Stacking Line Research Articles

Influence of the Sweep Stacking on the Performance of an Axial Fan

In modern turbomachinery blade design, nonradial stacking of the profiles is often assumed to be one of the ways to improve the performance of a machine. Instead of stacking the profiles radially, the stacking line is changed by several modifications such as sweep, dihedral, lean, or a combination of these. Nonradial stacking influences secondary flows that have effects on the aerodynamic parameters such as efficiency, pressure rise, blade loading, and stall margin. However, many of the studies in literature are limited by the comparison of two or three cases. This situation leads to conflicting results because a modification may cause a positive effect in one study while in another one, the same modification may have a negative effect. In this study, a modified free vortex axial fan (named as base fan (BF) for this study) is designed first and the profiles of the blades are stacked radially by joining the centroids of the profiles. Second, 45 deg, 30 deg forward sweep (FS) and backward sweep (BS) modifications are applied. The effects of these modifications on aerodynamic performance of the fans are investigated by means of numerical calculations. The results show that FS and BS do not significantly affect the overall performance of the fan at the design flowrate in spite of the occurring modifications of the local blade pressure distribution. However, at low flowrates, FS and BS have positive and negative effects on the fan performance, respectively.

Aerodynamic optimization design for high pressure turbines based on the adjoint approach

A first study on the continuous adjoint formulation for aerodynamic optimization design of high pressure turbines based on S2 surface governed by the Euler equations with source terms is presented. The objective function is defined as an integral function along the boundaries, and the adjoint equations and the boundary conditions are derived by introducing the adjoint variable vectors. The gradient expression of the objective function then includes only the terms related to physical shape variations. The numerical solution of the adjoint equation is conducted by a finite-difference method with the Jameson spatial scheme employing the first and the third order dissipative fluxes. A gradient-based aerodynamic optimization system is established by integrating the blade stagger angles, the stacking lines and the passage perturbation parameterization with the quasi-Newton method of Broyden–Fletcher–Goldfarb–Shanno (BFGS). The application of the continuous adjoint method is validated through a single stage high pressure turbine optimization case. The adiabatic efficiency increases from 0.8875 to 0.8931, whilst the mass flow rate and the pressure ratio remain almost unchanged. The optimization design is shown to reduce the passage vortex loss as well as the mixing loss due to the cooling air injection.

Blade shape optimization for transonic axial flow fan

Transonic axial flow fan has relatively high blade tip speed and produces higher pressure ratio than the subsonic. However, considerable losses are brought about by the shock waves close to blade tip and over part of span, leading to deteriorated overall efficiency and operating flow range. The present study is to mitigate shock wave and reduce losses through simultaneous variation of blade sectional profiles and their stacking line in blade design. Both sectional profiles and stacking line are varied simultaneously to provide more flexible blade shape tuning. To achieve a best blade shape and produce maximum performance gains, a global optimization method is incorporated in the blade shape design. It includes an improved CCEA (cooperative co-evolution algorithm) optimizer and one-stage Expected Improvement (EI) based adaptively updated Kriging surrogate model. The former has divided the high-dimension optimization problems into readily solved low-dimension ones, while the later has enabled the optimizer to jump out of from the local optima and search the solution towards the global optima. The optimization is conducted for Rotor67 at design condition with a single workstation, and considerable overall efficiency and pressure ratio gains are simultaneously obtained, while the flow range is also extended. This is supported by the significantly improved flow behavior in the optimized blade passages, where the chordwise shock wave is mitigated, leading to an increase in overall efficiency; the spanwise static pressure distribution is improved evidently and this improves the overall pressure ratio.

Three-dimensional electromagnetic simulation of monolithic radial transmission lines for Z-pinch

AbstractThe electromagnetic simulation of the monolithic radial transmission lines for future Z-pinch was performed. Focusing on the difference in the maximum transmitted power efficiency between the electromagnetic simulation and the circuit simulation, the monolithic radial transmission lines with different impedance profile (exponential, Gaussian, hyperbolic) were compared. The power efficiency for the exponential line is higher than that for the Gaussian lines and the hyperbolic line, which is similar to that from the circuit simulation. However, all the power efficiencies obtained with the electromagnetic simulation are about 15% lower than those obtained with the circuit simulation, indicating the existence of considerable non-TEM modes and a non-ignorable error in the circuit simulation based on the quasi-TEM mode approximation. In consideration of several monolithic radial transmission lines being stacked together and the flat electrodes required by the stacked lines, the hyperbolic line was compared with the exponential line with several wide radial slots cut on the flat electrodes. While the hyperbolic line has a little bit lower transmitted power efficiency than that of the exponential line, it is much easier in fabrication. For this reason, the hyperbolic line was recommended as the best choice.

