Search

The photoreceptor outer segment is a highly specialized primary cilium essential for phototransduction and vision. Biallelic pathogenic variants in the cilia-associated geneCEP290cause non-syndromic Leber congenital amaurosis 10 (LCA10) and syndromic diseases, where the retina is also affected. While RNA antisense oligonucleotides and gene editing are potential treatment options for the common deep intronic variant c.2991+1655A>G inCEP290, there is a need for variant-independent approaches that could be applied to a broader spectrum of ciliopathies. Here, we generated several distinct human models ofCEP290-related retinal disease and investigated the effects of the flavonoid eupatilin as a potential treatment. Eupatilin improved cilium formation and length in CEP290 LCA10 patient-derived fibroblasts, in gene-editedCEP290knockout (CEP290 KO) RPE1 cells, and in both CEP290 LCA10 and CEP290 KO iPSCs-derived retinal organoids. Furthermore, eupatilin reduced rhodopsin retention in the outer nuclear layer of CEP290 LCA10 retinal organoids. Eupatilin altered gene transcription in retinal organoids, by modulating the expression of rhodopsin, and by targeting cilia and synaptic plasticity pathways. This work sheds light into the mechanism of action of eupatilin, and supports its potential as a variant-independent approach forCEP290-associated ciliopathies.Abstract Figure

In an attempt to reduce engine frontal area, while maintaining a high single stage pressure ratio, mixed flow compressor stages are frequently used in micro gas turbine (MGT) engines. The expansion of the choke margin of such a mixed flow compressor is presented. The use of a crossover diffuser configuration in a mixed flow compressor stage has displayed superior performance results compared to legacy diffuser configurations, especially when geometric restrictions are enforced. A disadvantage of a crossover diffuser configuration is that it typically displays an inferior operating range compared to legacy diffuser configurations. In an attempt to expand the choke margin of a MGT mixed flow compressor, the use of tandem and splitter vane crossover diffuser configurations was evaluated. It was found that a low solidity first vane row configuration provided a 3% increase in choke margin. A splitter vane crossover diffuser configuration provided a 5.9% increase in choke margin. A tandem vaned diffuser with a reduced first row vane number provided a 7.8% increase in choke margin.

Wind generally reduces the thermal effectiveness of air-cooled condensers (ACCs). Therefore, this study investigates wind screens as a means to improve the performance of a 20-fan induced draft ACC under windy conditions. Two wind-screen configurations are tested: walls extending above the fan platform (termed wind walls) and walls extending below the fan platform (termed wind skirts). The performance of this five-by-four ACC is evaluated using the open-source computational fluid dynamics code, OpenFOAM. The performance is first analyzed under windless operating conditions and then when the ACC is subjected to wind speeds of 3, 6, and 9 m/s directed along the shorter and longer axes of the ACC. Under windless conditions, wind walls increase the ACC’s thermal effectiveness by 1.0%. Wind skirts, however, reduce the effectiveness by 1.8%. Depending on the wind speed and direction, wind walls increase the mean thermal effectiveness of the ACC by 0.3–3.9% under windy conditions. Wind skirts, on the other hand, are only beneficial at higher wind speeds: At 3 m/s, the effectiveness declines by 1.4–2.1%; at 6 m/s, the change in effectiveness ranges from −0.4% to 2.2%; and at 9 m/s, the effectiveness increases by 2.4–3.8%. Wind walls are therefore considered more effective than wind skirts for the tested range of wind speeds.

This study contributes to the ongoing research to develop a turbocharger based dual-shaft Micro Gas Turbine (MGT) for a commercialized solar-hybrid system. The work in this study developed an improved model to predict the performance of the MGT which comprises of two turbochargers, with one turbocharger representing the gas generator turbine and the other, bigger turbocharger used as the power turbine unit. It did so by including the effects of heat transfer through a One-Dimensional Thermal Resistance Network (1-D TRN) to determine diabatic outlet temperatures and by accounting for the supposed incomplete combustion. Overall, the model’s temperature estimations were found to be within a maximum deviation of 5 % of the measured values and, 8 % for pressure. Combustor outlet temperature estimates were substantially improved to within 4 % of the measured value, which is a 15 % improvement on previous work. Despite the increased accuracy, the model was only validated for the smaller gas generator turbine. The larger power turbine was reasoned to have not reached thermal equilibrium as temperature estimates had substantially increased levels of deviation from the measured values. A subsequent energy audit of the facility demonstrated the utility of the 1-D TRN. The results of which were used to determine the scale of the heat transfer. It showed that the power turbine is in fact operating outside of its optimal range which resulted in the heat loss rate of the gas through the turbine being greater than the power it produced. The usefulness of the combustion model is also highlighted as a technique to estimate the combustor outlet temperature with acceptable levels of accuracy and with a rapid turn-around time due to its simplicity. The 1-D TRN was shown to estimate heat flows in the MGT accurately despite employing correlations for the heat transfer coefficients that were not developed for the machines. A combustor designed for solarized operation was benchmarked against a standard unit and the results indicated the significance of reducing parasitic pressure losses as a means to improve MGT performance.

Air-cooled Condensers (ACCs) are often used as main cooling system in modern power generation applications. These systems employ a multitude of large diameter axial flow fans, which draw power and reduce the net power produced by the power station. The improvement of fan operational efficiencies could therefore have a considerable positive influence to reduce these parasitic loads. This study aims to reduce the effect of blade tip vortices in order to improve fan performance. This is achieved through the addition of endplates at the blade tips. Previous work only drew preliminary conclusions, due to constraints in testing at a representative large tip clearance and the necessity to test at reduced speeds to avoid contact between the tip appendages and the fan casing. Through the introduction of a new fan hub design, experimental investigations are repeated on the same ACC scale fan to evaluate the effect of two tip endplate designs on fan performance. Results from testing confirm previous preliminary findings — increased fan static pressure rise and fan static efficiency are found when incorporating blade tip endplates, compared to the unmodified fan.

