Abstract
Aiming at the demand of assembly assistance for complex industrial products, this paper studies the structure and key links of augmented reality aided assembly system, and takes a gear pump ...as an example to realize the parts detection function based on yolo neural network algorithm. On this basis, the assembly assistance system is built based on Vuforia, and the user interface is designed, realizing the functions of assembly progress identification and assembly information prompt.
•A model to evaluate fluid properties considering the dynamic features of cavitation is presented.•The new model for the evaluation of fluid properties is suitable for lumped parameters models.•The ...paper studies the operation of gear pumps under cavitating conditions.•Experimental activity on a gear pump was performed to validate the modelling approach.
This paper addresses the problem of predicting the effects of gas cavitation in fluid power components, accounting for the dynamic features of gas (including free air and vapour) release and adsorption. Several approaches to evaluate fluid properties under cavitating conditions have been proposed in the past, but those suitable to model hydraulic components with the classic lumped parameter approach do not consider the dynamic nature of the gas cavitation process. Cavitation can have a relevant impact on component operation, particularly for positive displacement machines directly connected to the oil reservoir. With the goal of studying the cavitation effects in hydrostatic units, in this paper a novel model to describe fluid properties – which utilizes a simplified formulation of the Full Cavitation Model – was integrated in an existing lumped parameter model for external gear machines previously developed by the authors’ research team. While the basic formulation of the new fluid model was previously validated for a single closed fluid chamber, the present study extends its formulation for the case of complete systems in which multiple chambers with variable volume are connected to each other. A proper experimental set-up was developed to permit the validation of the proposed model for the case of external gear pumps. Comparisons between measured and simulated instantaneous internal tooth space pressures as well as the outlet flow rates are presented. The significance of the proposed model is highlighted by comparing its predictions with those obtained using classic models of fluid properties, which cannot predict with accuracy the effects of cavitation.
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.
•The paper presents a methodology for modeling hydro-mechanical losses in external gear machines.•Friction at the gears’ tooth tips, lateral surfaces, shafts and meshing interfaces is considered.•The ...gear meshing friction is found to be the major contributor to the torque losses.•The simulated hydro-mechanical efficiency trends match the experimental data.
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.
•The paper describes the modelling of gear pumps operating with non-Newtonian fluids.•A lumped parameter approach is used to model the displacing action of the pump.•Experimental activity was ...performed on 3 pseudoplastic fluids for model validation.•Measured pressure-flow trends and outlet pressure ripple match the model predictions.
External Gear Pumps are used in various industries to pump non-Newtonian viscoelastic fluids like plastics, paints, inks, etc. For both design and analysis purposes, it is often a matter of interest to understand the features of the displacing action realized by meshing of the gears and the description of the behavior of the leakages for this kind of pumps. However, very limited work can be found in literature about methodologies suitable to model such phenomena. This article describes the technique of modelling external gear pumps that operate with non-Newtonian fluids. In particular, it explains how the displacing action of the unit can be modelled using a lumped parameter approach which involves dividing fluid domain into several control volumes and internal flow connections. This work is built upon the HYGESim simulation tool, conceived by the authors’ research team in the last decade, which is for the first time extended for the simulation of non-Newtonian fluids. The article also describes several comparisons between simulation results and experimental data obtained from numerous experiments performed for validation of the presented methodology. Finally, operation of external gear pump with fluids having different viscosity characteristics is discussed.
A systematic procedure is proposed to determine variable excitation loads coming from pressure evolution inside tooth spaces in external gear pumps. Pressure force and torque are estimated with ...respect to the angular position of the gears, taking into account the phenomena that occur during the meshing course. In particular, the paper proposes a general methodology aiming at determining pressure force and torque components along the three coordinate axes and suitable to be applied on both spur and helical gear configuration. Firstly, the method to calculate pressure loads acting on a single tooth space during a complete revolution is given, then the total pressure force and torque loading each gear is obtained. Particular attention is addressed on the description of the helical gear scenario. As an example, the method is applied to a tandem gear pump, characterized by the presence of two stages, one with spur gears and one with helical gears. An experimentally assessed model to calculate the pressure ripple inside the tandem pump is described and the proposed procedure for pressure load estimation is applied. Eventually, the pressure loads estimated with the present procedure are compared with other estimation methods already described in the literature. The comparison shows that the present methodology is able to describe a wider range of phenomena involved in the meshing evolution and to determine all the pressure force and torque components applied to helical gears. The method gives suitable results to study the balancing and the dynamic behavior of gear pumps.
