Blade of fan or compressor

Abstract

A blade of a fan or compressor that reduces loss by enlarging a laminar flow region over a blade surface is provided. The blade is divided into a subsonic region where the relative Mach number of the inlet air flow during rated operation of a turbofan engine is lower than 0.8 and a transonic region where the relative Mach number is equal to or higher than 0.8. A blade surface angle change rate is based on an angle formed by a tangent to the blade surface and the axis of the engine, the leading edge blade surface angle, and the trailing edge blade surface angle at. In each of the subsonic region and the transonic region, values of the blade surface angle change rate on the pressure and suction surfaces are defined at predetermined axial locations along the chord on the pressure and suction surfaces.

Claims

1. A blade of a fan or compressor that is a component of a turbofan engine, comprising: a blade part and a blade root, wherein the blade is divided into a subsonic region and a transonic region in a height direction, a relative Mach number of an air flow flowing to the blade during rated operation of the turbofan engine being lower than 0.8 in the subsonic region and equal to or higher than 0.8 in the transonic region, a cross section of the blade at each location in the height direction is formed by a concave pressure surface and a convex suction surface each of which extends between a leading edge and a trailing edge of the blade, and in the cross section, provided that an angle formed by a tangent at a point on the pressure surface or suction surface and an axial direction of the turbofan engine is referred to as a blade surface angle (β), the blade surface angle at the leading edge is referred to as an inlet blade surface angle (βin), the blade surface angle at the trailing edge is referred to as an exit blade surface angle (βex), a parameter (δ) defined by the formula (1) is referred to as a blade surface angle change rate:
δ=(βin−β)/(βin−βex)  formula (1) a segment connecting the leading edge and the trailing edge is referred to as a chord, and a parameter (x/c) defined as a distance (x) of a point on the pressure surface or suction surface from the leading edge in the axial direction divided by an axial length (c) of the chord is referred to as a chord ratio, a minimum value of the blade surface angle change rate is equal to or greater than −0.90 and the blade surface angle change rate at a first transition location where the chord ratio is 0.39 is equal to or less than 0.43 in the subsonic region on the pressure surface of the blade, the first transition location being a location where a boundary layer formed over the pressure surface of the blade in the subsonic region transitions from a laminar state to a turbulent state, the blade surface angle change rate at a location where the chord ratio is 0.05 is equal to or greater than 0.26 and the blade surface angle change rate at a second transition location where the chord ratio is 0.36 is equal to or less than 0.58 in the subsonic region on the suction surface of the blade, the second transition location being a location where a boundary layer formed over the suction surface of the blade in the subsonic region transitions from a laminar state to a turbulent state, the minimum value of the blade surface angle change rate is equal to or greater than −0.48 and the blade surface angle change rate at a third transition location where the chord ratio is 0.35 is equal to or less than 0.12 in the transonic region on the pressure surface of the blade, the third transition location being a location where a boundary layer formed over the pressure surface of the blade in the transonic region transitions from a laminar state to a turbulent state, and the blade surface angle change rate at a location where the chord ratio is 0.10 is equal to or greater than 0.29 and the blade surface angle change rate at a fourth transition location where the chord ratio is 0.43 is equal to or less than 0.47 in the transonic region on the suction surface of the blade, the fourth transition location being a location where a boundary layer formed over the suction surface of the blade in the transonic region transitions from a laminar state to a turbulent state.

2. The blade according to claim 1, wherein the blade surface angle change rate at the first transition location where the chord ratio is 0.39 is equal to 0.43 in the subsonic region on the pressure surface of the blade.

3. The blade according to claim 1, wherein the blade surface angle change rate at the second transition location where the chord ratio is 0.36 is equal to 0.58 in the subsonic region on the suction surface of the blade.

4. The blade according to claim 1, wherein the blade surface angle change rate at the third transition location where the chord ratio is 0.35 is equal to 0.12 in the transonic region on the pressure surface of the blade.

5. The blade according to claim 1, wherein the blade surface angle change rate at the fourth transition location where the chord ratio is 0.43 is equal to 0.47 in the transonic region on the suction surface of the blade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram for illustrating a cross-sectional shape (airfoil), at a location in a span direction, of a fan rotor blade according to an embodiment of the present disclosure for comparison with a conventional fan rotor blade.

(2) FIG. 2A is a graph showing a distribution in a chord direction of a blade surface angle change rate of the fan rotor blade according to the embodiment of the present disclosure in a subsonic region on a pressure surface, for comparison with the conventional fan rotor blade.

(3) FIG. 2B is a graph showing a distribution in the chord direction of the blade surface angle change rate of the fan rotor blade according to the embodiment of the present disclosure in the subsonic region on a suction surface, for comparison with the conventional fan rotor blade.

