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The Spray Characteristics of Twin Fluid Nozzle on Urea-SCR
ICFMCE 2017, November 24-26, 2017, Dubai The Spray Characteristics of Twin Fluid Nozzle on Urea-SCR Applied to Marine Diesel Engines Thank you. Chairman. My name is hyung sun park from kyungpook national university, korea Our study has focused on large marine engine’s Urea-SCR system. Today, I will present the spray characteristics of twin fluid nozzle on urea-SCR system. Hyung Sun Park, Sang Ji Lee and Jung Goo Hong School of Mechanical Engineering, Kyungpook National University
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Opportunity for the Environment
Various types of transport, marine vessels amount of emissions are nitrogen gas for the second and pm for the first. Therefore, it is urgent to reduce harmful substances on marine vessels. By Natural Resources Defense Council (NRDC)
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Opportunity for the Regulation
, 2000 , 2011 , 2016 ( ≥ 80 %) MARPOL (Marine pollution treaty) Annex VI NOx Emission Limits Recently, IMO has decided to enforce NOx reduction regulations. After Tier I as marine engine emission regulation was forced in 2000, we will meet the Tier 3 next year. As you can see, Tier 3 requires a reduction of NOx over 80% compare to the Tier 1. If we can not satisfy the Tier 3 regulation, We can not drive ships in ECA. So, an interest of de-NOx system is growing, and the marine engine manufacturers have made an effort for de-NOx systems. - International Maritime Organization (IMO) has decided to enforce NOx reduction regulations
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Opportunity for De-NOx tech.
IEM (Internal Engine Modification) LNG (Liquefied Natural Gas) Shipping NOx reduction potential by Azzara, A. et al. FEW (Fuel & Water Emulsion) or DWI (Direct Water Injection) EGR (Exhaust Gas Recirculation) De-NOX This slide shows the representative de-NOx technology developed from marine engine. The IEM is a way to reduce NOx by internal combustion engine control. FEM, DWI, HAM and EGR are by artificial combustion temperature drop. SCR is by exhaust gas treatment. According to their results, the SCR was promising technology for Tier 3. So, we were interested in the SCR system. SCR (Selective Catalytic Reduction) HAM (Humid Air Motors) 3
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Outline for Urea-SCR system
BLUENOX SCR System. Temp. sensor NOx sensor Catalyst Soot blowing system Soot blowing nozzles This slide shows SCR-system from BLUNOX. SCR system uses an ammonia as a reducing agent and consists of dosing system, injector, catalyst. Dosing system is to supply a reducing agent to the injector. The reducing agent is injected into exhaust pipe by injector. Finally, NOx is removed by reaction with reducing agent on the catalyst. Specially, the SCR of transportation equipment has used the urea as precursor of ammonia because of toxicity of ammonia, difficulty of storage. Dosing Injector Pulsation damper SCR control unit Nozzles Engine control unit Valves Temp. sensor Urea tank Digital dosing pump NOx sensor Pressure sensor Marine diesel engine Urea pipe
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Outline for Urea-SCR system
Temp. sensor NOx sensor Catalyst Soot blowing system Soot blowing nozzles In this study, we tried to obtain the experimental data according to the spray characteristic, especially by checking the spray characteristics of the spray nozzle in the scr system. Injector Pulsation damper SCR control unit Nozzles Engine control unit Valves Temp. sensor Urea tank Digital dosing pump NOx sensor Pressure sensor Marine diesel engine Urea pipe
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Problem of the present SCR tech.
Catalyst Exhaust pipe An example of deposit formation on the face of an SCR catalyst monolith. (By John M.E. Storey et al.) Since the exhaust gas temperature and the residence time in the exhaust pipe is insufficient for complete thermal urea decomposition, a major fraction of the injected urea and byproducts by side reaction remain intact before it enters the SCR catalyst. The spray characteristics of the spray nozzle are important in the Scr system because of the clogging phenomenon caused by the formation of the deposit formation. Since this clogging results in significant reduction of efficiency, the conversion efficiency of Urea's ammonia is the most important factor in the efficiency of the scr system. Stoichiometric imbalance of the urea consumption Degradation of the structural and thermal properties of the catalyst surface
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Basic Mechanism of Urea-SCR
(NH2)2CO + xH2O Urea Solution evaporation (NH2)2CO → NH3 + HNCO HNCO + H2O → NH3 + CO2 4NO + 4NH3 + O2 → 4N2 +6H2O 6NO2 + 8NH3 → 7N2 + 12H2O Urea thermal decomposition HNCO hydrolysis SCR reaction Urea Solution Injector Evaporation and thermal decomposition by exhaust gas temperature NOx CO O2 HC SCR Catalyst These reactions shows the process making ammonia from urea First, the injector before SCR sprays the urea solution into exhaust pipe. Injected urea solution is evaporated by hot exhaust gas. After that, remained pure urea is thermally decomposed into ammonia and HNCO HNCO is decomposed again into ammonia through hydrolysis on catalyst. These ammonia can convert NOx to Pure N2 through SCR reaction on catalyst. N2 CO2 H2O
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Caldyn’s Nozzle Caldyn’s nozzle Typical effervescent atomizer
Perforated Aerorator Liquid Inlet Exit Orifice Hole Caldyn’s nozzle Sovani et al. (Progress in energy and combustion science, 2001) - Two-phase flow through a nozzle chokes at a significantly lower velocity than that at which a single phase flow would choke - Atomization quality is greatly enhanced by the sudden pressure drop at the nozzle exit Typical effervescent atomizer The figure on the left is the twiin fluid nozzle manufactured by caldyn. This nozzle is an effervescent type nozzle, and atomization quality is greatly enhanced by the sudden pressure drop at the nozzle exit.
