Type of liquid fuel??

[momuzik]

just curious what the vast majority uses for liquid fuel once you have your jet turbo started with propane, and why...thanks

[jetjeff]

Hello,

Most turbines run on diesel or kerosene, simply because it contains the most energy per liter of fuel (kj or kilo joules)

Kurt Schreckling liked a mix of kerosene/diesel and 10 to 15% gasoline, because he felt the gas stabilized the flame front in the combustion chamber and made for easier starting.

Be careful using liquid fuel as fuel that has collected/pooled in the combustion chamber will eventually ignite causing a run-a-way situation. 

Regards

Jeff

[momuzik]

Ok super thanks Jeff, just kicking around ideas, I'll prob go with diesal since its easier for me to get..thanks again

[racket]

Yep , diesel is "safe" , but can smoke a bit at low power settings whereas kero is "cleaner" but harder to source in the quantities we use .

I'd take Jeff's advice and add a bit of petrol to the diesel , 10-15% will give the diesel a few more volatiles and more like kero .

We can run with high percentages of petrol but its a more "dangerous" fuel , easy to have an unwanted fire , I currently use 2 parts petrol to 1 part kero , sorta like JP-3 , as I need the extra volatiles to speed up my combustion , but I don't like all those petrol fumes hanging around when fueling up .

Cheers
John

[turboron]

As jetjeff said liquid fuel must not be allowed to collect in the combustion chamber where it is ignited at the next ignition creating a turbine run away. It is customary to have a weep hole or a spring loaded valve closed by compressor discharge pressure to prevent any liquid fuel collection.

Thanks, Ron

[momuzik]

Jul 23, 2019 19:10:52 GMT -5 racket said:

Yep , diesel is "safe" , but can smoke a bit at low power settings whereas kero is "cleaner" but harder to source in the quantities we use .

I'd take Jeff's advice and add a bit of petrol to the diesel , 10-15% will give the diesel a few more volatiles and more like kero .

We can run with high percentages of petrol but its a more "dangerous" fuel , easy to have an unwanted fire , I currently use 2 parts petrol to 1 part kero , sorta like JP-3 , as I need the extra volatiles to speed up my combustion , but I don't like all those petrol fumes hanging around when fueling up .

Cheers
John

OK THANKS JOHN, ALWAYS GREAT ADVICE 

[momuzik]

Jul 23, 2019 19:55:52 GMT -5 turboron said:

As jetjeff said liquid fuel must not be allowed to collect in the combustion chamber where it is ignited at the next ignition creating a turbine run away. It is customary to have a weep hole or a spring loaded valve closed by compressor discharge pressure to prevent any liquid fuel collection.

Thanks, Ron

Great idea with the weep hole or spring loaded valve...thanks a million 

[cebaero]

Jul 23, 2019 19:55:52 GMT -5 turboron said:

As jetjeff said liquid fuel must not be allowed to collect in the combustion chamber where it is ignited at the next ignition creating a turbine run away. It is customary to have a weep hole or a spring loaded valve closed by compressor discharge pressure to prevent any liquid fuel collection.

Thanks, Ron

I know this is an old thread, but what is turbine runaway?

[racket]

Turbine runaway is when you don't have control of the amount of fuel the engine is combusting , generally from fuel that has pooled in the outer can and suddenly starts to be consumed by the engine , the result is an increase in RPM , potentially to a level that is beyond design RPM creating a dangerous situation where an engine failure is possible from parts of the rotating assembly departing the engine .

[Richard OConnell]

I'm struggling to find the article, but I'm vaguely remembering a passenger plane crash where the culprit was found to be a massive oil leak burning within the combustor. If I recall, that actually caused an overspeed and destroyed the engine, but I do wonder if a mechanical oil pump could lead to an oil-fed runaway if there isnt a mechanism to stop oil flow. Also makes me wonder how large the oil reserves are on various aircraft or other applications.

[richardm]

I ve flown quite a few some jets and turbo props I remember the PW 123 on the Dash 8 held a total of about 20 quarts of oil but only 2quarts in the tank The rest is sitting here and there within the engine. Gear box accessory gear box lines pumps etc. Oil consumption was to be no more than 1 /10 of a quart per hour.

Your allusion to the oil leak causing a crash rings a bell but I can't remember exactly what it was. But there's basically no chance of this happening with a turbo charger based engine as the oil is confined to the core and a leak big enough to cause such a problem is vey unlikely since it would mean the bearing on the compressor side is worn to the point that the turbo would not run anyways.. At least thats what I think. On th turbine side you would get a lot of smoke from a major oil leak but it could not do much more.

On a real jet engine, oil can easily mix with compressor discharge air if one of the compressor labyrinth seal fails. It happened to me a couple of times and it's easily detected as some of this air is used to pressurize the cabin The fishy smell is unmistakable. But my guess is that it would take an huge leak ( more than a seal failure) to cause an engine to overspeed. Also those engine have overspeed protection of different kind but all of em act by reducing the fuel flow. So for an oil leak to cause an overspeed,I think something else that Im not aware of happened..

I would like to find d the report on that accident. Can you name the airline ?

[richardm]

I'm struggling to find the article, but I'm vaguely remembering a passenger plane crash where the culprit was found to be a massive oil leak burning within the combustor. If I recall, that actually caused an overspeed and destroyed the engine, but I do wonder if a mechanical oil pump could lead to an oil-fed runaway if there isnt a mechanism to stop oil flow. Also makes me wonder how large the oil reserves are on various aircraft or other applications.

www.faa.gov/lessons_learned/transport_airplane/accidents/VH-OQA

If this the one the failure was caused by an oil pipe failure and subsequent fire but did not cause an overspeed. That fire destroyed bearing seals and overheated a shaft ...

[richardm]

I'm struggling to find the article, but I'm vaguely remembering a passenger plane crash where the culprit was found to be a massive oil leak burning within the combustor. If I recall, that actually caused an overspeed and destroyed the engine, but I do wonder if a mechanical oil pump could lead to an oil-fed runaway if there isnt a mechanism to stop oil flow. Also makes me wonder how large the oil reserves are on various aircraft or other applications.

www.faa.gov/lessons_learned/transport_airplane/accidents/VH-OQA

If this the one the failure was caused by an oil pipe failure and subsequent fire but did not cause an overspeed. That fire destroyed bearing seals and overheated a shaft ...