Multi-Body Dynamics Simulation Analysis of Crankshaft Assembly in V-Type 12-Cylinder Large Diesel Based on Adams

Crankshaft assembly, as one of the most important parts of the engine, always suffers many kinds of cyclic loading during service. Due to the higher requirements for dynamic property of mechanical system, it is necessary to work on multi-body dynamics simulation of crankshaft assembly quick and accurately. The multi-body dynamics simulation analysis was carried out to the crankshaft assembly in V-type 12-cylinder large diesel by dynamics analysis software ADAMS in this work. The kinematic characteristics of piston and load characteristic of connecting rod are obtained via simulations. The comparison of loads on connecting rod between simulation result and analytical calculation result verified the accuracy of multi-body dynamics simulation of crankshaft assembly based on ADAMS. The simulation results can provided basis for finite element analysis of crankshaft and provided guidance for improving the dynamic characteristic of crankshaft assembly. Introduction Crank-connecting rod mechanism, as one of the most important parts of the engine, always suffers cyclic loadings during service [1, 2]. The operational state of crankshaft assembly can directly affect the performance and service life of engine. The more developments of engineering technology, the higher requirements for dynamic property of mechanical system. Therefore, it is very important to research multi-body dynamics simulation of crankshaft assembly by virtue of advanced method. It is of significance for optimizing the engine components design and improving the dynamic characteristic of crankshaft assembly. Since the multi-body dynamics has been developed, many researches in multi-body dynamics modeling, design, control, solution strategy and experiment of different mechanical system have been done [3-5]. The multi-body dynamics analysis of crankshaft assembly has been developed from rigid multi-body dynamics to flexible multi-body dynamics in order to improve the accuracy [6]. In former researches, most of multi-body dynamics simulations have been done for crankshaft assembly in single cylinder and in-line type x-cylinder engine [6, 7], while the multi-body dynamics simulation for crankshaft assembly in V-type 12-cylinder engine are rare, which is the novelty of this paper. The multi-body dynamics simulation analysis was carried out to the crankshaft assembly in Vtype 12-cylinder diesel by dynamics analysis software ADAMS in this work. The rigid multi-body dynamics model of crankshaft assembly has been created and simulated to obtain the kinematic characteristics of crank-connecting rod mechanism and load state of connecting rod journal. The accuracy of multi-body dynamics simulation analysis of crankshaft assembly based on ADAMS has been verified by the comparison between simulation results and calculation results by analytical method. It can provided guidance and basis for optimizing the engine components design and improving the dynamic characteristic of crankshaft assembly. 130 Advances in Engineering Research (AER), volume 105 3rd Annual International Conference on Mechanics and Mechanical Engineering (MME 2016) Copyright © 2017, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Multi-Body Dynamics Simulation In consideration of the structural complexity of the crankshaft assembly in V-type 12-cylinder internal combustion engine, rigid multi-body dynamic method was used to create the dynamics model of crankshaft assembly in this work. The components materials of crankshaft assembly in this paper are high strength structural alloy steel such as 35CrMo and 42CrMo which with high rigidity and little deformation. So accurate analysis results can be obtained by rigid multi-body dynamics simulation. Virtual Prototype Set Up The crankshaft assembly include cylinder piston group (piston and piston pin), connecting rod group (connecting rod and its accessories), and crankshaft group (crankshaft and flywheel, balance weight on it). The crankshaft, with total length of 2263 mm, contains six cranks with the phase angle of 120 between each other. The crankshaft in this four stroke engine rotates 720° in a working cycle. The CAD software UG was used to create the three-dimensional geometrical model of components and assemble. I.e., the axis of cylinder #1-#6 and cylinder #7-#12 were arranged by included angle of 120° and symmetric, the small end of connecting rod was connected with piston group and the big end of connecting-rod was connected with connecting rod of crankshaft, flywheel was connected with end of crankshaft. The assembled models were imported to ADAMS to analyse. The constraints and kinematic pairs should be set as well as the motion and gas force should be loaded on models before simulating. Figure 1 shows the dynamics models of crankshaft assembly in V-type 12-cylinder large diesel. Figure 1. Dynamics models of crankshaft assembly in V-type 12-cylinder large diesel Simulation Conditions Crankshaft was suffered from three kinds of force during its service: cylinder gas force, reciprocating inertia force and rotating inertia force of piston and connecting rod. The gas forces were transmitted to crankshaft by pistons and connecting rods. The inertia forces were contained in model system by setting gravity. Fixed constraint was set between crankshaft and flywheel. Rotation pairs were set between big end of connecting rod and connecting rod, small end of connecting rod and piston pin, piston pin and piston, the seventh main journal and the Ground, respectively. Sliding pair was set between piston and the Ground. Cylindrical pairs were set between all other main journals and the Ground. In ADAMS, the Ground equivalent to the engine body. The gas force curve of each cylinder is the same, only the phase angle is different. According to distribution of cranks and fire order of engine, cylinder numbering of #1#8#5#10#3#7#6#11#2#9#4#12 (interval of 60°), the gas force of each cylinder could be determined. Figure 2 shows the gas force curves of 12 cylinders in a working cycle. 131 Advances in Engineering Research (AER), volume 105