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Dr. Andrea Vacca
Maha Fluid Power Research Center, School of Mechanical Engineering, Agricultural and Biological Engineering, Purdue University, 1500 Kepner Dr. Lafayette 47905-6578 IN, USA

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Research Keywords & Expertise

0 Gear Pumps
0 Fluid power systems
0 Positive displacement machines
0 Hydraulic control valves
0 Aeration and cavitation in fluid power systems

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Gear Pumps
Positive displacement machines
Fluid power systems
Hydraulic control valves

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Journal article
Published: 01 July 2021 in Journal of Dynamic Systems, Measurement, and Control
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Counterbalance valves (CBVs) are widely used in hydraulic machines handling gravitational loads. They are usually adopted in hydraulic circuits that set the flow to the actuator with either metering control strategies or primary control strategies. In these circuits, the CBV does not determine the actuator velocity, but it establishes a proper counterpressure that balances the actuator during overrunning loads. A well-known problem of CBVs is the excessive power consumption introduced into the circuit, which is due to an excessive pressurization of the flow supply. This paper presents a solution for using CBVs to control the actuator velocity while also reducing energy consumption. The method consists in controlling the pilot port of the CBV through an external pressure source (adjustable pilot). The solution is first studied analytically, considering all the possible loading conditions at the actuator. Two different control strategies are presented: the "Smart CBV", where the CBV does not control the actuator velocity but it minimizes the system pressure; and the "Smart System" that uses the CBV to efficiently control the actuator velocity during overrunning load conditions. An experimental validation of the proposed solutions is also provided, taking as reference a truck-mounted hydraulic crane. The results of the proposed solutions are compared to those achieved by the traditional circuit of the reference hydraulic crane which uses standard CBVs. For both cases of "Smart CBV" and "Smart System", a remarkable power saving respectively up to 75% and up to 90% is observed.

ACS Style

Annalisa Sciancalepore; Andrea Vacca; Steven T. Weber. An Energy Efficient Method for Controlling Hydraulic Actuators Using Counterbalance Valves with Adjustable Pilot. Journal of Dynamic Systems, Measurement, and Control 2021, 1 .

AMA Style

Annalisa Sciancalepore, Andrea Vacca, Steven T. Weber. An Energy Efficient Method for Controlling Hydraulic Actuators Using Counterbalance Valves with Adjustable Pilot. Journal of Dynamic Systems, Measurement, and Control. 2021; ():1.

Chicago/Turabian Style

Annalisa Sciancalepore; Andrea Vacca; Steven T. Weber. 2021. "An Energy Efficient Method for Controlling Hydraulic Actuators Using Counterbalance Valves with Adjustable Pilot." Journal of Dynamic Systems, Measurement, and Control , no. : 1.

Journal article
Published: 30 April 2021 in Journal of Dynamic Systems, Measurement, and Control
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This paper proposes a novel hybrid power-split transmission to drive hydraulic implements in construction machinery. The highly efficient power-split hybrid transmission is combined with displacement controlled (DC) actuators to eliminate throttling losses within the hydraulic system and achieve higher fuel savings. The architecture design, sizing and power management are addressed. Simulation results considering a realistic truck-loading cycle on a mini excavator demonstrate the feasibility of the idea. A systematic comparison between the proposed system and the previously developed series-parallel hybrid is also carried out. The paper compares engine operation and fuel consumption of the previously mentioned hybrid system with the original non-hybrid load-sensing machine. It is shown that by implementing an efficient engine operation control, the proposed system can achieve up to 60.2% improvement in fuel consumption when compared to the original machine and consume 11.8% less than the previously developed series-parallel hybrid with DC actuation. Other advantages of the proposed solution include a much steadier engine operation, which opens to the possibility of designing an engine for optimal consumption and emissions at a single operating point as well as greatly reduce pollutant emissions. A steadier prime mover operation should also benefit fully electric machines, as the battery would not be stressed with heavy transients.

ACS Style

Mateus Bertolin; Andrea Vacca. An Energy Efficient Power-Split Hybrid Transmission System to Drive Hydraulic Implements in Construction Machines. Journal of Dynamic Systems, Measurement, and Control 2021, 1 .

