Understanding Behavior of Water Droplets in a Transonic Compressor Rotor With Wet Compression

2010 ◽  
Author(s):  
Lanxin Sun ◽  
Qun Zheng ◽  
Mingcong Luo ◽  
Yijin Li ◽  
Rakesh Bhargava
Keyword(s):  
Three Dimensional ◽  
Water Film ◽  
Spanwise Direction ◽  
Blade Surface ◽  
Three Dimensional Flow ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wet Compression ◽  
Wall Interaction

The process of wet compression in an axial compressor is an intricate two-phase flow involving not only heat and mass transfer processes but also droplet breakup and even formation of discontinuous water film on the blade surface and then breaking into droplets. The implementation of practical boundary conditions for water droplets on the blade surface is the key to the proper numerical simulation of the wet compression process. In this paper, the droplets-wall interactions are analyzed using the theory of spray wall impingement through two computational models for an isolated transonic compressor rotor (NASA rotor 37). The Model #1, representing spread phenomenon, assumes that all droplets impacting on the blade are trapped in the water film and subsequently released from its trailing edge and enter the wake region with an equivalent mass flow but bigger in diameter and smaller in number. Whereas, the Model #2, representing splashing phenomenon, assumes that upon impacting on the blade, the droplets will breakup into many smaller ones. The three-dimensional flow simulation results of these two models are analyzed and compared in this paper. The trajectory of droplets for the spread phenomenon clearly showed formation of larger size droplets on the rotor blade’s suction surface near its trailing edge which broke-up into larger number of smaller size droplets. Whereas, in the case of splashing, droplets breakup into many smaller size droplets upon impacting on the blades. The three-dimensional flow field, examined through Mach number and temperature contours, showed that the evaporation was much larger around the blade’s tip region indicated by a larger temperature reduction. The examination of limiting streamlines clearly showed that the wet compression moved shockwave towards blade’s tip region and separation region and vortex region became weaker for a given amount of water injection and for both droplets-wall interaction models. For a given amount of injection flow and downstream of the separation line, the extent of flow reversal region in the spanwise direction and near the blade’s trailing edge are influenced by the type of droplet-wall interaction. Also, the extent of flow reversal region in the spanwise direction reduces with the decrease in the injected droplets size.

On the Behavior of Water Droplets When Moving Onto Blade Surface in a Wet Compression Transonic Compressor

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Lanxin Sun ◽  
Qun Zheng ◽  
Mingcong Luo ◽  
Yijin Li ◽  
Rakesh Bhargava
Keyword(s):  
Computational Models ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Flow Simulation ◽  
Water Film ◽  
Droplet Breakup ◽  
Blade Surface ◽  
Two Phase ◽  
Transonic Compressor ◽  
Wet Compression

The process of wet compression in an axial compressor is an intricate two-phase flow involving not only heat and mass transfer processes but also droplet breakup and even formation of discontinuous water film on the blade surface and then breaking into droplets. In this paper, the droplet-wall interactions are analyzed using the theory of spray wall impingement through two computational models for an isolated transonic compressor rotor (NASA rotor 37). Model 1, representing spread phenomenon, assumes that all droplets impacting on the blade are trapped in the water film and subsequently released from its trailing edge and enter the wake region with an equivalent mass flow but bigger in diameter and smaller in number. Whereas, the model 2, representing splashing phenomenon, assumes that upon impacting on the blade, the droplets will breakup into many smaller ones. The three-dimensional flow simulation results of these two models are analyzed and compared in this paper.

Quantitative Density Visualization in a Transonic Compressor Rotor

1977 ◽  
Vol 99 (3) ◽  
pp. 460-475 ◽  
Author(s):  
A. H. Epstein
Keyword(s):  
Boundary Layer ◽  
Three Dimensional ◽  
Imaging Systems ◽  
Three Dimensional Flow ◽  
Transonic Compressor ◽  
Dimensional Flow ◽  
Compressor Rotor ◽  
Density Maps ◽  
Shock System ◽  
High Work

The flow in a 59-cm dia high work, transonic compressor rotor has been visualized using a fluorescent gas, 2,3, butanedione, as a tracer. The technique allows the three-dimensional flow to be imaged as a set of distinct planes. Quantitative static density maps were obtained by correcting the images for distortion and nonlinearities introduced by the illumination and imaging systems. These images and maps were used to analyze the three-dimensional nature of the blade’s boundary layer and shock system.

