Propulsion of 2,2-2,8 teu Container Vessel
Content Introduction...5 EEDI and Major Ship and Main Engine Parameters...6 Energy Efficiency Design Index (EEDI)...6 Major propeller and engine parameters...7 2,5 teu container vessel...8 Main Engine Operating Costs 2. knots...9 Fuel consumption and EEDI...1 Operating costs...12 Main Engine Operating Costs 19. knots...13 Fuel consumption and EEDI...13 Operating costs...15 Retrofit of Existing 7L7ME-C8.2 with EGB-LL for Reduced Ship Speeds...16 Exhaust gas bypass Low Load (EGB-LL)...17 Saving in operating costs and payback time...17 Summary...18 Propulsion of 2,2-2,8 teu Container Vessel 3
Propulsion of 2,2-2,8 teu Container Vessel Introduction The main ship particulars of 2,2-2,8 teu container vessels are normally approximately as follows: the overall ship length is 21 m, breadth 3 m and scantling draught 11.4-12. m, see Fig. 1. Recent development steps have made it possible to offer solutions which will enable significantly lower transportation costs for larger feeder container vessels as outlined in the following. One of the goals in the marine industry today is to reduce the impact of CO 2 emissions from ships and, therefore, to reduce the fuel consumption for the propulsion of ships to the widest possible extent at any load. This also means that the inherent design CO 2 index of a new ship, the socalled Energy Efficiency Design Index (EEDI), will be reduced. Based on an average reference of the CO 2 emission from existing earlier built container vessels, the CO 2 emission from new container vessels in gram per dwt per nautical mile must be equal to or lower than the reference emission figures valid for the specific container vessel. This drive may often result in operation at lower than normal service ship speeds compared to earlier, resulting in reduced propulsion power utilisation. The design ship speed at Normal Continuous Rating (NCR), including 15% sea margin, used to be as high as 22-23 knots. Today, the ship speed may be expected to be lower, possibly 19-2 knots, or even lower. A more technically advanced development drive is to optimise the aftbody and hull lines of the ship including bulbous bow, also considering operation in ballast condition. This makes it possible to install propellers with a larger propeller diameter and, thereby, obtaining higher propeller efficiency, but at a reduced optimum propeller speed, i.e. using less power for the same ship speed. Fig. 1: Large feeder container ship Propulsion of 2,2-2,8 teu Container Vessel 5
Furthermore, the wish to reduce fuel costs and thereby to reduce the design ship speed from 22-23 knots to about 19-2 or even lower, may involve lower main engine power, but also a demand to have lower engine speeds. As the two-stroke main engine is directly coupled with the propeller, the introduction of the ultra long stroke G6ME-C9.2 engine with even lower than usual shaft speed than the existing S6ME-C8.2 will meet this goal. The main dimensions for these engine types, and for the existing L7ME-C8 engine, normally used in the past, are shown in Fig. 2. Also K8 engine types were often used. On the basis of a case study of a 2,5 teu feeder container vessel in compliance with IMO Tier II emission rules, this paper shows the influence on fuel consumption when choosing the new G6ME-C9.2 engine compared with the existing S6ME-C8.2 and the earlier and normally used larger L7ME- C8.2 engine. The layout ranges of 6 and 7G6ME-C9.3 engines compared with 6 and 7S6ME-C8.2 together with the existing 7L7ME-C8.2 are shown later in Fig. 4. EEDI and Major Ship and Main Engine Parameters Energy Efficiency Design Index (EEDI) The IMO (International Maritime Organisation) based Energy Efficiency Design Index (EEDI) is a mandatory index required on all new ships contracted after 1 January 213. The index is used as an instrument to fulfil international requirements regarding CO 2 emissions on ships. EEDI represents the amount of CO 2 emitted by a ship in relation to the transported cargo and is measured in gram CO 2 per dwt per nautical mile. 3,77 1,99 1,3 2,67 1,262 2,33 1,5 1,418 1,738 11,588 3,98 4,22 S6ME-C8.2 L7ME-C8.2 G6ME-C9.2 Fig. 2: Main dimensions for the new G6ME-C9.2 and existing S6ME-C8.2 engines and the L7ME-C8 applied earlier 6 Propulsion of 2,2-2,8 teu Container Vessel
