Профессиональное развитие будущих инженеров-строителей средствами иностранного языка: Лексический практикум по английскому языку. Трубникова Н.В. - 49 стр.

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Oil-firing equipment

Fuel oil is graded in the Redwood no. 1 viscosity test according to its time

of flow through a calibrated orifice at 38 °C. Vaporizing and wall-flame burn-

ers in boilers of up to 35 kW heat output use 28 s oil, pressure jet burners use

gas oil class D (34 s), and industrial boiler plant uses grade E (250 s), grade F

(1000 s) and grade G (3500 s). Power stations may use 6000 s residual oil,

heated to make it flow. This is the tar residue from crude oil distillation and can

only be burnt economically on such a large scale.

In the United Kingdom domestic oils can be stored in outdoor tanks.

Grades E, F and G require immersion heaters in the tank and pipeline heating

to ensure flow.

Wall-flame burners have a rotating nozzle which sprays oil onto periph-

eral plates around the inside of a water-cooled vertical cylindrical combustion

chamber. An electric spark ignites the oil impinging on the plates, establishing a

ring of flame around the walls of the boiler. Correct oil flow rate from the res-

ervoir is controlled by a ball valve. Oil is pumped at high pressure through a

fine nozzle, forming a conical spray in the furnace. Combustion air is blown

into this oil mist from a centrifugal fan. The turbulent interaction of oil and air

causes further atomization of the oil droplets, and the mixture is ignited by an

electric spark.

Combustion

Combustion is an exothermic chemical reaction that liberates heat. Fuel

must be intimately mixed with sufficient oxygen and raised to a temperature

high enough for combustion to be maintained. All the carbon and hydrogen in

the fuel are burnt into gaseous products that can be safely vented into the at-

mosphere. Hydrocarbon fuels are highly energy-intensive. They require little

storage volume and their combustion is controllable.

The constituents of dry air are 21% oxygen, 79% nitrogen and less than

1% other chemicals such as carbon dioxide, carbon monoxide, nitrous oxides

and rare gases, measured by volume. Nitrogen is inert and takes no part in the

chemistry of combustion, but it is heated in its passage through the furnace. The

quantity of air required for complete combustion and the composition of the