ME and MC Engine Differences

Q1. Latest development in turbochargers

Ans: Adjustable nozzle ring

The intake air is compressed by the compressor wheel, which is driven by the turbine. Both the

compressor wheel and the turbine can be adjusted to engine requirements by choosing from a range of meridians and blading configurations. Diffusers and nozzle rings which are very finely stepped in their mass-flow areas allow the turbochargers to be fine-tuned to the engine. For

maximum variability an optional nozzle ring capable of adjustment during operation will be available in the near future.

Oil mist instead of water cooling

None of the TCA turbocharger bearing casings is water-cooled - not even in the largest framesizes,the TCA88 and TCA99. The heat brought in by the compressor and the turbine is dissipated in the luboil flung off the shaft of the rotating assembly. The oil mist thus generated can drop down the walls of the very generously-dimensioned interior of the bearing casing, thereby evenly absorbing the heat which is to be dissipated. The bearing casing boasts its own air vent, which can likewise be connected to the left or right. This air vent ensures that the leakage air which the compressor inevitably forces into the bearing casing through the shaft seal of the rotating assembly does not increase crankcase pressure in the engine, but instead is

dissipated directly.

The result is a turbine with 41 so-called "wide-chord" blades arranged in a fir-tree root in the turbine disc.The characteristic feature of wide-chord blades is their very high chord-to-height ratio. Thisproduces a compact-looking, very stiff and hard-wearing turbine blade. For engine matching theturbine blades can be of varying angles and lengths. With the aid of leading-edge design tools it is now possible to dispense with lacing wire to dampen exhaust-generated vibrations, even in four-stroke engine applications. Apart from improving the blade profile, this has also been an immense boost to efficiency.

A new design of compressor volute and new designs of nozzle ring ensure optimum

turbocharger matching and contribute to the high efficiency of the TCAturbochargers.

Q2. Difference between ME – MC

Ans: The ME series of engines have no camshaft. Instead, to provide power for fuel injection and exhaust valve lifting, they utilise a hydraulic oil loop with fine filtered oil from the main engine lubricating system at about 200 bar pressure.

The advantages of the ME series of engines come from the fact that the timing and intensity of fuel oil injection and exhaust valve opening and closing is optimal at all steady and transient loads, thus giving lower part load fuel oil consumption, lower emissions and particularly smoother and better low load operation. The balance between cylinders will be easier to adjust for smoother operation. All this will eventually mean longer MTBO (Mean Time Between Overhauls).

The engine can be changed over to different ‘low emission modes’ where its NOx exhaust emission can be reduced below the IMO limits if desirable due to local emission regulations

The electronic control of the fuel injection system and the exhaust valve operation, together with the fact that ME engines are normally delivered with on-line cylinder pressure measurement equipment and the engine diagnosis system CoCoS-EDS, provides a number of benefits:

• Well-proven conventional fuel injection pattern and technology

• Adjustable injection intensity by electronically variable cam “angle” and cam “length”

• The control system offers more precise timing and thereby better engine balance with equalized thermal load in and between cylinders

• Uniform combustion and heat load at any load

• Lower rpm possible for manoeuvring

• Sequential cylinder cut-off at low load

• High injection pressure at low load

• Slide type zero-sack-volume fuel valves

• Improved emission characteristics, i.e. lower NOx and less visible smoke at any load

• System comprising performance monitoring for longer time between overhauls.

• Monitoring of the engine (based on CoCoS-EDS) identifies running conditions which could lead to performance problems

• The Overload Protection System ensures compliance with the load diagram and ensures that the engine is not overloaded

Optimum crash stop and reverse running performance

• “Engine braking” may be obtained, reducing the stopping distance of the vessel

• Faster acceleration of the engine by opening the exhaust valves earlier during acceleration

• Significantly improved dead slow running with low minimum rpm and stable operation together with improved combustion due to the electronic control of fuel injection

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:

-Electronically Profiled Injection (EPIC)

-Exhaust valve actuation

-Fuel oil pressure boosters

-Start and reversing sequences

-Governor function

-Starting air valves

-Auxiliary blowers

# Crankshaft position sensing system

# Electronically controlled Alpha Lubricator

# Local Operating Panel (LOP)

Hydraulic cylinder unit

The hydraulic cylinder unit, of which there is one per cylinder, consists of a hydraulic oil distributor block with pressure accumulators, an exhaust valve actuator with ELVA control valve and a fuel oil pressure booster with ELFI control valve. Each individual HCU is interconnected by double-wall piping, through which the hydraulic oil is led.

