Finite Element Analysis of a Pulse Jet Engine

Dana BradburyBrandon FaulknerMarques Franklin

ME 450 Computer-Aided Engineering AnalysisSpring 2003

Instructor: Dr. H.U. Akay

German V1 Buzz Bomb

Current Uses and Models

Airplane Models

Mosquito Foggers

Simple models for PDE research

Why use F.E.A?

Very short life span on reed valve

Extremely loud when running

Very difficult to get one running

They get red hot when running

Our Model: The Tiger Jet

Our Model (cont.)

First Step: Build a Working Model

Design and build a working model in ProE

Export as an IGES file and then import into ANSYS

The ProE Model

In the Beginning, there was a problem

The model was imported into ANSYS

ANSYS likes to keep every thing in perspective and the microscopic thickness of the reed valve resulted in the need of over 1 million elements

Even if there were enough elements, the calculations would still be running today

the next day, ANSYS created more problems

The next thought was to only model a section of the pulse jet and then use the CYCLIC command to simulate cyclic symmetry about the x-axis

Still ANSYS required about 500,000 elements for a good mesh which took wall velocities and channel velocities into consideration (ex. Needed a more dense mesh near the wall because of the zero wall velocity b.c.)

You shouldnt assume because when you assume

A 2-D assumption had to be made at this point

Even though axisymmetry was a part of the assumed boundary conditions, this problem is not axisymmetric.

Many are called but the chosen are few

Several different attempts were made to model the fluid solid interaction (FSIN)

The first was an FSIN. However we could not get the surfaces to match up and kept getting an error

Finally we tried a dual approach with the physics environment and the FSSOLVE command and

EUREKA!!! We Got Results!!!

The results proved to be logical for the given problem

However they were not very agreeable with data attained by NASA research

The Fluid Mesh

Velocity Vectors

Von Mises Stress

Contour Pressure Plot

The Next Step

It is possible to create the working geometry in ANSYS, however it would be very time consuming (one would have to design a feasible mapped mesh)

Turns out that pulse jets do not operate based upon the flow of air, instead they depend upon pressure waves developed by the combusting fuel and compressed air. So after a working model was developed, a cycling pressure gradient should be added to the fluid to observe real life conditions

Acknowledgements

To an amazing and awesome support groupour fellow studentsDr. Razi NalimDaniel E. PaxsonDr. Akay