Posted on 02/20/2011 6:08:28 AM PST by saganite
Ford is working with the Center for Compact and Efficient Fluid Power and Folsom Technologies to develop a prototype F-150 light-duty pickup truck propelled by a hydraulic hybrid powertrain.
Hydraulic hybrids differ considerably from gas-electric hybrids, like the Chevrolet Silverado 1500 Hybrid, but the goal is the same: to improve fuel efficiency.
“We have the potential to reach 40 miles per gallon or higher with hydraulic power,” said Perry Li, co-deputy director of CCEFP and a mechanical engineering professor. “But we feel like we don’t give up anything versus an electric hybrid, and there are no batteries and nothing to recycle.”
(Excerpt) Read more at news.pickuptrucks.com ...
The system doesn’t have to recover 100% for city mileage to be better than highway. Yes, you are losing heat to braking. But you are also losing heat to friction with pavement and air.
Actually, it’s easy to get better mileage in the city than on the highway. Just jack up the gear ratio to the point that highway is well out of the power band so that the engine is running horribly inefficiently at highway speed.
You get efficient, or you'll freeze your butt off. (8^D)
While I will grant that they can work, it takes special fluid for the lower temps. We see an amazing amount of equipment up here which fails in the winter, from automobiles not set up for a real winter to trucks gelling up (no. 2 diesel), to oil rigs brought up from down south with hydraulic fluid which turns to putty in the cold.
I have seen transmissions with 90 wt. gear lube which turned to putty and would kill the engine when you let the clutch out in neutral.
It wouldn't be a problem if the vehicles came off the line ready to go anywhere and function, but they don't.
Where this is a real pain is in the used vehicle market. The retrofits (engine heaters and more) can get expensive and add to the cost.
“I’m not knocking the system - just the claim that city mileage is better than highway mileage.”
You really have to look at how highway mileage is calculated. I know that in my larger vehicles, there is a HUGE DIFFERENCE in mileage if I drive a long distance at 50 MPH, than 70 MPH...and it’s all due to wind resistance (which increases much faster than speed). City driving has virtually no wind resistance, instead it’s just stop and go. If grab some of that energy from stopping and use it to get going, you really don’t have much in the way of other losses...particularly if you shut off the engine each time you stop (as hybrids do).
That’s why the system is best/most effective in city driving with a lot of stops and starts.
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Don’t get me wrong - I like the idea of an hydraulic energy storage system. And it certainly will provide improved city mileage. But city mileage better than highway mileage? I don’t think so. If that were true then just periodically braking when you are out on the road cruising along would improve your mileage. Not a chance.
A couple of people have already said it, but highway fuel usage is mostly to overcome wind resistance. In stop and go city driving, it is mostly for acceleration. If you recover braking energy to do most of the acceleration, you will get better mileage in the city. Same thing as slowing down from 70 t0 50 on the highway.
You have a good point about wind resistance but generally speaking optimum highway mileage occurs at about 60 MPH. Now maybe it’s lower than that for F-150 but I doubt it. Plus a hydraulic system might have a problem with turning off the engine at stops. I’d be curious to see how that would work.
I don’t trust any instrument with vital mechanics that claims to capture expended energy and re-use it for another vital function. I see how well those wind turbines function in cold weather. I don’t want to get stuck in a traffic emergency or difficult situation and not be assured of having full power in my truck.
If you break it down, it is easier to understand.
On the highway, economy mostly constrained by air resistance. Braking has almost no contribution.
Stop and go city traffic is just the opposite. The vehicle moves very slowly, air resistance barely matters, in this case, economy is mostly constrained by brake losses and idling. If you can shut down the engine when stopped and capture braking energy, other energy losses are likely to be less than air resistance when driving down the highway thus giving a better mileage in town vs. highway.
60 MPH might be on the high side, unless the vehicle is very aerodynamic...and the 150 certainly is not. I would guess closer to 40 (or maybe less). You want the engine near its peak efficiency in high gear...but if that occurs at 60, the wind resistance is still killing you.
I’d be more worried about getting the diesel engine started than the hydraulic component.
I’ve owned and operated heavy equipment for years. When it gets below zero, diesel turns into a PIA. Block heaters, cold batteries, ether injectors, gelled diesel, frozen fuel lines, all sorts of things to worry about. Never thought about worrying about whether the hydraulics will work, never had to, they just do, very reliable technology.
Keep in mind that at typical highway driving speeds, a large percentage of your engine power goes to overcoming air resistance. Air resistance is much less at 30-40 mph city driving speeds, and negligible when you're stuck in a city traffic jam.
I work with high pressure hydraulic systems every day. They are extremely unreliable and maintenance prone.
There will be a requirement for a vast network of hoses as well, all contained on a very congested area, which makes hose replacement seriously difficult. Hydraulic hoses under a high work load fail often. They also leak often.
Imagine a fleet of pickups on all highways, dripping hydraulic oil in the traffic lanes. This just does not sit well with me.
You have obviously, not been around many industrial hydraulic systems then.
My 1994 Chevy Silverado 4WD in 2WD gets about 20mpg highway at 40mph but drops to 14mpg at 55-60mph.The other drivers really don’t care about my mpg and being passed on both sides or the threat of being rear-ended along with the certainty of being cussed out,AND the likelihood of being cited for causing a traffic hazard mean I must drive at th higher speed.
After the oil reserves found in the Bakken Reserve are fully developed, fuel efficiency is going to be less an issue.
These hydraulic add-on hybrids are being testing in rubbish truck applications, as one example.
Noise is a BIG issue with these, a lot of work remains to be done.
Nobody is gonna want to drive a pickup with screaming 4000 psi hydraulics.
The units are already running on delivery and garbage trucks so there is some service history to look at.
My guess is that there will be few or no hoses involved. If the pump and motor are centralized and connected only to the drive shaft, all the connections could be internal or external steel tubes. An automatic transmission has a lot of complex hydraulics, but they have been developed to the point that they seldom fail.
A lot of industrial machinery uses 5000 PSI hydraulic systems for propulsion. Any modern skid steer vehicle probably does. It’s not breaking new ground. Biggest problem I see is that the components cost a lot. Mass production could help that.
I designed and developed hydraulic propulsion systems in my previous life as an engineer. I am pretty comfortable with them and would buy a vehicle with this system AFTER the bugs were worked out for a couple of years and the prices were not prohibitive.
Run no. 1 diesel, and block heaters are a must. Water filters have to be changed religiously. Yep, they are a pain. We have a lot more hydraulic equipment out here on the oil rigs than we used to, and every rig moving in from the south has had trouble with hydraulics if they didn’t change out their fluid to something rated for arctic environments. It’s an annual thing here, so we’re usually ready for it.
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