Knock Resistance in a Small Turbocharged Spark-Ignition Engine 2006-01-2995
Spark-ignition engines are characterized by poor levels of thermal efficiency, it is known, especially when running at partial load.
Since part-load operating points are the most commonly used in engine average life, achieving a given torque value with small displacement, high mean effective pressure engines, the so-called “downsizing”, permits, in general, to limit some typical engine losses (for instance: pumping and friction losses), improving the fuel consumption in a wide range of engine operating points.
Small displacement engines, usually, achieve high toque values thanks to supercharging techniques.
In this paper, knock risks for a small displacement turbo-charged spark-ignition engine have been analyzed. A parametric analysis of numerous variable influencing engine performance and knock resistance has been carried out by means of 1-D numerical simulations.
At low engine speed, the influence of inlet valve close angle on engine octane requirement has been assessed for different values of the turbocharging pressure ratio.
Computations have been performed by means of the 1-D AVL Boost code. Initial and boundary conditions have been evaluated by experimental tests.
The model utilized in this study has been validated by comparing the obtained results to the measured data provided by the research center of the engine manufacturer.