analysis of the modified energy equation, a constant temperature equivalent to the cylinder wall temperature is assumed at the leading edge. From numerical results of the minimum film thickness, pressure and temperature distributions and friction force, the combined effects of surface roughness and oil film temperature variation on these lubrication characteristics are clarified.
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Yuan, Chenheng, Jing Xu, and Huihua Feng. "In-cylinder heat transfer and gas motion of a free-piston diesel engine generator." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, no. 8 (June 28, 2017): 739–52. http://dx.doi.org/10.1177/0957650917717627.
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The free-piston engine generator is an attractive alternative to the conventional reciprocating engine due to the feature that it moves without crankshaft system. This paper presented a simulation for the investigation on the characteristic of in-cylinder gas motion and heat transfer in a compression ignited free-piston engine generator. An operation experiment was performed to obtain the precise piston motion for the modeling of heat transfer and gas flow. The development of the multi-dimensional model was described, and simulation results were presented and showed good similarity with the experimental data. Then, the heat transfer and gas motion in the free-piston engine generator were discussed, on which the influences of piston motion were also investigated compared with a corresponding conventional reciprocating engine. The results indicated that compared with the conventional reciprocating engine, a higher level of squish and reverse squish effect was found for the free-piston engine generator due to its faster motion around top dead center, while its slower piston motion led to weaker gas turbulence in the compression process. Moreover, the free-piston engine generator and conventional reciprocating engine did not show a significant difference in heat transfer during the compression process, however, an obvious advantage of heat transfer was indicated for the free-piston engine generator in combustion and expansion processes due to its lower combustion temperature and the reduced time that is available for heat transfer caused by its faster expansion. The mechanism for such differences is that the free-piston engine generator moves with uneven equivalent speed.
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Li, Zekui, Shunhai Xu, Guofang Gong, Yankun Bi, Liping Xu, Liang Zhang, and Zhen Ren. "Study on Friction Characteristics of Slipper Pair of Large Displacement High-Pressure Piston Pump." Lubricants 10, no. 12 (December 15, 2022): 363. http://dx.doi.org/10.3390/lubricants10120363.
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The reference value of the oil film thickness and friction coefficient of the slipper pair is critical to the development of the piston pump, especially for 750 mL/r displacement piston pumps. To explore the computing method and range of the reference value mentioned applicable to 750 mL/r displacement piston pumps, this study aims to propose the modified calculation model of the oil film thickness based on the real clearance flowrate and obtain the value range of the friction coefficient of the slipper pair. Through the friction test of the slipper pair, the mean deviation ratio of the oil film thickness between the modified value, theoretical value, and the measured value was calculated and compared, respectively. The variation law of the friction under the influence of different speeds and working pressures was analyzed. Finally, the range of the equivalent friction coefficient with the upper and lower limit surfaces was obtained. The results show that the mean deviation ratio between the modified oil film thickness value and the measured value is mainly within 6%, while that of the theoretical method is mainly from 6% to 8%, and the mean of the difference between the two deviation ratios is about 3%, verifying the feasibility of the modified model used for the calculation of the reference value. Meanwhile, the value of the equivalent friction coefficient fluctuates in the range of 0.006–0.018, which is affected more significantly by the working pressure than the speed, suggesting that the working pressure can be given priority as the design basis of the friction coefficient for 750 mL/r displacement piston pumps.
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Guan, Dong, Harry H. Hilton, Zhengwei Yang, Li Jing, and Kuan Lu. "Lubrication regime analysis for spherical pump." Industrial Lubrication and Tribology 70, no. 8 (November 12, 2018): 1437–46. http://dx.doi.org/10.1108/ilt-07-2017-0207.
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Purpose This paper aims to investigate the lubrication regime in spherical pump, especially under different structural parameters and operational conditions. Design/methodology/approach A ball-on-plane configuration is adopted to represent the contact model between spherical piston and cylinder cover. The governing equations, which include the Reynolds and elasticity equations, are solved and validated by Jin–Dowson model. Both minimum film thickness and lambda ratio (ratio of minimum fluid film thickness to combined surface roughness of the piston and cylinder cover) of the equivalent model are obtained using an established model. Findings The results indicate that piston diameter and radial clearance are the two main factors affecting the pump lubrication regime. Other related parameters such as rotation speed of the piston, load, viscosity of working medium, material matching and surface roughness of piston and cylinder cover also have different impacts on the lubrication regime of the spherical pump. Originality/value These results emphasize the importance of the design and manufacturing parameters on the tribological performance of spherical pumps and these are also helpful in improving the spherical pump lubrication regime and enlarging its life cycle. This is to certify that to the best of the authors’ knowledge, the content of this manuscript is their own work. This manuscript has only been submitted to this journal and never been published elsewhere. The authors certify that the intellectual content of this manuscript is the product of their own work and that all the assistance received in preparing this manuscript and sources has been acknowledged.
