Variable Geometry Turbine Nozzle Ring Rib Control
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Solution Overview
Problem
Variable geometry turbochargers face challenges in controlling nozzle ring position at small inlet widths, leading to excessive engine cylinder pressures and temperatures during engine braking and exhaust gas heating modes, with issues of rapid load increase, snapping shut, and difficulty in maintaining optimal minimum flow.
Innovation Solution
Incorporating an annular rib on the nozzle ring face that extends above any exposed fasteners, allowing precise control of minimum inlet width and providing a bypass gas path to reduce turbine efficiency and ensure minimum leakage flow, combined with pressure balancing holes for improved positional control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inlet passageway width is reduced to control minimum flow during engine braking and exhaust gas heating modes, then the turbine efficiency is improved and gas velocity is maintained, but the engine cylinder pressures and temperatures become excessive
Solution Approach 1:
The inlet passageway is segmented into multiple independent control zones: the main annular inlet passageway width (controlled by nozzle ring position) and the bypass passage width (controlled by rib position). This segmentation allows independent optimization of each zone - the main passageway can be narrowed to maintain gas velocity and turbine efficiency, while the bypass passage provides a controlled leakage path to limit maximum pressures and temperatures in engine braking and exhaust gas heating modes.
2Speed
If the nozzle ring is moved to reduce the inlet passageway width to its minimum, then the gas velocity is maintained at high levels, but the control becomes difficult due to rapid load increase and snapping shut
Solution Approach 1:
The control function is segmented between the nozzle ring (controlling main passageway width) and the rib (controlling bypass passage width). The rib acts as a mechanical stop that prevents the nozzle ring from moving beyond a predetermined position, thereby preventing rapid load increase and snapping shut. This allows the nozzle ring to be positioned accurately for optimal gas velocity without the risk of excessive closing forces.
Solution Approach 2:
The rib serves as an intermediary mechanical element between the nozzle ring and the inlet passageway wall. It provides a controlled leakage path through the bypass passage while preventing the nozzle ring from closing completely. This intermediary structure mediates the conflict between achieving minimum passageway width for high gas velocity and maintaining controllable operation by limiting the maximum closing force.
3Power
If the inlet passageway is closed to minimum width to provide engine braking function, then the braking effect is enhanced, but the minimum flow control becomes difficult to maintain optimally
Solution Approach 1:
The flow control is segmented into two independent paths: the main annular inlet passageway (for primary flow control) and the bypass passage (for minimum flow assurance). During engine braking, the nozzle ring closes the main passageway to maximum extent to enhance braking effect, while the bypass passage maintained by the rib position ensures optimal minimum flow control. This segmentation allows both functions to be optimized simultaneously without compromise.
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
Enables precise control of nozzle ring position and minimum gas flow, preventing excessive pressures and temperatures, and maintaining efficient operation during engine braking and exhaust gas heating modes.
Implementation Method 1
pressure balancing apertures through its radial wall. The pressure balancing apertures ensure that pressure within the nozzle ring cavity is substantially equal to, but always slightly less than, the pressure applied to the nozzle ring face by gas flow through the inlet passageway
Implementation Method 2
bypass gas flow path from the inlet chamber to the turbine wheel which bypasses the inlet passageway and the inlet guide vanes
Data Source
Figure 1
Figure 2a~2b
Figure 3a~4
AI summary
A variable geometry turbine comprises 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 movable 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. A substantially annular rib is provided either on the face of the nozzle ring (such that the minimum width of the inlet passageway is defined between the rib and a the facing wall of the housing) or on the facing wall of the housing (such that the minimum width of the inlet passageway is defined between the rib and the nozzle ring).