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Modern MBTs pros and cons of diesel and gas turbine engines?


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lockonstratos002 #1 Posted Jul 19 2016 - 19:28

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I am doing some research between the advantages and disadvantages of diesel power engines and gas turbine powered engines, I am not a tanker so there are things I need advice on (for example maintenance, startup speed etc). It seems to me that most tanks use diesel rather then gas turbine, I am quite sure there must be a good reason for that but I am not sure what that is.

So far here is what I have got

 

Both have in common 

-Both can be mounted in power packs

 

Pros

Diesel 

-Longer range/better fuel economy

-Faster start up

Gas turbine

-Multi-fuel

-lighter and more compact

 

Cons

Diesel

-Heavier and larger

-Non multi-fuel

Gas turbine

-shorter range/high fuel consumption

-long start up 



ChekrdDemon #2 Posted Jul 19 2016 - 19:53

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As far as multi fuel IIRC diesel will take kerosene, bunker fuel, heating oil, jet fuel and several other flavors short of gasoline.
 
As far as turbines, one big problem is that the exhaust is super hot, to the point of producing a danger zone behind the tank for personell...


Harkonen_siegetank #3 Posted Jul 19 2016 - 20:48

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Heating oil is just an ordinary diesel with different name. Reason being it's for tax purposes, afaik heating oil are tax free diesel.

kebab6597 #4 Posted Jul 19 2016 - 20:56

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View PostHarkonen_siegetank, on Jul 19 2016 - 19:48, said:

Heating oil is just an ordinary diesel with different name. Reason being it's for tax purposes, afaik heating oil are tax free diesel.

 

Kero is also used as heating oil the point is diesel engines are also multi fuel heck they can run of peanut and any veg oil aswell i ran my Toyota off veg oil right off the shelf of the local super market for many years with no problems at all until the bugger made it more expensive than diesel

Cutthroatlemur #5 Posted Jul 19 2016 - 21:15

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Yep, the original Deisel engines (made by Rudolf Deisel) ran on vegetable oils, primarily peanut oil, and Ford made engines that ran on hemp oil.  

 

Too bad for everyone (and our environment) that oil companies got involved...



HowitzerBlitzer #6 Posted Jul 19 2016 - 21:20

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View Postlockonstratos002, on Jul 19 2016 - 14:28, said:

-Non multi-fuel

IIRC you can run most engines if the diesel percentage in the mix is high enough, it's the case for whatever engine the modern Leopard tanks use.



Burning_Haggis #7 Posted Jul 19 2016 - 21:49

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View PostChekrdDemon, on Jul 19 2016 - 12:53, said:

As far as multi fuel IIRC diesel will take kerosene, bunker fuel, heating oil, jet fuel and several other flavors short of gasoline.
 
As far as turbines, one big problem is that the exhaust is super hot, to the point of producing a danger zone behind the tank for personell...

 

There are multifuel diesels that burn anything from gasoline to old used motor oil, or any mixture of assorted heavy oils and gasoline the operator wants to dump in them. that technology has been around since the '50's

 

I dump whatever oil-like substance in the tank I find cheap (or better yet... free)    My favourite in the summer is used deep fry oil. Makes my truck smell like KFC.



lockonstratos002 #8 Posted Jul 19 2016 - 22:29

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I also hear that a gas turbine on max power has a lower sound signature compared to diesel.

WulfeHound #9 Posted Jul 19 2016 - 22:49

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View Postlockonstratos002, on Jul 19 2016 - 16:29, said:

I also hear that a gas turbine on max power has a lower sound signature compared to diesel.

 

A different sound signature. They're just as loud (if not more) but are higher pitched which can make it more difficult for the sound to carry in long distances

stalkervision #10 Posted Jul 19 2016 - 23:06

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I believe modern gas turbines run on kerosene.

WulfeHound #11 Posted Jul 19 2016 - 23:30

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View Poststalkervision, on Jul 19 2016 - 17:06, said:

I believe modern gas turbines run on kerosene.

