Cascade Of Profiles Research Articles

Experimental Study on the Endwall Aerothermal Performance of Turbine Cascades in a Novel Transient Test Facility

Abstract Linear turbine cascades have been widely used to conduct fundamental and applied investigations, but only a few transient test facilities with the linear turbine cascade are available in the open literature. A novel transient test facility was presented in this paper, including detailed design and structure, and various experimental measurements (aerodynamic and thermodynamic) were conducted to verify the transient test facility’s capability. This test facility mainly includes a main air supply line (bypass line and test line), a coolant supply line, a test section, and a control system (heater and various valves). The linear cascade holds up six equally spaced cascade profiles, forming five completed cascade passages, and the center passage is used for aerodynamic and thermodynamic measurements. The aerodynamic loss and heat transfer performance were measured at various flow conditions (incidence angle, Ma, and blowing ratio (BR)). The endwall heat transfer coefficient and film cooling effectiveness were estimated by adopting a dual linear regression technique. Results indicate that the mianstream pressure and temperature present a desired step change, and remain relatively steady in the test window. The magnitudes of endwall heat transfer significantly increase as the Maex increases from 0.2 to 0.5, but the thermal load distributions remain the same. The BR is a key parameter for endwall film cooling performance, and the optimal film cooling coverage is acquired at the critical value of BR. Both insufficient and excessive coolant flowrate can result in undesirable endwall film cooling coverage, and may cause unnecessary consumption of the coolant flow.

Hybrid LES/RANS Simulations of Compressible Flow in a Linear Cascade of Flat Blade Profiles

The paper reports on 3D numerical simulations of unsteady compressible airflow in a blade cascade consisting of flat profiles using a hybrid LES/RANS approach including a transition model. As a first step towards simulation of blade flutter in turbomachinery, various incidence angle offsets of the middle blade were modeled. All simulations were run for the flow regime characterized by outlet isentropic Mach number Mis=0.5 and zero incidence. The results of the LES/RANS simulations (pressure and Mach number distributions) were compared to a baseline RANS model, and to experimental data measured in a high-speed wind tunnel. The numerical results show that both methods overpredict flow separation taking place at the leading edge. In this regard, the hybrid LES/RANS method does not provide superior results compared to the traditional RANS simulations. Nevertheless, the LES/RANS results also capture vortex shedding from the blunt trailing edge. The frequency of the trailing edge vortex shedding in CFD simulations matches perfectly the spectral peak recorded during wind tunnel measurements.

Research on Separation Loss of Compressor Cascade Profile Based on Large Eddy Simulation

Research on Separation Loss of Compressor Cascade Profile Based on Large Eddy Simulation

Numerical and experimental study on the critical geometric variation based on sensitivity analysis on a compressor rotor

Abstract Different types of geometric variations often appear coupledly in manufactured blades. It is desired to identify the ones that have the strongest impact on the performance. In this paper, the influence of multiple geometric variations on the compressor rotor blade at the design point is studied. Two hundred and nine varied blades are constructed by adding variation data to the design-intent blade and assessed using steady-state Reynolds-Averaged Navier–Stokes (RANS) simulations. It is shown that the region near the lower and upper end of the blade is more sensitive to geometric variations. Spearman’s rank correlation coefficient is used to measure the sensitivity of rotor performance to geometric variations. The results show that the stagger angle variation is the most influencing variation. Local sensitivity analysis at different spans also shows that the stagger angle variation is an important geometric variation that needs more attention during blade manufacturing. Also, the influence of geometric variations can reach further than nearby regions. Consequently, experiments on linear cascades at different spans of the rotor are carried out to study the effect of stagger angle on flow characteristics. Results show that the stagger angle variation could lead to different changes in performance depending on the specific cascade profile.

Genome-wide binding analysis unveils critical implication of B-Myb-mediated transactivation in cancers.

