Row Of Holes Research Articles

Application of hydrodynamic cavitation to improve antioxidant activity in sorghum flour and apple pomace

To overcome the energy inefficiency and scale-up issues of ultrasonication, hydrodynamic cavitation was studied to release the bound phenolics in sorghum flour (SF) and apple pomace (AP) to enhance their antioxidant activity. In this study, SF and AP, naturally fermented at optimized conditions, were hydrodynamic cavitated at different flour to water (FWR) of 100, 275, 450g/L and 50, 87.5, 125g/L, respectively. In addition, three types of cavitators with 2, 3 and 4 rows of holes in rotor were used to cavitate SF and AP for the cavitation temperatures as 30, 35, 40°C and 40, 45, 50°C, respectively. For SF and AP, optimized conditions were determined as 100g/L and 87.5g/L FWR, 3 and 4 rows of rotor holes, 35°C and 45°C cavitation temperature, respectively. At these conditions, total phenolic content (TPC) and antioxidant activity (AA) of SF were 39.5% and 38.6%, respectively higher than the control SF, while for AP, these numbers were observed as 42% and 97%, respectively. IVSD in SF showed 4.7% increase, whereas AP exhibited 7.6% increment in TDF as compared to that of control samples. The study suggests that hydrodynamic cavitation can be successfully used for the preparation of processed foods with increased levels of phenolic antioxidants.

Conjugate heat transfer simulations of pulsed film cooling on an entire turbine vane

This paper presents a numerical investigation on pulsed film cooling using conjugate heat transfer with an entire NASA C3X vane model, which has nine rows of film hole: five in leading edge region, two at suction side and two at pressure side. Square and sinusoidal waves are considered to pulse the cooling air. The normalized Nusselt number distributions over the vane surface are calculated and discussed at three blowing ratios (BR=0.78, 1.17 and 1.56) and four Strouhal numbers (St=0.0029, 0.0058, 0.0116 and 0.0232). Based on the entire turbine vane and conjugate heat transfer algorithm, the present simulations exhibit three interesting phenomena: (1) At suction side, normalized Nusselt number increases with BR for pulsed flow, indicating pulsing film cooling with high BRs should not be used. (2) At pressure side, when BR increases, normalized Nusselt number of the pulsed flow becomes smaller than that of the steady flow, indicating pulsed film cooling with high BRs is more suitable. (3) In leading edge region, normalized Nusselt number decreases with an increasing of Strouhal number from 0.0029 to 0.0116, but then increases at St=0.0232 for both pulsed flow types. This phenomenon indicates the importance of choosing an appropriate pulsing frequency.

Simulation of the Sensing Performance of a Plasmonic Biosensor Based on Birefringent Solid-Core Microstructured Optical Fiber

A finite element method is used to analyze the performance of a microstructured optical fiber-based surface plasmon resonance sensors aimed for biomedical applications, such as the detection of blood carried species. Birefringence obtained by removing of a row of holes in a two-ring hexagonal lattice of holes in a gold covered silica fiber leads to a relatively high sensitivity of the fiber optical response to a refractive index of the analyte surrounding the fiber. This fiber structure supports two types (I and II) of resonant modes. In these modes, there is an opposite variation of some sensing parameters with the increase of the refractive index of the analyte between 1.36 and 1.39. Thus, for a smaller value (1.36) of the refractive index of the analyte n a, the resonance spectral width δλ 0.5 is large for the core mode I and small for the core mode II but for a larger value (1.39) of n a, δλ 0.5 is small for the core mode I and large for the core mode II. Also, for n a = 1.36, the amplitude sensitivity S A is small for the core mode I and large for the core mode II but for n a = 1.39, S A is large for the core mode I and small for the core mode II. By adjusting the radius of the gold layer, the proposed sensor shows high spectral sensitivity S λ and narrow δλ 0.5 at the same resonance wavelength and n a (1.39) where the figure of merit (FOM) is very large in comparison with the most recently published values.

Improvement of film cooling effectiveness with a small downstream block body

The aim of this study is to predict the improvement in film cooling performance over a flat plate through a single row of cylindrical holes with different streamwise angles by using the Ansys CFX software package. In order to improve the film cooling effectiveness, a short crescent-shaped block is placed downstream of a cylindrical cooling hole. The numerical results of the cylindrical hole without the downstream short crescent-shaped block are compared with experimental data.

