Transonic blade
View Patent ↗A transonic blade is provided that operates in a flow field where flow has a transonic speed or higher in an axial-flow rotating machine and that concurrently achieves a reduction in shock loss and in the local stress of the blade. The transonic blade includes a hub cross-sectional surface joined to a rotating shaft or an outer circumferential side casing of a rotating machine; a tip cross-sectional surface located furthest from the hub cross-sectional surface in a spanwise direction which is a vertical direction of the rotating shaft; a leading edge located on an upstream side; and a trailing edge located on a downstream side. At least a part of a passing working fluid flow has a transonic speed or higher. A portion of a stacking line which is a line connecting together respective gravity centers of cross-sectional surfaces located from the hub cross-sectional surface to the tip cross-sectional surface is located on a downstream side of a stacking center in a flow direction of a working fluid main flow.
1. A transonic blade comprising:
a hub cross-sectional surface joined to a rotating shaft or an outer circumferential side casing of a rotating machine;
a tip cross-sectional surface located furthest from the hub cross-sectional surface in a spanwise direction which is a vertical direction of the rotating shaft;
a leading edge located on an upstream side in a flow direction of a working fluid main flow; and a trailing edge located on a downstream side in the flow direction of the working fluid main flow;
wherein at least a part of a passing working fluid flow has a transonic speed or higher,
wherein a portion of a stacking line which is a line connecting together respective gravity centers of cross-sectional surfaces located from the hub cross-sectional surface to the tip cross-sectional surface is located on a downstream side of a stacking center which corresponds to a gravity center position of the hub cross-sectional surface in the flow direction of the working fluid main flow,
further comprising a third cross-sectional surface between the hub cross-sectional surface and the tip cross-sectional surface,
wherein the stacking line protrudes toward the downstream side of the main flow direction between the third cross-sectional surface and the tip cross-sectional surface,
the stacking line protrudes toward the upstream side in the main flow direction between the third cross-sectional surface and the hub cross-sectional surface,
a gravity center position of the tip cross-sectional surface is located on the upstream side of the stacking center in the flow direction of the working fluid main flow, and
a gravity center of the overall transonic blade is located on the downstream side of the stacking center.
2. The transonic blade according to claim 1 ,
wherein a difference ε in a lengthwise direction of the rotating shaft between the gravity center of an overall transonic blade and the stacking center is set not to exceed a strength limit of the leading edge of the hub cross-sectional surface.
3. The transonic blade according to claim 2 ,
wherein the ε is 1% or less of span.
4. The transonic blade according to claim 3 ,
wherein the ε is generally equal to 0.
5. The transonic blade according to claim 1 ,
wherein a gravity center of the transonic blade between the third cross-sectional surface and the tip cross-sectional surface is located on the main flow-directional downstream side of the stacking center.
6. The transonic blade according to claim 1 ,
wherein a position corresponding to a largest amount of shifting of the stacking line toward the upstream side lies between the third cross-sectional surface and the hub cross-sectional surface.
7. The transonic blade according to claim 1 ,
wherein the third cross-sectional surface is a mean cross-sectional surface.
8. The transonic blade according to claim 1 ,
wherein respective positions of maximum thicknesses relative each to chord length are aligned with one another in airfoils located from the tip cross-sectional surface to the hub cross-sectional surface.
9. A compressor including a rotating shaft, a casing, a plurality of rotor blades, and a plurality of stationary blades, at least a part of a passing working fluid flow having a transonic speed or higher,
wherein a rotor blade of the plurality of rotor blades on the most upstream side in a main flow direction comprises:
a hub cross-sectional surface joined to the rotating shaft;
a tip cross-sectional surface located furthest from the hub cross-sectional surface in a spanwise direction which is a vertical direction of the rotating shaft;
a leading edge located on an upstream side in a flow direction of a working fluid main flow; and
a trailing edge located on a downstream side in the flow direction of the working fluid main flow;
wherein a difference ε in a lengthwise direction of the rotating shaft between the gravity center of an overall transonic blade and a stacking center which corresponds to a gravity center position of the hub cross-sectional surface is set not to exceed a strength limit of the leading edge of the hub cross-sectional surface,
wherein a portion of a stacking line which is a line connecting together respective gravity centers of cross-sectional surfaces located from the hub cross-sectional surface to the tip cross-sectional surface is located on the downstream side of the stacking center in the flow direction of the working fluid main flow,
the blade further comprising a third cross-sectional surface between the hub cross-sectional surface and the tip cross-sectional surface,
wherein the stacking line protrudes toward the downstream side of the main flow direction between the third cross-sectional surface and the tip cross-sectional surface,
the stacking line protrudes toward the upstream side in the main flow direction between the third cross-sectional surface and the hub cross-sectional surface,
a gravity center position of the tip cross-sectional surface is located on the upstream side of the stacking center in the flow direction of the working fluid main flow, and
a gravity center of the overall transonic blade is located on the downstream side of the stacking center.
10. A method of designing a transonic blade, the transonic blade including a hub cross-sectional surface joined to a rotating shaft or an outer circumferential side casing of a rotating machine; a tip cross-sectional surface located furthest from the hub cross-sectional surface in a spanwise direction which is a vertical direction of the rotating shaft; a third cross-sectional surface between the hub cross-sectional surface and the tip cross-sectional surface; a leading edge located on an upstream side in a flow direction of working fluid; and a trailing edge located on a downstream side in the flow direction of working fluid; at least a part of a passing working fluid flow having a transonic speed or higher, the method comprising:
locating a portion of a stacking line which is a line connecting together respective gravity centers of cross-sectional surfaces located from the hub cross-sectional surface to the tip cross-sectional surface, on a downstream side of a stacking center which corresponds to a gravity center position of the hub cross-sectional surface in the flow direction of working fluid,
determining a difference ε in a lengthwise position of the rotating shaft between the gravity center of an overall transonic blade and the stacking center so as not to exceed a strength limit of the leading edge of the hub cross-sectional surface,
making the stacking line protrude toward the downstream side of the main flow direction between the third cross-sectional surface and the tip cross-sectional surface,
making the stacking line protrude toward the upstream side in the main flow direction between the third cross-sectional surface and the hub cross-sectional surface,
locating a gravity center position of the tip cross-sectional surface on the upstream side of the stacking center in the flow direction of the working fluid main flow, and
locating a gravity center of the overall transonic blade on the downstream side of the stacking center.