Turbine 101
10-14-2007, 04:50 PM
#91
Registered
Thread Starter
Great thread!
I do not have any experence w/ turbine boats, but have been burning jet a for 20+ years in a/c.
I have a question and opinion.
1) Why 6 batteries? I can see a seperate 12volt system for the boat (although finding 24 volt systems for the rest of the boat may be not a bad idea), but 4 engine airplanes can do fine with ONE battery. That is a LOT of extra weight/complexity/cost. For multi engine installs, you start one engine, let the battery charge till you see the rate go down to what is appropriate, and hit the other starter. Then you get a cross generator start, providing a lower start temp on the second engine. You alternate which engine gets the first start.
2) The key switch thing: you do NOT want your start motor wired to a spring loaded switch. You let go at the wrong time during a start (or a connection gets goofy in the switch) and you will have an expensive day. If it were me, I would have a master switch for the entire boat controlled by a on/off key and solenoid, or just the start solenoids armed with an on/off key switch. But just a simple on/off switch for the starter. On most set ups, selecting off on the starter throws it over to a generator mode on the starter/generator. I have seen the aftermath of start interuped, and it 'aint pretty. You have enough to concentrate on during a start, don't make keeping the start circuit energized an extra that you have to think about. BTW, most installs in a/c have a "starter energized light" on the panel.
And, always make sure your batterie(!)s are 100% before you start! For lead acid you need to see 24 volts minimum ( I like digital readouts for this) before the start. You can get by with weak batteries on everything but turbines!
Fwiw....
I do not have any experence w/ turbine boats, but have been burning jet a for 20+ years in a/c.
I have a question and opinion.
1) Why 6 batteries? I can see a seperate 12volt system for the boat (although finding 24 volt systems for the rest of the boat may be not a bad idea), but 4 engine airplanes can do fine with ONE battery. That is a LOT of extra weight/complexity/cost. For multi engine installs, you start one engine, let the battery charge till you see the rate go down to what is appropriate, and hit the other starter. Then you get a cross generator start, providing a lower start temp on the second engine. You alternate which engine gets the first start.
2) The key switch thing: you do NOT want your start motor wired to a spring loaded switch. You let go at the wrong time during a start (or a connection gets goofy in the switch) and you will have an expensive day. If it were me, I would have a master switch for the entire boat controlled by a on/off key and solenoid, or just the start solenoids armed with an on/off key switch. But just a simple on/off switch for the starter. On most set ups, selecting off on the starter throws it over to a generator mode on the starter/generator. I have seen the aftermath of start interuped, and it 'aint pretty. You have enough to concentrate on during a start, don't make keeping the start circuit energized an extra that you have to think about. BTW, most installs in a/c have a "starter energized light" on the panel.
And, always make sure your batterie(!)s are 100% before you start! For lead acid you need to see 24 volts minimum ( I like digital readouts for this) before the start. You can get by with weak batteries on everything but turbines!
Fwiw....
batteries.
But they are old. 99 I charged them and they came to life however like you said it needs alot of current.
I called concorde they list for $3300 each.
I can get the optimas for $125 each
I will have a 24 volt parrel switch to boost the start if needed.
I am series in two 12,s for the constant draw of all the
pumps and compressor on the boat.
The other batteries will be dedicated to the turbines.
I droped the Exhaust in today. And as I thought it will
interfare with the placement of the batteries for the
piston engine location.
The exhaust was way to close for comfort to the fuel pumps also. I will move them also.
10-14-2007, 05:53 PM
#93
Registered
Join Date: Aug 2007
Posts: 95
Likes: 0
Received 0 Likes
on
0 Posts
Was the battery you are quoting a ni-cad?
Because IIRC, you can 24 volt lead acid (acid mat type) for maybe $400 or so?
You certainly do not want nicad- major pita, especially for this application. I don't have any idea if the optima has a low enough internal resistance to be good for your app, but if others are using them, prolly OK.
yahoo- starting is not a big deal, but you have to be ready for when something goes wrong. Most of the time, thankfully, it is quite routine. But if you get half way into a start and the battery or starter drops off line, you have a lot of fuel, and not enough air, and you get what is called a "hot start", or maybe if it does not accelerate to idle speed, a hung start. Either of which can get expensive in a hurry. The burner cans in a turbine support the flame via the air blast running through the engine. If not enough air, the flame will start to actually touch the burner can, and burn right through it. On a start, you monitor fuel flow, acceleration, and temps carefully. If any are off, you have to be read to cut off fuel RIGHT now, and continue to motor the engine until the temps are down.
Also, I am curious. Is the fuel system being set up with a resivore and motive flow type pump with a continous loop system?
