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77-960: The Kempton Steam Museum is home to the Kempton Park steam engines (also known as the Kempton Great Engines ) which are two large triple-expansion steam engines , dating from 1926–1929, at the Kempton Park Waterworks in south-west London. They were ordered by the Metropolitan Water Board and manufactured by Worthington-Simpson in Newark-On-Trent . Each engine is of a similar size to that used in RMS Titanic and rated at about 1,008 horsepower (752 kW). Each could pump nineteen million imperial gallons (86,000 m) of water

154-441: A 3 a 2 , a 4 a 2 , α 2 , α 3 , α 4 {\displaystyle l_{1},l_{2},l_{3},l_{4},{\frac {a_{3}}{a_{2}}},{\frac {a_{4}}{a_{2}}},\alpha _{2},\alpha _{3},\alpha _{4}} . The YST system requires at least 4 cylinders. With 3 cylinders, the same derivation gives us only 6 variables to vary, which

231-396: A i x ¨ i = 0 {\displaystyle \sum _{i=1}^{4}M_{i}{\ddot {x}}_{i}=0;\quad \sum _{i=2}^{4}M_{i}a_{i}{\ddot {x}}_{i}=0} This can be achieved if ∑ i = 1 4 M i x i = C o n s t ; ∑ i = 2 4 M i

308-602: A i x i = C o n s t {\displaystyle \sum _{i=1}^{4}M_{i}x_{i}=Const;\quad \sum _{i=2}^{4}M_{i}a_{i}x_{i}=Const} Now, plugging in the equations, we find that it means (up to second-order) ∑ i = 1 4 M i ( r i cos ⁡ ϕ i − r i 2 2 l i cos ⁡ ( 2 ϕ i ) ) = 0 ; ∑ i = 2 4 M i

385-635: A i ( r i cos ⁡ ϕ i − r i 2 2 l i cos ⁡ ( 2 ϕ i ) ) = 0 {\displaystyle \sum _{i=1}^{4}M_{i}(r_{i}\cos \phi _{i}-{\frac {r_{i}^{2}}{2l_{i}}}\cos(2\phi _{i}))=0;\quad \sum _{i=2}^{4}M_{i}a_{i}(r_{i}\cos \phi _{i}-{\frac {r_{i}^{2}}{2l_{i}}}\cos(2\phi _{i}))=0} Plugging in ϕ i = ϕ 1 + α i {\displaystyle \phi _{i}=\phi _{1}+\alpha _{i}} , and expand

462-729: A n t 1 = 100 000   Pa × ( 0.001   m 3 ) 7 5 = 10 5 × 6.31 × 10 − 5   Pa m 21 / 5 = 6.31   Pa m 21 / 5 , {\displaystyle {\begin{aligned}P_{1}V_{1}^{\gamma }&=\mathrm {constant} _{1}\\&=100\,000~{\text{Pa}}\times (0.001~{\text{m}}^{3})^{\frac {7}{5}}\\&=10^{5}\times 6.31\times 10^{-5}~{\text{Pa}}\,{\text{m}}^{21/5}\\&=6.31~{\text{Pa}}\,{\text{m}}^{21/5},\end{aligned}}} so

539-466: A n t 1 = 6.31   Pa m 21 / 5 = P × ( 0.0001   m 3 ) 7 5 , {\displaystyle {\begin{aligned}P_{2}V_{2}^{\gamma }&=\mathrm {constant} _{1}\\&=6.31~{\text{Pa}}\,{\text{m}}^{21/5}\\&=P\times (0.0001~{\text{m}}^{3})^{\frac {7}{5}},\end{aligned}}} We can now solve for

616-575: A n t 2 = 10 5   Pa × 10 − 3   m 3 300   K = 0.333   Pa m 3 K − 1 . {\displaystyle {\begin{aligned}{\frac {PV}{T}}&=\mathrm {constant} _{2}\\&={\frac {10^{5}~{\text{Pa}}\times 10^{-3}~{\text{m}}^{3}}{300~{\text{K}}}}\\&=0.333~{\text{Pa}}\,{\text{m}}^{3}{\text{K}}^{-1}.\end{aligned}}} We know

693-422: A piston compressing a gas contained within a cylinder and raising the temperature where in many practical situations heat conduction through walls can be slow compared with the compression time. This finds practical application in diesel engines which rely on the lack of heat dissipation during the compression stroke to elevate the fuel vapor temperature sufficiently to ignite it. Adiabatic compression occurs in