Conference papers on the topic "Equivalent piston model"
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Ravinthrakumar, Senthuran, Babak Ommani, Trygve Kristiansen, Idunn Olimb, and Bernt Karsten Lyngvær. "A Physical-Based Damping Model of Gap and Moonpool Resonance in WAMIT." In ASME 2022 41st International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/omae2022-79673.
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Abstract An engineering model to estimate and incorporate quadratic damping of the piston-mode moonpool responses in the proximity of the piston mode period is proposed. The model provides a physical-based equivalent linearized damping coefficient. The method is not limited to forced motion, but applicable to freely floating moonpool vessels. Further, it is not limited to moonopools, but can be generalized to gap resonance problems, such as side-by-side operations. The soundness of the proposed physical-based method is demonstrated using the panel code WAMIT with a linear damping term in the free-surface boundary condition inside the moonpool using two existing moonpool experiments as case studies; (1) a two-dimensional rectangular box with a moonpool subject to forced heave, and (2) a freely floating offshore vessel in incident waves. The WAMIT computations using the proposed method reconstructs the experimentally obtained piston-mode and vessel responses well. We suggest that the proposed method can be used with fair degree of confidence in an early design or operational analysis phase, in the (often) case that the quadratic damping is not known from either experiments or CFD. To our knowledge, this is the first general, physical-based piston-mode damping model that does not require any tuning from experiments.
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Bade, Mehar, Nigel N. Clark, Terence Musho, and Parviz Famouri. "Piston Rings Friction Comparison in a Free Piston and Conventional Crankshaft Engines." In ASME 2018 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/icef2018-9774.
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The conventional internal combustion engines driven by crankshafts and connecting rod mechanisms are restrained by combustion, thermal and mechanical inefficiencies. The Oscillating Free Piston Linear Engine Alternator (OFPLEA) produces electric power with no need to modify the reciprocating motion to rotary motion. In the most common geometry it consists of a linear alternator driven cyclically by one or two internal combustion engines. With the elimination of crankshaft mechanism linkages, the free piston engine offers potential benefits over crankshaft engines in terms of total mechanical losses. A significant proportion of 5% to 12% of total fuel energy in conventional engines is consumed to overcome the frictional losses. This research investigation addresses an analytical and numerical model to simulate the tribological performance of piston rings in an OFPLEA engine. The results are then compared with results from an equivalent conventional crankshaft driven engine. This axisymmetric, mixed lubrication tribological model is developed on the hydrodynamic process defined by Patir and Cheng’s modified Reynolds equation and an asperity contact process as defined by Greenwood and Tripp’s rough surface dry contact model. The asperity contact pressure distribution, hydrodynamic pressure distribution, lubricant oil film thickness, frictional force and frictional power losses are calculated using an explicit finite difference approach. In the absence of spring-dominated OFPLEA system, dissimilarity in the piston motion profile for compression and power stroke exhibited two different oil film thickness peaks. Whereas a similar oil film thickness peaks are observed for conventional engine due to the controlled and stable operation maintained by crankshaft mechanism. The simulation results state that the frictional losses due to piston ring - cylinder liner contact are found to be lower for a free piston engine than for those of a corresponding crankshaft engine. The simulated piston ring frictional power losses are found to be 342.8 W for the OFPLEA system and 382.6 W for the crankshaft engine. Further, an overall system efficiency improvement of 0.6 % is observed for an OFPLEA engine due to these reduced frictional losses from piston rings.
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Kubicki, Maciej, Harry Watson, John Williams, and Peter Stryker. "Spatial and Temporal Stress Distributions in Spark Ignition Engine Pistons at Wide Open Throttle." In ASME 2007 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/icef2007-1726.
