Stacking Line Research Articles

Hybrid optimization of curvature continuous stacking line on the highly loaded diffuser cascade

Hybrid optimization of curvature continuous stacking line on the highly loaded diffuser cascade

Three-Dimensional Optimization of Blade Lean and Sweep for an Axial Compressor to Improve the Engine Performance

Nowadays, optimization methods have been considered as a practical tool to improve the performance of turbo-machines. For this purpose, the numerical study of the aerodynamic flow of the NASA Rotor-67 axial compressor has been investigated, and the results of this three-dimensional simulation show good agreement with experimental data. Then, the blade stacking line is changed using lean and sweep for Rotor-67 to improve the compressor performance. The third-order polynomial is selected to generate the lean and sweep changes from the hub to the shroud. The compressor flow field is solved by a Reynolds averaged Navier-Stokes solver. The genetic algorithm, coupled with the artificial neural networks, is implemented to find the optimum values for blade lean and sweep. Considering the three objective functions of pressure ratio, mass flow rate, and isentropic efficiency, the optimized rotor is obtained using the optimization algorithm. Two geometries are obtained using the optimization algorithm. The results of the optimized compressor include improving the isentropic efficiency, pressure ratio, and mass flow equal to 0.57%, 0.93%, and 1.8%, respectively. After compressor optimization, the effect of the changes in the compressor performance parameters is studied on a single spool turbojet engine. The engine is modeled by analyzing the Brayton thermodynamic cycle of the assumed turbojet engine under design point operating conditions. Results show that for the best test case, the engine with the optimized rotor, the thrust, and SFC are improved by 1.86% and 0.21%, respectively.

Cfd Analysis to Investigate the Effect of Leaned Rotor On the Performance of Transonic Axial Flow Compressor Stage

This paper describes the numerical study carried out to understand the impact of combination of forward and backward leaned rotor on the overall performance of a transonic axial flow research compressor of CSIR National Aerospace Laboratories (NAL), Bangalore. The analyses were carried out using commercial Computational Fluid Dynamics (CFD) solver Ansys-CFX. Initially CFD analysis was carried out for the baseline rotor configuration and validated the results with the experimental data. Then, three new configurations of combined Leaned rotors were modeled from the radially stacked baseline rotor by changing the circumferential curvature of original stacking line using three control points located at 0%, 50% and 100% of the blade span. Analyses were carried out for all the three configurations of modified geometries and the results were compared with the baseline configuration. The results revealed many interesting aspects which will be very useful for better understanding of the blade curvature effects on the shock and secondary losses within the transonic rotor. The discussions on the effect of combination of forward and backward leaned rotor and the consequent developments on the overall performance of the compressor are presented in detail in this paper.

Optimal Design and Analysis of a High-Load Supersonic Compressor Based on a Surrogate Model

To explore the internal flow mechanism and improve the performance of a supersonic compressor, an efficient global optimization design method was developed for an axial flow compressor and applied in the optimization design of a prototype supersonic compressor. Based on the multiple circular arc (MCA) blade parameters, the method can be used to parameterize the elementary stage of the blade. The optimized solution is obtained by changing the elementary stage and stacking lines of the blade during the optimization process. It has the advantages of fewer optimization variables, strong physical intuition, and a smooth surface. The optimization results show that a change in the rotor blade shape parameters has a significant effect on the compressor efficiency under design conditions, while a change in the skewed-swept parameters of the stator is the main factor that improves the compressor’s performance under near-stall conditions. Further numerical results show that the optimized rotor changes the form of the shock, weakens the degree of shock boundary layer interference, inhibits the radial migration flow of the supersonic rotor, reduces the loss of the rotor blade top, and improves the performance of the compressor under design conditions. The stator’s optimization restrains the generation of a concentrated shedding vortex at the root of the blades and greatly improves the stall margin of the compressor. Finally, the total pressure ratio and flow rate are less than 1% of the values based on the prototype operating conditions, the design mass flow of the optimized high-load supersonic compressor is increased by 0.25%, the isentropic efficiency is increased by 1.05%, and the stall margin is enhanced by 3.5%, thus verifying the effectiveness of the optimization method.

