Abstract
KEYWORDS:
diesel engine, injection system, injector, finite element method
ABSTRACT
The paper presents the model of the delivery fuel pipe and the injector of a Diesel fuel system in order to determine the natural frequencies of the system, global deformations of the assembly and the dynamic analyze of the injector’s parts under mechanical and thermal stresses. A continuous structure has a limited number of degrees of freedom thus an analyze in a static or dynamic regime of the structure implies an important number of initial simplified hypothesis, if the study methods are the classical ones. The FEM analysis allow the approaching of the structure without any initial simplified hypothesis, that’s why we choose it for the analyze of the components of the injection system of the Diesel engine.
After that analyze we obtain the following conclusions: ·
- the vibration’s natural frequencies of the components majority (without the spring of the delivery-valve and the delivery pipe) are overlapping with those of the fluid only in the high frequencies-low amplitude zone; ·
- the overlapping of the oscilation frequencies of the delivery-valve spring and of the delivery pipe over those of the fluid in the fundamental frequencies zone, characterized by high amplitudes could generate the resonance phenomena; ·
- the spatial shape of the delivery pipe and the variations of the pipe deformations indicate the possibility of a turbulent flow of the fuel on the entire length of the pipe; ·
- the calculated speeds in different cross-sections of the pipe are very diverse and distinct from the point of view of the variation law, thus due to the algebraic sum of whole waves that reach the considered cross-section at a specific moment, sum that differ from a section to another; ·
- the vibration of the injector’s spring could be considered as a cause of the post-injection phenomena; ·
- the cavitation is distinguished by the facts that the pipe deformation presents in few places pulses over the elasticity limits of the material; ·
- all these simulations which are based on the FEM analyze create opportunities for a large complex analyze concerning the reciprocal influence of the mechanical elements with the working fluid; ·
- the simulation of the mechanical parts of the injection system by FEM is very useful for a preanalyze on the experimental way.