The influence of inter-jet spacing and jet-swirl interaction on flame image velocimetry (FIV) derived flow fields in a small-bore diesel engine

2021 ◽  
pp. 146808742110384
Author(s):  
Jinxin Yang ◽  
Lingzhe Rao ◽  
Charitha de Silva ◽  
Sanghoon Kook
Keyword(s):  
Diesel Engine ◽  
Turbulence Intensity ◽  
High Speed ◽  
Jet Impingement ◽  
Flow Fields ◽  
Bulk Flow ◽  
Frame Rate ◽  
Wall Jet ◽  
Jet Interaction ◽  
Image Velocimetry

This study applies Flame Image Velocimetry (FIV) to show the in-flame flow field development with an emphasis on the jet-jet interaction and jet-swirl interaction phenomena in a single-cylinder small-bore optically accessible diesel engine. Two-hole nozzle injectors with three different inter-jet spacing angles of 45°, 90° and 180° are prepared to cause different levels of jet-jet interaction. The engine has a swirl ratio of 1.7, which is used to evaluate jet-swirl interaction of the selected 180° inter-jet spacing nozzle. High-speed soot luminosity imaging was performed at a high frame rate of 45 kHz for the FIV processing. For each inter-jet spacing angle, a total of 100 individual combustion cycles were recorded to address the cyclic variations. The ensemble averaged flow fields are shown to illustrate detailed flow structures while the Reynolds decomposition using spatial filtering is applied to analyse turbulence intensity. The results showed reduced bulk flow magnitude and turbulence intensity at smaller inter-jet spacing, suggesting the two opposed wall-jet heads colliding immediately after the jet impingement on the wall can cause flow suppression effects. This raised a concern on the mixing as lower inter-jet spacing creates more fuel-rich mixtures in the jet-jet interaction region. Despite lower flow magnitude, the cyclic variation was also estimated higher for narrower inter-jet spacing, which is another drawback of the significant jet-jet interaction. Regarding the jet-swirl interaction, the wall-jet head penetrating on the up-swirl side showed lower bulk flow magnitude as the counter-flow arrangement suppressed the flow, similar with the narrower interact-jet spacing results. However, the turbulence intensity was measured higher on the up-swirl side, suggesting the relatively weaker swirl flow vectors opposed to the penetrating wall-jet head could in fact enhance the mixing.

Flame image velocimetry analysis of reacting jet flow fields with a variation of injection pressure in a small-bore diesel engine

2020 ◽  
pp. 146808742096061
Author(s):  
Jinxin Yang ◽  
Lingzhe Rao ◽  
Yilong Zhang ◽  
Charitha de Silva ◽  
Sanghoon Kook
Keyword(s):  
Diesel Engine ◽  
Injection Pressure ◽  
Jet Flow ◽  
Flow Fields ◽  
Swirl Flow ◽  
Wall Jet ◽  
Jet Interaction ◽  
Image Velocimetry ◽  
Cyclic Variations ◽  
Flow Vectors

This study measures in-flame flow fields in a single-cylinder small-bore optical diesel engine using Flame Image Velocimetry (FIV) applied to high-speed soot luminosity movies. Three injection pressures were tested for a two-hole nozzle injector to cause jet-wall interaction and a significant jet-jet interaction within 45° inter-jet spacing. The high-pressure fuel jets were also under the strong influence of a swirl flow. For each test condition, soot luminosity signals were recorded at a high framing rate of 45 kHz with which the time-resolved, two-dimensional FIV post-processing was performed based on the image contrast variations associated with flame structure evolution and internal pattern change. A total of 100 combustion events for each injection pressure were recorded and processed to address the inherent cyclic variations. The ensemble-averaged flow fields were used for detailed flow structure discussion, and Reynolds decomposition using a spatial filtering method was applied to obtain high-frequency fluctuations that were found to be primarily turbulence. The detailed analysis of flow fields suggested that increased injection pressure leads to enhanced jet flow travelling along the bowl wall and higher flow vectors penetrating back towards the nozzle upon the impingement on the wall. Within the jet-jet interaction region, the flow vectors tend to follow the swirl direction, which increases with increasing injection pressure. The FIV also captured a turbulent ring vortex formed in the wall-jet head, which becomes larger and clearer at higher injection pressure. A vortex generated in the centre of combustion chamber was due to the swirl flow with its position being shifted at higher injection pressure. The bulk flow magnitude indicated significant cyclic variations, which increases with injection pressure. The turbulence intensity is also enhanced due to higher injection pressure, which primarily occurs in the wall-jet head region and the jet-jet interaction region.

