PD-01 Jet Engine

[madpatty]

Hi Racket,
Actually my question was:-

Is this the maximum performance that i can extract from my current setup??...because i had been targeting 3PR since the very beginning...

But according to the current rpm at which the setup is running i think reaching 3PR will be far from what it is generally recommended the safe rpm....

For instance:-

jetandturbineowners.proboards.com/thread/509/turboshaft-minibike-mrt-01

Miuge here is using same compressor and turbine setup as me but looking at the pressure P2 he is making at the Rpm, mine setup is varying to a very large degree with the same rotor....

In my setup:-
The NGV throat area is also not far from the exact calculated area and the TOTs are also good, RPMs are also towards the maximum.

Then how will i come to know that my engine is running to its fullest....

Should i be reducing the throat area by blocking off some NGVs to increase the P2 per rpm??

Cheers,
Patty

[racket]

Hi Patty

The output of your engine will depend on a multitude of variable, some you can't do anything much about , things like compressor and turbine design , but there are a number that relate to constructional variables which you can influence .

Your calculated NGV throat area assumes certain parameters are being met , but without measuring your actual air mass flow rate you have no idea if your throat area is appropriate .

You can be satisfied with your engines output if its within say 5% of the theoretical output from doing the calculations, but again there are assumptions in those calculations.

As for reducing the NGV throat area , thats a design decision only you can make after taking into consideration the theoretical flow from your compressor wheel and the desired T I T you wish to use.

I wouldn't be doing anything until you try the suggestion I made with the tubing and note the results.

Cheers
John

[madpatty]

Hi Racket,
i ran the engine today with a pipe installed on the compressor inlet...pipe was 200 mm long and of the same ID as the OD of the compressor cover(which was approx. 85 mm)...

TOTs reduced by about 20 degrees celsius. But overall no noticeable change in running than before.

i installed another P2 pickup point in the engine outer cover near the turbine end. But there also the pressure reading was almost same as i was getting from the point in the engine front cover just at max. 1 Psi more than the earlier reading.

cheers,
Patty

[racket]

Hi Patty

OK , every 20 degrees is an improvement , the addition of the tube with a reduction in temperatures probably means your bellmouth profile needs to be improved and another string test conducted to verify smooth flow into and across the entire cross section of the wheels inducer , once you have "perfect" inlet conditions you can then progress through the motor to make minor improvements at each station until you eventually reduce temperatures to reasonable levels by a compounding of small decreases .

The one glaring problem I see is your NGV stator , too much metal and not very efficient "nozzling"

Cheers
John

[finiteparts]

Hi Patty,

Glad to see your engine is running better, good job!

Now, if Miuge is using the same rotor and getting better pressure rise out of his compressor, that is sort of discouraging, since he has the standard housing with a vaneless diffuser. Your channel diffuser should be giving you a higher pressure rise at a given mass flow rate, if it is close to proper design, which I think it should be "close". So, that makes me wonder if you are still flowing "too much" airflow? Do you have a way to plug another NGV passage and test, without having to weld it up?

If you could measure the airflow through the engine, you would have a better idea of "where" you are operating relative to the standard vaneless diffuser. You should be at a higher pressure ratio for the same or lower mass flow. If you are opposite of that, then it would seem that your diffuser design has some serious flaws and you would have been better off making a vaneless diffuser.

With that in mind, the question arises, why are you trying to get a higher pressure ratio? A higher mass flow is way better for a thrust engine...the old drag racer adage "there's no replacement for displacement" still applies to jets! If you are trying for a turboshaft engine, then the pressure ratio is concerning only up to a point, but mass flow is still a big deal since it directly represents momentum. There is always a trade and you might be ok giving up some pressure rise, if it means getting more mass flow and still having enough pressure to meet the expansion requirements. It is always good to calculate it and see were you need to be.

Good luck,

Chris

[madpatty]

Hi racket,

I had already cured that NGV stator thing before these test runs...I had halved the NGV blade length.
Earlier the NGV blades were 50 mm long  and now they are about 25-27 mm long.

Hi finiteparts,

OK.I will do a manometer test at the compressor inlet as now it has got a 85 mm ID pipe fitted over it as suggested by Racket and i can fit two tubes for static and total pressure into the same pipe.

The idea for a high pressure ratio hasn't got any proper explanation behind just that similar setups are running at that pressure ratio, thats why.
Now Miuge's rotor may not be of the same make/model but from turbine/compressor specs it is very close.... 

cheers,
Patty

[racket]

Hi Patty

Are you running your " BIG " compressor wheel , or the "SMALL" comp wheel ??

Cheers
John

[madpatty]

Hi Racket,

Big compressor wheel.(54/83)

Cheers,
Patty

[racket]

Hi Patty

Big comp wheel , need I say more :-(

Cheers
John

[madpatty]

I tested with 3 smaller wheel with NGV throat adjusted accordingly...
And by now only this impeller had shown the best results....
And also, this engine is right now appearing to work just opposite to what we were expecting...A SURGING compressor (due to undersized turbine wheel) which is clearly not visible here....
Today i am going to do the air flow manometer test at the compressor inlet.....

Cheers,
Patty

[madpatty]

Hi Guys,

I ran the engine today with a water filled U-Tube manometer attached to a pipe at the compressor inlet.

Ambient temperature 20 degrees celsius. Pipe ID 82 mm.

The readings were as follows:-

P2     Manometer(mm of water)     Mass flow(Kg/s)(if i am not wrong)

13             150                                    0.31

14             170                                    0.33

15             180                                    0.34

16             194                                    0.356

17             206                                    0.367

18             212                                    0.37

19             236                                    0.39

cheers,
Patty

[madpatty]

cheers,
Patty

[racket]

Hi Patty

If your flow at 19 psi P2 was 0.39 Kgs/sec - 51.48 lbs/min you'd be flowing well into the choke region of your map for a 54mm inducer ............your method of calculating the flow is incorrect .

Try this link for some good info www.diyturbinejet.com/bellmouth.html

Cheers
John

[madpatty]

Hi Racket,
Please if you can explain what is wrong in this method....so that i can try and use the correct way to measure the correct airflow...

But one question:-
why you are against this fact that my impeller can run on choke side rather than surge side...when the whole data till now is pointing towards the compressor choke...

Cheers,
Patty

[finiteparts]

Patty,

Your numbers look right to me. I double checked your calculation for the mass flow and get 0.397 kg/s for the 19 psi P2 pressure. I plugged the numbers onto the H1E compressor map that I have (which is just a bit larger inducer than yours), so it looks like we thought, that you are over on the choke side of the compressor's operating range.



Good job on the manometer! In the future, if you can use smaller tubing it helps to keep the measurement device from impacting the inlet flow so much, but the larger tube gets the job done.

I forgot that you had tried to keep the diffuser sizing larger to stay closer to a sort of low-solidity style diffuser. My comments above were a little confusing, but what I was trying to say was that the diffuser wasn't behaving as expected.

I think you should bellmouth that tube and then you have a nice flow measuring device. Sure there are some errors, but you now have a way to see which way the mass flow of the compressor is changing. So even if it is only +/-10% accurate, it is still a valuable tool.

Good job!

Chris