An Investigation of the Effect of Cascade Area Ratios on Transonic Compressor Performance

1994 ◽  
Author(s):  
A. R. Wadia ◽  
W. W. Copenhaver
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Area Ratio ◽  
Peak Efficiency ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range ◽  
Boundary Layer Interaction ◽  
Compressor Performance

Transonic compressor rotor performance is highly sensitive to variations in cascade area ratios. This paper reports on the design, experimental evaluation and three-dimensional viscous analysis of four low aspect ratio transonic rotors that demonstrate the effects of cascade throat area, internal contraction and trailing edge effective camber on compressor performance. The cascade throat area study revealed that tight throat margins result in increased high speed efficiency with lower part speed performance. Stall line was also improved slightly over a wide range of speeds with a lower throat-to-upstream capture area ratio. Higher internal contraction, expressed as throat-to-mouth area ratio, also results in increased design point peak efficiency, but again costs performance at the lower speeds. Reducing the trailing edge effective camber expressed as throat-to-exit area ratio, results in an improvement in peak efficiency level without significantly lowering the stall line. Among all four rotors, the best high speed efficiency was obtained by the rotor with tight throat margin and highest internal contraction, but its efficiency was the lowest at part speed. The best compromise between high speed and part speed efficiency was achieved by the rotor with a large throat and a lower trailing edge effective camber. The differences in the shock structure and the shock boundary layer interaction of the four blades was analyzed using a three-dimensional viscous code. The analytical results are used to supplement the data and provide further insight into the detailed physics of the flow field.

Investigation of Water Film Formation on Blade Surfaces of a Wet Compression Transonic Compressor Rotor

2015 ◽  
Author(s):  
Hai Zhang ◽  
Bin Jiang ◽  
Mingcong Luo ◽  
Xiangkun Liu ◽  
Shuangming Fan ◽  
...  
Keyword(s):  
Film Formation ◽  
Water Injection ◽  
Water Film ◽  
Inertia Force ◽  
Blade Surface ◽  
Water Droplets ◽  
Suction Surface ◽  
Transonic Compressor ◽  
Pressure Surface ◽  
Wet Compression

As is known, when water injected at the inlet of the compressor, the water droplets will move onto the blade where water film could form on the blade surface. In this paper, the movement and formation of the water film on a transonic rotor, NASA Rotor 37, are simulated and analyzed by using unsteady numerical methods under different water injecting conditions. The motions of water droplets and flows in the blade passage are presented in detail. Tearing process of water film on the blade surface is also a key point of this research. The preliminary results indicate that the movement of water droplets is tending to deviate from the suction surface and pile on the pressure surface due to the effect of inertia force, and water film could be formed on the pressure surface. Continuity and scope of the water film on the blade surface will develop with the increasing of droplet sizes and water injection rate. Based on the simulation, it is found that more discrete water films are formed on the pressure side of blade when the droplets move onto the pressure surface, tearing phenomenon may occur where the area is of lower water film thickness. Smaller enough sprayed droplet size can not only ensure the compressor performance of wet compression, but also avoid the erosion caused by water film accumulation.

An Investigation of the Effect of Cascade Area Ratios on Transonic Compressor Performance

1996 ◽  
Vol 118 (4) ◽  
pp. 760-770 ◽  
Author(s):  
A. R. Wadia ◽  
W. W. Copenhaver
Keyword(s):  
High Speed ◽  
Three Dimensional ◽  
Area Ratio ◽  
Peak Efficiency ◽  
Trailing Edge ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range ◽  
Compressor Performance ◽  
The Difference

