Turbine powered tanks

[ysi_maniac]

Excuse my ignorance: Turbines like that of Abrams have air intake and exahust or the air circulates in closed circuit ?

[Rickshaw]

Excuse my ignorance: Turbines like that of Abrams have air intake and exahust or the air circulates in closed circuit ?

Intake and exhaust.  You cannot reuse the air after combustion - the oxygen is essentially used up and the volume would be so great you couldn't carry sufficient to do it.

[Gingie]

Mmm, turbine exhaust :) our ADATS had a turbine to power all the non-drivetrain components. Sucked down diesel like a mutha, but man that exhaust was nice to dry out a wet uniform or warm up some IMP's!

[arkon]

not sure if this helps but recirculateing the hot exhaust air back into the intake lowers the engine efficiency,raises intake temp,which raises exhaust temp, and goes into some what neverending loop untill the engine overheats and shuts down and/or catches fire.
 i have problems like this at work with touring buses and coaches generaters.

[ysi_maniac]

Thanks for your assistance.

Then, where are Intake and exhaust in Abrams, for instance?

Does this leave a hot fingerprint visible to an IR camera?

[AGRA]

Then, where are Intake and exhaust in Abrams, for instance?

The intakes are on the roof of the hull above the engine around the rear of the turret bustle. The exhaust is the three grills on the rear though only the central one is for actual turbine exhaust.

Does this leave a hot fingerprint visible to an IR camera?

Yep a big plume of gas though it isn’t as big as the actual tank

[GTX_Admin]

This book:



Has some good details on proposed Gas Turbine powered tank proposals.

[elmayerle]

I'll admit that my own prejudices are for using something like a large 6-rotor SCORE (Stratified Charge Omnivorous Rotary Engine) engine rather than a turbine.  You get the same smoothness and multi-fuel capability,  but somewhat more in the way of robustness and, I suspect, a lower overall thermal signature.

[Rickshaw]

And fuel consumption?  For Turbines to run most efficiently they need to run continiously at 90-100% of capacity so tend to chew through the fuel at enormous rates.

[GTX_Admin]

That's why it is often considered to hook them up to a generator/electric motor.

[AGRA]

It may be sacrilege in this thread but Continental had built a 1,500 hp evolution of their excellent air cooled AV-1790s. So who needs turbines? But in their defence from my experience of looking at M1s through FLIR I don’t think the plume makes that much of a difference. It is a big white jet (or black with colours reversed) out the back but it does dissipate quickly and won’t affect the frontal aspect.

[Logan Hartke]

Yeah, there's a lot of advantages and disadvantages to them.  I think it really depends on what your needs are as to whether you would want a diesel- or a turbine-powered tank.  I don't think one is inherently better or worse.  Despite all the disadvantages (and there are many), my perception of seeing Abrams and Challengers in operation is that the acceleration from a turbine is pretty awesome in a combat environment.  Some of the footage from Iraq showed Abrams getting out of trouble just as fast as they got in.

I really was surprised watching a speeding Abrams come to a complete halt and reversing down a city street at a considerable clip in what seemed like only a few seconds.  Challys in the same environment looked comparatively sluggish, though the logical part of my brain knows that they're more than mobile enough for a tank in all honesty.  It was just that the perception was striking.

Again, it wasn't the speed, it was the braking and acceleration that took me by surprise for M1 Abrams mobility.  Really surprising for a tank.

M1 Abrams - mobility and speed demo

Cheers,

Logan

[Volkodav]

My understanding is the transmission is as, if not more important than the engine, so long as the engine is powerful enough. i.e. a 1200bhp diesel with a good transmission will out perform a 1500bhp one with an inferior trans.

On the mobility of the Challenger, while I don't know about the Challenger II, the add on armor used on the Challenger I's during 1991, basically doubled the vehicles weight to 120t.

[Rickshaw]

While the M1 may have higher acceleration than the Challenger, the Challenger has a greater range.  I've read many accounts of British tanks passing US tanks which have had to stop and refuel.  In the sort of open, manoeuvre warfare like that experienced in the desert, its often more important to be able to reach your objective with the least logistical tail.  The US Army can afford to use turbines, the British Army can't.  The increased fuel and logistical requirements are such that it would be prohibitive for most armies, other than the US to be able to keep them running.

The S-Tank with its CODAG (Combined Diesel And Gas) engine system perhaps offered the best of both worlds, a diesel for cruising and a gas turbine for speed.

As Greg has noted, hooking a gas turbine up to an electrical system works well but no one has tried that in a tank yet.   I suspect it's because the combination of gas turbine, generator and electrical motors plus fuel is fairly space consuming.   Which may make it difficult to have a main gun of the 120+mm in size and it's ammunition and the crew and the electronics to sustain it a bit cramped in something the size of the present MBT volume. 

[AGRA]

The M1 has better acceleration than the Challenger because it rolls with 25% more engine power. Also in operation in ODS and OIF M1 tanks were lighter. Both M1A1 and CR2 has a core combat weight of 62 metric tonnes (start playing with long and short tons and nothing makes sense). But the CR1 and CR2s both went into action with heavy applique armour on the hull. Not quite 120 tonnes but the heaviest configuration used in recent years was well over 80 tonnes (including turret applique).