B-Myb, also known as MYB proto-oncogene like 2 (MYBL2), is an important transcription factor implicated in transcription regulation, cell cycle and tumorigenesis. However, the molecular mechanism underlying B-Myb-controlled transactivation in different cell contexts as well as its functional implication in cancers remains elusive. In this study, we have conducted a comprehensive genome-wide analysis of B-Myb binding sites in multiple immortalized or cancer cell lines and identified its critical target genes. The results revealed that B-Myb regulates a common set of core cell cycle genes and cell type-specific genes through collaboration with other important transcription factors (e.g. NFY and MuvB complex) and binding to cell type-invariant promoters and cell type-specific enhancers and super-enhancers. KIF2C, UBE2C and MYC were further validated as B-Myb target genes. Loss-of-function analysis demonstrated that KIF2C knockdown inhibited tumor cell growth both in vitro and in vivo, suppressed cell motility and cell cycle progression, accompanied with defects in microtubule organization and mitosis, strongly suggesting that KIF2C is a critical regulator of cancer cell growth and mitosis, and maintains high cancer cell motility ability and microtubule dynamics. Pan-cancer transcriptomic analysis revealed that the overexpression of both B-Myb and KIF2C presents as independent prognostic markers in various types of cancer. Notably, B-Myb associates with NFYB, binds to target gene promoters, enhancers and super-enhancers, and provokes a cascade of oncogenic gene expression profiles in cancers. Overall, our results highly suggest the critical implication of B-Myb-mediated gene regulation in cancers, and the promising therapeutic and prognostic potentials of B-Myb and KIF2C for cancer diagnosis and treatment.

Implementation of flow loss minimization incorporating the riblet technique on cascade profile and experimental validation

For the purpose of reducing the flow loss in the compressor cascade, the aerodynamic design of the blade geometry is essential. The traditional aerodynamic design focuses on curve modification, and the surface structure design is rarely considered in the optimization framework. Recent studies have revealed that micro riblet surface provides an excellent application prospect in drag reduction, which offers a new idea for the design of compressor cascade. In this paper, a concept of “geometry-flow loss” control is proposed, and an innovative optimization method combining profile and riblet design is developed further to improve the aerodynamic performances of the compressor cascade. In the design process of multiple iterations, the multi-scale simulations describing the whole flow field with a massive amount of grids would cause unaffordable costs. Therefore, the blade-riblets simplified simulation strategy is employed to evaluate the aerodynamic performances of the cascade profile with riblets and make the profile with riblet design practicable. The flow loss characteristics of the original cascade and two optimal cascades are assessed and verified by wind tunnel tests. The simulation and experimental results both indicate that the profile with the riblet design significantly further reduces the total pressure loss of the compressor cascade compared to the traditional profile design. The proposed concept in this paper increases the dimensionality of the geometry design and further exploits the design potential of the compressor cascade.

The weak Stokes problem associated with a flow through a profile cascade in Lr$L^r$‐framework

AbstractWe study the weak steady Stokes problem, associated with a flow of a Newtonian incompressible fluid through a spatially periodic profile cascade, in the ‐setup. The mathematical model used here is based on the reduction to one spatial period, represented by a bounded 2D domain Ω. The corresponding Stokes problem is formulated using three types of boundary conditions: the conditions of periodicity on the “lower” and “upper” parts of the boundary, the Dirichlet boundary conditions on the “inflow” and on the profile and an artificial “do nothing”‐type boundary condition on the “outflow.” Under appropriate assumptions on the given data, we prove the existence and uniqueness of a weak solution in and its continuous dependence on the data. We explain the sense in which the “do nothing” boundary condition on the “outflow” is satisfied.

