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Engineering Options for More Fuel Efficient Ships

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The paper surveys engineering options to save fuel in ships, both in design and operation. Both propul-sion and on-board consumers are discussed. Propulsion power depends on resistance and propulsive efficiency. Here, the main options are given, following a systematic breakdown of the individual resis-tance components and the efficiency losses at the propellers. For machinery and onboard consumers, a general discussion is followed by a description of simulation tools for design and operational guidance towards more fuel efficient designs and operations.
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Engineering Options for More Fuel Efficient Ships
Karsten Hochkirch, FutureShip GmbH, karsten.hochkirch@GL-group.com
Volker Bertram, FutureShip GmbH, volker.bertram@GL-group.com
Abstract
The paper surveys engineering options to save fuel in ships, both in design and operation. Both propul-
sion and on-board consumers are discussed. Propulsion power depends on resistance and propulsive
efficiency. Here, the main options are given, following a systematic breakdown of the individual resis-
tance components and the efficiency losses at the propellers. For machinery and onboard consumers, a
general discussion is followed by a description of simulation tools for design and operational guidance
towards more fuel efficient designs and operations.
1. Introduction
Mid-term and long-term fuel prices are expected to range from 500 to 1000 $/t including expected future
surcharges for CO
2
(carbon-dioxide) emissions. Therefore ship operators will put higher pressure on ship
owners to obtain fuel efficient ships. These in turn will put pressure on ship yards to supply fuel efficient
ships. As a result, we expect to see a paradigm shift in designs and refits to improve the fuel consumption
of ships.
There are any many ways to reduce fuel consumption.
- reduce required power for propulsion
- reduce required power for equipment on board
- use fuel energy more efficiently for propulsion and on-board equipment
- substitute fuel power (partially) by renewable energies like wind and solar energy
Surveys on partial aspects of fuel saving options have been published before. Several HSVA (Hamburg
Ship Model Basin publications, Hollenbach et al. (2007), Mewis and Hollenbach (2007), Hollenbach and
Friesch (2007), give rather comprehensive overviews of hydrodynamic options in design and operation of
ships. Hochhaus (2007) discusses various approaches to recuperate energy losses from the main engine to
use them for on-board equipment. New hull form features are developed to improve the fuel consumption
for given payload, Harries et. Al (2007). We will discuss more comprehensively the available options in
the following, but recommend them nevertheless for further studies.
2. Reduce required power for propulsion
We may use traditional hydrodynamic approaches to decompose the power requirements into resistance
and propulsion aspects. While propulsor and ship hull should be regarded as systems, the structure may
help to understand where savings may be (largely) cumulative and where different devices work on the
same energy loss and are thus mutually excluding alternative.
2.1. Reduce resistance
There are many ways to reduce the resistance of a ship. On the most global level, there are two (almost
trivial) options:
- Reduce ship size: The lightship weight may be reduced for example by (expensive) lightweight
materials, more sophisticated structural design involving possibly formal optimization and
reducing the ship length. None of these options is straightforward. The ship length should
consider hydrodynamic aspect as well as production and weight aspects. However, reducing the
required power during the design stage by the assorted measures discussed below will reduce in
turn the weight of engines, power trains and fuel tanks and yield considerable secondary savings
due to smaller ship size.
- Reduce speed: Speed reduction is a very effective way to reduce fuel consumption and emission.
Isensee et al. (1997) pointed already out that transport efficiency increases drastically with
decreasing speed, Fig.1. HSVA reports fuel savings of typically 13% for bulkers or tankers, 16-
19% for containerships, for a speed reduction by 5%, Mewis and Hollenbach (2007). Slow
steaming reduces in itself fuel consumption significantly. However, the ship is then operated in
off-design, thus sub-optimal condition. This offers assorted potential improvements to reduce the
fuel consumption further: electronically controlled main engines allowed better efficiencies at
slow steaming and reduce also lubrication oil consumption; controllable pitch propellers allow
better propeller efficiency over a wider range of rpm; adapted new bulbous bows may reduce
wave resistance considerably. On the other hand, waste heat from exhausts and cooling water is
considerably reduced and may require reconfiguration of auxiliary engine systems for slow
steaming. In sum, a supporting engineering analysis is recommended when deciding on slow
steaming for a longer time.
Fig.1: Transport efficiency vs speed for various vessels (modified Karman-Gabrielli diagram)
The largest levers in ship design lie in the proper selection of main dimensions and the ship lines. Ship
model basins should be consulted to assess the impact of main dimensions based on their experience and
data bases. On a more detailed level, for a given speed and ship weight, all components of the ship
resistance, Bertram (2000a), may offer fuel saving potential:
- Frictional resistance of bare hull: The frictional resistance (for given speed) depends mainly on
the wetted surface (main dimensions and trim) and the surface roughness of the hull (average hull
roughness of coating, added roughness due to fouling). Ships with severe fouling may require
twice the power as with a smooth surface. The battle against marine fouling is as old as seafaring,
Bertram (2000b). Silicone-based coatings create non-stick surfaces similar to those known in
Teflon coated pans. In addition to preventing marine fouling effectively, these smooth surfaces
may result in additional fuel savings. Figures of up to 6% are quoted by shipping companies. An
average hull roughness (AHR) of 65 μm is very good, AHR = 150 μm standard, and AHR > 200
μm sub-standard, Hollenbach and Friesch (2007). As a rule of thumb, every 25 μm of hull
roughness corresponds to 0.7-1% of propulsion power, N.N. (2008c). As a more exotic approach,
a film of air on part of the hull reduces friction and in turn fuel consumption. The air cavity ship
uses compressors to constantly pump air under the ship. However, the technical effort is
considerable. Researchers work on fuzzy acrylic paints that will contain thin air films. The air
film may even inhibit bio-fouling, preventing barnacles and other organisms from attaching
themselves.
- Wave resistance of bare hull: For given main dimensions, wave resistance offers large design
potential. Moderate changes in lines can result in considerable changes of wave resistance. As the
length of the created waves depends quadratically on speed, the interaction of bulbous bow and
forebody of the ship changes with speed. Thus a bulbous bow changes effectiveness with speed.
