Variable Geometry Turbine Hub Groove for Low Flow Efficiency
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Solution Overview
Problem
Variable geometry turbines experience efficiency reduction at low flow rates due to vortex flow generation near the hub of the turbine rotor, caused by exhaust gas entering at an angle, which is not effectively managed by existing technologies.
Innovation Solution
Incorporating a groove portion on the hub-side passage surface of the first plate member in the exhaust gas passage, which modifies the inflow angle of exhaust gas into the turbine rotor, reducing vortex flow and enhancing efficiency at low flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If nozzle vanes are oriented along the circumferential direction at low flow rates to reduce flow-path cross-sectional area, then the exhaust gas passage area is reduced, but a large vortex flow is generated near the hub of the turbine rotor reducing turbine efficiency
Solution Approach 1:
The patent applies local quality by introducing a groove portion specifically on the hub-side passage surface where the problem occurs. This localized modification changes the flow characteristics in the specific region where vortex flow is generated, without affecting the overall nozzle vane configuration or other parts of the exhaust gas passage.
Solution Approach 2:
The groove portion is designed to preliminarily modify the exhaust gas flow before it enters the turbine rotor. By pre-changing the flow direction and reducing vortex flow generation at the source (hub-side passage surface), the system prevents the harmful effect rather than addressing it after it occurs.
2Speed
If the flow-path cross-sectional area of the exhaust gas passage is reduced at low flow rates, then the exhaust gas flow velocity increases, but vortex flow is generated near the turbine rotor hub reducing efficiency
Solution Approach 1:
The groove portion is a localized structural modification on the hub-side passage surface that specifically addresses the flow characteristics in the region where vortex flow occurs. This local change allows the overall flow velocity to be maintained while preventing vortex flow generation at the critical hub region.
Solution Approach 2:
The patent converts the harmful vortex flow into a beneficial controlled flow pattern. By designing the groove portion to guide exhaust gas flow, the system transforms the potentially harmful high-velocity flow into a controlled pattern that enters the turbine rotor more smoothly, reducing vortex flow and improving efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified inflow angle reduces vortex flow, thereby improving the efficiency of the turbine at low flow rates by minimizing flow loss and turbulence.
Implementation Method 1
a large vortex flow is generated near the hub of the turbine rotor on the leading edge side
Implementation Method 2
the flow velocity and the pressure of exhaust gas introduced into the turbine rotor to enhance the supercharging effect
Data Source
AI summary
A variable geometry turbine includes: a turbine rotor; a scroll passage forming part which forms a scroll passage; an exhaust gas passage forming part which forms an exhaust gas passage for introducing an exhaust gas from the scroll passage to the turbine rotor; and a variable nozzle unit including a plurality of nozzle vanes disposed in the exhaust gas passage and configured to be rotatable about respective rotation centers. The exhaust gas passage forming part includes: a first plate member having an annular first plate part; and a second plate member having an annular second plate part which defines the exhaust gas passage between the first plate part and the second plate part and is disposed closer to a turbine outlet than the first plate part in an axial direction of the turbine rotor. The first plate member has, in a hub-side passage surface of the first plate part facing the exhaust gas passage, at least one groove portion extending from an inner peripheral edge of the first plate part toward an outer peripheral side.