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Spatial and temporal stress distributions in two piston geometries for a sinusoidal piston motion engine with different rigid piston-connecting rod attachments were investigated; one was a homogeneous, all-aluminum piston with a bolted connection located remote to the piston crown, and the second was a composite piston structure in which a steel connecting rod is imbedded into the aluminum piston crown. The piston stress response to the applied thermo-mechanical loads was predicted using LUSAS (London University Stress Analysis System). A dynamic finite element analysis of the homogeneous piston was performed for the duration of one complete combustion cycle and a static analysis modeled the two component piston with loads estimated at the time when stress was highest. Two types of thermo-mechanical fatigue were analyzed: low cycle high stress and high cycle low stress. Nodal stress histories at 2000 rpm are presented for equivalent Huber (stress fields equivalent to the three dimensional stress state), radial, hoop, longitudinal, and shear stresses. Specific locations of the maximum compressive and tensile stresses were identified and show that maximum stress occurs at different times for different locations. At nodal locations where mechanical loads counteract thermal expansion forces, stress levels peak at the time when gas pressure is low. Stresses peak at the time of maximum pressure where thermal and mechanical loads have the same sense. The principle of superposition was used to differentiate the thermal and mechanical stress contributions in the piston and, most notably, in the piston crown region. The maximum amplitude and frequency of the thermal and mechanical-thermal stresses indicated high cycle fatigue failure was not likely. However, high compressive stress developed in material weakened by high temperatures is the most likely cause of failure. The two component piston is formed with a steel cone insert cast into the piston. The static results show high local Huber (von Mises) stresses at the dissimilar material interface and the highest value of hoop stress and, consequently, the main cause of large equivalent stress levels is in the steel cone insert. A modified flexible tripod shaped cone resulted in significant reduction of hoop stress in the region of contact with the aluminum. However, the peak equivalent stress present in the aluminum crown of this model was too high for the material to withstand. The last results presented are for the homogeneous piston modified to lower stress concentrations and with boundary conditions modified to represent enhanced cooling of the piston underside. The peak piston temperatures were significantly reduced and consequently the Huber stress levels were reduced. Analysis of the dynamic stresses indicated a low probability for fatigue failure. These results indicated that a homogeneous aluminum piston could become a feasible concept, provided additional piston cooling mechanisms are installed.
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Hogan, Paul H., and James D. Van de Ven. "Dynamic Modeling of a Linear Electromagnetic Piston Pump." In ASME/BATH 2017 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fpmc2017-4324.
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Due to recent advances in technologies ranging from hydraulically-assisted prostheses to human-scale robotics, there is a growing need for compact and efficient delivery of hydraulic power. Existing electric driven pumps require conversion from electric to rotational power before generating hydraulic output power. This work presents a dynamic model and experimental results of a linear pump that uses an electromagnetic force applied directly to the piston, resulting in a more direct conversion of electrical to hydraulic power in a compact package at the human power level. The model uses a quasi-steady state magnetic equivalent circuit model for the linear electromagnetic actuator coupled to a numerical time-domain piston pump model. The coupled model calculates the piston trajectory, cylinder pressures, and flowrates as a function of time. The modeled force generation and resulting mechanical dynamics match results generated from finite element analysis within 7%, with a predicted power density of 0.19 W/cc and efficiency of 73% for an unoptomized geometry. A multi-objective genetic algorithm is used to determine the geometry and operating parameters that give maximum power density and maximum efficiency, demonstrating that power densities of 0.7 W/cc and efficiencies of 85% are achievable.
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Rahman, Mosfequr, Aniruddha Mitra, Sirajus Salekeen, Jeremy Buentello, Tyler Harden, and Timothy Masocol. "Finite Element Investigation of a Piston Assembly of a Diesel Engine." In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65991.
