scholarly journals Investigation of the spray formation and breakup process in an open-end swirl injector

2020 ◽  
Vol 103 (3) ◽  
pp. 003685042094616
Author(s):  
Chen Chen ◽  
Zhigong Tang
Keyword(s):  
Pressure Drop ◽  
Liquid Film ◽  
Formation Process ◽  
High Speed ◽  
Injection Pressure ◽  
Breakup Process ◽  
Filling Process ◽  
Spray Pattern ◽  
Spray Formation ◽  
Swirl Injector

The spray formation and breakup process in an open-end swirl injector were studied through experiments and numerical simulations. A high-speed shadowgraph system and a high-speed backlight system were adopted to record the spray. Volume of fluid was used as the interface tracking method to capture the evolution process. The filling process of the liquid film inside the injector was captured. The air core formation process as observed in the experiments differed from that depicted by the numerical simulation results. The results revealed that the spray pattern of the cross-section at the tangential inlets also varied during the filling process. The evolution of the holes on the liquid film and ligaments was observed. It was determined that the liquid sheet repeatedly exhibited thinning, instability, shedding, breakup, and coalescence in the spray formation and breakup process. The spray pattern underwent the distorted pencil stage, onion stage, tulip stage, and fully developed stage with the increased injection pressure drop. The formation process of the open-end swirl injector also underwent these four stages under an injection pressure drop of 0.5 MPa.

Film breakup of tilted impinging spray under various pressure conditions

2019 ◽  
Vol 21 (2) ◽  
pp. 330-339 ◽  
Author(s):  
Di Xiao ◽  
Ichikawa Yukihiko ◽  
Xuesong Li ◽  
David Hung ◽  
Keiya Nishida ◽  
...  
Keyword(s):  
Film Thickness ◽  
Boundary Conditions ◽  
Liquid Film ◽  
High Speed ◽  
Injection Pressure ◽  
Laser Induced Fluorescence ◽  
Parameter Study ◽  
Fluorescence Signal ◽  
Fuel Film ◽  
Various Boundary Conditions

Fuel film on engine walls caused by spray impingement would dramatically cause engine friction deterioration, incomplete combustion, and significant cycle-to-cycle variations. In a previous work, it has been demonstrated that fuel film would break up via wave entrainment induced by the high-speed coflow. Meanwhile, the film breakup dynamics depend on various boundary conditions, such as injection pressure, ambient pressure, and so on. However, such impact on the wall film formation was not investigated thoroughly in existing literature. This work aims to perform a parameter study to investigate possible means to enhance wave entrainment effect as to reduce the amount of impingement fuel mass. In this study, simultaneous measurements of macroscopic structure and its corresponding footprint of impinging spray are conducted using a single-hole, prototype injector in a constant volume chamber. The macroscopic spray structure was captured by high-speed backlit imaging, and the film was obtained using laser-induced fluorescence under different conditions. The laser-induced fluorescence signal is converted to film thickness following a calibration procedure where laser-induced fluorescence signals from a series of known-thickness film are captured. A mathematical processing method is used to analyze both the dynamic behavior of film thickness and amount of droplet detachment caused by high-speed coflow. It is found that at the leading edge of film waves, a remarkable amount of liquid droplets detaches from the liquid film and the quantity of film mass on the wall decreases during this process. Quantitative analysis is conducted and the mass ratio of detached droplets over residual liquid film is estimated. We hold that the film breakup percentage increases with both ambient and injection pressure due to the enhanced high-speed coflow. Then, variation laws for various boundary conditions are obtained based on the observations.

Ignition of Diesel Pilot Fuel in Dual-Fuel Engines

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Marcus Grochowina ◽  
Daniel Hertel ◽  
Simon Tartsch ◽  
Thomas Sattelmayer
Keyword(s):  
High Speed ◽  
Measurement Techniques ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Spray Formation ◽  
Fuel Concentration ◽  
Injection Parameters ◽  
Pilot Fuel ◽  
Ignition And Combustion

