GB2093373A

GB2093373A - Dual function nozzle for emergency oil/mist system

Info

Publication number: GB2093373A
Application number: GB8204648A
Authority: GB
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1981-02-24
Filing date: 1982-02-17
Publication date: 1982-09-02
Also published as: DE3201008A1; JPS57153750A; BR8201123A; SE8107798L; FR2500578A1; IT8219765A0

Abstract

A nozzle 22 is constructed to provide a stream of lubricant during normal operations and an atomized mist under emergency conditions. The interior of the nozzle consists of an air supply passage 30 which communicates with an expansion chamber 32. The relative lengths and diameters of the air passage 30 and chamber 32, examples of which are given, are designed to create a region 100 of low pressure adjacent to the outlet of the air passage 30 and a region of turbulence elsewhere in the chamber. The lubricant supply passage 28 communicates with the low pressure region 100. A mist 90 results only when a high pressure air is supplied to the air passage. An emergency oil/mist system utilizing this nozzle is described in Patent Specification No. 2075134. <IMAGE>

Description

SPECIFICATION Dual function nozzle for emergency oil/mist system The present invention relates to a dual function nozzle for an emergency oil/mist system. In particular, it relates to an emergency oil/mist system embodied in the main lubrication system for a bearing or gear box assembly of a gas turbine engine, and more particularly, to an emergency lubrication supply system for providing a pressurized spray of lubricant so as to create extremely small droplets of a uniform distribution of oil on the bearing for a limited period of time after failure of the main lubrication supply system.

In gas turbine engines, as employed in high speed aircraft, the rotational shafts are journalled within bearing boxes for rotation with respect to the engine frame members, and thus the bearings must be continually supplied with a stream of lubricant. Generally, the main lubrication supply system includes a large reservoir of lubricant, and pump means are provided for distributing the lubricant through conduits to the various bearings and gear box assemblies. The latter are usually housed within enclosed sumps such that the oil collected at the bottom of each sump is returned to the main reservoir by scavenging devices, after which the lubricant is again pumped in a continuous circuit back to the bearings or gear box assemblies.As is readily apparent, it is of extreme importance that the movable bearings or gear box assemblies are continuously lubricated in order to prevent premature failure by seizing of the relatively movable parts. The various components of the main lubrication supply system, because of their size, are generally located external to the engine casing where they are susceptible to damage, as in the case of a gas turbine engine as embodied in a military aircraft where the exposed components of the main lubrication supply system are vulnerable to enemy fire.As is readily apparent, in the case of a rupture or puncture in the oil lines or components in the main lubrication supply system, the oil pressure and flow to the individual bearings or gear box assemblies will be quickly interrupted, and continued operation of the gas turbine engine will rapidly result in seizure of the bearings and/or gear box assemblies, resulting in engine failure.

Heretofore in order that the gas turbine enqine and the aircraft may continue to safely overate for a limited period of time after rupture or puncture ofa component in the main lubrication supply system, an emergency oil reservoir has been suggested for providing lubricant to a lubricated part for a limited duration after failure of the main lubrication supply system. The inclusion of the emergency oil reservoir is of critical importance particularly for military aircraft operating under combat conditions, and generally it has been suggested that a plurality of emergency oil reservoirs be strategically located throughout the aircraft gas turbine engine in the vicinity of the bearings and gear box assemblies.

Generally each emergency oil reservoir is filled from the main oil supply system and may include either a gravity feed drain or an air pressure means for supplying a stream of oil to the bearings, with the supply of oil from each emergency reservoir being generally closed off by a series of check valves during normal operation. In the event of a loss of oil pressure or supply, manual or automatic actuation of the check valves is required to open the supply of emergency oil.The disadvantage of such an emergency supply system is that closing off the emergency oil reservoirs during normal engine operation results in oil stagnation which gradually leads to heat degradation of the oil, and the gravity feed system of most conventional emergency oil supply systems may not provide a sufficient stream of air to adequately lubricate the contacting surfaces of the lubricated parts and does not supply a cooling air flow to the lubricated parts.

