Automatic Model Calibration for Engine-Process Simulation with Heat-Release Prediction 2006-01-0655

The development of powertrains with DI diesel Engines as primary drive demands accurate analytic specification of the cylinder process, with sufficient consideration taken of gas-exchange, turbo charging, and - especially - combustion. Until now, engine-process simulation has proved to be a powerful tool for satisfaction of these requirements. In addition to simple modeling of the heat-release rate with Vibe functions, complex heat-release models based on injection-rate profiles have been developed and implemented in existing simulation tools such as GT Power. To calibrate the parameters to achieve satisfactory agreement between experimental data and three-dimensional Computational Reactive Fluid Dynamics Models (CRFD) simulations, an appreciable amount of expertise and time is required.This paper deals with a universal method that automatically identifies and calibrates the relevant model parameters to the experimental data. This technique simplifies and accelerates the application of engine-process simulation with more accurate heat-release models, which, however, allow heat-release prediction only with certain constraints. This approach allows intensification of the interface between engine-process simulation and combustion-rate development at the test bench or in CRFD simulation.A comprehensive cylinder process analysis represents the core of this method. It can additionally analyze transient operating points, and offers an algorithm that optimizes the model parameters. Comprehensive cylinder-process analysis provides the following from the plotted cylinder-pressure curve: the reference-input variable, the heat-release rate, as well as required model specific-input variables such as gas composition, cylinder temperature, and thermodynamic gas properties. The optimizer must be able, in stable operation, to optimize a system with many degrees of freedom.