Range Extenders?

[Geoff Shelley2]

I'm interested in your opinion about electric traction drive range extenders. Both generally and more specifically linear generators like this one www.youtube.com/watch?v=u4b0_6byuFU . Please comment.

 

[bwilson4web]

The example has too much vibration. Opposed piston engines have similar efficiency and inherently less vibration. The proposed Wankel even lower vibration in a smaller package and more compatible with smaller generators.

Bob Wilson

 

[Geoff Shelley2]

The example has too much vibration. Opposed piston engines have similar efficiency and inherently less vibration. The proposed Wankel even lower vibration in a smaller package and more compatible with smaller generators.

Bob Wilson

Bob
Can you point me to a website or other information about those two options. Because I thought 40% efficiency pretty awesome and the size 535 mm x 210 mm x 200 mm quite awesome too. Perhaps my conversion math is off, but isn't that 21" x 8.26" x 7.87"? About the size of an average carry on luggage? And it weighs about 40 lbs. Is the Wankel + generator or the opposed piston engines + generator you're referring to smaller and lighter than that?
Thanks!

 

[bwilson4web]

Bob
Can you point me to a website or other information about those two options. Because I thought 40% efficiency pretty awesome and the size 535 mm x 210 mm x 200 mm quite awesome too. Perhaps my conversion math is off, but isn't that 21" x 8.26" x 7.87"? About the size of an average carry on luggage? And it weighs about 40 lbs. Is the Wankel + generator or the opposed piston engines + generator you're referring to smaller and lighter than that?
Thanks!

• http://achatespower.com/our-formula/opposed-piston/
  
• https://jalopnik.com/mazda-officially-announces-the-return-of-the-rotary-eng-1829459947
• https://spectrum.ieee.org/cars-that...liquidpiston-unveils-tiny-but-powerful-engine

Each engine has its own challenges and we really need to see them sized for an existing range extender. For example, my BMW i3-REx, 24 kW, 640 cc, liquid cooled, motorcycle engine.

Bob Wilson

 

[Geoff Shelley2]

• http://achatespower.com/our-formula/opposed-piston/
  
• https://jalopnik.com/mazda-officially-announces-the-return-of-the-rotary-eng-1829459947
• https://spectrum.ieee.org/cars-that...liquidpiston-unveils-tiny-but-powerful-engine

Each engine has its own challenges and we really need to see them sized for an existing range extender. For example, my BMW i3-REx, 24 kW, 640 cc, liquid cooled, motorcycle engine.

Bob Wilson

Thanks for the info.
I could not see from the websites any stats on thermal efficiency or size or weight. I did find a website about why the Wankel engine had to died, https://www.carthrottle.com/post/engineering-explained-why-the-rotary-engine-had-to-die/. It mentions that thermal efficiency was low. Perhaps they've made some improvements. I did find an article about a rotary engine made by LiquidPiston which claims above a 50% thermal efficiency and has only 3 moving parts and less than 20 parts all together. Looks interesting.

Regardless none of these have a generator built right into the design, and I'm going to guess that they wouldn't fit into my carry on luggage, and I'm going to guess that they weigh more than 50 lbs, particularly when a generator is attached.

I think I'm still a fan of the linear generator for now, at least until more info on the LiquidPiston engine (size, weight) is available.

 

[bwilson4web]

Thanks for the info.

No problem. It is my hobby.

I could not see from the websites any stats on thermal efficiency or size or weight. . . .

Try to find a BSFC chart. One of my favorite sources are the SAE papers.

I think I'm still a fan of the linear generator for now . . .

The vibration problem can be solved in a 4-cylinder configuration with piston motion timed to avoid rotary and linear motion. Alternatively, 2-cylinders along along the piston center would work but be a little long.

Bob Wilson