Marine Diesel Engine Cooling Systems

Raw Water Cooling:

A flexible impeller pump provides an efficient solution to most raw water pumping needs. The primary advantage of flexible impeller pumps is that they are self-priming, which means that when the vanes of the impeller are depressed and rebound, they create their own vacuum, drawing fluid into the pump. A dry pump can lift water up to as much as three meters. Thus a flexible impeller pump being used for engine cooling does not need to be manually primed or located below the water line. An added feature of a flexible impeller pump is that it can pass fairly large solids without clogging or damaging the pump. This reduces the need for filtration of incoming fluids.

For general or fresh water applications, a standard long lasting neoprene rubber impeller is used.

A general feature of all flexible impeller pumps is that they cannot be permitted to run dry for more than 30 seconds. Both the impeller and the seals require water for lubrication and will soon burn out if run dry. 

Fresh Water Cooling:

For circulation of the internal, closed, fresh water circuit of the cooling system it is common to use a flexible rubber pump if it is located on the cold side of the system (max. 55°C). Other types of belt-driven centrifugal pumps are also used. The closed circuit normally transfers heat from the engine to the heat exchanger. The liquid used is water and anti-freeze.

Cooling Capacity:

The required output of the cooling pump is related to engine type and size, not to the size of the heat exchanger and exhaust system. This is true for both raw water as well as fresh water handling systems


Temperature Regulators (Thermostats)

Thermostats are usually placed in the outlet at the top of the cylinder head to prevent the coolant from moving to the header tank until the marine engine has nearly reached operating temperature.

There are different types of thermostats, the most common being the wax pellet type. The capsule on the lower part of the thermostat has a mixture of wax and copper (to increase the thermal conductivity) sealed in it. As the coolant temperature increases, the wax expands and forces a rod to open the poppet valve at the top of the thermostat, which allows the coolant to circulate.

Cooling System Checks

• To test your thermostat, boil a pot of water and drop in the thermostat. (The water must be 100 degrees celcius--the thermostat usually opens at 85 degrees celcius.) If the thermostat opens it is okay. If it doesn't open, replace or clean carefully as they can become sticky with deposits. Yanmar thermostats can and should be regularly serviced. Some thermostats cannot be serviced.
• If the thermostat doesn't work, do not remove it and run the engine without it, as the engine will run cold and tight. You can drill a series of 1/4 inch? holes to give equivalent flow to an open thermostat. This will get you home, but you must then replace it. Be careful not to fit thermostat upside down.
• Thermostat housings often corrode and need to be replaced. Some can be fabricated.
• The cooling system should be checked after 100 hours running, or at least once each season, for leakage, deposits, etc.
• The thermostat can be taken out of the housing on the front of the engine.
• The heat exchanger core should be removed bi-annually for cleaning and inspection.
• Many heat exchangers are fitted with anodes to protect the expensive core. Check regularly.
• Check all hoses and clamps regularly.

Replacing the sea-water pump impeller

The pump impeller is made of neoprene rubber and this can be damaged in the case of water deficiency if, for example, the sea-water intake should be blocked. The  pump impeller trouble shooting guide will be helpful in identifying impeller problems. The sea water pump impeller is changed as follows:

1. Remove the cover from the sea-water pump. Note that there is the risk of water getting into the boat. With the help of two screwdrivers pull the shaft with the pump impeller out of the housing as far as necessary to reach the bolt retaining the impeller. Place some kind of protection under thescrewdrivers in order not to damage the impeller housing. Alternatively, using channel-lock pliers, slide jaws between blades of impeller, rotate and withdraw.
2. Pull the impeller off the shaft. Clean the inside of the pump housing and fit the new impeller. Always have a spare impeller on board.
3. Check that the pump coupling is not damaged, by trying to turn the pump impeller. Fit the cover with the original gasket, which has the right thickness.

Twin Spark Theory

Twin S

park Theory

Twin Spark Theory

Twin Spark :

Normal engines have one spark plug per cylinder. However, since decades ago, Alfa Romeo insisted on putting 2 spark plugs in each cylinder, firstly in its racers and now in its cars. As ignition takes place in two locations rather than one, this enable more efficient combustion and cleaner emission. However, besides Alfa, in the past 15 years only Mercedes and Porsche have ever applied Twin Spark design to their engines. This is mainly because of the complexity of cylinder head - it would be too difficult to put 4 valves and 2 plugs into the small cylinder head area. ( Mercedes' and Porsche's engines are 3 valves and 2 valves per cylinder respectively, so they have no such problem.) Only Alfa Romeo have applied it to 4-valve engines.

In its Original 2 valve twin spark engines, Alfa actually used the twin spark plugs not to create extra power but to cure rough running at low rpm and to improve fuel economy.

