AFV Engines

[Walter_Sobchak]

I realized that we have a thread for transmissions and final drives, but not for engines.

I'll start with this post about the Japanese 10 ZF engine from the Type 74 tank.  As far as I know, not much has been published in English about this engine.  It's a rather interesting one in that it's an air-cooled 2 stroke diesel.  

[Xlucine]

A 2 stroke with exhaust valves?

[Walter_Sobchak]

Here is a fun chart

[Walter_Sobchak]

2 hours ago, Xlucine said:

A 2 stroke with exhaust valves?

 

[Collimatrix]

Does anyone have a good diagram of how the cooling system in the 5DTF engine works?  I recall it being something exotic; exhaust-driven or some such.

[Xoon]

The US is planning on standardizing their fleet on a modular opposed piston design, a little interesting:

http://www.calstart.org/Libraries/HTUF_2016/6_-_Major_-_Achates.sflb.ashx

 

And some info:
http://www.dtic.mil/dtic/tr/fulltext/u2/a566997.pdf

http://www.dtic.mil/dtic/tr/fulltext/u2/a626738.pdf

 

[Walter_Sobchak]

This would not be the first time the Army tried to develop a family of engines around a common cylinder.  

 

 

[Xlucine]

Why buy a whole new engine that produces the same power as the old one? If you're investing that much capital then you should hope to get more margin for future weight growth; maybe they just really really want to squeeze a bigger APU in there?

[Ramlaen]

The design should be able to be scaled larger than 1500hp if it was desired. But the desire is unified logistics and lower operating costs.

Edited May 15, 2017 by Ramlaen

[Xoon]

Free Piston linear generator. 

Crappy wikipedia link: https://en.wikipedia.org/wiki/Free-piston_linear_generator

 

 

And two videos:

 

 

 

Not sure where to post this, but I think this could be a really good option for Series Hybrid electric AFVs. 

[roguetechie]

I've been looking at very similar / related concepts for quite some time for similar reasons.

 

Really with modern FEA and sim capabilities along with our new manufacturing tricks there's whole rafts of engine concepts which previously failed that would actually totally kickass now.

[W. Murderface]

Regarding rafts of engine concepts, a vehicle with electric motors and an empty engine bay could offer a myriad of possibilities. Just add electricity.

 

Xoon mentioned free piston linear generators. A few of these, and whatever you want to feed them in the tank, and you can go do your thing. Additionally, if the vehicle were to take a hit, as long as some FPLGs remain operational, you do too (I think).

 

A group of students from Eindhoven built a formic acid fuelled range extender trolley to hang behind an electric city bus. If the contents of the trolley could be made to fit, that would be a pretty sweet means of electricity generation. It produces far less waste heat and noise than a combustion powered generator. Unlike petroleum-based fuels formic acid isn't flammable, and when you do it right it has no carbon footprint. But it's a big if. This approach assumes a rather high efficiency compared to fossil fuel systems.

Some links:

http://www.teamfast.nl/

https://www.tue.nl/en/university/news-and-press/news/07-07-2017-how-to-power-a-bus-on-formic-acid/

http://pubs.acs.org/doi/abs/10.1021/acsenergylett.6b00574

 

These two articles suggest other compounds as hydrogen carriers, most interestingly carbohydrates. The latter article suggests as much as 10 MJ of H₂ power from 1 kg of carbs, about twice as much as formic acid's 5.22 MJ/kg. But then again, I've seen the formic acid trolley on TV, but no sugar car so far. Maybe it's a good next step after you've bought your formic acid powered tanks. They have electric motors already.

http://www.nature.com/nature/journal/v495/n7439/full/nature11891.html?foxtrotcallback=true

http://bioenergycenter.org/besc/publications/zhang_renewable_carbohydrate.pdf

 

 

[Collimatrix]

6 hours ago, W. Murderface said:

Regarding rafts of engine concepts, a vehicle with electric motors and an empty engine bay could offer a myriad of possibilities. Just add electricity.