The M1’s gas turbine may burn more fuel but it is much smaller so more fuel can be fitted in the same hull volume compared to a diesel. On a straight road run the M1’s 1,900 L will get you 426 km while the CR2’s 1,600 L will get you 450 km. The differences are not significant nor is the idle fuel consumption (M1 only burns 38 L an hour on idle).

There are many, many more ‘anecdotes’ and journalists and thriller writers opinions out there that the M1 is a terrible fuel guzzler compared to people who actually worked on the tank. And best of all the turbine makes the M1 so much quieter than other tanks. Turbocharged diesel engines are fearsome in their noise signatures.

BTW S-Tank had terrible fuel efficiency because it couldn’t idle when stationary. To provide the available power to train the weapon one of the engines needed to keep running at a reasonable power level to charge the transmission. Also the twin engine arrangement wasn’t selected as much for road march fuel efficiency but rather to fit in a hull cut down the middle by a gun barrel and to provide a cold start engine (turbine).

[Logan Hartke]

That was my basic understanding of the situation, too, AGRA.  The tanks I was seeing were M1A2s and Chally 2s during the opening phases of OIF.

Cheers,

Logan

[GTX_Admin]

Folks,

No point getting into an argument re the M1's Gas Turbine. After all, the operators seem happy enough and aren't going to change.

Regards,

Greg

[GTX_Admin]

Further to my comment re the Panther tank:


(Click on image for more details).

And here

[GTX_Admin]

The other tank that was/is powered by a Gas Turbine is the T-80:



Of course, just because it has a jet engine doesn't mean it can fly:



or does it?

[elmayerle]

I can just see them doing a nap of the earth formation flight to background music of the Light Cavalry Overture.

[simmie]

This may not be totally relevant to the M-1 /Cr2 discussion.

I remember hearing reports during Iraqi Freedom, when the Abrams entered Baghdad, the Iraqis disabled them by shooting RPGs in the the exhaust vent in the rear of the hull.  This didn't penertrate the armour, but did kill the powerpack.

[AGRA]

That was my basic understanding of the situation, too, AGRA.  The tanks I was seeing were M1A2s and Chally 2s during the opening phases of OIF.

The road march fuel consumption difference between an M1 and Challenger/Leopard 2 is about 20% more per km for the M1. The big difference is when at idle where the M1 burns about three times as much as the diesels. But this is under 40 L per hour so you aren’t going to run out of fuel any time soon and the M1s now have the APU in the turret bustle rack so they don’t need to idle in overwatch.

In ODS the big thing that stoped the M1s more than fuel was their air filters. Turbines need clean air and lots of it to run placing a lot of strain on the filters. M1 crews stopped every 100-150 km (2-3 hours) to clean the air filters. They took advantages of these stops to refuel, do maintenance, stretch legs, etc. Challengers didn’t have this extreme need to maintain their air filters and also carried external fuel tanks in the pre battle phase. So could drive for longer before stopping.

But from a logistics perspective the burden of the M1 is marginal. Certainly when the Australian Army changed from Leopard 1 to M1 there was a need to upgrade the fuel supplies of 1 Armd Regt. And the Army was barraged by all the M1 burns to much fuel arguments. But none of these arguments took into account going from a 40 tonne Leopard 1 tank to a 60 tonne M1 with almost twice the engine power. Army simply increased the number of fuel trucks available per regiment to eight.

I remember hearing reports during Iraqi Freedom, when the Abrams entered Baghdad, the Iraqis disabled them by shooting RPGs in the the exhaust vent in the rear of the hull.  This didn't penertrate the armour, but did kill the powerpack.

The Iraqis only knocked out one M1 during the OIF Thunder Runs of Baghdad (the famous Cojone Eh). It was hit by a recoilless rifle round (not RPG) fired up and into the left rear side sponson. Where it started a fire amongst the batteries and fuel tanks that couldn’t be controlled. The grills at the rear are just as resilient to solid armour around them. Grills actually defeat shaped charge warheads better than solid armour does.

[Cliffy B]

What credibility is there to the story that during the First Gulf War the Iraqis gave up trying to find our tanks because it was easier to find our fuel truck convoys instead because the M1s needed gas so often?  Another stretched truth, falsehood, or what? 

[AGRA]

What credibility is there to the story that during the First Gulf War the Iraqis gave up trying to find our tanks because it was easier to find our fuel truck convoys instead because the M1s needed gas so often?  Another stretched truth, falsehood, or what? 

Complete fiction. For starters a tank has a much bigger signature than the heaviest truck. Also enemy tanks are closer to you than their fuel supply. But realistically how could the Iraqi's limited tactical recce tell the difference between a fuel truck, water truck and stores truck?

If there is any substance to the myth it is the massive size of the allied logistic convoys compared to the size of the combat units in column. But fuel for the tanks was only a small part of this logistics tail. Blaming it all on the M1 is the all too typical trait of story tellers to turn molehills into mountains.

[Rickshaw]

Folks,

No point getting into an argument re the M1's Gas Turbine. After all, the operators seem happy enough and aren't going to change.

Regards,

Greg

However, there have been several proposals which the US Army have considered seriously to re-engine the M1 with diesel engines.   The operators are happy with the turbine but their superiors aren't, particularly in the coming age of scarcity.  It is more than likely that the next US tank may be using a diesel engine.