THIS paper presents an analysis of the physical principles involved in knock and preignition as an approach to the solution of the problem of fuel rating. From this examination, the author proceeds to an analysis of the manner in which the different engine operating conditions affect these factors which cause knock and preignition.
Finally, he investigates the extent to which present methods of rating fuels are in accord with the analysis made in order to recommend the lines that future research should take so that knock and preignition can be understood better and so that fuels can be rated more adequately.
Among the conclusions reached are that the knocking characteristics of a fuel cannot be expressed adequately by a single value - that knock depends upon the interrelation of two factors, end-gas density and end-gas temperature; and that, for this reason, variation of actual service values from the laboratory value is unavoidable if a single knock rating is to be used.
The paper emphasizes that preignition and knock must be considered separately and points out the difficulties encountered in attempting to express both characteristics by a single method of fuel rating.
