# Geometry Variation of a Fuel Injector Design

## Geometry Variation of a Fuel Injector Design

When it comes to the optimization of e.g. diesel engines, we have another interesting component for you: the fuel injector! Basically, this component takes care that the fuel is optimally sprayed into the combustion chamber. This pretty sophisticated product is an impressive engineering and manufacturing master piece (BTW: Everything is really tiny!).

We recently needed to come up with a quick method to change the existing nozzle geometry of a fuel injector. The geometry was imported into CAESES®, using the STL format. The following screenshot shows a slightly changed design of what we had worked on:

Typical injector geometry

CAESES® offers the possibility to apply so-called free form deformations to existing geometries. So this is what we did: We created a box around one of the nozzles, and defined some expansion strategies. With this, the nozzle could be enlarged and even fully changed in its shape. Sure, there are limitations in terms of manufacturing etc. But at this point in time, we tried to set it up as flexible as possible. Here is a screenshot of the setup where the outer geometry was removed for visualization purposes:

Setup of a free form deformation to modify the nozzle

In a next step, we defined design variables for the expansion factors, to make it ready for automated studies. The following animation shows the deformation box and the effect on the geometry:

Change of the deformation box to apply shape changes

When we finished this setup for the nozzle, we applied it to the other nozzles, i.e. they were changed in the same way. We handed over the entire setup to the engineer who requested this shape changes. Being the expert in this field, he simply continued to fine-tune things a little bit further, according to his technical requirements and constraints. Finally, he run design studies where the entire process was fully automated (geometry changes / meshing / CFD analysis). For illustration purposes, here is a set of animations that show some automated shape changes:

Free form deformations are part of our pro edition of CAESES®, and it nicely complements the general CAD functionality for CFD engineers. In similar projects, we created a fully-parametric model for injectors (instead of deforming an existing one), which usually gives you even more control, while at the same time the number of variables can be reduced. More general details about CAESES® can be found on our product page:

### 2 thoughts on “Geometry Variation of a Fuel Injector Design”

1. Manjunatha

Hello team,
This study looks impressive. May I know what are the parameters you considered for optimization. Does it include spray angles, mass flow, phases of the flow and cavitation , axial and lateral forces… How many parameters you considered here. Also I have one small doubt, your grid looks more skewed how did you accompanied this..?

Keen to know this…

Regards,
Manjunatha S

1. FRIENDSHIP SYSTEMS Post author

Dear Manjunatha,

We have only prepared the variable geometry, i.e. we were not involved in the meshing and CFD. For this geometry, we used 3 design parameters, to keep it simple. We have no details about the simulation setup and the parameters that were used on the customer side. BTW: What you can see in the animations is the deformation of the surface triangulation (not the volume mesh). Hope this helps?