Variable Geometry Turbine Nozzle Ring Pressure Control
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Solution Overview
Problem
Variable geometry turbines face challenges in accurately controlling the position of the nozzle ring due to large fluctuations in pressure caused by engine exhaust pulses, leading to undesirable load variations on the actuating mechanism, which can affect turbine efficiency and braking torque.
Innovation Solution
The design incorporates a housing with a cavity that has a base surface matching the profile of the movable wall member, reducing the volume that can be filled with gas and featuring balance apertures to equalize pressure, thereby reducing pressure differences and time-varying loads on the movable wall member, and optionally using peripheral balance apertures to further stabilize pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If balance apertures are provided in the nozzle ring to reduce pressure differences, then the load on the nozzle ring is reduced, but the cavity volume increases allowing more gas to be stored
Solution Approach 1:
The base surface of the cavity is designed with a curved profile that generally matches the curved interior surface of the movable wall member, creating a complementary fit. This curvature design reduces the cavity volume while maintaining the pressure balancing function of the apertures, thereby reducing gas storage volume while still equalizing pressure across the nozzle ring.
Solution Approach 2:
The invention changes the geometric parameter of the cavity base surface from a conventional flat design to a curved profile that matches the movable wall member's interior surface. This parameter change optimizes the cavity volume by reducing the space available for gas storage while preserving the pressure equalization function through the balance apertures.
2Reliability
If the nozzle ring position is controlled accurately against pressure fluctuations, then turbine efficiency is maintained, but the actuating mechanism experiences large load variations
Solution Approach 1:
The balance apertures act as intermediaries that allow pressure equalization between the inlet and the cavity behind the nozzle ring. By providing these aperture pathways, the pressure difference across the nozzle ring is reduced, which decreases the load on the actuating mechanism while maintaining accurate position control and turbine efficiency.
Solution Approach 2:
The pressure equalization system creates a counterbalancing effect by allowing pressure to act on both sides of the nozzle ring through the balance apertures. This counterweight effect reduces the net force that the actuating mechanism must overcome, enabling accurate position control with reduced actuator load.
3Ease of manufacture
If a flat base surface is used in the cavity, then manufacturing is simpler, but the cavity volume is larger allowing more gas storage
Solution Approach 1:
The base surface of the cavity is designed with a curved profile that generally matches the curved interior surface of the movable wall member. This curvature creates a complementary fit that reduces the cavity volume, minimizing gas storage space while remaining manufacturable through conventional casting or machining processes.
Solution Approach 2:
The curved base surface design applies a specific geometric quality to the cavity region that interfaces with the movable wall member. This localized curvature matching optimizes the volume reduction in the critical interface region without requiring complex geometry throughout the entire cavity, maintaining ease of manufacture.
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 configuration reduces the magnitude of time-varying loads on the movable wall member, enhances turbine efficiency, and eliminates the need for secondary balance apertures, resulting in improved control and performance under varying engine conditions.
Implementation Method 1
a plurality of axially extending apertures are provided through the generally annular wall of the moveable member, such that the inlet and the cavity are in fluid communication via the plurality of apertures
Data Source
AI summary
A variable geometry turbine is disclosed comprising: a housing; a turbine wheel supported in the housing for rotation about an axis; a movable wall member; a cavity provided in the housing; and an inlet passageway extending radially inwards towards the turbine wheel. The movable wall member comprises a generally annular wall and radially inner and outer flanges extending axially from the generally annular wall, inner surfaces of the generally annular wall and radially inner and outer flanges defining an interior surface of the movable wall member. The cavity is suitable for receipt of the radially inner and outer flanges of the moveable member, the movable wall member being axially movable relative to the housing to vary the extent to which the radially inner and outer flanges of the moveable member are received in the cavity.