High-Powered ADD3OV Medium Speed Diesel Engine

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1 High-Powered ADD30V Medium Speed Diesel Engine 65 Technical Papers High-Powered ADD3OV Medium Speed Diesel Engine Shuhei Mizuhara**, Motomu Kunimitsu**, Osamu Beppu**, Motoyuki Takahashi**, Atsushi Sakane**, Masaki Tanaka** The world's first ADD30V medium speed diesel engines were produced and delivered for marine and stationary applications by Mitsui Engineering & Shipbuilding Co., Ltd. under the license of ADD Co., Japan. This engine achieves extremely high power with B.M.E.P. up to 2.7MPa and mean piston speed up to 12m/s, coupled with light weight and space saving compactness. In addition, high reliability as well as low fuel oil consumption is obtained. This paper describes the design features of principal components, such as the welded integral engine frame of steel modules, the crankshaft with cold-rolled fillets coupled with induction-hardening, the piston of diffusionbonded integral, the cylinder liner and the piston rings coated with wear-resistant ceramic, the single valve gas exchanging system, etc., which enable the ADD30V engine to achieve the above advantages under the extremely high power. Finally, the engine performance and the operating results are described on the basis of actual test results. 1. Introduction Marine diesel engines have built up the major position as the prime movers of vessels through the continual technological innovations concerning high power, high thermal efficiency, high reliability, flexibility against various fuels and clean emissions, etc.. On the other hand, an increasing demand for highspeed and mass marine transportation, which requires high-powered prime movers with light weight and small space, claims the great innovations to marine diesel engines. From this viewpoint, the medium speed diesel engine ADD30V (bore 300mm x stroke 480mm) with a power range 3,300-10, 300kW has been developed by ADD (Advanced Diesel Engine Development) Co., Japan, having the following features which yield substantial gains in operating economy. - outstanding increase in engine power - light and compact - low fuel consumption - high reliability - easy maintenance Various advanced technologies have been developed through extensive fundamental testing and analysis to achieve the above excellent features. A high degree of reliability was well proved through the 5,000- * Translated from Journal of MESJ Vol. 33, No. 12 (Manuscript received Aug. 29, 1998) ** Mitsui Engineering & Shipbuilding Co., Ltd. (Tama, Tamano City) hour endurance test of the prototype 6ADD30V including 2,200-hour running at 110% load between 1992 and Mitsui Engineering & Shipbuilding CO.,Ltd, the major stockholder of ADD Co., has fully cooperated through ADD's research and development, and started the production and sales activities of the ADD30V engine since early 1996 under the license of ADD Co.. In 1997, two sets of 6ADD30V (2,980kW x 720rpm), the world's first ADD30Vs, were built and installed in the observation vessel for Japan Maritime Agency where the engines are used for the main diesel-electric propulsion system. The second set of 6ADD30V (3,290kW x 720rpm) for 3.1MW stationary power plant was built and installed at Mitsui's Tamano works and put into service on April lst, In 1998, four sets of 16ADD30V (8,800kW x 750rpm) for 32MW IPP, as shown in Photo 1, were delivered to Saba, Malaysia and commissioned in March, The design features and the operating results of ADD30V are described in this paper, especially focusing on the new design concepts which enable the ADD30V to achieve the unbeaten advantages under the extremely high power. 2. Engine Particulars and Principal Features The principal engine data are given in Table 1 and a cross-section is shown in Fig.1. The principal structure and dimensions of the ADD30V is the same as the October 1999 (11)

The cylinder arrangement is 50 Vee from 6 to 18 cylinders.

