Virginia Tech and RIDE Partner on New Hydraulic Pump/Motor for Hydraulic Hybrid Vehicles
03 April 2008
Virginia Tech and RIDE Inc. are working together to develop a hydraulic pump/motor for hydraulic hybrids based on the RIDE (Rotational Inertial Dampening Engine) technology. (Earlier post.)
Al Kornhauser, associate professor in the Department of Mechanical Engineering at Virginia Tech, who specializes in internal combustion engines, fuel cells, and other energy-conversion systems, is working with RIDE. Mechanical engineering students under Kornhauser’s guidance will design, build, and test a hydraulic pump/motor for use in a hydraulic hybrid vehicle.
Current hydraulic hybrid vehicle designs use hydraulic pump/motor technology that has been developed for general industrial applications. These pump/motors are not ideal for vehicle applications. An alternate pump-motor concept has been devised, with a geometry similar to that of the World War I - era ‘Gnome’ aircraft engine. The students will build a pump/motor based on this concept to serve as a prototype and demonstrator.
—Al Kornhauser
Phil Vera, president of RIDE, estimates that the partners will have some solid data and a prototype within 6 months.
The RIDE (Rotational Inertial Dampening Engine) modifies the design of the Gnome rotary aircraft engine design of the WW I era to enable the rotating engine block to function as a freely-spinning flywheel, thereby offering an integrated flywheel-based hybrid power capability.
The Gnome featured a crankshaft mounted on the airplane, with the rotary engine block and cylinder heads—to which the propeller was attached—rotating around the crankshaft. RIDE inventor Gary Greenwell (who attended Virginia Tech) made a number of significant changes to the Gnome rotary design, including inverting the relationship between the cylinder heads and the pistons. Rather than have the cylinder heads rotate as part of the radial engine block, Greenwell has the pistons affixed to the exterior ring, with the cylinder heads attached to the crankshaft.
RIDE makes the crankshaft a separate part from the engine support bearings. This change is critical to the revised radial design, as it allows the crankshaft to move to be positioned exactly as the rotational axis of the moving engine block—which, in turn, changes the running engine to a freely-spinning flywheel.
The pistons go from relative reciprocation to stationery in their cylinders when the engine is in flywheel mode. The switching mechanism—Powerswitch—is one of the key inventions for which Greenwell filed a patent in 2004.
A mechanism for changing the position of a crankshaft relative to a housing was presented by FEV in the context of its variable compression ratio engine. Something similar could be behind the Powerswitch functionality discussed in the article for RIDE:
http://www.greencarcongress.com/2007/04/fev_displays_tu.html
The advantage of RIDE over hydrostatic systems such as the one developed by EPA and Eaton is that kinetic energy recuperated during braking is stored directly in a spinning disk, as opposed to bulky hydraulic accumulators. However, this does imply spinning the device up to very high rotational speeds with the help of a CVT. A rapidly spinning mass that is not isolated via a gimbal cage represents an internal gyroscope, which could interfere with vehicle steering.
Even if it doesn't, e.g. because the disk is spinning about a vertical axis, gradient changes in the road could still generate severe stresses on the device's bearings, even at moderate vehicle speeds. The disk itself will also experience significant friction heating at the outer rim, unless the whole device operates in a high vacuum - which would be problematic for the hydraulics and bearings.
Moreover, it's far from clear that the hydraulic cylinders will ever prove stiff enough to support high rotor speeds. Should either the disk or the bearings ever suddenly fail - e.g. during an accident - the high-velocity debris would have to be contained somehow. Compared to adding fuses to an electrical system or, defined breaking points in an accumulator, this is very hard to achieve.
Remember, the kinetic energy stored in a vehicle traveling at 25mph is equivalent to that required to lift it 27 feet into the sky. A failing flywheel is a small bomb.
Posted by: | 03 April 2008 at 07:51 AM
One of the problems with the old airplane engine is what I would call torque steer. They said that planes were very hard to fly, because under full throttle at take off they would bank to one side.
Posted by: sjc | 04 April 2008 at 08:27 AM
look up P Factor also in wikipedia, a more common effect than torque problems at takeoff..
Posted by: Herm | 08 April 2008 at 06:12 AM
look up inertial storage engine or transmission and you
will be amazed this is no new idea and carman made this
hydraulic energy storage, patented it, and drove it.
Where is it now? An accumulator with say a nitrogen
bladder to absorb the fluid excess when slowing down
and then when you reaccelerate could return that now
highly pressurized fluid into the engine.
We really need to look at the real problem tht we have
and that is road congestion and all the unique motors
in the world is not going to fix the infrastructure we
have. The reason they are squeezing us is they want to
reduce the number of cars on the road, since many places
do not have the room to add two, three or more extra
lanes. So the alternative is to take cars off the road.
We cannot even keep up on the bridge maintenence of the
small briges we have now, Imagine a monster 8 lane bridge or adding extra bridges!! We should demand they
build double decker highways where there isn't enough
room for extra lanes.
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