AMA Style

Mateus Bertolin, Andrea Vacca. An Energy Efficient Power-Split Hybrid Transmission System to Drive Hydraulic Implements in Construction Machines. Journal of Dynamic Systems, Measurement, and Control. 2021; ():1.

Chicago/Turabian Style

Mateus Bertolin; Andrea Vacca. 2021. "An Energy Efficient Power-Split Hybrid Transmission System to Drive Hydraulic Implements in Construction Machines." Journal of Dynamic Systems, Measurement, and Control , no. : 1.

Journal article
Published: 16 January 2021 in Tribology International
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Axial piston machines of swash plate design rely on three main lubricating interfaces to support the load on their slippers, pistons, and cylinder block. The respective loads on these parts are carried by the fluid pressure in these interfaces— pressure from hydrostatic sources (from the inlet and outlet ports of the pump), as well as hydrodynamic pressure, generated by the relative motion of the surfaces that border a fluid film. The present work investigates how the hydrostatic and hydrodynamic components of fluid pressure compare in terms of their importance to load support in the three interfaces. A methodology is proposed to calculate these two fluid pressure components, and their contributions to load support, for each interface in a given unit, at a given operating condition. Separating the interface's fluid pressure fields, and the forces they generate, into their hydrostatic and hydrodynamic components offers a novel view into the load-support mechanism of the interfaces, and how they compare to each other. Moreover, the proposed methodology can easily be adapted to bent axis machines. Through a case study involving a 75 cc commercial unit, the proposed methodology shows that the hydrodynamic contribution to load support in two of the interfaces of axial piston machines of swash plate design can significantly exceed the estimates typically provided in literature, and that in the third interface, the force from hydrostatic fluid pressure can be so large that less than 60% of it is required to balance the load, and over 40% of it is excess— i.e. it becomes the load force.

ACS Style

Meike Ernst; Andrea Vacca. Hydrostatic vs. hydrodynamic components of fluid pressure in the tribological interfaces of axial piston machines. Tribology International 2021, 157, 106878 .

AMA Style

Meike Ernst, Andrea Vacca. Hydrostatic vs. hydrodynamic components of fluid pressure in the tribological interfaces of axial piston machines. Tribology International. 2021; 157 ():106878.

Chicago/Turabian Style

Meike Ernst; Andrea Vacca. 2021. "Hydrostatic vs. hydrodynamic components of fluid pressure in the tribological interfaces of axial piston machines." Tribology International 157, no. : 106878.

Journal article
Published: 07 January 2021 in Mechanism and Machine Theory
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Gerotors are positive displacement machines known for being cost-effective, durable, compact, and quiet and are used in many low-pressure applications. Nearly any smooth curve can define a gerotor gearset, yet three conventional profile types that are based on either epitrochoids, hypotrochoids, or cycloids are used almost exclusively in industry. Although each of the profile types has been known since the early 20th century, no extensive comparison has been made between them. In the present work a multi-objective optimization strategy using a genetic algorithm is used to find the Pareto front for each profile type when considering seven performance goals. The optimal designs of each profile type were combined, and a new set of Pareto designs was identified. The results showed that no single profile type can be considered universally better than the others. However, some observations about the general trade-offs for each profile type are presented, and the work serves as a baseline for development of novel gerotor profiles.

ACS Style

Andrew J. Robison; Andrea Vacca. Performance comparison of epitrochoidal, hypotrochoidal, and cycloidal gerotor gear profiles. Mechanism and Machine Theory 2021, 158, 104228 .

AMA Style

Andrew J. Robison, Andrea Vacca. Performance comparison of epitrochoidal, hypotrochoidal, and cycloidal gerotor gear profiles. Mechanism and Machine Theory. 2021; 158 ():104228.

Chicago/Turabian Style

Andrew J. Robison; Andrea Vacca. 2021. "Performance comparison of epitrochoidal, hypotrochoidal, and cycloidal gerotor gear profiles." Mechanism and Machine Theory 158, no. : 104228.