In its original guise when being develop Alfa could extract a creditable 148bhp from its two litre two valve engine. The problem was that it had rough low speed running and poor low speed economy and emissions. The main cause being the high degree of overlap being used in the cams to get the high power.

What Alfa found though was that whereas in a normal high overlap engine running at low speed unburnt fuel was tumbling out of the exhaust port, and the inherently diluted mixture of the EGR system which was being used to clean up the emissions, was difficult for a single plug to fire. Under normal conditions, a single plug could ignite an air/fuel ratio of 17:1, whereas twin plugs could ignite a mixture as lean as 20.8:1.

Not only could they allow lean mixtures via EGR giving good economy, but they could ignite it reliably, giving better, smoother low speed running and cleaner emissions.

As the modern engine continues to develop though we may see more of the twin spark plug the reasons for this and its lack of previous use are many.

Older engines tended to have long stroke/ small bore combinations

Modern engines have ever-increasing bore dimensions

Modern fuesl are becoming slower burning.

Engines are getting ever higher revving

The result is that the flame at the point of ignition needs to travel ever further is shorter and shorter durations. Bigger bores means more area for plugs and valves, multiple spark plugs seems an obvious and cheap solution to getting a fast burning charge.

New Engines For 2013

New Engines For 2013

• Cat C-7 - 550HP
• Cat 12.9 - 1000HP
• New Cat 3126's
• New Cummins 6.7 to 600HP
• New Duramax's to 600HP

 New Caterpillar and Cummins Engines for Marine use, Industrial use, Power Generation and Marine Propulsion. We also offer Remanufactured, Rebuilt & High Performance Diesels. We are a  Marine Diesel Specialist, providing up To 50 Knot Conversion Packages. Our custom machine work and fabrication services have been in operation since 1969.

Piston Ring Failure Analysis

A piston ring is a ring used in conjunction with a piston to seal an engine's combustion chamber and regulate oil use. Piston rings often experience wear due to a number of different factors. As such, it is important to know how to analyze piston ring failures.

Scuffing

• Scuffing of the piston ring leads to wear on the ring face. Damage to the ring face can lead to a loss of ring control. When this occurs, it usually results in high base pressure, oil over-consumption and piston scoring. This can cause the piston to seize altogether.

Causes

• Three things are the primary cause of a piston ring becoming scuffed; they result from normal engine operation. These are fuel wash-down (which occurs when abrasive fuel comes into contact with the piston ring), debris ingestion (which occurs when materials from outside get stuck in the engine) and severe overloading (which occurs when the engine is overworked).

Improper Assembly

• Piston rings are sometime assembled improperly. If the piston ring is misaligned due to improper assembly, oil may bypass the rings. This can cause carbon buildup, which can lead to a piston ring becoming scuffed.

Life of Junior Engineer on Ship

IMPORTANCE OF JUNIOR ENGINEER/5TH ENGINEER

"Junior Engineer" is a very important rank with respect to the engine room. They are Engineers under training after completion of basic education for the sea service. The don't hold a "certificate of competency", (C.O.C), to become an "Officer In charge Of an Engineering Watch",(OOEW). They are under direct control of 2nd Engineers who is usually the operational/maintenance boss of the engine room. They are supposed to get training on operation/maintenance of various machineries under supervision of senior Engineers.
Out of all these engineers, since Junior Engineers are trainee engineers, they sail for comparatively more time than other engineering officers. This makes them well versed with the history, inventory, spares, records, log books, pipeline tracing & to some extent fault finding too..They usually help senior engineers to get familiarized with the engine room, shortly after their sign-on. They also indirectly share the responsibilities of the 2nd engineer and to some extent other engineers too. Some of the usual jobs of the Junior Engineers are 1. Complete Pipeline tracing 
2. Bilges handling
3. Sludge handling
4. 2nd engineers watch routines & log book updating
5. certain paper works for the month end reports.
6. Incineration
7. Learn the operation & maintenance of machineries
8. obey orders of 2nd engineer
9. Help other engineers if directed by 2nd engineer.
and many more...!!
Thus the Rank of Junior Engineer is very vital for the operation of the ship. It is also key for a persons technical knowledge as many engineers learn at this rank.

hybrid turbocharger

A hybrid turbocharger is an electric turbocharger consisting of an ultra high speed turbine-generator and an ultra high speed electric aircompressor. The turbine and compressor are high-speed aeromachines, as in a conventional turbocharger. The electrical motors run at speeds in excess of 120,000 rpm and when used as generators, generate electricity at up to 98.5% electrical efficiency. High electrical efficiency is paramount, because there is no mechanical link between the turbine and compressor. In other words, hybrid turbocharger refers to a series hybridsetup, in which compressor speed and power are independent from turbine speed and power. This design flexibility leads to further improvements in turbine and compressor efficiency, beyond a conventional turbocharger.

