Variable Geometry Turbine Wastegate Flow Control
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Solution Overview
Problem
Variable geometry turbines face low efficiency at the ends of the flow rate range, with existing solutions either compromising on maximum flow capacity or requiring smaller turbochargers that are not usable at desired rates.
Innovation Solution
A variable geometry turbine design with a movable inlet passageway and adjustable vanes, incorporating a wastegate port that allows gas bypass, enabling efficient operation across a range of flow rates by varying the inlet passageway size and bypassing gas through a chamber and wastegate port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the size of the annular inlet passageway is reduced to maintain gas velocity at low flow rates, then turbine efficiency is improved, but maximum flow capacity is limited
Solution Approach 1:
The inlet passageway is made variable in geometry through movable walls (nozzle ring or swing guide vanes) that can adjust the passage size dynamically. This allows the turbine to maintain optimal gas velocity at low flow rates while accommodating high flow rates when needed, resolving the contradiction between efficiency and flow capacity
Solution Approach 2:
The physical parameter of inlet passageway size is changed from fixed to variable. By adjusting the geometry parameter of the inlet passage, the turbine can optimize performance across different operating conditions, improving both efficiency at low flow and capacity at high flow
2Quantity of substance
If the annular inlet passageway size is increased to handle high exhaust gas flow, then flow capacity is improved, but turbocharger over-speeding occurs
Solution Approach 1:
The variable geometry inlet passageway dynamically adjusts its size in response to flow conditions. At high flow rates, the passage opens to accommodate the increased gas volume, preventing pressure buildup and turbocharger over-speeding while maintaining controlled turbine operation
Solution Approach 2:
The variable geometry mechanism responds to changing flow conditions, effectively providing feedback control. The inlet passage size adjusts automatically based on the exhaust gas flow rate, preventing over-speeding by opening the passage when flow increases and maintaining stable turbine operation
3Speed
If a wastegate valve is used to control boost pressure and shaft speed, then speed control is improved, but device complexity increases
Solution Approach 1:
The variable geometry inlet passageway serves multiple functions: it optimizes turbine efficiency at low flow rates, prevents over-speeding at high flow rates, and provides inherent speed control. This multi-functionality reduces the need for additional separate control mechanisms, thereby reducing overall device complexity while maintaining speed control capability
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 design enhances flow capacity and efficiency by optimizing turbine operation at both low and high flow rates, extending the usable range of the turbine without over-speeding at high rates.
Implementation Method 1
pressurised exhaust gas admitted to the inlet flows through the inlet passageway to the outlet passageway via the turbine chamber and rotates the turbine wheel
Data Source
AI summary
A variable geometry turbine comprises a turbine wheel (5) supported in a housing for rotation about a turbine axis with an annular inlet passageway (9) defined between a radial face of a nozzle ring (11) and a facing wall of the housing (10). The nozzle ring is movable along the turbine axis to vary the width of the inlet passageway and has a circumferential array of vanes (20) that are received in corresponding slots (24) in the facing wall. A wastegate valve (15) is provided in a chamber behind the facing wall and gas bypasses the turbine through the chamber to the wastegate port (14) at high flow rates.