Investigation of the Impact of Impingement Distance on Momentum Flux Rate of Injection Measurements of a Diesel Injector 2015-01-0933

Diesel combustion and emissions is largely spray and mixing controlled. Spray and combustion models enable characterization over a range of conditions to understand optimum combustion strategies. The validity of models depends on the inputs, including the rate of injection profile of the injector. One method to measure the rate of injection is to measure the momentum, where the injected fuel spray is directed onto a force transducer which provides measurements of momentum flux. From this the mass flow rate is calculated. In this study, the impact of impingement distance, the distance from injector nozzle exit to the anvil connected to the force transducer, is characterized over a range of 2 - 12 mm. This characterization includes the impact of the distance on the momentum flux signal in both magnitude and shape. At longer impingement distances, it is hypothesized that a peak in momentum could occur due to increasing velocity of fuel injected as the pintle fully opens. The study is completed at injection pressures of 620 and 2000 bar at 1 bar charge gas pressure, for 50 injection events per condition. The data is supplemented with micro-photography images of the first injection event to validate the impingement of the fuel spray on the anvil for complete momentum transfer. Results show no significant influence of impingement distance on peak momentum and a wide range of recommended impingement distances between 4 - 12 mm. At 2 mm impingement distance there is some anomalies in the behavior which is attributed to the gaseous momentum influence of neighboring sprays.