Calculating Endurance of the V6 Piston Engine Crankshaft with Offset Connecting Rod Journals

Abstract

Contemporary design solutions in the engine engineering are aimed at raising a great many technical and economic performances, and enhancing manufacturability. When producing the V-shaped six-cylinder engines, the camber angle is often taken to be equal to 90°, which is technologically advantageous in the production of V8 engines. However, this solution leads to the engine instability and deteriorates mass-dimension and vibration performances of the engine. A crankshaft with the offset connecting rod journals is the solution to which Western and Russian power plant developers have increasingly taken recourse. However, introducing such a shaft entails a number of difficulties, and what is the most important requires special methods of calculation.

There are no direct analytical methods to calculate this type of crankshafts. The article describes a technique to estimate endurance using a software complex "KVAL", developed at the BMSTU Department "Piston engines". This software disables direct examination of the crankshaft of this type, however, in conjunction with other calculations enables estimating endurance.

The main point of the technique is a two-staged calculation. The original crankshaft is represented at first as a crankshaft with the connecting rods, sitting side-by-side. The article studies its endurance in the fillets of the rod bearing journal transition to the cheek and also at the outlets of two oil-feed holes. The second stage presumes that the shaft has an articulated rod and using the same type of calculations studies the fillet transition of the rod bearing journals to the intermediate cheek by its representation as an oil hole.

Each of the stages refines theoretical coefficients of stress concentration through numerical simulation in the software package "ANSYS", thereby making calculation more stringent.

The results obtained are very evident and representative, but also allow us to suggest a number of hypotheses for further research.

The proposed technique enables us to study endurance of the crankshafts with offset connecting rod journals, as well as the Napoleone crankshafts of opposed reciprocating engines.