Pyramiding of gn1a, gs3, and ipa1 Exhibits Complementary and Additive Effects on Rice Yield.

Pyramiding of quantitative trait loci (QTLs) is a powerful approach in breeding super-high-yield varieties. However, the performance of QTLs in improving rice yield varies with specific genetic backgrounds. In a previous study, we employed the CRISPR/Cas9 system to target three yield-related genes, gn1a, gs3, and ipa1 in japonica ‘Zhonghua 11’, mutants of which featured large panicle, big grain, few sterile tillers, and thicker culm, respectively. In this paper, four pyramided lines, including gn1a-gs3, gn1a-ipa1, gs3-ipa1, and gn1a-gs3-ipa1, were further generated by conventional cross-breeding to be tested. Agronomic traits analysis showed that: (1) the stacking lines carried large panicles with an increased spikelet number in the main panicle or panicle; (2) the grain weight of the stacking lines, especially gs3-ipa1 and gn1a-gs3-ipa1, were heavier than those in single mutants; (3) both gn1a-gs3 and gs3-ipa1 produced more grain yield per plant than single mutant lines; (4) pyramided lines were higher than single mutants and transcriptome analysis found improved expression levels of genes related to lipid, amino acid, and carbohydrate transport and metabolism in lines pyramiding three mutant alleles, possibly as a result of complementary and additive effects. Accordingly, the alteration of gene-expression patterns relating to hormone signaling, plant growth, and seed size control was characterized in pyramided lines. The present study not only investigates the effects of pyramiding genes, but also may provide an efficient strategy for breeding super-high-yield rice by reducing the time cost of developing pyramided lines.

The Series of Reciprocals of Triangular Numbers

We provide a visual proof that the infinite sum of the reciprocals of the triangular numbers is 1. Such visual proofs usually stack line segments or rectangular blocks. Here we stack angles.

3D printing performance using radio frequency electromagnetic wave modified potato starch

In this study, the altered morphology, amylose content, microstructure, viscosity, and thermal properties of potato starch after being modified for different times (5, 10, 15, 20 and 30 mins) by radio frequency electromagnetic wave (RF) were studied. Obtained the most suitable RF modified time for 3D printing. The results showed that the RF treatment roughened the starch surface and reduced the amylose content, viscosity and pasting temperature of the starch. RF-treated starch gels displayed better print performance than untreated potato gels. Furthermore, RF-20 treatment offers better morphology indexes including clarity and the highest stack height, line uniformity and height retention of printed samples due to the fact that the RF treatment rearranges the internal structure of the potato starch granules, making the internal structure more stable and orderly. Overall, the RF treatment is an effective way to modify starch and optimize starch gels for 3D printing.

Study of flow characteristics affected by some blade structure elements based on a liquid hydrogen turbopump

In this paper, a simulation study on liquid hydrogen turbopump was carried out to obtain the basic flow characteristics of the inducer and impeller with and without cavitation phenomenon considered. The influence of pump structure was analyzed, and the influence of circumferential position, inlet inlet angle and other parameters on flow field and aerodynamic performance was explored. The results show that the influence of boundary layer can be reduced and blade performance can be improved by increasing the blade wrap angle of the centrifugal blade or using a smaller inlet inlet angle near the shroud. In addition, increasing the blade wrap angle can also increase the pressure on the inlet leading edge of the blade, thus reducing the possibility of cavitation. A higher flow rate of the pump may reduce the possibility of cavitation. Cavitation is likely to reduce when the blade leading edge has a slightly slant stacking line of the impeller. Based on these research results, some opinions are given to improve the design method of liquid hydrogen turbopump.

