Research

24 pages, 14428 KiB

Open AccessArticle

Analysis of the Effect of the Leading-Edge Vortex Structure on Unsteady Secondary Flow at the Endwall of a High-Lift Low-Pressure Turbine

by Shuang Sun, Jinhui Kang, Zhijun Lei, Zhen Huang, Haixv Si and Xiaolong Wan

Aerospace 2023, 10(3), 237; https://doi.org/10.3390/aerospace10030237 - 28 Feb 2023

Cited by 2 | Viewed by 1451

Abstract

The horseshoe vortex system at the leading edge of a low-pressure turbine (LPT) has unsteady flow characteristics, and the flow field in the downstream cascade channel also has unsteady characteristics. In this study, CFD simulations are performed with the help of commercial software [...] Read more.

The horseshoe vortex system at the leading edge of a low-pressure turbine (LPT) has unsteady flow characteristics, and the flow field in the downstream cascade channel also has unsteady characteristics. In this study, CFD simulations are performed with the help of commercial software CFX, and experimental checks are performed using a fan-shaped cascade test bench to investigate the flow characteristics of the endwall of the PACKB blade type of a high-lift LPT under the same incoming Reynolds number and two incoming boundary layer thickness conditions. The obtained results show that there are different flow alteration characteristics and alteration frequencies of the horseshoe vortex system, among which the vortex system with a thicker boundary layer is larger in size and less spaced from each other, which is more likely to induce the fusion of vortex systems. The centrifugal instability causes the instability of the horseshoe vortex system, and the instability frequency is inversely proportional to the thickness of the boundary layer. With two inlet boundary layers, the instability frequencies of the vortex system are 125 Hz and 175 Hz, respectively, and the ratio of the frequency to the thickness of the boundary layer is reciprocal to each other. The stimulation effect of the unstable horseshoe vortex system on the downstream secondary flow intensity is greater than that of the steady state. The thin boundary layer case generates a greater unsteady loss in the cascade channel than the thick boundary layer case due to the poor stability of the vortex system. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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18 pages, 8818 KiB

Open AccessArticle

A Stage Flow Parameter Analytical Model for Transonic Counter-Rotating Compressor and Its Application

by Hengtao Shi and Xianjun Yu

Aerospace 2023, 10(2), 144; https://doi.org/10.3390/aerospace10020144 - 05 Feb 2023

Viewed by 1302

Abstract

This paper proposes a stage flow parameter analytical model for rapid evaluation of a counter-rotating compressor’s performance for design optimization and its application in the design of a transonic counter-rotating fan. In the first part, the velocity diagram method, considering the influence of [...] Read more.

This paper proposes a stage flow parameter analytical model for rapid evaluation of a counter-rotating compressor’s performance for design optimization and its application in the design of a transonic counter-rotating fan. In the first part, the velocity diagram method, considering the influence of flow-path geometry variation for enhancing the accuracy, is used to correlate the aerodynamic parameter between the inlet guide vane (IGV), the upstream rotor (R1), and the downstream CR rotor (R2). A profile loss correlation based on Lieblein’s diffusion factor and a shock loss model from a high-speed fan database are incorporated for predicting the rotor efficiency. In the second part, to verify its effectiveness, the analytical model is used for aiding in the aerodynamic design of a transonic CR fan for indicating the optimized combination of design parameters for good efficiency and a high pressure ratio. According to the analytical model and the simulation results, the final selected samples have higher efficiency, with a moderate pressure ratio (0.949/2.67, 0.890/2.99, and 0.841/2.99 for R = 0.1, 0.5, and 0.9, respectively). Finally, the aerodynamic characteristics of the designed transonic CR fan at a relative rotating speed of N = 1.05~0.8 are calculated by using the CFD software Numeca. Simulations indicate that the designed transonic CR fan has a pressure ratio of 2.76, with an efficiency of 0.8405 at the design point, and the efficiency is maintained above 0.821 with a stall margin of 13.3% for N=1.0. The maximum pressure ratio of this CR fan reaches 3.08 and 3.36 for N = 1.0 and 1.05, respectively. If used to provide thrust, calculations indicate that the thrust of this transonic CR fan is 71.8, 65.9, and 35.8 kN for N = 1.05, 1.0, and 0.8 at the near-choke point for the sea-level condition. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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22 pages, 4096 KiB

Open AccessArticle

Influence of the Reynolds Number on the Aerodynamic Performance of a Small Rotor

by Andres M. Pérez Gordillo, Jaime A. Escobar and Omar D. Lopez Mejia

Aerospace 2023, 10(2), 130; https://doi.org/10.3390/aerospace10020130 - 31 Jan 2023

Cited by 2 | Viewed by 1359

Abstract

The use of small rotors has increased due their applications in drones and UAVs. In order to improve the global performance of these aerial vehicles, it is necessary to understand the aerodynamics of small rotors, since this is related to the global energy [...] Read more.

