scholarly journals A conceptual design and numerical analysis of the mixerless urea-SCR system

2021 ◽  
Author(s):  
Bartosz Kaźmierski ◽  
Krzysztof Górka ◽  
Łukasz Kapusta
Keyword(s):  
Catalytic Reduction ◽  
Film Deposition ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Flow Paths ◽  
Wall Film ◽  
Compact Design ◽  
Scr System ◽  
High Degree ◽  
Operating Points

In the present study, an innovative design of the urea-selective catalytic reduction (SCR) system without conventional mixing elements was developed. The aim was to obtain a high degree of urea decomposition, and uniform ammonia distribution at the inlet to the catalyst, while minimising the liquid film deposition and keeping the compact design. The concept of the design was based on creating high turbulences and elongating the flow paths of the droplets. The design was verified through a series of numerical simulations based on the Reynolds-averaged Navier–Stokes (RANS) approach and a discrete droplet model (DDM) spray representation. The analysis included various operating conditions as well as subcooled and superheated sprays. A uniform ammonia distribution was achieved regardless of the operating points and spray properties. Additionally, in the case of the flash-boiling injection, a further reduction of the wall film was observed.

scholarly journals The influence of the injection frequency on the urea selective catalytic reduction systems performance

2017 ◽  
Vol 170 (3) ◽  
pp. 73-77
Author(s):  
Rafał ROGÓŻ ◽  
Piotr JAWORSKI ◽  
Łukasz KAPUSTA ◽  
Andrzej TEODORCZYK
Keyword(s):  
Diesel Engine ◽  
System Performance ◽  
Catalytic Reduction ◽  
Film Formation ◽  
Flow Conditions ◽  
Wall Film ◽  
Injection Frequency ◽  
Crystallization Risk ◽  
Film Characteristics ◽  
Operating Points

This study presents the influence of the UWS injection frequency on a close coupled SCR systems performance. The investigation was performed with the CFD tool AVL Fire. In the paper the analysis of four different UWS injection frequencies in the three different operating points of diesel engine was shown. The assessments of the system performance was referred to the ammonia distribution at catalyst intake and wall film formation inside the investigated geometry, as these are considered as crucial in such a configuration. The results showed that injection frequency affects both factors on different level depending from the flow conditions. In addition, the wall film crystallization risk was discussed basing on the obtained wall film characteristics.

scholarly journals Thermal Decomposition of a Single AdBlue® Droplet Including Wall–Film Formation in Turbulent Cross-Flow in an SCR System

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2600
Author(s):  
Kaushal Nishad ◽  
Marcus Stein ◽  
Florian Ries ◽  
Viatcheslav Bykov ◽  
Ulrich Maas ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Relative Velocity ◽  
Pipe Wall ◽  
Film Formation ◽  
Droplet Diameter ◽  
Cross Flow ◽  
Operating Conditions ◽  
Wall Film ◽  
Wall Interaction ◽  
Scr System

The selective catalytic reduction (SCR) methodology is notably recognized as the widely applied strategy for NOX control in exhaust after-treatment technologies. In real SCR systems, complex unsteady turbulent multi-phase flow phenomena including poly-dispersed AdBlue® spray evolve with a wide ranging relative velocity between the droplet phase and carrier gas phase. This results from an AdBlue® spray that is injected into a mixing pipe which is cross-flowing by a hot exhaust gas. To reduce the complexity while gaining early information on the injected droplet size and velocity needed for a minimum deposition and optimal conversion, a single droplet with a specified diameter is addressed to mimic a spray featuring the same Sauter Mean Diameter. For that purpose, effects of turbulent hot cross-flow on thermal decomposition processes of a single AdBlue® droplet are numerically investigated. Thereby, a single AdBlue® droplet is injected into a hot cross-flowing stream within a mixing pipe in which it may experience phase change processes including interaction with the pipe wall along with liquid wall–film and possible solid deposit formation. First of all, the prediction capability of the multi-component evaporation model and thermal decomposition is evaluated against the detailed simulation results for standing droplet case for which experimental data is not available. Next, exploiting Large Eddy Simulation features the effect of hot turbulent co- and cross-flowing streams on the dynamic droplet characteristics and on the droplet/wall interaction is analyzed for various droplet diameters and operating conditions. This impact is highlighted in terms of droplet evaporation time, decomposition efficiency, droplet trajectories and wall–film formation. It turns out that smaller AdBlue® droplet diameter, higher gas temperature and relative velocity lead to shorter droplet life time as the droplet evaporates faster. Under such conditions, possible droplet/wall interaction processes on the pipe wall or at the entrance front of the monolith may be avoided. Since the ammonia (NH3) gas generated by urea decomposition is intended to reduce NOX emission in the SCR system, it is apparent for the prediction of high NOX removal performance that UWS injector system which allows to realize such operating conditions is favorable to support high conversion efficiency of urea into NH3.

