research article a voyage through the marine …ijamer.in/current-issue/paper1.pdf · engines named...

International Journal of Advances in Marine Engineering and Renewables, 2015, 1(2), 31 - 50 ISSN: Applied (printed version); ISSN: Applied (online version); url:http://www.ijamer.in

RESEARCH ARTICLE

A Voyage Through the Marine Intelligent Engines: RTA, RTflex ; MC, ME and UEC ECO Kalyan Mitra Faculty - SVF, Indian Maritime University, Kolkata Campus, India [email protected] Received 16 June 2015 / Accepted 27 July 2015 Abstract-World big international marine diesel engine manufacturers ,viz. MAN B&W, SULZER WÄRTSILÄ and MITSUBISHI have turned up to manufacture intelligent engines to cope up with rising fuel and cylinder oil cost and to have compliance with stringent environmental regulations and criteria. Main objectives of starting intelligent engines were to have electronics fuel oil injection control, electronic exhaust valve actuation control, low lubricating oil feed rate and also to have low system oil consumption for maximizing mean time between failures and efficient piston rod gland functions. The present study has made an attempt to analyze the recent advances in marine intelligent engines in three ways viz. by comparing the main characteristics of two slow speed marine engines :MAN B&W MC Vs ME Series,; SULZER WÄRTSILÄ RTA Vs RTflex series and lastly MITSUBISHI UEC Engines Key Words: Intelligent marine engines, Electronic Control system, Hydraulic Power Supply, Electronic fuel injection control

I. INTRODUCTION

To survive in the competitive shipping market, the ship owner has to choose proper type of main engine as the total harnessing cost between different engines can vary tremendously, mainly due to the variance in specific fuel and cylinder oil expenditure, as well as maintenance costs. For optimization, the owner during analysis should include all factors influencing to ship's harness costs, i.e. the market conditions, type of the ship, specific fuel oil and lube oil consumption and price, maintenance costs, emission control, voyage time in ballast and in laden condition, time spent in maneuvering, etc.This study has made an attempt to make a comparison of the main characteristics between two similar slow speed marine diesel engines couple: one couple are MC and ME series of MAN B&W and another include RTA and RT-flex series of Wärtsilä (ex. Sulzer) engines; MAN GI Engine and also UEC ECO. For these engines the main engine parameters and engines costs have been compared. The analysis comprises main working principles, fuel oil injection systems and exhaust valve actuating systems differences, specific fuel and lube oil consumption differences and emission reduction control.Large size of marine diesel engines, which run on heavy fuel oil, start to implement this kind of technology few years ago (since 2001. even researching started more than twenty years ago). To make analysis correct as much as possible, the method of ship's crew interview was used together with internet sources and test benches data from Croatian and Japanese shipyards as well as data from ship's trials.

II. WÄRTSILÄ (EX. SULZER)

The development of Wärtsilä (ex. Sulzer) is shown in table 1. Start of developing the modern slow speed diesel engines began in 1979. with Sulzer's RV series which had stroke/bore ratio 2.1 (RND series had 1.67). The reason of increasing stroke/bore ratio was intention to reduce engine speed (propeller rpm) which increases the efficiency of whole propulsion plant. Those changes required redesign of cylinder scavenging systems, so in 1982. started the production of RTA series, with exhaust valve on cylinder cover and uniflow scavenging. Stroke/bore ratio has been additionally increased to 3.45. The greatest care was put on the cylinder combustion space design. The intention was additionally in reducing thermal loads and thermal losses from the process, all caused by the increase of maximum combustion pressure. At the and of twentieth and beginning of twenty first century "Sulzer" introduced a new generation of two stoke slow speed diesel engines named RT- Flex with Common Rail technology and electronically controlled fuel injection and exhaust valve opening and cylinder lubrication. The economy in ship operation additionally asks for low lubricating oil feed rate and also for low system oil consumption, thus tribology and piston rod glands need to be of highest efficiency. Engine's first cost is still very important and needs to be further reduced. Primarily, it is related to the cost of production and used material but quality cost need more and more to be taken in account to get the real cost picture. Reliability is to be maintained in all respects. Sulzer RTA series is characterized by comprising three main lines of engines: the RTA-C, RTA-U and RTA-T. This differentiation allows the engines to be better tailored to match ship requirements. RTA-2 series in 1988 at the same time that the RTA84C engine was launched.