Bulbous bows should be designed based on CFD (computational fluid dynamics), but in most
cases fast codes based on simplified potential flow models suffice, Bertram (2000a). A formal
optimization is recommended as this may offer substantial savings on typical designs, Hutchison
and Hochkirch (2007), typically 4-5% can easily be gained and 1-2% improvement are feasible
even on hulls that are deemed already highly ‘optimized’ in limited form variations with CFD and
model tests in model basins, Fig.2, Abt and Harries (2007). Optimization of the aftbody lines
requires considerably higher computer resources due to the dominant effects of viscosity and
turbulence. However, pilot applications show the feasibility of the approach and formal
optimization of aftbody lines is expected to appear soon as a standard option in ship design. Hull
optimization, whether based on potential flow models or viscous flow models, is particularly
attractive for new designs where the ship owner can and should specify that such an optimization
is performed. For existing ships, refits of bulbous bows may have payback times of less than a
year, Hochkirch and Bertram (2009), but it is frequently problematic to obtain original hull
descriptions. Service providers (classification societies, model basins, consultants) cannot divulge
proprietary lines of one client (shipyard) to another (ship owner).
- Residual resistance of bare hull (mainly due to flow separation): Flow separation occurs when the
velocity gradients become too large in a flow. Large curvature in flow direction should then be
avoided. Flow separation in the aftbody is delayed by the flow acceleration due to the propeller
and different in model scale and full scale. CFD simulations may help in finding suitable
compromises between hydrodynamic and other design aspects.
- Resistance of appendages: Appendages contribute disproportionately to the resistance of a ship.
CFD simulations can determine proper alignment of appendages and design of high-performance
rudders, Fig.3. Rudders offer an often underestimated potential for fuel savings. Improving the
profile or changing to a highly efficient flap rudder allows reducing rudder size, thus weight and
resistance. Due to the rotational component of the propeller, conventional straight rudders at zero
rudder angle encounter oblique flow angles to one side at the upper part and to the other side in
the lower part. This creates opposing lift forces which cancel each other, but the associated
induced drag forces add. By twisting the rudder the
se unnecessary drag forces can be reduced.
Compared to a conventional semi-balanced rudder, a twisted rudder with Costa bulb may have
4% lower power consumption, Hollenbach and Friesch (2007). High-efficiency rudders combine
various approaches to save fuel: twisted rudders are combined with a bulb on the rudder as a
streamlined continuation of the propeller hub, e.g. Beek (2004), Lehmann (2007). In theory, the
gap between the hubcap and the forward part of the bulb should be as small as possible. In
practice there has to be gap sufficient to allow for structural deflection under load and propeller
aperture and rudder and also tolerances that can be realistically achieved under real shipbuilding
conditions. Savings of 2-8% are claimed by the manufacturers.
- Added resistance due to seaway: Intelligent routing (i.e. optimization of a ship’s course and
speed) may reduce the average added resistance in seaways. For example, the Ship Routing
Assistance system, Rathje and Beiersdorf (2005), was originally developed to avoid problems
with slamming and parametric roll, but may also be used for fuel-optimal routing. However, GL
experts estimate the saving potential to less than 1% for most realistic scenarios. In any case,
routing systems for fuel optimization should not only consider the added resistance to motions in
waves, but also the higher rudder resistance due compensation of drift forces.
- Added resistance due to shallow water: Routing systems may also consider shallow water and the
associated increased resistance, Friedhoff (2006).
- Added resistance due to wind: Wind adds power requirements in two ways: (a) direct
aerodynamic resistance on the ship and (b) indirect power demand due to drift in side winds. The
effect can be evaluated in wind tunnel tests and CFD simulations. Proposals for wind resistance
reductions include frontal spoilers, optimized container stowage and awnings. Savings of 1-1.5%
on the overall power demand have been estimated, Hollenbach et al. (2007). However,
operational constraints hinder practical applications so far.
For each draft and speed, there is a fuel-optimum trim. For ships with large transom sterns and bulbous
bows, the power requirements for the best and worst trim may differ by more than 10%, Mewis and Hol-
lenbach (2007). Systematic CFD simulations are recommended to assess the best trim and the effect of
different trim conditions. Decision support systems for fuel-optimum trim based on such simulations have
been proven to result in considerable fuel savings (typically 5% as compared to even keel) for relatively
low investment, Hansen and Freund (2010). They are expected to become a standard feature on larger
cargo ships within the next decade.
Fig.2: Hull lines optimization Fig.3: CFD for fuel efficient rudders
2.2. Improve propulsion
The propeller transforms the power delivered from the main engine via the shaft into a thrust power to
propel the ship. Typically, only 2/3 of the delivered power is converted into thrust power. A special
committee of the ITTC (1999) discussed extensively assorted unconventional options to improve
propulsion of ships and the associated problems in model tests. In short, model tests for these devices
suffer from scaling errors, making quantification of savings for the full-scale ship at least doubtful.
- Operate propeller in optimum efficiency point: The propeller efficiency depends among others on
rpm and pitch. Fixed pitch propellers are cheaper and have for a given operating point a better
efficiency than controllable pitch propellers (CPPs). They may be replaced if the operator decides
to operate the ship long-term at lower speeds. CPPs can adapt its pitch and thus offer advantages
for ships operating over wider ranges of operational points. Several refit projects have been
reported, with savings up to 17% quoted due to new blades on CPPs, N.N. (2008a).
- Reduce rotational losses: For most ships, there is substantial rotation energy lost in the propeller
slipstream. Many devices have been proposed to recover some of this energy. These can be
categorized into pre-swirl (upstream of the propeller) and post-swirl (downstream of the
propeller) devices. Pre-swirl devices are generally easier to integrate with the hull structure.