2 66 High-Powered ADD30V Medium Speed Diesel Engine Photo 1 MITSUI-ADD 16ADD30V (8,800kW x 750rpm) Table 1 Principal Engine Data of ADD30V prototype 6ADD30V except that two smaller exhaust gas receivers are arranged for multi-cylinders' engines. The cylinder arrangement is 50 Vee from 6 to 18 cylinders. The engine speed of 750rpm makes either reduction gear or generator more compact than that of 600 rpm for the conventional engines with the equivalent cylinder power. The principal features are as follows; Fig. 1 Cross-Section of ADD30V (12) Bulletin of the M.E.S.J., Vol. 27, No.2

3 High-Powered ADD30V Medium Speed Diesel Engine 67 Fig. 2 Transition of Power Rate of 4 Stroke Medium Speed Diesel Engines Fig. 3 Comparison of Engine Size between ADD30V and Conventional Engine a) Outstanding increase in engine power Fig. 2 shows the transition of power rate (B.M.E.P. x mean piston speed) for medium speed diesel engines. The ADD30V engine achieves extremely high power, 40-50% higher than the conventional engines of the same cylinder bore, with B.M.E.P. up to 2.7MPa and mean piston speed up to 12m/s. The max. cylinder pressure is raised up to 19.7MPa. b) light and compact In comparison with the Mitsui V42M engines of the equivalent cylinder power, as shown in Fig.3, the ADD30V engine is 45% lighter in weight and 60% smaller in space. i.e. the weight/power ratio of 7.0kgf/kW and the power/volume ratio of 140kW/m 3 for 12 cylinders' engine. This feature yields the big space saving. It is expected to greatly increase the performance of highspeed vessels, coupled with high power, in particular. c) Low fuel consumption The ADD30V engine achieves low fuel oil consumption of 184g/kWh under the extremely high power owing to the newly developed systems shown in Fig. 4, such as; - single valve gas exchanging system - fuel injection system with high injection pressure - side injection The engine is designed to burn heavy fuel oil up to 380cSt/50 C. In addition, NOx of <950ppm (13% O2) is obtained by adapting the water-emulsified fuel or the combination between high compression ratio and timing retard, minimizing losses in fuel economy. d) High reliability Many kinds of breakthroughs shown in Fig. 4 ensure the high degree of reliability under the extremely high power in combination with the modern production technologies, such as; - welded integral engine frame of steel modules - piston of diffusion-bonded integral without screw connections October 1999 (13)

4 68 High-Powered ADD30V Medium Speed Diesel Engine - crankshaft with cold-rolled fillets with induction hardening - cylinder liner and piston rings coated with wear- resistant ceramic These breakthroughs have been well-proven through the accelerated fatigue testing of individual components and other fundamental testing and analysis as well as through the longterm endurance tests of the prototype 6ADD30V. e) easy maintenance External piping and flange connections are greatly reduced by using drilled holes and air starters which require no piping along the engine. It makes the maintenance job easier. 3. Design Features The principal breakthroughs shown in Fig.4 are described below. 3.1 Engine Frame The engine frame composed of cylinder and crankcase parts is the key to weight-reduction since it comprises a third of the total weight. Instead of conventional cast iron or nodular cast iron, the engine frame is the welded integral of steel modules which ensures high rigidity to withstand high cylinder pressure and high inertia force as keeping the weight low. The engine frame is devided into several steel modules with simple shape in which cast steel is extensively used, and the whole is welded into an integral structure, as shown in Fig.5. This module construction is advantageous for mass-production, keeping common modules in stock. The cylinder liner of free standing type makes it possible to reduce the weight of a cylinder part, since a gas force is transmitted to a crankcase part through a cylinder liner made of high-strength steel which can be used owing to the wear-resistant ceramic described later. The module profile and the welded sections are well-designed through 3-D FEM analysis and the experiment with a test model under various loading conditions, taking both casting and welding qualities into consideration. The durability was confirmed through the accelerated hydraulic fatigue test of the 2-cylinder model of the actual size. The stress measurement made with the prototype 6ADD30V shows that the max. alternative stress is as low as 25MPa. 3.2 Crankshaft The crankshaft is a RR-forged integral. Journals and crankpins are induction-hardened and thereafter all the fillets are subjected to cold-rolling which compensates for residual tensile stress caused on the fillets by induction-hardening. The cold-rolled fillets ensure higher fatigue strength. The measured max. alternative stress is 190MPa on the prototype 6ADD30V, while the measured fatigue stress is approximately 800MPa on the cold-rolled crankthrow of the actual size[1]. The main bearing is a tri-metal type of leaded copper overlaid without nickel plating to be seizure-proof after the overlay is completely worn. The min. oil film thickness is more than 10µm. The crankpin bearing is a tri-metal type of leaded tin bronze with the same overlay as the main bearing. Unsymmetrical oil grooves are provided to minimize the cavitaion erosion as well as to increase the loading Fig. 4 Breakthroughs Against Increased Power Rate (14) Bulletin of the M.E.S.J., Vol. 27, No.2

