The propulsion systems of AFV - state of the art and trends

[Firn]

The Idea of this thread is to collect the facts and thoughts about very things which keep AFV going at the present and in the near future.

I will start with this flyer by MTU which presents the famous lines of engines which drive AFV on every continent bar Australia. The 890 is the latest model with very impressive weight-to-kw and volume-to-kw rates beside the usual advantages. It has already orders and would also have powered the FCS.

Their mbrid concept is certainly worth watching. Personally I feel that the clever integration of the battery and the energy densitiy of it are the major hurdles in this regard. It might be wise to implement it only as a relative short-term buffer, powerful starter and short-time booster until the weight goes down. An integrated APU would make sense.

BTW: The 890 is really ridiculously small, the standard Leopard 2 engine 873 with the same output has a roughly three times larger crossection!. Hard to believe, I must confess, but according to MTU it is the case. The Puma would have been even heavier and larger without that great downsizing.


Firn

 

[Firn]

I did also try to get some information about the latest gas turbines. The LV100-5will likely replace the old turbine of some M1A2.

Advantages of the LV100

The core of any hybrid propulsion system is a high power density, low weight, and fuel efficient electric energy producer. The LV100 recuperated turbine engine is such a system. This engine is well suited to provide electric power efficiently at a volume and weight significantly lower than current systems. Originally designed for vehicular use and environment to drive a Hydrokinetic transmission, the turbine's high output speed lends itself to incorporate into the engine design an advanced generating device. This LV100 engine-based electric energy producer will provide in excess of 1MW of electric power in a volume of under one cubic meter at a weight of about 2500 pounds at fuel efficiencies comparable to advanced vehicular diesel engines. Recent state-of-the-art improvements in materials and component technology will permit further reductions in volume/weight and increase the system fuel efficiency. The technologies required to reach a volume of under one cubic meter, the system performance projections obtainable by technology upgrades and the program achievements to date are discussed.

So far it seems not final version of this engine, so all this numbers are preliminary.


Firn

 

[Firn]

UPDATE: An interesting thesis concerning the LV100-5 and it's potential impact on the Abrams and the costs to operate it. The context and the implications of lower maintenance and lower fuel consumptions can be better understood by the paper More Capable Warfighting Through Reduced Fuel Burden. Note the date of both papers.

I will also take a look at the (french) Leclerc engine, an very interesting concept, which didn't make it into the tropical version, as UAE chose the MTU 883.



Firn

 

[Firn]

The huge benefits of an APU in many aspects have already been mentioned in the two papers I linked. It is thus not in the least surprising that both the "Afghan" Leopards have been outfitted with them and that APU will be integrated into the M1A2.

The APU of the Abrams . (Two parts)

The Wankel is also often used for the very same reasons in other roles, but he won't pass Euro 5.

More to come.


Firn

 

[Firn]

Two interesting but different concepts combining a diesel with a gas turbine are found in the Stridsvagn 103 and the Leclerc in French service.

Stridsvagn 103 (Wiki)

The commander and gunner/driver both had the same set of sights and controls to fire the gun and drive the tank. Additionally the tank was powered by two engines, a 240 hp Rolls-Royce K60 diesel for cruising and turning the tank for aim, and a 300 hp Boeing 502 turbine for dashing at high speed. This was the first use of a turbine engine in a production tank; the Soviet T-80 and US M1 Abrams would later be built with gas turbines for main propulsion.

Leclerc:

The Leclerc has an eight-cylinder, Wärtsilä (ex SACM) V8X-1500 1,500 hp Hyperbar diesel engine and a SESM ESM500 automatic transmission, with five forward and two reverse gears. The official maximum speed by road is 72 km/h and 55 km/h cross country (speeds in excess of 80 km/h were reported on road). The maximum range is given as 550 km, and can be extended to 650 km with removable external tanks. The "hyperbar" system integrates a Turbomeca TM 307B gas turbine in the engine, acting both as a turbocharger and an APU giving auxiliary power to all systems when the main engine is shut down.

