Smooth Blade Research Articles

FLOW MODELLING AT COMPRESSOR CASCADE WITH TURBULATORS ON BLADE SURFACE

The research of boundary layer control at compressor blade row is actually. It is practical interest to solve the problem of providing of gas-dynamic stability of compressors of gas turbine engines. Aim of work is to investigate the effect of the placement density of turbulators on blade surface at the loss level at the critical flow mode. Flow at airfoil cascade with different placement densities is studied in work. Roughness elements were placed at the entrance of the blade witch was 30% of the surface area of the blade. The characteristics of airfoil cascades at placement density coefficient 0.36, 0.24, 0.18 were investigated. Shape of roughness element is hemisphere. Using of roughness elements at the entrance of the blade with a placement density coefficient 0.18…0.36 lead to a decreasing in value of total pressure loss coefficient at critical flow mode from 0.084…0.12 (for cascade with smooth blades) to 0.03…0.041

The Limitations of Using “Ra” to Describe Surface Roughness

Current criteria used to determine whether rough surfaces affect skin friction typically rely on a single amplitude parameter to characterize the roughness. The most commonly used criteria relate the centerline averaged roughness, Ra, to an equivalent sandgrain roughness size, ks. This paper shows that such criteria are oversimplified and that Ra/ks is dependent on the roughness topography, namely, the roughness slope defined as the roughness amplitude normalized by the distance between roughness peaks, Ra/λ. To demonstrate the relationship, wake traverses were undertaken downstream of an aerofoil with various polished surfaces. The admissible roughness Reynolds number (ρ1u1Ra/μ1) at which the drag rose above the smooth blade case was determined. The results were used to demonstrate a 400% variation in Ra/ks over the roughness topographies tested. The relationship found held for all cases tested, except those where the roughness first initiated premature transition at the leading edge. In these cases, where the roughness was more typical of eroded aerofoils, the drag was found to rise earlier.

ABRASIVE WEAR IMPROVING OF BLADES ON EFFICIENCY OF BLADE ROW OF AXIAL-FLOW COMPRESSOR STAGE

In work the results of numerical modeling of abrasive wear improving of axialflow compressorblades on the losses due to viscous friction are presented. Abrasive wear reduces efficiency.When the regular roughness has relative height 0.002-0.005 efficiency is decreased by 3%,with a further increasing the roughness relative height to 0.01 efficiency is decreased by 8% ascompared with the efficiency of smooth axial-flow compressor blades.

Experimental Studies of Dimpled Surface Effect on the Performance of Linear Cascade under Different Incidence Angles

In this paper, preliminary experiments were conducted to investigate the effect of dimpled surface on the performance of linear cascade. Two dimple configurations with a diameter of 1.0mm and a depth-diameter ratio of 0.2, which were located in 30%-60% and 75%-95% axial chord lengths of suction side respectively, were studied to validate their effectiveness in reducing total pressure loss. Incidence angles of -5.3°, 0°, 5.3°, 7.5°, 10° and inlet Mach number of 0.4 were used in each experiment with 1.5% Tu. Total pressure loss coefficients and blade loading force measurements were made on the dimpled blades by a mini 5-hole pressure probe and compared to the smooth blades. The experimental results show that the reduction of the total pressure loss coefficients of dimpled blades is obvious at the incidence angle of 0°, 5.3°, and 7.5°, and the change of the total pressure loss coefficients of dimpled blades is very slight at the incidence angle of -5.3°, and 10°. In addition, there exists a slight increase of loading force with dimpled blades. The comparison results also indicate that dimples on 30%-60% of suction side is more effective in loss reduction than that on 75%-95% of suction side at all incidence angles.

