The Experts below are selected from a list of 10179 Experts worldwide ranked by ideXlab platform
Andrea Vacca - One of the best experts on this subject based on the ideXlab platform.
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modeling and validation of hydro mechanical losses in pressure compensated External Gear machines
Mechanism and Machine Theory, 2021Co-Authors: Rituraj Rituraj, Andrea Vacca, Manuel RigosiAbstract:Abstract During the operation of External Gear machines (EGMs), the friction between the internal components results in the loss of hydro-mechanical (or torque) performance of these units. However, current EGM simulation models either do not consider these losses or have significant limitations in their approach. This paper presents a novel methodology for modeling the hydro-mechanical losses in EGMs. The sources of torque losses considered are the friction at the Gears’ tooth tips, lateral surfaces, shafts, and meshing interfaces. The friction models are developed for each of these sources considering the effects of micromotion of the Gears and bushings. Further, the effects of elastohydrodynamic lubrication (EHL) are considered in the modeling of meshing friction. The friction models are integrated in a lumped parameter simulation tool, and the operation of a commercial Gear pump is simulated. From the simulation results, the meshing friction is determined to be the dominant source of torque losses. Further, the hydro-mechanical efficiencies predicted by the model are found to match those observed in the experiments indicating the validity of the model developed in this work.
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Thermal Modelling of External Gear Machines and Experimental Validation
Energies, 2020Co-Authors: Rituraj Rituraj, Andrea Vacca, Mario Antonio MorselliAbstract:The flow of energy within External Gear machines (EGMs) leads to the variation of fluid temperature in the EGMs, which affects their performance. However, the common approaches for the simulation of EGMs assume isothermal conditions. This isothermal assumption negatively impacts their modelling accuracy in terms of the internal flows which are dependent on the fluid temperature (via fluid properties). This paper presents a lumped parameter based thermal model of EGMs where the fluid temperature in the EGM is evaluated considering the effects of compression/expansion, internal flows, and power losses. Further, numerical techniques are developed to model each of these three aspects. The thermal model is validated via the outlet temperature and volumetric efficiency measurements obtained from experiments conducted on six units of an EGM taken as a reference with different internal clearances. The results from the model show that the fluid temperature increases as it is carried from the inlet side to the outlet side during the pumping operation. However, the fluid at the ends of the shafts has the highest temperature. By comparing the isothermal simulation results with the proposed thermal model, the results also point out how the isothermal assumption becomes inaccurate, particularly in conditions of low volumetric efficiency.
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on the lubrication performance of External Gear pumps for aerospace fuel delivery applications
Mechanical Systems and Signal Processing, 2019Co-Authors: Divya Thiagarajan, Andrea Vacca, Stephanie WatkinsAbstract:Abstract External Gear pumps (EGPs) are one of the most common choices in aerospace engines as a fuel delivery pump. These units usually include a pressure compensation system that defines the lubricating gap at the lateral side of the Gears. This lubricating interface is a critical design aspect, which strongly affects the reliability as well as the mechanical and volumetric efficiencies of the pump. Major challenges in designing these lubricating gaps in aero engine fuel pumps, include high operating speeds, delivery pressures and low viscosity of the working fluids. Virtual prototyping methods present a fast and efficient design tool and have the potential to improve the EGP’s reliability and efficiency. This paper presents a study on the pressure compensation system of a fuel delivery EGP and shows how the presence of frictional forces opposing the motion of the compensating element significantly affect the lubricating performance of the unit. The presence of these frictional forces produces an effect of hysteresis on the axial balance system, so that the lubricating gaps that develop within the pump at a certain operating condition depend on the previous operating state. This effect was captured in an experimental setup purposely developed for this study at Rolls-Royce. Within this work, this behavior was also reproduced numerically, through a coupled fluid structure interaction – elastohydrodynamic (EHD) model that includes the modeling of these frictional forces. After detailing the implementation of the lateral gap model, this paper presents measurements from carefully conducted experiments which correlate with the simulated predictions of the influence of frictional forces on the performance of a reference EGP design under study.
