76:. The inlet valves open to admit steam when minimum expansion volume has been reached at the start of the stroke. For a period of the crank cycle, steam is admitted, and the poppet inlet is then closed, allowing continued expansion of the steam during the stroke, driving the piston. Near the end of the stroke, the piston will uncover a ring of exhaust ports mounted radially around the centre of the cylinder. These ports are connected by a manifold and piping to the condenser, lowering the pressure in the chamber below that of the atmosphere causing rapid exhausting. Continued rotation of the crank moves the piston. From the animation, the features of a uniflow engine can be seen, with a large piston almost half the length of the cylinder, poppet inlet valves at either end, a camshaft (whose motion is derived from that of the driveshaft) and a central ring of exhaust ports.
105:
causes the opening times of the inlet valves to be very short, putting great strain on a delicate mechanical part. In order to withstand the huge mechanical forces encountered, engines have to be heavily built and a large flywheel is required both to smooth out the variations in torque as the steam pressure rapidly rises and falls in the cylinder and to compensate for the inertia of the heavy piston. Because there is a thermal gradient across the cylinder, the metal of the wall expands to different extents. This requires the cylinder bore to be machined wider in the cool center (sometimes described as "egg-shaped") than at the hot ends. If the cylinder is not heated correctly, or if water enters, the delicate balance can be upset causing seizure mid-stroke and, potentially, destruction.
96:
admitted may be increased for high torque at low speed, and may be decreased at cruising speed for economy of operation. Alternatively, designs using a more-complex cam surface allowed the varying of timing by shifting the entire camshaft longitudinally compared to its follower, allowing the admission timing to be varied. (The camshaft could be shifted by mechanical or hydraulic devices.) And, by changing the absolute phase, the engine's direction of rotation may be changed. The uniflow design also maintains a constant temperature gradient through the cylinder, avoiding passing hot and cold steam through the same end of the cylinder.
249:" fitted in place of the spark plug. As the rising piston nears the top of its stroke, it knocks open the bash valve to admit a pulse of steam. The valve closes automatically as the piston descends, and the steam is exhausted through the existing cylinder porting. The inertia of the flywheel then carries the piston back to the top of its stroke against the compression, as it does in the original form of the engine. Also like the original, the conversion is not self-starting and must be turned over by an external power source to start. An example of such a conversion is the steam-powered moped, which is started by pedalling.
51:
158:
89:
cylinder after the exhaust ports are closed is trapped, and this trapped steam is compressed by the returning piston. This is thermodynamically desirable as it preheats the hot end of the cylinder before the admission of steam. However, the risk of excessive compression often results in small auxiliary exhaust ports being included at the cylinder heads. Such a design is called a
95:
Engines of this type usually have multiple cylinders in an in-line arrangement, and may be single- or double-acting. A particular advantage of this type is that the valves may be operated by the effect of multiple camshafts, and by changing the relative phase of these camshafts, the amount of steam
104:
In practice, the uniflow engine has a number of operational shortcomings. The large expansion ratio requires a large cylinder volume. To gain the maximum potential work from the engine a high reciprocation rate is required, typically 80% faster than a double-acting counterflow type engine. This
88:
during the exhaust stroke. This condition allows higher thermal efficiency. The exhaust ports are open for only a small fraction of the piston stroke, with the exhaust ports closed just after the piston begins traveling toward the admission end of the cylinder. The steam remaining within the
364:
41:
is increased by having a temperature gradient along the cylinder. Steam always enters at the hot ends of the cylinder and exhausts through ports at the cooler centre. By this means, the relative heating and cooling of the cylinder walls is reduced.