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Ensure a safe, long life and efficient combustion within a diesel engine is an important challenge in the applications of engine technology. Much research has been done on thermal stress within engine cylinders and on engine piston heads, and how to reduce some of this stress in order to prevent failure or increase the life of the engine. The failure of a piston head tends to occur from it enduring the gas effect of the high pressures and temperatures. By performing static and dynamic Finite Element Analysis (FEA) on a piston mechanism of a diesel engine proper dimensions for different parts of an engine can be determined and failure of an engine in service can be avoided. In this research finite element analysis has been performed to determine the total deformation, stresses, and other parameters that are essential from design point of views. Real world input data for simulation obtained from running an existing diesel engine have been effectively used. Static structural and dynamic reaction of a piston assembly under the applied load of internal combustion in a diesel engine were closely observed. ANSYS workbench was utilized to perform these simulations. Using SolidWorks a piston assembly model consisting of the piston, connecting pin, connecting rod, cylinder head, crankshaft, and cranks was designed and used for simulation. Simulation results were being collected from the static structural and rigid body dynamics modules. The static structural simulation was conducted in order to obtain the structural response of the piston assembly under the combustion phase. This simulation was intended to replicate the pressure forces applied to the piston assembly at the moment of combustion. A pressure force of 7 MPa was applied to the top of the piston. From the simulation results, the maximum total deformation 1.9 mm occurred at the top edge of the piston head on the same side as the combustion chamber. Maximum equivalent Von Mises stress 323.9 MPa occurred at the joint of the connecting rod and crankshaft and the minimum equivalent stress 27 kPa occurred at the bottom of the connecting rod. Principal stresses were also examined, where the maximum principal stress 335.1 MPa occurred at the joint of the connecting rod and crankshaft and the minimum principal stress 63.5 MPa occurred inside of the connecting rod joint. The maximum shear stress 177.7 MPa occurred at the joint of the connecting rod and crankshaft and the minimum shear stress 14.26 kPa occurred at the bottom of the connecting rod. Two types of forces were considered acting upon the geometry in the rigid body dynamic simulation, one is standard earth gravity and the other is a linear dynamic load of 55,000 N applied to the top of the piston head which is used to simulate the act of combustion within the combustion chamber of a cylinder. From the rigid dynamic simulation, it was found that after the first combustion cycle, the linear velocity of the entire system, acceleration of the entire system, and the crank angular velocity reach to the maximum of 24.77 m/s, 17684 m/s2 and 5487 rpm respectively at 0.0187 seconds. Then after the second combustion cycle, the linear velocity of the entire system and the crank angular velocity reach to 27.56 m/s and 6043 rpm respectively at 0.0481 seconds; however the acceleration of the entire system took 0.0551 seconds to reach to 30115 m/s2.
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Hu, Wei, Nicholas Wilson, Gregory J. Hiemenz, and Norman M. Wereley. "Magnetorheological Shock Absorber for Crew Seats in the Expeditionary Fighting Vehicle." In ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-542.
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A magnetorheological shock absorber (MRSA) system is designed and tested to integrate semi-active shock and vibration mitigating technology into the existing EFV (Expeditionary Fighting Vehicle) forward seating positions. Based on the operational requirements of the vehicle, the MRSA is designed so that it can not only isolate occupants from harmful whole body vibration (WBV) during normal operations but also reduce injury risk during extreme events such as a “rogue” wave or ballistic/UNDEX shock event. The MRSA consists of a piston with a circular flow-mode valve, a magnetorheological (MR) fluid cylinder, and a nitrogen accumulator. Piston motion forces MR fluids enclosed in the fluid cylinder to flow through the valve where it is activated by a magnetic field in the valve. Based on the Bingham-plastic constitutive relation and a steady state fluid motion model, the valve parameters are determined using a magnetic circuit analysis tool and are validated by electromagnetic finite element analysis (FEA). The high-speed field-off viscous force of the MRSA is predicted using computational fluid dynamic analysis. To experimentally evaluate the damping performance of the MRSA and validate the design, the MRSA is tested under single frequency sinusoidal displacement excitation on a material dynamic testing machine for low piston velocities (up to 0.9 m/s) performance evaluation. For performance evaluation at high piston velocities (up to 2.2 m/s), the MRSA is tested under impact loading on a rail-guided mass-drop test stand. Equivalent viscous damping is used to characterize the controllable damping behavior of the MRSA. To describe the time response of the MRSA, a dynamic model is developed based on geometrical parameters and MR fluid properties.
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Lu, Min, Judah Ari-Gur, and John Garety. "Study of Automotive Hydrobushing in Off-Axis Vibration." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/de-23208.
