Comparisons of Initially Turbulent, Low-Velocity-Ratio Circular and Square Coaxial Jets

AIAA Journal ◽  
2003 ◽  
Vol 41 (2) ◽  
pp. 230-239 ◽  
Author(s):  
Dimitris E. Nikitopoulos ◽  
Jason W. Bitting ◽  
Sivaram Gogineni
Keyword(s):  
Velocity Ratio ◽  
Low Velocity ◽  
Coaxial Jets

A Numerical Study of Inlet Geometry for a Low Inertia Mixed Flow Turbocharger Turbine

2014 ◽  
Author(s):  
Thomas M. Leonard ◽  
Stephen Spence ◽  
Juliana Early ◽  
Dietmar Filsinger
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Cone Angle ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transient Performance ◽  
Blade Angle ◽  
Low Velocity ◽  
Mixed Flow

Mixed flow turbines can offer improvements over typical radial turbines used in automotive turbochargers, with regards to transient performance and low velocity ratio efficiency. Turbine rotor mass dominates the rotating inertia of the turbocharger, and any reductions of mass in the outer radii of the wheel, including the rotor back-disk, can significantly reduce this inertia and improve the acceleration of the assembly. Off-design, low velocity ratio conditions are typified by highly tangential flow at the rotor inlet and a non-zero inlet blade angle is preferred for such operating conditions. This is achievable in a Mixed Flow Turbine without increasing bending stresses within the rotor blade, which is beneficial in high speed and high inlet temperature turbine design. A range of mixed flow turbine rotors was designed with varying cone angle and inlet blade angle and each was assessed at a number of operating points. These rotors were based on an existing radial flow turbine, and both the hub and shroud contours and exducer geometry were maintained. The inertia of each rotor was also considered. The results indicated that there was a trade-off between efficiency and inertia for the rotors and certain designs may be beneficial for the transient performance of downsized, turbocharged engines.

Effect of Velocity Ratio on Noise Source Distribution of Coaxial Jets

AIAA Journal ◽  
2010 ◽  
Vol 48 (7) ◽  
pp. 1504-1512 ◽  
Author(s):  
Dimitri Papamoschou ◽  
Sara Rostamimonjezi
Keyword(s):  
Noise Source ◽  
Velocity Ratio ◽  
Source Distribution ◽  
Coaxial Jets

Influence of Inlet Velocity Ratio on the Outlet Flow Uniformity of a Fan-Shaped Film Cooling Hole

2009 ◽  
Author(s):  
James S. Porter ◽  
Alan D. Henderson ◽  
Gregory J. Walker
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Velocity Ratio ◽  
Internal Flow ◽  
Experimental Investigations ◽  
Low Velocity ◽  
Inlet Velocity ◽  
Cooling Hole ◽  
Outlet Flow ◽  
Inlet Conditions

Literature regarding the influence of inlet conditions on cooling hole flows is reviewed. A general failure to fully quantify inlet conditions and an inconsistent terminology for describing them is noted. This paper argues for use of an inlet velocity ratio (IVR) defined as the ratio of the coolant passage velocity to the jet velocity, together with additional parameters required to define the velocity distribution in the coolant supply passage. Large scale experimental investigations of the internal flow field for a laterally expanded 50 times scale fan-shaped hole are presented, together with a computational investigation of the flow, for three inlet velocity ratios. Inlet lip separation causes a jetting effect that extends throughout the length of the cooling hole. A low velocity region of separated fluid exists on the downstream wall of the diffuser which deflects the jetting fluid towards the upstream side of the hole. This effect is most pronounced at low IVR values. The exit velocity profiles and turbulence distributions are highly dependent on the IVR.

Heat Transfer Characteristics of Non-Uniform Flow Around a Circular Cylinder in a T-Junction Duct

2020 ◽  
Author(s):  
Xiaoyu Wang ◽  
Di Qi ◽  
Tong Li ◽  
Mei Lin ◽  
Hanbing Ke ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Velocity Ratio ◽  
Correlation Coefficients ◽  
Heat Transfer Characteristics ◽  
Low Velocity ◽  
Stagnation Points ◽  
Transfer Characteristics ◽  
Low Speed Wind Tunnel ◽  
Straight Duct

Abstract Heat transfer characteristics of a circular cylinder in the branch of a T-junction are experimentally investigated in a low-speed wind tunnel with Reynolds number of Rec = 9163. Local and average heat transfer distributions around the circular cylinder are obtained for the cylinder positions from x/Dh=0.5 to 13 and the velocity ratios from 0.117 to 0.614. It is found that the overall heat transfer characteristics in a T-junction duct at high velocity ratio are lower than those at low velocity ratio, and both are higher than those in the straight duct. The local Nusselt number in the T-junction duct is asymmetrical distribution and weakens with increasing velocity ratios and positions of the cylinder. The angles of the front and rear stagnation points in the T-junction duct are the same as those in the straight duct at certain velocity ratio and/or position of the cylinder. However, the angles of the front and rear separation points in the T-junction duct do not match those in the straight duct. Both the heat transfer correlation coefficients and the amplitude ratios increase with increasing positions of the circular cylinder and velocity ratios.

Flow Characteristics of Swirling Coaxial Jets From Divergent Nozzles

1987 ◽  
Vol 109 (3) ◽  
pp. 275-282 ◽  
Author(s):  
T. Mahmud ◽  
J. S. Truelove ◽  
T. F. Wall
Keyword(s):  
Bituminous Coal ◽  
Static Pressure ◽  
Reverse Flow ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Flow Zone ◽  
Mean Velocity ◽  
Coaxial Jets ◽  
Mass Flowrate

The aerodynamic characteristics of free, swirling, coaxial jets issuing from an air model of a typical burner for pulverized bituminous coal have been studied. Detailed measurements of mean velocity and static pressure have been obtained in the region near the nozzle exit. The boundary of the reverse-flow zone has been mapped and the recirculated-mass flowrate measured in order to quantify the effects of velocity ratio and swirl in the primary and secondary jets. The influence of burner geometry (divergent-nozzle length and centre-line blockage) has also been studied. The type of flow pattern is found to depend upon the level of swirl in the primary and secondary jets. The recirculated-mass flowrate is predominantly influenced by secondary swirl. The measurements have been compared with predictions obtained by numerical solution of the governing conservation equations in orthogonal curvilinear co-ordinates. The general features of the flows are adequately predicted although discrepancies in detail seem to indicate deficiencies in the turbulence model.

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