Miniature Flat Spray Nozzle

This invention relates to improvements in flat spray nozzles used in gas turbine combustors. Of particular concern are nozzles of miniature size and simple configuration which must perform well under a wide range of temperature and fuel viscosity conditions. Many different types of flat spray nozzles have been built for use in gas turbine engines. My previous inventions in the field, as represented by U.S. Pat. Nos. 3,834,627, 3,759,448, 3,713,591, 3,702,175 and 2,878,065, typify the present status of the art. All of the above are more complicated than my miniature flat spray nozzle. Due to its simplicity of design, it has been found particularly useful in conducting combustor research. Spray nozzles fabricated according to the principles of my invention can be easily positioned in a multiplicity of locations when attempting to optimize combustor performance.

The invention pertains to a miniature flat spray nozzle useful in gas turbine combustors. The nozzle consists of a specially formed metal part which is inserted into the end of a fuel-carrying conduit having a transverse slot made a short distance from the conduit's end. The specially formed part divides the end of the conduit into three chambers. The first chamber, a fuel outlet chamber, is in direct communication with the transverse slot. The other two chambers are fuel supply chambers and are in direct communication with the fuel flow in the conduit and they serve to divide the fuel flow. The two fuel supply chambers each have two orifices which provide for fuel flow from the fuel supply chambers to the fuel outlet chamber, one of the orifices being located upstream and one being located downstream of the slot. Thus, the flow path of fuel from the conduit divides into each of the fuel supply chambers and exits from two holes in each of the fuel supply chambers into the fuel outlet chamber. The fuel flow through the orifices and the subsequent turbulent mixing at the slot edge creates a finely atomized mist of fuel which exits from the slot in a flat spray.

The angular dimensions of the spray are fundamentally controlled by the slot dimensions. The spray quality and small changes to the spray angular dimensions can be controlled by proper positioning of the four orifices, both as a function of their spacing from the edge of the transverse slot and their spacing one from the next.

Having generally described the nature of the invention and how to assemble it from the two parts of which it is comprised, reference is made to the accompanying drawings, in which:

FIG. 1 shows a longitudinal cross section of a nozzle constructed in accordance with the invention;

FIG. 2 is a cross-sectional end view of the nozzle taken along line 2--2 of FIG. 1 and showing by line 1--1 the cross-sectional view depicted in FIG. 1;

FIG. 3 is a cross-sectional bottom view of the nozzle taken along line 3--3 of FIG. 1;

FIG. 4 is a cross-sectional end view taken at the same location as that of FIG. 2, but illustrating that the wall configuration of the inserted part can be proportioned differently to meet design needs; and

FIG. 5 illustrates the variations in spray pattern distribution characteristics achievable through alternate embodiments of this invention .

Referring to FIG. 1, there is shown a fuel conduit 10 having a circular cross section. A transverse slot 12 is cut through a segment of the conduit 10 to provide a fuel outlet a short distance from the downstream end of the conduit. The downstream end of the conduit is closed by means of an insert 14. Insert 14 is pressed into the open end of conduit 10 and may be bonded to it by brazing, welding or any similar means. As seen in FIG. 2, insert 14 divides the space immediately adjacent the end closure into three chambers, supply chamber 18 and 20, plus fuel outlet chamber 16. This is accomplished by providing the upstream end of insert 14 with three separately identifiable parts, as follows: chamber dividing wall 13 which lies in a plane parallel to the axis of conduit 10; chamber separator 15 which closes the upstream end of fuel outlet chamber 16; and structural support member 17 which holds chamber separator 15 in place and also serves as a separator between supply chambers 18 and 20. Chambers 18 and 20 communicate through their open ends with upstream region 22 of the interior of conduit 10. As seen in FIG. 3, orifices 24 and 26 serve as communication ducts between chamber 20 and 16. Orifices 24 and 26 are symmetrically located with respect to slot 12. In a like manner, orifices 28 and 30 allow chamber 18 to communicate with chamber 16. Slot 12 is symmetrically located such that a plane through its center is equidistant from the ends of fuel outlet chamber 16.

Functionally, what we have is as follows: Fuel flowing through the conduit 10 separates into two parts, filling supply chambers 18 and 20. From chambers 18 and 20 the fuel squirts out, respectively, through orifices 28/30 and 24/26. As depicted in FIG. 1, the fine spray of fuel issuing forth from orifices 28 and 30 head for open slot 12 from opposite directions. Molecular collisions and intermixing at the sharp edges of slot 12 create a turbulent condition which results in the spewing forth of a finely atomized mist of fuel from transverse slot 12.

There are several variables which control the characteristics of the fuel within fan angle 32 (see FIG. 2). One of these is the placement of the wall between chamber 16 and chambers 18/20. This placement variable is shown as dimension H in FIG. 4. Changing dimension H from the configuration shown in FIG. 2 to that shown in FIG. 4 will narrow the fan angle. Changes in dimension H will also affect another variable, the characteristic distribution of fuel within the spray pattern. This is shown in FIG. 5. However, the characteristic distribution is also affected by the relative placement of orifices 24, 26, 28 and 30. As shown in FIG. 3, separation of the orifices with respect to their distance from the slot is designated spacing P. The relative placement of each pair of orifices is designated spacing Q. Making spacing Q small will provide distribution curve C (FIG. 5). Making Q relatively large will result in a distribution curve more like B. A properly selected combination of H, P and Q will result in the uniform distribution shown in curve A of FIG. 5. The choice of spacing of dimension P will also influence the degree of fuel atomization achieved.

To give insight as to the size of the flow nozzle, it should be pointed out that in the unit reduced to practice, conduit 10 had an inside diameter of approximately 3/16 inch.

The nozzle described above is highly simplified and of miniature size. Insert 14 can be either machined from bar stock or cast. In either case production requires only the simplest of manufacturing techniques. This makes the unit very applicable, both as a tool for doing combustor research and as an operational unit in a low-cost engine.

While an illustrative embodiment of the present invention has been described, it should be apparent to those skilled in the art that other variations may be utilized without departing from the spirit and scope of the invention. For example, the three chambers and transverse slot making up the functioning part of the nozzle might all be machined from a piece of metal having a fitting at one end into which the fuel-carrying conduit was connected. In this way the nozzle could be made to emit a spray, either in line with or normal to the axis of the fuel-carrying conduit.