The EEDI value for container ships is calculated on the basis of 7% of the maximum cargo capacity, propulsion power, ship speed, SFOC (Specific Fuel Oil Consumption) and fuel type. Depending on the date of contract, the EEDI is required to be a certain percentage lower than an IMO defined reference value depending on the type and capacity of the ship. The main engine s 75% SMCR (Specified Maximum Continuous Rating) figure is as standard applied in the calculation of the EEDI figure, in which also the CO 2 emission from the auxiliary engines of the ship is included. However, certain correction factors are applicable, e.g. for installed waste heat recovery systems. According to the rules finally decided on 15 July 211, the EEDI of a new ship is reduced to a certain factor compared to a reference value. Thus, a ship built after 225 is required to have a 3% lower EEDI than the 213 reference figure, see later in Figs. 8 and 14. Major propeller and engine parameters In general, the highest possible propulsive efficiency required to provide a given ship speed is obtained with the largest possible propeller diameter d, in combination with the corresponding, optimum pitch/diameter ratio p/d. A lower number of propeller blades, for example when going from 5 to 4 blades if possible, means approximately 1% higher optimum propeller speed, and the propeller efficiency will be slightly increased, and vice versa when going from 5 to 6 blades, see later in Fig. 4. As an example, this is illustrated for a 2,5 teu feeder container ship with a 5-bladed FP propeller and with a service ship speed of 19 knots, see the black curve in Fig. 3. The needed propulsion SMCR (Specified Maximum Continuous Rating) power and speed is shown for a given optimum propeller diameter d and p/d ratio. According to the black curve, the existing propeller diameter of 6.8 m may have the optimum pitch/diameter ratio of.95, and the lowest possible SMCR shaft power of about 12,54 kw at about 97 r/min. The black curve shows that if a bigger propeller diameter of 7.2 m is possible, the necessary SMCR shaft power will be reduced to about 12,28 kw at about 87 r/min, i.e. the bigger the propeller, the lower the optimum propeller speed. 11,5 11, If the pitch for this diameter is changed, the propulsive efficiency will be reduced, i.e. the necessary SMCR shaft power will increase, see the red curve. The red curve also shows that propulsion-wise it will always be an advantage to choose the largest possible propeller diameter, even though the optimum pitch/diameter ratio would involve a too low propeller speed (in relation to the required main engine speed). Thus, when using a somewhat lower pitch/ diameter ratio, compared with the optimum ratio, the propeller/engine speed may be increased and will only cause a minor extra power increase. The efficiency of a two-stroke main engine particularly depends on the ratio of the maximum (firing) pressure and the mean effective pressure. The higher the ratio, the higher the engine efficiency, i.e. the lower the Specific Fuel Oil Consumption (SFOC). Furthermore, the higher the stroke/bore ratio of a two-stroke engine, the higher Propulsion SMCR power kw 5-bladed FP-propellers 13,5 d = Propeller diameter p/d = Pitch/diameter ratio S6ME-C8.2 Design Ship Speed = 19. kn Design Draught = 1. m 13, SMCR power and speed are inclusive of: 15% sea margin 1% engine margin 5% propeller light running 6.8 m 12,5.95 1.2 7.2 m.8 1.1.98.9 7.6 m 12, 1.1 G6ME-C9.2 Power and speed curve for various propeller diameters (d) with optimum p/d ratio Power and speed curve for the given propeller diameter d = 7.2 m with different p/d ratios 6 7 8 9 1 11 r/min Engine/propeller speed at SMCR Fig. 3: Influence of propeller diameter and pitch/diameter ratio on SMCR for a 2,5 teu feeder container vessel operating at 19. knots p/d d p/d Propulsion of 2,2-2,8 teu Container Vessel 7
