Optimization of an Axial Turbine Stage for Aerodynamic Inlet Blockage

2011 ◽  
Author(s):  
Mohammad Arabnia ◽  
Vadivel K. Sivashanmugam ◽  
Wahid Ghaly
Keyword(s):  
Pressure Loss ◽  
Suction Side ◽  
Loss Coefficient ◽  
Von Mises Stress ◽  
Optimization Approach ◽  
Design Point ◽  
Pressure Loss Coefficient ◽  
Design Variables ◽  
Blade Shape ◽  
Von Mises

This paper presents a practical and effective optimization approach to minimize 3D-related flow losses associated with high aerodynamic inlet blockage by re-stacking the turbine rotor blades. This approach is applied to redesign the rotor of a low speed subsonic single-stage turbine that was designed and tested in DLR, Germany. The optimization is performed at the design point and the objective is to minimize the rotor pressure loss coefficient as well as the maximum von Mises stress while keeping the same design point mass flow rate, and keeping or increasing the rotor blade first natural frequency. A Multi-Objective Genetic Algorithm (MOGA) is coupled with a Response Surface Approximation (RSA) of the Artificial Neural Network (ANN) type. A relatively small set of high fidelity 3D flow simulations and structure analysis are obtained using ANSYS Workbench Mechanical. That set is used to train and to test the ANN models. The stacking line is parametrically represented using a quadratic rational Bezier curve (QRBC). The QRBC parameters are directly related to the design variables, namely the rotor lean and sweep angles and the bowing parameters. Moreover, it results in eliminating infeasible shapes and in reducing the number of design variables to a minimum while providing a wide design space for the blade shape. The aero-structural optimization of the E/TU-3 turbine proved successful, the rotor pressure loss coefficient was reduced by 9.8% and the maximum von Mises stress was reduced by 36.7%. This improvement was accomplished with as low as four design variables, and is attributed to the reduction of 3D-related aerodynamic losses and the redistribution of stresses from the hub trailing edge region to the suction side maximum thickness area. The proposed parametrization is a promising one for 3D blade shape optimization involving several disciplines with a relatively small number of design variables.

Different Effects of Cantilevered and Shrouded Stators on Axial Compressor Performance

2017 ◽  
Author(s):  
Xiayi Si ◽  
Jinfang Teng ◽  
Xiaoqing Qiang ◽  
Jinzhang Feng
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Axial Position ◽  
Leakage Flow ◽  
Flow Angle ◽  
Design Point ◽  
Pressure Loss Coefficient ◽  
Total Pressure Loss Coefficient

Numerical simulations with the steady 3D RANS were performed on the rear stage of a modern high pressure compressor. The labyrinth seal cavity model of the shrouded stator was simplified according to the actual stator structure, which the seal cavity gap is 1% of blade height. Several typical configurations (shrouded stator, idealized stator and cantilevered stators) were designed and carried out, and cantilevered stators contained no gap, small gap (CS1%), design gap (CS2.5%) and large gap (CS4%/CS5%). The results indicate due to the effect of leakage flow from 1% span seal cavity gap, the total pressure loss of SS is larger than IS, while IS instead of SS in the process of the compressor design, the stall margin will be enlarged nearly 6% numerically. At the design point, when the hub gap is 3.5% span clearance CS has the same loss with IS, and when the hub gap is 4.5% span clearance CS has almost the same loss with SS. Among all operation range, the total pressure loss of S1 increases with the increase of the hub clearance. When the hub gap is 0 (CS0), there is no leakage flow and the loss is the least. At the design point, comparing with SS, the total pressure loss coefficient of CS0 decreases 18.34%, CS2.5% decreases 8.46% and IS decreases 6.45%. It means if the cantilevered stator with 2.5% span hub clearance were adopted in the HPC, the performance would be better than the shrouded stator. However, because of the matching condition, the rotor that follows after cantilevered stator should be redesigned according to blade loading and inlet flow angle changed. The performance of cantilevered stator is impacted of various hub clearance, the loss below 25% span increases significantly with hub clearance, the maximum value of outlet flow angle deviation is 2.3 degree. The stator hub peak loading is shifted upstream toward the leading edge when hub clearance size is increased. The total pressure loss coefficient and pressure coefficient at different axial position had the function relation. When the hub clearance increases, the position of double leakage flow start backwards, in the rear part of stator the secondary flow becomes stronger leading to more mixing loss and lower total pressure.

