Axial Flow Turbine Stage Research Articles

CFD Analysis of an Aircraft Turbofan Engine Combustion Process and the Effect on Turbine

In this paper, a two-dimensional computational fluid dynamics (CFD) study of Turbofan engine is presented using the ANSYS Fluent program, the navier–stokes equations is used for analysis, including a two-dimensional and symmetrical drawing of both the combustion chamber and in a 1.5 Stage Axial Flow Turbine. A GE-90 turbofan engine nacelle was used with Naca 63-412 type blades were used for the analysis of the flow on the turbine blades. Combustion chamber simulations were carried out using a previous study. The computational results were compared with other studies on the Exergetic analysis of a GE-21 turbojet engine. The GE-21 engine had a combustion chamber temperature of 2900 K, while the GE-90 engine had a temperature of around 2706 K. The previous study considered the velocity of fluid flow to be 200 m/s, whereas the velocity of flow in this study was 209 m/s as determined in the part of analysis and result.

Influence of fillet shapes on secondary flow field in a transonic axial flow turbine stage

Numerical experiments were conducted to investigate the effect of leading edge modifications via fillet shapes near vane/blade-endwall juncture in a transonic environment within the highly loaded high pressure turbine stage. The investigated fillet shapes were designed based on geometric parameters: leading edge radius and included angle. The geometrical modifications were achieved to achieve variation in fillet radii at vane/blade endwall juncture along the stream-wise direction, namely variable fillet and constant fillet. Further their influences were studied in both nozzle guide vane and rotor passage secondary flow field. Computational Fluid Dynamics (CFD) method was used to resolve the flow features inside the turbine passage for planar and fillet cases. The presented data highlight the secondary flow features and their behavior using topological properties of flow field aided with the streamline and iso-contour plots. The flow-field results show a significant reduction in the total pressure losses associated with the horse shoe vortex near the leading edge region as the fillet radii are varied. Overall in both vane and rotor passages, variable fillet outperforms the constant fillet by reducing the penetration length of three-dimensional regimes along its span, mitigating the boundary layer growth and improving the loss coefficients.

Improving the Performance of Gas Turbine Power Plant by Modified Axial Turbine

This research used the ALICE high performance computing facility at the University of Leicester. Graphical rendering software licenses were originally acquired with EPSRC support on Grant GR/N23745/01. The Higher Committee for Education Development in Iraq (HCED) is acknowledged. The supply of experimental data for the 1.5 stage axial flow turbine “Aachen Turbine” under license by RWTH Aachen is gratefully acknowledged.

EFFECTS OF VARYING TIP CLEARANCE AND AXIAL GAP ON AXIAL-FLOW TURBINE STAGE PERFORMANCE ( PRESENT STATE OF THE ART)

The leakage flow near the tip of rotor and stator blade rows of an axial-flow turbinestage imposes significant thermal loads on such blades. It is also responsible for theaerodynamic losses therein. This leakage flow is induced mainly by the pressuredifference across the tip section for both the rotor and the stator. Most research hashitherto focused on the effect of varying the tip clearance ratio, but a rather littleamount of published work on axial gap effect is found. This paper presents theoutcome of scanning the available research on tip clearance and axial gapparameters and effects of their variation on the flow characteristics andperformance of a typical axial–flow turbine stage. The prime objective here is tothrow some light upon the state of the art in this area of research. The surveyedliterature is discussed and criticized, giving suggestions for further investigation ofthe problem.

J051015 航空エンジン用低圧タービン段の高効率化に関する研究 : 回転試験機による実験及びCFD([J05101]流体機械の研究開発におけるEFD/CFD(1))

This paper presents an experimental study and numerical simulation of the unsteady flow mechanisms in a single stage axial flow turbine which is simulated the LP turbine airfoils. The target of this study is to verify the influence of the purge flow from the Rim-seal cavity on the flow field in the rotor passage, which leads to changes of the secondary flow behavior especially in the rotor hub region. To observe the unsteady flow pattern at rotor downstream, detailed 3-D unsteady measurements using a slant-type hot wire probe is performed. The result of unsteady measurement observed the secondary flow and the leakage flow in the tip region without the purge flow as well as the steady flow measurement with 5-hole probe. A three-dimensional, time-dependent numerical simulation shows the unsteady flow interactions between the main flow and purge flow.

