scholarly journals Flow visualization and analytical study on the exhaust gas diffusion of a frigate

Pomorstvo ◽  
2021 ◽  
Vol 35 (2) ◽  
pp. 308-317
Author(s):  
Erinc Dobrucali
Keyword(s):  
Flow Visualization ◽  
Analytical Study ◽  
Velocity Ratio ◽  
Gas Diffusion ◽  
Exhaust Gas ◽  
Plume Height ◽  
Low Velocity ◽  
Smoke Dispersion ◽  
Yaw Angle ◽  
Efflux Velocity

Wind tunnel flow visualization tests were conducted to analyse the efflux velocity impacts and the yaw angle on the smoke dispersion of the exhaust for a generic frigate. An analytical study was also implemented to obtain the exhaust plume trajectories. The 1/100 scale generic frigate, having a platform for helicopters on the aft of the ship, was built and employed during the experimental study. The forward and astern cruises of the frigate were considered. It is found that the plume height and the exhaust gases momentum increase with the velocity ratio. The problem of smoke nuisance was observed for the ratios with low velocity such as K=0.2. The plume was also directed towards the helicopter platform when the yaw angles are higher than 10°. The experimental results are compared with the analytical solutions for three different velocity ratios. The compliance between the experimental and analytical results is found to be consistent.

An investigation of exhaust smoke dispersion for a generic frigate by numerical analysis and experiment

2017 ◽  
Vol 233 (1) ◽  
pp. 310-324
Author(s):  
Erinc Dobrucali ◽  
Selma Ergin
Keyword(s):  
Velocity Ratio ◽  
Plume Height ◽  
Operation Condition ◽  
Conservation Of Energy ◽  
Operational Conditions ◽  
Smoke Dispersion ◽  
High Turbulence ◽  
Height Increase ◽  
Volume Method ◽  
Efflux Velocity

The effects of efflux velocity, operational conditions, stack geometry, and buoyancy on the exhaust dispersion for a generic frigate are investigated numerically. The conservation of energy, momentum, mass, species, and turbulence equations have been solved using the finite volume method. It is found that the exhaust smoke dispersion is affected by the efflux velocity, operational conditions, buoyancy, and turbulence, as well as the geometry of the stack. The momentum of the exhaust gases and the plume height increase as the velocity ratio increases. The results for the slow ahead operation condition show that the buoyancy effect is the strongest, and the plume height is minimum for this case. The exhaust temperatures and velocity values for the full ahead operation are found to be the highest. However, the plume height for this case is not maximum. This may be attributed to the high turbulence levels for this case. It is found that the effect of stack geometry on the exhaust smoke dispersion is not significant for the geometries considered in the study. The computations are validated with the flow visualization tests carried out in a wind tunnel. The agreement between the numerical and experimental results is found to be good.

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

Increasing Pulse Energy Recovery of Radial Turbocharger Turbines by 3D Inverse Design Method

2015 ◽  
Author(s):  
Jiangnan Zhang ◽  
Mehrdad Zangeneh
Keyword(s):  
Mechanical Performance ◽  
Design Method ◽  
Velocity Ratio ◽  
Inverse Design ◽  
Speed Ratio ◽  
Exhaust Gas ◽  
Peak Efficiency ◽  
Static Efficiency ◽  
Stage Performance ◽  
Inverse Design Method

Most radial turbines have a peak efficiency at around U/Cis (velocity ratio or jet speed ratio) of 0.7. It is a well-known fact that it is beneficial for radial turbocharger turbines to have a higher efficiency at low U/Cis region, since the pulsating engine exhaust gas at low U/Cis region (with high pressure and temperature) carries more energy compared to that at high U/Cis region (with low pressure and temperature). The improvement of Total to Static efficiency at low U/Cis region will help the turbine extract more energy from the exhaust gas and thereby increase the turbine cycle-averaged Total to Static efficiency. In the past there has been some attempts to move the peak U/Cis to lower values by using conventional or direct design approach on mixed flow impellers. But this approach usually results in reduction of stage performance. In this paper, a methodology is presented to control and move the radial turbine peak efficiency U/Cis to lower values by using a 3D inverse design method. The stage performance is measured by using steady CFD analysis. Furthermore detailed stress and vibration analysis are presented on the mechanical performance of the new design.

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.

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.

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