32 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50

Table 1. Development of " Wärtsilä " (ex. Sulzer) slow speed diesel engines

RD 1963

RND 1968

RND-M 1976

RL 1979

RTA- 1982.

RTA i RT-flex 96 C

2005 Diameter (mm) 900 1050 900 900 840 960

Stroke/bore 1.72 1.52 1.67 2.11 3.45 2.6 RPM (min-1) 120 122 122 90 56 102

Mean piston speed (m/s) 6.3 6.48 6.48 6.4 7.45 8.5 Power per cylinder (kW) 1700 2980 2390 2590 2490 5720

Mean effective pressure (bar) 8.65 10.6 12.3 14.3 16.6 19.5 Maximum combustion pressure (bar) 76 84 94 118 125 155

Specific fuel combustion (g/kWh) 201 201 187 172 171 RTA 167.2-171 RT-flex 166.7-171

A further upgrading of the RTA-2 series—to RTA-2U status— came in 1992, with a 9 per cent rise in specific power output.Generally, ships such as containerships, reefers, car carriers, etc., which generally have higher service speeds are served by the RTA-C and RTA-U lines with their higher rotational speeds. In contrast, the slower-running RTA-T engines are more appropriate for vessels such as bulkers and tankers.The RTA range was subsequently extended by the introduction in 1991 of the RTA84T ‘Tanker’ engine design, which, with a stroke-bore ratio of 3.75 and a speed range down to 54 rev/min, was tailored for the propulsion of VLCCs and large bulk carriers. The first production engine entered service in 1994. Even longer strokes (4.17 s/b ratio) were adopted in 1995/96 for RTA-T versions of the 480 mm, 580 mm and 680 mm bore models whose key parameters addressed the power and speed demands of bulk carriers up to Cape-size and tankers up to Suezmax size.

Figure.1 Compact main dimensions of the RTA60C engine

The RTA60C has fairly compact dimensions, see Fig. 1. The higher rotational speed to suit the intended ship types

allows a reduced piston stroke which together with the short connecting rod, allowed a significant reduction in engine height. It is 8.5 m tall above the shaft centreline, and requires a hook height of only 10.4 m for withdrawing pistons, or less by using special tools. Experience from the RTA48T and RTA58T allowed the engine length to be minimized, with a cylinder distance of just 1040 mm.The combined result is a major reduction in engine weight without affecting the structural integrity. The RTA60C is some five to ten per cent lighter than other comparable engines with the same number of cylinders, yet the RTA60C gives about five per cent higher power output. For example, the 14160 kW six-cylinder engine has an overall length of just 7620 mm, including the flywheel, and weighs 330 tonnes. Notwithstanding the improvements for manufacturing, the RTA60C is still recognizable as a Sulzer RTA-series engine. It also incorporates all the latest specific details that can be fully expected to give the high standard of performance, reliability and longevity that ship owners are today experiencing with the latest Sulzer RTA engine types currently in production. These include low piston crown temperatures given by well-adapted jet-shaker cooling, [Fig. 2], and the latest developments for excellent piston-running behaviour (the Sulzer TriboPack technology).The necessity to keep engine length to the minimum calls for particularly good bearing design. Thin-walled white metal shells are used for all bearings: crosshead, main and bottom end. For example, the main bearing housing is specifically designed to accommodate and support the thin-walled bearing shell. It has four elastic holding down bolts for each main bearing cap giving the most even holding down load.


Figure.2 Piston cooling for RTA60C compared to RTA62U

The pairs of studs also allow the tie rods to be located close to the bearing for efficient transfer of firing pressure loads, [Fig. 3].

Figure.3 Main bearing design of the RTA60C engine

The exhaust system features tangential gas inlet and outlet in the exhaust manifold which allow a smooth flow of exhaust gases from the exhaust valve to the turbocharger turbine inlet with an energy-saving swirl along the manifold. This concept has allowed some flexibility in the RTA-T engines for location of the turbocharger along the length of the engine by combining the turbocharger and scavenge air-cooler into a standardized module. This arrangement is continued in the RTA60C, [Fig 4].

Figure.4 RTA60C: Arrangement of the turbocharger and scavenge air cooler

At the end of 1998, the RTA84T-B engine was updated from 3880 kW/cylinder at 74 rpm to 4100 kW/cylinder at 76 rpm in the Version D, [Table 2]. However, the RTA84T-D is of exactly the same design as the Version B, except only

34 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 for adaptations for engine tuning and turbocharger matching. The updating is within the built-in design potential of the Version B.