 

Xoon mentioned free piston linear generators. A few of these, and whatever you want to feed them in the tank, and you can go do your thing. Additionally, if the vehicle were to take a hit, as long as some FPLGs remain operational, you do too (I think).

 

A group of students from Eindhoven built a formic acid fuelled range extender trolley to hang behind an electric city bus. If the contents of the trolley could be made to fit, that would be a pretty sweet means of electricity generation. It produces far less waste heat and noise than a combustion powered generator. Unlike petroleum-based fuels formic acid isn't flammable, and when you do it right it has no carbon footprint. But it's a big if. This approach assumes a rather high efficiency compared to fossil fuel systems.

Some links:

http://www.teamfast.nl/

https://www.tue.nl/en/university/news-and-press/news/07-07-2017-how-to-power-a-bus-on-formic-acid/

http://pubs.acs.org/doi/abs/10.1021/acsenergylett.6b00574

 

These two articles suggest other compounds as hydrogen carriers, most interestingly carbohydrates. The latter article suggests as much as 10 MJ of H₂ power from 1 kg of carbs, about twice as much as formic acid's 5.22 MJ/kg. But then again, I've seen the formic acid trolley on TV, but no sugar car so far. Maybe it's a good next step after you've bought your formic acid powered tanks. They have electric motors already.

http://www.nature.com/nature/journal/v495/n7439/full/nature11891.html?foxtrotcallback=true

http://bioenergycenter.org/besc/publications/zhang_renewable_carbohydrate.pdf

 

 

 

Welcome to SH Bill Murderface.  

 

Building on your point, the space penalty for a tank with non collocated engine and drive sprockets is lower if it has an electric drivetrain.  That said, I think that current AFV engine compartments tend to be closely wrapped around their powerplants.  The proposed diesel Abrams all had enlarged engine decks.  So I don't think that putting exotic new powerplants in tanks is primarily constrained by transmission compatibility.

[Belesarius]

9 hours ago, W. Murderface said:

Regarding rafts of engine concepts, a vehicle with electric motors and an empty engine bay could offer a myriad of possibilities. Just add electricity.

 

Xoon mentioned free piston linear generators. A few of these, and whatever you want to feed them in the tank, and you can go do your thing. Additionally, if the vehicle were to take a hit, as long as some FPLGs remain operational, you do too (I think).

 

A group of students from Eindhoven built a formic acid fuelled range extender trolley to hang behind an electric city bus. If the contents of the trolley could be made to fit, that would be a pretty sweet means of electricity generation. It produces far less waste heat and noise than a combustion powered generator. Unlike petroleum-based fuels formic acid isn't flammable, and when you do it right it has no carbon footprint. But it's a big if. This approach assumes a rather high efficiency compared to fossil fuel systems.

Some links:

http://www.teamfast.nl/

https://www.tue.nl/en/university/news-and-press/news/07-07-2017-how-to-power-a-bus-on-formic-acid/

http://pubs.acs.org/doi/abs/10.1021/acsenergylett.6b00574

 

These two articles suggest other compounds as hydrogen carriers, most interestingly carbohydrates. The latter article suggests as much as 10 MJ of H₂ power from 1 kg of carbs, about twice as much as formic acid's 5.22 MJ/kg. But then again, I've seen the formic acid trolley on TV, but no sugar car so far. Maybe it's a good next step after you've bought your formic acid powered tanks. They have electric motors already.

http://www.nature.com/nature/journal/v495/n7439/full/nature11891.html?foxtrotcallback=true

http://bioenergycenter.org/besc/publications/zhang_renewable_carbohydrate.pdf

 

 

Welcome to SH~!

[W. Murderface]

8 hours ago, Collimatrix said:

 

Welcome to SH Bill Murderface.  

 

Building on your point, the space penalty for a tank with non collocated engine and drive sprockets is lower if it has an electric drivetrain.  That said, I think that current AFV engine compartments tend to be closely wrapped around their powerplants.  The proposed diesel Abrams all had enlarged engine decks.  So I don't think that putting exotic new powerplants in tanks is primarily constrained by transmission compatibility.