High-Powered ADD30V Medium Speed Diesel Engine 69 capacity. The excellent durability of these bearings has been demonstrated through the overhaul inspection after 8,000-hour running of 6ADD30V for 3.

5 High-Powered ADD30V Medium Speed Diesel Engine 69 capacity. The excellent durability of these bearings has been demonstrated through the overhaul inspection after 8,000-hour running of 6ADD30V for 3.1MW power plant. 3.3 Piston The crown and the body are made of high-strength forged alloy steel and metallurgically integrated at horizontally devided surfaces by the method of diffusion-bonding. Photo 2 shows the macro structure of a diffusion-bonded piston. The liquid-phase diffusion-bonding is applied and the bonding conditions (filler material, surface roughness, temperature, load, holding time, etc.) are determined based on a lot of fundamental tests. Though the bonded lines can be distinguished in the macro structure shown in Photo 2 due to the uncontinuity of fiber flows between a crown and a body, the microscopic inspection of bonded area indicates the complete diffusion as shown in Photo 3. It was confirmed that the fatigue strength of diffusion-bonded area is as high as 470MPa, which is almost equal to that of the mother material. A solid integral without screw connections results in light weight, which contributes to the reduction of inertia force as keeping the high strength. Fig. 5 Welded Integral Engine Frame of Steel Modules Photo 2 Macro Structure of Diffusion-Bonded Piston October 1999 (15)

70 High-Powered ADD30V Medium Speed Diesel Engine Photo 3 Micro Structure of Diffusion-Bonded Area The durability of diffusion-bonded piston was well-proved through the accelerated hydraulic fatigue

Neither cracks nor corrosion was observed around the diffusion-bonded sections. The piston skirt of a floating type is made of nodular cast iron.

