Lecture 5 GEOS24705 Heat engines 1: the engineers build

Lecture 5 GEOS24705 Heat engines 1: the engineers build

Outline of upcoming lectures and labs • Tues 15th lab: chemical energy and steam engines • Tues 15th: Heat engines 1: the engineers build • Th. 17th: Heat engines 2: the scientists explain • thermodynamics of heat  work • limits on efficiency of heat engines • Tues 22nd: no Tuesday lab – or air pressure/ ideal gas law? • Tues. 22nd: Industrial Revolution and transition to modernity • framework for energy conversion technology • And then on to individual energy technologies… • Th. 24th: Electricity generation I • Tues 29th lab – electric motors I

What is a “heat engine”? • A device that generates converts thermal energy to mechanical work by exploiting a temperature gradient • Makes something more ordered: • random motions of molecules  ordered motion of entire body • Makes something less ordered: • degrades a temperature gradient (transfers heat from hot to cold)

Why was the first heat engine a steam engine? Newcomen“Atmospheric Engine”, 1712 (Note that “revolution” followed invention by ~100 years – typical for energy technology)

Physics: long understood that steam exerted force Evaporating water produces high pressure Pressure = force / area “aeliopile” “lebes”: demonstration of lifting power of steam Hero of Alexandria, “Treatise on Pneumatics”, 120 BC

Physics: condensing steam can produce suction force Low pressure in airtight container means air exerts force Same physics that lets you suck liquid through a straw

First conceptual steam engine Denis Papin, 1690, publishes design Set architecture of reciprocating engines through modern day – piston moves up and down through cylinder First attempt: explode gunpowder within cylinder to push piston up. Failure because: couldn’t figure out how to vent gases after the explosion and reset for next piston stroke Papin’s first design, now in Louvre. No patent, no working model.

First conceptual steam engine Denis Papin, 1690, publishes design Set architecture of reciprocating engines through modern day – piston moves up and down through cylinder 2nd attempt: condense steam within cylinder to pull piston down. Failure because: couldn’t make tight enough seals to hold vacuum. Papin’s first design, now in Louvre. No patent, no working model.

First conceptual steam engine Denis Papin, 1690, publishes design Note trend in the history of energy technology: the person who invents a technology is not the person who makes it practical (and yet a third person is the one who makes money off it). Also national differences in development of heat engines: the French explained without building, the British built without explaining. Papin’s first design, now in Louvre. No patent, no working model.

First commercial use of steam: the Savery engine “A new Invention for Raiseing of Water and occasioning Motion to all Sorts of Mill Work by the Impellent Force of Fire which will be of great vse and Advantage for Drayning Mines, serveing Towns with Water, and for the Working of all Sorts of Mills where they have not the benefitt of Water nor constant Windes.” Thomas Savery, patent application, filed 1698

Savery engine is not a commercial success “.. Savery’s engine was wholly unsuited for draining mines, and he failed to induce the miners to take it up. The greatest height to which it could raise water was.. not more than sixty or eighty feet...Moreover the miners [were]...afraid to introduce furnaces into their shafts, on account of ...their giving rise to explosions... ” Robert Galloway, “A History of Coal Mining in Great Britain”

Principles of Savery engine • Sucks water as one would with a straw • Heat water to make steam • Fill chamber with steam • Cool chamber, steam condenses • Pressure in chamber is now lower than atmospheric pressure • Open up valve connecting chamber to pipe in water • Atmospheric pressure causes water to flow up into chamber • Issues: • Good only for pumping liquids. Efficiency below 0.1% • Max pumping height: ~30 ft. Why used at all? Because the coal was essentially free and the industry was desperate for a solution.

Easier than sucking water directly ... pull on something else, make linear motion to drive a pump Same technology used today in oil wells The lift pump Animation from Scuola Media di Calizzano

First true steam engine: Thomas Newcomen, 1712, blacksmith “It was at this juncture that the miners had put into their hands the most wonderful invention which human ingenuity had yet produced – the Newcomen steam-engine.. a machine capable of draining with ease the deepest mines; applicable anywhere; requiring little or no attention; so docile that its movements might be governed by the strength of a child; so powerful that it could put forth the strength of hundreds of horses; so safe that... the utmost damage that can come to it, is its standing still for want of fire.” Robert Galloway, “A History of Coal Mining in Great Britain” Newcomen’s design is state of the art for 60+ years