The prevalence of breast cancer is steadily increasing with metastasis and thromboembolic complications identified as the most common causes of death. The acquisition of an aggressive phenotype by hormone-dependent breast cancers is mediated by Transforming Growth Factor Beta 1 (TGF-β1) expression and is associated with epithelial-mesenchymal transition (EMT) and, potentially, increased propensity for thrombosis. We investigated this phenomenon by assessing the effect of platelet-rich plasma (PRP) and whole blood (WB) on parameters of EMT and hypercoagulation in vitro. MCF-7 breast cancer cells were cultured under standard conditions, followed by co-culture with PRP or WB. Cells were processed for real-time PCR (TGF-β1 and vimentin), electron microscopy or immunocytochemistry (TGF-β1). Micrographs were qualitatively assessed, and real-time PCR data analyzed with PAST Statistical Software. The addition of blood components heightened TGF-β1 immunolocalization and significantly increased corresponding gene expression. Both PRP and WB significantly increased vimentin expression and induced a shape change from a typical epithelial phenotype to a spindle-shape morphology, indicative of EMT. Fibrin fiber, network and plaque formation indicated a hypercoagulatory environment. The results thus show that in preparation for hematogenous metastasis, hormone-dependent breast cancer cells assume an aggressive phenotype associated with EMT, simultaneously increasing the propensity for the formation of thrombo-emboli.

The use of micro gas turbines (MGTs) for once-off and unique applications means that a rapid turnaround design process is required. The development of a MATLAB® application-based program for the initial design and performance analysis of radial and mixed flow compressors is discussed. The program code is based on one dimensional (1D) mean line flow and loss model theory. For verification, 18 test compressors were developed, covering a wide range of design velocities, mass flow rates and meridional exit angles. Predicted performance results were verified using Numeca/FINE™ Turbo software. Initial comparisons between 1D and Computational Fluid Dynamics (CFD) results did not match well. The 1D software over-predicted compressor performance and provided poor choke prediction. Consequently, empirical models to correct these deviations were derived and implemented into the 1D Application code. The updated 1D code provided a mean choke prediction difference of 1.59% compared to an initial 14.98% difference at the design point. Mean total-to-total isentropic efficiency and pressure ratio reduced to differences of 0.74 and 1.24% from values of 11.23 and 9.31% respectively.

This study investigates the potential gains in operating volume flow rate and static efficiency of an induced draught axial flow fan system. These gains are achieved through pressure recovery, i.e. the conversion of dynamic pressure at the fan exit into static pressure. Pressure recovery is achieved using downstream diffusers, stator blade rows, and combinations of these. Three different diffuser lengths are considered. Of the shortest diffusers, a conical diffuser increases the operating volume flow rate by 3.2 % and the fan static efficiency by 9.8 % (absolute). A longer conical diffuser increases it by 3.9 % and 11.9 %, respectively. Of the longest diffusers, an annular diffuser increases the flow rate by 5.5 % and the fan static efficiency by 16.8 %.

This study numerically investigated the performance of a 64-fan induced draft Air-Cooled Condenser (ACC) subjected to crosswind conditions. An Actuator Disk Model (ADM) was used to model the axial flow fans and a combination of the Darcy-Forchheimer porosity model and the Effectiveness Number of Transfer Units (ε-NTU) heat transfer model were used to model the heat exchangers. Crosswind conditions were applied to the ACC model in multiple directions and multiple reference velocities, with the results compared to a reference case where no wind was present. The induced draft ACC attained a mean fan volumetric effectiveness of 1.065, a mean heat transfer effectiveness of 1.039 and a mean heat-to-power ratio of 120.6 when no crosswinds were present. At relatively high crosswind velocities of 9 m/s the mean volumetric effectiveness decreased by 10.1% from wind coming from the primary direction, and by 10.3% from wind coming from the secondary direction. Similarly, the mean heat transfer effectiveness decreased by 21.7% under primary cross-winds, and by 31.3% under secondary crosswinds. Finally, the heat-to-power ratio of the ACC decreased to 92.5 under primary crosswinds, and by 77.6 under secondary crosswinds.

The MinWaterCSP project was defined with the aim of reducing the cooling system water consumption and auxiliary power consumption of concentrating solar power (CSP) plants. A full-scale, 24 ft (7.315 m) diameter model of the M-fan was subsequently installed in the Min WaterCSP cooling system test facility, located at Stellenbosch University. The test facility was equipped with an in-line torque arm and speed transducer to measure the power transferred to the fan rotor, as well as a set of rotating vane anemometers upstream of the fan rotor to measure the air volume flow rate passing through the fan. The measured results were compared to those obtained on the 1.542 m diameter ISO 5801 test facility using the fan scaling laws. The comparison showed that the fan power values correlated within +/− 7% to those of the small-scale fan, but at a 1° higher blade setting angle for the full-scale fan. To correlate the expected fan static pressure rise, a CFD analysis of the 24 ft (7.315 m) diameter fan installation was performed. The predicted fan static pressure rise values from the CFD analysis were compared to those measured on the 1.542 m ISO test facility, for the same fan. The simulation made use of an actuator disc model to represent the effect of the fan. The results showed that the predicted results for fan static pressure rise of the installed 24 ft (7.315 m) diameter fan correlated closely (smaller than 1% difference) to those of the 1.542 m diameter fan at its design flowrate but, once again, at approximately 1° higher blade setting angle.

