Interpretation of the Oscillating Signals of the Smart NOx Sensors Used in Urea Selective Catalyst Reduction Systems via Spectral Analysis

2013 ◽  
Vol 479-480 ◽  
pp. 719-723
Author(s):  
Chih Cheng Chou ◽  
Chia Jui Chiang ◽  
Yu Hsuan Su ◽  
Yong Yuan Ku
Keyword(s):  
Spectral Analysis ◽  
Catalytic Reduction ◽  
Ammonia Concentration ◽  
Nonlinear Characteristic ◽  
Sensor Signal ◽  
Reciprocating Motion ◽  
Selective Catalyst ◽  
Nox Sensor ◽  
Higher Harmonic ◽  
Catalyst Reduction

The oscillating signals of NOx sensor observed in urea selective catalytic reduction (SCR) tests are explained via spectral analysis. The NOx sensor built by NGK / Continental requires decoding following the SAE J1939 protocol and thus higher harmonic induced by the discretization is observed in the spectral analysis. The reciprocating motion of the urea pump induces fluctuation of the ammonia dosage, which combined with the nonlinear characteristic from ammonia dosage to NOx downstream SCR result in oscillating NOx sensor readings with different amplitude. The cross-sensitivity of the NOx sensor to ammonia concentration for higher-than-stoichiometric ammonia dosage also results in oscillating NOx sensor signal at lower frequencies.

Urea Mixing in Selective Catalytic Reduction Systems

2007 ◽  
Author(s):  
Fawaz Fadul ◽  
Amarnath Nelli ◽  
Ahmad Fakheri
Keyword(s):  
Gas Flow ◽  
Catalytic Reduction ◽  
Particulate Emissions ◽  
Exhaust Gas ◽  
Selective Catalyst ◽  
Emission Standards ◽  
Aqueous Mixture ◽  
Catalyst Reduction ◽  
The Impact ◽  
State Of Art

The tightening of emission standards mandates NOx and particulate emissions to be reduced by more than 90 percent by 2010 in Europe, United States, and Japan. Selective Catalyst Reduction (SCR) using Urea as the NOx reducing agent is fast becoming the preferred technology. This paper provides an overview of the state of art on the topic. It also examines the use of urea vapor instead of spraying an aqueous mixture and the impact of different spraying strategies on mixing. It is shown that by injecting urea vapor opposite to direction of the exhaust gas flow, better mixing with the exhaust and thus better conversion can be achieved as compared with injecting the urea vapor parallel to the gas. The increase in pressure drop does not appear significant.

Optimal design of selective catalyst reduction denitrification system using numerical simulation

2019 ◽  
Vol 231 ◽  
pp. 909-918 ◽  
Author(s):  
Xiang Gao ◽  
Ben Wang ◽  
Xudong Yuan ◽  
Siyuan Lei ◽  
Qinggong Qu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Optimal Design ◽  
Selective Catalyst ◽  
Catalyst Reduction

Impacts of Halogen Additions on Mercury Oxidation, in A Slipstream Selective Catalyst Reduction (SCR), Reactor When Burning Sub-Bituminous Coal

2008 ◽  
Vol 42 (1) ◽  
pp. 256-261 ◽  
Author(s):  
Yan Cao ◽  
Zhengyang Gao ◽  
Jiashun Zhu ◽  
Quanhai Wang ◽  
Yaji Huang ◽  
...  
Keyword(s):  
Bituminous Coal ◽  
Mercury Oxidation ◽  
Selective Catalyst ◽  
Catalyst Reduction

NUMERICAL STUDY ON OPTIMIZING MIXER PERFORMANCE IN SELECTIVE CATALYST REDUCTION SYSTEMS

2017 ◽  
Vol 20 (1) ◽  
pp. 141-168
Author(s):  
Changhee Lee ◽  
Hyunku Park ◽  
Geunjong Yoo ◽  
Hoonki Choi ◽  
Sangjoon An
Keyword(s):  
Numerical Study ◽  
Selective Catalyst ◽  
Catalyst Reduction