 

JP-8, which is kerosene based with additives for better stability. That's for land-based aircraft and vehicles. The Navy uses JP-5 which is also kerosene based but has a higher flash point than JP-8 and does not contain some of the additives of the other fuel

Walter_Sobchak #12 Posted Jul 28 2016 - 02:53

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View Postlockonstratos002, on Jul 19 2016 - 13:28, said:

I am doing some research between the advantages and disadvantages of diesel power engines and gas turbine powered engines, I am not a tanker so there are things I need advice on (for example maintenance, startup speed etc). It seems to me that most tanks use diesel rather then gas turbine, I am quite sure there must be a good reason for that but I am not sure what that is.

So far here is what I have got

 

Both have in common 

-Both can be mounted in power packs

 

Pros

Diesel 

-Longer range/better fuel economy

-Faster start up

Gas turbine

-Multi-fuel

-lighter and more compact

 

Cons

Diesel

-Heavier and larger

-Non multi-fuel

Gas turbine

-shorter range/high fuel consumption

-long start up 

 

Fuel economy between the two types of engine is different as you note.  When running at full power, the difference between a turbine and a diesel is not all that extreme.  The problem comes when at idle, the turbine is far less fuel efficient at low RPMs than the diesel.  When the US army came up with the specs for the M1 Abrams in the 1970's, one of the things they wanted was an APU (auxiliary power unit). This is a small diesel engine that can power all the tanks systems when it is stationary, saving fuel over running the primary powerpack.  However, an APU was excluded from the Abrams in an attempt to keep initial costs down on the vehicle.  The thinking was to first get the vehicle funded by congress and into production, then add whatever extras they wanted later.  In retrospect, this was probably a mistake, the Abrams really should have had an APU from the start. 



collimatrix #13 Posted Jul 30 2016 - 12:55

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Re: multi-fuel capability

A diesel engine can run on a number of possible fuels, provided they have the right cetane number.  This is sort of like an octane number, but backwards.  So yes, you can run most diesels on vegetable oil.  Good luck running them on petrol.


A gas turbine can run on damn near anything provided it burns.  JP8?  Obviously.  Diesel?  No sweat.  Gasoline?  Sure thing.  Natural gas?  There are only a gazillion LM1500 gas turbines (basically a J79 out of a phantom modified for industrial use) running on natural gas doing various jobs.  Ethanol?  Sure, why not.  

 

It's possible to make a diesel that's multi-fuel-ish, through various contrivance.  The track record hasn't been entirely encouraging with regard to mass produce-ability or reliability.

 

Any gas turbine will be able to run on virtually anything flammable, provided it has enough energy in it when burned, and doesn't clog or corrode the pumps.  In the Brayton Cycle the air is compressed and the ignition is continuous, so there are no concerns whatsoever with pre-ignition, knock, or engine timing.  It is simply not possible to make a piston engine that is as omnivorous as a turbine.

 

Turbines have a number of further advantages in practice.  They are easier to start up in cold weather, which is an area that especially bedevils diesels.  They have far less vibration than any reciprocating engine, which is a factor in crew fatigue.  Turbines have a better ratio of gross power to net power.  A nominally 1500 HP diesel will deliver less power to the transmission than a 1500 HP turbine, because the diesel needs to drive large fans to cool the radiator (or the cylinder fins in an air-cooled engine).  Turbines are self-cooling (nearly).

 

Turbines have a number of additional advantages in theory, although perhaps not in practice.  All tanks so far produced with turbines (S-tank, T-80 and M1) use rather old gas turbine designs that are not at all representative of what modern technology is capable of.  Using modern metallurgy, gas turbines can go an absurdly long time between major overhauls:

 

 

Block Quote

 "It would take the average engine 10,000 TACs, or more than 25 years of operation, to experience the same levels of time and temperature exposure built into this test plan. 

 

Block Quote

 The F100-PW-229 is designed to extend the periodic engine inspection requirement from 4,300 to 6,000 cycles 

 

 

So the F100-PW-229 can go better than a decade between inspections with normal use.  Not bad.  The elimination of reciprocating parts makes turbines potentially much less maintenance intensive than piston engines.

 

Additionally, the efficiency of gas turbines has improved, a lot.  Here's a chart of idealized efficiencies vs. overall pressure ratio for Brayton Cycle engines:

 

Posted Image

 

AGT1500 manages 14:1 overall pressure ratio at design point.  The GE9X manages 60:1.

 

 



darkhorsey #14 Posted Jul 30 2016 - 19:06

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Something you didn't mention is turbines use a lot of air.....if it's dusty you have to clean the filters daily.  It's a huge pain in the [edited].