It has also been known to provide an emergency lubrication supply system including an oil reservoir in substantial proximity to the lubricated part, with conduit means extending from the emergency reservoir having an outlet located adjacent the bearing to be lubricated. Pressurized air flow is continuously provided over the emergency reservoir outlet means for creating a suction therein for drawing lubricant through the conduit both during normal operation, and during emergency operation when the main oil source has been disabled. Accordingly, with this emergency lubrication supply system, lubricant within the emergency reservoir is continually being depleted during normal operation of the aircraft engine.

Accordingly, it is an aim of the invention to provide a new and improved emergency oil supply system for providing, for a limited duration after failure of the main lubrication supply system, a pressurized spray of lubricant mist to the bearing in the form of small droplets of a uniform distribution of oil on the bearing for preventing seizure of the relatively movable parts, thereby precluding catastrophic engine failure.

It is still a further aim of the invention to provide an emergency oil supply system wherein the oil is aspirated from an emergency oil reservoir and is sprayed under high pressure in order to form extremely small droplets of oil which are uniformly distributed over the bearing, thereby expanding the period of time during which the emergency oil system is operative.

It is another aim of the invention to provide a dual purpose nozzle in an emergency oil supply system which is fully operative following failure of the main lubrication supply system to apply an atomized spray while providing a standard stream of lubricant flow during normal operation, said nozzle also providing an aspirator action to draw the lubricant from the emergency supply reservoir.

The above and other objects and advantages of the invention are achieved by the subject emergency oil/mist system embodied in the main lubrication system of an aircraft gas turbine engine and including an auxiliary reservoir which is operatively connected in the conduit means extending between the main source of pressurized lubricant and the nozzle for applying oil onto a bearing or gear box assembly. The nozzle is capable of either directing a stream of oil to the bearing (when the main lubrication system is fully operative) or a mist of lubricant comprised of lubricant aspirated from the emergency reservoir and high pressure air (when the main supply lubrication supply system has failed).

A control piston valve interconnects the emergency reservoir to an atmospheric vent, and also connects a source of pressurized air to the air aspirator nozzle. Upon failure of the main lubrication system, the control valve is actuated such that pressurized air is provided to the nozzle and, by air aspiration, withdraws oil remaining in the emergency reservoir. The valve also connects the emergency reservoir to the atmospheric vent thereby providing an effective control on the amount of oil aspirated from the emergency reservoir. By this arrangement, the emergency oil/mist lubrication system provides an ultrasonic impingement of droplets of oil as it leaves the nozzle, thereby creating extremely small droplets of uniform distribution of oil in the bearing or gear box assembly.Actuation of the control valve may be effected by the pressure balance piston type or solenoid valves triggered by low oil pressure in the main supply system or by excessive bearing or gear box temperatures. The nozzle therefore is designed to provide normal lubricant flow, an aspirator action and an atomizer action.

The present invention provides a dual purpose nozzle for use in a lubrication system for providing a stream of lubricant under normal conditions and an atomized mist under emergency conditions comprising: a nozzle housing being constructed with an interior channel having an inlet and an outlet, said channel containing an air supply passage and an expansion chamber, said air supply passage extending from the channel inlet to the expansion chamber and said expansion chamber directly communicating with the channel outlet, said passage and chamber being designed to create a region of low pressure in the chamber adjacent the junction of said elements and a region of turbulence throughout the remainder of said chamber when air is supplied to the air passage under a predetermined pressure;; said housing being further constructed with a lubricant supply passage extending from the channel inlet and communicating with the expansion chamber within the region of low pressure to draw lubricant into the turbulent region of the chamber where it would be atomized and expelled from the channel outlet as a mist when lubricant is supplied to the lubricant supply passage.

Further objects and advantages of the invention will become apparent from a reading of the following detailed description of a preferred embodiment of the subject invention taken in conjunction with the drawings in which: FIG. 1 is a schematic view of the emergency oil/mist lubrication system of the subject invention when the main lubrication system is fully operational; FIG. 2 is a schematic illustration of the control valve of the subject invention when the main lubrication supply system is fully operational as in FIG. 1; FIG. 3 is a schematic illustration of the subject emergency oil/mist lubrication system when the main supply system is disabled and the emergency lubrication supply system is fully operational; FIG. 4 is a schematic illustration of the control valve of the subject invention during the time when the emergency lubrication supply system is operational as in FIG. 3; and FIG. 5 is a schematic illustration of a sectional view of the nozzle of this invention.

