Questions and Answers

 

1. What was the major objective of your project and what was your plan to achieve it? 

A novel centrifugal vortex scrubber integrated into a Flettner rotor creates a hybrid wind and fossil fuel powered vessel that cleans exhaust while generating propulsive power. New environmental actions and developments such as the concept of “carbon pricing” impact maritime transport costs, particularly affecting developing economies. 

An objective was to build upon past flettner vortex scrubber research and development to integrate an active system of seakeeping, thus making the design more marketable and a better investment for ship owners, who are primarily concerned with maximizing profit and efficiency, as opposed to environmental and health concerns. 

Seakeeping is the ability of a vessel to limit motion due to waves and weather, resulting in increased crew comfort, safety, and performance. Improving seakeeping broadens the operating envelope of the vessel, adding significant value by allowing vessel goals to be achieved in a wider range of weather conditions. 

Ships such as research vessels and cruise ships where crew and passenger comfort is a priority are often fitted with active seakeeping measures such as hydraulically controlled hydrofoils, gyroscopes, or powerful pumps transferring water between large port and starboard tanks as the ship rolls. On a ship, all of these active systems consume valuable cargo space and energy, and require costly hardware and hull appendages. This makes them cost prohibitive, especially to developing economies. 

Enhancing the Flettner Vortex Scrubber with active seakeeping control would make this climate change mitigation technology an even more attractive investment for ship owners and operators, by allowing the same rotor and scrubber hardware to also act as an active seakeeping system. 

To achieve the goal of adding seakeeping functionality, my plan was to complete development of the following: 

1. A motor and drive system that could quickly accelerate and decelerate the rotation of the Flettner Vortex Scrubber in response to wave action.
2. A cargo ship scale test mule that approximated the characteristics of a cargo ship: hull shape, mass distribution, center of buoyancy, metacentric height.  
3. Outfitting this cargo ship test mule with accelerometers, sensors, software, controls, motor, and mechanical linkage to drive the Flettner Vortex Scrubber.
4. A wave pool to run tests that simulated open ocean conditions. 
5. Control algorithms tuned for optimal seakeeping. 

       a. Was that goal the result of any specific situation, experience, or problem you encountered?  

Being at sea, having been a lifelong sailor, I have observed many cargo ships enter harbors and clearly see the amount of particulate matter coming from them and can only imagine the climate change emissions that are not visible. 

After working on further research on this area and spending a large part of the summer on the ocean, I have become even more aware of these problems and the importance of finding solutions.

I can understand why people who live near harbors see cargo ship emissions as even more of a critical issue particularly with regards to health.

Ships began using oil as an energy source around 1900, however use of exhaust scrubbers on ships was very limited until recently, due to light regulation. In 1973 the regulation of pollution in international waters was first discussed at the first marine pollution convention, or MARPOL. Sulfur emissions restrictions did not go into effect until 2012 with a 3.5% sulfur cap. In 2020 this cap was reduced to 0.5%, prompting ships to either consume less residual fuels, or install scrubbers. Because of this, it seems like scrubber technology is designed around land-based applications like power generating stations that have been more regulated, and not marine applications. Heavy fuel oil is a residual product of petroleum refining for gasoline and diesel. Marine fuel oil engines are a mature, low cost, and reliable technology. I feel that marine exhaust scrubbers and cargo ship wind power are very important technologies to advance. Large ships contribute to 4% of global climate change emissions. According to the Yale School of the Environment, we are just learning that the combustion products of heavy fuel oil are especially noxious pollutants which can travel hundreds of miles leading to roughly 7.6 million childhood asthma cases and 150,000 premature deaths annually. 

       b. Were you trying to solve a problem, answer a question, or test a hypothesis?

I was trying to do all three.

I was trying to solve the problem of climate change by reducing emissions.

I was trying to answer questions regarding applying scientific principles to design a new solution.

I was testing my hypothesis that the Flettner Vortex Scrubber rotor and scrubber hardware could also act as an active seakeeping system.

2. What were the major tasks you had to perform in order to complete your project?

1. I had to use computational fluid dynamics to understand the forces generated by the Flettner Vortex Scrubber, and how these forces could be used to generate a righting moment to keep the ship level. This required: 
   1. Adapting my 3D model for computational fluid dynamics by defeaturing and creating a domain boundary. 
   2. Developing a mesh for finite element analysis
   3. Selecting an appropriate complexity of analysis model. I selected the k–epsilon two equation turbulence model as an appropriate balance of resolution and complexity. This model is used to approximate Reynolds-averaged Navier–Stokes equations for viscous fluid flow.
   4. Validating the CFD model
   5. Running various input conditions
2. I had to use principles of naval architecture to design a cargo ship scale test mule. This test mule had to:
   1. float without permitting entry of water into the hull 
   2. support the Flettner Vortex Scrubber
   3. approximate the characteristics of a cargo ship: hull shape, mass distribution, center of buoyancy, metacentric height
   4. support accelerometers, sensors, software, controls, motor, and mechanical linkage to drive the Flettner Vortex Scrubber
3. In order to complete my project, I needed to gain programming skills beyond the few introductory lessons that I had done in the STEM program in my school. I used online resources, webinars, and Codecademy.
4. I had to develop and build a 309 gallon wave pool for the cargo ship test mule to float in. 

       a. For teams, describe what each member worked on.

 This was not a team project.

3. What is new or novel about your project?

My research indicates that Flettner Rotors used for capture of wind energy for ship propulsion have not been designed or controlled in such a way to also act as active seakeeping systems, which is what I am developing in this project. 

