2. DK Group Marine Innovators at a
glance● Established in 2000, DK Group develops
and markets fuel saving technologies to the
global shipping industry
● DK Group has developed a unique and
patented technology for the commercial
shipping industry, the Air Cavity System
Super Micro Bubble Generator ACS/SMBG
● Numerous tank tests support bunker
consumption reduction of 5% to 10% from
applying the ACS/SMBG technology on
different vessel types
● Tests are carried out together with leading
market participants and potential customers
● Savings translate directly into financial
benefits as well as a cleaner environment
from reduced CO2
emission and other
Introducing DK Group
3. Two methods of reducing frictional
resistance by air lubrication, both DK
Group patent● Super Micro Bubble Generator ACS-
SMBG
● Air bubbles inside the boundary layer of
the vessel.
● Expected efficiency improvement 5-10%
Air lubrication - ACS/SMBG
● Air Cavity System (ACS)
● Long cavities in the bottom for reducing
the wetted surface of the vessel.
● Expected efficiency improvement 5-15%
4. ACS Demonstrator
ACS Demonstrator the first vessel
with ACS
ACS trials
● Build in 1975 at Sietas Schiffswerft, B.No. 697
● Converted in 2008 with ACS at Gryfia Repair yard
● 2800 DWT Mini Bulker
● Length 81.0m and Breadth 13.40 m
● Draft 5.80 m /speed 12 kn
Full scale trials of the vessel
Purpose:
● Demonstration of the concept
● Confidence of scaling method
for the model tests
● Making test at a high
Reinoldsnumber.
● Real life test of the Automation
system for the cavities.
● ACS Demonstrator is a model
for VLCC.
5. ACS trials - results
Results of full scale tests of ACS
Demonstrator● The measured savings from the full
scale trials confirms results from
model tests.
● The effect from the ACS is scalable
from model to ships.
● The cavities are behaving more
stable on the ship than on the
model.
● The automation system which
controls the cavities are acting as
planed.
● ACS Demonstrator can sail with
the ACS system without any
limitation.
● The cavities produce super micro
bobbles
6. ACS trials
Automation of the Air Cavity System
● The ACS system is a part
of the vessel and should
not increase the complexity
in the vessels operation
● Development of suitable
sensors
● Development of
automation strategy
● Reliability of the
automation system.
7. Drag reduction by Kelvin-Helmholtz
Instability
Super Micro Bubble
Generator
Super Micro Bubbles generated by the cavities
Stationary air above fast flowing water leads to Kelvin-Helmholtz instability, resulting in microscopic
bubbles trapped in and carried on by fast flowing water.
Series of tests made at different institutes have proven that small bubbles inside the boundary layer
reduces frictional resistance, super micro bobbles (10-40µm) are superior to larger bubbles (0.5-
4mm).
Surface tension of water makes micro bubbles
smaller and smaller resulting very high inner
pressure.
8. Super Micro Bubbles in water
Billions of Micro Bubbles are
generated and filling the
water tank quickly, resulting
in milky water.
Super Micro Bubble
Generator
9. Cavity geometry
Super Micro Bubble Generator ACS-SMBG
Cavity
Typical geometry of the cavity for producing Super Micro Bubbles
Size and positing of the cavities are adjusted for each vessel type
Number of cavities varies from 4 – 12
Length ranging from 5m to 10m and the Breath 1-2m
11. Other efficiency opportunities
● More efficient propeller (Kappel or NBS)
● Twisted Rudder
● Wake equalising ducts
● Hull Cleaning, algae growing on the hull
increases ship resistance. Hull coating
● Grids at bow thruster openings
● Autopilot adjustment, minimizing rudder
movements (self tuning, adaptive autopilot)
● Cooling water pumps, speed control.
Optimizing flow according to actual needs.
Both on salt water side and fresh water.
● Ventilators speed control.
● Voyage planning
● Scrubber
● Other efficiency opportunities
● By combining the above technologies a
efficiency gain of 20-30% can be expected.
Efficiency by DK Group
12. Fine tuning of the SMBG system:
Test in Cavitation tank
Test with ACS Demonstrator
Preparation of installing SMBG on
Aframax:
Feasibility Study
Design of the SMBG system for the vessel
Approval
Selection of the yard and contract
Yard planning and purchase
Conversion of the vessel and tests
Timeline for the 1st
installation of the ACS-SMBG
system
2 months
1 2 3 4 75 6
2 months
1 month
1 month
1 month
2 months
Timeline