Dual-fuel (DF) engines offer great fuel flexibility combined with low emissions in gas mode. The main source of energy in this mode is provided by gaseous fuel, while the diesel fuel acts only as an ignition source. For this reason, the reliable autoignition of the pilot fuel is of utmost importance for combustion in DF engines. However, the autoignition of the pilot fuel suffers from low compression temperatures caused by Miller valve timings. These valve timings are applied to increase efficiency and reduce nitrogen oxide (NOx) emissions. Previous studies have investigated the influence of injection parameters and operating conditions on ignition and combustion in DF engines using a unique periodically chargeable combustion cell. Direct light high-speed images and pressure traces clearly revealed the effects of injection parameters and operating conditions on ignition and combustion. However, these measurement techniques are only capable of observing processes after ignition. In order to overcome this drawback, a high-speed shadowgraph technique was applied in this study to examine the processes prior to ignition. Measurements were conducted to investigate the influence of compression temperature and injection pressure on spray formation and ignition. Results showed that the autoignition of diesel pilot fuel strongly depends on the fuel concentration within the spray. The high-speed shadowgraph images revealed that in the case of very low fuel concentration within the pilot spray, only the first stage of the two-stage ignition occurs. This leads to large cycle-to-cycle variations and misfiring. However, it was found that a reduced number of injection holes counteract these effects. The comparison of a diesel injector with ten-holes and a modified injector with five-holes showed shorter ignition delays, more stable ignition and a higher number of ignited sprays on a percentage basis for the five-hole nozzle.

Precursor Film Formation Process Ahead Macroscopic Contact Line of Spreading Droplet on Smooth Substrate

2009 ◽  
Author(s):  
Ichiro Ueno ◽  
Kanji Hirose ◽  
Yusuke Kizaki ◽  
Yoshiaki Kisara ◽  
Yoshizumi Fukuhara
Keyword(s):  
Liquid Film ◽  
Contact Line ◽  
Formation Process ◽  
High Speed ◽  
Thin Liquid Film ◽  
Solid Substrate ◽  
Precursor Film ◽  
Boundary Line ◽  
Brewster Angle Microscopy ◽  
Droplet Spreading

The authors pay their special attention to formation process of wafer-thin liquid film, known as ‘precursor film,’ ahead moving macroscopic contact line of a droplet spreading on a solid substrate. The spreading droplet on the solid substrate is accompanied with the movement of a visible boundary line so-called ‘macroscopic contact line.’ Existing studies have indicated there exits a thin liquid film known as ‘precursor film’ ahead the macroscopic contact line of the droplet. The present author’s group has dedicated their special effort to detect the formation process of the precursor film by applying a convectional laser interferometry and a high-speed camera, and to evaluate the spreading rate of the precursor film. In the present study, existing length of the precursor film at a very early stage of the droplet spreading is evaluated by applying a Brewster-angle microscopy as well as the interferometer. The authors extend their attention to the advancing process of the precursor film on inclined substrate.

Design of Solid Rocket Engine

2015 ◽  
Author(s):  
Ryoichi S. Amano ◽  
Yi-Hsin Yen
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Gas Flow ◽  
Volume Fraction ◽  
Length Scale ◽  
Breakup Process ◽  
Flow Conditions ◽  
Solid Rocket Motor ◽  
Breakup Length ◽  
Solid Rocket

This paper presents both experiment and simulation of alumina molten flow in a solid rocket motor (SRM), when the propellant combusts, the aluminum is oxidized into alumina (Al2O3) which, under the right flow conditions, tends to agglomerate into molten droplets, impinge on the chamber walls, and then flow along the nozzle wall. Such agglomerates can cause erosive damage. The goal of the present study is to characterize the agglomerate flow within the nozzle section by studying the breakup process of a liquid film that flows along the wall of a straight channel while a high-speed gas moves over it. We have used an unsteady-flow Reynolds-Averaged Navier-Stokes code (URANS) to investigate the interaction of the liquid film flow with the gas flow, and analyzed the breakup process for different flow conditions. The rate of the wave breakup was characterized by introducing a breakup-length-scale for various flow conditions based on the Volume Fraction (VF) of the liquid, which is an indicator of a two-phase flow liquid breakup level. A smaller breakup-length-scale means that smaller drops have been created during the breakup process. The study covers the breakup and fluid behaviors based on different gas-liquid momentum flux ratios, different surface tension and viscosity settings, different Ohnesorge numbers (Oh), and different Weber numbers. Both water and molten aluminum flows were considered in the simulation studies. The analysis demonstrates an effective method of correlating the liquid breakup with the main flow conditions in the nozzle channel path.

