Cascade Of Profiles Research Articles

Development of methods of modeling and computer-aided design of compressors

Discusses the methods of calculation allowing to calculate the characteristics of cascades of profiles, rowsblade, the compressor as a whole. Make improvements to previously known methods of calculation. It is proposedto allocate an additional (along the surface current) elementary channels that can achieve output of rowsdiagrams parameters. Preparation thus permits the compressor, in turn, to calculate the characteristic of the developedengine steady and unsteady modes with high accuracy. The proposed method allows the selection ofgeometric parameters of blade rows, and in operation - perform account the influence on the characteristics ofchanges in the geometry of the blades (due to erosion, dirt, etc.). Allows you to analyze the effect of prepollutionand erosion of the blades to change the characteristics of the nodes, and the results of the identificationof the plant model to solve the inverse problem - to identify the actual values of pollution and erosion in specificstages and crowns. The resulting geometry of the rims may be used as an initial approximation for the boundaryconditions at the solid-state 3D modeling and gas-dynamic calculations in СAE- systems such as Ansys CFX.

Investigations of shock wave boundary layer interaction on suction side of compressor profile

The shock wave boundary layer interaction on the suction side of transonic compressor blade is one of main objectives of TFAST project (Transition Location Effect on Shock Wave Boundary Layer Interaction). In order to look more closely into the flow structure on the suction side of a blade, a design of a generic test section in linear transonic wind tunnel was proposed. The test section which could reproduce flow structure, shock wave location, pressure distribution and boundary layer development similar to the obtained on a cascade profile is the main objective of the presented here design. The design of the proposed test section is very challenging, because of shock wave existence, its interaction with boundary layer and its influence on the 3-D flow structure in the test section.

Spanwise Penetration Depth with Turbine Disk Inclination

Spanwise penetration depth as a new correlating parameter was introduced in the cascade profile loss correlation of a new loss breakdown scheme for turbine cascade reported in the literature. For the case of an inclined turbine disk, when a turbine disk is inclined to its design position, the blade incidence or inlet flow angle varies with the position of blade on the turbine disk circumference, leading to the variation of spanwise penetration depth. To examine the influences of turbine disk inclination on the spanwise penetration depth, new correlations were developed and numerical simulations were performed with MATLAB. The role that turbine disk inclination plays in the spanwise penetration depth is manifested in a modified inlet flow angle expression on account of turbine disk inclination. It is concluded that the turbine disk inclination has considerable influences on the spanwise penetration depth in the turbine cascade passage.

On the Existence of a Weak Solution of Viscous Incompressible Flow Past a Cascade of Profiles with an Arbitrarily Large Inflow

The paper deals with the analysis of a stationary viscous incompressible flow through a cascade of profiles representing a blade row of a turbine. The initial-boundary value problem for the Navier–Stokes system is formulated in a domain having the form of one spatial period of the cascade. In comparison to previous results, we solve the problem with an arbitrarily large inflow into the turbine. We formulate the “artificial” boundary condition on the outflow (the modification of the so called do-nothing condition) that enables us to prove the existence of a weak solution.

Causes and Solution of Aperiodicity of Supersonic Flow Field Downstream of a Profile Cascade

The paper deals with problems of transonic flow field periodicity downstream of a profile cascade with finite number of blades. The origin of phenomena generating this aperiodicity in transonic wind tunnel is described. The solution of this problem by means of adjustable perforated tailboard is documented by results of optical measurements (interferometry, schlieren methods) on a turbine profile cascade consisting of six blades only. The conditions of formation of limit load regime are described.