770-514: A 4-cylinder compound, the individual pistons within the group are usually balanced at 180°, the groups being set at 90° to each other. In one case (the first type of Vauclain compound ), the pistons worked in the same phase driving a common crosshead and crank, again set at 90° as for a two-cylinder engine. With the 3-cylinder compound arrangement, the LP cranks were either set at 90° with the HP one at 135° to

847-500: A closed system, one may write the first law of thermodynamics as Δ U = Q − W , where Δ U denotes the change of the system's internal energy, Q the quantity of energy added to it as heat, and W the work done by the system on its surroundings. Naturally occurring adiabatic processes are irreversible (entropy is produced). The transfer of energy as work into an adiabatically isolated system can be imagined as being of two idealized extreme kinds. In one such kind, no entropy

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924-599: A day, to reservoirs at Cricklewood , Fortis Green and Finsbury Park for the supply of drinking water to the north, east & west of London . Raw water was supplied to the waterworks by the Staines and Queen Mary Reservoirs , which stored water collected from the River Thames . They were the last working survivors when they were finally retired from service in 1980. The engines are of an inverted vertical triple-expansion type, 62 feet (19 m) tall from basement to

1001-402: A diagram (Figure 17) that is not reproduced for copyright reasons. Consider a 4-cylinder engine on a ship. Let x be the vertical direction, z be the fore-aft direction, and y be the port-starboard direction. Let the 4 cylinders be mounted in a row along the z-axis, so that their pistons are pointed downwards. The pistons are connected to the same crankshaft via long vertical rods. Now, we set up

1078-404: A gas, there is no time for heat conduction in the medium, and so the propagation of sound is adiabatic. For such an adiabatic process, the modulus of elasticity ( Young's modulus ) can be expressed as E = γP , where γ is the ratio of specific heats at constant pressure and at constant volume ( γ = ⁠ C p / C v ⁠ ) and P is the pressure of the gas. For

1155-625: A high-pressure (HP) cylinder , then having given up heat and losing pressure, it exhausts directly into one or more larger-volume low-pressure (LP) cylinders. Multiple-expansion engines employ additional cylinders, of progressively lower pressure, to extract further energy from the steam. Invented in 1781, this technique was first employed on a Cornish beam engine in 1804. Around 1850, compound engines were first introduced into Lancashire textile mills. There are many compound systems and configurations, but there are two basic types, according to how HP and LP piston strokes are phased and hence whether

1232-416: A larger cylinder volume as this steam occupies a greater volume. Therefore, the bore, and in rare cases the stroke as well, are increased in low-pressure cylinders, resulting in larger cylinders. Double-expansion (usually just known as 'compound') engines expand the steam in two stages, but this does not imply that all such engines have two cylinders. They may have four cylinders working as two LP-HP pairs, or

1309-469: A monatomic gas, 5 for a diatomic gas or a gas of linear molecules such as carbon dioxide). For a monatomic ideal gas, γ = ⁠ 5 / 3 ⁠ , and for a diatomic gas (such as nitrogen and oxygen , the main components of air), γ = ⁠ 7 / 5 ⁠ . Note that the above formula is only applicable to classical ideal gases (that is, gases far above absolute zero temperature) and not Bose–Einstein or Fermi gases . One can also use

1386-430: A rise in the temperature of that mass of air. The parcel of air can only slowly dissipate the energy by conduction or radiation (heat), and to a first approximation it can be considered adiabatically isolated and the process an adiabatic process. Adiabatic expansion occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand in size, thus causing it to do work on its surroundings. When

1463-441: A series of double-acting cylinders of progressively increasing diameter and/or stroke (and hence volume) designed to divide the work into three or four, as appropriate, equal portions for each expansion stage. Where space is at a premium, two smaller cylinders of a large sum volume might be used for the low-pressure stage. Multiple-expansion engines typically had the cylinders arranged in-line, but various other formations were used. In

1540-427: A system, so that Q = 0 , is called adiabatic, and such a system is said to be adiabatically isolated. The simplifying assumption frequently made is that a process is adiabatic. For example, the compression of a gas within a cylinder of an engine is assumed to occur so rapidly that on the time scale of the compression process, little of the system's energy can be transferred out as heat to the surroundings. Even though

