Quantitative measurement of binary liquid distributions using multiple-tracer x-ray fluorescence and radiography

The complex geometry and large index-of-refraction gradients that occur near the point of impingement of binary liquid jets present a challenging environment for optical interrogation. A simultaneous quadruple-tracer x-ray fluorescence and line-of-sight radiography technique is proposed as a means of distinguishing and quantifying individual liquid component distributions prior to, during, and after jet impact. Two different pairs of fluorescence tracers are seeded into each liquid stream to maximize their attenuation ratio for reabsorption correction and differentiation of the two fluids during mixing. This approach for instantaneous correction of xray fluorescence reabsorption is compared with a more time-intensive approach of using stereographic reconstruction of x-ray attenuation along multiple lines of sight. The proposed methodology addresses the need for a quantitative measurement technique capable of interrogating optically complex, near-field liquid distributions in many mixing systems of practical interest involving two or more liquid streams

Recent Developments in X-Ray Diagnostics for Cryogenic and Optically Dense Coaxial Rocket Sprays

The mixing and atomization of propellants is often characterized by optically dense flow fields and complex breakup dynamics. In the development of propulsion systems, the complexity of relevant physics and the range of spatio-temporal scales often makes computational simulation impractical for full scale injector elements; consequently, continued research into improved systems for experimental flow diagnostics is ongoing. One area of non-invasive flow diagnostics which has seen widespread growth is using synchrotron based x-ray diagostics. Over the past 3 years, a series of water and cryogenic based experiments were performed at the Advanced Photon Source, Argonne National Lab, on a NASA in-house designed swirl co-axial rocket injector, designed for operation using liquid oxygen and liquid methane in support of Project Morpheus. A range of techniques, such as x-ray fluorescence and time-averaged radiography were performed providing qualitative and quantitative mass and phase distributions, and were complemented by investigations using time-resolved radiography and white beam imaging, which provided information on breakup and mixing dynamics. Results of these investigations are presented, and conclusions regarding the viability of x-ray based diagnostics are discussed

Coupled/decoupled spray simulation comparison of the ECN spray a condition with the Sigma-Y Eulerian atomization model

This work evaluates the performance of the Σ-Y Eulerian atomization model at reproducing the internal structure of a diesel spray in the near- field. In the study, three different computational domains have been used in order to perform 3D and 2D coupled simulations, where the internal nozzle flow and external spray are modeled in one continuous domain, and 2D decoupled simulations, where only the external spray is modeled. While the 3D simulation did the best job of capturing the dense zone of the spray, the 2D simulations also performed well, with the coupled 2D simulation slightly outperforming the decoupled simulation. The similarity in results between the coupled and the decoupled simulation show that internal and external flow calculations can be performed independently. In addition, the use of spatially averaged nozzle outlet conditions, in the case of an axisymmetric (single-hole) convergent nozzle, leads to a slightly worse near-field spray predictions but to an accurate far-field ones. Finally, a novel constraint on turbulent driven mixing multiphase flows is introduced which prevents the slip velocity from exceeding the magnitude of the turbulent fluctuations through a realizable Schmidt number. This constraint increased model stability, allowing for a 4x increase in Courant number.Authors acknowledge that part of this work was possible thanks to the Programa de Ayudas de Investigacion y Desarrollo (PAID-2013 3198) of the Universitat Politecnica de Valencia. Also this study was partially funded by the Spanish Ministry of Economy and Competitiveness in the frame of the COMEFF(TRA2014-59483-R) project.Desantes Fernández, JM.; García Oliver, JM.; Pastor Enguídanos, JM.; Pandal-Blanco, A.; Baldwin, E.; Schmidt, DP. (2016). Coupled/decoupled spray simulation comparison of the ECN spray a condition with the Sigma-Y Eulerian atomization model. International Journal of Multiphase Flow. 80:89-99. https://doi.org/10.1016/j.ijmultiphaseflow.2015.12.002S89998

Quantitative time-averaged gas and liquid distributions using x-ray fluorescence and radiography in atomizing sprays

A method for quantitative measurements of gas and liquid distributions is demonstrated using simultaneous x-ray fluorescence and radiography of both phases in an atomizing coaxial spray. Synchrotron radiation at 10.1 keV from the Advanced Photon Source at Argonne National Laboratory is used for x-ray fluorescence of argon gas and two tracer elements seeded into the liquid stream. Simultaneous time-resolved x-ray radiography combined with timeaveraged dual-tracer fluorescence measurements enabled corrections for reabsorption of x-ray fluorescence photons for accurate, line-of-sight averaged measurements of the distribution of the gas and liquid phases originating from the atomizing nozzle

