Lean Exhaust Aftertreatment with Oxygen Removal
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Solution Overview
Problem
Compression ignition engines face challenges in reducing Nitrogen Oxides (NOx), Carbon Monoxide (CO), Hydrocarbon (HC), and Particulate Matter (PM) emissions due to their lean combustion nature, which complicates the use of aftertreatment devices like DPFs and SCR systems, leading to fuel penalties and inefficiencies.
Innovation Solution
A system that removes oxygen from the exhaust gas using a fuel reactor, followed by an oxidation catalyst to reduce NOx, CO, and HC, with energy recovery through turbines and heat exchangers to minimize fuel penalty, and includes a DPF for PM removal, utilizing an electrical heater for low-temperature regeneration and an oxygen sorption device to further lower energy costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a high efficiency particulate filter (DPF) is used to remove PM, then PM emission is reduced, but fuel penalty increases due to periodic regeneration requiring heating to 500-600°C
Solution Approach 1:
The invention changes the temperature parameter of exhaust gas by injecting fuel into the DPF to generate heat locally, enabling regeneration at lower overall exhaust temperatures and reducing the fuel penalty associated with periodic regeneration
Solution Approach 2:
The DPF uses a portion of the exhaust gas itself as the heating source for regeneration, with fuel injection creating a self-sustaining combustion process within the filter that eliminates the need for external heating systems
2Object-generated harmful factors
If SCR technology is used to remove NOx from lean exhaust gas, then NOx conversion efficiency is maximized, but fuel penalty increases due to urea consumption and ammonia generation requiring extra heat energy
Solution Approach 1:
The invention extracts oxygen from the lean exhaust gas using a fuel reactor before the oxidation catalyst, creating a rich environment that enables NOx reduction without requiring SCR technology and its associated urea consumption and ammonia generation processes
Solution Approach 2:
The invention converts the harmful lean combustion nature of CI engines into a benefit by using a fuel reactor to deliberately create rich conditions in the exhaust stream, enabling the oxidation catalyst to reduce NOx efficiently without requiring external reducing agents
3Object-generated harmful factors
If a selective catalyst with high selectivity is used to reduce NOx, then NOx conversion efficiency improves, but device volume must be increased to compensate for poor conversion efficiency
Solution Approach 1:
The invention changes the oxygen concentration parameter in the exhaust gas by using a fuel reactor to remove oxygen, creating optimal conditions for the oxidation catalyst to achieve high NOx conversion efficiency in a compact volume
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
Effectively reduces NOx and other pollutants in lean exhaust gases without significant fuel economy sacrifice, achieving high deNOx efficiency and minimizing fuel penalty by recovering heat energy and controlling engine backpressure, while maintaining efficient PM filtration.
Implementation Method 1
a fuel reactor in which hydrocarbon fuel provided in in-cylinder late injection or injected with a dedicated doser reacts with oxygen
Implementation Method 2
an oxidation catalyst to reduce NOx, CO, and HC
Implementation Method 3
energy recovery through turbines
Implementation Method 4
energy recovery through heat exchangers
Implementation Method 5
an electrical heater for low-temperature regeneration
Implementation Method 6
an oxygen sorption device to further lower energy costs
Data Source
AI summary
An aftertreatment device for reducing NOx, PM, HC, and CO generated by a compression-ignition engine. In this device, lean exhaust air generated in the engine is enriched using a reactor together with an oxygen sorption device according to a target deNOx efficiency value, and heat energy is recovered. The enriched exhaust gas then passes through an oxidation catalyst, where NOx is reduced with CO and HC. PM in the exhaust gas is further trapped in a DPF. To lower energy cost, an heat exchanger is used for more effectively heating the DPF during regeneration, and an exhaust gas compressor positioned upstream from the DPF is employed to control engine back pressure. When exhaust gas temperature is low, to regenerate the DPF with minimum energy consumption, an electrical heater is used to heat dosing fuel before it is mixed with exhaust gas, and a regeneration heating process is then jump-started.