Ikanator #15 Posted Nov 21 2016 - 13:37

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Also note that on a modern battlefield there may be many units and weapons systems with thermal ir sensors. That could potentially put an operating turbine engine at a disadvantage versus a diesel engine because the hot exhaust plume from the turbine would likely stand out more.

Edited by Ikanator, Nov 21 2016 - 13:38.


Anlushac11 #16 Posted Nov 21 2016 - 16:39

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Last I saw (dated 2014) GE and Honeywell were still developing the LV100-5 gas turbine as the intended future replacement for the AGT1500.

 

With cancellation of the Crusader SPG the LV100-5 was being groomed as the future AGT1500 replacement.

 

Compared to the AGT1500 design the LV100-5 design is said to use 43% fewer parts and have 33% better fuel efficiency running and 57% better fuel efficiency at idle.



The_Chieftain #17 Posted Nov 22 2016 - 18:07

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View PostIkanator, on Nov 21 2016 - 12:37, said:

Also note that on a modern battlefield there may be many units and weapons systems with thermal ir sensors. That could potentially put an operating turbine engine at a disadvantage versus a diesel engine because the hot exhaust plume from the turbine would likely stand out more.

 

Honestly, I don't see it as being a problem. Vehicles show up nice and bright on a thermal imager, turbine exhaust or not. Frankly, the 'really, really hot' bit is hidden behind the tank. Or, at least, it should be if the tank commander remembers which way the enemy's supposed to be.

 

If memory serves, turbines have more torque, resulting in faster acceleration.



zloykrolik #18 Posted Nov 22 2016 - 23:57

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The heat from friction in roadwheels & track, or tires, show up really well in TI. I suppose hot turbine exhaust would be a problem for a tank if it had been sitting in a defensive position for a long time and the tracks had cooled down to ambient temperature. But that has to be a minor concern.

moon111 #19 Posted Nov 23 2016 - 02:50

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When you compare the two, I would think diesel would be the best overall choice.  Unless you're the United States.

 

Just checking the Wikipedia site: 

M1 1,900 litres of fuel with a range of 426 kms.

Leopard 2, 1,200 litres of fuel with a range of 550kms.

 

The U.S. is a massive army.  The 'machine' will always be there.  The ability to last two hours longer is a much better

for others that might have to act more independent for longer periods of time and could face compromised supply

chains. 



collimatrix #20 Posted Dec 01 2016 - 04:26

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View Postdarkhorsey, on Jul 30 2016 - 19:06, said:

Something you didn't mention is turbines use a lot of air.....if it's dusty you have to clean the filters daily.  It's a huge pain in the [edited].

 

You're right about the filters, although according to Ogorkiewicz the airflow for a turbine and a diesel of equal output is comparable.  I think the difference is that most of the air for a diesel is air that's getting pulled around the radiators, while all the air for the turbine is going through the engine, so it has to be filtered.

 

On the other hand, turbines have no radiators to maintain.

 

View PostIkanator, on Nov 21 2016 - 13:37, said:

Also note that on a modern battlefield there may be many units and weapons systems with thermal ir sensors. That could potentially put an operating turbine engine at a disadvantage versus a diesel engine because the hot exhaust plume from the turbine would likely stand out more.

 

I've actually heard that an Abrams stands out less on thermals than a Leo 2.  I know, I was pretty surprised too.  The reason is that the diesel puts out a cloud of fine particulate that scatters the IR emissions, and rises above the tank and is thus obvious from a long ways off.  Turbines (or at least the AGT-1500) apparently don't do this.

 

View PostAnlushac11, on Nov 21 2016 - 16:39, said:

Last I saw (dated 2014) GE and Honeywell were still developing the LV100-5 gas turbine as the intended future replacement for the AGT1500.

 

With cancellation of the Crusader SPG the LV100-5 was being groomed as the future AGT1500 replacement.

 

Compared to the AGT1500 design the LV100-5 design is said to use 43% fewer parts and have 33% better fuel efficiency running and 57% better fuel efficiency at idle.

 

There was even a modified version of the AGT-1500 that had some new parts swapped in that had significantly better idle efficiency and time between overhauls.

 

The AGT-1500 simply isn't remotely representative of what modern turbines are capable of.






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