Modeling of the Hub Cavity Leakage Flows in Axial Compressors

2012 ◽  
Author(s):  
Hasham H. Chougule ◽  
Anand Dhamarla ◽  
Shraman Goswami ◽  
Mahmoud L. Mansour
Keyword(s):  
Boundary Conditions ◽  
Transfer Functions ◽  
Axial Compressor ◽  
Cfd Modeling ◽  
Leakage Flow ◽  
Axial Compressors ◽  
Leakage Flows ◽  
Cfd Models ◽  
High Pressure Compressor ◽  
Computational Analyses

Computational analyses are carried out to predict the effect of the hub leakage flow from the inner banded stator cavities on the overall performance of an axial high pressure compressor. The results of a full fidelity simulation model, which includes cavities, sealing and main flow, is compared with models without the hub leakage flow. The CFD prediction confirms a significant effect from the hub leakage on the performance of the multistage axial compressor. A simpler and faster CFD modeling technique is explored and discussed for the modeling of the effect of the hub cavity leakage. In this approach, costly details of the stator cavities are ignored. Transfer functions or correlations are derived from the 1.5 stage (IGV-Rotor1-Stator1) of a multistage compressor having inner banded stator cavity. These correlations are used as boundary conditions to the primary flow path of the compressor while carrying out the simplified CFD models for the complete 4 stage compressor model. A MINITAB study is conducted to understand the most influencing parameters and their interactions in deriving the correlations. Analyses are then carried out using the simplified model with the hub leakage boundary conditions derived from these correlations. The CFD results of the full fidelity simulation and the simplified models are compared in this paper.

Optimization of the Workflow of Multistage Axial Compressors Using Modern Gas Dynamics Computing Systems

2020 ◽  
Author(s):  
Grigorii Popov ◽  
Evgenii Goriachkin ◽  
Oleg Baturin ◽  
Valerii Matveev ◽  
Igor Egorov ◽  
...  
Keyword(s):  
Gas Dynamics ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Calculation Model ◽  
Cfd Modeling ◽  
Compressor Blades ◽  
Stability Margins ◽  
Axial Compressors ◽  
Cfd Models ◽  
Multi Stage

Abstract Current developmental level of computers and numerical methods of gas dynamics makes it possible to optimize compressors using 3D CFD models. Design variants for the compressor can be automatically generated that best suit all the design requirements and limitations. However, the methods and tool for optimizing compressors are not sufficiently developed for the successful application. The problems lie in the large size of the calculation model, the solution time and the requirements for computer resources. In present study, a method for finding the optimal configuration of the blades of multi-stage axial compressors using 3D CFD modeling and commercial optimization programs as the main tools was developed. The basic parameters of the compressor (efficiency, pressure ratio, mass flow rate, etc.) can be improved using the created method correcting the shape of the blade profiles and their relative position. The method considers presence of various constraints. When developing the method, special attention was paid to the creation of an algorithm for parameterizing the blade shape and a program based on it, which can automatically change the shape of the axial compressor blades. They were used by the authors during optimization as a tool that converts variable parameters into the “new” blade geometry. Recommendations were also found on the rational settings for the CFD models used in the optimization of axial compressors. The paper provides a brief overview of several works related to the optimization of multi-stage gas turbine axial compressors for various purposes (number of stages from 3 to 15), successfully performed using the developed method. As a result, an increase was achieved in efficiency, pressure ratio and stability margins.

Numerical Investigation of a Cantilevered Compressor Stator at Varying Clearance Sizes

2015 ◽  
Author(s):  
Chengwu Yang ◽  
Xingen Lu ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
Junqiang Zhu
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
High Flow ◽  
Leakage Flow ◽  
Streamwise Direction ◽  
Stall Margin ◽  
Axial Compressors ◽  
Pressure Surface ◽  
The Impact ◽  
Highly Loaded

The clearance size of cantilevered stators affects the performance and stability of axial compressors significantly. Numerical calculations were carried out using the commercial software FINE/Turbo for a 2.5-stage highly loaded transonic axial compressor, which is of cantilevered stator for the first stage, at varying hub clearance sizes. The aim of this work is to improve understanding of the impact mechanism of hub clearance on the performance and the flow field in high flow turning conditions. The performance of the front stage and the compressor with different hub clearance sizes of the first stator has been analyzed firstly. Results show that the efficiency decreases as clearance size varies from 0 to 3% of hub chordlength, but the operating range has been extended. For the first stage, the efficiency decreases about 0.5% and the stall margin is extended. The following analysis of detailed flow field in the first stator shows that the clearance leakage flow and elimination of hub corner separation is responsible for the increasing loss and stall margin extending respectively. The effects of hub clearance on the downstream rotor have been discussed lastly. It indicates that the loss of the rotor increases and the flow deteriorates due to increasing of clearance size and hence the leakage mass flow rate, which mainly results from the interaction of upstream leakage flow with the passage flow near pressure surface. The affected region of rotor passage flow field expands in spanwise and streamwise direction as clearance size grows. The hub clearance leakage flow moves upward in span as it flows toward downstream.

