Two-dimensional Convergent-divergent Nozzle Research Articles

Carbon dioxide separation from natural gas using a supersonic nozzle

Carbon Dioxide (CO2) is often released in the process of natural gases and is one of greenhouse gases that are being treated as the most troublesome environmental issues. One of the promising ways to economically remove CO2 in natural gas processes is to use the technology of supersonic separation that makes use of non-equilibrium condensation in supersonic swirling flows in convergent-divergent nozzle using wet outlet. In the present study, the mixture of Methane (CH4) and CO2 was considered as natural gas. Two-dimensional convergent–divergent nozzle was employed to produce supersonic swirling flow with non-equilibrium condensation. The Peng–Robinson real gas model was used for the mixture gas. A nucleation equation and a droplet growth equation were incorporated into the governing equations of the compressible Navier–Stokes with the k-ω turbulence closure. The predicted results were verified and validated with existing experimental data. The convergent–divergent nozzle was varied to investigate its effect on the non-equilibrium condensation of CO2 in the mixture flow. The Technique for Order of Preference by Similarity to Ideal Solution method was applied to achieve the optimum case with amounts of wetness (the mass fraction of liquid CO2 to the summation of the mass fraction of liquid and vapor CO2 at the outlet of the nozzle) and kinetic energy. Three locations of wet outlets for the optimum case were analyzed. The results show that an increase in the divergent angle of the nozzle, swirling intensity, and inlet supply pressure results in more nucleation of CO2. However, the enhancement of mole fractions of CO2 decreases the nucleation rate and wetness. The exit wetness from wet outlets was increased with increasing distance from the throat.

Experiments on water vapour condensation within supersonic nozzle flow generated by an impulse tunnel

An impulse facility for analysis of water vapour nozzle flows using both shock tunnel and Ludwieg tube operating modes has been developed and tested at the University of Southern Queensland. Unique high-speed flow visualisation of the water vapour condensation shock has been acquired in the throat region of a nominally two-dimensional convergent-divergent nozzle with a 120 mm2 throat area. This paper presents the facility performance and the time-resolved visualisation results for the nozzle flow, and the results are analysed with the aid of image post-processing tools and quasi-one-dimensional (Q1D) thermodynamic calculations. The experiments have produced qualitative and quantitative data on the flow conditions at four different relative humidity values from 25% to 100%, and over a range of nozzle supply temperatures between 293 K and 343 K. The direct measurement of the pressures and wave speeds within the tunnel resulted in a good agreement with the ideal gas Q1D calculations, particularly for the first incident shocks and expansion waves. Differences progressively increased with the number of reflections, due to the effect of viscous dissipation and the non-ideal end-wall interaction caused by the presence of the nozzle inlet. Moreover, flow visualizations of the location and orientation of both the weak disturbance waves and the condensation shock enabled the investigation of the supersonic water vapour condensation within the nozzle of this impulse facility. Based on these measurements, the nozzle flow downstream of the condensation shock was demonstrated to have a lower Mach number relative to the dry nitrogen flow case. This phenomenon is due to the phase change heat release, which appeared to be more significant when the condensation shock intensity was higher. Although further development of the apparatus is possible, the impulse test-rig configuration that we have developed permits a relatively high flow rate of test gas for a short period of time, leading to significantly reduced operating expenses relative to a continuous flow facility with the same mass flow rate. It is therefore suggested that future studies further improve and test the impulse facility techniques for studying condensation phenomena as a potential alternative to high-power, continuous flow facilities.

Fourier Mode Decomposition of Unsteady Flows in a Single Injection Port Fluidic Thrust Vectoring Nozzle

The flow field structure of a single injection port fluidic thrust vectoring nozzle was studied by introducing secondary flow injection in the expansion section of the two-dimensional convergent-divergent nozzle. To determine the motion characteristics of unsteady flow in a shock-induced fluidic vectoring nozzle, detached eddy simulation was conducted to simulate the three-dimensional flow field, and the flow mechanism in the nozzle was analyzed. Fourier mode decomposition was used to analyze the pressure coefficient on the symmetrical surface of the nozzle. Results show three natural frequencies in the flow field of the shock-induced fluidic vectoring nozzle. The first-order mode corresponding to frequency f1 = 512.8 Hz mainly illustrates the oscillation of shock waves. The second-order mode corresponding to frequency f2 = 2825 Hz illustrates the shedding of vortices. The third-order mode corresponding to frequency f3 = 4650 Hz is similar to the second-order mode; however, the spatial scales of vortices decrease.

CFD simulation analysis of two-dimensional convergent-divergent nozzle

ABSTRACT Computational fluid dynamics is one of the parts of fluid mechanics and calculating numerical methods are solving the various flows of fluid. Two-dimensional models, which is to solve the flow rate of supersonic flow and analyzed the mathematical operations, which has solved the energy equations. This iteration process has analyzed and shown better results of temperature and static pressure, velocity, static temperature. The investigating results showing better temperature and velocity flows. The 2D nozzle line diagram is done in Ansys 14.5 geometry modular and calculated iteration process can be done in fluid flow. The nozzle is done and meshes using automatic method and sizing of different value of the meshing process. In the order to analyzed the Ansys fluent software and solved the flow process of the convergent-divergent iteration nozzle. Standard nozzle equation manually calculated and compared with analyzing the results.