Transonic compressor rotor performance is highly sensitive to variations in cascade area ratios. This paper reports on the design, experimental evaluation, and three-dimensional viscous analysis of four low-aspect-ratio transonic rotors that demonstrate the effects of cascade throat area, internal contraction, and trailing edge effective camber on compressor performance. The cascade throat area study revealed that tight throat margins result in increased high-speed efficiency with lower part-speed performance. Stall line was also improved slightly over a wide range of speeds with a lower throat-to-upstream capture area ratio. Higher internal contraction, expressed as throat-to-mouth area ratio, also results in increased design point peak efficiency, but again costs performance at the lower speeds. Reducing the trailing edge effective camber, expressed as throat-to-exit area ratio, results in an improvement in peak efficiency level without significantly lowering the stall line. Among all four rotors, the best high-speed efficiency was obtained by the rotor with a tight throat margin and highest internal contraction, but its efficiency was the lowest at part speed. The best compromise between high-speed and part-speed efficiency was achieved by the rotor with a large throat and a lower trailing edge effective camber. The difference in the shock structure and the shock boundary layer interaction of the four blade was analyzed using a three-dimensional viscous code. The analytical results are used to supplement the data and provide further insight into the detailed physics of the flow field.

An Entropy Based Evaluation of Efficiency of a Transonic Compressor Rotor With Water Injection

2008 ◽  
Author(s):  
Istvan Szabo ◽  
Mark G. Turner
Keyword(s):  
Viscous Dissipation ◽  
Entropy Generation ◽  
Dissipation Function ◽  
Entropy Generation Rate ◽  
Thermodynamic Efficiency ◽  
Compression Process ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wet Compression ◽  
Isentropic Efficiency

Defining the thermodynamic efficiency of the wet compression process in a compressor is not trivial, since the flow in this case has multiple phases present which interact with each other. In this paper, an approach is presented that calculates the overall entropy creation and thus the isentropic efficiency of a wet compression process in a transonic compressor rotor. The viscous dissipation function is calculated everywhere in the domain in the post-processing phase of the CFD simulation and integrated to the wall, with special treatment in the near-wall regions where high rates of entropy generation occur. The isentropic efficiency of the wet compression is then determined from the entropy generation rate. Analytical integration of wall functions and numerical integration of the viscous dissipation function allows for reasonable results even with relatively coarse grids and can be applied for single-phase flows. The methodology presented is also useful to quantify the efficiency of thermodynamic processes in devices that introduce streams into the flow path, such as cooled turbines and compressors with flow control.

Effects of Inlet Distortion on the Flow Field in a Transonic Compressor Rotor

1996 ◽  
Author(s):  
Chunill Hah ◽  
Douglas C. Rabe ◽  
Thomas J. Sullivan ◽  
Aspi R. Wadia
Keyword(s):  
Boundary Layer ◽  
Flow Field ◽  
Viscous Flow ◽  
Total Pressure ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Aerodynamic Loss ◽  
Transonic Compressor ◽  
Inlet Distortion ◽  
Compressor Rotor

The effects of circumferential distortions in inlet total pressure on the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio, transonic compressor rotor are investigated in this paper. The flow field was studied experimentally and numerically with and without inlet total pressure distortion. Total pressure distortion was created by screens mounted upstream from the rotor inlet. Circumferential distortions of 8 periods per revolution were investigated at two different rotor speeds. The unsteady blade surface pressures were measured with miniature pressure transducers mounted in the blade. The flow fields with and without inlet total pressure distortion were analyzed numerically by solving steady and unsteady forms of the Reynolds-averaged Navier-Stokes equations. Steady three-dimensional viscous flow calculations were performed for the flow without inlet distortion while unsteady three-dimensional viscous flow calculations were used for the flow with inlet distortion. For the time-accurate calculation, circumferential and radial variations of the inlet total pressure were used as a time-dependent inflow boundary condition. A second-order implicit scheme was used for the time integration. The experimental measurements and the numerical analysis are highly complementary for this study because of the extreme complexity of the flow field. The current investigation shows that inlet flow distortions travel through the rotor blade passage and are convected into the following stator. At a high rotor speed where the flow is transonic, the passage shock was found to oscillate by as much as 20% of the blade chord, and very strong interactions between the unsteady passage shock and the blade boundary layer were observed. This interaction increases the effective blockage of the passage, resulting in an increased aerodynamic loss and a reduced stall margin. The strong interaction between the passage shock and the blade boundary layer increases the peak aerodynamic loss by about one percent.

