Abstract
The stricter fuel consumption and emission regulations put the worldwide carmakers and suppliers under pressure to develop more efficient vehicle systems. Simulation-based design and virtual prototyping can insure greater product performance and quality of both the time and cost required by traditional build-and-test approach for the vehicle development process in general (1).
Numerical simulation of the fuel consumption and emissions behaviour of an internal combustion engine fitted to a vehicle is today an indispensable aid to development (2). Most simulation concepts use empirical 1-d models to predict fuel economy and emissions for homologation cycles as well as other cycles. In most cases either the simulations are carried under steady state warm conditions or simplified warm up models are used for predicting cold/warm transient cycle results which are data driven and the accuracy is not sufficient.
In order to improve the accuracy of vehicle simulation under transient conditions and thus predict fuel consumption, consideration of the complete system engine/drivetrain/vehicle is needed. The coupling of otherwise independent simulation programs therefore becomes necessary for the vehicle and engine.
In this work, an integrated approach has been undertaken where the cyclic engine model and cooling circuit model are incorporated into the vehicle simulation model. AVL Boost has been used to simulate the engine model and Flowmaster has been used to build the cooling circuit model. The vehicle modelling is done in AVL Cruise. In this approach, Cruise is used to provide the load, operating and environmental conditions of the vehicle to the other 1-D codes. Cruise is also used to control the execution sequence and the data exchange between the different 1-D software packages.
The approach enables us to predict the fuel economy and emissions for a cold start cycle. With this transient online calculation more accurate results can be obtained for various engine and vehicle outputs.
KEYWORDS: Cold start, Fuel economy, Emissions, Cycle, Simulation