An Investigation on Knock and Pre-ignition with Tumble Induced Turbulence

A study on the effect of induction manifold angles in tumble induced turbulence on detonation and pre-ignition in spark-ignition engines was conducted on a Ricardo E6 variable compression engine. A new cylinder head was designed and manufactured with four induction manifold inserts with angles of 30°, 40°, 50° and 60° in addition to the original angle of 90°. The onset of pre-ignition and detonation were defined by a piezo-electric pressure transducer. Knock was characterized by the “knock-limited compression ratio” concept. However pre-ignition was characterized by the input electrical power consumed by a pre-igniter acting as an artificial hot spot. A set of experiments were carried out on each induction manifold to cover the effect of the design and operating parameters of the engine on detonation and pre-ignition. The experiments revealed that the pre-ignition and detonation tendency increase with the increase of engine load, compression ratio, inlet air temperature, advancing the ignition timing and lowering the engine speed. Correlations were developed for the optimum angles of 40° and 50° to enable the onset of knock and pre-ignition to be predicted.