Variable Valve Actuation for Exhaust Gas Temperature Control
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Solution Overview
Problem
Existing exhaust systems for internal combustion engines, particularly diesel engines, face challenges in maintaining adequate exhaust gas temperatures for particulate filter regeneration during engine idling or low output torque conditions, leading to clogging and potential filter failure, and the recirculation of sulfuric acid can corrode system components.
Innovation Solution
A variable valve actuation system utilizing a low-pressure fluid supply, hydraulic actuation, and a braking control valve to adjust the timing and flow of exhaust gases, ensuring sufficient temperature for regeneration and preventing corrosion by controlling the recirculation of acidic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive particulate filter is used relying on exhaust gas temperature, then filter regeneration can occur during normal operation, but under certain engine operating conditions (idling, high speeds, low torque) exhaust temperatures drop below regeneration temperature causing filter clogging
Solution Approach 1:
A recirculation line is introduced as an intermediary pathway that redirects a portion of exhaust gas back to the engine intake. This mediator allows the system to maintain sufficient exhaust temperature for filter regeneration even during engine conditions that would normally produce insufficient heat, by controlling the mixing and recirculation of exhaust gases.
Solution Approach 2:
The system changes the temperature parameter of the exhaust gas by recirculating it and mixing with fresh intake air. This parameter modification ensures the exhaust gas maintains temperatures above the regeneration threshold across varying engine operating conditions, including idle and low-load scenarios.
2Reliability
If recirculation loop is implemented to maintain exhaust temperature, then filter regeneration is improved, but sulfur in exhaust converts to sulfate which combines with condensed water to form sulfuric acid causing corrosion
Solution Approach 1:
The harmful sulfuric acid component is extracted and removed from the recirculation loop through a dedicated removal device. This extraction prevents the corrosive substance from circulating back to the engine and damaging components, while still allowing the beneficial recirculation of non-corrosive exhaust gases to maintain regeneration temperatures.
Solution Approach 2:
The system converts the potentially harmful recirculated exhaust gas into a beneficial thermal resource for filter regeneration. By removing the corrosive sulfuric acid component and recirculating only the beneficial hot gases, the system transforms what could be a corrosive problem into a solution that maintains exhaust temperature without causing damage.
3Reliability
If active particulate filter with heaters is used, then filter regeneration can be ensured, but device complexity and energy consumption increase
Solution Approach 1:
The system uses the engine's own exhaust gas as the heating source for filter regeneration, eliminating the need for external heaters or separate energy sources. The recirculation of hot exhaust gases self-regenerates the filter using waste heat already present in the system, reducing complexity and energy consumption.
Solution Approach 2:
The exhaust gas recirculation system serves multiple functions simultaneously: it maintains exhaust temperature for filter regeneration, provides cooling for the engine, and reduces nitrogen oxide emissions. This multi-functionality eliminates the need for dedicated heater components, simplifying the overall system architecture.
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
The system effectively maintains elevated exhaust gas temperatures for filter regeneration, reducing clogging and corrosion issues, thereby extending filter life and preventing unscheduled maintenance.
Implementation Method 1
A variable valve actuation system utilizing a low-pressure fluid supply, hydraulic actuation, and a braking control valve to adjust the timing and flow of exhaust gases
Implementation Method 2
ensuring sufficient temperature for regeneration and preventing corrosion by controlling the recirculation of acidic components
Data Source
AI summary
A variable valve actuation system is disclosed for providing exhaust to at least one component downstream of an engine. The system includes a supply of low pressure fluid, an engine fluid sump, and an exhaust valve disposed in an engine cylinder. The system also includes a hydraulic actuation system operably connected to the exhaust valve of the engine cylinder and a braking control valve operably connected to the hydraulic actuation system. The system further includes a device for accumulating fluid and a device for fluidly coupling the hydraulic actuation system to the accumulating device.