Table.2 Principal parameters of the Sulzer RTA84T-D

Bore: 840 mm Stroke: 3150 mm S/B: 3.75 Power, R1 MCR: 4100 kW/cyl Speed range, R1–R3: 76–61 rev/min BMEP at R1: 18.5 bar Mean Piston speed at R1: 8.0 m/s Maximum cyl. pressure: 140 bar Number of cylinders: 5–9 BSFC at full-load, R1–R2: 168–160 g/kWh Piston rod glands : The piston rod glands also enhance the TBO, in the sense that their removal for exchange of elements is often connected to a withdrawal of the piston and piston rod assembly. Therefore, the gland elements and the piston rods need to have a long life expectation (TBO three years or more), but in the same time they have to assure sealing between the piston under-side space and the crankcase, limit the contamination of the crankcase system oil, and keep the crankcase oil consumption at a reasonable level for maintaining the quality of the system

.

Figure.5 Newly designed piston rod gland with increased drain areas

Latest developments have succeeded by introducing additional gas-tight top scraper rings, increased spring forces, enlarged drain channels for the scraped off oil, and the exclusive application of bronze scraper rings on fully hardened rods, see Fig. 5. The drain quantities from the neutral space were reduced by a factor of three. Additionally, the scraped off oil is reusable without any treatment and therefore can directly fed back internally in the gland box to the crankcase. System oil consumption figures were thereby reduced to less than 50 litres per day and engine. A further developed piston rod gland is used on the new RTA68T-B engine.

Exhaust valve behavior : The exhaust valve is subjected to hot gases and therefore the temperature resistance of it's seat and valve body is crucial. Nimonic valves combined with proper seat cooling have led to excellent service behaviour and long life times. When the RTA96C engine was introduced, and its shallow combustion space created the most difficult conditions for the design of combustion chamber components, some exhaust valves were additionally coated with Inconel alloy. However, after limited running times, there was some cracking of the coating, originating from the centre hole, with loosened material, making removal by grinding necessary, see Fig 6.


Figure.6 Cracks in coated exhaust valves of a RTA96C engine

Non-coated valves, however, show excellent performance, remaining free of cracks after 14,262 running hours, without any loss of material, see Fig. 7.

Figure.7 Non coated exhaust valves of RTA96C engines: Excellent condition even after 14,262 running hours. No loss of

material was measurable. The today's standard is the non-coated valves.

Piston crowns : Burning off of material on piston crowns is very dangerous as hole formation would lead to direct contact of the combustion flame with the piston cooling oil system and all the worst consequences. The application of the combined shaker and jet cooling system as applied in RTA engines assures piston crown temperatures below 400°C and thus eliminates such burning[Fig.8]

Figure.8 Combustion chamber temperatures of RTA96C engine

36 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 Characteristics of RTA

1. Super long stroke engine with Scavenge air flow longitudinally directed to make an Uniflow system. 2. RTA engine started with a stroke/bore ratio of around 3, increased in same later design to 4 to reduce shaft speed

and thereby gain in fuel economy 3. Controlled valve rotation contribute against the thermal distortion of valve disc and thus enhances the life of valve

seat 4. Exhaust valve dynamic has to be controlled for an instant opening at a predetermined time and soft seating at the

close of the cycle 5. A hydraulic push rod is developed to operate the valve against an air spring instead of mechanical spring, which

avoid fatigue in a leafy spring and parasitic vibration of the spring resulting its failure 6. The exhaust valve provided full area of escape of exhaust gases instantly after lined and smart opening of valve

and valve is seated softly by damping effect of oil and air against back pressure on their respective piston 7. Lower part of cylinder liner combined with higher efficiency turbocharger give an overall reduction in fuel

consumption and expansion to air to reduce temperature (Miller Cycle) 8. Camshaft remain in same position during reversing and is used drive external balancers

i) Exhaust valve cam fitted on camshaft are not displace because CAM TOE is so profiled that it maintains optimum condition for both ahead and astern running.

ii) Two fuel pump (valve controlled ) are combined with a reversing hydraulic servomotor that will rotate the cams to astern position when engine is reverse

9. In fuel injection system: two to three fuel injectors have been used depending on dimension of bore Fuel circulation in fuel oil injection lines when the engine is not running, Injectors are uncooled, Pintle type with satellite tips fuel injection pump are double valve controlled type

10. Cross head bearing is modified to introduce full width bearing in the lower half shell retaining the lubrication of bearing with high pressure separate pumps

11. Flexibility in timing is possible through Variable fuel injection timing (VIT ) for improved part load fuel consumption and for the fuel quality setting ( FQS) lever to adjust the injection timing according to the fuel quality.

