Today, Avery's turbine. The University of Houston's
College of Engineering presents this series about
the machines that make our civilization run, and
the people whose ingenuity created them.
Most of the power we use
today is generated by nuclear energy or coal or
oil. What's not so well understood is that all such
power plants, like their cousin, the hydroelectric
dam, ultimately use turbines to generate
power.
At the base of a dam are water turbines.
Oil, coal, and nuclear energy are used to boil
water and drive steam turbines. A burned
fuel/air mixture is used to drive a gas
turbine. In every case, fluid passes through some
kind of turbine blading to provide a huge portion
of the power we use today. (Automobile engines are
among the few types that haven't been taken over by
it.)
Any book on turbine origins begins with
steam-powered toys in Egypt, two thousand years
ago. But that's a bit of a red herring. Steam
turbines didn't become commonplace until Charles
Parsons be-gan building them in the 1890s. So what
came in between?
Engineer Frederic Lyman tells about a little-known
figure in the creation of the steam turbine. He was
William Avery. Born in 1793, he grew up working as
a mechanic in New York State.
In 1831, he and a friend were granted a patent for
a steam-powered device very similar to one of those
ancient Egyptian toys. Jets of steam, emitted from
either end of a whirling propeller-like tube, drove
it. By that time, Watt and others had already tried
and failed at creating rotary steam-driven
machines. And the French had just be-gun developing
the water turbine.
Modern steam turbines don't work the same way as
Avery's. They direct steam through a succession of
rotating blades. Each stage removes energy and
reduces the steam pressure. The aerodynamics of
those blades gets very complex.
In Avery's turbine, steam flowed from the hub out
through the tip where it escaped as a driving jet.
The tips approached the speed of sound and, when
one of Avery's cast iron rotors failed, its
fragments tore through three floors of a building.
To get power out at useful speeds, Avery
used a series of belts and pulleys. Yet the machine
worked. By 1837, he'd built maybe seventy engines.
They developed around twenty horsepower and were
put work driving sawmills, cotton gins, gristmills
...
Among his other engineering accomplishments, Avery
also built what was probably the first steamboat on
the Erie Canal. But he died at 47, and the company
that manufactured his turbines went bankrupt soon
after. Another half century passed before Parsons'
turbines appeared.
Then the electric generator came on the scene, and
it required a high-speed drive. The
turbine was the natural mate to the gen-erator,
which was now the perfect means for putting its
power to use. The ghost of William Avery could now
smile at last.
What Avery had begun Parsons could now bring to
fruition -- and bring to resounding success as
well.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
F. A. Lyman, A Practical Hero: Or how an obscure New
York mechanic got a steam-powered toy to drive
sawmills. Mechanical Engineering, February
2004, pp. 36-38.
