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Singapore Polytechnic. Singapore Maritime Academy. & Maritime Institute Of William Barentsz. Bachelor Degree in Maritime Operations (BMO) Diesel Technology & Emissions Assignment : Direct Water Injection in Marine Diesel Engine Toh Ai Pei Jannell Date:5 th Sept 2006.
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Singapore Polytechnic Singapore Maritime Academy & Maritime Institute Of William Barentsz Bachelor Degree in Maritime Operations (BMO) Diesel Technology & Emissions Assignment : Direct Water Injection in Marine Diesel Engine Toh Ai Pei Jannell Date:5th Sept 2006
BASIC PRINCIPLES OF DIRECT WATER INJECTION • equipped with a combined injection valve and nozzle that allows injection of water and fuel into the cylinder separately. • nozzle has two separate needles that are controlled separately which means that neither of the modes (water on/off) will affect the operation of the engine • Water injection takes place before fuel injection, resulting in cooler combustion space and therefore lower NOx emissions. Water injection stops before injection of the fuel oil into the cylinder so that ignition and combustion process is not disturbed • Water is fed into the cylinder head at high pressure about 210-400 bar • High water pressure is generated in a high pressure water pump module. A low pressure pump is also necessary to ensure a sufficiently stable water flow to the high pressure pump • Before the low pressure pump, the water needs to be filtered to remove all solid particles. The pumps and filters are built into modules to enable easy installation.
CONTINUED • A flow fuse is installed on the cylinder head side. The flow fuse acts as a safety device, shutting off the water flow into the cylinder if the water needle gets stuck. • Water injection timing and duration is electronically controlled by the control unit, which gets its input from the engine output. • Timing and duration can easily be optimized for different applications. NOx reduction will be most efficient from 40% load and higher nominal output. Electronic control unit for water injection
BENEFITS OF DIRECT WATER INJECTION • NOx emissions are reduced by 50-60 % • NOx when running on marine diesel oil(MDO) typically 4-6 g/kWh; in HFO operation typically 5-7 g/kWh • No negative impact on the engine components • The engine can also be operated without water injection if required • The engine can be transferred to “non-water” operational mode at any load
CONTINUED • In alarm situations, transfer to “non-water” mode is automatic and instant • Space requirements for the equipment are minimal and therefore the system can be installed in all installations • Investment and operational costs are low • Ratio of injected water to injected fuel typically 0.4- 0.7 • Can be installed while the ship is in operation
COMPARISON OF DIRECT WATER INJECTION AND WATER FUEL EMULSION • Direct Water Injection (DWI) • Water is injected directly into the combustion chamber. • DWI directly reduces cycle temperatures and thus NOX formation. • Water is handled by a fully independent injection system under electronic control. • Injection timing can be optimized with regard to fuel consumption and engine performance.
