The Pursuit of Effectivity and the Science of Steam – Creatures of Thought
On April 19th, 1866, Alfred Holt, a Liverpudlian engineer who had apprenticed on the Liverpool & Manchester railroad earlier than taking over steamship design within the 1850s, launched a singular ship that he dubbed the Agamemnon. Because the third quickly of a affluent banker, cotton dealer, and insurer, he had entry to much more private capital to launch this new enterprise than the standard engineer. This was a fortunate factor for him, as a result of the standard investor of the time thought-about his ambition—to enter the China tea commerce on the premise of steam energy—foolhardy. A typical oceangoing steamship used 5 kilos of coal per horsepower per hour and couldn’t compete with sail over such lengthy distances: they might both should fill most of their potential cargo house with coal or make repeated, expensive stops to refuel.[1]
But, in the long run, Holt pulled off his gamble. He benefited from good timing (maybe a mixture of luck and foresight): the opening of the Suez Canal in 1869 give steamships an amazing leg up in commerce between Europe to the Indian and Pacific Oceans. However in designing ships dainty sufficient of their coal consumption to pay their approach to the Pacific, he additionally benefited from the late convergence of two complementary developments that had every begun within the early 1800s however didn’t intersect till the 1850s. First was a sequence of incremental, empirical enhancements to steam engine design: After the huge leap ahead from Newcomen to Watt, additional will increase in steam engine effectivity can be much less dramatic. Concurrently, a principle of warmth steadily developed that would clarify what made engines kind of environment friendly, and thus level engineers in essentially the most fruitful course.
Double-Cylinder Engines
Boulton & Watt erected most of its early pumping engines in Cornwall. Trevithick developed his high-pressure “puffer” there. So, it’s only becoming that the final main architectural innovation in piston steam engine design—that includes a wholly new structural element—was Cornish, too. In that area, an ample provide of British engineering expertise met an always-eager demand for environment friendly engines. The ever-deeper mines for extracting metallic ore wanted ever extra pumping energy, regardless of considerably larger coal costs than the coal-rich North.
Joseph Hornblower, born within the 1690s, was one of many first engineers to construct Newcomen engines for the mines of Cornwall within the 1720s. Sixty years later, his grandson Jonathan constructed the primary recognized double-cylinder engine (later referred to as a compound engine). Cornwall’s homegrown pure thinker, Davies Giddy (later Gilbert), served in the identical workplace he later served for Richard Trevithick, as Hornblower’s scientific advisor. In precept, the concept was fairly easy: as an alternative of instantly condensing the remaining steam after the enlargement cycle of the piston, the still-warm steam was fed into one other cylinder to let it do nonetheless extra work. Nevertheless, this added friction, complexity, and price to the machine. In observe, subsequently, Hornblower’s tried enchancment present no extra environment friendly than a standard Watt engine.[2]
A era later, nevertheless, one other Cornishman took up the concept and carried it additional. Arthur Woolf, like many eighteenth-century engineers, obtained his begin as a millwright, however by 1797 was working for the agency of Jabez Carter Hornblower (brother to Jonathan), at a brewery in London, erecting a steam engine. He continued to function engineer for the brewery for a decade afterward, and witnessed the operation of Trevithick’s steam carriage within the metropolis in 1803. Woolf realized that he might mix the double-cylinder engine of his former employer’s brother with Trevithick’s really high-pressure engines (working at forty kilos per-square-inch or extra). The upper-pressure steam, nonetheless fairly sizzling after increasing within the first cylinder, would be capable to do extra work within the second cylinder somewhat than merely “puffing” out into the ambiance. Each Watt and Trevithick had (from reverse points-of-view) seen low- and high-pressure steam as rivals, however in Woolf’s machine they complemented each other.[3]
However, as Hornblower had already realized, the trail didn’t all the time run straight and simple from thought to execution. Woolf led himself astray with a wholly unsound theoretical mannequin for the internal workings of his engine: he believed that steam at twenty kilos per sq. inch (psi) would develop to twenty instances its quantity earlier than equaling the strain of the ambiance, steam at thirty psi would develop thirty instances, and so forth advert infinitum. This turned out to be a considerably exaggerated expectation, and led him to start with a drastically undersized high-pressure cylinder, which let off far too little steam to successfully work its low-pressure mate. Relatively than main him to doubt his principle, the failure of this engine led him right into a wild goose chase for a non-existent leak in his pistons.[4]