1617-592: A vertical force on its mounting frame equaling M i x ¨ i {\displaystyle M_{i}{\ddot {x}}_{i}} . The YST system aims to make sure that the total of all 4 forces cancels out as exactly as possible. Specifically, it aims to make sure that the total force (along the x-axis) and the total torque (around the y-axis) are both zero: ∑ i = 1 4 M i x ¨ i = 0 ; ∑ i = 2 4 M i

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1694-445: A very high gas pressure, which ensures immediate ignition of the injected fuel. For an adiabatic free expansion of an ideal gas , the gas is contained in an insulated container and then allowed to expand in a vacuum. Because there is no external pressure for the gas to expand against, the work done by or on the system is zero. Since this process does not involve any heat transfer or work, the first law of thermodynamics then implies that

1771-579: Is a final temperature of 753 K, or 479 °C, or 896 °F, well above the ignition point of many fuels. This is why a high-compression engine requires fuels specially formulated to not self-ignite (which would cause engine knocking when operated under these conditions of temperature and pressure), or that a supercharger with an intercooler to provide a pressure boost but with a lower temperature rise would be advantageous. A diesel engine operates under even more extreme conditions, with compression ratios of 16:1 or more being typical, in order to provide

1848-470: Is a logical extension of the compound engine (described above) to split the expansion into yet more stages to increase efficiency. The result is the multiple-expansion engine . Such engines use either three or four expansion stages and are known as triple- and quadruple-expansion engines respectively. These engines use a series of double-acting cylinders of progressively increasing diameter and/or stroke and hence volume. These cylinders are designed to divide

1925-415: Is always some heat loss, as no perfect insulators exist. The mathematical equation for an ideal gas undergoing a reversible (i.e., no entropy generation) adiabatic process can be represented by the polytropic process equation P V γ = constant , {\displaystyle PV^{\gamma }={\text{constant}},} where P is pressure, V is volume, and γ

2002-415: Is desired to know how the values of dP and dV relate to each other as the adiabatic process proceeds. For an ideal gas (recall ideal gas law PV = nRT ) the internal energy is given by where α is the number of degrees of freedom divided by 2, R is the universal gas constant and n is the number of moles in the system (a constant). Differentiating equation (a3) yields Equation (a4)

2079-592: Is in general possible if there are at least 8 variables of the system that we can vary. Of the variables of the system, M i , r i {\displaystyle M_{i},r_{i}} are fixed by the design of the cylinders. Also, the absolute values of a 2 , a 3 , a 4 {\displaystyle a_{2},a_{3},a_{4}} do not matter, only their ratios matter. Together, this gives us 9 variables to vary: l 1 , l 2 , l 3 , l 4 ,

2156-486: Is insufficient to solve all 8 equations. The YST system is used on ships such as the SS Kaiser Wilhelm der Grosse and SS Deutschland (1900) . ^   Cylinder phasing:   With two-cylinder compounds used in railway work, the pistons are connected to the cranks as with a two-cylinder simple at 90° out-of-phase with each other ( quartered ). When the double-expansion group is duplicated, producing

2233-449: Is irreversible, with Δ S > 0 , as friction or viscosity are always present to some extent. The adiabatic compression of a gas causes a rise in temperature of the gas. Adiabatic expansion against pressure, or a spring, causes a drop in temperature. In contrast, free expansion is an isothermal process for an ideal gas. Adiabatic compression occurs when the pressure of a gas is increased by work done on it by its surroundings, e.g.,

2310-400: Is more than a simple 10:1 compression ratio would indicate; this is because the gas is not only compressed, but the work done to compress the gas also increases its internal energy, which manifests itself by a rise in the gas temperature and an additional rise in pressure above what would result from a simplistic calculation of 10 times the original pressure. We can solve for the temperature of

2387-578: Is named Bessie after Sir Prescott's wife. The engine house also houses two steam turbine water pumps. One of these steam turbines has now been motorised to demonstrate its inner workings. The waterworks is adjacent to the A316 (just before it becomes the M3 motorway ), between Sunbury-on-Thames and Hanworth . The same site also features a 2-foot gauge steam railway, the Kempton Steam Railway ,

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2464-423: Is produced within the system (no friction, viscous dissipation, etc.), and the work is only pressure-volume work (denoted by P d V ). In nature, this ideal kind occurs only approximately because it demands an infinitely slow process and no sources of dissipation. The other extreme kind of work is isochoric work ( d V = 0 ), for which energy is added as work solely through friction or viscous dissipation within