scholarly journals Tomographic particle image velocimetry of desert locust wakes: instantaneous volumes combine to reveal hidden vortex elements and rapid wake deformation

2012 ◽  
Vol 9 (77) ◽  
pp. 3378-3386 ◽  
Author(s):  
Richard J. Bomphrey ◽  
Per Henningsson ◽  
Dirk Michaelis ◽  
David Hollis
Keyword(s):  
Particle Image Velocimetry ◽  
High Speed ◽  
Particle Image ◽  
Aerodynamic Force ◽  
Three Dimensional ◽  
Flow Fields ◽  
Diagnostic Methods ◽  
Tomographic Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Spatio Temporal

Aerodynamic structures generated by animals in flight are unstable and complex. Recent progress in quantitative flow visualization has advanced our understanding of animal aerodynamics, but measurements have hitherto been limited to flow velocities at a plane through the wake. We applied an emergent, high-speed, volumetric fluid imaging technique (tomographic particle image velocimetry) to examine segments of the wake of desert locusts, capturing fully three-dimensional instantaneous flow fields. We used those flow fields to characterize the aerodynamic footprint in unprecedented detail and revealed previously unseen wake elements that would have gone undetected by two-dimensional or stereo-imaging technology. Vortex iso-surface topographies show the spatio-temporal signature of aerodynamic force generation manifest in the wake of locusts, and expose the extent to which animal wakes can deform, potentially leading to unreliable calculations of lift and thrust when using conventional diagnostic methods. We discuss implications for experimental design and analysis as volumetric flow imaging becomes more widespread.

Velocity Measurements in Microchannels With a Laser Scanning Microscope and Particle Linear Image Velocimetry

2004 ◽  
Author(s):  
S. H. Chao ◽  
M. R. Holl ◽  
J. H. Koschwanez ◽  
R. H. Carlson ◽  
L. S. Jang ◽  
...  
Keyword(s):  
High Speed ◽  
Laser Scanning ◽  
Frame Rate ◽  
Planar Imaging ◽  
Velocity Measurements ◽  
Optical Sectioning ◽  
One Dimensional ◽  
Microscale Flow ◽  
Imaging Results ◽  
Image Velocimetry

A novel velocity measurement method for microscale flow field characterization is reported, particle linear image velocimetry (PLIV). The method records a series of one-dimensional images that represent the trace of particles in the flow across a one-dimensional imager. Linear imaging results in a faster frame rate than planar imaging, allowing observation of larger microscope magnification or measurement of faster flow rates in real-time than comparable techniques. In contrast to particle image velocimetry (PIV), PLIV does not require high-speed cameras or shutters. Furthermore, PLIV is adaptable to multiple linear imager formats and, as one example, can use laser scanning confocal microscopes (LSCM) that acquire images slowly but with high spatial resolutions and optical sectioning ability. Higher resolution can be obtained for flows where in-plane velocity gradient in the direction of the optical path (z-direction) is important. This paper presents the PLIV algorithm, and demonstrates its utility by measuring Poiseuille flow with 1-μm resolution in a microfluidic environment.

Induction System Effects on Small-Scale Turbulence in a High-Speed Diesel Engine

1987 ◽  
Vol 109 (4) ◽  
pp. 491-502 ◽  
Author(s):  
A. E. Catania ◽  
A. Mittica
Keyword(s):  
Diesel Engine ◽  
Turbulence Intensity ◽  
High Speed ◽  
Engine Speed ◽  
Small Scale ◽  
Cylinder Wall ◽  
System Configuration ◽  
Intake System ◽  
Induction System ◽  
Scale Turbulence

The influence of the induction system on small-scale turbulence in a high-speed, automotive diesel engine was investigated under variable swirl conditions. The induction system was made up of two equiverse swirl tangential ducts, and valves of the same size and lift. Variable swirl conditions were obtained by keeping one of the inlet valves either closed or functioning, and by changing engine speed. The investigation was carried out for two induction system configurations: with both ducts operating and with only one of them operating. Two different engine speeds were considered, one relatively low (1600 rpm) and the other quite high (3000 rpm), the latter being the highest speed at which engine turbulence has been measured up to now. Cycle-resolved hot-wire anemometry measurements of air velocity were performed throughout the induction and compression strokes, under motored conditions, along a radial direction at an axial level that was virtually in the middle of the combustion chamber at top dead center. The velocity data were analyzed using the nonstationary time-averaging procedure previously developed by the authors. Correlation and spectral analysis of the small-scale turbulence so determined was also performed. The turbulence intensity and its degree of nonhomogeneity and anisotropy were sensibly influenced by the variable swirl conditions, depending on both the intake system configuration and engine speed; they generally showed an increase with increasing swirl intensity, at the end of the compression stroke. A similar trend was observed in the cyclic fluctuation of both the mean velocity and turbulence intensity. The micro time scale of turbulence was found to be almost uniform during induction and compression, showing a slight dependence on the measurement point and on the intake system configuration, but a more sensible dependence on the engine speed. No effect of the cylinder wall on turbulence was apparent.

