Turbocharger Vane and Slot Clearance Design
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Solution Overview
Problem
Existing vane and shroud arrangements in turbochargers face inefficiencies due to gas leakage and foreign object damage, which affect the conformity between vanes and slots, leading to reduced turbine performance.
Innovation Solution
The vanes and slots are designed with a leading surface portion in close contact and a trailing surface portion spaced apart by a controlled distance to minimize gas leakage and foreign object damage, allowing for improved conformity and reduced risk of thermal trapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the vanes and slots are designed to be in close contact to minimize gas leakage, then gas leakage is reduced, but foreign object damage and thermal expansion cause the contact to break down, reducing reliability
Solution Approach 1:
The vane and slot are designed with different clearance characteristics at different locations: the leading surface portion has close contact (small clearance) to minimize gas leakage, while the trailing surface portion has larger clearance to accommodate foreign object damage and thermal expansion. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The interaction interface between the vane and slot is segmented into two distinct portions: a leading surface portion with close contact for gas sealing, and a trailing surface portion with spaced apart design for damage tolerance. This segmentation allows each portion to be optimized independently for its specific requirements.
2Productivity
If the vanes and slots are designed with close contact to improve conformity, then gas flow efficiency is improved, but thermal expansion causes the vanes to trap against the slots, reducing operation reliability
Solution Approach 1:
The clearance between the vane and slot is differentiated locally: close clearance at the leading surface for optimal gas flow conformity, and larger clearance at the trailing surface to prevent thermal trapping. This local quality variation allows the system to achieve both high productivity and thermal operation reliability.
Solution Approach 2:
The design accommodates thermal expansion dynamically by providing varying clearance along the vane-length. As thermal expansion occurs, the trailing portion with larger clearance allows the vane to expand without trapping against the slot, while the leading portion maintains sufficient contact for gas flow efficiency.
3Loss of energy
If the vanes and slots are designed with close contact to reduce gas leakage, then energy loss is reduced, but manufacturing tolerances and foreign object damage cause deviation from optimal conformity
Solution Approach 1:
The design accepts that manufacturing precision varies along the vane-length by providing different clearance characteristics: close clearance at the leading portion where conformity is critical for gas sealing, and larger clearance at the trailing portion where manufacturing variations and foreign object damage are more likely to occur.
Solution Approach 2:
The larger clearance at the trailing surface portion acts as a cushioning design that anticipates and accommodates future deviations from optimal conformity caused by manufacturing tolerances and foreign object damage, ensuring that the leading portion's close contact design remains effective.
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
This design reduces gas leakage and minimizes the impact of foreign object damage and thermal expansion, enhancing the efficiency and reliability of the turbocharger by maintaining optimal contact between vanes and slots.
Implementation Method 1
Each vane is generally laminar, and is positioned with one radially outer surface arranged to oppose the motion of the exhaust gas within the inlet passageway, i.e. the radially inward component of the motion of the exhaust gas in the inlet passageway is such as to direct the exhaust gas against the outer surface of the vane, and it is then redirected into a circumferential motion.
Implementation Method 2
the conformal portion of a lateral surface of each vane substantially conforms to the shape of a corresponding conformal portion of a lateral surface of the corresponding slot, so as to enable the respective conformal portions of the surfaces to be placed relative to each other with only a small clearance between them
Implementation Method 3
the trailing portion of the vane is spaced from the trailing portion of the slot by a distance which is in the range 10 microns to 250 microns
Data Source
Figure 1~1(b)
Figure 2
Figure 3
AI summary
A turbine for a turbo-machine is proposed in which, at a gas inlet for a turbine wheel (9), vanes (7) extend from a nozzle ring (5) though slots in a shroud (6). The vanes (7) are formed with a leading portion which is arranged to contact a leading portion of a corresponding slot and a trailing portion which is shaped, when the leading portion of the vane and slot are together, to be spaced from a corresponding trailing portion of the slot with a substantially constant spacing at room temperature. The contact may be a point contact, e.g. close to the leading edge of the vane. Alternatively, the vane may include a leading surface portion which conforms closely with the shape of a corresponding leading surface portion of one of the slots.