12. Bore cooling is extended to all combustion chamber components including upper part of cylinder cover and pistons. Pistons are cooled by combined action of pressure jet and splash cooling by shaker principle.

13. First piston ring is plasma coated. The liner surface temperature is carefully controlled by adding insulation to mid part of liners to maintain a liner surface temperature sufficient to eliminate acid corrosion.

14. Scavenged airports with reduced heights have an effect of better combustion and saving in fuel consumption 15. To obtain full compliance of IMO NOx emission regulation nozzles are redesigned and fuel injection timing are

adjusted 16. Fuel economy of RTA 84T, a slow speed super charged crude oil tankers- VLCC & ULCC Classes) is achieved by

a combination of setting Variable Exhaust valve closing and opening (VEC & VEO) , Variable Injection Timing (VIT). VIT improves engine efficiency at upper-load range by maintaining full load maximum cylinder pressure at a deaerateed engine by advancing timing of injection whereas VEC is employed in the mid load range to increase effective compression ratio and thereby lower fuel consumption. . VEC controls the actuation of exhaust valve by releasing the hydraulic pressure earlier than usual.

Sulzer Rt-Flex Engine : In 1998th the Sulzer changing concept and moves to the “Common Rail” fuel injection system ("CR"), which was introduced in marine harness in beginning of 2001. The system is called RT Flex and is shown in Figure 9. Characteristics of RTflex Engine:

1. Electronically controlled common rail technology as a standard feature of fuel injection system. 2. Eliminates camshaft and its driving mechanism along with all camshaft driven components 3. Eliminates jerk type fuel pump 4. Eliminates Exhaust valve actuation pump 5. Eliminates servomotor on camshaft that reverses the engine 6. Common rail separate the function of fuel pump, that gives flexibility for optimising combustion process with

more precise control of variables. 7. Fuel pumps, driven by main engine , are required to pump preheated oil to pressurize the common rail to a normal

pressure of 1000 bars 8. The engine driven pumps 4 in number and operated on multilobe cams in Sulzer RTflex 60C Engine


Figure.9 Fuel Oil Injection system, exhaust valve control system and starting valves control system on Wartsila RT-flex engines

On RT-Flex series all the mechanical parts that control the injection and the opening and closing of the exhaust valve, as well as engine starting and all control functions, are replaced with hydraulic oil system (200 bar) and high-pressure fuel system (1000 bar), which presses the fuel in the common rail. All these systems are controlled by WECS 9500.

Figure.10 Different mode of fuel injection on Wӓrtsilӓ RT Flex engine


.

Figure.11 Some of the Fuel Injection Patterns possible with common rail system ( Wartsila)

On figure 12 it can be seen that specific fuel consumption has been reduced especially in low engine loads range. Combustion pressures are decreased in the power range above of 70%, which have direct influence to longer service life of pistons, piston rings, cylinder liners, cylinder heads, cross heads, main and crank pin bearings, etc. Lower pressures reduce temperatures, as well as thermal loads, prolonging so time between overhaul. This directly reduces servicing costs and total harness costs. WÄRTSILÄ RTA Vs. RTflex En:

Figure.12 Comparison of WÄRTSILÄ RTA Vs. RTflex Engine

In figure 12 it can be seen that specific fuel consumption has been reduced especially in low engine loads range. Combustion pressures are decreased in the power range above of 70%, which have direct influence to longer service life of pistons, piston rings, cylinder liners, cylinder heads, cross heads, main and crank pin bearings, etc. Lower pressures reduce temperatures, as well as thermal loads, prolonging so time between overhaul. This directly reduces servicing costs and total harness costs.


