Turbocharger CLOC Bypass Valve Pressure Drop Control
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Solution Overview
Problem
Aftertreatment systems in turbocharged engines face inefficiencies during engine startup due to low exhaust temperatures, which hinder the conversion of pollutants like NOx, CO, and HC, as they require high temperatures to achieve optimal catalyst efficiency.
Innovation Solution
A control system that includes a cold light off catalyst (CLOC) positioned in a bypass passage around the turbocharger, with a CLOC valve to divert exhaust flow and a controller to manage the valve's position based on pressure drops, ensuring increased airflow and compensating for negative work conditions during CLOC mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If exhaust flow is diverted to the CLOC during cold start, then pollutant conversion efficiency is improved, but compressor pressure drop increases causing negative work
Solution Approach 1:
The controller continuously monitors compressor pressure drop and dynamically adjusts the CLOC valve position and actuator commands based on real-time feedback. When pressure drop exceeds thresholds indicating negative work conditions, the system automatically reduces CLOC flow or closes the valve, preventing energy loss while maintaining pollutant conversion efficiency during normal operation
Solution Approach 2:
The system transitions from static exhaust routing to dynamic control by using the CLOC valve and actuator to continuously adjust exhaust flow distribution. The valve can operate in multiple positions (fully open, partially open, fully closed) and the actuator provides continuous adjustment capability, allowing the system to adapt exhaust routing in real-time based on engine operating conditions and pollutant conversion requirements
2Productivity
If the CLOC valve is fully opened to maximize exhaust flow through CLOC, then pollutant treatment is improved, but compressor performance deteriorates due to increased backpressure
Solution Approach 1:
The system changes the operational parameters of the CLOC valve from binary (fully open/closed) to continuous partial positioning. By adjusting the valve to intermediate positions, the system optimizes the balance between exhaust flow through the CLOC for pollutant treatment and maintaining acceptable backpressure levels for compressor performance, achieving both goals simultaneously
Data Source
AI summary
A control system for an engine comprising a turbocharger includes a throttle valve, a cold light off catalyst (CLOC), a CLOC valve, and a controller. The CLOC is positioned in a bypass passage around a turbine of the turbocharger. The CLOC valve selectively routes exhaust flow from the engine between the turbine and the CLOC. The controller is configured to command the CLOC valve to a first position whereby exhaust flow is routed to the CLOC in a CLOC mode; determine, based on operation in the CLOC mode, a pressure drop within the turbocharger; and command the actuator to move resulting in increased airflow into the engine while in the CLOC mode.