•We propose a novel method for load estimation in gear pumps.•Analytical determination of variable pressure excitation.•The method is assessed via a tandem gear pump dynamic model.
Abstract
The present work employs an experimental and analytical method to investigate the wear of an external gear pump. The first part of experimental method involves, running the gear pump on test ...rig for set number of working hours and the performance curves are plotted for studying any variation during the course of experiments. In the second part of experimental method the circulated oil was studied for any contamination. Contaminated oil is an indication of wear which is to be detected using ferrography. The gear pump therefore was run for maximum number of hours to study the variation in performance of gear pump due to wear during the running operation. The oil samples were collected after the pump has been run at a set discharge pressure for a certain number of hours. Wear was expected to occur to detect the presence of ferrous particles for checking whether the gear pump components have worn out after the operation. Direct ferrogram reading machine was used to detect small and large particle size concentration and based on this the wear severity index was found out analytically. Also the necessary conclusions using graphical trend are obtained between particle size concentrations and wear severity index with respect to time.
Abstract
The micro-ORC systems are widely considered a reliable solution for domestic power production from renewable sources. The investigation of the optimal operating conditions to maximize system ...efficiency is an interesting challenge. In this study, a preliminary experimental campaign has been carried out on a biomass-fired micro-ORC system. The system is designed for stationary applications for domestic users, with a gear pump, a scroll expander and R245fa as the working fluid. The performance characterization of the micro-ORC under steady-state conditions has been obtained varying the water flow rate in the condenser at constant pump and expander speeds. The temperature of the hot source (thermal oil) is the maximum achievable in each operating condition. The temperature at the expander inlet and the condenser and evaporator pressure strongly influence the system performance. The increase in water flow leads to a decrease in the condenser pressure and a reduction of the superheating degree of the organic fluid. The system reaches the maximum electric power output of approximately 2565 W with a water flow rate of about 20 l/min. The highest electrical efficiency increases as the refrigerant flow rate decreases and reaches the highest value of 8.1% for the minimum investigated water flow rate.
Abstract
Gear pumps are widely employed in hydraulic circuit but they carry the major drawback represented by the pulsating flow they produce. To improve the capability of the pump to produce a clean ...and smooth flow rate, many methods have been investigated over time: from the optimization of pump features itself to the introduction of additional systems on the pump delivery side. One system that has demonstrated to be particularly effective is the in-line bladder hydraulic pulsation suppressor, which is part of the passive systems category. This device consists of a bladder gas accumulator with a particularly clever geometry and is the focus of many studies. The study illustrated in this paper has the aim of proposing a lumped parameter model capable of predicting the hydraulic suppressor ripple reduction performance. To test the actual performance of the suppressor and validate the lumped parameter model, an experimental study was conducted, which demonstrated the good effectiveness of device, while a good agreement between modeling results and experimental data was obtained.
In order to analyse the influence of gear parameters on the internal pressure pulsation of the aviation gear pump, the flow field analysis software PumpLinx is used to calculate the internal flow ...field of the aviation gear pump. By setting monitoring points inside the gear pump under different gear parameters, the pressure pulsation results at different positions under different gear parameters are obtained and analysed. The results show that the larger the modulus, the greater the pressure pulsation in the oil inlet area, oil trapped area and the oil outlet area; the greater the number of teeth, the greater the pressure pulsation in the oil trapped area, and the smaller the impact on the oil inlet area and oil outlet area; the larger the index circle pressure angle, the smaller the pressure pulsation in the trapped oil area, and the smaller the impact on the oil inlet area and the oil outlet area. The analysis results provide a reference for further optimizing the internal pulsation and oil trapping problems of aviation gear pumps.
PDF
