US3451215A - Fluid impingement starting means - Google Patents

Description

June 24, 1969 s. R. BARR 3,451,215

FLUID IMPINGEMENT STARTING MEANS Filed A ril's, 1967 Sheet 012 1A 3 23 I 22 if 5 I 4 Z 5' 5 4 2/ f j :7 A5 I J: 7 M U [1 l Filed April as, 1 967 l une 24, 1969 Sheet. 2 of 2 7 2 L 22 IE. l 4-? 37 l m I w /4 -l* W INVENTOR fi/I/flfd 1?. iie

United States Patent US. Cl. 6039.14 6 Claims ABSTRACT OF THE DISCLOSURE A fluid impingement starting means in which a starter nozzle ring member is mounted in an engine casing upstream of a bladed rotor in a zone of relatively constant pressure. Small nozzle openings in the ring direct starter fluid streams to impinge upon the rotor blades of the engine to initiate engine starting. Radially elongated slots are provided at intervals along the circumference of a radially extending sidewall of the ring. Axially extending pins that project from a removable support member in the engine casing are cooperatively associated with the elongated slots. The removability of the support member permits the axial assembly to and disassembly from the engine of the ring member while the pin and slot arrangement allows the ring member to expand radially, during engine operation when high temperatures occur, without disturbing its position relative to the axial centerline of the engine.

This invention relates to a starter assembly for a turbine engine and more particularly to an improved fluid impingement starter assembly construction.

Fluid impingement starting is one of several methods available for starting turbine engines. By this method fluid under pressure from an outside source is conducted through the engine casing and introduced into the turbine section of the engine to impinge at an appropriate angle of incidence upon the bladed members or buckets of the turbine rotor thereby initiating engine starting.

While starting turbine engines by fluid impingement has achieved widespread acceptance and is widely utilized, there are several disadvantages to current state of the art constructions for effecting this method. One disadvantage is the structural complexity of current art fluid impingement starters. It has been the practice of fluid impingement starter designers to incorporate the starter nozzles in the structure of the turbine nozzle diaphragm immediately upstream of the turbine buckets, which are to be impinged. In such constructions, the starter nozzles are positioned between the partition members of the turbine diaphragm. This type of an arrangement requires that, in designing the turbine diaphragm, allowances be made not only for the starter structure, including the starter fluid ducting system, but also the cooling air system which delivers cooling air to the diaphragm partitions. The resulting diaphragm construction is complex and not only increases the costs of manufacturing the diaphragm, but also increases the costs of maintaining the member once embodied in the engine. Furthermore, once such a costly starter diaphragm construction is included in an engine, it would be uneconomical to employ another method of starting although other considerations might deem it advisable to do so.

Another disadvantage of prior art starters is that they do not extend over the full circumference of the engine casing. One probable reason for this is the difliculty in effectively sealing against leakage of motive fluid while allowing some degree of freedom for the starter to expand under thermal conditions. In the past it was thought that, by limiting the starter to only a partial arc of the engine circumference, the sealing problem would be reduce-d. Ex-

perience, however, has taught otherwise. Partial arc starters create serious problems of heat distribution during engine operation. Because the partial arc starter 0ccupies only a small portion of the full engine circumference, uniform heat distribution throughout the circumferential structure of the engine at the starter cannot be achieved. As a result of non-uniform heat distribution in the engine structure local areas of pronounced stress appear which disturb the alignment and concentricity of engine components. This condition facilitates leakage of motive fluid from the engine flow path and not only reduces the operational efliciency of the engine but also reduces the useful life of engine components.

A further disadvantage of prior art starters is due to the practice of providing relatively large starter nozzle openings. While the large nozzle openings effectively deliver a large mass of air to impinge upon the turbine buckets, during engine starting, they create a significant problem once the engine is running on its own. The large starter nozzles allow a substantial amount of motive fluid leakage to occur. This problem is aggravated by the practice of locating the starter nozzles, as discussed above, in zones between partition members of a turbine diaphragm. During engine operation, the motive fluid stream passing through the turbine diaphragm experiences a significant pressure drop in these zones. As a consequence, turbulent conditions are created in the fluid stream and leakage of motive fluid in the form of crossflows between strater nozzles is facilitated. The leakage that occurs by way of the large starter nozzles located as they are in pressure gradient zones not only reduces engine operational efiiciency, but also leads to the creation of hot spots and non-uniform heat distribution throughout the engine structure with all the harmful consequences such conditions entail.