scholarly journals A study on the high-efficiency mixer of the SCR system

2021 ◽  
Vol 22 ◽  
pp. 7
Author(s):  
Kai Lu ◽  
Dewen Liu ◽  
Yan Wu ◽  
Shusen Liu ◽  
Shuzhan Bai
Keyword(s):  
High Efficiency ◽  
Catalytic Reduction ◽  
Treatment System ◽  
Bench Test ◽  
Durability Test ◽  
Wall Film ◽  
Emission Regulation ◽  
Calculation Results ◽  
Analysis Engine ◽  
Scr System

A new mixer for a diesel engine after-treatment system is developed to meet the requirements of China VI emission regulation. As for the structure of the mixer, it is surrounded by spiral blades, and the center is staggered with small blades, which is conducive to the crushing of urea droplets and can make the droplets fully mixed with air, improve the conversion efficiency of nitrogen oxides (NOx) and reduce ammonia leakage. The numerical analysis, engine bench test, and vehicle road test were carried out on the after-treatment system equipped with the new mixer. The numerical calculation results show that the velocity uniformity index of the selective catalytic reduction (SCR) carrier can reach 0.98, as well as the ammonia uniformity can reach 0.95, meanwhile, the low wall film height shows excellent anti-crystallization properties. engine bench test results are consistent with numerical results. The crystallization status of the mixer after the vehicle durability test is acceptable and well performed.

Flow Modeling for a Simple Cycle Turbine Equipped With Selective Catalytic Reduction System for NOx Control

2005 ◽  
Author(s):  
Khoa Nguyen ◽  
Dani Fadda ◽  
Mark Buzanowski
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Velocity Profiles ◽  
Design Flow ◽  
Simple Cycle ◽  
Cfd Modeling ◽  
Compact Design ◽  
Calculated Velocity ◽  
Scr System ◽  
Flow Devices

A selective catalytic reduction (SCR) system, when designed for a simple cycle turbine, presents a significant calculation and modeling challenge due to its compact design and stringent performance requirements. In particular, uniform flue gas velocity profiles, required by environmental catalysts installed in the ductwork of this system, must be met. Custom flow devices optimized for the turbine. SCR system and ductwork are required. Cold flow and computational fluid dynamics (CFD) modeling are employed to design flow devices that provide adequate velocity profiles. The purpose of this paper is to present (1) steps taken to optimize the ductwork internals and (2) measured and calculated velocity profiles.

scholarly journals Monitoring of Basic Parameters for Selective Catalytic Reduction System Used in an Agricultural Tractor

2014 ◽  
Vol 62 (1) ◽  
pp. 225-230
Author(s):  
Antonín Skřivánek ◽  
Pavel Sedlák ◽  
Adam Polcar ◽  
Petr Dostál
Keyword(s):  
Selective Catalytic Reduction ◽  
Emission Reduction ◽  
Catalytic Reduction ◽  
Catalytic Converter ◽  
Operating Conditions ◽  
Measurement Results ◽  
Basic Parameters ◽  
Reduce Emissions ◽  
Scr System ◽  
Agricultural Tractor

Presented paper describes monitoring of basic parameters for selective catalytic reduction (SCR) system used in an agricultural tractor. SCR systems are used to reduce emissions of nitrogen oxides (NOx) produced by combustion of fuel. The usage of SCR catalytic converters entails certain disadvantages in the use of reducing agent and the necessity of suitable operating conditions to achieve optimum efficiency of the catalytic converter. This paper aims to predict consumption of AdBlue depending on the temperature of SCR catalytic converter, which reflects the engine load and monitoring the effectiveness of SCR catalytic converter when operating a tractor engine with a maximum dose of fuel. To fulfill those aims, the measurements have been performed on the Case Puma 185 CVX agricultural tractor. As the measurement results indicate, the lowest NOx emissions correspond to high consumption of AdBlue. Other studies imply that the catalytic converter operates at optimal operating temperature and with the highest efficiency of NOx emission reduction. The effectiveness of NOx emission reduction is thus affected not only by quantity of injected reagent but also by catalytic converter thermal load. Further measurement results indicate that the lowest amount of emissions of NOx (and the highest efficiency rate) is achieved by catalytic converter in a range in which the engine operates with the highest engine efficiency.

scholarly journals SCR Performance Evaluations in Relation to Experimental Parameters in a Marine Generator Engine

2019 ◽  
Vol 7 (3) ◽  
pp. 67 ◽  
Author(s):  
Dongkyu Kim ◽  
Changhee Lee
Keyword(s):  
Performance Test ◽  
Catalytic Reduction ◽  
Nox Reduction ◽  
Reduction Rate ◽  
Operating Conditions ◽  
Exhaust Pipe ◽  
Regulatory Requirements ◽  
International Maritime Organisation ◽  
Experimental Parameters ◽  
Scr System

