turbine boat question??

[Jesse James]

I have heard the turine boats around the docks make a noise like a am radio losing tune... it is in this video at around 2:40 and throughout the rest of the video

http://www.youtube.com/watch?v=KQdY_...eature=related


also in the powerboat article they were talking about the throttle set up in copelands phenomenon...and it lead me to believe they had to do some engineering to get it down from 12 levers, and they indicited a seperate throttle for n1 and n2......

what is n1 and n2 and do they require sperate throttles and if so why?

thanks...

[GENERAL LEE]

As little interest as I have in owning a turbine boat, I'll ALWAYS watch them run!

Was that Hellfire? It doesn't really look like I remember it, but it's been a few years since I've seen it.

[phragle]

this might help...

http://www.aircav.com/cobra/T53-703.html

[Chris]

N1 is the compressor stage. The turbine compresses air prior to combustion just as a piston engine does, but in a linear fashion using a multiple-stage turbine compressor. Each stage having a more aggressive blade pitch. The output of the compressor stage is ported into a combustion chamber, the fuel is injected and ignited and the output is ducted to the power turbine, N2.

Just like an engine there are RPM limitations. Both stages' RPM is a function of fuel input and load. The other limitation is exhaust gas temperature. Essentially, too much fuel and not enough load will overspeed the turbine- typically the N2 side first. Too much fuel and too much load will probably cause EGT related failure before the N1 overspeed issue occurs.

A gas turbine is in simple terms a jet engine blowing against a fan. The fan is connected to a shaft and then a gearbox that reduces output RPM and converts that speed into torque.

All you need to control a turbine engine is a single lever to either mechanically or electrically open the valve on the fuel metering system.

[boostbros]

the really loud screeching at idle is from the bleed band being wide openreducing the air into the combustion chamber so as to not blow the flame out the more power a turbine makes the quieter it gets as all the air is forced thru the engine... some of the sounds you hear docking are there is a large disk brake on the output shaft with often 2 calipers they use a trim pump for brake pressure and can stop the n2 or power turbine to shift when released it sounds like blowing compressed air on a bearing as the blades spin up to speed.....all the blades in a turbine are hollow and have air blowing thru them to cool them thats what a hot start is to big of fire with not enough cooling air inside the blades then they can melt or bend with not good results!

[Brownie]

I wish I had a picture of the throttle for the 4,500 HP Lycoming turbine in the 110' "Genrty Eagle". It was a ten-cent knob, about 1/2" in diameter.

[tommymonza]

What does the starter sytem look like and how does it work?

[ZBODaytona]

didn't turbine marine say they have a 50'V NorTech that has turbines with sound output at 89db? I seem to remember a post about that one day, just don't remember which forum and when. Though there was never any video posted of the boat.

[GENERAL LEE]

According to Randy Sweers, Canada Thrust has the biggest turbines in a pleasure boat. He said it pulls like a solid rocket booster.

[Chris]

Geico just sold their BIG motors to Bill Tomlinson for his new Mystic.

[waterboy222]

So does the N1 and N2 require seperate levers or is it automatic?

[Chris]

So does the N1 and N2 require seperate levers or is it automatic?

N1 and N2 are just measurements. Seeing what one is doing relative to the other tells the opertaor alot about what's going on load wise. But they can only be controlled by the amount of fuel put into the engine (N1) and the output load (N2). Turbines are typically coupled to things like props or rotors so output load is adjusted via changes in pitch.

One lever.

[waterboy222]

so output load is adjusted via changes in pitch.

One lever.

Gotcha.. This is where I was confused.. Im with ya now.

[40FlatDeck]

N1 and N2 are just measurements. Seeing what one is doing relative to the other tells the opertaor alot about what's going on load wise. But they can only be controlled by the amount of fuel put into the engine (N1) and the output load (N2). Turbines are typically coupled to things like props or rotors so output load is adjusted via changes in pitch.

One lever.

Obviously, when you stall N2 to shift, I assume you can only stall it for a short time before bad things happen.

[Chris]

Some turbines can't be stalled at all. The Lycoming is tolerant of it, but not for any great amount at time and only at idle speed. Idle speed is sort of a funny term- Idle on a turbine is only about 20% less than max RPM. At that speed, it's not putting enough energy into the N2 stage to move it very fast.


John Arruda would pop in here now and again- he's obviously way more knowledgeable on this stuff. Hopefully he sees this.

[Bradz]

This a good thread. I have always wondered how they shift into gear. Turbines are really quiet at speed. It is almost odd how quiet they are cruising. I wonder what the DB test is at idle? Would they pass many state laws of 90DB at idle? That would be great if they did as I can keep dreaming of the someday...

[skaterdave]

no expert but what little time i spent around one setup with t-53s you can stop the n2 for around a minute or less. the only setup i've seen is pieces that Elstrom makes for Whispering which aruda also uses. basically a bellhousing that bolts to the back of the t-53 where the n2 out put shaft comes out. the bellhousing had a machined opening for a disc brake caliper and a standard SCS crashbox bolts up to it. the scs crash box has a longer input shaft with spines for the rotor which floats on the input shaft that couples up to the n2. the setup i saw used a electric-over-hydraulic brake actuator, like you'd see on a boat trailer, to apply pressure to the caliper.

this is very similar to SCS shiftable crash box. as far as stopping the n2, you could compare it to pressing on a clutch pedal to shift a car, your only stopping the n2 when you pressing on the clutch. once the crash box is in neutral the n2 spools up agian.

[tommymonza]

When you stop n2 does the hot exhaust get diverted during that process some how?

[skaterdave]

When you stop n2 does the hot exhaust get diverted during that process some how?

i think it was Knot-right that explained it best. picture two fans. the first fan (n1) blows air on the second fan, its that second fan (n2) that connects to the output shaft.

no the exhaust gases are forced threw the second fan's blade. the blades themselves are cooled when air is flowing but when their stopped so does the cooling air. the blades can only handle so much heat before damage occurs.

so no the exhaust is forced thru the n2 blades

[Rik]

When you stop n2 does the hot exhaust get diverted during that process some how?

No, it still flows out the exhaust, just not as fast as the PT wheel is providing more resistance when not rotating.

There are two throttle controls on the Fuel control of the T-53's that are being referenced here. Apply named N1 and N2.

There are several ways of "throttling" these engines. One can use one throttle or two as N2 acts as a governor in some regards. I've seen people set N2 and throttle with N1.

The T55 L11C's have the same basic layout as the T53 L13's. One can throttle either of these two together, seperate or singular when settting the N2 Throttle.