Rudders behind the propeller recover automatically some of the rotational energy. Therefore
potential gains should always be considered with rudder behind the propeller to avoid overly
optimistic estimates. Pre-swirl devices include the SVA Potsdam (Potsdam model basin) pre-
swirl fin, pre-swirl stator blades, Liljenberg (2006), and asymmetric aftbodies, Schneekluth and
Bertram (1998). Probably the best known post-swirl device is the Grim vane wheel, Schneekluth
and Bertram (1998). The original Grim vane wheel is located immediately behind the propeller
generating extra thrust. The vane wheel is composed of a turbine section inside the propeller
slipstream and a propeller section (vane tips) outside the propeller slipstream. The vane wheel
became unpopular after several reports of mechanical failures, most notably for the ‘Queen
Elizabeth 2’. IHI and Lips BV developed a modified vane wheel supported on the rudder,
overcoming the mechanical problems of the original Grim vane wheel, Fig.3, N.N. (1992). Other
post-swirl devices are stator fins and rudder thrust fins. Stator fins are fixed on the rudder and
intended for slender, high-speed ships like car carriers, Hoshino et al. (2004). Rudder thrust fins
are single foils attached at the rudder, proposed by Hyundai H.I. Typically 4% fuel savings are
claimed for all these devices by manufacturers. As all these devices target at the same energy
loss, only one of them should be considered. Gains are certainly not cumulative. CFD simulations
are the suitable tool to evaluate effects of these devices at full scale and aid their detailed design.
Contra-rotating propellers are a traditional device to recover the rotational energy losses,
Schneekluth and Bertram (1998). More recently, podded drives and conventional propellers have
been combined to hybrid CRP-POD propulsion, Ueda and Numaguchi (2006), claiming 13% fuel
savings.
- Reduce frictional losses: Smaller blades with higher blade loading decrease frictional losses,
albeit at the expense of increased cavitation problems. A suitable tradeoff should be found using
experienced propeller designers and numerical analyses.
- Reduce tip vortex losses: The pressure difference between suction side and pressure side of the
propeller blade induces a vortex at the tip of the propeller. This vortex (and the associated energy
losses) can be suppressed (at least partially) by tip fins similar to those often seen on aircraft
wings. The general idea has resulted in various implementations, differing in the actual geometric
form of the tip fin, ITTC (1999), namely contracted and loaded tip (CLT) propellers (with blade
tips bent sharply towards the rudder), Sparenberg-DeJong pr
opellers (with two-sided shifted end
plates), or Kappel propellers (with integrated fins in the tip region).
- Reduce hub vortex losses: Devices added to the propeller hub may offer cost effective fuel
savings. Propeller boss cap fins (PBCF) were developed in Japan, ITTC (1999), N.N. (1991).
Publications of the patent holders report 3-7% gains in propeller efficiency in model test and 4%
for the power output of a full-scale vessel. Reported gains have to be considered with caution,
Junglewitz (1996). “The presence of the rudder significantly reduces the strength of the hub
vortex and hence the gain in propeller efficiency due to PBCF can be reduced by 10-30%”, ITTC
(1999). The Hub Vortex Vane (HVV), jointly developed by SVA Potsdam and Schottel, offers an
alternative to PBCF. The HVV is a small vane propeller fixed to the tip of a cone shaped boss
cap. It may have more blades than the propeller. The vendors claim increases of 3% in propeller
efficiency.
- Operate propeller in better wake: The propeller operates in an inhomogeneous wake behind the
ship. This induces pressure fluctuations on the propeller and the ship hull above the propeller,
which in turn excite vibrations. The magnitude of these vibrations poses more or less restrictive
constraints for the propeller design. A more homogeneous wake translates then into potentially
better propeller efficiency, for example by a larger propeller diameter or larger blade loading on
the outer radii. For new designs, wake equalizing devices like Schneekluth nozzles (a.k.a. wake
equalizing ducts (WED)), Grothues spoilers, vortex generators, Schneekluth and Bertram (1998),
may therefore improve propulsion and save fuel. For existing ships, despite several refits more
recent independent analyses shed doubts concerning the effectiveness of WEDs, Ok (2005). “In
conclusion, partial ducts [like WED] may result in energy saving at full scale, but this was not,
and probably cannot be proven by model tests […]”, ITTC (1999). The Mewis duct combines pre-
swirl fins and wake-equalizing duct, Fig.5. 4% savings appear realistic for full hulls like tankers
or bulkers.
Fig.4: CFD for wake and propulsion improvement
source: www.friendship-system.de
Fig.5: Mewis duct
2.3. Other aspects
Resistance and propulsion and main engine interact. Partial improvements of individual components as
possible as discussed so far, but the system analyses considering the interaction of the components offers
additional saving potential.
Ships are frequently hydrodynamically tuned for a design speed, but later operated most of the time at
lower speeds, even when they are not “slow-steaming”. If designed for a more realistic mix of operational
speeds, ships are estimated to exploit further fuel saving potential. Similarly, an even speed profile in
operation saves fuel. This is largely a question of awareness. Fuel monitoring systems have proven to be
effective in instigating more balanced ship operation with fuel (and emission) savings of up to 2%.
3. Reduce required power for equipment on board
There are various options to save power in the assorted energy consuming equipment onboard ferries. The
saving potential depends on the ship type. Examples are in more efficient electronically controlled pumps,
HVAC (heat, ventilation and air conditioning) ventilation systems, and energy saving lighting. Energy-
saving lamps not only reduce the energy requirements for lighting, they also reduce the waste heat from
the lamps and thus the energy needed by air conditioning systems to cool lighted rooms down again.
Avoid oversized main engines. Sea margins should be adapted to ship type, ship size and intended opera-
tional trade. This is especially true for fast ships. Sea margins should be selected based on simulations or
experience for specific ship types, but not globally imposed. Margins for rare high-speed operation are
expensive and may be better covered by falling back on the auxiliary engine power (power take-in (PTI)
via shaft generator). Detailed engineering analyses can be used to assess feasibility and cost aspects of
alternative configurations, Fig.6. For slow-steaming ships with controllable pitch propeller, it is better to
reduce the brake mean effective pressure than the rpm. Intelligent monitoring and simulation software can
combine engine supplier data and standard onboard monitoring data for a given operational profile to
determine optimum combinations of propeller pitch and rpm.