Referring to FIGS. 1 and 2, the lubrication supply system of the subject invention is generally designated by the numeral 10 and is operative to provide lubricant to a bearing 12 which supports rotating shaft 14 of, for example, a gas turbine engine of an aircraft. The bearing 12 may be encased within a bearing cavity (not shown) having an oil scavenging line for recirculating lubricant provided to the bearing 1 2 to the main reservoir (not shown) for the lubrication supply system 10. Although the lubrication supply system of the subject invention is described in relation to an engine bearing, it is understood to have substantially broader application and may be applied to any engine part requiring lubrication.

The lubrication supply system 10 includes a main source of pressurized fluid, such as from a main supply reservoir (not shown) and suitable pump means (not shown) which are indicated in FIG. 1, as "oil flow" to the conduit 20 which extends to an air aspirating nozzle 22. The latter is located in proximity to the bearing 1 2 for providing a stream 26 of oil to the bearing 12. The air aspirating nozzle 22 is of generally tubular construction and includes two elongated passageways 28 and 30 leading to an enlarged outlet 32. Conduit 20 is connected to passageway 28 and during normal operation of the lubrication supply system 10, pressurized oil is passed through the conduit 20, through passageway 28 of nozzle 22, and onto the bearing 12.

The emergency oil/mist lubrication system of the subject invention is embodied in and forms a portion of the lubrication supply system 10 and includes an emergency oil reservoir 40 that is disposed in series in the conduit 20. Accordingly, during normal operation of the lubrication supply system 10, pressurized lubricant provided through the conduit 20 is likewise passed through the emergency oil reservoir 40 and then to the passageway 28 of the air aspirating nozzle 22, and is sprayed as stream 26 onto the bearing 12. Accordingly, the lubricant within the emergency oil reservoir 40 is constantly being replenished and depleted, thereby precluding stagnation of lubricant within reservoir 40 due to heat developed within the engine.Preferably, emergency oil reservoir 40 is located in proximity to the bearing 12, and is of a size in order to hold a quantity of approximately 100 cubic centimeters of oil whereby the emergency oil reservoir 40 is of sufficiently small size to be readily positioned within the confines of the engine housing. The emergency oil/mist lubrication system also includes an emergency control valve means 50 (see FIGS. 1 and 2) which may be of the piston valve type. Piston valve 50 may be of the pressure valance piston type and includes an outer cylindrical housing 52 in which piston 54 is slidably movable. One end 56 of the cylindrical housing 52 includes an opening 58 which is in communication via conduit 21 with the source of pressurized oil from the main supply reservoir.

Opening 58 leads into the inner chamber of the cylinder and bears against the left hand end 60 of piston 54. The opposite end of piston 54 includes an extension 62 having a single through aperture 64.

Cylindrical portion 52 of the piston valve includes two through passageways 70 and 72, as well as an aperture 53 interconnecting passageway 70 with the chamber on the right hand end of piston 54.

During normal operation of the lubrication supply system 10, the pressurized oil flow from the main supply source bears against the end 60 of the piston such that the piston is seated as shown in FIG. 2 and the piston extension 62 effectively closes off the passageways 70 and 72. At such time the force of the pressurized oil against the end 60 of piston 54 is greater than the force of the pressurized air applied to the right hand end of piston 54 through aperture 53. The upper end 70A of passageway 70 is connected to a source of pressurized air via supply conduit 84, while the lower portion 70B of passageway 70 is connected via a conduit 86 to the elongated passageway 30 in the air aspirating nozzle 22. The upper portion 72A of passageway 72 is connected via a conduit 80 to the atmosphere, while the lower portion 72B is connected via line 82 to the emergency oil reservoir 40.

As indicated above, during normal operation of the main lubrication/supply system 10, the extension 62 of the piston 54 is disposed as shown in FIG. 2 so as to block passageways 70 and 72, thereby preventing the emergency oil reservoir from being vented to the atmosphere via conduits 80 and 82, and also preventing the source of pressurized air flow from conduit 84 from being provided to the air aspirating nozzle 22.

