US3283995A

US3283995A - Splitter vane construction for turbofan engine

Info

Publication number: US3283995A
Application number: US451477A
Authority: US
Inventors: Jr James A Fligg
Original assignee: United Aircraft Corp
Current assignee: RTX Corp
Priority date: 1965-04-28
Filing date: 1965-04-28
Publication date: 1966-11-08
Anticipated expiration: 1983-11-08

Description

Nov. 8, 1966 J. A. FLIGG, JR 3,

SPLITTER VANE CONSTRUCTION FOR TURBOFAN ENGINE Filed April 28, 1965 2 Sheets-Sheet 1 Nov. 8, 1966 J. A. FLIGG, JR 3,283,995

SPLITTER VANE consmucwxou FOR TURBOFAN ENGINE Filed April 28. 1965 2 Sheets-Sheet z ws/v 7a,? J/QML J A F1 /66, (M

United States Patent Ofiice 3,233,995 SPLITTER VANE CONSTRUCTION FOR TURBOFAN ENGINE James A. Fligg, Jr., East Hartford, Conn, assrgnor to United Aircraft Corporation, East Hartford, Conn, a corporation of Delaware Filed Apr. 28, 1965, Ser. No. 451,477 3 Claims. (Cl. 230-122) This invention relates to a turbofan gas turbine engine and particularly to the splitter that divides the air from the fan stages of the compressor.

One feature of the present invention is the arrangement of the splitter so as to increase the stalling pressure ratio of the fan stages. More particularly a feature of the invention is a splitter so positioned that a higher pressure ratio across the last fan stage will be reached before that stage will stall.

It has been found that the fan stage which is directly upstream of the splitter is the limiting factor in achieving adequate fan stall. If the pressure ratio at which stalling oocurs can be raised, the fan operating pressure ratio can be increased. Accordingly, one feature of the invention is a splitter that will obtain a higher surge pressure ratio.

One feature of the invention is that the splitter is so located and arranged as to adjust the velocity leaving the downstream tan stage and thereby control the radial flow distribution across the last stage of fan blades.

Other features and advantages will be apparent from the specification and claims, and trom the accompanying drawings which illustrate an embodiment of the invention.

FIG. 1 is a fragmentary longitudinal sectional view through a portion of the compressor.

FIG. 2 is a diagram of compressor performance.

FIG. 3 is a schematic view showing the flow as affected by the splitter.

The invention as shown is applied to the compressor of a turbofan engine of the type shown by way of example in Hopper 2,979,900. In this type of engine the first few stages of compression occur in the fan stages of which the last stage represented by a row stator vanes 2 and a row of rotor blades 4 is shown. From these fan stages the compressed air is divided between a tan duct 6 and the remainder of the compressor stages represented by spaced rows of

stator vanes

8 and 10 and intervening rows of rotor blades 12 and 14. A splitter 16 is supported from the fan duct wall 18 by straightening vanes 20 in the fan duct spaced downstream from the leading edge of the splitter and the compressor case 22, also supported by the vanes 20, supports the rows of

vanes

8 and 10 in the compressor air path, the vanes 8 also being spaced downstream from the leading edge of the splitter.

The splitter 16 thus divides the air from the fan blades into fan .air, the air from the blades between the splitter and the blade tips 24, and compressor air which is the air from the blades between the splitter and the roots 26 of the blades. In the arrangement shown, the compressor stages and the fan stages of blading are connected together to rotate as a unit, the disc 28 supporting the fan blades 4 and the disc 30 for the compressor blades 12 being interconnected by a ring 32 bolted to both discs. Suitable bearings position the rotor assembly within the stator, as will be apparent.

The splitter is positioned with its tip or leading edge 34 projecting forwardly beyond the

vanes

8 or 20 and closely spaced from the trailing edges 36 of the row of fan blades 4. It has been found that this spacing, to be most effective, must be a distance less than about onehalf the chord of the blade measured at the same radius 3,283,995 Patented Nov. 8, 1966 from the compressor axis as that of the splitter. Thus, as shown in the drawing, the leading edge of the splitter is spaced close enough to give the necessary axial clearance to avoid contact between the splitter and the blades. With the splitter closely spaced in this manner the velocity of air entering the compressor stages may be determined and thus the flow of air over the fan blades 4, at least for the portion of the blades adjacent their trailing edges, may be controlled. By proper positioning of the splitter, for example, the ve ocity of the air leaving the rotor trailing edge of the rotor blade 4 may be increased. The closeness of the splitter to the blading minimizes any radial component of flow 'at the trailing edge of the fan blade 4. The result is to stabilize the flow adjacent the root end of the fan blade.