Fig.6: Machinery simulation tool, Freund et al. (2009)
Avoid oversized auxiliary engines. Better overall energy management systems may balance the energy
demand of the consumers on board reducing peak demands allowing in turn a reduction of the generator
capacity. This in turn reduces the weight of the ship. Simulations of the overall machinery system are able
to predict fuel consumptions for provided energy consumer profile. These simulations allow assessment
of alternatives and ultimately better balanced energy profiles.
Our simulations are based on the software ITI SimulationX. The simulations can be adapted easily to
different ships using a library of predefined machinery components. The simulations were validated for
two ships, Freund et al. (2009). The fuel consumption was calculated within 2% deviation of the reported
noon data over periods of 4-8 weeks. Installed onboard, the current consumption of mechanical and elec-
trical energy can be displayed in combination with the fuel consumption of the engines and their effi-
ciency of power generation, Hansen and Freund (2010). In conjunction with the displayed time lines, the
crew can evaluate their actions with regard to energy consumption, e.g. avoiding unnecessary peak loads
requiring a higher number of running engines. An example is displayed in Fig.7, with the current values
of the main engine displayed on the left with the related timelines on the right.
Fig.7: Energy Efficiency Monitoring for main engine
4. Increase use of renewable energies
Wind has been the predominant power source for ships until the late 19
th
century. Wind-assistance has
enjoyed a recent renaissance. Wind-assisted ships use predominantly other means of power (typically
diesel engines) and wind power plays only a secondary role. With increasing ship speed, wind assistance
makes less sense as increasingly efficient sails are needed. Constraints are initial investment, space re-
quirements, stability and required man-power for operation and maintenance. Despite these constraints,
several industrial projects have been realized in the past decade. Wind kites have been brought to com-
mercial maturity by the company Skysails, Fig.8, drawing also on expert advice from Germanischer
Lloyd. Kites harness wind power at larger heights without the stability penalties of high masts. The de-
velopment has enjoyed large media attention, and in 2007 the first prototype was tested successfully on
the MS “Beluga Skysails” and the “Michael A”, N.N. (2008b). Fuel savings in excess of 10% quoted by
the manufacturer apply for slower ships. Flettner rotors are another technology harnessing wind energy
for ship propulsion. After 80 years of obscurity, they have resurfaced in 2008 when Lindenau shipyards
delivered a GL-class freighter equipped with Flettner rotors. These four cylinders, each 27 m tall and 4 m
in diameter, are predicted to save nearly half of the conventional fuel needed by the ship.
Fig.8: Towing kite harnessing wind energy, source:
www.skysails.de
Fig.9: SolarSailor catamaran ferry,
source: www.colarsailor.com
Solar energy may supply an environmentally friendly part to the total energy balance of a ship. For inland
ferries, solar power and fuel cells are an attractive option to have zero-emission ships. For other ships,
diesel and solar energy may be combined. Diesel-electric drive systems are already quite common. Future
ships may combine then diesel generators for 50% of the total power consumed, fuel cells providing 30%
and a solar generator accounting for the remaining 20%. Solar-power and wind-power can be combined,
using fixed sails equipped with solar panels. This option is employed successfully on the SolarSailor fer-
ries operated in Sydney and San Francisco, Fig.9.
5. Conclusion
There are many technical levers to save fuel and thus emissions for ships. Unfortunately, there is large
scatter in saving potential and quoted saving potential is unreliable. Manufacturers frequently quote best
cases and sometimes extrapolate erroneously results from model tests to full scale ships. Despite these
uncertainties, the compiled information may serve for a first assessment on a case by case basis and
identification of most promising options. This requires interdisciplinary team work of clients and
consulting experts. For a more quantitative assessment, dedicated analyses often based on simulations are
required.
Despite these words of caution, there is wide consensus that significant potential for fuel saving exists and
dedicated consultancy companies can support ship owners and operators in tapping into these potentials.
Acknowledgements
Many colleagues at Germanischer Lloyd have supported this paper with their special exper
tise, namely
(in alphabetical order) Bettar El Moctar, Malte Freund, Volker Höppner, Andreas Junglewitz, Ralf Plump,
Gerd-Michael Würsig.
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per143_090630.pdf
... There is no direct method to improve the efficiency of the small boats used for riverine transportation in remote regions. In fact, reducing the fuel consumption and increasing the performance of the boat requires several optimization projects since there are different fuel-optimal working conditions for each boat draft and speed [22]. ...
... Hochkirch and Bertram [22] explained that there are several ways of decreasing the consumption of fuel by a vessel: reducing the required power for operation and propulsion; using fuel energy for propulsion and on-board equipment more efficiently; and using hybrid technologies for operation, combining fossil fuels with renewables, such as solar energy. According to [22], there are several factors to be considered to reduce the power required for propulsion, thus improving the performance of a ship. ...
... Hochkirch and Bertram [22] explained that there are several ways of decreasing the consumption of fuel by a vessel: reducing the required power for operation and propulsion; using fuel energy for propulsion and on-board equipment more efficiently; and using hybrid technologies for operation, combining fossil fuels with renewables, such as solar energy. According to [22], there are several factors to be considered to reduce the power required for propulsion, thus improving the performance of a ship. These can be classified into improving the propulsion system and reducing the boat's hydrodynamic resistance, as shown in Figure 1. ...
Article
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This paper explores means of achieving more efficient and sustainable river transport in remote regions by making relatively simple, practical modifications to boats or implementing new technologies for propulsion and energy generation. The research focuses on the case of the simple boats used to transport children to school in riverine communities of the Brazilian Amazon. A range of options to improve the efficiency of existing boats is described. Under normal operational conditions, small improvements to these boats may have long-term environmental and socioeconomic benefits. Implementing changes such as those suggested, it may also be possible to boost sources of employment in these regions and elsewhere, where industrial and technological limitations are significant.