Design of large Francis turbine using optimal methods

Among a high number of Francis turbine references all over the world, covering the whole market range of heads, Alstom has especially been involved in the development and equipment of the largest power plants in the world : Three Gorges (China −32×767 MW - 61 to 113 m), Itaipu (Brazil- 20x750 MW - 98.7m to 127m) and Xiangjiaba (China - 8x812 MW - 82.5m to 113.6m - in erection). Many new projects are under study to equip new power plants with Francis turbines in order to answer an increasing demand of renewable energy. In this context, Alstom Hydro is carrying out many developments to answer those needs, especially for jumbo units such the planned 1GW type units in China. The turbine design for such units requires specific care by using the state of the art in computation methods and the latest technologies in model testing as well as the maximum feedback from operation of Jumbo plants already in operation. We present in this paper how a large Francis turbine can be designed using specific design methods, including the global and local optimization methods. The design of the spiral case, the tandem cascade profiles, the runner and the draft tube are designed with optimization loops involving a blade design tool, an automatic meshing software and a Navier-Stokes solver, piloted by a genetic algorithm. These automated optimization methods, presented in different papers over the last decade, are nowadays widely used, thanks to the growing computation capacity of the HPC clusters: the intensive use of such optimization methods at the turbine design stage allows to reach very high level of performances, while the hydraulic flow characteristics are carefully studied over the whole water passage to avoid any unexpected hydraulic phenomena.

Profile and secondary flow losses in a high-lift LPT blade cascade at different reynolds numbers under steady and unsteady inflow conditions

The aerodynamic flow field downstream of a Low-Pressure High-Lift (HL) turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows, in order to analyse the cascade performance under real engine operating conditions. The Reynolds number has been varied in the range 100000<Re<300000, where lower and upper limits are typical of cruise and take-off/landing conditions, respectively. The effects induced by the incoming wakes at the reduced frequency f +=0.62 on both profile and secondary flow losses have been investigated. Total pressure, velocity and secondary kinetic energy distributions at the downstream tangential plane have been measured by means of a miniaturized 5-hole probe. These quantities provide information on both blade wake and secondary flow structures (passage and horse-shoe vortices). The analysis of the results allows the evaluation of the aerodynamic performance of the HL front-loaded blade in terms of both profile and secondary losses.

The Q-Cascade Explanation

The physical meaning of a continuous profile cascade, which is frequently used in the study of multicomponent isotope separation and named as the Q-cascade is explained. It is found that the parameter Q for a component at a stage is nothing but the relative increase of the concentration of the component, and is constant at all cascade stages. The Q-cascade is classified as the quasi-ideal cascade playing an importantrole for fast evaluation of the separation cascade parameters for multi-isotope mixture separation.

Effects of free-stream turbulence on high pressure turbine blade heat transfer predicted by structured and unstructured LES

Recent developments and demonstrations for the prediction of turbulent flows around blades point to Large Eddy Simulations (LES) as a very promising tool. Indeed and despite the fact that this numerical method still requires modeling and intense computing effort compared to Reynolds Average Navier–Stokes (RANS), this fully unsteady simulation technique provides valuable information on the turbulent flow otherwise inaccessible. Theoretical limits and scales of wall bounded flows are now well mastered in simple cases but complex industrial applications usually introduce unknowns and mechanisms that are difficult to apprehend beforehand especially with LES which is usually computationally intensive and bounded to code scalability, mesh quality, modeling performances and computer power. In this specific context, few studies directly address the use of fully structured versus unstructured, implicit versus explicit flow solvers and their respective impact for LES modeling of complex wall bounded flows. To partly address these important issues, two dedicated structured and unstructured computational solvers are applied and assessed by comparing the predictions of the heat transfer around the experimental high pressure turbine blade profile cascade of Arts et al. [6]. First, both LES predictions are compared to RANS modeling with a particular interest for the accuracy/cost ratio and improvement of the physical phenomena around the blade. LES’s are then detailed and further investigated to assess their ability to reproduce the inlet turbulence effect on heat transfer and the development of the transitioning boundary layer around the blade. Quantitative comparisons against experimental findings show excellent agreement especially on the pressure side of the profile. Detailed analysis of the flow predictions provided by both the structured and unstructured solvers underline the importance of long stream-wise streaky structures responsible for the augmentation of the heat transfer and leading to the transition of the suction-side boundary layer.