This paper presents the numerical optimization of a tip appendage design for the passive control of tip leakage vortices in subsonic axial flow cooling fans. The studied class of fan was designed in the conventional manner without the consideration of tip clearance effects. As such, the objective of this investigation is the improvement of the aerodynamic performance characteristics of the datum fan through consideration of the blade tip geometry. Based on previous studies involving fan performance enhancement using various tip end-plate configurations, the most promising end-plate geometry which is found to best improve the fan’s performance characteristics is selected for further development through optimization. Before the optimization process can begin, initialization of the chosen end-plate’s design space using the Design of Experiments (DoE) technique is performed. Formulation of the response surface is based on a multi-objective multi-point objective function which considers the fan’s various performance metrics. Considering the optimization process, the Design and Analysis of Computer aided Experiments (DACE) method is used in the development of the Kriging based surrogate model’s (SM) database. The resulting database is coupled with an Efficient Global Optimization (EGO) algorithm which completes the workflow of the optimization routine. The Pareto-front of non-dominated solutions is used to guide the optimal design selection, on which the experimental evaluations are based. The experimental results of the optimized design indicate improved fan performance characteristics at greater than peak efficiency flow rates. This design is found to increase the datum fan’s design point performance characteristics by a value of 32.90 percent in total-to-static pressure rise and a 7.66 percentage point increase in total-to-static efficiency at the fan’s design speed of 722 rpm.

This study illustrates that downstream diffusers can significantly aid the performance of an induced draught axial flow fan. Two conical diffusers of length 0.2 and 0.4 times the fan diameter and an annular diffuser with a length equal to the fan diameter are tested. At the design flow rate of the fan, the short conical diffuser increases the available static pressure by 17.6 % and the static efficiency by 8.9 %. The medium-length conical diffuser increases it by 21.9 % and 11.7 %, respectively. The long annular diffuser produces a 28.2 % pressure increase and a 14.2 % efficiency increase. The paper also compares the obtained pressure recovery coefficients of the different discharge diffusers using two-dimensional axisymmetric and three-dimensional computations. It shows that the pressure at the outlet of the fan cannot be assumed to be equal to atmospheric pressure, as is prescribed by the fan testing standards. A new method of measuring pressure recovery from two-dimensional computations is proposed. Additional keywords: Pressure recovery, axial flow fan, diffuser.

Axial flow fans used in air-cooled condensers are typically analysed with smooth rounded hubs as they offer superior performance when compared to other hub configurations. However, such a hub configuration is impractical and may increase the manufacturing and installation costs of air-cooled condensers. As such, it is desirable to use a simpler, yet effective, hub configuration in order to reduce the installation cost. This paper assesses the impact that a simpler hub configuration may have on the performance of an axial flow fan. This is done through a comparison of three hub configurations: a cylindrical hub with a flat nose, a cylindrical hub with a hemispherical nose, and a disk hub, installed on the B2a-fan. Computational fluid dynamics modelling, utilising OpenFOAM, is used to simulate each hub configuration. It is found that the impact on performance due to hub configuration is dependent on the volumetric flow rate through the fan. A thin disk hub exhibits superior performance at low flow rates, resulting in a 8.4% improvement in total-to-static pressure rise and a 5.7% point improvement in total-to-static efficiency. As volumetric flow rate increases, the effectiveness of the disk hub configuration reduces while the hemispherical and flat nosed cylindrical hub configurations result in similar performance metrics at the design point flow rate. At above design point flow rate, the flat nosed cylindrical hub configuration shows an improvement in performance over the hemispherical nose cylindrical hub configuration, with a 9.5% increase in total-to-static pressure rise and a 5.1% point improvement in total-to-static efficiency.

Fan performance characteristic tests of axial flow fans provide information on the global flow field, based on stable inlet flow field distribution. More information is often required on the local flow distribution existing in the vicinity of the fan blades under installed conditions. A 1.542 m diameter scale model of an axial flow fan, termed the M-Fan is tested in an ISO 5801, type A, test facility. The M-fan was specifically designed for low-pressure, high flow rate application in air-cooled or hybrid condensers. The scaled version of the M-fan was designed to have a fan static pressure rise of 116.7 Pa at a flow rate of 14.2 m3/s. Two specially constructed M-Fan blades are manufactured to conduct blade surface pressure measurements on the blades. The fan blades are equipped with 2 mm diameter tubes that run down the length of the fan blades in order to convey the measured pressure. Piezo-resistive pressure transducers, located on the hub of the fan, measure the static pressure distribution on the blades and the data is transferred to a stationary computer using a wireless telemetry setup. The blade pressure measurement setup is re-commissioned from a previous research project and its performance is qualified by testing and comparing to experimental results obtained on the B2a-fan. Excellent correlation to previous results is obtained. The experimental M-fan results are compared against results from a periodic numerical CFD model of a fan blade modelled in an ISO 5801, Type A test facility configuration. The experimental tests and numerical model correlate well with each other. The experimental blade surface pressure measurements have a minimum Pearson correlation to the numerically determined values of 0.932 (maximum 0.971).

This study investigates the potential gain in operating volume flow rate and static efficiency for an induced draught fan arrangement by reducing the outlet kinetic energy loss. The reduction is achieved through pressure recovery, which is the conversion of dynamic pressure into static pressure. Downstream diffusers, stator blade rows, or a combination of these can recover pressure. Six different discharge configurations are tested for a fan. An annular diffuser with equiangular walls at an angle of 22° from the axial direction and a length equal to the fan diameter recovers the most pressure over a range of volume flow rates. The diffuser causes the operating volume flow rate and static efficiency to increase by 6.3 % (relative) and 20 % (absolute), respectively, compared to the initial design point of the particular fan.

An investigation is performed to determine the dynamic flow phenomena that dampen a fan blade’s oscillation amplitude using numerical fluid structure interaction (FSI) simulations. Both a mesh-based and meshless numerical model are used to perform the FSI simulation and are compared according to their accuracy, robustness and computational cost. The meshless FSI simulation is performed by coupling the Finite Pointset Method (FPM) with a simplified 1D beam model. Experimental results from a separate investigation are used to validate the two numerical models. This paper shows that both numerical models are suitable for modelling the aerodynamic damping of an axial fan used in an air cooled condenser fan unit. The observed flow effects include the formation and shedding of leading edge vortices, downwash, tip vortices and the added mass effect. Leading edge vortices are a major damping contributor and are found to mainly depend on the blade’s effective angle of attack. The mesh-based and meshless FSI simulations are able to predict the experimentally determined tip displacement within an accuracy of 13% for 5 out of 6 simulations.

