An indicator diagram is a chart used to measure the thermal, or cylinder, performance of reciprocating steam and internal combustion engines and compressors.[1] An indicator chart records the pressure in the cylinder versus the volume swept by the piston, throughout the two or four strokes of the piston which constitute the engine, or compressor, cycle. The indicator diagram is used to calculate the work done and the power produced in an engine cylinder[2] or used in a compressor cylinder.
Watt's indicator diagramIndicator diagram for steam locomotiveRichard's indicator instrument of 1875
The indicator diagram was developed by James Watt and his employee John Southern to help understand how to improve the efficiency of steam engines. In 1796, Southern developed the simple, but critical, technique to generate the diagram by fixing a board so as to move with the piston, thereby tracing the "volume" axis, while a pencil, attached to a pressure gauge, moved at right angles to the piston, tracing "pressure".
The gauge enabled Watt to calculate the work done by the steam while ensuring that its pressure had dropped to zero by the end of the stroke, thereby ensuring that all useful energy had been extracted. The total work could be calculated from the area between the "volume" axis and the traced line. The latter fact had been realised by Davies Gilbert as early as 1792 and used by Jonathan Hornblower in litigation against Watt over patents on various designs. Daniel Bernoulli had also had the insight about how to calculate work.
Watt used the diagram to make radical improvements to steam engine performance and long kept it a trade secret. Though it was made public in a letter to the Quarterly Journal of Science in 1822,[3] it remained somewhat obscure, John Farey, Jr. only learning of it on seeing it used, probably by Watt's men, when he visited Russia in 1826.
Later instruments for steam engine (illus.) used paper wrapped around a cylindrical barrel with a pressure piston inside it, the rotation of the barrel coupled to the piston crosshead by a weight- or spring-tensioned wire.
Indicators developed for steam engines were improved for internal combustion engines with their rapid changes in pressure, resulting from combustion, and higher speeds. In addition to using indicator diagrams for calculating power they are used to understand the ignition, injection timing and combustion events which occur near dead-center, when the engine piston and indicator drum are hardly moving Much better information during this part of the cycle is obtained by offsetting the indicator motion by 90 degrees to the engine crank, giving an offset indicator diagram. The events are recorded when the velocity of the drum is near its maximum and are shown against crank-angle instead of stroke.[5]
^Engineering Thermodynamics Work and Heat Transfer, Second edition, Rogers and Mayhew 1967, Longman's Green and Co. Ltd., p. 350-354.
^Pounders Marine Diesel and Gas Turbine Engines, Eighth edition 2004, edited by Doug Woodyard, ISBN0 7506 5846 0, p. 3.
^(Anonymous), "Account of a steam-engine indicator," Quarterly Journal of Science, vol. 13, page 95 (1822).
^Clapeyron, E. (1834) "Mémoire sur la puissance motrice de la chaleur" (Memoir on the motive power of heat), Journal de l'École Royale Polytechnique, vol. 14, no. 23, pages 153–190, 160–162.
^Internal Combustion Engines Theory and Design, Maleev, First edition 1933, McGraw-Hill Book company, Inc., p. 33.
Bibliography
Cardwell, D.S.L. (1971). From Watt to Clausius: The Rise of Thermodynamics in the Early Industrial Age. Heinemann: London. pp. 79–81. ISBN0-435-54150-1.
Pacey, A.J. & Fisher, S.J. (1967) "Daniel Bernoulli and the vis viva of compressed air", The British Journal for the History of Science3 (4), pp. 388–392, doi:10.1017/S0007087400002934
British Transport Commission (1957) Handbook for Railway Steam Locomotive Enginemen, London : B.T.C., p. 81, (facsimile copy publ. Ian Allan (1977), ISBN0-7110-0628-8)
External links
Walter, John. "The Engine Indicator. A collectors' guide to mechanical and optical/mechanical designs, 1800 to date". Canadian Museum of Making.
Wikimedia Commons has media related to Indicator diagrams.
