Features Of The Diffusion Combustion Of Hydrogen Microjet At Various Spatial Orientation Of The Nozzle Exit With Top – Hat Mean Velocity Profile At The Nozzle Exit

2017 ◽  
Vol 12 (1) ◽  
pp. 66-78
Author(s):  
Genrich Grek ◽  
Maria Litvinenko ◽  
Grigory Kozlov ◽  
Valentin Vikhorev
Keyword(s):  
Velocity Profile ◽  
Nozzle Exit ◽  
Spatial Orientation ◽  
Velocity Vector ◽  
Turbulent Flame ◽  
Diffusion Combustion ◽  
Mean Velocity ◽  
Jet Velocity ◽  
Basic Characteristics ◽  
Vector Orientation

The purpose of the given work will consist in the experimental studies of features diffusion combustion of a hydrogen round microjet, effusing from micronozzle with top – hat mean velocity profile at the nozzle exit, depending on spatial orientation of the nozzle exit. It is revealed, that in conditions of a jet velocity vector orientation towards terrestrial gravitation vector «g» (opposite or perpendicular) the basic characteristics of the flame evolution depending on gas consumption (Q) (or jet velocity U) are rather close to each other. To these characteristics concern such as ranges of the «bottleneck flame area» presence, flame separation at presence of the «bottleneck flame area», presence of the «bottleneck flame area» but absence of a turbulent jet combustion and finally ending of the microjet combustion. On the contrary, in situation of the hydrogen round microjet diffusion combustion in conditions of a jet velocity vector orientation towards terrestrial gravitation vector «g» (orientability – like) the basic characteristics of the flame evolution depending on a jet velocity are sharply differed from two previous cases. The range of existence of the «bottleneck flame area» is reduced, flame separation occurs in absence of the «bottleneck flame area», there is no situation of the «bottleneck flame area» combustion at turbulent flame separation and there is no situation of the «bottleneck flame area» combustion at burn termination of the turbulent part of a microjet and finally ending of the microjet combustion occurs at the much greater jet velocity.

Features Of The Diffusion Combustion Of Hydrogen Microjet At Various Spatial Orientation Of The Nozzle Exit

2015 ◽  
Vol 10 (4) ◽  
pp. 60-76
Author(s):  
Genrich Grek ◽  
Viktor Kozlov ◽  
Oleg Korobeinichev ◽  
Yuriy Litvinenko ◽  
Andrey Shmakov
Keyword(s):  
Nozzle Exit ◽  
Spatial Orientation ◽  
Velocity Vector ◽  
Experimental Studies ◽  
Diffusion Combustion ◽  
Jet Velocity ◽  
Basic Characteristics ◽  
Vector Orientation ◽  
The Given ◽  
Combustion Of Hydrogen

The purpose of the given work will consist in the experimental studies of features diffusion combustion of a hydrogen round microjet depending on spatial orientation of the nozzle exit. It is revealed, that a hydrogen round microjet at diffusion combustion in conditions of a jet velocity vector orientation towards terrestrial gravitation vector «g» (opposite or perpendicular) the basic characteristics of the flame evolution depending on a jet velocity are practically coincided. To these characteristics concern such as ranges of the «bottleneck» flame area presence, flame detachment at presence of the «bottleneck» flame area, presence of the «bottleneck» flame area, but absence of a turbulent jet combustion and finally ending of the microjet combustion. On the contrary, in situation of the hydrogen round microjet diffusion combustion in conditions of a jet velocity vector orientation towards terrestrial gravitation vector «g» (orientability – like) the basic characteristics of the flame evolution depending on a jet velocity are sharply differed from two previous cases. The range of existence of the «bottleneck» flame area is reduced, flame detachment occurs in absence of the «bottleneck» flame area and finally ending of the microjet combustion occurs at the much greater jet velocity.

