Axial Flow

This technical brief is focused on the research area of fault detection and diagnosis in a complex thermodynamical system: in this case, an axial flow compressor. Its main contribution is a new approach which combines a physical model and a multilayer perceptron (MLP) model using the best advantages of both types of modeling. Fault detection is carried out by an MLP model whose residuals against the real outputs of the system determine which observations could be considered abnormal. A physical model is used to generate different fault simulations by shifting physical parameters related to faults. After these simulations are performed, the different fault profiles obtained are collected within a fault dictionary. In order to identify and diagnose a fault, the anomalous residuals observed by the MLP model are compared with the fault profiles in the dictionary and a correlation that provides a hypothesis with respect to the causes of the fault is obtained. This methodology has been ap...

The finite element software ABAQUS was used to analyze 22 high strength concrete-filled square high strength tubular short columns with inner I-shaped CFRP, all analysis results based on the finite element analysis data, six characteristic points were defined in the loadlongitudinal strain curve of composite columns. The shared load of core concrete, square steel tube and inner I-shaped CFRP at different height sections of typical specimen corresponding to each characteristic point were analyzed and the cooperative work behavior of inner I-shaped CFRP, square steel tube and core concrete was analyzed. The results show that the existence of the inner I-shaped CFRP can effectively improve the ultimate bearing capacity composite columns, the middle region I-shaped CFRP sharing more longitudinal load than the end region CFRP and the shared load of concrete at the end region section is bigger than that of middle region section, before the CFRP brittle failure. The longitudinal load of square steel tube does not change with the change of the crosssection height.

Static instability of flexible structures forced by a parallel flow, a.k.a. divergence, has been the subject of a relatively small amount of studies, unlike flutter. In order to prepare future studies of the collective behaviour of several slender structures coupled by the fluid in axial flow, the canonical case of a flat flexible plate clamped at both ends is investigated numerically and experimentally. The onset of divergence is determined throughout a series of calculation of the fluid forces generated by a prescribed deformation of the plate. Using the Galerkin method, these fluid forces are expanded in the basis of the natural modes; they exactly balance the mechanical forces when the fluid velocity reaches the instability threshold. The instability velocity can be determined by an eigenvalue calculation involving the fluid force expansion and the modal stiffnesses of the plate. Comparisons are provided with 2D analytical calculations and with an experiment performed with a 0.3...

> 1300 m), 38 mm diameter cylinder towed from a vertical strut at speeds of 7 to 30 kts. The experiments were performed in the high speed tow tank at NSWCCD. 3-D velocity fields were obtained. The cylinder was ballasted to be approximately neutrally buoyant and towed through a stationary laser sheet oriented perpendicular to the tow direction. The objective of the study was to quantify the boundary flow along the cylinder for correlation with simultaneous wall pressure data. Algorithms were developed to track the center of the model through the field of view to provide the spatial relation of the velocity data with the cylinder boundary. This procedure required raw image analysis and isolation of the shadow and solid body regions of the data field. This data is used to collocate subsequent image data for averaging the boundary layer velocity information along the array. Approximately 40 instantaneous vector fields were obtained for each location. Mean and fluctuating streamwise and cross-stream velocities will be presented.

High resolution stereo-PIV measurements were made on a long, small diameter cylinder towed from the control surface of a 1/18^th scale submarine model. The experiments were performed in the tow tank at NSWCCD at 5 kts. 3-D velocity fields over ten body lengths downstream were obtained. The cylinders were approximately neutrally buoyant and towed through a stationary laser sheet oriented

High resolution stereo-PIV measurements were made on a long (> 1300 m), 38 mm diameter cylinder towed from a vertical strut at speeds of 7 to 30 kts. The experiments were performed in the high speed tow tank at NSWCCD. 3-D velocity fields were obtained. The cylinder was ballasted to be approximately neutrally buoyant and towed through a stationary laser

High resolution stereo-PIV measurements were made on a long (> 1300 m), 38 mm diameter cylinder towed from a vertical strut at speeds of 7 to 30 kts. Wall pressure measurements were collected simultaneously at select axial locations. The experiments were performed in the high speed tow tank at NSWCCD. The cylinder was ballasted to be approximately neutrally buoyant and

With the present trend in axial flow compressor design towards low aspect ratio, a greater fraction of the annulus flow is subjected to end-wall effects. Although one might expect the losses at the end-walls to produce increasing temperature and velocity defects in this ...