2541-424: Is the adiabatic index or heat capacity ratio defined as γ = C P C V = f + 2 f . {\displaystyle \gamma ={\frac {C_{P}}{C_{V}}}={\frac {f+2}{f}}.} Here C P is the specific heat for constant pressure, C V is the specific heat for constant volume, and f is the number of degrees of freedom (3 for

2618-440: Is the absolute or thermodynamic temperature . The compression stroke in a gasoline engine can be used as an example of adiabatic compression. The model assumptions are: the uncompressed volume of the cylinder is one litre (1 L = 1000 cm = 0.001 m ); the gas within is the air consisting of molecular nitrogen and oxygen only (thus a diatomic gas with 5 degrees of freedom, and so γ = ⁠ 7 / 5 ⁠ );

2695-494: Is zero, δQ = 0 . Then, according to the first law of thermodynamics, where dU is the change in the internal energy of the system and δW is work done by the system. Any work ( δW ) done must be done at the expense of internal energy U , since no heat δQ is being supplied from the surroundings. Pressure–volume work δW done by the system is defined as However, P does not remain constant during an adiabatic process but instead changes along with V . It

2772-480: The Earth's atmosphere when an air mass descends, for example, in a Katabatic wind , Foehn wind , or Chinook wind flowing downhill over a mountain range. When a parcel of air descends, the pressure on the parcel increases. Because of this increase in pressure, the parcel's volume decreases and its temperature increases as work is done on the parcel of air, thus increasing its internal energy, which manifests itself by

2849-498: The Olympic class ), but was ultimately replaced by the virtually vibration-free steam turbine . The development of this type of engine was important for its use in steamships as by exhausting to a condenser the water could be reclaimed to feed the boiler, which was unable to use seawater . Land-based steam engines could simply exhaust much of their steam, as feed water was usually readily available. Prior to and during World War II ,

2926-518: The Sahara desert . Adiabatic expansion does not have to involve a fluid. One technique used to reach very low temperatures (thousandths and even millionths of a degree above absolute zero) is via adiabatic demagnetisation , where the change in magnetic field on a magnetic material is used to provide adiabatic expansion. Also, the contents of an expanding universe can be described (to first order) as an adiabatically expanding fluid. (See heat death of

3003-469: The water vapor pressure to exceed the saturation vapor pressure . Expansion and cooling beyond the saturation vapor pressure is often idealized as a pseudo-adiabatic process whereby excess vapor instantly precipitates into water droplets. The change in temperature of an air undergoing pseudo-adiabatic expansion differs from air undergoing adiabatic expansion because latent heat is released by precipitation. A process without transfer of heat to or from

3080-584: The 1870s. Mallet locomotives were operated in the United States up to the end of mainline steam by the Norfolk and Western Railway . The designs of Alfred George de Glehn in France also saw significant use, especially in the rebuilds of André Chapelon . A wide variety of compound designs were tried around 1900, but most were short-lived in popularity, due to their complexity and maintenance liability. In

3157-425: The 20th century the superheater was widely adopted, and the vast majority of steam locomotives were simple-expansion (with some compound locomotives converted to simple). It was realised by engineers that locomotives at steady speed were worked most efficiently with a wide-open regulator and early cut-off, the latter being set via the reversing gear. A locomotive operating at very early cut-off of steam (e.g. at 15% of

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3234-416: The HP exhaust is able to pass directly from HP to LP ( Woolf compounds ) or whether pressure fluctuation necessitates an intermediate "buffer" space in the form of a steam chest or pipe known as a receiver ( receiver compounds ). In a single-expansion (or 'simple') steam engine, the high-pressure steam enters the cylinder at boiler pressure through an inlet valve. The steam pressure forces the piston down

3311-489: The Manchester area, of which 32,282 ihp was provided by compounds though only 41,189 ihp was generated from boilers operated at over 60psi. To generalise, between 1860 and 1926 all Lancashire mills were driven by compounds. The last compound built was by Buckley and Taylor for Wye No.2 mill, Shaw . This engine was a cross-compound design to 2,500 ihp, driving a 24 ft, 90 ton flywheel, and operated until 1965. In