6 70 High-Powered ADD30V Medium Speed Diesel Engine Photo 3 Micro Structure of Diffusion-Bonded Area The durability of diffusion-bonded piston was well-proved through the accelerated hydraulic fatigue test and thereafter through the endurance test of the prototype. The piston was cut and inspected after the endurance test of the prototype. Neither cracks nor corrosion was observed around the diffusion-bonded sections. The piston skirt of a floating type is made of nodular cast iron. The skirt profile is well-designed through 3-D FEM analysis so that the excessively high surface pressure is not loaded on the ceramic layer of the cylinder liner described later when a side force is loaded. The piston is provided with one oil-scraper ring and three compression rings coated with wear-resistant ceramic. This ring set yields the specific lub. oil consumption of lg/kwh. 3.4 Cylinder Liner and Piston Rings The conventional materials and surface treatments have limited the mean piston speed to 8-10m/s. Instead of these, a newly developed wear-resistant ceramic is coated on the sliding surfaces of both cylinder liner and piston rings by the method of low-pressure plazma spray. [2] The coated layer is shown in Photo 4 and its thickness is 0.5mm after finish-grinding and honing. The spray powder is a composite of chrominium oxide and molybdenum for the top coat, and a mixture of molybdenum and other metal components for the bond coat. The composition and the grain size of spray powder are optimized so that high strength is obtained without losing the excellent wear-resistance. The ceramic layer is extremely wear-resistant in comparison with cast iron used in the conventional engines. The comparison test, which was carried out with Mitsui 12V42M (6,000kW x 514rpm), shows that the wear amount of ceramic layers is 1/8 to 1/4 as compared with cast iron. [3] This allows the piston Photo 4 Wear-Resistant Ceramic Layer speed to be increased up to 12m/s while ensuring the long service life. The wear rate of ceramic layers was measured on 6ADD30V for the 3.1MW power plant after 8,000 operating hours, i.e mm/1,000h in diameter for the cylinder liner and 0.020mm/1,000h in radius for the top piston ring. Neither cracks nor separation was observed on the ceramic layers. 3.5 Cylinder Cover and Gas Exchanging Valves The unique single valve gas exchanging system shown in Fig.6 has been developed in order to enlarge the aerodynamic area of the valves greatly, in place of the conventional four valve system with two intake and exhaust valves respectively. This system reduces pressure losses during the gas exchanging period, which results in higher thermal efficiency even under the high B.M.E.P. as well as the high piston speed. The single valve system consists of the main valve Fig. 6 Single Valve Gas Exchanging System (16) Bulletin of the M.E.S.J., Vol. 27, No.2

7 High-Powered ADD30V Medium Speed Diesel Engine 71 Fig. 7 Measured Valve Lift and Hydraulic Oil Pressure of Main and Sub Valves made of heat-resistant Nimonic, which is located at the cylinder center, and the sub valve made of stainless steel, which is placed coaxially against the main valve. The sub valve turns the channels, air intake or exhaust, which are arranged in the cylinder cover made of cast steel. Both air and exhaust gas passages are optimized through 3-D CFD analysis and the aerodynamic testing using a wooden model. The swirl intensity is adjustale by replacing the swirler to optimize the engine performance depending on the engine specification. Both main and sub valves are opened by hydraulic oil pressure, which is fed through the high pressure pipes from the hydraulic pumps driven by the cams, and closed by common spring air pressure. The system oil is used as the hydraulic oil. The hydraulic system is well-designed through the unsteady oil flow calculation coupled with the reduction in weight of moving parts as keeping the strength. Fig. 7 shows the valve lifts and the hydraulic oil pressure measured on the prototype. This system ensures the stable and quiet operation. In addition, a reduced number of parts makes the maintenance job easy in combination with the unnecessity of regular oiling. The overhaul inspection of 6ADD60V for the 3.1MW power plant made after 8,000 operating hours showed that every component had been working in good order. It should be noted that both valve seats are kept clean owing to the cleaning effect of intaken air. 3.6 Fuel Injection System The side injection system, in which two fuel valves are placed on the cylinder periphery, is applied to the single valve gas exchanging system instead of the conventional center injection system. The fuel injection pressure is raised up to 200MPa in order to achieve the good combustion under the high B.M.E.P, by improving the air-fuel mixture. All the high pressure passages are extrude-honed so that they withstand the high pressure by rounding sharp edges and corners. Each fuel injection pump of Bosch type is provided with the compact damper of an air spring type to allow for the stable injection. The plunger, the speed of which is increased up to 4m/s to minimize the size, is coated with TiN for seizure-proof. The durability of the high-pressure fuel injection system is well-proven through the endurance test on the motor-driven test stand as well as the prototype under the max. pressure of 200MPa. The high injection pressure does not always yield the high thermal efficiency since the increased power for pressurizing compensates the gain in combustion. Consequently, the practical injection pressure is reduced to 160MPa by reducing the plunger speed to 3.4m/s. 4. Test Results Since there was no precedent for the single valve gas exchanging system coupled with the side injection system, many kinds of fundamental analyses and experiments were made in order to evaluate the effects of various parameters on thermal efficiency and exhaust emission. Thereafter, the performance tests were car- October 1999 (17)