Axial flow compressor blade optimization through flexible shape tuning by means of cooperative co-evolution algorithm and adaptive surrogate model

The present study is to explore potential benefits of axial flow compressor blade optimization through a flexible tuning. Modifications of blade sectional profiles and their stacking line can control spanwise blade loading distribution, reduce shock losses, and extend operating flow range. Most previous studies focused on tuning either sectional profiles or stacking line, but little work was conducted by collaboratively varying both, which may be due to abrupt rise of optimization variables and complexity. An efficient optimization method is developed to handle highly nonlinear high-dimension blade optimization problem with simultaneous variation of both sectional profiles and stacking line. It incorporates an improved cooperative co-evolution algorithm optimizer and one-stage expected improvement based adaptive surrogate model. The former decomposes the high-dimension problem into low-dimension subproblems and they can be readily solved; the latter enables the optimizer to jump out of the local minima and conduct the aim-oriented optimal search toward global optimum. A coarse surrogate model is firstly constructed with some DOE samples but it is refined during optimization process with newly identified and evaluated samples. The model prediction accuracy is gradually improved, thus it captures the distinct features (especially global optimum) of optimization problem. Both blade sectional profiles and their spatial positions are simultaneously varied. Four sectional profiles of hub, 33% span, 67% span, and shroud are parameterized, and each is defined by a mean camber line and thickness distribution. Both of them are represented, respectively, by a third-order B-Spline curve. Spatial position of each profile varies in term of sweep and lean. Blade design optimization is conducted for Rotor67 at design flow on a single workstation of Dell 7500. Performance gains are significant: at design flow, overall efficiency and pressure ratio are increased, respectively, by 1.44 and 7.24%; off-design performances are also improved over the entire flow range.

Design and Strand Tests of a Fusion Cable Composed of Coated Conductor Tapes

The design of a flat cable suitable for future fusion reactors has been carried out. The cable consists of twisted round strands, which are composed of tapes stacked between copper profiles. According to calculations, the strand twist pitch and the cable twist pitch should be at least 1.5 or 2 m long to limit the strain and thus the reduction of the critical current. A 4-m-long strand (Ø6.2 mm) was fabricated on a continuous stacking and soldering line to demonstrate that the scaling up to industrial production is feasible. The strand can carry about 940 A in self-field at 77 K. The critical current evolution under bending strain was measured but it turned out to be rather fragile in “hard” bending direction. Three types of joints between strands were also manufactured and tested at 77 K.

True-amplitude single-stack redatuming

Based on the chaining of diffraction-stack migration and isochron-stack demigration, we derive a general true-amplitude Kirchhoff-type single-stack operator for 3D and 2.5D redatuming. It consists of performing a single weighted stack along adequately chosen stacking surfaces or lines. The corresponding traveltimes and weight functions can be calculated using quantities obtained from dynamic ray tracing. The operator simplifies when specified for zero-offset data. For simple types of media, we derive analytic expressions for the stacking lines and weight functions and demonstrate their functionality with numerical examples.

Design Optimization of a Transonic-Fan Rotor Using Numerical Computations of the Full Compressible Navier-Stokes Equations and Simplex Algorithm

The design of a transonic-fan rotor is optimized using numerical computations of the full three-dimensional Navier-Stokes equations. The CFDRC-ACE multiphysics module, which is a pressure-based solver, is used for the numerical simulation. The code is coupled with simplex optimization algorithm. The optimization process is started from a suitable design point obtained using low fidelity analytical methods that is based on experimental correlations for the pressure losses and blade deviation angle. The fan blade shape is defined by its stacking line and airfoil shape which are considered the optimization parameters. The stacking line is defined by lean, sweep, and skews, while blade airfoil shape is modified considering the thickness and camber distributions. The optimization has been performed to maximize the rotor total pressure ratio while keeping the rotor efficiency and surge margin above certain required values. The results obtained are verified with the experimental data of Rotor 67. In addition, the results of the optimized fan indicate that the optimum design is found to be leaned in the direction of rotation and has a forward sweep from the hub to mean section and backward sweep to the tip. The pressure ratio increases from 1.427 to 1.627 at the design speed and mass flow rate.

