Since the extensive use of oil fuel during the war, many minor improvements have been introduced into the various oil fuel systems, and, for the benefit of the student of the subject, a brief descriptions is presented of each of the chief systems now generally adopted.
The Holden Burner. This burner consists primarily of a coned body into which oil is admitted through a specially designed regulating valve. Inside the body an annular steam jet is introduced. This pos sesses a central passage for assisting in the supply of air and for enabling a wire to be passed through the burner without shutting off either oil or steam. Imme diately behind the nozzle a hollow ring is attached, I Specification from the Petroleum year Book.
and to this steam is admitted and allowed to escape from six very fine jet holes. Another requirement fulfilled by this ring is that the jets induce a strong current of atmospheric air, which is carried forward and mixed with the spray as it emerges from the nozzle, ensuring complete combustion. The valve used for regulating the flow of the oil fuel is of special construc tion, and in this burner a small reservoir of oil is formed by the body of the valve, a tube with a slit in it being moved up and down inside. Very fine adjustments in the flow of oil are possible with this valve.
The Kermode Steam-Jet Burner. The oil enters the burner B (Fig. 2), and is given a whirling motion by the long special stem of the valve spindle G, the quantity of oil being governed by the hand-wheel N at the end of spindle A. The steam enters at C round the hollow cone H and passes through slots in the cylindrical portion of this cone, where it fits the inside of the hollow air-cone F. This air-cone is fitted with special guides, and the air is drawn past these guides through the open ing D by the inductive action of the steam. The amount of air may be regulated by means of the movable perforated strap E. The part marked F can be screwed in or out as a whole, being turned by the spider M. When moved it carries with it the cone F, and in so doing regulates the space between this and the oil-cone H for the escape of the steam.
The " Kermode" Pressure-Jet Burner. The oil enters
the burner (Fig. 3) through the channel A, and passes between the outer wall of the burner D and the inner cylinder B, which abuts against the cap nut E. The end of the cylinder B is a true fit for the outer body D at the end where it abuts against the cap. A series of grooves are cut in the plug end of B parallel to the centre line of the burner, and similar grooves are cut in the face of the plug B at right angles to the axis of the burner. These grooves are shown in sketch H, and are tangential to the cone end of the spindle C, which serves to contract or enlarge the opening through the cap nut B. The movement of the spindle is indicated on the graduated wheel F by being forced through a restricted opening with a rotary motion, and the oil is pulverized very completely. The fixed pointer, G, indicates the degree to which the wheel F has been rotated, either to increase or decrease the opening through the cap nut.
Kermode's Air-Jet Burner. In this burner the oil is sprayed by means of air, at from half-a-pound to four pounds pressure. Furnaces for industrial purposes will sometimes work satisfactorily with an air pressure of half-a-pound, on the other hand, in extreme cases, four pounds pressure may be required. The oil entering the burner is met by air passing in, and both travel on together, and there is a complete commingling of the air and oil. All the elements of the combustion are under complete control. The oil as it passes the nozzle beyond the valve is swept forward by a sharp current of air which envelops the nozzle ; this current can be regulated with great exactitude. A further compressed air supply is given where combustion is about to commence, while a third supply is caused by the induction of the flame or by the draught.
By the use of this system 83 per cent of the calorific value of the fuel used is recovered in actual work. Less than 2 per cent of steam is used to drive the air compressing plant, and if this is condensed no fresh water is lost. For industrial operations the air compressor is electrically driven when current is available. In some cases it may be belt-driven from an existing power shaft.