The use of small rotors has increased due their applications in drones and UAVs. In order to improve the global performance of these aerial vehicles, it is necessary to understand the aerodynamics of small rotors, since this is related to the global energy consumption of such vehicles. Most of the computational fluid dynamics (CFD) studies found in the literature that are related to the analysis of small rotors employ fully turbulent models, despite the low-to-moderate Reynolds numbers of these applications. This paper presents CFD simulations for a small rotor at hover at different Reynolds numbers using fully turbulent and transitional SST

k - ω

turbulence models. Numerical results show that thrust and torque are close to experimental measurements, showing differences of less than 5% for both fully turbulent and transitional models. However, significant differences were observed between the fully turbulent and the transitional models when studying the boundary-layer development and separation. As the Reynolds number was increased, it was observed that at the tip of the blade, these differences were reduced, but at mid-span, the differences were more obvious. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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22 pages, 20101 KiB

Open AccessArticle

DNS Study on Turbulent Transition Induced by an Interaction between Freestream Turbulence and Cylindrical Roughness in Swept Flat-Plate Boundary Layer

by Kosuke Nakagawa, Takahiro Tsukahara and Takahiro Ishida

Aerospace 2023, 10(2), 128; https://doi.org/10.3390/aerospace10020128 - 30 Jan 2023

Cited by 4 | Viewed by 1846

Abstract

Laminar-to-turbulent transition in a swept flat-plate boundary layer is caused by the breakdown of the crossflow vortex via high-frequency secondary instability and is promoted by the wall-surface roughness and the freestream turbulence (FST). Although the FST is characterized by its intensity and wavelength, [...] Read more.

Laminar-to-turbulent transition in a swept flat-plate boundary layer is caused by the breakdown of the crossflow vortex via high-frequency secondary instability and is promoted by the wall-surface roughness and the freestream turbulence (FST). Although the FST is characterized by its intensity and wavelength, it is not clear how the wavelength affects turbulent transitions and interacts with the roughness-induced transition. The wavelength of the FST depends on the wind tunnel or in-flight conditions, and its arbitrary control is practically difficult in experiments. By means of direct numerical simulation, we performed a parametric study on the interaction between the roughness-induced disturbance and FST in the Falkner–Skan–Cooke boundary layer. One of our aims is to determine the critical roughness height and its dependence on the turbulent intensity and peak wavelength of FST. We found a suppression and promotion in the transition process as a result of the interaction. In particular, the immediate transition behind the roughness was delayed by the long-wavelength FST, where the presence of FST suppressed the high-frequency disturbance emanating from the roughness edge. Even below the criticality, the short-wavelength FST promoted a secondary instability in the form of the hairpin vortex and triggered an early transition before the crossflow-vortex breakdown with the finger vortex. Thresholds for the FST wavelengths that promote or suppress the early transition were also discussed to provide a practically important indicator in the prediction and control of turbulent transitions due to FST and/or roughness on the swept wing. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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20 pages, 6990 KiB

Open AccessArticle

Computational Fluid Dynamics Analyses of a Wing with Distributed Electric Propulsion

by Oreste Russo, Andrea Aprovitola, Donato de Rosa, Giuseppe Pezzella and Antonio Viviani

Aerospace 2023, 10(1), 64; https://doi.org/10.3390/aerospace10010064 - 08 Jan 2023

Viewed by 2331

Abstract

The efficiency increase that distributed propulsion could deliver for future hybrid-electric aircraft is in line with the urgent demand for higher aerodynamic performances and a lower environmental impact. Several consolidated proprietary tools (not always available) are developed worldwide for distributed propulsion simulation. Therefore, [...] Read more.

