The effect of high-pressure injection variations on the mixing state of underexpanded methane jets

2020 ◽  
pp. 146808742096089
Author(s):  
VD Sakellarakis ◽  
W Vera-Tudela ◽  
U Doll ◽  
D Ebi ◽  
YM Wright ◽  
...  
Keyword(s):  
High Pressure ◽  
Scaling Laws ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Injection Pressure ◽  
Distribution Functions ◽  
Navier Stokes ◽  
Chamber Pressure ◽  
Gaussian Shape ◽  
Fuel Concentration

This work presents a joint experimental and numerical study of global characteristics and mixing behavior of underexpanded methane jets at high-pressure conditions in a Constant Volume Chamber. Injection pressures of 200, 250, and 300 bar and pressure ratios of 4, 5, 6, 8, and 10 at each of those pressures have been investigated. Tracer LIF with acetone as tracer has been applied to experimentally quantify the mixing of methane and quiescent air. In order to exploit the symmetry of the configuration, accompanying simulations have been carried out in Reynolds-Averaged Navier-Stokes framework with the k – w SST turbulence model and real-gas modelling based on the Soave-Redlich-Kwong Equation of State has been employed to account for high-pressure corrections in thermodynamic and caloric properties. The experiments confirm the hyperbolic decay of axial fuel concentration and the Gaussian shape of traverse concentration profiles in the self-similar region of the jets, while simulation results match well with experimentally determined fuel concentration fields. It is found that scaling laws proposed in literature for steady-state jet propagation can qualitatively interpret the effect of injection variations on jet tip penetration and volume. Increasing pressure ratio at fixed injection pressure leads to the formation of slightly richer jets, with slightly smaller mass percentage in the range of air-to-fuel ratios most favorable to autoignition. By contrast, increasing pressure ratio at fixed chamber pressure leads to virtually identical Probability Distribution Functions of local air-to-fuel ratios and the same is observed when employing a fixed pressure ratio at higher pressure levels.

Numerical Study of Viscous Effects on Acoustic Waves

2012 ◽  
Author(s):  
N. Mohd. Ghazali
Keyword(s):  
Standing Wave ◽  
Acoustic Waves ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Viscous Effects ◽  
Half Wavelength ◽  
Mean Pressure ◽  
Acoustic Chamber

Simulasi kaedah berangka 2-dimensi telah dilakukan terhadap gelombang akustik di dalam kebuk akustik tertutup segi empat tepat. Penyelesaian dilakukan terhadap persamaan sistem tak lelurus Navier-Stokes 2-dimensi, aliran tak mantap dengan kelikatan yang berbeza. Kaedah perbezaan tak terhingga digunakan dengan kejituan tertib dua terhadap masa dan ruang. Sempadan halaju ialah tanpa gelincir dan tanpa telus aliran, dengan fluks haba sifar pada dinding kebuk. Gelombang akustik dihasilkan oleh pemacu akustik selaput atau omboh yang terletak pada salah satu dinding menegak. Suhu hasil kajian didapati sama dengan penyelesaian teori dan ujikaji untuk gelombang akustik di dalam suatu kebuk tertutup. Nod suhu (minimum) dan antinod suhu (maksimum) masing-masing wujud pada dinding dan di tengah kebuk. Kata kunci: Kajian berangka; gelombang akustik; selaput; omboh A two-dimensional numerical simulation of acoustic waves in a closed rectangular acoustic chamber is completed. Numerical computations are performed by solving the two-dimensional, unsteady, viscous, non-linear Navier-Stokes system of equations. Finite difference methodology was used accurate to second order both in time and space. No-slip, no through flow and zero heat flux are set boundary conditions. Acoustic waves are generated by a vibrating membrane or piston on one wall. Computations are completed for variation in viscosity of the fluid. Results of the temperature profiles seem to agree with analytical solutions for a standing wave in an enclosure and those obtained experimentally with low perturbation to mean pressure ratio. Temperature nodes and anti-nodes each was found to occur near walls and midway through the chamber respectively, results associated with a half wavelength standing wave. Key words: numerical study; acoustic waves; membrane; piston

Heat Transfer Measurements and Predictions for a Modern, High-Pressure, Transonic Turbine, Including Endwalls

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
James A. Tallman ◽  
Charles W. Haldeman ◽  
Michael G. Dunn ◽  
Anil K. Tolpadi ◽  
Robert F. Bergholz
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Turbulence Modeling ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Test Facility ◽  
Navier Stokes ◽  
Local Measurements ◽  
Transonic Turbine ◽  
The Ohio State University

This paper presents both measurements and predictions of the hot-gas-side heat transfer to a modern, 112 stage high-pressure, transonic turbine. Comparisons of the predicted and measured heat transfer are presented for each airfoil at three locations, as well as on the various endwalls and rotor tip. The measurements were performed using the Ohio State University Gas Turbine Laboratory Test Facility (TTF). The research program utilized an uncooled turbine stage at a range of operating conditions representative of the engine: in terms of corrected speed, flow function, stage pressure ratio, and gas-to-metal temperature ratio. All three airfoils were heavily instrumented for both pressure and heat transfer measurements at multiple locations. A 3D, compressible, Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) solver with k-ω turbulence modeling was used for the CFD predictions. The entire 112 stage turbine was solved using a single computation, at two different Reynolds numbers. The CFD solutions were steady, with tangentially mass-averaged inlet/exit boundary condition profiles exchanged between adjacent airfoil-rows. Overall, the CFD heat transfer predictions compared very favorably with both the global operation of the turbine and with the local measurements of heat transfer. A discussion of the features of the turbine heat transfer distributions, and their association with the corresponding flow-physics, has been included.