Statistical analysis of focused beam radiographs taken from a coaxial airblast spray

Studying the near-field region of sprays is particularly challenging because it is optically dense. However, energy in the X-ray range is capable of penetrating this dense region and obtaining information that would otherwise be unavailable. Through time-resolved X-ray radiography, a better understanding of the near-field region is currently being developed. The 7-BM beamline at the Advanced Photon Source at Argonne National Lab was focused down to a 5 x 6 μm cross-sectional area. The attenuation in the beam, which is used to calculate the effective path length of liquid, was then collected at an effective rate of 270 kHz for 10 seconds. Various statistical measures were applied to the X-ray focused beam radiographs including average, standard deviation, skewness, and kurtosis, to quantify the spray from a canonical coaxial airblast nozzle. Results show that the average effective path length is useful in determining the intact length and spray angle. The capabilities of additional statistical measures in determining important spray characteristics are also discussed

Measurement of Liquid Core Length of a Coaxial Two-fluid Spray

Shadowgraphs, tube-source X-ray radiographs, and synchrotron X-ray radiographs from a coaxial two-fluid spray are analyzed to measure the liquid core length of the spray. Two flow conditions: Rel = 1,100, Reg = 21,300, We = 40, and Rel = 1,100, Reg = 46,700, We = 196 are investigated. The standard deviation of the fluctuating intensity values are calculated and analyzed to estimate the liquid core length. Additionally, the largest connected domain is used to find an instantaneous breakup position of the spray. The results show that the high standard deviation region is related to the ligament development region, and the instantaneous position identifies ligament formation in the spray

Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level

Detailed imaging of n-dodecane and ethanol sprays injected in a constant-flow, high-pressure, high-temperature optically accessible chamber was per-formed. High-speed, diffused back-illuminated long-distance microscopy was used to resolve the spray structure in the near-nozzle field. The effect of injection and ambient pressures, as well as fuel temperature and composition have been studied through measurements of the spray penetration rates, hydraulic delays and spreading angles. Additional information such as transient flow velocities have been extracted from the measurements and compared to a control-volume spray model. The analysis demonstrated the influence of outlet flow on spray development with lower penetration velocities and wider spreading angles during the transients (start and end of injection) than during the quasi-steady period of the injection. The effect of fuel com-position on penetration was limited, while spreading angle measurements showed wider sprays for ethanol. In contrast, varying fuel temperature led to varying penetration velocities, while spreading angle remained constant during the quasi-steady period of the injection. Fuel temperature affected injector performance, with shorter delays as fuel temperature was increased. The comparisons between predicted and measured penetration rates showed differences suggesting that the transient behavior of the spreading angle of the sprays modified spray development significantly in the near-field. The reasonable agreement between predicted and measured flow velocity at and after the end of injection suggested that the complete mixing assumptions made by the model were valid in the near nozzle region during this period, when injected flow velocities are reduced.The authors wish to thank Chris Carlen from Sandia National Laboratories for designing and manufacturing specific ultra-fast LEDs, as well as Jose Enrique del Rey and Juan Pablo Viera from CMT-Motores Termicos for their support during the experiments. Support for the research carried out by Julien Manin at CMT-Motores Termicos was provided by the U.S. Department of Energy, Office of Vehicle Technologies. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.Manin, J.; Bardi, M.; Pickett, LM.; Payri Marín, R. (2016). Boundary condition and fuel composition effects on injection processes of high-pressure sprays at the microscopic level. International Journal of Multiphase Flow. 83:267-278. https://doi.org/10.1016/j.ijmultiphaseflow.2015.12.001S2672788

Measurement of Liquid Core Length of a Coaxial Two-fluid Spray

Shadowgraphs, tube-source X-ray radiographs, and synchrotron X-ray radiographs from a coaxial two-fluid spray are analyzed to measure the liquid core length of the spray. Two flow conditions: Rel = 1,100, Reg = 21,300, We = 40, and Rel = 1,100, Reg = 46,700, We = 196 are investigated. The standard deviation of the fluctuating intensity values are calculated and analyzed to estimate the liquid core length. Additionally, the largest connected domain is used to find an instantaneous breakup position of the spray. The results show that the high standard deviation region is related to the ligament development region, and the instantaneous position identifies ligament formation in the spray

Linking instantaneous rate of injection to X-ray needle lift measurements for a direct-acting piezoelectric injector