Optimization Method of the Multistage Axial Compressors Using CFD Simulation

2021 ◽  
pp. 2141006
Author(s):  
Grigorii Popov ◽  
Igor Egorov ◽  
Evgenii Goriachkin ◽  
Oleg Baturin ◽  
Daria Kolmakova ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Optimization Problems ◽  
Search Algorithm ◽  
Pressure Ratio ◽  
Optimization Method ◽  
Cfd Modeling ◽  
Turbine Engines ◽  
Stability Margins ◽  
Axial Compressors ◽  
Cfd Models

The current level of numerical methods of gas dynamics makes it possible to optimize compressors using 3D CFD models. However, the methods and means are not sufficiently developed for their wide application. This paper describes a new method for the optimization of multistage axial compressors based on 3D CFD modeling and summarizes the experience of its application. The developed method is a complex system of interconnected components (an effective mathematical model, a parameterizer, and an optimum search algorithm). The use of the method makes it possible to improve or provide the necessary values of the main gas-dynamic parameters of the compressor by changing the shape of the blades and their relative position. The method was tested in solving optimization problems for multistage axial compressors of gas turbine engines (the number of stages from 3 to 15). As a result, an increase in efficiency, pressure ratio, and stability margins was achieved. The presented work is a summary of a long-years investigation of the research team and aims at creating a complete picture of the obtained results for the reader. A brief description of the results of industrial compresses optimization contained in the paper is given as an illustration of the effectiveness of the developed methods.

Numerical Simulation of Particulates in Multistage Axial Compressors

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Swati Saxena ◽  
Giridhar Jothiprasad ◽  
Corey Bourassa ◽  
Byron Pritchard
Keyword(s):  
High Pressure ◽  
Axial Compressor ◽  
Airborne Particulate Matter ◽  
Spherical Particles ◽  
Nonspherical Particles ◽  
Qualitative Comparison ◽  
Axial Compressors ◽  
Sand Erosion ◽  
High Pressure Compressor ◽  
Pressure Compressor

Aircraft engines ingest airborne particulate matter, such as sand, dirt, and volcanic ash, into their core. The ingested particulate is transported by the secondary flow circuits via compressor bleeds to the high pressure turbine and may deposit resulting in turbine fouling and loss of cooling effectiveness. Prior publications focused on particulate deposition and sand erosion patterns in a single stage of a compressor or turbine. This work addresses the migration of ingested particulate through the high pressure compressor (HPC) and bleed systems. This paper describes a 3D CFD methodology for tracking particles along a multistage axial compressor and presents particulate ingestion analysis for a high pressure compressor section. The commercial CFD multiphase solver ANSYS CFX® has been used for flow and particulate simulations. Particle diameters of 20, 40, and 60 μm are analyzed. Particle trajectories and radial particulate profiles are compared for these particle diameters. The analysis demonstrates how the compressor centrifuges the particles radially toward the compressor case as they travel through the compressor; the larger diameter particles being more significantly affected. Nonspherical particles experience more drag as compared to spherical particles, and hence a qualitative comparison between spherical and nonspherical particles is shown.

Adiabatic Effectiveness Measurements and Predictions of Leakage Flows Along a Blade Endwall

2005 ◽  
Vol 127 (3) ◽  
pp. 609-618 ◽  
Author(s):  
W. W. Ranson ◽  
K. A. Thole ◽  
F. J. Cunha
Keyword(s):  
High Pressure ◽  
Turbine Blades ◽  
Leakage Flow ◽  
Leakage Flows ◽  
High Pressure Compressor ◽  
Flow Through ◽  
Cooling Air ◽  
Low Speed Wind Tunnel ◽  
Paper Address ◽  
Good Agreement

Traditional cooling schemes have been developed to cool turbine blades using high-pressure compressor air that bypasses the combustor. This high-pressure forces cooling air into the hot main gas path through seal slots. While parasitic leakages can provide a cooling benefit, they also represent aerodynamic losses. The results from the combined experimental and computational studies reported in this paper address the cooling benefit from leakage flows that occur along the platform of a first stage turbine blade. A scaled-up, blade geometry with an upstream slot, a mid-passage slot, and a downstream slot was tested in a linear cascade placed in a low-speed wind tunnel. Results show that the leakage flow through the mid-passage gap provides only a small cooling benefit to the platform. There is little to no benefit to the blade platform that results by increasing the coolant flow through the mid-passage gap. Unlike the mid-passage gap, leakage flow from the upstream slot provides good cooling to the platform surface, particularly in certain regions of the platform. Relatively good agreement was observed between the computational and experimental results, although computations overpredicted the cooling.