The designers claim that hybrid turbocharger technology (HTT) virtually eliminates turbo lag and enables engine downsizing without compromising engine performance. This means that a HTT equipped engine can save up to 30% on CO₂ emissions and fuel economy compared to an equivalent naturally aspirated engine.

Physical arrangement

The electric motors utilize permanent magnets which have a higher efficiency than standard high speed induction motors. Induction motors induce an electro-magnetic field into a solid rotor core. The induction motor is much simpler to control, but there are substantial losses involved in generating the magnetic field in the rotor.

The HTT motor will accelerate from 40,000 to 120,000 rpm in less than 450 ms. The HTT motor control therefore requires a fast acting CPU to match the magnetic field of the stator to the changing position of the roto

Acceleration

When the driver depresses the throttle, the HTT initially acts like an electric supercharger. The compressor motor is powered from the energy storage medium allowing it to accelerate to full operating speed in <500 ms. This rate of acceleration eliminates the turbo lag which is a major limiting factor on the performance of standard turbocharged engines.

During this transient stage, the engine control unit (ECU) on a standard turbocharged engine uses a combination of sensors such as lambda sensors and air mass flow sensors to regulate the fuel flow rate. In an HTT equipped engine the ECU can deliver the precise fuel flow rate for complete combustion more accurately. This is achieved by directly controlling the air flow rate and boost pressure via control of the compressor speed.

Aeristech's prototype motor delivers 26 kW (35 PS; 35 hp) at 120,000 rpm, weighs under 3.5 kg (8 lb) and is approximately 10 centimetres (4 in) in length.

Charging

At high engine speeds there is more energy generated by the turbine than is required by the compressor. Under these conditions, the excess energy can be used to recharge the energy storage for the next acceleration phase or used to power some of the auxiliary loads such as an electric air conditioning system.

When combined with a variable geometry turbine, the back pressure on the engine can be varied according to the electrical demands of the vehicle and charge state of the energy storage medium.

Development is underway for replacing battery energy storage with a super capacitor which can be charged and discharged very quickly

System benefits

Aeristech claim many other benefits to running a hybrid turbocharged engine:

• Improved packaging by enabling the turbine and compressor to be placed in separate parts of the engine bay.
• Higher density charge air by reducing the length of intake ducts and increasing the size of the compressor wheel.
• ECU controlled boost levels will enable tighter predictive control of in-cylinder combustion.
• Similar engine downsizing benefits to a hybrid vehicle, but with far less (approx 1/7th) energy storage capacity to achieve the same level of downsizing.

Other types of electric turbochargers and electric superchargers are under development with varying degrees of success:

• eBooster by BorgWarner - a small auxiliary electric compressor powered by the vehicle's electric system.
• TurboPac by TurboDyne - Electric supercharger
• Garrett electrically-assisted turbo
• Valeo - Electric supercharger using a low-inertia switched-reluctance motor

Homogeneous Charge Compression Ignition

What is HCCI?

As stated above, the acronym means Homogeneous Charge Compression Ignition. Yes, yes, but what does that mean? What does it do? An HCCI engine is a mix of both conventional spark-ignition and diesel compression ignition technology. The blending of these two designs offers diesel-like high efficiency without the difficult--and expensive--to deal with NOx and particulate matter emissions. In its most basic form, it simply means that fuel (gasoline or E85) is homogeneously (thoroughly and completely) mixed with air in the combustion chamber (very similar to a regular spark ignited gasoline engine), but with a very high proportion of air to fuel (lean mixture). As the engine's piston reaches its highest point (top dead center) on the compression stroke, the air/fuel mixture auto-ignites (spontaneously and completely combusts with no spark plug assist) from compression heat, much like a diesel engine. The result is the best of both worlds: low fuel usage and low emissions.

How Does HCCI Work?

In an HCCI engine (which is based on the four-stroke Otto cycle), fuel delivery control is of paramount importance in controlling the combustion process. On the intake stroke, fuel is injected into each cylinder's combustion chamber via fuel injectors mounted directly in the cylinder head. This is achieved independently from air induction which takes place through the intake plenum. By the end of the intake stroke, fuel and air have been fully introduced and mixed in the cylinder's combustion chamber.

As the piston begins to move back up during the compression stroke, heat begins to build in the combustion chamber. When the piston reaches the end of this stroke, sufficient heat has accumulated to cause the fuel/air mixture to spontaneously combust (no spark is necessary) and force the piston down for the power stroke. Unlike conventional spark engines (and even diesels), the combustion process is a lean, low temperature and flameless release of energy across the entire combustion chamber. The entire fuel mixture is burned simultaneously producing equivalent power, but using much less fuel and releasing far fewer emissions in the process.

