Validating the Iterative Design Procedure for an Axial Flow Turbine Test Rig

2021 ◽  
Author(s):  
Rajat Arora ◽  
Ramraj H. Sundararaj ◽  
T. Chandra Sekar ◽  
Abhijit Kushari
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Secondary Flows ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Airflow Rate ◽  
Rotor Speed ◽  
Flowing Fluid ◽  
Air Mass

Abstract Turbines remain one of the most efficient devices for extracting energy from a flowing fluid. In a gas turbine engine, axial flow turbines are used to extract energy from the working fluid and drive the compressor, to which they are mechanically connected. To maximize the performance of the axial flow turbine, it is necessary to carry out a design optimization of the components while suitably accounting for losses generated by secondary flows. An axial flow turbine rig is designed, fabricated, and installed to better understand and improve upon secondary flow models used in design procedures. The rig is driven by a blower operating at a constant speed, capable of delivering a maximum airflow rate of 0.4 kg/s and a maximum pressure rise of 500 mbar across the device. The axial flow turbine is mechanically connected to a dynamometer capable of operating at a full load capacity of 5 kW and a maximum rotational speed of 10,000 RPM. The axial flow turbine, housed between the blower and dynamometer, consists of nozzle guide vanes followed by a rotor. The design pressure ratio is chosen as 1.04, based on the blower delivery conditions and dynamometer specifications. For an initial design, a low-pressure ratio low rotor speed design was selected, allowing for easy installation and testing of the rotating components. The design space for the axial flow turbine was generated by varying flow and geometrical parameters in suitable steps, using a program written in MATLAB 2020a. Using the input variables and applying free vortex theory for three-dimensional blade design, the aerodynamic design of the axial flow turbine was carried out. The axial flow turbine design is experimentally tested with suitable pressure measurements at every station. Experiments are conducted for four different air mass flow rates. At each air mass flow, the rotor speed is varied by increasing/decreasing the dynamometer load. The data is recorded and compared with the design point. The difference between the design and measured performance parameters is observed to be within acceptable limits.

Leakage and Cavity Pressures in an Interlocking Labyrinth Gas Seal: Measurements vs. Predictions

2019 ◽  
Author(s):  
Luis San Andrés ◽  
Tingcheng Wu ◽  
Jose Barajas-Rivera ◽  
Jiaxin Zhang ◽  
Rimpei Kawashita
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Inlet Pressure ◽  
Steam Turbines ◽  
Rotor Speed ◽  
Labyrinth Seals ◽  
Gas Seals

Abstract Gas labyrinth seals (LS) restrict secondary flows (leakage) in turbomachinery and their impact on the efficiency and rotordynamic stability of high-pressure compressors and steam turbines can hardly be overstated. Amongst seal types, the interlocking labyrinth seal (ILS), having teeth on both the rotor and on the stator, is able to reduce leakage up to 30% compared to other LSs with either all teeth on the rotor or all teeth on the stator. This paper introduces a revamped facility to test gas seals for their rotordynamic performance and presents measurements of the leakage and cavity pressures in a five teeth ILS. The seal with overall length/diameter L/D = 0.3 and small tip clearance Cr/D = 0.00133 is supplied with air at T = 298 K and increasing inlet pressure Pin = 0.3 MPa ∼ 1.3 MPa, while the exit pressure/inlet pressure ratio PR = Pout/Pin is set to range from 0.3 to 0.8. The rotor speed varies from null to 10 krpm (79 m/s max. surface speed). During the tests, instrumentation records the seal mass flow (ṁ) and static pressure in each cavity. In parallel, a bulk-flow model (BFM) and a computational fluid dynamics (CFD) analysis predict the flow field and deliver the same performance characteristics, namely leakage and cavity pressures. Both measurements and predictions agree closely (within 5%) and demonstrate the seal mass flow rate is independent of rotor speed. A modified flow factor Φ¯=m.T/PinD1-PR2 characterizes best the seal mass flow with a unique magnitude for all pressure conditions, Pin and PR.