Diseño, construcción y evaluación de una máquina para deshojar la mazorca de maíz para envoltura de tamal

The present research was developed to mechanize the process of corn husking that would permit the husks to be used as wrapping for tamales or for their use in the making of handicrafts. After determining the physical-mechanical properties of the ears of corn, a conceptual design and the details of the machine were made. The prototype was then constructed and evaluated. The technological process consisted of two principle activities: cutting off the butt of the ear of corn and husking the remains. The cut is made with a smooth blade, while the husking takes place as a result of friction between the surface of the ear of corn and the rollers that turned in the opposite direction and at a different speed. The corncob is expulsed to the side because of the movement of the rollers and the husk that goes between these. The productivity of the machine is 790 ears of corn•h 1 at a feeding speed of 0.03 m•s 1. Tests showed husking at 95 %, mechanical damage to the husks at 1.4 % and up to 11 % of the husked corn had husks with a humidity of 50.4 %. The dependence of the energy of court depending on the diameter of the ear was determined. An evaluation of the amount of electricity used in the case of a smooth blade as compared to a toothed one determined that the latter requires 6.5 % more electricity.

A lifting surface optimization method for the design of marine propeller blades

A lifting surface optimization method is coupled with a blade alignment procedure for the design of propeller in marine applications. The method is characterized by the use of a vortex lattice discretization of the true blade mean camber surface for the determination of the optimum circulation distribution, which is found by numerically solving a variational problem. The blade mean camber surface is deformed to satisfy the kinematic boundary condition that the normal component of velocity becomes zero on that surface, in an iterative way with the optimization problem. The smooth blade geometry and the robust solution of the alignment are guaranteed by the use of a B-spline surface representation. A validation calculation is carried out for DTNSRDC propeller 4119 operating in uniform flow. A comparative study with literature for some DTNSRDC parametric propeller series is given to demonstrate the proposed algorithm for the design of propellers that have complex geometry.

Effect of surface roughness on the aerodynamic performance of turbine blade cascade

The effect of surface roughness on the boundary development and loss behavior of turbine blades is investigated with different Reynolds numbers in this paper. The result shows that the velocity profile in boundary layer is plumper on rough surface than on smooth blade. The aerodynamic loss is lowered at low Reynolds number, but becomes significantly large at high Reynolds number. The total pressure loss coefficient of cascade can reach a top increase of 129% for rougher blades comparing with smooth blades at Re=300000.

Development of a Numerical Based Correlation for Performance Losses due to Surface Roughness in Axial Turbines

AbstractIn the present work, a recently developed in-house 2D CFD code is used to study the effect of gas turbine stator blade roughness on various performance parameters of a two-dimensional blade cascade. The 2D CFD model is based on a high resolution flux difference splitting scheme of Roe (1981). The Reynolds Averaged Navier-Stokes (RANS) equations are closed using the zero-equation turbulence model of Baldwin-Lomax (1978) and two-equation Shear Stress Transport (SST) turbulence model. For the smooth blade, results are compared with experimental data to validate the model. Finally, a correlation between roughness Reynolds number and loss coefficient for both turbulence models is presented and tested for three other roughness heights. The results of 2D turbine blade cascades can be used for one-dimensional models such as mean line analysis or quasi-three-dimensional models e.g. streamline curvature method.

RAISING GAS-DYNAMIC STABILITY MARGIN OF AXIAL AND CENTRIFUGAL COMPRESSOR STAGES BY MEANS OF VANED DIFFUSER BOUNDARY LAYER CONTROL / DUJŲ DINAMINIO STABILUMO RIBOS AŠINIO IR IŠCENTRINIO KOMPRESORIAUS PAKOPOSE DIDINIMAS ATLIEKANT STABILIZUOTO DIFUZORIAUS PARIBIO SLUOKSNIO KONTROLĘ

