Near Nozzle Field Conditions in Diesel Fuel Injector Testing

The measurement of the rate of fuel injection using a constant volume, fluid filled chamber and measuring the pressure change as a function of time due to the injected fluid (the so called “Zeuch” method) is an industry standard due to its simple theoretical underpinnings. Such a measurement device is useful to determine key timing and quantity parameters for injection system improvements to meet the evolving requirements of emissions, power and economy. This study aims to further the understanding of the nature of cavitation which could occur in the near nozzle region under these specific conditions of liquid into liquid injection using high pressure diesel injectors for heavy duty engines. The motivation for this work is to better understand the temporal signature of the pressure signals that arise in a typical injection cycle. A preliminary CFD study was performed, using OpenFOAM, with a transient (Large Eddy Simulation -LES), multiphase solver using the homogenous equilibrium model for the compressibility of the liquid/vapour. The nozzle body was modelled for simplicity without the nozzle needle using a nozzle hole of 200μm diameter and the body pressurised to values typical for common rail engines. Temperature effects were neglected and the wall condition assumed to be adiabatic. The chamber initial static pressure was varied between 10 and 50 bar to reflect typical testing conditions. Results indicate that vapour formation could occur in areas 10-30mm distant from the nozzle itself. The cavitation was initiated around 100 μs after the jet had started for low ΔP cases and followed the development period required for the formation of vortices associated with the vortex roll up of this jet. These vortices had localised sites, in their core region, below the vapour pressure and were convected downstream of their initial formation location. It was also found that vapour formation could occur at chamber static pressures up to 50 bar (the highest tested) due to cavitation in the shear layer and this vortex effect. The pressure signal received at the chamber would therefore be more difficult to interpret with additional error components

Insight into the Design of Aerosol Spray Systems for Cell Therapies for Retinal Diseases using Computational Modelling and Experimental Assessment

Retinal degenerative diseases affect numerous people worldwide and in the UK; they lead to dysfunction of retinal cells and retinal dysfunction, in turn leading to vision loss and in some cases blindness. Existing treatments aim to alleviate current risk factors leading to retinal degeneration, such as increased high pressure. However, these procedures do not restore lost cell, vision nor retinal function, and therefore may still lead to blindness. Developing cell-based therapies to replace lost cells provides one option for retinal tissue repair in order to restore retinal function. These therapies involve delivering stem cells to encourage neural cell-like functions within the retinal tissue. Despite progress in developing stem-cells compatible with the retinal layers, there is also a need to developing a minimal invasive technique for cell delivery, without damaging the neighbouring optical structure. After evaluating several methods of cell delivery, this thesis explores the need for developing aerosol spraying systems for stem-cell delivery into the human eye. Mathematical modelling is used as a tool to define spraying parameters which, alongside experimental work, may accelerate the design of aerosol spraying systems to treat retinal degenerative disease such as glaucoma. Firstly, an organic biomaterial is developed and used as scaffold to spray and protect cells from aerodynamic forces and stresses associated with aerosolization. The rheological properties of this biomaterial are incorporated within a computational model to predict cell-spraying into a human eye. Boundary and initial conditions mimic the experimental spraying conditions, and the parameterised model is used to explore the link between operator-defined conditions (namely volume flow rate of the cell-laden hydrogel, external pressure needed for aerosolization and angle of the spraying) and spraying outputs (surface area of the retina covered, droplets speed, wall shear stress on the retinal surface). Data from both computational and experimental analyses were gathered. Computational modelling is used to explore the impact of spraying parameters (pressure and volume flow rate at the injector nozzle, outer cone angle for the spray) on key outputs of high priority, namely the spatial distribution of the delivered hydrogel on the retinal wall, the surface area of the retina covered and droplet speed. Droplets speed at the retinal wall appeared to increase with increasing pressure conditions and were observed at a constant volume flow rate. Experimental assessments were used to validate the computational data and determine cell viability under set environmental conditions (external pressure and volume flow rate of cell-laden hydrogel) through in-vitro testing. This thesis defines indicative spraying parameters for delivering therapeutic cells to the human retina, based on a combination of computational modelling and experimental studies. Mathematical modelling provides the potential to transfer these findings to other organ systems, aligning with broader effects to develop cell delivery systems to treat organ disease and repair

Catalog of selected heavy duty transport energy management models

A catalog of energy management models for heavy duty transport systems powered by diesel engines is presented. The catalog results from a literature survey, supplemented by telephone interviews and mailed questionnaires to discover the major computer models currently used in the transportation industry in the following categories: heavy duty transport systems, which consist of highway (vehicle simulation), marine (ship simulation), rail (locomotive simulation), and pipeline (pumping station simulation); and heavy duty diesel engines, which involve models that match the intake/exhaust system to the engine, fuel efficiency, emissions, combustion chamber shape, fuel injection system, heat transfer, intake/exhaust system, operating performance, and waste heat utilization devices, i.e., turbocharger, bottoming cycle