Finally, prior art constructions are designed for radial assembly to and disassembly from the engine. While this approach is basically an adaptation to split casing engines, radial assembly and disassembly represents a complicated operation which involves a radial stacking of surrounding parts, during engine assembly, and removal of the same surrounding parts during disassembly. Such an arrangement of parts eliminates the possibility of individual access to engine parts, particularly the starter assembly nozzles. As a consequence, maintenance and overhaul become complicated and costly operations.

Therefore, it is a primary object of the invention to provide an improved fluid impingement starting structure of relatively simple construction for guiding streams of starter fluid to the bladed members of a turbine rotor.

It is also an object of the invention to provide an improved fluid impingement starting structure having a starter fluid nozzle element which may readily be assembled or disassembled from the engine.

It is a further object of the invention to provide a fluid impingement starter structure in which the starter fluid nozzle element is in the form of a ring and is axially assembled to and disassembled from the engine.

It is a further object of the invention to provide a fluid impingement starter structure in which the starter fluid nozzle element is permitted to expand radially during engine operation Without disturbing its position relative to the axial centerline of the engine.

It is another object of the invention to provide an improved fluid impingement starting means which reduces excessive leakage of motive fluid from the engine flow path.

It is yet another object of the invention to provide a fluid impingement starting means which extends over a full circumference of the engine flow path thereby permitting the relatively uniform distribution of heat created during engine operation throughout the circumference of the engine structure.

Further objects and advantages of the invention will become apparent as the following description of the invention unfolds.

Briefly stated, the invention relates to a fluid impingement starting means assembly comprising a starter fluid nozzle ring which is mounted in and surrounded by a horizontally non-split annular engine casing. The casing includes means for ducting starter fluid under pressure from a source of supply to circumferentially spaced apart nozzles provided in the nozzle ring. The nozzle ring is located in the engine turbine section in a zone of relatively constant pressure within the engine motive fluid path, downstream of a turbine nozzle diaphragm and upstream of a row of turbine rotor buckets. The starter fluid delivered to the nozzles is emitted therefrom at an appropriate angle of incidence to impinge upon the rotor buckets to bring the rotor, hence the engine, up to selfsustaining speed.

By a further aspect of the invention, the nozzle ring is provided with means for cooperating with surrounding supporting structure to allow some measure of freedom for it to expand radially during high temperature engine operation without disturbing its position relative to the axial centerline of the engine.

While the subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification, the invention both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an illustration of a portion of a turbine engine incorporating the impingement starting means of the present invention.

FIG. 2 is a perspective view of the starter nozzle of the fluid impingement starting means according to the invention.

FIG. 3 is an enlarged sectional view of the turbine section including the fluid impingement starting means of a turbine engine according to the invention.

FIG. 4 is a fragmentary sectional view of the starter ring in position taken along 1VIV of FIG. 3.

Referring now to the drawings, particularly to FIG. 1 a portion of an axial flow gas turbine engine 1 of the non-split casing type is shown therein. The engine 1 includes an outer casing composed of annular sections 2, 3 and 4 which are secured together by suitable fastening means at 5 and 6.

An annular combustor indicated, as 7, is positioned between casing section 2 and annular inner casing 8. Once the engine 1 is started by means generally indicated, as 9, the combustor 7 is continuously fed with high pressure air from a compressor generally designated 10 which is partially shown and located upstream from or forwardly of the combustor 7. The compressor 10 is driven by an annular shaft 11 which in turn is connected to and driven by a gas generator turbine assembly designated generally as 12. As is characteristic, of turbine engines when operating the compressor 10 takes in air at atmospheric pressure and compresses it to a pressure of several atmospheres depending upon the engine cycle. Fuel is mixed with the high pressure air in the combustor 7 and after being ignited the hot gases of combustion referred to also as the motive fluid of the engine exhaust out the downstream end of the combustor 7 towards turbine assembly 12 there driving rows of bladed members 35 and 13 of the turbine rotor 14. As is well-known, turbine engines such as engine 1 are self-sustaining once brought up to speed. However, a starting means must be employed to bring such engines up to self-sustaining operation.

