Heard about Volvo's KERS?

Post by **matthew1** » 28 May 2011, 10:38

https://www.matthewsvolvosite.com/2011/0 ... e-braking/

Mechanical regenerative braking. I love it.

Post by **VCA** » 28 May 2011, 11:02

I remember the Williams F1 team got an award for their flywheel KERS (and then they never used it), I hope this works out better than that

Post by **matthew1** » 28 May 2011, 11:18

Didn't know it's been used (or sat unused) for years.

I've always lamented that we've had cars for 100 years, and we're still doing the same thing they did back then. Gasoline (potential) energy is converted to actual energy to accelerate, then all that is thrown away by simply braking.

If you've ever pushed your car, you can feel how heavy it is, and how much energy it takes to accelerate to 30mph or 60mph or whatever.

In city driving we're wasting much of the energy our cars produce to move forward on heat (braking -- brake pads). We don't capture and use it, except for hybrids, which started recapturing this and putting that energy back into storage -- its battery.

Post by **jimmy57** » 28 May 2011, 18:45

Captured energy from braking is something several methods have been developed to handle.
Packaging and weight have been real problems.
UPS fitted trucks in some cities with a system with a unit on the driveshaft. Braking pressurized oil in an accumulator and the unit on driveshaft also housed a hydraulic motor so the fluid from accumulaot could assist take off when vehicle started to go again.
I have not heard whether the study is over or how the system fared.

Post by **tjts1** » 29 May 2011, 04:48

60,000 rpm flywheel? What could possibly go wrong?

Post by **FlyingVolvo** » 29 May 2011, 16:12

tjts1 wrote:60,000 rpm flywheel? What could possibly go wrong?

Turbocharger turbines can spin in excess of 200,000 RPM!

Post by **VCA** » 29 May 2011, 18:59

ecbsykes wrote:
tjts1 wrote:60,000 rpm flywheel? What could possibly go wrong?
Turbocharger turbines can spin in excess of 200,000 RPM!

Yup, and the GE90-115B turbofan engine spins its large fan (itself the diameter of a 737's fuselage) at 2,500 RPM (N1 spool) during takeoff, making the tips of the fan blades move at 1.2 times the speed of sound...while the inner core (N2 spool) is pushing 11,000 RPM, generating temperatures of 1,700F (950 C) and spinning some of those blades at supersonic velocities as well. Did I mention it's pushing out thrust at 115,000 lbs (~500 kN) while doing this?

What could possibly go wrong?

[Oh, and I'll answer that--the IFSD rate of a GE90-115B is 0.0003 per 1,000 hours or 99.96% dispatch reliability...I'd like to see a car do that.]

As an engineer I'll add this: don't worry about it, stuff around you spins more mass at higher relative speeds all the time without catastrophic failure. There are commercial UPS systems in use right now that use flywheel technology to generate electricity long enough to ride out the time it takes for generators to switch on in datacenters.

Post by **Ozark Lee** » 29 May 2011, 22:15

This is kinda funny. Back in a Junior High (1972ish) science class I wrote up a plan to use braking energy to spin a flywheel and re-use the energy to power the car. The real problem with my plan, after I took much more advanced science and engineering courses, was the basic design of my flywheel. It ran the flywheel horizontally under the car and was the width of the car

That plan would have worked great on a perfectly flat surface and a road with no turns.

I think I got an "A" on the paper just for creativity.

...Lee

Post by **tjts1** » 30 May 2011, 05:56

ecbsykes wrote:
tjts1 wrote:60,000 rpm flywheel? What could possibly go wrong?
Turbocharger turbines can spin in excess of 200,000 RPM!

A turbo has substantially less mass and is not mechanically driven through a gear box. From the articles I found, the volvo KERS flywheel weighs 13.2 lb. Now lets spin that up to 60,000rpm and have a bearing fail or better yet how about and old worn bearing and a crash. Any takers?

This is all interesting racecar technology but they would be better served by bringing a conventional hybrid to market. The technology is far more mature and components are off the shelf for a manufacturer. They don't need to reinvent what already works. I doubt you will ever see Volvo put this into production. Even Porsche is limiting KERS to its racecars and as a very expensive option on its high end models.

Post by **VCA** » 30 May 2011, 07:38

tjts1 wrote:A turbo has substantially less mass and is not mechanically driven through a gear box. From the articles I found, the volvo KERS flywheel weighs 13.2 lb. Now lets spin that up to 60,000rpm and have a bearing fail or better yet how about and old worn bearing and a crash. Any takers?

I'll bite. Let's go back to that example of the GE90-115B; Volvo Aero builds a fiber composite braid primary fan casing, designed to fully contain a fan blade breaking loose at takeoff speed. That's a blade weighing ~35 lbs (~16 kg) with a tip velocity of 400 m/s or ~900 mph (at Standard Sea Level) going at right angles into a composite casing lighter than its aluminum equivalent. I have no doubt that Volvo's engineers will design a flywheel casing capable of containing a loose flywheel as well as, if not better than, their Volvo Aero counterparts which make parts of the most reliable jet engine in the world.

[Man, what is it with those Swedish engineers? Must be something in the water...

]