RETROFIT PROPULSION IMPROVEMENT BEFORE AFTER HYDRODYNAMICS SAVE UP TO 15% ON FUEL COSTS The total propulsion efficiency of a propeller FRICTIONAL LOSSES varies between 50%and 70%.The losses Water in contact with the propeller blade The fuel prices have risen considerably the for an average propeller can be traced to 3 surface causes friction,and thus losses.The last years,resulting in an increase of ship physical phenomena: total blade surface,speed of rotation and operating costs.To maintain the economic surface roughness are the dominating factors profitability of the vessel,a large focus is AXIAL LOSSES conceming frictional losses. nowadays on fuel saving devices in the A propeller generates thrust,due to the broadest sense of the word. acceleration of the incoming water.Behind ROTATIONAL LOSSES A number of options is available to the vessel,the out coming flow mixes with the Rotation of the blade causes a rotation in the improve the efficiency of the propulsion environmental flow.Due to turbulence,energy wake too;consequently this energy is lost to system,depending on the type of propeller will be lost generate a thrust in axial direction. and vessel.In this leaflet we explain the propulsion improvements through retrofits and the economic effects by means of the axial losses 20% Return On Investment (ROI). frictional 55es15% efficiency 60% 600 -HF0 3%S 500 -HF0 1%S =LF00.035%S 400 Visualization of axial losses. Example of type of losses general ship propeller. 300 200 0的09129郎94569789的00120的040防 Year Increase in fuel prices. WARTSILA
RETROFIT PROPULSION IMPROVEMENT HYDRODYNAMICS The total propulsion effi ciency of a propeller varies between 50% and 70%. The losses for an average propeller can be traced to 3 physical phenomena: AXIAL LOSSES A propeller generates thrust, due to the acceleration of the incoming water. Behind the vessel, the out coming fl ow mixes with the environmental fl ow. Due to turbulence, energy will be lost. FRICTIONAL LOSSES Water in contact with the propeller blade surface causes friction, and thus losses. The total blade surface, speed of rotation and surface roughness are the dominating factors concerning frictional losses. ROTATIONAL LOSSES Rotation of the blade causes a rotation in the wake too; consequently this energy is lost to generate a thrust in axial direction. Visualization of axial losses. SAVE UP TO 15% ON FUEL COSTS The fuel prices have risen considerably the last years, resulting in an increase of ship operating costs. To maintain the economic profi tability of the vessel, a large focus is nowadays on fuel saving devices in the broadest sense of the word. A number of options is available to improve the effi ciency of the propulsion system, depending on the type of propeller and vessel. In this leafl et we explain the propulsion improvements through retrofi ts and the economic effects by means of the Return On Investment (ROI). efficiency 60% axial losses 20% frictional losses 15% rotational losses 5% Example of type of losses general ship propeller. 0 100 200 300 400 500 600 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 HFO 3% S HFO 1% S LFO 0.035% S US$/ton Year Increase in fuel prices. BEFORE AFTER
■■■Fuel saving devices are categorized on 4-5 years,since a new propeller is required. absorbed at a higher rpm,and the engine percentage of efficiency improvement:up to With the help of modern hydrodynamic operation is shifted out of the"red"area. 5%,up to 10%and up to 15%. software,more reliable cavitation predictions Fuel savings,after trailing edge cutting, are made.This way higher power densities can of 6%to 8%are reported.Payback period is UP TO 5%IMPROVEMENT be allowed,and thus a lower blade area can 2 months. PROPELLER POLISHING AND/OR REPAIR OF be applied.A reduction in frictional losses can EDGE DAMAGE result in efficiency improvements up to 3% UP TO 15%IMPROVEMENT Propeller polishing in combination with With the combination of tip rake and a By conversion of an open propeller to a ducted repair of edge damage easily increases the lower blade area it is possible to realize fuel propeller,efficiency gains up to 15%are propeller's operating efficiency with 2%to savings up to 5%.Payback period is 3 years. established. 4%.The Return On Investment(ROI)period The idea of surrounding a propeller by a is quite short.After 1 to 3 months,the UP TO 10%IMPROVEMENT nozzle is already very old.Today about 25% maintenance costs are already paid back. MODERN DESIGN PROPELLER WITH of all Wartsila controllable pitch propellers are INCREASED DIAMETER AND LOW SPEED running in a nozzle. MODERN DESIGN PROPELLER In general a larger propeller diameter in In an accelerating nozzle the water speed A redesign of the current propeller,based combination with a low rotational speed leads at the propeller is higher then that of the on the state-of-the-art,without optimizing to an improvement in efficiency.The axial open propeller.The increase in axial velocity the boundary conditions like propeller speed losses will be reduced.Basically we can apply reduces the propeller load especially for and diameter.can lead to an improvement of this for all ship/propeller types. heavily loaded propellers.This then leads approximately 5%. In case the diameter can not be increased.to an increase in overall performance of Tip rake reduces the local rotation around sometimes a larger number of blades(5 