First true steam engine: • Thomas Newcomen, 1712, blacksmith • Copy of Papin’sengine of design of 1690 • First reciprocating engine: linear motion of piston that transmits force • Steps • Fill chamber with steam • Cool the chamber to condense steam • Low pressure in chamber pulls piston down, lifts pump side • Open valve at bottom of piston, let gravity pull pump side down again • Steam fills chamber as piston rises • Issues: • Very low efficiency: 0.5% • Intermittent force transmission Newcomen’s design is state of the art for 60+ years

First modern steam engine: James Watt, 1769 patent (1774 production model) Similar to Newcomen’s engine, but with steam now condensing in a separate condenser that is kept always cool. In Newcomen’s engine, the metal cylinder would alternately heat and cool when filled with steam or when cooling water is added in condensing step. In Watt’s engine, steam enters alternately at top and bottom of cylinder. As piston begins to move down, steam flushes into condenser where it condenses, providing the suction that is most of the force on the engine. ¼ fuel usage of Newcomen’s engine.

First modern steam engine: James Watt, 1769 (patent), 1774 (prod.) Higher efficiency than Newcomen by introducing separate condenser Reduces wasted heat by not heating and cooling entire cylinder

Improved Watt steam engine: • James Watt, 1783 model • Albion Mill, London • As before: • Separate condenser • Improvements: • Force on both up- and downstroke • Continuous force transmission • Rotational motion • Engine speed regulator • Higher efficiency: ca. 3%

Gearing lets the linear-motion engine produce rotation sun and planet gearing

No need for electronics for controls – can use mechanical system engine speed governor

First locomotives – attempts to convert stationary steam engines built by Richard Trevithick, mining engineer Experimented with “high-pressure” steam (50 psi), double-acting cylinders. 1804 Pen-y-Darren locomotive, carrying iron in Wales, replacing horse-drawn tramway. Ran ~10 miles at ~2 mph but destroyed track. Image: 1804 Coalbrookdale locomotive, which failed. No images of Pen-y-Darren survive

First practical locomotives begin 1814 “Puffing Billy”, designed by William Hedley, (mine manager), built by the mine’s blacksmith and enginewright Coal hauler, 9” x 36”cylinders Still basically a stationary steam engine placed on wheels Image: source unknown

First passenger locomotive, 1829 George Stephenson’s “Rocket”, built for Liverpool and Manchester Railway won the Rainhill trials at 29 mph (unloaded), 14 mph loaded first example of single pair of drive wheels Stephenson was a mine engineman and brakeman, then enginewright. Illiterate til age 18. Built first locomotive in 1814. Image: source unknown

Double-action steam engine Piston pushed by steam on both up- and down-stroke. No more need for a condenser. Steam is simply vented at high temperature slide valve alternates input & exhaust

Double-action steam engine slide valve alternates input & exhaust

Double-action steam engine primary use: transportation

Double-action steam engine What are benefits? What are drawbacks?

Double-action steam engine What are benefits? Faster cycle – no need to wait for condensation. Can get more power, higher rate of doing mechanical work. Also lighter and smaller – no need to carry a condenser around. What are drawbacks? Inefficiency – venting hot steam means you are wasting energy. High water usage – since lose steam, have to keep replacing the water

Double-action steam engine: Images top, left: Sandia Software Image bottom: Ivan S. Abrams water-intensive, fuel-intensive – requires many stops to take on water and fuel.

History of locomotives Central Pacific Railroad locomotive #173, Type 4-4-0, 1864 Image: Central Pacific Railroad Photographic History Museum

History of locomotives Northern Pacific Railway steam locomotive #2681, 1930 Image: Buckbee Mears Company, Photograph Collection ca. 1930, Location no. HE6.1N p11, Negative no. 25337. Source: Minnesota Historical Society

The two technological leaps of the Industrial Revolution that bring in the modern energy era • “Heat to Work” • Chemical energy  mechanical work via mechanical device • Use a temperature gradient to drive motion • Allows use of stored energy in fossil fuels • Late 1700’s: commercial adoption of steam engine • 2. Efficient transport of energy: electrification • Mechanical work electrical energy mech. work • Allows central generation of power • Late 1800’s: rise of electrical companies

Lecture 5 GEOS24705 Heat engines 1: the engineers build