The effect of the forward extension of the splitter is shown in FIG. 2 in which the solid line shows the stall line on the compressor map with the closely spaced splitter and the dotted line shows the stall line on the compressor map for the same compressor with a remote splitter. In this figure the remote splitter was 1.50 inches from the trailing end and the proximate splitter was 0.300 inch from the trailing ends of the blades. The chord of the blade at this point was 2.56 inches in the apparatus used. Since the surge pressure ratio is substantially increased, it is apparent that the compressor may be operated stall that would occur with a remote splitter.

Tests have indicated that when the splitter has its leading edge close to the blades, radial components of flow occur within the 'blade row, this being exemplified in FIG. 3 where the streamline shift is shown to be radial in the trailing half of the blades thereby causing a higher velocity of air at the root of the fan rotor. This effect prevents separation at the root and thereby delays the stall that would occur with a remote splitter.

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. An axial flow compressor having a row of stator vanes, a row of rotor blades directly downstream of and closely adjacent to the vanes, each of said blades having a root, a tip, a trailing edge, and a chord that varies from root to tip, and a splitter downstream of the row of blades and located at a position radially of the rotor between the root and tip of the blade, the blades having no spanwise obstruction to the flow over the blade adjacent to the splitter, said splitter dividing the flow from the blade and having its leading edge closely adjacent to the trailing edge of the blade, said leading edge being spaced firom the trailing edge of the blade a distance less than one-half the chord length of the blade at said position of said splitter whereby said splitter affects the radial component of flow over the surfaces of the blades.

2. An axial flow compressor having at least one stage of fan blading, including 'a row of rotor 'blades, each of said rotor blades having a root, a tip, a trailing edge and a chord that varies from root to tip, at least one stage of compressor blading including stator vanes and rotor blades downstream of the fan blading to which the fluid from a portion of the fan stage is delivered, a dividing splitter directly downstream of the fan rotor blades concentric to the axis of the fan rotor blades and surrounding the compressor stage for directing the fluid from the inner portion of the fan blading to the compressor stage, said rotor fan blades having no spanwise obstruction to the flow over the blade adjacent to the splitter, said splitter dividing the flow from the blade and having its leading edge closely adjacent to the trailing edge of the fan rotor blades, the leading edge of the splitter being spaced from the trailing edges of the row of fan rotor blades a distance 3 less than one-half the chord length of the blade at said position of said splitter whereby said splitter afiects the radial component of flow over the surface of the fan rotor blades.

3. An axial flow compressor as in claim 1 in which the splitter is Wedge-shape in cross section with the point of the wedge extending upstream and forming the leading edge of the splitter, this configuration of the splitter producing an increased velocity of flow into the compressor stages and thereby an increase in the pressure ratio across the fan blades for substantially any operating condition of the compressor.

References Cited by the Examiner UNITED STATES PATENTS 2,046,737 7/1936 Gosslau s 230-122 4 Ponomarefi 230-120 Ryan et a1. h 230-122 Rogers 60-356 Fletcher 230-122 Hewson 230-116 FOREIGN PATENTS Canada.

France.

12/ 1954 Great Britain.

MARK NEWMAN, Primary Examiner.

HENRY F. RADUAZO, Examiner.

Claims

1. AN AXIAL FLOW COMPRESSOR HAVING A ROW OF STATOR VANES, A ROW OF ROTOR BLADES DIRECTLY DOWNSTREAM OF AND CLOSELY ADJACNET TO THE VANES, EACH OF SAID BLADES HAVING A ROOT, A TIP, A TRAILING EDGE, AND A CHORD THAT VARIES FROM ROOT TO TIP, AND A SPLITTER DOWNSTREAM OF THE ROW OF BLADES AND LOCATED AT A POSITION RADIALLY OF THE ROTOR BETWEEN THE ROOT AND TIP OF THE BLADE, THE BLADES HAVING NO SPANWISE OBSTRUCTION TO THE FLOW OVER THE BLADE ADJACENT TO THE SPLITTER, SAID SPLITTER DIVIDING THE FLOW FROM THE BLADE AND HAVING ITS LEADING EDGE CLOSELY ADJACENT TO THE TRAILING EDGE OF THE BLADE, SAID LEADING EDGE BEING SPACED FROM THE TRAILING EDGE OF THE BLADE A DISTANCE LESS THAN