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Marine Diesel Engines

Diesel Engines

How a diesel operates - If you have ever pumped up a bicycle tire with a small hand pump you know that the pressure end gets hot. All of the energy that was in the pump air plus the energy added by compressing the air is still there. It shows up as higher temperature. A diesel is a compression ignition engine that works on the same principle. On the compression stroke, the piston compresses the air in the cylinder above the ignition temperature of the fuel.  Injected fuel burns and creates engine power.

The diesel engine cylinder has an inlet and outlet valve plus an injection nozzle. The cycle of opening the inlet valve, compressing the air in the cylinder, injecting and igniting the fuel then exhausting the combustion products from the cylinder may be seen in several internet video’s.

Suggested web sites for viewing “how a diesel works”.

      www.explainthatstuff.com/diesel-engine.html

             www.cummins.com/how-a-diesel-engine-works

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Great Lakes ore carrier Edgar B. Spear, built for United States Steel company. 1004 feet long, 2 Colt Pielstick diesel engines for propulsion.

Brief History of Diesel engine development.

             1876 – Nikolaus Otto builds first internal combustion engine.

             1894 – 1899 Rudolph Diesel patents design for compression ignition engine and starts manufacturing engines.

             1912 – MS Selander – first ocean going diesel ship.

              !931 – Clessie Cummins builds first successful diesel engine automobile.

             1931 – Man diesel (Germany) and its chief designer Gustav Pielstick developed a two stroke opposed piston diesel engine that met the specification of Reich Navy for an engine of 6 kilograms per horsepower.

             1932 – German Junker opposed piston diesel aircraft engine developed.

             1934-1939 – Diesel powered locomotive using Winton/GM diesel engines operated faster and lower cost than steam train. General Motors develops a diesel electric locomotive.

             1946 – At the behest of the victorious powers, Gustave Pielstick left the employment of MAN Diesel. He joined the French Firm of SEMT.

             1987 – Passenger liner Queen Elizabeth 2 replaces steam turbines with diesel engines for economic reasons.

SMET/Pielstick -The French firm SEMT hires Gustave Pielstick and developes a series of diesel engines for a variety of applications between 1946 and 2006. It is now operated as a brand of MAN diesel. 

      1951 – PC series – Early design of an in line 6 cylinder engines using heavy fuel oil. 180 kw per cylinder. 1960 designed engines developed 750 kw/cylinder.

            Late 1950s  – PA series – high speed (1000 RPM) that initially developed 46 kw/cylinder. Later versions developed 184 kw/cylinder (twin stage turbo, 1978).

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             1966 -1995 -PA6 Series – A new series starting in 1966 with several versions provided.

Large ships are traditionally provided with medium speed PC series engines while smaller ships are provided with high speed PA series engines.

Examples of Diesel Powered Ships

Great Lakes ore carrier Edgar B Spear is built for United States Steel company. It uses 2 Colt-Pielstick 18 cylinder, 19630 HP, 520 RPM diesel engines built by Fairbank Morse, a licensee of SMET/Pielstick. Edgar B Spear is 1004 feet long, 105 feet wide and draft of 56 feet.

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USS Bonefish (SS 582) 1958 – Produced by New York Shipbuilding, Camden NJ.  The submarine used 3 Fairbanks Morse opposed piston diesel engines. Fairbanks Morse was a licensee of SMET. The engines were modelled after German Junker aircraft engines of 1930s.

USS San Antonio (LPD 17) 2006 – Troop transport, two PA6B STC engines. 

German pocket battleship and commerce raider, Graff Spree,  sunk off the river Plate in 1939. Diesel powered.

United States Coast Guard—378 foot high endurance cutter Munro (1971). Retired after 50 years service. 2 opposed piston Fairbanks Morse diesel engines. Engines rebuilt in 1986.

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Fuel Injection systems

Spark Ignition - There are two Fuel Injection Schemes applied to "Otto Cycle" gasoline engines. The first replaces the carburetor and provides atomized fuel to the intake manifold. The second is called "Direct Injection" and injects the fuel into the cylinder. Both systems provide metered and atomized fuel for internal combustion.   Many new cars are using the "Direct Injection" system such as the new Honda Accord. The spark ignition system is not discussed here.

Compression ignition fuel injection system

In this system, fuel is injected into the combustion chamber at high pressure and is called “compression ignition” and sometimes called “internal mixture” (fuel and air) system.

Mechanical injection (older system) – In this system a positive displacement, high pressure mechanical pump, pumps fuel up to the injection nozzle for each cylinder. The pump is operated by a cam and has a fuel metering device (usually helical) to meter the amount of fuel delivered to the cylinder. The pump operates to provide high pressure fuel on the compression stroke of the engine. The nozzle is spring operated and only opens when the pump delivers pressure exceeding the spring closing pressure. When open the nozzle provides a spray of fuel into the cylinder. At the time of injection, the temperature of the cylinder exceeds ignition temperature of the fuel and it burns to provide the engines power. There is a separate pump for each cylinder.

Common rail injection system (electronic controlled fuel injection)– in this system a high pressure pump provides fuel to a “common rail” for each cylinder nozzle. When fuel is to be injected into a cylinder, the nozzle is opened electronically by an “engine control unit” (ECU or ECM) and fuel is sprayed into the cylinder. The timing and duration (fuel quantity) is determined by the ECM. The injectors are opened by a solenoid valve or piezoelectric system. In a piezoelectric  system, a crystalline materiel changes shape under the influence of an electrical signal. The shape change is used to open or close the injection nozzle.

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Advantages of Common Rail System – Common rail injection allows improved combustion so that sources of pollution are not produced in the first place. The system more precisely controls the amount and timing of injection and improves efficiency of using fuel. The system optimizes pre-main injection or post-main injection to reduce engine emissions. The main injection provides fuel for the engines power output. Pre-injection reduces nitrogen oxide emissions. Post-injection reduces particulate emissions.

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Source – internet “How does common rail injection work?-MTU Solutions” (Rolls Royce Power Systems).

Most diesel engine manufacturers use a common rail fuel injection system for their new engines. Viking yachts uses mostly MTU diesel engines in their 58 foot to 92 foot yachts where the size of the yacht is compatible with the size of MTU engines. They may use other manufacturer engines where the size of engine is compatible with the boat size. Other engine manufacturers may have a proprietary fuel injection system similar to common rail.

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