The starting means 9, located near turbine section 12 of engine 1, is a fluid impingement starter according to the invention. As shown in FIG. 1 and more clearly in the enlarged view shown in FIG. 3, a ducting means 15 forming part of starting means 9 is provided in the casing section 3. The ducting means 9 conveys pressurized starter fluid from a source of supply (not shown) and delivers the fluid to an annular path or receiving area 16 by way of interconnecting means 17 as the flow arrows in FIG. 3 indicate. It should be noted that the starter fluid flow path just described is physically separated from the engine flow path as well as the cooling air duct 23 which delivers cooling air to a turbine nozzle diaphragm 18 of turbine assembly 12. As shown in FIG. 3, the flow of starter fluid through interconnecting means 17 to receiving area 16 is direct. The starter fluid then flows from the receiving area 16 and is emitted through nozzles 21 provided in an annular member or nozzle ring 22, which partially defines receiving area 16. Streams of starter fluid emitted from nozzle openings 21 impinge upon buckets 13 of rotor 14.

As best depicted in FIG. 3, a channel 24 is defined by the radially outwardly facing surface 36 of nozzle ring 22. The radially inwardly facing surface 37 defines the outer radial boundary of a zone 25 located in the engine motive fluid path between turbine nozzle diaphragm 18 and second stage buckets 13 of rotor 14. While nozzle ring 22 is thus positioned in the second stage of the gas generator turbine, it should be understood that locating ring 22 at this stage, though preferred, is not critical to the invention. However, a particularly important aspect of the invention is locating the ring 22 in a zone, such as 25, which is between a turbine diaphragm and the next row of rotor blades. It has been found that in such locations the motive fluid stream after having undergone a significant pressure drop passing through openings between partition members of the turbine diaphragm, is characterized by relatively constant pressure. Under such conditions fluid turbulence is substantially absent, thus providing a preferred location for the nozzle ring 22 of the invention. By locating ring 22 in such a zone, the chances of damaging crossflows circulating between the nozzles 21 are reduced and hot spots and the stresses they cause in the engine structure are avoided.

Turning now to FIG. 2, a more detailed description of nozzle ring 22 will be given. In FIG. 2, ring 22 is shown with a section removed to more graphically illustrate its cross-sectional shape. Ring 22 is depicted, as a one-piece member, although it could be formed as well from a plurality of segments, and includes an annularly extending base portion 31. Radially projecting from each axial side of base portion 31 and co-extensive therewith is a pair of sidewalls 32 and 33, which together with base portion 31 form channel 24. Base portion 31 includes a plurality of circumferentially spaced apart openings or holes 21, which serve as nozzles and are quite small relative to the surrounding surface. The nozzles 21 extend rearwardly at an angle to direct streams of starter fluid against buckets 13. The angular disposition of nozzles 21 and their relatively small size reduces the possibility of leakage of motive fluid from the engine flow path in the form of crossflows between them. The sidewalls 32 and 33 cooperate with a ring supporting means which will be discussed later on in the description in more detail. The outer surfaces of the sidewalls are flat and relatively smooth in order to better effect a seal with the adjacent supporting means thereby preventing leakage of motive fluid from the engine flow path and to facilitate the unimpeded radial growth of ring 22 during engine operation. One of the sidewalls, preferably the downstream sidewall 33, includes a plurality of radially elongated circumferentially spaced apart slots 30 which are cooperatively associated with the ring supporting means in a manner to be discussed in the following description.

Referring to FIG. 3, it will be noted that the ring supporting means in engine 1 is of relatively simple construction. The suppotring means includes a flange-like support member 27 which is integral to and extends radially from inner casing wall 20. The supporting means also includes an annular support member 28, which is separately formed and removably attached to casing section 3 from which it extends radially inwardly. The support member 28, not only supports ring 22 and shroud 19, but also facilitates, by its removability, the axial assembly and disassembly of ring 22 with respect to engine 1. On its radially inward portion the support member 28 is provided with a plurality of axially extending pins 29. The pins 29 project upstream from the support member 28 in a direction towards the nozzle ring 22 and are circumferentially spaced apart to correspond to the location of the similarly spaced apart slots 30 described above. The pins 29 are intended to cooperate wtih the slots 30 to maintain the ring 22 radially centered with respect to the axis of the engine 1 while at the same time permitting some degree of radial growth on the part of ring 22. Being allowed some freedom to expand radially due to the cooperative relationship between ring 22 and its support means, the ring 22 is said to be floating. The cooperative relationship between the pins 29 of support member 28 and slots 30 of ring 22 is perhaps best depicted by the cutaway illustration, FIG. 4. It should be noted that while ring 22 is firmly seated against support member 28, it is allowed to grow radially in response to thermal conditions during engine operation. Because pins 29 are mated with slots 30 the relative position of ring 22 with respect to the surrounding engine structure remains centered.