Journal article
Published: 16 December 2020 in Energies
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This paper presents the experimental characterization of the vibroacoustic fields and the evaluation of noise performances of hydraulic pumps. Research on hydraulic pump noise has traditionally focused on the fluid-borne noise sources, and very often the analyses of vibration and noise have been performed focusing on a few local points. This trend results in the lack of investigation on the overall behaviors of vibroacoustic fields of hydraulic pumps, and it has been one of the obstacles to understand the complete mechanisms of noise generation. Moreover, despite the existence of the ISO standards for the determination of noise levels, diverse metrics have been used for the evaluation of noise performances of the pumps, but the adequacy of these metrics has not been carefully examined. In this respect, this paper aims at introducing a way to characterize and interpret the measured vibroacoustic field and providing proper methods which are also capable of applying the ISO standards for the fair assessment of pump noise performances. For the characterization of the vibroacoustic field, operational deflection shapes (ODS) and corresponding radiated sound fields are visualized at harmonics of the pumping frequency by using a spectral analysis. Observations are made regarding the motions of the pump and its mounting plate and the resultant radiated noise, depending on the frequency, as well as their correlation. A numerical analysis using the Rayleigh integral equation is also performed to further investigate the contribution of the mounting plate motion on the noise radiation. For the evaluation of noise performance, two different units are tested at multiple operating conditions, and comparisons are made based on their measured sound power levels (SWLs) and sound pressure levels (SPLs). The results emphasize the importance of SWL measurement for the fair noise performance evaluation, and the two methods are proposed as practices to determine the minimum number of measurement points for practicability and to have reliable sound power determination for hydraulic pumps.

ACS Style

Sangbeom Woo; Andrea Vacca. Experimental Characterization and Evaluation of the Vibroacoustic Field of Hydraulic Pumps: The Case of an External Gear Pump. Energies 2020, 13, 6639 .

AMA Style

Sangbeom Woo, Andrea Vacca. Experimental Characterization and Evaluation of the Vibroacoustic Field of Hydraulic Pumps: The Case of an External Gear Pump. Energies. 2020; 13 (24):6639.

Chicago/Turabian Style

Sangbeom Woo; Andrea Vacca. 2020. "Experimental Characterization and Evaluation of the Vibroacoustic Field of Hydraulic Pumps: The Case of an External Gear Pump." Energies 13, no. 24: 6639.

Journal article
Published: 11 December 2020 in Mechanical Systems and Signal Processing
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The internal leakage flows in external gear and gerotor pumps are often represented by flow through curved constrictions. The nature of this flow can vary from laminar to turbulent and the flow can experience localized cavitation too. In the current literature, there is a scarcity of techniques for accurately modelling such curve-constricted flows which limits the accuracy of the current simulation tools for gear pumps. This paper presents a novel flow model for curve-constricted geometries that is applicable over a wide range of flow regimes including localized cavitation. Using a dimensionless form, the proposed model characterizes the constriction flow velocity as the function of the constriction shape, the pressure difference, and a properly defined cavitation indicator. The functional relationships between these dimensionless parameters are developed based on CFD simulations. The flow model is validated by the means of several experiments conducted on a custom test apparatus. The model presented in this paper can be incorporated in the lumped parameter simulation tools widely used for modelling gear pumps, improving their accuracy in predicting the internal leakages. Consequently, this model will also aid the development of novel energy efficient gear pump designs, where such leakages are kept to a minimum.

ACS Style

Rituraj Rituraj; Andrea Vacca. Investigation of flow through curved constrictions for leakage flow modelling in hydraulic gear pumps. Mechanical Systems and Signal Processing 2020, 153, 107503 .

AMA Style

Rituraj Rituraj, Andrea Vacca. Investigation of flow through curved constrictions for leakage flow modelling in hydraulic gear pumps. Mechanical Systems and Signal Processing. 2020; 153 ():107503.

Chicago/Turabian Style

Rituraj Rituraj; Andrea Vacca. 2020. "Investigation of flow through curved constrictions for leakage flow modelling in hydraulic gear pumps." Mechanical Systems and Signal Processing 153, no. : 107503.