Evaluation of the Influence on the Efficiency Curvature of the Surface Film Cooling

The results of numerical simulation of film cooling of the turbine rotor blade with the flow of coolant to the area of the leading edge through three rows of cylindrical holes. To determine the effect of surface curvature on film cooling effectiveness, and a comparison of results obtained with the results of simulation modeling of flow of a plate with film cooling at the inlet cylindrical region. The studies were conducted at the magnitude of the blowing ration of 0.5 to 2.0. Dimensions calculation model and input data received characteristic of the high pressure turbine blades of high-temperature gas turbine engine. Modelling performed using software package ANSYS CFX. The result obtained by calculations that the presence of the cylindrical profiled surfaces instead of flat surface leads to a significant decrease in the average film cooling effectiveness, both cylindrical and the concave surfaces in the investigated range blowing ration values. For all blowing ration film cooling effectiveness parameter values on the suction side is much higher than the pressure side. At the same time, the average efficiency of the film cooling on the suction side when m < 1.5 is higher than on a plot of flat wall, and when m > 1.5 marginally below. Application dependencies obtained on models with flat walls, for the calculation of the film cooling efficiency of suction side and pressure side of the blades is only possible with such amendments as may be determined by the results of this work.

Jet impingement heat transfer on a concave surface in a wing leading edge: Experimental study and correlation development

Extensive experimental studies of the heat transfer characteristics of jet impingement on a variable-curvature concave surface in a wing leading edge were conducted for aircraft anti-icing applications. The experiments were performed using a piccolo tube with three rows of aligned jet holes over a wide range of parameters: the jet Reynolds number (Rej) from 50,000 to 90,000, the relative tube-to-surface distance (H/d) from 1.74 to 20.0, the jet impingement angle (α) from 66° to 90°, and the relative chordwise arc length in the jet impingement zone (r/d) from 13.2 to 34.8. Experimental results indicated that the heat transfer performance at the stagnation point was enhanced with increasing Rej and α, and an optimal H/d existed to achieve the best heat transfer performance at the stagnation point corresponding to specific operating parameters. It was found that the attenuation coefficient curve of jet impingement heat transfer in the chordwise direction exhibited an approximate bell shape with the peak located at the stagnation point, affected only by r/d in the peak zone. In the non-peak zone, however it was affected significantly by a variety of factors including Rej, H/d and r/d. Experimental data-based correlations of the Nusselt number at the stagnation point and the distribution of the attenuation coefficient in the chordwise direction were developed and validated, which contributes significantly to the future design of a wing anti-icing system with three rows of aligned jet holes.

Assessment of backbreak due to blasting operation in open pit mines: a case study

One of the major problems related to blasting operations in open pit mines is the formation of cracks on the benches behind the last row of blast holes (backbreak). Prediction of backbreak plays an important role in the safety of open pit mining and the reduction of the detrimental effects resulting from blasting operations. In this study, we have tried to develop predictive models for anticipating backbreak. For this purpose, two of the most popular techniques, regression tree (RT) analysis and adaptive neuro-fuzzy inference system (ANFIS), were taken into account and a predictive model was constructed based on each. For training and testing of these models, a database including 175 blasting events in the Sungun Copper Mine (SCM), Iran, was used. These models predict backbreak based on the major blast design parameters (i.e., burden, spacing, stemming length, powder factor, and geometric stiffness ratio). It was found that both models can be used to predict the backbreak, but the comparison of two models, in terms of statistical performance indices, shows that the ANFIS model provides better results than the RT.

Study of Film Cooling Appliedon a Fixed Blade of a Sector HPT of the CFM56-7B Engine

Abstrac t—We consider in this work a numerical three-dimensional study of the interaction of two row of discrete jets in a wall with an incompressible flow for an injection rate M=0.5. This simulation is applied to the stator blade of the CFM56-7B engine and is performed using the computational fluid dynamics (CFD) simulation tool, with CFX5.7.1 software. This code use the finite volume method to solve the equations of Navier-Stokes and offer several turbulences models. In this study, the shear stress turbulence model (SST) is used.The velocity and temperature distributions are presented and discussed. The results obtained show some information. The two rows of holes on the leading edge is not sufficient to cool the blade because the injection faces the hot flow (crossflow), and is found on the stagnation line of the leading edge. The cooling is only localized at the leading edge for the first row and extends over a certain distance from the intrados to the second row. More, the results show the existence of two tourbillions contrarotatifs. These vortices transport the hot gas in the jet and thus degrade the protective wall. . Index Terms—Film cooling, heat transfer, numerical simulation, turbulent flows. I. INTRODUCT ION I T is well known from thermodynamic analysis that the performance of a gas turbine is strongly influenced by the temperature at inlet to the turbine. Modern gas turbine engines are designed to operate at inlet temperatures of 1800-2200 °K which are far beyond the allowable metal temperatures. Thus, to maintain acceptable life and safety standards, the structural elements need to be protected against the severe thermal environment. This calls for an efficient system. On such cooling technique currently used for high temperature turbines, is film cooling. The present paper aims to contributein the development of a prediction method for the simulation and to know the cooling behaviour. The application of computational fluids dynamics to film cooling problem is assessed in this study. Results are presented in terms of temperature and velocity calculation in the flow field.

