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This paper aims to present the designing and investigating various types of impulse blade profiles to find the optimal profile that has better performance than the first or original blade. The studied model is a turbine with an output power below 1 MW and a large pressure ratio up to 20, which is used to gain relatively high specific work output. As a result of its low mass flow rate, the turbine is used under partial-admission conditions. The turbine’s stator is a group of convergence–divergence nozzles that provide supersonic flow.

More than 10 types of two-dimensional blade profiles were designed using the developed preliminary design calculations and numerical analysis. The numerical results are validated using the existing experimental results. Finally, the case with improved performance is introduced as the final optimum case.

It was found that the performance parameters such as efficiency, power and torque are increased by more than 8% in the selected best model, in comparison with the original model. Moreover, the total pressure loss is 12% decreased for the selected model. Finally, the selected profile with superior performance is proposed.

Simultaneous numerical tests are conducted to examine the interaction of different supersonic blade profiles with the partially injected flow to the rotor.

The blade profile and its geometrical features play an important role in the separation of the boundary layer on the blade. Modifying the blade geometry, which might lead to the delay or elimination of the flow separation, can be considered as a passive flow control methodology. This study aims to find a novel and inexpensive way to reduce loss with appropriate modifications on the leading edge of the turbine blade.

Three types of wave leading edges were designed with different wavelengths and amplitudes. The selected numbers for the wave characteristics were based on the best results of previous studies. Models with appropriate and independent meshing have been simulated and studied by a commercial software. The distribution of the loss at different planes and mid-plane velocity vectors were shown. The mass flow average of loss at different incidence angles was calculated for the reference blade and modified ones for the sake of comparison.

The results show that in all three types of modified blades compared to the reference blade, the elimination of flow separation is observed and therefore the reduction of loss at the critical incidence angle of I = –15°. As the amplitude of the wave increased, the amount of loss growing up, while the increase in wavelength caused the loss to decrease.

The results of the present numerical analysis were validated by the laboratory results of the reference blade. The experimental study of modified blades can be used to quantify numerical solutions.

The purpose of this paper is to show the superior turbulence method in CFD analysis of radial turbo machines and to introduce the best way to choose turbulence parameters whenever FLUENT user applies this software as a complementary design tool for high‐speed turbo machinery components.

One of the most important issues in CFD is analysis of flow field in turbo machines. Flow in high‐speed radial turbo machinery is a 3D, turbulent and unsteady behavior so needs suitable method for converging. It is clear that the turbulence model has an extraordinary effect on investigation of 3D flows in high‐speed turbo machinery. A centrifugal compressor of micro and radial turbines have been designed and simulated 3D using the commercial CFD‐code FLUENT 6. Three turbulence models k‐ε/standard, renormalization‐group (RNG) and RSM were considered and results of three models were compared with experimental and 1D design results.

The study showed numerical results are compatible with experimental performance data. It determined that RNG method in CFD analysis of radial turbo machines has provided better results than the standard k‐ε method. In addition, when using the RNG method, the phenomena of flow field were more visible than other methods.

This paper offers use of the RNG method as a superior turbulence method in CFD analysis of radial turbo machines.

This paper is concerned with improving the flow pattern in the nozzle-rotor axial gap in impulse turbines using a genetic algorithm (GA) and 3D numerical analysis. The paper aims to discuss these issues.

The appropriate model was used to estimate the turbine performance introduced in the beginning of the work. Then, the nozzle design parameters that are effective in the axial gap flow pattern are optimized using a non-linear optimization code. This code works based on the GA theory. Since the GA results are not conclusive, the selected cases were evaluated using 3D numerical analysis. For a detailed comparison of the flow pattern in initial and improved cases, a transient analysis was done. Experimental tests were performed in order to validate the work. For this purpose, the characteristic curves of the turbines were studied and compared with each other.

Improving the nozzle-rotor axial gap flow pattern leading to increase in the total-to-total efficiency of the turbine by more than two points.

Partially injected flow forced to use the full model computational analysis.

Weight reduction in a feeding system.

New loss modeling method presented for partial admission condition.

