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In this study, a spiral ring cavity (SRC) is proposed to improve the operational stability of a centrifugal compressor. Aerodynamic performance of the compressor was analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. To prove the superiority of the proposed cavity, adiabatic efficiency and stall margin of an SRC were compared with those of the smooth casing and conventional cavities, i.e., ring cavity and discrete ring cavities. To find the optimum shape of the cavity, a parametric study was performed for the SRC using three geometric parameters, i.e., the axial location, width of the cavity port, and circumferential location of the SRC. The operation stability was sensitive to the width of cavity port and circumferential location. The SRC improved the stall margin considerably compared to other cavities.

This study numerically evaluates the performance of flow control using fluidic oscillators on the NACA 0015 airfoil with a flap at different flap angles and different pitch angles of the oscillators. An inline array of fluidic oscillators is located just in front of the flap. Aerodynamic analysis was carried out using three-dimensional unsteady Reynolds-averaged Navier-Stokes equations in a computational domain that consists of the external domain around the airfoil and the internal domains in three fluidic oscillators. Flap angles of 20°, 40°, and 60° were tested with a fixed angle of attack of 8°. For each flap angle, the effects of the pitch angle of the oscillators on the aerodynamic performance were evaluated in a range of 60° to the negative value of the corresponding flap angle. It was found in this work that the oscillator jets parallel to the flap showed the best performance, which was achieved by using negative pitch angles and also bending the outlets of the oscillators. The results indicate that the aerodynamic performance varies significantly with the flap and pitch angles.

This study investigates the effects of inlet guide vane (IGV) and blade pitch angles on the steady and unsteady performance of a submersible axial-flow pump. To analyze the interaction between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations were used with shear stress transport turbulence closure. Hexahedral meshes were used in the computational domain. The numerical results for performance curves showed good agreement with experimental data. The results showed that the steady and unsteady performance characteristics were dependent on both the IGV and blade pitch angles. Adjusting these angles affected the total pressure rise and thus caused variation in the efficiency in overload conditions. But adjusting these angles affected the unsteady pressure fluctuations in partial-load conditions. Detailed flow analyses were performed to find the root-cause of these phenomena.

In this work, a numerical investigation was analyzed to exhibit the mixing behaviors of non-Newtonian shear-thinning fluids in Kenics micromixers. The numerical analysis was performed using the computational fluid dynamic (CFD) tool to solve 3D Navier-Stokes equations with the species transport equations. The efficiency of mixing is estimated by the calculation of the mixing index for different cases of Reynolds number. The geometry of micro Kenics collected with a series of six helical elements twisted 180° and arranged alternately to achieve the higher level of chaotic mixing, inside a pipe with a Y-inlet. Under a wide range of Reynolds numbers between 0.1 to 500 and the carboxymethyl cellulose (CMC) solutions with power-law indices among 1 to 0.49, the micro-Kenics proves high mixing Performances at low and high Reynolds number. Moreover the pressure losses of the shear-thinning fluids for different Reynolds numbers was validated and represented.

A double-bridge shape is proposed as a novel flow channel cross-sectional shape of a membraneless microfluidic fuel cell, and its electrochemical performance was analyzed with a numerical model. A membraneless microfluidic fuel cell (MMFC) is a micro/nano-scale fuel cell with better economic and commercial viability with the elimination of the polymer electrolyte membrane. The numerical model involves the Navier–Stokes, Butler–Volmer, and mass transport equations. The results from the numerical model were validated with the experimental results for a single-bridge channel. The proposed MMFC with double-bridge flow channel shape performed better in comparison to the single-bridge channel shape. A parametric study for the double-bridge channel was performed using three sub-channel widths with the fixed total channel width and the bridge height. The performance of the MMFC varied most significantly with the variation in the width of the inner channel among the sub-channel widths, and the power density increased with this channel width because of the reduced width of the mixing layer in the inner channel. The bridge height significantly affected the performance, and at a bridge height at 90% of the channel height, a higher peak power density of 171%was achieved compared to the reference channel.

In this work, numerical and experimental analyses have been conducted to analyze the effect of different shapes of obstructions (diamond, rectangular, and circular) on mixing performance of a micro...

