As European and US vehicle emissions regulations tighten, more effective methods of reducing diesel engines pollutants must be devised. Increasing the injection pressure results in smaller fuel droplets and consequently more efficient combustion with a reduction in emissions output. However, to gain acceptable levels of NOx and particulates, required pressures must be of the order of 1800 to 2400 bar. At this level the components within the diesel injector and pump experience an appreciable level of distortion, that can, in severe cases, lead to leakage and a loss in pumping efficiency. It is therefore critical that an accurate means of determining the distortion and associated leakage is established.
An efficient analytical method of solution for the problem of mechanical distortion of a diesel pump is presented. Both the EUI (Electronic Unit Injector) and CR (Common Rail) injection systems use essentially in-line pumps for which this technique allows the individual components (principally the plunger and barrel) to be analysed. Also, combined fluid-elastic systems are considered in both CR and EUI cases. An elastic integral equation formulation is optimised for a cylindrical geometry and this is used to evaluate key features of the system such as pressure distributions and variations in film thickness during the pumping stroke. It is then straightforward to evaluate other parameters such as leakage and both magnitude and direction of fluid flow within the film thickness.
Simplification of elastic models is not required and as such this thesis also considers the effect of ports on the fluid flow and pressure distribution and also the relative orientation and axial position of the plunger within the barrel. This allows a detailed description and explanation to be made of the behaviour of the diesel pump. A key advantage of the method is that the fluid and elastic solvers may be decoupled and developed separately. This provides a means of extending the scope of the method beyond that presented here.
|Date of Award
|12 Dec 2001
|Patrick Keogh (Supervisor)