Knock detection based on main vibration frequencies analysis in spark ‎ignition turbocharged engine

One of main factors that affects outputs, thermal efficiencies and lifetimes of ‎the engine is "knock". Experimental results revealed that vibrating signals ‎generated from knocks has certain frequencies related to vibration modes of ‎the combustion chamber. In this paper, the behavior of the engine during ‎different operating conditions has been simulated using the GT-POWER ‎software. Based on simulation results, speeds of sound waves within the ‎combustion chamber have been predicted at knock conditions. Then, a ‎mathematical correlation was used to predict vibration frequencies based on ‎the speed of sounds in the combustion chamber and cylindrical geometries. ‎Vibration frequencies have also been measured experimentally using knock ‎sensor data. Comparing simulation results with experimental data ‎demonstrated an appropriate correlation between two methods and confirmed ‎that the effect of other parameters on the vibration frequency could be ‎negligible. Finally, a method for determining the occurrence and the severity of ‎knocks and a threshold for the detection of this phenomenon has been ‎proposed.‎