Emma Frosina

Numerical analysis and experimental validation of Gerotor pumps: A comparison between a lumped parameter and a computational fluid dynamics-based approach

In this paper, two alternative numerical approaches for the simulation of Gerotor units are compared: a fast lumped parameter approach for the fluid dynamics through the unit that permits the co-simulation of the radial micro-motion of the rotors, and a computational fluid dynamics approach that puts emphasis on the description of the detailed features of the flow through the unit. Each approach provides unique insights on the unit operation, although with different assumptions and level of result details. For an objective comparison of these two state-of-art models, the authors compared their results with experiments. A commercial pump taken as reference, and tests focused on steady-state volumetric performance as well as the transient features of the outlet port pressure oscillations. The results presented in the paper permit to gain a high level of understanding of the operation of the unit and of the critical aspects that a designer should consider while analyzing such design of positive displacement machines. While comparing the two simulation approaches, the paper highlights the limits and the strengths of each one of the two approaches. In particular, it is shown how both models can match the experimental results considering proper assumptions, in terms of technological clearances and rotors’ micro-motions. The paper constitutes a unique contribution in the field of numerical simulation of Gerotor units and represents a useful reference to the designers looking for suitable methods for simulating existing or novel design solutions.

Analysis and Simulation of an Oil Lubrication Pump for Internal Combustion Engines

This paper presents a simulation model of an oil-lubrication gerotor pump for internal combustion engines. The model was constructed by using a monodimensional commercial code that accounted for all phenomena that occur during the revolution of the pump shaft. Several geometric considerations and theoretical observations are presented. An experiment was also performed to validate the simulation model. In these experimental tests, particular attention was paid to the behavior of the pressure oscillations during the pump shaft revolutions. The final aim of this activity is to obtain an instrument that allows the in-depth analysis of the functioning of the pump and lubrication circuit. Additionally, this instrument can be coupled with other models (e.g., variable valve actuation (VVA) and variable valve timing (VVT)) to account for different problems experienced by the hydraulic components of engines.

Gerotor pump cavitation monitoring and fault diagnosis using vibration analysis through the employment of auto-regressive-moving-average technique

Abstract Gerotor pumps, as well known, are widely used in lubrication circuits of internal combustion engines for their simplicity, high efficiency and low costs. In this paper an experimental characterization of a Gerotor pump is shown. The research is a collaboration between the Hydraulic Power Research Group (HPRG) of the University of Naples “Federico II” and the Istituto Motori of CNR. The aim of this research is to investigate the possibility of using simple data to acquire, as vibrational data, on the pump under investigation to detect possible cavitation problem by implementing a proper mathematical procedure to this aim. As been demonstrated that these pumps are particularly subject to cavitation. The gerotor pumps are much subject to cavitate than expected, especially under particular operating conditions of the engine. Cavitation is also correlate to vehicle dynamics particularly with the recent tendency to reduce the mass of oil in the sump. Therefore, the research to avoid cavitation is crucial nowadays. Consequently this study has been firstly performed with an experimentation on the pump by monitoring the delivered oil flow-rate and the adsorbed torque on the pump shaft. An accurate analysis of the pressure oscillations in cavitation conditions, has been, also, conducted. Then, an accelerometer sensor has been properly located to study the cavitation with a fault diagnosis system based on vibration detection. The experimental tests have been performed on a test bench of the Hydraulic Laboratory of the University of Naples “Federico II” in Italy. The bench allows testing the pump working by varying the shaft speed, the oil temperature, the suction and the delivery pressure. The main measured parameters are shaft torque, oil flow rate, mean suction and delivery pressure and the instantaneous suction and delivery pressure. As expected, tests revealed the high influence of the suction pressure on the delivered oil flow rate, while no significant influence has been noted on the adsorbed torque. Furthermore, the pressure oscillations in the pump delivery are highly influenced by the suction pressure. A non intrusive accelerometer has been installed during the experimentation on the oil pump. Since the vibration due to cavitation is the main concern of this study, the accelerometer has been mounted at the suction port in the radial direction. More precisely, the paper presents a fault diagnosis system based on vibration detection. Firstly, a Fast Fourier Transform of the vibration signal has been computed. The investigation has been made with and without the presence of cavitation varying the pump rotation speeds. Limitations due to the detecting of the on line cavitation problems by monitoring the FFT vibration spectra have been overcame by implementing an alternative method based on stochastic approach. This diagnosis method of accelerometer time series analysis based on an Auto Regressive and Moving Average (ARMA) method has been used to determine the pump failure. The diagnosis results have demonstrated the ability of the proposed mathematical technique in the identification of cavitation phenomena proving that the proposed approach is a useful methodology to detect the presence of fault. The approach can predict, with good accuracy, pump failure in real time operation. In addition, a threshold vibration level in decibel scale is also fixed.

Improving the Performance of a Two Way Flow Control Valve, Using a 3D CFD Modeling

The paper introduces a methodology aimed to optimize the performance of hydraulic components; in particular the design of a new two way flow control valve studying the valve internal fluid-dynamic behavior will be introduced. The methodology is based on the definition of a CFD tridimensional fluid-dynamic model. In fact, the model can help engineers to develop the best geometry, to optimize the valve performance, reducing the prototyping requirement and finally the time-to-market and, consequently, the development costs. At first, the original spool internal geometry has been evaluated and studied to tune the mathematical model and to validate it comparing its results with the data obtained through an experimental campaign.Then, the same approach has been applied to investigate several different internal spool geometries to define the best one in all operating conditions. A limited number of solutions have been prototyped and tested to verify the mathematical model predictions, in order to find the best configuration whose performances are consistent with the assigned objective for the component.Copyright

Analysis and Simulation of an Oil Lubrication Pump for the Internal Combustion Engine

This paper presents the simulation model of an oil lubrication gerotor pump for the internal combustion engine.The model was constructed by using a mono-dimensional commercial code taking into account all the phenomena that occur during the revolution of the pump shaft. First of all, several geometric considerations and theoretical observation are presented.An experimental campaign was also performed to validate the simulation model. In these experimental tests particular attention was regarded to the behavior of the pressure oscillations during the pump shaft revolutions.The final aim of this activity is to obtain an instrument that allows in-depth analysis of pump and lubrication circuit functioning and that can be coupled with other models (e.g. VVA, VVT, etc.) in order to take into account different problems of the hydraulic components of engines.Copyright

Vane Pump Power Split Transmission: Three Dimensional Computational Fluid Dynamics Modeling

A three dimensional CFD analysis of a novel vane pump power split transmission is studied in this paper. The model was built using PumpLinx®, a three-dimensional CFD commercial code developed by Simerics Inc.® The Mathers Hydraulics® vane pump is a double-acting vane pump with a floating ring. By coupling the floating ring to an output shaft, the vane pump becomes a hydrostatic transmission. The focus of this activity is the optimization of the vane pump analyzing the internal fluid dynamics of each part during the pump operation and redesign. The study is a result of collaboration between the University of Minnesota and the University of Naples “Federico II” research groups. The universities involved in this project worked in close cooperation on these simulations. A prototype pump will be tested on a hydraulic test bench at the University of Minnesota, and the experimental data will be used to validate the simulation model.Copyright