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Abstract A model was developed for the dynamic behavior of a misaligned hydrobushing, which is forced to oscillate in directions that are not aligned with the axis of the fluid chambers. It was found that the displacement of the fluid in the inertia track and of the equivalent piston peak at the fluid resonant frequency, but they decrease when the off-axis angle increases. Similarly, the fluid pressure difference between the chambers peaks at the fluid resonant frequency and it decreases when the off-axis angle increases. The dynamic stiffness and loss angle are functions of the off-axis angle and become less and less sensitive to the frequency when the off-axis angle increases. At high frequencies, the dynamic stiffness is the sum of the static stiffness and the equivalent volumetric stiffness. A comparison of the measured and calculated equivalent volumetric stiffness shows good correlation. But further work is needed to improve the accuracy of the dynamic stiffness and loss angle prediction.
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Zhang, X. Y., J. Guo, and Zhang Wenping. "Dynamic Analysis of the Crank Train in a Single Cylinder Diesel Engine Using a Lumped Parameter Method." In ASME 2016 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icef2016-9337.
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The kinematic and dynamic behaviors of the crank train in a single cylinder diesel engine are analyzed in the paper. The crank train mechanism consists of four parts: a crank without counterweight, a connecting rod, a piston associated with a cylinder and two stops at both ends of a stroke. The dynamic model is developed using a lumped parameter method. The inertia of mass or moment are considered by an equivalent treatment in the centers of the piston pin, the crank pin, the main journal, respectively. The longitudinal deformations of the connecting rod are simulated by spring-damping elements, as well as the angular and bending deformations of the crank. As a result, it was possible to predict the effects of the component inertia of mass or moment and stiffness on the internal force and rotating speed of the crank under the cylinder pressure.
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Robinson, Ryan, Wei Hu, and Norman M. Wereley. "Magnetorheological Energy Absorbers Employing a Valve Filled With Porous Media." In ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2008. http://dx.doi.org/10.1115/smasis2008-563.
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The effects of porous media selection on the performance of a porous-valve-based magnetorheological (MR) damper are evaluated. Important media parameters affecting the damper performance, i.e. porosity and morphology (shape), are identified using flow analysis. The relationship between the controllable force of the damper and the porous valve characteristics is studied for three types of porous media. Equivalent damping is determined, and damping performance is compared. Effects of piston-valve area ratio on damper performance are also evaluated. A nonlinear hysteretic biviscous model is applied to the damper and the experimental results are compared with predicted results.
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Diaz, German Amador, John Turizo Santos, Elkin Hernandez, Ricardo Vasquez Padilla, and Lesme Corredor. "Maximum Power From Fluid Flow: Results From the First and Second Laws of Thermodynamics." In ASME 2012 6th International Conference on Energy Sustainability collocated with the ASME 2012 10th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/es2012-91216.
Full textAbstract:
The heat transfer principle of power maximization in power plants with heat transfer irreversibilities was cleverly extended by Bejan [1] to fluid flow, by obtaining that the energy conversion efficiency at maximum power is ηmax = 1/2(1 − P2/P1). This result is analog to the efficiency at maximum power for power plants, ηmax = 1 − (T2/T1)1/2 which was deduced by Curzon and Ahlborn [2]. In this paper, the analysis to obtain maximum power output delivered from a piston between two pressure reservoir across linear flow resistance is generalized by considering the piston cylinder friction, by obtaining relations of maximum power output and optimal speed of the piston in terms of first law efficiency. Expressions to relate the power output, cross sectional area of the chamber and first law efficiency, were deduced in order to evaluate the influence of the overall size constraints and fluid regime in the performance of the piston cylinder system. Flow in circular ducts and developed laminar flow between parallel plates, are considered to demonstrate that when two pressure reservoirs oriented in counterflow, with different and arbitrary cross sectional area, must have the same area in order to maximize the power output of the system. These results introduce some modifications to the results obtained by Bejan [1] and Chen [3]. This paper extends the Bejan and Chen’s work by estimating under turbulent regime the lost available work rate associated with the degree of irreversibilities caused by the flow resistances of the system. This analysis is equivalent to evaluate the irreversibilities in an endoirreversible Carnot heat engine model caused by the heat resistance loss between the engine and its surrounding heat reservoirs. This paper concludes with an application to illustrate the practical applications by estimating the lost available work of an actual steady-flow turbine and the layout pipes upstream and downstream of the same device.