Theoretical analyses and computer codes have been developed for predicting compressible the three analyses axe demonstrated via applications to unsteady flows through compressor and turbine cascades. The numerical results pertain to unsteady flows excited by prescribed vortical disturbances at inlet, acoustic disturbances at inlet and exit and blade bending and torsional vibrations. Recommendations axe also given for the future research needed for extending and improving the foregoing asymptotic analyses, and to meet the goal of providing an efficient inviscid/viscid interaction capability for subsonic and transonic unsteady cascade flOWS.

Unsteady 3-D RANS simulations have been performed on a highly loaded transonic turbine stage and results are compared to steady calculations as well as to experiment. A low Reynolds number k-epsilon turbulence model is employed to provide closure for the RANS system. A phase-lag boundary condition is used in the tangential direction. This allows the unsteady simulation to be performed by using only one blade from each of the two rows. The objective of this work is to study the effect of unsteadiness on rotor heat transfer and to glean any insight into unsteady flow physics. The role of the stator wake passing on the pressure distribution at the leading edge is also studied. The simulated heat transfer and pressure results agreed favorably with experiment. The time-averaged heat transfer predicted by the unsteady simulation is higher than the heat transfer predicted by the steady simulation everywhere except at the leading edge. The shock structure formed due to stator-rotor interact...

Abstract: Axial flow compressor is one of the most important parts of Gas turbine. In design of Axial flow compressor the work presented comprises of basic flow parameters and dimensions of parts, this makes the further design process quite simple and the results will be helpful to take further changes or improvement at the time of detailed design. The objective of work presented is to design Axial flow compressor by using mean line method for a given mass flow rate and required pressure ratio. The parameters determined also include thermodynamic properties of the working fluid, stage efficiency, number of rotor and stator blades, tip and hub diameters, blade dimensions (chord, length and space) for both rotor and stator, Mach number, flow and blade angles (blade twist). The same parameters are also determined for all five 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...

Experimental investigation of the coherent vortex structure in pipe on the axial fan pressure side, by use of the velocity optical measurement techniques, is reported in this paper. Generated vortex structure, its velocity and turbulent statistical values are revealed and discussed.

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

axial flow compressor is used to get the compressed pressurized air as an input the gas turbine. Generally it is used in the aircraft engine and the industrial application. Compressor is composed with the rotor and stator blades at each stage. Aerodynamic shapes of the blades play important role to improve the efficiency of the compressor.

The design of an axial flow compressor stage has been formulated as a nonlinear mathematical programming problem with the objective of minimizing the aerodynamic losses and the weight of the stage, while maximizing the compressor stall margin. Aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem with a pitchline analysis is presented. The optimization problem is solved by using the penalty function method in which the Davidon-Fletcher-Powell variable metric minimization technique is employed. Designs involving the optimization of efficiency, weight of the stage, and stall margin are presented and the results discussed with particular reference to a multivariable objective function.

This article introduces a unique miniaturization process of a magnetically levitated axial flow blood pump from a functional prototype to a pump suitable for animal trials. Through COMSOL three-dimensional finite element analysis and experimental verification, the hybrid magnetic bearings of the pump have been miniaturized, the axial spacing between magnetic components has been reduced, and excess material in mechanical components of the pump was reduced. Experimental results show that the pump performance was virtually unchanged and the smaller size resulted in the successful acute pump implantation in calves.