Determination of averaged axisymmetric flow surfaces according to results obtained by numerical simulation of flow in turbomachinery

In the increasing need for energy saving worldwide, the designing process of turbomachinery, as an essential part of thermal and hydroenergy systems, goes in the direction of enlarging efficiency. Therefore, the optimization of turbomachinery designing strongly affects the energy efficiency of the entire system. In the designing process of turbomachinery blade profiling, the model of axisymmetric fluid flows is commonly used in technical practice, even though this model suits only the profile cascades with infinite number of infinitely thin blades. The actual flow in turbomachinery profile cascades is not axisymmetric, and it can be fictively derived into the axisymmetric flow by averaging flow parameters in the blade passages according to the circular coordinate. Using numerical simulations of flow in turbomachinery runners, its operating parameters can be preliminarily determined. Furthermore, using the numerically obtained flow parameters in the blade passages, averaged axisymmetric flow surfaces in blade profile cascades can also be determined. The method of determination of averaged flow parameters and averaged meridian streamlines is presented in this paper, using the integral continuity equation for averaged flow parameters. With thus obtained results, every designer can be able to compare the obtained averaged flow surfaces with axisymmetric flow surfaces, as well as the specific work of elementary stages, which are used in the procedure of blade designing. Numerical simulations of flow in an exemplary axial flow pump, used as a part of the thermal power plant cooling system, were performed using Ansys CFX.

Abstract A131: Drugging the telomere: A rational approach for the selection quadruplex DNA targeting agents for the treatment of cancer.

Abstract The pentacyclic acridinium class of small molecule telomere targeting agents have been shown to stabilise the 3'single-stranded guanine-rich telomeric overhang to fold into a G-quadruplex structure. Stabilisation of the latter is incompatible with an attachment of telomerase and a collection of protective proteins referred to as the shelterin complex to the telomere. G-quadruplex ligands can effectively inhibit the telomere maintenance functions of telomerase while revealing the chromosomal termini to the unwanted attention of DNA repair proteins resulting in telomere specific damage. Potent antitumor properties of the G-quadruplex ligand 3,11-difluoro-6,8,13-trimethyl-8H-quino[4,3,2-kl]acridinium methosulfate (RHPS4) have been reported and shown to be driven by telomere uncapping events. However, in preliminary toxological studies the original lead compound (RHPS4) revealed cardiovascular liabilities related to interactions with hERG receptor (IC50 0.2 uM) as well as additional receptor interactions including muscarinic M1, M2 and M3 and Beta2 adrenergic receptors. Pharminox have designed and synthesised second generation agents with significantly improved on and off target profiles. Here we describe the modification and optimisation of new telomere targeting agents with an emphasis on their specific effect on telomeres. Specific bio-molecular assays have been performed on the best compounds of the series, as defined by telomeric DNA binding characteristics and cancer cell activities, “normal” cell selectivities and off target affinities. It was found that all new compounds examined were more potent than RHPS4 as telomere damage inducers. Specifically, at the dose of 0,1 uM, the compounds PMX-000177-761-785 trigger a percentage of TIF-positive cells comparable to that induced by RHPS4 at a 5 fold higher drug concentration. Activation of damage response mainly occurred in replicating cells for the compounds PMX-000177 and -785, suggesting that they can work with a RHPS4-like mechanism of action. As part of a defined screening cascade and candidate target profile, these studies are being used to differentiate between compounds as they progress towards pre-clinical candidate selection status. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A131.

Improving the aerodynamic efficiency of blade profile cascade used in a cooled turbine

Good effect from using rotor blade cascades, the pressure side’s profile of which has a bend near the trailing edge at an angle of no larger than 15°, is confirmed from the results of experimental studies.

Numerical Simulation of the Flow Pulsations Origin in Cascades of the Rear Blade Rows in a Gas Turbine Axial Compressor Using Low Calorific Fuel

Fatigue failure of the last three stator rows vanes (S17, EGV1, and EGV2) in the 17 stage gas turbine axial compressor occurred in the power plant where low calorific fuel syngas, was used. Causes of this dangerous phenomenon were flow pulsations with the frequency of 380–400 Hz that were found by the experimental investigation of the duty gas turbine. Mechanism of the flow unsteadiness origin was studied with the help of flow simulations in the 2D stator cascade system. Three numerical experiments were carried out. The first experiment investigated the flow simulation in the stator cascade system with a steady undisturbed inlet flow with increased turbulence intensity. Obtained data did not meet the standards of the actual compressor operations. In the remaining two numerical experiments, a purposely designed rotor cascade was located in front of the stator cascades. Shedding of vortex structures from the cascade profile surfaces at positive incidence angles is responsible for the flow pulsation origin. The interaction of rotor wakes/stator S17 cascade plays an important role in the investigated phenomenon, as follows from CFD data. Aerodynamic loading of both cascades is equal in the second group of numerical experiments. Computed results were in good qualitative agreement with the experimental ones. As the flow in rotor cascade was not separated, owing to the different aerodynamic loading of rotor and stator S17 cascades, the vortices shedding in stator cascade S17 had a significantly higher frequency of f=2200–2300 Hz than in other investigated cases.