(4) FIG. 3A is a graph showing a distribution in the chord direction of the blade surface angle change rate of the fan rotor blade according to the embodiment of the present disclosure in a transonic region on the pressure surface, for comparison with the conventional fan rotor blade.

(5) FIG. 3B is a graph showing a distribution in the chord direction of the blade surface angle change rate of the fan rotor blade according to the embodiment of the present disclosure in the transonic region on the suction surface, for comparison with the conventional fan rotor blade.

(6) FIG. 4 is a schematic perspective view of a fan rotor blade of a turbofan engine.

(7) FIG. 5 is a cross-sectional view taken along the line I-I in FIG. 4, showing the cross-sectional shape (airfoil) of the fan rotor blade.

MODE FOR CARRYING OUT THE DISCLOSURE

(8) In the following, an embodiment of the present disclosure will be described in detail with reference to the drawings.

(9) As described above, with the conventional fan rotor blade, a sharp deceleration of the air flow occurs in a relatively upstream region on both the pressure surface and the suction surface. In particular, a sharp deceleration of the air flow occurs in a region where a chord ratio is about 0.05 on the pressure surface, and in a region where the chord ratio is about 0.15 on the suction surface. This means that the blade surface angle sharply decreases or, in other words, the blade surface angle change rate sharply increases in these regions. The chord ratio (x/c), which is a non-dimensional value, is the distance (x) from the leading edge in the axial direction divided by the axial length (c) of the chord.

(10) In view of this, a fan rotor blade according to the embodiment of the present disclosure has an airfoil obtained by modifying the airfoil of the conventional fan rotor blade based on the following principles.

(11) (1) To reduce the deceleration of the air flow in the region where the chord ratio is about 0.05 on the pressure surface, a peak of the blade surface angle change rate appearing in this region is reduced. In other words, the absolute value of a minimum value in this region where the blade surface angle change rate is negative is reduced.

(12) (2) In the region where the chord ratio is about 0.15 on the suction surface, the change of the blade surface angle is reduced in order to reduce the deceleration of the air flow. To this end, the change of the blade surface angle is increased in a region upstream of that region where the chord ratio is about 0.05.

(13) FIG. 1 shows a cross-sectional shape (airfoil), at a location in a span direction, of the fan rotor blade according to the embodiment of the present disclosure provided as described above for comparison with the airfoil of the conventional fan rotor blade. FIGS. 2A to 3B show distributions in the chord direction of the blade surface angle change rate of the fan rotor blade according to the embodiment of the present disclosure for comparison with the conventional fan rotor blade. FIG. 2A shows a distribution in a subsonic region on the pressure surface, FIG. 2B shows a distribution in the subsonic region on the suction surface, FIG. 3A shows a distribution in a transonic region on the pressure surface, and FIG. 3B shows a distribution in the transonic region on the suction surface. In the graphs in these drawings, the vertical axis indicates the blade surface angle change rate, the horizontal axis indicates the location in the chord direction, and the location in the chord direction is indicated in terms of chord ratio.

(14) The term “subsonic region” refers to a range in the span direction where the relative Mach number of the flow of air flowing to the blade during rated operation of the turbofan engine incorporating the fan rotor blade is lower than 0.8, and the term “transonic region” refers to a range in the span direction where the relative Mach number of the flow of air flowing to the blade during rated operation of the turbofan engine incorporating the fan rotor blade is equal to or higher than 0.8. For the rotor blade, the subsonic region is an inner region where the circumferential velocity component added to the flow by the rotation is smaller, and the transonic region is an outer region where the circumferential velocity component added to the flow by the rotation is greater.

(15) As shown in FIGS. 2A to 3B, on the pressure surface (see FIGS. 2A and 3A), the absolute value of the minimum value (negative) of the blade surface angle change rate that appears in the region where the chord ratio is about 0.05 is small, and as a result, a sharp increase of the blade surface angle change rate is suppressed in the region downstream of that region. On the suction surface (see FIGS. 2B and 3B), the blade surface angle change rate significantly increases in the region where the chord ratio is about 0.05, and as a result, a sharp increase of the blade surface angle change rate is suppressed in the region downstream of that region.

(16) As can be seen from the above description, with the fan rotor blade according to the embodiment of the present disclosure, compared with the conventional fan rotor blade, the deceleration of the flow around the blade is appropriately controlled through adjustment of the way of variation of the blade surface angle change rate, and as a result, a location where a boundary layer formed over the blade surface transitions from a laminar state to a turbulent state is shifted to the downstream side as described below. The following are the transition locations (in terms of chord ratio) for the fan rotor blade according to the embodiment of the present disclosure followed by the transition locations (in terms of chord ratio) for the conventional fan rotor blade in parentheses.