Hot gas ingestion into the turbine rim seal cavity is an important concern for engine designers. To prevent ingestion, rim seals use high-pressure purge flow; however, the penalty is that excessive use of the purge flow decreases engine thermal efficiency. In this paper, a one-stage turbine operating at engine-representative conditions was used to study the effect of steady and time-resolved under-platform cavity temperatures and pressures across a range of coolant flowrates in the presence of vane trailing edge (VTE) flow. This study correlates time-resolved pressure with time-resolved temperature to identify primary frequencies driving ingestion. At certain flowrates, the time-resolved pressures are out of phase with the temperatures, indicating ingestion. Measurements from highfrequency response pressure sensors in the rim seal and vane platform were also used to determine rotational speed and quantity of large-scale structures (cells). In a parallel effort, a computational model using Unsteady Reynolds-averaged Navier-Stokes (URANS) was applied to determine swirl ratio in the rim seal cavity and time-resolved rim sealing effectiveness. The experimental results confirm that at low purge flowrates, the VTE flow influences the unsteady flow field by decreasing pressure unsteadiness in the rim seal cavity. Results show an increase in purge flow increases the number of unsteady large-scale structures in the rim seal and decreases their rotational speed. However, VTE flow was shown to not significantly change the cell speed and count in the rim seal. Simulations point to the importance of the large-scale cell structures in influencing rim sealing unsteadiness, which is not captured in current rim sealing predictive models.

This paper deals with both blade passing and low engine order forced response predictions of an LP turbine. The aeroelasticity model uses both viscous and inviscid representations of the unsteady flow. The rotor blade flexibility is included via a linear FE model and the vibration mode shapes are extrapolated onto the dynamic mesh which is moved at each time step according to the structural motion. The predicted forced response vibration amplitudes for a 24 nodal diameter resonance were found to be in good agreement with measured data but one of the main uncertainties was identified as the accurate determination of the inherent mechanical damping. In addition, using a whole-annulus 2-row model, it was shown that non-uniform spacing of the stator blades could give rise to low engine order excitation.

In this paper an attempt has been made to calculate the natural frequencies of aerofoil section blades using the finite element method. The effect of varying the aspect ratio and thickness on the frequencies has also been studied. It is observed that by increasing the value of aspect ratio, the natural frequency in all the modes is increased. It is also concluded that, there is some optimum value of thickness at which the natural frequencies in different modes of vibration are minimum.

The finite element software ABAQUS was used to analyze 22 high strength concrete-filled square high strength tubular short columns with inner I-shaped CFRP, all analysis results based on the finite element analysis data, six characteristic points were defined in the loadlongitudinal strain curve of composite columns. The shared load of core concrete, square steel tube and inner I-shaped CFRP at different height sections of typical specimen corresponding to each characteristic point were analyzed and the cooperative work behavior of inner I-shaped CFRP, square steel tube and core concrete was analyzed. The results show that the existence of the inner I-shaped CFRP can effectively improve the ultimate bearing capacity composite columns, the middle region I-shaped CFRP sharing more longitudinal load than the end region CFRP and the shared load of concrete at the end region section is bigger than that of middle region section, before the CFRP brittle failure. The longitudinal load of square steel tube does not change with the change of the crosssection height.

A liquid-gas-solid system has been studied at higher solids concentration (up to 40% by wt) and gas flow rates (up to 2 vvm) than previously. Two different radial flow impellers (Scaba 6SRGT and a standard Rushton turbine) and a six-bladed mixed flow impeller with pitch angle of 45°, either in its downward (6MFD) or upward pumping (6MFU) mode were used. Power input, mixing time, the speed to achieve complete suspension of the solids (ungassed and gassed) as well as the amount of suspended solids and the height of the liquid-solid interface were measured. In addition, a new technique for measuring the amount of suspended solids in two-phase systems was extended successfully to three phases. When compared to the situation without solids, the mixing time, t m , in the solid-liquid case at the higher solid concentrations was much greater, as previously reported, but for the three-phase case, the increase was relatively small, especially with the Scaba and 6MFU impellers. In general, the power and speed required to suspend the solids increased with increasing solids concentration but once suspended, with the Scaba and the 6MFU impellers, even the highest solids concentration and gas flow rates only required a very small further increase. It has recently been proposed (Pantula and Ahmed, 1997) that by maintaining constant agitator torque on gassing, solids suspension would be sustained. The present work showed this to be broadly valid for the 6SRGT and the 6MFU but not for the Rushton and the 6MFD impellers. Overall, the most stable impeller, requiring the least specific energy dissipation rate for solids suspension and gas dispersion under the most demanding conditions, was the 6MFU.

