JPH11190201A - Turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain peeling caused on an impeller of a turbine, to maintain efficiency in an extensive flow rate region and to miniaturize the turbine by providing the impeller having a vane provided with an overhung part or a cutout part having an angle of sweep back on a front edge. SOLUTION: Exhaust gas from an engine flows in a trubine casing 1 and flows in a turbine impeller 3 through a scroll 4. At the time when a turbine is driven at a design point, a relative inflow angle and an inlet blade angle of exhaust gas to the impeller 3 coincide with each other, and exhaust gas smoothly flows along an impeller vane 3a. At the time when the turbine is driven separated from the design point, there is made a difference between the relative inflow angle and the inlet blade angle, and when a flow flows in a front edge of the impeller 3a at a large angle of attack, a vortex growing from an overhung part 3b having an angle of sweep back or a cutout part is a screw type vertical vortex in aparallel with the flow, and a central axis is in parallel with the flow. This vortex flow 6 strong and stable, supplies a flow high in total pressure to peeling caused on the overall vane and restrains a scale of peeling small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a turbine such as a radial turbine or a mixed flow turbine.

[0002]

2. Description of the Related Art FIG. 7 is a partial front view of a turbine of a turbocharger having a conventional variable nozzle. In the drawing, a is an impeller provided in a turbine casing (not shown). b denotes a plurality of wings fixed to the impeller a. Reference numeral c denotes a plurality of rotatable variable nozzles provided at the inlet of the exhaust gas to the impeller a.

[0003] Exhaust gas discharged from the engine is introduced into a turbine casing via an exhaust pipe (not shown). The introduced exhaust gas flows into the impeller a from the gas passage via the variable nozzle c, drives the impeller a, and is discharged from the outlet.

[0004] Generally, when the operating point of the turbine deviates from the design point, the impeller of the turbine is separated from the blade, and the efficiency is reduced. In order to prevent this decrease in efficiency, a variable nozzle c as shown in FIG. 7 is used to control the relative inflow angle of gas into the impeller a to prevent separation of a gas flow flowing inside the impeller. ing.

[0005]

However, the variable nozzle has problems such as a complicated structure, high cost, and difficulty in downsizing.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and does not provide a nozzle at the impeller inlet, or suppresses separation occurring in the turbine impeller while using a fixed nozzle. It is an object of the present invention to provide a turbine that can maintain efficiency in a wide flow rate range and can be downsized.

[0007]

According to the present invention, there is provided a radial turbine provided with an impeller having a wing provided with an overhanging portion or a notch at a leading edge. Note that the receding angle is an angle β formed by a direction perpendicular to the leading edge with respect to the flow, as shown in FIG.

According to another embodiment of the present invention, there is provided a mixed flow turbine provided with an impeller having blades provided with a protrusion or notch having a swept angle at a leading edge.

According to another preferred embodiment of the present invention,
The angle of the receding angle is 30 ° to 70 °.

Next, the operation of the present invention will be described. Exhaust gas discharged from the engine flows into the turbine casing and flows into the impeller of the turbine via the scroll. In this case, a fixed nozzle may be provided at the impeller inlet or may flow directly from the scroll into the impeller. When the turbine is operating at the design point, the relative inflow angle of the exhaust gas to the impeller and the inlet blade angle match, and the exhaust gas flows smoothly along the impeller blades.
When the turbine is operating away from the design point, there is a difference between the relative inlet angle of the exhaust gas to the impeller and the inlet blade angle, and the flow flows at a large angle of attack to the leading edge of the impeller blade. Flakes occur on either side of the wing. The present invention was conceived inspired by the fact that when flying at a large angle of attack during takeoff and landing of an aircraft, separation occurring on the wing is suppressed by a vortex generator and a leading edge strake. When the flow comes into the leading edge of the impeller at a large angle of attack, the vortex due to the separation that occurs on the entire wing is such that the central axis of the vortex is perpendicular to the flow so that the rollers roll along the flow on the surface of the wing, The swirl resulting from the swiveling overhang or notch is a screw-like vertical swirl parallel to the flow, the central axis of which is parallel to the flow. This vortex is strong and stable,
It has the effect of supplying a flow with a high total pressure and suppressing the scale of separation. As a result, the impeller can operate at near design performance. On the other hand, at the design point, this overhang or notch has no effect on the flow and causes only a slight increase in frictional resistance. Therefore, the efficiency decrease at the design point is slight.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the radial turbine of the present invention. FIG. 2A is a partial front view of the impeller, and FIG. 2B is a projection view of the impeller blade.
FIG. 3 is an enlarged cross-sectional view of an impeller having a projecting portion, and FIG. 4 is an enlarged cross-sectional view of an impeller having a cutout portion. FIG. 5 is a diagram showing the eddy flow, and FIG. 6 is a diagram showing the sweepback angle.