At a combat weight of just 56 tons, the Leclerc is one of the lightest main battle tanks in the world; this gives it one of the best power-to-weight ratios among the Western tanks (27 hp per tonne) and makes it one of the fastest MBTs of its generation (0 to 32 km/h in 5 seconds).

Firn

 

[Waylander]

I have to say I like the engine of the Leclerc and how they tried to get the best of both worlds. (just like I really like the Leclerc as a whole)

This engine also enabled the french to go with a short hull which helped to keep the weight down without having to make compromises regarding the protection.

All this comes with a higher complexicity but nevertheless the engine gives the Leclerc an amazing agility without needing too much fuel.

 

[Firn]

I have to say I like the engine of the Leclerc and how they tried to get the best of both worlds. (just like I really like the Leclerc as a whole)

This engine also enabled the french to go with a short hull which helped to keep the weight down without having to make compromises regarding the protection.

All this comes with a higher complexicity but nevertheless the engine gives the Leclerc an amazing agility without needing too much fuel.

I thought it neat too. The gas turbine seems to draw its air in before it flows into the compressor of the turbocharger but blows the intrinsically hot exhaust into the charger-turbine. The GT is not coupled directly to the engine but is stil able to increase the compression of the air destined for the engine. Not too complex at the first glance, but of course it took some effort to get the regulation right.

The GT might not be designed to be able to connect through a clutch to the shaft of the turbocharger to avoid further complications, but we don't know that for sure. With clever regulation it might have increased the responsivness and the acceleration of the tank further by increasing the rate of the compression but it would been a huge pain to work such a complicated combination out.

I also guess that by setting the limits differently one could get quite a bit more out of the engine, but then the very high stress caused by such a high and hot charging by the turbo must raise durability issues.

To confuse the non-technical folk here one could say that the GT acts as an indirect supercharger by charging the turbocharger through additional hot exhaust but can also run as an APU.



Firn

 

[Firn]

Reading through the mbrid concept of MTU I wondered just how effective such a system could be for warfighting. The quantities of the capability set would of course vary from mission to mission and must match about against additional cost and complexity.

Toyota demos

Opel Ampera

The sheer amount of available models is huge compared to just 10 years ago, with a lot of R&D going into it and many different concepts.


Firn

 

[Firn]

Reading through the mbrid concept of MTU I wondered just how effective such a system could be for warfighting. The quantities of the capability set would of course vary from mission to mission and must match about against additional cost and complexity.

Toyota demos

Opel Ampera

The sheer amount of available models is huge compared to just 10 years ago, with a lot of R&D going into it and many different concepts.


Firn

Several big carmakers have shown studies of diesel-hybrids, from Mercedes, VW, BMW to Peugeot. Probably the Peugeot 3008 Hybrid4 will be the first commercially available model, launching in early 2011. The design is pretty interesting with one engine on each axle with no mechanical link between them, so see yourself.

So we see a rapid strenghtening of the industrial and technological base of hybrid drives, increasingly also with diesels. This could lay the foundation for a not-too-distant use of such systems in AFV.


Advantages of the mbrid Parallel drive according to their flyer:

> Improvement of mobility and acceleration performance
‘Silent Move’
– Near silent slow speed operation

> Higher peak power and boost capability
– Additional peak power is available by using the gene-
rator as electric motor

> Low risk
– Conventional transmission including braking and stee-
ring system can be used

> Smaller diesel engine possible (downsizing)
– Due to the use of an additional power source (electric
motor) in the drive train, a more compact diesel engine
can be used – with improved driving dynamics, fuel
economy and low emissions

> High availability of electrical energy
– Strong on-board electrical system

> External power supply
– Flywheel starter generator together with generator
controller and power supply converter can be used for
external power supply for 100 kVA up to higher levels


Firn