scholarly journals Numerical Simulation on the Influence of Rotating Speed on the Hydraulic Loss Characteristics of Desalination Energy Recovery Turbine

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Bing Qi ◽  
Desheng Zhang ◽  
Qi Zhang ◽  
Mengcheng Wang ◽  
Ibra Fall
Keyword(s):  
Flow Separation ◽  
Energy Recovery ◽  
Internal Flow ◽  
Leading Edge ◽  
Suction Side ◽  
Radial Pressure ◽  
Hydraulic Loss ◽  
Rotating Speed ◽  
The Impact ◽  
Loss Mechanisms

The performance of energy recovery turbine (ERT) directly determines the cost and energy consumption of reverse osmosis desalination. In order to study the performance and loss mechanisms of ERT under different conditions, the external characteristics and the losses of different components were quantitatively analyzed. The loss mechanisms of each component in the turbine were revealed through the comparative analysis of the internal flow field. The results show that the efficiency is 2.2% higher than that at the design speed when turbine runs at n = 22000 r/min. The impeller losses account for more than 67% of the total losses. The impeller loss is mainly observed at the leading edge. The vortex on the pressure side of the leading edge is caused by the impact effect, while the vortex on the suction side of the leading edge is caused by the flow separation. With the increase in the rotating speed, the loss caused by flow separation in impeller decreases obviously. The volute loss is mainly observed near the tongue, which is caused by the flow separation at the tongue. The design of the tongue is very important to the performance of the volute. The turbulent kinetic energy (TKE) and loss decrease with the increase in the rotating speed. The loss in the draft tube is mainly observed at the inlet core. With the increase in the rotating speed, the turbulence pulsation and the radial pressure fluctuation amplitude reduce. Therefore, the turbine can be operated at the design or slightly higher than the design rotating speed under the condition that both the hydraulic condition and the intensity are satisfied, which are conducive to the efficient utilization of energy.

On the Role of Leading-Edge Bumps in the Control of Stall Onset in Axial Fan Blades

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Anthony G. Sheard
Keyword(s):  
Numerical Study ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Fan ◽  
Early Recovery ◽  
Viscosity Models ◽  
Flow Mechanisms ◽  
The Impact

Taking a lead from the humpback whale flukes, characterized by a series of bumps that result in a sinusoidal-like leading edge, this paper reports on a three-dimensional numerical study of sinusoidal leading edges on cambered airfoil profiles. The turbulent flow around the cambered airfoil with the sinusoidal leading edge was computed at different angles of attack with the open source solver OpenFOAM, using two different eddy viscosity models integrated to the wall. The reported research focused on the effects of the modified leading edge in terms of lift-to-drag performance and the influence of camber on such parameters. For these reasons a comparison with a symmetric airfoil is provided. The research was primarily concerned with the elucidation of the fluid flow mechanisms induced by the bumps and the impact of those mechanisms on airfoil performance, on both symmetric and cambered profiles. The bumps on the leading edge influenced the aerodynamic performance of the airfoil, and the lift curves were found to feature an early recovery in post-stall for the symmetric profile with an additional gain in lift for the cambered profile. The bumps drove the fluid dynamic on the suction side of the airfoil, which in turn resulted in the capability to control the separation at the trailing edge in coincidence with the peak of the sinusoid at the leading edge.

The Impact of Leakage Flow Tangential Velocity on Secondary Losses in a Shrouded Compressor Cascade

2012 ◽  
Author(s):  
J. W. Kim ◽  
J. S. Lee ◽  
S. J. Song ◽  
T. Kim ◽  
H-. W. Shin
Keyword(s):  
Secondary Flow ◽  
Tangential Velocity ◽  
Leading Edge ◽  
Suction Side ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Trailing Edge ◽  
Leading Edge Vortex ◽  
Edge Vortex ◽  
The Impact

Experimental and numerical studies have been performed to investigate the effects of the leakage flow tangential velocity on the secondary flow and aerodynamic loss in an axial compressor cascade with a labyrinth seal. Six selected leakage flow tangential (vy/Uhub = 0.15, 0.25, 0.35, 0.45, 0.55 and 0.65) have been tested. In addition to the classical “secondary” flow, shroud trailing edge vortex and shroud leading edge vortex are examined. The overall loss decreases with increasing leakage flow tangential velocity. Increased leakage flow tangential velocity underturns the hub endwall flows through the blade passage, weakening the suction side hub corner separation. Due to the suction effect of the downstream cavity, increasing leakage flow tangential velocity weakens the shroud trailing edge vortex. Also, increasing leakage flow tangential velocity strengthens the shroud leading edge vortex, weakening the pressure side leg of the horseshoe vortex, and, in turn, the passage vortex. Thus, the overall loss is reduced with increasing leakage flow tangential velocity.

