Experimental and Numerical Investigation of Near-Nozzle Flow Behaviour Under Flash Boiling Conditions

2017 ◽  
Author(s):  
Bo Wang ◽  
Xinyu Zhang ◽  
Yuying Yan ◽  
Jean-Paul Kone
Keyword(s):  
High Speed ◽  
Flow Behavior ◽  
Near Field ◽  
Air Entrainment ◽  
Nozzle Flow ◽  
Ambient Conditions ◽  
Fuel Temperature ◽  
Long Distance ◽  
Significant Difference ◽  
Flash Boiling

Precise control of the spray behavior is key to fully realize the potential benefits of modern GDI engines. Flash boiling is known to alert the spray behavior significantly; and thus, a complete understanding of its mechanism is essential. In this work, a study of the effect of the fuel properties on the near-nozzle flow characteristics of a single-hole GDI injector under the flash boiling conditions is presented. The performance of hexane and a typical gasoline surrogate iso-octane has been studied both experimentally and numerically. Fuel temperature varied from 20 and 100 °C with ambient pressures of 20, 50 and 100 kPa. For the experiment, microscopic imaging was conducted with a high-speed camera coupled with a long-distance microscope; and a convex lens was used to provide enough illumination to the interested area. The numerical studies were performed at the maximum needle lift using OpenFOAM, an open-source Computational Fluid Dynamics (CFD) code. Phase change was captured with the Homogeneous Relaxation Model (HRM); and turbulence was modeled using RNG k–ε model. The results have shown that while the near-field flow behavior of hexane and isooctane was similar under ambient conditions, a significant difference was observed between the two under the flash boiling conditions. The onset and development of flash boiling of isooctane was retarded compared to hexane due to its much lower vapor pressure. Spray contraction has been observed in the down-stream due to fuel vaporization and air entrainment. The CFD results were shown to agree well with the experimental data.

Study of Gas/Liquid Behavior Within an Aeroengine Bearing Chamber

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Budi Chandra ◽  
Kathy Simmons ◽  
Stephen Pickering ◽  
Steven H. Collicott ◽  
Nikolas Wiedemann
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Flow Behavior ◽  
Ambient Pressure ◽  
Current Model ◽  
Test Chamber ◽  
Experimental Program ◽  
Working Fluid ◽  
Rotating Shaft ◽  
Significant Difference

Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Some regions of the chamber contain a highly rotating air flow such that there are zones where the flow is gravity dominated and zones where it is rotation dominated. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems, is conducting an ongoing experimental program investigating liquid and gas flow behavior in a relevant highly rotating environment. Previously reported work by the UTC has investigated film thickness and residence volume within a simplified chamber consisting of outer cylindrical chamber, inner rotating shaft and cuboid off-take geometry (termed the generic deep sump). Recently, a more aeroengine relevant bearing chamber offtake geometry has been studied. This geometry is similar to one investigated at Purdue University and consists of a “sub-sump” region approached by curved surfaces linked to the bearing chamber. The test chamber consists of an outer, stationary cylinder with an inner rotating shaft. The rig runs at ambient pressure and the working fluid (water) is introduced either via a film generator on the chamber wall or through holes in the shaft. In addition to visual data (high speed and normal video), liquid residence volume within the chamber and film thickness were the two numerical comparators chosen. Data was obtained for a number of liquid supply rates, scavenge ratios and shaft rotation speeds. The data from the current model is compared to that from the earlier studies. The data shows that in contrast to the previously reported generic deep sump study, the residence volume of the curved wall deep sump (CWDS) designs is far less sensitive to shaft speed, liquid supply rate and scavenge ratio. The method of liquid supply only makes a significant difference at the lowest scavenge ratios. Residence volume data for the Nottingham CWDS is comparable, when appropriately scaled, to that for the Purdue design. The film thickness data shows that at the lower shaft speeds investigated the flow is gravity dominated whereas at higher shaft speeds shear dominates.