The efficiency increase that distributed propulsion could deliver for future hybrid-electric aircraft is in line with the urgent demand for higher aerodynamic performances and a lower environmental impact. Several consolidated proprietary tools (not always available) are developed worldwide for distributed propulsion simulation. Therefore, prediction and comparisons of propeller performances, with computational fluid dynamic codes featuring different implementation of solvers, numerical schemes, and turbulence models, is of interest to a wider audience of research end-users. In this framework, the paper presents a cross-comparison study among different CFD solvers, the SU2 Multiphysics Simulation and Design Software, the CIRA proprietary flow solver UZEN, and the commercial ANSYS-FLUENT code, for the simulation of a wing section with a tractor propeller at different flow attitudes. The propeller is modelled as an actuator disk according to the general momentum theory and is accounted for in the flow solvers as a boundary condition, for the momentum and energy equations. In this study, a propeller with a fixed advance ratio

J = 0.63

is considered, while propeller performances are assumed variable along with the radius. To perform the comparisons among the solvers, an in-house procedure, which provides the input thrust and torque distributions in a unified format among the three solvers, is developed. Steady RANS simulations are performed at

R e_{\infty} = 1.7 \times 10^{6}

and

M_{\infty} = 0.11

, for the flowfield of an isolated propeller. Successively, a wing section with a fixed forward-mounted propeller configuration with no nacelle, is studied at

α = 0^{\circ}, 4^{\circ},

and

8^{\circ}

angles of attack. The comparisons in terms of the lift coefficient show a good agreement among the three flow solvers both in power-off and power-on conditions. Simulations also evidenced the strong stability preserving property of upwind schemes, applied to propeller simulation at low-Mach number. Some discrepancies in the drag coefficient are observed and related to different levels of numerical diffusion between the three codes, which affects the downstream wake. Differences in flow properties in near disk region are observed and explained considering the different hub implementations. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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20 pages, 6245 KiB

Open AccessArticle

Experimental and Numerical Studies on the Effect of Airflow Separation Suppression on Aerodynamic Performance of a Ducted Coaxial Propeller in Hovering

by Junjie Wang, Renliang Chen and Jiaxin Lu

Aerospace 2023, 10(1), 11; https://doi.org/10.3390/aerospace10010011 - 23 Dec 2022

Cited by 2 | Viewed by 1578

Abstract

The ducted coaxial propeller (DCP) has great application value in eVTOL aircraft because of its high safety, compactness, and low noise. A numerical simulation method for the DCP is established using the sliding mesh technique. A DCP was designed and manufactured for the [...] Read more.

The ducted coaxial propeller (DCP) has great application value in eVTOL aircraft because of its high safety, compactness, and low noise. A numerical simulation method for the DCP is established using the sliding mesh technique. A DCP was designed and manufactured for the lift and power test to verify the numerical method. The characteristics of airflow separation inside the DCP were studied, and the influence of the vortex restrain ring (VRR) on the suppression of airflow separation and on lift augmentation of the duct is analyzed. Results show that, when the tip clearance ratio increases from 0.336% to 1.342%, both the total lift and aerodynamic efficiency decrease by about 11.3%. The influence is mainly reflected in the formation of the tip vortex, airflow separation in the straight, and diffusion sections of the duct. Tip vortex and airflow separation increases DCP energy dissipation and clogs the inner wall of the duct, reducing the effective inner diameter and airflow through the duct. Moreover, the role of the duct is weakened, and the wake is contracted, which increases the induced power loss. By adding a VRR to the diffusion section, the tip vortex and airflow separation can be effectively suppressed, which can increase the aerodynamic efficiency by 5.1%. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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17 pages, 5462 KiB

Open AccessArticle

Atomization Characteristics of Special-Design Pneumatic Two-Fluid Nozzles for Helicopter Main Reducers: A Numerical and Experimental Investigation

by He Liu, Huiyun Cheng, Yu Dai and Xiang Zhu

Aerospace 2022, 9(12), 834; https://doi.org/10.3390/aerospace9120834 - 15 Dec 2022

Cited by 3 | Viewed by 1748

Abstract

Oil mist lubrication can be utilized as an emergency lubrication system in the main reducer of a helicopter. A special-design pneumatic two-fluid nozzle is the crucial system component for atomizing lubricant oil, so exploring the atomization characteristics of the nozzle has a significance [...] Read more.