Generalised research results that consider the upgradability of axial and centrifugal gas turbine engine compressors by means of gas-dynamic boundary layer control on bladed disks are demonstrated. Active and passive methods are used. Comparative analysis of the results has been carried out. The analysis is purposed to determine the influence of the flow circulation around the aerofoils on the performance of compressor single-row bladed disks with smooth blades and rough blades and under the condition that vortex generators are installed. An increase in the efficiency of aviation gas-turbine engines and in their gas-dynamic stability margin support leads to the enhancement of the parameters and performance of compressors: increase in loading of aerodynamic bladed disks, improvement of their economical efficiency, improvement of margin of the continuous flow around the compressor grids, etc. Airflow in the compressor grid is characterised by the flow region in the flow core and also by the flow regions in the wall boundary layers on the grid blades where shock waves, vortices, air swirls, and flow separation phenomena take place. The principle objective of the work is to research the possibilities of influence on the parameters of the elements of compressors and overall performance of gas-turbine engines via the methods of active and passive flow regulation. Active flow regulation is realised either by rendering the auxiliary gas mass to the blades boundary layer, or by suction (withdrawal) of the boundary layer (its part) from the surfaces of blades. Passive flow around regulation is characterised by influence on the boundary layer by means of energy redistribution in the flow itself. Santrauka Šiuo tyrimu siekiama nustatyti sparno profilio aptekejimo įtaką vienos eiles menčių kompresoriaus su lygiomis ir šiurkščiomis mentemis darbui, esant įdiegtiems sūkurio generatoriams. Pagrindinis darbo tikslas – ištirti kompresoriaus elementų ir bendro dujų turbininių variklių darbo įtaką parametrams, taikant pasyvų ir aktyvų srauto reguliavimo metodus. Padidinus dujų turbininių variklių našumą ir jų dujų dinamikos stabilumo ribas, pagereja kompresorių darbas ir parametrai: padideja aerodinaminių diskų su mentemis apkrova, jie tampa ekonomiškai našesni, padideja nepertraukiamo srauto riba aplink kompresoriaus plokšteles.

Striated abrasions from a knife with non-serrated blade—identification of the instrument of crime on the basis of an experiment with material evidence

This paper presents an experiment with a knife seized as material evidence in a homicide case. The reason for the experiment was the necessity to determine whether the injuries of the deceased could have been inflicted with this instrument since in the course of the investigation doubt arose as to the origin of linear, parallel scratches around one of the wounds and on the abdominal integuments suggesting a serrated blade. The knife found near the crime scene had a smooth blade and small serrations only on the borderline between its blade and hilt. However, the performed experiment showed that if the knife is directed towards the integuments of the body in a special way, its serrations, even though not located on the blade itself, may leave such striated marks on the body, as those found during the autopsy, suggesting their origin from a serrated blade.

Finite Element Analysis on the Blade Structure of Centrifugal Pump

The centrifugal pump is the common mechanical equipment, which is extensively applied in the water conservancy, ships and other projects, and the blade structure is a very important part in the centrifugal pump. In this paper, the stress distribution and concentration of single blade in the impeller are analyzed under the different pressure field of the blade structure surface, and the fatigue failure of blade is also studied. The research results show that the we can get the stress and strain of the blade accurately and intuitively through the analysis for the blade structure, the stress concentration of the centrifugal pump blade is mainly in the root and junction of the wheel cover, and the import value of stress concentration is larger than the outlet; the stress concentration may be caused easily as the stress increases rapidly in the blade, which has a great impact on the fatigue strength, the fatigue limit of the blade with the stress concentration is decreased more obviously than the fatigue limit of the smooth blade.

Aerodynamic Performance of Suction-Side Gill Region Film Cooling

The performance of suction-side gill region film cooling is investigated using the University of Utah transonic wind tunnel and a simulated turbine vane in a two-dimensional cascade. The effects of film cooling hole orientation, shape, and number of rows, and their resulting effects on the aerodynamic losses, are considered for four different hole configurations: round axial (RA), shaped axial (SA), round radial (RR), and round compound (RC). The mainstream Reynolds number based on axial chord is 500,000, exit Mach number is 0.35, and the tests are conducted using the first row of holes, or both rows of holes at blowing ratios of 0.6 and 1.2. Carbon dioxide is used as the injectant to achieve density ratios of 1.77–1.99 similar to values present in operating gas turbine engines. Presented are the local distributions of total pressure loss coefficient, local normalized exit Mach number, and local normalized exit kinetic energy. Integrated aerodynamic losses (IAL) increase anywhere from 4% to 45% compared with a smooth blade with no film injection. The performance of each hole type depends on the airfoil configuration, film cooling configuration, mainstream flow Mach number, number of rows of holes, density ratio, and blowing ratio, but the general trend is an increase in IAL as either the blowing ratio or the number of rows of holes increase. In general, the largest total pressure loss coefficient Cp magnitudes and the largest IAL are generally present at any particular wake location for the RR or SA configurations, regardless of the film cooling blowing ratio and number of holes. The SA holes also generally produce the highest local peak Cp magnitudes. IAL magnitudes are generally lowest with the RA hole configuration. A one-dimensional mixing loss correlation for normalized IAL values is also presented, which matches most of the both rows data for RA, SA, RR, and RC hole configurations. The equation also provides good representation of the RA, RC, and RR first row data sets.