... Furthermore, minimized rudder torque can also reduce the fuel consumed by the steering gear. In general, 2-8% saving can be achieved by optimizing the rudder configuration in terms of profiles, types, and efficiency-improving devices [43]. ...
... Hochkirch and Bertram [43] pointed out that the rudder has an underestimated potential for fuel reduction, for instance, reducing the rudder size (weight and resistance) by improving the rudder profile or changing to a highly efficient flap rudder. Lehmann [70] summarized that an efficient rudder system should have a slim and low drag rudder profile, generate high lift at small rudder angles, have a smooth surface, be tuned with the propeller, be light-weighted, and be easy to maintain. ...
... Rudder cavitation has become more and more serious [2,38] in the past years. However, the service speed of ships tends to be decreased to save fuel and meet the EEDI requirements [43,45,70]. Thus, cavitation may become less significant in the future. ...
Chapter
This chapter elaborates on the factors that should be considered to design a rudder. Accordingly, how to evaluate the performance of a rudder is introduced. Section 2.1 gives an introduction of the study on ship rudders. To achieve reasonable results, experiments and simulations of rudders should be carried out at relevant Reynolds numbers and angles of attack, which are discussed in Sect. 2.2. The rudder induced maneuvering forces and moments are affected by, including, but not limited to, the rudder profile, the rudder parameters, the rudder type, the number of rudders, the spacing between rudders, and the relative positions among the hull, the propeller, and the rudder. The key factors are identified through a review of each of the above-mentioned impacts on the rudder hydrodynamics in Sect. 2.3, which are further studied through CFD simulations in Chap. 4. To judge the quality of the rudder design, Sect. 2.5 presents the evaluation perspectives of the rudder performance in ship maneuverability, fuel consumption, and rudder cavitation. Section 2.6 draws a summary of this chapter.
... Furthermore, a rudder may increase the total resistance by 1 % at the neutral position and 2 % to 6 % at moderate angles [5]. Correspondingly, optimising the rudder profile and type can reduce the total resistance by 2 % to 8 %. [98]. ...
... In general, rudders have significant impacts on ship manoeuvring performance as well as an underestimated potential for fuel savings [98]. Molland and Turnock [206,p. ...
... Furthermore, minimised rudder torque can also reduce the fuel consumed by the steering gear. In general, 2 % to 8 % saving can be achieved by optimising the rudder configuration in terms of profiles, types, and efficiency-improving devices [98]. ...
Thesis
Ship manoeuvrability is fundamental for the navigation safety of ships. Furthermore, through the equipment used for manoeuvring, it also affects investment, operation, and maintenance cost of these ships. Ships are primarily designed from an economic point of view. To ensure and improve the maritime efficiency, research on inland vessel manoeuvrability deserves more attention than the present situation. Most of the research on manoeuvrability has been performed for seagoing ships. Since sailing conditions and ship particulars between seagoing ships and inland vessels are different, the impacts of these differences on manoeuvring prediction and evaluation should be carefully considered. Inland vessels should be designed in such a way that they should always be capable of manoeuvring without significantly harming the cost-effectiveness of operations. One of the biggest differences between seagoing ships and inland vessels is the rudder configuration. Conventionally, seagoing ships have similar single-rudder configurations while inland vessels have more complex multiple-rudder configurations. Although multiple-rudder configurations can have a positive effect on manoeuvrability, they often have a negative effect on resistance and, therefore, also a negative effect on the fuel consumption. Quantitative impacts of the rudder configuration on ship manoeuvrability have not been fully understood, especially for multiple-rudder configurations with complex rudder profiles. These differences in the rudder configuration may significantly change the ship manoeuvring behaviours and, therefore, should require further research. Moreover, to compare and evaluate the manoeuvring performance of inland vessels with different configurations, the existing manoeuvring tests and standards for inland vessels are less elaborate than those for seagoing ships. The above-mentioned considerations formulate the following main research question: What are the proper rudder configurations to achieve well manoeuvrable inland vessels without significant loss of navigation efficiency? The main research question of this thesis can be answered through resolving four key research questions as follows: Q1. What are the practical manoeuvres to evaluate and compare the manoeuvring performance of inland vessels? Q2. How does the rudder configuration affect the rudder hydrodynamic characteristics? Q3. How do changes in the rudder configuration affect the ship manoeuvrability in specific manoeuvres? Q4. How to choose a proper rudder configuration according to the required manoeuvring performance? An accurate estimation of rudder forces and moments is needed to quantify the impacts of the rudder configurations on ship manoeuvring performance. This thesis applied Reynolds-Averaged Navier-Stokes (RANS) simulations to obtain rudder hydrodynamic characteristics and integrated the RANS results into manoeuvring models. Additionally, new manoeuvres and criteria have been proposed for prediction and evaluation of inland vessel manoeuvrability. Simulations of ships with various rudder configurations were conducted to analyse the impacts of rudder configurations on ship manoeuvrability in different classic and proposed test manoeuvres. Accordingly, guidance on rudders for inland vessel manoeuvrability has been summarised for practical engineers to make proper design choices. Through the research presented in this thesis, it is clear that different rudder configurations have different hydrodynamic characteristics, which are influenced by the profile, the parameters, and the type of a specific configuration. New regression formulas have been proposed for naval architects to quickly estimate the rudder induced forces and moments in manoeuvring. Furthermore, an integrated manoeuvring model has been proposed and validated for both seagoing ships and inland vessels. Using the proposed regression formulas and manoeuvring model, the impacts of rudder configurations on inland vessel manoeuvrability have been studied. The manoeuvring performance of a typical inland vessel can be improved by 5% to 30% by changing the rudder configuration. The rudder configuration should be capable of providing sufficient manoeuvring forces and then optimised to reduce the rudder induced resistance. In general, well-streamlined profiles are good for efficiency but not as good as high-lift profiles for effectiveness. As a summary, the ship manoeuvring performance can be improved by using effective profiles, enlarging the total rudder area, accelerating the rudder inflow velocity, increasing the effective rudder aspect ratios, and enlarging the spacing among multiple rudders.