or the propeller and nozzle compared to that the tip.For large fixed pitch propellers the 6)provides a solution for further optimization. of a propeller alone.Additionally.the nozzle positive effect can be up to 3%.The ROI is Payback period is 1.5 to 2.5 years. generates forward thrust caused by the EFFICIENCY RUDDER The efficiency rudder is a successful new Extemal profile development.Axial and rotational losses in the slip stream of the hub are eliminated by the 效 torpedo,which is fitted in between the propeller Internal profile and the rudder.Highly loaded propellers and ships with speeds exceeding 15-20 knots, Better flow around nozzle can benefit from an efficiency rudder.For new -Curved exterior Curved interior building vessels it can be attractive since a rudder and propeller is needed anyway.For Flow pattern HR nozzle the retrofit market the investment is quite large,and therefore the Retum On Investment exceeds a period of 5 years. PROPELLER-ENGINE INTERACTION Vessels equipped with a fixed pitch propeller HR-nozzle:No flow separation at the outside of the nozzle. can suffer from a so called heavy running propeller.The terminology is somewhat Flow pattern 19A or 37 nozzle misleading;the propeller loading and engine characteristics are not matching. 2) The propeller curve crosses the load limit of the engine before full power is reached. As a consequence the engine is overloaded. leading to increased fuel consumption as well Conventional nozzle:Flow separation. as increased wear of internal engine parts. Conventional propeller LIPS tip rake propeller A pitch modification of the propeller can Advantage of LIPS high efficiency(HR)nozzle design. design. be conducted.This way the same power is
Internal profile External profile Flow pattern HR nozzle Flow pattern 19A or 37 nozzle Better flow around nozzle - Curved exterior - Curved interior HR-nozzle: No flow separation at the outside of the nozzle. Conventional nozzle: Flow separation. Advantage of LIPS high effi ciency (HR) nozzle. Conventional propeller design. LIPS tip rake propeller design. 4-5 years, since a new propeller is required. With the help of modern hydrodynamic software, more reliable cavitation predictions are made. This way higher power densities can be allowed, and thus a lower blade area can be applied. A reduction in frictional losses can result in effi ciency improvements up to 3%. With the combination of tip rake and a lower blade area it is possible to realize fuel savings up to 5%. Payback period is 3 years. UP TO 10% IMPROVEMENT MODERN DESIGN PROPELLER WITH INCREASED DIAMETER AND LOW SPEED In general a larger propeller diameter in combination with a low rotational speed leads to an improvement in effi ciency. The axial losses will be reduced. Basically we can apply this for all ship/propeller types. In case the diameter can not be increased, sometimes a larger number of blades (5 or 6) provides a solution for further optimization. Payback period is 1.5 to 2.5 years. EFFICIENCY RUDDER The effi ciency rudder is a successful new development. Axial and rotational losses in the slip stream of the hub are eliminated by the torpedo, which is fi tted in between the propeller and the rudder. Highly loaded propellers and ships with speeds exceeding 15-20 knots, can benefi t from an effi ciency rudder. For new building vessels it can be attractive since a rudder and propeller is needed anyway. For the retrofi t market the investment is quite large, and therefore the Return On Investment exceeds a period of 5 years. PROPELLER - ENGINE INTERACTION Vessels equipped with a fi xed pitch propeller can suffer from a so called heavy running propeller. The terminology is somewhat misleading; the propeller loading and engine characteristics are not matching. The propeller curve crosses the load limit of the engine before full power is reached. As a consequence the engine is overloaded, leading to increased fuel consumption as well as increased wear of internal engine parts. A pitch modifi cation of the propeller can be conducted. This way the same power is absorbed at a higher rpm, and the engine operation is shifted out of the “red” area. Fuel savings, after trailing edge cutting, of 6% to 8% are reported. Payback period is 2 months. UP TO 15% IMPROVEMENT By conversion of an open propeller to a ducted propeller, effi ciency gains up to 15% are established. The idea of surrounding a propeller by a nozzle is already very old. Today about 25% of all Wärtsilä controllable pitch propellers are running in a nozzle. In an accelerating nozzle the water speed at the propeller is higher then that of the open propeller. The increase in axial velocity reduces the propeller load especially for heavily loaded propellers. This then leads to an increase in overall performance of the propeller and nozzle compared to that of a propeller alone. Additionally, the nozzle generates forward thrust caused by the Fuel saving devices are categorized on percentage of effi ciency improvement: up to 5%, up to 10% and up to 15%. UP TO 5% IMPROVEMENT PROPELLER POLISHING AND/OR REPAIR OF EDGE DAMAGE Propeller polishing in combination with repair of edge damage easily increases the propeller’s operating effi ciency with 2% to 4%. The Return On Investment (ROI) period is quite short. After 1 to 3 months, the maintenance costs are already paid back. MODERN DESIGN PROPELLER A redesign of the current propeller, based on the state-of-the-art, without optimizing the boundary conditions like propeller speed and diameter, can lead to an improvement of approximately 5%. Tip rake reduces the local rotation around the tip. For large fi xed pitch propellers the positive effect can be up to 3%. The ROI is