Note that stabilization systems using underwater foils or underwater flettner rotors do exist. This is a completely different application than Flettner rotors employed for wind propulsion which are otherwise known as rotor sails. Stabilization systems using rotors and the Magnus effect do not serve any propulsion or efficiency purpose, are below the waterline, and require dedicated seakeeping hardware.

       a. Is there some aspect of your project's objective, or how you achieved it that you haven't done before?

I had never used principles of naval architecture to design a functioning ship or model before.

I had never engineered, built or tested a wave pool before. 

I had never built a functioning ship or model before.

I had never attempted programming challenges beyond the basic introduction in my engineering class.

I had never designed such a complex mechanical system before.

       b. Is your project's objective, or the way you implemented it, different from anything you have seen?

Ships such as research vessels and cruise ships where crew and passenger comfort is a priority are often fitted with active seakeeping measures such as hydraulically controlled hydrofoils, gyroscopes, or powerful pumps transferring water between port and starboard tanks as the ship rolls. On a ship, all of these active systems consume valuable cargo space and energy, and require costly hardware and hull appendages. This makes them cost prohibitive, especially to developing economies.

I have not seen any Flettner Rotors for capture of wind energy for ship propulsion also enhanced with functionality to use rotational speed control as an active seakeeping system.

I have not seen a proposal to utilize the volume inside Flettner Rotors. It seems that scrubber technology designed around land-based applications like power generating stations is being “cut-and-pasted” into new and retrofit marine applications due to increased pollution regulation in international waters. 

My Flettner Vortex Scrubber recaptures unused shipboard volume and augments auxiliary wind propulsion in an innovative way for climate change emissions reduction and for an expanded vessel operating envelope.

       c. If you believe your work to be unique in some way, what research have you done to confirm that it is?

I researched Flettner Rotors for capture of wind energy for ship propulsion and have not seen any that use rotational speed control as an active seakeeping system.

I researched shipboard systems with a focus on pollution reduction and have not seen any that combine engine exhaust scrubbers and Flettner Rotors.

I have never seen anything like this. The closest concept that I could find was a seakeeping method for using the rudder to control roll. This required heavier rudder bearings and drive system. According to my review of current literature, the addition of Flettner rotor controls for active seakeeping is a novel concept.

4. What was the most challenging part of completing your project?

      a. What problems did you encounter, and how did you overcome them?

I am a novice programmer but needed to use programming to demonstrate proof of concept.

I had selected a 4.2 Amp stepper motor for low speed torque, speed control, and deceleration, and paired this motor with a stepper driver to provide sufficient current. The stepper driver has inputs to enable the motor, select the direction of rotation, and a pulse input to step the motor 

Using the ATMEGA2560 processor on the Arduino Mega 2560 to generate an input signal to the stepper motor driver was very straightforward. However my initial attempt was tied to the clock speed of the processor, so it worked fine until I started asking more of the processor, such as 

reading sensor inputs and performing calculations.  

Finding a way to prioritize the signal to the stepper driver proved to be a challenge. There are onboard timers on the arduino mega for Pulse Width Modulation (PWM) control, however the selection of frequencies is very limited negating the very fine control of rotor speed required for seakeeping. 

A straightforward solution was to add a 1Hz-150kHz PWM generator board as an input to the stepper driver, and use the TTL serial port on the Arduino to send instructions to the frequency generator board. This effectively decoupled the pulse input required by the stepper driver from the processor clock speed. There are Arduino stepper control libraries which would have likely provided the same function. A more elegant solution would have been to use the Timer/Counters on the ATMEGA2560 processor.

The PWM generator board provided the benefit of a display, but increased the hardware cost by about $5.00, which is acceptable for a proof of concept prototype but could have been a barrier had this been a high volume consumer product. 

      b. What did you learn from overcoming these problems?

From overcoming these problems, I learned more about the system architecture of Arduino Mega 2560 and the ATMEGA2560 processor. I learned how to read some of the information in a processor data sheet. I also learned how to use the TTL serial inputs and outputs on the Arduino. 

This effort also reinforced that complex test equipment and expensive testing facilities are not always required for accuracy and precision. Accuracy and precision can be achieved through creative application of physics principles and careful mathematical calculations.

5. If you were going to do this project again, are there any things you would you do differently the next time?

One improvement I would make is to use C++ and ATMEL Studio for programming and download my code directly to the ATMEGA2560 processor. 

Another improvement I would make is to position the motor higher above the bilge of the cargo ship test mule so that small leaks would be less likely to contact the motor. This would make the system more robust. 

6. Did working on this project give you any ideas for other projects? 

I am fascinated by all of the engineering solutions that can be developed to make cargo shipping cleaner. There are so many concepts currently being explored, from capturing waste engine heat and generating electricity, to optimizing float plans for optimal weather, currents, and sea state. 

I am especially interested in how recent advances in materials and machine learning technology can be used to apply wind power to today’s cargo ships. 

I would love to use an oscilloscope to gain more precise control of the stepper motor. 

7. How did COVID-19 affect the completion of your project?

I was invited to present at several international conferences that were moved to a virtual format due to the pandemic. I would have appreciated attending these conferences in person as it facilitates networking. 

I had to further postpone the invitation to work in a nanotechnology lab at Rutgers University due to the pandemic. 

On a more positive note I was invited to engage in a virtual mentorship program and gained feedback from an engineer at the Department of Defense.