The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier-Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upperairway disorders.

Within the Collaborative Research Center 1029 new combustion technologies are examined. They might increase the efficiency of modern gas turbines. Especially the Pulsed Detonation Combustion is promissing, though the rising pressure challenges the turbine cooling and hot gas sealing. The current work examines the impact of an unsteady combustion to the turbine sealing cavity, which prevents hot gas ingestion into the inner machine. Sealing flow is ensured by relatively cold secondary air blowing radially through the rotor-stator-wheel space. The interaction between the sealing flow and the main gas flow however causes aerodynamic losses. These losses as well as the secondary compressor air should be kept at a minimum in order to increase the efficiency of the whole engine.

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the "Axial Flow Turbine Research Facility" (AFTRF) of the Pennsylvania State University. The streamwise length of these "partial squealer tips" and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new "channel arrangement" diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of "partial squealer rims" in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers are aerodynamically superior to the pressure side squealers and the channel arrangement. The suction side partial squealers are capable of reducing the stage exit total pressure defect associated with the tip leakage flow to a significant degree.

Preliminary notes The kinetic energy of river currents is weakly researched for the possibility of production of electrical energy. Thus there are very few new suggestions for the exploitation of this energy form. This paper shows a method of exploiting the hydrokinetic energy of river currents created by combining the traditional water wheel and the Darrieus turbine. The water wheel is used due to its historic and traditional meaning and the Darrieus turbine is added due to the increase of the overall power of such a facility. Considering the small dimensions of a micro hydroenergy power plant of this type it is necessary to precisely determine the most favorable locations. For these locations the most important data are the speed and depth of the water flow because the power in using hydrokinetic energy depends upon the third exponent of speed, and depth is important because the Darrieus turbine is immersed in water. Thus, the model of optimizing locations is done based on the data received by measuring the hydrological characteristics of the watercourse using the ADCP (Acoustic Doppler Current Profiler) device.

A numerical and experimental investigation of the Tesla turbine is presented in the paper. The experiment is conducted for various inlet pressure and load. The roughness of the rotor disc is determined as it is a key factor to obtain high turbine efficiency and power. The numerical investigations are performed for the same conditions as in the experiment. The computational results are compared with the analytical model. Comparison of performance characteristics show a relatively good agreement between the experiment and CFD. The analytical model overestimates distributions of pressure and circumferential velocities, although the predicted power is on the similar level as in the experiment and CFD.

A direct-adjoint mean flow global stability investigation of self-excited instabilities in an idealized, two-dimensional compressor blade row at off-design conditions is carried out, with a focus on acoustic feedback mechanisms underlying the observed instabilities. This paper is the first part of this work, where nonlinear flows, impulse responses and the global modes are computed for a single-passage system, with good agreement between the linear and nonlinear structures. Structural sensitivities and feedback loops are identified with the aid of wavemakers and show that dominant structures arise due to feedback mechanisms linking the pressure and suction sides of the aerofoil via acoustic waves emanating from the trailing edge. A separate, second part extends this analysis to multiple-blade passages per period window by exploiting the theory of block-circulant matrices and Bloch-wave theory.

Surrogate modeling is applied to a compressor blade shape optimization to modify its stacking line and thickness to enhance adiabatic efficiency and total pressure ratio. Six design variables are defined by parametric curves and three objectives; efficiency, total pressure and a combined objective of efficiency and total pressure are considered to enhance the performance of compressor blade. Latin hypercube sampling of design of experiments is used to generate 55 designs within design space constituted by the lower and upper limits of variables. Optimum designs are found by formulating a PRESS (predicted error sum of squares) based averaging (PBA) surrogate model with the help of a gradient based optimization algorithm. The optimum designs using the current variables show that, to optimize the performance of turbomachinery blade, the adiabatic efficiency objective is improved substantially while total pressure ratio objective is increased a very small amount. The multi-objective optimization shows that the efficiency can be increased with the less compensation of total pressure reduction or both objectives can be increased simultaneously.

