Effect Of Non-equilibrium Condensation Research Articles

Characteristics of non-equilibrium condensing flow in three-dimensional supersonic rectangular nozzles

Abstract Fluid flow inside a supersonic nozzle with a rectangular cross-section induces secondary flow due to the shape of the upper wall curvature. The secondary flow forms longitudinal vortices near the wall of the nozzle corner which destabilizes the nozzle outlet flow due to the early transition of the flow from laminar to turbulent. It is known that non-equilibrium homogeneous condensation occurs in a supersonic rectangular nozzle due to the rapid expansion of the condensable fluid with large latent heat such as water vapor. Homogeneous condensation takes place through the formation of water nuclei from its vapor when foreign nuclei are absent in the flow. The irreversibility of the non-equilibrium condensation process causes loss in flow transportation energy in the form of total pressure loss. Although numerous researches have been conducted about the effect of non-equilibrium condensation process in supersonic nozzles, however, the interactions between nozzle shape, non-equilibrium condensation, and longitudinal vortices have not been studied convincingly. Therefore, numerical simulations have been carried out for two supersonic three-dimensional rectangular nozzles in order to understand the effect of nozzle shape and non-equilibrium condensation on the longitudinal vortices at the nozzle corner. Furthermore, total pressure distribution in the nozzle was analysed to understand the effect of degree of supersaturation and expansion rate on the total pressure loss. In this research, characteristics of simulated flow fields including total pressure loss were in good agreement with the published literature.

Effects of non-equilibrium condensation on aerodynamics of the flow field in a steam turbine cascade

In the present paper an in-house CFD code is developed using Roe scheme to simulate condensing two-phase flow in blade to blade passage of a steam turbine. Effects of condensation on the flow field of steam turbine rotor tip section are investigated for different outlet pressures. Firstly, comparison is performed between results of wet and dry cases. Then effects of outlet pressure variations on the flow field are studied. Finally effects of condensation on different specifications of the flow field (total pressure loss coefficient, entropy generation and deviation angle) are investigated. Also the mechanism of flow deviation in the cascade flow field is described. Condensation has a great influence on the behavior of the flow field based on the numerical results of this paper. It changes the outflow direction and consequently the flow entering to the next blade deviates from its on-design condition, thus additional losses are produced. For example, the value of deviation angle reaches to 7.62for wet case and exit Mach number Me=1.45. Also there are stagnation pressure loss and entropy generation due to non-equilibrium condensation that reduce the efficiency of the steam turbine

Effects of Non-Equilibrium Condensation on Deviation Angle and Performance Losses in Wet Steam Turbines

Effects of Non-Equilibrium Condensation on Deviation Angle and Performance Losses in Wet Steam Turbines

Effects of non-equilibrium condensation on deviation angle and efficiency in a steam turbine stage

In this paper, the AUSM-van Leer hybrid scheme is extended to solve the governing equations of two-phase transonic flow in a steam turbine stage. The dominant solver of the computational domain is the non-diffusive AUSM scheme (1993), while a smooth transition from AUSM in regions with large gradients to the diffusive scheme by van Leer (1979) guarantees a robust hybrid scheme throughout the domain. The steam is assumed to obey non-equilibrium thermodynamic model. The effects of condensation on different specifications of the flow field are studied at subsonic/supersonic flow regimes. It is observed that as a result of condensation, the aerothermodymics of the flow field changes. For example in supersonic wet case (Pb = 14.55 kPa), pressure loss coefficient of rotor and total entropy generation are, respectively, 77% and 29% more than those in dry conditions. Also the value of rotor deviation angle reaches 6.27° in wet case and Pb = 14.55 kPa.

D-09 超音速矩形ノズル流れに及ぼす非平衡凝縮の影響

D-09 超音速矩形ノズル流れに及ぼす非平衡凝縮の影響

The effect of non-equilibrium condensation on the coefficients of force with the angle of attack in the transonic airfoil flow of NACA0012

