Crankpin Offset for Dedicated EGR Cylinder Combustion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Dedicated exhaust gas recirculation (EGR) systems face challenges in balancing indicated mean effective pressure and combustion stability across cylinders due to varying air-fuel ratios and combustion behaviors between main and dedicated EGR cylinders, leading to unstable operation and reduced fuel efficiency.
Innovation Solution
The implementation of variable crankpin offsets in a four-stroke internal combustion engine allows for independent alteration of volumetric efficiency, exhaust gas recirculation rate, and combustion stability by adjusting the position of crankpins associated with the dedicated EGR cylinder relative to the main crankshaft axis, enabling better control of exhaust gas rate and indicated mean effective pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If higher levels of exhaust gas are used for EGR, then fuel efficiency is improved and emissions are reduced, but EGR tolerance challenges arise that reduce fuel efficiency improvement
Solution Approach 1:
The engine is divided into main cylinders and a dedicated EGR cylinder. The dedicated EGR cylinder operates independently with rich combustion to produce high levels of CO and H2, which are then recirculated to the main cylinders. This segmentation allows the EGR system to handle higher exhaust gas levels without adversely affecting the performance and fuel efficiency of the main cylinders.
2Reliability
If dedicated EGR cylinders operate fuel rich to produce higher levels of H2 and CO, then octane number increases and EGR tolerance improves, but combustion stability decreases at part load conditions
Solution Approach 1:
Crankpin offset is used as a control parameter to adjust the volumetric efficiency of the dedicated EGR cylinder. By varying the crankpin offset, the system can optimize combustion stability at part load while maintaining rich operation for high EGR tolerance at higher loads. This parameter change allows dynamic adaptation to different operating conditions.
3Stability of the object's composition
If crankpin offset is used to control volumetric efficiency and EGR rate, then combustion stability and indicated mean effective pressure are improved, but device complexity increases
Solution Approach 1:
The crankpin offset mechanism is integrated into the existing crankshaft structure of the engine. The offset is achieved by positioning the crankpin at a different radial distance from the crankshaft axis, merging the EGR control function with the fundamental crankshaft mechanism rather than adding a separate complex control system.
Data Source
AI summary
A four stroke internal combustion engine with dedicated exhaust gas recirculation and method of operating such engine, wherein the engine comprises a plurality of combustion cylinders including main cylinders and a dedicated exhaust gas recirculation cylinder, wherein each cylinder includes a piston; a crankshaft, which is rotatable in a direction, and defines a main crankshaft axis, and includes a plurality of crankpins. Each of the crankpins is coupled to at least one of the pistons. The crankpins affixed to the pistons of the main cylinders are spaced at an interval around the main crankshaft axis. The crankpin affixed to the piston of the dedicated exhaust gas recirculation cylinder is spaced at an offset of 5 to 50 degrees from the interval in either direction relative to the direction of crankshaft rotation.