Many researchers have conducted experiments on the position and nozzle conditions in the exhaust pipe of a stage/swirl mixer, as well as the injection position required to satisfy the International Maritime Organisation (IMO) regulations. In this study, an SCR (Selective catalytic reduction) system was designed through basic and detailed designs. The performance of the components was verified through a single-component performance test for the detailed design components, and the total nitrogen oxide (NOx) reduction efficiency was predicted using the proven system. Subsequently, the system was applied to an actual engine, and the performance was verified according to the engine operating conditions using the experimental variables. The NOx reduction rate and NH3 slip characteristics in relation to MCR (Maximum Continuous Rating) conditions using the optimised SCR system indicate that the NOx reduction rate exceeds 80% in all MCR conditions. Finally, the SCR system developed in this study proves that the performance of the SCR system satisfies the IMO regulatory requirements.

A basic study on a urea-selective catalytic reduction system for a medium-duty diesel engine

2005 ◽  
Vol 6 (1) ◽  
pp. 11-19 ◽  
Author(s):  
J Kusaka ◽  
M Sueoka ◽  
K Takada ◽  
Y Ohga ◽  
T Nagasaki ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Direct Injection ◽  
Chemical Species ◽  
Operating Conditions ◽  
Basic Study ◽  
Catalyst Temperature ◽  
Scr System ◽  
Load Conditions

NOx conversion performance of a urea-selective catalytic reduction (SCR) system comprising V2O5/TiO2 catalyst under steady state operating conditions of an 8-litre, common-rail turbo direct injection (TDI) diesel engine was investigated. It was shown that the urea-SCR system achieves 70–90 per cent NOx conversion under medium and high load conditions at 1440 r/min and that NOx conversion is low under low load conditions because of the low catalyst temperatures and the NO/NO2 ratio being higher than unity. It was also shown that NOx conversion exceeds 90 per cent when the catalyst temperature is higher than 530 K. To investigate the details of the chemistry and thermofluid dynamics within the urea-SCR system, a computational fluid dynamics (CFD) code that incorporates detailed surface chemistry was developed based on the modified subroutines of CHEMKIN-II. The spatial variations of chemical species including NO and NH3 in a thin catalyst channel was calculated using the model. The calculated result of NO conversion showed relatively good agreement with experimental results.

Flow Field Unsteadiness in the Tip Region of a Transonic Compressor Rotor

1997 ◽  
Vol 119 (1) ◽  
pp. 122-128 ◽  
Author(s):  
S. L. Puterbaugh ◽  
W. W. Copenhaver
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vortex Interaction ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Operating Points

An experimental investigation concerning tip flow field unsteadiness was performed for a high-performance, state-of-the-art transonic compressor rotor. Casing-mounted high frequency response pressure transducers were used to indicate both the ensemble averaged and time varying flow structure present in the tip region of the rotor at four different operating points at design speed. The ensemble averaged information revealed the shock structure as it evolved from a dual shock system at open throttle to an attached shock at peak efficiency to a detached orientation at near stall. Steady three-dimensional Navier Stokes analysis reveals the dominant flow structures in the tip region in support of the ensemble averaged measurements. A tip leakage vortex is evident at all operating points as regions of low static pressure and appears in the same location as the vortex found in the numerical solution. An unsteadiness parameter was calculated to quantify the unsteadiness in the tip cascade plane. In general, regions of peak unsteadiness appear near shocks and in the area interpreted as the shock-tip leakage vortex interaction. Local peaks of unsteadiness appear in mid-passage downstream of the shock-vortex interaction. Flow field features not evident in the ensemble averaged data are examined via a Navier-Stokes solution obtained at the near stall operating point.

Improving Gerotor Pump Performance Trough Design, Modeling and Simulation

2021 ◽  
Author(s):  
Lozica Ivanović ◽  
Miloš Matejić
Keyword(s):  
Low Noise ◽  
Operating Conditions ◽  
Design Parameters ◽  
Pump Efficiency ◽  
Hydraulic Systems ◽  
Wear Process ◽  
Gerotor Pump ◽  
Gerotor Pumps ◽  
Negative Effect ◽  
Compact Design

Gerotor pumps are well known by a compact design, simple structure and low noise level, which makes them suitable for use in the automotive industry, and especially in hydraulic systems for engine lubrication. One of the main disadvantages of gerotor pumps is the inability to adjust to wear, which significantly reduces the pump efficiency. In order to mitigate the negative effect of the inevitable wear process, this paper presents a methodology for determining the optimal combination of trochoid gears design parameters for a defined aspect. An appropriate mathematical model has been developed to analyze the effect of changes in gear design parameters in relation to maximum contact stresses, pressure changes in gerotor pump chambers and wear rate proportional factor (WRPF). Verification of the developed models was performed by realizing physical pairs of gears and laboratory experiments with simulation of pump operating conditions. The results and conclusions presented in this paper, with an emphasis on the actual work processes, bring very important perspectives for the gerotor pumps design with improved performance.

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