Reciprocating Engine EGR Injection for NOx Reduction
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Solution Overview
Problem
Existing reciprocating engines that use both liquid and gaseous fuel nozzles tend to produce high levels of NOx due to rapid combustion and local high temperatures, which is a concern for emission control.
Innovation Solution
A reciprocating engine design that incorporates a liquid fuel supply unit and a gas supply unit, which includes exhaust gas recirculation (EGR) gas from the combustion chamber to reduce NOx production by injecting fuel gas and EGR gas into the combustion chamber, utilizing a uniflow scavenging two-cycle engine configuration with specific supply routes and timing to minimize oxygen concentration and temperature extremes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If both liquid fuel and fuel gas nozzles are used for combustion, then combustion efficiency is improved, but NOx emission increases due to rapid combustion and local high temperature
Solution Approach 1:
EGR gas is introduced into the cylinder before fuel combustion occurs, pre-cooling the combustion chamber and reducing peak combustion temperatures. This preliminary action prevents the formation of NOx by lowering the temperature threshold required for NOx generation, while still allowing efficient combustion of both liquid fuel and fuel gas
Solution Approach 2:
The patent changes the temperature parameter of the combustion environment by introducing cooled EGR gas. This parameter change reduces the peak combustion temperature to below the NOx formation threshold while maintaining combustion efficiency through the dual-fuel approach
2Object-generated harmful factors
If EGR gas is introduced to reduce NOx, then NOx emission is reduced, but combustion stability may deteriorate due to reduced oxygen concentration
Solution Approach 1:
The patent applies local quality by introducing EGR gas selectively to specific zones within the combustion chamber where temperature is highest, rather than uniformly throughout. This localized approach reduces NOx formation in hot spots while maintaining adequate oxygen concentration in other regions to support stable combustion
Solution Approach 2:
The combustion mixture becomes a composite of fresh air, EGR gas, liquid fuel, and fuel gas. This composite approach allows optimization of each component's contribution - fresh air provides oxygen for combustion stability, EGR gas controls temperature for NOx reduction, and the dual-fuel system ensures efficient energy release
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 engine effectively reduces NOx production during combustion of liquid and gaseous fuels by leveraging the EGR gas to mitigate temperature and oxygen levels, thereby decreasing NOx generation.
Implementation Method 1
a gas supply unit that supplies, into the cylinder, fuel gas and EGR gas as exhaust gas which is produced from combustion in the combustion chamber and is discharged from the combustion chamber
Data Source
Figure 1
Figure 2A~3
Figure 4A~4B
AI summary
A reciprocating engine has a piston which reciprocates in a cylinder due to explosion pressure produced in a combustion chamber (124) formed in the cylinder (110). The reciprocating engine includes: a liquid fuel supply unit (148) that supplies a liquid fuel to the combustion chamber; and a gas supply unit (a fuel gas supply unit (150) and an EGR supply unit (152)) that supplies, into the cylinder, fuel gas and EGR gas as exhaust gas which is produced from combustion in the combustion chamber and is discharged from the combustion chamber.