Impacts of Circular Liquid Jet Injection Angle Into Low Subsonic Crossflow

One of the most common ways to obtain mixing between liquid and air, is by injecting the liquid jet into an incoming gaseous crossflow. The physics of this mixing flow is very complicated due to the presence of many flow interfacial instabilities. Usually, a perpendicular liquid jet into the cross flow airstream is used as the standard method of mixing. In the present work, the effect of the injection angle of the liquid flow emanated from a circular nozzle into airstream was experimentally investigated. The flow characteristics of the liquid jet were visualized by diffused backlight shadowgraph technique and high-speed photography. Water was used as the working liquid and tests were conducted into an incoming airstream at room temperature and pressure. A circular nozzle with 1.5 mm in diameter was used. The injection angles of the 30, 45, 60 and 90 degrees of the liquid jet into the airstream were considered. Different parameters of liquid jet flow such as breakup length and trajectory were measured. It was found that at low angles the path was independent from the momentum ratio.

Flow Development of a Liquid Sheet Issued Into Low-Speed Airstream

In this study, a liquid sheet with an aspect ratio of 90 and a thickness of 0.35 was experimentally investigated when issued into a low-speed subsonic crossflow. High speed photography and shadowgraphy technique were employed to capture the instantaneous physics of the liquid sheet. Flow visualizations were used to investigate the flow development of the liquid sheet. It was found that this flow exhibited a completely different flow structure than circular or other non-circular liquid sheets. It was found that the liquid sheet developed a concave-like shape in the presence of the transverse airstream. This phenomenon, named as inflated sheet, was absent in regular circular liquid jets injected into gaseous crossflow. It was revealed the inflated sheet was the main feature of the liquid sheet that made the jet characteristics unique. The flow feature of the inflated sheet structure and its alteration with flow condition was fully examined. Moreover, the width and trajectory of the liquid sheet were quantitatively studied at different Weber numbers and for the constant momentum ratio of 40. It was found that the fluid width could be a useful parameter to distinguish different regimes of the flow.

Flow Characteristics of Rectangular Liquid Jets Injected Into Low Subsonic Crossflow

Perpendicular injection of liquid jets into gaseous crossflow is well-known as an effective way to obtain good mixing between liquid fuel and air crossflow. Mostly, injectors with circular holes were used as the standard method of fuel spraying. However, recently a great attention to injectors with non-circular holes has emerged that aims to improve the quality of fuel mixing and consequently combustion efficiency. In the present work, rectangular injectors with different aspect ratios varying from 1 to 4 were experimentally studied. Using a wind tunnel with maximum air velocity of 42 m/s, tests were performed for a wide range of flow conditions including liquid-to-air momentum ratios of 10, 20, 30 and 40. Backlight shadowgraphy and high speed photography were employed to capture the instantaneous physics of the liquid jets discharged into gaseous crossflow. The flow physics of the rectangular liquid jets were investigated by means of flow visualizations. Different regimes of flow breakup including capillary, arcade, bag and multimode were observed for rectangular jets. Moreover, a new technique was used to calculate the trajectory of the liquid jets. It was shown the nozzle’s shape has no significant effect on jet trajectory. Also, the momentum ratio was found to has a profound effect on jet trajectory.

Experiments on the Injection of Elliptical Liquid Jets Into a Low Speed Airflow

An experimental investigation was performed to study the physics of liquid jets injected into a low subsonic crossflow. The jets are issued from elliptical and circular injectors with equivalent exit area. The liquid jet was visualized using shadowgraph technique and a high speed camera was used to record the instantaneous status of the jet. The liquid / air momentum flux ratio and air Weber number were varied to examine their effects on different parameters of the flow like liquid jet column trajectory, breakup point and breakup regimes. The major axis of the elliptical nozzle was aligned parallel and perpendicular to the air crossflow direction. Two different breakup modes were observed, column breakup and bag breakup. Based on the obtained results some characteristics of injected liquid jets into the air crossflow such as penetration depth and the trajectory of liquid jet were affected by changing the nozzle exit shape.