Blue INNOship fact #13
Dynamic propeller shaft speed control
|Goals and objectives|
The project is expected to develop and test a solution that can be implemented on two-stroke engines on large seagoing vessels. The technology has the potential of improving total propulsion efficiency by 2-3% predicted for North Atlantic passage and reducing fuel consumption and emissions accordingly.
Propeller Control ApS
Wärtsila Lyngsø Marine
DTU Mechanical Engineering
DTU Electrical Engineering
The project is supported by the Danish Maritime Fund.
|Outcome from the project|
The Dynamic Propeller Shaft Speed Control Project has resulted in a technology readiness level 8 prototype based on patented technology. The unit has been at sea since October 2016, on board Clementine Maersk. Real time data are collected by the equipment and sent back for analysis every month. Results are so promising that analysis continues in order to explore the commercial potential.
Following theoretical analysis of cross inflow to propellers, using model test data from earlier experiments at FORCE Technology, and recordings made on the full scale Maersk vessel (Luna Maersk) back min the 1980ties, we identified the wake parameters for the Luna Maersk propeller and hull form. Based on this, we scrutinized the natural propulsion losses that occur in waves. We made an estimation of the losses for Clementine Maersk using statistical year-round weather information, and we designed comprehensive simulation facilities that could run faster than real time on a myRio hardware platform (National Instruments). This simulator was later used for hardware in the loop testing at Lyngsø Marine, and it was used on board Clementine for testing every time we had made a code change, before porting the updated code to the control platform. When controlling a 60 MW diesel engine, there is no room for mistakes.
We developed a prototype of the DPC unit using Lyngsø Marine type approved hardware and firmware, on top of which we integrated our software. The DPC unit was installed without problems on Clementine Maersk, and has been in daily use on board since the second sea test in October 2016.
The DPC hardware plus software has proven to be a reliable test platform that has demonstrated the dependability and capability of the DPC product.
With the product being in daily operation at sea for 7 months by now, we have obtained a technology readiness level TRL 8.
|Reporting from the project|
How would you describe the results obtained in the project?
It has been very interesting to move into new frontiers of knowledge.
The scientific novelty is there, based on observation of what nature does: how the dynamic flow in a wave changes the flow field around a marine propeller to create propulsion losses that nobody had discovered earlier. It is still up to technical science to explain the flow phenomena we have observed from both model scale and the full size ship.
It has been very satisfactory to see how dynamic control of the propeller shaft speed, in response to estimated inflow variation, can reduce the natural losses.
It has been an eye opener both to the developers and to the ships officers, that a very large diesel engine can be controlled to give constant power with fluctuations much smaller than any of us had seen before.
It was also very satisfactory for the development team to receive an email from the Chief stating: we used the power level recommended by our voyage planning system and did not touch the handles for ten days. We arrived at Suez half an hour before schedule. “This is the way we like to sail”.
It has been interesting and challenging for the scientific partners to bringing real-world nonlinear dynamics and theory together.
How would you describe the process leading to these results?
We have had a very smooth collaboration. Weekly update and coordination meetings have helped keeping everybody on track.
Please summarize the key activities conducted in the project
- Project management (Maersk)
- Daily project coordination (Propelco)
- Identification of dynamic wake variations in waves (Propelco)
- Attempt to confirm dynamic wake variation with computational fluid dynamics software (DTU Mek). Attempt failed as the software could not cope with such dynamic phenomena.
- Motion response operators and added resistance formula were calculated for Clementine (DTU Mek)
- Develop an inflow estimator and predictor, based on torque and shaft speed measurements. Test on simulated and on real data (DTU Elektro)
- Develop theory and algorithms for predictive control of shaft speed (Propelco)
- Develop a comprehensive simulation of ship, diesel engine, governor loop and wave environment on a hard real time platform. (Propelco)
- Change EGS 2000 code to accommodate interface with the DPC (Lyngsø Marine)
- Build the hardware platform using certified marine computer hardware from Lyngsø Marine (Lyngsø and Propelco).
- Conduct hardware in the loop tests (Lyngsø Marine and Propelco)
- Install onboard Clementine Maersk (Lyngsø Marine and Propelco)
- Make code updates and conduct sea test 2 (Propelco)
- Make comprehensive software to decode ship data files store and analyze data (Propelco)
- Compensate power measurements for effects of wind and sea data (Maersk)
- Conduct analysis of performance based on observations (Maersk and Propelco)
Were there any concerns about the projects outcome during the project and how did you overcome them?
The average natural losses appeared to be smaller than we estimated before starting the project. We have not changed the course, but believe we could still have a product with a reasonably short period of return of investment.
Which positive findings or news did your project disclose?
We have discovered and documented dynamic wake phenomena due to waves and hull motions that have not been reported before.
Why was the project worth the invested resources?
Interesting problem, challenging project and promising results.
What key learnings did you obtain through the project?
Even though you have a well prepared idea it is a tough effort to integrate all details of algorithms and get to a working product.
Even though we were aware of the benefits of simulation based testing, the hard real time “digital twin” of vessel, engine and environment, proved invaluable for hardware in the loop testing. We had literally no defects when installing the new equipment onboard.
How was the cooperation between the partners?
What could have made the cooperation work better (regardless of the answer of the question above)?
It is difficult to imagine how we could have made a perfect collaboration even better.
Did any partners not deliver as anticipated? And what did you do about it?
When a partner had temporal difficulties, due to workload on other duties, others took over as far as possible. All partners have been extremely dedicated to make this collaboration a success.
What could have made the project work better?
It was a pity with respect to scientific publications that the CFD software could not deal with dynamic inflow, but this is the kind of small setbacks one encounters when getting into new frontiers.
Did you have to change scope or process during the process in order to finalize the project?
No, the scope is the original one. We were, however, inspired by the vessels’ officers to make an enhancement in form of a “constant power mode” that we implemented.
|Presentations, articles and media coverage from the project|