... Furthermore, minimised rudder torque can also reduce the fuel consumed by the steering gear. In general, 2%-8% saving can be achieved by optimising the rudder in profiles and types (Hochkirch and Bertram 2010). Hochkirch and Bertram (2010) pointed out that the rudder has an underestimated potential for fuel reduction, for instance, reducing the rudder size (weight and resistance) by improving the rudder profile or changing to an efficient flapped rudder. ...
... In general, 2%-8% saving can be achieved by optimising the rudder in profiles and types (Hochkirch and Bertram 2010). Hochkirch and Bertram (2010) pointed out that the rudder has an underestimated potential for fuel reduction, for instance, reducing the rudder size (weight and resistance) by improving the rudder profile or changing to an efficient flapped rudder. Lehmann (2007) summarised that an efficient rudder system should have a slim and low drag rudder profile, generate high lift at small rudder angles, have a smooth surface, be tuned with the propeller, be lightweighted, and be easy to maintain. ...
... The rudder cavitation has become more and more serious (Han et al. 2001;Ahn et al. 2012). As the service speed tends to be decreased to save fuel and meet the EEDI requirements (Hollenbach and Friesch 2007;Lehmann 2007;Hochkirch and Bertram 2010). The cavitation may become less significant in the future. ...
Article
Rudders are primary steering devices for merchant ships. The main purpose of using rudders is to generate forces for course-keeping and manoeuvring. In exceptional cases, rudders are also used for emergency stopping and roll stabilisation. Furthermore, rudders affect propeller thrust efficiency and total ship resistance. Therefore, rudders are important to navigation safety and transport efficiency. The performance of rudders depends on the rudder hydrodynamic characteristics, which are affected by the design choices. Scholarly articles concerning the design of rudders date back more than 60 years. Moreover, a lot of knowledge fragments of rudders exist in literature where ship manoeuvrability and fuel consumption are discussed. It is worthwhile to gather this information not only for researchers to advance the state-of-the-art development but also for designers to make proper choices. To have a contemporary vision of the rudders, this paper presents a consolidated review of design impacts on rudder performance in ship manoeuvrability, fuel consumption, and cavitation. The discussed design choices are rudder working conditions (Reynolds numbers and angles of attack), profiles (sectional shapes), properties (area, thickness, span, chord, and rudder aspect ratios), types (the position of the stock and the structural rudder-hull connection), and interactions (among the hull, the propeller, and the rudder). Further research is suggested on high-lift rudder profiles, multiple-rudder configurations and interactions among the hull, the propeller, and the rudder. Recommendations for industry practices in the selection of the rudder design choices are also given.
... Policies regulating carbon dioxide emissions from ships were yet to see implementation by IMO regardless of their immense emission reduction potentials achievable via available operational and technical measures (Harrould-Kolieb and Savitz 2010). In study of Hochkirch and Bertram (2010), the energy consuming equipment on the ship could be reduced by adopting a number of approaches. Energy savings could be achieved by adopting efficient electronically controlled pumps, HVAC ventilation system, and energy saving lighting. ...
... Energy savings could be achieved by adopting efficient electronically controlled pumps, HVAC ventilation system, and energy saving lighting. The exhaust heat could be used for steam generation and hot coolant could be used for producing fresh water from sea water (Hochkirch and Bertram 2010). In one study, Mewis and Hollenbach (2007), illustrated that the typical fuel savings was 13 % for bulkers or tankers, 16-19 % for containerships, for a speed reduction of 5 % (Mewis and Hollenbach 2007). ...
Chapter
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This study is focused on the natural gas production in the pre-salt area, in Brazil, where much of the expansion of the Brazilian oil industry is projected to occur. The oil production is based on a previous study, which indicates that in 2050 the pre-salt oil production can reach up to 3,160,000 bpd, and the total Brazilian oil production can be up to 3,765,000 bpd. Simulations were made to try to estimate the natural gas production for the period between 2015 and 2050. One great challenge of the petroleum production in this area is to deal with the large amount of CO2 present in these fields. This study considered Carbon Capture and Storage (CCS) as a mitigating option for the CO2 that would be emitted during the petroleum extraction. Carbon capture and storage (CCS) is recognised as a technology capable of reducing the large-scale emissions of carbon dioxide (CO2), which is an important part of the portfolio of alternatives necessary to achieve significant reductions in the global emissions of greenhouse gases (GHG). This study identified that the most suitable carbon capture method for the platforms (Floating Production, Storage, and Offloading (FPSOs)) that will operate in Brazil’s pre-salt fields is the use of membranes. Based on this capture method (membranes), the UOP Separex™ module system is selected as the standard to be tested. It is a compact module that can be installed on FPSOs. Because there remains considerable uncertainty over the precise amount of CO2 present in the natural gas from the pre-salt fields, a wide range, between 10 and 45 %mol of CO2 content was considered. The membrane area for each module was considered to be equal for both 10 %mol and for 45 %mol of CO2. The results show that in 2050, the gas production in the pre-salt region can be around 35,000 Mm3 per year, considering that the amount of CO2 in the natural gas is 10 %mol. However, it can be up to 20,000 Mm3 when considering that the amount of CO2 present in the natural gas is around 45 % mol.
... Generalmente el propulsor se analiza conjuntamente al timón desde que se mejoraron los medios de simulación con modelos de fluidos (Computational Fluid Dynamics (CFD)). Las posibles mejoras en el diseño de la hélice y modificadores de las formas de los miembros como aletas o conductos de propulsores [65]. ...
Thesis
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The energy production and consumption systems are affected by a large number of dynamic variables. Thus, these variables are defined by their relationship and its dependence in time. Due to, the number and typology of variables which are present in energy systems is very large. So, actions developed to seek for Energy Efficiency improvement and optimization is too complicated.