Experimental measurements from a new single stage turbine are presented. The turbine has 26 vanes and 59 rotating blades with a design point stage expansion ratio of 2.5 and vane exit Mach number of 0.96. A variable sealing flow is supplied to the disc cavity upstream of the rotor and then enters the annulus through a simple axial clearance seal situated on the hub between the stator and rotor. Measurements at the annulus hub wall just downstream of the vanes show the degree of circumferential pressure variation. Further pressure measurements in the disc cavity indicate the strength of the swirling flow in the cavity, and show the effects of mainstream gas ingestion at low sealing flows. Ingestion is further quantified through seeding of the sealing air with nitrous oxide or carbon dioxide and measurement of gas concentrations in the cavity. Interpretation of the measurements is aided by steady and unsteady computational fluid dynamics solutions, and comparison with an elementary model of ingestion.

Gas turbine engine performance requires effective and reliable internal cooling over the duty cycle of the engine. Life predictions for rotating components subject to the main gas path temperatures are vital. This demands increased precision in the specification of the internal air system flows which provide turbine stator well cooling and sealing. This in turn requires detailed knowledge of the flow rates through rim seals and interstage labyrinth seals. Knowledge of seal movement and clearances at operating temperatures is of great importance when prescribing these flows. A test facility has been developed at the University of Sussex, incorporating a two stage turbine rated at 400 kW with an individual stage pressure ratio of 1.7:1. The mechanical design of the test facility allows internal cooling geometry to be rapidly reconfigured, while cooling flow rates of between 0.71 C W, ENT and 1.46 C W, ENT , may be set to allow ingress or egress dominated cavity flows. The main annulus and cavity conditions correspond to in cavity rotational Reynolds numbers of 1.71 Â 10 6 < Re u <1.93 Â 10 6. Displacement sensors have been used to establish hot running seal clearances over a range of stator well flow conditions, allowing realistic flow rates to be calculated. Additionally, gas seeding techniques have been developed, where stator well and main annulus flow interactions are evaluated by measuring changes in gas concentration. Experiments have been performed which allow rim seal and re-ingestion flows to be quantified. It will be shown that this work develops the measurement of stator well cooling flows and provides data suitable for the validation of improved thermo-mechanical and CFD codes, beneficial to the engine design process.

Based on the pulp refinery data on October 2020, the total average of lignin content in the digester was about 20.5%. This high amount of lignin during the pulping process was due to the non-uniformity mixing between white liquor and lignin. Therefore, the objective of this research was to simulate delignification process in digester with two inlets white liquor using CFD Ansys 19.2. The various NaOH concentrations (16%-22%) and operating temperatures (151C-160C) were also investigated. The simulation results using CFD Ansys Fluent 19.2 showed the optimum condition of the remaining lignin of 16.7% obtained at NaOH 14 g/l and the temperature of 151C, which was lower than the actual data (20.7%)Data obtained from the simulation results can be used to analyze several aspects such as mass fraction of each compound, temperature distributions, velocity profile, and vector. CFD simulations can be used by researchers as a guide for experiment.

An in dept review of the Development of Operating Model for the Design of Stirrer Arms of Slurries is reported. The works of several authors were reviewed. These works covered research on the importance of slurries, application of different slurries in the area of Agriculture and agricultural farming, construction and allied industries, foods and pharmaceutical industries, chemical and paints industries. Also considered were the research works on the design, fabrication and test investigation of performance of different stirrer arms. From the review, three key outcomes from three set of researchers were identified thus: Researcher team 1:  the TTP propeller was the most efficient in liquid phase mixing; Researcher team 2: the TEET geometry contributed the best quality of the mixing and significantly reduced the cost of the mixing process; Researcher team 3: the two Z blade stirrer arm was considered as the best in terms of mixing effectiveness. These three outcomes appear as standal...