Journal article
Published: 17 November 2020 in Energies
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A novel virtual prototyping algorithm has been developed to design one of the most critical lubricating interfaces in axial piston machines of the swash plate type—the piston–cylinder interface—for operation with water as the working fluid. Due to its low viscosity, the use of water as a lubricant can cause solid friction and wear in these machines at challenging operating conditions. The prototyping algorithm compensates for this by tailoring the shape of the bore surface that guides the motion of each piston in this type of positive displacement machine to conform with the piston surface, taking into account both the piston’s tilt and its deformation. Shaping these surfaces in this manner can render the interface more conducive to generating hydrodynamic pressure buildup that raises its load-carrying capacity. The present work first outlines the structure of the proposed algorithm, then presents a case study in which it is employed to design a bore surface shape for use with two prototypes, one virtual and one physical—both modified versions of a 444 cc commercial axial piston pump. Experimental testing of the physical prototype shows it to achieve a significantly higher maximum total efficiency than the stock unit.

ACS Style

Meike Ernst; Andrea Vacca; Monika Ivantysynova; Georg Enevoldsen. Tailoring the Bore Surfaces of Water Hydraulic Axial Piston Machines to Piston Tilt and Deformation. Energies 2020, 13, 5997 .

AMA Style

Meike Ernst, Andrea Vacca, Monika Ivantysynova, Georg Enevoldsen. Tailoring the Bore Surfaces of Water Hydraulic Axial Piston Machines to Piston Tilt and Deformation. Energies. 2020; 13 (22):5997.

Chicago/Turabian Style

Meike Ernst; Andrea Vacca; Monika Ivantysynova; Georg Enevoldsen. 2020. "Tailoring the Bore Surfaces of Water Hydraulic Axial Piston Machines to Piston Tilt and Deformation." Energies 13, no. 22: 5997.

Journal article
Published: 13 November 2020 in Energy
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This paper proposes a cost-effective, robustly practical solution for a high-efficient electro-hydraulic actuator (EHA) for linear drives. The solution addresses the challenges of high costs and limited efficiency that limit the application of EHA for the electrification of many off-road vehicles. Based on a variable-speed electric motor and a low-cost technology for a fixed-displacement pump, the proposed solution is suitable for a compact implementation and it is capable of energy regeneration under overrunning load conditions. Two different architectures—an open circuit and a closed circuit one—are considered to determine the most practical and efficient configuration as well as the control features. Both architectures minimize throttling losses associated with the conventional regulation of hydraulic actuators. Actuator velocities below the minimum and beyond the maximum allowable pump flow rate are achieved in both architectures using a proportional valve that bypasses the pump flow. The paper describes the design methodology as well as the simulation and experimental activities performed to verify the control strategies as well as energy efficiency. Considering an EHA system of about 20 kW, a complete efficiency map of the system is determined for all the possible four quadrants of operation thus including both resistive and overrunning loads, where energy recuperation is implemented. Simulation and experimental results show that the energy efficiency of the hydraulic systems can reach 84.7% in resistive phases. In assistive phases, the hydraulic system can recover up to 81.8% of the actuator energy. The comparison between open-circuit and closed-circuit structures shows the advantages of the former in terms of energy efficiency. The proposed solution is suitable for electrified hydraulic actuation systems, in both industrial and mobile applications. With the advantages of the low cost of the hydraulic unit and high energy efficiency, it is particularly suitable for mobile applications such as construction machines, that are recently experiencing a significant electrification trend.

ACS Style

Shaoyang Qu; David Fassbender; Andrea Vacca; Enrique Busquets. A high-efficient solution for electro-hydraulic actuators with energy regeneration capability. Energy 2020, 216, 119291 .

AMA Style

Shaoyang Qu, David Fassbender, Andrea Vacca, Enrique Busquets. A high-efficient solution for electro-hydraulic actuators with energy regeneration capability. Energy. 2020; 216 ():119291.

Chicago/Turabian Style

Shaoyang Qu; David Fassbender; Andrea Vacca; Enrique Busquets. 2020. "A high-efficient solution for electro-hydraulic actuators with energy regeneration capability." Energy 216, no. : 119291.

