Internal EGR Engine Cylinders for NOx Reduction
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Solution Overview
Problem
Modern internal combustion engines face challenges in achieving high volumetric efficiency and reducing NOx emissions, as external exhaust gas recirculation systems are costly and prone to fouling, and often require additional components like turbochargers.
Innovation Solution
An internal combustion engine with dual compression and dual expansion, featuring interconnected cylinders that enable internal exhaust gas recirculation through timed valve operations, eliminating the need for external EGR systems and potentially reducing the requirement for turbochargers by utilizing two-stage compression and expansion processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an external EGR system is used to reduce NOx emissions, then emissions are reduced, but device complexity and cost increase due to additional components like EGR valves and coolers
Solution Approach 1:
The patent merges the EGR function with the existing cylinder arrangement by using internal passages to recirculate exhaust gas between cylinders, eliminating the need for separate external EGR components like valves and coolers while achieving the same emissions reduction goal
Solution Approach 2:
The engine cylinders serve their own EGR needs by recirculating exhaust gas internally through passages connecting the cylinders, allowing the system to perform the EGR function using its own structural components without requiring external service systems
2Productivity
If forced induction devices like turbochargers are added to enhance volumetric efficiency, then volumetric efficiency improves, but device complexity and cost increase
Solution Approach 1:
The patent combines the compression and expansion functions within the cylinder arrangement itself by having exhaust gas from power cylinders drive compression in inductor cylinders, eliminating the need for separate turbocharger or supercharger devices while maintaining enhanced volumetric efficiency
3Object-generated harmful factors
If external EGR passages and components are installed, then exhaust gas recirculation is achieved, but fouling issues and maintenance problems occur
Solution Approach 1:
The patent extracts the EGR function from external passages and components and relocates it entirely within the internal cylinder structure, removing the external pathways that are prone to fouling while preserving the exhaust gas recirculation capability
Solution Approach 2:
By using the cylinders' own internal structure and passages for EGR recirculation, the system eliminates external components that would require maintenance and are susceptible to fouling, making the system self-sufficient and more reliable
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 enhances volumetric efficiency, reduces emissions by enabling higher EGR percentages while maintaining a high air-to-fuel ratio, and eliminates the need for external EGR components, thereby saving costs and avoiding fouling issues.
Implementation Method 1
The internal exhaust gas recirculation may be by recompression in the inductor cylinders
Implementation Method 2
Fluid flow through the passages is controlled by the valves. Opening and closing of the valves is timed to accomplish internal exhaust gas recirculation
Implementation Method 3
Combustion occurs in a first two of the four cylinders (referred to as power cylinders)
Implementation Method 4
By mixing the incoming air with recirculated exhaust gas, the fluid mixture is diluted with inert gas (the recirculated gas), lowering the flame temperature and reducing the amount of excess oxygen in diesel engines. The exhaust gas also increases the specific heat capacity of the mix, lowering the peak combustion temperature, thereby limiting the formation of NOx
Data Source
AI summary
An internal combustion engine has four cylinders, each having a respective piston positioned therein and connected with a crankshaft for movement in the respective cylinder. Each cylinder has a plurality of ports with a plurality of valves openable and closable to control fluid flow into and out of the cylinder through the ports. Combustion occurs in a first two of the four cylinders (power cylinders) that are each interconnected between a second two of the four cylinders (inductor cylinders) via passages connecting ports of the respective cylinders. Opening and closing of the valves is timed to accomplish internal exhaust gas recirculation, i.e., such that fluid directed from the power cylinders to the inductor cylinders via the passages after combustion is redirected via the passages from the inductor cylinders to the power cylinders. A method of internal exhaust gas recirculation for an engine as described above is also provided.