Novel design for transparent high-pressure fuel injector nozzles

Zachary Falgout, Mark Linne

Research output: Contribution to journalArticlepeer-review


The efficiency and emissions of internal combustion (IC) engines are closely tied to the formation of the pre-ignition air-fuel mixture. Direct-injection engines have become more common due to their increased practical flexibility and efficiency, and sprays dominate mixture formation in these engines. Spray formation, or rather the transition from a cylindrical liquid jet to a field of isolated droplets, is not completely understood. However, it is known that nozzle orifice flow and cavitation have an important effect on the formation of fuel injector sprays, even if the exact details of this effect remain unknown. A number of studies in recent years have used injectors with optically transparent nozzles (OTN) to allow observation of the nozzle orifice flow. A relatively small number of studies have shown results at or near the injection pressures used by commercially available injectors, and neither the technical details of nor the reasoning behind the OTN designs in these studies are explained in detail. In addition, nozzle fatigue lifetime is rarely examined. A OTN design that achieves realistic injection pressures and grants visual access to the interior flow and spray formation will be explained in detail. The design uses an acrylic nozzle, which is ideal for imaging the interior flow. This nozzle is compressed from the outside with metal clamps that include transparent sapphire inserts, which minimizes tensile stresses in the nozzle. An ensemble of nozzles was mechanically tested to prove this design concept
Original languageEnglish
Article number085108
JournalReview of Scientific Instruments
Issue number8
Early online date9 Aug 2016
Publication statusPublished - Aug 2016


  • sprays
  • fuel injectors


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