A transonic flow with a non-equilibrium condensation past NACA0012 profile whose aspect ratio AR is 1.0 with the angle of attack was analyzed by numerical analysis using a TVD scheme, and investigated using an intermittent indraft type supersonic wind tunnel. Transonic flows of 0.70–0.90 in free stream Mach number with variations of Φ0 and α were tested. For the same M∞ and α, the increase in stagnation relative humidity Φ0 caused a decrease in the drag coefficient of profile (that is total) which is composed of the components of form, viscous, wave and condensation; however, the lift coefficient up to Φ0 = 50% increased in the opposite direction. As an example, in the case of M∞ = 0.83, Φ0 = 50%, α = 3○ and T0 = 298 K, the decreasing rate of the coefficient of profile drag and the increasing rate of the lift coefficient compared to the case of Φ0 = 0% caused by non-equilibrium condensation amounted to 65% and 52%, respectively. In addition, for the same Φ0 and α, as the free stream Mach number M∞ increased, at first, the lift coefficient increased slightly, and then suddenly severely dropped, and finally remained nearly constant. The suddenly dropped free stream Mach number in CL became larger with an increase of Φ0. It turned out that the drag coefficients of form and viscous were almost independent of Φ0. The contribution of wave drag to the coefficient of profile drag for M∞ = 0.83, Φ0 = 30%, α = 3° and T0 = 298 K amounted to approximately 79%, and in the case of Φ0 = 60%, the contribution of the non-equilibrium condensation to the reduction in the coefficient of the profile drag compared to the case without condensation amounted to 75%. Especially, for the case of Φ0 = 0% and α = 0°, there was an oscillatory flow region around M∞ = 0.87.

NUMERICAL ANALYSIS OF IDEALLY-EXPANDED SUPERSONIC JETS WITH NONEQUILIBRIUM HOMOGENEOUS CONDENSATION

Steam or moist air is used as working gas in a wide range of engineering applications of supersonic jets. In these cases, nonequilibrium homogeneous condensation may occur at the downstream of nozzle throat. The surrounding gas will be heated by the release of latent heat of condensation, and may results a change in the flowfield. The present report will describe numerical investigations predicting the effect of nonequilibrium condensation on the flow characteristics of ideally-expanded supersonic free jets. A TVD numerical method is applied to solve RANS and droplet growth equations. The predicted results are compared with the experimental data.

Effect of Non-Equilibrium Condensation in Shear Layer on Supersonic Impinging Jets

Abstract Impinging jet on a solid surface can be found in various engineering applications. In the flow fields, the characteristics of impinging jet are generally found to become complex extremely. In various industrial jet technologies such as jet burner, steam turbine and so on, condensable gas is often used as working gas. In these cases, the non-equilibrium condensation may occur at the region between nozzle exit and an object. On the other hand, in reality, there is a variety of engineering applications for discharge of the dry air into the atmosphere with moisture. In this case, non-equilibrium condensation may occur in the shear layer and affect the jet structure or energy loss in the flow field. However, the feature of non-equilibrium condensing flow in the jet shear layer are not investigated so far satisfactorily. In the present study, the effect of local occurrence of non-equilibrium condensation in shear layer on the characteristics of an under-expanded supersonic impinging jet was investigated numerically. As a result, non-equilibrium condensation occurred in shear layer and increased the displacement thickness on flat plate.

Transonic moist air flow around a circular arc blade with bump

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vibration. In recent years, the effect of bump wall on the flow field around an airfoil has been investigated experimentally and as a result, it was observed that the bump wall is effective for the control of shock wave on the airfoil. In the transonic or supersonic flow field, a rapid expansion of moist air or steam gives rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation around a circular arc blade with or without a bump on the blade was investigated numerically. The results showed that the non-equilibrium condensation significantly reduced the flow field unsteadiness such as root mean of pressure oscillation and frequency compared to the case without the non-equilibrium condensation.

A study on the flow with nonequilibrium condensation in a minimum length nozzle

As recognized previously, a minimum-length nozzle has the smallest possible throat-to-exit length that is still capable of maintaining uniform supersonic flow at the nozzle exit. In the present study, for the flow of moist air through a nearly minimum-length nozzle designed by the method of characteristics, the effects of nonequilibrium condensation on the uniformity of flow properties, the momentum efflux, and the flow distortion at the nozzle exit plane are discussed by experiment and numerical analysis of a third-order Total Variation Diminishing (TVD) finite difference scheme. The onset and zone of nonequilibrium condensation in a minimum-length nozzle are quite different from those of a general convergent-divergent supersonic nozzle. We know that the uniformity of flow properties at the nozzle exit with regard to the flow with nonequilibrium condensation in a minimum-length nozzle cannot be guaranteed. On the other hand, owing to the positions of the onset of condensation at the incident region of expansion waves from the sharp corner just downstream of the nozzle throat, the deceleration gradient and magnitude of heat released from the process of nonequilibrium condensation to the surrounding of ϕ0=60% are greater than those of ϕ0=70% in the case of T0=290K. Furthermore, it has been determined that the decrease in efflux of momentum from the nozzle exit for the stagnation relative humidity of ϕ0=70%(T0=290K), which corresponds to the case with nonequilibrium condensation shock, is 6.8% smaller than that of isentropic expansion.

