Flow Conditions near the Intersection of a Shock Wave with Solid Boundary

2012 ◽  
pp. 473-478
Author(s):  
Hsue-shen Tsien
Keyword(s):  
Shock Wave ◽  
Solid Boundary ◽  
Flow Conditions

Investigation on the flow characteristics of a VNT turbine under pulsating flow conditions

2017 ◽  
Vol 233 (2) ◽  
pp. 396-412 ◽  
Author(s):  
Mingxu Qi ◽  
Xinguo Lei ◽  
Zhen Wang ◽  
Chaochen Ma
Keyword(s):  
Shock Wave ◽  
Rotor Blade ◽  
Strong Influence ◽  
Flow Characteristics ◽  
Turbine Rotor ◽  
Pulsating Flow ◽  
Flow Conditions ◽  
Turbine Performance ◽  
Turbine Inlet ◽  
Excitation Force

The turbines used in turbochargers naturally experience unsteadiness caused by inlet pulsating flow conditions and stator–rotor interaction. The unsteadiness has an influence on turbine performance. Meanwhile, under certain small-nozzle opening conditions, strong shock waves can be generated. The synergistic effect of turbine inlet pulsation and shock waves has a significant influence on the turbine performance, rotor blade loading as well as the excitation force exerted on the turbine rotor, which is responsible for turbine rotor high cycle fatigue. In order to understand the influence of pulsating flows on turbine performance and the shock wave characteristic at nozzle trailing edge as well as the incidence angle characteristic of the rotor blade, unsteady numerical simulations were performed to investigate the effect of pulsating flow conditions on the performance, flow characteristics in frequency domain and shock wave behavior in a variable nozzle turbine. The results indicate that the turbine inlet pressure pulsation has strong influence on the turbine performances. Meanwhile, the turbine inlet pulsation flow has a strong influence on the intensity of the shock wave and clearance leakage flow in the nozzle, which causes significant flow losses in the turbine. In addition, at the turbine rotor inlet, the unsteadiness caused by the turbine inlet pulsation varies significantly along the circumferential direction and spanwise. Up to two-thirds of the unsteadiness caused by the turbine inlet pulsation dissipates before entering the rotor due to the flow dissipation and mixing process along the nozzle streamwise. The excitation force exerted on the rotor blade leading edge caused by the turbine inlet pulsation is about the same level as that caused by the stator–rotor interaction.

Transonic Turbine Vane Endwall Film Cooling Using PSP Measurement Technique

2019 ◽  
Author(s):  
Chao-Cheng Shiau ◽  
Izzet Sahin ◽  
Izhar Ullah ◽  
Je-Chin Han ◽  
Alexander V. Mirzamoghadam ◽  
...  
Keyword(s):  
Shock Wave ◽  
Film Cooling ◽  
Density Ratio ◽  
Cross Flow ◽  
Flow Conditions ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Cooling Flow ◽  
Turbine Vane ◽  
Endwall Film Cooling

Abstract This work focuses on the parametric study of film cooling effectiveness on turbine vane endwall under various flow conditions. The experiments were performed in a five-vane annular sector cascade facility in a blowdown wind tunnel. The controlled exit isentropic Mach numbers were 0.7, 0.9, and 1.0, from high subsonic to transonic conditions. The freestream turbulence intensity is estimated to be 12%. Three coolant-to-mainstream mass flow ratios (MFR) in the range 0.75%, 1.0%, and 1.25% are studied. N2, CO2, and Argon/SF6 mixture were used to investigate the effects of density ratio (DR), ranging from 1.0, 1.5 to 2.0. There are 8 cylindrical holes on the endwall inside the passage. Pressure-sensitive paint (PSP) technique was used to capture the endwall pressure distribution for shock wave visualization and obtain the detailed film cooling effectiveness distributions. Both the high-fidelity effectiveness contour and the laterally (spanwise) averaged effectiveness were measured to quantify the parametric effect. This study will provide the gas turbine designer more insight on how the endwall film cooling effectiveness varies with different cooling flow conditions including shock wave through the endwall cross-flow passage.

Non-Equilibrium Relaxing Gas Flow Behind Three Dimensional Unsteady Curved Shock Wave

1980 ◽  
Vol 35 (11) ◽  
pp. 1166-1170
Author(s):  
V. D. Sharma ◽  
Radhe Shyam
Keyword(s):  
Shock Wave ◽  
Unsteady Flow ◽  
Gas Flow ◽  
Three Dimensional ◽  
Flow Conditions ◽  
Shock Surface ◽  
Flow Parameters ◽  
Upstream Flow ◽  
Relaxing Gas ◽  
Non Equilibrium

Abstract A shock wave is assumed to exist in a three-dimensional unsteady flow of a relaxing gas. The variation of flow parameters at any point behind the shock surface is determined in terms of the shock geometry and the upstream flow conditions. The expressions for the vorticity and the curvature of a streak line at the rear of the shock surface are also determined in terms of the known quantities.