Influence Of Initial Conditions At The Micro Nozzle Exit On Hydrogen Diffusion Combustion

2016 ◽  
Vol 11 (3) ◽  
pp. 34-45
Author(s):  
Viktor Kozlov ◽  
Genrich Grek ◽  
Oleg Korobeinichev ◽  
Yuriy Litvinenko ◽  
Andrey Shmakov
Keyword(s):  
Velocity Profile ◽  
Nozzle Exit ◽  
Hydrogen Diffusion ◽  
Initial Conditions ◽  
Diffusion Combustion ◽  
Mean Velocity ◽  
Micro Nozzle ◽  
Flame Region ◽  
Region Size ◽  
Efflux Velocity

The purpose of the given work will consist in an experimental study of influence of initial conditions at the micro nozzle exit on hydrogen diffusion combustion. It is shown, that the mean velocity profile and presence/absence of a heatcapacious material at the nozzle exit play an essential role on a flame structure and process of a round hydrogen microjet combustion. Velocity ranges of existence of a round hydrogen microjet diffusion combustion, flame separation and «bottleneck flame» region for a case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are found. Dependences of the «bottleneck flame» region size from a hydrogen microjet efflux velocity for case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are shown. Decrements of reduction of the «bottleneck flame» region size with growth of the hydrogen microjet efflux velocity for three situations of changes of initial conditions at the nozzle exit are determined.

scholarly journals Air Round Microjet Interaction with Coaxial Hydrogen Jet at It Combustion for Supersonic Speed Jets Efflux

2019 ◽  
Vol 14 (3) ◽  
pp. 53-63
Author(s):  
V. V. Kozlov ◽  
G. R. Grek ◽  
M. V. Litvinenko ◽  
Yu. A. Litvinenko ◽  
A. S. Tambovzev ◽  
...  
Keyword(s):  
Nozzle Exit ◽  
Acoustic Noise ◽  
Turbulent Flame ◽  
Experimental Studies ◽  
Supersonic Combustion ◽  
Small Scale ◽  
Diffusion Combustion ◽  
Supersonic Speed ◽  
Combustion Region ◽  
Flame Region

Results of experimental studies of the round air microjet interaction with a coaxial hydrogen jet at its combustion for supersonic speed jets efflux are presented in this work. It is revealed that combustion of the coaxial hydrogen jet with growth of its speed efflux is accompanied by all scenarios, observed at study of the round and plane hydrogen microjets diffusion combustion. However, “bottleneck flame region” undergoes considerable geometrical deformations because of specifics of a flame of a coaxial jet. It is shown that “bottleneck flame region” is transformed from Y-shaped to spherical shape in the activity of growth of a coaxial jet speed efflux. It is found that a round air microjet interaction with a coaxial hydrogen jet at its combustion is accompanied by several new phenomena: existence of cone-shaped area a coaxial jet combustion near a nozzle exit; existence of small-scale supersonic cells on a resultant flame; absence of the hydrogen combustion efflux from combustion region of a coaxial jet near nozzle exit; flame-out from combustion region of a coaxial jet near nozzle exit that leads to hydrogen ignition downstream, its intensive combustion and sharp acoustic noise occurrence; existence of a turbulent flame, to its separation from a nozzle exit and transition to supersonic combustion of a resultant jet.

Different Conditions Of The Round Hydrogen Jets Diffusion Combustion In Air

2015 ◽  
Vol 10 (2) ◽  
pp. 27-41
Author(s):  
Andrey Shmakov ◽  
Genrich Grek ◽  
Viktor Kozlov ◽  
Oleg Korobeinichev ◽  
Yuriy Litvinenko
Keyword(s):  
Experimental Study ◽  
Density Gradient ◽  
Near Field ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Nozzle Diameter ◽  
Turbulent Jet ◽  
Diffusion Combustion ◽  
Jet Velocity ◽  
Spatial Size

The purpose of this work is experimental study of diffusion combustion of the round hydrogen microjets with different nozzle diameter. The new phenomenon is revealed during combustion of a hydrogen microjet, which we have named «bottleneck». The special attention has been given to research of characteristics of the «bottleneck» development and its role during of a hydrogen round microjet combustion. It is shown, that «bottleneck» represents the closed spherical area of the hydrogen with air mixture combustion in a jet near-field. The «bottleneck» area is closed by a powerful density gradient. It is found, that the laminar hydrogen jet in this area overcomes a density gradient of gas, becomes turbulent and combustion process is accompanied both a turbulent jet, and a turbulent flame further downstream evolution. It is shown, that the spatial size of a «bottleneck» decreases with growth of a jet velocity.