Study of Gas/Liquid Behaviour Within an Aeroengine Bearing Chamber

2012 ◽  
Author(s):  
Budi Chandra ◽  
Kathy Simmons ◽  
Stephen Pickering ◽  
Steven H. Collicott ◽  
Nikolas Wiedemann
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Flow Behavior ◽  
Ambient Pressure ◽  
Current Model ◽  
Test Chamber ◽  
Experimental Program ◽  
Working Fluid ◽  
Rotating Shaft ◽  
Significant Difference

Aeroengine bearing chambers typically contain bearings, seals, shafts and static parts. Oil is introduced for lubrication and cooling and this creates a two phase flow environment that may contain droplets, mist, film, ligaments, froth or foam and liquid pools. Some regions of the chamber contain a highly rotating air flow such that there are zones where the flow is gravity dominated and zones where it is rotation dominated. The University of Nottingham Technology Centre in Gas Turbine Transmission Systems, is conducting an ongoing experimental program investigating liquid and gas flow behavior in a relevant highly rotating environment. Previously reported work by Chandra et al [1, 2] has investigated film thickness and residence volume within a simplified chamber consisting of outer cylindrical chamber, inner rotating shaft and cuboid off-take geometry (termed the generic deep sump). Recently a more aeroengine relevant bearing chamber offtake geometry has been studied. This geometry is similar to one investigated by Chandra [3] at Purdue University and consists of a “sub-sump” region approached by curved surfaces linked to the bearing chamber. The test chamber consists of an outer, stationary cylinder with an inner rotating shaft. The rig runs at ambient pressure and the working fluid (water) is introduced either via a film generator on the chamber wall or through holes in the shaft. In addition to visual data (high speed and normal video), liquid residence volume within the chamber and film thickness were the two numerical comparators chosen. Data was obtained for a number of liquid supply rates, scavenge ratios and shaft rotation speeds. The data from the current model is compared to that from the earlier studies [1, 2, & 3]. The data shows that in contrast to the previously reported generic deep sump study, the residence volume of the curved wall deep sump (CWDS) designs is far less sensitive to shaft speed, liquid supply rate and scavenge ratio. The method of liquid supply only makes a significant difference at the lowest scavenge ratios. Residence volume data for the Nottingham CWDS is comparable, when appropriately scaled, to that for the Purdue design. The film thickness data shows that at the lower shaft speeds investigated the flow is gravity dominated whereas at higher shaft speeds shear dominates.

The effect of transient needle lift on the internal flow and near-nozzle spray characteristics for modern GDI systems investigated by high-speed X-ray imaging

2021 ◽  
pp. 146808742098675 ◽  
Author(s):  
Dmitrii Mamaikin ◽  
Tobias Knorsch ◽  
Philipp Rogler ◽  
Jin Wang ◽  
Michael Wensing
Keyword(s):  
High Speed ◽  
Near Field ◽  
Internal Flow ◽  
Transient Behavior ◽  
Liquid Jet ◽  
Nozzle Flow ◽  
Spray Characteristics ◽  
X Ray ◽  
X Ray Imaging ◽  
Primary Breakup

The development of the injector nozzle is a dynamic area in regard of several technical aspects. At first, the internal flow influences the near-field spray characteristics via various phenomena such as cavitation and turbulence. However, these phenomena are not fully understood due to their extremely fast, complex and multiscale nature. Furthermore, it governs the spray targeting inside the combustion chamber. High-speed X-ray imaging of GDI injector nozzles is performed in this study. The experimental results presented are related to the internal flow and primary breakup of discharged liquid jets. The injectors used are equipped with nozzles made of aluminum which have been specially developed for these investigations to enhance optical accessibility. The visualization of the needle motion, in-nozzle flow and the primary breakup region provides several exciting observations. First, the needle lift tracking exhibits short overshooting right before the steady-state of the injection phase. This event leads to a short-term, however, significant change in the associated performance of the breakup. This phenomenon is found to be a consequence of the transient behavior of the in-nozzle flow. It is shown that under some circumstances hydraulic flip may occur during this overshooting period. The primary jet breakup region is visualized and evaluated by means of image processing. Thus, the transient behavior of liquid jet expansion is quantified in the vicinity of the nozzle. It is observed that the liquid jet direction deviates from the hole axis already at the nozzle outlet, which is caused by internal flow characteristics.