Influence of Dihedral Stacking on The Performance of An Axial Fan

This paper presents the effect of positive dihedral (lean) on the aerodynamic performance of a low speed axial fan. The blade profiles of the reference (base) fan are stacked on a radial line at the centre of gravity of each profile. The stacking line of the fan with the dihedral, along which the blade profiles are shifted in the direction perpendicular to the chordline, makes an angle of 45 in the radial direction. The performances of the both fans are investigated by means of ANSYS CFX commercial CFD software and are validated by experiments. Both of the computational and the experimental results show that positive dihedral removes the unstable operation region of the fan. Moreover, the total pressure rise and the total-to-total efficiency are increased at low flowrates. The detailed investigation shows that the induced radial velocity in the outward direction may be the reason of the positive effect of the dihedral at low flowrates. As a result, dihedral stacking extends the stable working range of the fan by removing the unstable region.

DYNAMICAL VERSUS STELLAR MASSES IN COMPACT EARLY-TYPE GALAXIES: FURTHER EVIDENCE FOR SYSTEMATIC VARIATION IN THE STELLAR INITIAL MASS FUNCTION

Several independent lines of evidence suggest that the stellar initial mass function (IMF) in early-type galaxies becomes increasingly `bottom-heavy' with increasing galaxy mass and/or velocity dispersion, sigma. Here we consider evidence for IMF variation in a sample of relatively compact early-type galaxies drawn from the Sloan Digital Sky Survey. These galaxies are of sufficiently high stellar density that a dark halo likely makes a minor contribution to the total dynamical mass, Mdyn, within one effective radius. We fit our detailed stellar population synthesis models to the stacked absorption line spectra of these galaxies in bins of sigma and find evidence from IMF-sensitive spectral features for a bottom-heavy IMF at high sigma. We also apply simple `mass-follows-light' dynamical models to the same data and find that Mdyn is significantly higher than what would be expected if these galaxies were stellar dominated and had a universal Milky Way IMF. Adopting Mdyn M_* therefore implies that the IMF is `heavier' at high sigma. Most importantly, the quantitative amount of inferred IMF variation is very similar between the two techniques, agreeing to within 0.1 dex in mass. The agreement between two independent techniques, when applied to the same data, provides compelling evidence for systematic variation in the IMF as a function of early-type galaxy velocity dispersion. Any alternative explanations must reproduce both the results from dynamical and stellar population-based techniques.

Design Optimization of Blade's Stacking Line Based on Fluid-Structure Coupling Technique

This paper presents an approach for numerical optimization design of blade stacking line for fan/compressor blade. In the present method, the linear interpolation method and Constant-Volume Tetrahedron approach are developed to exchange data between a Navier–Stokes equation solver which is adopted to evaluate the aerodynamic performance and a commercial software which is used to attain the structural characteristics. Both of those two data exchange method have been demonstrates. A simple Genetic Algorithm as a robust design optimization tool is employed to achieve the multi-objective optimization. The proposed approach is then used to optimized a fan rotor blade with different optimization goals to verify the feasibility of the reliability. The results show that, the single objective optimization design can improve the aerodynamic performance or structural characteristics remarkably, but might not promote both of those performances. On the contrary, the multi-objective and multidisciplinary design can improve the aerodynamic performance and structural strength at the same time. So, it can attain higher aerodynamic performance while satisfying the blade strength requirements.

Complex multidisciplinary optimization of turbine blading systems

The paper describes the methods and results of direct optimization of turbine blading systems using a software package Opti_turb. The final shape of the blading is obtained from minimizing the objective function, which is the total energy loss of the stage, including the leaving energy. The current values of the objective function are found from 3D RANS computations (from a code FlowER) of geometries changed during the process of optimization. There are constraints imposed on the mass flow rate, exit swirl angle and reactions, as well as on changes of stresses in the metal. Among the optimized parameters are those of the blade itself (such as the blade number and stagger angle as well as the stacking blade line parameters) and those of the blade section (profile). Two new hybrid stochastic-deterministic methods are used for the optimization of flow systems. The first method is a combination of a genetic algorithm and a simplex method of Nelder–Mead. The other method is a combination of a direct search method of Hooke–Jeeves and simulated annealing. Also two methods of parametrization of the blade profile are described. They make use of a set of circle arcs and Bezier functions. In the course of optimization, the flow efficiency of a group of two low pressure (LP) exit stages of a 50 MW turbine operating over a wide range of load is increased by means of optimization of 3D blade stacking lines. Another practical example of efficiency optimization of turbine blading systems is modification of low load profiles PLK-R2 for high pressure (HP) steam turbine stages. It is shown that optimization of geometry of turbine blading systems can give considerable efficiency gains. Optimization of 3D blade stacking lines in LP turbine stages can give over a 2% efficiency rise. Up to 1% efficiency, increase can be obtained from optimization of HP blade profiles and their restaggering.