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Theoretical Investigation into the Ripple Source of External Gear Pumps
MDPI AG, 2019Co-Authors: Xinra Zhao, Andrea VaccaAbstract:External Gear pumps are among the most popular fluid power positive displacement pumps, however they often suffer of excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power system, a better understanding of the ripple source of Gear pumps is desirable. This paper presents a novel approach for the analysis of the ripple source of Gear pumps based on decomposition into a kinematic component and a pressurization component. The pump ripple can be regarded as the superposition of the displacement solution and the pressurization solution. The displacement solution is driven by the kinematic flow, and it can be derived from the kinematic flow theory; instead, the pressurization solution can be approximated by overlapping the pressurization flow for a single displacement chamber. Furthermore, in this way the changes of these two components with modification of the delivery circuit are determined in both analytical and numerical ways. The result of this analysis provides a good interpretation of the pulsation simulated by a detailed lumped-parameter simulation model, thus showing its validity. The result also indicates that the response of two ripple sources to the change of the loading in the downstream hydraulic circuit is very different. These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work
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A comparison of helical and spur External Gear machines for fluid power applications: Design and optimization
Mechanism and Machine Theory, 2019Co-Authors: Thomas Ransegnola, Xinran Zhao, Andrea VaccaAbstract:Abstract This paper addresses the problem of determining the relative performance of spur and helical External Gear pumps (EGPs) for fluid power applications. Helical EGPs are commonly considered as quieter units than spur ones; however, there is no specific study reported in literature that proves such claim. Similarly, it is hard to find data indicating which design is better in terms of compactness or energy performance. To tackle this problem, a procedure is developed for virtual design optimization of both helical and spur Gear EGPs. This includes addressing the two fundamental challenges of the work, parameterizing a generic EGP design and quantifying its performance. By applying this procedure, a genetic algorithm can continue improving from generation to generation, until the pareto optimal set of designs is identified for both helical and spur units. In the comparison of these, the differences between the two configurations will be identified and the fundamental question of this work can be answered; are helical Gears ‘better’ than spur Gears?
Sujan Dhar - One of the best experts on this subject based on the ideXlab platform.
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improvement of lubrication performance in External Gear machines through micro surface wedged Gears
Tribology Transactions, 2017Co-Authors: Divya Thiagarajan, Sujan Dhar, Andrea VaccaAbstract:ABSTRACTThis article demonstrates how a properly designed micro-surface linear wedge added to the lateral surfaces of the Gear teeth can improve the lubricating ability of External Gear machines (EGMs), resulting in lower power losses and chance of wear during their operation. The approach of study is based on the use of a fluid structure interaction (FSI) model for the analysis of the lateral lubricating gaps developed in the authors' research team. Such a model is used to determine the best design of the wedged Gear by considering the overall axial balance problem of pressure compensated EGMs for high-pressure applications. The article shows the numerical predictions along with the experimental verifications of the advantages offered by the proposed solution in terms of torque loss reduction for a particular reference pump.
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a novel fluid structure interaction ehd model and optimization procedure for an asymmetrical axially balanced External Gear machine
Tribology Transactions, 2015Co-Authors: Divya Thiagarajan, Sujan Dhar, Andrea VaccaAbstract:This article presents a novel fluid structure interaction (FSI) model for lateral lubricating interfaces in an asymmetrically balanced External Gear pump. Due to the asymmetry in the geometry of the floating lateral bushes responsible for sealing the displacement chambers in such machines, the lubricating interfaces on either side of the Gears have been modeled as distinct but coupled lubricating films. An elastohydrodynamic (EHD) lubrication regime was modeled in all simulations and film thickness predictions for both lubricating interfaces have been achieved. The novel FSI model for the asymmetric lateral gaps is then used in an automatic optimization procedure to design the optimal axial balance in the reference External Gear machine (EGM). The optimal axial balance is achieved by determining the optimal balance area on the lateral bush by considering specific design variables associated with it. The procedure aims to find the best feasible design solution that minimizes the total power losses in the l...
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A novel FSI–thermal coupled TEHD model and experimental validation through indirect film thickness measurements for the lubricating interface in External Gear machines
Tribology International, 2015Co-Authors: Sujan Dhar, Andrea VaccaAbstract:Abstract A novel fluid–structure interaction–thermal coupled model for the lateral lubricating gaps between Gears and lateral bushes in External Gear machines (EGM) is presented in this study. The model is the first of the lateral lubricating interface in EGMs capable of considering heat transfer, thermal effects in the fluid film and solid components as well as thermo-elastic deformation of the solids enabling prediction of the film thickness in EGM lateral gaps considering thermoelastohydrodynamic lubrication. Model validation is performed using lateral gap leakage measurement which is dependent on absolute film thickness. A novel relative lubricant film thickness measurement method in Gear machines using capacitive sensors is also presented, and used to validate the spatial film thickness predictions from the model.