August 22, 2023
indicator, diagram, indicator, diagram, chart, used, measure, thermal, cylinder, performance, reciprocating, steam, internal, combustion, engines, compressors, indicator, chart, records, pressure, cylinder, versus, volume, swept, piston, throughout, four, stro. An indicator diagram is a chart used to measure the thermal or cylinder performance of reciprocating steam and internal combustion engines and compressors 1 An indicator chart records the pressure in the cylinder versus the volume swept by the piston throughout the two or four strokes of the piston which constitute the engine or compressor cycle The indicator diagram is used to calculate the work done and the power produced in an engine cylinder 2 or used in a compressor cylinder Watt s indicator diagramIndicator diagram for steam locomotiveRichard s indicator instrument of 1875The indicator diagram was developed by James Watt and his employee John Southern to help understand how to improve the efficiency of steam engines In 1796 Southern developed the simple but critical technique to generate the diagram by fixing a board so as to move with the piston thereby tracing the volume axis while a pencil attached to a pressure gauge moved at right angles to the piston tracing pressure The gauge enabled Watt to calculate the work done by the steam while ensuring that its pressure had dropped to zero by the end of the stroke thereby ensuring that all useful energy had been extracted The total work could be calculated from the area between the volume axis and the traced line The latter fact had been realised by Davies Gilbert as early as 1792 and used by Jonathan Hornblower in litigation against Watt over patents on various designs Daniel Bernoulli had also had the insight about how to calculate work Watt used the diagram to make radical improvements to steam engine performance and long kept it a trade secret Though it was made public in a letter to the Quarterly Journal of Science in 1822 3 it remained somewhat obscure John Farey Jr only learning of it on seeing it used probably by Watt s men when he visited Russia in 1826 In 1834 Emile Clapeyron used a diagram of pressure against volume to illustrate and elucidate the Carnot cycle elevating it to a central position in the study of thermodynamics 4 Later instruments for steam engine illus used paper wrapped around a cylindrical barrel with a pressure piston inside it the rotation of the barrel coupled to the piston crosshead by a weight or spring tensioned wire Indicators developed for steam engines were improved for internal combustion engines with their rapid changes in pressure resulting from combustion and higher speeds In addition to using indicator diagrams for calculating power they are used to understand the ignition injection timing and combustion events which occur near dead center when the engine piston and indicator drum are hardly moving Much better information during this part of the cycle is obtained by offsetting the indicator motion by 90 degrees to the engine crank giving an offset indicator diagram The events are recorded when the velocity of the drum is near its maximum and are shown against crank angle instead of stroke 5 E850 Lord Nelson with an indicator shelter c 1926 1927References Edit Engineering Thermodynamics Work and Heat Transfer Second edition Rogers and Mayhew 1967 Longman s Green and Co Ltd p 350 354 Pounders Marine Diesel and Gas Turbine Engines Eighth edition 2004 edited by Doug Woodyard ISBN 0 7506 5846 0 p 3 Anonymous Account of a steam engine indicator Quarterly Journal of Science vol 13 page 95 1822 Clapeyron E 1834 Memoire sur la puissance motrice de la chaleur Memoir on the motive power of heat Journal de l Ecole Royale Polytechnique vol 14 no 23 pages 153 190 160 162 Internal Combustion Engines Theory and Design Maleev First edition 1933 McGraw Hill Book company Inc p 33 Bibliography EditCardwell D S L 1971 From Watt to Clausius The Rise of Thermodynamics in the Early Industrial Age Heinemann London pp 79 81 ISBN 0 435 54150 1 Pacey A J amp Fisher S J 1967 Daniel Bernoulli and the vis viva of compressed air The British Journal for the History of Science 3 4 pp 388 392 doi 10 1017 S0007087400002934 British Transport Commission 1957 Handbook for Railway Steam Locomotive Enginemen London B T C p 81 facsimile copy publ Ian Allan 1977 ISBN 0 7110 0628 8 External links EditWalter John The Engine Indicator A collectors guide to mechanical and optical mechanical designs 1800 to date Canadian Museum of Making Wikimedia Commons has media related to Indicator diagrams Retrieved from https en wikipedia org w index php title Indicator diagram amp oldid 1105160634, wikipedia, wiki, book, books, library,