Comparative Layout Study of Stacked CMOS Synthetic Quasi-TEM Lines Separated by the Meshed Ground Shield and its Application to 180$^{\circ}$ Hybrid Design

This work investigates the coupling phenomena of the synthetic quasi-TEM transmission lines (TLs) with the differential layout in multilayer structure. The numerical method based on the normal mode parameters calculates the couplings between two stacking TLs shared with a common mesh ground plane. The theoretical investigations show that the TL in the orthogonal layout has the lowest coupling. This result is applied to design a 60 GHz 180 ° hybrid using the standard 0.18 μm 1P6M CMOS process. The prototype is realized by the TLs with an orthogonal stacked layout in a size of 180 μm × 240 μm without the contact pads. Both measurements and the simulations show the return loss lower than 15 dB and the isolation higher than 20 dB at the frequency between 55 and 65 GHz. Two insertion losses (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">31</sub> | and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> |) are 4.9 ±0.2 dB and 5.4 ±0.3 dB, respectively. From 56 to 64 GHz, the phase difference between two output ports is about 180° ±10°.

Detection of transgenes in three genetically modified rice lines by fluorescence in situ hybridization

Fluorescence in situ hybridization (FISH) using T-DNA probes was applied to localize transgenes onto specific chromosomes and confirm the steady integration of transferred genes in three genetically modified (GM) rice lines, LS28 (event LS30-32-20-1), Cry1Ac1 (event C7-1-9-1) and LS28×Cry1Ac1 (event L/C1-1-3-1), which are a rice leaf blast-resistant single trait GM line, a leaf folder-resistant single trait GM line, and a rice leaf blast-resistant and leaf folder-resistant stacked GM hybrid line, respectively. The FISH signals were clearly detected on the arms of one homologous chromosome pair for LS28, and on the arms of another chromosome pair for Cry1Ac1 when using the transformation vector pSBM AtCK containing the rice leaf blast-resistant gene (LS28) and pMJ-RTB containing the leaf folder-resistant gene (mCry1Ac1) as a probe, respectively. As expected, we detected two pairs of FISH signals, each on the arms of different chromosome pairs in the stacked GM rice line LS28×Cry1Ac1 when using both pSBM AtCK and pMJ-RTB as probes. These results indicate that the transgenes are located at specific homologous loci and show position stability among generations in both single trait and stacked GM rice lines. The usefulness and the necessity of FISH to detect inserted genes in transformed plants will be discussed for the purpose of future studies to develop breeding programs and conduct risk assessment of GM plants.

Reliability Study for Creep Life of Single Crystal Turbine Blade under Random Crystal Orientations and Random Loads

For the single crystal (SC) Ni-based superalloys, it is difficult to avoid orientation variation along airfoil stacking line of the SC turbine blade. At the mean time, the loading of turbine blade is uncertainly during the working. In this work, the creep life of the SC turbine blade is determined by the finite element analysis (FEA) based on the crystal slip theory. The orientation variations are measured based larger numbers commercial turbine blade made of SC superalloys. Furthermore, Monte-Carlo method and the forth moment method are presented to analysis the reliability for creep life of SC turbine blade under random crystal orientations and random loads based on the FEA method. The basic variables sensitivity are comprehensively analyzed by the forth moment method.