Design and Performance Analysis of Blades Based on the Equal–Variable Circulation Method

With the aim of improving the aerodynamic performance of axial turbomachinery, a new type of blade is designed using the equal–variable circulation method. Taking an axial flow fan as the research object, this article describes the development of a new type of turbomachinery by changing the design method and producing a blade with forward sweep. The aerodynamic performance of the fan is simulated and compared with the experimental data. The numerical results show that the equal circulation design method improves the aerodynamic performance of the blade roots, while the variable circulation design method enhances the aerodynamic performance of the blade tips. By adopting the equal–variable circulation design method, the total pressure of the experimental fan is increased by about 4%, while the efficiency remains unchanged. Forward-swept blades with an equal–variable circulation design also improve performance over the conventional blades by changing the center-of-gravity stacking line. At low flow rates, the efficiency of the experimental fan can be increased by 7.5%, and the working range of the flow is expanded. Under high flow rates, the restriction of the blade tip on the airflow is decreased and the fluidity is slightly reduced.

An optimization on the stacking line of low-pressure axial-flow fan using the surrogate-assistant optimization method

An optimization on the stacking line of low-pressure axial-flow fan using the surrogate-assistant optimization method

Effects of Sweep, Dihedral and Skew on Aerodynamic Performance of Low-Pressure Axial Fans With Small Hub-to-Tip Diameter Ratio

Abstract Axial fans with a small hub-to-tip diameter ratio are used in many branches of industry. Optimization of their aerodynamic performance is important, for which using sweep, dihedral, and skew of the blades' stacking line form an important method. Investigations on axial fans with medium to high hub-to-tip diameter ratio have shown that forward sweep of blades can give an improved aerodynamic performance, especially the total-to-total efficiency. However, only a few studies for fans with a small hub-to-tip diameter ratio have been reported. For such fans, extensive regions of backflow are present behind the fan near the hub. Based on a validated computational fluid dynamics simulation method, the effects of a sweep, dihedral and skew in axial and circumferential directions (in forward and backward direction) on the aerodynamic performance of small hub-to-tip ratio fans are investigated, with a linear stacking line. Current results show that forward sweep and circumferential skew are beneficial for higher total-to-total efficiency and that higher total-to-static efficiency can be obtained by forward dihedral and axial skew. The backward shape variety generally gives negative aerodynamic effects. Forward sweep and circumferential skew shorten the radial migration path, but more flow separation is present near the hub. With forward dihedral and axial skew, the backflow region is reduced in size and axial extent, but a more significant hub corner stall region is found. The pressure reduction due to sweep and dihedral is more limited than what could be expected from wing aerodynamics.

Research on Aerodynamic Optimization Method of Multistage Axial Compressor under Multiple Working Conditions Based on Phased Parameterization Strategy

Multistage axial compressor is the key component of aeroengine and gas turbine to realize energy conversion. In order to avoid the “curse of dimensionality” problem in the global optimization process of AL-31F four-stage low-pressure compressor under multiple working conditions, an optimization method based on phased parameterization strategy is proposed. The method uses the idea of “exploration before exploitation” for reference and divides the optimization process into two phases. In the first phase, the traditional parametric modification method based on stacking line is adopted; in the second phase, the full-blade surface parametric modification method with significant low-dimensional characteristics is adopted. Based on the improved artificial bee colony algorithm, a multitask concurrent optimization system is built on the supercomputing platform, and the engineering optimization solution is obtained within 91 hours. The optimization results are as follows: under the condition of meeting the constraints, the adiabatic efficiency is increased by 0.3% and the surge margin is 4.0% at the design speed; the adiabatic efficiency is increased by 0.8% and the surge margin is 2.3% at the off-design speed. These results verify the usefulness and reliability of the optimization method in the field of aerodynamic optimization of a multistage axial flow compressor.