Experimental and Numerical Investigation of a Centrifugal Compressor and Numerical Study of the Area Ratio and Tip Clearance Effects on the Performance Characteristic

2008 ◽  
Author(s):  
Mahdi Nili-Ahmadabadi ◽  
Ali Hajilouy-Benisi ◽  
Mohammad Durali ◽  
Sayyed Mostafa Motavalli
Keyword(s):  
Flow Field ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Area Ratio ◽  
Tip Clearance ◽  
Performance Characteristics ◽  
Navier Stokes ◽  
Sst Turbulence Model

In this research, the centrifugal compressor of a turbocharger is investigated experimentally and numerically. Performance characteristics of the compressor were obtained experimentally by measurements of rotor speed and flow parameters at the inlet and outlet of the compressor. Three dimensional flow field in the impeller and diffuser was analyzed numerically using a full Navier-Stokes program with SST turbulence model. The performance characteristics of the compressor were obtained numerically, which were then compared with the experimental results. The comparison shows good agreement. Furthermore, the effect of area ratio and tip clearance on the performance parameters and flow field was studied numerically. The impeller area ratio was changed by cutting the impeller exit axial width from an initial value of 4.1 mm to a final value of 5.1 mm, resulting in an area ratio from 0.792 to 0.965. For the rotor with exit axial width of 4.6 mm, performance was investigated for tip clearance of 0.0, 0.5 and 1.0 mm. Results of this simulation at design point showed that the compressor pressure ratio peaked at an area ratio of 0.792 while the efficiency peaked at a higher value of area ratio of 0.878. Also the increment of the tip clearance from 0 to 1 mm resulted in 20 percent efficiency decrease.

Numerical Study of Supersonic Mixed Compression Air Intake with an Array of Air Jets

2020 ◽  
Author(s):  
Neeraj Kumar Gahlot ◽  
N. K. Singh
Keyword(s):  
Stream Flow ◽  
Numerical Study ◽  
Computational Study ◽  
Pressure Ratio ◽  
Injection Pressure ◽  
Flow Distortion ◽  
Air Jets ◽  
Air Jet ◽  
Air Intake ◽  
Equal Spacing

Abstract Computational study of flow physics inside the mixed compression air intake has been carried out with and without air jets at design Mach number of 2.2. RANS equations were solved with k-? turbulence model by using commercially available software ANSYS. The scope of this research is to improve the flow field inside the air intake and efficiency of supersonic air intake by implementing air jets on the ramp surface. An array of air jets containing two, four and five air jet holes respectively have been made on the ramp surface perpendicular to the flow with equal spacing between them. The injection pressure through air jet has kept constant for all the cases. Flow Distortion and Total pressure recovery were selected to measure the performance of air intake. All the simulations have been performed at a back-pressure ratio of 6. The results obtained suggest that implementation of proper spacing between air jets can improve the performance of air intake due to the mixing of vortices generated by air jets with free stream flow. It is revealed that an array of air jets containing four holes on ramp surface works best and helps in controlling the shock induced separation.

A Survey of Fluidic Thrust Vectoring Nozzle by Numerical Analysis

2013 ◽  
Vol 423-426 ◽  
pp. 1685-1688
Author(s):  
Li Li ◽  
Zhi Hui Shi ◽  
Tsutomu Saito
Keyword(s):  
Deflection Angle ◽  
Stokes Equations ◽  
Pressure Ratio ◽  
Injection Pressure ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Thrust Vectoring ◽  
Numerical Investigations ◽  
The Deflection Angle ◽  
Fluidic Thrust Vectoring

Numerical investigations are conducted to simulate the flow field of a 2D converging-diverging nozzle, for fluidic thrust vectoring. The numerical simulation of nozzle flow is carried out with Navier-Stokes equations model. Simulations are done with different primary and secondary jet conditions. The numerical results show that the smaller of the distance between secondary jet and exit, the larger is the thrust deflection angle. As the injection pressure ratio increases, the deflection angle increases followed on the premise of not far between secondary jet port and exit. The parameters play important roles on thrust vectoring capability.

Experimental and Computational Investigation of the Time-Averaged and Time-Resolved Pressure Loading on a Vaneless Counter-Rotating Turbine

2000 ◽  
Author(s):  
C. W. Haldeman ◽  
M. G. Dunn ◽  
R. S. Abhari ◽  
P. D. Johnson ◽  
X. A. Montesdeoca
Keyword(s):  
Experimental Data ◽  
High Pressure ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Low Pressure ◽  
Navier Stokes ◽  
Experimental Program ◽  
Time Resolved ◽  
Design Point ◽  
High Pressure Ratio

The experimental program reported here was executed using full-scale vaneless counter-rotating engine hardware operating at nondimensionally scaled aerodynamic design point conditions. Measurements were obtained for three different pressure ratio values: design point, low pressure ratio, and high pressure ratio. For brevity, only the design point data will be presented in this paper. Time-averaged and time-resolved surface pressures on the high pressure turbine (HPT) vane, HPT blade, and low pressure turbine (LPT) blades are presented. Additionally, three-dimensional (3D) Navier-Stokes computational fluid dynamics (CFD) predictions are presented for comparison with experimental data. The results presented show that the predictions qualitatively capture the flowfield physics, but require some additional calibration to fully match experimental data quantitatively.

Numerical study on the effect of injection pressure on high-pressure diesel spray

2020 ◽  
pp. 1-27
Author(s):  
Yong Liang Ong ◽  
Fatemeh Salehi ◽  
Mohammadmahdi Ghiji ◽  
Vikram Garaniya
Keyword(s):  
High Pressure ◽  
Numerical Study ◽  
Injection Pressure ◽  
Diesel Spray
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