Recent advances in micro-electro-mechanical devices for controlled drug release applications

In recent years, controlled release of drugs has posed numerous challenges with the aim of optimizing parameters such as the release of the suitable quantity of drugs in the right site at the right time with the least invasiveness and the greatest possible automation. Some of the factors that challenge conventional drug release include long-term treatments, narrow therapeutic windows, complex dosing schedules, combined therapies, individual dosing regimens, and labile active substance administration. In this sense, the emergence of micro-devices that combine mechanical and electrical components, so called micro-electro-mechanical systems (MEMS) can offer solutions to these drawbacks. These devices can be fabricated using biocompatible materials, with great uniformity and reproducibility, similar to integrated circuits. They can be aseptically manufactured and hermetically sealed, while having mobile components that enable physical or analytical functions together with electrical components. In this review we present recent advances in the generation of MEMS drug delivery devices, in which various micro and nanometric structures such as contacts, connections, channels, reservoirs, pumps, valves, needles, and/or membranes can be included in their design and manufacture. Implantable single and multiple reservoir-based and transdermal-based MEMS devices are discussed in terms of fundamental mechanisms, fabrication, performance, and drug release applications.Fil: Villarruel Mendoza, Luis A.. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; ArgentinaFil: Scilletta, Natalia Antonela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; ArgentinaFil: Bellino, Martin Gonzalo. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes | Comision Nacional de Energia Atomica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia. Unidad Ejecutora Instituto de Nanociencia y Nanotecnologia - Nodo Constituyentes.; ArgentinaFil: Desimone, Martín Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Catalano, Paolo Nicolás. Comisión Nacional de Energía Atómica. Gerencia de Área de Investigación y Aplicaciones no Nucleares. Gerencia de Desarrollo Tecnológico y Proyectos Especiales. Departamento de Micro y Nanotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentin

An optical investigation of cavitation phenomena in true-scale high-pressure diesel fuel injector nozzles

Efforts to improve diesel fuel sprays have led to a significant increase in fuel injection pressures and a reduction in nozzle-hole diameters. Under these conditions, the likelihood for the internal nozzle flow to cavitate is increased, which potentially affects spray breakup and atomisation, but also increases the risk of causing cavitation damage to the injector. This thesis describes the study of cavitating flow phenomena in various single and multi-hole optical nozzle geometries. It includes the design and development of a high-pressure optical fuel injector test facility with which the cavitating flows were observed. Experiments were undertaken using real-scale optical diesel injector nozzles at fuel injection pressures up to 2050 bar, observing for the first time the characteristics of the internal nozzle-flow under realistic fuel injection conditions. High-speed video and high resolution photography, using laser illumination sources, were used to capture the cavitating flow in the nozzle-holes and sac volume of the optical nozzles, which contained holes ranging in size from 110 micrometers to 300 micrometers. Geometric cavitation in the nozzle-holes and string cavitation formation in the nozzle-holes and sac volume were both observed using transient and steady-state injection conditions; injecting into gaseous and liquid back pressures up to 150 bar. Results obtained have shown that cavitation strings observed at realistic fuel injection pressures exhibit the same physical characteristics as those observed at lower pressures. The formation of string cavitation was observed in the 300 micrometers multi-hole nozzle geometries, exhibiting a mutual dependence on nozzle flow-rate and the geometry of the nozzle-holes. Pressure changes, caused by localised turbulent perturbations in the sac volume and transient fuel injection characteristics, independently affected the geometric and string cavitation formation in each of the holes. String cavitation formation was shown to occur when free-stream vapour was entrained into the low pressure core of a sufficiently intense coherent vortex. Hole diameters less than or equal to 160 micrometers were found to suppress string cavitation formation, with this effect a result of the reduced nozzle flow rate and vortex intensity. Using different hole spacing geometries, it was demonstrated that the formation of cavitation strings in a particular geometry became independent of fuel injection and back pressure once a threshold pressure drop across the nozzle had been reached