Marker-assisted stacking of null Kunitz trypsin inhibitor and off-flavour generating lipoxygenase-2 in soybean

AbstractSoybean varieties genetically free from Kunitz trypsin inhibitor (KTI) and lipoxygenase-2 (Lox2) are desirable to increase human consumption, as the former is an antinutritional factor that affects protein digestibility while the latter is a principal contributor to off-flavour. In the present investigation, soybean genotypes free from both these undesirable components were developed by introgression of null allele of Lox2 from NRC109 (lox2lox2) into two KTI-free soybean genotypes derived from genotypes JS97-52 and NRC7. Foreground selection of plants in F1, F2, BC1F1, BC1F2, BC2F1 and BC2F2 generations developed from two cross combinations i.e. NRC7-derived KTI-free genotype (N7KTIF)×NRC109 (parental combination 1) and JS97-52 derived KTI free genotype (JKTIF)×NRC109 (parental combination 2) was performed using null allele specific markers and tightly linked simple sequence repeat (SSR) markers for both KTI and Lox2 genes for the identification of homozygous recessive (titilox2lox2) plants. Background selection was performed using 239 and 241 polymorphic SSR markers across the genome. This resulted in the development of 9 and 13 soybean lines stacked for null alleles of both KTI and Lox2 (titilox2lox2) exhibiting recurrent parent genome content more than 97 and 96%, respectively. Days-to-flowering, days-to-maturity, 100-seed weight and yield per plant of the stacked lines developed from both the parental combinations were at par with the respective recurrent parents.

HCF Weak Link Optimization for Wide-Chord Fan Blades Based on Circumferential Stacking Line Design

This paper describes the combination of a Kriging surrogate model with a micro-genetic algorithm for studying the influence of circumferential perturbations from the stack line on the high-cycle fatigue (HCF) weak link of a fan blade in a high-bypass-ratio turbofan engine. Based on the circumferential perturbations of the fan blade stack line, an automated system is developed for the parameterized modeling and meshing of the blade, and an integral platform is established for parameterized modeling, finite-element simulation, and optimization. The static stress, index of strain energy density, and vibratory stress margin of the 1st flex mode are set as the objective functions for the optimization of a fan blade. The results show that the optimized blade has three areas of low static stress, unlike the single “bull’s eye” distribution of the baseline blade. Optimization reduces the maximum static stress by 5.87% and the strain energy density index by 0.77%, while increasing the vibratory stress margin under the same dynamic load by 9.51%. The natural frequencies, mode shapes, resonance margins, and aerodynamic parameters exhibit no significant changes, which illustrates that the optimization method can improve the static stress and vibratory stress distribution of the fan blade without negatively influencing the other vibration and aerodynamic characteristics. The proposed method is an effective means of fan blade design optimization, and could be applied alongside other design variables and objective functions, such as the swept and skewed configuration of the stack line and twist angle of the blade, to optimize the vibration characteristics and aero-elastic performance.

Design of a Ka-Band U-Shaped Bandpass Filter with 20-GHz Bandwidth in 0.13-μm BiCMOS Technology

In this work, the design of a novel Ka-band miniaturized bandpass filter with broad bandwidth is demonstrated by using inversely coupled U-shaped transmission lines. In the proposed filter, two transmission zeros can be generated within a cascaded U-shaped structure and it can also be proven that, by inversely coupling two stacked U-shaped transmission lines, the notch frequency at the upper stopband can be shifted to a lower frequency, which results in a smaller chip size. The key parameters affecting the performance of the proposed filter are investigated in detail with the effective lumped-element circuit illustrated. Fabricated in a 0.13-μm SiGe BiCMOS process, the proposed filter achieves an insertion loss of 3.6 dB at a frequency of 28.75 GHz and the measured bandwidth is from 20.75 GHz to 41 GHz. The return loss is better than −10 dB from 20.5 GHz to 39 GHz. The lower transmission zero is located at 11.75 GHz with a suppression of 54 dB while the upper transmission zero is around 67 GHz with an attenuation of 34.6 dB. The measurement agrees very well with the simulation results and the overall chip size of the proposed filter is 176 × 269 μm2.

