jet engine air flow

Depends on the engine being tested. Larger engines require higher flow.

You seem to want to simulate the working environment of a jet engine at full power in a wind tunnel.

At what altitude do you want to simulate? The volume of a given mass of air will change due to altitude changes.

The relative size of your engine to the 100 square ft will also have an effect on the volume and velocity in the tunnel.

I haven't tested a jet engine yet but would imagine that increasing the pressure at the intake of the engine cannot yield any useful results.

Maybe you should restrict the flow in the tunnel to simulate the correct pressure. This equipment is widely available, I have seen it with my own eyes.

Thanks for reply.

I am looking for the air volume required for a jet engine to operate properly at ground level. The required air volume at a high level is also required. Obviously the engine has to function at several levels. In order to produce the needed amount of power, a jet engine needs a certain air volume, and a certain amount of fuel. What volume is required at sea level, assuming it receives the necessary amount of fuel.?

I gave you a GA, but have to point one thing out

Yoda's quote is wrong.

Should be "Do, or do not. There is no try."

and it should also be "Jedi Master Yoda" not just "Master Yoda"

Petty I know but you still got a GA

Al

Is this a "homework" question?

Sorry but this question is way too vague. CFM and velocity will vary from 10's of cfm's for an aeromodelling turbine and 100,000's for the biggest commercial jet engines. Without a definition of the test subject, there is no answer.

There is missing data for any equation.

"Better questions will yield better answers."

Might be better to rethink the question. Given that you know the wind tunnel, you can provide the engine person information / charts on wind tunnel velocities, pressures, etc for defined inlet flow rates and engine exhaust flow rates (if the engine exhaust is handled separately from the main tunnel exhaust/loop). Then the engine person can determine if the wind tunnel is adequate for simulating desired engine conditions.

Thanks for response.

I am looking for a generic answer, and not one related to a specific engine, or set of circumstances. E.G. What rate of air flow is required at the intake of a jet engine to enable take off of a single jet aricraft? A generic answer will permit me to transfer contitions to each example and situation.

Well, there is no generic answer for the intake airflow needed for the takeoff of a single jet aircraft. The answer depends on the required takeoff thrust of the aircraft, and the engine design (i.e. turbojet vs. increasing bypass ratio turbofans). For reference, two engine business jets that I have worked on in the past had anywhere from 1400 lbf to 7200 lbf of take-off thrust at standard day conditions. Consequently, the intake airflow varied considerably.

The best that can be done is to map out the wind tunnel capability for different exhaust flow ratios. Beyond that, you really need to know the engine specifications at the wind tunnel conditions.

Well. Thanks.

What volume of air is needed for the jet with 1400 lbft of thrust, to takper off? And, ongoing, what volume of air is needed for the 7200 lbft of thrust, to support take-off.

[For the aircraft you personally worked on]

Even for the examples given, there are too many variables. What direction and speed is the wind? What is the inclination of the runway? What is the weight of the plane? Are there external wing tanks?

All of these questions will change the airflow needed for takeoff. A slow gradual take off can be accomplished with less throttle- airflow than a "carrier" style takeoff.

I am not trying to kill your project, just trying to help you get useful information. Good luck.

Well put BobC as ever....

Thanks again.

I am trying to get an answer to a partly defined project. I will have to re-define the question to get the information I am looking for.

Is there a relationship between the volume of air used, and the amount of thrust produced by any specific engine? Is it a direct relationship. e.g. does 10,000 lbs of thrust require ten times the air volume that 1000 lbs of thrust require. ? Does the intake of the engine require special design care to maximize intake for all conditions anticipated for that particular aircraft. ?

Please forgive me if I sound rude, but I see that you did not understand the basics of your question and is refusing to do so: A jet engine does not obbey any fixed conditions for load carrying, take-off, etc. All depends on pressure, temperature, humidity, wind conditions, ... It seems that you are about to ask then what's the output power of a jet engine. Guess what the answer will be? DEPENDS. Answering your simpler questions in this later post: Is there a direct relation between the required amount of air according to thrust? Yes, definitely. Because thrust is made by air mass being accelerated by the engine, so, the answer is easy. Does the engine intake require special care? Yes. As posted before, to take in account side wind effects, rain water ingestion, and even to create shock wave effect to allow the intake air to loose speed before entering the fan and the compressor (or it would just stall and...). I insist that you better look for a good basic book on the matter. Try Savaramutoo or some similar one on basics for jet machinery. You'll see your question with completely different eyes.

Unfortunately, specific information for engines is generally proprietary information. But if you need an estimate, assume a mach number of around 0.7 at the engine inlet throat at maximum takeoff power. That should yield a decent upper bound mass flow into the engine (mach 0.7 on the highside, from my recollection). From there, you can back calculate wind tunnel conditions to deliver the flow rate for defined inlet throat diameters. Further, charts could be made versus inlet throat diameter and inlet throat mach number. Then the charts could be used in future work with future customers for evaluating test needs.

Otherwise, poll potential wind tunnel customers for general engine information. Or get further detailed information from an existing customer.

The generic answer is:

The airflow into the engine must equal the airflow out of the engine, tempered by the change in volume, temperature and pressure created by the effects of combustion of the fuel. Have I forgotten anything?

what ya gonna do with the exhaust from your test cell?

what ya gonna do with the noise of your test cell?

how ya gonna keep your engine from taking off at full power?

how ya gonna keep the fuel supply cool in your test cell? what temp do you expect the egt to be? ??

how much is the fuel flow at idle? at crusie ? at 106 N2 ?

I can guess that a "generic" answer will be too general and prone to being wildly inaccurate......

Ridiculous!

Your question lacks specificity and your project demonstrates a general lack of comprehension of the technologies you appear to wish to test.

And your lack of name implies that you lack conviction.

Each of us "lack conviction" when we work in areas that are not famailiar to us. Am I to assume that you never do.? The name is George.

Unfortunately just when I think I have all of the idiosyncrasies of a vehicle mastered, It gets replaced, and I start over again. Even with that being said, I never lack the conviction that I can solve the problem presented.

I just have a hard time understanding someone posting a solution to a problem, while posting anonymously. I feel that a suggestion from guest, would not be my first choice under most conditions. Thank you for signing on.