Oil mist lubrication can be utilized as an emergency lubrication system in the main reducer of a helicopter. A special-design pneumatic two-fluid nozzle is the crucial system component for atomizing lubricant oil, so exploring the atomization characteristics of the nozzle has a significance on effectively improving oil mist lubrication performance. A CFD (computational fluid dynamics) model with a DPM (discrete phase model) technique and a specialized atomization test system were set up to both numerically and experimentally investigate the nozzle’s atomization characteristics. For the atomization properties of the nozzle, the impacts of air pressure, gas–liquid pressure ratio, lubricant oil flow rate, and lubricant oil property factors, including viscosity and surface tension, were investigated. Combining the experimental and the numerical findings reveals that an increasing air pressure and gas–liquid pressure ratio contribute to the atomization effect of the nozzle, especially the air pressure. In addition, a higher lubricant oil flow rate is slightly unfavorable for atomization, but a rise in viscosity and surface tension prevents the atomization of the lubrication oil. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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14 pages, 1672 KiB

Open AccessArticle

Validation for Aerodynamic Performance on Over-Expanded State of Single Expansion Ramp Nozzle Configuration

by Ye Chen, Zhongxi Hou, Bingjie Zhu, Zheng Guo and Boting Xu

Aerospace 2022, 9(11), 715; https://doi.org/10.3390/aerospace9110715 - 14 Nov 2022

Cited by 1 | Viewed by 1964

Abstract

The performance of a single expansion ramp nozzle (SERN) drastically declines on over-expanded conditions. A numerical code can accurately predict nozzle performance in the over-expanded state, which is crucial for the SERN configuration design. A Reynolds-averaged Navier–Stokes (RANS) simulation of the SERN jet [...] Read more.

The performance of a single expansion ramp nozzle (SERN) drastically declines on over-expanded conditions. A numerical code can accurately predict nozzle performance in the over-expanded state, which is crucial for the SERN configuration design. A Reynolds-averaged Navier–Stokes (RANS) simulation of the SERN jet in an over-expanded state was performed to verify the numerical performance of the well-established commercial CFD solver (ANSYS Fluent

^{TM}

v202) and rhoCentralFoam solver in OpenFOAM. The wall pressure distributions and flow field characteristics including the shock structures and the width of the jet were studied in detail with an inlet nozzle pressure ratio (NPR) of 1.5, 3, 4, and 8. The SERN aerodynamic performance with an inlet NPR ranging from 1.5 to 9 was then calculated. The results showed that the Fluent 3D simulation could qualitatively predict the characteristics of the internal and external flow of the nozzle, because it overestimated the wall pressure and shock wave position. Two-dimensional (2D) simulations made it difficult to capture the external flow structure due to the 3D effects. The simulation results of rhoCentralFoam for over-expanded SERN flow were not ideal. The Fluent can produce physical solutions, and it achieved limited success. The existing errors were mainly caused by the inlet boundary setting. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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31 pages, 11029 KiB

Open AccessArticle

Numerical Investigation of Nanofluid Flow over a Backward Facing Step

by Wen-Chung Wu and Ankit Kumar

Aerospace 2022, 9(9), 499; https://doi.org/10.3390/aerospace9090499 - 07 Sep 2022

Cited by 4 | Viewed by 2124

Abstract

Nanofluid flow over a backward facing step was investigated numerically at low Reynolds number and the heat transfer was analyzed and reported. Al₂O₃–H₂O nanofluids of different volume fractions (

φ

= 1–5%) were used as the material [...] Read more.

Nanofluid flow over a backward facing step was investigated numerically at low Reynolds number and the heat transfer was analyzed and reported. Al₂O₃–H₂O nanofluids of different volume fractions (

φ

= 1–5%) were used as the material with uniform heat flux (UHF) of 5000 W/m² at bottom wall for Reynolds number 200–600. The backward facing step of two geometries was investigated for two expansion ratios, 1.9432 and 3.5. The SIMPLE algorithm was used in the finite volume solver to solve the Naiver–Stokes equation. Temperature difference at inlet and boundaries, heat transfer coefficient, Nusselt number, coefficient of skin friction, and temperature contours were reported. The results show that when nanofluids are used, the coefficient of heat transfer and Nusselt number increased at all volume fractions and Reynolds number for both the expansion ratios. The coefficient of heat transfer at