Airfoil self-noise at high Reynolds numbers is caused by turbulent boundary layers. In modelling such a case with Large Eddy Simulation (LES) or Direct Numerical Simulation (DNS), the acoustic source and thus surface pressure fluctuations are incoherent along the modelled spanwise length, assuming the simulated span is wide enough to capture turbulent flow structures. In literature, the spanwise coherence of surface pressure is normally inspected at 0.95% of the chord. A sound pressure level (SPL) correction for an increase in spanwise length can be applied, for example, for comparison of the modelled SPL spectra with experimental measurements. For a larger spanwise surface pressure coherence length, the SPL correction increases. In contrast, airfoils at low Reynolds numbers emit self-noise with a tonal signature. An acoustic feedback mechanism propagates instabilities upstream and is responsible for the tonal amplification. Consequently, the source of noise is not highly localized and may not be fully incoherent at all frequencies. Therefore, the chordwise position at which the surface pressure coherence length is to be calculated for a SPL correction for spanwise length, is not straightforward. In this paper, the sources of tonal acoustic noise and the effect of the position of spanwise coherence length calculation for SPL correction is investigated. A NACA 0012 airfoil is modelled using LES, at a chord-based Reynolds number of Rec = 1.1×105 and an angle of attack of α = 3°. The far field acoustic pressure is calculated with the Ffowcs-Williams Hawkings acoustic analogy Formulation 1C. The airfoil source regions are separated by their boundary layer flow characteristics and their relative contributions to the far field SPL are analysed to find a chordwise point on the airfoil surface which has a spanwise coherence length that is representative of the nature of the far field acoustic radiation. The spanwise coherence length at this position can be used to calculate the SPL correction for an increase in spanwise length. Two chordwise points are identified for which the resulting corrected SPL spectra agree well overall with experimental data.

The design and validation of a Compact Crossover Diffuser (CCD) to replace the size-limited radial diffuser and axial de-swirl cascade of an existing Micro Gas Turbine (MGT) is discussed. A CCD strives to combine the performance of a channel diffuser with the operating range and efficiency of a vaneless diffuser. The development of a one-dimensional Mean-Line Code (MLC) is presented, which aids the designer in preliminary design and performance evaluation of the CCD. Design graphs indicating the performance effects of changing the primary design variables are developed and shown. The MLC is numerically validated using Computational Fluid Dynamics (CFD). Good agreement is seen between the MLC and CFD results, predicting the design point PRss(2-4) to within 1.4 %. A CFD optimized CCD was manufactured and tested. Agreement between the CFD and experimental results for PRts(0-4) is within 7.58 % at 106 kRPM. A numerically predicted increase in PRts(0-4) from 3.31, to 3.53, to 3.83 is seen for the vaneless-, MLC optimized-, and CFD optimized-design respectively. An experimental increase of 82.3 % in engine thrust and 80.0 % in total-to-static pressure recovery across the compressor stage was measured when retrofitting the BMT120KS with a new impeller and CCD.

A vibration excitation system has been developed to excite the rotor blades of an axial compressor, in the specified nodal diameter mode and at the specified frequency, by injecting additional compressed air into the compressor flow path. The system was fitted to the Rofanco compressor test bench at the University of Stellenbosch in South Africa. A two-way staggered fluid–structure interaction (FSI) model was constructed that was capable of simulating the vibrations of the rotor blades excited by the vibration excitation system. The results of the FSI simulations were verified using available experimental data. It was concluded that the FSI model is able to recreate the vibrations of the rotor blades with sufficient accuracy. The results of the FSI simulations also indicated that the vibration excitation system should be capable of exciting the blades in the selected mode shape and at the selected frequency, provided the excitation frequency is close to the natural frequency of the first bending mode of each rotor blade.

The design of gas turbine combustors is an iterative process which is often limited by the available modelling tools. While high degrees of modelling accuracy have been achieved using high fidelity tools, these are computationally expensive and not appropriate for design space exploration. By contrast, reduced order models carry low computational expense, but cannot fully reconstruct the combustion problem which spans multiple branches of physics and is characterised by 3D phenomena. As a result, empirical correlations are often relied upon, but these limit the designer to a narrow range of validity, preventing the exploration of novel design solutions. To facilitate the design of new low emissions combustors, for which empirical models are not valid, a multi-fidelity design process has been followed. In this process, physics-based low order models are built; calibrated by high fidelity simulations and then used in multi-objective optimisation studies. This provides detailed insight early in the design process, leading to more fruitful optimisation studies and a shorter design cycle. This approach has been successfully demonstrated on other turbomachinary sub-systems, but has not yet been applied to combustors using publicly available methods. In the current work, the multi-fidelity design process is demonstrated on the design and analysis of an impingement/effusion cooling layout for a lean direct injection combustor liner. A novel mutli-fidelity methodology was followed which used only publicly available methods. By following this approach, an indication of liner wall temperature distributions could be obtained very early in the design process, prior to any prototyping or testing. As such, applying a mutli-fidelity design approach to gas turbine combustors was shown to be both feasible and beneficial. The results from the high fidelity simulations were compared to those of the low order model, revealing a number of discrepancies due to physics not captured - most notably a strong interaction between the swirling flow and liner wall. These detailed interactions resulted in failure of the initial cooling layout, leading to the liner exceeding its limit temperature by 10%. Inclusion of models to predict these phenomena have been recommended to improve the low order code fidelity. In doing so, the multi-fidelity modelling loop will be closed, yielding a more capable design code to be used for executing design space exploration.

