Zeuch method-based injection rate analysis of a common-rail system operated with advanced injection strategies

Peculiar attention is devoted to the injection process start detection, which is of special interest in case of multiple injections. An accurate analysis of the injection rate time-history suggests that in the initial part of the process the flow is directed toward the injector nozzle (negative flow) and only after a short time the injection rate profile becomes positive, apparently indicating the start of the injection process. In order to define a proper start time detection criterion, the results of the hydraulic analysis were compared with the spray evolution analysis based on imaging carried out by an ensemble-averaged approach. This comparison suggested that the injection start can be derived by the hydraulic analysis: the outflow onset is generally synchronized with the first positive values of the injected volume, computed as the time integral of the injection rate profile.