Diffusion Hydrogen Microjet Combustion (Round Bevelled Nozzle)

2015 ◽  
Vol 10 (2) ◽  
pp. 42-51
Author(s):  
Genrich Grek ◽  
Mikhail Katasonov ◽  
Grigory Kozlov ◽  
Maria Litvinenko
Keyword(s):  
Experimental Study ◽  
Density Gradient ◽  
Near Field ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Turbulent Jet ◽  
Diffusion Combustion ◽  
Side View ◽  
Jet Velocity ◽  
Spatial Size

The purpose of this work is experimental study of diffusion combustion of the round hydrogen microjet at the 45° bevelled nozzle. The new phenomenon is revealed during combustion of a given hydrogen microjet, which we have named «bottleneck», as well as in a situation of the round and plane microjet combustion. The special attention has been given to research of characteristics of the «bottleneck» development and its role during of a hydrogen round microjet combustion. It is shown, that «bottleneck» represents the closed spherical area of the hydrogen with air mixture combustion in a jet near-field. The «bottleneck» area is closed by a powerful density gradient. It is found, that the laminar hydrogen jet in this area overcomes a density gradient of gas, becomes turbulent and combustion process is accompanied both a turbulent jet, and a turbulent flame further downstream evolution. It is shown, that the spatial size of a «bottleneck» decreases with growth of a jet velocity. It is found, that shadow patterns of the microjet combustion obtained for two shooting positions (normal and side view to the bevelled nozzle) were identical.

Structure Of The Attached Flame During Diffusion Hydrogen Microjet Combustion (Slotted Nozzle)

2015 ◽  
Vol 10 (2) ◽  
pp. 52-66
Author(s):  
Yuriy Litvinenko ◽  
Genrich Grek ◽  
Viktor Kozlov ◽  
Oleg Korobeinichev ◽  
Andrey Shmakov
Keyword(s):  
Experimental Study ◽  
Density Gradient ◽  
Near Field ◽  
Turbulent Flame ◽  
Combustion Process ◽  
Turbulent Jet ◽  
Diffusion Combustion ◽  
Jet Velocity ◽  
Spatial Size

The purpose of this work is experimental study of diffusion combustion of the plane hydrogen microjet with different slotted nozzle dimensions. The new phenomenon is revealed during combustion of a plane hydrogen microjet, which we have named «bottleneck», as well as in a situation of a round microjet combustion. The special attention has been given to research of characteristics of the «bottleneck» development and its role during of a hydrogen plane microjet combustion. It is shown, that «bottleneck» represents the closed spherical area of the hydrogen with air mixture combustion in a jet near-field. The «bottleneck» area is closed by a powerful density gradient. It is found, that the laminar hydrogen jet in this area overcomes a density gradient of gas, becomes turbulent and combustion process is accompanied both a turbulent jet, and a turbulent flame further downstream evolution. It is shown, that the spatial size of a «bottleneck» decreases with growth of a jet velocity. It is found, that «bottleneck» does not arise in case of the big nozzle lengthening (l/h > 10)

Disorganization of a hole tone feedback loop by an axisymmetric obstacle on a downstream end plate

2014 ◽  
Vol 757 ◽  
pp. 908-942 ◽  
Author(s):  
K. Matsuura ◽  
M. Nakano
Keyword(s):  
Nozzle Exit ◽  
Passive Control ◽  
Control Method ◽  
Three Dimensional ◽  
Acoustic Power ◽  
Shear Layers ◽  
Mean Velocity ◽  
End Plate ◽  
Air Jet ◽  
Practical Engineering

