Research On Torsional Excitation For The CODAD Propulsion System With Different Firing Angle

The CODAD propulsion system is composed of two diesel engines, which are parallel connected to gear box, in that case, three kinds of excitation should be considered while study the torsional characteristics of the CODAD system,that is the excitation caused by different firing order with different V angle, the excitation caused by the connection of two engines and the excitation caused by shafting and propeller.Based on domestic research status and relative achievement, This article apply systemic study on the difference of torsional excitation caused by different V angle for the CODAD system. Firstly, this article studied the excitation caused by single engine, which is the main contribution. For V type engine used in CODAD system, the excitation caused by firing within cylinder and the inertia moment should be considered, besides, the firing interval between the two lines of cylinder also be important factor, which is the main job of this article's research.Secondly, with some existing research achievement, the excitation difference caused by the parallel connection also been studied and summarized. Usually, the connection phase and one cylinder misfiring will contribute to the difference, for the CODAD system, the condition of simultaneously misfiring of two engine should also be taken into account to guarantee the shafting safty.Lastly, the propeller's asymmetrically absorbing of torque will cause disturbing with seasonal change of torque, which can also bring difference to the total torsional excitation。The sum vector of relative amplitude∑(α|→)_k are introduced to study the torsional excitation under various firing angle, computing program are written based on that method, an example of CODAD system are calculated to study the difference under various condition, with all this job, the method of research on torsional excitation difference caused by different V firing angle are summarized.