This study reports on a modeling strategy for large Air-Cooled Condensers (ACCs). A large 64-fan ACC was modeled under various crosswind conditions that investigated the ACC’s specific axial flow fan configuration. The ACC model was developed in two parts, an axial flow fan model and a heat exchanger model. The axial flow fans were modeled using an Actuator Disk Model (ADM). The heat exchangers’ pressure drop was modeled using the Darcy-Forchheimer porosity model, and the Effectiveness Number of Transfer Units (ε-NTU) method was used to determine the air heat transfer rate. The ACC was configured using two different axial flow fans, identified in this study as the L-fan and the N-fan. Comparatively the L-fan has a steeper fan static pressure characteristic curve than that of the N-fan, at the cost of a greater shaft power consumption. Under normal operating conditions the average heat-to-power ratios were calculated at 89.91 W/W for the L-fan and 102.48 W/W for the N-fan. Under crosswind conditions of 9 m/s the heat-to-power ratios of the leading edge fan-units decreased by 80.6% and 87.0% for the L-fan and N-fan respectively. However, at the fan-units immediately downstream of the leading edge the heat-to-power ratios only decreased by 34.1% for the L-fan and 64.2% for the N-fan.

The cooling effectiveness of air-cooled steam condenser units is impacted by the performance of the large diameter axial flow cooling fans, which ultimately affects the overall efficiency of the power plant. Because of the large diameters of these fans, performance tests are carried out at test facilities with smaller, standardized diameters and measuring equipment. The performance of the large scale fans can be predicted based on the small scale test results using the similarity laws and scale-up formulae. This article details the results of small scale experimental tests and numerical simulations that were performed on a pair of 1.25 m diameter axial flow fans. Full scale, 10.360 m, diameter simulations of the same axial flow fans were subsequently performed and compared with the experimental results that were scaled up using the fan scaling laws.

Modelling air-cooled condensers (ACCs) incorporating hundreds of fans, necessitates the use of simplified fan models when performing a computational fluid dynamics (CFD) analysis of the condenser. The perimeter fans in these ACCs are subjected to distorted inlet flow conditions. This paper compares the accuracy of three different simplified fan models and proposes an improved model, based on numerical and experimental results from representative fan configurations. Three different fan configurations are tested as perimeter fans in a three-fan test facility, and their results compared to CFD results. The experimental evaluation by particle image velocimetry (PIV) reveals the shape of the velocity profiles immediately upstream of the perimeter fan. The accuracy of the CFD-predicted flow field directly upstream of the perimeter fan varies according to the model used to represent the fan as well as the configuration of the specific perimeter fan. The paper indicates a discrepancy of as much as 30% between experimental and simulated volumetric effectiveness values for a specific simulation model and fan configuration. The standard and extended actuator disc fan models perform better than the pressure jump model in predicting the volumetric effectiveness of the perimeter fans, and the extended actuator disc model performs best at predicting fan inlet velocity profiles.

The performance of large mechanical draft air-cooled heat exchangers is directly related to fan performance which is influenced by atmospheric wind conditions, as well as the plant layout. It is often necessary to numerically model the entire system, including fans, under a variety of operating conditions. Full three-dimensional, numerical models of axial flow fans are computationally expensive to solve. Simplified models that accurately predict fan performance at a lesser expense are therefore required. One such simplified model is the actuator disk model (ADM). This model approximates the fan as a disk where the forces generated by the blades are calculated and translated into momentum sources. This model has been proven to give good results near and above the design flow rate of a fan, but not at low flow rates. In order to address this problem two modifications were proposed, namely the extended actuator disk model (EADM) and the reverse engineered empirical actuator disk model (REEADM). The three models are presented and evaluated in this paper using ANSYS FLUENT. The models are simulated at different flow rates representing an axial flow fan test facility. The resulting performance results and velocity fields are compared to each other and to previously simulated three dimensional numerical results, indicating the accuracy of each method. The results show that the REEADM gives the best correlation with experimental performance results at design conditions (ϕ = 0.168) while the EADM gives the best correlation at low flow rates. A comparison of the velocity profiles shows that none of the three models predict the radial velocity distribution at low flow rates correctly, however the correlation improves at flow rates above ϕ = 0.105. In general the upstream velocity profiles, where reversed flow occurs through the fan, are poorly predicted at low flow rates. At the flow rates above ϕ = 0.137 the correlation between the velocity profiles for the simplified modes and the three dimensional results is good.

In this paper the procedure and results of the aeromechanical optimization of a mixed-flow compressor impeller to be used in a 600 N micro gas turbine (MGT) are presented. Today’s unmanned aerial vehicles (UAVs) demand high thrust-to-weight ratios and low engine frontal area. This may be achieved using mixed-flow compressors. The initial impeller design was obtained using a 1-D turbomachinery layout tool. A multi-point optimization of the impeller aerodynamic performance was completed, followed by a mechanical optimization to reduce mechanical stresses in the impeller. A coupled aero-mechanical optimization was concluded with the purpose of increasing the choke limit and reducing stresses while conserving aero-performance. Subsequently, a modal analysis of the rotor was conducted to determine its vibrational characteristics. The optimization process was set up and controlled in an integrated environment that includes a 3-D Navier-Stokes flow solver and a 3-D finite element (FE) structural solver. The optimization process is based on the use of a database, an artificial neural network (ANN), a user-defined objective function and a genetic algorithm (GA). The overall optimization process achieved an increase in pressure ratio (total-to-total) of 30.6% compared to the initial design while the efficiency (isentropic total-to-total) was increased by 5% at design conditions. A decrease in the surge margin was experienced, but the final surge margin was still acceptable (12%). The choke limit was increased meaningfully. This was achieved while also decreasing the peak von Mises stress from far above the material yield strength to 30% below the yield limit.