Research article
Published: 24 June 2020 in SN Applied Sciences
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Fluid borne noise sources in realistic hydraulic circuits can be affected by many geometric line details and the changing properties of working fluid. These phenomena need to be better understood and quantified for achieving inherent quietness through computationally designed hydraulic circuits. This paper uses one-dimensional finite element based modeling strategies to predict pressure waves generation and propagation in a realistic novel hydraulic hybrid transmission and compares simulations to measured data. The model is improved progressively with configurations that consider variable diameter, duct materials, and the presence of curvature of the lines. The modeling technique is composed of a one-dimensional method-of-characteristics solver bounded by two flow sources—lumped parameter axial piston units. Diameter and duct material were discretized into a grid along the length of the line. The effect of variation in the speed of sound was considered at each element of the one-dimensional grid. The differences between isothermal and adiabatic properties for the working fluid are also considered. The impact of aeration is also studied. A covariance algorithm is used in order to determine the aeration of the working fluid.

ACS Style

Leandro Danes; Andrea Vacca. The influence of line and fluid parameters on pressure ripple in hydraulic transmissions. SN Applied Sciences 2020, 2, 1 -14.

AMA Style

Leandro Danes, Andrea Vacca. The influence of line and fluid parameters on pressure ripple in hydraulic transmissions. SN Applied Sciences. 2020; 2 (7):1-14.

Chicago/Turabian Style

Leandro Danes; Andrea Vacca. 2020. "The influence of line and fluid parameters on pressure ripple in hydraulic transmissions." SN Applied Sciences 2, no. 7: 1-14.

Journal article
Published: 06 June 2020 in Energies
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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.

ACS Style

Rituraj Rituraj; Andrea Vacca; Mario Antonio Morselli. Thermal Modelling of External Gear Machines and Experimental Validation. Energies 2020, 13, 2920 .

AMA Style

Rituraj Rituraj, Andrea Vacca, Mario Antonio Morselli. Thermal Modelling of External Gear Machines and Experimental Validation. Energies. 2020; 13 (11):2920.

Chicago/Turabian Style

Rituraj Rituraj; Andrea Vacca; Mario Antonio Morselli. 2020. "Thermal Modelling of External Gear Machines and Experimental Validation." Energies 13, no. 11: 2920.

Journal article
Published: 01 March 2020 in Journal of Verification, Validation and Uncertainty Quantification
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Gerotors are inexpensive positive displacement pumps commonly used in hydrostatic transmissions, fuel injection, and automotive lubrication systems. In these pumps, leakages at the tooth tips of the gears are the major source of volumetric losses that prevents their usage in high pressure applications. However, due to the curvature of typical gear profiles, the flow relations available in the literature do not accurately model this leakage flow. In this paper, a novel tooth tip leakage flow model is developed based on dimensional analysis. Key geometric and flow parameters are identified and a set of computational fluid dynamics (CFD) simulations are conducted on the tooth tip geometry to establish the flow relationship. This relationship is first verified with the analytical formulation derived from Reynolds equation. Then, an experimental setup is designed to reproduce the flow conditions at the tooth tip of gerotors. Experiments are conducted for a range of geometric and flow parameters, and results from the experiments are used to validate the proposed leakage flow model. The tooth tip leakage flow model developed and validated in this work is valuable for pump designers in determining the impact of gear geometry and clearances on volumetric performance of the pump. Moreover, the model can be readily used in any lumped parameter based simulation tool permitting a fast and accurate prediction of the tooth tip leakage flow and hence the volumetric efficiency of the unit.

ACS Style

Fnu Rituraj; Andrea Vacca. An Investigation of Tooth Tip Leakages in Gerotor Pumps: Modeling and Experimental Validation. Journal of Verification, Validation and Uncertainty Quantification 2020, 5, 1 .

AMA Style

Fnu Rituraj, Andrea Vacca. An Investigation of Tooth Tip Leakages in Gerotor Pumps: Modeling and Experimental Validation. Journal of Verification, Validation and Uncertainty Quantification. 2020; 5 (1):1.

Chicago/Turabian Style

Fnu Rituraj; Andrea Vacca. 2020. "An Investigation of Tooth Tip Leakages in Gerotor Pumps: Modeling and Experimental Validation." Journal of Verification, Validation and Uncertainty Quantification 5, no. 1: 1.

