A Simulated Analysis of the Lubrication Circuit of an In-Line Twin Automotive Engine

In recent years, the need to optimize the performance and reduce exhaust emissions of internal combustion engines has caused the design of the auxiliary (like lubrication and cooling pumps) to assume a particular importance. This is especially due to the necessity to obtain higher efficiency with less expense in terms of work assigned to these organs. With respect to the lubrication circuit, this means the use of solutions that allow the optimization of the fluid dynamics of both the ducts and the pump. This work is based on a simulated analysis carried out on the lubrication circuit of a light duty internal combustion engine, developed by Fiat and equipped with a hydraulic VVT system. The lubrication circuit model was build up with the commercial 1D code LMS Imagine.Lab AMESim®, developed by LMS® (a Siemens Business division) with the aim to estimating the variation of the oil consumption of the circuit components (crankshaft bearings, piston cooling jets, etc.) with varying engine speed, load and oil temperature. The simulation model reproduced all the lubrication circuit components and ducts. Special attention was dedicated to the detailed modelling of the pump by simulating its volume variation during the pump shaft revolutions. The oil was also modeled taking into account the variation in viscosity with changes in temperature and cavitation phenomena. The complete model was validated with experimental data (oil pressure/flow rate) achieved in the course of experiments performed on the test bench of a manufacturer's engine. The model allowed the simulation of several engine running conditions, including idle, in order to obtain a map of the oil consumption of the different circuit users in different conditions. An investigation was carried out to analyze and identify the causes underlying pressure oscillations, observed during the first experimental tests in idle condition, by studying the oil consumption of each component during an engine cycle.