A kind of injection nozzle manufactured since 1990 and utilized for ten thousands of motors, has recently showed a series of failures. These failures have happened only in one naval equipment and during a short period of time. In any case an uncertainty relative to sizing criteria arose. With reference to this problem, in the present work a methodology for performing a more careful structural analysis of a nozzles injection class is suggested. This procedure is based on the finite element method and allows an accurate evaluation of the stress in the region where the failure has happened. Particular care has been taken to understand where singular and non singular stresses are superimposed. The methodology suggested is illustrated with reference to an injector that has shown a failure in a characteristic part of the nozzle. The conclusion of the analysis shows that this failure has been caused by a poor quality fuel supply.