Comparing N3-60 cascade exit angles obtained from tunnel measurements and numerical simulations

The article compares the results of the measurements performed in the aerodynamic tunnel owned by the Czestochowa University of Technology and the numerical simulation done using the code FLUENT for a plane cascade of N3-60 profiles. The comparison study aims at assessing differences between the exit angles measured experimentally and those obtained from numerical calculations. Variable parameters in the measurements and the calculations were the relative pitch and the profile stagger angle. The measurements were performed in the flow of air. The same medium and having the same inlet parameters was assumed in the calculations. The calculations were performed in two dimensions for the compressible flow. The k-e RNG turbulence model was used to complete the equation system. Comparing the measured and calculated results provides opportunities for assessing the range of differences between the experiment and the simulation. The obtained results and formulated conclusions will find the application not only in the power industry, but also in the shipbuilding industry for analysing the operation of steam and gas turbines used as main and auxiliary propulsion systems on both merchant vessels and battle ships.

A new method for observing the shower cascade profile at the Yakutsk EAS array

An empirical approach is presented for reconstruction of the extensive air shower (EAS) cascade curve according to data of the Cherenkov track detector. The proposed method, unlike conventional ones, is based on experimentally measured parameters and on calculated values which weakly depend on the model of shower development.

Transonic turbine vane tests in a new miniature cascade facility

A new two-dimensional mini-cascade blow-down tunnel, with eight vane passages of only 20 mm true chord, 15 mm pitch, and 40 mm span, has been developed for testing gas turbine nozzle guide vane profiles at transonic exit Mach numbers ( M) and realistic Reynolds numbers ( Re) with a quick turnaround and high accuracy. The small size of the cascade has many advantages. Vane profiles can be tested at adjustable engine representative Re at room temperature with exit static pressures above atmospheric and Re and M can be independently varied. The mass flow is small and the long run times (&gt;3 min) allow downstream traversing with a three-hole miniature probe. The inaccuracies inherent in the traditional method of mounting the vanes/blades on pegs in the Schlieren windows have been eliminated by accurately computer numerical control (CNC) machining the whole cascade of vanes integral with the tunnel side walls, with re-usable, plug-in Schlieren windows. Cascades of new test vane profiles are quickly machined and tested, with a fast turn-around for comparative studies. A new Schlieren photography lens arrangement is demonstrated, which captures numerous flow visualization images per run directly into a digital SLR camera. Lower-than-atmospheric exhaust pressures were achieved by using a long exhaust designed to maximize exit flow dynamic pressure recovery using the self-ejector pumping effect. Exhaust pressures as low as 0.7 bar were achieved using the self-pumping exhaust, allowing M up to 1.6 with 3 bar inlet pressure and an exhaust at atmospheric pressure. An analytical model is developed for the mildly supersonic exit flow condition and validated against experimental data. Excellent agreement is achieved. Results presented for a typical transonic cascade show that the tunnel performs well in the subsonic and low supersonic region, but, as the exit M increases, shock-wave reflections from the free jet boundary, seen on the Schlieren, cause non-periodicity. Deep in the cascade, the flow is still periodic and can be used for investigations of loss and shock boundary-layer interaction. Interestingly, if the downstream pressure is reduced further to give even higher (but unrealistic) M, the cascade becomes axially supersonic and excellent periodicity is restored. Schlieren results are compared with computational fluid dynamics (CFD) simulations of the tunnel flow, and the loss measurements are validated against measurements conducted using a large-scale cascade at Göttingen.