Controlled formation of bubbles in a planar co-flow configuration

We present a new method that allows to control the bubble size and formation frequency in a planar air-water co-flow configuration by modulating the Water velocity at the nozzle exit. The forcing process has been experimentally characterized determining the amplitude of the water velocity fluctuations from measurements of the pressure variations in the water stream. The effect of the forcing on the bubbling process has been described by analyzing the pressute signals in the air stream in combinatiOn with visualizations performed with a high-speed camera. We show that, when the forcing amplitude is sufficiently large, the bubbles can be generated at a rate different from the natural bubbling frequency, f(n), which depends on the water-to-air velocity ratio, Lambda u(n)/u(q), and the Weber number, We rho(w)u(n)(2)H(0)/sigma, where 110 is the half-thickness of the air stream at the exit slit, rho(w), the water density and a the surface tension coefficient. Consequently, when the forcing is effective, monodisperse bubbles, of sizes smaller than those generated without stimulation, are produced at the prescribed frequency, f(f) > f(n). The effect of the forcing process on the bubble size is also characterized by measuring the resulting intact length, 1, i.e. the length of the air stem that remains attached to the injector when a bubble is released. In addition, the physics behind the forcing procedure is explained as a purely kinematic mechanism that is added to the effect of the pressure evolution inside the air stream that would take place in the unforced case. Finally, the downstream position of the maximum perturbation amplitude has been determined by a one-dimensional model, exhibiting a good agreement with both experiments and numerical simulations performed with OpenFOAM.This work has been supported by the Spanish MINECO (Subdirección General de Gestión de Ayudas a la Investigación), Junta de Andalucía and European Funds, grants Nos. DPI2014-59292-C3-1-P, DPI2014-59292-C3-3-P, P11-TEP7495. Financial support from the University of Jaén, Project No. UJA2013/08/05, is also acknowledged

Air-Powered Liquid Needle Free Injectors: Design, Modeling and Experimental Validation

Liquid needle free injectors are biomedical devices that deliver medication via the creation of high speed liquid jets without the use of hypodermic needles, have been a topic of interest in the scientific community for quite some time. This study focuses on the development and analysis of liquid jet injectors powered by air. Studies demonstrate that the majority of commercially available injectors are gas/air powered units; however there is no indication of a model that prescribes the performance characteristics of this particular type of injector. Consequently the main goal of this research is to develop and validate a model capable of predicting the behaviour of such devices. In this study, the development and analysis of a model for air-powered injectors is accomplished first by constructing a prototype injector that functions in a very similar fashion and produces jets of similar geometry and velocities as the vast majority of commercially available units. Furthermore, the injector is designed in such a way that the parameters such as, driver pressure, injection chamber length and volume as well as nozzle geometry can be varied. An initial evaluation of the prototype injector is performed to ensure it can be used to accurately conduct testing. The prototype injector is then used to validate a fluid mechanics model constructed based on previous work from Baker and Sanders [IEEE Trans. Biomed. Eng. 46:235-242, 1999]. Experiments that map stagnation pressures of the jet through the use of a piezoelectric force transducer are performed in order to validate the performance of the model. These experiments describe the peak and average stagnation pressures of the jet based on the effect of different parameters such as driver pressure (400-800 kPa), nozzle size (130-250 μm) and injection chamber length (10-25 mm). The results of these tests are then compared to the behaviour prescribed by the model. An analysis of these results indicates that the present model can accurately be used to predict the performance of air-powered needle free liquid jet injectors

Lorentz-force actuated needle-free injection for intratympanic pharmaceutical delivery

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 113-118).Delivery of pharmaceuticals to the inner ear via injection through the tympanic membrane is a method of local drug delivery that provides a non-invasive, outpatient procedure to treat many of the disorders and diseases that plague the inner ear. The real-time controlled linear Lorentz-force actuated jet injector developed in the MIT BioInstrumentation lab was found to be a feasible technology for possible improvement over current intratympanic drug delivery methods. Jet injection holes using a nozzle with a 50 [mu]m orifice were found to be significantly smaller than those made using a standard, 0.31 mm (30-gauge) hypodermic needle. The feasibility of using the jet injector to deliver drug to the inner ear with less tissue damage than seen in standard procedures is shown offering an avenue for improved inner ear drug delivery methods and technology.by Alison Cloutier.S.M

Small Engine Flash Vapor JP-8 Fuel Injector Testing, Simulation and Development

Following U.S. Army’s single fuel initiative, Wankel rotary engines used in U.S. Army’s shadow unmanned aerial vehicles (UAVs) need to be retrofitted from running on aviation gasoline (AVGAS) to JP-8. The feasibility of retrofitting the engine with a flash vapor direct fuel injector was investigated. A commercial off-the-shelf direct fuel injector was used in the study. A photo detector measurement tool was developed to measure high frequency (>100 Hz) injection event. A coupled electrical-electomagnetics-fluid-mechanical system was simulated to understand the pintle dynamics during an injection event. Optimal injector power drive was revealed to be a multi-stage current profile. A flash heater was designed and tested to be capable of heating up JP-8 from room temperature to its vaporization temperature (>310F) under one tenth of a second at the required flow rate. An ignition test rig was built to compare ignition behavior between AVGAS and heated JP-8. Test result showed that the 550F pre-heated JP-8 had equal or superior ignition pressure rise / ignition delay time than AVGAS