 

For wheeled vehicles at least, I think there's the possibility to increase the protected volume by moving the motors away from the hull and into the wheels. As for tracked stuff, I'm not sure putting your primary sources of locomotion on the relatively stickie-outtie top rear corners of the hull is a smart move. You could bury them deeper, but that'll cost you at least some of your hard won protected volume. Either way, I think there's a case to be made for copper or aluminium wires for drive trains.

 

Not necessarily engine related, but: having a huge generator on board opens up windows to directed energy weapons, and further down the line maybe even rail guns. 

[Xoon]

1 hour ago, W. Murderface said:

 

For wheeled vehicles at least, I think there's the possibility to increase the protected volume by moving the motors away from the hull and into the wheels. As for tracked stuff, I'm not sure putting your primary sources of locomotion on the relatively stickie-outtie top rear corners of the hull is a smart move. You could bury them deeper, but that'll cost you at least some of your hard won protected volume. Either way, I think there's a case to be made for copper or aluminium wires for drive trains.

 

Not necessarily engine related, but: having a huge generator on board opens up windows to directed energy weapons, and further down the line maybe even rail guns. 

Only places I find aluminum useful would be for the motor casings and the cables between the Generator, battery, and controller. 

[W. Murderface]

Just now, Xoon said:

Only places I find aluminum useful would be for the motor casings and the cables between the Generator, battery, and controller. 

Why not connect the motors with aluminium cables as well?

[Xoon]

3 minutes ago, W. Murderface said:

Why not connect the motors with aluminium cables as well?

Because optimally, the VSD (speed controller) should be right next to the motor or a part of the motor housing. 

This leaves no space for cables. 

[Collimatrix]

5 hours ago, W. Murderface said:

 

For wheeled vehicles at least, I think there's the possibility to increase the protected volume by moving the motors away from the hull and into the wheels. As for tracked stuff, I'm not sure putting your primary sources of locomotion on the relatively stickie-outtie top rear corners of the hull is a smart move. You could bury them deeper, but that'll cost you at least some of your hard won protected volume. Either way, I think there's a case to be made for copper or aluminium wires for drive trains.

 

Not necessarily engine related, but: having a huge generator on board opens up windows to directed energy weapons, and further down the line maybe even rail guns. 

The power pack on a modern MBT doesn't really stick out into the top rear corners.

The engine bay only fills the center and rear of the hull:

 

The hull sponsons don't contain anything essential to the function of the engine.

Furthermore, if you look at the powerpack:



The portion in the raised section of the engine deck is the cooling system.

The part of the powerpack that's essential to the immediate ability of the tank to move is fairly well buried.

[Mighty_Zuk]

I'm currently trying to do a little research on how conventional tank design could evolve, as well as the future of the Merkava family (due to their frontally placed engine), when hybrid or purely electric engines become the norm.

 

Can anyone make a simplified comparison of the required volume for each type as well as purchase cost and maintenance costs.

 

i.e if certain type of engine would take a little more volume, or much more volume. And if it would cost just a little more or a lot more. 

 

I believe that if there is a substantial difference in the parameters of volume and cost, and not just performance, then this could cause a pretty serious shift in the way tanks are designed.

[Collimatrix]

Quickly:

-Four Stroke, liquid-cooled turbodiesels are the engines of choice for most tanks (e.g. T-90, Leo 2, export Leclercs, K2).  These have very good efficiency, and there is a lot of industry experience in getting them to work.  They have the lowest power to volume ratio, but that has improved significantly in recent years.  That said, the more power you squeeze out of an engine the more chance there is of problems.  Problems include relatively slow throttle response, a high amount of particulate in the exhaust which scatters IR radiation and makes them more visible on thermals, usually a lack of multi-fuel capability, high vibration, and a relatively high requirement for maintenance.