Because IIRC, you can 24 volt lead acid (acid mat type) for maybe $400 or so?
You certainly do not want nicad- major pita, especially for this application. I don't have any idea if the optima has a low enough internal resistance to be good for your app, but if others are using them, prolly OK.
yahoo- starting is not a big deal, but you have to be ready for when something goes wrong. Most of the time, thankfully, it is quite routine. But if you get half way into a start and the battery or starter drops off line, you have a lot of fuel, and not enough air, and you get what is called a "hot start", or maybe if it does not accelerate to idle speed, a hung start. Either of which can get expensive in a hurry. The burner cans in a turbine support the flame via the air blast running through the engine. If not enough air, the flame will start to actually touch the burner can, and burn right through it. On a start, you monitor fuel flow, acceleration, and temps carefully. If any are off, you have to be read to cut off fuel RIGHT now, and continue to motor the engine until the temps are down.
Also, I am curious. Is the fuel system being set up with a resivore and motive flow type pump with a continous loop system?
Last edited by Fast Algae; 10-14-2007 at 05:56 PM.
10-15-2007, 09:42 AM
#95
Registered
Thread Starter
Not really that dumb
Its all about heat. Like Fast Algae stated.
If the turbine crank speed is not sufficiant the amount of air
flowing through will be low. So you have fuel alot of it
on start and not enough air will cause a hot start.
The turbine has a xtra start fuel. If this is controlable
at the cockpit if your Pyro starts to climb you can kill the xtra fuel this should lower the start temp.
Same applies on a hot engine.
Having the ability to completly cut fuel yet still be able to crank
(spool) would cool the turbine considerably faster.
It seems somewhat complicated but as long as you
keep your eye on your Pyrometer.
I,m sure I will become a freakin rocket scientist before this is all over.
Here is the one engine complete waiting for the Test Cell.
The other should be done by the end of this week.
Its all about heat. Like Fast Algae stated.
If the turbine crank speed is not sufficiant the amount of air
flowing through will be low. So you have fuel alot of it
on start and not enough air will cause a hot start.
The turbine has a xtra start fuel. If this is controlable
at the cockpit if your Pyro starts to climb you can kill the xtra fuel this should lower the start temp.
Same applies on a hot engine.
Having the ability to completly cut fuel yet still be able to crank
(spool) would cool the turbine considerably faster.
It seems somewhat complicated but as long as you
keep your eye on your Pyrometer.
I,m sure I will become a freakin rocket scientist before this is all over.
Here is the one engine complete waiting for the Test Cell.
The other should be done by the end of this week.
10-15-2007, 04:46 PM
#98
Registered
Join Date: Aug 2007
Posts: 95
Likes: 0
Received 0 Likes
on
0 Posts
RPM's are not usually measured directly, but as a percentage.
So say the gas generator turns 40,000 rpms, that would be expressed as 100% Ng.
For start, usually somewhere around 10-15 percent before you throw the fuel to it. (ignition on FIRST!) Depends on the engine.
Here is an interesting fact, the compressor of a turboshaft engine eats about3-4 times horsepower of the output. So, if you are using a engine that will output 700 hp, the compressor will require somewhere in the neighborhood of 2200 hp or so.
The starter motor of these things are powerful, somewhere around 5-10 hp, maybe more.
Hope you don't mind me Knot Right, but it is turbine 101, right?
So say the gas generator turns 40,000 rpms, that would be expressed as 100% Ng.
For start, usually somewhere around 10-15 percent before you throw the fuel to it. (ignition on FIRST!) Depends on the engine.
Here is an interesting fact, the compressor of a turboshaft engine eats about3-4 times horsepower of the output. So, if you are using a engine that will output 700 hp, the compressor will require somewhere in the neighborhood of 2200 hp or so.
The starter motor of these things are powerful, somewhere around 5-10 hp, maybe more.
Hope you don't mind me Knot Right, but it is turbine 101, right?
10-15-2007, 05:01 PM
#99
Registered
Thread Starter
I beleave N1 (Gas producer) must be at close to 40% to fire.
N1 at 100% rpm is 25,400.
so that would indicate a speed of 10,160 of n1 to fire.
N2 is the Power turbine this at 100% spins at 21,074
this goes through a gear reduction reducing to 6,600
rpm. If I can spin my 38 Herrings to 6,600 hold on to ya
cuhnyangas
It will produce 1400 SHP Shaft rated horsepower
at t5 temp of 1720 farenheight. with SFC of .580lbs/shp/hr.
I am as green as a sick leprichaun.
I,m Just reading this from the T53 for dummies book that Jim sent me.
Here is a nice cutaway of the T53 L13B