3388-430: The adiabatic constant for this example is about 6.31 Pa m . The gas is now compressed to a 0.1 L (0.0001 m ) volume, which we assume happens quickly enough that no heat enters or leaves the gas through the walls. The adiabatic constant remains the same, but with the resulting pressure unknown P 2 V 2 γ = c o n s t

3465-405: The compound engine, high-pressure steam from the boiler first expands in a high-pressure (HP) cylinder and then enters one or more subsequent lower pressure (LP) cylinders. The complete expansion of the steam occurs across multiple cylinders and, as there is less expansion in each cylinder, the steam cools less in each cylinder, making higher expansion ratios practical and increasing the efficiency of

3542-809: The compressed gas has V  = 0.1 L and P  = 2.51 × 10  Pa , so we can solve for temperature: T = P V c o n s t a n t 2 = 2.51 × 10 6   Pa × 10 − 4   m 3 0.333   Pa m 3 K − 1 = 753   K . {\displaystyle {\begin{aligned}T&={\frac {PV}{\mathrm {constant} _{2}}}\\&={\frac {2.51\times 10^{6}~{\text{Pa}}\times 10^{-4}~{\text{m}}^{3}}{0.333~{\text{Pa}}\,{\text{m}}^{3}{\text{K}}^{-1}}}\\&=753~{\text{K}}.\end{aligned}}} That

3619-396: The compressed gas in the engine cylinder as well, using the ideal gas law, PV  =  nRT ( n is amount of gas in moles and R the gas constant for that gas). Our initial conditions being 100 kPa of pressure, 1 L volume, and 300 K of temperature, our experimental constant ( nR ) is: P V T = c o n s t

3696-469: The compression ratio of the engine is 10:1 (that is, the 1 L volume of uncompressed gas is reduced to 0.1 L by the piston); and the uncompressed gas is at approximately room temperature and pressure (a warm room temperature of ~27 °C, or 300 K, and a pressure of 1 bar = 100 kPa, i.e. typical sea-level atmospheric pressure). P 1 V 1 γ = c o n s t

3773-559: The cosine functions, we see that with ϕ 1 {\displaystyle \phi _{1}} arbitrary, the factors of sin ⁡ ( ϕ 1 ) , cos ⁡ ( ϕ 1 ) , sin ⁡ ( 2 ϕ 1 ) , cos ⁡ ( 2 ϕ 1 ) {\displaystyle \sin(\phi _{1}),\cos(\phi _{1}),\sin(2\phi _{1}),\cos(2\phi _{1})} must vanish separately. This gives us 8 equations to solve, which

3850-438: The cylinder, until the valve shuts (e.g. after 25% of the piston's stroke). After the steam supply is cut off the trapped steam continues to expand, pushing the piston to the end of its stroke, where the exhaust valve opens and expels the partially depleted steam to the atmosphere , or to a condenser. This " cut-off " allows much more work to be extracted, since the expansion of the steam is doing additional work beyond that done by

3927-399: The cylinders are not insulated and are quite conductive, that process is idealized to be adiabatic. The same can be said to be true for the expansion process of such a system. The assumption of adiabatic isolation is useful and often combined with other such idealizations to calculate a good first approximation of a system's behaviour. For example, according to Laplace , when sound travels in

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4004-430: The engine. There are other advantages: as the temperature range is smaller, cylinder condensation is reduced. Loss due to condensation is restricted to the LP cylinder. Pressure difference is less in each cylinder so there is less steam leakage at the piston and valves. The turning moment is more uniform, so balancing is easier and a smaller flywheel may be used. Only the smaller HP cylinder needs to be built to withstand

4081-469: The expansion and heating it in the later part. These irreversible heat flows decrease the efficiency of the process, so that beyond a certain point, further increasing the expansion ratio would actually decrease efficiency, in addition to decreasing the mean effective pressure and thus the power of the engine. A solution to the dilemma was invented in 1804 by British engineer Arthur Woolf , who patented his Woolf high pressure compound engine in 1805. In

4158-429: The expansion engine dominated marine applications where high vessel speed was not essential. It was superseded by the steam turbine when speed was required, such as for warships and ocean liners . HMS Dreadnought of 1905 was the first major warship to replace the proven technology of the reciprocating engine with the then-novel steam turbine. For railway locomotive applications the main benefit sought from compounding