ELVA and ELFI valves were substituted by one common FIVA valve controlling both the exhaust valve actuation and the fuel oil injection.

ELFI valves

On the Print Circuit Board (PCB) components have come loose due to vibrations. Improvements by means of resilient mountings have been introduced on all vessels in service with ELFI valves, and performance has been Good

ELVA valves

Early service experience proved that low ambient temperatures, as often experienced during shop tests in the winter season, gave rise to sticking high response valve spools in the ELVA valve due to low hydraulic oil temperatures. The diameter of the spool was reduced in order to obtain correct functioning of the high-response valve Initially, the ME tacho system was designed on the basis of trigger segments with a sine-curved tooth profile mounted on the turning wheel. The total trigger ring was built from eight equal segments.

Two redundant sets of sensors were applied. This initial tacho system is relatively expensive, and the system The new tacho system is based on optical angular encoders installed on the free end of the crankshaft. This system, consisting of two redundant encoders.

 

Alpha Lubrication system

The ME engine has the advantage of an integrated Alpha lubrication system, which utilises the hydraulic oil as the medium for activation of the main piston in the lubricators. Thus, a separate pump station and control are not needed compared to the MC counterpart.

Q3. What are the basic features of ME – GI engines

Ans: the new modified parts of the ME-GI engine pointed out, comprising gas supply piping, large-volume accumulator on the (slightly modified) cylinder cover with gas injection valves, and HCU with ELGI valve for control of the injected gas amount.

High-pressure gas compressor supply system, including a cooler, to raise the pressure to 250-300 bar, which is the pressure required at the engine inlet.

• Pulsation/buffer tank including a condensate separator.

• Compressor control system.

• Safety systems, which ex. includes a hydrocarbon analyser for checking the hydro-carbon content of the air in the compressor room and in the double-wall gas pipes.

Sealing oil system, delivering sealing oil to the gas valves separating the control oil and the gas.

• Inert gas system, which enables purging of the gas system on the engine with inert gas.

the gas supply system is a common rail system, the gas injection valve must be controlled by another system, i.e. the control oil system. This, in principle, consists of the ME hydraulic control (servo) oil system and an ELGI valve, supplying high-pressure control oil to the gas injection valve, thereby control-ling the timing and opening of the gas valve. the normal fuel oil pressure booster, which supplies pilot oil in the dual fuel operation mode, is connected to the ELGI valve by a pressure gauge and an on/ off valve incorporated in the ELGI valve.

By the control system, the engine can be operated in the various relevant modes: normal “dual-fuel mode” with minimum pilot oil amount, “specified gas mode” with injection of a fixed gas

amount, and the “fuel-oil-only mode”.

The principle of the gas mode control system is that it is controlled by the error between the wanted discharge pressure and the actual measured discharge pressure from the compressor system. Depending on the size of this error the amount of fuel-gas (or of pilot oil) is either increased or decreased. If there is any variation over time in the calorific value of the fuel-gas it can be measured on the rpm of the crankshaft. Depending on the value measured, the amount of fuel-gas is either increased or decreased.

Q4. comparison between ME- MC engine

Ans:

• Power, speed and nominal Specific Fuel Oil Consumption (SFOC) are the same for the ME series as for their MC counterparts.

• The SFOC has been reduced significantly at part load as the maximum pressure can be maintained down to 65-70 percent of the engine load.

• SFOC is the same as for the mechanically controlled engines at nominal output

• At lower load, the SFOC is lower for the electronically controlled engines

• Easy to change between various running modes.

Q5. What is intelligent cylinder lubrication

Ans;

• Alpha Lubricator system

-ensures considerable cylinder oil savings

• controllable wear rates, scuffing control and

• longer intervals between engine overhauls.

• However, over lubrication is not only expensive - it may even be counter productive in promoting scuffing through excessive carbon deposits and/or "bore-polished" running surfaces.

