Large Two-Stroke Marine Diesel Engine Operation with a High-Pressure SCR System in Heavy Weather Conditions

2020 ◽  
pp. 1-15 ◽  
Author(s):  
Michael I. Foteinos ◽  
George I. Christofilis ◽  
Nikolaos P. Kyrtatos
Keyword(s):  
High Pressure ◽  
Weather Conditions ◽  
Irregular Waves ◽  
Ship Motions ◽  
Exhaust Gas ◽  
Time Varying ◽  
Gas Temperature ◽  
Marine Diesel ◽  
Exhaust Gas Temperature ◽  
Scr System

The transient performance of a direct-drive large two-stroke marine diesel engine, installed in a vessel operating in a seaway with heavy weather, is investigated via simulation. The main engine of the ship is equipped with a selective catalytic reduction (SCR) after treatment system for compliance with the latest International Maritime Organization (IMO) rules for NOx reduction, IMO Tier III. Because of limitations of exhaust gas temperature at the inlet of SCR systems and the low temperature exhaust gases produced by marine diesel engines, in marine applications, the SCR system is installed on the high-pressure side of the turbine. When a ship sails in heavy weather, it experiences a resistance increase, wave-induced motions, and a time-varying flow field in the propeller, induced by ship motions. This results in a fluctuation of the propeller torque demand and, thus, a fluctuation in engine power and exhaust gas temperature, which can affect engine and SCR performance. To investigate this phenomenon and take into account the engine–propeller interaction, the entire propulsion plant was modeled, namely, the slow-speed diesel propulsion engine, the high-pressure SCR system, the directly driven propeller, and the ship's hull. To simulate the transient propeller torque demand, a propeller model was used, and torque variations due to ship motions were taken into account. Ship motions in waves and wave-added resistance were calculated for regular and irregular waves using a 3D panel code. The coupled model was validated against available measured data from a shipboard propulsion system in good weather conditions. The model was then used to simulate the behavior of a Tier III marine propulsion plant during acceleration from low to medium load, in the presence of regular and irregular waves. The effect of the time-varying propeller demand on the engine and the SCR system was investigated. 1. Introduction The effect of waves on a marine propulsion system is a complex phenomenon involving interactions between different subsystems of the propulsion plant, i.e., the prime mover, the propeller, and the ship's hull. Ships sailing in heavy weather conditions experience a resistance increase, wave-induced motions, and a time-varying flow field in the propeller. This leads to a fluctuation of the propeller torque demand which results in a fluctuation in engine-produced power and exhaust gas temperature.

Response of a direct-drive large marine two-stroke engine coupled to a selective catalytic reduction exhaust aftertreatment system when operating in waves

2020 ◽  
Vol 234 (3) ◽  
pp. 651-667
Author(s):  
Michael I Foteinos ◽  
George I Christofilis ◽  
Nikolaos P Kyrtatos
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Weather Conditions ◽  
Ship Motions ◽  
Gas Temperature ◽  
Regular Waves ◽  
Selective Catalytic Reduction System ◽  
Reduction System ◽  
Marine Diesel ◽  
Exhaust Gas Temperature

Large two-stroke marine diesel engines are used as the prime mover in the majority of ocean going commercial vessels and are currently facing new stringent NOx emission reductions. Selective catalytic reduction is an aftertreatment technology which is able to reduce emitted NOx at allowable levels. In most marine applications, the selective catalytic reduction system is placed on the high pressure side of the turbine, due to limitations at the exhaust gas temperature at the inlet of selective catalytic reduction system. In this article, the operation of a large two-stroke marine diesel with a selective catalytic reduction aftertreatment system, is investigated in heavy weather conditions. Operation of a vessel in heavy weather results in increased ship resistance, wave-induced ship motions, and a highly varying flow field in the propeller due to ship motions. This results in a fluctuation of propeller demanded torque and hence a fluctuation in engine load and exhaust gas temperature which may affect engine and selective catalytic reduction performance significantly. To investigate this phenomenon and taking into account the engine–propeller interaction, the entire propulsion system was modeled, namely the propulsion engine, the high pressure selective catalytic reduction system, the directly driven propeller, and the ship’s hull. A propeller model was employed to simulate the transient propeller torque demand and torque fluctuations due to ship motions. A three-dimensional six degrees of freedom panel code was used to calculate ship motions and wave added resistance in regular waves. The coupled model of the marine propulsion plant was validated against available measured data from a ship-board propulsion system on good weather conditions. The model was then used to simulate the behavior of the system during transient loading conditions in the presence of regular waves.

scholarly journals Ammonium-Salt Formation and Catalyst Deactivation in the SCR System for a Marine Diesel Engine

Catalysts ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 21 ◽  
Author(s):  
Yuanqing Zhu ◽  
Qichen Hou ◽  
Majed Shreka ◽  
Lu Yuan ◽  
Song Zhou ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Decomposition Reaction ◽  
Marine Diesel Engine ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Scr Catalyst ◽  
Marine Diesel ◽  
Fast Scr ◽  
Exhaust Gas Temperature ◽  
Scr System