8 72 High-Powered ADD30V Medium Speed Diesel Engine Fig. 9 Measured Temperature of Cylinder Parts (3.1MW Power Plant) Fig. 8 Performance Curves of 6ADD30V ried out with the prototype 6ADD30V as well as the single cylinder engine by changing the geometry of comustion chamber, the geometry of atomizer holes, the swirl intensity etc.. The optimum combination can be selected depending on the operating mode and the environmental regulations in accordance with these performance test results ADD30V for 3.1MW Power Plant The power plant using 6ADD30V (3,290kW x 720rpm) has been put into service under WSS(Weekly Start & Stop) operating mode in Mitsui's Tamano works since April lst, 1997, using heavy fuel oil (180cSt/ 50 C). Fig.7 shows the engine performance curves. The specific fuel oil consupmtion of 184g/kWh is obtained, optimized at full load. The dust concentration is as low as 0.024g/Nm 3. Fig.8 shows the measured temperature of cylinder parts at full load. The temperature levels are acceptable for the piston as well as for the bore-cooled cylinder cover and liner. The temperature level of the main valve is higher than that of the exhaust valves for the conventional four valve system, but satisfactory in comparison with the exhaust valves of two stroke diesel engines. 8,000 operating hours were accumulated by the end of July, The availability reached up to more than 98% for this period and a very high degree of reliability was demonstrated through a few times of scheduled overhaul inspections which were carried out as a pilot plant ADD30V for Diesel-Electric Propulsion System The first two sets of 6ADD30V (2,980kW x 720rpm) for Japan Maritime Agency were built and subjected to the shop trial between 1996 and The performance curves are shown in Fig.7. The atomizers and the swirler were optimized to cope with the low load operation for a long expected period in service. The specific fuel oil consumption was reduced by more than 7g/kWh below 50% load as compared with that of the 3.1MW power plant, while losing 3g/ kwh at full load. The dust concentration was 60% lower than that of the power plant at 50% load. The 500-hour endurance test and the cycle test were carried out satisfactorily after the performance test according to the regulations of Japanese Government. The engines were used for the main diesel-electric propulsion system of the observation vessel, in which the special attention was paid to noise and vibration by utilizing the compactness and the light weight of the ADD30V engines. The engines, which are accurately (18) Bulletin of the M.E.S.J., Vol. 27, No.2

9 balanced by the moment compensator, are resiliently mounted and covered with the common package. The vessel has been in service since March 20th, Conclusions 6ADD30V engines, the world's first ADD30V, were built under the license of ADD Co.. Many kinds of well-proven breakthroughs, which withstand higher B.M.E.P. as well as higher piston speed, enable the ADD30V engines to achieve the extremely high power, the light weight, the compactness and the higher thermal efficiency which would yield substantial gains in operating economy in both marine and stationary applications. The operating experiences as well as test results have demonstrated a high degree of reliability under the extremely high power. In addition to these advantages, the ADD30V engine meets the requirements for modern engines in the environmental aspect, although the detail is not described in this paper. 6. Acknowledgement The authors would like to thank ADD CO. for the permission to publish this paper. High-Powered ADD30V Medium Speed Diesel Engine 73 References [1] Arai, S., Takami, M., Hada, S., Kobayashi, M. and Yonezawa, J., CIMAC, 1995, D17 [2] Tanaka, M., Kitajima, Y., Watanabe, M., Endo, Y. and Nagita, Y., ISME, 1990, B [3] Tanaka, M., Kitajima, Y., Nakamura, N. and Ito, T., Japan Tribology Society, Bore 300mm Stroke 480mm Speed 720 / 750rpm Piston speed 11.5 / 12.0m/s B.M.E.P. 2.70MPa Power 550 / 575kW/Cyl Cylinder arrangement 50 Vee Reversing non self-reversing System Starting air starters System October 1999 (19)

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