-Gas turbines in current tanks (M1, T-80) are several generations older than the cutting edge in gas turbine technology and are poor representatives of the state of the art.  Overall pressure ratio has nearly tripled and turbine inlet temperatures have increased as well.  State of the art turbine material technology is two generations better than what the AGT-1500 has.  State of the art gas turbines also have a significantly better power to volume ratio than AGT-1500-level engines, mainly due to improvements in compressor compactness.  The problem is that all the advanced materials that make these advances possible are very expensive, and it's not clear if it's cost-effective to use cutting edge gas turbine technology in anything less than an airliner or fighter.  Gas turbines are multi-fuel, offer unparalleled power to volume, are easier to start in extremely cold climates than diesels, have extremely long periods between overhauls, and create very little vibration or exhaust particulates.  Gas turbines do not require radiators, they are almost entirely self-cooling.  Even with the latest improvements gas turbines still suffer inferior fuel economy to turbodiesels, although the gap is closing.  Notably, the fuel consumption of a turbine when it is idling is not much lower than when it is at full power.  Efficiency can be improved by adding a recuperator, but recuperators are bulky and sacrifice a lot of the compactness.  On the other hand, recuperators have no moving parts and also reduce thermal signature.  The M1 has one, the T-80 does not.  Gas turbines require a large mass flow rate of very well-filtered air, which basically offsets the advantage of not needing a radiator.  Very few companies in the world can design and produce cutting-edge gas turbines.

-Two stroke diesels have better power to volume than four strokes, but not as good as turbines.  They're fidgety and in the past haven't worked well, although supposedly Kharkov in Ukraine has got a marvelous design used in the Oplot-BM.  Pros and cons are otherwise similar to four stroke diesels.

-Diesel wankels are an interesting possibility, but so far three companies have tried and failed to make them actually work.  If they could be made to work they would be a halfway house between a four stroke and a turbine.  Like a turbine it would have low vibration and better power to volume than a four stroke diesel.  Efficiency would probably fall between the two.  Due to the high ratio of surface area inside the combustion chamber to volume, heat leakage would be higher and this would necessitate larger radiators for a given output than a four stroke diesel.  A diesel wankel would not be multi-fuel.  Like the turbine but unlike the four stroke diesel the engine could run at its maximum rated power for long periods of time without breaking, since it produces power by rotation rather than reciprocation.  Maintenance of the rotor tip seals would likely be an issue.

-Air cooled four stroke diesels have basically the same pros and cons as liquid-cooled ones except that the bulk of the radiator system is built into the engine and can't be moved somewhere more convenient.  On the flip side, it has fewer moving parts and no vulnerable radiator.

[Mighty_Zuk]

47 minutes ago, Collimatrix said:

Quickly:

-Four Stroke, liquid-cooled turbodiesels are the engines of choice for most tanks (e.g. T-90, Leo 2, export Leclercs, K2).  These have very good efficiency, and there is a lot of industry experience in getting them to work.  They have the lowest power to volume ratio, but that has improved significantly in recent years.  That said, the more power you squeeze out of an engine the more chance there is of problems.  Problems include relatively slow throttle response, a high amount of particulate in the exhaust which scatters IR radiation and makes them more visible on thermals, usually a lack of multi-fuel capability, high vibration, and a relatively high requirement for maintenance.