Purpose To investigate the radiographic length and width of the new thumb metacarpal in relation to the middle finger proximal phalanx; to assess the incidence of premature physeal closure of the new metacarpal; and to consider whether there is a relationship between growth characteristics and the presence of union or nonunion of the new trapezium to the retained index finger metacarpal base. Methods Forty pollicizations were assessed with preoperative or immediate postoperative radiographs and follow-up radiographs to establish the growth characteristics of the new thumb metacarpal. Functional outcomes comprising grip strength, pinch strength, and range of motion were correlated with radiological findings of presence or absence of open physes and presence or absence of union of the new trapezium to the metacarpal base. Results The new thumb metacarpal physis was open in 28 pollicizations and closed in 12. In the latter group, all physes of the hand had closed indicating skeletal maturity. The length and width indices of the new thumb metacarpal in relation to the middle finger proximal phalanx were equivalent to or greater than the perioperative growth indices. There was a reduced postoperative length ratio in those patients with nonunion of the new trapezium to the base of the metacarpal. There was no change in strength and range of motion parameters with growth other than that related to normal improvement with age. Conclusions We are unable to demonstrate premature physeal closure following routine pollicization. The growth of the metacarpal continues in a normal manner to skeletal maturity. A failure of union of the new trapezium to the metacarpal base may compromise growth. Type of study/level of evidence Therapeutic IV.

Actuator-disk models (ADMs) use blade element theory to numerically simulate the flow field induced by axial fans. These models give a fair approximation at near design flow rates, but are of poor accuracy at low flow rates. Therefore, the lift/drag (LD) characteristics of two-dimensional (2D) sections along the span of an air-cooled heat exchanger (ACHE) axial fan are numerically investigated, with the future prospect of improving ADMs at these flow conditions. It is found that the blade sectional LD characteristics are similar in shape, but offset from the 2D LD characteristics of the reference airfoil (NASA LS 413 profile) at small angles of attack (αatt5deg always remain lower compared to the maximum lift coefficient of the reference airfoil. Conversely, the blade sectional drag coefficients are always higher compared to that of the reference airfoil for αatt>5deg.

Large-scale cooling system fans often operate under distorted inlet air flow conditions due to the presence of other fans and the prevalent wind conditions. Strain gauge measurements have been used to determine the blade loading as a result of the unsteady aerodynamic forces. However, these measurements are of the blade’s response to the aerodynamic forces and include the deformation as a result of the first natural frequency being excited. When considering the dominant first natural frequency and bending mode of the fan blade, one can approximate the fan blade as a cantilever beam that acts as a single degree-of-freedom system. The response of a single degree-of-freedom system can be calculated analytically for any excitation if the system’s properties are known. The current investigation focuses on using these equations to create an algorithm that can be applied to the measured response of a fan blade to then extract the aerodynamic forces exciting it. This is performed by using a simple non-linear, least-squares optimization algorithm to fit a complex Fourier series to the response and using the coefficients of each harmonic term to determine the Fourier series representing the excitation function. The algorithm was first tested by applying it to the response of a finite element cantilever beam representing a simplified model of the fan blade. Good results were obtained for a variety of excitation forces and as such the algorithm was then applied to the measured response of a full-scale fan blade. The full-scale blade was excited with a shaker where the forcing function could be accurately controlled. Once validated, the algorithm was applied to a set of strain gauge measurements that were recorded at a full-scale fan while in operation. The reconstructed aerodynamic loading showed increased forces when the blade passed beneath the fan bridge as well as when it approached the windward side of the casing.Copyright © 2015 by ASME

Numerical modeling of the flow field in the vicinity of large axial flow fans finds application in various engineering investigations, whether for fan design purposes, fan induced flow fields or fan system modeling. These three-dimensional fan models generally require verification with experimental results to establish validity. For this purpose a comparison is generally made between the numerically and experimentally obtained fan performance characteristics (fan static pressure and static efficiency curves) to verify the model. Although this method provides a means to validate the numerical model on a global flow level, some uncertainty on the accuracy of this validated model on a local flow level (flow structures close to the fan blade) might still exist. In the present study an experimental technique is presented to measure blade surface static pressures that can be used to validate numerical fan models on a local flow level. These measurements are obtained for a specific fan by means of piezo-resistive pressure transducers mounted in a capsule on the fan axis and connected to pressure taps in specially manufactured fan blades. The transducers are also coupled to a telemetry system that samples the measured pressures and enables wireless communication between the fan and a laptop/PC. Blade surface pressure measurements are obtained for a series of volumetric flow rates through the fan and compared to the numerical data simulated using a RANS approach. A good comparison between the experimental and numerical blade surface static pressure data exists, with the largest discrepancies occurring near the hub as well as the leading and trailing edges of the blade. The reason for this discrepancy could be attributed, amongst others, to low y+ values (y+ < 30) on the blade surface in these regions, leading to errors in the calculation of the wall condition by the wall function. The experimental technique therefore provides CFD engineers with an additional tool for numerical fan model validation on a local flow level.Copyright © 2015 by ASME

The use of air-cooled steam condensers (ACSCs) is preferred in the chemical and power industry due to their ability to adhere to stringent environmental and water use regulations. ACSC performance is, however, highly dependent on the prevailing wind conditions. Research has shown that the presence of wind reduces the performance of ACSCs. It has been found that cross-winds (wind perpendicular to the longest side of the ACSC) cause distorted inlet flow conditions, particularly at the upstream peripheral fans near the symmetry plane of the ACSC. These fans are subjected to what is referred to as “two-dimensional” wind conditions, which are characterized by flow separation on the upstream edge of the fan inlets. Experimental investigations into inlet flow distortion have simulated these conditions by varying the fan platform height. Low platform heights resulted in higher levels of inlet flow distortion, as also found to exist with high cross-wind velocities. The similarity between platform height and cross-wind velocity is investigated in this study by conducting experimental and numerical investigations into the effect of distorted inlet flow conditions on the performance of various fan configurations (representative of configurations used in the South-African power industry). A correlation between system volumetric effectiveness, platform height, and cross-wind velocity is derived which provides a means to compare platform height and cross-wind velocity effects.

