A contribution to the diagnosis of internal combustion engines through rolling block oscillations

This paper presents a non-intrusive fault detection technique for thermal reciprocating engines, based on the analysis of rolling block oscillations produced in engines mounted on elastic supports and assuming the engine is a rigid body. These considerations allow an approximation of the instantaneous crankshaft torque through the measurement of the tangential acceleration of the engine block. These oscillations can provide information about possible failures, especially those related to differences among the behaviour of cylinders. A simplified physical model of an engine mounted on elastic supports was used to estimate the engine behaviour under different working conditions. This model was validated with experimental measurements carried out in a standard experimental engine test bench and in different types of diesel engines mounted on light and medium automotive vehicles. Tangential acceleration measurements in different block points have also been carried out, in order to analyse the influence of the accelerometer position. The final goal of this study is to provide awareness and limiting values for certain failures and to detect the source of these abnormalities by comparing the different behaviour of the cylinders. In order to do this, the time and the frequency domain of the tangential acceleration need to be analysed.