English

The paper deals with the Stokes problem, associated with a flow of a viscous incompressible fluid through a spatially periodic profile cascade. We use results from [32] (the maximum regularity property in the $L^2$-framework) and [33] (the weak solvability in $W^{1,r}$), and extend the findings on the maximum regularity property to the general $L^r$-framework (for $1<r<\infty$). Using the reduction to one spatial period $\Omega$, the problem is formulated by means of boundary conditions of three types: the conditions of periodicity on curves $\Gamma_0$ and $\Gamma_1$, the Dirichlet boundary conditions on $\Gamma_{\rm in}$ and $\Gamma_P$ and an artificial do nothing-type boundary condition on $\Gamma_{\rm out}$ (see Fig. 1). We show that, although domain $\Omega$ is not and different types of boundary conditions meet in the vertices of $\partial\Omega$, the considered problem has a strong solution with the maximum regularity property for smooth data. We explain the sense in which the do nothing boundary condition is satisfied for both weak and strong solutions.

Investigation of aerodynamic schemes of reversible mine fans

The article considers the aerodynamic scheme of the main ventilation fan with high aerodynamic properties in reverse operation mode based on the use of a rotating input guide vanes. The dependences of the setup angles of the blades of the input guide vanes and the rotor, when the fan is switched to the reverse mode, on the required flow coefficients and fan pressure at certain parameters of the profile cascades at a mean radius are revealed. Using the example of the designed aerodynamic schemes, the influence of the swirl of the flow in the guide device, the solidity of the blade cascades of the rotors and the torsion of the blades on the aerodynamic characteristics of the reversible fan operation mode, calculated in the ANSYS CFX, is shown. Obtained fan aerodynamic scheme provides a performance in the reverse mode operation equal to 0.96 of the performance of the direct mode in the same ventilation network.

Existence of steady flows of a viscous incompressible fluid through a profile cascade and their Lr‐regularity

The paper deals with the steady Navier–Stokes problem, describing a flow of a viscous incompressible fluid through a spatially periodic profile cascade. Using the reduction to one spatial period Ω, the problem is formulated by means of boundary conditions of three types: the conditions of periodicity on curves Γ0 and Γ1, the Dirichlet boundary conditions on and ΓP, and an artificial boundary condition on (see Figure 1). For “small data,” we consider the so‐called “do nothing” boundary condition on and prove the existence and uniqueness of a weak and strong solution in the Lr–framework. For “large data,” we consider an appropriately modified “do nothing” condition on and prove the existence of a weak and strong solution.

The Maximum Regularity Property of the Steady Stokes Problem Associated with a Flow Through a Profile Cascade

We deal with a steady Stokes-type problem, associated with a flow of a Newtonian incompressible fluid through a spatially periodic profile cascade. The used mathematical model is based on the reduction to one spatial period, represented by a bounded 2D domain \(\varOmega \). The corresponding Stokes–type problem is formulated by means of the Stokes equation, equation of continuity and three types of boundary conditions: the conditions of periodicity on the curves \(\varGamma _{\hspace {-1.1pt} 0}\) and \(\varGamma _{\hspace {-1.1pt} 1}\), the Dirichlet boundary conditions on \(\varGamma _{\hspace {-1.1pt} \mathrm {in}}\) and \(\varGamma _{\hspace {-1.1pt} p}\) and an artificial “do nothing”–type boundary condition on \(\varGamma _{\hspace {-1.1pt} \mathrm {out}}\). (See Fig. 1.) We explain on the level of weak solutions the sense in which the last condition is satisfied. We show that, although domain \(\varOmega \) is not smooth and different types of boundary conditions meet in the corners of \(\varOmega \), the considered problem has a strong solution with the so called maximum regularity property.

The role of pioglitazone in antioxidant, anti-inflammatory, and insulin sensitivity in a high fat-carbohydrate diet-induced rat model of insulin resistance.

