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royal belgian institute of marine engineers marine fuels and engines by chris townsend e i naval architect guido perla associates inc marine propulsion starts at the prime a combination of ...

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                                Royal Belgian Institute of Marine Engineers
         Marine Fuels and Engines
                                                                                                                        By Chris Townsend, E.I.
                                                                                                    Naval Architect, Guido Perla & Associates, Inc.
         Marine propulsion starts at the prime  A combination of these factors can  Heavy Fuel Oil (HFO) 
         mover and ends at the propeller. In this,    also be cost-effective over the life of  -Historically the least expensive of in 
         the second article in our series of marine   the engine.One of the flaws in choosing      use marine fuels, heavy fuel oil is used 
         propulsion systems, we will discuss the      an engine that burns the cheapest fuel  extensively in the  low-speed recipro-
         most common types of marine prime  available is the unpredictable nature of  cating engines that power many of the 
         movers and the different fuels that they     both global and local marine fuel mar-      worlds largest commercial vessels.
         use. Many factors go into deciding which     kets. Prices could go up, prices could go   Though the cost of the fuel is low, the 
         prime mover best fits a given vessel.         down, or regulations could limit or pro-    use of heavy fuel oil for marine propul-
         These factors include the intended serv-     hibit the use of certain types of fuel.     sion requires a cleaning system to re-
         ice of the vessel, as well as the weight,                                                move excess impurities, as well as a 
         size, regulatory compliance, and cost of                                                 heating system to lower the viscosity 
         the prime mover. Cost considerations  Fuels                                              for efficient combustion. The energy re-
         typically include the initial cost of the                                                quired to deliver the fuel to the engine 
         engine, lifetime maintenance expenses,  The selection of a primary fuel can be  ready for combustion is quite high.   The 
         and fuel cost.                               influenced by other factors, such as  space and weight required for the heat-
         Optimization of fuel costs can be  storage arrangements and auxiliary sys-               ing and treatment systems associated 
         achieved one of two ways: choosing  tems associated with the chosen fuel  with HFO make using this type of fuel 
         an engine that burns the cheapest fuel  type.   Consider briefly the major types  impractical for smaller vessels.
         possible, or choosing an engine that is  of marine fuel in use today:                    Ever growing emissions standards are 
         particularly fuel-efficient.                                                              also making the primary use of HFO 
          SeaNG Rendering One of three Compressed Natural Gas (CNG) carrier versions designed by 
          Guido Perla & Associates, Inc. This 118-meter vessel carries 50 mmsCF of CNG in 16 coselles 
          and features a dual-fuel mechanical drive propulsion system.
          more expensive and less practical.              Current and future regulation will further     provides, without being unduly bur-
          New regulations allow for the creation  restrict the allowable levels of sulphur in            dened by the size and weight associated 
          of Sulfur Emission Control Areas (SECA),        distillate fuels, reducing pollution but al-   with the nuclear reactor. The high power 
          in which levels of sulfur emissions must        most certainly increasing costs as well.       density and high endurance capability of 
          be below those achievable when burn-                                                           a nuclear propulsion system also makes 
          ing currently available HFO.                    Natural Gas                                    it an attractive choice for icebreaking 
          This requires that a vessel be rerouted  First commonly used in marine propul-                 operations. However, there are certain 
          around the SECA, install a scrubber sys-        sion on LNG vessels, natural gas is now        drawbacks to nuclear propulsion that 
          tem to remove sulfur from emissions, or         becoming a more popular marine fuel,  generally limit its use to military ves-
                                                                                                     -
          switch to a more expensive low-sulfur  primarily due to its clean burning char                 sels.
          distillate fuel while transiting the SECA.      ac-teristics, producing signi-ficantly less     These constraints include the necessity 
          Reports from refiners indicate that there        carbon dioxide than other fossil fuels  for specialized (and expensive) manning, 
          is little interest in developing the tech-      for the same amount of heat generated.         high initial cost, the complexities of han-
          nologies necessary to dramatically re-          LNG additionally produces less NOx,  dling and disposing of nuclear materi-
          duce the sulfur content of HFO.                 SOx, and particulate matter than tradi-        als, and extremely stringent worldwide 
          Instead, the refiners argue money should         tional liquid fuels.                           regulation.
          be spent on increasing the overall refin-        Natural gas must be stored as a liquid 
          ing process, yielding more distillates  under pressure, and then warmed to a  Biodiesel
          from residual wastes.                           gas before combustion, creating some  Biodiesel is a clean burning alternative 
                                                          challenges in storage and piping ar
                                                                                                     -   fuel that is gaining traction in the marine 
                                                          rangements.                                             . As its name suggests, biodiesel 
          Marine Diesel Fuel/Marine Gas Oil                                                              industry
          These fuels are blends of distilled fuel                                                       is a fuel similar to diesel, but contains no 
                                                      .   Nuclear                                        petroleum products. Biodiesel is created 
          combined with small amounts of HFO
          They have lower levels of sulfur content        Nuclear fuel for marine propulsion, per-       through a chemical process called trans 
          than HFO and are cleaner burning.               haps the most controversial of all pro-        esterification, which separates glycerin 
          Though these fuels are more expensive,          pulsion fuels, is typically limited to large   from fat (such as soybean oil). When 
          elimination of heating and extensive  capital military vessels. These vessels  done in the presence of alcohol, this 
          treatment systems help justify the higher       tak
                                                             e advantage of the essentially unlim-       process leaves behind methyl esters, 
          costs.                                          ited cruising range nuclear propulsion  more commonly called biodiesel. 