Design, Performance Evaluation and Endwall Flow Structure Investigation of an S-Shaped Intermediate Turbine Duct

2007 ◽  
Author(s):  
Lars-Uno Axelsson ◽  
Carlos Arroyo Osso ◽  
David Cadrecha ◽  
T. Gunnar Johansson
Keyword(s):  
Performance Evaluation ◽  
Flow Visualization ◽  
Pressure Loss ◽  
Loss Coefficient ◽  
Flow Angle ◽  
Guide Vanes ◽  
Design Point ◽  
Intermediate Turbine Duct ◽  
Pressure Loss Coefficient ◽  
And Performance

Annular S-shaped intermediate turbine ducts are used in modern multi-spool jet engines to connect the high pressure turbine with the low-pressure turbine. The trend towards engines with larger by-pass ratios requires the future intermediate turbine ducts to be shorter and have larger radial off-set. This paper deals with the design and performance evaluation of a state-of-the-art annular S-shaped intermediate turbine duct. The details of the design of the intermediate turbine duct are presented together with static pressure measurements and oil film flow visualization along the endwalls, and area traverses at the inlet and outlet planes using a 5-hole probe. The measurements were done for three operating points of the turbine. From the flow visualization no separation could be detected at design point conditions, but for off-design conditions regions of separation were detected on the guide vanes located within the inter-turbine duct. The pressure loss coefficient was shown to be comparable for the two cases with lowest swirl angle, but the design point showed a slightly lower pressure loss. For the case with the largest flow angle the pressure loss coefficient was clearly larger than for the other two cases, which can be associated with the separation found on the guide vanes.

Numerical Investigation of Flow Separation Control of Low-Pressure High-Lift Blade With Different Grooves and Protrusions

2013 ◽  
Author(s):  
Huancheng Qu ◽  
Ping Li ◽  
Jianhui Chen ◽  
Zhongyang Shen ◽  
Yonghui Xie ◽  
...  
Keyword(s):  
Flow Separation ◽  
Pressure Loss ◽  
Total Pressure ◽  
Suction Side ◽  
Loss Coefficient ◽  
Total Pressure Loss ◽  
Flow Separation Control ◽  
Pressure Loss Coefficient ◽  
Flow Loss ◽  
Total Pressure Loss Coefficient

The shear stress transport (SST) turbulence model and γ-Reθ transition model were employed when solving the Reynolds-averaged Navier-Stokes (RANS) equations. The flow separation in the suction side of the typical high-lift low-pressure gas turbine PakB blade was investigated. Different sets of mesh were adopted and the results of grid independence study show that the precision is maintained when the grid system of 126,780 is adopted. And the computational results were compared with the existing experimental and computational results, which indicate that the numerical method can predict the separated transition flow reliably. Different kinds of structures including V grooves and protrusions, curved grooves and protrusions, rectangular grooves and protrusions were used to passive control of the flow separation in the suction side of the PakB blade. The structures have the same locations including 65%Cax, 68%Cax and 71%Cax on the suction side of the blade as well as length and height for better comparison. All of these cases are compared with the flow of PakB cascade without control with Re = 86,000 and FSTI = 1%. The shear layer is uplifted when the flow passes the passive device. And the separation bubble inside the grooves almost occupies the whole groove space which makes the length of the separation shorter than that in the case without control. The separation inside the grooves joins into the downstream separation in the case of grooves located in 71%Cax. The flow starts to separate in the leeside of the protrusion wherever the protrusion locates. And the attachment point moves forward significantly in the comparison with the case of without control. However, it brings in more flow loss because of the protrusion’s resistance to the boundary flow. In the total pressure loss coefficient comparison with the case without control, the grooves produce less flow loss while the protrusions at all the locations bring more flow loss. The nearer the groove is away from the separation point in the case without control, the higher the efficiency could be in the view of total pressure loss coefficient. The rectangular grooves are considered as a more effective structure for the flow separation control of PakB blade. Moreover, the flow separation bubble length and the total pressure loss coefficient decrease as Reynolds number increases in the cases without control. The total pressure loss coefficient in the different Reynolds numbers cases with rectangular groove is lower than that in the cases without control and the flow control performance gets much better when Reynolds number increases.

