Variable Twin-Scroll Turbine Cylinder Deactivation
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Solution Overview
Problem
Turbocharged internal combustion engines face limitations in cylinder deactivation due to the flow and boost pressure capabilities of single turbochargers, which restrict operating ranges and compromise performance at both low and high engine speeds.
Innovation Solution
A variable twin-scroll turbine system is implemented, where a single compressor is driven by two turbine scrolls, with a scroll control valve directing exhaust gases from deactivated cylinders to either scroll based on engine conditions, allowing for optimized turbine usage across speed and load ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single fixed geometry turbine is used, then the system simplicity is maintained, but the turbocharger cannot meet performance requirements at both low and high engine speeds
Solution Approach 1:
The turbine system is divided into two separate scrolls (first scroll and second scroll), each optimized for different operating conditions. The first scroll handles exhaust from all cylinders during normal operation, while the second scroll handles exhaust from deactivated cylinders during cylinder deactivation mode, allowing each scroll to be sized appropriately for its specific function
Solution Approach 2:
A variable geometry mechanism is implemented in the first scroll, allowing the turbine inlet area to be dynamically adjusted. This enables the first scroll to adapt its effective size based on operating conditions, providing both a smaller effective area for low-speed operation and a larger effective area for high-speed operation, thus meeting performance requirements across the full speed range
2Speed
If a smaller turbine is used, then low engine speed performance is improved, but high engine speed performance is compromised
Solution Approach 1:
The turbine function is segmented between two scrolls: the second scroll (for deactivated cylinders) provides the smaller turbine area optimized for low-speed response, while the first scroll (for all cylinders) with variable geometry provides the larger effective area needed for high-speed performance when activated
Solution Approach 2:
The variable geometry mechanism changes the physical parameters of the first scroll's inlet area dynamically. At low speeds, the inlet area is reduced to match the lower exhaust flow, improving response. At high speeds, the inlet area is increased to handle the higher exhaust flow and maintain power
3Power
If a larger turbine is used, then high engine speed performance is improved, but low engine speed response is compromised
Solution Approach 1:
The variable geometry mechanism makes the first scroll's inlet area dynamic rather than fixed. The inlet area can be adjusted based on engine speed and load conditions, providing a smaller effective area at low speeds for better response and a larger effective area at high speeds for maintained power
4Adaptability or versatility
If multiple separate turbochargers are used, then engine performance across speed and load ranges is fulfilled, but system complexity and packaging complexity increase
Solution Approach 1:
Two separate turbocharger systems are merged into a single integrated unit with a common compressor and housing, but with separate turbine scrolls. This combines the adaptability benefits of multiple turbochargers (each scroll can be optimized for different functions) while maintaining the system simplicity, packaging, and cost advantages of a single turbocharger
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 solution enhances turbocharger response at low engine speeds, extends the engine's operating range with deactivated cylinders, and improves overall fuel economy and performance.
Implementation Method 1
A turbocharger having a twin scroll turbine includes a first turbine scroll in communication with the exhaust passages from the first plurality of cylinders and a second turbine scroll in communication with the exhaust passages from the second plurality of cylinders
Implementation Method 2
A single compressor is driven by the twin-scroll turbine for supplying compressed air to the intake ports of the cylinders
Data Source
AI summary
An internal combustion engine defines a plurality of cylinders including full-time active cylinders and cylinders capable of being deactivated. A turbocharger having a twin scroll turbine includes a first turbine scroll in communication with the exhaust passages from the full-time active cylinders and a second turbine scroll in communication with the exhaust passages from the cylinders capable of being deactivated. A scroll control valve is provided in communication with the exhaust passages from the cylinders capable of being deactivated and being operable in an open position to allow exhaust gases from the cylinders capable of being deactivated to pass through the second turbine scroll, and being operable in a closed position to direct exhaust gases from the plurality of second cylinders capable of being deactivated to pass through the first turbine scroll.