In the event of an emergency, such as a puncture or rupture in the main oil reservoir or the pump means for pressurizing the main source of lubricant flow, pressure and flow in the conduit 20 will rapidly decrease. The possibiiity of a rupture or puncture in any component of the main oil supply system is of particular concern to military aircraft flying combat missions where the oil supply components, which are generally situated external to the engine casing, are more vulnerable to damage from enemy fire.

Without lubrication, it is apparent that the high speed rotating shaft 14 would quickly seize, or the bearing 12 will become damaged thereby possibly resulting in catastrophic engine failure. The emergency oil/mist supply system of the subject invention is designed to provide a limited period during which an emergency ultrasonic spray of high pressure lubricant is provided to the bearing 12, as well as pressurized air flow capable of cooling the bearing 12 during the limited emergency period of the pressurized lubrication spray.

During an emergency condition, the pressurized flow provided to the opening 58 of valve 50 rapidly decreases, thereby enabling the pressure balance piston 54 to be actuated toward the left, to the position as illustrated in FIG, 4, by virtue of the pressurized flow provided through aperture 53.

Alternatively, actuation of piston valve 50 may be solenoid controlled in response to the rapid decrease in pressure cf the main oil supply or a temperature sensor may be provided in the vicinity of the bearing 12 and may provide a triggering signal to a suitable solenoid operated valve for actuating piston 54 to the position as shown in FIG. 4. At such time, as shown in FIGS. 3 and 4, the emergency oil/mist lubrication system is operational, and the passageways 70 and 72 are opened, with aperture 64 being aligned with passageway 70. At such time the emergency oil reservoir 40 is vented to the atmosphere via conduits 82 and 80 which extend through passageway 72. In addition, pressurized air flow is provided via conduit 84, through passageway 70 to aperture 53 and also to conduit 86 leading to the passageway 30 in the air aspirating nozzle 22.The high pressurized air flowing through the passageway 30 emerges into the enlarged outlet 32 thereby effectively creating a partial vacuum in the nozzle 22 for aspirating lubricant from the emergency oil reservoir 40 via conduit 20 and passageway 28. The fact that the emergency oil reservoir 40 is vented to the atmosphere assures that the withdrawal of the emergency oil from the reservoir 40 is at a controlled rate in order to prolong emergency lubrication to the bearing 12 for a sufficient period of time to enable the pilot of the aircraft to make the necessary emergency maneuvers. The intermixture of the pressurized air and the oil aspirated from the emergency oil reservoir 40 results in a fine mist of small droplets of oil 90 (see FIG. 3) provided to the bearing 1 2.

The emergency lubrication mist 90 automatically continues to flow and impinge on the contacting bearing surfaces 12 at a slow metered rate until the emergency oil reservoir 40 is emptied. It is estimated that with an emergency oil reservoir 40 having a capacity of approximately 100 cubic centimeters of oil, the emergency oil/mist system will be capable of operating for approximately onehalf of an hour during which time high pressurized mist 90 provided to the bearing 1 2 would be sufficient lubrication for continued operation of the bearing 1 2. In addition, the pressurized air is effective to aid in cooling of the bearing.

An important part of the emergency oil supply system is the atomizer nozzle 22. This nozzle 22 provides a dual purpose. It must provide a consistent stream of oil 26 during normal operation while providing an eductor action to draw oil through conduit 20 during emergency loss of the main oil supply 10.

It was found that in order to maximize the use of the emergency oil supply, it is necessary that it be applied to the bearing 12 as a mist. Standard shear type atomizer nozzles create a mist having a greater diversity of droplet size. This creates the possibility of droplet fall-out which impairs thorough application of the lubricant.

It was found that by introducing an airstream traveling at high velocity into an expansion chamber, a low pressure area is created surrounding the entrance of the air flow. Nozzle 22 was then constructed having an air passage 30 and a lubricant passage 28 communicating with open ended expansion chamber 32. Passage 30 has a length 30L and a diameter 30D. Expansion chamber 32 has a length 32L and a diameter 32D. By varying the relative size of passage 30 and chamber 32, it was found that suitable eductor action can be created when the passage 30 is designed to create a high speed air stream entering chamber 32. This air stream will create a low pressure area 100 which will draw lubricant through conduit 20 to passage 28. The size of chamber 32 is chosen to allow the formation of low pressure area 100 while allowing the air stream to expand into a turbulent flow.Since the outlet 101 of passage 28 is in the low pressure area, lubricant will be drawn into the expansion chamber 32.