Vibration suppression investigation and parametric design of tri-axle straight heavy truck with pitch-resistant hydraulically interconnected suspension

2021 ◽  
pp. 107754632110396
Author(s):  
Fei Ding ◽  
Jie Liu ◽  
Chao Jiang ◽  
Haiping Du ◽  
Jiaxi Zhou ◽  
...  
Keyword(s):  
Surface Area ◽  
Dynamic Load ◽  
Pressure Loss ◽  
Vibration Suppression ◽  
Parametric Design ◽  
Suspension System ◽  
Loss Coefficient ◽  
The Body ◽  
Impedance Matrix ◽  
Pressure Loss Coefficient

The vibration suppression of the proposed pitch-resistant hydraulically interconnected suspension system for the tri-axle straight truck is investigated, and the vibration isolation performances are parametrically designed to achieve smaller body vibration and tire dynamic load using increased pitch stiffness and optimized pressure loss coefficient. For the hydraulic subsystem, the transfer impedance matrix method is applied to derive the impedance matrix. These hydraulic forces are incorporated into the motion equations of mechanical subsystem as external forces according to relationships between boundary flow and mechanical state vectors. In terms of the additional mode stiffness/damping and suspension performance requirements, the cylinder surface area, accumulator pressure, and damper valve’s pressure loss coefficient are comprehensively tuned with parametric design technique and modal analysis method. It is found the isolation capacity is heavily dependent on installation scheme and fluid physical parameters. Especially, the surface area can be designed for the oppositional installation to separately raise pitch stiffness without increasing bounce stiffness. The pressure loss coefficients are tuned with design of experiment approach and evaluated using all conflict indexes with normalized dimensionless evaluation factors. The obtained numerical results indicate that the proposed pitch-resistant hydraulically interconnected suspension system can significantly inhibit both the body and tire vibrations with decreased suspension deformation, and the tire dynamic load distribution among wheel stations is also improved.

The Characteristics Study of Helium-Xenon Mixture in Closed Brayton Cycle for Space Nuclear Reactor Power

2018 ◽  
Author(s):  
Xie Yang ◽  
Lei Shi
Keyword(s):  
Physical Properties ◽  
Pressure Loss ◽  
Nuclear Reactor ◽  
Reactor Power ◽  
Loss Coefficient ◽  
Working Fluid ◽  
System Efficiency ◽  
Pressure Loss Coefficient ◽  
Molar Weight ◽  
Xenon Mixture

Differing from the adoption of helium as working fluid of closed Brayton cycle (CBC) for terrestrial high temperature gas cooled reactor (HTGR) power plants, helium-xenon mixture with a proper molar weight was recommended as working fluid for space nuclear reactor power with CBC conversion. It is essential to figure out how the component of helium-xenon mixture affects the net system efficiency, in order to provide reference for the selection of appropriate cycle working fluid. After a discussion of the physical properties of different helium-xenon mixtures, the related physical properties are studied to analyze their affection on the key parameters of CBC, including adiabatic coefficient, recuperator effectiveness and normalized pressure loss coefficient. Then the comprehensive thermodynamics of CBC net system efficiency is studied in detail considering different helium-xenon mixtures. The physical properties study reveals that at 0.7 MPa and 400 K, the adiabatic coefficient of helium-xenon mixture increases with increased molar weight, from 0.400 (pure helium) to 0.414 (pure xenon), while recuperator effectiveness firstly increases and then decreases with the increase of molar weight, and the normalized pressure loss coefficient increases monotonically with molar weight increases. The thermodynamic analysis results show that the adiabatic coefficient has less effect on the net system efficiency, while the net system efficiency increases with increased recuperator effectiveness, and the net system efficiency decreases with normalized pressure loss coefficient increases. Finally, the mixture of helium-8.6% xenon was adopted as working fluid, instead of pure helium, for ensuring less turbine mechanicals (turbine and compressor) stages, and resulting maximum recuperator effectiveness. At the given cold / hot side temperature of 400 / 1300 K, the net system efficiency can reach 29.18% theoretically.