Article
Energy efficiency has become increasingly relevant in the current economic and environmental situations. This paper aims to create a map of the state of the art of the energy efficiency on the marine sector, both in the scale of the individual ships and the entire industry. The first point of interest will be an examination of the regulatory framework of the shipping sector in regards of energy efficiency. Next there are the procedures implemented on ships with the aim of diminishing their consumption and emissions. These measures range from modifications of the design to the operational practices. Following that will be the potential advances that the industry could implement on a bigger scale to enhance the efficiency of the whole sector. Finally, an overview of the main obstacles for the implementation of these measures will be examined. While the current standards are a temporary solution and several of the most prominent improvements require further investigation, the continuous effort increases the potential of this sector for optimization. These factors emphasize the utility of this review as an introduction to help other studies have a solid understanding of the state of the art of energy efficiency in the naval industry.
Article
In the Global Maritime Supply Chains (GMSCs), sustainable development and growth of containerized freight (cargo stuffed in maritime containers for transportation) transport system and container port/terminal business have attracted attention of regional governments, financial institutions and regulatory bodies across the globe. Particularly, growing worries about the unpropitious impacts on the environment caused by containerized freight transport industry. The industry has contributed immensely in growth and expansion of global trade and therefore increased trade promises sustainable growth of global port and shipping activities. Competition in liner shipping industry has shrunk profits of the carriers while struggling to grab more market share, which has led them to work upon creating value to the customers in order to gain edge over others. Therefore, this study is conducted from business perspective that how the global container shipping sector can create value to its customers and stakeholders and also go tandem with environmental aspect. The objective of the study is to identify and examine the value creating factors and sub-factors of GMSCs of containerized freight. Data on value creating factors is collected by consulting 57 ports and shipping industry experts globally. We propose FAHP (Fuzzy Analytic Hierarchy Process) framework for evaluating these value creating factors and develop this study which will not just help carriers but also the stakeholders in the containerized freight transport industry to measure their competitive edge over rivals. This study concludes with sensitivity analysis, results and discussions, managerial and practical implications of the conceptual framework.
Chapter
Emissions threaten not only human health but also the human environment and air quality. The most well-known emissions sources are ships, air planes, motor vehicles, and various industrial facilities. Among these emissions sources, ships are the biggest emitters of air pollution. Increasing numbers of ships and new port investments near the coast exacerbate health risks. If measures are not taken, the threat will increase incrementally in the near future with the contribution of ship operations in new port investments, such as Asyaport. Asyaport is in the Tekirdag region, which serves as bridge connecting the continents of Asia and Europe. The Tekirdag region is also one of the most highly populated and industrialized areas in Turkey. Because of population density and industrialization, the amounts of emissions are very important for local residents of Tekirdag. In this study, the authors aim to reveal how the new port affects air quality and human health risk in the Tekirdag region. For this aim, two-step analyses were conducted. First, a theoretical perspective of the ship emissions was considered based on chemical reactions during combustion per fuel oil kilogram and different navigation phases, i.e., cruising, maneuvering, and hotelling. Second, various scenarios were considered in cases of different sulfur limitation policies and use of alternative fuel (liquified natural gas (LNG)) for the numerical investigation. Finally, these scenarios were implemented in Asyaport. The emissions (CO2, SO2, SO3, NO, NO2, total nitrogen oxides (NOx), and sulfur oxides (SOx)) were illustrated for different fuels and different percentages of sulfur until the year 2045, and the grand total of SOx and NOx emissions was estimated as 1,249,278 tons.
Chapter
Energy efficiency is very important in maritime sector. One of the important factors that affect the energy efficiency of ships is pollution in the fluid system. One of the most important issues of our time in the field of science and technology is energy efficiency. The higher energy efficiency, the less global warming. In this study effects of turbulent, corrosion, pollution which are the issues that have the most effect on problems and energy losses which cause emissions, operating costs, material fatigue and defects are analyzed and focused on a case study of a significant vessel and potential solutions. To what extent these effects affect energy efficiency is calculated and the potential risks that they might cause are discussed. Consequently, the reason why turbulent, corrosion, pollution effects are needed to be kept at minimum extent has been determined.
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Manson Construction Company's 12,000 cu.yd. (9175 m 3) trailing suction hopper dredge M/V Glenn Edwards is the newest and largest hopper dredge in the U.S. fleet. Unusual among large hopper dredges, the Glenn Edwards is propelled by three 1,920 kW azi-muthing Z-drive units fitted with nozzles. This paper describes the formal CFD hull form optimization proc-ess for the Glenn Edwards. An unusual feature of this formal hull form optimization process was the CFD evaluation of performance both in deep and shallow water operations, as both regimes are important to the operation of a hopper dredge. The paper describes the development of the constraint set, CFD modeling con-siderations, the optimization process and the results obtained. Comparison is made between CFD results and results obtained from model tests of the selected optimum hull at MARINTEK in Trondheim, Norway. Mention will also be made of observations and results from sea trials and early service.
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FRIENDSHIP SYSTEMS, Germany. SUMMARY Increasing size and speed and rising fuel prices require that a container ship's hydrodynamics need to be at the highest level of sophistication. The integration of geometric modeling and flow simulation offers new opportunities to improve design processes and the quality of the resulting ships. The paper presents considerations of economic aspects, design methods and results from a comprehensive optimization project for a medium-size container carrier. A novel hull design element was established that improves transport efficiency without impairing operational qualities. The element reduces resistance and increases payload and is based on an innovative layout of the sectional area curve (InSAC). The novel volume distribution influences a ship's free wave pattern advantageously, reducing the energy loss in the free waves generated by the steadily advancing vessel. Benefits are shared by shipyards, operators and owners alike resulting from the options of installing smaller engines, unloading the propulsion plant, utilizing added displacement or further pushing design speed.