Robust Filtering for Ammonia Coverage Estimation in Diesel Engine Selective Catalytic Reduction Systems

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Hui Zhang ◽  
Junmin Wang ◽  
Yue-Yun Wang
Keyword(s):  
Diesel Engine ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Critical Role ◽  
Approximation Error ◽  
Ammonia Concentration ◽  
Nonlinear Observer ◽  
Coverage Ratio ◽  
Vehicle Simulation ◽  
Measurement Noises

In this paper, we investigate the nonlinear observer designs to estimate the ammonia coverage ratio in the diesel engine selective catalytic reduction (SCR) systems. The ammonia coverage ratio is an important variable due to its critical role in the SCR NOx conversion and the ammonia slip. However, the ammonia coverage ratio cannot be directly measured by onboard sensors. Therefore, it is necessary to develop effective observers to estimate the ammonia coverage ratio online. Based on a three-state SCR model, we develop two nonlinear observers. The first one only employs the dynamics of the ammonia concentration. The structure and the algorithm are simple. But it is sensitive to the measurement noises and the uncertainties in the system parameters. The second one is a discrete-time smooth variable structure estimator which is robust to the measurement noises, the approximation error, and the system uncertainties. Both estimators are implemented on a full-vehicle simulation of the FTP75 test cycle. The simulation results have verified the theoretical analysis.

Regeneration of commercial selective catalyst reduction catalysts deactivated by Pb and other inorganic elements

2016 ◽  
Vol 47 ◽  
pp. 100-108 ◽  
Author(s):  
Yanke Yu ◽  
Jinxiu Wang ◽  
Jinsheng Chen ◽  
Xinjiang He ◽  
Yujing Wang ◽  
...  
Keyword(s):  
Inorganic Elements ◽  
Selective Catalyst ◽  
Catalyst Reduction ◽  
Reduction Catalysts

Ammonia Slip Estimation Based on ASC Control-Oriented Modelling And OBD NOx Sensor Cross-Sensitivity Analysis

2021 ◽  
Author(s):  
Pedro Piqueras ◽  
Benjamín Pla ◽  
Enrique José Sanchis ◽  
André Aronis
Keyword(s):  
Internal Combustion Engines ◽  
Catalytic Reduction ◽  
Injection System ◽  
Diagnostic Tools ◽  
Exhaust Gas ◽  
Passenger Cars ◽  
Cross Sensitivity ◽  
Nox Sensor ◽  
Ammonia Slip ◽  
Aftertreatment Systems

Abstract The incoming emission regulations for internal combustion engines are gradually introducing new pollutant species, which requires greater complexity of the exhaust gas aftertreatment systems concerning layout, control and diagnostics. This is the case of ammonia, which is already regulated in heavy-duty vehicles and to be included in the emissions standards applied to passenger cars. The ammonia is injected into the exhaust gas through urea injections for NOx abatement in selective catalytic reduction (SCR) systems and can be also generated in other aftertreatment systems as three-way catalysts. However, ammonia slip may require removal on a dedicated catalyst called ammonia slip catalyst (ASC). The set consisting of the urea injection system, SCR and ASC requires control and on-board diagnostic tools to ensure high NOx conversion efficiency and minimization of the ammonia slip under real driving conditions. These tasks are based on the use of NOx sensors ZrO2 pumping cell-based, which present as a drawback high cross-sensitivity to ammonia. Consequently, the presence of this species can affect the measurement of NOx and compromise SCR-ASC control strategies. In the present work, a methodology to predict ammonia and NOx tailpipe emissions is proposed. For this purpose, a control-oriented ASC model was developed to use its ammonia slip prediction to determine the cross-sensitivity correction of the NOx sensor placed downstream of the ASC. The model is based on a simplified solution of the transport equations of the species involved in the main ASC reactions. The ammonia slip model was calibrated using steady- and quasi-steady-state tests performed in a Euro 6c diesel engine. Finally, the performance of the proposed methodology to predict NOx and ammonia emissions was evaluated against experimental data corresponding to Worldwide harmonized Light vehicles Test Cycles (WLTC) applying different urea dosing strategies.

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