the engine efficiency. This means, for example, that an ultra long stroke engine type, as the G6ME-C9.2, may have a higher efficiency compared with a shorter stroke engine type, like a super long stroke S6ME-C8.2 and a long stroke L7ME-C8.2. The application of new propeller design technologies may also motivate use of main engines with lower rpm. Thus, for the same propeller diameter, these propeller types can demonstrate an up to 4% improved overall efficiency gain at the same or a slightly lower propeller speed. This is valid for propellers with Kappel technology available at MAN Diesel & Turbo, Frederikshavn, Denmark. Furthermore, due to lower emitted pressure impulses, the kappel propeller requires less tip clearance that can be utilised for installing an even larger propeller diameter, resulting in a further increase of the propeller efficiency. Hence, with such a propeller type, the advantage of the new low speed G6ME-C9.2 engine can be utilised also in case a correspondingly larger propeller cannot be accommodated. 2,5 teu container vessel For a new 2,5 teu feeder container ship, the following case study illustrates the potential for reducing fuel consumption by reduced ship speed and by increasing the propeller diameter and introducing the G6ME-C9.2 as main engine. Propulsion SMCR power kw 3, 4, 5 and 6-bladed FP-propellers constant ship speed coefficient =.19 25, 2, 15, 1, 5, SMCR power and speed are inclusive of: 15% sea margin 1% engine margin 5% light running T des = 1. m 7G6ME-C9.2 M5 M6 M4 M4 M5 M3 M2 7.6 m 4 7.2 m 4 6.8 m 4 D prop = N blade : 8L7ME-C8.2 7L7ME-C8.2 M3 M2 M1 97 r/min 6 7 8 9 1 11 12 13 14 r/min Engine and propeller speed at SMCR M1 M 6L7ME-C8.2 7S6ME-C8.2 6S6ME-C8.2 Future 7.6 m 5 MM 15 r/min 18 r/min Existing 7. m 6 Existing 7.2 m 5 18. kn 21. kn 2. kn 19. kn Existing 6.8 m 5 22. kn 23. kn 23. kn (for EEDI calculations) 23. kn, 7. m 6 MM = 26,16 kw 18 r/min (8L7ME-C8.2) 22. kn 22. kn, 7.1 m 5 M = 21,78 kw 18 r/min (7L7ME-C8.2) 2. kn 2. kn, 6.7 m 5 M1 = 15,2 kw 15 r/min (7S6ME-C8.2) 2. kn, 7. m 5 M2 = 14,97 kw 97 r/min (7S6ME-C8.2) 2. kn, 7. m 5 M3 = 14,97 kw 97 r/min () 2. kn, 7.4 m 5 M4 = 14,73 kw 89 r/min () 2. kn, 7.4 m 5 M5 = 14,73 kw 89 r/min (7G6ME-C9.2) 2. kn, 7.6 m 5 M6 = 14,57 kw 84 r/min (7G6ME-C9.2) 19. kn 19. kn, 6.7 m 5 M1 = 12,57 kw 98 r/min (6S6ME-C8.2) 19. kn, 7. m 5 M2 = 12,42 kw 92 r/min (6S6ME-C8.2) 19. kn, 7. m 5 M3 = 12,42 kw 92 r/min () 19. kn, 7.4 m 5 M4 = 12,18 kw 83 r/min () 19. kn, 7.6 m 5 M5 = 12,7 kw 79 r/min () Fig. 4: Different main engine and propeller layouts and SMCR possibilities (M1, M2, M3, etc. for 2. knots and M1, M2, M3, etc. for 19. knots) for a 2,5 teu container ship operating at 2. knots and 19. knots, respectively 8 Propulsion of 2,2-2,8 teu Container Vessel
The ship particulars assumed are as follows: Deadweight, scantling dwt 34,8 Scantling draught m 11.4 Deadweight, design dwt 27,7 Design draught m 1. Length overall m 23. Length between pp m 197. Breadth m 3. Sea margin % 15 Engine margin % 1 Design ship speed kn (22) 2. and 19. Type of propeller FPP No. of propeller blades 5 Propeller diameter m target Based on the above-stated average ship particulars assumed, we have made a power prediction calculation (Holtrop & Mennen s Method) for different design ship speeds and propeller diameters, and the corresponding SMCR power and speed, point M, for propulsion of the container ship is found, see Fig. 4. The propeller diameter change corresponds approximately to the constant ship speed factor α =.19 [ref. P M2 = P M1 (n2/n1) α. Referring to the two reduced ship speeds of 2. knots and 19. knots, respectively, three potential main engine types, pertaining layout diagrams and SMCR points have been drawn-in in Fig. 4, and the main engine operating costs have been calculated and described. For the reduced ship speeds, but without increasing the propeller diameter, the old S6ME-C8.2 may be relevant. The existing L7ME-C engine type (18 r/min) has often been used in the past as prime movers in the existing 2,2-2,8 teu large feeder container ships with a relatively high ship speed