Computational Investigation of Effect of Axial Spacing on Blade Row Interaction in a 1½ Stage Axial Flow Turbine

This paper presents computational investigation of the flow in a 1½ stage axial turbine using finite volume based commercial CFD package namely CFX 5.7.1. The blade row interaction effect is studied in unsteady computations. The effect of axial spacing on the flow field of the turbine is studied for four different axial spacings between the nozzle-rotor and rotor-stator, viz. Xs=15%, 25%, 35% and 50%. The computational results are utilized to suggest the optimum axial spacing between nozzle-rotor and rotor-stator blade rows. The results of static pressure coefficient distribution, spanwise variation of lift coefficient in nozzle, rotor and stator, variation of lift coefficient at midspan with axial spacing, contours of total loss coefficient at 5% down stream of nozzle, rotor and stator, distribution of mass averaged total pressure loss coefficient with axial distance, and variation of mass averaged total pressure loss coefficient with axial spacing are presented. The total pressure loss coefficient contours show the clear structure of the vortices and loss cores.

J0501-2-2 軸流タービン空力性能に及ぼす動静翼間距離の影響(流体機械の研究開発におけるEFD/CFD(2))

The purpose of this study is to investigate the effects of the axial gap between stator and rotor upon the performance and secondary flow field of a single axial flow turbine stage. We performed experiments for three axial gaps. In our test rig, it is possible to change the axial gap by moving the stator vane in axial direction. The tests were carried out at two different conditions, that is design and off-design conditions. The unsteady three-dimensional flow field was analyzed by time-accurate RANS (Reynolds-Averaged Navier-Stokes) simulations. The simulation results were compared with the experiments, in which total pressure loss and time-averaged flow field upstream and downstream of the rotor were obtained by five-hole probe measurements. The effect of the axial gap was confirmed in the endwall regions, and obtained relatively at the off-design condition. The turbine stage efficiency was improved almost linearly to reduce the axial gap at the off-design condition.

1712 単段軸流タービンの動静翼列間隔による非定常効果(S19-2 流体機械に関連した流動現象とその解析・計測(2)不安定流動・非定常流動の計測と解析,21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

This paper provides experimental investigations of unsteady flow behaviors in a single axial flow turbine stage with two axial gaps. The aim of this study is to clarify the effect of the axial gap on the unsteady flow field, where the 3-D unsteady flow field downstream of rotor blades is measured using a slant-type hot wire probe. Since the flow field is likely to be affected by the disk and tip cavity flow when the stator-rotor axial gap increased, the cavities on both hub side and casing side were kept constant (about 1 mm) by attaching several rings to openings of the cavities. In addition, we have compared time-averaged flow fields measured by a five-hole probe with unsteady experimental results.

Aerodynamics of Tip Leakage Flows Near Partial Squealer Rims in an Axial Flow Turbine Stage

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

Massively Parallel Simulation of the Unsteady Flow in an Axial Turbine Stage

The results from two numerical simulations of the unsteady flow in a 11 stage axial-flow turbine are presented and compared with experimental data to show both the effect of blade count on the solution accuracy and the time-averaged and unsteady flow physics present. TFLO, the three-dimensional, multiblock, massively parallel turbomachinery flow solution procedure is used to simulate the flow through the Aachen 36-vane/41-blade/36-vane 1 ½-stage turbine rig. Comparisons of the time-averaged and unsteady flow solutions of 1-vane/1-blade/1-vane and 6-vane/7-blade/6-vane configurations with the available experimental data are used to show the importance of matching actual blade counts in unsteady flow simulations as closely as possible. In addition, these comparisons are used to quantify the predicted aerodynamic performance differences and highlight the different unsteady flow physics in the two simulations.

