Turbocharger Turbine Back-Surface Protrusion for Thrust Balance
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Solution Overview
Problem
The increasing diameter of compressor impellers in turbochargers leads to a greater thrust force on the compressor impeller compared to the turbine impeller, resulting in increased mechanical loss and reduced efficiency due to the increased load on the bearing.
Innovation Solution
A turbine design with a back-surface side member featuring a protruding portion that extends in the circumferential direction, enhancing the static pressure on the turbine impeller by guiding exhaust gas flow effectively, thereby reducing the difference in thrust forces between the compressor and turbine impellers and minimizing mechanical loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the diameter of the compressor impeller is increased to increase the pressure ratio, then the pressure ratio of the turbocharger is improved, but the thrust force on the compressor impeller back surface increases, causing increased mechanical loss
Solution Approach 1:
The invention applies a protruding portion at a specific location on the turbine impeller back surface to locally modify the flow characteristics. This local modification increases the thrust force specifically at the turbine impeller back surface, counterbalancing the increased compressor impeller thrust force without requiring a global change to the entire impeller structure.
Solution Approach 2:
The invention changes the geometric parameters of the turbine impeller back surface by adding a protruding portion with specific dimensions (radial length, circumferential extent, and axial position). This parameter change modifies the local flow field and pressure distribution, thereby adjusting the thrust force to reduce mechanical loss while maintaining the increased pressure ratio.
2Power
If the diameter of the compressor impeller is increased, then the thrust force difference between compressor and turbine impellers increases, but this leads to increased load on the bearing and reduced efficiency
Solution Approach 1:
The protruding portion on the turbine impeller back surface acts as a counterbalancing feature that generates additional thrust force to offset the increased compressor impeller thrust. This creates a more balanced load distribution on the bearing, reducing mechanical loss and improving overall efficiency while maintaining the required thrust force difference for high pressure ratio operation.
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 effectively reduces mechanical loss across the entire rotor while promoting higher pressure ratios in the turbocharger by increasing the thrust force on the turbine impeller, thus improving overall efficiency.
Implementation Method 1
A flow of exhaust gas introduced into a gap between the back surface of the turbine impeller and the impeller facing surface from the scroll outlet portion is contracted by the protruding portion
Implementation Method 2
a turbine impeller coupled to a compressor impeller via a rotational shaft
Data Source
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AI summary
A turbine for a turbocharger includes: a turbine impeller coupled to a compressor impeller via a rotational shaft; a turbine casing disposed so as to cover the turbine impeller, the turbine casing including a scroll flow passage and a scroll outlet portion disposed on an inner side, in a radial direction, of the scroll flow passage, for guiding exhaust gas from the scroll flow passage to the turbine impeller; and a back-surface side member disposed so as to face a back surface of the turbine impeller. The back-surface side member includes a protruding portion disposed on an impeller facing surface which faces the back surface of the turbine impeller, the protruding portion protruding toward the back surface and extending in a circumferential direction.