III. MAN B&W MC & ME ENGINES

Features of ME-C Engines: MAN B&W has made first significant change in construction in 1978. when the new LGH model was introduced. It had increased stroke/bore ratio to 2,4 (22 %) and power increased for 50 % per cylinder - compared to previous model. The development has continued with LMC model (1982.) which had stroke/bore ratio of 3,24 and a lot of new design innovations; The new variable injection timing (VIT) was introduced, mean effective pressure was increased to 16,2 bar, maximum combustion pressure was increased to 112 bar and specific fuel oil consumption was reduced to 174 g/kWh. Compared to equivalent engine ,MC-C version has higher output per cylinder, about 13 p.c less weight of the engine with higher stroke/ bore ratio to obtain higher propulsive , efficiency and reduce in length of the engine by about 1000mm. The improved version adapted large area in main bearings, improved scavenging and exhaust valve designs.The first electronically controlled slow speed diesel engine has been installed onboard the ship at the end of 2000. That series of engines, at the beginning, were called "Intelligent engines". Later those types of engines join ME series. The mechanical difference between an MC-C engine and its electronically controlled counterpart, the ME-C engine, constitutes a number of mechanical parts made redundant and replaced by hydraulic and mechatronic parts with enhanced functions, as illustrated in Fig. 13 and summarized below: The following parts are omitted:

Chain drive Chain wheel frame Chain box on frame box Camshaft with cams Roller guides for fuel pumps and exhaust valves Fuel injection pumps Exhaust valve actuators Starting air distributor Governor Regulating shaft Mechanical cylinder lubricator Local control stand

The above-mentioned parts are replaced by

Hydraulic Power Supply (HPS) Hydraulic Cylinder Units (HCU) Engine Control System (ECS), controlling the following: i)Electronically Profiled Injection (EPIC) ii)Exhaust valve actuation

The necessary power for fuel injection and exhaust valve operation – previously provided via the chain drive – is now provided from a Hydraulic Power Supply (HPS) unit located at the front of the engine at bedplate level. The main components of the Hydraulic Power Supply unit are the following :

Self cleaning filter with 10-micron filter mesh Redundancy filter with 25-micron filter mesh Start up pumps::

i)High-pressure pumps with supply pressure of 175 bar ii)Low-pressure pumps for filling the exhaust valve push rod with supply pressure of 4 bar

Engine driven axial piston pumps supplying high pressure oil to the Hydraulic Cylinder Unit with oil pressures up to 250 bar

Man B&W Me Series Engines :

vii)Auxiliary blowers

Crankshaft position sensing system Electronically controlled Alpha Lubricator Local Operating Panel (LOP)


Figure13. MAN B& W series functional scheme ( Hydraulic Loop)

Figure14: Fuel injection system

Figure.13 MAN B& W series functional scheme ( Hydraulic Loop)

Figure.14 Fuel injection system

MAN B&W developed another system of fuel injection control and exhaust valve actuation control. ELFI and ELVA are the electro-hydraulic valves where the electric signals come from ECU. ECU is receiving commands from three operating panels; bridge and engine room, where MOP is installed, and from the local control, where LOP is placed.

Figure.15 Actuation of electrical impulses on electro-hydraulic valve (ELFI ) valve The most important part of MAN B&W ME series injection system is ELFI valve. It must be very fast acting to provide optimal opening period depending of engine mode and ECU request. The working principle of ELFI valve can be seen on

41 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 figure 15.Variation of electric signals causes different valve opening which influencing to injection shape. Injection shape directly impact to combustion process which can be optimized according to ship's demands

Figure.16 Injection Pressure profiles depending on types of Injection ( Injection typed could be changed by ECU )