                                                                                                         This type of fuel can be used in a typical 
                                                                                                         com-pression type reciprocating engine 
                                                                                                         with little or no modification.
                                                                                                         Biodiesel burns cleaner than conven-
                                                                                                         tional diesel distillates, in addition to 
                                                                                                         being made from renewable sources - 
                                                                                                         these factors mak
                                                                                                                              e biodiesel very envi-
                                                                                                         ronmentally friendly.  
                                                                                                         Engines
                                                                                                         The generation of power, whether to 
                                                                                                         send down a shaft or an electrical cable, 
                                                                                                         has been at the core of marine propulsion 
                                                                                                         since the application of steam power to 
                                                                                                         ships in the late 19th century. Years of 
                                                                                                         refinement and fine-tuning have resulted 
                                                                                                         in a large array of possible prime movers 
                                                                                                         suited to many different ships in a wide 
                                                                                                         variety of services.
                                                                                                         Internal Combustion Reciprocating
                                                                                                         The most common type of marine pro-
                                                                                                         pulsion prime mover is a reciprocating 
                                                                                                         internal combustion engine (such as 
                                                                                                         a diesel engine). This type of engine is 
                                                                                                         characterized by the intermittent rapid 
                                                                                                         burning of air and fuel inside a com-
                                                                                                                            , releasing energy that 
                                                                                                         bustion chamber
           MAN Diesel Engine Cross Section                                                               moves a piston, yielding linear motion 
           A cross sectional view of the vee configuration version of the MAN Diesel 51/60DF dual-        that is converted into rotational motion.
           fuel gas engine. This versatile prime mover is being installed in LNG carriers, as well as    Reciprocating internal combustion en-
           car and passenger ferries. (Image courtesy of MAN Diesel)
          gines typically fall into one of three cat-   engine speeds. Natural gas can be used        engine eases maintenance and down-
          egories describing the speed at which  in a slightly modified diesel engine in a  time - the small size makes it possible 
          the engine rotates. Low-speed engines  dual-fuel arrangement. Diesel is injected            to quickly swap out turbines instead of 
          typically rotate between 100 and 500  as pilot fuel to ignite the natural gas,  spending time at the dock doing in-place 
          RPM.                                          which will not detonate under extreme  maintenance or repair. The relative sim-
          Medium-speed engines rotate at speeds         compression alone. Alternatively, natu-       plicity of the engine is another second-
          of 700-1200 RPM. High-speed engines  ral gas can be used as a sole fuel source              ary advantage - there are fewer moving 
          generally rotate at 1800-4000 RPM. The        in a spark-ignited reciprocating internal     parts, none that reciprocate.
          particular advantages and disadvantages       combustion engine. As mentioned previ-        Some of the disadvantages of gas tur-
          of each of these types of engines must be     ously, diesel engines can also be made  bines are the strict inlet and exhaust 
          understood to properly match the engine       to run on biodiesel with little or no modi-   pressure requirements, the need for 
          to the application. Low-speed engines  fication necessary.                                   large, heavy gearboxes - particularly if 
          are large, heavy, and expensive, but pay      Diesel engines are well suited for a wide     used in a direct drive configuration, high 
          dividends on lower fuel, operating, and  variety of marine applications - in fact die-      exhaust gas temperatures, higher initial 
          maintenance costs when compared to a          sel engines can be found in nearly every      cost, and lower relative fuel economy 
          high-speed engine of the same output.  type of commercial marine vessel, from               - particularly at idle. A gas turbine can 
          Installation of a low-speed engine can  passenger vessels to tug boats. Diesel  burn nearly any grade of refined petro-
          also eliminate the need for a gearbox,  engines have recently gained traction in            leum such as marine diesel fuel and 
          saving further cost and weight.               LNG tanker propulsion, marking a shift  kerosene, as well as natural gas. Though 
          Perhaps one of the primary advantages  away from burning boil-off gas. Though  these fuels are expensive, the gas tur-
          of a recipro-cating internal combustion  the installation of a reliquefaction plant  bines fuel flexibility makes it attractive 
          engine is the widespread acceptance  adds complexity and cost to the ves-                   for volatile fuel markets.
