# C++ modelling of axial turbocharger

1. Oct 30, 2012

### chowchekkee

HI, i am a student taking final year project in my university, my project title was C++ modelling of axial turbocharger, it was a counter-rotating turbocharger, can anyone help me to get some useful information to complete my project? thanks

2. Oct 30, 2012

### Mech_Engineer

What part of the turbocharger are you modeling? What result are you hoping for? There's a lot that can be looked at but short of writing your own multiphysics finite element code you'll probably need to limit it to a single physical regime, e.g. heat transfer, fluid flow, mechanical dynamic analysis, etc.

3. Oct 30, 2012

### chowchekkee

i am writing the part for the efficiency for the turbocharger, including total to total efficiency, velocity triangle of the rotor blade and smith diagram, stuff like that

4. Oct 30, 2012

### AlephZero

The first thing you need to do is write some equations that describe everything that you want to model.

Once you have those, you can start thinking about how to write a program to solve them, how to display the results graphically, etc.

5. Oct 31, 2012

### chowchekkee

but the problem is the turbine and compressor blade of the turbocharger was contra rotating, which have no stator row in it. i have search all over the net and books, but still i not able to come out with the eqaution.

6. Oct 31, 2012

### Mech_Engineer

What excatly do you mean by "counter-rotating"? Two axial fans which are counter-rotating?

7. Oct 31, 2012

### Aero51

If you have contra rotating blades in your project you can forget about modeling in C. Modern CFD methods cannot accurately model a flow that complex. In short, there may not be any available analytical equations and you may have to resort to empirical models or highly specialized solvers.

8. Oct 31, 2012

### AlephZero

That is nonsesnse. You can make a simple model two contra-rotating blade rows in terms of blade inlet and outlet angles exactly the same way as a rotor followed by a stator.

If your assertion is about CFD methods is true, how do you think people have been designing jet engines with contra-rotating shafts for decades already? They certainly don't do it by experimental trial and error!

9. Oct 31, 2012

There's always a simple way, something I'm usually the one suggesting, but in this case it might not be a good idea. Although, I've seen more complicated things modelled in MATLAB that have given ok results. But yeah, CFD can model something like this, if you know what you're doing.

10. Oct 31, 2012

### Aero51

Aleph, I didnt say it couldn't be modeled, I said it couldn't be done accurately, especially as a final year project. I'm not in the jet engine business but as far as I know both CFD and empirical methods are used. CFD will give you preliminary results while testing is used for confirmation. I also don't believe this model is "simple" since we don't even have a solid theory/model of turbulent flows.

11. Oct 31, 2012

CFD and empirical methods are used. The turbulent solvers aren't that great, but they're getting better. I used a new one recently, which I can't give details on, that was giving much better turbulent results than other solvers like CFD++. This was comparing the results with experimental results.

12. Nov 1, 2012

### chowchekkee

Hi, i have upload the 2D sketch of the axial turbocharger.

it was a 4 stages axial turbocharger.

my problem is i cant solve for the velocity triangle for the counter rotating blade, which mean all are rotor, no stator involved. plus all the pressure drop and rise in the turbine and compressor respectively. i search through all the books for turbomachinery, all the stated theory was only apply for the rotor and stator only. therefore i am stucked.
thanks

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13. Nov 1, 2012

### Aero51

If you are a member of a professional society (AIAA, ASME, etc) try searching through technical papers on their websites.

14. Nov 3, 2012

### chowchekkee

hi Aero 51, i am not afford to buy the article to read, they cost too much for me.

15. Nov 3, 2012

### Aero51

I cant tell you what to do step by step - you have to exercise some "outside the box" thinking. As a start, why not ask one of your professors for access to a technical paper database?

16. Nov 3, 2012

### AlephZero

If you understand how velocity triangles work (compared with just following a method from a book without understanding it) there is no real difference for contra rotating stages.

You don't need CFD software for this. People were designing contra rotating turbomachinery back in the 1950s, before CFD even existed.

Google "contra rotating triangle of velocities" found lots of relevant (and free) documents.