This study aims to presenting an empirical model for partially admitted turbine efficiency. When the design mass-flow rate is too small that a normal full-admission design would give very-small blade height, it may be advantageous to use partial admission. The losses due to partial admission with long blades may be less than the losses due to leakage and low Reynolds-number of the full-admission turbines with short blades. The turbine efficiency is highly dependent on the degree of partial admission. The empirical model of turbine efficiency is necessary for simulation and analysis of dynamic performances of the turbine system. In this work, appropriate empirical loss correlations are introduced and a proper model is proposed for turbine efficiency.

Experimental and numerical tests are conducted to evaluate the proposed model and the results are compared with the results of existing models. In this work, the effect of nozzles overlapping on the flow pattern is emphasized. Therefore, various models with different degrees of overlapping are simulated and their effects on the turbine efficiency are subsequently evaluated.

A suitable cubic polynomial expression for small axial supersonic turbine efficiency in experiments is suggested. The overlapping nozzles cause change in the flow pattern and the entropy distribution. Therefore, any change in the degree of overlapping of nozzles changes the efficiency of the turbine.

In this work, time-consuming numerous experimental and numerical tests of the turbine are required.

Implication of a proper formula for a partially admitted turbine may result in enhanced prediction and dynamic performance evaluation of the test turbine.

A proper empirical model for a partially admitted supersonic turbine is introduced. This model is suitable for one blocked partially admitted turbine with Mach number between 1.2 and 1.8.

This study aims to investigate the effects of organizational culture factors on the selection of software process development models and develops a conceptual model for selecting and adopting process development models with an organizational culture approach, using 12 criteria and their sub-criteria defined in Fey and Denison’s model (12 criteria).

The research hypotheses were investigated using statistical analysis, and then the criteria and sub-criteria were selected based on Fey and Denison’s model and the experts’ viewpoints. Afterward, the organizational culture of the selected company was measured using the data from 2016 and 2017, based on Fey and Denison’s questionnaire. Due to the correlation between the criteria, using the decision-making trial and evaluation technique, the correlation between sub-criteria were determined, and by analytical network process method and using Super-Decision software, the process development model was preferred to the 12 common models in information systems development.

Results indicated a significant and positive effect of organizational culture factors (except the core values factor) on the selection of development models. Also, by changing the value of organizational culture, the selected process development model changed either. Sensitivity analysis performed on the sub-criteria implied that by changing and improving some sub-criteria, the organization will be ready and willing to use the agile or risk-based models such as spiral and win-win models. Concerning units where the mentioned indicators were at moderate and low limits, models such as waterfall, V-shaped and incremental worked more appropriately.

While many studies were performed in comparing development models and investigating their strengths and weaknesses, and the impact of organizational culture on the success of information technology projects, literature indicated that the impact of organizational sub-culture prevailing in the selection of development process models has not been investigated. In this study, new factors and indicators were addressed affecting the selection of development models with a focus on organizational culture. Correlation among the factors and indicators was also investigated and, finally, a conceptual model was proposed for proper adoption of the models and methodologies of system development.

Nowadays flaps and winglets are one of the main mechanisms to increase airfoil efficiency. This study aims to investigate the power performance of vertical axis wind turbines (VAWT) that are equipped with diverse gurney flaps. This study could play a crucial role in the design of the VAWT in the future.

In this paper, the two-dimensional computational fluid dynamics simulation is used. The second-order finite volume method is used for the discretization of the governing equations.

The results show that the gurney flap enhances the power coefficient at the low range of tip speed ratio (TSR). When an angled and standard gurney flap case has the same aerodynamic performance, an angled gurney flap case has a lower hinge moment on the junction of airfoil and gurney flap which shows the structural excellence of this case. In all gurney flap cases, the power coefficient increases by an average of 20% at the TSR range of 0.6 to 1.8. The gurney flap cases do not perform well at the high TSR range and the results show a lower amount of power coefficient compare to the clean airfoil.

The angled gurney flap which has the structural advantage and is deployed to the pressure side of the airfoil improves the efficiency of VAWT at the low and medium range of TSR. This study recommends using a controllable gurney flap which could be deployed at a certain amount of TSR.