-Gas turbines in current tanks (M1, T-80) are several generations older than the cutting edge in gas turbine technology and are poor representatives of the state of the art.  Overall pressure ratio has nearly tripled and turbine inlet temperatures have increased as well.  State of the art turbine material technology is two generations better than what the AGT-1500 has.  State of the art gas turbines also have a significantly better power to volume ratio than AGT-1500-level engines, mainly due to improvements in compressor compactness.  The problem is that all the advanced materials that make these advances possible are very expensive, and it's not clear if it's cost-effective to use cutting edge gas turbine technology in anything less than an airliner or fighter.  Gas turbines are multi-fuel, offer unparalleled power to volume, are easier to start in extremely cold climates than diesels, have extremely long periods between overhauls, and create very little vibration or exhaust particulates.  Gas turbines do not require radiators, they are almost entirely self-cooling.  Even with the latest improvements gas turbines still suffer inferior fuel economy to turbodiesels, although the gap is closing.  Notably, the fuel consumption of a turbine when it is idling is not much lower than when it is at full power.  Efficiency can be improved by adding a recuperator, but recuperators are bulky and sacrifice a lot of the compactness.  On the other hand, recuperators have no moving parts and also reduce thermal signature.  The M1 has one, the T-80 does not.  Gas turbines require a large mass flow rate of very well-filtered air, which basically offsets the advantage of not needing a radiator.  Very few companies in the world can design and produce cutting-edge gas turbines.

-Two stroke diesels have better power to volume than four strokes, but not as good as turbines.  They're fidgety and in the past haven't worked well, although supposedly Kharkov in Ukraine has got a marvelous design used in the Oplot-BM.  Pros and cons are otherwise similar to four stroke diesels.

-Diesel wankels are an interesting possibility, but so far three companies have tried and failed to make them actually work.  If they could be made to work they would be a halfway house between a four stroke and a turbine.  Like a turbine it would have low vibration and better power to volume than a four stroke diesel.  Efficiency would probably fall between the two.  Due to the high ratio of surface area inside the combustion chamber to volume, heat leakage would be higher and this would necessitate larger radiators for a given output than a four stroke diesel.  A diesel wankel would not be multi-fuel.  Like the turbine but unlike the four stroke diesel the engine could run at its maximum rated power for long periods of time without breaking, since it produces power by rotation rather than reciprocation.  Maintenance of the rotor tip seals would likely be an issue.

-Air cooled four stroke diesels have basically the same pros and cons as liquid-cooled ones except that the bulk of the radiator system is built into the engine and can't be moved somewhere more convenient.  On the flip side, it has fewer moving parts and no vulnerable radiator.

First of all, thank you for the explanation. But I'd like to know if any of them could be coupled with an electric engine to serve as a backup. In 2020 the Mark 4 'Barak' should enter service, and it's said it would have a hybrid-electric engine with some form of diesel generator without any further elaboration. Basically what I wanted to know is whether to expect the whole thing to take up less space, more space, or about the same. 

[Xoon]

2 hours ago, Mighty_Zuk said:

I'm currently trying to do a little research on how conventional tank design could evolve, as well as the future of the Merkava family (due to their frontally placed engine), when hybrid or purely electric motors become the norm.

 

Can anyone make a simplified comparison of the required volume for each type as well as purchase cost and maintenance costs.

 

i.e if certain type of engine would take a little more volume, or much more volume. And if it would cost just a little more or a lot more. 

 

I believe that if there is a substantial difference in the parameters of volume and cost, and not just performance, then this could cause a pretty serious shift in the way tanks are designed.

I guess I can add my two cents about electric and hybrid systems, going from soft hybrid-electric to fully electric. 

 

Soft hybrid-electric:

 

A soft hybrid electric vehicle is about as bare-bone as possible for the most amount of advantages. To take a example from the car world: The ICE would still power the wheels though a gearbox like usual, but the electric motor starter is replaced with a more powerful motor which can power the vehicle on it's own, though mostly for added power and better torque characteristics in sprints or slow driving.  The motor is lighter and uses usually a 48V system, with a small battery, requiring minimally extra space and changes. The motor serves also as a engine starter, generator and regenerative break, giving the car all the advantages of a full fledged HEV. This system is also often combined with a electric supercharger which spools up the turbocharger for close to zero turbo lag, and it can also harvest excess kinetic power from the turbo which charges the battery and can be used later by the electric motor. Modern vehicles also include a heat scavenger system, which creates electricity out of the hot exhaust, which in turn can power the electric motor. 

The flowchart above is purely for the soft hybrid system, not the best in the world, but I sadly lack the software for better. 