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Previous Work : Flow rate
𝐴𝑖𝑟 𝑡𝑜 𝐿𝑖𝑞𝑢𝑖𝑑 𝑚𝑎𝑠𝑠 𝑅𝑎𝑡𝑖𝑜 (𝐴𝐿𝑅)= 𝐴𝑖𝑟 𝑚𝑎𝑠𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 𝐿𝑖𝑞𝑢𝑖𝑑 𝑚𝑎𝑠𝑠 𝑓𝑙𝑜𝑤 𝑟𝑎𝑡𝑒 Caldyn’s nozzle Jewe Schroder et al. 2011 Relative high ALR ALR means the air to liquid mass ratio, which is the ratio of air mass flow rate to liquid mass flow rate. According to the data provided by Caldyn, it can be seen that the ALR value is about 0.5 at 100% load. Also, according to a previous study of jewe, it can be seen that the nozzle of the effervescent type has an ALR value of about 0.3 or less. - Generally, effervescent nozzle is operated with 0.1 ~ 0.3 of ALR
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Effervescent Nozzles Liquid Air Air Air Liquid Liquid
There are two types of Effervescent type nozzles. Experiments were carried out using nozzles of outside in type. Liquid & Air Mixture Liquid & Air Mixture (A) Outside-in air injection (B) Inside-out air injection
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Configuration of Test Nozzle
Aerorator D2 The following figure shows the aerorator and exit orifice of the nozzle used in the experiment. Here, the exit orifice (D1) is the outlet for the mixed liquid and gas. The aerator is the entrance to the air. Each of the aerators has 12 holes. Exit orifice D1
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Experimental Setup Compressor N2
Water Air Signal Compressor On-off valve Regulator Stroboscope CCD camera Image grabber & DAQ board Detector Laser for SMD Flow meter N2 Pressure transducer Needle valve The experimental apparatus can be divided into three parts. Fluid supply system, spray visualization system, and measurement system. The pressure of the surge tank was kept constant by the nitrogen gas and the injection pressure was adjusted by the pressure regulator located between the nitrogen tank and the surge tank. Assist air compressed by the compressor is regulated through a needle valve. The flow rate of the assist air was measured by a digital flow meter. As the spray visualization device, the Strobe scope was used as a CCD camera and a light source to capture the image of the spray downstream. To obtain the droplet size, SMD was obtained through the equipment using laser diffraction principle. The flow rate of water and air was measured by a flow meter and recorded on a DAQ board. *The drop size at 200mm from nozzle tip
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Configuration of Test Nozzle
*Area ratio = 𝐴𝑒𝑟𝑜𝑟𝑎𝑡𝑜𝑟 𝐴𝑟𝑒𝑎 𝐸𝑥𝑖𝑡 𝑜𝑟𝑖𝑓𝑖𝑐𝑒 𝐴𝑟𝑒𝑎 Nozzle Configuration Spray Condition Exit orifice Dia. (mm) Aerorator Dia. Exit orifice Area (mm2) *Area ratio 2.6 1.2 5.31 13.57 2.56 1.5 21.21 3.99 1.7 27.24 5.13 2.1 41.56 7.83 2.5 58.90 11.09 2.9 79.26 14.93 3.2 8.04 1.69 2.64 3.39 5.17 7.32 9.86 3.7 10.75 1.26 1.97 2.53 3.87 5.48 7.37 Injection pressure (bar) 2, 2.5 and 3 Liquid mass flowrate (kg/min) 0.1 ~ 1.0 Density (kg/m3) Water 1000 Air 1.226 This slide shows configuration of test Nozzle. Area ratio means aerorator area to exit orifice area. The liquid used water and the gas used air. Experiments were carried out under three conditions of spray pressure of 2, 2.5 and 3 bar. The flow rate of liquid was experimented at 10 flow rates from 0.1 kg / min to 1.0 kg / min at 0.1 kg / min. Experimental conditions are totally 540 cases. [실험조건 (540 cases)] - Exit orifice Dia. (3) - Aerorator Dia. (6) - Injection Pressure (3) - Liquid flow rate (10)
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Comparison of Mass Flow rate