of 22. kn. This engine type is also included in the main engine comparisons when operating at 2. and 19. knots, respectively. A comparison between the new G6ME-C9.2 and the existing S6ME- C8.2 and L7ME-C8.2 therefore is of major interest in this paper. It should be noted that for the S6ME- C8.2 and the G6ME-C9.2, the ship speed stated refers to normal continuous rating NCR = 9% SMCR including 15% sea margin. If based on calm weather, i.e. without sea margin, the obtainable ship speed at NCR = 9% SMCR will be about.8 knots higher than the design ship speed. If based on 75% SMCR and 7% of maximum dwt., as applied for calculation of the EEDI, the ship speed will be about.2 knots higher than the design ship speed, still based on calm weather conditions, i.e. without any sea margin. As the existing L7ME-C8.2 has a relatively high SMCR power, where NCR = 9% refers to the high design ship speed of 22. knots, the corresponding NCR at 2. and 19. knots is lower than 9% SMCR, namely 61.7% and 51.% SMCR, respectively. Referring to an existing 2,5 teu container ship earlier designed for 22. knots and with the main engine 7L7ME-C8.2 installed, a retrofit solution of the main engine is also described later for operation at 19. knots. Main Engine Operating Costs 2. knots The calculated main engine examples are as follows: 2. kn 1 D prop = 6.7 m 5 M1 = 15,2 kw 15 r/min 7S6ME-C8.2 2 D prop = 7. m 5 M2 = 14,97 kw 97 r/min 7S6ME-C8.2 3 D prop = 7. m 5 M3 = 14,97 kw 97 r/min 4 D prop = 7.4 m 5 M4 = 14,73 kw 89 r/min 5 D prop = 7.4 m 5 M5 = 14,73 kw 89 r/min 7G6ME-C9.2 6 D prop = 7.6 m 5 M6 = 14,57 kw 84 r/min 7G6ME-C9.2 22. kn 1 D prop = 7.1 m 5 M = 21,78 kw 18 r/min 7L7ME-C8.2 The selected main engine examples, among others, make it possible to see the influence of the propeller diameter, installation of one extra cylinder and engine type. The main engine fuel consumption and operating costs at N = NCR = 9% SMCR, but N = 61.7% SMCR for the existing 7L7ME-C8.2, have been calculated for the above seven main engine/propeller cases operating on the reduced ship speed of 2. knots, as often used today. Furthermore, the corresponding EEDI has been calculated Propulsion of 2,2-2,8 teu Container Vessel 9
Propulsion power demand at N = NCR kw 16, Including a 15% sea margin Relative power reduction % 8 14, 13,68 kw 13,473 kw 13,473 kw 13,257 kw 13,257 kw 13,113 kw 13,428 kw 7 12, 6 1, 8, 6, 4, 1.5% 1.5% 3.1% 3.1% 4.1% 1.8% 5 4 3 2 2, Dprop: % 7S6ME-C8.2 N1 6.7 m 5 7S6ME-C8.2 N2 7. m 5 N3 7. m 5 N4 7.4 m 5 7G6ME-C9.2 N5 7.4 m 5 7G6ME-C9.2 N6 7.6 m 5 7L7ME-C8.2 N 7.1 m 5 1 Fig. 5: Expected propulsion power demand at N=NCR = 9% SMCR for 2. knots (N = 61.7% SMCR for 7L7ME-C8.2) on the basis of the 75% SMCR-related figures for 7% of max. dwt. (without sea margin). Fuel consumption and EEDI Fig. 5 shows the influence of the propeller diameter with five propeller blades when going from about 6.7 m to 7.6 m. Thus, N6 for the 7G6ME-C8.2 with a 7.6 m propeller diameter has a propulsion power demand that is about 4.1% lower compared with N1 used as basis valid for the 7S6ME-C8.2. with a propeller diameter of about 6.7 m. Fig. 6 shows the influence on the main engine efficiency, indicated by the Specific Fuel Oil Consumption, SFOC, for the seven cases. For N1 = 9% M1 used as basis with the 7S6ME-C8.2 SFOC is 164.2 g/kwh, for N5 = 9% M5 with 7G6ME-C8.2 SFOC is 16.5 g/kwh and for N = 61.7% M with 7L7ME-C8.2 SFOC is 165.4 g/kwh. In N5, the SFOC is about 2.3% lower compared with N1. When multiplying the propulsion power demand at N (Fig. 5) with the SFOC (Fig. 6), the daily fuel consumption is found and is shown in Fig. 7. Compared with N1 for the existing 7S6ME-C8.2, the total reduction of fuel consumption of the new 7G6ME-C9.2 at N6 is about 5.6% (see also the above-mentioned savings of 4.1% and 1.5% stated in Figs. 5 and 6). SFOC g/kwh 176 175 174 173 IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg 172 171 17 Standard high-load optimised engines 169 Dprop 168 M2 7S6ME-C8.2 7. m x 5 167 M4 7.4 m x 5 166 N2 M1 7S6ME-C8.2 6.7 m x 5 Basis N 165 M3 7. m x 5 N4 (M) 7L7ME-C8.2 7.1 m x 5 164 N1 M6 7G6ME-C9.2 7.6 m x 5 163 N3 M5 7G6ME-C9.2 7.4 m x 5 162 N6-1.1% 161 -.7% N5 16 -.4% Basis.% 159 158.9% Savings in SFOC 157 1.5% 156 2.3% 25 3 35 4 45 5 55 6 65 7 75 8 85 9 95 1% SMCR Engine shaft power Fig. 6: Expected SFOC for 2. knots N = NCR M = SMCR For 7L7ME-C8.2 61.7% 68.6% 1 Propulsion of 2,2-2,8 teu Container Vessel
