Simultaneous high-speed internal and external flow measurements for a high-pressure diesel nozzle

TL;DR

This study combines high-speed internal and external flow measurements in a high-pressure diesel nozzle to analyze cavitation effects and spray characteristics, providing new insights into fuel injection dynamics.

Contribution

It introduces a novel experimental approach for simultaneous high-speed measurement of internal cavitation and external spray behavior in diesel nozzles.

Findings

Cavitation onset and probability mapped inside the nozzle.

Spray penetration and cone angles characterized at 300 bar.

New method for measuring large liquid structures in spray boundary.

Abstract

We present an extensive experimental study focused on understanding the impact of cavitation in a high-pressure diesel nozzle on the macroscopic properties of fuel spray. Several high-speed videos of the liquid flow through a transparent, asymmetric cylindrical nozzle with a single orifice (phi = 0.35 mm) are recorded along with the videos of the resulting spray in the near-nozzle region, issued with an injection pressure of 300 bar at a frame-rate of 75 kHz. The high-repetition images of the internal flow are then used to estimate the onset of cavitation inside the transparent nozzle and the probability of development of cavitation in different regions of the nozzle with an average estimate of the amount of cavitation with time. On the other hand, recorded spray images are used to study spray penetration, cone-angles and velocity from the start of fuel injection. A novel approach is proposed for the measurement of perturbations that occur in form of big liquid structures along the spray boundary.