US3452933A

US3452933A - Oil fuel burning equipment

Info

Publication number: US3452933A
Application number: US634335A
Authority: US
Inventors: John Philip Dabbs Hakluytt
Original assignee: National Research Development Corp UK
Current assignee: National Research Development Corp UK
Priority date: 1966-04-30
Filing date: 1967-04-27
Publication date: 1969-07-01
Anticipated expiration: 1986-07-01
Also published as: DE1551710A1; DE1551710B2; FR1521152A; DE1551710C3; SE325362B; GB1165163A

Description

July 1, 1969 J. P. D. HAKLUYTT OIL FUEL BURNING EQUIPMENT Filed April 2'7, 1967 United States Patent US. Cl. 239-399 3 Claims ABSTRACT OF THE DISCLOSURE A fuel spray distributor comprises ejection chambers fed with fuel and ejecting fluid and the ejection chambers are arranged with their longitudinal axes converging in the general direction of fuel discharge and skewed relative to the axis of the distributor for suitable divergence of the spray.

This invention relates to fuel burning apparatus and more particularly to multi-jet distributors by means of which fuel is distributed in a burner by the use of an ejecting fluid which is introduced, together with fuel, into ejection chambers formed in the distributor. Thus the invention is applicable to oil fuel distributors where the fuel oil is caused by a second fluid to be distributed as an atomised spray; but it is also applicable to pulverised fuel distributors in which the ejecting fluid causes the fuel to be discharged from the distributor in spray form.

Although the invention will hereinafter be described with particular reference to oil burners, it is not intended that the invention shall be so limited in scope, since it is considered that its application to pulverised fuel burners U will be self-evident.

In the case of oil distributors where, for example, fuel oil is atomised by steam or air, it is understood that fouling of the atomiser surface occurs as a consequence of oil accumulations which carbonise. Such fouling leads inevitably to shutdown for cleaning purposes since the deterioration of atomisation associated with the fouling and blockage is cumulative and unacceptably serious.

It is considered that the accumulation of fouling due to oil carbonisation is governed principally by the temperature of the surface and by the area thereof presented to the radiation sources. In the one case, the temperature should be minimised and, in the other, the area should be minimised.

It is an object of the present invention to provide a form of spray distributor in which such disadvantages are minimised.

In accordance with the present invention, in a spray distributor for fuels in which an ejecting fluid and the fuel are introduced into a plurality of ejection chambers, said ejection chambers are arranged with their longitudinal axes converging in the general direction of fuel discharge and in a skew disposition relative to the axis of the distributor so as to provide a desired divergence of the fuel spray. in a distributor in accordance with the invention, it will be observed that by skew convergence of the axes of the ejection chambers a desired pattern of spray divergence may be achieved without impingement one upon the other of the spray streams issuing from the ejection chambers.

As further refinements, it is possible to design a distributor in accordance with the invention with one or more of the following objects in view:

(a) To reduce the size of the distributor face and to shape the distributor head profile in such a way that the location of the breakaway of the boundary layer is changed and thereby cooling may be improved,

3,452,933 Patented July 1, 1969 (b) To reduce the bluff body" effect of the distributor head diameter by fairing the head so that the vertical recirculation, with its axial zone of low pressure, may be minimised,

(c) To exploit the expansion potential of the ejecting fluid to fill the low pressure axial zone to the extent that the return recirculation is entirely prevented, and

'(d) Especially in the case of the oil fuel distributor, to provide the maximum cooling effect which is to be derived from the two fluids at the distributor face where said cooling is required in order to keep the surface temperature below a certain point, above which carbonisation may occur and below which, it may not.

'By grouping the discharge ports of the distributor very closely together and thereby being enabled to make the distributor face of a comparatively small area, the temperature can be held below that level at which the surface dries and carbonisation commences.

In order that the present invention may be more fully understood reference will now be made, by way of example, to the accompanying drawing illustrating a distributor according to the present invention for use with oil fuel which is to be burnt as an atomised spray. In the drawing, the atomiser head 1 is faired-oif to present a face 2 having a comparatively small area. Grouped symmetrically round the atomiser face are a number of discharge orifices 3 which form the outlets for the atomising-fluid/ oil ejection chambers 4 (which in oil distributors are usually referred to as mixing chambers) which are inclined with respect to the atomiser face and to the axis of the head so that the discharge from the portings forms a skew jet. Oil is supplied through the oil portings 5 which lead through oil feed ducts 6 into the ejection (mixing) chamber portions. Ejection fluid is fed to the chambers 4 through ejection fluid feed ducts 7 which are coaxial with their respective chambers '4.

The length and diameter of the ejection (mixing) chambers are preferably characterised to promote the highest efliciency of mixing and, for convenience, may have a small arboring at the discharge orifice for calibrating purposes.