RELAXATION PROCESSES BEHIND THE SHOCK WAVE IN AIR

2020 ◽  
Author(s):  
A. I. Bryzgalov ◽  
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
High Temperature ◽  
Space Missions ◽  
Relaxation Processes ◽  
Flow Conditions ◽  
Chemical Nonequilibrium ◽  
Atmospheric Entry ◽  
Qualitative And Quantitative ◽  
High Enthalpy

This work is relevant to numerical simulation of atmospheric entry phase of space missions and in high enthalpy facilities producting flow conditions close to flight conditions. Such flows are featured by low pressure and high temperature, which induces thermal and chemical nonequilibrium, while calculations with equilibrium assumption give both qualitative and quantitative errors.

scholarly journals SUCTION INLET VORTEX INVESTIGATION AT LOW REYNOLDS NUMBERS

2015 ◽  
Vol 39 (1) ◽  
pp. 115-123
Author(s):  
Wei Hua Ho ◽  
Omar Faruq bin Idris ◽  
Tze How New
Keyword(s):  
Reynolds Number ◽  
High Speed ◽  
Reynolds Numbers ◽  
Solid Boundary ◽  
Jet Engines ◽  
Flow Conditions ◽  
Basic Relationship ◽  
Low Reynolds ◽  
High Reynolds ◽  
Relationship Of

Under certain flow conditions, when an inlet is aspirated in close proximity to a solid boundary, a vortex will form between the surface and the inlet. The formation and ingestion of such vortices could potentially lead to inefficient fluid suction by pumps or catastrophic damages in high-speed jet engines. Previous studies established the basic relationship of such inlet vortices formation threshold and geometry and flow conditions, though they were typically considered at significantly high Reynolds numbers. It remains unclear if there is a lower limit to the Reynolds number at which this phenomenon ceases to exist. This study shows that this phenomenon exists even at low Reynolds number of Re = 160. In particular, the results are generally in agreement with the previously established relationships at much higher Reynolds numbers but certain correlations are not as significant. This suggests that formation of inlet vortices may be less sensitive to Reynolds numbers effects than previously thought.

scholarly journals Shock Waves Asymmetry in a Symmetric Nozzle

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1477 ◽  
Author(s):  
Janusz Telega ◽  
Ryszard Szwaba ◽  
Piotr Doerffer
Keyword(s):  
Shock Wave ◽  
Mach Number ◽  
Opening Angle ◽  
Flow Conditions ◽  
Flow Parameters ◽  
Flow Asymmetry ◽  
Apparent Reason ◽  
Full Symmetry ◽  
The Asymmetry ◽  
Nozzle Opening

The results of the experimental research on the symmetry of supersonic flow in a symmetric convergent-divergent nozzle are presented. The investigations were focused on the fact that for some flow conditions the flow in a precisely symmetric nozzle becomes asymmetric. Starting from a specific value of Mach number, the flow becomes asymmetric in terms of shock wave λ-foot geometry on both sides of a symmetric nozzle. The evolution of the abovementioned asymmetry has been analysed for Mach number value ranging from M = 1.26 to M = 1.59 with the nozzle opening angle of up to 6.5° on each side. The presented results indicate that for the same flow parameters as Mach number and Reynolds number, and for the same geometry of the nozzle, different λ-foot size is formed at each wall. This unexpected behaviour is responsible for the flow asymmetry. Numerical simulations carried out earlier confirm the appearance of shock wave asymmetry. The side in which the asymmetry takes place is accidental, as the full symmetry of simulation mesh and experiment setup was secured. In numerical simulation the asymmetry follows always the same direction. In experiments the direction of asymmetry happens alternatively without any apparent reason. The explanation of the phenomena is provided in this paper.

THERMO-CHEMICAL NONEQUILIBRIUM PHENOMENA OF THE STRONG SHOCK WAVE TO GENERATE HYPERVELOCITY TEST FLOW

2014 ◽  
Vol 34 ◽  
pp. 1460383
Author(s):  
HU ZONG MIN ◽  
WANG CHUN ◽  
JIANG ZONG LIN ◽  
KHOO BOO CHEONG
Keyword(s):  
Shock Wave ◽  
Experimental Study ◽  
Strong Shock ◽  
Strong Shock Wave ◽  
Test Facility ◽  
Flow Conditions ◽  
Expansion Tube ◽  
Chemical Nonequilibrium ◽  
Nonequilibrium Phenomena ◽  
Test Flow

To generate the hypervelocity (above 5 km/s) test flow for the experimental study of reentry physics, a shock-expansion tube or tunnel is the only qualified test facility by far. In such a facility, the working gas shall be compressed by an extremely strong shock wave, e.g., Ms=27.7 for the 8 km/s test condition. Therefore, thermo-chemical nonequilibrium phenomena may occur in the gas post the shock wave. Such phenomena, consequently, can incur difficulties in diagnostic and measurement to experimental study, and instability problems to numerical analysis on the other hand. The present paper will focus on the numeric-aid diagnostics of the flow conditions.

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