Questions and Answers

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

My major objective was to find a way to reduce climate change causing cargo ship exhaust by integrating a novel centrifugal vortex scrubber into a Flettner rotor to clean cargo ship exhaust. The Flettner Rotor generates propulsive power that more than compensates for the engine power loss through the scrubber, and the initial capital investment. 

To achieve this goal, I set out to first design the proposed assembly using 3D modeling, then optimize it with CFD. Once the design was iterated based on the 3D model and CFD analysis, I built a prototype of the scrubber inside a Flettner Rotor, and developed test stands to study the performance of the prototype. 

       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. 

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 believed 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 a novel centrifugal vortex scrubber integrated into a Flettner rotor cleans exhaust while generating propulsive power that more than compensates for the engine power loss through the scrubber, and the initial capital investment. 

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

1. In order to complete my project, I needed to improve my 3D modeling and CFD skills. When my school curriculum was not sufficient, I used online resources, webinars, and a free ANSYS university class.
2. I used 3D modeling to design an exhaust scrubber into a Flettner Rotor geometry. In addition to documenting my design, 3D modeling was a great design tool to use to ensure proper fit of rotating cylinders.
3. I used computational fluid dynamics to optimize the exhaust scrubber geometry. 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–omega 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 and monitoring the pressure drop across the scrubber as well as the maximum velocity
   6. Running as an injection in a discrete phase model to track the behavior of exhaust particulate matter. 
   7. Improving and iterating exhaust scrubber geometry to maximize centrifugal force, maximize particulate matter retained, and minimize pressure drop.
4. I constructed a prototype exhaust scrubber to fit inside a scale model Flettner rotor.
5. I developed and constructed a drive mechanism for the Flettner rotor, and a test stand to measure the efficiency of the exhaust scrubber.
6. I developed and constructed a wind tunnel, water test tank and floating Flettner rotor base to confirm the propulsion force generated by the Flettner rotor at various RPM.

       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 work is novel in that it combines two shipboard environmental technologies in a way that makes both more economically attractive for ship owners to deploy on their fleets.

The exhaust scrubber is of low density compared to tanks or other shipboard mechanical systems, which makes it ideal to locate above the center of mass without significantly increasing the metacentric height and affecting ship stability or seakeeping. My scrubber design is improved and optimized for shipboard deployment by replacing high maintenance moving parts with cyclonic separation geometry. 

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

I had never designed, built or tested an exhaust scrubber before.

I had never designed, built or tested  a Flettner rotor before.

I had never created a computational fluid dynamics model that was this complex before.

I had never used ANSYS software before.

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

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.

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

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

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

A large challenge early on in my planning was that I needed to find a way to accurately measure the propulsion force of the Flettner rotor and minimize interference from friction. This led to my water test tank to minimize friction during the wind tunnel test. The floating test platform was not a ship model and did not have mass or volume proportional to an actual cargo ship that would hold the Flettner Vortex Scrubber prototype upright. Therefore the floating test platform had to be carefully trimmed with foam floats, and removable two liter bottles that could serve as partially filled ballasted columns similar to the design of a semi-submersible oil rig. 

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

In order to make some of the complex modeling geometries in Onshape that were not covered in my school curriculum, I found online tutorials.

Exhaust from the test stand interfered with the flow of the engine-simulating-lantern. I developed a baffle to diffuse the flow.

Finding a way to design a drive for the prototype Flettner rotor that had the right speed and torque output was challenging. I tested and overstressed some repurposed motors designed for high speed low torque air handling applications before settling on repurposing a cordless drill. I tried to use a pulley drive but the lateral load on the turntable caused increased friction on the bearing and inconsistent motion. I ended up redesigning the drive to use a polyurethane wheel that exerted a vertical force on the turntable instead of a horizontal force. This also made it easy to disengage the drive mechanism and let the Flettner rotor spin freely. 

An overall challenge was identifying repurposed and commercial materials that met all the dimensional requirements for fitting scrubber components inside of a Flettner rotor cylinder geometry in a way that would not make the entire prototype unmanageably large and therefore more difficult to build test stands for. Sizing the prototype appropriately so that it was small enough to build test stands for, but easy enough to adapt materials to was a fun puzzle.

      b. What did you learn from overcoming these problems?

From overcoming these problems, I learned 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 putting wheels under the wind tunnel so that it could be easily moved to change tack angle relative to the water test tank and floating Flettner Vortex Scrubber prototype.

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

Absolutely! 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. 

Using a filter media to capture nanometer-scale particles also got me thinking about testing the masks we use to protect ourselves and others from COVID-19. 

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

I was invited to present some of my research to two professors at Rutgers University and one has invited me to work in their nano lab, specifically to use their equipment to better understand spray technology. This was postponed to this Spring, however, I am very excited to be heading there soon.