Variable Geometry Turbine Vane Recesses for Engine Braking Control
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Solution Overview
Problem
Variable geometry turbochargers face challenges in engine braking and exhaust gas heating modes, where controlling the nozzle ring position at small inlet widths is difficult due to rapid load increases and potential for excessive pressures or inadequate airflow, leading to inefficiencies and potential system failure.
Innovation Solution
Incorporating recesses on the vanes and a perforated or discontinuous annular rib to provide a controlled leakage flow path when the nozzle ring is in a closed position, allowing for precise control of the inlet passageway size and maintaining a minimum gas flow, while reducing turbine efficiency at small gaps to prevent excessive pressures and ensure optimal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the nozzle ring position is controlled at small inlet widths to optimize turbine output, then the gas velocity is maintained at an efficient level, but the load on the nozzle ring increases rapidly making precise control difficult
Solution Approach 1:
The patent applies local quality by providing recesses at specific locations on the vanes (inlet and outlet edges) to create localized leakage flow paths. This allows different parts of the vane structure to have different functions: the main vane surfaces control primary gas flow for turbine output, while the recesses provide localized controlled leakage to reduce load on the nozzle ring, making control easier without sacrificing overall productivity.
2Productivity
If the inlet passageway width is reduced to maintain gas velocity at low exhaust gas flow, then turbine efficiency is optimized, but excessive pressures may occur leading to system failure
Solution Approach 1:
The patent applies preliminary anti-action by incorporating recesses in the vanes that create controlled leakage flow paths before excessive pressures can build up. This preliminary leakage mechanism prevents the harmful effect of excessive pressure by allowing a portion of the gas to bypass the narrow inlet passageway, thereby protecting the system while maintaining efficient operation.
Solution Approach 2:
The patent converts the potentially harmful effect of gas leakage (which would normally reduce efficiency) into a beneficial feature. The recesses are strategically designed to create controlled leakage that prevents excessive pressure buildup, and this leakage is used to reduce nozzle ring load and improve control, thereby turning what could be a harmful effect into a protective mechanism.
3Productivity
If the inlet passageway is closed down in engine braking mode to control exhaust gas flow, then braking efficiency is improved, but inadequate airflow may occur
Solution Approach 1:
The patent applies local quality by providing recesses at specific locations on the vanes to create localized leakage flow paths. This allows different parts of the vane structure to have different functions: the main vane surfaces control primary gas flow for braking efficiency, while the recesses provide localized controlled leakage to maintain adequate exhaust gas flow even when the inlet passageway is closed down.
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 solution enables precise control of the nozzle ring position and maintains a minimum gas flow, preventing excessive pressures and ensuring efficient operation in engine braking and exhaust gas heating modes, while optimizing the heating effect and braking efficiency.
Implementation Method 1
at least one vane having at least one recess in a vane surface such that when the walls are in a predetermined position the recess is substantially aligned with its respective opening so that it affords a clearance between the vane and the second wall so as to provide an exhaust gas leakage flow path
Data Source
AI summary
A variable geometry turbine comprising a turbine wheel supported in a housing for rotation about a turbine axis with an annular inlet passageway defined between a radial face of a nozzle ring and a facing wall of the housing. The nozzle ring is movable along the turbine axis to vary the width of the inlet passageway and of vanes that are received in corresponding slots in the facing wall. Each vane major surface such that at a predetermined axial position of the nozzle ring relative to the facing wall the recess is in axial alignment with the slot and affords an exhaust gas leakage path through the inlet passageway. The recess is configured to reduce the efficiency of the turbine at small inlet gaps appropriate to engine braking or exhaust gas heating modes.