Influence of Connecting Passage on Diesel Knock in Divided Chamber Type Engines

Abstract

Combustion noise of the Diesel engine of a pre-combustion chamber type will be originated by some mechanical cause involved with sharp pressure rise in the main chamber. This pressure rise is determined by the rate of heat release in it and the quantity of gas issued from the auxiliary chamber. In order to clarify the latter effect, which will be closely related with the pressure rise in the auxiliary chamber and the area of the connecting passage, an air model was proposed. The pressure rise in the main chamber caused by a sudden pressure jump in the auxiliary chamber was measured in various areas of the connecting passage, and was compared with the theoretical calculation in which gas inertia was neglected. As the result, it was found that the rate of pressure rise in the main chamber is proportional to the area ratio of the passage and inversely proportional to the volume ratio of the main chamber. Application of the result to the actual engines shows that transmission of rapid pressure rise in the pre-chamber to the main chamber is strongly suppressed, resulting in a smooth pressure rise with the pre-combustion chamber type engine, while it cannot be with the swirl chamber type.