φ

= 5% was higher by 9.14% and 9.68% than the pure water for ER = 1.9432 and ER = 3.5 at Re. 500. At

φ

= 5%, the outlet temperature for the duct decreased by 10 K and 5 K when compared to the pure water for ER = 1.9432 and ER = 3.5 at Re. 500. Coefficient of skin friction and outlet temperature decreased for both the volume fractions in both the expansion ratios. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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41 pages, 19592 KiB

Open AccessArticle

Versatile Tool for Parametric Smooth Turbomachinery Blades

by Kiran Siddappaji and Mark G. Turner

Aerospace 2022, 9(9), 489; https://doi.org/10.3390/aerospace9090489 - 31 Aug 2022

Cited by 3 | Viewed by 3682

Abstract

Designing blades for efficient energy transfer by turning the flow and angular momentum change is both an art and iterative multidisciplinary engineering process. A robust parametric design tool with few inputs to create 3D blades for turbomachinery and rotating or non-rotating energy converters [...] Read more.

Designing blades for efficient energy transfer by turning the flow and angular momentum change is both an art and iterative multidisciplinary engineering process. A robust parametric design tool with few inputs to create 3D blades for turbomachinery and rotating or non-rotating energy converters is described in this paper. The parameters include axial–radial coordinates of the leading/trailing edges, construction lines (streamlines), metal angles, thickness-to-chord ratio, standard, and user-defined airfoil type among others. Using these, 2D airfoils are created, conformally mapped to 3D stream surfaces, stacked radially with multiple options, and they are transformed to a 3D Cartesian coordinate system. Smooth changes in blade curvature are essential to ensure a smooth pressure distribution and attached flow. B-splines are used to control meanline curvature, thickness, leading edge shape, sweep-lean, and other parameters chordwise and spanwise, making the design iteration quick and easy. C2 curve continuity is achieved through parametric segments of cubic and quartic B-splines and is better than G2. New geometries using an efficient parametric scheme and minimal CAD interaction create watertight solid bodies and optional fluid domains. Several examples of ducted axial and radial turbomachinery with special airfoil shapes or otherwise, unducted rotors including propellers and wind and hydrokinetic turbines are presented to demonstrate versatility and robustness of the tool and can be easily tied to any automation chain and optimizer. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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23 pages, 11626 KiB

Open AccessArticle

Anisotropic Turbulent Kinetic Energy Budgets in Compressible Rectangular Jets

by Kalyani Bhide and Shaaban Abdallah

Aerospace 2022, 9(9), 484; https://doi.org/10.3390/aerospace9090484 - 30 Aug 2022

Cited by 5 | Viewed by 1756

Abstract

Turbulence is governed by various mechanisms, such as production, dissipation, diffusion, dilatation and convection, which lead to its evolution and decay. In high-speed flows, turbulence becomes complicated due to compressibility effects. Therefore, the goal of the current work is to characterize these mechanisms [...] Read more.

Turbulence is governed by various mechanisms, such as production, dissipation, diffusion, dilatation and convection, which lead to its evolution and decay. In high-speed flows, turbulence becomes complicated due to compressibility effects. Therefore, the goal of the current work is to characterize these mechanisms in rectangular supersonic jets by directly evaluating their contributions in turbulent kinetic energy (TKE) budget equation. The budgets are obtained using high-fidelity Large Eddy Simulations that employ WALE subgrid-scale model. Jet nearfield data are validated with PIV experimental measurements, available from the literature, which include mean flow and second-order statistics. To ensure spatial resolution and temporal convergence of higher-order statistics, qualitative performance metrics are presented. The results indicate that TKE production is the major source term, while pressure-dilatation term acts as a sink throughout the development of the jet. The diffusion term has the highest contribution from triple-velocity correlations, followed by pressure diffusion and molecular diffusion. Subgrid-scale diffusion and dissipation are also evaluated and their contributions are minimal. Each term is presented on both minor and major axis plane and reveals asymmetry in the statistics. A detailed explanation of budget contributions is provided, leading to the mechanisms responsible for the anisotropy of TKE. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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21 pages, 19295 KiB

Open AccessArticle

Numerical Study of the Ratio of Depth-to-Print Diameter on the Performance and Flow Characteristics for a Dimpled, Highly Loaded Compressor Cascade

by Long Wang, Huawei Lu, Zhitao Tian, Yi Yang, Shuang Guo, Hong Wang and Xiaozhi Kong

Aerospace 2022, 9(8), 422; https://doi.org/10.3390/aerospace9080422 - 03 Aug 2022

Cited by 1 | Viewed by 1604

Abstract

The influence of the ratio of dimple depth-to-print diameter (

λ

) on the highly loaded compressor cascade NACA0065-K48 is investigated based on the Reynolds-averaged Navier–Stokes (RANS) method. Simulations are conducted with a validated shear-stress transportation (SST) turbulence model coupled with the Gamma-Theta [...] Read more.