*Area ratio = 𝐴𝑒𝑟𝑜𝑟𝑎𝑡𝑜𝑟 𝐴𝑟𝑒𝑎 𝐸𝑥𝑖𝑡 𝑜𝑟𝑖𝑓𝑖𝑐𝑒 𝐴𝑟𝑒𝑎 Exit orifice Dia. (mm) Aerorator Dia. 2.6 1.2 3.2 1.5 3.7 1.7 *Area ratio 2.56 This slide shows comparison of mass flow rate. A pressure of 3 bar and an area ratio of The exit orifice and the aerators were exchanged and the liquid mass flow rate and the assist air mass flow rate were compared. As the liquid mass flow rate increases, the tendency of the assist air mass flow rate decreases. In addition, when the diameter of the exit orifice increases from 2.6 mm to 3.2 mm, the difference between the value of the assist air mass flow and the liquid mass flow rate is not large, but when the diameter of the exit orifice increases from 2.6 to 3.7, the assist air mass flow rate and the liquid mass flow rate are considerably increased. Injection Pressure (bar) 3 - At the same liquid mass flow rate, air mass flow rate increases with increasing of exit orifice diameter.
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Comparison of Mass Flow rate
Exit orifice Dia. (mm) Injection Pressure (bar) 2.6 3
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Comparison of Mass Flow rate
Exit orifice Dia. (mm) Injection Pressure (bar) 3.2 3
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Comparison of Mass Flow rate
Exit orifice Dia. (mm) Injection Pressure (bar) 3.7 3 This is a graph comparing the liquid mass flow rate and the assist air mass flow rate while changing the aerators to the exit orifices of 2.6, 3.2, and 3.7 mm at a pressure of 3 bar. This graph shows that the variation of the mass flow rate of the assist air is not large at the same liquid mass flow rate. It can be seen that the diameter of the exit orifice affects the mass flow rate of the liquid and assist air, but the aeratorat has little effect on the mass flow rate.
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Droplet Size Measurement
One graph shows the SMD values according to the ALR for the experimental conditions set in this study. When the ALR value is 0.3 or more, it can be seen that the SMD value converges to a substantially constant value. It can be seen from these results that even if a large amount of assist air is injected, there is a limit to making the droplet size smaller. - Compared with Caldyn’s data, it has same tendency. - SMD is not a large difference in the value of ALR ratio in 0.3 or more.
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Droplet Size Measurement
Exit orifice Dia. (mm) Aerorator Dia. *Area ratio 2.6 1.2 2.56 1.7 5.13 2.5 11.09 Injection Pressure (bar) 3 This is a graph showing the SMD according to the ALR value using an exit orifice of 2.6 mm at a pressure of 3 bar and changing the area ratio by changing only the aerator. As the ALR value increases, the tendency of the SMD decreases. SMD is not affected by area ratio of an efferverscent nozzle.
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Droplet Size Measurement
Exit orifice Dia. (mm) Aerorator Dia. *Area ratio 3.7 1.2 1.26 1.7 2.53 2.5 5.48 Injection Pressure (bar) 3 This is a graph showing the SMD according to the ALR value by varying the area ratio while changing the air flow rate using a 3.7 mm exit orifice at a pressure of 3 bar. As the ALR value increases, the tendency of the SMD decreases. We tried to identify the difference as the area ratio increased by about 2 times and 4 times, but it was confirmed that there was almost no deviation. As a result, it was confirmed that there is almost no difference in SMD due to the difference in area ratio. SMD is not affected by area ratio of an efferverscent nozzle.
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Summary [Conclusion] [Application]
The liquid flow rate of the effervescent nozzle used in this study is affected by the diameter of the exit orifice. It was found that the change of the liquid and air flow rate according to the aerorator diameter was not large at the same exit orifice diameter. In the case of ALR above 0.3, there is almost no change in SMD even if the air flow rate increases. In the efferverscent nozzle, the droplet size is not affected by the area ratio. [Application] From the results of this study, the droplet size can be predicted according to various ALR and area ratios. It can be applied to Urea-SCR nozzle design technology according to various engine power.
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