Flow Field Unsteadiness in the Tip Region of a Transonic Compressor Rotor

1997 ◽  
Vol 119 (1) ◽  
pp. 122-128 ◽  
Author(s):  
S. L. Puterbaugh ◽  
W. W. Copenhaver
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Vortex Interaction ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Operating Points

An experimental investigation concerning tip flow field unsteadiness was performed for a high-performance, state-of-the-art transonic compressor rotor. Casing-mounted high frequency response pressure transducers were used to indicate both the ensemble averaged and time varying flow structure present in the tip region of the rotor at four different operating points at design speed. The ensemble averaged information revealed the shock structure as it evolved from a dual shock system at open throttle to an attached shock at peak efficiency to a detached orientation at near stall. Steady three-dimensional Navier Stokes analysis reveals the dominant flow structures in the tip region in support of the ensemble averaged measurements. A tip leakage vortex is evident at all operating points as regions of low static pressure and appears in the same location as the vortex found in the numerical solution. An unsteadiness parameter was calculated to quantify the unsteadiness in the tip cascade plane. In general, regions of peak unsteadiness appear near shocks and in the area interpreted as the shock-tip leakage vortex interaction. Local peaks of unsteadiness appear in mid-passage downstream of the shock-vortex interaction. Flow field features not evident in the ensemble averaged data are examined via a Navier-Stokes solution obtained at the near stall operating point.

scholarly journals A Three-Dimensional Shock Loss Model Applied to an Aft-Swept, Transonic Compressor Rotor

1996 ◽  
Author(s):  
Steven L. Puterbaugh ◽  
William W. Copenhaver ◽  
Chunill Hah ◽  
Arthur J. Wennerstrom
Keyword(s):  
Flow Rate ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Numerical Results ◽  
Design Flow ◽  
Design System ◽  
Loss Model ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Shock Loss

An analysis of the effectiveness of a three-dimensional shock loss model used in transonic compressor rotor design is presented. The model was used during the design of an aft-swept, transonic compressor rotor. The demonstrated performance of the swept rotor, in combination with numerical results, is used to determine the strengths and weaknesses of the model. The numerical results were obtained from a fully three-dimensional Navier-Stokes solver. The shock loss model was developed to account for the benefit gained with three-dimensional shock sweep. Comparisons with the experimental and numerical results demonstrated that shock loss reductions predicted by the model due to the swept shock induced by the swept leading edge of the rotor were exceeded. However, near the tip the loss model under-predicts the loss because the shock geometry assumed by the model remains swept in this region while the numerical results show a more normal shock orientation. The design methods and the demonstrated performance of the swept rotor is also presented. Comparisons are made between the design intent and measured performance parameters. The aft-swept rotor was designed using an inviscid axisymmetric streamline curvature design system utilizing arbitrary airfoil blading geometry. The design goal specific flow rate was 214.7 kg/sec/m2 (43.98 lbm/sec/ft2), the design pressure ratio goal was 2.042, and the predicted design point efficiency was 94.0. The rotor tip sped was 457.2 m/sec (1500 ft/sec). The design flow rate was achieved while the pressure ratio fell short by 0.07. Efficiency was 3 points below prediction, though at a very high 91 percent. At this operating condition the stall margin was 11 percent.

The Extension of a Solution-Adaptive Three-Dimensional Navier–Stokes Solver Toward Geometries of Arbitrary Complexity

1993 ◽  
Vol 115 (2) ◽  
pp. 283-295 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Wide Range ◽  
Nozzle Guide Vane ◽  
Recent Developments ◽  
Nozzle Guide

This paper describes recent developments to a three-dimensional, unstructured mesh, solution-adaptive Navier–Stokes solver. By adopting a simple, pragmatic but systematic approach to mesh generation, the range of simulations that can be attempted is extended toward arbitrary geometries. The combined benefits of the approach result in a powerful analytical ability. Solutions for a wide range of flows are presented, including a transonic compressor rotor, a centrifugal impeller, a steam turbine nozzle guide vane with casing extraction belt, the internal coolant passage of a radial inflow turbine, and a turbine disk cavity flow.

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