We explored the cascade effects of a high fat-carbohydrate diet (HFCD) and pioglitazone (an anti-diabetic therapy used to treat type 2 diabetes mellitus (T2DM)) on lipid profiles, oxidative stress/antioxidant, insulin, and inflammatory biomarkers in a rat model of insulin resistance. Sixty albino rats (80-90 g) were randomly divided into three dietary groups; 1) standard diet; 2) HFCD diet for 12 weeks to induce an in vivo model of insulin resistance; and 3) HFCD diet plus pioglitazone. Blood and tissue samples were taken to assess hepatic function, lipid profiles, oxidative biomarkers, malondialdehyde (MDA) levels, antioxidant defense biomarkers, including reduced glutathione (GSH), superoxide dismutase (SOD), and the inflammatory markers interleukin-6 (IL-6) and tumor necrotic factor (TNF-α). HFCD-fed rats had significantly (P≤0.05) increased serum triacylglycerol (TG), total cholesterol (TC), low-density lipoprotein (LDL), alanine transaminase (ALT), and bilirubin levels, but decreased high-density lipoprotein (HDL) levels compared with the normal group. Moreover, serum leptin, resistin, TNF-α, and IL-6 levels were increased significantly in HFCD animals compared with controls. Similarly, HFCD-induced insulin resistance caused antioxidant and cytokine disturbances, which are important therapy targets for pioglitazone. Importantly, administration of this drug ameliorated these changes, normalized leptin and resistin and inflammatory markers by reducing TNF-α levels. Metabolic cascades of elevated lipid profiles, oxidative stress, insulin, and inflammatory biomarkers are implicated in insulin resistance progression. HFCD induced metabolic cascades comprising hypertriglyceridemia, hyperglycemia, insulin resistance, obesity-associated hormones, and inflammatory biomarkers may be alleviated using pioglitazone.

Erratum to: Optimization of the Number, Distribution of Work by Stages, and Solidity of Profile Vane Cascades during Compressor Design

The method of choosing the optimal number and distribution of work by stages is considered (based on providing the same total pressure recovery coefficient in stages and blade rows). A method is proposed for choosing the solidities of the profile cascades. The method effectiveness is confirmed by an example of choosing the optimal number of stages (three) and the distribution of work in a low-pressure compressor with a given of pressure ratio and peripheral speed.

Solution of Inverse Mixed Boundary Value Problem of Aerohydrodynamics for Cascade of Profiles without Additional Restrictions

We consider an inverse boundary-value problem for a aerohydrodynamical cascade of profiles streamlined by a potential flow of an incompressible inviscid fluid. It is required to find the shape of the profile of the cascade, by a given velocity distribution as a function of the arc abscissa, and determine the period of the cascade.

Separating Loss in Axial-Flow-Turbine Cascades

The use of a system of basic hydrogasdynamic equations, which was written for the portion of contraction of the flow at entry into a cascade of axial-flow turbine profiles at large angles of reattachment to the walls of a blade passage, has enabled the authors to obtain analytical dependences (characteristics) of the loss on the angles of entry of the flow into the cascade. The obtained procedure of calculating the loss permits taking account of the radius of rounding of the profiles at entry, on which the region of insensitivity to the angle of attack is dependent, and also determining relevant flow-entry angles limiting the insensitivity region. The authors have proposed variants of the procedure for both an incompressible-fluid model and a compressible gas, where use is made of the gasdynamic functions of the reduced velocity. The calculated characteristics of the turbine cascades are in good agreement with the existing experimental data in a wide range of angles of attack and radii of rounding of the profiles′ leading edges. The influence of the flow compressibility on the loss has been shown. To test the procedure under the conditions of pulsed flow through the turbine where the angles of attack are particularly large, the authors carried out investigations whose results are also in good agreement with the results of corresponding calculations.

