TO IMPROVE THE KNOWLEDGE OF AERODYNAMIC, THERMIC AND CHEMICAL MECHANISM GOVERNING THE HOMOGENEOUS COMBUSTION IN SPARK IGNITED ENGINES, PARTICULARLY THE FLAME INITIATION AND PROPAGATION PHASE AND KNOCK MECHANISM. TO CONTRIBUTE TO BUILD UP A MULTIDIMENSIONAL CODE DEALING WITH FLOW COMBUSTION IN I.E. ENGINE BY SETTING UP CORRESPONDING SPECIES SUB-MODELS. TO EVALUATE RESULTS ISSUED OF THE USE OF THESE MODELS INTO THE CODE (SPEED).
Work on homogeneous combustion and knock in spark ignited (SI) engines focussed on experimental knowledge of turbulent flame initiation and propagation in real engines up to the point where knocking combustion occurs, taking into account air flow and turbulence effects. This led to the setting up of a database which could be used to validate 3-dimensional codes and combustion predictions.
An experimental and modelling programme was also conducted to measure the autoignition delay in engines and to model the complicated chemical kinetic process either on extended scheme bases or reduced scheme bases. The numerical algorithms of the SPEED flow simulation code developed in a separate parallel project were extended to allow homogeneous combustion calculations. The SPEED mesh, because of its generality, is capable of a wider range of topologies than appears to be available from even sophisticated state of the art mesh generators. Its development has also opened areas of research into dynamic engine meshing.
Flame propagation and flow velocities were measured in a 4-cylinder SI engine with optical access to the combustion chamber via transparent pistons. Another engine was equipped to allow optical access in the combustion chamber to a single cylinder, and set up on a bench, for measurements at given crank angles.
Different numerical models were tested for simulating knock in engines and their performances compared with experimental results. All these models were based on the principle that knock is caused by autoignition of the air/fuel mixture and were thus built on more or less complex chemical kinetics mechanisms.
THE PROJECT HAS THREE PARTS :
- FLAME INITIATION
- FLAME PROPAGATION
- KNOCK INDUCING PHENOMENA STUDY.
EACH PART COMPRISES :
- EXPERIMENTAL WORK FOR DATA ACQUISITION MAINLY BY OPTICAL AND SPECTROSCOPIC DIAGNOSTIC
- MODELLING WORK (IMPERIAL COLLEGE)
- EVALUATION WORK OF THE MODELLING APPROACH RETAINED FOR INSERTION INTO THE MULTIDIMENSIONAL CODE (JRC COMPANIE)
Funding SchemeCSC - Cost-sharing contracts