181:
The final commercial evolution of the uniflow engine occurred in the United States during the late 1930s and 1940s by the
Skinner Engine Company with the development of the Compound Unaflow Marine Steam Engine. This engine operates in a
169:, in 1918. Only one such steam wagon is known to be still in existence; it was built in 1918, spent its working life and a period of dereliction in Australia, and was then repatriated to England and restored by
215:
design in history, used two 5-cylinder
Skinner Unaflow engines, but these were not steeple compounds. A non-compound Skinner Uniflow remained in service until 2013 in the Great Lakes cement carrier
84:
Uniflow engines potentially allow greater expansion in a single cylinder without the relatively cool exhaust steam flowing across the hot end of the working cylinder and steam ports of a
20:
149:. Experiments were also made in France, Germany, the United States and Russia. In no case were the results encouraging enough for further development to be undertaken.
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internal combustion engine, and it is possible to convert a two-stroke engine to a uniflow steam engine by feeding the cylinder with steam via a "
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133:
The uniflow principle was mainly used for industrial power generation, but was also tried in a few railway locomotives in
England, such as the
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In small sizes (less than about 1,000 hp (750 kW)), reciprocating steam engines are much more efficient than steam turbines.
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365:"BBC North West Regional News Material 1973-1986: Programme Details - Further details for Look North West: Friday 22/4/1977"
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The poppet valves are controlled by the rotating camshaft at the top. High pressure steam enters, red, and exhausts, yellow.
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by E. de Ville, published by The
English Universities Press Limited, London, 1960, pp 40–41
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in 1909, with the first commercial stationary engine produced a year previously in 1908.
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The single-acting uniflow steam engine configuration closely resembles that of a
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uses steam that flows in one direction only in each half of the cylinder.
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233:"-type admission valves to generate about 25 kW electrical output.
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The first large-scale utilization of a
Uniflow engine was in Atkinson
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A restored 1918 Atkinson
Uniflow steam wagon, photographed in 1977
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and provides efficiencies approaching contemporary diesels. Many
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The Museum of Retro
Technology – Uniflow Steam Locomotives
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The uniflow engine was first used in
Britain in 1827 by
431:
The Museum of Retro
Technology – Uniflow Steam Engines
222:, installed when the vessel was re-powered in 1950.
194:were so equipped, one of which is still operating,
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1399:
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276:
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23:Schematic animation of a uniflow steam engine.
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337:"V-E-V Odds & Ends The Riley Register's"
271:
237:Home-made conversions of two-stroke engines
229:used a three-cylinder uniflow engine with "
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121:. It was popularised by German engineer
49:
18:
1333:Glossary of steam locomotive components
86:conventional "counterflow" steam engine
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68:(which act similarly to those used in
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331:
64:Steam entry is usually controlled by
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59:Thinktank, Birmingham Science Museum
13:
1185:National Museum of Scotland engine
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14:
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465:
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300:French High-Pressure Locomotives"
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1367:List of steam technology patents
227:White Cliffs Solar Power Station
147:Midland Railway Paget locomotive
99:
152:
1352:Murdoch's model steam carriage
1338:History of steam road vehicles
396:
313:
184:steeple compound configuration
1:
1279:Murray's Hypocycloidal Engine
264:
79:
57:uniflow steam engine, now in
1002:Return connecting rod engine
117:and was patented in 1885 by
7:
1423:History of the steam engine
926:Condensing steam locomotive
418:Teach yourself heat engines
252:
70:internal combustion engines
10:
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1233:"Coalbrookdale Locomotive"
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1239:"Pen-y-Darren" locomotive
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259:Advanced steam technology
72:) that are operated by a
1078:Newcomen Memorial Engine
1382:Timeline of steam power
1377:Stationary steam engine
1260:Woolf's compound engine
1167:Soho Manufactory engine
1022:Steeple compound engine
689:straight line mechanism
370:North West Film Archive
1387:Water-returning engine
1361:Lean's Engine Reporter
1134:Chacewater Mine engine
1007:Six-column beam engine
162:
61:
26:
1227:London Steam Carriage
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135:North Eastern Railway
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22:
1173:Bradley Works engine
997:Reciprocating engine
820:Babcock & Wilcox
663:Centrifugal governor
219:St. Marys Challenger
211:, the most prolific
137:uniflow locomotives
119:Leonard Jennett Todd
16:Type of steam engine
714:Sun and planet gear
403:Steam-powered moped
91:semi-uniflow engine
1214:Richard Trevithick
812:Water-tube boilers
626:Gresley conjugated
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39:Thermal efficiency
27:
1418:Engine technology
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145:of 1918, and the
129:Steam locomotives
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1345:fardier à vapeur
1179:Whitbread Engine
1140:Smethwick Engine
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866:Feedwater heater
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46:Design details
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393:- description
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345:. p. 676
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335:(June 1977).
