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    Discussion in 'The main mechanical design forum' started by Ahmedabdlehady, Dec 11, 2018.

    1. Ahmedabdlehady

      Ahmedabdlehady Member

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      Introduction

      • Marine fields now a day is the backbone of any great country as we have 71% of the world is water so all the countries decide to use these criteria to help their needs in many directions as:

      • Navy and war ships to protect coasts and the economical values of the country.

      • Marine transportation which is the cheapest and the more effective as it can transport massive weights with low cost in comparison with other methods.

      • Ships use fuel with its different types but within the next century we will have no more fuel and this situation will lead us to a big disaster in this field specially and this will be the end of the world trade

      • So, the scientists decide to:

      • find other methods to run these machines

      • manage the fuel usage to increase the time available until we find equivalent to our traditional fuel

      • we will talk about how to manage energy consumption on board ships with different ways and in the different ship systems and here are some solutions that had been done:

      • Using of ECU for Diesel engines

      • Cylinders shutoff during engine operation

      • Combination of propulsion methods

      • Propeller design enhancement & variable pitch propeller

      • Waste heat management

      • Chillers enhancement

      • Use maneuvering propellers with low energy consumption

      • Water making instead of big tanks

      • I will take about three of these methods that in my opinion is the most important methods and I will talk later on each method separately; these three methods are:

      • Combination of propulsion methods

      • Waste heat management

      • Chillers enhancement

      1- The first method is adding waste heat system on board ship:

      · Marine diesel engines on a ship are used only for two purposes

      a) Main propulsion engines

      b) Auxiliary engines

      · The engine operation always need cooling circuits to maintain the engine temperature at the optimum working temperature ,so we use heat exchanger to cool the engine water which can be ,fan on the heat exchanger which make cooling by air flow and this is not possible on board as the ship is closed and we will increase all the air temperature in the ship and this a very bad thing for crew and equipment so marine engineers decide to use heat exchanger which cool the engine jacket water by sea water

      · So we will take heat (energy) from the engine by jacket water then we will throw it into the sea water (lose it) and this will be a great loss for energy so they decide to build waste heat circuit that will make part of the outlet hot sea water inter another heat exchanger with fresh water with additives so we will transfer part of the energy lost to water which used to heat fresh water that have several usages ( shower , cooking , distillation systems,……etc.) so we don’t use heaters any more except on shore power.

      · We will control the engine jacket water temperature by 3-way valve.

      Heat-Capture.jpg



      2- The second method is chiller enhancement:

      · Chiller is one of the most important equipment on the ship as its used to cool down all the electrical equipment and some of the mechanical equipment but it uses huge amount of power


      • In the past we were using one reciprocating compressor per each chiller unit and this unit consume a lot of energy in comparison with the modified chillers as it has high losses due to:

      • Mechanical friction and heat loss to oil due to heat generation from friction

      • Oil resistance losses

      • Valves opening and mechanical movement …… etc.

      • To save all these losses we use oil free bearing less compressors which has 500 less friction and losses than the ordinary compressors

      • These compressors use magnetic bearings that prevent the mechanical friction due to rotation also don’t need any oil so we save the oil changing and money for maintenance



      · The starting consumes only two amps while the other compressor uses about 32 amps and this is called saving.

      · We also use multi compressors instead of only one compressor so at low loads we use only 1 compressor as shown

      o Note :(we can use the three compressors on low speed will be more economic than only one at higher speed)


      3- The third method is the combined propulsion system:

      • We were using on old ships gas turbines or diesel engines as a main propulsion method but this is not economic for this reason:
        • The minimum speed of the gas turbine and diesel engines as a main propulsion method will make about 6 knots of the ship so if I need lower speed, I will use another thruster in the opposite direction and this is a great loss of energy
        • By using gas turbine, we need a gear box so we will increase the mechanical losses which will by the way increase the fuel consumption
        • High maintenance and spare parts cost
      • For the previous reasons we used combined propulsion systems which have many configurations as:
        • Combination of gas turbine or electric power motor
        • Combination of gas turbine and electric power motor
        • Combination of diesel engines or electric power motor
       
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    3. john12

      john12 Well-Known Member EngineeringClicks Expert

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      I read that they're just implementing, or about to implement a new law that makes ships use cleaner fuel, although I'm not sure how this is enforced in International Waters (I feel like I've posted this before!).

      I wonder if there's ever a chance of them becoming electric. I guess that the power demands are just too huge for it to work any time soon (short of having a nuclear reactor!).
      I did some work for a company creating batteries for electric trains and their power demand was huge, so for a ship which is thousands of times larger (and travelling thousands of miles longer) the (giga/terra/peta)Watthours must be mammoth.
       
    4. Ahmedabdlehady

      Ahmedabdlehady Member

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      hello john
      yes it is very hard to make ships work as all electric machine so batteries is not applicable on board ships but we can use hypered systems as i mention
      thanks
       

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