Performance evaluation of the inter-stage labyrinth seal for different tooth positions in an axial compressor

2017 ◽  
Vol 232 (6) ◽  
pp. 579-592 ◽  
Author(s):  
Xiaozhi Kong ◽  
Gaowen Liu ◽  
Yuxin Liu ◽  
Zhao Lei ◽  
Longxi Zheng
Keyword(s):  
Axial Compressor ◽  
Labyrinth Seal ◽  
Tip Clearance ◽  
Test Facility ◽  
Leakage Flow ◽  
Rotating Disc ◽  
Labyrinth Seals ◽  
Leakage Flows ◽  
Sealing Performance ◽  
Set Up

Labyrinth seals are normally used to control the leakage flow in the compressor stator well. The upstream and downstream rotor-stator cavities of the labyrinth seal can cause complex reverse leakage flows. Remarkable temperature increases and high swirl velocities are observed in this region. In addition, another characteristic of inter-stage labyrinth seal is that large expansions of rotor and stator may easily lead to severely rubbing between the teeth and shrouds, which can shorten the lifetime of the compressor obviously. Experiments were conducted at a rotating compressor inter-stage seal test facility. Different labyrinth rings were tested to compare the performances of inter-stage labyrinth seals with different tooth positions. Leakage flow rates, windage heating and swirl ratios in the outlet cavity were measured at different rotating speeds and pressure ratios. In order to get the working tip clearance accurately, the set up tip clearance was measured with plug gauges, while the radial displacements of rotating disc and stationary casing were measured separately with two high precision laser distance sensors. Numerical simulations were carried out to present the important flow physics responsible for the effects of different tooth positions. In this article, performances of different cases for single, double and triple teeth were investigated and the experimental data provide a new way for the design of inter-stage seals. This method can reduce the leakage flow and avoid severely rubbing at the same time by changing axial positions of teeth in the stator well. When teeth are placed downstream of the model and the tooth pitch is larger, the inter-stage seal would have better sealing performance. For triple teeth cases, N = 3-Case1 has the lowest discharge coefficients, 15% less than that of N = 3-Baseline.

Influence of the Leakage Flow Tangential Velocity on the Loss Generation and Leakage Flow Kinematics in Shrouded Axial Compressor Cascades

2006 ◽  
Author(s):  
D. W. Sohn ◽  
T. Kim ◽  
S. J. Song
Keyword(s):  
Tangential Velocity ◽  
Axial Compressor ◽  
Suction Side ◽  
Velocity Variation ◽  
Leakage Flow ◽  
Compressor Blades ◽  
Blade Passage ◽  
Leakage Flows ◽  
And Behavior ◽  
The Impact

Although compressor blades have long been shrouded for aerodynamic and structural reasons, the impact of the leakage flow in the shroud cavities on passage flows has only recently been investigated. Furthermore, the tangential velocity of the leakage flow, set by the blading and the relative motion between rotating and stationary surfaces, has a strong influence on the passage flow. Yet the influence of the tangential velocity variation on the kinematics and dynamics (loss) of the leakage flow (from its ingress to egress) in the shrouded cavity and main flow in the blade passage are unknown. Therefore, this paper reports on an experimental investigation of the axial evolution of loss generation in the blade passage and behavior of the leakage flow in the seal cavity in shrouded axial compressor cascades subject to the variation of leakage tangential velocity. The newly found results are as follows. First, increasing tangential velocity of the leakage flow reduces loss at 10% and 50% chordwise locations in the passage. However, most of the blockage and loss reductions occurs in the aft half chord and downstream of the blade passage. Second, the increasing tangential velocity spreads the loss core, which is originally concentrated in the suction side hub corner, in the pitchwise direction. Thus, the loss core becomes more two-dimensional, and the region’s radial extent is reduced. Third, increasing tangential velocity of the leakage flow makes the near hub passage flow more radially uniform. Consequently, the shear and resultant mixing loss between the passage and leakage flows are reduced near the hub, reducing the overall loss. Finally, the leakage flow is ingested through the downstream cavity and makes an abrupt turn at the seal tooth. Thus, two distinct flow regions — downstream and upstream of the single-tooth seal — are found. Before the leakage flow rejoins the mainstream via the upstream cavity trench, the leakage flow circumferentially migrates in the direction of rotation. The magnitude of the circumferential shift depends strongly on the leakage tangential velocity.