Un-shrouded turbine blades are more common than shrouded ones in gas turbine aero-engines since they reduce the weight and avoid the centrifugal loading caused by the blades’ shrouds. Despite these important advantages, the absence of the shroud leads to leakage flows across the tip gap and exposes the blade tip to high thermal load and thermal damages. In addition, the leakage flows can contribute up to 30% of the aerodynamic loss in a turbine stage. In this study, the effect of in-service burnout is explored using a fundamental flat tip model of a high-pressure gas turbine blade. This investigation is carried out both experimentally in a transonic wind tunnel and computationally using the Reynolds Averaged Navier-stokes approach at high-speed conditions. It is found that exposing the tip to the in-service burnout effect changes the leakage flow behaviour significantly when compared with the tip with sharp edges (i.e. the tip at the start of its operational life). Different flow ac...

Aerodynamic losses due to the formation of a leakage vortex near the tip section of rotor blades form a significant part of viscous losses in axial flow turbines. The leakage flow, mainly induced by the pressure differential between the pressure side and suction side of a rotor tip section, usually rolls into a streamwise vortical structure near the suction side part of the blade tip. The current study uses the concept of a tip platform extension that is a very short “winglet” obtained by slightly extending the tip platform in the tangential direction. The use of a pressure side tip extension can significantly affect the local aerodynamic field by weakening the leakage vortex structure. Phase averaged, time accurate total pressure measurements downstream of a single stage turbine facility are provided from a total pressure probe that has a time response of 150 kHz. Complete total pressure maps in all of the 29 rotor exit planes are measured accurately. Various pressure and suction s...

This paper deals with an experimental investigation of aerodynamic characteristics of full and partial-length squealer rims in a turbine stage. Full and partial-length squealer rims are investigated separately on the pressure side and on the suction side in the “Axial Flow Turbine Research Facility” (AFTRF) of the Pennsylvania State University. The streamwise length of these “partial squealer tips” and their chordwise position are varied to find an optimal aerodynamic tip configuration. The optimal configuration in this cold turbine study is defined as the one that is minimizing the stage exit total pressure defect in the tip vortex dominated zone. A new “channel arrangement” diverting some of the leakage flow into the trailing edge zone is also studied. Current results indicate that the use of “partial squealer rims” in axial flow turbines can positively affect the local aerodynamic field by weakening the tip leakage vortex. Results also show that the suction side partial squealers...

Abstract: A wind tunnel investigation of low speed flow over flapping airfoils and airfoil combinations was performed using flow visualization and laser Doppler velocimetry. Specifically, three cases were studied: A NACA0014 airfoil oscillating in a sinusoidal ...

Preliminary notes The kinetic energy of river currents is weakly researched for the possibility of production of electrical energy. Thus there are very few new suggestions for the exploitation of this energy form. This paper shows a method of exploiting the hydrokinetic energy of river currents created by combining the traditional water wheel and the Darrieus turbine. The water wheel is used due to its historic and traditional meaning and the Darrieus turbine is added due to the increase of the overall power of such a facility. Considering the small dimensions of a micro hydroenergy power plant of this type it is necessary to precisely determine the most favorable locations. For these locations the most important data are the speed and depth of the water flow because the power in using hydrokinetic energy depends upon the third exponent of speed, and depth is important because the Darrieus turbine is immersed in water. Thus, the model of optimizing locations is done based on the dat...

Electrical resistance tomography (ERT) as a non-invasive technique based on conductivity measurement of the continuous phase was employed for the study of phase holdup in a liquid-solid circulating fluidized bed (LSCFB). Local solid holdup was also measured by an optical fibre probe and pressure transducers to compare and verify the results obtained by ERT. Good agreement was observed among the three methods. Tap water was used as the continuous and conductive phase and glass beads (spherical shape) and lava rocks (irregular shape) of two different sizes were used as the solid and non-conductive phase. Radial non-uniformities of solid holdups were observed for all four types of particles under different superficial liquid velocities in different axial locations. The solid holdup was higher in regions close to the wall and low in the central region. Non-uniformity in the phase holdup decreased with increasing liquid velocity. The axial flow profile was found uniform along axial locations of the riser except at the lower location closer to the distributor zone.

