Variable Geometry Turbine Bypass Passage for Engine Braking
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Solution Overview
Problem
Conventional variable geometry turbines face challenges in controlling bypass flow efficiently, leading to excessive heat generation and reduced efficiency during engine braking and exhaust gas heating modes, and are prone to clogging due to particulate matter accumulation.
Innovation Solution
A variable geometry turbine design featuring an annular primary inlet passageway with a bypass passage and axially spaced inlet and outlet bypass ports, allowing controlled bypass flow by varying the axial position of the movable wall member, which reduces turbine efficiency and compressor outflow pressure, thereby managing engine cylinder pressures and exhaust gas temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the inlet passage width is reduced to control exhaust gas temperature and manage engine cylinder pressures, then the desired temperature ranges are maintained, but excessive heat generation occurs and turbine efficiency is reduced
Solution Approach 1:
The inlet passage is segmented into a primary inlet passageway and a bypass passage, allowing exhaust gas to flow through separate paths. The bypass passage diverts a portion of the gas flow around the turbine wheel, enabling independent control of temperature (via primary passage restriction) and efficiency (via bypass flow adjustment).
Solution Approach 2:
The bypass passage acts as an intermediary flow path that mediates between the restricted primary inlet passage and the turbine wheel. It provides a controlled leakage path that reduces the harmful effects of excessive restriction (heat generation) while maintaining the beneficial temperature control, thus resolving the contradiction between temperature management and efficiency preservation.
2Force
If the inlet passage is closed to a minimum flow area during engine braking mode, then engine braking effectiveness is improved, but excessive heat generation in engine cylinders occurs
Solution Approach 1:
The bypass passage serves as an intermediary that allows controlled exhaust gas flow to bypass the restricted primary inlet passage. This maintains sufficient backpressure for engine braking while preventing complete flow restriction that would cause excessive cylinder heat generation, thus resolving the contradiction between braking effectiveness and temperature control.
3Quantity of substance
If conventional bypass arrangements with circumferential slots are used, then bypass flow is provided, but the system is prone to clogging due to particulate matter accumulation
Solution Approach 1:
The design extracts the bypass function from the traditional circumferential slot configuration and relocates it to a dedicated bypass passage with axially spaced ports. This separates the bypass flow path from the particulate-laden primary flow, reducing particulate accumulation in the bypass passage and improving resistance to clogging while maintaining bypass flow capability.
4Productivity
If the axial position of the movable wall member is fixed, then the inlet passage width is constant, but the turbine cannot optimise gas flow velocities over a range of mass flow rates
Solution Approach 1:
The movable wall member enables dynamic adjustment of the primary inlet passage width by changing its axial position. This allows the turbine to optimize gas flow velocities and maintain high efficiency across a range of mass flow rates and operating conditions, transforming a static system into an adaptive one that responds to varying engine demands.
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
The design enhances engine braking and exhaust gas heating by reducing boost pressures and maintaining desired temperature ranges, while minimizing the need for additional valves and reducing the risk of clogging through controlled bypass flow and particulate filtration.
Implementation Method 1
the size of the inlet passage can be varied to optimise gas flow velocities over a range of mass flow rates so that the power output of the turbine can be varied in line with varying engine demands
Implementation Method 2
a bypass passage is provided in the other of said movable wall member and housing member, the bypass passage extending from an inlet bypass port to an outlet bypass port... such that flow in the secondary inlet passageway bypasses at least a portion of the primary inlet passageway
Implementation Method 3
the bypass passage and the annular seal being arranged such that as the movable wall member moves axially, the annular seal moves axially relative to the inlet and outlet bypass ports so as to vary the extent of flow that may pass from a region of the cavity inboard of the seal, through the bypass passage to the secondary inlet passageway
Implementation Method 4
an exhaust gas driven turbine wheel mounted on a rotatable shaft within a turbine housing. Rotation of the turbine wheel rotates a compressor wheel mounted on the other end of the shaft
Implementation Method 5
The compressor wheel delivers compressed air to the engine intake manifold
Implementation Method 6
The turbocharger shaft is conventionally supported by journal and thrust bearings, including appropriate lubricating systems
Implementation Method 7
journal and thrust bearings, including appropriate lubricating systems
Data Source
AI summary
A variable geometry turbine having a turbine wheel, an inlet passageway, a movable wall member being moveable axially to vary the width of the inlet passageway, an annular seal being mounted to the movable wall member or an adjacent housing member to provide a seal between adjacent surfaces of the movable wall member and housing member respectively, wherein a bypass passage is provided in the other of said movable wall member or housing member, extending from an inlet bypass port to an outlet bypass port, said ports being spaced from each other and provided in said adjacent surface of said other of the movable wall member or housing member, arranged such that as the movable wall member moves axially, the annular seal moves axially relative to the ports to vary the flow that may pass from a region of the cavity inboard of the seal, through the bypass passage.