Friday, April 15, 2011

Catching The Wave

Sounds pretty amazing to me. According to Carnot the efficiency of an ideal engine is 1 - Tc/Th. Where Tc is the exhaust temperature and Th is the burning temperature (this is somewhat simplified). The temperatures are absolute (i.e. Kelvin scale in the metric system). The Wave Engine according to some designs operates at a peak temperature of 1070°K with an exhaust at 300°K (room temperature roughly). So what is the ideal efficiency for such an engine? 1 - (300/1070) multiplied by 100 to get percent. And the answer is almost 72%. So a practical realization giving 60% efficiency is not unreasonable. That is about 83% of ideal. Not bad. In fact very good.

Some geeks (not as geeky as me) have a few words to say.
Mueller envisions his wave disc motor powering a generator, making it an ultra-light ultra-efficient hybrid electric vehicle. That’s a lot of ultras, but Mueller says he has the numbers to back it up. The wave disc apparently uses 60% of its fuel for propulsion, compared to 15% of fuel used for propulsion in conventional engines. And because the wave disc powered cars would be much lighter — perhaps 20% lighter — the fuel efficiency is even greater.

This all might seem very pie-in-the-sky, and that’s quite understandable. However, Mueller’s team has received $2.5 million in federal dollars from the Advanced Research Projects Administration – Energy (ARPA-E), which will be put towards creating a 25kw engine perhaps as early as next year. According to Mueller, that’s enough power to run an SUV.

I’m hoping Mueller’s checked his math on this, because I am very excited to have a car running on something as efficient as it is elegant.
Well I checked the math and it doesn't look out of the question. Some folks from Warsaw, Poland and Zurich, Switzerland [pdf] have checked the math with computerized flow simulations and think it looks pretty good. The concept goes back to at least 1906. So it is not a new idea. What is new is this particular realization. And of course we have computers for simulation and automated milling machines to make prototypes and small production volumes. Things not available in 1906.

Of course the engine is just the beginning. Once that is proved you have to design the whole hybrid drive train. And then you have to wrap an automobile around it. I don't expect to see them on the market as a production vehicle for about ten years. Unless some really big money (or the Japanese) get behind it.

Some more places to visit to get a handle on the technology:

Daily Tech

Green Cars

Cross Posted at Classical Values


RavingDave said...

I'm still waiting to hear a good theory on how it imparts an impulse on the rotor in one direction but not the other.

M. Simon said...

I wonder why windmills only turn in one direction in response to the wind.

RavingDave said...

The Rotary bladed windmills turn because of Bernoulli's principle. The attic ventilators turn because the friction in one direction is greater than in the other.

How this thing turns i'm not sure. I have two theories.

1. The heated air produced by combustion pushes against the forward wall of the rotor like pressure pushing a hinged door open.

2. Pulse detonation occurs at the focal point of the curve in the forward wall, and the wave imparts an impulse into the forward wall, but by the time it has reached the trailing wall, it is mostly dissipated at a tangent (due to it's initial forward velocity and centrifugal force) through the suddenly open exhaust port.

I actually favor the second theory more, because Pratt and Witney research on Pulse Detonation engines produce substantial efficiency gains using the shockwave of combustion. It takes far less fuel to initiate the shockwave than it does to heat the air to expand it, and most of the energy can be directed in one direction.

But I don't know for sure that this engine works like this.

M. Simon said...

Or the exhaust is in such a direction as to apply impulse.

Look at the pdf.

RavingDave said...

I should have done that in the first place. I had already read several articles about the engine so I didn't read your's closely enough, thinking it was similar to the others.

It is my belief that if the numbers hold up, THIS THING is our salvation. It is almost a magic bullet for America's fiscal aliments. It will also have a massive impact on foreign policy. (Won't need middle east oil.)

This thing might be one of the most important inventions ever.