Time-Accurate Three-Dimensional Navier-Stokes Analysis of One-and-One-Half Stage Axial-Flow Turbine

Anew three-dimensionalNavier–Stokesmethod for the analysisof the unsteady  ow inmultiple turbomachinery blade rows is presented. To take into account turbulent effects, a low-Reynolds-numberk–2model is used. Smooth wave propagationaccross the sliding rotor/stator interfaces is accomplished with a fully conservative interface  ux algorithm. The use of physically motivated time-step scales is enabled by an implicit relaxation strategy, where Newton subiterations are applied to provide time accuracy. The code system is validated for a one-and-one-halfstage axial- ow turbine, which is documented as an ERCOFTAC SIG test case. Detailed experimental data are exploited to evaluate the predictive capability of the code. The analysis focuses on typical unsteady effects such as negative jets in the wakes, general effects of unsteadiness, as well as the representation and the unsteady generation of losses.

Three-Dimensional Blade Boundary Layer and Endwall Flow Development in the Nozzle Passage of a Single Stage Turbine

The three-dimensional viscous flow field development in the nozzle passage of an axial flow turbine stage was measured using a “x” hot-wire probe. The measurements were carried out at two axial stations on the endwall and vane surfaces and at several spanwise and pitchwise locations. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. The boundary layers on the vane surface were found to be very thin and mostly laminar, except on the suction surface downstream of 70 percent axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong radial flow velocities in the trailing edge regions of the blade. On the endwalls, the boundary layers were much thicker, especially near the suction corner of the casing surface, caused by the secondary flow. The secondary flow region near the suction surface-casing corner indicated the presence of the passage vortex detached from the vane surface. The boundary layer code accurately predicts the three-dimensional boundary layers on both vane surfaces and endwall in the regions where the influence of the secondary flow is small.

Analysis of Hot Streak Effects on Turbine Rotor Heat Load

The influence of inlet hot streak temperature distortion on turbine blade heat load was explored on a transonic axial flow turbine stage test article using a three-dimensional, multiblade row unsteady Euler code. The turbine geometry was the same as that used for a recently reported testing of hot streak influence. Emphasis was placed on elucidating the physical mechanisms by which hot streaks affect turbine durability. It was found that temperature distortion significantly increases both blade surface heat load nonuniformity and total blade heat load by as much as 10–30 percent (mainly on the pressure surface), and that the severity of this influence is a strong function of turbine geometry and flow conditions. Three physical mechanisms were identified that drive the heat load nonuniformity: buoyancy, wake convection (the Kerrebrock–Mikolajczak effect), and Rotor–Stator interactions. The latter can generate significant nonuniformity of the time-averaged relative frame rotor inlet temperature distribution. Dependence of these effects on turbine design variables was investigated to shed light on the design space, which minimizes the adverse effects of hot streaks.

Three-dimensional flowfield in a turbine nozzle passage

Detailed measurements were taken in the nozzle of a low speed single stage axial flow turbine at two axial planes inside the nozzle and on the nozzle and endwall surfaces. Velocity, turbulence and angle measurements were taken at midchord with an LDV while a five hole probe was used to measure the pressure, velocities and angles just upstream of the trailing edge. Nozzle surface and endwall static pressures were also measured. These measurements were compared to measurements previously completed at two axial planes downstream of the nozzle. The results show that at midchord, the secondary flow seems to be weak and it is in the early stages of development. Just upstream of the trailing edge, the secondary flow is clearly visible. The radially inward flow near the suction surface augments the casing passage vortex, while counteracting the hub passage vortex. Traveling downstream, the casing passage vortex remains strong while at the hub, the radially inward flow of the suction surface boundary layer has reversed direction due to the rotating hub. The blade static pressures and the passage averaged velocities compare well with Katsanis' quasi-three-dimensional code. These and other data are presented, interpreted and synthesized to understand the nozzle flow field.