When the lubricant enters the turbulent air stream, it is atomized into a fine mist. By adjusting the length and diameter of passage 30 and chamber 32, the efficiency of the eductor and atomizer actions may be maximized. Several examples of the relative size of these parameters and the resulting vacuum in area 100 in inches of water are shown below: 30D 30L 32D 32L Vacuum Nozzle #1 .104 1.225 .285 .390 0 &num;2 .104 1.300 .250 .290 .3 &num;3 .104 1.375 .220 .275 5 &num;4 .104 1.375 .215 .245 8 &num;5 .104 1.450 187 .400 25 The above experimental results were obtained by placing a vacuum gauge in area 100 and sensing the pressure in the nozzle having the sizes indicated. Clearly nozzle &num;5 illustrates a preferred configuration.

It will be appreciated that the absolute relative dimensions of the nozzle may be adapted to suit the velocity and pressure of air into the nozzle.

In this manner a dual purpose nozzle 22 is constructed in an extremely simple design. Unless there is high pressure air in conduit 86, the lubricant will flow in a fluid stream which may be directed at the bearings.

Accordingly, there is provided a new and improved emergency oiVmist lubrication system which is formed as an integral part of the main lubrication system of a gas turbine engine and is designed to function as a mist lubricant generator in the event of failure of the main lubrication system. The emergency oil/mist lubrication system may be employed for bearings or gear box assemblies of a gas turbine engine, and the auxiliary or emergency reservoir has sufficient capacity to provide lubrication to the bearing assembly for approximately thirty minutes following failure of the main lubrication system.

The subject system produces an ultrasonic impingement of the oil as it leaves the air aspirating nozzle 22 thereby creating extremely small droplets of uniform distribution of lubricant over the bearing. In addiction, the flow of pressurized air to the bearing is effective in cooling the bearing during the emergency operation. The emergency oil/mist supply system can be actuated by a pressure balance piston-type valve or a suitable solenoid valve triggered by low oil pressure in the main supply system, or a solenoid valve which is triggered by suitable sensor for sensing excessive bearing temperatures.

While the invention has been described with respect to a specific embodiment thereof, it is readily apparent that various modifications, alterations, or the like may be apparent to those skilled in the art, and thus the invention is not to be limited by the illustrative embodiment, but by the spirit and scope of the following appended claims.

Claims

1. A dual purpose nozzle for use in a lubrication system for providing a stream of lubricant under normal conditions and an atomized mist under emergency conditions, comprising: a nozzle housing comprising an interior channel having an inlet and an outlet, said channel having an air supply passage and an expansion chamber, said air supply passage extending from the channel inlet to the expansion chamber and said expansion chamber directly communicating with the channel outlet, said passage and chamber being adapted to create in use a region of low pressure in the chamber adjacent the junction of the passage and chamber and a region of turbulence throughout the remainder of said chamber when air is supplied to the air passage under a predetermined pressure;; said housing further comprising a lubricant supply passage communicating with the expansion chamber within the region of low pressure to draw lubricant into the turbulent region of the chamber where in use it would be atomized and expelled from the channel outlet as a mist when lubricant is supplied to the lubricant supply passage.

2. An emergency lubricant/mist system for providing a pressurized spray of lubricant to a lubricated part for a limited period of time after failure of a maim lubrication system comprising: a nozzle as defined in claim 1; a source of pressurized lubricant; conduit means interconnecting said source of pressurized lubricant to said nozzle; an emergency lubricant reservoir provided in said conduit means intermediate said source of pressurized lubricant and said nozzle; atmospheric vent means; a source of pressurized air; control means interconnecting: (1) said atmospheric vent means with said emergency lubricant reservoir; and (2) said source of pressurized air with said nozzle, said control means being operatively connected to said source of pressurized lubricant whereby when the main lubrication system is operational, said control means is operative to inhibit the flow of pressurized air from said source of pressurized air to said and to inhibit said emergency lubricant reservoir from being vented to the atmosphere, whereas upon failure of the main lubrication system, said control means is effective to vent the emergency lubricant reservoir and simultaneously allow pressurized air to be provided to the nozzle from the source of pressurized air, such that the pressurized air passing through the nozzle is effective to aspirate lubricant from the emergency lubricant reservoir to create a pressurized spray of lubricant to said lubricated part