4235-612: The final pressure P 2 = P 1 ( V 1 V 2 ) γ = 100 000   Pa × 10 7 / 5 = 2.51 × 10 6   Pa {\displaystyle {\begin{aligned}P_{2}&=P_{1}\left({\frac {V_{1}}{V_{2}}}\right)^{\gamma }\\&=100\,000~{\text{Pa}}\times {\text{10}}^{7/5}\\&=2.51\times 10^{6}~{\text{Pa}}\end{aligned}}} or 25.1 bar. This pressure increase

4312-1056: The fundamental quantities of the engine: Now, as the engine operates, the vertical position of cylinder i {\displaystyle i} is equal to x i {\displaystyle x_{i}} . By trigonometry, we have x i = r i cos ⁡ ϕ i + l i 2 ( r i sin ⁡ ϕ i ) 2 = l 1 + r i cos ⁡ ϕ i − r i 2 l i ( 1 − cos ⁡ ( 2 ϕ i ) ) / 2 + O ( r i 3 / l 2 ) {\displaystyle x_{i}=r_{i}\cos \phi _{i}+{\sqrt {l_{i}^{2}(r_{i}\sin \phi _{i})^{2}}}=l_{1}+r_{i}\cos \phi _{i}-{\frac {r_{i}^{2}}{l_{i}}}(1-\cos(2\phi _{i}))/2+O(r_{i}^{3}/l^{2})} As each cylinder moves up and down, it exerts

4389-438: The highest pressure, which reduces the overall weight. Similarly, components are subject to less strain, so they can be lighter. The reciprocating parts of the engine are lighter, reducing the engine vibrations. The compound could be started at any point in the cycle, and in the event of mechanical failure the compound could be reset to act as a simple, and thus keep running. To derive equal work from lower-pressure steam requires

4466-456: The ideal gas law to rewrite the above relationship between P and V as P 1 − γ T γ = constant , T V γ − 1 = constant {\displaystyle {\begin{aligned}P^{1-\gamma }T^{\gamma }&={\text{constant}},\\TV^{\gamma -1}&={\text{constant}}\end{aligned}}} where T

4543-464: The largest steam railway offering rides to the public on selected days, in London. The steam engines now form a museum operated by Kempton Great Engines Trust, a registered charity. Triple-expansion engine A compound steam engine unit is a type of steam engine where steam is expanded in two or more stages. A typical arrangement for a compound engine is that the steam is first expanded in

4620-526: The late 19th century, the Yarrow-Schlick-Tweedy balancing 'system' was used on some marine triple-expansion engines. Y-S-T engines divided the low-pressure expansion stages between two cylinders, one at each end of the engine. This allowed the crankshaft to be better balanced, resulting in a smoother, faster-responding engine which ran with less vibration. This made the 4-cylinder triple-expansion engine popular with large passenger liners (such as

4697-431: The marine environment, the general requirement was for autonomy and increased operating range, as ships had to carry their coal supplies. The old salt-water boiler was thus no longer adequate and had to be replaced by a closed fresh-water circuit with condenser. The result from 1880 onwards was the multiple-expansion engine using three or four expansion stages ( triple- and quadruple-expansion engines ). These engines used

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4774-456: The mills by running water. Cotton spinning required ever larger mills to fulfil the demand, and this drove the owners to demand increasingly powerful engines. When boiler pressure had exceeded 60 psi, compound engines achieved a thermo-dynamic advantage, but it was the mechanical advantages of the smoother stroke that was the deciding factor in the adoption of compounds. In 1859, there was 75,886 ihp (indicated horsepower ) of engines in mills in

4851-476: The need was for increased power at decreasing cost, and almost universal for marine engines after 1880. It was not widely used in railway locomotives where it was often perceived as complicated and unsuitable for the harsh railway operating environment and limited space afforded by the loading gauge (particularly in Britain). Compounding was never common on British railways and not employed at all after 1930, but

4928-401: The net internal energy change of the system is zero. For an ideal gas, the temperature remains constant because the internal energy only depends on temperature in that case. Since at constant temperature, the entropy is proportional to the volume, the entropy increases in this case, therefore this process is irreversible. The definition of an adiabatic process is that heat transfer to the system

5005-546: The other two, or in some cases all three cranks were set at 120°. ^   ihp:   The power of a mill engine was originally measured in Nominal Horse Power , but this system understated the power of a compound McNaught system suitable for compounds, ihp or indicated horse power. As a rule of thumb ihp is 2.6 times nhp, in a compound engine. Adiabatic process Some chemical and physical processes occur too rapidly for energy to enter or leave