scholarly journals An Experiment on Flashing-Spray Jet Characteristics of Supercritical CO2 from Various Orifice Geometries

2021 ◽  
Vol 9 ◽  
Author(s):  
Lin Teng ◽  
Jinbao Bai ◽  
Yuxing Li ◽  
Cailin Wang
Keyword(s):  
High Speed ◽  
Dispersion Model ◽  
Near Field ◽  
Geological Storage ◽  
Measurement Instruments ◽  
Long Distance ◽  
Accidental Release ◽  
And Shock Waves ◽  
Gas Leaks ◽  
Jet Characteristics

Supercritical CO2 pipelines usually are used to link the CO2 capture system to the geological storage. There are severe hazards once the asphyxiating gas leaks from the long-distance pipeline. The uncertainty of near-field jet characteristics results in imprecise consequences assessment of accidental release of supercritical CO2. To improve the prediction of consequences of accidental release accuracy, the near-field mechanisms of flashing-spray jet was investigated. In this work, an experimental setup with multiple measurement instruments was developed to impose controllable CO2 release from a high-pressure vessel. The flashing-spray jet structures of supercritical CO2 from circular and rectangular orifices were recorded by a high-speed camera. Results indicate that the near-field structures of supercritical CO2 jet from circular and rectangular orifices are totally different, which causes the different dispersion consequences. The jet angle and shock waves were analyzed quantitatively. Lastly, the models of flashing-spray based on the two different phenomena from rectangular and circular orifices were discussed. The combination of macroscopic and microscopic data in the jet can help to understand the complex physics and improve discharge and dispersion model. This work provides a fundamental data to consequences assessment of accidental release of supercritical CO2.

scholarly journals Transcritical mixing of sprays for multi-component fuel mixtures

2017 ◽  
Author(s):  
Julien Manin ◽  
Cyril Crua ◽  
Lyle M. Pickett
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Theoretical Calculations ◽  
Near Field ◽  
Model Development ◽  
Ambient Conditions ◽  
High Speed Imaging ◽  
Mixing Processes ◽  
Reduce Emissions ◽  
Fuel Mixtures

The mixing of fuels with oxidizer has been an increasingly interesting area of research with new engine technologiesand the need to reduce emissions, while leveraging efficiency. High-efficiency combustion systems such as diesel engines rely on elevated chamber pressures to maximize power density, producing higher output. In such systems, the fuel is injected under liquid state in a chamber filled with pressurized air at high temperatures. Theoretical calculations on the thermodynamics of fuel mixing processes under these conditions suggest that the injected liquid can undergo a transcritical change of state. Our previous experimental efforts in that regard showed through high- speed imaging that spray droplets transition to fluid parcels mixing without notable surface tension forces, supporting a transcritical process. Only mono-component fuels were used in these studies to provide full control over boundary conditions, which prevented extrapolation of the findings to real systems in which multi-component fuels are injected. Multi-component fuels add another layer of complexity, especially when detailed experiments serve model development, requiring the fuels to be well characterized. In this work, we performed high-speed microscopy in the near-field of high-pressure sprays injected into elevated temperature and pressure environments. A reference diesel fuel and several multi-component surrogates were studied and compared to single component fuels. The results support that a transition occurs under certain thermodynamic conditions for all fuels. As anticipated, the transition from classical evaporation to diffusive mixing is affected by ambient conditions, fuel properties, droplet size and velocity, as well as time scales. Analogous to previous observations made with the normal alkane sprays, the behavior of the multi-component fuels correlate well with their bulk critical properties.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5065