The influence of the ratio of dimple depth-to-print diameter (

λ

) on the highly loaded compressor cascade NACA0065-K48 is investigated based on the Reynolds-averaged Navier–Stokes (RANS) method. Simulations are conducted with a validated shear-stress transportation (SST) turbulence model coupled with the Gamma-Theta (

γ - {Re}_{θ}

) transition model at the inlet Mach number of 0.7. At 5~25% of the axial chord on the suction surface, four rows of dimples are arranged in parallel, and the dimples’ spacing is 4 mm. Moreover, there are five kinds of

λ

, ranging from 0.125 to 0.875, which determine the pressed arc of a spherical dimple. Three flow regimes (diffuser–confuser flow, tornado-like vortex and horseshoe vortex) with the same topological structure are observed in these dimples, which affect the flow and performance of the cascade by changing the energy distribution. The distribution of turbulent kinetic energy (TKE) reflects the disturbance of the tornado-like vortex in the inferior arc dimples (

λ = 0.375

) intensely, whereas the disturbance of the horseshoe vortex in superior arc dimples (

λ = 0.625, 0.875

) is relatively weak. Numerical results indicate that the loss of the corner separation can be reduced with a dimples array, which is mainly related to the vertical climbing of the lateral flow that delays the starting point of the corner separation and weakens the mixing process. However, the loss in the wake of the dimpled cascades increases, which is caused by the thickened boundary layer induced by the high turbulent vortices. The dimpled cascade with

λ = 0.625

can achieve the most significant loss reduction (13.47%), while ensuring the pressurization capacity. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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16 pages, 8178 KiB

Open AccessArticle

Parametric Research and Aerodynamic Characteristic of a Two-Stage Transonic Compressor for a Turbine Based Combined Cycle Engine

by Hengtao Shi

Aerospace 2022, 9(7), 346; https://doi.org/10.3390/aerospace9070346 - 28 Jun 2022

Cited by 3 | Viewed by 1522

Abstract

This paper researches the parametric optimization of a two-stage transonic compressor having a large air bypass at partial rotating speed according to flow analysis for a turbine-based combined cycle engine (TBCC). To obtain adequate thrust, the inlet transonic compressor of the turbofan part [...] Read more.

This paper researches the parametric optimization of a two-stage transonic compressor having a large air bypass at partial rotating speed according to flow analysis for a turbine-based combined cycle engine (TBCC). To obtain adequate thrust, the inlet transonic compressor of the turbofan part of the TBCC is required to have a wider frequently used corrected rotating speed range and a larger mass-flow rate at low rotating speed, which is different from a typical transonic compressor. The one-dimensional blade design parameters and flow path of the baseline two-stage transonic compressor are introduced. With the widely used CFD software Numeca, the three-dimensional flow fields of the baseline transonic compressor and effects of the flow path between Stage 1 and Stage 2 on the inlet mass flow rate are analyzed for indicating the further improvement direction. For design speed (N_C = 1.0), to improve the efficiency at the design point, parametric research is carried out on Rotor 2 to optimize the shock structure and strength, resulting in enhanced efficiency at the design point due to reduced shock loss of Rotor 2. For partial speed (N_C = 0.8 and 0.7), since the flow field analysis indicates that the flow blockage in S1 limits the entire mass flow rate, the parametric redesign of stator S1 aims at obtaining an increased blade throat width to enhance the flow capacity of S1. Simulation confirms the increase in the mass-flow rate and efficiency at partial speed due to the reduction in flow blockage and related viscous losses. Aerodynamic analysis at representative operation points indicates that the modifications of R2 and S1 lead to obvious aerodynamic improvement at all rotating speeds (N_C = 1.0 to 0.7), while maintaining sufficient stall margin. Full article

(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))

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