pressure distribution round the nozzle. resulting in a force in the forward direction. To extend the application of ducted propellers towards higher ship speeds in combination with a larger bollard pull,Wartsila has introduced the high efficiency nozzle (HR-nozzle).The HR-nozzle has a curved exterior and interior,leading to absence of flow separation and consequently a higher efficiency. Replacing an open propeller with an HR ducted propeller,the bollard pull can be increased with about 25%,while the free running efficiency can be increased with 10% to 15%.This mainly depends on the power density of the propeller and the sailing speed of the vessel. A number of conducted retrofits were improvement device.Each type of device reviewed with respect to investment and fuel has a wide field of application,depending ECONOMICS OF RETROFITS savings.Data for the fuel consumption were on ship type,size,engine,type of fuel etc. To judge the profitability of a propulsion supplied by the ship operator,or otherwise Therefore an envelope is sketched in the improvement,the increase in hydrodynamic estimated based on the mission profile. chart,identifying a range of hydrodynamic efficiency needs to be known in relation with Figure below shows the estimated Return improvements and pay back time. investment or total costs. On Investment of each discussed propulsion Efficiency rudder 5 Less interesting Modern design propeller More interesting Modern design propeller diameter and rpm adapted Ducted propellers Grinding and repai Propeller-engine interaction 10 Efficiency improvement [% Return On Investments of propulsion improvement devices
0 1 2 3 4 5 6 0 5 10 15 Efficiency improvement [%] Return on investment [year] Grinding and repair Modern design propeller Efficiency rudder Modern design propeller diameter and rpm adapted Propeller-engine interaction Ducted propellers More interesting Less interesting Return On Investments of propulsion improvement devices. pressure distribution round the nozzle, resulting in a force in the forward direction. To extend the application of ducted propellers towards higher ship speeds in combination with a larger bollard pull, Wärtsilä has introduced the high effi ciency nozzle (HR-nozzle). The HR-nozzle has a curved exterior and interior, leading to absence of fl ow separation and consequently a higher effi ciency. Replacing an open propeller with an HR ducted propeller, the bollard pull can be increased with about 25%, while the free running effi ciency can be increased with 10% to 15%. This mainly depends on the power density of the propeller and the sailing speed of the vessel. ECONOMICS OF RETROFITS To judge the profi tability of a propulsion improvement, the increase in hydrodynamic effi ciency needs to be known in relation with investment or total costs. A number of conducted retrofi ts were reviewed with respect to investment and fuel savings. Data for the fuel consumption were supplied by the ship operator, or otherwise estimated based on the mission profi le. Figure below shows the estimated Return On Investment of each discussed propulsion improvement device. Each type of device has a wide fi eld of application, depending on ship type, size, engine, type of fuel etc. Therefore an envelope is sketched in the chart, identifying a range of hydrodynamic improvements and pay back time
SUMMARY AND CONCLUSION ■■ Due to the focus on environmental issues and the increasing fuel prices,ship owners are more and more interested in solutions to save fuel.Wartsila can offer several different options for fuel savings. With modem design propellers,grinding and repair and modification of heavy running propellers considerable hydrodynamic improvement can be established,with attractive Return On Investments. By the application of ducted propellers however,and especially the Lips high efficiency nozzle,an increase of free running propeller efficiency of 15%can be reached,with a payback period of 1 to 1.5 years WARTSILA is a registered trademark.Copyright@2006 Wartsila Corporation. Wartsila Propulsion Netherlands B.V. Lipsstraat 52,P.O.Box 6,5150 BB Drunen,The Netherlands ●Tel.+31416388115●Fax+31416373162●www.wartsila.com WARTSILA WARTSILA COM
WÄRTSILÄ® is a registered trademark. Copyright © 2006 Wärtsilä Corporation. Wärtsilä Propulsion Netherlands B.V. Lipsstraat 52, P.O. Box 6, 5150 BB Drunen, The Netherlands ! Tel. +31 416 388115 ! Fax +31 416 373162 ! www.wartsila.com WARTSILA.COM SUMMARY AND CONCLUSION Due to the focus on environmental issues and the increasing fuel prices, ship owners are more and more interested in solutions to save fuel. Wärtsilä can offer several different options for fuel savings. With modern design propellers, grinding and repair and modifi cation of heavy running propellers considerable hydrodynamic improvement can be established, with attractive Return On Investments. By the application of ducted propellers however, and especially the Lips high effi ciency nozzle, an increase of free running propeller effi ciency of 15% can be reached, with a payback period of 1 to 1.5 years