The Effect of the Geometric Modifications of the Venturi on the Non-Reactive Flow and Combustion Behavior Using a Counter-Rotating Radial-Radial Swirler

2017 ◽  
Author(s):  
Sheng-Chieh Lin ◽  
Xionghui Wang ◽  
Wessam Estefanos ◽  
Samir Tambe ◽  
San-Mou Jeng
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Behavior ◽  
Dynamic Pressure ◽  
Vertical Plane ◽  
Reactive Flow ◽  
Combustion Instabilities ◽  
Acoustic Oscillations ◽  
Ambient Conditions ◽  
Cross Sectional

An experimental study was conducted to perform an analysis of the effect of the geometric modifications of the venturi on the non-reactive and reactive flow behavior using a counter-rotating radial-radial swirler. In the non-reactive flow tests, measurements were taken in a central vertical plane and horizontal (cross-sectional) plane at the exit of the swirler, using a High-Speed, Two Dimensional, Particle Image Velocimetry (2D PIV) system. The size of the swirler used in the non-reactive flow tests is a 4.76X scaled size of the swirler used in combustion. The 4.76X swirler models were tested in air flow seeded with olive oil at Re = 51,500, corresponding to the pressure drop across the 1X swirler models of 4% of atmospheric pressure at ambient conditions. Compared with the 1X swirler models, the 4.76X swirler models provide high spatial and temporal resolutions from the enhanced visibility of the flow characteristics and lower velocities at the same Re. Four swirler configurations of high swirl number (SN ≈ 1.0) were used, with no modification for the baseline configuration (configuration 1), and with the chevrons on the venturi for the straight chevrons configuration (configuration 2). The design of the inclined venturi was used for the converging venturi configuration (configuration 3), and chevrons were added on the converging venturi for the converging chevrons configuration (configuration 4). In the combustion tests, the 1X swirler models were tested using 478K preheated air at 4% pressure drop across the swirler, and different chamber lengths. Measurements were conducted using a regular camera to capture the flame image, and dynamic pressure transducers to obtain the acoustic pressure oscillations. Four configurations were studied and compared in the non-reactive and reactive flows with the objective of understanding the mechanisms responsible in reducing the extent of the combustion instabilities. Results of this study show that the converging venturi in configuration 3 appears to be the best design in eliminating the combustion instabilities in the fuel-lean region as compared to the other configurations. This indicates that the prevention of the frequencies coupling between the heat release rate and acoustic oscillations has been achieved by using the design of the converging venturi.

scholarly journals Experimental study on flash-boiling spray structure of multi-hole gasoline direct injection injector in a constant volume chamber

2020 ◽  
Vol 12 ◽  
pp. 175682772093243
Author(s):  
Jian Wu ◽  
Jiakun Du ◽  
Hong Chen ◽  
Yuhuai Li ◽  
Wenfeng Zhan ◽  
...  
Keyword(s):  
Optical Measurement ◽  
Ambient Pressure ◽  
Direct Injection ◽  
Measurement Techniques ◽  
Gasoline Direct Injection ◽  
Fuel Temperature ◽  
Droplet Distribution ◽  
Spray Structure ◽  
Significant Difference ◽  
Flash Boiling

The macroscopic and microscopic characteristics of flash-boiling spray were experimentally investigated with various optical measurement techniques. The effects of ambient pressure and fuel temperature on flash-boiling characteristics in multi-hole gasoline direct injection injector were analyzed. The analysis was focused on the spray structure and atomization droplet size distributions. In order to increase the understanding of the flash-boiling spray targeting, three injectors with different spray patterns were investigated under strong flash-boiling condition. The results show that ambient pressure and fuel temperature have significant influence on flash boiling. Both lower ambient pressure and higher fuel temperature could accelerate the flash-boiling process. For the macroscopic characteristics, similar influences could be found with the ambient pressure decreased by 0.4 bar and the fuel temperature increased by 10°C. Further, significant difference could be found within cold-jet spray and strong flash-boiling spray, such as the spatial structure. The spray structure always turns from hollow cone into solid when flash boiling occurs. With a higher fuel superheat degree, the spray droplet distribution moves toward smaller sizes and let the larger droplets reduce due to the promotion of atomization. For the strong flash-boiling spray, the Sauter mean diameter has decreased by 50% compared with cold-jet spray. There is a corresponding relationship between collapsed flash-boiling spray target and weighted geometric center of the injector. Spray collapse could be avoided by increasing the plume distance.