Journal article
Published: 21 November 2019 in Energies
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In the context of improving energy efficiency and fuel consumption of mobile hydraulic equipment, it is important to analyze all the sources of power loss occurring within the hydraulic systems. While plenty of analyses have been performed on the working implements and the main transmission systems, very little attention has been paid to low-pressure (LP) systems until recently. LP systems are required on closed-circuit hydraulic systems to replenish losses, provide cooling flow, and maintain a pilot pressure necessary to operate hydraulic control valves and variable displacement units. It is shown that these circuits, which are often thought to have minimal impact on power consumption, actually cause significant, continuous power loss. A new method of power savings in these circuits is investigated through management of charge pump flow by application of an accumulator-sense pump-unloading (ASPU) valve. This work further proposes the combination of a split LP architecture with an ASPU valve. Three systems are simulated using Simcenter Amesim® and MATLAB/Simulink®. Using realistic duty cycles and unit loss models on a circuit for mobile off-road hydraulic equipment, it is shown that a standard LP system can consume about 5 kW of power. Power savings of up to 65% over a standard LP system are demonstrated by the proposed architecture.

ACS Style

Patrick M. Stump; Nathan Keller; Andrea Vacca. Energy Management of Low-Pressure Systems Utilizing Pump-Unloading Valve and Accumulator. Energies 2019, 12, 4423 .

AMA Style

Patrick M. Stump, Nathan Keller, Andrea Vacca. Energy Management of Low-Pressure Systems Utilizing Pump-Unloading Valve and Accumulator. Energies. 2019; 12 (23):4423.

Chicago/Turabian Style

Patrick M. Stump; Nathan Keller; Andrea Vacca. 2019. "Energy Management of Low-Pressure Systems Utilizing Pump-Unloading Valve and Accumulator." Energies 12, no. 23: 4423.

Journal article
Published: 04 May 2019 in Mechanical Systems and Signal Processing
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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.

ACS Style

Divya Thiagarajan; Andrea Vacca; Stephanie Watkins. On the lubrication performance of external gear pumps for aerospace fuel delivery applications. Mechanical Systems and Signal Processing 2019, 129, 659 -676.

AMA Style

Divya Thiagarajan, Andrea Vacca, Stephanie Watkins. On the lubrication performance of external gear pumps for aerospace fuel delivery applications. Mechanical Systems and Signal Processing. 2019; 129 ():659-676.

Chicago/Turabian Style

Divya Thiagarajan; Andrea Vacca; Stephanie Watkins. 2019. "On the lubrication performance of external gear pumps for aerospace fuel delivery applications." Mechanical Systems and Signal Processing 129, no. : 659-676.

Journal article
Published: 08 February 2019 in Energies
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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.

ACS Style

Xinran Zhao; Andrea Vacca. Theoretical Investigation into the Ripple Source of External Gear Pumps. Energies 2019, 12, 535 .

AMA Style

Xinran Zhao, Andrea Vacca. Theoretical Investigation into the Ripple Source of External Gear Pumps. Energies. 2019; 12 (3):535.

Chicago/Turabian Style

Xinran Zhao; Andrea Vacca. 2019. "Theoretical Investigation into the Ripple Source of External Gear Pumps." Energies 12, no. 3: 535.

Journal article
Published: 12 December 2018 in Energies
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In this paper, a novel approach for the simulation of cavitation and aeration in hydraulic systems using the lumped parameter method is presented. The presented approach called the Hybrid Rayleigh–Plesset Equation model is derived from the Rayleigh–Plesset Equation representative of bubble dynamics and overcomes several shortcomings present in existing lumped parameter based cavitation modeling approaches. Models based on static approximations do not consider the non-equilibrium effects of phase change on the system and incorrectly predict the system dynamics. On the other hand, the existing dynamic cavitation modeling strategies account for the non-equilibrium effects of phase change but express the evolution of phases through approximations of the Rayleigh–Plesset Equation (such as exclusion of nonlinear interactions in bubble dynamics), which often lead to physically unrealistic time-scales of bubble growth or dissolution. This paper presents a dynamic model for cavitation which is capable of predicting cavitation in hydraulic systems while preserving the nonlinear dynamics arising from the Rayleigh–Plesset Equation. The derived model determines the evolution of phases in terms of physically realizable parameters such as the bubble radius and the nuclei density, which can be estimated or determined experimentally. The paper demonstrates the effectiveness of the derived modeling approach with the help of numerical simulations of an External Gear Machine. Results from the simulations employing the proposed model are compared with an existing dynamic cavitation modeling approach and validated with experimental results over a range of dynamic parameters.

