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HeliTorque :: View topic - Feeding Jet A1 into the intake of a Turbine?
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HeliTorque Forum Index » Flight Dynamics

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Feeding Jet A1 into the intake of a Turbine?
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PostPosted: Thu Dec 16, 2004 7:03 pm    Post subject: Feeding Jet A1 into the intake of a Turbine? Reply with quote

Out of curiosity I would like to know what would happen when one were to spray JETA1 into the engine Air intake?
Would it drown the engine and therefor flame out?
Or would there be an enormous Flame coming out the back?
Or an explosion?

I personaly think it would generate an enormous Flame out the back.

Would does everyone else think?
I haven't managed to ask our engineers yet.

Looking forward to your thinking.

regards Toby
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PostPosted: Thu Dec 16, 2004 9:13 pm    Post subject: Reply with quote

1. Guess it would depend if a spray or jet and whether it completely prevented any air (O2).
2. Guess it would depend on the type of jet engine.. if high bypass then most of the fuel would go around the combustion part of the engine and probably ignite behind the engine.
3. Why do you want to know?

..... Think subject to being enough air to allow combustion it would product an afterburner type flame. Along with possible thermal distruction of the engine/airframe... or flash back to the fuel source.

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Thomas Coupling
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PostPosted: Thu Dec 16, 2004 9:31 pm    Post subject: Reply with quote

Hmm - why would anyone want to do that is beyond me, but hey! it's Christmas Wink

I take it you are not referring to the after-burner scenario, which In addition to the basic components of a gas turbine engine is occasionally employed to increase the thrust of a given engine. Afterburning (or reheat) is a method of augmenting the basic thrust of an engine to improve the aircraft takeoff, climb and performance.

Afterburning consists of the introduction and burning of raw fuel between the engine turbine and the jet pipe propelling nozzle, utilising the unburned oxygen in the exhaust gas to support combustion. The resultant increase in the temperature of the exhaust gas increases the velocity of the jet leaving the propelling nozzle and therefore increases the engine thrust. This increased thrust could be obtained by the use of a larger engine, but this would increase the weight, frontal area and overall fuel consumption. Afterburning provides the best method of thrust augmentation for short periods.

Afterburners are very inefficient as they require a disproportionate increase in fuel consumption for the extra thrust they produce. Afterburning is used in cases where fuel efficiency is not critical, such as when aircraft take off from short runways, or where a rapid increase in speed may occasionally be required.

Gas turbine engines for aircraft have an exhaust system which passes the turbine discharge gases to atmosphere at a velocity in the required direction, to provide the necessary thrust. The design of the exhaust system, therefore, exerts a considerable influence on the performance of the engine. The cross sectional areas of the jet pipe and propelling or outlet nozzle affect turbine entry temperature, the mass flow rate, and the velocity and pressure of the exhaust jet.

A basic exhaust system function is to form the correct outlet area and to prevent heat conduction to the rest of the aircraft. The use of a thrust reverser (to help slow the aircraft on landing for instance), a noise suppresser (to quieten the noisy exhaust jet) or a variable area outlet (to improve the efficiency of the engine over a wider range of operating conditions) produces a more complex exhaust system.

Lets empty some into the combustion chamber for a laugh...

The combustion chamber has the difficult task of burning large quantities of fuel, supplied through fuel spray nozzles, with extensive volumes of air, supplied by the compressor, and releasing the resulting heat in such a manner that the air is expanded and accelerated to give a smooth stream of uniformly heated gas. This task must be accomplished with the minimum loss in pressure and with the maximum heat release within the limited space available.

The amount of fuel added to the air will depend upon the temperature rise required. However, the maximum temperature is limited to within the range of 850 to 1700 ??C by the materials from which the turbine blades and nozzles are made. The air has already been heated to between 200 and 550 ??C by the work done in the compressor, giving a temperature rise requirement of 650 to 1150 ??C from the combustion process. Since the gas temperature determines the engine thrust, the combustion chamber must be capable of maintaining stable and efficient combustion over a wide range of engine operating conditions.

The temperature of the gas after combustion is about 1800 to 2000 ??C, which is far too hot for entry to the nozzle guide vanes of the turbine. The air not used for combustion, which amounts to about 60 percent of the total airflow, is therefore introduced progressively into the flame tube. Approximately one third of this gas is used to lower the temperature inside the combustor; the remainder is used for cooling the walls of the flame tube.

In conclusion, if you were really silly enough to empty a gallon of A1 down the pipes of a Jet Ranger - I'd suggest that you don a face mask or some other breathing apparatus to prevent inhalation of the smoke and fumes that would undoubtedly occur as a result.

No boom, no bang - just a (big) poof of smoke and a pop Wink

Very Happy
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PostPosted: Fri Dec 17, 2004 12:15 pm    Post subject: Reply with quote

T.C.
Thank you for that very informative reply, very much appreciated.

I was thinking only of Helicopters and only if it were to happen inadvertantly whilst an enginewash for instance.

Regards Toby
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PostPosted: Fri Dec 17, 2004 7:49 pm    Post subject: Reply with quote

.

Last edited by weekend warrior on Mon Jun 05, 2006 4:10 pm; edited 1 time in total
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PostPosted: Sat Dec 18, 2004 5:22 pm    Post subject: Reply with quote

I would not dream of trying it.
I do not want to add to the insurance cost's.
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PostPosted: Mon Dec 20, 2004 7:38 am    Post subject: Reply with quote

Flyer wrote:
T.C. and only if it were to happen inadvertantly whilst an enginewash for instance.

Regards Toby


You use Jet A1 for engine washes? Confused
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PostPosted: Mon Dec 20, 2004 3:32 pm    Post subject: Reply with quote

I have heard of an incident where an engine-wash was done with an unmarked cannister.
The result was that the engines flamed out, as it turned out later it was de-icing fluid which had been pourred into the engines therfore writing both engines off.As it turned out later they could have used the other unmarked cannister, which was next to the first unmarked cannister, for the engine-wash which would have been JETA1. Hence my question.
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PostPosted: Mon Dec 20, 2004 5:47 pm    Post subject: Reply with quote

Ahha.

Remind me not to use that maintenance organisation would you? Shocked

Under those circumstances (Jet A1) poured into the exhaust outlet, due to the low (ish) flash point of A1 would only cause smoke and a pop.

I had a seal go in flight once that caused a flow of oil from the engine to the combustion chamber. Apart from the smoke it was okay (for a short while of course). The engine had to be de-coked and checked but everything was ok.

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