Woolf’s double-cylinder engine, not like Hornblower’s, did eventually succeed, after years of trial and error, in reaching higher effectivity than a Watt engine. However as a result of it was costlier to construct (and thus purchase), and extra complicated to function, it discovered favor solely in markets with out quick access to different, cheaper choices. One such instance was France, to which Woolf’s erstwhile companion Humphrey Edwards, decamped in 1815: there he offered at the very least fifteen engines and licensed twenty-five extra to a French mining firm. Woolf in the meantime returned to Cornwall in 1811, the place he discovered some great benefits of his double-cylinder engine quickly surpassed by the incremental enhancements made by different native engineers to the Boulton and Watt design. He deserted it after 1824 and constructed single-cylinder engines till 1833, when he retired to the island of Guernsey.[5]
In the meantime, steam engine builders carried on with tweaks to get but yet another increment of effectivity out of their engines. They extracted benefits from changes to the regulatory equipment of the engine: components like “launch mechanisms,” “dashpots,” and “wrist plates.” The Corliss engine, designed by George Corliss in 1849, turned an icon of American industrial design after his firm produced a gargantuan specimen to energy the 1876 Centennial Exhibition in Philadelphia. Mighty because it was, nevertheless, it didn’t characterize an excellent leap ahead in steam engine structure. Corliss’ design drew its relative benefits over prior engines from a intelligent mixture of earlier improvements within the valves that allowed steam to enter and depart the cylinder, and particularly within the valve gear that managed them.[6]
Within the meantime, the double-cylinder engine, having did not show itself within the 1810s and 1820s, lay dormant. It could be restored to life a long time later, by the engineers most determined to eke as a lot energy as doable out of each ounce of coal: the designers of ocean steamships. However to facilitate the consummation of that match, a stable principle of the steam engine was wished, one that may dispel, as soon as and for all, the confusions like Woolf’s that continued to journey up engineers’ efforts at enchancment.
Measuring Energy
The shortage of a sound theoretical foundation for steam energy is obvious within the fitful historical past of cylinder “lagging,” or insulation. Steam engineers borrowed the time period lag (a barrel stave) from coopers, as a result of they usually insulated early steam boilers with such timbers, held in place with metallic straps (that is evident in photographs of early locomotives like Rocket, with their distinctive wood cladding).
As early as 1769, Watt had acknowledged the worth of insulating not simply the boiler, but in addition the working cylinder of the engine (emphasis mine):
My methodology of lessening the consumption of steam, and consequently gas, in fire-engines, consists of the next ideas:—First, That vessel during which the powers of steam are to be employed to work the engine, which known as the cylinder in widespread fire-engines, and which I name the steam-vessel, should, throughout the entire time the engine is at work, be saved as sizzling because the steam that enters it; first by enclosing it in a case of wooden, or every other supplies that transmit warmth slowly; secondly, by surrounding it with steam or different heated our bodies; and, thirdly, by struggling neither water nor every other substance colder than the steam to enter or contact it throughout that point.[7]
But, regardless of Watt’s imprimatur, steam engine builders lagged their cylinders sporadically all through the primary half of the nineteenth century; it was a matter of whim, not precept.[8]
On this period, engineers tended to think about the steam engine as analogous to its predecessor, the water wheel. Steam changed liquid water because the mechanical working fluid, however simply as water drove the wheel by pushing on its vanes, of their minds steam carried out work by increasing and pushing on the piston. A typical description of the time acknowledged that “[t]he drive of the steam-engine is derived from the property of water to develop itself, in a tremendous diploma, when heated above the temperature at which it turns into steam.”[9] Engineers knew that the cylinder should be saved sizzling to stop condensation of the steam inside, however inside this framework it was not apparent that it should be saved as sizzling as doable. Watt, emphasizing the distinction between the new cylinder and the cool condenser, had drawn consideration to the function of warmth within the engine, however the introduction and success of high-pressure engines with no condenser, the place the first issue gave the impression to be the expansive drive of steam, muddled issues as soon as once more.