Multilevel inverters (MLIs) have been studied widely over the past two decades because of their inherent advantages and interesting features. However, most of the newly introduced structures suffer from the increased standing voltage of the switches, which is defined as the maximum off-state voltage on the switches, losing modularity and increased number of direct current (DC) voltage sources. The purpose of this study is to propose a new hybrid MLI topology to alleviate the mentioned problems.

The proposed approach in this study includes using the advantage of two different topologies and combine them in a way that the advantages of both of the topologies are achieved. Therefore, the approach is to design a hybrid topology from two existing topologies so that a new topology has resulted.

This paper proposes a new hybrid MLI with lower power electronic switches and lowers DC voltage sources in comparison with the classic structures. The proposed MLIs maintain a balance between the number of switches, the standing voltage on the switches and the number of DC sources. The topology description, modulation method and comparative study have been presented. Also, another more reduced structure is presented for higher power factor operation. The MATLAB simulation and experimental results of a nine-level inverter have been presented to verify its operation.

The hybrid topology has a new structure that has not been presented before. It is important to emphasize that the topology combination and achieving the hybrid topology is wisely accomplished to improve some features of the MLI.

This study aims to use computational fluid dynamics (CFD) to understand and quantify the overall blockage within a transonic axial flow compressor (AFC), and to develop an efficient collaborative design optimization method for compressor aerodynamic performance and stability in conjunction with a surrogate-assisted optimization technique.

A quantification method for the overall blockage is developed to integrate the effect of regional blockages on compressor aerodynamic stability and performance. A well-defined overall blockage factor combined with efficiency drives the optimizer to seek the optimum blade designs with both high efficiency and wide-range stability. An adaptive Kriging-based optimization technique is adopted to efficiently search for Pareto front solutions. Steady and unsteady numerical simulations are used for the performance and flow field analysis of the datum and optimum designs.

The proposed method not only remarkably improves the compressor efficiency but also significantly enhances the compressor operating stability with fewer CFD calls. These achievements are mainly attributed to the improvement of specific flow behaviors oriented by the objectives, including the attenuation of the shock and weakening of the tip leakage flow/shock interaction intensity.

CFD-based design optimization of AFC is inherently time-consuming, which becomes even trickier when optimizing aerodynamic stability since the stall margin relies on a complete simulation of the performance curve. The proposed method could be a good solution to the collaborative design optimization of aerodynamic performance and stability for transonic AFC.

The high lift devices are effective at high angle of attack to increase the coefficient of lift by increasing the camber. But it affects the low angle of attack aerodynamic performance by increasing the drag. Hence, they have made as a movable device to deploy only at high angles of attack, which increases the design and installation complexities. This study aims to focus on the comparison of aerodynamic efficiency of different conventional leading edge (LE) slat configurations with simple fixed bioinspired slat design.

This research analyzes the effect of LE slat on aerodynamic performance of CLARK Y airfoil at low and high angles of attack. Different geometrical parameters such as slat chord, cutoff, gap, width and depth of LE slat have been considered for the analysis.

It has been found that the LE slat configuration with slat chord 30% of airfoil chord, forward extension 8% of chord, dip 3% of chord and gap 0.75% of chord gives higher aerodynamic efficiency (C_l/Cd) than other LE slat configurations, but it affects the low angles of attack aerodynamic performance with the deployed condition. Hence, this optimum slat configuration is further modified by closing the gap between LE slat and the main airfoil, which is inspired by the marine mammal’s nose. Thus increases the coefficient of lift at high angles of attack due to better acceleration over the airfoil nose and as well enhances the aerodynamic efficiency at low angles of attack.

The two-dimensional computational analysis has been done for different LE slat’s geometrical parameters at low subsonic speed.

This bio-inspired nose design improves aerodynamic performance and increases the structural strength of aircraft wing compared to the conventional LE slat. This fixed design avoids the complex design and installation difficulties of conventional movable slats.

The findings will have significant impact on the fields of aircraft wing and wind turbine designs, which reduces the design and manufacturing complexities.

Different conventional slat configurations have been analyzed and compared with a simple fixed bioinspired slat nose design at low subsonic speed.