At the end of the power stroke, the piston reverses direction again and initiates the exhaust stroke, but before all of the exhaust gases can be evacuated, the exhaust valves close early, trapping some of the latent combustion heat. This heat is preserved, and a small quantity of fuel is injected into the combustion chamber for a pre-charge (to help control combustion temperatures and emissions) before the next intake stroke begins.

Challenges for HCCI

An ongoing developmental problem with HCCI engines is controlling the combustion process. In traditional spark engines, combustion timing is easily adjusted by the engine management control module changing the spark event and perhaps fuel delivery. It's not nearly so easy with HCCI's flameless combustion. Combustion chamber temperature and mixture composition must be tightly controlled within quickly changing and very narrow thresholds that include parameters such as cylinder pressure, engine load and RPMs and throttle position, ambient air temperature extremes and atmospheric pressure changes. Most of these conditions are compensated for with sensors and automatic adjustments to otherwise normally fixed actions. Included are: individual cylinder pressure sensors, variable hydraulic valve lift and electromechanical phasers for camshaft timing. The trick isn't so much as getting these systems to work as it is getting them to work together, very quickly, and over many thousands of miles and years of wear and tear. Perhaps just as challenging though will be the problem of keeping these advanced control systems affordable.

Advantages of HCCI

• Lean combustion returns 15 percent increase in fuel efficiency over a conventional spark ignition engine.
• Cleaner combustion and lower emissions (especially NOx) than a conventional spark ignition engine.
• Compatible with gasoline as well as E85 (ethanol) fuel.
• Fuel is burned quicker and at lower temperatures, reducing heat energy loss compared to a conventional spark engine.
• Throttleless induction system eliminates frictional pumping losses incurred in traditional (throttle body) spark engines.

Disadvantages of HCCI

• High cylinder pressures require stronger (and more expensive) engine construction.
• More limited power range than a conventional spark engine.
• The many phases of combustion characteristics are difficult (and more expensive) to control.

It is clear that HCCI technology offers superior fuel efficiency and emissions control compared to the conventional tried-and-true spark ignition gasoline engine. What's not-so-certain yet is the ability of these engines to deliver these characteristics inexpensively, and, probably more importantly, reliably over the life of the vehicle. Continued advancements in electronic controls has brought HCCI to the precipice of workable reality, and further refinements will be necessary to push it over the edge into everyday production vehicles.

New, large-bore, marine engine development with high power density

. MAN Diesel has broadened its product portfolio with the development of its new, Type K80ME-C9 two-stroke, low-speed engine. The ME-C9 engine recently passed the final milestone on its way to commercial applications in the marine sector with a successful Type Approval Test (TAT).

The first production version of the MAN B&W-branded engine successfully completed its TAT programme at Hyundai’s (HHI-EMD) works in Ulsan, Korea. HHI-EMD’s two-stroke engine assembly and test shop #2 was the venue for the test and hosted representatives from the shipyard, ship owner and leading Classification Societies.

The MAN B&W 7K80ME-C9 engine develops 31,710 kW at 104 rpm and is destined for a vessel operated by the A.P. Møller Mærsk group that also includes Waste Heat Recovery technology. The ME-C9 engine enhances the green credentials of the same vessel that can also boast of a highly efficient waste-heat recovery system. The engine is the first of four large-bore, Mk. 9 engines, all displaying high power density, and due for production during 2009.

The four engines are based on the well-proven technology of MAN Diesel’s mechanical MC and MC-C engine ranges. Broadly speaking, the ME-concept represents an upgrade of the mechanical engines with electronic controls that provide improved, operational economy and flexibility, better manoeuvrability and easier overhauls.

Exceptional performance
Søren Jensen, Vice President and Head of Research and Development, Marine Low-Speed, MAN Diesel, commented: “The electronic, two-stroke ME-C range is among the most popular available on today’s market. A major advantage is its ability to operate at even very low load for indefinite periods of time, whilst offering a substantial reduction in fuel-oil consumption compared to conventional engines at such low loads.”

“During testing, the performance of the 7K80ME-C9 engine, an engine that is fully compatible with IMO Tier-II regulations, exceeded expectations and delivered a lower fuel-consumption than we anticipated.”

He continued: “We are proud of this new engine type, which has a 20% higher power density compared to the previous mark. We have been able to achieve this using a new construction and calculation methodology as we now have more know-how in terms of where to distribute weight. With the ME-C9, we have not only a more compact engine but also one that is easier to overhaul as we have focused on making all components easily accessible for inspection and service.”

ME-C9 featuresThe list of advantages inherent to the ME-C9 range is comprehensive and includes:
•  20% higher power density
•  differentiated distances between cylinders to aid compactness and maintain overall weight
•  integrated scavenge air receivers and cylinder frame
•  weight-optimised connection rods
•  low-friction crosshead
•  fuel system with new servo pressure from 200 to 300 bars where it has been possible to reduce component size