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a novel fsi thermal coupled tehd model and experimental validation through indirect film thickness measurements for the lubricating interface in External Gear machines
Tribology International, 2015Co-Authors: Sujan Dhar, Andrea VaccaAbstract:Abstract A novel fluid–structure interaction–thermal coupled model for the lateral lubricating gaps between Gears and lateral bushes in External Gear machines (EGM) is presented in this study. The model is the first of the lateral lubricating interface in EGMs capable of considering heat transfer, thermal effects in the fluid film and solid components as well as thermo-elastic deformation of the solids enabling prediction of the film thickness in EGM lateral gaps considering thermoelastohydrodynamic lubrication. Model validation is performed using lateral gap leakage measurement which is dependent on absolute film thickness. A novel relative lubricant film thickness measurement method in Gear machines using capacitive sensors is also presented, and used to validate the spatial film thickness predictions from the model.
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a fluid structure interaction ehd model of the lubricating gaps in External Gear machines formulation and validation
Tribology International, 2013Co-Authors: Sujan Dhar, Andrea VaccaAbstract:Abstract This paper presents a fluid structure interaction (FSI) model for the simulation of the flow in the lubricating gaps between Gears and lateral bushes in External Gear machines (EGMs). The proposed model is capable of accounting for elasto-hydrodynamic effects in the lubricant film, and can predict the lubricant film thickness. Three different constraint methods are considered as concerns the structural problem: “ideally supported”, “inertia relief” and a “low pressure” constraint specifically formulated for EGMs. The proposed model is validated against measurements performed on an experimental prototype. Detailed formulation of the FSI model as well as significant simulation results are presented for a wide range of operating conditions along with comparison to experimental results.
Manuel Rigosi - One of the best experts on this subject based on the ideXlab platform.
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modeling and validation of hydro mechanical losses in pressure compensated External Gear machines
Mechanism and Machine Theory, 2021Co-Authors: Rituraj Rituraj, Andrea Vacca, Manuel RigosiAbstract:Abstract During the operation of External Gear machines (EGMs), the friction between the internal components results in the loss of hydro-mechanical (or torque) performance of these units. However, current EGM simulation models either do not consider these losses or have significant limitations in their approach. This paper presents a novel methodology for modeling the hydro-mechanical losses in EGMs. The sources of torque losses considered are the friction at the Gears’ tooth tips, lateral surfaces, shafts, and meshing interfaces. The friction models are developed for each of these sources considering the effects of micromotion of the Gears and bushings. Further, the effects of elastohydrodynamic lubrication (EHL) are considered in the modeling of meshing friction. The friction models are integrated in a lumped parameter simulation tool, and the operation of a commercial Gear pump is simulated. From the simulation results, the meshing friction is determined to be the dominant source of torque losses. Further, the hydro-mechanical efficiencies predicted by the model are found to match those observed in the experiments indicating the validity of the model developed in this work.
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study of a high pressure External Gear pump with a computational fluid dynamic modeling approach
Energies, 2017Co-Authors: Emma Frosina, Adolfo Senatore, Manuel RigosiAbstract:A study on the internal fluid dynamic of a high-pressure External Gear pump is described in this paper. The pump has been analyzed with both numerical and experimental techniques. Starting from a geometry of the pump, a three-dimensional computational fluid dynamics (CFD) model has been built up using the commercial code PumpLinx®. All leakages have been taken into account in order to estimate the volumetric efficiency of the pump. Then the pump has been tested on a test bench of Casappa S.p.A. Model results like the volumetric efficiency, absorbed torque, and outlet pressure ripple have been compared with the experimental data. The model has demonstrated the ability to predict with good accuracy the performance of the real pump. The CFD model has been also used to evaluate the effect on the pump performance of clearances in the meshing area. With the validated model the pressure inside the chambers of both driving and driven Gears have been studied underlining cavitation in meshing fluid volume of the pump. For this reason, the model has been implemented in order to predict the cavitation phenomena. The analysis has allowed the detection of cavitating areas, especially at high rotation speeds and delivery pressure. Isosurfaces of the fluid volume have been colored as a function of the total gas fraction to underline where the cavitation occurs.