Effect of geometric and operating parameters on the spray characteristics of an open-end swirl injector

2019 ◽  
Vol 233 (12) ◽  
pp. 4457-4467 ◽  
Author(s):  
Chen Chen ◽  
Yang Yang ◽  
Xiaorong Wang ◽  
Wenxian Tang
Keyword(s):  
Pressure Drop ◽  
Discharge Coefficient ◽  
Cone Angle ◽  
Injection Pressure ◽  
Operating Parameters ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Breakup Length ◽  
Swirl Chamber ◽  
Swirl Injector

To study the influence of geometric and operating parameters on the spray characteristics of an open-end swirl injector, seven injectors with different tangential inlet diameters ( D p) and injector length to injector orifice diameter ( L/D) ratios were tested and simulated. Using high-speed backlight, the evolution laws of liquid film thickness, discharge coefficient, spray cone angle, breakup length, and velocity distribution in the swirl chamber under different geometric and operating parameters were captured after unified image processing. Low-injection pressure drop is directly proportional to the discharge coefficient and the spray cone angle. When the injection pressure drop approaches or reaches a critical value of 0.4 MPa, the discharge coefficient and spray cone angle remain nearly constant with maximum fluctuations of 1% and 5%, respectively. With an increase in the geometric characteristic constant A, the liquid film thickness, discharge coefficient, breakup length, and velocity in the swirl chamber decrease, whereas the spray cone angle increases. As the viscous effect increases for increasing L/D, the discharge coefficient and breakup length increase, whereas the spray cone angle decreases. Based on experiment results, empirical formulas for the discharge coefficient, spray angle, and breakup length were put forward as reference for engineering applications, including the effect of the geometric and operating parameters.

Ignition of Diesel Pilot Fuel in Dual-Fuel Engines

2018 ◽  
Author(s):  
Marcus Grochowina ◽  
Daniel Hertel ◽  
Simon Tartsch ◽  
Thomas Sattelmayer
Keyword(s):  
High Speed ◽  
Measurement Techniques ◽  
Injection Pressure ◽  
Operating Conditions ◽  
Dual Fuel ◽  
Spray Formation ◽  
Fuel Concentration ◽  
Injection Parameters ◽  
Pilot Fuel ◽  
Ignition And Combustion

Dual-Fuel (DF) engines offer great fuel flexibility combined with low emissions in gas mode. The main source of energy in this mode is provided by gaseous fuel, while the Diesel fuel acts only as an ignition source. For this reason, the reliable autoignition of the pilot fuel is of utmost importance for combustion in DF-engines. However, the autoignition of the pilot fuel suffers from low compression temperatures caused by Miller valve timings. These valve timings are applied to increase efficiency and reduce nitrogen oxide emissions. Previous studies have investigated the influence of injection parameters and operating conditions on ignition and combustion in DF-engines using a unique periodically chargeable combustion cell. Direct light high-speed images and pressure traces clearly revealed the effects of injection parameters and operating conditions on ignition and combustion. However, these measurement techniques are only capable of observing processes after ignition. In order to overcome this drawback, a high-speed shadowgraph technique was applied in this study to examine the processes prior to ignition. Measurements were conducted to investigate the influence of compression temperature and injection pressure on spray formation and ignition. Results showed that the autoignition of Diesel pilot fuel strongly depends on the fuel concentration within the spray. The high-speed shadowgraph images revealed that in the case of very low fuel concentration within the pilot spray only the first-stage of the two-stage ignition occurs. This leads to large cycle-to-cycle variations and misfiring. However, it was found that a reduced number of injection holes counteracts these effects. The comparison of a Diesel injector with 10-holes and a modified injector with 5-holes showed shorter ignition delays, more stable ignition and a higher number of ignited sprays on a percentage basis for the 5-hole nozzle.

Precursor Film Formation Process Ahead Macroscopic Contact Line of Spreading Droplet on Smooth Substrate

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Ichiro Ueno ◽  
Kanji Hirose ◽  
Yusuke Kizaki ◽  
Yoshiaki Kisara ◽  
Yoshizumi Fukuhara
Keyword(s):  
Liquid Film ◽  
Contact Line ◽  
Formation Process ◽  
High Speed ◽  
Thin Liquid Film ◽  
Solid Substrate ◽  
Precursor Film ◽  
Boundary Line ◽  
Brewster Angle Microscopy ◽  
Droplet Spreading