5082-491: The piston stroke) allows maximum expansion of the steam, with less wasted energy at the end of the stroke. Superheating eliminates the condensation and rapid loss of pressure that would otherwise occur with such expansion. Large American locomotives used two cross-compound steam-driven air compressors, e.g. the Westinghouse 8 1/2" 150-D, for the train brakes. The presentation follows Sommerfeld's textbook, which contains

5159-479: The pressure applied on a parcel of gas is reduced, the gas in the parcel is allowed to expand; as the volume increases, the temperature falls as its internal energy decreases. Adiabatic expansion occurs in the Earth's atmosphere with orographic lifting and lee waves , and this can form pilei or lenticular clouds . Due in part to adiabatic expansion in mountainous areas, snowfall infrequently occurs in some parts of

5236-428: The shallower the material is in the Earth. Such temperature changes can be quantified using the ideal gas law , or the hydrostatic equation for atmospheric processes. In practice, no process is truly adiabatic. Many processes rely on a large difference in time scales of the process of interest and the rate of heat dissipation across a system boundary, and thus are approximated by using an adiabatic assumption. There

5313-409: The steam at boiler pressure. An earlier cut-off increases the expansion ratio, which in principle allows more energy to be extracted and increases efficiency. Ideally, the steam would expand adiabatically , and the temperature would drop corresponding to the volume increase. However, in practice the material of the surrounding cylinder acts as a heat reservoir, cooling the steam in the earlier part of

5390-402: The system as heat, allowing a convenient "adiabatic approximation". For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings. In meteorology , adiabatic expansion and cooling of moist air, which can be triggered by winds flowing up and over a mountain for example, can cause

5467-480: The system. A stirrer that transfers energy to a viscous fluid of an adiabatically isolated system with rigid walls, without phase change, will cause a rise in temperature of the fluid, but that work is not recoverable. Isochoric work is irreversible. The second law of thermodynamics observes that a natural process, of transfer of energy as work, always consists at least of isochoric work and often both of these extreme kinds of work. Every natural process, adiabatic or not,

5544-505: The top of the valve casings and each weighing over 800 tons. The engines are thought to be the biggest ever built in the UK. Engine No 6, also called The Sir William Prescott , has been restored to running order and is the largest fully operational triple-expansion steam engine in the world. It may be seen in steam on various weekends throughout the year, and as a static display every Sunday between March and November. The other engine, Engine No 7,

5621-415: The universe .) Rising magma also undergoes adiabatic expansion before eruption, particularly significant in the case of magmas that rise quickly from great depths such as kimberlites . In the Earth's convecting mantle (the asthenosphere) beneath the lithosphere , the mantle temperature is approximately an adiabat. The slight decrease in temperature with shallowing depth is due to the decrease in pressure

5698-415: The work into three or four equal portions, one for each expansion stage. The adjacent image shows an animation of a triple-expansion engine. The steam travels through the engine from left to right. The valve chest for each of the cylinders is to the left of the corresponding cylinder. Though the first mills were driven by water power , once steam engines were adopted the manufacturer no longer needed to site

5775-411: The work of the large LP cylinder can be split across two smaller cylinders, with one HP cylinder exhausting into either LP cylinder, giving a 3-cylinder layout where the cylinder and piston diameter of all three are about the same, making the reciprocating masses easier to balance. Two-cylinder compounds can be arranged as: The adoption of compounding was widespread for stationary industrial units where

5852-463: Was economy in fuel and water consumption plus high power/weight ratio due to temperature and pressure drop taking place over a longer cycle, this resulting in increased efficiency; additional perceived advantages included more even torque. While designs for compound locomotives may date as far back as James Samuel 's 1856 patent for a "continuous expansion locomotive", the practical history of railway compounding begins with Anatole Mallet 's designs in

5929-432: Was used in a limited way in many other countries. The first successful attempt to fly a heavier-than-air fixed-wing aircraft solely on steam power occurred in 1933, when George and William Besler converted a Travel Air 2000 biplane to fly on a 150 hp angle-compound V-twin steam engine of their own design instead of the usual Curtiss OX-5 inline or radial aviation gasoline engine it would have normally used. It

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