Does a FOD screen cause loss of power and if so how much?
Thanks.... [sm=72_72.gif]

That is an easy question actually...an FOD blocks 1.274% of air, a pebble or piece of wood...100% - take your pick -

It should not. If the compressor wheel is starved, your EGT will rise.
Loss of power will not be seen. The range of use of a turbine is set after the max EGT and the max RPM.
A good care must be taken when designing a FOD guard so enough air can pass through.
For example, an old wren 44 sucks over 81 liters of air per second, when running at full throttle at sea level.
You can have an idea of how much is needed for a bigger engine.

jc,
How much does 1.274% of air loss translate to power loss? If it were 1.274% of thrust I can figure that out but air loss leaves me at a loss.. hehheh

Even if you were able to ride in the jet , You would NOT be able to detect a proformance difference, But if a foreign object goes thru your turbine, it's could wind up " a Paper Weight".

Yan,
I think you are saying whatever loss is created in restricting the air flow by using a FOD screen is compensated for by the EGT adjustment?
Thanks,
Don

I am not thinking about NOT using a FOD screen I was just wondering about power loss. Flying off of a grass runway I don't think I could sleep at night without having a FOD screen installed!

drdoom,
No, that would be an "expensive" paper weight! hehehhe...

drdoom,
That was interesting...when you made the post above...your post count and my post count were the same. That's freaky!

the easy way is:
get a method to measure your turbine thrust.

start your turbine and make a measurement without FOD

install the FOD restart the turbine and measure again..


may sound dumb...but i don'tsee other way to answer

Yes, your combustion will be less efficient, therefore rising the EGT.
Tu engine needs more fuel to run at the same speed. If the engine is running at full speed, you will damage it.
FOD guards made by wren are really nice, ,since there is no airflow restriction. The mesh is larger than the air intake of the turbine.
An other problem that can be met with custom made FOD guard is when the mesh is too close the the compressor wheel.
Specially true on small turbines, the airflow can be disturbed causing the compressor wheel to cavitate.

Alessio,You need to monitor your EGT, not your thrust. Max RPM (or max thrust) must be adjusted to get the max EGT your engine can take.
So in a way, yes, a FOD screen can lead to a loss of power. But you'll have to set it in the ECU.

Yann,
So since there is an air loss, a person would need to increase the rpm of the turbine to compensate for it but in turn you are also using more fuel for more rpm and the turbine will wear out earlier due to the increased turbine rpm? Does that sound correct?
Thanks,
Don

Alessio,
I think what you are saying makes a lot of sense. If thrust loss is what I am looking for..then measuring thrust before and after installing FOD screen will tell me.

Now, I am not sure what I could use to measure the actual thrust that is accurate in small increments to allow a difference to be measured without spending a considerable amount of money to purchase a precise instrument to measure thrust.
Thanks,
Don

Don,
that's the other way around.
If you have an air loss, the EGT rises, closing to the limit your turbine can take.
Therefore you have to lower the max RPM in the ECU so the turbine never exceed its max EGT.
Just think you shift up the range of use of your turbine on the EGT curve.
Got it ? Sorry my english might not be perfect.

Yann,
Can a person buy the Wren FOD screen for other types of turbines or just for Wren turbines? Since they are bigger than the actual turbine opening I am not sure if purchasing one from Wren for a non Wren turbine will work.
Thanks,
Don

Don,
I don't think it will work. Keep in mind this issue is less likely ot happen on bigger turbines.
You can use a seeve or anything, as long as the sum of the surface of the holes is at least the same as the open surface of your turbine air intake.

Yann,
No your english is great! It is my understanding that was faulty. Now I understand what you are saying. That makes sense to me. I don't think it's a problem at all for me but I was just curious as to loss of power with FOD screen.

If you would compare my "French" to your "English" use....trust me...you would be way ahead of me. ehehheheh....
Thanks,
Don

I ran my turbine in a teststand and chekced it witout a FOD-guard and then with the FOD-guard.

Without FOD-guard 9,5 kg thrust
With FOD-guard 9,25 kg thrust.

Any variation in temp etc I didnt chek.

So I will be using my homemade FOD-guard, no doubt.

brg

Thanks...