English

The main objective of the paper is creating a method on how one can model an axial flow compressor. A systematic design approach has been used in the present study in order to design an axial flow compressor. The design calculations were based on thermodynamics, gas dynamic, fluid mechanics, aerodynamic and empirical relations. A two- dimensional compressible flow is assumed with constant axial and rotor blade velocities. A free-vortex swirl distribution was used in the design. These calculations include thermodynamic properties of the working fluid, number of rotor and stator blades, tip and hub diameters, blade dimensions (chord, length and space) for both rotor and stator, velocity triangles before and after the rotor and stator, mach number, solidity, flow and blade angles (blade twist). A repeated stage calculation is made to calculate the above parameters along compressor stages. The twist of the blades can be calculated along the blade length at any required number of sections selected by the designers to obtain smooth blade twist profile. NACA 65010 has been selected as a blade profile for the compressor at root, mean and tip. Here it is calculated at three main sections, the hub, the mean and the tip. The blade selected for this study is NACA 65010. The data obtained from the systematic approach has been utilised to generate three dimensional compressors.

Asplenium Badinii (Aspleniaceae), A New Endemic Fern Species from Minas Gerais, Brazil

A new species of Asplenium L. (Aspleniaceae) is described and illustrated. Asplenium badinii Sylvestre & P. G. Windisch is an endemic species of the isolated forest clumps (capoes) from Itacolomi State Park, from Minas Gerais, Brazil, in areas dominated by open rocky sites (campos rupestres). This environment is known for its high level of generic and specific endemism. The new species belongs to the A. salicifolium L. species group, with apical pinnae similar to lateral ones, smooth blades, and spores with echinate perispore. It is related to A. juglandifolium Lamark and A. bradeanum Handro. Diagnostic characters for A. badinii are the long basal segment on the acroscopic side of the proximal pinnae as well as the linear to linear-lanceolate scales on the stem.

Effects of a kind of non-smooth blade on the unsteady flow field at the exit of an axial fan

An experimental investigation of effects of a kind of streamwise-grooved blade on the unsteady flow field at an exit of an axial-flow fan was performed. The flow field at 25% chord downstream from the trailing edge at hub was measured using a fast-response five-hole pressure probe at different mass-flow conditions. The unsteady flow of the grooved blades was compared with that of the smooth blades. The measurement results indicate that: (1) the grooved blades restrain the velocity fluctuation and the pressure fluctuation by modulating the blade boundary layers, which contributes to the flow loss reduction in the hub region and in the rotor wake region at the design condition; (2) the stream-wise grooves play an important role in restraining the radial migration in the blade boundary layer and abating the tip flow mixing, which contributes to the flow loss reduction in the tip region at the design condition; (3) at the near stall condition, the grooved surface can not reduce the flow loss, even in-crease the loss nearby when the separation happens in the blade boundary layer.

Comparison between loss coefficients of smooth, smooth-thickened, and rough-thickened axial turbine blades

Experiments have been performed in a six-blade-cascade with smooth, smooth-thickened, and rough-thickened blades. After performing experiments with smooth blades, plastic sheet for smooth-thickened and 50-grade emery paper for rough thickened (both of same thickness) are pasted on suction, pressure surface separately and over both surfaces together to study the effects of roughness caused by erosion and deposition over the turbine blades. Static and total pressures at cascade inlet, static pressure over the suction and pressure surfaces of the blades forming middle channel, total and static pressures and outlet flow angle at 15 per cent of chord downstream are measured at midspan height. Difference in loss coefficients with smooth-thickened and rough-thickened represents the effect of roughness without thickening, similar to the roughness generated by erosion. The results of rough-thickened blade can be used to simulate the effect of roughness generated by deposition. For the same roughness level, roughness caused by deposition is more detrimental than that by erosion. It is also observed that the performance deterioration and non-uniformity of flow at cascade exit is more for rough-thickened blades.

