

New car engine said to be a few times more efficient than conventional ones - egor83
http://news.discovery.com/autos/new-car-engine-sends-shockwaves-through-auto-industry-110405.html

======
ColinWright
See also the discussion from when this was submitted 3 months ago:

<http://news.ycombinator.com/item?id=2337237>

Also:

<http://news.ycombinator.com/item?id=2422867>

<http://news.ycombinator.com/item?id=2424987>

~~~
egor83
(wrt <http://news.ycombinator.com/item?id=2422867>)

So HN Search still misses some posts. I searched for discovery.com before
submitting - got two links from 1 and 2 years ago, but not this one.

~~~
thaumaturgy
Ironically, it looks like hnsearch isn't taking full advantage of the hnsearch
api.

It appears to be just doing a text search for "discovery.com"; if there's a
way to search by submission domain on hnsearch, I'm not seeing it at a quick
glance.

For example:
[http://shomi.associatedtechs.com/#submissions+from+news.disc...](http://shomi.associatedtechs.com/#submissions+from+news.discovery.com+with+%22car+engine%22+in+the+title)

------
reitzensteinm
"It has been estimated for the same horsepower, a Wave Disk Engine could weigh
a thousand pounds less than a conventional engine."

Erm... are there any conventional engines that weigh 1000 pounds to begin
with? Even high end V8s aren't that heavy. I wonder what they mean by that.

~~~
jpitz
Where did that quote come from? In the linked article, the closest I see is
this:

"Researchers estimate the new model could shave almost 1,000 pounds off a
car's weight currently taken up by conventional engine systems."

A somewhat different statement, though I still share your skepticism.

~~~
reitzensteinm
I'm sorry - I was actually reading an article linked somewhere else in this
thread, and forgot it wasn't the OP.

(<http://peswiki.com/index.php/Directory:Wave_Disk_Engine>)

Still, even if we're talking about total savings for the car, 1000 pounds is a
hell of a lot, and I'm not sure I buy it. For reference, that's 3x the weight
of an average V6 (or some light V8s), so it would have to remove a lot and add
nothing back.

I found an engine weight list here that seems to be legitimate:

<http://fixrambler.com/engineweightchart.txt>

~~~
brudgers
Extrapolating from the article there's no transmission or cooling system
either - that probably doesn't get you to 1000 pounds, but removing the
structure which supports those heavy components might get you close.

On the other hand, I don't think this would apply to cars with 25 kilowatt
engines - a 1958 VW beetle only weighed 1600 pounds
[[http://www.conceptcarz.com/vehicle/default.aspx?carID=10196&...](http://www.conceptcarz.com/vehicle/default.aspx?carID=10196&i=2#menu)]

------
anamax
> The Wave Disk Generator uses 60 percent of its fuel for propulsion; standard
> car engines use just 15 percent. As a result, the generator is 3.5 times
> more fuel efficient than typical combustion engines.

I'm skeptical.

Thermodynamic limits apply. While piston engines aren't near the limits, I'm
pretty sure that they're around 50% of the limit and would be very surprised
if this engine is over 80% of carnot.

So, the only way this engine can be 2x as efficient is if it runs at a
significantly higher temperature (which moves the limit).

And, the only way that it can run without a transmission is if it has a very
wide operating range. That's hard to do with combustion. And, unless the
engine is both reversible and has torque at zero RPM, they'll need both a
clutch and a reverse gear.

If they use it to run a generator, they need to account for the electric
motor, said generator, and maybe batteries. See diesel-electric locomotives.
The prius combines the electric motor and the generator, but needs a
transmission.

~~~
ent
50% sounded like a lot to me so I checked wikipedia, according to which, most
internal combustion engines have an average efficiency of 18-20%. So I guess
it could be true if the Wave Disk Generator lives up to those promises.

[http://en.wikipedia.org/wiki/Internal_combustion_engine#Ener...](http://en.wikipedia.org/wiki/Internal_combustion_engine#Energy_efficiency)

~~~
anamax
> 50% sounded like a lot to me so I checked wikipedia, according to which,
> most internal combustion engines have an average efficiency of 18-20%.

From the wikipedia article that you cited: "Most steel engines have a
thermodynamic limit of 37%. Even when aided with turbochargers and stock
efficiency aids, most engines retain an average efficiency of about 18%-20%."

I wrote that IC engines are running about 50% of the thermodynamic limits
because 18/37 is around 50%.

18x2 is about 37, so there's no way for wave engines to be more than 2x as
efficient as current engines unless they run at much higher temperatures.
Since the relevant temperature is determined by the fuel....

Getting close to the thermodynamic limit is really hard.

You didn't read the wiki article very carefully

The 18-20% is of the total energy in the fuel. Heat engines, which includes
both wave and piston engines, are subject to thermodynamic limits. The
thermodynamic limits tell us the maximum efficiency, which is about 40% for
the temperature at which ther

------
maeon3
Description about how it works:

<http://peswiki.com/index.php/Directory:Wave_Disk_Engine>

Seems to be a new take on the Wankel rotary engine:

<http://en.wikipedia.org/wiki/Wankel_engine>

The rotary engine was found to be less efficient than piston engines. I think
it's because the streamlined approach of intake an exhaust needs to be
babysat, with a chamber and an object to (Make exhaust go away 100%) and (Make
fresh air-fuel mixture come in) then a timed predictable ignite.

Is the wave disk engine just a modification of the Turbine engine?

<http://en.wikipedia.org/wiki/Turbine>

~~~
nodata
What are the disadvantages? (none are listed on that page)

~~~
andrewcooke
i would guess that it's hard to get a good (reliable, long-life) seal between
the rotating part and the upper surface (i don't think this is much like a
wankel engine, but it probably does share that problem).

also, it looks like it's supposed to spin at a constant, high speed - that
might imply high pitched whine (see someone else's comparison with a gas
turbine).