Figure.17 Exhaust valve actuator

The exhaust valve opens hydraulically using a two-stage hydraulic servo actuators driven by servo oil which is brought by ELVA at the right time, depending on the CCU and ECU signals (Figure 17). Similar with the signals for the high-pressure pump, the exhaust valve actuating signal can vary depending on the operation and optimization of the engine working point. The exhaust valve closes by air spring9, as in the MC series. Exhaust system has to stop the valve spindle before it reaches the end position, and to prevent excessive force on the spindle piston in this position is also incorporated hydraulic damper (shock absorber) which reduces the oil flow before the spindle reaches its end position. The difference between MAN B& W ME engine and Wartsila SULZER RTflex engine: The both manufacturers’ of 2 stroke cross head engines have introduced a camshaft less engine. Both engine use electrical and engine driven axial piston pumps to pressurize servo oil rails to 200 bar which are then used for fuel injection and exhaust valve operation. In addition MAN use the servo oil to drive cylinder lubricator units ( Alpha Lubricator) Although both work without a camshaft and use computers to control fuel injection, exhaust valve operation and air starting, the method of fuel injection is different. Unlike SULZER RT-flex engine, MAN ME engine does not operate fuel injection on a common rail system. Instead a solenoid operated proportioning valve ( the FIVA- fuel injection valve valve activation) allows the pressurized servo oil under a hydraulic piston. This then moves the fuel piston upwards, raising the fuel pressure and opening injection valves. A nitrogen filled accumulator maintains a hydraulic servo oil pressure during the operation of the pump. To be able to time the fuel injection, the control systems must know the crank angle of the individual units.. To do this two crank angle sensors are fitted at the free end of the engine. These sensors are accurate to 0.1 % cylinder pressure and power are continuously monitored by the strain gauges built in the cylinder head and the computer. automatically compensated for the twist in the crankshaft when relating crank shaft position to cylinder pressure, the systems give complete flexibility over start and end of injection and take into account fuel quality, dead time ( the time between injection start command given and actual injection ) and variable injection timing (VIT). The biggest difference, compared to the MAN B&W ME system, is the possibility of a separate management of injectors. So, while in the MAN.B&W system the fuel enters into the cylinder through the (two) three injectors simultaneously regardless of the load, the RT Flex system allows the possibility that the fuel is injected through one, two or all three injectors, depending on the load and the desired mode (Fig. 10 & 11).

42 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 It should be also noted that in every stroke another injector is in operation. Such a mode is possible because of the injection volumetric control unit (Figure 4), which in its case has separate electro-hydraulic valves for each injector. At MAN B&W system the ELFI valve leads the servo oil below high pressure pump actuating piston which lift the plunger and brings that the fuel oil is compressed on both11 or all three injectors simultaneously. It should be noted the differences in injection pressures that at RT Flex series range of about 1000 bar, while the ME series are about 700 bar. Unlike conventional generation of engines, where fuel injection pressure significantly decreases with engine (camshaft) rpm reducing (at lower loads), on the new engine generation the fuel injection pressure are same in all modes (because of electrically or hydraulically driven HP pump). High injection pressures, the optimal start and end of injection, and unlimited possibility of the exhaust valve open/close control, are the main reasons for smokeless operation and reduced specific fuel consumption of such engines. Also the harmful substances (especially NOx and PM) are significantly reduced. MAN B&W MC and ME series Comparison:

Figure.18 Engines performances curves comparison between MAN B&W MC and ME series On MAN B&W ME series combustion pressure is slightly increased which will probably have reverse result as

described when comparing Wartsila RTA vs. RT-Flex series. Exhaust valve temperatures on cylinder outlets are decreased which probably prolonged exhaust valves lifetime and TBO. These will surely reduce engine operating costs

Wärtsilä RTflex and MAN B& W ME series Comparison:


Figure.19 Engines performance Curves comparisons between Wärtsilä RTflex and MAN B& W ME series

On figure 19 there can be seen big differences in end-of-compression pressures and maximum combustion pressures. Advantage is on the Wartsila's side. Specific fuel oil consumptions are almost the same - there is an slight advantage on Wartsila's side. It should be mentioned that both system have great advantages when compared with conventional engines. Wartsila engines are running with higher injection pressures and they are able to run with one, two or three injectors separately, which explains slightly better performance curves.

IV. MITSUBISHI UEC – ECO SERIES

Concept : The new engine is named for the letters of “Eco“, which are found in its design goals of ecology, economy, easy control (better maneuverability), and excellent engine condition (higher reliability) The fuel injection, exhaust valve actuating and starting air systems are controlled electronically., sea trial was in May 2005. Ecology: NOx emission can be reduced and smoke less operation achieved. In addition water injection system, a drastic NOx reduction technology, may be applied in combination with Eco-system Economy: Lower specific fuel oil consumption, especially in partial loads and less maintenance cost can be obtained. Easy Control: The Eco-Engine assures stable low load operation with good engine performance. Easy change of operating modes and fine-tuning of operating conditions are possible during operation. Excellent engine condition (higher reliability): Appropriate fuel injection pressure and optimum injection timing, most favorable for the combustion condition at any load, will further enhance the reliability of the hot components proven on the UEC engine. MHI’S low emission technology:


Figure.20 Application of NOx emission technology In general, technological plans to cope with further strict NOx regulation are described in Figure 20 Fundamental structure: The fundamental structure of the engine is seen in Figure 21, compared with the conventional engine. By electronic control, the engine structure is much simplified by eliminating conventional large mechanical parts, such as the fuel and exhaust cams, camshaft, and driving gears. On the other hand, the electronic control system with the hydraulic oil supply system is added. Accordingly, the maintenance work on these mechanical components is eliminated and the computational tuning of engine operating conditions also eliminates the delicate adjusting work on these parts both in the shop and on board. The ease and fine-tuning of the operating conditions are possible during operation. This means that operation of the engine will be much more flexible compared with the conventional type of engine.