Leakage and Cavity Pressures in an Interlocking Labyrinth Gas Seal: Measurements Versus Predictions

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Luis San Andrés ◽  
Tingcheng Wu ◽  
Jose Barajas-Rivera ◽  
Jiaxin Zhang ◽  
Rimpei Kawashita
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Labyrinth Seal ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Inlet Pressure ◽  
Steam Turbines ◽  
Rotor Speed ◽  
Labyrinth Seals ◽  
Gas Seals

Gas labyrinth seals (LS) restrict secondary flows (leakage) in turbomachinery and their impact on the efficiency and rotordynamic stability of high-pressure compressors and steam turbines can hardly be overstated. Among seal types, the interlocking labyrinth seal (ILS), having teeth on both the rotor and the stator, is able to reduce leakage up to 30% compared to other LSs with either all teeth on the rotor (TOR) or all teeth on the stator. This paper introduces a revamped facility to test gas seals for their rotordynamic performance and presents measurements of the leakage and cavity pressures in a five teeth ILS. The seal with overall length/diameter L/D = 0.3 and small tip clearance Cr/D = 0.00133 is supplied with air at T = 298 K and increasing inlet pressure Pin = 0.3–1.3 MPa, while the exit pressure/inlet pressure ratio PR = Pout/Pin is set to range from 0.3 to 0.8. The rotor speed varies from null to 10 krpm (79 m/s max. surface speed). During the tests, instrumentation records the seal mass flow (m˙) and static pressure in each cavity. In parallel, a bulk-flow model (BFM) and a computational fluid dynamics (CFD) analysis predict the flow field and deliver the same performance characteristics, namely leakage and cavity pressures. Both measurements and predictions agree closely (within 5%) and demonstrate that the seal mass flow rate is independent of rotor speed. A modified flow factor Φ¯=m˙T/(PinD1−PR2) characterizes best the seal mass flow with a unique magnitude for all pressure conditions, Pin and PR.

Design and Internal Flow Analysis of a Ducted Contra-Rotating Axial Flow Fan

2014 ◽  
Author(s):  
Ali Mohammadi ◽  
Masoud Boroomand
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Optimum Operating ◽  
Axial Flow Fan ◽  
Design Algorithm ◽  
Flow Solver ◽  
Operating Points

This paper presents the design procedure of a ducted contra-rotating axial flow fan and investigates the flow behavior inside it using ANSYS CFX-15 flow solver. This study investigates parameters such as pressure ratio, inlet mass flow rate and efficiency in different operating points. This system consists of two rotors with an outer diameter of 434 mm and an inner diameter of 260 mm which rotate contrary to each other with independent nominal rotational speeds of 1300 rpm. Blades’ maximum thickness and rotational speeds of each rotor will be altered as well as the axial distance between the two rotors to investigate their effect on the overall performance of the system. Designed to deliver a total pressure ratio of 1.005 and a mass flow rate of 1.8 kg/s at nominal rotational speeds, this system proves to be much more efficient compared to the conventional rotor-stator fans. NACA-65 airfoils are used in this analysis with the necessary adjustments at each section. Inverse design method is used for the first rotor and geometrical constraints are employed for the second one to have an axial inlet and outlet flow without using any inlet or outlet guide vanes. Using free vortex swirl distribution method, characteristic parameters and the necessary data for 3D generation of this model are obtained. The appropriate grid is generated using ATM method in ANSYS TurboGrid and the model is simulated in CFX-15 flow solver by employing k-ε turbulence model in the steady state condition. Both design algorithm and simulation analysis confirm the high anticipated efficiency for this system. The accuracy of the design algorithm will be explored and the most optimum operating points in different rotational speed ratios and axial distances will be identified. By altering the outlet static pressure of the system, the characteristic map is obtained.

