Posted on 03/02/2009 6:16:40 AM PST by saganite
Mechanical transmission of power using gears is very energy inefficient. The familiar automotive multi-speed gearbox and differential suffers from the friction losses that result in 20 – 30% of engine power being lost between a car's engine and the wheels. Many techniques are being developed to eliminate mechanical transmission including Wheel Motors and Hydraulic transmissions that we have seen being trialed in UPS delivery vans. Now in an innovative new approach, Scottish company Artemis Intelligent Power has developed a hydraulic hybrid transmission system it says can double a vehicle's MPG in city driving.
The heart of the system is a six piston radial digital displacement hydraulic pump/motor. This hydraulic motor replaces the port plates and swash plates in conventional hydraulic machines with computer controlled high-speed solenoid valves. Driven by a microprocessor, these solenoids actively control poppet valves that rectify the flow into and out of each cylinder. The hydraulic pump attaches to the flywheel an conventional combustion motor replacing the gearbox. It is hydraulically connected to Digital Displacement Motors coupled to the wheels, so the only connection between the internal combustion motor and the wheels is the hydraulic system.
In operation the system is conceptually similar to an electric series hybrid but with a pressure accumulator taking the place of the battery. The combustion engine generates hydraulic pressure at a steady rpm that can either drive the wheels with the hydraulic motor coupled to the wheels, or be added to the accumulator for later use. When the vehicle slows down the wheel coupled motor turns into a pump and regenerates braking energy into hydraulic pressure that is stored in the accumulator.
Artemis says Independent tests have confirmed that a prototype car, a BMW 530i, gave double the MPG in city driving compared to the same car with a six speed manual transmission. Overall, including highway driving, the prototype had approximately 30% lower carbon dioxide emissions than it had before the company fitted its energy saving transmission.
The company is working with Bosch Rexroth and Sauer-Danfoss APS to bring this technology to on-highway vehicles and agricultural and handling machinery.
Great, bring it on. If the technology is superior, it will be widely adopted.
Hydrostatic drives are not uncommon. This sounds like a great improvement. It sounds, however, like this uses an accumulator tank for energy storage. I wonder how big the tank is?
To “double” fuel mileage
wouldn’t that mean that other transmissions have a 50% power loss?
This I cannot believe. 10%, maybe.
I’ve followed this technology for a while now because I saw an article some years ago about Ford coming out with a hydraulic hybrid F-150, supposedly in 2008, that would get 60 miles per gallon. Obviously that didn’t happen. The UPS vans mentioned in the article and some garbage trucks being retrofitted with hydraulic hybrid drives are about the only vehicles out there using the technology right now. This looks like a new approach and the trial vehicle was a car. Previous attempts at this required larger vehicles (like the UPS vans) to support the weight and size of the accumulators.
Hmmm.
I thought that a manual transmission had a drivetrain loss of about 10-15%, and an automatic was more like 20-25%.
20-30% seems like kind of a high number to me.
That said, hydraulic drive systems are generally pretty efficient, so whatever the conventional losses are, an improvement would be great (unless the weight of such a system is such that the friction losses through the tires are greater than the savings).
Regenerative breaking certainly makes sense with hydraulic drive systems. Instead of losing momentum to heat via friction, use the energy to store energy. Simple efficinency gains versus the very poor and innefficient system currently commonplace make sense.
Well...they laughed at Edgar de Normanville too...
Sounds good to me! /sarc
Seriously, this is a good thing. The amount of raw energy waste inherent in Internal Combustion is enormous. I'm waiting for someone to come up with a way to capture the heat energy and convert it to electrical or some other usable form. Perhaps via Thermocouple.
It specifically said city driving. The system uses brake regenerative technology as well as the hydraulic accumulators. It would be easy to greatly improve mileage in stop and go city driving especially if you could turn the engine off while stopped and use the hydraulic technology to “launch” the car from a stop. Like any other hybrid, the results wouldn’t be as good on the open road.
Sounds good in theory at least for a stop n' go service vehicle.
pfl
At what cost to the consumer during purchase and maintenance period...
You may only gain 10% with elimination of driveline losses, but the way you make up bigtime is by using the braking foce to pressurize the accumulator through regenerative braking, kind of like downshifting and letting the engine slow you down, but instead, you are driving a hydraulic pump with the decelleration braking energy as opposed to wasting it with heat via friction.
I see where you’re coming from,
but the numbers you usually see for city/highway mpg are like 15/20, etc.
Doubling doesn’t make sense...
For a vehicle getting 10 mpg in stop & go city type driving, it wouldn't be too hard to get at least a 50% increas in efficiency, if you can recapture half of the energy expended in braking. Doubling mileage might be pretty difficult.
Also, the system could work at a constant RPM, in it's most efficient range, through the use of a hydraulic accumulator and RPM fluctuations for accereration would be minimized.
Time spent idling would similarly not be wasted, as it would be charging the accumulator, like an alternator feeding a battery.
That’s the key isn’t it? If the cost to the consumer outweighs the benefit it will never work-—unless it’s mandated by govt. However, these hydraulic hybrids are much more efficient than electric hybrids and we’ve been working with hydraulic systems forever so I’m hopeful.
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