Performance and Stability Enhancement of NASA Rotor 37 Applying Abradable Coating

2005 ◽  
Author(s):  
Behnam H. Beheshti ◽  
Bijan Farhanieh ◽  
Kaveh Ghorbanian ◽  
Joao A. Teixeira ◽  
Paul C. Ivey
Keyword(s):  
Flow Characteristics ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Compressors ◽  
Compressor Rotor ◽  
Abradable Coating ◽  
Blade Tip ◽  
Stability Enhancement

Improvements in sealing mechanism between the rotating and the stationary parts of a turbomachine can extensively reduce the endwall leakage flow. In this regard, abradable seals are incorporated into compressor and turbine blade-tip region. In a gas turbine, equipped with abradable seals, tip of the rotor blade is designed to cut into the material coating of the casing and to form a close fitted circumferential groove for the movement of the blade tip. As a result, the resistance to the leakage flow in the tip gap region increases due to smaller tip clearances (available without any rub-induced damages). Minimizing the tip clearance size can lead to an increase in performance and stability. This paper presents a numerical investigation of abradable coating as a means to seal the tip leakage flow in NASA Rotor 37, a transonic axial compressor rotor. In order to validate the multi block model used in the tip gap region, various flow characteristics are verified with the experimental data for smooth casing at a design clearance of 0.5% span. To have a better understanding of how an abradable seal affects the passage flow field, smooth casing and abradable coating are studied and results are compared for various models including two different incursion depth and width. Results indicate that the application of abradable coating in transonic axial compressors can efficiently improve the performance and stability.

Investigation Into Core Compressor Tip Leakage Modelling Techniques Using a 3D Viscous Solver

2001 ◽  
Author(s):  
Jonathan P. Glanville
Keyword(s):  
Transport Model ◽  
Axial Compressor ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Tip Leakage ◽  
Leakage Flows ◽  
Modelling Techniques ◽  
Flow Through ◽  
Tip Leakage Flows

The leakage flow through the tip clearance gap of an axial compressor has a significant effect on loss production and stall behaviour. Accurate modelling is essential if improved designs are to be developed which control such flows. Studies have been carried out using the DERA TRANSCode 3D Reynolds-Averaged Navier-Stokes code to predict the tip leakage flows in a low speed research compressor. Calculations were carried out using both a simple pinched-tip model and an improved mesh which allowed the true square-tip geometry to be represented. Comparisons between the Baldwin-Lomax algebraic turbulence model and the Spalart-Allmaras one-equation transport model were also made. The results showed that the predictions of both the detailed flows and the loss levels were sensitive to the modelling and that substantial improvements in accuracy were possible.

Numerical Research on Effects of Shroud Contraction on Tip Leakage Flow and Overall Performance of Axial Compressors

2017 ◽  
Author(s):  
Yufan Zhang ◽  
Jiabin Li ◽  
Lucheng Ji
Keyword(s):  
Great Influence ◽  
Axial Compressor ◽  
Detailed Comparison ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Axial Compressors ◽  
Tip Leakage ◽  
Numerical Research ◽  
Overall Performance ◽  
Inclined Angle

In the design of an axial compressor, many designers take advantage of this technology and employ contracted shroud. What is its impact on tip leakage flow and overall performance of the axial compressor? What is its mechanism? In this paper, the NASA Rotor67 is taken as a research case, and parameterized study is conducted to investigate the effects of shrouds with different inclined angles. The inclined angles range from 0° to 13°. Based on the above described plan, numerical simulations are conducted to the original rotor67 and its modified versions with inclined shroud. To remove factors that might interfere the results, original Rotor 67 and all the blades with modified shroud should be compared to their optimal design status. Adjoint optimization is used to give the optimum blade corresponding to each shroud with different blade inclined angles. Then adjoint optimization was used again to give the optimum meridional flowpath for all the cases with different shroud inclined angles. This provides a powerful tool to evaluate the accuracy of the aforementioned prediction. A detailed comparison is made between the original flowpath and the optimized ones. Numerical results are analyzed in detail between original Rotor67 and its modified versions. The results show that the shroud inclined angle has an effect on the overall performance of the blade. It will also redistribute the velocity triangles and the chordwise distribution of aero load in the tip region. Hence it exerts great influence on the tip leakage flow field in the meantime. Shroud with suitable inclined angles can suppress the developing of leakage vortex , and the best-inclined angle for rotor 67 is found to be roughly 11°.

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