This paper presents the effects of airflow bleed from the rotor shroud surface between leading and trailing edges on aerodynamic and structural performances of a single-stage transonic axial compressor, NASA stage 37, using three-dimensional Reynolds-averaged Navier–Stokes equations with the k–e turbulence model. A small airflow mass flow rate is bleed throughout a rotor-bleeding ejector which designed by seven parameters: bleeding angle (°) and ejection angles (°), ejection depth (D), bleeding thickness (H), bleeding position from rotor leading edge (L) in flow direction, bleeding ejection curvature (R), and bleeding width contacted on rotor shroud surface (W). The numerical results for aerodynamic performance: total pressure ratio, adiabatic efficiency, and stall margin of a transonic axial compressor were validated with a smooth casing experimental data. A parametric study of seven design parameters of rotor-bleeding ejector above combined with a small ejection mass flow rate in a single-stage transonic axial compressor for aerodynamic and structural performances was performed. The numerical results show that all aerodynamic performance increases with bleeding airflow from rotor shroud surface, the total deformation on rotor tip leading edge in spanwise direction reduces with a very small increasing in Von-Mises stress in a reference-bleeding airflow as compared to the results of smooth casing.

The installation conditions of fluidic oscillators embedded in a hump surface were numerically investigated to improve the separation control of the flow over the hump. Unsteady flow analysis was p...

This article reports a novel design of a micromixer showing efficient mixing by creating vortex flow in a microchannel. The main microchannel splits and recombines into two sub-channels at a tangential position that facilitates the generation of vortex flow. The height and width of the sub-channels are half the height and width of the main microchannel. The fluid flow and the mixing characteristics of the micromixer were demonstrated by performing numerical and experimental studies at different Reynolds numbers (Re = 2.5≈40). The micromixer was fabricated using a standard soft lithography process. The fluid streams from the subchannels create vortex flow in the main microchannel which increases the interface area. The idea of creating multiple vortex flow zones by repeating the design of vortex T-mixer was successfully shown in mixing enhancement. The design of the micromixer is promising for mixing the fluids in a short length of the microchannel (5.5 mm at Re = 10 and 2.6 mm at Re = 40).

A converging-diverging film-cooling hole was designed by combining a converged inlet with a fan-shaped exit. The performance of the proposed design was analyzed numerically and compared to that of a fan-shaped hole. The film-cooling effectiveness was evaluated using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. The numerical results for fan-shaped and cylindrical holes were compared with previous experimental data. Compared to the fan-shaped hole, the converging-diverging hole improved the spatially averaged film-cooling effectiveness by 4.3%, 5.9%, and 9.9% at blowing ratios of 0.5, 1.0, and 1.5, respectively. These improved film-cooling performances were achieved by reducing the size of the separation bubble in the hole, thus increasing the thickness of the coolant layer downstream of the hole.

The present work proposes a micromixer consisting of circular mixing modules and three-dimensional subchannels, which uses a split and recombination process and unbalanced collisions as the main mi...

The present work investigated the effects of bending the outlet nozzles of fluidic oscillators installed on the NACA0015 airfoil with a flap on the flow control performance and, thus, the aerodynamic performance of the airfoil. The effects of bending on fluidic oscillators have not been reported so far in previous works. The aerodynamic analysis was performed numerically using unsteady Reynolds-averaged Navier-Stokes equations. Three different cases were considered: Case 1 changes only the bending angle with a fixed pitch angle, Case 2 changes only the pitch angle without bending, and Case 3 changes both the bending and pitch angles. Although the bending of the oscillators was introduced inevitably due to a geometrical limitation in the installation, the results indicated that the bending rather improved the lift coefficient and lift-to-drag ratio of the airfoil by improving the characteristics of the fluidic oscillators, such as the jetting angle and peak velocity ratio.

A fluidic oscillator with a bent outlet nozzle was investigated to find the effects of the bending angle on the characteristics of the oscillator with and without external flow. Unsteady aerodynamic analyses were performed on the internal flow of the oscillator with two feedback channels and the interaction between oscillator jets and external flow on a NACA0015 airfoil. The analyses were performed using three-dimensional unsteady Reynolds-averaged Navier-Stokes equations with a shear stress transport turbulence model. The bending angle was tested in a range of 0–40°. The results suggest that the jet frequency increases with the bending angle for high mass flow rates, but at a bending angle of 40°, the oscillation of the jet disappears. The pressure drop through the oscillator increases with the bending angle for positive bending angles. The external flow generally suppresses the jet oscillation, and the effect of external flow on the frequency increases as the bending angle increases. The effect of external flow on the peak velocity ratio at the exit is dominant in the cases where the jet oscillation disappears.