ACS Style

Yash Girish Shah; Andrea Vacca; Sadegh Dabiri. Air Release and Cavitation Modeling with a Lumped Parameter Approach Based on the Rayleigh–Plesset Equation: The Case of an External Gear Pump. Energies 2018, 11, 3472 .

AMA Style

Yash Girish Shah, Andrea Vacca, Sadegh Dabiri. Air Release and Cavitation Modeling with a Lumped Parameter Approach Based on the Rayleigh–Plesset Equation: The Case of an External Gear Pump. Energies. 2018; 11 (12):3472.

Chicago/Turabian Style

Yash Girish Shah; Andrea Vacca; Sadegh Dabiri. 2018. "Air Release and Cavitation Modeling with a Lumped Parameter Approach Based on the Rayleigh–Plesset Equation: The Case of an External Gear Pump." Energies 11, no. 12: 3472.

Journal article
Published: 10 October 2018 in Journal of Mechanical Design
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This paper describes a unique design concept that is capable of electronically controlling the flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (HPs) (p > 100 bar). This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure (LP) applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and for maximizing the flow variation range. Also, the low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the electrically commanded position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate analytical expressions for the instantaneous flow rate and the flow nonuniformity of the pump. The paper details the design principle of the proposed variable flow pump and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

ACS Style

Srinath Tankasala; Andrea Vacca. Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications. Journal of Mechanical Design 2018, 141, 013401 .

AMA Style

Srinath Tankasala, Andrea Vacca. Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications. Journal of Mechanical Design. 2018; 141 (1):013401.

Chicago/Turabian Style

Srinath Tankasala; Andrea Vacca. 2018. "Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications." Journal of Mechanical Design 141, no. 1: 013401.

Proceedings article
Published: 12 September 2018 in BATH/ASME 2018 Symposium on Fluid Power and Motion Control
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The concept of continuous-contact helical gear pumps (CCHGP) has been proposed and successfully commercialized in the recent past. Thanks to the continuous-contact rotor profile design and to the helical gear structure, this design eliminates the kinematic flow oscillation. This has important implications on the fluid borne noise generation, which is considered as one of the major sources of noise emissions and mechanical vibrations for positive displacement machines. Although the commercial success of the CCHGP concept, there is very little published studies about the underling physics at the basis of the functioning of this type of design. This is mostly due to the complexity of the fluid domain that characterize the functioning of CCHGP units. In this paper, a transient 3D CFD study is conducted for a reference CCHGP unit for high-pressure (up to 200 bar) fluid power applications. The results of the 3D CFD simulation are compared with those given by a lumped-parameter model developed at the Maha Fluid Power Research Center of Purdue University (USA), which was previously validated against experimental results. The results show how with a proper discretization of the fluid domain the CFD simulation approach can be used for the case of helical CCHGP units. Both models provide a good description of the main features of operation of the unit. The lumped parameter model is quicker, thus suitable for fast optimization studies. However, the CFD results not only can be used to support the main assumptions done on the lumped parameter model, they also permit to gain further insight on the operation of the CCHGP unit, particularly with respect to the flow features of the meshing process.

ACS Style

Xinran Zhao; Andrea Vacca; Sujan Dhar. Numerical Modeling of a Helical External Gear Pump With Continuous-Contact Gear Profile: A Comparison Between a Lumped-Parameter and a 3D CFD Approach of Simulation. BATH/ASME 2018 Symposium on Fluid Power and Motion Control 2018, 1 .

AMA Style

Xinran Zhao, Andrea Vacca, Sujan Dhar. Numerical Modeling of a Helical External Gear Pump With Continuous-Contact Gear Profile: A Comparison Between a Lumped-Parameter and a 3D CFD Approach of Simulation. BATH/ASME 2018 Symposium on Fluid Power and Motion Control. 2018; ():1.