Study of a Highly Loaded Centrifugal Compressor With Pipe Diffuser at Design and Off-Design Operating Conditions

2015 ◽  
Author(s):  
Ge Han ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
Junqiang Zhu
Keyword(s):  
Centrifugal Compressor ◽  
Flow Separation ◽  
Incidence Angle ◽  
Leading Edge ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Flow Distortion ◽  
Flow Angle ◽  
Rotating Speed ◽  
Highly Loaded

This present work is aimed at providing detailed understanding of the flow mechanisms in a highly loaded centrifugal compressor with different diffusers. Performance comparison between compressor stages with pipe diffuser and its original wedge diffuser was conducted by a validated state-of-the-art multi-block flow solver at different rotating speeds. Stage with pipe diffuser achieved a better performance above 80% rotating speed but a worse performance at lower rotating speeds near surge, than that of stage with wedge diffuser. Four operating points including the design point were analyzed in detail. The inherent diffuser leading edge of pipe diffuser could alleviate the flow distortion upstream diffuser throat and created a better operating condition for the downstream diffusion, which reduced the possibility of flow separation in discrete passages at design rotating speed. At 60% rotating speed operating point, there was a misalignment between the leading edge absolute flow angle and the metal angle of diffuser, resulted in an acceleration near diffuser leading edge due to the large negative incidence angle. The sharp leading edge of pipe diffuser could largely accommodate this negative incidence as comparison of the round leading edge of wedge diffuser. As a result, the flow separation was depressed and a better performance was achieved in the pipe diffuser. At 60% rotating speed near surge, performance of the pipe diffuser dropped below wedge diffuser. Total pressure loss of pipe diffuser exceeded that of the wedge diffuser due to the larger friction loss near wall at throat and cone, meanwhile ineffective static pressure recovery for pipe diffuser was triggered by the strong boundary layer blockage in the front of pipe diffuser cone.

Fracture Analysis of a First Stage Turbine Blade

2010 ◽  
Author(s):  
Reza Ghorbani ◽  
Saeed Asadikouhanjani ◽  
Karsten Kusterer ◽  
Anis Haj Ayed
Keyword(s):  
Crack Propagation ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Service Failure ◽  
Leading Edge ◽  
Suction Side ◽  
Turbine Engines ◽  
Nickel Base Superalloy ◽  
Premature Failure ◽  
The Impact

Blade failures in gas turbine engines often lead to the loss of all downstream stages and it can have a dramatic effect on the availability of the turbine engines. This paper presents the analysis of an in service failure of a first stage gas turbine blade. The premature failure of the blade, made of nickel-base superalloy Inconel 738 LC, occurred after a service life of 8,127 EOH with normal start/stop and caused extensive damage to the unit. Crack growth mechanism has been evaluated based on macroscopic and microscopic observations of the fracture surfaces. Chemical analyses were carried out to identify the possible causes of the failures by examining anomalies in the chemical composition and microstructure analysis through SEM observations. The analysis of the different regions of fracture surface shows that crack propagation is mainly related to fatigue mechanism. Typical fatigue striations could be identified under a homogeneous oxide layer. The crack propagation occurred in the pressure-suction side direction and the initial crack origin is located on the missing part near leading edge area. The impact marks on the first stage leading edge of the blade and the general damage of the turbine give indication that the crack initiation was caused by an impact of a broken piece from first stage vanes or another object of unknown source.

Quantitative CFD Analyses of Particle Deposition on a Subsonic Axial Compressor Blade

2015 ◽  
Author(s):  
Alessio Suman ◽  
Rainer Kurz ◽  
Nicola Aldi ◽  
Mirko Morini ◽  
Klaus Brun ◽  
...  
Keyword(s):  
Particle Deposition ◽  
Fluid Dynamic ◽  
Axial Compressor ◽  
Leading Edge ◽  
Suction Side ◽  
Sticking Probability ◽  
Particle Impact ◽  
Kinematic Characteristics ◽  
The Impact ◽  
Dynamic Phenomena