The gradual improvement of a brand new, extra strong principle started with a sensible downside: tips on how to measure the quantity of energy an engine generates. This turned a very urgent downside for Boulton & Watt within the late eighteenth century, as they expanded from the standard enterprise of pumping engines into the brand new market of driving cotton mills. The standard approach of measuring the output of a steam engine, by way of “responsibility” (the kilos of water lifted by one foot per bushel of coal burned) had steadily been supplemented with the idea of “energy,” usually expressed in horsepower: kilos lifted over a given distance, however over a given time period somewhat than with a given quantity of gas. Thomas Savery had begun to grope in direction of the idea in his 1702 guide on the virtues of his steam pump, The Miner’s Buddy:
I’ve solely this to induce, that water, in its fall from any determinate peak, has merely a drive answerable and equal to the drive that raises it. In order that an engine which can increase as a lot water as two horses working collectively at one time in such a piece can do, and for which there have to be consistently saved ten or twelve horses for doing the identical, then, I say, such an engine will do the work or labour of ten or twelve horses…[10]
Observe right here that Savery proposes to measure the muscular equal of the engine not by way of the output of simply the pair of horses operating the equipment, however by way of the whole inventory of horses {that a} mine proprietor would require to keep up the identical energy over a protracted time period. This mannequin of horsepower by way of financial equivalency didn’t stick, nevertheless, and by the late eighteenth century horsepower turned mounted to Watt’s determine of 33,000 foot-pounds per minute.
But this remained a measure of energy greatest suited to pumping work: if a mine wanted to lift 20,000 kilos of water per hour from a 200-foot-deep shaft, one might readily calculate the engine horsepower required. Cotton spinning equipment—which different in dimension, perform, and design—didn’t lend itself to such easy arithmetic. So as to correctly dimension engines to mills, Boulton & Watt wanted a way measure the horsepower produced by an engine whereas driving numerous combos of equipment.
From the start, Watt had connected gauges to his engines to measure the strain contained in the engine, by connecting a small indicator cylinder to the primary engine cylinder in order that steam might stream between them. The extent of strain within the indicator might function a proxy for energy output. However to truly seize the information was a maddening train, as a result of the strain different consistently because the piston labored up and down. A method of capturing this steady knowledge got here from a long-time Watt worker, John Southern. He had joined the corporate as a draftsman in 1782, and regardless of a predilection for music that the strait-laced Watt discovered suspicious, shortly turned indispensable.[11]
In 1796, Southern devised a easy machine to unravel the facility measurement downside. He connected a chunk of paper above the indicator, rigged in order that it might transfer backwards and forwards as the primary piston operated. Then he connected a pencil to the tip of the strain gauge. Because the strain went up and down, so would the pencil, whereas the paper moved left and proper beneath it with the cycle of the engine. The end result, when operating easily, can be a closed form, which Southern referred to as an indicator diagram, and the averagepressure through the operation of the engine might be computed from the common distance between the highest and backside strains of that form, which might in flip be proportional to the facility. By calibrating the diagramwhile an engine was pumping water, the place the facility output was well-defined, Boulton & Watt might then decide the facility produced by the identical engine whereas working a given set of mill equipment.[12]
Thermodynamics
Engineers now had a instrument at hand for diagnosing the internals of a operating engine. That instrument, in flip, supplied the seed for the start of the science of thermodynamics, which started because the science of the steam engine. The primary nice leap in that course was made by Sadi Carnot.