Effects of a kind of non-smooth blade on the performance of an axial fan

This paper presents an experimental investigation of effects of a kind of streamwise-grooved blade on the performance of an axial-flow fan. The flow field at 25% chord downstream from the trailing edge at hub was measured using a 5-hole pressure probe at different mass-flow conditions. The fan performance of the groove blades was compared with that of the smooth blades. The measurement results indicate that: (1) the non-smooth blades increase mass flow of the fan at the same throttle conditions except a near stall condition; (2) the non-smooth blades reduce the relative total pressure loss in the rotor passage and increase the fan’s total pressure rise at the test mass-flow conditions except the near stall condition; (3) Negative benefits are obtained at a near stall condition when the smooth blades are replaced by the non-smooth ones. The fan mass flow decreases 0.9% while the total-pressure rise decreases 2.4% at the near stall condition.

Experimental investigation of bionic rough curved soil cutting blade surface to reduce soil adhesion and friction

The phenomenon of soil adhesion occurs often when machines interact with soil. Adhesion increases the working resistance and energy consumption of cutting or tillage tools and often decreases the working quality. The problem of soil adhesion has been solved by some soil-burrowing animals, such as the dung beetle, ant, pangolin and others. It was found that some exterior parts of soil-burrowing animals have geometrical rough structures, which was one of the reasons why soil-burrowing animals do not stick to the soil so much. In order to study the effects of the rough surface characteristics on bulldozer blades to reduce soil adhesion, several curved bulldozer blades with different “bionic” rough surface characteristics were designed and tested in comparison to smooth blades. In addition, the mean normal force on the blade surface was measured through small sensors mounted on certain points of the blade surface to study the soil to blade mechanics. The blades designed with rough surfaces were found to reduce the mean draft force. A considerable amount of soil adhered to the surface of the smooth blades, but little adhered to the rough blades. The mean normal pressure measured by the sensors mounted on the blade roughness convex curves was much larger than that between the convexes. The mean normal pressure was greatest on the blade bottom edge.

Influence of Surface Roughness on Three-Dimensional Separation in Axial Compressors

Surface roughness on a stator blade was found to have a major effect on the three-dimensional (3D) separation at the hub of a single-stage low-speed axial compressor. The change in the separation with roughness worsened performance of the stage. A preliminary study was carried out to ascertain which part of the stator suction surface and at what operating condition the flow is most sensitive to roughness. The results show that stage performance is extremely sensitive to surface roughness around the leading edge and peak-suction regions, particularly for flow rates corresponding to design and lower values. Surface flow visualization and exit loss measurements show that the size of the separation, in terms of spanwise and chordwise extent, is increased with roughness present. Roughness produced the large 3D separation at design flow coefficient that is found for smooth blades nearer to stall. A simple model to simulate the effect of roughness was developed and, when included in a 3D Navier–Stokes calculation method, was shown to give good qualitative agreement with measurements.

Heat transfer research on gas turbine airfoils at NASA GRC

The turbine gas path is a very complex flow field due to a variety of flow and heat transfer phenomena encountered in turbine passages. This manuscript provides an overview of the current work in this field at the NASA Glenn Research Center (GRC). Based on the author's preference, however, more emphasis is on the computational work. There is much more experimental work in progress at GRC than that reported here. Specifically, the external flow and heat transfer characteristics are described over smooth and rough turbine blades for a range of parameter values. For smooth blades, the effect of film-cooling holes as well as internal cooling channels with ribs and bleed holes is considered. Studies on the blade tip region, susceptible to burnout and oxidation due to high thermal loading, are also described. Wherever possible, predictions of heat transfer coefficient on the real blade surface, obtained using in-house-developed codes, are compared with the available experimental data. Suggestions for further work are outlined.