177,017 research outputs found
Experimental Procedure for Measuring the Energy Consumption of IC Engine Lubricating Pumps during a NEDC Driving Cycle
No full textThe paper presents an experimental procedure for comparing different families of IC Engine lubricating pumps in terms of total consumed energy in a NEDC driving cycle. Measures are performed on a test rig able to reproduce the oil temperature profile, the lubrication circuit permeability and its variation during the engine warm-up. The pump under test is driven by a variable speed electric motor supplying the engine velocity profile of the driving cycle. The load on the pump is generated by means of a variable restrictor controlled in a closed loop by a proper combination of speed, temperature, flow rate and pressure signals in order to replicate the typical permeability of the lubricating circuit. The method has been applied to a 15 cc/rev crankshaft mounted gerotor pump for a medium displacement Diesel engine; the flow-pressure characteristics of the lubricating circuit at different temperatures and the oil heating rate measured on the engine have been supplied to the test rig control system. The reference pump has been contrasted with a crankshaft mounted variable displacement vane pump with absolute pressure limiter device and an off-axis external gear pump with the same displacement and pressure setting. Experimental tests bring to evidence the advantage of the variable displacement pump during short trips with cold start, while the external gear pump prevails at the end of NEDC cycle where highest engine speeds and oil temperatures are reached
Modelling and Simulation of Brake Booster Vacuum Pumps
No full textAim of this work is the development of a lumped parameters simulation model of single-vane vacuum pumps for pneumatically actuated brake boosters. Kinematic and fluid-dynamic models are integrated in a simulation environment to create a tool aimed at evaluating the vacuum pump performance and at guiding the designer during the prototype development. The paper describes extensively the mathematical model, the time domain simulation and experimental analyses performed on a camshaft mounted unit. Great emphasis is placed on the evaluation of the geometric quantities of the control volumes into which the vacuum pump has been divided. For each control volume the mass and energy conservation equations lead to the determination of the instantaneous pressure. The volume of each variable chamber and the respective angular derivative are calculated as function of the shaft position starting from the stator track profile supplied as a generic closed polyline. Flow areas between each chamber and the inlet/outlet volumes during a complete shaft revolution are evaluated directly from a data file containing the x-y coordinates of the passage area contour. Different leakage paths are also taken into account. Specific attention is dedicated to the simulation of the lubricating fluid throughout the vacuum pump in order to take into account possible overpressures due to the presence of a trapped volume of oil, above all during cold starts. To achieve this target the equations describing the behavior of the liquid and gaseous phases are applied simultaneously and the current fraction of oil is evaluated for each variable volume chamber. The model is able to work with an oil fraction ranging from 0% to 100% without introducing discontinuities in the differential equations. Experimental tests have confirmed a good matching with the simulation results in terms of pressure vs. time characteristics and absorbed torque
Numerical and experimental analysis of variable displacement vane pumps
No full textVariable displacement vane pumps represent one of the most innovative type of pump for automotive engines. The vane pump with a sliding ring, is a mechanism that makes it possible to change the capacity of the pump as a function of the engine speed, allowing to optimize of
the oil flow, according to the engine demand, with considerable power saving. The main components of a variable displacement vane pumps are: vanes, rotor, inner rings and a sliding
ring. During operation, the vanes are in contact with the inner surface of the outer (sliding) ring due to the effect of centrifugal loads; in addition high slip velocities occur in the contact area; as a consequence, a critical aspect of this kind of pumps is represented by the wear which takes place on the contact surfaces. Another potential mechanism of damaging process is attributed to vanes sticking in rotor cavities, causing a sudden increase in contact loads. This paper illustrates
a summary of a research activity, which was carried out with the aim of analyzing the operating conditions of vanes pumps. The study was conducted with reference to pumps with vanes number ranging from 5 to 9, in order to evidence the influence of some design parameters on
results. The numerical analysis were carried out by using multi-body models, that were developed with MSC.Adams® code. In these analyses any effect of the viscous oil inside the
pump was neglected, focusing the attention on mechanisms geometry; moreover, the hypothesis of plane analysis was assumed. Some experimental tests were also carried out with a prototype,
which was tested up to very hard conditions in order to highlight wear and damage mechanisms
Comparison of two sealing coupling geometries for a direct fuel injector
No full textThe present paper describes some Finite Elements simulations carried out in order to investigate the contact problem in the sealing region of a direct fuel injector. In particular two different design solutions have been analyzed, both patent pending, one characterized by a conformal contact of two conic surfaces and the other one by a non-conformal contact between a cone and a sphere. Pressure distribution, contact width and von Mises equivalent stress have been calculated and employed as comparison parameters. Two different loading conditions have been considered: nominal loads and nominal loads plus undesired effects. Also deviations from the nominal geometry, obtained from profile detection of 40 samples, have been introduced for considering a real-like case. Numerical results stress the robustness of the non-conformal solution with respect to geometrical tolerances and real loading conditions
Analisi delle soluzioni tecniche attualmente allo studio nei programmi di ricerca Europei e degli Stati Uniti per i reattori a confinamento magnetico, alla luce degli ultimi sviluppi relativi alla riduzione delle dimensioni del progetto ITER
No full textA magnetorheological clutch for efficient automotive auxiliary device actuation
Get PDFIn this paper the results of a project funded by Regione Toscana aimed at reducing the power absorption of auxiliary devices in vehicles are presented. In particular the design, testing and application of a magnetorheological clutch (MR) is proposed, aimed at disengaging the vacuum pump, which draws in air from the power-brake booster chamber, in order to reduce the device power absorption. Several clutch preliminary studies done to choose the clutch geometry and the magnetic field supply are illustrated. The final choice consisted in an MR clutch with permanent magnet, which satisfied size, torque and fail-safe specifications. The clutch characteristics, in terms of torque versus slip, were obtained experimentally for three different clutch prototypes on an ad-hoc developed test bench.As result of a preliminary simulation, a comparison between the power absorption of a current production vacuum pump, an innovative vacuum pump and both vacuum pumps coupled with the MR clutch is presented. The New European Driving Cycle is considered for simulating the vacuum pump operation both in urban and highway driving. Results show that the use of the innovative vacuum pump reduces the device consumption of about 35%, whereas the use of MR clutch coupled with the innovative vacuum pump reduces it up to about 44% in urban driving and 50% in highway driving
Numerical multilevel investigation for the evaluation of pressure distribution in EHL circular contacts from film thickness measurements
No full textAn analysis of circular contacts under elastohydrodynamic lubrication using a hybrid technique is presented. In particular, attention has been focused on the pressure distribution calculation. A versatile code has been developed to evaluate the pressure distribution starting from three-dimensional film thickness maps obtained from the analysis of interferometric images. The code has been developed in C++ and is based on the multigrid technique. This hybrid technique has a basic advantage over the full numerical approach in that the pressure is obtained without making any assumptions about the lubricant itself. The main drawback of the method is that high-resolution interferometric images are required
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