Membraneless microfluidic fuel cells (MMFCs) are being studied extensively as an alternative to batteries and conventional membrane fuel cells because of their simple functioning and lower manufacturing cost. MMFCs use the laminar flow of reactant species (fuel and oxidant) to eliminate the electrolyte membrane, which has conventionally been used to isolate anodic and cathodic half-cell reactions. This review article summarizes the MMFCs with six major categories of flow configurations that have been reported from 2002 to 2020. The discussion highlights the critical factors that affect and limit the performance of MMFCs. Since MMFCs are diffusion-limited, most of this review focuses on how different flow configurations act to reduce or modify diffusive mixing and depletion zones to enhance the power density output. Research opportunities are also pointed out, and the challenges in MMFCs are suggested to improve cell performance and make them practical in the near future.

In this study, a wavy microchannel heat sink with grooves using water as the working fluid is proposed for application to cooling microprocessors. The geometry of the heat sink was optimized to improve heat transfer and pressure loss simultaneously. To achieve optimization goals, the average friction factor and thermal resistance were used as the objective functions. Three dimensionless parameters were selected as design variables: the distance between staggered grooves, groove width, and groove depth. A modified Latin hypercube sampling (LHS) method that combines the advantages of conventional LHS and a three-level full factorial method is also proposed. Response surface approximation was used to construct surrogate models, and Pareto-optimal solutions were obtained with a multi-objective genetic algorithm. The modified LHS was proven to have better performance than the conventional LHS and full factorial methods in the present optimization problem. A representative optimal design showed that both the thermal resistance and friction factor improved by 1.55% and 3.00%, compared to a reference design, respectively.

Micromixers are classified into two types: active and passive micromixers. Active micromixers promote mixing using moving parts or some external agitation/energy to stir the fluids. Magnetic energy, electrical energy, pressure disturbance, and ultrasonic are examples of the external energies to enhance mixing. Passive micromixers use geometrical modification to cause chaotic advection or lamination to promote the mixing of the fluid samples, and allow easy fabrication and integration with lab-on-a-chip and μ-TAS. In this chapter, both active and passive micromixers are discussed, but the major emphasis is laid on passive micromixer designs and mechanisms. Extensive referencing on active and passive micromixers is not possible due to the limited length of the book, but the diversity of micromixers is introduced as much as possible.

The mixing performance of a passive micromixer is sensitive to the geometry of the flow passages. Therefore, it is important to determine optimal configuration which maximizes the mixing performance of the micromixer. But, unfortunately, in some micromixers, enhancement of mixing performance is accompanied by a corresponding increase in pressure drop. Therefore, it is important to determine several configurations which represent the trade-offs between mixing efficiency and pressure drop. Numerical optimization techniques coupled with CFD analyses of flow and mixing have been proved to be an important tool for micromixer design. Both the single-objective and multi-objective optimization procedures for the shape optimization of micromixers are presented.

Micromixers are essential components of lab-on-a-chip and micro-total analysis systems used for a variety of chemical and biological applications such as sample preparation and analysis, protein folding, DNA analysis, and cell separation. Due to the small characteristic dimension of micromixers, the flow is laminar in a Reynolds number range from 0.01 to 100 for typical microfluidic applications. In microfluidic devices, the laminar flow condition poses a challenge for the mixing of liquid samples. Therefore, for high performance lab-on-a-chip and micro-total analysis systems, it is essential to develop and devise micromixers to achieve fast and compact mixing at the micro-scale. Although mixing can involve different phases (solid, liquid and gases), the present book focuses on liquid–liquid mixing such as water–ethanol mixing. This chapter provides an introduction to application of micromixers, flow dynamics and mixing in micromixers, and dimensionless numbers which characterize flow and mixing regimes.