Internal combustion engines have been and still are key players in today's world. Ever increasing fuel consumption standards and the ongoing concerns about exhaust emissions have pushed the industry to research new concepts and develop new technologies that address these challenges. To this end, the diesel direct injection system has recently seen the introduction of direct-acting piezoelectric injectors, which provide engineers with direct control over the needle lift, and thus instantaneous rate of injection (ROI). Even though this type of injector has been studied previously, no direct link between the instantaneous needle lift and the resulting rate of injection has been quantified. This study presents an experimental analysis of the relationship between instantaneous partial needle lifts and the corresponding ROI. A prototype direct-acting injector was utilized to produce steady injections of different magnitude by partially lifting the needle. The ROI measurements were carried out at CMT-Motores Termicos utilizing a standard injection rate discharge curve indicator based on the Bosch method (anechoic tube). The needle lift measurements were performed at the Advanced Photon Source at Argonne National Laboratory. The analysis seeks both to contribute to the current understanding of the influence that partial needle lifts have over the instantaneous ROI and to provide experimental data with parametric variations useful for numerical model validations. Results show a strong relationship between the steady partial needle lift and the ROI. The effect is non-linear, and also strongly dependent on the injection pressure. The steady lift value at which the needle ceases to influence the ROI increases with the injection pressure. Finally, a transient analysis is presented, showing that the needle velocity may considerably affect the instantaneous ROI, because of the volume displaced inside the nozzle. Results presented in this study show that at constant injection pressure and energizing time, this injector has the potential to control many aspects of the ROI and thus, the heat release rate. Also, data presented are useful for numerical model validations, which would provide detailed insight into the physical processes that drive these observations, and potentially, to the effects of these features on combustion performance.The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (Argonne). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.Viera-Sotillo, JP.; Payri, R.; Swantek, AB.; Duke, DJ.; Sovis, N.; Kastengren, AL.; Powell, CF. (2016). Linking instantaneous rate of injection to X-ray needle lift measurements for a direct-acting piezoelectric injector. Energy Conversion and Management. 112:350-358. https://doi.org/10.1016/j.enconman.2016.01.038S35035811

A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles

[EN] Gasoline direct injection (GDI) nozzles are manufactured to meet geometric specifications with length scales on the order of a few hundred microns. The machining tolerances of these nominal dimensions are not always known due to the difficulty in accurately measuring such small length scales in a nonintrusive fashion. To gain insight into the variability of the machined dimensions as well as any effects that this variability may have on the fuel spray behavior, a series of measurements of the internal geometry and fuel mass distribution were performed on a set of eight nominally duplicate GDI “Spray G” nozzles provided by the Engine Combustion Network. The key dimensions of each of the eight nozzle holes were measured with micron resolution using full spectrum x-ray tomographic imaging at the 7-BM beamline of the Advanced Photon Source at Argonne National Laboratory. Fuel density distributions at 2 mm downstream of the nozzle tips were obtained by performing x-ray radiography measurements for many lines of sight. The density measurements reveal nozzle-to-nozzle as well as hole-to-hole density variations. The combination of high-resolution geometry and fuel distribution datasets allows spray phenomena to be linked to specific geometric characteristics of the nozzle, such as variability in the hole lengths and counterbore diameters, and the hole inlet corner radii. This analysis provides important insight into which geometrical characteristics of the nozzles may have the greatest importance in the development of the injected sprays, and to what degree these geometric variations might account for the total spray variability. The goal of this work is then to further the understanding of the relationship between internal nozzle geometry and fuel injection, provide input to improve computational models, and ultimately aid in optimizing injector design for higher fuel efficiency and lower emissions engines.This research was performed at the 7-BM beamline of the APS at Argonne National Laboratory. Use of the APS is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-06CH11357. We gratefully acknowledge the computing resources provided on Blues, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. We thank Dr. Doga Gürsoy for the use of TomoPy and corresponding user support, as well as Dr. Xianghui Xiao at the APS 2-BM beamline for technical guidance in performing x-ray tomography. Argonne’s x-ray fuel injection research is sponsored by the DOE Vehicle Technologies Program under the direction of Gurpreet Singh and Leo Breton.Matusik, K.; Duke, D.; Sovis, N.; Swantek, A.; Powell, C.; Payri, R.; Vaquerizo, D.... (2017). A study on the relationship between internal nozzle geometry and injected mass distribution of eight ECN Spray G nozzles. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 313-320. https://doi.org/10.4995/ILASS2017.2017.4766OCS31332