Design and Fabrication of a Dielectricless Substrate-Integrated Waveguide

A process for the fabrication of dielectricless rectangular waveguides (RWGs) integrated in the substrate is presented and experimentally validated. First, two complementary circuits are realized through milling the guide in a substrate and, then, are metallized with traditional additive processes used in printed-circuit board industry. Next, the circuits are joined together, and electric continuity is enforced through two additional rows of conductive holes along the guide sidewall, as it occurs in the substrate-integrated waveguide technology. A comparison between the propagative characteristics of a classic RWG and a waveguide with this methodology is reported. Finally, a slotted waveguide realized by this technology is fabricated and measured.

Taguchi Based Regression Analysis of End-Wall Film Cooling in a Gas Turbine Cascade with Single Row of Holes

AbstractNumerical investigations were conducted on a turbine cascade, with end-wall cooling by a single row of cylindrical holes, inclined at 30°. The mainstream fluid was hot air and the coolant was CO

Computation of leading edge film cooling from a CONSOLE geometry (CONverging Slot hOLE)

The aim of this study is to investigate the effect of mass flow rate on film cooling effectiveness and heat transfer over a gas turbine rotor blade with three staggered rows of shower-head holes which are inclined at 30° to the spanwise direction, and are normal to the streamwise direction on the blade. To improve film cooling effectiveness, the standard cylindrical holes, located on the leading edge region, are replaced with the converging slot holes (console). The ANSYS CFX has been used for this computational simulation. The turbulence is approximated by a k-e model. Detailed film effectiveness distributions are presented for different mass flow rate. The numerical results are compared with experimental data.

On the Effect of an Aggressive Inlet Swirl Profile on the Aero-thermal Performance of a Cooled Vane

A high-pressure vane equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side while the leading edge is protected by a showerhead system. Steady three-dimensional Reynolds-Averaged Navier-Stokes (RANS) simulations have been performed. A preliminary grid sensitivity analysis has been performed (with uniform inlet flow) to quantify the effect of the spatial resolution. Turbulence model has been assessed in comparison with available experiment data. The effects of a realistic inlet swirl on the aero-thermal performance of the cooling system are then investigated by means of comparison between two different kinds of simulations. The first one using a uniform inlet flow while the second one with aggressive swirl derived from the EU-funded project TATEF2. Clocking effects are also accounted for. The effect of the swirling flow in determining the coolant transport are investigated, evidencing the key role that these phenomena have in determining the effectiveness of the cooling.

Clocking Effects of Inlet Nonuniformities in a Fully Cooled High-Pressure Vane: A Conjugate Heat Transfer Analysis

A high-pressure vane (HPV) equipped with a realistic film-cooling configuration has been studied. The vane is characterized by the presence of multiple rows of fan-shaped holes along pressure and suction side, while the leading edge (LE) is protected by a showerhead system of cylindrical holes. Steady three-dimensional Reynolds-averaged Navier–Stokes simulations have been performed. A preliminary grid sensitivity analysis with uniform inlet flow has been used to quantify the effect of spatial discretization. Turbulence model has been assessed in comparison with available experimental data. The effects of the relative alignment between combustion chamber and HPVs are then investigated, considering realistic inflow conditions in terms of hot spot and swirl. The inlet profiles used are derived from the EU-funded project TATEF2. Two different clocking positions are considered: the first in which hot spot and swirl core are aligned with passage; and the second in which they are aligned with the LE. Comparisons between metal temperature distributions obtained from conjugate heat transfer (CHT) simulations are performed, evidencing the role of swirl in determining both the hot streak trajectory within the passage and the coolant redistribution. The LE aligned configuration is determined to be the most problematic in terms of thermal load, leading to increased average and local vane temperature peaks on both suction side and pressure side with respect to the passage-aligned case. A strong sensitivity to both injected coolant mass flow and heat removed by heat sink effect has also been highlighted for the showerhead cooling system.