Referring now once more to FIG. 3, a clearer understanding of the relationship of the nozzle ring 22 to its support structure and the neighboring gas generator turbine parts will be had by a discussion of how the parts are assembled. After the second stage turbine nozzle diaphragm 18 of the gas generator turbine is assembled in engine 1, the casing section 3 which includes ducting means and interconnecting means 17 is axially positioned in concentric relationship to the turbine parts assembled and secured by suitable fastening means at 5 to a support means 34 and casing section 2. The nozzle ring 22 is then axially introduced into the engine 1 and abuttingly positioned against support member 27. The support member 28 is next assembled, capping the ring 22 such that each pin 29 provided on its radially inward portion as discussed above, mates with a corresponding expansion slot 30 provided in nozzle ring 22, while its radially outward portion is suitably anchored by fastening means at 6 to casing section 3. Once the support member 28 is thus anchored, and the turbine parts downstream of nozzle ring 22 are assembled to the engine 1, the casing section 4 is abuttingly positioned adjacent support member 28 and the two casing sections 3 and 4, with support member 28 sandwiched between them, are fastened together. as shown in FIGS. 1 and 3. The nozzle ring thus assembled is floating free to move radially as operating thermal conditions demand while remaining centered with respect to the axial centerline of the engine. The disassembly of the starting means from the engine 1 simply involves taking the procedure just described in reverse order.

In operation, the fluid impingement starter according to the invention functions as follows. Referring to FIGS. 1 and 3, to start the engine 1, the ducting means 15 provided in casing section 3 is connected to a source (not shown) of starter fluid under pressure. The pressurized starter fluid flows through the ducting means 15 then through interconnecting means 17. The fluid then enters receiving area 16 where it fills the channel 24 of nozzle ring 22. The starter fluid is then emitted under pressure from nozzles 21 provided at intervals in the base portion of the nozzle ring 22. The streams of fluid thus emitted from nozzles 21 impinge upon the circumferentially extending row of buckets 13 of the turbine rotor 14 forcing them thereby to move and turn the rotor 14. The rotor 14 then turns the compressor 10 which feeds pressurized fluid to the combustor 7 in which ignition occurs. Once the engine 1 is thus brought up to self-sustaining speed, the ducting means is disconnected from the source (not shown) of pressurized starter fluid. Under self-sustained engine operation, the floating nozzle ring 22, arranged and supported in the engine 1 in the manner described above, is adapted to radially move as the engine thermal conditions demand, without undue stresses and without disturbing the alignment of engine parts.

The construction of a fluid impingement nozzle assembly according to the foregoing description will provide a means for the relatively uniform distribution of heat along the circumferential extending casing wall. Furthermore, hot spots and the stresses they cause will be avoided thus increasing the useful life of engine parts while reducing the chances of their becoming misaligned and leaking motive fluid from the engine flow path.

The relatively simple construction of the fluid impingement starter according to the invention provides not only for its ready assembly and disassembly from the engine but also facilitates its purpose of effecting engine starting while at the same time allowing and enhancing the efficient operation of the engine once started.

What is claimed as new and is desired to secure by Letters Patent of the United States is:

1. In a turbine engine a fluid impingement starting means comprising:

an annular engine casing having an upstream and a downstream end enclosing a motive fluid path,

a ducting means provided in said casing for conveying starter fluid from a source of supply,

a turbine rotor including a row of circumferentially extending bladed members mounted in said casing for rotation in the motive fluid path,

an annular member mounted in said casing upstream of said bladed members,

said annular member having defined therein a fluid flow path to which pressure starter fluid is delivered by said ducting means from a source of supply,

said annular member including a plurality of circumferentially spaced apart, angularly disposed openings which serve as nozzles from which pressurized starter fluid is directed to impinge upon said bladed members of said rotor, thereby starting said engine,

support means for supporting said annular member extending radially from said casing into the motive fluid flow path,

said support means having an upstream member attached to said casing which radially extends therefrom into said motive fluid path and abuttingly engages an upstream end of said annular member,

said support means also having a downstream member attached to said casing which radially extends therefrom into said motive fluid path and abuttingly engages the downstream end of said annular member, and

at least said downstream support member is removably attached to said casing in order to facilitate the axial assembly to or disassembly from said engine of said annular member.

