INTRODUCTION

The gas flow in the cylinder has a profound influence on the performance of the engine, whether intended or not. In the early days of the automobile, it was seldom intended, because relatively little was understood about turbulence, the primary player in this drama. Engines were designed largely by empiricism; from time to time a particularly successful design emerged, and its characteristics (to the extent that their relevance was recognized) were preserved in subsequent engines.

There are a couple of notable exceptions to this: In the first, between 1903 and 1907 H. R. Ricardo [45] (the father of the octane number), working at Cambridge University with Professor Bertram Hopkinson, did pioneering work on the effect of turbulence on combustion and heat transfer in the IC engine, particularly on the effect of the increased effective flame speed on knock, and on the possibility of stratified charge, among other things. This led, during the First World War, to great improvements in the design of tank engines (giving short flame travel and high turbulence levels, permitting higher compression ratios without knock), and after the war led to design modifications of the flat-head, or side-valve engine, which resulted in the same performance as the overhead valve engine, and which were generally adopted, and resulted in patents.

The other notable exception involved measurements made of the swirl and tumble produced by various inlet configurations, and the effect of the swirl and tumble on combustion [63], [86]. The flow measurements were made using high speed photography of goose down(!) in a glass cylinder. The combustion measurements used schlieren techniques.