In literature there are some studies related to the fouling phenomena in transonic compressors, but, in industrial applications (heavy-duty compressor, pump stations, etc.) the subsonic compressors are widespread. It is of great interest to the manufacturer to discover the fouling phenomenon related to this type of compressor. This paper presents three-dimensional numerical simulations of the micro-particle ingestion on a subsonic axial compressor rotor carried out by means of a commercial computational fluid dynamic code. Particle trajectory simulations use a stochastic Lagrangian tracking method that solves the equations of motion separate from the continuous phase. The number of particles, sizes, and concentrations are specified in order to perform a quantitative analysis of the particle impact on the blade surface. In this paper the particle impact pattern and the kinematic characteristics (velocity and angle) of the impact are shown. Both of the blade zones affected by particle impact and the blade zones affected by particle deposition are analyzed. The particle deposition is established by using the quantity called sticking probability. The sticking probability links the kinematic characteristics of particle impact on the blade with fouling phenomenon. The results show that micro-particles tend to follow the flow by impacting at full span with a higher impact concentration on the leading edge. The suction side is affected only close to the leading edge and, at the hub, close to the trailing edge. Particular fluid-dynamic phenomena such as separation, stagnation and tip leakage vortex strongly influence the impact location of the particles. The kinematic analysis showed a high tendency of particle adhesion on the suction side, especially for smaller particles for which the fluid dynamic phenomena play a key role regarding particle impact velocity and angle.

Numerical Prediction of Film Cooling and Heat Transfer on the Leading Edge of a Rotating Blade With Two Rows Holes in a 1-1/2 Turbine Stage at Design and Off Design Conditions

2005 ◽  
Author(s):  
Huitao Yang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Rotating Speed ◽  
Rotating Blade

Numerical simulations were performed to predict the film cooling effectiveness and the associated heat transfer coefficient on the leading edge of a rotating blade in a 1-1/2 turbine stage using a Reynolds stress turbulence model together with a non-equilibrium wall function. Simulations were performed for both the design and off-design conditions to investigate the effects of blade rotation on the leading edge film cooling effectiveness and heat transfer coefficient distributions. It was found that the tilt stagnation line on the leading edge of rotor moves from the pressure side to the suction side, and the instantaneous coolant streamlines shift from the suction side to the pressure side with increasing rotating speed. This trend was supported by the experimental results. The result also showed that the heat transfer coefficient increases, but film cooling effectiveness decreases with increasing rotating speed. In addition, the unsteady characteristics of the film cooling and heat transfer at different time phases, as well as different rotating speeds, were also reported.

Loss Mechanisms and Flow Control for Improved Efficiency of a Centrifugal Compressor at High Inlet Prewhirl

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Xinqian Zheng ◽  
Qiangqiang Huang ◽  
Anxiong Liu
Keyword(s):  
Flow Control ◽  
Mass Flow ◽  
Centrifugal Compressor ◽  
Flow Separation ◽  
Flow Instability ◽  
Reverse Flow ◽  
Leading Edge ◽  
Flow Region ◽  
Impeller Blade ◽  
Loss Mechanisms

Variable inlet prewhirl is an effective way to suppress compressor flow instability. Compressors usually employ a high degree of positive inlet prewhirl to shift the surge line in the performance map to a lower mass flow region. However, the efficiency of a compressor at high inlet prewhirl is far lower than that at zero or low prewhirl. This paper investigates the performances of a centrifugal compressor with different prewhirls, discusses the mechanisms which are responsible for the production of extra loss induced by high inlet prewhirl and develops flow control methods to improve efficiency at high inlet prewhirl. The approach combines steady three-dimensional Reynolds average Navier–Stokes (RANS) simulations with theoretical analysis and modeling. In order to make the study universal to various applications with inlet prewhirl, the inlet prewhirl was imposed by modifying the velocity direction of inlet boundary condition. Simulation results show that the peak efficiency at high inlet prewhirl is reduced by over 7.6% points compared with that at zero prewhirl. The extra loss occurs upstream and downstream of the impeller. Severe flow separation, which reduces efficiency by 2.3% points, was found near the inlet hub. High inlet prewhirl works like a centrifuge gathering low-kinetic-energy fluid to hub, which induces the separation. A dimensionless parameter C was defined to measure the centrifugal trend of gas and indicate the flow separation near the inlet hub. As for the extra loss which is produced downstream of the impeller, the flow mismatch of impeller and diffuser at high prewhirl causes a violent backflow near the diffuser vanes' leading edges. An analytical model was built to predict diffuser choking mass flow. It proves that the diffuser has already operated unstably at high prewhirl. Based on these two loss mechanisms, the hub curve and the diffuser stager angle were modified and adjusted, respectively, for higher efficiency at high prewhirl. The efficiency improvement benefited from the modification of the hub is 1.1% points, and that benefited from the combined optimization is 2.4% points. During optimizing, constant distribution of inlet prewhirl was found to be another factor for inducing reverse flow at the leading edge of the impeller blade root, which turned out being blamed on the misalignment of the swirl angle and the blade angle.