The reference and the actual EEDI figures have been calculated and are shown in Fig. 8 (EEDI ref = 174.22 x max. dwt -.21, 15 July 211). As can be seen for all six cases with S6ME-C8.2 and G6ME-C9.2 and layouted for 2. knots, the actual EEDI figures are relatively low with the lowest EEDI (6%) for cases 5 and 6 with 7G6ME-C9.2. All these cases may also meet the stricter EEDI reference figure valid after 225. For information, the calculated EEDI valid for the old cases 7L7ME-C8.2 (22 kn.) and 8L7ME-C8.2 (23 kn.) is also shown in Fig. 8. The old 8L7ME-C8.2 (23 kn.) is more or less the reason for the 1% EEDI reference figure used today. Fuel consumption of main engine 7 IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg Relative saving of fuel consumption % 14 6 5 53.91 53.68 52.63 52.42 51.6 5.9 53.3 12 1 4 8 3 5.3% 5.6% 6 2 1 Dprop: % 7S6ME-C8.2 N1 6.7 m 5.4% 7S6ME-C8.2 N2 7. m 5 2.4% N3 7. m 5 2.8% N4 7.4 m 5 7G6ME-C9.2 N5 7.4 m 5 7G6ME-C9.2 N6 7.6 m 5 1.1% 7L7ME-C8.2 N 7.1 m 5 4 2 Fig. 7: Expected fuel consumption at N = NCR = 9% SMCR for 2. knots (N = 61.7% SMCR for 7L7ME-C8.2) Reference and actual EEDI CO 2 emissions gram per dwt/n mile Actual/Reference EEDI % 75% SMCR and 7% of max dwt: 2.2 kn without sea margin 25 EEDI reference (21.29/1%) EEDI actual 11 2.44 1 2 17.69 96% 9 83% 8 15 1 5 13.49 13.43 13.19 63% 63% 62% 7S6ME-C8.2 N1 Dprop: 6.7 m 5 7S6ME-C8.2 N2 7. m 5 N3 7. m 5 13.13 62% N4 7.4 m 5 12.81 12.76 6% 6% 7G6ME-C9.2 N5 7.4 m 5 Fig. 8: Reference and actual Energy Efficiency Design Index (EEDI) for 2. knots 7G6ME-C9.2 N6 7.6 m 5 7L7ME-C8.2 N 7.1 m 5 (22. kn) 8L7ME-C8.2 NN 7. m 5 (23. kn) 7 6 5 4 3 2 1 Year 213 215 22 225 Contract date before 1 January Propulsion of 2,2-2,8 teu Container Vessel 11
Annual operating costs Million USD/Year 1. 9. 8. IMO Tier ll ISO ambient conditions 25 days/year NCR = 9% SMCR (61.7% for 7L7ME-C8.2) Fuel price: 7 USD/t Relative saving in operating costs % 1 9 8 Maintenance Lubricating oil Fuel oil 7. 7 6. 5. 5.1% 5.4% 6 5 4. 4 3. 2. 2.5% 2.9% 3 2 1.. Dprop: % 7S6ME-C8.2 N1 6.7 m 5.4% 7S6ME-C8.2 N2 7. m 5 N3 7. m 5 N4 7.4 m 5 7G6ME-C9.2 N5 7.4 m 5 7G6ME-C9.2 N6 7.6 m 5.8% 7L7ME-C8.2 N 7.1 m 5 1 Fig. 9: Total annual main engine operating costs for 2. knots Saving in operating costs (Net Present Value) Million USD 11 1 9 8 7 IMO Tier ll ISO ambient conditions N = NCR = 9% SMCR (61.7% for 7L7ME-C8.2) 25 days/year Fuel price: 7 USD/t Rate of interest and discount: 6% p.a. Rate of inflation: 3% p.a. N6: 7.6 m 5 7G6ME-C9.2 N5: 7.4 m 5 7G6ME-C9.2 Operating costs The total main engine operating costs per year, 25 days/year, and fuel price of 7 USD/t, are shown in Fig. 9. The lube oil and maintenance costs are shown too. As can be seen, the major operating costs originate from the fuel costs about 96%. 6 5 4 3 N4: 7.4 m 5 N3: 7. m 5 2 N:7.1 m 5 7L7ME-C8.2 1 N2: 7. m 5 7S6ME-C8.2 N1: 6.7 m 5 7S6ME-C8.2 5 1 15 2 25 3 Years Lifetime Fig. 1: Relative saving in main engine operating costs (NPV) for 2. knots After some years in service, the relative savings in operating costs in Net Present Value (NPV), see Fig. 1, with the existing 7S6ME-C8.2 used as basis N1 with the propeller diameter of about 6.7 m, indicates an NPV saving for the new 7G6ME-C9.2 engine. After 25 years in operation, the saving is about 8.7 million USD for N5 with 7G6ME-C9.2 with the SMCR speed of 89. r/min and propeller diameter of about 7.4 m. 12 Propulsion of 2,2-2,8 teu Container Vessel
