Electronic Operation
Posted by: MarinerGalaxyThe signal received by the electro hydraulic servo valve and the control valve is from cylinder control unit installed for each cylinder.
The engine control system is connected to ship's control system. This ship’s control system has two control units.
- Cylinder control unit for each cylinder.
- A local control terminal.
Engine Control Unit’s Function:
It relates to overall situation of the engine and connects plant control system, safety system and supervision and alarm system with inputs from sensors and actuators.
Cylinder Control Unit’s Function:
It connects all functional components to be controlled at each cylinder, e.g. fuel injection, exhaust valve, starting valve and cylinder lubrication. As faults can never be completely ruled out each cylinder has a cylinder controller, whose failure will result in temporary loss of power of concerned unit until the standby engine controller takes over and continues the operation without any change in performance.
Electronic Control of Fuel Timing
Operation of fuel valve is governed by a microprocessor (computer). For correct operation, inputs of engine speed and crank angle is given to the microprocessor, which controls the operation of fuel valve.
Here the metering of fuel volume for one cylinder is not governed by delivery volume per stroke but by limiting the duration of injection. This is made possible by an electronic controller i.e. a low voltage signal that controls the opening and closing action of electro-hydraulic servo valve. This opening and closing of electro-hydraulic servo valve connects and isolates the fuel valve from the servo oil accumulator, which finally operates the fuel valve.
Each cylinder unit is provided with a servo oil accumulator to ensure sufficient fast delivery of servo oil per injection requirement.
A number of injections patterns are stored in the microprocessor, which are selected by the control system so as to operate the engine with optimum injection characteristics from dead slow to overload, as well as during astern running and crash stop.
Electronic Control of Exhaust Valve Timing
The exhaust valve is driven by the same servo oil system as that for the fuel injection system, using pressurized cool, clean lube oil as the working medium. The operation of exhaust valve only controls the time of opening and closing the valve. This is obtained by using a simple fast acting ON/OFF control valve to control the movement of the exhaust valves. The control valve being again operated by the microprocessor, which operated the fuel valve.