The authors pay their special attention to formation process of wafer-thin liquid film, known as “precursor film,” ahead moving macroscopic contact line of a droplet spreading on a solid substrate. The spreading droplet on the solid substrate is accompanied with the movement of a visible boundary line so-called “macroscopic contact line.” Existing studies have indicated there exits a thin liquid film known as precursor film ahead the macroscopic contact line of the droplet. The present author’s group has dedicated their special effort to detect the formation process of the precursor film by applying a convectional laser interferometry and a high-speed camera, and to evaluate the spreading rate of the precursor film. In the present study, existing length of the precursor film at a very early stage of the droplet spreading is evaluated by applying a Brewster-angle microscopy as well as the interferometer. The authors extend their attention to the advancing process of the precursor film on inclined substrate.

scholarly journals A quantitative analysis of nozzle surface bound fuel for diesel injectors

2017 ◽  
Author(s):  
Jack Turner ◽  
Dan Sykes ◽  
Guillaume De Sercey ◽  
Viacheslav Stetsyuk ◽  
Martin Gold ◽  
...  
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Injection Pressure ◽  
Spreading Rate ◽  
Operating Conditions ◽  
Fuel Injector ◽  
Surface Wetting ◽  
Long Distance ◽  
Coverage Area ◽  
Fluid Behaviour

In a fuel injector at the end of the injection, the needle descent and the rapid pressure drop in the nozzle leads todischarge of large, slow-moving liquid structures. This unwanted discharge is often referred as fuel ‘dribble’ and results in near-nozzle surface wetting, creating fuel-rich regions that are believed to contribute to unburnt hydrocarbon emissions. Subsequent fluid overspill occurs during the pressure drop in the expansion stroke when residual fluid inside the nozzle is displaced by the expansion of trapped gases as the pressure through the orifices is equalised, leading to further surface wetting. There have been several recent advancements in the characterisation of these near nozzle fluid processes, yet there is a lack of quantitative data relating the operating conditions and hardware parameters to the quantity of overspill and surface-bound fuel. In this study, methods for quantifying nozzle tip wetting after the end of injection were developed, to gain a better understanding of the underlying processes and to study the influence of engine operating conditions. A high-speed camera with a long- distance microscope was used to visualise fluid behaviour at the microscopic scale during, and after, the end of injection. In order to measure the nozzle tip temperature, a production injector was used which was instrumented with a type K thermocouple near one of the orifices. Image post-processing techniques were developed to track both the initial fuel coverage area on the nozzle surface, as well as the temporal evolution and spreading rate of surface-bound fluid. The conclusion presents an analysis of the area of fuel coverage and the rate of spreading and how these depend on injection pressure, in-cylinder pressure and in-cylinder temperature. It was observed that for this VCO injector, the rate of spreading correlates with the initial area of fuel coverage measured after the end of injection, suggesting that the main mechanism for nozzle wetting is through the impingement of dribble onto the nozzle. However, occasional observations of the expansion of orifice-trapped gas were made that lead to asignificant increase in nozzle wetting.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4661

Visualization of Spray Structure at the Outlet of the Micro Orifices

2015 ◽  
Author(s):  
Morteza Ghorbani ◽  
Ali Koşar
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Injection Pressure ◽  
Experimental Investigations ◽  
Small Scale ◽  
Spray Characteristics ◽  
Visualization System ◽  
Spray Formation ◽  
Cavitation Phenomenon ◽  
Visualization Techniques

Spray formation occurring at the outlet of short microchannels/micro orifices due to the cavitation phenomenon is of great importance in biomedical and engineering applications. The spray characteristics are affected dramatically by the flow regime in the micro orifice. If properties of the flow are identified in the outlet of the nozzle, the treatment of the spray can be predicted. These properties can be used as boundary conditions. The experimental investigations show that the cavitation phenomenon occurs in the orifice and strongly affects the spray characteristics. However, visualization of the spray at the outlet of the micro orifice is a challenging task, since the phenomena related to the spray are occurred in very small scale and also the region near to the micro orifice is not clear. Therefore there is an urgent need to new and advanced visualization techniques and measurement equipments. In this study, spray formation and atomization, bubble evolution at the outlet of a short microchannel of an inner diameter of 152 μm were experimentally studied at different injection pressures with the use of a high speed visualization system. High speed visualization was performed at four different segments to cover ∼15 mm distance beginning from the microchannel outlet to understand the spray formation mechanism. It was observed that cavitating bubbly flow is strongly affected by injection pressure. Up to an injection pressure of 50 bars bigger size droplets form at the outlet, while beyond 50 bar injection pressure, cavitation erosion of intensified cavitation becomes dominant leading to smaller droplet sizes and a more conical spray. The results showed a good agreement with previous studies. This energy could be exploited in several applications, where destructive effects of bubbly cavitating flows are needed.

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