A Finite-Element Model of the Cyclic Aerodynamic Loading of a Turbine Rotor Due to an Upstream Stator

A finite-element model has been developed to predict the unsteady flow field in an axial turbine rotor cascade as a result of the wakes shed from an upstream stator blade row. The numerical model is based on a three-dimensional, time dependent, fully elliptic, finite element formulation of the Navier-Stokes equations cast in cylindrical coordinates. The relative motion between the blade rows is introduced through time-dependent inlet boundary conditions for the rotor cascade. The governing equations in the rotor passage are solved in a rotating frame of reference using the weighted-residual method, coupled with a twenty-noded curve-sided isoparametric finite element for discretization. Time-averaged and instantaneous pressure loadings for the rotor blade as generated along with the passage velocity fields. The computed results are compared with existing experimental data for a typical axial-flow turbine stage. Assessment of the results is also made in light of those obtained through a thin-layer model of ...

Endwall and Unsteady Flow Phenomena in an Axial Turbine Stage

Detailed experimental and numerical studies have been performed in a subsonic, axial-flow turbine stage to investigate the secondary flow field, the aerodynamic loss generation, and the spanwise mixing under a stage environment. The experimental study includes measurements of the static pressure distribution on the rotor blade surface and the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The rotor exit flow field was measured with an unsteady hot-wire probe, which has high temporal and spatial resolution. Both steady and unsteady numerical analyses were performed with a three-dimensional Navier–Stokes code for the multiple blade rows. Special attention was focused on how well the steady multiple-blade-row calculation predicts the rotor exit flow field and how much the blade interaction affects the radial distribution of flow properties at the stage exit. Detailed comparisons between the measurement and the steady calculation indicate that the steady multiple-blade-row calculation predicts the overall time-averaged flow field very well. However, the steady calculation does not predict the secondary flow at the stage exit accurately. The current study indicates that the passage vortex near the hub of the rotor is transported toward the midspan due to the blade interaction effects. Also, the structure of the secondary flow field at the exit of the rotor is significantly modified by the unsteady effects. The time-averaged secondary flow field and the radial distribution of the flow properties, which are used for the design of the following stage, can be predicted more accurately with the unsteady flow calculation.

Effects of Stator Wakes and Spanwise Nonuniform Inlet Conditions on the Rotor Flow of an Axial Turbine Stage

Detailed measurements have been performed in a subsonic, axial-flow turbine stage to investigate the structure of the secondary flow field and the loss generation. The data include the static pressure distribution on the rotor blade passage surfaces and radial-circumferential measurements of the rotor exit flow field using three-dimensional hot-wire and pneumatic probes. The flow field at the rotor outlet is derived from unsteady hot-wire measurements with high temporal and spatial resolution. The paper presents the formation of the tip clearance vortex and the passage vortices, which are strongly influenced by the spanwise nonuniform stator outlet flow. Taking the experimental values for the unsteady flow velocities and turbulence properties, the effect of the periodic stator wakes on the rotor flow is discussed.

Redistribution of an inlet temperature distortion in an axial flow turbine stage

The results of an experimental program aimed at determining the extent of the redistribution of an inlet temperature distortion in an axial flow turbine stage are presented. The program was conducted in a large-scale, low-speed, single-stage turbine where air, seeded with CO2, was introduced at one circumferential location upstream of the inlet guide vane. The migration of the seeded air through the turbine was determined by sensing CO2 concentration inside the stage. A temperature distortion was introduced by heating the seeded air. The CO2 concentration contours measured downstream of the vane showed h'ttle change with heating, indicating that the vane flowfield was relatively unaffected by the introduction of the temperature distortion. However, the CO2 contours observed on the rotor airfoil surfaces for the case with inlet heating indicated segregation of hot and cold gas with the higher temperature gas migrating to the pressure side and the lower temperature gas migrating to the suction side. Significant increases in rotor secondary flow were also observed. Two separate physical mechanisms are postulated to explain the observed experimental trends. Calculations performed by using a three-dimensional Euler solver show qualitative agreement with the experimental data.