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41 Priestman, William Dent
SUBJECT AREA: Steam and internal combustion engines[br]b. 23 August 1847 Sutton, Hull, Englandd. 7 September 1936 Hull, England[br]English oil engine pioneer.[br]William was the second son and one of eleven children of Samuel Priestman, who had moved to Hull after retiring as a corn miller in Kirkstall, Leeds, and who in retirement had become a director of the North Eastern Railway Company. The family were strict Quakers, so William was sent to the Quaker School in Bootham, York. He left school at the age of 17 to start an engineering apprenticeship at the Humber Iron Works, but this company failed so the apprenticeship was continued with the North Eastern Railway, Gateshead. In 1869 he joined the hydraulics department of Sir William Armstrong \& Company, Newcastle upon Tyne, but after a year there his father financed him in business at a small, run down works, the Holderness Foundry, Hull. He was soon joined by his brother, Samuel, their main business being the manufacture of dredging equipment (grabs), cranes and winches. In the late 1870s William became interested in internal combustion engines. He took a sublicence to manufacture petrol engines to the patents of Eugène Etève of Paris from the British licensees, Moll and Dando. These engines operated in a similar manner to the non-compression gas engines of Lenoir. Failure to make the two-stroke version of this engine work satisfactorily forced him to pay royalties to Crossley Bros, the British licensees of the Otto four-stroke patents.Fear of the dangers of petrol as a fuel, reflected by the associated very high insurance premiums, led William to experiment with the use of lamp oil as an engine fuel. His first of many patents was for a vaporizer. This was in 1885, well before Ackroyd Stuart. What distinguished the Priestman engine was the provision of an air pump which pressurized the fuel tank, outlets at the top and bottom of which led to a fuel atomizer injecting continuously into a vaporizing chamber heated by the exhaust gases. A spring-loaded inlet valve connected the chamber to the atmosphere, with the inlet valve proper between the chamber and the working cylinder being camoperated. A plug valve in the fuel line and a butterfly valve at the inlet to the chamber were operated, via a linkage, by the speed governor; this is believed to be the first use of this method of control. It was found that vaporization was only partly achieved, the higher fractions of the fuel condensing on the cylinder walls. A virtue was made of this as it provided vital lubrication. A starting system had to be provided, this comprising a lamp for preheating the vaporizing chamber and a hand pump for pressurizing the fuel tank.Engines of 2–10 hp (1.5–7.5 kW) were exhibited to the press in 1886; of these, a vertical engine was installed in a tram car and one of the horizontals in a motor dray. In 1888, engines were shown publicly at the Royal Agricultural Show, while in 1890 two-cylinder vertical marine engines were introduced in sizes from 2 to 10 hp (1.5–7.5 kW), and later double-acting ones up to some 60 hp (45 kW). First, clutch and gearbox reversing was used, but reversing propellers were fitted later (Priestman patent of 1892). In the same year a factory was established in Philadelphia, USA, where engines in the range 5–20 hp (3.7–15 kW) were made. Construction was radically different from that of the previous ones, the bosses of the twin flywheels acting as crank discs with the main bearings on the outside.On independent test in 1892, a Priestman engine achieved a full-load brake thermal efficiency of some 14 per cent, a very creditable figure for a compression ratio limited to under 3:1 by detonation problems. However, efficiency at low loads fell off seriously owing to the throttle governing, and the engines were heavy, complex and expensive compared with the competition.Decline in sales of dredging equipment and bad debts forced the firm into insolvency in 1895 and receivers took over. A new company was formed, the brothers being excluded. However, they were able to attend board meetings, but to exert no influence. Engine activities ceased in about 1904 after over 1,000 engines had been made. It is probable that the Quaker ethics of the brothers were out of place in a business that was becoming increasingly cut-throat. William spent the rest of his long life serving others.[br]Further ReadingC.Lyle Cummins, 1976, Internal Fire, Carnot Press.C.Lyle Cummins and J.D.Priestman, 1985, "William Dent Priestman, oil engine pioneer and inventor: his engine patents 1885–1901", Proceedings of the Institution ofMechanical Engineers 199:133.Anthony Harcombe, 1977, "Priestman's oil engine", Stationary Engine Magazine 42 (August).JBBiographical history of technology > Priestman, William Dent
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42 low
