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Experimental Assessment of a Novel Instrument for the Injection Rate Measurement of Port Fuel Injectors in Realistic Operating Conditions
Abstract:
In the present paper an innovative approach for the shot-to-shot hydraulic characterization of low pressure injection systems is experimentally assessed. The proposed methodology is an inverse application of the Zeuch’s method, which in this case is applied to a closed volume upstream the injector instead of downstream of it as in conventional injection analyzers. By this approach, the well-known constraint of having a finite volume pressurized with the injected liquid downstream the injector is circumvented. As a consequence, with the proposed instrument low pressure injectors - such as PFI, fed with gasoline or water, SCR injectors - can operate with the prescribed upstream-downstream pressure differential. Further, the injector can spray directly in atmosphere or in any ambient at arbitrary pressure and temperature conditions, allowing the simultaneous application of other diagnostics such as imaging, momentum flux measurement or sizing instruments.
The developed instrument - named dINJ - is designed for the simultaneous measurement of both global injected quantity and injection rate time-history over a statistically significant basis of consecutive events, thus obtaining a complete hydraulic characterization of the tested injector.
In this paper, the proposed experimental approach is introduced and discussed. The validation process was carried out by comparing the dINJ instrument injection rate with the corresponding quantity obtained by a conventional injection analyzer during simultaneous hydraulic tests. During the validation phase, the abnormal low pressure injector operation caused by conventional injection analyzers occurs. The same injector was then characterized by the standard dINJ configuration evidencing the proposed approach capabilities.