1. 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

2. 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)

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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.

10. 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

11. 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

12. 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

13. 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

14. 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)

15. 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.

16. Comparison of Mass Flow rate
Exit orifice Dia.
(mm)
Injection
Pressure
(bar)
2.6 3

17. Comparison of Mass Flow rate
Exit orifice Dia.
(mm)
Injection
Pressure
(bar)
3.2 3

18. 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.

19. 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.

20. 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.

21. 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.

22. 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.