600 kW / 850Nm hydraulic pump - need advice

[MortenHansen]

Hello all fluid power professionals!

We are in the early planning stage of designing an hydraulic engine dynamometer for internal use. We are looking at using a hydraulic pump as the load for the engine. We are planning to apply load to the hydraulic pump with a servo valve partially obstructing the flow of the hydraulic fluid. To measure power, we can either measure the pressure of the fluid and multiply with the RPM and a correction factor or measure the torque with a strain gauge and multiply with the rpm.

We need some advice on where to find a reasonably priced hydraulic pump that can transmit approx 600 kw / 850 Nm thru its shaft reliably.

The RPM of the engine is max 8500 RPM.
We might have to gear down this to a RPM the hydraulic pump can handle.

I was thinking about hydraulic pumps for dumper trucks and digging equipment like CAT or Komatsu. This kind of equipment is mass produced and I would think a lot of spare parts suppliers exist.

Also, where can we find servovalves that can handle this pressure with a fast response ?

We would like to cool the fluid via a water to oil heat exchanger. Any hints on suppliers ?

This has actually been done before in an chassis dyno application for cars.

The unit in left front of the picture looks like the hydraulic pump they use (does anybody on this forum recognize the brand of this pump by any chance?).

http://www.flyinmiata.com/images/misc_images/rototest/DSCN0238.jpg

Looks like the unit on the right with the piping is the servovalve unit that applies load to the hydraulic pump. The black unit on top is probably the servomotor for controlling the servovalve. A pc is attached that runs some real time control software.

The brake assembly is attached directly to the driveshaft of the car.
I think there is a gearbox attached between the driveshaft and the hydraulic pump. Anyone that know a manufacturer compact of gearboxes that can handle this much power and torque (600kW / 850Nm) ?

Here is a link to a pic of the servovalve they use

http://www.flyinmiata.com/images/misc_images/rototest/DSCN0237.jpg

Anybody recognize any of the components or is it custom?

We are not going to attach our dynamometer to the driveshafts, but directly to the engine crankshaft thru an axle. Therefore we need it to be able to handle at least double the power of this unit since the car differential distrubutes power to two driveshafts and two units.

Regards
Morten

 

[unclesyd]

From your picture the company that makes the "ROTOTEST".

http://www.rototest.com/

 

[MortenHansen]

Yes that is correct. However Rototest make chassis dynamometers and we are making a dynamometer to attach to an engine driveshaft directly. We have a different budget and different control software requirements. Therefore we have decided to design it in house. Any hints / tips to what type og hydraulic pump, gearbox and servovalve components that can be fasible for this application ?

regards
Morten

 

[budt]

Morten;

600KW equals 805 HP if I did the math right and at 5,000 PSI that would require 276 GPM of flow which would produce over 34,132 BTU/Min. of heat. At lower pressure flow would increase but heat would remain constant.

I recently priced some pumps that would give that type flow with servo control and in quantities of 4 were $45,000.00 ea. Actually overkill for your project but real flexible as far as operating parameters.

The pump in your pictures appears to be a fixed volume Tyrone aluminum Gear pump. I'm not up on their offering so I can't say if they make a pump as large as you need. Almost any hydraulic pump you find would need some hefty gear reduction since most will not go above 2,000-2,400 RPM due to their Inlet line size not being able to get enough flow to keep it from cavitating..

You need to talk with a salesman from a local Fluid Power distributor or find a retired salesman that would help you for compensation. At present I am not able to doo any extra work.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[amorrison]

Check out here - bottom of page.

http://www.oemdynamics.com.au/power.shtml

 

[MortenHansen]

Hi, did you mean the unit to the lower left ?
Perhaps you meant using more than one hydraulic pump attached to a common shaft via a distribution gearbox ?
We have sent a mail to OEM Hydraulics to inquire.

Anybody know of fast low cost servovalves that can handle this
load ?