 

 

Parallel hybrid:

A parallel hybrid is built up in much the same way as soft hybrid with a few changes. Usually the power is split between the ICE and the electric motor, meaning the electric motor usually provides 30-70% of the power. This requires a much bigger battery, but usually the range is only big enough for short trips, like to and from the store. Also here the motor runs commonly on around 400V, which is unique for the motor and inverter. Most modern parallel hybrids are also Plug-in battery hybrids, meaning that they can charge their battery with a charger, instead of using the ICE.  This system is usually easy to retrofit into conventional layouts, provided there is enough space. This system takes up more volume and is heavier than a pure ICE and loses out in terms of fuel efficiency over long marches, but easily beats it in short trips, frequent start stops, and sprints. 

 

Series hybrid:

In a series hybrid, the ICE powers a generator. Because of this, it is set to its optimal RPM, this also causes the frequency and the voltage to stay stable. The load can either be variable or locked, were the ICE charges the battery in tune with the power the motor consumes, or the ICE goes at max load until the battery is full, and engages again when the battery is low on charge.  This setup usually provides better acceleration because of the electric motors torque curve and instant throttle response. It also provides the most amount of regenerative breaking, since it is equal to the motors power output.  Like the parallel setup, this setup requires a large battery, which gives it enough range for short trips of silence. The downsides is that this setup is the heaviest and takes the most volume, however. You can chose where the ICE is and the electric motors are, no driveshaft needed. 

 

 

Series-Hybrid:
A series hybrid is a like a weird combination of them both. Simply take a parallel hybrid and add one or two electric motors after the gearbox. This way the starter/generator/motor can be used as a generator to power the other electric motors. Koningegg uses this system:

 

 

 

Range extended battery electric vehicles:

A range extended electric vehicle looks a lot like a series hybrid vehicle, only the in a opposite relationship.  Here the vehicle is usually built in a electric vehicle architecture, usually not designed to run at full power with the range extender. Imagine a electric car with a generator in the trunk, which provides roughly 50-80% the power the electric motors do, charging the vehicle, giving it extra range.

 

 

 

Linear generator series hybrid electric vehicle:
Skipping the crankshaft and drive shaft, and uses the motion of the pistons directly to charge the battery:

 

 

In general, you can see a trend that the harder the hybrid, the heavier the vehicle becomes, until you are fully electric. It usually takes more volume too, however new technologies are closing the gap. 

 

This is about as much as I care to write today, and can fill in more with electric vehicles and motor technology later. 

 

I am reposting a 84 page report on hybrid technology in military vehicles too:
http://www.ffi.no/no/Rapporter/08-01220.pdf

[Collimatrix]

10 hours ago, Mighty_Zuk said:

First of all, thank you for the explanation. But I'd like to know if any of them could be coupled with an electric engine to serve as a backup. In 2020 the Mark 4 'Barak' should enter service, and it's said it would have a hybrid-electric engine with some form of diesel generator without any further elaboration. Basically what I wanted to know is whether to expect the whole thing to take up less space, more space, or about the same. 

 

Any engine can be connected to a generator that is connected to an electric motor in lieu of a mechanical transmission, or you can have the intermediate hybrid systems @Xoon described.  But whether that's preferable a question about tank transmissions, not powerplants.

[T___A]

5TDF, the engine in the T-64:

 

An engine that was notorious for only being capable being built at Kharkov, which was not surprising since it couldn't even be produced at Kharkov for a few years. Meanwhile in Buzuluk, where they know what they are doing, we got the UTD-30, a short stroke design that was meant to be 15/15, a engine with 150mm stroke and 150 cylinder. But because of an arbitrary height requirement set by Morozov it was canned.

If that looks small its because it's 1350mm long 940mm wide 775 tall

 

 

ChKZ decided it was a cool idea to transversely mount a 1000hp engine so made the DTN-10. 10 clyinder engine and in a Soviet first ChKZ used exhaust gas in the supercharger:

Note engine placement

The backup engine was even smaller. It's the super charged variant of the UTD-30.