Numerical Simulation of Steady Air Injection Flow Control Effects on a Transonic Axial Flow Compressor

2012 ◽  
Vol 224 ◽  
pp. 352-357
Author(s):  
Islem Benhegouga ◽  
Ce Yang
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Leading Edge ◽  
Air Injection ◽  
Axial Flow Compressor ◽  
Blade Tip ◽  
Flow Compressor

In this work, steady air injection upstream of the blade leading edge was used in a transonic axial flow compressor, NASA rotor 37. The injectors were placed at 27 % upstream of the axial chord length at blade tip, the injection mass flow rate is 3% of the chock mass flow rate, and 3 yaw angles were used, respectively -20°, -30°, and -40°. Negative yaw angles were measured relative to the compressor face in opposite direction of rotational speeds. To reveal the mechanism, steady numerical simulations were performed using FINE/TURBO software package. The results show that the stall mass flow can be decreased about 2.5 %, and an increase in the total pressure ratio up to 0.5%.

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1998 ◽  
Vol 120 (3) ◽  
pp. 477-486 ◽  
Author(s):  
D. W. Thompson ◽  
P. I. King ◽  
D. C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Percent Improvement ◽  
Flow Compressor

The effects of stepped-tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine causing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100 percent design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0 percent increase in mass flow and a 1.5 percent improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

Semi-Closed Cycle O2/CO2 Combustion Gas Turbines: Influence of Fluid Properties on the Aerodynamic Performance of the Turbomachinery

2002 ◽  
Author(s):  
S. K. Roberts ◽  
S. A. Sjolander
Keyword(s):  
Mass Flow ◽  
Gas Turbines ◽  
Pressure Ratio ◽  
Working Fluid ◽  
Working Fluids ◽  
Combustion Gas ◽  
Isentropic Flow ◽  
Isentropic Exponent ◽  
Fluid Properties ◽  
Compressor Map

Many gases, including carbon dioxide and argon, have been considered as alternatives to air as working fluids in a number of design studies for closed and semi-closed gas turbine engines. In many of these studies, it has been assumed that if the gas constant R and specific heat ratio (isentropic exponent) γ are included in the speed and flow parameters, the compressor map or turbine characteristic is applicable to other working fluids. However, similarity arguments show that the isentropic exponent itself is a criterion of similarity and that the turbomachinery characteristics, even when appropriately non-dimensionalized, will in principle vary as the γ of the working fluid varies. This paper examines the effect of γ on turbomachinery characteristics, mainly in terms of compressors. The performance of a centrifugal compressor stage was measured using air (γ = 1.4), CO2 (γ = 1.29), and argon (γ = 1.67). For the same values of the non-dimensional speed and mass flow, the pressure ratio, the efficiency, and the choking mass flow were found to be significantly different for the three test gases. The experimental results have been found to be consistent with a CFD analysis of the impeller. Finally, it is shown that the changes in performance can be predicted reasonably well with simple arguments based mainly on one-dimensional isentropic flow. These arguments form the basis for correction procedures that can be used to project compressor characteristics measured for one value of γ to those for a gas with a different value.

Experimental Investigation of Stepped Tip Gap Effects on the Performance of a Transonic Axial-Flow Compressor Rotor

1997 ◽  
Author(s):  
Donald W. Thompson ◽  
Paul I. King ◽  
Douglas C. Rabe
Keyword(s):  
Mass Flow ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Compressor Rotor ◽  
Compressor Performance ◽  
Flow Compressor

The effects of stepped tip gaps and clearance levels on the performance of a transonic axial-flow compressor rotor were experimentally determined. A two-stage compressor with no inlet guide vanes was tested in a modern transonic compressor research facility. The first-stage rotor was unswept and was tested for an optimum tip clearance with variations in stepped gaps machined into the casing near the aft tip region of the rotor. Nine casing geometries were investigated consisting of three step profiles at each of three clearance levels. For small and intermediate clearances, stepped tip gaps were found to improve pressure ratio, efficiency, and flow range for most operating conditions. At 100% design rotor speed, stepped tip gaps produced a doubling of mass flow range with as much as a 2.0% increase in mass flow and a 1.5% improvement in efficiency. This study provides guidelines for engineers to improve compressor performance for an existing design by applying an optimum casing profile.

