NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/sci/energy/5545

Text File | 1992-11-18 | 5.1 KB | 107 lines

Newsgroups: sci.energy
Path: sparky!uunet!charon.amdahl.com!pacbell.com!sgiblab!swrinde!emory!kd4nc!ke4zv!gary
From: [e-mail] (Gary Coffman)
Subject: Re: More External-Combustion Info
Message-ID: <[e-mail]>
Reply-To: [e-mail] (Gary Coffman)
Organization: Gannett Technologies Group
References: <[e-mail]> <[e-mail]>
Date: Wed, 18 Nov 1992 19:21:13 GMT
Lines: 95

In article <[e-mail]> [e-mail] (Sherwood Botsford) writes:
>Some observations:
>
>1.  My diesel pickup requires that I turn the key, and wait 17 seconds for
>the glowplugs to heat up.  In winter I may have to do this three times before
>the engine will start.  30 seconds is no big deal.  But then, I don't use my
>truck to go 6 blocks to the corner store.  I can see where it wouldn't
>be popular with some people.
>
>2.  Some of these 30 second boilers work as 'flash boilers'   Flame heats
>a plate, and the water is sprayed on.  With some work, I bet that you could
>trade increased fuel consumption for faster heating.

I don't see the 30 second startup as a problem. Some mornings I have to
*crank* my truck that long. :-( The owner's manual says you should do
a minute's warmup before driving off in a gasoline engined vehicle.
I think this is a false concern.

>3.  As long as the lubricant is immiscable with water, I don't see a problem.
>A sump, a centrifugal filter, a final separation filter.  Bush pilots used to
>filter water from their fuel by  wetting a piece of thin fine weave cloth with
>gasoline.  The gas could go through, the water wouldn't.

Steam engines normally use the wet steam as a cylinder lubricant.
No additional oils are required. The "rings" are normally leather
wetted by the steam. In old locomotives, they lasted 6 months of
*continous* hard pulling between servicing. Remember that a piston
steam engine develops maximum torque at stall and is a low RPM
device. Bearing lubrication can be a simple drip oiler.


>4.  I think that the original reason Stanley's had pilot lights was to keep
>the boiler from freezing in winter.  Some clever design is called for here,
>with either pilot light and/or systems that self drain into a holding tank
>won't get bent out of shape by freezing, and could be warmed easily with
>either a plug or a torch.
>
>5.  Good insulation around the engine would help efficiency.  The closer the
>engine is to the temperature of the working fluid, the less energy you lose
>to heating metal.

Very true. Only a small pilot light need be maintained in most climates
to prevent a well insulated engine from freezing. And, you can always
add alcohol to the water as an anti-freeze. It lowers the efficiency of
the engine a little, but it's no big deal. Glycol is right out though.

>6.  One of the claimed advantages of the Stanley Steamers was their noise.
>They were very quiet.  This would be a big selling point with me.  They
>were also very simple mechanically, although messy in terms of plumbing.
>I think the entire drive train had 24 moving parts.

They were open loop steam. They made a "chuffing" noise under load. They
were quiet compared to the gasoline engined autos of their day, but
mufflers have gotten a lot better over the years. Open loop steam had
another problem, they got about 10 miles to the gallon of *water*. A
closed loop system should be very quiet with no water losses.

>7.  One of the big advantages of steam is the idling efficiency.  You
>use very little fuel sitting still.  This could be significant for trucks,
>busses, and city delivery vehicles.

This is a *major* advantage.

>Questions:
>
>1.  What kind of gas mileage did the Stanley's get compared to other
>vehicles of the time?

They got between 8 and 15 MPG of fuel and about 10 MPG of water.

>2.  Given reasonable engineering assumptions about the change in the art,
>what would the comparison be now?

That's hard to say. The very best superheat compound cycle steam plants
have an efficiency of around 50% while the best IC engines have an
efficiency around 28%. To approach a big compound plant in a car though,
that would be really tough. I'd *guess* from what I've read that the
steam plant would be about 30% worse than the IC plant for the same
peak horsepower. One thing should be noted, however, the characteristics
of the two engines are wildly different and a lower peak horsepower steam
plant should offer the same driving characteristics as a bigger IC plant.

>3.  Given a closed system is there a better choice of working fluid than
>water (Something that wouldn't freeze, and could act as a lubricant.)

Steam is a really good working fluid. It's thermal characteristics are
ideal for automotive temperatures. And it acts as it's own lubricant
at the piston speeds required. In a closed system, vapor/liquid transistion
is important to develop the necessary condenser vacuum. The freezing
problem is easily dealt with in the areas where it's an issue by using
good insulation and a pilot flame. Higher molecular weight fluids wouldn't
develop as much pressure at the same temperature in a dynamic system.

Gary