Tesis doctoral de Sushil Kumar
In the field of fluid power, piston pumps possess the most sophisticated designs, in fact, pistons pumps are the only ones capable of working at high pressures, besides possessing the best performance (efficiency) of the entire group of existing pumps. However, it is noted that all the designs of piston pumps, are mostly based on the experience of the designers, thus there exist no mathematical tools for optimizing the design of the different parts of the pumps. On the other hand, there are now companies like oilgear towler, who inserted slots (grooves) in the slippers and in the pistons, (two major parts of these pumps) but there is no scientific study to analyze its advantages or disadvantages. There is therefore a need to understand mathematically to study the advantages and disadvantages due to the presence of the groove on the surface of different pump parts. There are four sliding surfaces in the piston pump, slipper-swash plate gap, barrel-valve plate gap, piston-barrel chamber gap and spherical bearing, where lubrication exists and leakages through these channels occur. In this project, our aim is to analyze each of these different sliding surfaces separately to understand its design constrains and the effect of the design parameters on the pump behavior. After having a better understanding of all the different parts of the piston pump, the aim is to model the dynamic behavior of pressure and flow at the outlet of the pump. slipper plate gap – to understand static and dynamic characteristics of a piston pump slipper with a groove. three dimensional navier stokes equations in cylindrical coordinates have been applied to the slipper/plate gap, including the groove. The results presented in this thesis include, pressure distribution, leakage, force and torque variations when groove dimensions and position are being modified, the effect of slipper tangential velocity and turning speed are also considered. Design instructions to optimize slipper/groove performance are also given. barrel-valve plate gap – present thesis, analyses the pressure distribution, leakage, force and torque between the barrel and the port plate of an axial piston pump by simulating reynolds equations of lubrication by fdm (finite difference method). The overall mean force and torques over the barrel are evaluated from simulated pressure and it shows that the torque over the xx axis is much smaller than the torque over the yy axis. A detailed dynamic analysis is then studied by using the temporal torque calculated by bergada. piston-barrel chamber gap – it is being investigated the piston performance by modifying the number of grooves and their position, pressure distribution in the clearance piston-cylinder, leakage force and torque acting over the piston will be discussed, also the locations where cavitation is likely to appear will be presented, discussing how to prevent cavitation from appearing via using grooves. A finite volume based reynolds equation model has been formulated for the piston-cylinder clearance which considers the piston eccentricity and the relative tangential movement between piston and barrel. Different configurations of the grooves have been evaluated in search of finding minimum leakage, minimum appearance of cavitation and maximum restoring torque. Design instructions to optimize the piston behavior are also given. full pump model – an extensive set of explicit equations for every pump gap will be presented. All of the equations will be checked via performing a numerical analysis of the specified pump clearance, the equations will then be combined to study dynamically pressure ripple and leakages. The effect on the flow ripple when modifying the pump design will also be presented. Therefore in present thesis, a simulation model based on analytical equations has been developed which produce very fast results and clarify very precisely the effect of different leakages happened through the pump clearances.
Datos académicos de la tesis doctoral «Cfd analysis of an axial piston pump«
- Título de la tesis: Cfd analysis of an axial piston pump
- Autor: Sushil Kumar
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 16/07/2010
Dirección y tribunal
- Director de la tesis
- Josep M. Bergada Graño
- Tribunal
- Presidente del tribunal: ramón Codina rovira
- perumal Nithiarasu (vocal)
- ferran Escanes (vocal)
- eduard Egusquiza estéfez (vocal)