The preliminary answer came out.
Three design schemes of ships without ballast water
Dr mihir Parsons of the University of Michigan, USA, delivered a paper at the annual meeting of the American Society of Shipbuilding and Marine Engineers on September 29th, 2004, focusing on the design of ships without ballast water and discussing three design schemes.
1 .5 Hull
The idea of the hull project of the super-large oil tanker without ballast water was originally put forward by Professor Anders Ulwassen of Chalmers University in Gothenburg, Sweden. On the basis of their ideas, American shipbuilding experts gradually developed into the design idea of a ship without ballast water in the second half of 2003. Its biggest feature is that the lower part of the hull is more slender, showing a V-shape that obviously protrudes downward, so that the draft of the ship is enough to match the weight of the ship when it is empty.
First of all, after further modifying the two ship design schemes preliminarily selected by shipbuilding experts, the economic parameters such as stability, resistance and cargo capacity are evaluated on the computer, and the results are as follows:
Code-named "Best", the first design scheme of a ship without ballast water is mainly aimed at designing and building a ship without ballast water when sailing in a channel without water depth restrictions, such as the Persian Gulf. Its hull is 35 meters deep, with a full draft of 27 meters, a maximum width of 56 meters and a cargo capacity of over 300,000 tons.
The development direction of the second design scheme of the ballastless water hull code-named "Malacca type" is to build ships suitable for sailing from the Persian Gulf to the Far East, China, Japan and South Korea via the Straits of Malacca. The maximum width of the hull can reach 79 meters, the depth of the hull is 30 meters, the full draft is 2 1 meter, and the cargo capacity is 280,000 tons.
Through computer simulation test, it is preliminarily confirmed that the so-called "best" ballastless water tank car sails very smoothly on the rough sea. However, the navigation situation of Malacca ballastless water tanker is poor, because the depth of the bottom part in the water is not enough after the hull is widened; In bad weather, it is necessary to pump 15 000 tons and 35 000 tons of ballast water into the spare ballast tanks of these two so-called ballastless tankers respectively to ensure the safety of the ships. However, under the same conditions, the traditional VLCC must carry at least 80,000 tons of ballast water in order to reach the standard that the draft of ships is not less than 8.4 meters stipulated in the International Convention for the Prevention of Pollution from Ships. It can be seen that the advantages of the so-called ballastless tank car are still very obvious.
It can be seen that the V-boat without ballast water does not absolutely reject ballast water, and its design concept is to make the hull as slender as possible to achieve the effect of reducing hull resistance, in which the "best" type reduces resistance by 33% and the "Malacca type" reduces resistance by 25%. In a word, the V-shaped hull design can greatly reduce the problems caused by ballast water. Dr. mihir Parsons pointed out that a V-hull tanker sailing safely in stormy seas can certainly be successfully built by increasing the height of sewage ditch and increasing the plane width of the bottom appropriately.
2. The hull of the flow passage system
The so-called through-flow system is the traditional ballast tank, which is used to replace the longitudinal structure below the waterline around the cargo hold. Its biggest feature is to change the original closed type into front-back open type, with the water inlet located below the waterline of the bow and the water outlet located at the stern. The seawater continuously flows in from the inlet of the bow and then is quickly discharged from the outlet of the stern, which can not only play the role of ballast tank, but also reduce the load of the ship. Using the different pressures of water inlet and outlet at the bow and stern to control the speed of water flow through the ballast tank; However, the seawater passing through the flowing water tank is always the seawater in the local sea area, and will not bring seawater from one place to another.
Undoubtedly, the so-called through-flow ballast tank is by far the most innovative shipbuilding concept. Its biggest feature is that it keeps the actual ballast tank, but only changes the stagnant water in the ballast tank into longitudinal flowing water, thus fundamentally solving the problem of the diffusion of microorganisms and pollutants in the global ocean. Its biggest disadvantage is that the ballast tanks still occupy a considerable space of the ship, and due to the needs of the ship structure, in addition to the longitudinal ballast tanks, some traditional horizontal ballast tanks have to be retained. At present, shipbuilding experts are concentrating on overcoming this difficulty, trying to reduce the volume of horizontal ballast tanks that can not be completely cancelled for the time being, that is, to minimize the ballast water volume of ships. One of the disadvantages of this through-flow system is that it increases the navigation resistance of the ship. Dr mihir Parsons pointed out that most of these problems can be solved by further improving the hydrodynamic design.
3. Single hull
The biggest advantage of this design scheme is that the bottom of the ship is in the shape of inverted slippers, and the opening is backward, which can make the ship produce a large draft when it is lightly loaded. However, the disadvantage of this scheme is that compared with the traditional ship type, the contact area between the hull and seawater is greatly expanded. However, Dr. mihir Parsons believes that these shortcomings can be minimized by air lubrication generated by downward cicada wings on both sides of the bottom of the ship.
The designers of Monomara hull combine air lubrication with engine exhaust, that is to say, the exhaust of marine engine is not discharged upward into the air, but downward to the stern direction through the groove on the hull. On the one hand, it exerts its air lubrication function, on the other hand, it dissolves carbon dioxide, carbon monoxide, various particulate pollutants and sulfides in the tail gas in seawater, thus reducing the threat to marine air and port environment.
At present, the single-structure hull ship has been successfully built in Delft University, the Netherlands, with a deadweight of 4 000 tons and a ship speed of 14 knots. It has no ballast tank, and basically meets the standard of the so-called ballastless water ship from the trial.
The trouble is the first step.
Captain graham greene Smith, a senior expert of Lloyd's Register of Shipping, said that there is no feasible and competitive ship design scheme to eliminate ballast water fundamentally, but this does not mean that ships without ballast water cannot be built. Marine life, microorganisms and sediments will still be produced on the inner wall of the so-called longitudinal cross-flow pressurized water tank and carried from one place to another; Water in the ballast tanks of ships with spare ballast tanks can still be discharged to other places.
The most difficult part is actually that at the beginning, the application of IMO rules, standards, equipment and facilities is very complicated, and the appearance of ships without ballast water is no exception. From the introduction of the above three so-called ship design concepts and schemes without ballast water system, it seems that people can see the dawn of solving the ballast water problem. At present, shipowners, operators and managers of the world shipping industry must highly rely on the technology of ballast water treatment agent.