The properties of cylinder oil scraped from the cylinder liner wall reflect the chemical environment in the cylinder as well as the physical condition of rings and liner; and there is a direct relationship between some of the key parameters in the scrape-down oil and the actual cylinder condition. A lubrication algorithm - based on scrape-down oil analysis data, cylinder oil dosage, engine load and cylinder wear rate can thus be created.

Q6. Alpha adaptive lubrication

Ans: The main element of cylinder liner wear is of a corrosive nature, and the amount of neutralizing alkalinic components needed in the cylinder will therefore be proportional to the amount of sulphur (which generates sulphurous acids) entering the cylinders. A minimum cylinder oil dosage is set

in order to satisfy other requirements of a lubricant, such as providing an adequate oil film and detergency properties

The cylinder oil must be injected into the cylinder at the exact position and time where the effect is optimal, which is not always possible with the conventional lubricators of today.

The following two criteria determine the control:

• The cylinder oil dosage shall be proportional to the sulphur percentage in the fuel

• The cylinder oil dosage shall be proportional to the engine load (i.e. the amount of fuel entering the cylinders). a standard TBN 70-80 cylinder oil. For operation in long periods with fuels with a

sulphur content below 1%, we recommend changing to a cylinder oil with a lower TBN (i.e. TBN 40-50 cylinder oils). the control of the cylinder oil dosage proportional to the engine load, together with rpm-proportional and mep-proportional lubrication. At part load, load-proportional cylinder oil dosage will provide large cost savings and also reduce the environmental impact from excessive lubrication. Below 25% load, the load-proportional lubrication is stopped, and rpm-proportional

lubrication takes over,.

In the present version of the Alpha Lubricator System the ship staff inputs the so-called ‘HMI( human machine interface-setting’ based on the sulphur percentage of the fuel used and a conversion table. An input is made at the appropriate system panel each time the fuel specification is changed. This is done by one input on the

HMI-panel of the Alpha Lubricator System each time the fuel specification is changed.

Typical feed rate (mechanical lubriator), 1.2 g/bhph, rpm proportional control

# Basic feed rate (mechanical lurbicator), 0.9 g/bhph, rpm proportional control

# Basic feed rate (Alpha Lubricator System), 0.8 g/bhph, MEP proportional control

# Alpha ACC, 0.25 g/bhph/S%

Significant savings in daily cylinder oil consumption through Alpha ACC of this 12K90MC engine – monitored over a five-month period since system implementation – equate to annual savings of 340 000 USD on cylinder oil.

Q7. What is alpha – pulse cylinder lubrication system

Ans: The new lubricating system is based on the principle of injecting a specific volume of oil into the cylinder, via a number of injectors, for every four (or every five, six, etc.) revolutions. Furthermore, the precise timing ensures that all cylinder oil is delivered directly onto the piston ring pack where it is needed.

a small piston for each lubricator quill in the cylinder liner, and the power for injecting the oil comes from the system pressure, supplied by a pump station. A common rail system is used on the driving side, but the injection side has a high-pressure positive displacement system, thus giving equal amounts to each quill and providing the best possible safety margin against clogging of single lubricator quills.

The pump station includes two pumps (one operating, the other on stand-by with automatic

start up). The computer unit comprises a main computer, controlling the normal operation,

a switch-over unit and a (simple) back-up unit. The injection function is controlled by the computer sending an on/off signal to a solenoid valve.

A shaft encoder (which can be shared with the PMI system, or timing system on the Intelligent Engine) supplies the necessary timing signal.

The amount of oil injected can be adjusted automatically or manually as required, e.g. at load changes, start/stop, at reduced engine load (different modes are available), sulphur % in the fuel,

temperature level on liner surface, variation in cylinder oil BN, etc. Pre-lubrication before start can be made manually or be a sequence in the bridge manoeuvring system.

The pump station supplies the Alpha Lubricators with 40-50 bar oil pressure.

Q8. What is multistage turbo charging

Ans:

1. exhaust flow is bypassed from one stage to another, in doing so energy contained in the exhaust is preserved.

2. bypass flow is passed through a VGT vane outletas other variable geometry nozzle. Thus converting pressure energy to kinetic energy. Such high kinetic energy exhaust gas is made to exert mechanical rotational force on thelower pressure turbine wheel. The VGT mechanism is only in one turbine volute.