Experimental study on shear behaviour of recycled concrete hollow block masonry

To study the shear behavior of recycled concrete block masonry with three rows of holes, the experiments were carried out on the type 240 specimens. The results showed that the shear damage mode of recycled concrete block masonry was brittle failure; the majority of destroy was double shear; the shear pin could greatly improve the shear strength; the influences of block type and intensity level on shear strength were small; the shear strength was mainly determined by the strength of mortar, and the shear strength increased with the increasing of the strength of mortar. The influence of difference of block material on the shear strength coefficient of variation was small, but the coefficient of variation was easily influenced by the water absorption, the construction quality. Considering the influence of the construction quality, the expressions on shear strength average value, standard value and design value were modified.

A NEW METHOD TO ASSESS FUNCTIONAL ACTIVITY OF SERUM COMPLEMENT SYSTEM

Complement system is an important component of innate immunity, providing primary protection against pathogens invading the body. In addition, it was shown that the complement system is associated with many diseases, not only autoimmune and infectious, but also mental disorders. In this regard, it is necessary to develop affordable and fast method of measuring activity of the complement system in real-time mode. We present a new semi-automated method for assessment of serum complement activity. The assay is based on cytolytic action of complement system upon the ciliate organism Tetrahymena pyriformis. This method consists in repeated counting of live Tetrahymena motile cells by means of specially developed Biolat device, which consists of two video cameras, light sources, and movable round plate. The plate has two rows of holes. The device also includes microprocessor control unit based on AutoCiliata software, intended for control of operation module and counting the surviving cell. The calculations are based on fixation of two sequential video-frames, with subsequent software image processing. Cell death events were observed upon incubation in triethanolamine (TEA) buffer containing 5% of blood serum. We have also compared complement activity in different buffers, i.e., standard medium for culturing of ciliates, Veronal-Medinalum buffer, and the TEA buffer. TEA buffer was found superior to the Veronal buffer when applied in the test system. The time of cell death in the TEA-buffered medium containing 5% serum was < 15 minutes for all the sera studied. The parameters denoting serum complement activity were as follows: a half-life time for the moving cells (TLD50), and a similar value for 100% cell inactivation (1/TLD50, functional activity of the complement system, ACS). The sensitivity of this assay was calculated from dependencies between TLD50 and ACS, and actual serum concentrations. We have suggested an opportunity for evaluation of an integral complement activity, and interrelations between the intensity of synthesis and consumption of its major effector proteins. In the course of this study, we have tested different concentrations of Ca++ and Mg++ ions in the incubation buffer, with optimal physiological concentrations of2.5 mMand1.5 mM, respectively. We have also estimated statistical precision characteristics for pre-analytical and analytical steps of the method. The average coefficients of variation (CV) were 3.9% and 2.7%, respectively, thus satisfying the reliability criteria in research. A short performance time of the study suggests its potential application in clinical practice, including online examination regimens. A method for semi-automatic measurement of serum complement activity could be applicable in daily clinical practice, including the online performance.

Numerical Investigation of Rotation Effects on Anti-vortex Film-Cooling Holes

The anti-vortex film-cooling technique under rotating conditions is investigated using large eddy simulation (LES) due to its complex mixture between the main stream flow, film-cooling flow, and the flow through the anti-vortex holes. The film-cooling was enhanced by placing two small injection holes (anti-vortex holes) just downstream of the main cooling hole in order to modify the approaching boundary layer flow and its interaction with the film-cooling jet. A geometry of a single row of rectangular holes inclined normally on a flat plate is used as the baseline case. The finite volume method and the unsteady SIMPLE algorithm were applied on a non-uniform staggered grid. The simulations were performed for four different values of rotation number (Ro) of 0.0, 0.03021, 0.06042, and 0.12084 and a jet Reynolds number of 4,700. Three different values of velocity ratio (coolant jets / main jet velocity), namely 0.5, 1, and 1.5, were studied. One position of the anti-vortex holes is investigated with density ratio (coolant density / main stream density), namely 1.04. The present simulation is carried out using an in-house FORTRAN code. Numerical calculations of flow field and film-cooling effectiveness are validated with reported LES results. It was shown that the rotational speed is the dominant factor in determining the cooling effectiveness level. The jet footprint of the anti-vortex is broader than for the single jet case and increases as Ro increases. Furthermore, it was also found that the anti-vortex technique used in this study reduces the mixing of the main stream and the coolant jets and improves the film-cooling effectiveness using the same amount of coolant fluid as was used in the case of a single jet. It was also shown that the anti-vortex holes create reverse vortices against the main vortices that are created by the main hole. These reverse vortices help to keep the coolant jet flow near the wall.