Rotating Annulus Component Performance Characterisation Based on CFD Analyses

2018 ◽  
Author(s):  
Youming Yuan ◽  
David Hunt
Keyword(s):  
Test Data ◽  
Pressure Loss ◽  
Model Performance ◽  
Internal Flow ◽  
Loss Coefficient ◽  
Performance Data ◽  
Pressure Loss Coefficient ◽  
1D Model ◽  
Torque Coefficient ◽  
Secondary Air

FloMASTER is a 1-D thermo-fluids system simulation tool and its component models depend on the characterisation data of the component performance. Such performance data is mainly based on data banks established from extensive tests exemplified by the books like “Internal Flow” by Miller [1] and “Handbook of Hydraulic Resistance” by Idelchik [2]. One of the key components of the gas turbine secondary air system is the rotating annulus. However, reliable data and correlations for performance characteristics like pressure loss coefficient, torque coefficient, windage and heat transfer for this component are rare and non-existent in the open literature for the case of both walls rotating simultaneously, which is becoming more common in today’s multi-spool military aero engines. To overcome this challenge of lack of reliable performance data and correlations, in this paper the Mentor Graphics 3D CFD tool “FloEFD” is used to model both inner wall rotating and outer wall rotating annulus flow, and to verify the 3D CFD results of performance data in terms of pressure loss coefficient and torque coefficient versus some published test data in the open literature. It is shown that the CFD gives results on pressure loss and torque coefficients that are in good agreement with test data based correlations used in FloMASTER. This demonstrates that 3D CFD can be used as a powerful tool for verifying the existing 1D model, extending the 1D model performance data range and generating new performance data for developing new components where such data is not available from open literature. A future project is to extend this approach to provide performance data for rotating annuli with both walls rotating. Such data will form the basis for developing a new component model for a rotating annulus with both walls rotating.

A Study of the Fabrication and Analysis of Micro Diffuser/Nozzles

2003 ◽  
Author(s):  
Kai-Shing Yang ◽  
Ing-Young Chen ◽  
Bor-Yuan Shew ◽  
Chi-Chuan Wang
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Pressure Loss ◽  
Measured Data ◽  
Loss Coefficient ◽  
Opening Angle ◽  
Velocity Change ◽  
Pressure Loss Coefficient ◽  
Micro Nozzle ◽  
Volumetric Flowrate

In this study, an analysis of the performance of micro nozzle/diffusers is performed and fabrication of the micro nozzle/diffuser is conducted and tested. It is found that the pressure loss coefficient for the nozzle/diffuser decreases with the Reynolds number. At a given Reynolds number, the pressure loss coefficient for nozzle is higher than that of the diffuser due to considerable difference in the momentum change. For the effect of nozzle/diffuser length on the pressure loss coefficient, it is found that the influence is rather small. At a fixed volumetric flowrate, a “minimum” phenomenon of the pressure loss coefficient vs. nozzle/diffuser depth is encountered. This is related to the interactions of velocity change and friction factor. Good agreements of the measured data with the predicted results are found in this study except at a diffuser having an opening angle of 20° . It is likely that the departure of this case to the prediction is due to the separation phenomenon in a larger angle of the diffuser.

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