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322:. 1918-08-15.
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141:of 1913, and
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123:Johann Stumpf
120:
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115:Jacob Perkins
106:
100:Disadvantages
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77:
75:
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67:
66:poppet valves
60:
56:
52:
43:
40:
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21:
1372:Modern steam
1359:
1344:
1306:Porter-Allen
1285:
1219:
1146:
1126:
1083:
1017:Safety valve
946:"Pickle-pot"
840:Thimble tube
500:
417:
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374:. Retrieved
368:
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347:. Retrieved
340:
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304:. Retrieved
302:. 2006-01-03
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173:in 1976-77.
167:steam wagons
164:
153:Steam wagons
132:
112:
103:
94:
90:
83:
63:
35:steam engine
30:
28:
1103:Watt engine
903:Oscillating
859:Boiler feed
704:Plate chain
683:Tusi couple
596:Walschaerts
481:Atmospheric
342:Motor Sport
333:Boddy, Bill
192:Great Lakes
188:car ferries
1402:Categories
1312:Ljungström
1298:High-speed
1191:Lap Engine
1147:Resolution
1051:Precursors
936:Kirchweger
898:Locomotive
845:Three-drum
825:Field-tube
792:Locomotive
774:Lancashire
694:Link chain
678:Crankshaft
645:Mechanisms
573:Valve gear
391:Bash Valve
306:2019-10-21
265:References
247:bash valve
243:two-stroke
204:Casablanca
171:Tom Varley
80:Advantages
1343:Cugnot's
1286:Salamanca
987:Hydrolock
972:Crosshead
918:Condenser
754:Egg-ended
376:8 January
349:8 January
1326:See also
1252:Compound
1127:Old Bess
967:Blowback
890:Cylinder
876:Injector
835:Stirling
830:Sentinel
744:Haystack
658:Cataract
631:Southern
621:Caprotti
496:Compound
253:See also
217:SS
196:SS
74:camshaft
55:Galloway
33:type of
1042:History
951:Surface
769:Cornish
729:Boilers
611:Corliss
548:Corliss
531:D slide
501:Uniflow
491:Cornish
412:Sources
190:on the
143:No.2212
109:History
31:uniflow
1354:(1784)
1348:(1769)
1314:(1908)
1308:(1862)
1289:(1812)
1281:(1805)
1271:Murray
1262:(1803)
1241:(1804)
1235:(1803)
1229:(1803)
1223:(1801)
1193:(1788)
1187:(1786)
1181:(1785)
1175:(1783)
1169:(1782)
1150:(1781)
1142:(1779)
1136:(1778)
1130:(1777)
1122:(1768)
1094:(1795)
1088:(1760)
1080:(1725)
1061:(1698)
1027:Stroke
992:Piston
977:Cutoff
850:Yarrow
802:Launch
797:Scotch
558:Sleeve
553:Poppet
538:Piston
519:Valves
511:Valves
206:-class
198:Badger
139:No.825
960:Other
764:Flued
749:Wagon
673:Crank
616:Lentz
606:Baker
601:Allan
526:Slide
1112:Beam
653:Beam
563:Bash
543:Drop
486:Watt
378:2023
351:2023
231:Bash
29:The
931:Jet
759:Box
591:Joy
581:Gab
1404::
367:.
339:.
273:^
459:e
452:t
445:v
380:.
353:.
309:.
296:"
285:.
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