scholarly journals Detailed Measurements of Three-Dimensional Flows and Losses Inside an Axial Flow Turbine Rotor

1994 ◽  
Author(s):  
Atsumasa Yamamoto ◽  
Junichi Tomlnaga ◽  
Takayuki Matsunuma ◽  
Eisuke Outa
Keyword(s):  
Three Dimensional ◽  
Axial Flow ◽  
Turbine Rotor ◽  
Frame Of Reference ◽  
Secondary Flows ◽  
Low Energy ◽  
Generation Process ◽  
Rotating Frame ◽  
Rotor Speed ◽  
Speed Variation

Detailed traverse measurements of three dimensional flows and the associated losses inside a turbine rotor passage were carried out in the rotating frame of reference by using small five hole Pitot tubes. Strong secondary flows including passage vortices, a leakage vortex and various separation vortices were found to occur in the passage, and they are significantly influenced by the rotor speed, variation of which corresponds to different test incidences and blade loadings. Loss generation process in the rotor is described in relation to the migration of low energy fluids which are driven by the various vortices and their interaction at different rotor incidences.

Stator-Rotor Interactions in a Transonic Compressor— Part 1: Effect of Blade-Row Spacing on Performance

2003 ◽  
Vol 125 (2) ◽  
pp. 328-335 ◽  
Author(s):  
Steven E. Gorrell ◽  
Theodore H. Okiishi ◽  
William W. Copenhaver
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Transonic Compressor ◽  
Blade Row ◽  
Spacing Variation ◽  
Stator Blade ◽  
Flow Compressor

Usually less axial spacing between the blade rows of an axial flow compressor is associated with improved efficiency. However, mass flow rate, pressure ratio, and efficiency all decreased as the axial spacing between the stator and rotor was reduced in a transonic compressor rig. Reductions as great as 3.3% in pressure ratio, and 1.3 points of efficiency were observed as axial spacing between the blade rows was decreased from far apart to close together. The number of blades in the stator blade-row also affected stage performance. Higher stator blade-row solidity led to larger changes in pressure ratio efficiency, and mass flow rate with axial spacing variation. Analysis of the experimental data suggests that the drop in performance is a result of increased loss production due to blade-row interactions. Losses in addition to mixing loss are present when the blade-rows are spaced closer together. The extra losses are associated with the upstream stator wakes and are most significant in the midspan region of the flow.

Numerical Simulation of Tip Leakage Flows in Axial Flow Turbines, With Emphasis on Flow Physics: Part I — Effect of Tip Clearance Height

2000 ◽  
Author(s):  
J. Tallman ◽  
B. Lakshminarayana
Keyword(s):  
Mass Flow ◽  
Axial Flow ◽  
Numerical Procedure ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Flow Physics ◽  
Tip Leakage ◽  
Inlet Conditions

A pressure-correction based, 3D Navier-Stokes CFD code was used to simulate the effects of turbine parameters on the tip leakage flow and vortex in a linear turbine cascade to understand the detailed flow physics. A baseline case simulation of a cascade was first conducted in order to validate the numerical procedure with experimental measurements. The effects of realistic tip clearance spacing, inlet conditions, and relative endwall motion were then sequentially simulated, while maintaining previously modified parameters. With each additional simulation, a detailed comparison of the leakage flow’s direction, pressure gradient, and mass flow, as well as the leakage vortex and its roll-up, size, losses, location, and interaction with other flow features, was conducted. Part I of this two-part paper series focuses on the effect of reduced tip clearance height on the leakage flow and vortex. Reduced tip clearance resulted in less mass flow through the gap, a smaller leakage vortex, and less aerothermal losses in both the gap and the vortex. The shearing of the leakage jet and passage flow to which leakage vortex roll-up is usually attributed to was not observed in any of the simulations. Alternative explanations of the leakage vortex’s roll-up are presented. Additional secondary flows that were seen near the casing were also discussed. A more thorough thesis on the research presented in this paper can be found at the World Wide Web address http://navier.aero.psu.edu/∼jat.

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