Teknillinen tiedekunta, 2014
Fredrik Östman/Seppo Niemi
Sähkö- ja energiatekniikan koulutusohjelma (DI)
In this thesis, an implementation is presented for a cylinder balancing algorithm that is based on torsional vibration measurement of the crankshaft. This algorithm has been originally presented by Fredrik Östman in his doctoral dissertation “Cylinder Balancing of Medium-Speed Internal Combustion Engines”.
Gas pressure torque caused by fuel combustion inside the cylinder is determined, which can be used to calculate the individual torque contribution of each cylinder. Using this information, cylinder-specific fueling control parameters can be calculated that minimize unwanted torsional vibration.
Cylinder balancing in medium-speed engines is very important, as the masses of the reciprocating components are large which increases the forces and stresses that the components will experience due to torsional vibration. Thus, reduction of torsional vibration via cylinder balancing leads to lesser wear, better comfort, lower emissions and lower fuel consumption, when compared to traditional cylinder balancing methods typically used in medium-speed diesel engines. Traditional cylinder balancing methods do not take into account the actual torsional vibrations of the crankshaft, as they only balance the exhaust gas temperatures of the cylinders with each other.
The determination of the gas pressure torque is performed by precisely measuring the rotational speeds of both the engine and the load (e.g. generator), by partially using preexisting production engine sensor equipment. This measurement yields the complete torsional vibration signal, which is then filtered by removing the reciprocating mass torque component that can be calculated by knowing the dimensions and masses of the engine. The actual calculations are performed by a dedicated Wärtsilä CCM-20 cylinder control module, running a software module developed in the C programming language during the course of this thesis.
As the final deliverable of this work, this software module running on the UNIC engine automation platform was tested on the W7L32CR diesel engine in the engine laboratory. The TVMCylBal module can be used to calculate gas torque from the rotational speeds of the engine and its generator, to be used in cylinder balancing for example.
diesel engine, medium-speed, cylinder balancing, torsional vibration, calculation algorithm