Internal Combustion Engine Exhaust Fuel Injection for SCR Thermal Management
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Solution Overview
Problem
Multistage expansion internal combustion engines face challenges in achieving improved energy output and emission characteristics, particularly in reducing nitrogen oxides (NOx) during low-load operations, where Selective Catalytic Reduction (SCR) devices may not operate effectively due to temperature issues.
Innovation Solution
A method is introduced that involves repeated fuel injections, where a second fuel injection is provided into the exhaust gases upstream of a pre-expander exhaust treatment device, allowing reactions with stored NOx to produce nitrogen, and subsequent ammonia production to reduce NOx levels, which is then converted to nitrogen in a post-expander SCR catalyst, thereby enhancing power output and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multistage expansion is implemented to increase energy output, then power output is improved, but exhaust temperature drops below SCR device operating range
Solution Approach 1:
Fuel is injected into the exhaust gases before they enter the expander, allowing combustion to occur in advance. This preliminary combustion action heats the exhaust gases to appropriate temperatures for SCR device operation while still enabling subsequent expansion for power generation.
Solution Approach 2:
The exhaust gases, which would otherwise be too cool for SCR operation after multistage expansion, are utilized as a medium for secondary combustion. The 'harm' of low temperature is converted into a benefit by injecting fuel that combusts in the exhaust, generating both heat for SCR operation and additional energy for expansion work.
2Object-generated harmful factors
If SCR device is used for NOx reduction, then emission characteristics are improved, but system complexity increases due to dedicated urea dosing system
Solution Approach 1:
The exhaust system serves multiple functions: it guides exhaust gases for expansion work, provides a combustion chamber for secondary fuel injection, and delivers heated gases to the SCR device. This multi-functionality eliminates the need for separate urea dosing systems, reducing overall system complexity while maintaining NOx reduction capability.
Solution Approach 2:
The exhaust system itself performs the heating function traditionally requiring separate components. By utilizing fuel injection and combustion within the exhaust stream, the system self-generates the necessary thermal energy for SCR operation, eliminating dependence on external urea dosing infrastructure.
3Power
If second fuel injection is provided into exhaust gases upstream of pre-expander exhaust treatment device, then power output increases through additional expansion work, but fuel consumption increases
Solution Approach 1:
Fuel that would otherwise be wasted or burned inefficiently in the exhaust stream is converted into a useful energy source. The secondary fuel injection transforms what would be lost energy in the exhaust into productive work through combustion-driven expansion, improving overall fuel utilization efficiency.
Solution Approach 2:
The system changes the state of exhaust gases from a waste product to an active energy carrier by introducing fuel that combusts in the exhaust stream. This parameter change transforms the thermal and chemical properties of the exhaust, enabling it to perform additional expansion work and generate power.
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 approach increases power output by converting heat from the exhaust treatment process into mechanical energy and minimizes the fuel cost for NOx reduction, while simplifying the exhaust treatment process and reducing the need for a dedicated urea dosing system, thereby improving engine efficiency and emission reduction.
Implementation Method 1
a reaction of fuel from the second fuel second fuel injection with air in the received exhaust gases and at least a portion of the stored nitrogen oxides (NOx) to produce nitrogen (N2)
Implementation Method 2
allowing a second expansion of the received exhaust gases in the expander
Data Source
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AI summary
The invention provides an internal combustion engine system (1) comprising a combustor (3) arranged to repetitively receive air and fuel, combust the received air and fuel, and expand the combusted air and fuel, an expander (6) comprising a cylinder (602) and a piston (601) arranged to reciprocate in the cylinder, the piston (601) being connected to a crankshaft (2) of the engine system, and an exhaust guide (9) arranged to guide exhaust gases from the combustor (3) to the expander (6), characterized in that the system is arranged to provide an injection of fuel into the exhaust guide (9) and/or arranged to provide an injection of fuel into the combustor after a combustion in the combustor (3) and before a reception of air and fuel in the combustor for a subsequent combustion.