Turbine Twin-Entry Volute Tongue Angular Spacing
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Solution Overview
Problem
Twin-entry turbines experience uneven mass flow rates and pressures in their volutes, leading to non-uniform pressure distributions on the turbine wheel, which can cause blade deformation and potential failure due to excessive strain from resonant frequency excitations.
Innovation Solution
The tongues of each inlet volute are angularly spaced about the turbine axis, resulting in a zero or positive turbine scroll tongue overlap, reducing strain on the turbine wheel by altering the leading edge pressure distribution and minimizing blade excitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the volutes are configured with conventional tongue positioning, then the turbine wheel receives exhaust gas flow, but non-uniform pressure distribution causes blade strain and potential failure
Solution Approach 1:
The patent applies asymmetry by angularly offsetting the tongues of the first and second inlet volutes relative to each other about the turbine axis. Instead of symmetric positioning, the tongues are placed at different angular positions, creating an asymmetric flow distribution pattern that balances the pressure forces on the turbine wheel and reduces resonant excitation of blades.
Solution Approach 2:
The patent transitions from a single-dimension radial volute configuration to a multi-dimensional solution by introducing angular positioning of the volute tongues as an additional degree of freedom. This angular dimension allows optimization of pressure distribution by controlling the phase relationship between flows from different volutes.
2Device complexity
If the volutes are spaced along the rotational axis with aligned tongues, then the structure is simple, but pressure waves excite blade resonant frequencies causing deformation
Solution Approach 1:
The patent introduces asymmetry in the angular positioning of volute tongues while maintaining the simple spaced configuration along the rotational axis. This asymmetric angular offset breaks the symmetry that causes constructive interference of pressure waves, thereby reducing blade excitation without complicating the overall volute structure.
3Power
If the turbine wheel operates at high speed, then power output increases, but blade resonant frequency excitation from pressure distribution causes metal fatigue
Solution Approach 1:
The patent addresses periodic pressure variations by angularly offsetting the volute tongues, which changes the phase relationship of periodic pressure waves entering the turbine wheel. This phase shift prevents synchronous excitation of blade resonant frequencies, reducing cumulative fatigue damage over the turbine's operational cycle.
Solution Approach 2:
The patent changes the angular position parameter of the volute tongues to optimize the pressure distribution characteristics. By adjusting this geometric parameter, the patent modifies the pressure wave patterns acting on the turbine wheel to minimize resonant excitation and extend service life.
Data Source
AI summary
A turbine comprises a housing defining a turbine chamber with a turbine wheel supported for rotation about an axis. The housing further defines first and second inlet volutes which each spiral radially inwards and extend from a respective inlet to adjoin the turbine chamber and a volute tongue for each inlet volute. The tongue of the first volute radially separating a downstream portion of the first volute adjacent the chamber from an upstream portion of the first volute adjacent said inlet of the first volute, and the tongue of the second volute radially separating a downstream portion of the second volute adjacent the chamber from an upstream portion of the second volute adjacent said inlet of the second volute. The tongues having a turbine scroll tongue overlap which is substantially zero or positive; and the first volute tongue is angularly spaced about the axis from the second volute tongue.