Mar
24
A New Engine Driven By Shock Waves
March 24, 2011 | 5 Comments
Norbert Müller at Michigan State University in East Lansing has developed a prototype engine using a shock wave from the air/fuel valve closure compressing the mixture to ignition to drive a disk or rotor. Müller presented the new engine last week at a meeting organized by the US Department of Energy’s Advanced Research Projects Agency – Energy.
As the rotor spins its channels allow an air-fuel mixture to enter from central inlet ports. The ignited mixture then would escape through the outlet ports in the walls of the surrounding chamber. When the inlet closes the fuel mix is trapped with a closing shock wave, ignition occurs and turns the rotor to a position where the channels are pointing at the outlets. Really very simple, but the execution and gas management must be elegant, precise and very fast moving.
Wave Engine Flow Diagram. Click image for the largest view. Image credit: Michigan State University College of Engineering.
But Müller might just have the details worked out. He’s been at this at least since before the first noted paper he published in 2003.
What Müller is managing is sudden build-up of pressure in the chamber generating a shock wave that travels inwards, compressing the air-fuel mixture as it does so. Just before the wave reaches the central inlet ports, which are shut off by the turning of the rotor, the mixture is ignited. Its rather counter intuitive.
Where the power is delivered is when the rotor’s channels are pointing towards the outlet ports again, releasing the hot exhaust. As the gas escapes at high speed, it pushes against the blade-like ridges inside the rotor, keeping it spinning. Its not a turbine, but uses some of the mechanical functions of external combustion.
Wave Engine Disk Block Diagram. Click image for the largest view. Image credit: Michigan State University College of Engineering.
The design needs none of the many components of an internal combustion conventional engine, including pistons, camshaft and valves. Thus it’s much smaller and lighter than a conventional engine.
Nearly 80% of automobile fuel is lost to friction and heat. Only about 20% of fuel is actually used for propulsion. The new engine connected to a generator would make better use of automobile fuel. Its projected that the engine generator set will use 60% of the fuel for propulsion, thus tripling the percentage of fuel that is put to work cutting fuel use by 2/3rds for the same power.
The engine generator set is compact in size at about the size of a cooking pot. As an automobile power unit it would replace about 1,000 lbs. of engine, transmission, cooling system, emissions, and fluids. As a result, automobile companies will be able to produce lighter, more fuel-efficient hybrid vehicles. If successful in commercialization, the project would significantly increase fuel consumption efficiency and reduce automobile emissions by up to 90 percent.
One other point made during the ARPA discussion – the projection is the cost of a vehicle could be reduced by 30%.
Now that’s a closing point. Thirty percent coming in, 66% less operating fuel costs, consumers would be joyous.
On the other hand, having a lab bench design running isn’t a production ready design. There must be a mountain of problems known and yet to be discovered. But keep in mind the target isn’t a variable speed engine; rather it’s to drive an electric generator, which in turn powers the electric propulsion motors. Smartly engineered, this would be a grand way to extend the petroleum based personal vehicle future and still leave options for more electric energy input to the vehicles.
For now the design is in ARPA, Advanced Research Projects, a taxpayer supported research agency. Its not private money, but there just might be enough research and understanding at hand now for some very interesting looks from the automobile industry.
It’s a long way from Müller’s lab to your garage. But if the controls for starting, running and throttling to load can be made utterly reliable for steady state speed operation across the bulk of the operating conditions in North America, the little engine might have a very good shot at saving all of us a lot of money.
Just keep in mind, saving that 66% of fuel use would about eliminate the U.S. imported oil bill. It’s going to take time, but Müller and his wave engine are about as interesting as it gets in the power unit field.
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I’m not sure why you worry in the second last paragraph about controlling this kind of engine across varying operating conditions. You already answer that problem in the paragraph before! Given this engine is best coupled with a generator, then with the simple addition of some basic electric storage capacity (to absorb output energy when it’s not immediately required) then the vehicle using it becomes no more than an electric vehicle (with a built-in generator) and we already have the problem of controlling an electric vehicle entirely solved. With decent batteries or capacitors it would simply run as needed, and automatically, while driving to keep the vehicle charged up.
This is a steady state engine. As such, it would never be connected to the drive train because it does not deliver a variable speed output. But, it would be very efficient for powering a generator that could always run at the same speed.
Great read. Thanks for the info!
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