Modelling counter-current and dual counter-current chromatography using longitudinal mixing cell and eluting counter-current distribution models

Two well known approaches are considered to analyze the processes of counter-current and dual counter-current chromatography: the longitudinal mixing cell model and the Craig's counter-current distribution model. The cell model represents perfectly mixed, equally sized cells in series. The number of cells characterizes the rates of longitudinal mixing in the stationary and mobile phases. In the eluting counter-current distribution (CCD) model, the CCC process is considered as a continuous form of Craig's counter-current distribution. For a cascade of equilibrium stages theoretical elution profiles of the CCC process by using the CCD and cell model approaches have been compared. It is shown that in general, distribution functions of the CCD and cell models differ. It is established that the distribution of a solute between two solvent phases in the dual CCC process is determined by the extraction factor c, the total number of equilibrium stages n and the position of the sample inlet m by the equation Q x = (1 − c m)/(1 − c n + 1 ) with c = F 2 K D/ F 1 ( K D, F 1, F 2 and Q x are the distribution constant, the phase flow-rates and the portion of solute eluted by the first phase, respectively).

On non-stationary viscous incompressible flow through a cascade of profiles

The paper deals with theoretical analysis of non-stationary incompressible flow through a cascade of profiles. The initial-boundary value problem for the Navier–Stokes system is formulated in a domain representing the exterior to an infinite row of profiles, periodically spaced in one direction. Then the problem is reformulated in a bounded domain of the form of one space period and completed by the Dirichlet boundary condition on the inlet and the profile, a suitable natural boundary condition on the outlet and periodic boundary conditions on artificial cuts. We present a weak formulation and prove the existence of a weak solution. Copyright © 2006 John Wiley & Sons, Ltd.

Hybrid design methods of cascade profile based on variational principles

PurposeProvides two hybrid methods for the aerodynamic design of cascade profiles, of which the design constraints are the combination of aerodynamic and geometric conditions.Design/methodology/approachIn the first method, the design constrain is composed of the velocity (or pressure) distribution on part of the blade surface and the geometry of the rest part. In the second method, the aerodynamic load distribution, i.e. the pressure difference between the suction and pressure surfaces, and the blade thickness distribution are employed as the design constrain. These constraints, together with all the other boundary conditions, are involved in the stationary conditions of a variational principle. The solution domain, i.e. the blade‐to‐blade passage, is transformed into a square in the image plane, while the blade contour is projected to a straight line; thus, the difficulty caused by the unknown geometry of profile is avoided. Finite element method is employed to produce the calculation code.FindingsApplications show the accuracy and the flexibility of the two methods, which can satisfy the different needs from blade design. Finally, the possibility of combining the hybrid methods with the through‐flow method is discussed, which would develop the present methods to three‐dimensional design of cascades.Research limitations/implicationsThe design methods are limited to frictionless flow.Practical implicationsA design software of cascade profiles based on this method has been developed, and will be provided to the engineering users for cascade design.Originality/valueThe hybrid methods developed in this paper can satisfy the demands from different aspects of engineering designs: aerodynamics, strength, manufacture, etc.

The ATIC long duration balloon project

Long Duration Balloon (LDB) scientific experiments, launched to circumnavigate the south pole over Antarctica, have particular advantages compared to Shuttle or other Low Earth Orbit (LEO) missions in terms of cost, weight, scientific “duty factor” and work force development. The Advanced Thin Ionization Calorimeter (ATIC) cosmic-ray astrophysics experiment is a good example of a university-based project that takes full advantage of current LDB capability. The ATIC experiment is currently being prepared for its first LDB science flight that will investigate the charge composition and energy spectra of primary cosmic-rays over the energy range from about 10 10 to 10 14 eV. The instrument is built around a fully active, Bismuth–Germanate (BGO) ionization calorimeter to measure the energy deposited by cascades formed by particles interacting in a thick carbon target. A highly segmented silicon matrix, located above the target, provides good incident charge resolution plus rejection of “backscattered” particles from the cascade. Trajectory reconstruction is based on the cascade profile in the BGO calorimeter, plus information from the three pairs of scintillator hodoscope layers in the target section above it. A full evaluation of the experiment was performed during a test flight occurring between 28 December 2000 and 13 January 2001 where ATIC was carried to an altitude of ∼37 km above Antarctica by a ∼850,000 m 3 helium filled balloon for one circumnavigation of the continent. All systems behaved well, the detectors performed as expected, >43 GB of engineering and cosmic-ray event data were returned and these data are now undergoing preliminary data analysis. During the coming 2002–2003 Antarctica summer season, we are preparing for an ATIC science flight with ∼15 to 30 days of data collection in the near-space environment of Long Duration Balloon (LDB) float altitudes.