The inclination of the ejecting fluid jet axes is preferably used advantageously to induce rotational velocity in the ejection (mixing) with benefit to the efiiciency of the mixing process.

A particular feature of a distributor in accordance with the invention is its presentation, in the spray pattern, of transit paths for the passage of combustion air from the outside of the axisymmetric flame to its inside, to promote flame stability.

'Distributors in accordance with the invention may be machined from any solid material capable of withstanding the wear due to flow and which has both sufficient thermal conductivity to sustain the essential rate of heat transfer and strength to support the loads due to fluid pressures. Alternatively, thin-wall porting assemblies may be comprised of one material, for example steel, and set in a supporting matrix of another material, for example, white metal.

An oil fuel distributor manufactured in brass to the design illustrated, has been burned for over seventy hours without any cleaning and it is expected that it will continue to burn without fouling indefinitely or until such time as one of the orifices is blocked adventitiously. It has been established that this design of distributor is not susceptible to carbonisation reuslting from excessive face temperatures and is capable of protracted service in furnaces with very high rates of heat release in close proximity to other distributors providing similarly large flames. The distributor has proved to be superior to other two-fluid distributors and is capable of producing a well-defined compact flame of exceptional heat release for its volume (in excess of 2,000,000 B.t.u./cu. ft./hr. at 4,000 lb./hr. output with excess air less than 3 percent); also it can be designed to be operated at very small ejection-fluid/fuel pressure differentials at full turn-down, where the nonfouling capability is retained even at negative differentials (i.e. fuel pressure greater than ejecting fluid pressure).

It is to be noted that, in the present design of distributor the flow of fuel, which has a cooling potential far superior to that of normal ejecting fluids, is enabled to be conducted very close to the exposed surface of the distributor head of which the superficial temperature must be held below a certain level if carbonisation is to be prevented; and also that the very small cross-sectional area of the face allows the use of swirlers which have small centre-tube sections with benefit both from the combustion standpoint and also by reducing the bluff body effect downstream which is the principal cause of the deposition mechanism. A further important potential development concerns the flexibility of orifice groupings. For example a typical orifice may deliver about 125 lb./ hr. at a steam pressure of 140 p.s.i. and fuel pressure of 100 p.s.i. Thus an eight-hole distributor will deliver 1,000 lb./hr. at these conditions. If the steam pressure is held constant, the output is doubled when a fuel pressure of about 155 p.s.i. is reached. Although steam consumption is higher in the former case, it is generally observed that the quality of the spray distribution is superior at 1,000 lb./hr. output to that at 2,000 lb./hr. output.

Where spray distribution, per se, is at a premium, advantage may be gained by increasing the number of orifices. Thus, to use the previous example, with identical orifices, a sixteen-hole grouping will, at the originally mentioned pressures of steam and fuel, deliver 2,000 lb./ hr. at the preferred conditions of spray distribution.

The skew configuration, by which adjacent individual jets lie in different planes without impingement of the jets one upon the other, specifically enables close clustering of orifices in a single distributor head which is necessary to realise this benefit in a practical design.

I claim:

1. A distributor for spray ejection of a fuel in the group consisting of liquid fuels, pulverised fuels and combined liquid and pulverised fuels, said distributor comprising a plurality of fuel feed ducts, a plurality of ejecting fluid feed ducts and a plurality of ejection chambers, each said ejection chamber being associated with at least one fuel feed duct and at least one ejecting fluid duct and said ejection chambers being arranged with their longitudinal axes converging in the general direction of fuel discharge and in skew disposition relative to the axis of the distributor so as to provide a desired divergence of the fuel spray.

2. An oil fuel distributor for spray ejection of oil comprising a plurality of oil feed ducts, a plurality of ejecting fluid feed ducts and a plurality of ejection chambers, each ejection chamber being associated with one said oil feed duct and, co-axially, with one said ejection fluid feed duct, and said ejection chambers being arranged with their longitudinal axes converging in the general direction of fuel discharge and in a skew disposition relative to the axis of the distributor so as to provide a desired divergence of the fuel spray.

3. A distributor for spray ejection of a fuel as claimed in claim 1, wherein the end of the distributor in the vicinity of the spray ejection and facing the said general direction of fluid flow is small in comparison to the remainder of the distributor, whereby the said vicinity of the distributor is subject to advantageous cooling by virtue of relative proximity of the oil feed and by virtue of delayed boundary layer breakaway from the distributor.

References Cited UNITED STATES PATENTS 1,578,101 3/1926 Stacey 239-434 FOREIGN PATENTS 147,891 1922 Great Britain.

M. HENSON WOOD, 112., Primary Examiner.

MICHAEL Y. MAR, Assistant Examiner.

US. Cl. X.R.