Inhibiting sorbent stripping by designing a sorbent-packed porous probe for headspace solid-phase microextraction.

To prevent the stripping of coating sorbents in headspace solid-phase microextraction, a porous extraction probe with packed sorbent was introduced by using a porous stainless steel needle tube and homemade sol-gel sorbents. The traditional stainless-steel needle tube was punched by a laser to obtain two rows of holes, which supply a passageway for analyte vapor during extraction and desorption. The sorbent was prepared by a traditional sol-gel method with both poly(ethylene glycol) and hydroxy-terminated silicone oil as coating ingredients. Eight polycyclic aromatic hydrocarbons and six benzene series compounds were used as illustrative semi-volatile and volatile organiccompounds in sequence to verify the extraction performance of this porous headspace solid-phase microextraction probe. It was found that the analysis method combining a headspace solid-phase microextraction probe and gas chromatography with mass spectrometry yielded determination coefficients of no less than 0.985 and relative standard deviations of 4.3-12.4%. The porous headspace solid-phase microextraction probe showed no decrease of extraction ability after 200 uses. These results demonstrate that the packed extraction probe with porous structure can be used for headspace solid-phase microextraction. This novel design may overcome both the stripping and breakage problems of the conventional coating fiber.

LES of rotational effects on film cooling effectiveness and heat transfer coefficient in a gas turbine blade with one row of air film injection

The effects of rotation on film cooling effectiveness and heat transfer coefficient distributions on the suction and pressure surfaces of a gas turbine blade were numerically simulated using large eddy simulation method. The flow is in the low Mach number (incompressible) regime. The suction (convex) side has simple angled cylindrical film-cooling holes; the pressure (concave) side has compound angled cylindrical film-cooling holes. The blowing ratio (BR) is 0.5 on both the suction and pressure sides and the inlet Reynolds number based on the axial chord is 3 × 105. The effects of turbine rotating conditions on the film cooling effectiveness and heat transfer coefficient distributions were investigated at four rotating speeds of 0 rpm, 125 rpm, 250 rpm, and 500 rpm. Air was injected through one row of film holes each on the pressure and suction surfaces. The commercial code STAR-CCM+ was used in the prediction. The results indicate that film cooling effectiveness increases with an increase in the rotating speed. Higher turbine rotating speeds show more local film cooling effectiveness spread on pressure surface. The film cooling effectiveness and Nusselt number distributions were presented along with the discussions on the influences of rotating speed. Results showed that the rotation promotes an earlier boundary layer transition and increases the transition length on the suction surface.

Effect of discrete-hole arrangement on film-cooling effectiveness for the endwall of a turbine blade cascade

This paper investigates film cooling in a turbine cascade endwall for two discrete-hole configurations using liquid crystal thermography. The discrete holes, arranged in rows aligned in the pitchwise direction, gave rise to relative maxima of film-cooling effectiveness downstream of each row, followed by a marked decrease of effectiveness along the gap between adjacent rows of holes. This resulted in a not efficient coverage of the endwall surface, with succession of over- and under-cooled regions. The re-design of discrete-hole configuration, based on knowledge of the heat transfer coefficient map on the endwall without film cooling, enabled the redistribution of the coolant to provide a better coverage of the endwall and a significant increase of the area-averaged film-cooling effectiveness.

Effect of Coolant Jet Holes Direction on Film Cooling Performance

The film cooling effectiveness and local heat transfer coefficient for coolant jet holes direction (orientation angle), have been investigated. Experimental investigations were done on a flat plate by using a single test transient IR thermograph technique.Evaluation of the cooling performance is obtained by estimated both film cooling effectiveness and heat flux ratios. Three models of coolant jet holes are investigated,each model consists of two rows of holes arranged in a staggered way with different orientation angles. Model (1) downstream row with acute angle and the upstream row with obtuse angle; model (2) both rows with obtuse angles, while model (3) both rows with acute angles. The holes diameter is 4mm, the longitudinal distance between the upstream and downstream rows (X/D) is 4D, and the span distance between two neighboring holes (S/D) is 3D. Three blowing ratios of (BR= 0.5, 1.0, and 1.5) were used in the investigation program.In order to predict the flow behavior numerically for the cases under investigation CFD code is introduced.The numerical investigation shows two large vortices, pair of counter rotating vortex and horseshoe vortices,both vortices have major effects on cooling performance.The experimental results showed that the film cooling effectiveness increases as blowing ratio increases for models (1 and 2), while decreases for model (3), and model (1) provide better performance than the others a thigh blowing ratios.