Carnot’s story carries greater than a whiff of the tragic. Although later honored as a founding father of thermodynamics, he achieved no recognition in his lifetime, and died of cholera as a still-young man in 1832. His father Lazare was an completed engineer and a significant political determine in revolutionary France, however what we all know of the son comes nearly totally from a fifteen-page biography sketched a long time after the very fact by his youthful brother Hippolyte, which begins, pathetically, with the assertion that: “the lifetime of Sadi Carnot was not marked by any notable occasion…”[13]
Actually, Carnot’s quick life was remarkably eventful. He grew up in Napoleon’s court docket, attended the elite engineering college École polytechnique at age 16, and was on the Chateau Vincennes through the 1814 assault on Paris that ended Napoleon’s first reign. He returned to Paris as a workers lieutenant in 1819, filling his free time together with his passions: music, artwork, and scientific research. There, in 1824, he produced his seminal work, Réflexions sur la puissance motrice du feu (Reflections on the Motive Energy of Hearth). In it he endeavored to elucidate how warmth produces movement. I’ll permit him to elaborate in his personal phrases:
Each one is aware of that warmth can produce movement. That it possesses huge motive-power nobody can doubt, in lately when the steam-engine is in all places so well-known. To warmth are also due the huge actions which happen on the earth. It causes the agitations of the ambiance, the ascension of clouds, the autumn of rain and of meteors, the currents of water which channel the floor of the globe, and of which man has so far employed however a small portion.[14]
As now we have seen, the tendency of engineers to conceive of steam hydraulically, as a fluid that generated work by strain very like water in a water wheel, had engendered some confusion about tips on how to construct and function an engine most effectively. Mockingly, Carnot moved the understanding of the steam engine ahead by taking the analogy of a steam engine to a water wheel much more critically than his contemporaries. Nevertheless, for him the important thing power-generating agent was not the strain of steam, however the fall of warmth. Simply as a waterwheel required a head from which water descended by gravity to show the wheel, so the steam engine required a reservoir of excessive warmth, which then flowed all the way down to a chilly physique and thereby did work.
For Carnot this fall of warmth in a steam engine was fairly literal: it consisted of an imponderable fluid referred to as caloric, that drained out from the new physique to the cool one:
The manufacturing of movement in steam-engines is all the time accompanied by a circumstance on which we should always repair our consideration. This circumstance is the re-establishing of equilibrium within the caloric; that’s, its passage from a physique during which the temperature is kind of elevated, to a different during which it’s decrease. …The steam is right here solely a method of transporting the caloric.[15]
This caloric principle of warmth as a substance nonetheless predominated in Carnot’s day, regardless of subversives like Depend Rumford who advocated for a mechanical principle of warmth, which understood warmth purely as a type of movement.
If the stream of warmth from the new to the chilly physique produced all of the work within the steam engine, then making an environment friendly engine meant minimizing any spillage of warmth that did no helpful work. It additionally implied that to maximise the work produced by the engine, one should maximize the distinction between the supply of excessive temperature and the sink of low temperature—the peak by which the caloric fluid falls.
Carnot’s guide was largely ignored. However his insights had their first likelihood to be rescued from obscurity shortly after his loss of life. Émile Clapeyron, only a few years youthful than Carnot, was an completed engineer who specialised in locomotives, and a fellow-graduate of the École Polytechnique. In 1834, he revealed a paper within the college’s journal exhibiting that Carnot’s warmth engine principle might be expressed within the language of calculus and seen graphically within the indicator diagram: the realm contained in the diagram (which might be expressed as an integral) corresponded to the work carried out by the warmth switch within the engine. Clapeyron’s work revived Carnot’s abstractions, put them on a firmer mathematical foundation, and publicized them to the group of engine builders. But as soon as once more, they reached a lifeless finish. Steeped within the traditions of their craft, neither Clapeyron nor his friends appear to not have understood the warmth engine principle as having sensible functions to real-life engineering.[16]
Vindication for Carnot must wait one other fifteen years, when a sequence of exchanges between William Thomson (later Lord Kelvin), Rudolf Clausius, and James Joule shortly earlier than and after 1850 resolved numerous issues with the Carnot-Clapeyron warmth engine, together with reconciling it with the mechanical principle of warmth: what flowed from the new to the chilly physique was not a literal fluid however an abstraction referred to as power, which might tackle many varieties, however might solely carry out helpful work over a fall in temperature. By way of the medium of power, a sure amount of warmth was instantly equal to a specific amount of energy.[17] The scientist who greatest synthesized this new science of warmth for a wider engineering viewers was Thomson’s colleague on the College of Glasgow, Macquorn Rankine.