A wide range of existing passive micromixers are reviewed, and quantitative analyses of ten typical passive micromixers were performed to compare their mixing indices, pressure drops, and mixing costs under the same axial length and flow conditions across a wide Reynolds number range of 0.01–120. The tested micromixers were selected from five types of micromixer designs. The analyses of flow and mixing were performed using continuity, Navier-Stokes and convection-diffusion equations. The results of the comparative analysis were presented for three different Reynolds number ranges: low-Re (Re ≤ 1), intermediate-Re (1 < Re ≤ 40), and high-Re (Re > 40) ranges, where the mixing mechanisms are different. The results show a two-dimensional micromixer of Tesla structure is recommended in the intermediate- and high-Re ranges, while two three-dimensional micromixers with two layers are recommended in the low-Re range due to their excellent mixing performance.

An energy-efficient micro heat sink is presented for the thermal management of microprocessors with heterogeneous power distributions. The performance of the proposed microchannel-pinfin hybrid heat sink was evaluated numerically and compared with that of a simple microchannel heat sink. The hybrid heat sink was designed with two separate zones: rectangular microchannels were used over the low-heat-flux zone (background area), and an array of cylindrical pinfins were incorporated over the high-heat-flux zone (hotspot area) of the heat sink. Conjugate heat transfer analysis was performed by solving the three-dimensional Navier-Stokes and energy equations with the temperature-dependent thermophysical properties of the fluid. The thermal resistance, pumping power, temperature non-uniformity, and maximum temperature rise at the hotspot were selected as the performance parameters. The hybrid heat sink exhibited remarkable improvement in the thermal performance compared to the non-hybrid heat sink with a reasonable increase in the pumping power.

A configuration of multiple inlets is proposed for a micro laminar flow fuel cell with a bridge-shaped channel cross section. The operation of the micro laminar flow fuel cell involves the complex interplay of electrochemical and mass transport processes. A fully coupled three-dimensional numerical model is developed to evaluate the micro laminar flow fuel cell performance. The numerical model solves the three-dimensional Navier-Stokes, mass transport, and Butler-Volmer equations for the electrode kinetics. A novel concept of multiple inlets is introduced to deal with the greater mass transport losses associated with the larger channel length. The numerical model is validated using experimental data from a micro laminar flow fuel cell with a bridge-shaped microchannel. Up to 8 inlets are tested with various bridge aspect ratios to observe the peak power and current density. The multi-inlet configurations enhance the current density by multiple times in comparison to a simple bi-inlet micro laminar flow fuel cell.

Computational evaluation of three design modifications of a membraneless microfluidic fuel cell (MMFC), i.e., inlets located midway along the microchannel, multiple compartments in the channel cross section, and a multi-stream (oxidant-fuel-oxidant) configuration, is performed in this work. The first two modifications are novel concepts proposed in this work. These adjustments to the microchannel are introduced to decrease the negative effects caused by the increased channel length, width, and height on the performance of MMFCs. Formic acid and oxygen are dissolved in sulfuric acid solution as the fuel and oxidant, respectively. Simulations are executed by employing three-dimensional Navier-Stokes equations and mass transport equation for the analyses of flow and species concentration. The electro-chemical reaction is modeled using Butler-Volmer equations. Based on the study that investigated the inlet location, inlets placed at the center of the microchannel are shown to be the best option among the selected inlet positions. Additionally, the multi-compartment configuration enhances the current density by as much as three times compared to a simple square microchannel.

The performance of double-layer microchannel heat sinks are evaluated comparatively for the parallel flow, counter flow, and transverse flow configurations with and without hotspots as heating cond...

A micromixer with a three-dimensional serpentine split-and-recombination structure is proposed to provide a high mixing index in a short length, even at low Reynolds numbers. The fluid flow and mixing performance were analyzed numerically using three-dimensional Navier-Stokes equations and the convection-diffusion equation for mass transport in a Reynolds number range of 0.1–200. The mixing performance is represented by the mixing index, which is defined using the mass fraction variance of mixing fluids in a plane. The overall mixing performance of the proposed micromixer is compared with that of previous micromixers. The effects of the number of mixing units on the mixing performance were estimated. A parametric study was performed using five geometric parameters of the micromixer. The proposed micromixer shows mixing indices larger than 0.87 throughout the Reynolds number range in a short length of 1500 μm, which is hardly achieved in previous micromixers.