Figure.21 Fundamental structure of engine


Figure.22 Diagram of the injection and the exhaust valve control on Mitsubishi UEC - ECO series

The overview of the fuel injection and exhaust valve actuating mechanism are described in Figure 22. The fuel injection pump and the lower exhaust valve driving gear are actuated by 320bar hydraulic oil. This pressurized oil is accumulated in the accumulator block mounted at each cylinder. The connection blocks are applied to connect each manifold block. The accumulating mechanism is simple and reliable in that pressure compensation during actuating is carried out by the volume in the accumulating chamber. Therefore, a pressurized gas enclosed-type accumulator is not necessary. The hydraulic power for fuel injection and exhaust valve actuation is controlled by an on-off type solenoid valve unit and engine control system. The timing of the fuel injection and exhaust valve open/close are also controlled electronically to achieve the best condition for any operation mode. This concept simplifies readjustments needed to maintain better operating conditions. In the down-stream from the fuel injection pump and the lower exhaust valve driving gear, the same design concepts of the conventional system are applied in order to reduce crew education for new maintenance work about such components. Analyzing the system from figure 16 it can be seen a great similarity with MAN B&W ME system, which is not surprising because it is well known that Mitsubishi with his previous series of two-stroke slow-speed marine diesel engines was always following MAN B&W. One of the major differences is the much higher servo oil pressure which is around 320 bar while on the MAN B&W ME series is around 200 bar. Fuel Injection System : Figure 23 shows a cross section of the fuel injection system for UEC Eco-Engine. The fuel injection pump has a similar structure to the conventional mechanical one but is rather simplified. Two sets of on-off type solenoid valves are mounted to control the injection pattern, depending on the operating load, in order to improve the trade-off relationship between thermal efficiency and NOx emission.

Figure.23 Fuel Injection System

46 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 The mechanism for changing the fuel injection pattern is shown in Figure 24 which is put into practice by a pair of on-off type solenoid valves.

Figure.24 Controlled Fuel Injection system

In addition, MITSUBISHI is undertaking incorporation of a water injection system with the Eco-Engine in order to comply with the stricter NOx emission regulation expected in the near future. The feedback control function is applied to the control of fuel injection volume to compensate the equivalent thermal load and individual cylinder control. The fuel pump stroke is monitored by twin gap sensors at each cycle. This emphasizes the reliability of the system through observation in the control system. Exhaust Valve Actuating System : Figure 25 shows a cross section of the exhaust valve actuating system for the UEC Eco-Engine. The exhaust valve open and close timing is controlled by the electro-hydraulic system using the on-off solenoid valve unit. Accordingly, the timings are optimized depending on the operating load. For precise timing control, the feedback control function is applied by observation of the exhaust valve lift. The actuating mechanism is similar to the conventional mechanical ones and inherits their reliability and the method of maintenance.


Figure.25 Exhaust valve actuating system

Control Valve Unit : The solenoid valve units are key components of the electronically controlled engine. For the valve unit of a large electronically controlled engine, a very quick response, high flow rate, and long life cycle are required. Starting Air System : Figure 26 shows a comparison of the starting air system. The conventional starting air control valve is eliminated and solenoid valves and a control air pipe are added. The starting valves are controlled electronically to achieve better performance and flexibility for engine starting and crush-astern. About EMC : For redundancy purposes, the controller is comprised of two units operating parallel and performing the same task, as they are duplicates of each other. If the active EMC fails, the stand-by unit will take over control without any interruption. The EMC performs such tasks as:

Speed governor functions Start/stop sequences Timing control of fuel injection, exhaust valve actuation, and starting air systems Control of the hydraulic oil supply system Alternative operation and control modes Network function Malfunction observation of entire control system


Figure.26 Comparison of Starting air Systems ECC: Each ECC is mounted on an individual cylinder. It performs the orders for timing of fuel injection, exhaust valve actuating and starting air systems. For redundancy purposes, the ECC has the capacity to be able to control two cylinders. If an ECC fails, the one of another cylinder takes over automatically.