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Modeling noise sources and propagation in External Gear pumps
Energies, 2017Co-Authors: Sangbeom Woo, Timothy Opperwall, Andrea Vacca, Manuel RigosiAbstract:As a key component in power transfer, positive displacement machines often represent the major source of noise in hydraulic systems. Thus, investigation into the sources of noise and discovering strategies to reduce noise is a key part of improving the performance of current hydraulic systems, as well as applying fluid power systems to a wider range of applications. The present work aims at developing modeling techniques on the topic of noise generation caused by External Gear pumps for high pressure applications, which can be useful and effective in investigating the interaction between noise sources and radiated noise and establishing the design guide for a quiet pump. In particular, this study classifies the internal noise sources into four types of effective load functions and, in the proposed model, these load functions are applied to the corresponding areas of the pump case in a realistic way. Vibration and sound radiation can then be predicted using a combined finite element and boundary element vibro-acoustic model. The radiated sound power and sound pressure for the different operating conditions are presented as the main outcomes of the acoustic model. The noise prediction was validated through comparison with the experimentally measured sound power levels.
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a general method to determine the optimal profile of porting grooves in positive displacement machines the case of External Gear machines
2016Co-Authors: Sidhant Gulati, Andrea Vacca, Manuel RigosiAbstract:In all common hydrostatic pumps, compressibility affects the commutation phases of the displacing chambers, as they switch their connection from/to the inlet to/from the outlet port, leading to pressure peaks, localized cavitation, additional port flow fluctuations and volumetric efficiency reduction. In common pumps, these effects are reduced by proper grooves that realizes gradual port area variation in proximity of these transition regions. This paper presents a method to automatically find the optimal designs of these grooves, taking as reference the case of External Gear pumps. The proposed procedure does not assume a specific geometric morphology for the grooves, and it determines the best feasible designs through a multi-objective optimization procedure. A commercial Gear pump is used to experimentally demonstrate the potentials of the proposed method, for a particular case aimed at reducing delivery flow oscillations.
Adolfo Senatore - One of the best experts on this subject based on the ideXlab platform.
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A Numerical Analysis of an Innovative Flow Ripple Reduction Method for External Gear Pumps
Energies, 2021Co-Authors: Gianluca Marinaro, Emma Frosina, Adolfo SenatoreAbstract:In this paper, an innovative solution to minimize noise emission, acting on the flow ripple, in a prototype External Gear Pump (EGP) is presented. Firstly, a new tool capable to completely simulate this pump’s typologies, called EgeMATor, is presented; the hydraulic model, adopted for the simulation, is based on a lumped parameter method using a control volume approach. Starting from the pump drawing, thanks to different subroutines developed in different environments interconnected, it is possible to analyze an EGP. Results have been compared with the outputs of a three-dimensional CFD numerical model built up using a commercial code, already used with success by the authors. In the second section, an innovative solution to reduce the flow ripple is implemented. This technology is called Alternative Capacitive Volumes (ACV) and works by controlling and uniformizing the reverse flow, performing a consistent reduction of flow non-uniformity amplitude. In particular, a high reduction of the flow non-uniformity is notable in the frequency domain on the second fundamental frequency. The technology is easy to accommodate in a pump housing, especially for high-pressure components, and it helps with reducing the fluid-borne noise.
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study of a high pressure External Gear pump with a computational fluid dynamic modeling approach
Energies, 2017Co-Authors: Emma Frosina, Adolfo Senatore, Manuel RigosiAbstract:A study on the internal fluid dynamic of a high-pressure External Gear pump is described in this paper. The pump has been analyzed with both numerical and experimental techniques. Starting from a geometry of the pump, a three-dimensional computational fluid dynamics (CFD) model has been built up using the commercial code PumpLinx®. All leakages have been taken into account in order to estimate the volumetric efficiency of the pump. Then the pump has been tested on a test bench of Casappa S.p.A. Model results like the volumetric efficiency, absorbed torque, and outlet pressure ripple have been compared with the experimental data. The model has demonstrated the ability to predict with good accuracy the performance of the real pump. The CFD model has been also used to evaluate the effect on the pump performance of clearances in the meshing area. With the validated model the pressure inside the chambers of both driving and driven Gears have been studied underlining cavitation in meshing fluid volume of the pump. For this reason, the model has been implemented in order to predict the cavitation phenomena. The analysis has allowed the detection of cavitating areas, especially at high rotation speeds and delivery pressure. Isosurfaces of the fluid volume have been colored as a function of the total gas fraction to underline where the cavitation occurs.
Giorgio Dalpiaz - One of the best experts on this subject based on the ideXlab platform.
