State the difference between ME engine and RT flex engine?
The two major manufactures of two stroke cross head engines have both introduced a camshaft less engine.
Sulzer calls as RT flex engine and MAN B&W cal as intelligent engine.
Both engine use electrical and engine driven axial piston pumps to pressurize servo oil rails to 200bar which are then used for fuel injection and exhaust valve operation. In addition MAN use the servo oil to drive the cylinder lubricator units(alpha system).
Although both work without a camshaft and use computers to control fuel injection, exhaust valve operation and air starting, the method of fuel injection is different.
Unlike the sulzer RT flex engine the MAN ME engine does not operate the fuel injection on a common rail system.
Instead a solenoid operated proportioning valve (the FIVA valve - fuel injection valve activation ) allows the pressurised servo oil under a hydraulic piston. This then moves the fuel piston upwards, raising the fuel pressure and opening the injection valves.
A nitrogen filled accumulator maintains the hydraulic servo oil pressure during the operation of the pump.
To be able to time the fuel injection the control systems must know the crank angle of the individual units. To do this two crank angle sensors are fitted at the free end of the engine. These sensors are accurate to 0.1%. Cylinder pressures and powers are continously monitored by using strain gauges built in to the cylinder head and the computer automatically compensated for twist in the crankshaft when relating crankshaft position to cylinder pressure, the systems give complete flexibility over start and end of injection and take into account fuel quality, dead time (the time between injection start command being given and actual injection), and variable injection timing (VIT)