Linestacker: a spectral line stacking tool for interferometric data

ABSTRACT linestacker is a new open access and open source tool for stacking of spectral lines in interferometric data. linestacker is an ensemble of casa tasks, and can stack both 3D cubes or already extracted spectra. The algorithm is tested on increasingly complex simulated data sets, mimicking Atacama Large Millimeter/submillimeter Array, and Karl G. Jansky Very Large Array observations of [C ii] and CO(3–2) emission lines, from z ∼ 7 and z ∼ 4 galaxies, respectively. We find that the algorithm is very robust, successfully retrieving the input parameters of the stacked lines in all cases with an accuracy ≳90 per cent. However, we distinguish some specific situations showcasing the intrinsic limitations of the method. Mainly that high uncertainties on the redshifts (Δz > 0.01) can lead to poor signal-to-noise ratio improvement, due to lines being stacked on shifted central frequencies. Additionally, we give an extensive description of the embedded statistical tools included in linestacker: mainly bootstrapping, rebinning, and subsampling. Velocity rebinning is applied on the data before stacking and proves necessary when studying line profiles, in order to avoid artificial spectral features in the stack. Subsampling is useful to sort the stacked sources, allowing to find a subsample maximizing the searched parameters, while bootstrapping allows to detect inhomogeneities in the stacked sample. linestacker is a useful tool for extracting the most from spectral observations of various types.

(Invited) Radiation Effects on the Self-Heating of AlGaN/GaN High Electron Mobility Transistors

Gallium nitride (GaN) has emerged as one of the most attractive wide bandgap materials for near-future electronics technology, specifically for applications that require high-power and high-frequency devices. The spontaneous and piezoelectric polarization of GaN utilized in AlGaN/GaN high electron mobility transistors (HEMT), provides significantly low ON-resistance due to the formation of a two-dimensional electron gas (2-DEG) channel at the AlGaN/GaN heterointerface without any intentional doping. The fact that these devices do not rely upon dopants to carry the current, in conjunction with superior material property of GaN, makes AlGaN/GaN HEMTs perfect candidates for deep space applications. However, the high voltage operation and the inherently low ON-resistance in AlGaN/GaN HEMTs result in extremely high power densities. Consequently, intense self-heating deteriorates device performance and more importantly, reliability.In order to counter the potential thermal problems associated with these device technologies for deep space applications, it is necessary to advance the knowledge of device irradiation and its effect on self-heating, material interfaces, and properties of constituent materials. To achieve this goal, a set of AlGaN/GaN HEMTs were irradiated with a proton flux at an energy level of 1 MeV at a fluence of 2x1015/cm2. Diverse optical thermography techniques including infrared thermography, thermoreflectance thermal imaging, and micro-Raman spectroscopy were used to quantify the effect of radiation on the device temperature distribution. It was observed that, as compared to pre-irradiated devices, irradiated devices show a 40% higher device peak temperature under identical power dissipation (5 W/mm). To understand the contributing factors behind the observations (and the resulting deterioration of device mean-time-to-failure), the device material stack and transmission line measurement (TLM) structures were analyzed further. Steady-state thermoreflectance (SSTR) measurement, standard electrical characterization, and 3D coupled electro-thermal modeling were performed to capture changes in the thermal conductivity, interfacial thermal boundary resistance, ohmic contact resistance, and sheet resistivity of the devices. This comprehensive study will support the exploitation of the full potential of GaN electronics for deep space and other applications that require radiation hardness.