A numerical investigation of a fluidic oscillator was performed to understand the unsteady internal flow field and geometrical effects on the performance using three-dimensional unsteady Reynolds-averaged Navier-Stokes equations. Effects of the two geometrical parameters, i.e., the inlet width of the mixing chamber and outlet throat width, on peak jet velocity ratio at the exit and pressure drop through the oscillator, were evaluated. The unsteady simulation was performed using shear stress transport turbulence model with air as working fluid at Reynolds number 30000. Computational results showed good qualitative and quantitative agreements with available experimental results for the flow structure and frequency of the oscillating jet. Results of the parametric study suggested that the inlet width affected significantly the flow in the fluidic oscillator, while effects of the throat width on the performance parameters were not remarkable.

A novel design is presented for a chaotic micromixer using two-layer serpentine crossing microchannels. The performance of the micromixer was analyzed both numerically and experimentally. The numerical analysis was performed using three-dimensional Navier-Stokes equations with a convection–diffusion model for the species concentration in a Reynolds number range of 0.2–120. An experimental model of the micromixer was fabricated by soft lithography with polydimethylsiloxane (PDMS). Two working fluids, water and dye-water mixture were used for numerical analysis except for the experimental validation of numerical results. Both the numerical and experimental analyses confirm that the micromixer achieves a high level of mixing over a wide range of Reynolds numbers through splitting, enlarging, recombination, and folding mechanisms. The micromixer showed over 95% mixing throughout the tested range of Reynolds number. Especially, about 99% mixing was achieved at Reynolds numbers less than ten. Thus, the proposed micromixer can be used in microfluidic systems which require fast mixing at low Reynolds numbers.

The effects of stator shroud air injection on aerodynamic performance were investigated for a single-stage axial compressor. Multiobjective optimization of the air injector was performed to maximiz...

The effects of the cross-sectional area of a volute on suction recirculation and cavitation in a centrifugal pump were investigated. The pump performance and fluid flow were analyzed using both steady and unsteady three-dimensional Reynolds-averaged Navier–Stokes analyses. The shear stress transport (SST) model was adopted as a turbulence closure model, and a simplified Rayleigh–Plesset cavitation model and a homogeneous two-phase mixture model were used to simulate the cavitating flow inside the pump. A constant to determine the designed circumferential velocity of the volute was selected as the geometric parameter for a parametric study. The hydraulic efficiency, head coefficient, blockage in front of the impeller, and critical cavitation number for a head-drop of 3% were selected as the performance parameters to evaluate the hydraulic performance. The results show that unlike the blockage, the hydraulic and suction performances were affected significantly by the volute shape. Both steady and unsteady flow analyses showed that the onset and development of suction recirculation were relatively unaffected by the volute geometry and the best efficiency point of the pump.

The present work proposes a planar micromixer design comprising hybrid mixing modules of split-and-recombine units and curved channels with radial baffles. The mixing performance was evaluated numerically by solving the continuity and momentum equations along with the advection-diffusion equation in a Reynolds number range of 0.1&ndash, 80. The variance of the concentration of the mixed species was considered to quantify the mixing index. The micromixer showed far better mixing performance over whole Reynolds number range than an earlier split-and-recombine micromixer. The mixer achieved mixing indices greater than 90% at Re &ge, 20 and a mixing index of 99.8% at Re = 80. The response of the mixing quality to the change of three geometrical parameters was also studied. A mixing index over 80% was achieved within 63% of the full length at Re = 20.

A laminar flow micro fuel cell comprising of bridge-shaped microchannel is investigated to find out the effects of the cross-section shape of the microchannel on the performance. A parametric study is performed by varying the heights and widths of the channel and bridge shape. Nine different microchannel cross-section shapes are evaluated to find effective microchannel cross-sections by combining three bridge shapes with three channel shapes. A three-dimensional fully coupled numerical model is used to calculate the fuel cell&rsquo, s performance. Navier-Stokes, convection and diffusion, and Butler-Volmer equations are implemented using the numerical model. A narrow channel with a wide bridge shape shows the best performance among the tested nine cross-sectional shapes, which is increased by about 78% compared to the square channel with the square bridge shape.

This paper presents a study of the effects of blade pitch angle and inlet guide vane (IGV) angle on the performance of a submersible axial-flow pump. To analyze the interaction effects between the IGVs and the rotor blades, both steady and unsteady three-dimensional Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model were solved. Hexahedral meshes were used in the computational domain and a grid-dependency test was performed to obtain an optimal number of grid nodes. The performance curves obtained by numerical simulation showed good agreement with experimental data. The results show that the fluctuation of hydraulic efficiency and head coefficient increased significantly under overload conditions as the IGV setting angle increased. Additionally, both the steady and unsteady performance characteristics were shown to be quite dependent on the combination of IGV angle and blade pitch angle, because the relative velocity at leading edge played an important role in the performance under overload conditions.