          and use of this type of engine in the ma-     sel, rising market prices of LNG cargo  A gas turbine works well in high-speed 
          rine industry. The high production num-       and the greater achievable efficiency of       applications, where weight is always a 
          bers drive down cost and promote reli-        dual-fuel and diesel-electric propulsion  concern. Additionally, there is a growing 
          ability, while allowing for easy access to    systems has made this option attractive       market for gas turbines in vessels that 
          parts and trained mechanics.                  and financially viable.                        cannot afford excessive downtime, such 
          Reciprocating internal com-bustion en-                                                      as shuttle tankers 
          gines are not without fault. At the larger    Internal Combustion Rotational
          end of the spectrum, they do not have  Rotational internal com-bustion engines  External Combustion Rotational
          good power-to-weight ratios, though  (such as a gas turbine) are also utilized  Though internal com-bustion engines 
          this is generally offset by greater vessel    for marine propulsion. This type of engine    (parti-cularly diesel internal combus-
          displacement.                                 is charac-terized by continuous combus-       tion engines) are the dominant source 
          Reciprocating internal com-bustion en-        tion of air and fuel and conversion of this   of power in the marine industry, a ro-
          gines are capable of burning a variety of     energy directly into rotational motion.       tational external combustion propulsion 
          different fuels. Use of heavy fuel oil is  The principle advantage of installing a  plant (such as a nuclear-powered steam 
          traditionally limited to use in low-speed     gas turbine engine is the large power-        plant) still plays an important role in cer-
          engines, but marine diesel fuel and natu-     to-weight ratio this type of prime mover      tain services. An external combustion 
          ral gas are suited for a wider range of  can achieve. The compactness of the  engine heats the working fluid (typically 
          MaK Diesel 
          The MaK 9 M 43C propulsion engine shown here is a four-
          stroke medium-speed diesel engine, well suited to a variety of 
          common applications on intermediate-sized vessels.
          (Image Copyright Caterpillar Marine Power Systems 2008)
         steam) outside the mechanism (turbine), upon which the 
         working fluid expands, producing rotational motion.
         Like their gas turbine counterparts, a steam turbines advan-
         tages include the simplicity of fewer moving parts that rotate, 
         a good power-to-weight ratio, and compact size. The steam 
         boilers, however, which are neither small nor light, are a nec-
         essary compromise in this type of system.
         A steam system also requires constant upkeep and mainte-
         nance. Further disadvantages include a slower response time 
         compared to internal combustion engines, both from a cold 
         start and while underway.
         In most modern steam applications, steam is generated one 
         of three ways - burning marine diesel, burning natural gas, or 
         using nuclear fuel.
         Large vessels are the most practical platform for a traditional 
         steam power plant, regardless of the heat source. The nature 
         of their size requires a substantial installation of power, but 
         also allows for the installation of a large, heavy propulsion 
         system without an excessive penalty to the vessels perform-
         ance.
         Conclusion
         The real change in marine propulsion in recent times hasnt 
         been the types of engines installed, but the fuels that power 
                 egulatory and environ-mental changes are shifting 
         them. R
         the industry away from the exclusive use of HFO, towards 
         cleaner burning distillates. LNG is undergoing a radical shift 
         as it becomes less popular as a fuel for LNG tankers but 
         more common in environmentally friendly ferry, tug, and PSV          Teamwork alone is not 
         operations.
         Even nuclear power for commercial ships is an old idea being         enough – you also have to 
         resurrected. In this day and age, prime mover selection must 
         be a balance of modern environmental consciousness and old           be in the right boat
         world economic savvy. 
         References:
         ti#JPEJFTFM#BTJDTw
          
         ti/BUVSBM(BTBOEUIF&OWJSPONFOUw  
             < http://www.naturalgas.org/environment/ naturalgas.asp>
         t1BMPNBSFT
.JHVFMi*.05BLFTPOUIF&OWJSPONFOUBM
             Challenege.” Surveyor. Fall 2008. 2-4.
         t3BVUB
%SBHPTi5PXBSET$MFBOFS'VFMw4VSWFZPS'BMM
             2008. 21-23.
         SOURCE: MARITIME REPORTER & ENGINEERING NEWS NOVEMBER 2008   
         WWW.MARINELINK.COM
          
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...Royal belgian institute of marine engineers fuels and engines by chris townsend e i naval architect guido perla associates inc propulsion starts at the prime a combination these factors can heavy fuel oil hfo mover ends propeller in this also be cost effective over life historically least expensive second article our series engine one aws choosing use is used systems we will discuss an that burns cheapest extensively low speed recipro most common types available unpredictable nature cating power many movers different they both global local mar worlds largest commercial vessels go into deciding which kets prices could up though best ts given vessel down or regulations limit pro for propul include intended serv hibit certain sion requires cleaning system to re ice as well weight move excess impurities size regulatory compliance heating lower viscosity considerations efcient combustion energy typically initial quired deliver lifetime maintenance expenses selection primary ready quite high...

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