3. An emergency lubricant/mist system as claimed in claim 2, wherein said control means comprises a piston valve including an outer cylindrical casing and a piston slidably mounted therein, said cylinder including a plurality of aligned passageways extending therethrough, which passageways are connected to said atmospheric vent means, said source of pressurized air, said emergency lubricant reservoir, and the nozzle, with the position of the slidable piston being a function of the flow of pressurized lubricant.

4. An emergency lubricant/mist system as claimed in claim 2 or 3, wherein said nozzle is generally tubular and comprises the air supply and lubricant supply passageways leading to an enlarged outlet main passageway forming the expansion chamber, the lubricant supply passageway connected to said conduit means extending to the source of pressurized lubricant, while the air supply passageway is connected to the conduit extending to the source of pressurized air.

5. An emergency lubricant/mist system as claimed in claim 2, 3 or 4, wherein the volume of the emergency lubricant reservoir is approximately 100 cubic centimetres.

6. An emergency oil/mist system for providing a pressurized spray of oil to a lubricated part for a limited period of time after failure of a main lubrication system comprising: a source of pressurized oil; a nozzle as defined in claim 1; conduit means interconnecting the source of pressurized oil to said nozzle; an emergency lubricant reservoir disposed in the conduit means intermediate said source of pressurized oil and the nozzle; atmospheric vent means; a source of pressurized air; a piston control valve interconnecting: (1) said atmospheric vent means with said emergency lubricant reservoir; and (2) the source of pressurized air with the nozzle, with the piston of said piston control valve being actuated in response to the pressurized lubricant in the conduit means such that when the main lubrication system is operational, the piston is operative to inhibit interconnection between said atmospheric vent means and the emergency lubricant reservoir, as well as inhibit interconnection between the source of pressurized air with the nozzle, whereas, upon failure of the main lubrication supply system, the piston is actuated so as to interconnect the emergency lubricant reservoir with the atmospheric vent means and simultaneously interconnect the source of pressurized air with the nozzle such that the pressurized air passing through one of the passageways in the nozzle is effective to aspirate oil from the emergency lubricant reservoir to create a pressurized mist of lubricant which is sprayed out of the enlarged nozzle outlet for providing lubricant to the lubricated part, as well as providing cooling pressurized air flow to the lubricated part.

7. An emergency oil/mist system as claimed in claim 6, wherein the volume of the emergency lubricant reservoir is approximately 100 cubic centimeters.

8. An emergency oil/mist system as claimed in claim 6 or 7, wherein the piston control valve includes an outer cylindrical casing and a piston slidably mounted therein, said cylindrical casing including a plurality of aligned passageways extending therethrough, which passageways are connected to said aspirating vent means, said source of pressurized air, said emergency lubricant reservoir, and the nozzle.

9. An emergency oil/mist system as claimed in claim 6, wherein the piston control valve is of the pressure balance type and the position of the slidable piston is responsive to the oil pressure drop and the introduction of the pressurized air source acting on the pressure balance piston.

10. An O. An emergency oil/mist system as claimed in claim wherein the position of the slidable piston is responsive to the temperature of the lubricated part.

11. An emergency lubricant/mist system for providing a pressurized spray of lubricant to a lubricated part, substantially as hereinbefore described, with reference to the accompanying drawing.

12. An engine including an emergency lubricant/mist system according to any one of the preceding claims.

13. An engine as claimed in claim 12, wherein the emergency system is adapted to lubricate a bearing of the engine.

14. An aircraft including an engine as claimed in claim 12 or 13.

1 5. A dual purpose nozzle for use in a lubrication system for providing a stream of lubricant under normal conditions and an atomized mist under emergency conditions, substantially as hereinbefore described with reference to FIG. 5 of the accompanying drawing.

16. The features hereinbefore disclosed, or their equivalents, in any novel combination.