Turbocharger Scroll Part Flow Control for Low Speed Response
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Solution Overview
Problem
Existing two-stage turbo systems face challenges in improving supercharging response, particularly at low engine speeds, due to the complexity of nozzle vane mechanisms and limited turbine efficiency in regions with low turbine operation speed ratios, as seen in VG and VFT turbines.
Innovation Solution
A turbocharger with a scroll part featuring non-overlapping scroll passages and a flow-rate control valve, allowing exhaust gas to flow through either the radially inner or both scroll passages, enhancing flow velocity and pressure, and improving turbine efficiency at low speed ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a large-sized turbocharger is mounted to the low-pressure stage side to expand the operational range, then the flow rate range is improved, but the turbine weight increases causing slower rotation speed at low engine speeds
Solution Approach 1:
The scroll part is divided into multiple scroll passages (first, second, and third scroll passages) that segment the exhaust gas flow into different paths. This allows the large turbine to receive concentrated exhaust flow through selected passages, improving rotation speed response while maintaining the ability to handle various flow rates across the operational range.
2Speed
If a VG turbocharger with variable nozzle vane mechanism is used to improve response at low speed, then the turbine response is improved, but the device complexity increases
Solution Approach 1:
The flow-rate control valve dynamically adjusts the distribution of exhaust gas among the first, second, and third scroll passages based on engine operating conditions. This dynamic flow control achieves variable turbine response characteristics without requiring complex mechanical nozzle vane mechanisms, as the valve simply redirects exhaust flow paths.
3Adaptability or versatility
If a twin scroll structure is applied to introduce exhaust gas through two separate passages, then the flow rate range is improved, but the turbine efficiency at low speed ratios remains limited
Solution Approach 1:
Different scroll passages are designed with different characteristics: the first scroll passage handles high flow rates, while the second and third passages are optimized for low flow rates. The flow-rate control valve selectively activates specific passages based on local flow conditions, ensuring optimal turbine efficiency across the entire operational range rather than using a uniform structure.
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 enables quicker and more efficient driving of the turbine, enhancing supercharging response and boost pressure generation across a broad engine operational range.
Implementation Method 1
a scroll part for introducing exhaust gas into a nozzle flow passage of a turbine disposed in an exhaust passage of an engine
Data Source
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AI summary
A turbocharger includes: at least two scroll passages, and a first range of the nozzle flow passage into which the exhaust gas flowing through the first scroll passage is introduced does not overlap with a second range of the nozzle flow passage into which the exhaust gas flowing through the second scroll passage is introduced, in a circumferential direction of the nozzle flow passage. The first scroll passage includes: a division wall disposed along a flow direction of the exhaust gas within a predetermined range in the first scroll passage, the division wall dividing the first scroll passage into a radially outer side scroll passage and a radially inner side scroll passage positioned on a radially inner side of the radially outer side scroll passage, and having a communication hole which brings the radially outer side scroll passage and the radially inner side scroll passage into communication; and a flow-rate control valve disposed on an upstream side of the division wall, for adjusting a flow rate of the exhaust gas flowing through the radially outer side scroll passage and the radially inner side scroll passage.