(17) Transition location in the subsonic region on the pressure surface: 0.39 (0.27)

(18) Transition location in the subsonic region on the suction surface: 0.36 (0.17)

(19) Transition location in the transonic region on the pressure surface: 0.35 (0.03)

(20) Transition location in the transonic region on the suction surface: 0.43 (0.11)

(21) The following are the blade surface angle change rates at the transition locations for the fan rotor blade according to the embodiment of the present disclosure.

(22) Blade surface angle change rate in the subsonic region on the pressure surface: 0.43

(23) Blade surface angle change rate in the subsonic region on the suction surface: 0.58

(24) Blade surface angle change rate in the transonic region on the pressure surface: 0.12

(25) Blade surface angle change rate in the transonic region on the suction surface: 0.47

(26) It can be considered that the laminar flow region over the blade surface can be enlarged beyond that of the fan rotor blade according to the embodiment of the present disclosure by setting the blade surface angle change rate at each transition location to be equal to or less than the blade surface angle change rate for the fan rotor blade according to the embodiment of the present disclosure. Specifically, conditions for achieving this are as follows (see (b) in the graphs in FIGS. 2A to 3B).

(27) In the subsonic region on the pressure surface, the blade surface angle change rate at the location where the chord ratio is 0.39 is set at 0.43 or less.

(28) In the subsonic region on the suction surface, the blade surface angle change rate at the location where the chord ratio is 0.36 is set at 0.58 or less.

(29) In the transonic region on the pressure surface, the blade surface angle change rate at the location where the chord ratio is 0.35 is set at 0.12 or less.

(30) In the transonic region on the suction surface, the blade surface angle change rate at the location where the chord ratio is 0.43 is set at 0.47 or less.

(31) With regard to the principle (1) concerning the modification of the airfoil described above, it can be considered that a sharp deceleration of the air flow in a region near the leading edge can be suppressed by setting the absolute value of the minimum value of the blade surface angle change rate on the pressure surface to be equal to or less than the same value for the fan rotor blade according to the embodiment of the present disclosure. Specifically, conditions for achieving this are as follows (see (a) in the graphs in FIGS. 2A and 3A).

(32) The minimum value of the blade surface angle change rate in the subsonic region is set to be equal to or greater than −0.90.

(33) The minimum value of the blade surface angle change rate in the transonic region is set to be equal to or greater than −0.48.

(34) Furthermore, with regard to the principle (2) concerning the modification of the airfoil described above, it can be considered that, by setting the blade surface angle change rate in a region near the leading edge on the suction surface to be equal or greater than the same value for the fan rotor blade according to the embodiment of the present disclosure, a sharp increase of the blade surface angle change rage can be suppressed and thus a sharp deceleration of the air flow can be prevented in the region downstream of that region. Specifically, conditions for achieving this are as follows (see (a) in the graphs in FIGS. 2B and 3B).

(35) The blade surface angle change rate at the location where the chord ratio is 0.05 in the subsonic region is set to be equal to or greater than 0.26.

(36) The blade surface angle change rate at the location where the chord ratio is 0.10 in the transonic region is set to be equal to or greater than 0.29.

(37) With the foregoing in mind, the fan rotor blade according to the embodiment of the present disclosure meets the following conditions.

(38) In the subsonic region on the pressure surface, the minimum value of the blade surface angle change rate is equal to or greater than −0.90, and the blade surface angle change rate at the location where the chord ratio is 0.39 is equal to or less than 0.43.

(39) In the subsonic region on the suction surface, the blade surface angle change rate at the location where the chord ratio is 0.05 is equal to or greater than 0.26, and the blade surface angle change rate at the location where the chord ratio is 0.36 is equal to or less than 0.58.

(40) In the transonic region on the pressure surface, the minimum value of the blade surface angle change rate is equal to or greater than −0.48, and the blade surface angle change rate at the location where the chord ratio is 0.35 is equal to or less than 0.12.

(41) In the transonic region on the suction surface, the blade surface angle change rate at the location where the chord ratio is 0.10 is equal to or greater than 0.29, and the blade surface angle change rate at the location where the chord ratio is 0.43 is equal to or less than 0.47.

(42) Although an example where the blade according to the present disclosure is used as a rotor blade of a fan that is a component of a turbofan engine has been described above, the blade according to the present disclosure has a wide variety of applications and can also be used as a rotor blade or stator vane of a compressor of a gas turbine other than the turbofan engine or a fan or compressor as a stand-alone device.

EXPLANATION OF REFERENCE SIGNS

(43) RB fan rotor blade AF blade part RT blade root part PS pressure surface SS suction surface LE leading edge TE trailing edge β blade surface angle δ blade surface angle change rate