Tuesday, January 7, 2020

ME-GI injection system

  • Dual fuel operation requires the injection of both pilot fuel and gas fuel into the combustion chamber. Different types of valves are used for this purpose.
  • wo are fitted for gas injection and two for pilot fuel. 
The auxiliary medium required for both fuel and gas operation is as follows:
  1. High-pressure gas supply.
  2. Fuel oil supply (pilot oil).
  3. Control oil supply for actuation of gas injection valves.
  4. Sealing oil supply. 
  • The gas injection valve design complies with traditional design principles of the compact design. Gas is admitted to the gas injection valve through bores in the cylinder cover. 
  • To prevent a gas leakage between the cylinder cover/gas injection valve and the valve housing/ spindle guide, sealing rings made of temperature and gas resistant material have been installed.
  • Any gas leakage through the gas sealing rings will be led through bores in the gas injection valve to the space between the inner and the outer shield pipe of the double-wall gas piping system. This leakage will be detected by HC sensors.
  • The gas acts continuously on the valve spindle at a max. pressure of about250 bar. To prevent gas from entering the control oil actuation system via the clearance around the spindle, the spindle is sealed by sealing oil at a pressure higher than the gas pressure (25-50 bar higher). 
  • The pilot oil valve is a standard ME fuel oil valve without any changes, except for the nozzle. The fuel oil pressure is constantly monitored by the GI safety system in order to detect any malfunctioning of the valve. The oil valve design allows operation solely on fuel oil up to MCR.
  • The gas engine can be run on fuel oil at 100% load at any time, without stopping the engine. For prolonged operation on fuel oil, it is recommended to change the nozzles and gain an increase in efficiency of around 1% when running at full engine load. 
  • ME-GI injection system consists of two fuel oil valves, two fuel gas valves, ELGI for opening and closing of the fuel gas valves and a FIVA (fuel injection valve actuator) valve to control - via the fuel oil valve – the injected fuel oil profile. Furthermore, it consists of the conventional fuel oil pressure booster, which supplies pilot oil in the dual fuel operation mode.
  • The fuel oil pressure booster is equipped with a pressure sensor to measure the pilot oil on the high pressure side. As mentioned earlier, this sensor monitors the functioning of the fuel oil valve. If any deviation from a normal injection is found, the GI safety system will not allow opening for the control oil via the ELGI valve. In this event no gas injection will take place.

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