Figure.27 Control System Overview LCB: This controller provides for the engine side control as an emergency if the Remote Control System or both EMCs fail. This means that the operator can choose two operating modes and the third redundancy of the EMC [fig 27]


Figure.28 Improvement of engine performance and NOx emission characteristics

The improvement of engine performance [fig.28] are achieved by optimization of the fuel injection timing and injection pattern and the timings of exhaust valve actuating according to engine operating load, atmospheric condition, and fuel properties

.

Figure.29 Smokeless operation

Appropriate fuel injection pressure : The fuel injection system is improved significantly with the electro-hydraulic system. Thus, smokeless operation can be achieved at any load. Figure 29 is shown the comparison of the fuel injection pressure and the Bosch Smoke Number measured on the research engines. Optimization of the exhaust valve timing : By electronic control, the timings of the exhaust valve open/close are optimized flexibly according to engine operating load.

CONCLUSION

From all the experience so far, both manufacturers of slow speed diesel engines have clearly made a major step forward in the technology of large marine diesel engines. The combination of common rail fuel injection, like Wartsila RT-Flex, or hydraulically operated high pressure pumps for fuel injection, like MAN B&W ME and integrated electronic control of Mitsubishi UEC Series, are the only solutions giving high degree of flexibility, together with reliability and

50 Int. J. Adv. Mar. Eng. Ren., 2015, 1(2), 31 - 50 safety. That combination is required to meet the challenges in future marine engine applications in terms of emissions control, optimized fuel consumption, insensitivity to fuel quality, easy of use and operation flexibility. The results from harness show that new generation of slow sped diesel engines have advantages, so they surely have the future. The great advantages are also noticed by ship owners, so the future orders of electronically controlled slow speed diesel engines will increase rapidly.

NOMENCLATURE

ATDC After top dead centre CCU Cylinder Control Unit- Control unit ECS Engine control system EEDI Energy efficiency design index ELFI Electronic fuel Injection ELVA Electronic valve actuation HFO Heavy Fuel Oil iSFO Indicated specific oil LOP Local operating control MDO Marine Diesel Oil MDT MAN Diesel & Turbo m.e.p mean effective pressure NOx Nitrogen oxide MOP Main operating control Parameters are Engine rpm, engine cooling water & oil temp.,

Scavenging air press & temp Air mass flow Atmospheric press & temp Oxygen quantity in exhaust gases Injected fuel quantity Time of lifting injector nozzle

Pgas Gas supply pressure SCR Selective Catalytic Reduction SFOC Specific fuel oil consumption SOI Start of Injection TBO Time between overhaul UPI Unit pump indicator WECS Wartsila Electronic control system

REFERENCES

1. Annex VI of MARPOL 73/78 Regulations for the Prevention of Air Pollution from Ships and NOx Technical Code, 2002. 2. Aeberli K., Large Common Rail Engines at Sea, The Motor Ship, December 2004. 3. Bertola Andrea G., Technologies for Lowest NOx and Particulate Emissions in DIDiesel Engine Combustion Influence of Injection Parameters,

EGR and Fuel Composition, Dissertation, ETH Zurich, 2003. 4. Dolenc A., Sistemi za neposredno vbrizgavanje goriva za nove hitrotekoče dizelske motorje, Inovativna avtomobilska tehnologija – IAT'01,

Ljubljana, 5.-6. april, 2001. 5. Glöckner M., Universal Electronic Fuel Injection Control Device for Marine, Locomotive and Genset Application, CIMAC Congress,

Hamburg 2001. 6. Gröne Ole & Aabo Kjeld: The Latest Two-Stroke Control Technology, Motorship 2004. 7. Hlousek J., Bernhaupt M. & Kögler B., Electronically Controlled Injection Rate Shaping for Medium Speed Diesel Engines, CIMAC Congress,

Hamburg 2001. 8. Lustgarten G., Acert for emissions reduction, MER, December/January 2005. 9. Operation Manual for RT-flex 60 C, 2002. 10. Series 4000 Common Rail Fuel System Technician Guide, Detroit Diesel 11. Sørensen P & Pedersen P.S., The Intelligent Engine Design Status and Service Experience, CIMAC Congress, Hamburg 2001. 12. http://www.epa.gov (2002.) 13. http://www.manbw.com (2005.) 14. http://www.wartsila.com (2005.)

research article a voyage through the marine …ijamer.in/current-issue/paper1.pdf · engines named...

Documents