Rotating Film Cooling Performance of the Hole Near the Leading Edge on the Suction Side of the Turbine Blade

2018 ◽  
Author(s):  
Zhi-yu Zhou ◽  
Hai-wang Li ◽  
Hai-chao Wang ◽  
Guo-qin Zhao ◽  
Feng Han ◽  
...  
Keyword(s):  
Film Cooling ◽  
Leading Edge ◽  
Suction Side ◽  
Axial Direction ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Rotating Speed ◽  
Blowing Ratio ◽  
Numerical Studies

This paper reports the experimental and numerical studies on the effects of rotating speed and blowing ratio on the film cooling performance of the hole near the leading edge on the suction side of the turbine blade. The chord and height of the blade are 60mm and 80mm respectively. The film hole with diameter of 0.8mm is located in the mid span on the suction side at axial location of 8%. The injection angle of the hole is 45° to the suction surface of the blade and is nearly perpendicular to the axial direction. Both experimental and numerical studies were carried out with rotating speeds of 300rpm, 450rpm and 600rpm, and with blowing ratios of 0.5, 1.0, 1.5 and 2.0. CO2 was used as the coolant. Experimental data was measured by applying the Thermochromic Liquid Crystal (TLC) technique and the Stroboscopic Imaging Technique. Mainstream and coolant were heated to 308K and 318K respectively. Numerical studies were performed to assist the analysis of the experimental results. The SST turbulence model was applied in the simulations. Results show that the film cooling performance of the hole near the leading edge is different from that of the hole further downstream on the suction side. This is because the direction of the jet is nearly perpendicular to the axial direction, which increases the effect of the Coriolis force. Besides, the mainstream from leading edge also has effects on film cooling performance. With the increase of the blowing ratio, the film coverage area and spatially averaged film cooling effectiveness increase first and then decrease. The maximum film coverage and averaged film cooling effectiveness appear at blowing ratio of 1.0 and rotating speed of 300rpm. Moreover, the upward deflection angle of the film trajectory increases slightly with the increase of the blowing ratio. Higher rotating speed intensifies the deflection of the film trajectory. Therefore, the film coverage and the averaged film cooling effectiveness decrease rapidly.

Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge

1999 ◽  
Vol 122 (2) ◽  
pp. 334-339 ◽  
Author(s):  
Dieter E. Bohn ◽  
Karsten A. Kusterer
Keyword(s):  
Secondary Flow ◽  
Gas Turbines ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Leading Edge ◽  
Suction Side ◽  
Back Side ◽  
Stagnation Line ◽  
Flow Phenomena ◽  
The Impact

A leading edge cooling configuration is investigated numerically by application of a three-dimensional conjugate fluid flow and heat transfer solver, CHT-flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multiblock technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45 deg. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three-dimensional and asymmetric jet flow field. Within a secondary flow analysis, the cooling fluid jets are investigated in detail. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a respectable agreement concerning the vortex development. [S0889-504X(00)00102-1]

Impact of Tip Clearance Size and Rotation Speed on the Surge Onset in a High Pressure Centrifugal Compressor

2012 ◽  
Author(s):  
Nicolas Buffaz ◽  
Isabelle Trébinjac
Keyword(s):  
Centrifugal Compressor ◽  
Rotation Speed ◽  
Pressure Sensors ◽  
Leading Edge ◽  
Suction Side ◽  
Boundary Layer Separation ◽  
Tip Clearance ◽  
Vaned Diffuser ◽  
The Impact ◽  
Blade Leading Edge

The results presented in the paper aim at investigating the impact of tip clearance size and rotation speed on the surge onset in a transonic single-stage centrifugal compressor composed of a backswept splittered unshrouded impeller and a vaned diffuser. For that purpose, various slow throttle ramps into surge were conducted from 100% to 60% design speed of the compressor and two different tip clearance heights were investigated. The 1MW LMFA-ECL test rig was used to carry out the tests in the compressor stage. Unsteady pressure measurements up to 150 KHz were carried out in the inducer (i.e. the entry zone of the impeller between the main blade leading edge and the splitter blade leading edge) and in the diffuser thanks to nine and fifteen static pressure sensors respectively. At cruise rotation speed (92.7% of the nominal rotation speed), the surge is triggered by a boundary layer separation on the diffuser vane suction side whatever the tip clearance height may be. No precursor of surge or pre-surge activity has been recorded in the diffuser or in the impeller. The surge reveals a spike-type inception and the tip clearance increase does not change the path into instability. At lower rotation speeds high frequency disturbances (nearly half the BPF) have been recorded in the inducer before surge. These disturbances can be understood as “tip clearance rotating disturbances” because they are generated at the leading edge of the main blades and move along the tip clearance trajectory. These disturbances reveal a very unstable behavior while the compressor runs into a stable operating point even if the flow at the tip of impeller is dramatically affected by these disturbances. But these disturbances do not trigger the surge which always originates in the diffuser.

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