Broadband and Low-Loss 1 : 9 Transmission-Line Transformer in 0.18- $\mu\hbox{m}$ CMOS Process

This letter proposes a transmission-line transformer (TLT) with high impedance-transformation ratio of 1 : 9 for wideband power amplifier design. The 1 : 9 TLT is realized with broadside-coupled and multiple-metal stacked transmission lines and achieves a broadband impedance transformation from 5.0 ±0.1Ω optimal load impedance of the power cell to 50-Ω load with a bandwidth of 4.4 to 6.6 GHz, which covers the required bandwidth of the IEEE 802.11a WLAN application. The measured minimum insertion loss is 1.07 dB at 5.8 GHz with a 3-dB bandwidth of 164%. This 1 : 9 TLT is fabricated in standard 0.18-μm CMOS process with a chip area of 426 μm × 589 μm including the test pad.

Fully-integrated CMOS class-E power amplifier using broadband and low-loss 1:4 transmission-line transformer

A broadband and low-loss 1:4 transmission-line transformer (TLT) fabricated in 0.18 μm CMOS process is proposed. Using broadside-coupled and multiple-metal stacked transmission lines, the broadband impedance transformation is from 12.2 ± 0.1 to 50 Ω within a 1.2 GHz bandwidth from 2.1 to 3.3 GHz, and the minimum insertion loss is 1.0 dB at 2.6 GHz with a 3 dB bandwidth of 180%. In addition, a fully-integrated CMOS class-E power amplifier (PA) is designed to demonstrate the capability of the proposed 1:4 TLT, which is used as the output impedance transformer of the class-E PA. The maximum output power is 24.7 dBm at 2.6 GHz, where the power-added efficiency is 33.2% and the power gain is 13.2 dB under 3.6 V supply voltage. The class-E PA achieves broadband and flat output power of 24.6 ± 0.2 dBm from 2.4 to 3.5 GHz.

Half-Buried Structure Cu Bus Line in TFT LCD

As we know, we normally used stacked aluminum bus line as the Gate or Source/Drain layer in LCD now, but the next general LCD needs larger display area, higher resolution, and faster response time, so we need develop the new TFT bus line structure and select the appropriate metallization materials to decrease the resistance of bus line. There are many new kinds of structure and material were used, for example copper, silver and their alloys, pure copper have some advantages among them because of its low electric resistance and cost, but it is restricted by the problem of pure copper’s lifting and etching. In this paper, we not only use electroless copper plating to decrease the resistance and cost of bus line but also use the half-buried structure to increase the thickness of bus line, it can combine these two new technologies well in LCD. We use the half-buried structure copper bus line to make some panel samples, it can decrease the delay of RC greatly (it is lower than 1/4 of normal aluminum bus line panel in the same size).

Genetic Algorithm-based Buffer Allocation of a Robot Production Line

A genetic algorithm-based optimization method of a robot production line's buffer allocation problem is proposed. The productivity of a production system is closely related to reliability,productivity and buffer capacity of each process. The total buffer of a robot production line is limited. It should be allocated to each production process. The approximation and decomposition way is used to establish the relationship between availability and buffer allocation of the continuous production line model. A new genetic algorithm is proposed to optimize the buffer allocation subjected to the total buffer number. The half-parent crossover and single-parent mutation are used in the new genetic algorithm. A case study of automatic infusion bag packing and stacking line based on the 2-DOF parallel robot is shown. The application of several production lines shows the effectiveness of the method.

Improvement of reverse-engineered turbine blades using construction geometry

The paper reports the latest outcomes of using design-based reverse engineering on turbine blades. For a long time, the focus of the reverse engineering methods has been the trend toward higher accuracies and faster measurements. Authors introduce a different viewpoint which focuses on design intent of a part. How to reverse engineer a complex shape like a turbine blade is the subject of current research. The attempt toward taking advantage of the construction geometry behind a sample heavy duty turbine blade is thoroughly discussed in three phases. First phase consists of 2D analysis of the reference sections. Then, the stacking axis is introduced as an important non-tangible feature which has the main role to connect the sections in 3D in lean and tilt directions. The third phase uses the concept of blade twist to provide a constraint to define rotational position of the sections with respect to neighbor sections. All the three phases have been applied to different types of original and non-original products which are available in the gas turbine market. The presented comparisons show clearly that the new method of reverse engineering incorporating construction geometry and design intent of the part is quite useful and recognizes many features behind the external geometry which is impossible to follow by the previous conventional methods. The turbine blade 3D model resulted from this new method will have a smooth arc-based surface, straight stacking line passing through turbine axis with maximum section tilt of 0.2 mm and maximum section lean of 0.3 mm to original equipment manufacturer parts and linearly increasing stagger angle from hub to tip which are some of considerable improvements compared to conventional method.