Investigation of inner cavitation and nozzle exit flow patterns for elliptical orifice GDI injectors with various aspect ratios

2021 ◽  
Vol 129 ◽  
pp. 105682
Author(s):  
Shenghao Yu ◽  
Bifeng Yin ◽  
Hekun Jia ◽  
Chen Chen ◽  
Bin Xu
Keyword(s):  
Nozzle Exit ◽  
Flow Patterns ◽  
Aspect Ratios

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

scholarly journals Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 78
Author(s):  
Kalyani Bhide ◽  
Kiran Siddappaji ◽  
Shaaban Abdallah
Keyword(s):  
Boundary Layer ◽  
Aspect Ratio ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Internal Flow ◽  
Shear Stresses ◽  
Loss Mechanism ◽  
Potential Core ◽  
Jet Mixing ◽  
Aspect Ratios

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

Flow and Heat Transfer in an Upper Half Cooled Lower Half Heated Enclosure With Horizontal Temperature Deviations

2003 ◽  
Author(s):  
H. Li ◽  
G. Paudel ◽  
M. J. Braun ◽  
E. A. Evans ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Experimental System ◽  
Flow Patterns ◽  
Wall Layer ◽  
Fluid Exchange ◽  
Solution Flow ◽  
Temperature Deviation ◽  
Transfer Resistance ◽  
Aspect Ratios

The nature and patterns of solution flow in hydrothermal autoclaves are critical to the quality, growth uniformity, and growth rates of synthetic single crystals. Small horizontal temperature deviations, which exist in industrial practice, were found to be critical in establishing flow patterns. However, the mechanism that determines how temperature deviations affect flow pattern is not well understood. In this study, an experimental system is set-up to study the flow in a model reactor (an enclosure). Temperature in the enclosure is visualized using liquid crystals. With the experimental results, a numerical model is validated and then used to simulate flows in enclosures that are subjected to similar thermal condition as industrial autoclaves. Flow patterns are obtained with various temperature deviations, for various aspect ratios and various Rayleigh (Ra) number between 4.05E8 to 3.24E9. Flows studied are unsteady in nature. Without temperature deviations, the overall flow pattern is anti-symmetric. With a temperature deviation, the wall layers are un-balanced. The impingement of streams on the wall layers does not affect the wall layer flow at low Ra numbers. At high Ra number, wall layers are broken by the impinging streams. The dominant heat transfer mechanism in the enclosure changes significantly as the aspect ratio of the enclosure changes. In enclosures of high aspect ratios that heat transfer resistance is mainly at the fluid exchange between the two halves, temperature deviations significantly affect heat transfer by stabilizing the direction of the streams.

Secondary Flow and Hydraulic Losses Within Sinuous Conduits of Rectangular Cross Section

1992 ◽  
Vol 114 (4) ◽  
pp. 593-600 ◽  
Author(s):  
Yukimaru Shimizu ◽  
Yoshiki Futaki ◽  
C. Samuel Martin
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Patterns ◽  
Geometric Configuration ◽  
Hydraulic Losses ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Relationship

This paper describes the relationship between hydraulic losses and secondary flow within sinuous conduits with complicated bends. It has been found that the nature of secondary flow present in the bends is quite sensitive to the geometric configuration of the bend and the actual aspect ratio of the conduit section. Indeed, many different secondary flow patterns have been found to exist as the bend geometry is altered. A wide range of experiments has been conducted for various aspect ratios of a rectangular conduit with different curvatures.

Nozzle Aspect Ratio Effect on Supersonic Elliptic Jet Mixing

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
S. M. Aravindh Kumar ◽  
E. Rathakrishnan
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Pressure Gradients ◽  
Ratio Effect ◽  
Jet Mixing ◽  
Free Jet ◽  
Aspect Ratios ◽  
Nozzle Pressure ◽  
Axis Switching ◽  
The Waves

Nozzle aspect ratio effect on the mixing of Mach 2 elliptic free jet, issuing from convergent–divergent elliptic nozzles of aspect ratios 2, 3, and 4, in the presence of adverse and marginally favorable pressure gradients at the nozzle exit has been studied experimentally. The results show that AR4 jet enjoys better mixing than AR2 and AR3 jets at all nozzle pressure ratios. The AR2 and AR3 jets displayed axis switching, whereas there is no axis switching for AR4 jet. The shadowgraph shows that the waves in AR4 jet are weaker than those in AR2 and AR3 jets.

Supersonic jet control with shifted tabs

2016 ◽  
Vol 232 (3) ◽  
pp. 433-447 ◽  
Author(s):  
K Maruthupandiyan ◽  
E Rathakrishnan
Keyword(s):  
Pressure Gradient ◽  
Nozzle Exit ◽  
Supersonic Jet ◽  
Pressure Oscillation ◽  
Adverse Pressure Gradient ◽  
Mixing Enhancement ◽  
Aspect Ratios ◽  
Core Length ◽  
Expansion Level ◽  
Length Width

Mixing characteristics of a Mach 2 jet controlled by shifted tabs have been studied at different levels of expansion at the nozzle exit. Two identical rectangular flat tabs of aspect ratios (length/width) 3, 4, 5 and 6, offering 2.5% blockage each, located diametrically opposite, found that the mixing promotion caused by the shifted tab increases with increase of adverse pressure gradient (that is, below NPR 5). On the contrary, the mixing enhancement caused by tab placed at the nozzle exit decreases with increase of adverse pressure gradient. At higher NPRs from 5 to 8 for shifted tab configuration, the amplitude of centerline pitot pressure oscillation is considerably smaller than the uncontrolled jet. At lower NPRs, corresponding to expansion level pe /pa, from 0.383 to 0.511, shifted tab is found to be a better mixing promoter than the tab at the nozzle exit. But for expansion levels from 0.511 to 1.022, mixing promoted by tab at nozzle exit is better than the shifted tabs. Shifted tab at 0.5D results in about 55% reduction in core length, at NPR 3, and the corresponding core length reduction by tabs at 0.25D, 0.5D, and 0D is 25.93%, 22.2%, and 14.81%, respectively.

Jet Reattachment to Walls of Various Shapes

1971 ◽  
Vol 93 (1) ◽  
pp. 74-79
Author(s):  
Donald O. Rockwell ◽  
Preston M. Fiske
Keyword(s):  
Nozzle Exit ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Velocity Versus ◽  
Aspect Ratios ◽  
Pressure Profiles ◽  
Straight Wall ◽  
Control Port ◽  
And Control ◽  
Arc Lengths

Velocity fields for jets reattaching to walls of various shapes (curved and inclined straight), setbacks, and control port conditions were examined experimentally for the case of undeveloped velocity profiles at the nozzle exit. A canting of the nozzle exit profile occurred for cases where the wall was set back from the lip of the nozzle exit. Significantly different growth characteristics were observed for the case of the inclined straight wall, relative to the curved walls, due to the sharp turning angle which the jet was required to negotiate in the vicinity of the nozzle exit. For each jet, a well-defined settling length was noted by plotting the position of the maximum velocity versus arc length from the nozzle exit. Whenever possible, results were compared with previous investigations for fully developed conditions at the nozzle exit. Off-midplane total pressure profiles were taken for the inclined straight wall and a curved wall at several arc lengths, and three-dimensional effects were found to be significant for arc lengths and nozzle aspect ratios of interest in digital flueric amplifiers.

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

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