An Instrument for Measuring Orifice-Specific Fuel-Injection Rate From a Multi-Orifice Nozzle

Understanding fuel-injection processes is important for improving combustion in compression-ignition engines. To understand and model injection processes in detail, it is necessary to measure the instantaneous mass flow rate of fuel through each orifice of the injector nozzle. Due to constraints from injector design and operation, injection rate is typically measured downstream from the orifice exit. Measuring injection rate from a multi-orifice nozzle adds several geometric constraints, particularly when measuring fuel flow from a single orifice. The injection ratemeter discussed in this paper is designed to fit inside an optical research engine so that the injection rate can be measured without having to place the injector in an external fixture. The injection rate is calculated from a measurement of the momentum flux of a jet of fuel impinging upon the surface of a piezoelectric force (or pressure) transducer, combined with a measurement of the quantity of fuel injected, as demonstrated previously [1–3]. The ratemeter includes a thermal shield to limit the effects of temperature fluctuations on the transducer output. Data were acquired for one injector nozzle at several different injection durations and compared to results from literature for similar injector designs. Estimates for the uncertainty of the measured injection rates are provided and the calibration technique used is presented.