aircraft low tension wiringэлектропроводка низкого напряжения на воздушном суднеauthorized low flyingразрешенные полеты на малой высотеfly at a low levelлетать в режиме бреющего полетаfuel low level switchсигнализатор остатка топлива(в баке) low air areaнижнее воздушное пространствоlow air routeмаршрут нижнего воздушного пространстваlow altitude en-route chartмаршрутная карта полетов на малых высотахlow altitude flight planning chartкарта планирования полетов на малых высотахlow annoyance aircraftмалошумное воздушное судноlow aspect wingкрыло малого удлиненияlow bypass ratio engineдвигатель с низкой степенью двухконтурностиlow ceilingнизкая облачностьlow cloudsоблака нижнего ярусаlow control areaнижний диспетчерский районlow drifting snowпоземкаlower airspaceнижнее воздушное пространствоlower atmosphereнижние слои атмосферыlower coaxial rotorнижний соосный винтlower flight levelнижний эшелон полетаlower limitнижняя границаlower linkнижнее звеноlower pitch propellerоблегченный воздушный винтlower stayнижнее звено(складывающегося подкоса шасси) lower the nose wheelопускать носовое колесоlower wingнижнее крылоlowest admissible minimaнаименьший допустимый минимумlowest weather conditionsнаиболее неблагоприятные погодные условияlow fareльготный тарифlow fare ticketльготный билетlow flightполет на малых высотахlow float switchпоплавковый сигнализатор остатка(топлива) low flyingполеты на малых высотахlow flying operationполет на малой высотеlow latitudesнизкие широтыlow level wind-shear alert systemсистема предупреждения о сдвиге ветра на малых высотахlow pitchмалый шагlow pressure filterфильтр низкого давленияlow pressure pumpнасос низкого давленияlow pressure rotorротор низкого давленияlow pressure tireпневматическая шина низкого давленияlow pressure turbineтурбина низкого давленияlow quantity indicatorуказатель остаткаlow visibilityслабая видимостьlow visibility conditionsусловия ограниченной видимостиlow visibility landingпосадка при ограниченной видимостиlow visibility takeoffвзлет в условиях плохой видимостиlow weatherсложные метеоусловияlow weather minima pathтраектория полетов по низким минимумам погодыlow weather operationsполеты по низким метеоминимумамlow wingнизкорасположенное крылоpractice low approachтренировочный заход на посадкуwing lower surfaceнижняя поверхность крыла -
43 lower
lowering vвыпускaircraft low tension wiringэлектропроводка низкого напряжения на воздушном суднеfly at a low levelлетать в режиме бреющего полетаfuel low level switchсигнализатор остатка топлива(в баке) low air areaнижнее воздушное пространствоlow air routeмаршрут нижнего воздушного пространстваlow altitude en-route chartмаршрутная карта полетов на малых высотахlow altitude flight planning chartкарта планирования полетов на малых высотахlow annoyance aircraftмалошумное воздушное судноlow aspect wingкрыло малого удлиненияlow bypass ratio engineдвигатель с низкой степенью двухконтурностиlow ceilingнизкая облачностьlow cloudsоблака нижнего ярусаlow control areaнижний диспетчерский районlow drifting snowпоземкаlower airspaceнижнее воздушное пространствоlower atmosphereнижние слои атмосферыlower coaxial rotorнижний соосный винтlower flight levelнижний эшелон полетаlower limitнижняя границаlower linkнижнее звеноlower pitch propellerоблегченный воздушный винтlower stayнижнее звено(складывающегося подкоса шасси) lower the landing gearвыпускать шассиlower the legsвыпускать шассиlower the nose wheelопускать носовое колесоlower wingнижнее крылоlowest admissible minimaнаименьший допустимый минимумlowest weather conditionsнаиболее неблагоприятные погодные условияlow fareльготный тарифlow fare ticketльготный билетlow flightполет на малых высотахlow float switchпоплавковый сигнализатор остатка(топлива) low flyingполеты на малых высотахlow flying operationполет на малой высотеlow latitudesнизкие широтыlow level wind-shear alert systemсистема предупреждения о сдвиге ветра на малых высотахlow pitchмалый шагlow pressure filterфильтр низкого давленияlow pressure pumpнасос низкого давленияlow pressure rotorротор низкого давленияlow pressure tireпневматическая шина низкого давленияlow pressure turbineтурбина низкого давленияlow quantity indicatorуказатель остаткаlow visibilityслабая видимостьlow visibility conditionsусловия ограниченной видимостиlow visibility landingпосадка при ограниченной видимостиlow visibility takeoffвзлет в условиях плохой видимостиlow weatherсложные метеоусловияlow weather minima pathтраектория полетов по низким минимумам погодыlow weather operationsполеты по низким метеоминимумамlow wingнизкорасположенное крылоmanual loweringручной выпускpractice low approachтренировочный заход на посадкуwing lower surfaceнижняя поверхность крыла -
44 polychlorinated biphenyl
полихлорированный бифенил
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[ http://www.eionet.europa.eu/gemet/alphabetic?langcode=en]EN
polychlorinated biphenyl
PCBs are a family of chemical compounds which do not exist in nature but which are man-made. Commercial mixtures are clear, pale yellow liquids, manufactured by the replacement of hydrogen atoms on the biphenyl molecule by chlorine. Because of their physical properties, PCBs are commonly found in electrical equipment which requires dielectric fluid such as power transformers and capacitors, as well as in hydraulic machinery, vacuum pumps, compressors and heat-exchanger fluids. Other uses include: lubricants, fluorescent light ballasts, paints, glues, waxes, carbonless copy paper, inks including newspapers, dust-control agents for dirt roads, solvents for spreading insecticides, cutting oils. PCBs are stable compounds and although they are no longer manufactured they are extremely persistent and remain in huge quantities in the atmosphere and in landfill sites. They are not water-soluble and float on the surface of water where they are eaten by aquatic animals and so enter the food chain. PCBs are fat-soluble, and are therefore easy to take into the system, but difficult to excrete. (Source: PZ / PHC)
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