US2878065A

US2878065A - Liquid fuel discharge nozzles

Info

Publication number: US2878065A
Application number: US670413A
Authority: US
Inventors: Sidney C Watkins
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1956-07-23
Filing date: 1957-07-08
Publication date: 1959-03-17
Anticipated expiration: 1976-03-17

Description

March 17, 1959 s. c. WATKINS 2,878,065

LIQUID FUEL DISCHARGE NOZZLES Filed July 8, 1957 y z t f e P x 1 l\ T 4 7 d f, h 1 K 3L 1 IV 0 a X U flzcezzizr 6. CHa/ikuzw Unite Sates LIQUID FUEL DISCHARGE NOZZLES Sidney C. Watkins, Burnley, England, assignor to Joseph Lucas (lnclusnies) Limited, Birmingham, England This invention relates to liquid fuel discharge nozzles of the swirl type for supplying fuel in a nebulised condition to a combustion chamber.

In a nozzle of conventional form the liquid is supplied tangentially to a conical swirl chamber having a small discharge orifice at its apex. While passing through the swirl chamber a rapid rotary or eddy motion is imparted to the fuel, so causing it to issue from the nozzle in the form of a thin hollow conical film which quickly disintegrates into the condition of a fine mist. To obtain satisfactory nebulisation it is necessary to supply the fuel at a sufiiciently high rate, and in this condition an axial air core is set up in the liquid in the swirl chamber. When the liquid is supplied at a low rate at which no air core is formed, the issuing jet breaks up into relatively coarse drops, and the resulting fuel-air mixture is unsatisfactory where a high rate of combustion is required.

For some purposes it is necessary to be able to vary the rate of fuel supply over a wide range, and for such a purpose a swirl nozzle of conventional form is unsatisfactory in that it does not effect proper nebulisation of the fuel when the latter is supplied at a low rate.

The object of the present invention is to provide a nozzle of the aforesaid type in an improved form which enables satisfactory nebulisation of the fuel to be obtained over a wide range of rate of supply of the fuel.

A nozzle in accordance with the invention includes a swirl chamber having a discharge orifice at its apex and an axial orifice in its base, a cavity into which fuel can flow from the swirl chamber when no air core exists in the said chamber, and an air duct in communication with the said cavity and terminating in a discharge orifice coaxial with the discharge orifice of the swirl chamber, the arrangement being such that at a low rate of fuel supply air-nebulisation of the fuel is effected in the air duct, and at a high rate of fuel supply, swirl-nebulisation is effected by discharge from the swirl chamber.

In the accompanying drawing, Figure l is a sectional side elevation of a nozzle embodying the invention, and Figure 2 is an end view of one of the components of the nozzle.

Referring to the drawings, the body part a has formed in it a passage b for conveyance of the liquid fuel supplied by a pump, and a passage c for conveyance of air supplied by a blower or other convenient source. At the front end of the body part is placed a hollow nipple d. The rear end of the nipple is of hollow cylindrical form and in it are contained two inserts e, f. The forward end of the nipple is of conical shape and on its outer periphery are formed helical or like air grooves g (Fig ure 2) adapted to impart a Swirling motion to the air flowing therein. Also within the forward end of the nipple is formed a conical chamber h forming part of atent 2 the swirl chamber and terminating in an axial discharge orifice 1'.

At the centre of the front face of the insert e is formed a cylindrical recess 1' of the same diameter as the larger end of the chamber h and forming the inner end of the swirl chamber. This recess communicates by way of a central hole k with a shallow recess m in the rear face of the insert e. In this insert are formed three equispaced ports 11 which communicate with the swirl chamber through tangential grooves 0 formed in the front face of the insert. Also in this insert are formed three other equi-spaced ports p which communiacte with the said recess in through grooves q formed in the rear face of the insert. The ports n are arranged between the ports p as shown in Figure 2. Further the ports p communicate with the grooves g through holes r. Preferably each groove is so shaped that at a position adjacent to the associated hole it is of less width than at its ends in order to form a venturi threat at that position.

In the insert are formed three equi-spaced ports s (of which only one appears in Figure 1) through which the fuel is conveyed from the passage b to the ports n in the insert 2, and air is conveyed from the passage 0 to an annular space 2 surrounding the nipple through a pas sage u.

'Over the front end of the body a is placed a sleeve v which is shaped internally to form the outer boundary of the annular air passage t and of the grooves g, and in the front end of this sleeve is formed a central orifice w.

The various components above described are secured in position on the body part by an outer sleeve x having a screw thread connection with the body part. Preferably the sleeve x is shaped to form with the sleeve 1 a narrow annular air space y into which an air stream can flow through ports z from the surrounding air in the combustion chamber, this passage being adapted at its outlet end to deflect the air across the front of the sleeve v for minimising the formation of carbon deposits on the front of the nozzle, this being a device which is already known and forms no essential part of the present invention.

The arrangement is such that with a low rate of fuel supply at which no air core is formed in the swirl chamber, the fuel passes from the recess 1' through the hole k and thence through the recess m, grooves q, ports p and holes r to the air grooves g. Here the fuel is nebulised by the air stream flowing along the said grooves from the annular space t and the mixture of air and fuel is discharged through the orifice w. When the fuel is supplied at a sufliciently high rate to cause an air core to be set up in the swirl chamber, the air core confines the fuel to the said chamber. No fuel then flows through the hole k and the nebulisation of the fuel then depends on the swirl of the fuel issuing through the orifice i.

Having thus described my invention What I claim as new and desire to secure by Letters Patent is:

A liquid fuel discharge nozzle comprising in combination a body part having therein a fuel supply passage and an air supply passage, means defining at one end of said body part a conical swirl chamber having its apex directed away from said body part and provided with a discharge orifice, and having an axial orifice in its base, and a cavity situated between the base of said swirl chamber and the adjacent end of said body part, and communicating with said swirl chamber through said axial orifice, said swirl chamber having tangentially arranged fuel inlets, an air duct surrounding said means and having a discharge orifice coaxial with and adjacent a 3 i e the discharge orifice in the apex of said swirl chamber, core set up therein by the swirling fuel prevents fuel air swirling means in said duct, ports establishing comflow from said swirl chamber to said cavity. municatlon between said fuel supply passage and the fuel References Cited in the file of this Patent inlets of said swirl chamber, and additional ports establishing communication between said cavity and said air 5 UNITED STATES PATENTS duct, so that at a low rate of fuel supply to said swirl 1,474,603 Morse Nov. 20, 1923 chamber fuel flows therefrom to said cavity and thence 2,303,104 Abbey Nov. 24, 1924 through said additional ports to said air duct, whereas at 2,701,164 Plln has Feb. 1, 1955 a high rate of fuel supply to said 'swir'l chamber the air 2,762,657 W n S p 9