Split Exhaust Turbine Control via Cylinder Valve Deactivation
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Solution Overview
Problem
Split exhaust engine systems face inefficiencies due to energy losses in extensive exhaust manifolds and challenges in controlling turbine speed, noise, vibration, and component overheating, leading to sub-optimal performance.
Innovation Solution
The method involves grouping cylinders to reduce the exhaust manifold volume between cylinders and the turbine, selectively deactivating first exhaust valves to control turbine speed and energy delivery, thereby minimizing energy losses and noise, and optimizing engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If exhaust from all cylinders is directed to the turbine via extensive exhaust manifolds, then turbine speed and generator output are increased, but energy losses in the exhaust manifold increase and engine efficiency decreases
Solution Approach 1:
The exhaust system is segmented into multiple independent pathways: one pathway directs exhaust to the turbine while another pathway bypasses the turbine and directs exhaust to the exhaust catalyst. This segmentation allows selective routing of exhaust flow to different destinations based on operational requirements, reducing unnecessary energy losses in the exhaust manifold while maintaining turbine power output when needed.
Solution Approach 2:
The system dynamically controls exhaust flow distribution using variable valve timing mechanisms that adjust the timing and duration of exhaust valve opening. By dynamically modulating the exhaust flow to the turbine versus bypassing it, the system optimizes the balance between turbine power generation and energy loss reduction under different operating conditions.
2Power
If exhaust flow to the turbine is increased to improve generator output, then turbine speed increases, but turbine over-speed conditions and generator NVH increase
Solution Approach 1:
The system incorporates feedback control through the engine control unit (ECU) that continuously monitors turbine speed and generator output. Based on this feedback, the ECU dynamically adjusts the exhaust valve timing and duration to modulate exhaust flow to the turbine, maintaining turbine speed within optimal ranges and preventing over-speed conditions that would generate excessive noise and vibration.
Solution Approach 2:
The system uses periodic modulation of exhaust valve timing and duration to control exhaust flow pulses to the turbine. This periodic action allows smooth control of turbine speed fluctuations, preventing sudden spikes that would cause over-speed conditions and associated noise and vibration issues.
3Use of energy by moving object
If exhaust flow is directed to the turbine, then energy is recovered to power the generator, but component temperatures (cylinder head, exhaust valves, turbine, catalyst) increase causing overheating
Solution Approach 1:
The exhaust system is divided into separate pathways that can be independently controlled: one pathway routes exhaust through the turbine for energy recovery, while another pathway provides a bypass route that directs exhaust away from the turbine. This segmentation enables the system to manage thermal loads by selectively routing exhaust flow based on temperature conditions, preventing overheating of components while maintaining energy recovery when temperatures are acceptable.
4Stress or pressure
If split exhaust manifold is used to control turbine speed and reduce pumping penalty, then turbine backpressure is reduced, but engine efficiency decreases due to energy losses in exhaust manifolds
Solution Approach 1:
The exhaust system is segmented into multiple controlled pathways that allow selective routing of exhaust flow. By segmenting the exhaust flow paths and using intelligent control of exhaust valve timing, the system maintains low turbine backpressure when needed while minimizing energy losses in the exhaust manifold through optimized flow distribution and bypass routing.
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 approach enhances engine efficiency by reducing energy losses and noise, allowing for better control of turbine speed and generator output, while preventing component overheating and improving overall engine performance.
Implementation Method 1
a first exhaust valve of each cylinder of the first and second cylinder groups connected to a first exhaust manifold leading to an exhaust turbine
Data Source
AI summary
Methods and systems are provided to control exhaust energy delivered to a turbine of a turbine-generator coupled to a split exhaust engine system in order to limit turbine over-speed conditions and/or reduce generator vibration or reduce component over-heating conditions. In one example, a method may comprise in response to turbine speed greater than a threshold speed, selectively deactivating a first exhaust valve of one or more cylinders of a first and second cylinder group.