Downstream Wastegate for Split Exhaust Engine
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Solution Overview
Problem
In turbocharged engines with split exhaust systems, high engine speeds can lead to increased exhaust gas flow through the first exhaust manifold to the turbine, causing compressor degradation due to elevated gas temperatures and speeds, and the traditional placement of the wastegate adjacent to the turbine increases costs and hinders catalyst activation.
Innovation Solution
Positioning the wastegate downstream of the turbocharger turbine and coupling it to a single exhaust runner rather than the merging region of all runners allows for reduced temperature exposure and use of lower-cost materials, reducing packaging constraints and enhancing catalyst activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wastegate is positioned adjacent to the turbine in the traditional configuration, then the turbine speed and boost pressure can be controlled effectively, but the material costs increase due to exposure to high temperatures and the catalyst activation time increases
Solution Approach 1:
The wastegate is extracted from its traditional position adjacent to the turbine and relocated to a new position in the exhaust manifold. This extraction removes the wastegate from the high-temperature zone, allowing the use of lower-cost materials while maintaining the speed control function through the new positioning that still provides effective exhaust flow regulation.
Solution Approach 2:
By relocating the wastegate away from the high-temperature turbine area, the patent enables the use of cheaper, less heat-resistant materials for the wastegate body and surrounding components. The wastegate valve itself may still be made of heat-resistant material, but the housing and passage can use standard stainless steel or even aluminum alloys, significantly reducing material costs.
2Reliability
If the wastegate is positioned adjacent to the turbine, then the turbine speed control is effective, but the packaging space requirements increase and catalyst activation is hindered
Solution Approach 1:
The wastegate is extracted from the compact turbine housing area and repositioned in the exhaust manifold where there is more available space. This relocation reduces the packaging constraints by distributing components more evenly throughout the engine bay and eliminates the heat barrier that previously prevented efficient catalyst activation.
Solution Approach 2:
The exhaust manifold serves as an intermediary location that provides both adequate packaging space and a thermal environment suitable for catalyst activation. By positioning the wastegate in the manifold rather than directly at the turbine, the system uses the manifold's larger volume and its position upstream of the catalyst to simultaneously satisfy space requirements and thermal activation requirements.
3Power
If high engine speeds are operated with increased exhaust gas flow to the turbine, then the engine power output increases, but the compressor degradation occurs due to elevated gas temperatures and speeds
Solution Approach 1:
The wastegate provides a feedback control mechanism for the exhaust flow to the turbine. At high engine speeds, when compressor degradation risks increase, the wastegate can be opened to divert excess exhaust flow away from the turbine, thereby limiting turbine speed and the resulting compressor inlet temperature and speed, protecting the compressor while still allowing high power operation.
Solution Approach 2:
The wastegate enables dynamic control of the exhaust flow path based on operating conditions. At lower speeds, the wastegate remains closed to maximize turbine drive and power output. At higher speeds where compressor protection is needed, the wastegate dynamically opens to regulate exhaust flow, creating a adaptive system that protects the compressor during high-power operation.
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 reduces the risk of compressor degradation, lowers material costs, and shortens catalyst light-off time, improving engine efficiency and emission control effectiveness.
Implementation Method 1
coupling a wastegate to a blowdown exhaust path may control turbine speed and boost pressure
Implementation Method 2
flowing a first portion of the exhaust gas (e.g., higher pressure exhaust) through the turbine
Implementation Method 3
increased exhaust gas may flow through the first exhaust manifold to the turbine of the turbocharger, thereby driving an increase in the speed, boost pressure and temperature of the compressor
Data Source
AI summary
Methods and systems are provided for split exhaust engine system including a blowdown exhaust manifold coupled to an exhaust passage and a scavenge exhaust manifold coupled to an intake passage. In one example, a turbine wastegate couples a single exhaust runner out of a plurality of exhaust runners of the blowdown exhaust manifold to an exhaust passage, downstream of a turbocharger turbine. Additionally, the turbine wastegate may couple the single exhaust runner to the exhaust passage, downstream of the turbocharger turbine arranged in the exhaust passage.