Variable Geometry Turbine Sleeve Alignment
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Solution Overview
Problem
Variable geometry turbochargers face issues with torque imparted to nozzle rings due to gas flow, leading to potential jamming and wear, as well as differential thermal expansion and over-constraint in radial directions, which can result in mechanical failure and inefficiency.
Innovation Solution
A variable geometry turbine design featuring an annular axially moveable member supported by an annular biasing member that applies a circumferentially distributed radial force to maintain concentric alignment and constant radial clearance, while allowing axial movement, and includes a seal to prevent gas leakage and accommodate thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the nozzle ring is provided with vanes to deflect gas flow towards the turbine wheel, then turbine power output is improved, but torque is imparted to the nozzle ring causing potential jamming and wear
Solution Approach 1:
The nozzle ring is segmented into multiple independent nozzle segments that can rotate freely within the inlet passageway. Each segment is supported by a bearing assembly, allowing it to deflect gas flow while accommodating torque without jamming. The segmentation enables each vane to independently respond to gas flow forces, maintaining turbine power output while preventing cumulative torque buildup that would cause jamming in a fixed structure.
2Loss of energy
If the moving component is sealed with respect to the cavity walls to prevent leakage flow, then gas leakage is reduced, but differential thermal expansion and over-constraint can occur
Solution Approach 1:
A flexible sealing arrangement is employed between the nozzle ring and cavity walls, allowing for differential thermal expansion while maintaining effective sealing. The flexible seal can accommodate dimensional changes due to thermal effects, preventing over-constraint and mechanical failure, while still reducing gas leakage loss by maintaining contact between the sealing surfaces.
3Measurement precision
If the linkage connection is made stiff in the radial direction to control axial position, then control precision is improved, but over-constraint and wear increase
Solution Approach 1:
The linkage connection transitions from a static stiff structure to a dynamic system where the nozzle ring can rotate freely within the inlet passageway. The bearing assembly provides radial support while allowing rotational movement, accommodating gas flow forces and thermal expansion. This dynamic approach maintains axial position control through the actuator while preventing over-constraint and wear by allowing the nozzle ring to self-adjust its position in response to operating conditions.
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 solution ensures stable operation by maintaining concentric alignment and reducing friction, preventing jamming and wear, and enhancing the control of airflow through the turbine, thereby improving the efficiency and reliability of the variable geometry mechanism.
Implementation Method 1
at least one biasing member disposed between the moveable member and the support, the biasing member applying a substantially circumferentially distributed force in substantially the radial direction so as to maintain substantial concentric alignment of the annular support and the annular axially moveable member
Implementation Method 2
In addition, there may be a seal disposed between the moveable member and the support
Implementation Method 3
The at least one biasing member may be radially resilient. It is also preferably annular... maintaining substantial concentric alignment... while allowing axial movement
Data Source
AI summary
A variable geometry turbine comprises a turbine wheel supported in a housing for rotation about a turbine axis. An exhaust gas inlet passageway is defined between a shroud and a wall of a nozzle ring. The shroud is moveable in the axial direction to vary the size of the inlet passageway. The nozzle ring has an array of vanes that extends across the inlet passageway. An array of openings is provided in the shroud for receipt of the array of vanes. The shroud is part of a substantially annular axially moveable sleeve that is slidably disposed on an annular supporting wall. At least one biasing member is disposed between the moveable sleeve and the support and is designed to apply a circumferentially distributed force in the radial direction so as to maintain concentric alignment of the supporting wall and the sleeve.