skip to main content

Title: Feasibility of using negative pressure for jet injection applications
We report on an experimental study of high-speed micro-scale liquid jets ejected into low-pressure environments, which has applications for the use of negative pressure modules in jet injector systems. The jets were impulsively started by the action of a stiff spring-piston and ejected through a narrow orifice, D_{0} ~ 100 μm, into partial vacuums ranging from atmospheric pressure down to -80 kPa. We find that due to the high exit velocity, V_{j} ~ 100 m/s, the main jet stream is largely unaffected, but we reveal some fascinating fine features during the startup phase, largely due to the presence of a small liquid volume pulled through the orifice prior to actuating the jet. In particular, as the pressure decreases, the start-up time increases and the initial spray becomes more pronounced. However, the primary outcome of this feasibility study is that use of negative pressures is viable for jet injector applications, and we hypothesize an optimal range of working pressures and configurations.  more » « less
Award ID(s):
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Journal of drug delivery science and technology
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Needle-free jet injections are actuated by a pressure impulse that can be delivered by different mechanisms to generate high-speed jets (Vj ∼ 102 m/s). During filling and transportation of disposable cartridges and ampoules, bubbles can form, which can be problematic especially for viscous fluids. Here, we report on the effect of location and size of entrapped air pockets in cartridges used in spring-powered jet injections. As air bubbles pass through the orifice, they undergo depressurization, which results in intermittent atomization and spray formation, temporarily increasing the jet dispersion. Atomization and dispersion of the jet can lead to product loss during an injection. We find that the effect of bubble location on the jet exit speed, delivery efficiency, and the projected area of the blebs formed after the injection was statistically significant (p < 0.05). The findings of this study have implications for the development of pre-filled cartridges for jet injection applications. 
    more » « less
  2. The spray characteristics of fuels when sprayed under superheated and elevated fuel pressure are markedly different than traditional fuel injection sprays. Studying fuel sprays under these conditions will help us understand the complex behaviors that may provide us with information to optimize future applications of certain technologies like supercritical spray combustion. In this work optical diagnostics are used to study the behavior of Jet A-1 under subcritical, transcritical, and supercritical sprays into open air test chambers. The experimental setup includes a high-pressure air driven pump to create the required high fuel pressure and a special heated injector to increase the temperature of the fuel inside the injector before injection to the required temperatures. Optical techniques like Schlieren and backlit shadowgraph are used to capture and study the sprays from a single hole high pressure diesel injector. A combination of 4 different temperatures and 4 different pressures are tested and the resultant images are processed to obtain quantitative measurements such as spray penetrations, spray cone angle, and spray optical density for each case. Moreover, the spray plume structure transition with changing parameters from subcritical, transcritical, and supercritical states for the fuel are also studied. The results show that with the fuel being in a transcritical state before injection there is a measurable variation in the spray cone formation and penetration for any fixed pressure. At this state the spray cone shows a bimodal spray angle distribution with increasing penetration. An increase in vapor turbulence is also observed indicating the occurrence of flash boiling of the fuel. With the fuels pushed to a supercritical state, the spray shows a thinner spray jet near the injector with a reduced overall penetration and reduced optical density near nozzle. The transition between the three different states as shown in this study gives us an interesting relationship between the spray penetration, spray cone angle and the spray optical density. This can be used as an indicator in understanding spray atomization of the fuels under supercritical spray conditions. 
    more » « less
  3. Two-color, toluene based, planar laser induced fluorescence (PLIF) is utilized to characterize the thermal structure of a turbulent, free jet. The PLIF technique has been used to measure concentration gradients for combustion applications, but its use to quantify thermal gradients is limited. To validate the method, compressed air is seeded with toluene particles. The seeded airflow is heated to temperatures varying from 300 – 375 K, and the heated jet exits a 1.27-cm diameter orifice into quiescent, room temperature air. The jet Reynolds number is varied from 5,000 to 15,000. As the jet exits the orifice, the toluene particles fluorescence across a 266 nm laser light sheet which ultimately provides a two-dimensional temperature distribution of the free jet. The rigorous calibration procedure for the PLIF technique is described along with the seeding nuisances needed to quantify the thermal structure of the jets. The PLIF technique has been demonstrated for this fundamental flow field, and it has proven to be applicable to more complex heat transfer and cooling applications. Furthermore, the time averaged temperature distributions obtained in this investigation can be used in the validation of turbulent CFD solvers. 
    more » « less
  4. Recent trends in decarbonizing efforts have brought ammonia to the forefront of research as a fuel for energy and transportation. But several previous studies have strongly suggested that ammonia has difficulties in ignition and heat release when used in a gaseous form due to its physical properties. On the other hand, working with liquid ammonia presents countless problems like difficulty in pressurizing, damage to elastomers and other metals, etc. In this study, pure liquid ammonia is injected into a CVCC (constant volume combustion chamber) using a hollow cone injector to understand the behavior of liquid ammonia when pressurized. Specifically, varying ambient temperature and pressure conditions encompassing the fuel’s subcritical to the supercritical regimes are studied as liquid ammonia tends to rapidly vaporize and flash-boil at pressures and temperatures above 50 bar and 315 K. High-speed shadowgraph and Schlieren imaging techniques are used to characterize the spray and understand the effects of varying conditions. Based on the formation of the central plume due to collapsing spray, many measurements like the plume ratio and penetration are studied to indicate the fuel's transition into the transcritical regime. A measurement of the flash-boiling spray plume ratios along with the spray penetration data give us a correlation of the environmental conditions to the spray transitioning into the supercritical regime. Interestingly, increasing the injection pressure from 75 bar to 150 bar shows 3 distinct regimes forming in the central spray plume penetration and the sprat plume ratio. This study has novel contribution to the development of direct injection of liquid ammonia spray for applications in high-power density engine systems. 
    more » « less
  5. In the present work, we model and simulate the injection and atomization of a gasoline surrogate jet by detailed numerical simulation. The surrogate fuel has a low volatility and thus no phase change occurs in the process. The nozzle geometry and operation conditions are similar to the Engine Combustion Network (ECN) “Spray G”. We focus the present study on the near field where inter-jet interaction is of secondary importance. Therefore, we have considered only one of the eight jets in the original Spray G injectors. The liquid is injected from the inlet into a chamber with stagnant gas. A tangential component of velocity is introduced at the inlet to mimic the complex internal flow in the original spray G injector, which leads to the jet deflection. A parametric study on the inlet tangential velocity is carried out to identify the proper value to be used. Simulations are performed with the multiphase flow solver, Basilisk, on an adaptive mesh. The gas-liquid interface is captured by the volume-of-fluid method. The numerical results are compared to the X-ray experimental data for the jet deflection angle and the temporal variation of penetration length. The vortex dynamics in the near field are also presented by the assistance of the vortex-identification criterion. 
    more » « less