AbstractThis study investigates the suppression of the sound produced when a jet, issued from a circular nozzle or hole in a plate, goes through a similar hole in a second plate. The sound, known as a hole tone, is encountered in many practical engineering situations. The mean velocity of the air jet $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}u_0$ was $6\text {--}12\ \mathrm{m}\ {\mathrm{s}}^{-1}$. The nozzle and the end plate hole both had a diameter of 51 mm, and the impingement length $L_{im}$ between the nozzle and the end plate was 50–90 mm. We propose a novel passive control method of suppressing the tone with an axisymmetric obstacle on the end plate. We find that the effect of the obstacle is well described by the combination ($W/L_{im}$, $h$) where $W$ is the distance from the edge of the end plate hole to the inner wall of the obstacle, and $h$ is the obstacle height. The tone is suppressed when backflows from the obstacle affect the jet shear layers near the nozzle exit. We do a direct sound computation for a typical case where the tone is successfully suppressed. Axisymmetric uniformity observed in the uncontrolled case is broken almost completely in the controlled case. The destruction is maintained by the process in which three-dimensional vortices in the jet shear layers convect downstream, interact with the obstacle and recursively disturb the jet flow from the nozzle exit. While regions near the edge of the end plate hole are responsible for producing the sound in the controlled case as well as in the uncontrolled case, acoustic power in the controlled case is much lower than in the uncontrolled case because of the disorganized state.

Оdrеđivаnjе brzinе struјаnjа vаzduhа u prаvоugаоnоm zаtvоrеnоm cevovodu korišćenjem metoda polja brzina

2021 ◽  
Vol 23 (2) ◽  
pp. 57-63
Author(s):  
Marija Lazarevikj ◽  
◽  
Valentino Stojkovski ◽  
Viktor Iliev
Keyword(s):  
Velocity Profile ◽  
Flow Rate ◽  
Air Flow ◽  
Displacement Transducer ◽  
Linear Displacement ◽  
Local Velocity ◽  
Air Flow Rate ◽  
Mean Velocity ◽  
Measured Velocity ◽  
Integration Techniques

In the technical practice, it is often necessary to measure or control the fluid flow rate in pipelines and channels. The velocity-area method requires a number of meters located at specified points in a suitable cross-section of closed conduits. Simultaneous measurements of local mean velocity with the meters are integrated over the gauging section to provide the discharge. In this paper, three approaches of this method are applied on a rectangular closed conduit to determine the air flow rate with integration techniques used to compute the discharge assume velocity distributions that closely approximate known laws, especially in the neighborhood of solid boundaries. For this purpose, meters for velocity were 7 Pitot tubes placed vertically in predefined measurement points covering the conduit height, and moved horizontally along the conduit width. The position of the Pitot tubes along the conduit width was monitored and controlled by a linear displacement transducer. Pressure is measured using digital sensors. The first technique for determination of air flow rate is on basis of fixed (stopping) measuring points across the conduit width as averaged values of local velocity, the second one is semi continual measurement of velocity profile by applying interpolation between the average local velocity on fixed (stopping) points and measured velocity in the movement between two positions, and the third is by continuously moving the Pitot tubes without stopping. The results of the three techniques are calculated and presented using different types of software. Considering the last technique, comparison of results is made applying different movement speeds of the Pitot tubes in order to examine their influence on the velocity profile.

scholarly journals Effect of the Flame Dome Depth and Improvement of the Pressure Loss in the Dump Diffuser

1998 ◽  
Author(s):  
Shinji Honami ◽  
Wataru Tsuboi ◽  
Takaaki Shizawa
Keyword(s):  
Velocity Profile ◽  
Reynolds Stress ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Flow Behavior ◽  
Sudden Expansion ◽  
Mean Velocity ◽  
The Mean ◽  
Stress Profiles

This paper presents the effect of flame dome depth on the total pressure performance and flow behavior in a sudden expansion region of the combustor diffuser without flow entering the dome head. The mean velocity and turbulent Reynolds stress profiles in the sudden expansion region were measured by a Laser Doppler Velocitmetry (LDV) system. The experiments show that total pressure loss is increased, when flame dome depth is increased. Installation of an inclined combuster wall in the sudden expansion region is suggested from the viewpoint of a control of the reattaching flow. The inclined combustor wall is found to be effective in improvement of the diffuser performance. Better characteristics of the flow rate distribution into the branched channels are obtained in the inclined wall configuration, even if the distorted velocity profile is provided at the diffuser inlet.

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