scholarly journals Airflow Characteristics Investigation of a Diesel Engine for Different Helical Port Openings and Engine Speeds

2021 ◽  
Vol 53 (3) ◽  
pp. 210306
Author(s):  
Willyanto Anggono ◽  
Mitsuhisa Ichiyanagi ◽  
Reina Saito ◽  
Gabriel J. Gotama ◽  
Chris Cornelius ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Turbulence Intensity ◽  
Engine Speed ◽  
Control Valve ◽  
Swirl Ratio ◽  
Airflow Velocity ◽  
Mean Velocity ◽  
Image Velocimetry ◽  
Port Opening ◽  
The Difference

Intake airflow characteristics are essential for the performance of diesel engines. However, previous investigations of these airflow characteristics were mostly performed on two-valve engines despite the difference between the airflow of two-valve and four-valve engines. Therefore, in this study, particle image velocimetry (PIV) investigations were performed on a four-valve diesel engine. The investigations were conducted under different engine speeds and helical port openings using a swirl control valve (SCV). The results suggest that the position of the swirl center does not significantly shift with different engine speeds and helical port openings, as the dynamics of the flow remained closely similar. The trends of the airflow characteristics can be best observed during the compression stroke. A higher engine speed increases the angular velocity of the engine more compared to the increase of the airflow velocity and results in a lower swirl ratio of the flow. On the other hand, a higher engine speed leads to a higher mean velocity and the variation of velocity results in a larger turbulence intensity of the flow. Increasing the helical port opening brings a reduction in the swirl ratio and turbulence intensity as more airflow from the helical port disturbs the airflow from the tangential port.

Modelling of the Wall Jet in a Direct Injection Diesel Engine

1992 ◽  
Vol 206 (3) ◽  
pp. 185-196 ◽  
Author(s):  
J M Desantes ◽  
M Lapuerta ◽  
J M Salavert
Keyword(s):  
Diesel Engine ◽  
Initial Conditions ◽  
Direct Injection ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Wall Jet ◽  
Jet Interaction ◽  
Direct Injection Diesel Engine ◽  
Free Jet ◽  
Good Agreement

As a part of a phenomenological model, a method for simulating the wall/jet interaction in a direct injection diesel engine is proposed. The method is based on the application of the momentum conservation equation in the different directions in which the wall jet is spread, and takes into account both the interaction with the combustion chamber geometry and with swirl. It takes as initial conditions the results of calculating the free jet, which is divided into packages. The predictions provide good agreement with those by other researchers.

An explanation for the phase lag in supersonic jet impingement

2017 ◽  
Vol 815 ◽  
Author(s):  
Joel L. Weightman ◽  
Omid Amili ◽  
Damon Honnery ◽  
Julio Soria ◽  
Daniel Edgington-Mitchell
Keyword(s):  
Acoustic Waves ◽  
High Speed ◽  
Feedback Loop ◽  
Supersonic Jet ◽  
Jet Impingement ◽  
Phase Lag ◽  
Loop Equation ◽  
Image Velocimetry ◽  
Impinging Flows ◽  
First Time

For the first time, a physical mechanism is identified to explain the phase lag term in Powell’s impinging feedback loop equation (Powell, J. Acoust. Soc. Am., vol. 83 (2), 1988, pp. 515–533). Ultra-high-speed schlieren reveals a previously unseen periodic transient shock in the wall jet region of underexpanded impinging flows. The motion of this shock appears to be responsible for the production of the acoustic waves corresponding to the impingement tone. It is suggested that the delay between the inception of the shock and the formation of the acoustic wave explains the phase lag in the aeroacoustic feedback process. This suggestion is quantitatively supported through an assessment of Powell’s feedback equation, using high-resolution particle image velocimetry and acoustic measurements.

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