DOC Preheating for Diesel Cold Start Emission Control
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Solution Overview
Problem
Cold start conditions of diesel engines lead to increased pollutant emissions due to the slow activation of exhaust gas aftertreatment systems, which requires higher engine loads and thus more fuel, contradicting the goal of reduced emissions.
Innovation Solution
A method involving pre-heating the Diesel Oxygen Catalyst (DOC) using an electric device with the fuel supply shut off, optimizing NOx emissions by controlling the engine towards a predetermined limit value, and using EGR to minimize combustion temperature, along with a bypass system for temperature regulation in the exhaust gas aftertreatment system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the engine load is increased during cold start to reduce pollution, then emissions are reduced, but fuel consumption increases
Solution Approach 1:
The DOC is pre-heated before the engine starts operating under normal conditions. This preliminary heating action ensures that the catalyst reaches its active temperature range before the engine begins to emit pollutants, allowing the EATS to be effective from the start without requiring increased engine load.
Solution Approach 2:
An electric heating device acts as an intermediary to heat the DOC during cold start conditions. This intermediary device enables the catalyst to reach operating temperature without requiring the engine itself to operate at high load, thus resolving the contradiction between reducing emissions and limiting fuel consumption.
2Temperature
If the engine load is increased during cold start to activate the EATS, then the aftertreatment system reaches operating temperature, but the time required for activation increases
Solution Approach 1:
The DOC is heated in advance before the engine starts under normal operating conditions. This preliminary action ensures that the catalyst is already at or near its active temperature when the engine begins to run, significantly reducing the activation time during cold start without requiring excessive engine load.
Solution Approach 2:
The electric heating device replaces the conventional mechanical approach of using high engine load to heat the EATS. This substitution allows for more efficient and faster heating of the DOC, reducing the time required to reach operating temperature while minimizing fuel consumption.
3Use of energy by moving object
If electric heating is used to pre-heat the DOC, then fuel consumption is reduced, but device complexity increases
Solution Approach 1:
The electric heating device is integrated into the existing engine starting system, allowing it to serve multiple functions: pre-heating the DOC during cold start, and potentially assisting with normal engine operation. This multi-functionality justifies the added complexity by providing benefits beyond just cold start heating.
Solution Approach 2:
The heating system is designed to automatically activate based on engine operating conditions (cold start detection), eliminating the need for manual intervention or complex control mechanisms. The system self-regulates by detecting when the DOC needs heating and activating the electric heater accordingly, simplifying the overall control 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
This approach reduces fuel consumption and emissions during cold starts by efficiently heating the DOC and controlling NOx emissions, allowing the engine to reach operating temperatures while meeting pollution requirements without increasing fuel usage.
Implementation Method 1
heating the DOC prior to cold starting said internal combustion engine by cranking the internal combustion engine with an electric device with the fuel supply to said internal combustion engine shut off
Implementation Method 2
Selective Catalytic Reduction (SCR) catalysts, in which NOx is continuously removed through active injection of a reductant, such as urea, into the exhaust gas mixture entering the catalyst
Implementation Method 3
using at least 50% EGR
Data Source
AI summary
The present invention relates to a method for achieving reduced emissions at cold start of an internal combustion engine having an exhaust gas after treatment system comprising at least one Diesel Oxygen Catalyst (DOC), at least one Diesel Particulate Filter (DPF) and a Selective Catalytic Reduction (SCR) unit, comprising the steps of: heating the DOC prior to cold starting said internal combustion engine, starting and controlling the internal combustion engine towards low NOx emission when said DOC has reached a predetermined temperature, optimizing the fuel consumption at a given total emission level when said DPF and SCR has reached a predetermined temperature.