Regards
Morten

 

[budt]

Morten;

Perhaps a Generator would be a better choice or even a large Fan such as found on a big ventilation system.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[PNachtwey]

That is a lot of oil for just one servo valve. The Moog 79-200 can handle 200 GPM and it is not cheap. This is the biggest servo valve I know of. I would be looking for a big proportional valve to save money, not a servo valve. One could save if there were parallel paths with fixed orifices that can be switch on and off. Only one path has a 'servo' valve for fine metering control of the oil. The problem is the bump in the load as the orifices are 'switched' in and out. Two or three of the bigger proportional valves will do the trick. They are more common once you get to the 100 GPM range.

 

[MortenHansen]

Hi Bud, what kind of generator do you mean ? Please give more details. Did you mean to use a electric generator as the load instead of a hydraulic pump as the load?

Large fans are used in existing aplications i have seen. Here you can see a picture of some fans that somebody doing this use today:

http://www.flyinmiata.com/images/misc_images/rototest/DSCN0198.jpg

Probably the oil return have quite low pressure so there is no need for a cooling element that can withstand high pressure.
Who sells theese kinds of fans and cooling elements to a low cost ?

Regards
Morten

 

[budt]

If youare still going with hydraulics and are controlling pressure to get a load then look at a Proportional Relief valve such as found here. Look at the valves on page 54

http://hydraulics.eaton.com/products/pdfs/504300en0499a.pdf

These valves go up to around 700 GPM and are infinutely variable pressure from an electrical input signal.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[MortenHansen]

Hello PNachtwey.
Thank you very much for your reply. You are one of many experienced people on this forum that can help ignorant beginners like me. Thank you again for your patience. I really appreciate your help !

I understand your point of using fixed orifices to switch in "load ranges" and then use a valve that is possible to regulate to do "fine regulation". However the "load bumps" is an effect that we probably need to avoid since this might impact our measuring repeatability and it might also impose transient loads that might be dangerous to internal components on a stressed turbocharged engine at high RPM and high load.

Also, your point of finding a _proportional valve_ that is not as expensive as the Moog ones is excactly the type of advice we need.

However, I dont know the difference between a servo valve and a proportional valve. Can you kindly please explain the difference ?

Who sells proportional valves at lowest possible cost ?
(We dont need a Rolls Royce for the first prototype).
How do we electronically control a proportional valve ?
How fast control response can we get ? The loop response must be relatively fast as the point is to lock the engine RPM and hold it regardless of the throttle opening (torque of the engine).

Regards
Morten

 

[MortenHansen]

Hello Bud, thank you very much!
Will this valve give a fast system response enough to hold the RPM steady ? We need to control the system via a real time control software.

(An external completely independent RPM sensing safety system will shut down the ignition and fuel supply and apply full oil brake if the loop becomes unstable and the RPM surges).

Some of our engineers will do a numeric system simulation by figuring out the transfer functions of the different components in the system. Also the mass and torque of the enggine will be modelled. However I need to present a draft for a feasability study to start working on with as much details as possible.

Regards
Morten

 

[MortenHansen]

Btw, I know this has been done with water brakes as the load element as well. However we want a "portable" system. This means the water flow neccessary to feed a water turbine as the load element will be far too high. We will need upstream water reservoirs and that is not feasable as it is too bulky. Water resirculation might be possible but there are steam expansion problems etc.

Also the rotational mass of a water turbine system is too high I have learned. This will prevent us to see transients in the enngine torque because of the rotational inertia of the system will be too high and have a lowpass effect of the response.

The rotational inertia of a hydraulic system is probably lower because the pump mass is smaller and the mass of the oil volume in motion (oil in the pump and in the line to the valve is smaller. This is probably the reason that the guys that sell commercial products for similar applications use oil.

Regards
Morten

 

[budt]

"Hello Bud, thank you very much!
Will this valve give a fast system response enough to hold the RPM steady ? We need to control the system via a real time control software."

Morten;

Peter can tell you more about response. I have only used this valve as a way to have the PLC control presure throughout a cycle and response was not a problem for the circuit.