Purpose To investigate the presence or absence of union of the new trapezium to the retained metacarpal base after pollicization and to relate this to stability of the new trapezium and the new carpometacarpal joint. Methods Thirty-six patients (46 pollicizations) were assessed at clinical review. Mean time from surgery to review was 96 months (range, 9–260 mo). Clinical assessment measured range of motion (ROM) at the carpometacarpal joint, stability of the carpometacarpal joint, and extrinsic and intrinsic strength of both hands. Radiological review evaluated 3 parameters: bony union between the new trapezium and retained metacarpal base, stability of the new trapezium in relationship to the metacarpal base, and carpometacarpal joint stability. Results There was radiographic nonunion between the new trapezium and the retained metacarpal base in 8 (1 treated) of 46 pollicizations. Relative risk of instability of the new trapezium was 39 times more likely if nonunion was present. Nine pollicizations were unstable at the carpometacarpal joint, 8 in those with union and 1 with nonunion. Relative risk of instability was 1.4 times more likely for those with union. For patients with nonunion, ROM and grip strength variables were reduced but only grip strength reached statistical significance. In patients with carpometacarpal joint instability, ROM and grip strength variables were reduced but none of the variables reached statistical significance. Conclusions This study suggests that when the surgeon is attempting to obtain union of the new trapezium to the retained metacarpal base, failure to do so results in a poorer thumb with a significantly increased risk of trapezial instability and decreased grip strength. There is a mildly increased risk of carpometacarpal joint instability with union, but significantly poorer function as a consequence of this has not been demonstrated. Type of study/level of evidence Therapeutic IV.

Fans operating at the edges of large-scale air-cooled steam condensers often do so under distorted inlet air flow conditions. These conditions create variations in the aerodynamic loads exerted on a fan blade during rotation which causes it to vibrate. In order to isolate the sources of the unsteady aerodynamic loads as well as their effects on blade vibration, a potential flow fluid dynamics code was written to determine the aerodynamic loads exerted on a fan blade as a function of its rotation. The lift and drag forces were exported to a finite element code approximating the fan blade as a cantilever beam. With these two sets of code the response of the blade when subjected to varying aerodynamic loads could be determined. Furthermore, the effect of changing certain parameters such as blade stiffness or damping can be investigated. It was found that the blade’s response closely resembles that which was measured at the full-scale facility and that slight changes to the blade’s stiffness can potentially reduce the vibrational amplitude but may also lead to resonance.

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-e turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.Copyright © 2014 by ASME

A phase-controllable air injection exciter system was developed to enable measurement of the forced response properties of a transonic axial compressor blisk. The project was performed as part of the FP7 European framework programme project FUTURE. The eventual aim of this project is to improve existing turbomachinery blade flutter prediction methods. The development and manufacturing of the exciter system was performed by the Council for Scientific and Industrial Research (CSIR) in Pretoria, South Africa. The exciter system consists of 15 air injectors, each with its own servo motor and controller. The injectors consist of a small rotating disc with a specific number of holes equispaced around the periphery, rotating within a pressurised volume. When the holes are rotated, using a servo motor, past an exit tube an air pulse is generated that is injected upstream of the compressor. The controllers enable adjustment of the relative phase angle between the exciters and in this way a pattern that resembles different nodal diameters can be excited on the rotor blisk. Once the construction of the system was completed, it was transferred to Stellenbosch University, South Africa for sub-scale testing on a low speed compressor. The purpose of the sub-scale tests was to commission and verify the operation of the exciter system. The tests started with simple in-phase tests and then worked towards more complex test parameters that included frequency sweeps through the natural frequency of the compressor blades. The tests showed that it is possible to generate a blade response of different nodal diameters using the exciters. The blade response was also found to vary depending on the number of rotor holes, air supply pressure and sweep rate used for the exciters. Following completion of the sub-scale tests, the completed system was transferred to the transonic compressor test facility of the Technical University Darmstädt (TUD) where both free flutter and forced response experiments were performed on a purpose-designed blisk in the transonic compressor test rig. The experimental campaign was successfully completed with the forced response experiments showing that the air injection system could be used to measure the response characteristics of the blisk.

Mutations in the AIPL1 (aryl hydrocarbon receptor interacting protein-like 1) cause the blinding disease Leber's congenital amaurosis. AIPL1 is a homologue of the AIP. AIP functions as part of a chaperone heterocomplex to facilitate signalling by the AhR and plays an important role in regulating the nuclear translocation of the receptor. We review the evidence for the role of AIP in protein translocation and compare the potential functions of AIPL1 in the translocation of its interacting partner the NEDD8 ultimate buster protein 1.

The heat-shock protein 70 chaperone machine is functionally connected to the ubiquitin–proteasome system by the co-chaperone CHIP. In this article, we discuss evidence that the neuronal DnaJ proteins HSJ1a and HSJ1b may represent a further link between the cellular protein folding and degradation machineries. We have demonstrated that HSJ1 proteins contain putative ubiquitin interaction motifs and can modulate the cellular processing of rhodopsin, a protein that is targeted for degradation by the proteasome when it is misfolded.

