1,720,998 research outputs found
Influence of Design and Operational Parameters on the Dynamic Behaviour of Gear Pumps.
No full textThis work concerns external gear pumps for automotive applications, which operate at high
speed and low pressure and presents a sensitivity analysis about the influence of design and
operational parameters on the pump dynamic behaviour. In previous work, a non-linear
lumped-parameter kineto-elastodynamic model was developed, with the aim of including all
the important effects, as well as to get a rather simple model. Two main sources of noise and
vibration can be considered: pressure variation and gear meshing. The model has been
validated by comparison with experimental vibration data, in a wide range of operational
conditions and for different gear designs and several profile errors. This paper is focused on
the analysis of the influence of the main design and operational parameters on the pump
dynamic behaviour. In particular, the effect of operational pressure and speed, the influence of
the clearance in the journal bearing and between tooth tip and pump case, and the effect of the
dimension of the relief grooves in the bushes will be thoroughly discussed in the paper.
Finally, the model could be a very useful and powerful tool in order to evaluate design
improvements for noise and vibration reduction
A Model for the Elastodynamic Analysis of the Geared Timing System of a Motorbike Engine.
No full textThis work deals with the elastodynamic model of the geared valvetrain of a four-cylinder “L” engine of a Ducati racing motorbike. The model, which is an evolution of the author’s research, is obtained as a combination of lumped parameter and finite element parts. The model is able to inspect the dynamic behaviour of both the geartrain and the cam-valve mechanisms. The paper mainly describes the model validation process that is based on several experimental tests and it is achieved by means of different steps. The information obtained from the validation stages have been finally employed for the tuning of the combined lumped/finite element model of the geared timing system. The experimental procedures are also illustrated, together with some details on the signal treatments. The comparison between simulations an experiments shows that the effectiveness of the model is satisfactorily assessed, thus permitting the use of the model as a tool for the design optimisation of the motorbike timing system. The results obtained for the competitive motorbike engine can also be utilized for common production engines, where conformity to vibration and noise standards must be fulfilled
Multibody Analysis of the Desmodromic Valve Train of the Ducati MotoGP Engine.
No full textThis paper presents a preliminary study concerning a multibody model of the desmodromic
valve train used in the Ducati MotoGP engines. The desmodromic mechanism has
a positive cam that causes the dynamic effects to be partly different from common valve trains,
where the valve spring plays an important role. The presented model includes only one camvalve
mechanism. In a further step of the research, it will be possible to develop and expand the
model by introducing the other cam-valve mechanisms and other mechanical parts that compose
the system in order to obtain a complete model of the valve train. In the first part of this
work, the generation of the cam profiles is explained. The second part is focused on the description
of the multibody model employed for the dynamic simulations. Finally, the experimental
validation is presented and discussed. The comparison between the numerical results and the
experimental data is encouraging even if it shows that the effectiveness of the model is not completely
achieved. Therefore, it will be necessary to improve the model by including the presence
of other mechanical parts of the valvetrain, as well as other important dynamic effects as, for
example, the link flexibility
Elastodynamic analysis of a gear pump. Part II: meshing phenomena and simulation results.
No full textA non-linear lumped kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps is presented. It takes into account the most important phenomena involved in the operation of this kind of machines. Two main sources of noise and vibration can be considered: pressure and gear meshing. Fluid pressure distribution on gears, which is time-varying, is computed and included as a resultant external force and torque acting on the gears. Parametric excitations due to timevarying meshing stiffness, the tooth profile errors (obtained by a metrological analysis), the backlash effects between meshing teeth, the lubricant squeeze and the possibility of tooth contact on both lines of action were also included. Finally, the torsional stiffness and damping of the driving shaft and the non-linear behaviour of the hydrodynamic journal bearings were also taken into account. Model validation was carried out on the basis of experimental data concerning case accelerations and force reactions. The model can be used in order to analyse the pump dynamic behaviour and to identify the effects of modifications in design and operation parameters, in terms of vibration and dynamic forces. Part I is devoted to the calculation of the gear eccentricity in the steady-state condition as result of the balancing between mean pressure loads, mean meshing force and bearing reactions, while in Part II the meshing phenomena are fully explained and the main simulation results are presented
Modelling dynamic behaviour and noise generation in gear pumps: Procedure and validation
No full textThe paper presents a methodology for noise and vibration analysis of gear pumps and its application to an external gear pump for automotive applications. The methodology addresses the use of a combined numerical model and experimental analyses. The combined model includes a lumped-parameter model, a finite-element model and a boundary-element model. The lumped-parameter (LP) model regards the interior parts of the pump (bearing blocks and gears loaded by the pressure distribution and the driving torque), the finite element (FE) model regards the external parts of the pump (casing and end plates), while the boundary element (BE) model enables the estimation of the emitted noise in operational conditions. Based on experimental evidences, attention has been devoted to the modelling of the pump lubricant oil: the fluid-structure interaction between the oil and pump casing was taken into account. In the case of gear pumps all these important effects have to be considered in the same model in order to take their interactions into account. The model has been assessed using experiments: the experimental accelerations and acoustic pressure measured in operational conditions have been compared with the simulated data coming from the combined LP/FE/BE model. The combined model can be considered a very useful tool for design optimisation. (C) 2013 Elsevier Ltd. All rights reserved
Torsional Vibration Analysis of a Test Rig Driveline Equipped with a Flexible Coupling
No full textThe paper deals with a case study from the automotive industry and relative to a test rig of internal combustion engines: the output shaft of the engine transmission is connected with an electromechanical brake by means of a transmission shaft which hosts a torsional coupling with rubber elements. The engine test cell was developed several years ago; over years, the engine operations and performance have been changed, in terms of output power and torque, entailing more severe dynamic loads affecting the driveline members. In this scenario, early failures of the rubber elements of the flexible coupling have occurred. The goal is to solve the problem by bringing the fewest possible modifications to the cell layout. An experimental campaign was thus carried out, with the aim of characterizing the current system dynamic behavior and finding possible modifications able to solve the problem. In particular, torsional vibration measurements have been achieved by a coder-based technique using high-quality optical sensors and equidistantly spaced markers (zebra tape) on the rotating components. The measured data were analyzed in the Time, Frequency, Time-Frequency, and Order domains. The paper presents the experimental setup, the data processing and the results obtained from tests performed on the original system and on a modified version of the transmission driveline, after changing the elastodynamic properties of the coupling
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