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Nowadays, the design of luxury motor yachts is focussed on ever higher speeds. Froude numbers between 0.6 and 0.8 are no longer an exception. The typical load profile of a motor yacht often consists of long range cruising at low speeds and only short periods of time at higher and maximum speeds. This indicates the need for focussing hull design over the entire speed range rather than on maximum speed only. For this purpose the concept of the Fast Displacement Hull Form (FDHF) is introduced. The concept and the use of design features that have a large effect on the resistance over the speed range, such as the area of the immersed transom, bulbous bows, trim control and spray rails are discussed. A design methodology using a formal optimization method for the bulbous bow is described and it is shown that bulbous bows are also effective in the semi-displacement speed range. A comparison of the FDHF concept, in terms of resistance, with model tests of displacement and semi- displacement motor yachts, shows a significant resistance improvement over the entire speed range, but especially at displacement speeds when comparing to semi-displacement hull forms. Issues such as stability, interior space and building cost are addressed.
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In times of increasing fuel prices the operational fuel efficiency of ships is becoming more and more important. The ECO-Assistant is a modular tool for optimising different aspects of a Ship's operational fuel efficiency. This paper discusses two ECO-Assistant modules; the ECO-Trim-Assistant to allow the crew to sail the ship at optimum trim all the time by calculating the optimum trim angle for different operating conditions and the ECO-Energy-Assistant which enables the crew to monitor the energy consumption of the different consumers such as main and auxiliary engines, generators and pumps. The paper shows the fuel savings potential of utilising the ECO-Assistant onboard a ship. With assistance tools such as the ECO-Assistant the operational fuel efficiency of ships in service can be improved significantly without making expensive modifications to the vessel.
Article
Mr. A knows the CAD (computer aided design) system available in his design environment by heart and produces hull forms, appendages, rudders and other functional surfaces with great skill and know- how. Dr. B is a CFD (computational fluid dynamics) expert who sets up and runs the CFD system of choice with aptitude and long-time experience. Ms. C is in charge of the current new building and needs to know if the performance of the design can still be improved by a few per cent to meet the customer's expectations - she might have to win the contract yet or cares to avoid falling short of earlier promises. Now, Mr. A already is fully involved in another project and hardly finds the time to squeeze in any changes let alone realize hull form modifications of suitable quality in a short period of time. Dr. B just left for a business trip and probably struggles with his jet lag. Dr. D might actually be able to help since she is a CFD expert, too. However, she has not worked with the CFD code needed for the specific investigation. She would certainly be able to interpret the CFD results and use them for comparison with the previous baseline but it would take her quite some time to run the new computations as there are several files to be touched and preparations to be made. One week later: The other design that Mr. A was busy with when he was asked to assist in the new building project now is ready for detailed studies. It is a complicated situation in which many constraints need to be observed, a few of which require some computational effort while others are rather simple. Nevertheless, taking care of all of them at once is tricky and any change introduced to the neatly balanced baseline might cause havoc. Two alternatives are finally ready for CFD based investigations. Unfortunately, both fall short of the team's ambitious hopes. Well, it has been a rather new hull concept after all. Dr. B has returned from abroad and now proposes two changes to the shape. Mr. A will bring them about but it takes precious time before the next CFD runs can be started. Ship design is a complicated matter. Not only because ships constitute complex systems but also because there are multi-level relationships and dependencies - between people, tools, organizations etc. The complexity of ships will continue to increase in order to meet market requirements and so will specialization and, hence, division of labor. Therefore, most companies have long invested in team building, appreciating that a team is more than just a group of people. The same holds for tighter integration of CAD and CFD: The outcome of the synthesized effort is more than the sum of its individual parts. Having realized this and knowing the design scenarios described above from both own experience and direct consultancy, FRIENDSHIP SYSTEMS has introduced a new CAE (Computer Aided Engineering) environment to allow for better use of CAD and CFD. The system was called FRIENDSHIP-Framework to acknowledge the fact that, firstly, there are established codes in the market which need to be utilized rather than replaced and that, secondly, design teams have their individual preferences and mode of operation. The system provides views on and access to the various aspects of interest and aims at supporting the hydrodynamic design process, Fig.1. The new approach to integration of CAD and CFD will be discussed in the sections to come. Light will be cast on (i) closer communication along with direct and non-redundant access to common data,
Article
Stator fin, an energy-saving device applicable to a high-speed slender ship, is installed to the rudder behind of the propeller for recovering the rotational energy loss of the propeller. The stator fin was designed for a car carrier and evaluation was carried out using theoretical calculations and model tests. Further, in addition to the full-scale speed trial, the stress measurement, vibration measurement and observations of the stator fin were carried out in order to confirm the reliability and performance and to acquire the basic data regarding the stator fin. The results showed that the stator fin had no problem whatsoever regarding energy-saving effect, strength and vibration. The stator fin is on the verge of being regarded as a standard device to be installed in car carriers built by MHI. Its application to the ships equipped with higher-power main engines, such as container ships, etc. is under study. Energy saving in ships has become all the more an im- portant factor from the standpoint of reduction of operating cost and CO2 emissions for preservation of global environ- ment. So it becomes more necessary to optimize hull form and develop various energy-saving devices. Among such energy-saving devices, Mitsubishi Heavy Industries, Ltd. (MHI) has developed reaction fins to in- stall at the front of the propeller for recovering the rotational energy loss of the propeller, and has installed them in low-speed, full ships such as tankers, etc., with excellent results. MHI has further developed a stator fin as an energy-saving device to be installed to the rudder behind of the propeller that can be applied also to high- speed, slender ships. This paper describes the principle and design of stator fin as well as the full-scale validation. 2. Principle of stator fin 2. Principle of stator fin 2. Principle of stator fin 2. Principle of stator fin 2. Principle of stator fin
Technology Guidelines for Efficient Design and Operation of Ship Propulsors, Marine News
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Beek, T. van (2004), Technology Guidelines for Efficient Design and Operation of Ship Propulsors, Marine News, Wärtsilä.
Past, present and prospects of antifouling methods, 32 nd WEGEMT School, Plymouth
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Bertram, V. (2000b), Past, present and prospects of antifouling methods, 32 nd WEGEMT School, Plymouth, pp.85-97.