Influence of Elevated Fuel Temperatures on the Spray Characteristics of Gasoline - Ethanol Blends

2021 ◽  
Author(s):  
Niranjan Miganakallu ◽  
Ashwin Karthik Purushothaman ◽  
William R. Atkinson ◽  
Nathan Peters ◽  
Tadeu Miguel Malago Amaral ◽  
...  
Keyword(s):  
High Speed ◽  
Injection Pressure ◽  
Gasoline Direct Injection ◽  
Spray Angle ◽  
Fuel Injector ◽  
Ambient Conditions ◽  
Spray Characteristics ◽  
Fuel Blends ◽  
Flash Boiling ◽  
Ethanol Blends

Abstract In this study, the effect of elevated fuel temperatures on the spray characteristics of gasoline-ethanol blends were studied in an optically accessible constant volume spray and combustion vessel. MAHLE SmartHeat® is a fuel heater located directly upstream of the fuel injector. High speed images of the spray injected from a six-hole gasoline direct injection injector typical of a side-injection engine were captured with shadowgraph imaging technique. Two fuel blends, gasoline with 10% ethanol (E10) and 85% ethanol (E85) were investigated at ambient conditions of 1 bar, 45°C and 4 bar, 180°C respectively at an injection pressure of 100 bar. Fuel temperatures were varied from 75 to 250°C. A comparison of the near nozzle and the global spray characteristics was made for the two fuels at those temperatures. Results showed that flash boiling leads to two primary effects for the two fuel blends: (i) an appreciable increase in spray angle near the exit of the nozzle followed by (ii) a decrease in spray angle downstream of the nozzle due to the interaction of the plumes and the collapsing of the spray. Furthermore, for both fuel blends, upon flash boiling, entrainment and mixing were reduced downstream of the nozzle because of the collapse of the spray. To reduce this effect, nozzle orientations and geometries should be modified.

scholarly journals Experimental Study on Flow Behavior of Unshrouded Impeller Centrifugal Pumps under Inlet Air Entrainment Condition

2021 ◽  
Vol 6 (3) ◽  
pp. 31
Author(s):  
Minquan Liao ◽  
Qiaorui Si ◽  
Meng Fan ◽  
Peng Wang ◽  
Zhonghai Liu ◽  
...  
Keyword(s):  
High Speed ◽  
Pressure Pulsation ◽  
Reverse Flow ◽  
Flow Behavior ◽  
Air Entrainment ◽  
Pulsation Frequency ◽  
Centrifugal Pumps ◽  
Local Flow ◽  
Void Fractions ◽  
Starting Point

Results on overall pump head and efficiency performance, pressure pulsation and high speed camera visualization of flow patterns behavior are presented for different inlet air-water void fractions at a given rotational speed. With the increase of inlet void fractions and decrease of the flow rates, the size of bubbles increase and tend to agglomerate in specific impeller passage locations along the blade chord. The starting point of pump breakdown is related to a strong inward reverse flow occurring in a specific location near the shroud gap of the impeller and volute tongue region. Using a constant air void fraction value of 2%, pressure pulsation frequency results are analyzed in relation with local flow mixture patterns and flow rate modification.

High-Speed, Long-Distance Electric Traction

1905 ◽  
Vol 59 (1537supp) ◽  
pp. 24627-24628
Author(s):  
Charles A. Mudge
Keyword(s):  
High Speed ◽  
Long Distance ◽  
Electric Traction
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