Analysis Method of Compressor Stability Based on Eigenvalue Theory

Abstract In order to analyze the flow stability of compressors rapidly in the design stage, a fast analysis method is developed in this paper. This method takes the base flow on each streamline at different spanwise locations as the research object and characterizes the effect of blade rows on the internal flow by establishing a body force model. Therefore, it is capable of taking the complex three-dimensional blade geometry and the abundant flow details into account, and what's more, it has a significantly high computational efficiency, which makes it available to engineering practice. Based on the eigenvalue theory, the flow stability problem is transformed into the eigenvalue problem, and the system stability is determined by the eigenvalue obtained by utilizing the singular value decomposition method. The flow stability of NASA Rotor 37 is analyzed to validate the reliability of the developed approach, and the results show that this analysis method is able to capture the process of stability deterioration with throttling and identify the blade tip region as the most unstable area. In order to further study the influence of blade geometry on compressor stability, a number of swept rotors are designed by modifying the stacking line of NASA Rotor 37. The assessment results via the developed method indicate that the forward sweep defined in this work can significantly improve the stability of the flow field in the tip region, while the backward sweep has the opposite effect.

Optimization of a transonic axial-flow compressor under inlet total pressure distortion to enhance aerodynamic performance

In a boundary layer ingestion (BLI) propulsion system, the compressor rotor operates under the condition of a severe inflow distortion because the boundary layers on the surface of aircraft have been ingested. In this situation, the low-momentum fluid would inevitably raise the blade load and aggravate the local aerodynamic losses, thus severely deteriorating the compressor overall aerodynamic performance. The paper has applied a sweep optimization design based on surrogate model and genetic algorithm to a transonic axial-flow compressor at the condition of total pressure distorted inflow. The optimization objective is to improve the compressor efficiency. The sweep design has been implemented through controlling the shape of the blade stacking line and the time-saving steady numerical simulations are mainly utilized in the optimization process. Then, the full-annulus unsteady CFD calculations have been conducted for validating the optimized design and further analyzing the flow mechanisms of performance improvements. The computational results show that the inflow distortion has led to non-uniform distributions of the tip leakage loss and the hub flow separation loss along the circumferential direction. It is found that the rotor blade has suffered from the highest tip leakage losses and hub separation losses during the blade leaving the distorted region. After rotor sweep optimization, both tip leakage and hub separation losses have been notably reduced along the full circumferential direction. Moreover, for different pitchwise locations, the optimized rotor sweep design has achieved more aerodynamic performance improvements in the process of the rotor blade leaving the distorted region than those in the processes of the rotor blade moving out of, moving towards and entering the distorted region. Overall, the optimized design performs better than the baseline design in terms of adiabatic efficiency in the entire operating range. In the meanwhile, the total pressure ratio has been maintained. Specifically, an approximately 0.5% increment of efficiency has been achieved by the optimized design at the optimization point. For this paper, the major purpose is to offer useful guidelines for fan/compressor design strategy to achieve high aerodynamic performances under distorted inflow working condition.

A new curvature-controlled stacking-line method for optimization design of compressor cascade considering surface smoothness

The paper presents an advanced parametric method of blade stacking lines in terms of sweep and lean based on controlled curvature. To the knowledge of the authors, there is no related approach reported in open literature that uses Bezier spline as the radial curvature distribution to improve the smoothness of the blade surface; most previous studies ignored the discontinuous slopes of curvature of the parametric curves. The parametric method called curvature-controlled stacking-line method (CCSLM) is performed by changing the magnitude of the sweep or lean. A fourth Bezier spline is adopted to define the curvature of spanwise stacking line directly ensuring surface smoothness. Then, the redesign cascades are created by sectional profiles stacked along the radial stacking lines which are obtained by twice integrating the Bezier spline. Then, the advanced method is conducted to optimize a high-subsonic controlled diffusion airfoil at design point, where the blade shape is generated in terms of lean. A single-objective optimization is performed using Kriging model and genetic algorithm to optimize total pressure loss, and the optimized geometry is obtained. The optimization results show that the blade design CCSLM has significant effects on the endwall flow vortex as well as radial loading distribution. The reduction of total pressure loss and secondary flow is also observed, and the aerodynamic performance is well improved compared with the original cascade.