If you look further on the web page I sent you will also find a Propoortional Flow Control mounted on the same high flow Slip-In Cartridge valves. BTW Vickers is not the only manufacturer. Parker and Rexroth also make the same item.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[ScottyUK]

Hi Morten,

Many of the drive manufacturers can use a reasonably standard COTS induction motor and a power electronic drive to provide a load which can regenerate the braking power back into the mains supply. Dynos based on this technique can provide very accurate control of loading, and with remarkably fast step changes if required. The induction machine is about as robust as it gets in terms of rotating electrical plant, so mechanically it should be quite favourable. The only requirement will be an electrical service large enough to handle the braking energy - that depends where the unit is to be used.

It would be well worth speaking to the applications guys from the likes of ABB, Control Techniques, Siemens, etc.

I will post a link to this thread in the Motors forum where there are a lot of people who know more about this type of thing than I do.


----------------------------------

I don't suffer from insanity. I enjoy it...

 

[itsmoked]

MortenHansen; I concur with ScottyUK. Your task can be done very nicely with a VFD. This will often allow you to return energy to your utility in lieu of heat to your facility. Also even if you cannot use your utility as an energy sink consider that you can place a load bank(a bunch of cheap resistors with a fan)anywhere convenient to your facility, like out back.

A VFD system would allow easy ramping and profiling of your dynamometer's functions. Also since VFD are electrical/electronic animals that depend heavily on knowing about many mechanical/electrical variables they are usually very easy to interface with and control. All the things you could want to know will generally be available by just inquiring of the VFD.

Alternatively remember that all locomotives are dyno'd regularly. They just use the generator that is coupled to the prime-mover. They unplug the cables going to the traction motors and hook the output to a dynamic braking load resistor unit. They then firewall the prime-mover and read the ammeter and the volt meter, multiply the result and they have the HP.

Either way would seem eminently less expensive, more flexible, and more adept at providing data than a hydraulic solution.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

Hello MortenHansen
"Also the rotational mass of a water turbine system is too high I have learned. This will prevent us to see transients in the engine torque because of the rotational inertia of the system will be too high and have a lowpass effect of the response."
I understood that you were looking for torque response.
I understand that inertia may be a problem if you are trying for rapid speed changes, but if you are interested in torque, the higher inertia will make your system more stable.

Have you considered looking at the hydraulic retarders used on heavy equipment and some highway trucks. They will absorb a lot of horsepower in a fairly small, reasonably self contained unit. You can do most of the braking with the retarder and add a smaller unit of a different technology to give you fine control.
yours

 

[MortenHansen]

Hello I know some ppl use a Thelma brake to do this in fixed installations. Thelma brakes are normally used as a manually applied brake for trucks. I think those thelma brakes are quite expensive as well.

I would assume a 600 kw generator + switched control electronics is very expensive

Regards
Morten

 

[MortenHansen]

Waross, this could be an option.
Do you know any manufacturers of this kind of retarders ?

Btw, I was thinking of the possibility of mounting several lower cost hydraulic pumps in paralell on a common axle driving them all. Then the paralell outputs of the pumps can drive a common flow restriction mechanism. This would perhaps enable us to use mass produced pumps and thereby getting the cost down.

Anybody have experience with Taiwan / Asian suppliers of
hydraulic spareparts for dumpers etc ? I would think the price level of that kind of equipment is significantly lower than what you would have to pay in Europe ?

Regards
Morten

 

[waross]

Hi MortenHansen
I would phone up the local truck dealers and heavy equipment dealers and ask about retarder options. Pump them for as much information as you can get and then start phoning the wrecking yards looking for used units.
Kenworth, Mack, Caterpillar, and any others you can think of.
Re. the electric option. With a VFD drive, you can use appropriately sized, used, three phase induction motors as the generators. That should help hold your price down.
I suggest reading thread237-149826. Read it a couple of times and you will probably have a good idea of who the VFD experts are. You will know who to listen to when you ask for advice on choosing electric hardware to compare with hydraulic hardware.
respectfully