Effect of non-equilibrium condensation of moist air on unsteady behaviour of shock waves around a circular arc blade

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this often causes serious problems such as the aeroacoustic noise, the vibration. In the transonic or supersonic flow where vapour is contained in the main flow, the rapid expansion of the flow may give rise to a non-equilibrium condensation. However, the effect of non-equilibrium condensation on the transonic internal flows around the airfoil has not yet been clarified satisfactorily. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation on a circular arc blade was investigated numerically. The results showed that in the case with non-equilibrium condensation, frequencies of the flow oscillation became smaller than those without the non-equilibrium condensation.

The effect of non-equilibrium condensation on supersonic air flows over rectangular cavities

Numerical simulations have been carried out for a supersonic two-dimensional flow over open, rectangular cavities (length-to-depth ratios are L/D = 1.0 and 3.0) in order to investigate the effect of non-equilibrium condensation of moist air on supersonic internal flows around the cavity for the flow Mach number 1.83 at the cavity entrance. In the present computational investigation, a condensing flow was produced by an expansion of moist air in a Laval nozzle. The computational results showed that the upstream traveling compression waves become weaker than those without the condensation. Consequently, the weaker compression waves cannot excite the shear layer strongly and amplitudes of oscillation in the cavity became smaller than those without the condensation. The occurrence of the non-equilibrium condensation in case of L/D = 1.0 affected strongly the amplitude and frequency of oscillation in the cavity compared with L/D = 3.0.

부족팽창 습공기제트에 관한 수치해석적 연구

The under-expanded jet discharged from a nozzle or an orifice has been extensively employed in industrial applications and aerospace technologies. A number of studies have been made to investigate the under-expanded jet structures such as Mach disk, barrel shock wave, jet boundary configuration, etc. In the current study, a computational work is performed to investigate the effect of non-equilibrium condensation of moist air on the under-expanded jet, which is discharged from a sonic nozzle. The results obtained are compared with an available experimental data. It is found that non-equilibrium condensation of moist air alleviates the oscillations of the under-expanded jet, and can increase Mach disk diameter, without changing the location.

オリフィスを有する管内非定常流れに及ぼす非平衡凝縮の影響(S26-2 高速流れと衝撃波現象の基礎と応用その2,S26 高速流れと衝撃波現象の基礎と応用)

オリフィスを有する管内非定常流れに及ぼす非平衡凝縮の影響(S26-2 高速流れと衝撃波現象の基礎と応用その2,S26 高速流れと衝撃波現象の基礎と応用)

オリフィスを有する管内流れに及ぼす非平衡凝縮の影響(OS3-1高速流れと衝撃波現象(その1))

オリフィスを有する管内流れに及ぼす非平衡凝縮の影響(OS3-1高速流れと衝撃波現象(その1))

417 ルトビーク管内流れに及ぼす湿り空気の非平衡凝縮の影響(O.S.4-5 凝縮相を伴う圧縮性流れ)(O.S.4 圧縮性流れ・衝撃波)

417 ルトビーク管内流れに及ぼす湿り空気の非平衡凝縮の影響(O.S.4-5 凝縮相を伴う圧縮性流れ)(O.S.4 圧縮性流れ・衝撃波)

Effect of nonequilibrium condensation of moist air on transonic flow fields

When condensation occurs in a supersonic flow field, the flow is affected by the latent heat released. In the present study, a condensing flow was produced by an expansion of moist air in nozzle with circular bump models and shock waves occurred in the supersonic parts of the flow fields. The experimental investigations were carried out to show the effects of initial conditions in the reservoir and nozzle geometries on the shock wave characteristics and the turbulences in the flow fields. Furthermore, in order to clarify the effect of condensation on the flow fields with shock waves, Navier-Stokes equations were solved numerically using a 3rd-order MUSCL type TVD finite-difference scheme with a second order fractional step for time integration. As a result, the effect of condensation on the aspect of flow field has been clarified.

115 湿り空気の非平衡凝縮が後流に及ぼす影響

115 湿り空気の非平衡凝縮が後流に及ぼす影響

湿り空気の非平衡凝縮が遷音速流れ場に及ぼす影響

湿り空気の非平衡凝縮が遷音速流れ場に及ぼす影響