The heat transfer characteristics of industrial air-cooled heat exchangers (ACHEs) are dependent on the ability of the fan system to deliver sufficient cooling air. However, under normal operating conditions, variable flow direction and strength often subject peripheral fans to distorted inlet conditions with an attendant reduction in overall volumetric flow rate and cooling capacity. In this paper, a design methodology for single-rotor axial flow fans, appropriate for use in large industrial ACHE’s is presented. The primary motivation for this work was to address the issues of robust off-design performance, in particular, distorted inlet flow tolerance. Using this methodology, two 8-bladed prototype fans (B1 and B2) were designed, built and tested in accordance with BS 848 (Type A) standards. The two B-fans have a hub-tip ratio of xh = 0.4 and employ the Clark Y and NASA LS airfoil profiles respectively. Measured performance characteristics were compared to commercial fan designs (V-, DL- and L-fan) used in existing ACHEs. Results indicate that the B-fans have a higher design point operating efficiency. The B-fans also show a steeper fan static pressure rise characteristic compared to the commercial fans, except for the DL-fan, implying a greater tolerance to pressure fluctuations caused by distorted inflows.Copyright © 2012 by ASME

The compressor section of a diesel locomotive turbocharger was re-designed to increase its maximum total-to-total pressure ratio and efficiency. Tests conducted on the prototype compressor showed possible rotating stall in the diffuser section before the designed higher pressure ratio could be achieved. It was decided to simulate the prototype compressor’s operation by using one-dimensional theory [1], followed by a three-dimensional CFD analysis of the compressor. This publication focuses on implementation of the impeller, vaneless annular passage and vaned diffuser one-dimensional theories. A verification process was followed to show the accuracy of the one- and three-dimensional modelling methods using two well-known centrifugal compressor test cases found in the literature [2–5]. Comparing the test case modelling results to available experimental results indicated sufficient accuracy to investigate the prototype compressor’s impeller and diffuser. Conclusions drawn on the prototype compressor’s performance using the one- and three-dimensional modelling methods led to a recommendation to redesign the impeller and diffuser of the prototype compressor.Copyright © 2012 by ASME

This article describes the development and validation of the McMaster Clinical Rating Scale (MCRS). The MCRS is a 7-item scale designed to be completed by a trained rater after completion of an in-depth interview of the family. We present data from four new studies and review previously published articles concerning the reliability, validity, and clinical utility of the MCRS. Adequate interrater reliability and rater stability were obtained. The MCRS was found to correlate significantly with the self-report Family Assessment Device and to discriminate between families in different phases of a depressive disorder.

The large number of axial flow fans used in modern dry-cooled power plant air-cooled steam condensers necessitates the use of simplified numerical models when simulating the perfromance of such a condenser. Three simplified fan models are presented and implemented using computational fluid dynamics (CFD). These are referred to as the pressure jump, actuator disc and extended actuator disc models. The paper compares the CFD results obtained using these three models to experimental results obtained on a multiple axial flow fan test facility. The test facility was configured in such a way that it could accommodate different fan platform heights to vary the level of inlet flow distortion for the facility. The simulations show that the general flow field adjacent to the facility is independent of the simplified fan model that is used in the CFD analysis. However, the predicted flow field directly upstream of the edge fan varies according to the method used to represent the fan. It is also found that the more sophisticated fan models give a more accurate estimate of fan operation at higher levels of inlet flow distortion than the less sophisticated fan models.Copyright © 2011 by ASME

Simplified fan models are often used to simulate the effect of axial flow fans in large arrays of air-cooled condensers. The actuator disc method and its shortcomings are discussed and illustrated using computational fluid dynamics. A full 3-dimensional analysis of the fan is also performed at a single operating point to evaluate the flow conditions around the blade. This analysis confirms the results of the actuator disc method at the specific operating point. An adaptation of the actuator disc method, to improve its ability to model fan operation at low flow rates, is proposed. The effectiveness of the adaptation is evaluated by comparing the fan static pressure curve obtained from experimental results to the fan static pressure curve obtained from the simulations. The comparison shows that an analysis using the adapted actuator disc method produces results that correlate well with experimental values.Copyright © 2011 by ASME

To obtain baseline data on the incidence of acute alcohol intoxication, chronic alcoholism and illicit drug usage among a cohort of injured patients.A prospective, descriptive study of 254 injured patients presenting at the trauma unit of Groote Schuur Hospital over an idealized week in 1997. Alcohol consumption was assessed by means of the Lion SD2 alcolmeter. Chronic alcoholism was assessed using the CAGE questionnaire. Each patient's urine was analysed for four drugs (cannabis, morphine, opiates and methaqualone) using conventional 'wet' analysis. Sweat was tested for cannabis using a Drugwipe.Socio-demographics, cause of injury, injury severity, acute alcohol intoxication, chronic alcohol usage and illicit drug involvement.Patients were predominantly male, coloured and an average of 31.3 years old. The majority had been injured as a result of interpersonal violence. Self-reported alcohol consumption was reliable but this was not so for self-reported drug usage. Sixty per cent of patients had positive alcohol levels on breath analysis. More than one-quarter of all the patients could be classified as chronic alcoholics on the CAGE questionnaire. On urine analysis, 40% of patients were found to have used at least one illicit drug in the recent past. The most commonly abused drugs were cannabis or a combination of cannabis and Mandrax, locally called a 'white pipe'. Use of the white pipe was confined almost exclusively to patients injured as a result of interpersonal violence.Alcohol remains the most commonly abused substance among trauma patients, but there are growing numbers of patients who simultaneously abuse illicit drugs. This study will be conducted annually to detect trends and identify emerging problems.

Health managers need trauma data, but appropriate information is often lacking. The challenge is to develop affordable and sustainable information systems. The article describes the development of a regional trauma database and an evaluation of a basic surveillance methodology. A comprehensive survey was conducted of first-time attenders with fatal and nonfatal trauma from both state and private sectors in metropolitan Cape Town, South Africa, and a hospital-based survey was conducted of nonfatal trauma in the surrounding rural areas. In four state hospitals, a standardized adaptation of casualty attendance registers was evaluated to determine whether such registers could be used to establish a trauma surveillance system. The two cross-sectional studies covered a population of 3.4 million and provided detailed data. The evaluation of the register highlighted problems and indicated how to establish a register-based trauma surveillance system. Although such surveys yield comprehensive local data, there is a need for salient regional and national surveillance data. Minor modifications of casualty attendance registers may provide this without much additional effort and expense.