Due to the low temperature and complex composition of the exhaust gas of the marine diesel engine, the working requirements of the selective catalytic reduction (SCR) catalyst cannot be met directly. Moreover, ammonium sulfate, ammonium nitrate, and other ammonium deposits are formed at low temperatures, which block the surface or the pore channels of the SCR catalyst, thereby resulting in its reduction or even its loss of activity. Considering the difficulty of the marine diesel engine bench test and the limitation of the catalyst sample test, a one-dimensional simulation model of the SCR system was built in this paper. In addition, the deactivation reaction process of the ammonium salt in the SCR system and its influencing factors were studied. Based on the gas phase and the surface reaction kinetics, the models of the urea decomposition, the surface denitrification, the nitrate deactivation, and the sulfate deactivation were both constructed and verified in terms of accuracy. Moreover, the formation/decomposition reaction pathway and the catalytic deactivation of ammonium nitrate and ammonium bisulfate, as well as the composition concentration and the exhaust gas temperature range were correspondingly clarified. The results showed that within a certain range, the increase of the NO2/NOx ratio was conducive to the fast SCR reaction and the NH4NO3 formation’s reaction. Increasing the exhaust gas temperature also raised the NO2/NOx ratio, which was beneficial to both the fast SCR reaction and the NH4NO3 decomposition reaction, respectively. Furthermore, the influence of the SO2 concentration on the denitrification efficiency decreased with the increase of the exhaust gas temperature because of increasing SCR reaction rate and reversibility of ammonia sulfate formation, and when the temperature of the exhaust gas was higher than 350 °C, the activity of the catalyst was almost unaffected by ammonia sulfate.

Modeling and simulation of marine SCR system based on Modelica

2022 ◽  
pp. 146808742110722
Author(s):  
Jie Shi ◽  
Yuanqing Zhu ◽  
Hui Peng ◽  
Haoyu Yan ◽  
Tinghui Li ◽  
...  
Keyword(s):  
Flow Rate ◽  
Great Influence ◽  
Slip Rate ◽  
Urea Solution ◽  
Bench Test ◽  
Stoichiometric Ratio ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Exhaust Gas Temperature ◽  
Scr System

With the increasing awareness of global marine environmental protection, the emission of ship exhaust pollutants is strictly restricted. Selective catalytic reduction (SCR) technology is the mainstream technology to reduce ship NOx emission and make it meet IMO tier III regulations. A SCR reaction kinetic model based on Modelica language was established by Dymola software to predict the denitration efficiency, ammonia slip rate, and other parameters of SCR system. According to the functional structure of marine SCR system, the SCR system model is divided into urea injection module, mixer module, and SCR reactor module. The model was verified by SCR system bench test of WD10 diesel engine, which proved that the model can preferably reflect the actual situation. Using the established model, the effects of temperature, flow rate, NH3/NOx Stoichiometric Ratio (NSR), and cell density on the denitration performance of SCR system were analyzed. The results showed that the exhaust gas temperature and NSR have a great influence on the denitration efficiency. The injection amount of urea solution in marine SCR system should be based on the exhaust gas temperature and exhaust flow rate.

Compound Control Strategy Based on Active Disturbance Rejection for Selected Catalytic Reduction systems

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Jinbiao Ning ◽  
Fengjun Yan
Keyword(s):  
Control Strategy ◽  
Disturbance Rejection ◽  
Catalytic Reduction ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Model Uncertainties ◽  
Compound Control ◽  
Active Disturbance Rejection ◽  
Exhaust Gas Temperature ◽  
Scr System

Urea-based selected catalytic reduction (SCR) systems are effective ways in diesel engine after-treatment systems to meet increasingly stringent emission regulations. To achieve high NOx reduction efficiency and low NH3 slip, the control of the SCR system becomes more challenging, especially in transient operating conditions with model uncertainties. To effectively address this issue, this paper proposed a compound control strategy with a switching mechanism between an active disturbance rejection (ADR) controller and a zero-input controller. The ADR controller estimates and rejects the total (internal and external) disturbances from the SCR system when the exhaust gas temperature is high and its variation is small. The zero-input controller is used to lower ammonia surface coverage ratio to avoid high ammonia slip when exhaust gas temperature suddenly rises. The proposed control strategy is validated through a high-fidelity GT-Power simulation for a light-duty diesel engine over steady states and federal test procedure (FTP-75) test cycle. Its effectiveness is demonstrated especially in rapidly transient conditions with model uncertainties.

scholarly journals A Three-Zone Scavenging Model for Large Two-Stroke Uniflow Marine Engines Using Results from CFD Scavenging Simulations

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1719 ◽  
Author(s):  
Michael I. Foteinos ◽  
Alexandros Papazoglou ◽  
Nikolaos P. Kyrtatos ◽  
Anastassios Stamatelos ◽  
Olympia Zogou ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Diesel Engines ◽  
Zone Model ◽  
Exhaust Gas ◽  
Mixing Zone ◽  
Gas Temperature ◽  
Cfd Simulations ◽  
Mixing Coefficients ◽  
Marine Diesel ◽  
Exhaust Gas Temperature