Bioactivity and Apoptotic Efficacy of the Purified Terpenoid Extract from the Moss Brachythecium Buchananii (Hook.) A. Jaeger against MG 63 Cells

Bryophytes are primitive non vascular plants. A little is explored regarding the medicinal effects of bryophytes on carcinoma. This study investigated the biological effects of purified terpenoids from Brachythecium buchananii on selected cell lines such as HeLa, MDAMB-231 and MG63 human osteosarcoma cells and also elucidating the regu­latory signaling pathways underlying the effects of terpenoids towards caspase cascade and the antioxidant enzyme system. The cell lines were treated with various concentrations of purified terpenoid extracts interms of evaluating viability (MTT assay). Interestingly, MG63 cell lines showed poor viability as compared to other ongo cells and was subjected to further molecular evaluations. Migration and invasion assay results using wound-healing and transwell assays, respectively reveal the pro-antimetastatic potential of the purified terpenoids from the moss. The flow cytometry study substantiated terpenoid induced apoptosis in MG63 cells. Cell cycle analysis revealed the significant increase in the number of cells arrested at the S growth phase. Terpenoid extract also displayed DNA fragmentation in the cells. Western blot analysis revealed the down regulation of the anti‑apoptotic proteins Bcl‑2, pro‑caspase 3 and over expression of the pro‑apoptotic protein Bax. In addition, the caspase cascade profile of the terpenoid extract substantiated their efficacy in tumour inhibition. Thus, the overall results confirmed the biological features of terpenoid induced apoptosis in the MG63 cells.

Optimization of the Number, Distribution of Work by Stages, and Solidity of Profile Vane Cascades during Compressor Design

The method of choosing the optimal number and distribution of work by stages is considered (based on providing the same total pressure recovery coefficient in stages and blade rows). A method is proposed for choosing the solidities of the profile cascades. The method effectiveness is confirmed by an example of choosing the optimal number of stages (three) and the distribution of work in a low-pressure compressor with a given of pressure ratio and peripheral speed.

Near-Wall Flow in the Blade Cascades Representing Last Rotor Root Sections of Large Output Steam Turbines

This paper investigates the flow past two variants of root section profile cascades for a last stage rotor considering three-dimensional flow structures in the near-wall region. Analyses were drawn based on RANS numerical simulations of both variants and on the experimental data obtained by the 3D traversing in the exit flow field of one of the variants. Extent of 3D structures at two different regimes and its influence on aerodynamic characteristics of the blade cascades was assessed. The distributions of Mach number along the profiles were compared with 2D optical measurements and its distortion due to the presence of the sidewall was explored. The interaction between main vortical structures was described and its influence on the loading of the blades, mechanical energy losses and exit flow angle was discussed. The results showed that for a front loaded blade the vortical structures appeared earlier and at a larger extent than for an aft loaded variant. However, due to different Mach number distribution, contribution of end wall flow to the energy losses was lower in the case of the aft loaded variant. The influence of the near wall flow on the loading was found to be rather weak while the deviation of the exit flow angle appeared to be comparable for both of the variants.

Решение обратной краевой задачи аэрогидродинамики решеток без дополнительных условий

Решение обратной краевой задачи аэрогидродинамики решеток без дополнительных условий

Fabrication of cascade micropattern by maskless electrochemical micromachining

Cascade micropattern is the basic complex textured surface, which is generated on different microdevices for various advanced micromanufacturing applications. This paper highlights the experimental analysis into generation of cascade micropatterns on stainless steel (SS 304) by maskless electrochemical micromachining (EMM). The experimental setup consisting of electrode fixtures, EMM cell, power supply unit and electrolyte flow system is indigenously developed for fabrication of cascade micropatterns inexpensively without fabrication of one by one complex microfeature of cascade profile by a single microtool. One textured tool with SU-8 2150 mask can fabricate more than 25 cascade micropatterns. Influences of EMM parameters such as electrolyte concentration, electrolyte flow rate, pulse frequency and inter electrode gap on depth, width overcut and surface roughness (Ra) are studied during generation of cascade micropattern. An attempt has also been done to analysis the micrographs of generated cascade micropattern for investigating the suitable parameter setting. This investigation will be needful and fruitful for machining of need-based cascade micropatterns on microdevices like micromixers, microactuators, microcoolers, etc.