Main Engine Operating Costs 19. knots The calculated main engine examples are as follows: 19. kn 1 D prop = 6.7 m 5 M1 = 12,57 kw 98 r/min 6S6ME-C8.2 2 D prop = 7. m 5 M2 = 12,42 kw 92 r/min 6S6ME-C8.2 3 D prop = 7. m 5 M3 = 12,42 kw 92 r/min 4 D prop = 7.4 m 5 M4 = 12,18 kw 83 r/min 5 D prop = 7.6 m 5 M5 = 12,7 kw 79 r/min 22. kn 1 D prop = 7.1 m 5 M = 21,78 kw 18 r/min 7L7ME-C8.2 The main engine fuel consumption and operating costs at N = NCR = 9% SMCR, but N = 51% SMCR for the existing 7L7ME-C8.2, have been calculated for the above six main engine/propeller cases operating on the reduced ship speed of 19. knots, which is probably going to be a more normal choice in the future. Furthermore, the EEDI has been calculated on the basis of the 75% SMCR-related figures for 7% of max. dwt. (without sea margin). Fuel consumption and EEDI Fig. 11 shows the influence of the propeller diameter with five propeller blades when going from about 6.7 m to 7.6 m. Thus, N5 for the with an about 7.6 m propeller diameter has Propulsion power demand at N = NCR kw 14, 12, 1, 8, 6, 4, 11,313 kw 2, % 6S6ME-C8.2 N1 Dprop: 6.7 m 5 11,178 kw 6S6ME-C8.2 N2 7. m 5 Including a 15% sea margin 11,178 kw 1.2% 1.2% N3 7. m 5 1,962 kw 3.1% N4 7.4 m 5 1,863 kw 4.% N5 7.6 m 5 11,117 kw 1.7% Relative power reduction % 7 7L7ME-C8.2 N 7.1 m 5 Fig. 11: Expected propulsion power demand at N = NCR = 9% SMCR for 19. knots (N = 51% SMCR for 7L7ME-C8.2) SFOC g/kwh 176 175 174 173 IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg 172 171 17 Standard high-load optimised engines Dprop 169 M2 6S6ME-C8.2 7. m x 5 168 N 167 M1 6S6ME-C8.2 6.7 m x 5 Basis N2 (M ) 7L7ME-C8.2 7.1 m x 5 166 165 N1 M5 7.6 m x 5 164 M4 7.4 m x 5 163 N5 162 161 N4 M3 7. m x 5 Basis 16 159 N3 158 157 156 25 3 35 4 45 5 55 6 65 7 75 8 85 9 95 1% SMCR Engine shaft power Fig. 12: Expected SFOC for 19. knots N = NCR M = SMCR For 7L7ME-C8.2 51.% 56.7% a propulsion power demand that is about 4.% lower compared with the N1 used as basis for the 6S6ME-C8.2 with an about 6.7 m propeller diameter. Fig. 12 shows the influence on the main engine efficiency, indicated by the Specific Fuel Oil Consumption, SFOC, for the six cases. For N1 = 9% M1 with the 6S6ME-C8.2 used as basis SFOC is 165.1 g/kwh compared with the 159.2 g/kwh for N3 = 9% M3 for the, i.e. an SFOC reduction -1.3% -.9%.% 1.6% 2.2% 3.6% for N3 of about 3.6%. For N = 51.% M with 7L7ME-C8.2 SFOC is 167.3 g/kwh, i.e. an SFOC increase of about 1.3%. The daily fuel consumption is found by multiplying the propulsion power demand at N (Fig. 11) with the SFOC (Fig. 12), see Fig. 13. The total reduction of fuel consumption of the new 6G6ME- C9.2, N5 with propeller diameter 7.6 m, is about 5.5% compared with N1 for the existing 6S6ME-C8.2. 6 5 4 3 2 1 Savings in SFOC Propulsion of 2,2-2,8 teu Container Vessel 13
The reference and the actual EEDI figures have been calculated and are shown in Fig. 14 (EEDI ref = 174.22 max. dwt -.21, 15 July 211). As can be seen for all five cases with 6S6ME- C8.2 and and layouted for 19. knots, the actual EEDI figures are much lower than the reference figure because of the relatively low ship speed of 19. knots. All these cases may also meet the stricter EEDI reference figure valid after 225. As for the earlier stated cases based on 2 knots, the EEDI for the old cases 7L7ME-C8.2 (22 kn.) and 8L7ME- C8.2 (23 kn.) is also shown in Fig. 14 for information. Fuel consumption of main engine 7 6 5 4 3 2 1 44.83 % 6S6ME-C8.2 N1 Dprop: 6.7 m 5 44.69.3% 6S6ME-C8.2 N2 7. m 5 IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg 42.72 4.7% N3 7. m 5 42.46 N4 7.4 m 5 42.36 5.3% 5.5% N5 7.6 m 5 Relative saving of fuel consumption % 14 44.64.4% 7L7ME-C8.2 N 7.1 m 5 Fig. 13: Expected fuel consumption at N = NCR = 9% SMCR for 19. knots (N = 51% SMCR for 7L7ME-C8.2) 12 1 8 6 4 2 Reference and actual EEDI CO 2 emissions gram per dwt/n mile 75% SMCR and 7% of max dwt: 19.2 kn without sea margin 25 EEDI reference (21.29/1%) EEDI actual 2 15 17.69 83% Actual/Reference EEDI % 2.44 96% 11 Year 1 213 9 8 7 215 22 225 Contract date before 1 January 1 11.86 56% 11.82 56% 11.33 11.26 53% 53% 11.23 53% 6 5 4 5 3 2 1 6S6ME-C8.2 N1 Dprop: 6.7 m 5 6S6ME-C8.2 N2 7. m 5 N3 7. m 5 N4 7.4 m 5 N5 7.6 m 5 7L7ME-C8.2 N 7.1 m 5 (22. kn) 8L7ME-C8.2 NN 7. m 5 (23. kn) Fig. 14: Reference and actual Energy Efficiency Design Index (EEDI) for 19. knots 14 Propulsion of 2,2-2,8 teu Container Vessel