A simple cavitation model for unsteady simulation and its application to cavitating flow in two-dimensional convergent-divergent nozzle

In this paper, a simple cavitation model is developed under the framework of homogeneousone-fluid model, in which the perfect mixture of liquid and vapor phases is assumed. In most of conventional models, the vapor phase is considered as a dispersed phase against the liquid phase as a continuous phase, while in the present model, two extreme conditions are considered: for low void fraction, dispersed vapor bubbles in continuous liquid phase, while for high void fraction, dispersed droplets in continuous vapor phase. The growth of bubbles and droplets are taken into account in the mass transfer between vapor and liquid phases, and are switched according to the local void fraction. The model is applied for the simulation of cavitating flow in a two-dimensional convergent-divergent nozzle, and the result is compared with that using a conventional model. To enhance the unsteadiness of cavitation due to the instability at the cavity interphase, the turbulent shear stress is modified depending upon the continuous phases in combination with the proposed cavitation model, which drastically reduces the turbulent viscosity for high void fraction region. As a result, the unsteadiness of cavitation observed in experiments is well reproduced.

630 二次元超音速ノズルから発生する空力騒音に関する研究

630 二次元超音速ノズルから発生する空力騒音に関する研究

Simulation of truncated ideal contour nozzle separation considering external stream interactions

The multi-block computational approach is used to study the physics of shock and turbulent flow separation in the truncated ideal contour nozzle, considering the jet and external stream interactions. The code employs a fully implicit finite volume, lower—upper symmetric successive overreaction scheme with van Leer flux vector splitting using monotone upstream-centred schemes for conservation law technique to get a higher-order spatial accuracy for the total variation diminishing property. Several combustion-chamber-to-ambient pressure ratios at surrounding Mach range from 0.5 to 1.2 for both cold and hot gases are investigated to study their effects on the wall pressure, the separation point, and the thrust force. It is observed that although the flight Mach number and ambient pressure decrements delay the separation and raise the specific impulse, the combustion chamber temperature has a reverse effect on the separation point. Crisscrossing (or diamond-shaped) shock waves in the supersonic exit jet enforce the compressible flow properties to oscillate because of the external jet and ambient flow interactions. These oscillations are damped effectively by viscous and turbulent dissipations as one goes farther from the jet centreline and/or moves downstream. The position of separation point, oblique shock, and lambda shock structure angles are compared rigorously with experimental data of a two-dimensional convergent—divergent nozzle, and reasonable agreements are achieved.

On the Characteristics of Bubble Flow with Low Void Fraction in a Two-Dimensional Convergent-Divergent Nozzle

On the Characteristics of Bubble Flow with Low Void Fraction in a Two-Dimensional Convergent-Divergent Nozzle

Subsonic/supersonic aeropropulsive characteristics of nonaxisymmetric nozzles installed on an F-18 model

The Langley Research Center has conducted an experimental program on a model of the F-18 airplane to determine the performance of nonaxisymmetr ic nozzles relative to the aircraft's baseline axisymmetric nozzle at Mach numbers from 0.60 to 2.20. The performance of a two-dimensional convergent-divergent nozzle, a single expansion ramp nozzle (ADEN), and a wedge nozzle were compared to the baseline axisymmetric nozzles. The nonaxisymmetric nozzle did not have these capabilities. The comparisons presented here are for the nozzles in their full forward thrust mode and for the aircraft at zero angle of attack. The results demonstrate that nonaxisymmetric nozzles can be installed on a close-spaced twin-engine fighter with equal or higher performance than the axisymmetric nozzle over the range of Mach numbers tested.

Influence of free-stream turbulence intensity on heat transfer in the two-dimensional turbulent boundary layer of an accelerated compressible flow

For the accelerated compressible flow in a two-dimensional convergent-divergent nozzle the influence of free-stream turbulence on heat transfer in the turbulent boundary layer has been investigated empirically. The turbulence intensity varied from nearly zero to about 20%, the nozzle entrance Reynolds number reached up to about 10 7. The experimental set-up and the turbulence measurement technique are carefully described. For three different loading cases the measured data of free-stream turbulence intensity and fluctuation are given along the nozzle axial length as well as the local Stanton number in comparison to those of accelerated flow without free stream turbulence. For low Reynolds numbers ( Re x < 10 6) no clear change of heat transfer has been observed, while for Re x < 10 6 a weak and nearly linear dependency of Stanton number on free-stream turbulence intensity can be pointed out.

Performance Characteristics of Nonaxisymmetric Nozzles Installed on an F-18 Propulsion Model

The Langley Research Center has conducted an experimental program on a model of the F-18 airplane to determine the performance of nonaxisymmetr ic nozzles relative to the aircraft's baseline axisymmetric nozzle. The performance of a single-expansion ramp and a two-dimensional convergent-div ergent nozzle were compared to the baseline axisymmetric nozzles. The effects of vectoring and reversing were also studied. The results of this investigation indicate that nonaxisymmetric nozzles can be installed on a twin-engine fighter airplane with equal or better performance than axisymmetric nozzles. The nonaxisymmetric nozzles also offer potential for innovative and improved aircraft maneuver through thrust vectoring and reversing.

Experimental and Theoretical Studies of Two-Dimensional Fixed-Type Cavities

Theoretical and experimental studies have been made of the growth and collapse of fixed cavities in a two-dimensional convergent-divergent nozzle. In this particular configuration an important feature was a re-entrant liquid jet which invaded the growing cavity from the downstream end, travelling upstream along the wall and interrupting the cavity when it reached the nozzle throat. A simple two-dimensional unsteady potential flow theory, developed to model the cycle, gave reasonable agreement with cinephotography and predicted the jet behavior. Because vaporization was neglected the theory overestimated the speed of the cycle.