The introduction of modern aftertreatment systems in marine diesel engines call for accurate prediction of exhaust gas temperature, since it significantly affects the performance of the aftertreatment system. The scavenging process establishes the initial conditions for combustion, directly affecting exhaust gas temperature, fuel economy, and emissions. In this paper, a semi-empirical zero-dimensional three zone scavenging model applicable to two-stroke uniflow scavenged diesel engines is updated using the results of CFD (computational fluid dynamics) simulations. In this 0-D model, the engine cylinders are divided in three zones (thermodynamic control volumes) namely, the pure air zone, mixing zone, and pure exhaust gas zone. The entrainment of air and exhaust gas in the mixing zone is specified by time varying mixing coefficients. The mixing coefficients were updated using results from CFD simulations based on the geometry of a modern 50 cm bore large two-stroke marine diesel engine. This increased the model’s accuracy by taking into account 2-D fluid dynamics phenomena in the cylinder ports and exhaust valve. Thus, the effect of engine load, inlet port swirl angle and partial covering of inlet ports on engine scavenging were investigated. The three-zone model was then updated and the findings of CFD simulations were reflected accordingly in the updated mixing coefficients of the scavenging model.

Aeroengine Exhaust Gas Temperature Prediction Using Process Neural Network with Time-Varying Threshold Functions

2013 ◽  
Vol 423-426 ◽  
pp. 2341-2346
Author(s):  
Gang Ding ◽  
Xiong Wei Wang ◽  
Da Lei
Keyword(s):  
Neural Network ◽  
Neural Network Model ◽  
Orthogonal Basis ◽  
Basis Functions ◽  
Exhaust Gas ◽  
Time Varying ◽  
Gas Temperature ◽  
Threshold Functions ◽  
Exhaust Gas Temperature ◽  
Threshold Process

To predict the aeroengine exhaust gas temperature (EGT) more precisely, a process neuron with time-varying threshold function is proposed in this paper, and then the time-varying threshold process neural network model comprised of the presented process neurons is used for EGT prediction. By introducing a group of appropriate orthogonal basis functions, the input functions, the weight functions and the threshold functions of the time-varying threshold process neural network can be expanded as linear combinations of the given orthogonal basis functions, thus to eliminate the integration operation, then to simplify the time aggregation operation. The corresponding learning algorithm is also presented, and the effectiveness of the time-varying threshold process neural network model is evaluated through the prediction of EGT series from practical aeroengine condition monitoring.

Effect of Exhaust Gas Temperature on Oxidation of Marine Diesel Emission Particulates with Nonthermal-Plasma-Induced Ozone

2015 ◽  
Vol 37 (6) ◽  
pp. 518-526 ◽  
Author(s):  
Takuya Kuwahara ◽  
Keiichiro Yoshida ◽  
Kenichi Hanamoto ◽  
Kazutoshi Sato ◽  
Tomoyuki Kuroki ◽  
...  
Keyword(s):  
Nonthermal Plasma ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Marine Diesel ◽  
Diesel Emission ◽  
Exhaust Gas Temperature

A Study on the Factors Affecting the Uniformity of Urea and Exhaust Gas Using an SCR Simulator

2020 ◽  
Vol 399 ◽  
pp. 145-153
Author(s):  
Munseok Choe ◽  
Dogyeong Kang ◽  
Dooseuk Choi
Keyword(s):  
Negative Pressure ◽  
Exhaust Pipe ◽  
Exhaust Gas ◽  
Mixing Ratio ◽  
Gas Temperature ◽  
Flow Uniformity ◽  
Factors Affecting ◽  
Exhaust Gas Temperature ◽  
Scr System ◽  
Type Mixer

As it is difficult to confirm mixed shape and mixing ratio which depend on the actual mixer inside the SCR, the present study on mixed shape and mixing ratio has been conducted by producing an SCR system simulator. Total 19 sensors were installed and the system was designed not to allow formation of a negative pressure inside the exhaust pipe. The experiment was conducted setting engine rpm, temperature, mixer shape, and distance as the experiment variables. As a result of the experiment, in the case of non-mixer type, a phenomenon was found where urea became locally packed as the exhaust gas and urea were not mixed and, when an R-type mixer was applied, urea was formed being spread on the whole. It was also confirmed that uniformity index was increased by 8 % in average when an R-type mixer was used in comparison to that of the non-mixer type, and the non-mixer type failed to achieve flow uniformity of 90 % or higher while the case where an R-type mixer was used could achieve it when the distance was 20 cm or bigger. Based on such a result, changes in the uniformity of urea and exhaust gas depending on existence of a mixer, exhaust gas temperature, engine rpm, and distance could be confirmed. It is thought that additional studies are required to be conducted later on the effect of a change in the mixer shape on flow uniformity.

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