Perfecting the Marine Engine
Rankine’s place was one thing of a novelty: he was solely the second particular person to carry a chair of Civil Engineering at Glasgow, a place established by Queen Victoria in 1840. From the times of Watt and past, the College of Glasgow had been extra practical-minded than the good Oxbridge faculties of the South. However the institution of a school chair in engineering didn’t simply point out that the college supported extra hardheaded duties than absorbing classical studying, it additionally signaled a want to raise engineering right into a extra theoretical, scientific self-discipline.[18]
Rankine, embodying this new spirit, straddling the worlds of principle and observe, preached thermodynamics to the engineering world: his 1859 A Guide of the Steam Engine and Different Prime Movers (1859), a 500-page, densely mathematical treatise, explicated the brand new principle and its applicability to sensible issues in nice element and popularized the time period “thermodynamics.” Nevertheless he additionally knew tips on how to attain a wider viewers: in an 1854 handle to the Liverpool assembly of the British Affiliation for the Development of Science (BAAS) he concisely expressed the legal guidelines of thermodynamics by way of strange English and easy arithmetic: “As absolutely the temperature of receiving warmth is to absolutely the temperature of discharging warmth, so is the entire warmth obtained to the required lack of warmth.” That’s, the extra precipitous the autumn of temperature from the excessive (receiving) to the low (discharging) level of the engine cycle, the extra environment friendly the engine might be.[19]
Amongst these in Rankine’s circle of affect within the 1850s was an skilled builder of marine steam engines in Glasgow named John Elder, who turned the primary to include a double-cylinder engine right into a profitable steamship. Elder had marine engines in his blood: his father David had joined Robert Napier’s engine constructing agency and started designing steamboat engines in 1821. Along with household custom and his pure abilities, Elder had two different benefits on this endeavor. First, he had entry to Glasgow’s “thermodynamic community” (because the historian Crosbie Smith put it); he had tutors within the new thermodynamic science and doubtless obtained particular recommendation from Rankine to introduce steam jacketing to stop condensation within the cylinder. Second, he had an keen purchaser.[20]
The Pacific Steam Navigation Firm (PSNC) of Liverpool had overextended itself within the South American Pacific-coast commerce, the place high-quality steam coal might arrive solely by a 19,000-mile round-trip provided by sail. Revenue margins had been slim to none, and enterprise stayed within the black solely by advantage of a authorities mail contract. This made the corporate keen to attend out teething issues as a way to get a extra environment friendly engine. From the time Elder and his companion took out their engine patent in January 1853, it took 4 years earlier than PSNC ratified the prevalence of their ship Valparaiso, which consumed 25% much less coal than an equal single-cylinder mannequin.[21]
Elder’s success set the stage for Holt’s additional vault ahead within the 1860s. Among the many latter’s achievements was to persuade the Board of Commerce that marine engines might function safely at larger pressures; permitting a larger fall of temperature and thus extra environment friendly use of gas. This, in flip, set the stage for triple-expansion engines later within the century, to extract nonetheless extra work from the warmth because it falls from boiler to condenser. This polyphonic fugue of equipment heralded the age of steam’s baroque interval, which engendered the fantasias of steampunk a century later. By about 1890, a triple-expansion engine, operating at 160 pounds-per-square-inch, might devour one-and-a-half kilos of coal per-horsepower per-hour, lower than a 3rd of the going price just a few a long time earlier than, and about 5 instances lower than Watt’s engine.[22]
But even because it thrust the age of steam up in direction of its apex, thermodynamics identified the weak spot that may result in its downfall. In his 1854 speech to the BAAS, Rankine had touted some great benefits of the air engine, a tool devised by the Scotsman Robert Stirling that used sizzling air as its working fluid. As Rankine identified, the legal guidelines of thermodynamics don’t have anything specifically to do with steam, however maintain “true for all substances by any means in all situations…” Air had a determined benefit over steam insofar because it might be pushed to very excessive temperatures with out creating very harmful pressures: “For instance, on the temperature of 650 ° Fahr. (measured from the strange zero,) a temperature as much as which air engines have truly been labored with ease and security, the strain of steam is 2100 kilos upon the sq. inch; a strain which plainly renders it impracticable to work steam engines with security….”[23] The Stirling air engine didn’t, within the occasion, show to be the slayer of steam. Its use by no means expanded past occasional low-power home functions. However it introduced the primary adumbration of the approaching eclipse.
