Ammonia Engine Exhaust Purification via Inflow Ratio Control
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Solution Overview
Problem
Internal combustion engines fueled by ammonia face challenges in efficiently removing nitrogen oxides (NOX) from exhaust while maintaining high heat efficiency and reducing fuel consumption, particularly when using three-way catalysts, which require expensive precious metals and have lower NOX removal rates during lean combustion.
Innovation Solution
An internal combustion engine equipped with an ammonia feeder and an NOX selective reduction catalyst that adjusts the ammonia to NOX concentration ratio in the exhaust to maximize NOX and ammonia removal rates, using a cracker to produce hydrogen and an oxidation catalyst to optimize air-fuel ratios and ignition timing for enhanced purification performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a three-way catalyst is used in the exhaust passage to remove NOX, then the NOX removal rate is improved, but the system requires expensive precious metals and precise air-fuel ratio control
Solution Approach 1:
The patent changes the operating parameters by allowing lean combustion (air-fuel ratio greater than stoichiometric) instead of requiring precise stoichiometric control. This is achieved by introducing a reducing agent (ammonia or hydrocarbon) into the exhaust passage, which enables effective NOX reduction under lean combustion conditions, thereby eliminating the need for precise air-fuel ratio control while maintaining high NOX removal rates
Solution Approach 2:
The patent introduces a reducing agent (ammonia or hydrocarbon) as an intermediary substance that facilitates NOX reduction. This reducing agent acts as a mediator between the exhaust gases and the catalyst, enabling the three-way catalyst to function effectively under lean combustion conditions without requiring precise air-fuel ratio control, thus resolving the contradiction between NOX removal efficiency and control precision requirements
2Use of energy by moving object
If lean combustion is used to improve heat efficiency and reduce fuel consumption, then the heat efficiency is improved, but the NOX removal rate of the three-way catalyst becomes lower
Solution Approach 1:
The patent introduces a reducing agent (ammonia or hydrocarbon) as an intermediary that enables the three-way catalyst to maintain high NOX removal rates under lean combustion conditions. The reducing agent compensates for the reduced catalytic activity under lean conditions, allowing the engine to operate efficiently with improved heat efficiency while maintaining effective NOX purification
Solution Approach 2:
The patent changes the chemical composition parameters of the exhaust gas by adding a reducing agent. This parameter change allows the system to operate under lean combustion conditions (improved heat efficiency) while maintaining high NOX removal rates, as the reducing agent provides the necessary chemical environment for effective catalytic reduction
3Object-affected harmful factors
If the air-fuel ratio is controlled at stoichiometric ratio to maximize NOX removal, then the NOX removal rate is improved, but the fuel consumption increases
Solution Approach 1:
The patent changes the air-fuel ratio parameter from stoichiometric to lean (greater than stoichiometric), which improves fuel efficiency and reduces fuel consumption. The addition of a reducing agent compensates for the reduced NOX removal capability of lean combustion, allowing the system to maintain high NOX removal rates while operating at more fuel-efficient lean conditions
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 system achieves high NOX and ammonia removal rates without relying on expensive precious metals, improving heat efficiency and reducing fuel consumption by maintaining optimal air-fuel ratios and adjusting the ammonia to NOX concentration ratio within a controlled range.
Implementation Method 1
an NOX selective reduction catalyst which is arranged in an engine exhaust passage and which selectively reduces NOX by the feed of a reducing agent comprised of ammonia
Implementation Method 2
the catalyst of the cracker may have the function of oxidizing ammonia and may be formed so that ammonia and air are fed so that the ammonia is cracked and hydrogen is produced and so that ammonia is oxidized and the heat required for the cracking reaction is produced
Implementation Method 3
the ammonia gas which is led into the heat exchange pipe is cracked into hydrogen and nitrogen by an endothermic reaction which absorbs the heat of the exhaust gas
Implementation Method 4
the exhaust gas of the combustion chambers is used to heat a heat exchange pipe in the ammonia cracking reactor
Data Source
AI summary
The internal combustion engine has an ammonia feeder which feeds ammonia to a combustion chamber and an NOX selective reduction catalyst which is arranged in an engine exhaust passage. The removal rate of the NOX selective reduction catalyst depends on a ratio of concentration of ammonia to NOX of the exhaust which flows into the NOX selective reduction catalyst, that is, a ratio of concentration of inflow. A high removal rate range where the NOX removal rate in the NOX selective reduction catalyst becomes substantially maximum and, furthermore, the ammonia removal rate becomes substantially maximum, is set in advance. The internal combustion engine is controlled so that the ratio of concentration of inflow becomes inside the high removal rate range.