SCR Injection Plate Apertures for Exhaust Mixing
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Solution Overview
Problem
Current SCR systems face challenges in achieving ideal mixing of ammonia with exhaust gases due to stringent package constraints, which affect the performance of urea injection systems, and existing flow mixers struggle to evaluate performance experimentally.
Innovation Solution
A selective catalytic reduction (SCR) injection system that includes a plate separating the entrance and egress sections of an exhaust pipe, with a reductant-introducing conduit having apertures that direct exhaust gases through the conduit, enhancing flow impingement, turbulence, and bulk rotation to improve droplet atomization and evaporation, and featuring a perforated conduit and 'Z' shaped plate to optimize gas flow and pressure reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a flow mixer or atomizer is implemented right after the urea injector to improve mixing, then mixing performance is improved, but device complexity increases and evaluation difficulty increases
Solution Approach 1:
The patent extracts the flow mixing function from complex dedicated mixers and atomizers, and instead uses the exhaust pipe geometry itself (entrance and egress sections) to achieve mixing through pure flow dynamics, eliminating the need for additional mixing devices
Solution Approach 2:
The exhaust pipe structure performs the mixing function automatically through its design features (entrance section, egress section, and flow path) without requiring external mixing devices or complex evaluation systems
2Manufacturing precision
If a flow mixer or atomizer is implemented right after the urea injector to improve mixing, then mixing performance is improved, but difficulty of detecting and measuring increases
Solution Approach 1:
The system uses the exhaust pipe's inherent flow characteristics to achieve mixing, making the performance evaluation straightforward by simply measuring the flow conditions in the egress section without complex experimental setups
3Manufacturing precision
If direct flow impingement is used to improve atomization and evaporation, then mixing performance is improved, but device complexity increases
Solution Approach 1:
The patent removes the need for complex atomization devices by using the exhaust pipe flow itself to create direct impingement between the urea spray and exhaust gases, achieving atomization through pure flow mechanics
Solution Approach 2:
The exhaust pipe geometry automatically creates the optimal flow impingement conditions for atomization and evaporation without requiring additional devices or complex configuration
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 significantly improves flow mixing performance by increasing turbulent intensity and evaporation, enhancing ammonia distribution and NOx reduction efficiency, while allowing for experimental evaluation of mixing performance.
Implementation Method 1
increases flow impingement: help for droplet atomization and evaporation
Implementation Method 2
increases turbulent intensity; help for evaporation and flow mixing
Implementation Method 3
increase bulk rotation help flow mixing
Implementation Method 4
The heat in the exhaust gas causes the aqueous urea solution to decompose into ammonia and hydro-cyanic acid (HNCO)
Implementation Method 5
Urea solution will atomize and dissolve as ammonia and carbon dioxide when mixes with exhaust gas of certain temperature
Implementation Method 6
Selective catalytic reduction (SCR) catalyst injection systems
Implementation Method 7
4NH3+4NO+O2→4N2+6H2O
Data Source
AI summary
A Selective Catalytic Reduction (SCR) injection system for mixing reductant with exhaust gasses. The system includes a plate disposed between walls of an entrance portion and an egress section of the exhaust pipe. The plate intercepts exhaust gasses entering the entrance section of the exhaust pipe and directs such exhaust gasses through apertures in a wall of a reductant-introducing conduit. The conduit has an outlet disposed in the egress section of the exhaust pipe. The wherein dimensions of the apertures in the wall and dimensions in the outlet of the conduit being selected to increase the velocity of the exhaust leaving the outlet of the conduit into the egress section of the exhaust pipe relative to the velocity of the exhaust gases in the entrance section.