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simulation of the running in process in External Gear pumps and experimental verification
Meccanica, 2012Co-Authors: Emiliano Mucchi, Gianluca Delia, Giorgio DalpiazAbstract:Before marketing External Gear pumps are subjected to a running in process to increase their efficiency. However, this is one of the most time-consuming tasks of the entire manufacturing process. Therefore, a mathematical model for optimizing the running in process can be a useful tool for time-to-market reduction. In particular, in this paper a model for the analysis of the dynamic behaviour of External Gear pumps, developed by the authors in previous works, is modified and used for simulating the running in process. The modified model is presented and validated via experimental data. A good correlation between simulation and test results guarantees the effectiveness of the model in determining the amount and the distribution of the removed material during the running in process. A meaningful reduction (16%) of the global running in time has been achieved with the introduction of a modified running in process drawn from simulation results.
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A Robust Design Optimization Methodology for External Gear Pumps
ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis Volume 4, 2010Co-Authors: Emiliano Mucchi, Gabriele Tosi, Roberto D’ippolito, Giorgio DalpiazAbstract:This work addresses the topic of External Gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors, a hybrid lumped-parameter/finite-element model has been developed, in order to foresee the pump dynamic behaviour in terms of Gear and casing acceleration. The model includes the main important phenomena involved in the pump operation and it has been validated on the basis of experimental data. In this research, an original optimization process has been applied to such a hybrid model in order to reduce the pump vibration level, i.e. the acceleration of the External casing. The set up of the optimization process comprises a single objective (case accelerations) and some operational and geometrical input variables (oil viscosity, oil Bulk modulus, relief groove dimension and radial clearance in the journal bearings). This paper compares three optimization methodologies for the optimization of the pump vibration level. In particular common optimization processes based on simulations are compared with a combined analysis based, firstly, on Design Of Experiments (DOE) and Response Surface Modelling (RSM) and, secondly, on the application of evolutionary algorithms to reach the optimal variable combination. The different methodologies are compared in terms of time efficiency and accuracy in the solution. Finally, a robust design process has been carried out in order to consider the manufacturing tolerances of the real pump and assess their effect on the performance of the component. The results offer important information and design insights that would be very difficult to obtain without such procedures.© 2010 ASME
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A Hybrid LP/FE Model for the Dynamic Analysis of External Gear Pumps
Volume 9: Mechanical Systems and Control Parts A B and C, 2007Co-Authors: Emiliano Mucchi, Valerio Venturi, Giorgio DalpiazAbstract:In this work a hybrid lumped-parameter finite-element model of an External Gear pump for automotive applications is presented and experimentally assessed; the finite element (FE) model regards the External parts of the pump (case and end plates) while the lumped-parameter (LP) model regards the interior parts (bushes and Gears). The LP model is a non linear kineto-elastodynamic model and includes the most important phenomena involved in the pump operation as time-varying oil pressure distribution on Gears, time-varying meshing stiffness and hydrodynamic journal bearing reactions. A forced vibration analysis has been carried out by means of the FE model for the evaluation of the acceleration levels on the External surfaces of the pump; for this analysis, the damping has been estimated using data coming from an experimental modal analysis (EMA) whereas the excitation forces, acting on the internal surface of the case due to bearing reactions and pressure forces, have been obtained from the LP model. In this sense the model is globally a hybrid LP/FE model. The model has been assessed using experiments: the experimental accelerations measured during run-up tests have been compared with the simulated accelerations coming from the FE/LP model. Finally the assessed model has been used in order to identify the effects of design parameters in terms of case vibrations.Copyright © 2007 by ASME
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Modeling Run in Process in External Gear Pumps
Volume 3: Dynamic Systems and Controls Symposium on Design and Analysis of Advanced Structures and Tribology, 2006Co-Authors: Giorgio Dalpiaz, Gianluca D’elia, Emiliano MucchiAbstract:In this work, the authors have developed a mathematical model that simulates the run in of External Gear pumps, as an useful tool in the optimization of this time-consuming process. The model calculates the wear profile of the case by enveloping the tip circle of the Gears concerning all the run in steps. For each step, the positions of the Gear centers are obtained by the equilibrium between pressure forces and torques due to the pressure distribution, meshing forces and hydrodynamic journal bearing reactions. The pressure distribution depends on the clearance between case and Gears, so for each run in step, since the positions of the Gear centers change, the pressure distribution is recalculated considering the wear profile obtained in the previous step. Besides, the model also estimates the quantity of material taken away in each step and it shows the effects of modifications in the run in parameters (time, pressure and speed). In particular, the simulation results indicate that a meaningful reduction of run in global time, can be obtained by increasing the duration of the steps that remove the greater part of material and by decreasing the duration of the other steps. This model is used by TRW Automotive Italia S.p.A. (section Automotive Pumps, Ostellato, Italy) to improve the run in process with good reduction in manufacturing-time.Copyright © 2006 by ASME