Annual operating costs Million USD/Year 9. 8. 7. IMO Tier ll ISO ambient conditions 25 days/year NCR = 9% SMCR (51.% for 7L7ME-C8.2) Fuel price: 7 USD/t Relative saving in operating costs % 9 Maintenance Lubricating oil 8 Fuel oil 7 6. 5. 4.5% 5.1% 5.4% 6 5 4. 4 3. 3 2. 2 1.. -1. Dprop: % 6S6ME-C8.2 N1 6.7 m 5.3% 6S6ME-C8.2 N2 7. m 5 N3 7. m 5 N4 7.4 m 5 N5 7.6 m 5 -.3% 7L7ME-C8.2 N 7.1 m 5 1-1 Fig. 15: Total annual main engine operating costs for 19. knots Saving in operating costs (Net Present Value) Million USD 9 8 7 6 5 IMO Tier ll ISO ambient conditions N = NCR = 9% SMCR (51.% for 7L7ME-C8.2) 25 days/year Fuel price: 7 USD/t Rate of interest and discount: 6% p.a. Rate of inflation: 3% p.a. N5 : 7.6 m 5 N4 : 7.4 m 5 N3 : 7. m 5 Operating costs The total main engine operating costs per year, 25 days/year, and fuel price of 7 USD/t, are shown in Fig. 15. Lube oil and maintenance costs are also shown at the top of each column. As can be seen, the major operating costs originate from the fuel costs about 96%. 4 3 2 1 N2 : 7. m 5 6S6ME-C8.2 N1 : 6.7 m 5 Basis 6S6ME-C8.2 N :7.1 m 5 1 7L7ME-C8.2 5 1 15 2 25 3 Years Lifetime Fig. 16: Relative saving in main engine operating costs (NPV) for 19. knots After some years in service, the relative savings in operating costs in Net Present Value, NPV, see Fig. 16, with the existing 6S6ME-C8.2 with the propeller diameter of about 6.7 m used as basis, indicates an NPV saving after some years in service for the new 6G6ME- C9.2 engine. After 25 years in operation, the saving is about 7.3 million USD for N4 with the with the SMCR speed of 83. r/min and propeller diameter of about 7.4 m. Propulsion of 2,2-2,8 teu Container Vessel 15
Retrofit of Existing 7L7ME-C8.2 with LL-EGB for Reduced Ship Speeds As mentioned earlier in this paper, the container ships built a few years ago were designed for sailing in service at relatively high ship speeds, which at that time was beneficial due to the high freight rates and low fuel prices. Expansion Joint (Compensator) Pipe Support (Slide Point) Pipe Support (Fix Point) Expansion Joint (Compensator) EGB-Valve Exhaust Gas Manifold Today, the high fuel prices, low freight rates, and stricter EEDI demands have forced the shipowners to sail with a relatively low ship speed compared to what was originally intended, i.e. to operate the main engine continuously at reduced main engine loads. 6 Exhaust Gas Bypass, EGB open and closed EGB (for guidance only) ME/ME-C Closed Partly open Open 7 Exhaust Receiver Main Engine Orifice MAN B&W Supply Yard Supply Low-Load (LL) Engine load 8 9 1% SMCR Fig. 17: Exhaust gas bypass for Low Load tuning (LL-EGB) SFOC g/kwh 176 175 174 173 172 171 17 169 168 167 166 165 164 163 162 161 16 159 158 157 New average service 168.7 163.7 156 25 3 35 4 45 5 55 6 A B Retrofit 7L7ME-C8.2 with LL-EGB SMCR = 21,78 kw 18 r/min IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg Case A: 7L7ME-C8.2 HL-standard tuned (Existing) Case B: 7L7ME-C8.2 with LL-EGB (Retrofit) B A LL-EGB HL-Standard 65 7 75 8 85 9 95 1% SMCR Fig. 18: SFOC reduction for 7L7ME-C8.2 with LL-EGB operating at 45% SMCR at reduced ship speed 16 Propulsion of 2,2-2,8 teu Container Vessel
Fuel consumption of main engine 7 6 5 4 3 2 1 Annual operating costs Million USD/Year 1. 9. 8. 7. 6. 5. 4. 3. 2. 1.. IMO Tier ll ISO ambient conditions LCV = 42,7 kj/kg Retrofit 7L7ME-C8.2 with LL-EGB SMCR = 21,78 kw 18 r/min 39.67 % 7L7ME-C8.2 HL-Standard A Fig. 19: Expected fuel consumption in average service on 45% SMCR Retrofit 7L7ME-C8.2 with LL-EGB SMCR = 21,78 kw 18 r/min 25 days/year Fuel price: 7 USD/t % 7L7ME-C8.2 HL-Standard A 2.9% 38.5 3.