1 to 5, reference numeral 1 denotes a turbine casing of a radial turbine. 2 is a turbine shaft. Reference numeral 3 denotes an impeller fixed to the turbine shaft 2,
3a is a wing. Reference numeral 3b denotes an overhang portion provided at the front edge of the impeller 3 and having a receding angle of 30 ° to 70 °, and 3c denotes a cutout portion provided in place of the overhang portion 3b. 4 is a scroll and 5 is a gas outlet. 6 is a vertical vortex (FIG. 5).

Next, the operation based on the embodiment will be described. Exhaust gas discharged from the engine flows into the turbine casing 1 and flows into the impeller 3 of the turbine via the scroll 4. In this case, a fixed nozzle may be provided at the inlet of the impeller 3 or may flow directly from the scroll 4 into the impeller 3. When the turbine is operating at the design point, the relative inflow angle of the exhaust gas to the impeller 3 and the inlet blade angle match, and the exhaust gas is
Flows smoothly along a. When the turbine is operating away from the design point, there is a difference between the relative inlet angle of the exhaust gas to the impeller 3 and the inlet blade angle, and the flow at a large angle of attack with respect to the leading edge of the impeller blade 3a. Because of the inflow, separation occurs on one surface of the wing 3a. When the flow comes into the leading edge of the impeller at a large angle of attack, the vortex caused by the separation that occurs on the entire wing causes the center axis of the vortex to be perpendicular to the flow so that the rollers roll along the flow on the surface of the wing
The vortex generated from the overhang 3b or the notch 3c having the sweepback angle is a screw-shaped vertical vortex 6 parallel to the flow, and the central axis is parallel to the flow. The vortex 6 is strong and stable, and has a function of supplying a flow having a high total pressure and suppressing the scale of the separation to the separation occurring on the entire blade. As a result, the impeller 3 can operate in a state close to the design performance. On the other hand, at the design point, the overhang 3b or the notch 3c does not affect the flow and causes only a slight increase in frictional resistance. Therefore, the efficiency decrease at the design point is slight.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, in the embodiment, the radial turbine of the turbocharger has been described. However, a gas turbine may be used, and a diagonal flow turbine may be used instead of the radial turbine.

[0015]

According to the turbine of the present invention described above, it is possible to suppress the separation occurring in the impeller of the turbine, to maintain high efficiency in a wide flow rate range, and to reduce the size.

[Brief description of the drawings]

FIG. 1 is a sectional view of a radial turbine according to the present invention.

2A is a partial front view of an impeller, and FIG. 2B is a projection view of an impeller blade.

FIG. 3 is an enlarged sectional view of an impeller having an overhang portion.

FIG. 4 is an enlarged sectional view of an impeller having a cutout portion.

FIG. 5 is a diagram showing a vertical vortex flow.

FIG. 6 is an explanatory diagram of a backward angle.

FIG. 7 is a partial front view of a turbine of a turbocharger having a conventional variable nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Turbine casing 2 Turbine shaft 3 Impeller 3a Blade 3b Overhang 3c Notch 4 Scroll 5 Gas outlet 6 Vertical vortex

Claims (3)

[Claims] 1. A radial turbine having an impeller having a wing provided with an overhanging portion or a notch at a leading edge thereof. 2. The mixed flow turbine according to claim 1, further comprising an impeller having a wing provided with an overhanging portion or a notch at the leading edge. 3. The radial turbine or the mixed flow turbine according to claim 1, wherein the swept angle is 30 ° to 70 °.