It is an established fact that the efficiency of a gas turbine engine has an inverse relationship with the clearance between the rotor blades and the casing (Tip Clearance, or TC). TC is an essential measurement during the testing of development engines. While commercial TC measurement systems are available, their applicability to an engine is dictated by engine size, geometry, physical accessibility, and temperature distribution around the measurement region. This paper describes the development of a TC measurement system, based on the capacitive measurement principle, which was undertaken to satisfy the application requirements of a specific class of gas turbine engines. The requirements included a relatively long and flexible cable to route the electrical signals out of the engine. The TC measurement system was successfully used during engine testing and valuable data were obtained.

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Detailed time resolved Hot Wire Anemometry (HWA) measurement have been made of the over tip leakage (OTL) flow field, from a shrouded HP rotor blade. The objective of this study being to investigate the sensitivity of the flow conditions presented to the IP Nozzle Guide Vane (IPNGV), resulting from changes to the HP blade tip gap clearance and shroud geometry. An extensive experimental data set has been produced in the outer 25% of the annulus height. Post-processing of this data has allowed both the absolute & rotor relative velocity and whirl angle to be calculated, which has been presented in both a graphical and semi-animated form. A detailed analysis of the flow field has been undertaken, which has been compared with the exit flow field predicted by a comprehensive CFD simulation of the HP blade and shroud. Good agreement between the measured and the predicted flow field has been obtained. This has permitted the salient features, which influence the flow conditions presented to...

This paper discusses the numerical computation of unsteady eigenmodes superimposed upon an annular mean flow which is uniform axially and circumferentially, but non-uniform in the radial direction. Both inviscid and viscous flows are considered, and attention is paid to the separation of the eigenmodes into acoustic, entropy and vorticity modes. The numerical computations are validated by comparison to analytic test cases, and results are presented for more realistic engineering applications, showing the utility of the approach for

Small remote communities often lack basic utilities such as electricity supply for lighting, refrigeration, communications etc. It is usually uneconomic to provide mains power, even when high voltage lines pass by a village. Dieselpowered generators require fuel which is expensive and difficult to bring into remote areas. They are noisy and they require maintenance which is neglected in remote area. Neither wind nor sun provide reliable power in humid tropical regions where there is a lot of still, overcast weather, even when wind turbines or solar panels can be located above the trees. Towers attract lightning strikes which can destroy electronic controls, fungus grows on solar panels, and the multiple electrical connections on photovoltaic arrays corrode away in hot, humid climates. Micro-hydro is an attractive option in mountainous areas, and author 1 has built a 30 kw high head and a 3 kw low head plant, using village labor, surplus and discarded materials. Both are operating satisfactorily. However conventional micro-hydro is not possible in flat country where there is little elevation, and work is now in progress (by the team) to evaluate suitable hydrokinetic turbines on rivers in the humid tropics. Numerous companies around the world are now developing hydrokinetic turbines to harvest tidal and river flows, but a major problem with most designs is clogging by floating debris, which could be worst when used in tropical rivers.

The three-dimensional revolving flow of a particle-fluid suspension above a plane surface is considered. The flow represents an extension of the classical Bo¨dewadt flow to a two-fluid problem. The governing equations for the two phases are coupled through an interaction force with the particle relaxation time s as a free parameter. By means of a similarity transformation, the coupled set of non-linear ODEs becomes a two-point boundary value problem. The numerical results show that the radial inward particle velocity increases whereas the circumferential velocity decreases by shortening s, thereby strengthening the spiralling particle motion. These predictions are consistent with the so-called teacup effect, i.e. accumulation of tea leaves at the centre of the cup. On the contrary, the revolving fluid motion is reduced as a result of the particle-fluid interactions.