Chicago/Turabian Style

Xinran Zhao; Andrea Vacca; Sujan Dhar. 2018. "Numerical Modeling of a Helical External Gear Pump With Continuous-Contact Gear Profile: A Comparison Between a Lumped-Parameter and a 3D CFD Approach of Simulation." BATH/ASME 2018 Symposium on Fluid Power and Motion Control , no. : 1.

Journal article
Published: 01 June 2018 in Mechanical Systems and Signal Processing
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ACS Style

Fnu Rituraj; Andrea Vacca. External gear pumps operating with non-Newtonian fluids: Modelling and experimental validation. Mechanical Systems and Signal Processing 2018, 106, 284 -302.

AMA Style

Fnu Rituraj, Andrea Vacca. External gear pumps operating with non-Newtonian fluids: Modelling and experimental validation. Mechanical Systems and Signal Processing. 2018; 106 ():284-302.

Chicago/Turabian Style

Fnu Rituraj; Andrea Vacca. 2018. "External gear pumps operating with non-Newtonian fluids: Modelling and experimental validation." Mechanical Systems and Signal Processing 106, no. : 284-302.

Editorial
Published: 07 May 2018 in Energies
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Note: In lieu of an abstract, this is an excerpt from the first page.Excerpt Fluid power refers to the discipline that involves the use of fluids to perform mechanical actuations, it is a well-established and independent discipline that has a defined research area and scholarly activities since at least seven decades.

ACS Style

Andrea Vacca. Energy Efficiency and Controllability of Fluid Power Systems. Energies 2018, 11, 1169 .

AMA Style

Andrea Vacca. Energy Efficiency and Controllability of Fluid Power Systems. Energies. 2018; 11 (5):1169.

Chicago/Turabian Style

Andrea Vacca. 2018. "Energy Efficiency and Controllability of Fluid Power Systems." Energies 11, no. 5: 1169.

Journal article
Published: 31 January 2018 in Energies
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Hydrostatic transmissions (HT) are widely applied to heavy-duty mobile applications because of the advantages of layout flexibility, power to weight ratio, and ease of control. Though applications of fluid power in light-duty vehicles face challenges, including the unavailability of off-the-shelf components suitable to the power scale, there are potential advantages for HTs in human-powered vehicles, such as bicycles, the most important one being the energy-saving advantage achievable through regenerative braking in a hybrid HT. This paper describes an innovative design for a hydraulic hybrid bicycle, i.e., the PurdueTracer. The PurdueTracer is an energy-efficient human-powered hydraulic bicycle with flexible operation and software aids. An open-circuit hydraulic hybrid transmission allows PurdueTracer to operate in four modes: Pedaling, Charging, Boost, and Regeneration, to satisfy users’ need for different riding occasions. An aluminum chassis that also functions as a system reservoir was customized for the PurdueTracer to optimize the durability, riding comfort, and space for components. The selection of the hydraulic components was performed by creating a model of the bicycle in AMESim simulation software and conducting a numerical optimization based on the model. The electronic system equipped users with informative feedback showing the bicycle performance, intuitive execution of functions, and comprehensive guidance for operation. This paper describes the design approach and the main results of the PurdueTracer, which also won the 2017 National Fluid Power Association Fluid Power Vehicle Challenge. This championship serves to prove the excellence of this vehicle in terms of effectiveness, efficiency, durability, and novelty.

ACS Style

Gianluca Marinaro; Zhuangying Xu; Zhengpu Chen; Chenxi Li; Yizhou Mao; Andrea Vacca. The PurdueTracer: An Energy-Efficient Human-Powered Hydraulic Bicycle with Flexible Operation and Software Aids. Energies 2018, 11, 305 .

AMA Style

Gianluca Marinaro, Zhuangying Xu, Zhengpu Chen, Chenxi Li, Yizhou Mao, Andrea Vacca. The PurdueTracer: An Energy-Efficient Human-Powered Hydraulic Bicycle with Flexible Operation and Software Aids. Energies. 2018; 11 (2):305.

Chicago/Turabian Style

Gianluca Marinaro; Zhuangying Xu; Zhengpu Chen; Chenxi Li; Yizhou Mao; Andrea Vacca. 2018. "The PurdueTracer: An Energy-Efficient Human-Powered Hydraulic Bicycle with Flexible Operation and Software Aids." Energies 11, no. 2: 305.