[1] Francis E. Hyde, Blue Funnel: A Historical past of Alfred Holt and Firm of Liverpool from 1865 to 1914 (Liverpool: Liverpool College Press, 1956), 1-19.
[2] John Farey, A Treatise on the Steam Engine (London: Longman, Rees, Orme, Brown, and Inexperienced, 1827), 384-392; Hills, Energy from Steam, 147-148; D.S.L. Cardwell From Watt to Clausius: The Rise of Thermodynamics within the Early Industrial Age (Ithaca: Cornell College Press, 1971), 78-79.
[3] Rhys Jekins, “A Cornish Engineer: Arthur Woolf, 1766-1837,” Transactions of the Newcomen Society 13, 1 (1932), 55-56.
[4] Rhys Jekins, “A Cornish Engineer,” 57-58.
[5] Rhys Jekins, “A Cornish Engineer,” 59-63.
[6] Hills, Energy from Steam, 178-184.
[7] Quoted in James Alfred Ewing, “Steam Engine,” Encyclopedia Britannica, vol.25 (Cambridge: Cambridge College Press, 1911), 820.
[8] Hills, Energy from Steam, 236-267.
[9] Quoted in D.S.L. Cardwell, “Science and Steam within the Early Nineteenth Century Reconsidered,” Transactions of the Newcomen Society 49, 1 (1977), 111.
[10] Thomas Savery, The Miner’s Buddy (London: W. Clowes, 1827 [1702]), 26.
[11] H.W. Dickinson, James Watt: Craftsman and Engineer (Cambridge: Cambridge College Press, 2010 [1935]), 131.
[12] Hills, Energy From Steam, 91-93.
[13] Sadi Carnot (R.H. Thurston, ed.), Reflections on the Motive Energy of Warmth (New York: John Wiley & Sons, 1897), 20.
[14] Carnot, Reflections on the Motive Energy of Warmth, 37-38.
[15] Carnot, Reflections on the Motive Energy of Warmth, 44-45.
[16] Milton Kerker, “Sadi Carnot and the Steam Engine Engineers,” Isis 51, 3 (September 1960), 260-263.
[17] Hunt, Pursuing Energy and Mild, 37-40.
[18] “Division of Civil Engineering,” Data of the College of Glasgow, Scotland (https://archiveshub.jisc.ac.uk/search/archives/5423a1c4-bcfe-3c21-8dcd-0ebf353a9207?component=0b5e6a0f-6850-3a0f-8aa9-27b1d6c59d23); R. A. Buchanan, “The Rise of Scientific Engineering in Britain,” The British Journal for the Historical past of Science 18, 2 (July 1985), 218-233.
[19] W.J. Macquorn Rankine, “On the Technique of Realizing the Benefits of the Air-Engine,” Journal of the Franklin Institute, 60, 4 (October 1855), 253.
[20] Crosbie Smith, “Witnessing Energy: john Elder and the Making of the Marine Compound Engine, 1850-1858,” Know-how and Tradition 55, 1 (January 2014), 76-106; David F. Channell, “The Concord of Concept and Follow: The Engineering Science of W. J. M. Rankine, ” Know-how and Tradition 23, 1 (January 1982), 48
[21] Smith, “Witnessing Energy,” 86-87, 89, 102.
[22] Adrian Jarvis, “Alfred Holt and the Compound Engine,” in Robert Gardiner, ed., The Creation of Steam: The Service provider Steamship Earlier than 1900 (London: Conway Maritime Press, 1993), 156-159; Hills, Energy from Steam, 241-242.
[23] Rankine, “On the Technique of Realizing the Benefits of the Air-Engine,”