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

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.

Efflux velocity of oligomers of various viscosity

The efflux velocity of oligomers based on carbamide-phenol formaldehyde resins plays a significant role in the manufacture of various types of glued materials, especially laminated beams for housing construction. The efflux velocity of carbamide-phenol formaldehyde oligomer was studied in the context of laminated timber technology.

Optimal Configuration Selection Through Experimental Tests on Branched Heat Exchanger With R134 Organic Fluid

The aim of this work the analysis of compact branched heat exchangers, by measuring thermal efficiency and the pressure drop in several experimental tests. Three different heat exchanger configuration have been considered. In the first device, the constant efflux velocity, in the internal channels, was imposed. The second exchanger was realized by imposing constant the value of the Reynolds number. The last device was created according to the instructions of the constructal theory. All three exchangers are aluminum made. In addition, in order to have a more detailed knowledge of the phenomenon and to identify what are the parameters that govern heat transfer, an organic fluid has been used and tested. In our case R1234 organic fluid. It was therefore necessary to realize an appropriate test bench for the use of the organic fluid. Once realized, several tests were conducted. Finally in order to be able to indicate which configuration results the optimal one, the Prandtl and Nusselt numbers were obtained and compared.

Features of the Round Hydrogen Microjet Combustion in a Coaxial Jet of the Air and Nanopouder Mixture

Results of the experimental studies of a round hydrogen microjet combustion in a coaxinal jet of air and SiO2 nanopouder mixture efflux from a slot-hole (multinozzle) coaxial nozzle at subsonic and supersonic efflux velocity are presented. It is shown that scenarios of a hydrogen microjet combustion in a coaxinal jet of air and nanopouder mixture are similar to scenarios of diffusion combustion of a hydrogen microjet at subsonic and supersonic efflux velocity. Existence of “bottleneck flame region” is revealed at subsonic and a flame separation from a nozzle exit at supersonic efflux velocity. It is found that with efflux velocity growth of jets it is possible to observe intensification of the luminescence of the flame at the boundary between the jet of hydrogen and air / nanopowder mixture and existence of «bottleneck flame region» as in a laminar coaxial jet and in a flame of a hydrogen microjet combustion. On the other hand, it is possible to observe actually disappearance of the «bottleneck flame region» at approach to transonic efflux velocity.

Features of the Round Hydrogen Microjet Combustion in a Coaxial Air Jet

Results of experimental studies of features of the round hydrogen microjet combustion in a coaxial air jet are presented in this work. It is shown that the combustion scenario is connected with existence of the «bottleneck flame region». This fact correlates with the similar scenarios of the diffusion hydrogen microjet combustion at subsonic efflux velocity investigated by us earlier. It is revealed that the spherical shape of the “bottleneck flame region” is transformed to a cylindrical shape. It is found that the round hydrogen microjet combustion in a coaxial air jet at supersonic efflux velocity is accompanied by existence of supersonic cells both in a hydrogen microjet and in a wake of coaxial air jet. Round hydrogen microjet supersonic combustion in a coaxial air jet is connected with a flame separation from a nozzle exit.

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

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.

Verification of Torricelli’s Efflux Equation with the Analytical Momentum Equation and with Numerical CFD Computations

The efflux velocity equation from Torricelli is well known in fluid mechanics. It can be derived analytically applying Bernoulli’s equation. Bernoulli’s equation is obtained integrating the momentum equation on a stream line. For verification purposes the efflux velocity for a large tank or vessel was also computed analytically applying the momentum equation, delivering, however, a different result as the Torricelli equation. In order to validate these theoretical results the vertical and the horizontal efflux velocity case was simulated with computational fluid dynamics CFD. Furthermore, simple experiments for the horizontal and vertical efflux equation were performed.

Influence Of Initial Conditions At The Micro Nozzle Exit On Hydrogen Diffusion Combustion

The purpose of the given work will consist in an experimental study of influence of initial conditions at the micro nozzle exit on hydrogen diffusion combustion. It is shown, that the mean velocity profile and presence/absence of a heatcapacious material at the nozzle exit play an essential role on a flame structure and process of a round hydrogen microjet combustion. Velocity ranges of existence of a round hydrogen microjet diffusion combustion, flame separation and «bottleneck flame» region for a case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are found. Dependences of the «bottleneck flame» region size from a hydrogen microjet efflux velocity for case of a top – hat mean velocity profile at the nozzle and two cases of a parabolic mean velocity profile with presence/absence of a heatcapacious material at the nozzle exit are shown. Decrements of reduction of the «bottleneck flame» region size with growth of the hydrogen microjet efflux velocity for three situations of changes of initial conditions at the nozzle exit are determined.