% 7L7ME-C8.2 LL-EGB B 7L7ME-C8.2 LL-EGB B Relative saving in operating costs % Fig. 2: Total annual main engine operating costs in average service on 45% SMCR Relative saving of fuel consumption % 7 5 4 3 2 1 6 5 4 3 2 1 Maintenance Lubricating oil Fuel oil Exhaust Gas Bypass Low Load (LL-EGB) A reduction of SFOC when operating at low loads is possible but is limited by NO x regulations on two-stroke engines. Thus, NO x emission will increase if the SFOC is reduced and vice versa. Compared to a standard high load optimised ME-C engine, an SFOC reduction of 5g/kWh at low load is possible, but at the expense of a higher SFOC in the high-load range without exceeding the IMO NO x limit. This is possible by means of an exhaust gas bypass, low load optimised, see Fig. 17. The corresponding SFOC curve for a 7L7ME-C8.2 with SMCR = 21,78 kw x 18 r/min is shown in Fig. 18. Saving in operating costs and payback time The existing standard high load optimised 7L7ME-C8.2 with SMCR = 21,78 kw x 18 r/min and design ship speed of 22. knots has been used as basis. The SFOC and fuel consumptions have been calculated valid for the new average engine service load of 45% SMCR which more or less corresponds to the reduced average ship speed of 19 knots, case A, see Figs. 18 and 19. The corresponding SFOC and fuel consumptions valid for LL-EGB, case B, is also shown in Figs. 18 and 19. The LL-EGB case B has an about 3% lower fuel consumption than for the HLstandard tuned engine, case A. The annual operating costs are shown in Fig. 2, and the saving in operating Propulsion of 2,2-2,8 teu Container Vessel 17
and investment costs (net present value) is shown in Fig. 21. However, the total extra investment costs needed for retrofit with LL-EGB and indicated in Fig. 21, depend very much on the existing turbochargers as some turbocharger layouts may need more comprehensive modifications than others. Each retrofit project, therefore, has to be checked individually from case to case. In general, the payback time of the LL- EGB modification may be about 2 years. Summary Traditionally, short and long stroke K8 and L7 engines, with relatively high engine speeds, have been applied as prime movers in large feeder container vessels. Following the efficiency optimisation trends in the market, including reduced ship speeds, the possibility of using even larger propellers has been thoroughly evaluated with a view to using engines with even lower speeds for propulsion. Container ships with lower ship speeds are indeed compatible with propellers with larger propeller diameters than the current designs, and thus high propeller efficiencies following an adaptation of the aft hull design to accommodate the larger propeller, together with optimised hull lines and bulbous bow, considering operation in ballast conditions. Even in cases where an increased size of the propeller is limited, the use of propellers based on the new propeller technology will be an advantage. Saving in operating and investment costs (Net Present Value) Million USD 4. 3.5 3. 2.5 2. 1.5 1..5.5 IMO Tier ll ISO ambient conditions 25 days/year Fuel price: 7 USD/t Rate of interest and discount: 6% p.a. Rate of inflation: 3% p.a. 1. 5 1 15 2 25 3 Years Lifetime Fig. 21: Relative saving in Net Pressent Value costs in average service on 45% SMCR 7L7ME-C8.2 LL-EGB 7L7ME-C8.2 HL-Standard The new and ultra long stroke G6ME- C9.2 engine type meets this trend in the large feeder container market. This paper indicates, depending on the propeller diameter used, an overall efficiency increase of up to 5-6% when using G6ME-C9.2, compared with the existing main engine type S6ME-C8.2. The Energy Efficiency Design Index (EEDI) will also be reduced when using the G6ME-C9.2. However, the use of lower design ship speed may by itself reduce the EEDI involving that the stricter EEDI demands in the future may always be met. For existing container ships designed for high ship speeds, the retrofit of the main engine with a LL-EGB may reduce the operating costs with about 3% when sailing at reduced ship speeds. The payback time may be about 2 years, but depends on the existing turbocharger configuration. 18 Propulsion of 2,2-2,8 teu Container Vessel
All data provided in this document is non-binding. This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions. Copyright MAN Diesel & Turbo. 551-145-ppr Oct 213 Printed in Denmark MAN Diesel & Turbo Teglholmsgade 41 245 Copenhagen SV, Denmark Phone +45 33 85 11 Fax +45 33 85 1 3 info-cph@mandieselturbo.com www.mandieselturbo.com MAN Diesel & Turbo a member of the MAN Group