2. Fluid impingement starting means as in claim 1 wherein:

said annular member is a one-piece member and includes a base portion from which a sidewall member extends radially, outwardly,

said sidewall member having a plurality of circumferentially spaced apart radially elongated slots, and

at least one of said support members being annularly extending an having a plurality of axially extending circumferentially spaced apart pins which cooperate with said expansion slots in said sidewall to allow said annular member to expand radially the length of said slot without disturbing the relative position of said annular member with respect to the axial centerline of said engine.

3. Fluid impingement starting means, as in claim 2,

wherein:

said slotted sidewayy member is provided on the downstream end of said annular member,

said supporting member having said pins in the said removably attached downstream supporting member.

4. A fluid impingement starter as in claim 1, wherein:

said annular member includes a pair of radially extending sidewall members,

said annular casing having a duct means defined by an inner wall and an outer wall for conveying fiuid and a plurality of nozzles angularly disposed and circumferentially positioned at spaced apart locations along the length of said ring member axially upstream of said bladed members so that fluid supplied to the ring members will emit from said nozzles and imone of said pair located respectively on the upstream inge upon aid rotatable bladed members,

and downstream ends of Said annular member, said ring members continuously formed and including said upstream sidewall in abutting relationship to said an i ll extending b portion i h ti fluid upstream pp member, flow path of the engine, Said d0WI1$tfeflm Sidfiwall in abutting relationshlp to 10 said base portion including a flange-like side element F downstream Pupport m radially extending outwardly from an axial end Sald dwnstream.sldewall havmg provlded therem a of said base portion, at least partially defining said .plurahty of radlany elongated Slots fluid receiving area, and cooperating with said supsaid downstream support means further charactenzed port means b a luralit of axially extendin ins, and said abuttiri g relationship betwe n said downstream sald portion also mcludmg a plurahty i cucumsidewall and said downstream support member matfeiennany spaciad apart no.zzles each f sald nozzles ing Said pin and Said Slot to each other thereby being comparatively small in area relative to the surtablishing between them a cooperative relationship, Foundlng Surface 1? 83 d bas portlon thereby reducd mg leakage of motive fluid from said flow path, said upstream and downstream sidewalls each having Said slde element of Sald rll'lg member lncludlng 3 P a relatively fiat, smooth outer surface, thereby to y 0f radially elongated Opening, and facilitate the radial expansion of said annular member said support means including a plurality of circumferunder engine operating conditions and also to provide entially spaced apart axially extending pin members a substantially leak proof engagement with said upwhich are located at positions corresponding to posisfream and downstream Support members, P tions of said radially elongated openings to mate ytherewith in cooperative association thereby to permit turb1ne engine fluld lmpmgement stamng means radial expansion of said ring during engine operation compnsmg: while at the same time maintaining said ring centered an annular casmg contammg a mom/e fluld flow path with respect to the axial centerline of said engine.

6. An air impingement starter as in claim 5 wherein said support means includes a removable member which will facilitate the axail assembly and disassembly of said ring with respect to said casing.

from a source of supply, a turbine assembly mounted in said casing and surrounded thereby, said turbine assembly comprising in cooperative arrangement a row of circumferentially extending sta- References Cited tionary bladed members and a row of circumferen- UNITED STATES PATENTS tially extending rotatable bladed members, 2 457 333 1/1949 Redding 60-39.14 XR support means extending radially inward from said cas- 2,959 919 11 1960 Chiera et a1 6039.14

P8 2,971,333 2/1961 Mendelsohn et a1. 6039.14 a Ilng member mounted 1n said casing and supported 3,009,320 11 19 1 aiem nt 60 39.14

by said means in a. position at least partially upstream 3,085,396 4/ 1963 Kent et a1 60 -39.14

of said rotatable bladed members and downstream 3,323,775 6/1967 Snell 6039.14 XR of said stationary bladed members in a zone of relatively constant pressure,

a receiving area defined at least in part by said casing and said ring member, together, for receiving fluid from said source of supply delivered by said duct means,

CARLTON R. CROYLE, Primary Examiner.

U.S. Cl. X.R. 60-39.32; 253-77

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