Kinematics and Load Formulation of Engine Crank Mechanism

Abstract

This paper presents the kinematics formulation of an internal combustion engine crank mechanism. The kinematics formulation of the crank mechanism is done using vector loop method and cosine rule are applied to de- scribe the position of the piston. Following the velocity of piston and connecting rod is performed by differentiating the position in terms of the crank angle and connecting rod angle respectively. The acceleration equation with brief form is derived from the velocity in the same principle. Based on the kinematics, the equations of motion of crank mechanism components are formulated for each moving link and platform then, all motion parameters of each component about its crank angle are readily derived. Furthermore the 2D model is provided by using 2D Auto CAD software in order to vis- ualize the system and mathematical algorithm solved by using software MATLAB. The forces acting on the crank mechanism and the torque applied are also formulated based on the angles of the crank and connecting rod. Introduction. The Internal combustion engine is those that burn their fuel which is mixture of air and petrol from carburetor inside the cylinder or compress air only on the cylinder and injects diesel from injector nozzle. These IC engines convert the chemical energy stored in their fuel into heat en- ergy during the power stroke of piston. The energy produced from burning of fuel is used for mo- tion of piston; the working of a four stroke engine is based on simple slider crank mechanism. The kinematics of IC engine is not altering from simple slider crank mechanism. The kinematics formu- lation of the crank mechanism such as piston motion and connecting rod motion utilizes different software and methodologies for which it is suitable for manipulation The crank mechanism com- prised of components like crank shaft, connecting rod and piston which changes the sudden dis- placement to a smooth rotary output which is the input to many devices such as pumps generators and compressors. A detailed procedure of getting stresses in the fillet area of a crank mechanism particularly crank shaft was introduced by Henry et al. (1), in which FEM and BEM (Boundary Element Method) were used. Obtained stresses were ratified by experimental results on turbocharged compression ig- nition engine with Ricardo type combustion chamber configuration. The crank mechanism durabil- ity assessment tool used in this study was developed by RENAULT Guagliano et al. (2) conducted a study on a marine diesel engine crankshaft and connecting rod. Payer et al. (3) developed a two- step technique to perform nonlinear transient analysis of crank mechanism combining a beam-mass model and a solid element model and Prakash et al. (4) performed stress and fatigue analysis on three example parts belonging to three different classes of engines, light automotive crankshaft was studied by Borges et al. (5). The geometry of the crank mechanism was geometrically restricted due to limitations in the computer resources available to the authors. Shenoy and Fatemi (6) con- ducted dynamic analysis of loads in the connecting rod and piston components, which is in contact with the crankshaft. Dynamic analysis of the connecting rod is similar to dynamics of the crank- shaft, since these components form a slide-crank mechanism and the connecting rod motion applies dynamic load on the crank-pin bearing.. Shenoy and Fatemi (7) optimized the crank mechanism considering dynamic service load on the component. It was shown that dynamic analysis is the proper basis for fatigue performance calculation and optimization of dynamically loaded compo- nents. A literature survey by Zoroufi and Fatemi (8) focused on durability performance evaluation and comparisons of forged steel and cast iron crankshafts. The piston-connecting rod-crankshaft assembly in the reciprocating piston-engines is used to transform the gas forces generated during combustion within the working cylinder into a piston stroke, which the crankshafts converts into useful torque available at the flywheel. The cyclic opera- tion leads to unequal gas forces, and the acceleration and deceleration of the reciprocating power-