The effects of a rotor–stator interface model on the hydraulic and suction performance of a single-stage centrifugal pump have been evaluated. A three-dimensional Reynolds-averaged Navier–Stokes (RANS) analysis was performed using the shear-stress transport turbulence model. The cavitating flow was simulated using a homogeneous two-phase mixture model and a simplified Rayleigh–Plesset cavitation model. Three performance parameters were selected to compare different cases: the hydraulic efficiency, head coefficient, and critical cavitation number for a head-drop of 3%. Frozen-rotor and stage models were evaluated for the rotor–stator interface. The evaluation was done using three different computational domains: one with a single passage of the impeller with a vaneless diffuser, one with a single passage of the impeller with the whole shape of volute casing, and another with the whole passage of the impeller with the whole shape of volute casing. Two different volute shapes were also tested. The results show that it is desirable to use the whole domain of the impeller and volute with the frozen-rotor model for accurate prediction of the suction performance. The stage model is not recommended for the prediction of the suction performance of the centrifugal pump with the volute in severe off-design conditions.

The review article introduces the development in membraneless microfluidic fuel cells (MMFCs) focusing on the microchannel geometry and electrode architecture and arrangement. Lamination of fuel and oxidant streams in a microchannel lets an MMFC work without physical membrane. The lack of convective mixing across liquid–liquid interface of two streams forms a distinct diffusive mixing region, which acts as a pseudo membrane. The ions can transport across the channel through the mixing region to reach the other side of the channel and complete the ionic conduction. The advantage of MMFCs lies in the absence of the membrane, as the problems associated with the membrane are eliminated. The channel geometry and electrode architecture have been investigated extensively to eliminate the problems caused by the mixing and depletion regions, which affect the performance significantly, such as power and current densities. The absence of instabilities due to the convective mass transer along the channel allows streams containing different substances with different concentrations to flow side by side axially through a microchannel, whereas the reactant’s mass transfer across the channel in an MMFC is mainly diffusion-limited. This review article mostly focuses on how the channel and electrodes can be designed effectually to enhance the mass transfers by reducing mixing and depletion regions. Additionally, the current status of theoretical and computational modeling for MMFCs to improve the performance are discussed. Moreover, the key issues and main challenges for prospective development of MMFCs are presented.

A casing treatment using inclined oblique slots (INOS) is proposed to improve the stability of the single-stage transonic axial compressor, NASA Stage 37, during operation. The slots are installed on the casing of the rotor blades. The aerodynamic performance was estimated using three-dimensional steady Reynolds-Averaged Navier-Stokes analysis. The results showed that the slots effectively increased the stall margin of the compressor with slight reductions in the pressure ratio and adiabatic efficiency. Three geometric parameters were tested in a parametric study. A single-objective optimization to maximize the stall margin was carried out using a Genetic Algorithm coupled with a surrogate model created by a radial basis neural network. The optimized design increased the stall margin by 37.1% compared to that of the smooth casing with little impacts on the efficiency and pressure ratio.

This paper investigates a novel casing treatment for an axial compressor that combines a circumferential casing groove with flow recirculation channels. This casing treatment is located in the rotor's tip region and comprises a single shallow circumferential groove with 36 recirculation channels that are distributed equally around the annulus. The effects of the casing treatment on the stability and aerodynamic performance were evaluated numerically on a NASA Stage 37 single-stage transonic axial compressor. The results show that the addition of the recirculation channels improved the gain in stall margin while mitigating the penalty in the adiabatic efficiency and pressure rise compared to a casing groove without recirculation channels. Six geometric parameters were examined in a parametric study. The maximum increase in stall margin was 42.5% with small reductions in the efficiency and pressure ratio. To maximize the stall margin and minimize efficiency loss, two design variables were selected to perform a multi-objective optimization using a multi-objective genetic algorithm coupled with surrogate models using a radial basis neural network. The optimization successfully improved both the objective functions for all representative designs compared to the reference design.