Hub-tip Ratio Research Articles

Aerodynamic modification and optimization of intermediate pressure compressor in marine intercooled recuperated gas turbine

The intercooling recuperated cycle (ICR) is commonly employed in marine gas turbines to enhance thermal efficiency. However, the addition of an intercooler may lead to the increased dimension and structural complexity of marine ICR gas turbines. To address this issue, we propose an improved configuration of the intermediate pressure compressor – an axial-centrifugal combined compressor (ACC) with high inlet hub-tip ratio and high flow rate. The aerodynamic performance of the ACC at multi-operating points is optimized via an improved free-form deformation method for the parametric modeling of the flow paths and blades of turbomachinery. The result indicates that the number of stages decreases from 6 to 3 and the axial length is reduced by 38.3% after modification. The adiabatic efficiency of the optimized ACC at the design and low-speed operating points is improved by 1.18% and 6.48% respectively. Additionally, the ACC redesigned scheme can reduce the axial length, maximize the flow path space utilization, enhance the stage load capacity, and significantly improve the low-speed performance. This provides a reference for developing advanced marine ICR gas turbines with high power and low fuel consumption.

Численное исследование сверхзвуковой ступени осевого компрессора. Влияние втулочного отношения на ее параметры

Countless combinations of sizes and shapes of the flow path could ensure the specified flow rate and pressure ratio of the axial compressor stage. Programs based on the mathematical models are an effective tool in initial design and preliminary selection of the optimal option. The RROK-GPD-22 software program is briefly being described, it solves the problem on the basis of the pressure loss model and deflection capacity of the A. Komarov lattice, theoretic rigorous calculation of oblique and direct shocks, as well as empirical equations and coefficients. Models were checked by comparison with data on the Rotor 37 NASA test stage. Stages were calculated with different ratio of the cross-sectional area at the outlet of the impeller to that at its inlet and stages with the hub-tip ratios of 0.400 ... 0.728 with different swirl at the impeller inlet. Results are provided in determining the hub-tip ratio influence on the efficiency, pressure ratio and specific stage performance.

Review of Numerical Simulation Research on Submersible Mixer for Sewage

Submersible mixer is the core machinery of sewage treatment, which has a profound effect on the efficiency and performance of the submersible mixing system of sewage treatment. This paper summarizes the scientific research results of submersible mixer in recent years from four aspects: structure and energy characteristics of submersible mixer, numerical simulation calculation method, flow field characteristics, and factors affecting the flow field characteristics. The existing published literature indicates that the structure of submersible mixer for sewage is complicated and the parameters of energy characteristics are special. Few experimental studies are conducted, and mostly numerical calculations are based on clear water as the medium. The mixture model based on the Euler–Euler method is the multiphase flow model currently applied in the field of submersible mixer research. Many factors affect the mixing effect of a submersible mixer, such as installation factors (the location and angle of installation) and impeller design parameters (blade gap, hub-tip ratio, blade angle, etc.), all having a significant impact on the mixing performance. Meanwhile, the development and trends of submersible mixer technology are prospected, and the future directions of further research are proposed: establishing a more suitable numerical calculation method for submersible mixer based on the Euler–Lagrange model; constructing the calculation model with real fluid—solid-liquid two-phase flow as the medium; exploring the influence of various parameters on flow field characteristics of mixing fluid; getting the mixing mechanism of submersible mixer; promoting the development of submersible mixer; and realizing the efficient and stable operation of submerged mixing system.

Influence of Hub Contouring on the Performance of a Transonic Axial Compressor Stage with Low Hub-Tip Ratio

Influence of Hub Contouring on the Performance of a Transonic Axial Compressor Stage with Low Hub-Tip Ratio

Parametric Study of Magnus Wind Turbine with Spiral Fins using BEM Approach

The aim of this work is to carry out an aerodynamic analysis to assess the power and identify the characteristics of the horizontal axis Magnus type wind turbine with spiral fins. A parametric study is achieved to analyze the effects of the different influence parameters such as the turbine tip speed ratio, the cylinder spinning ratio, the blade aspect ratio and the cylinder hub-tip ratio. The analysis approach adopted in this study is the Blade Element Momentum BEM using the experimental lift coefficient data for the configuration of spinning cylinders with spiral fins. In this analysis, losses are not taken in consideration. Both axial and angular interference coefficients are evaluated for this type of wind turbine. The former is assessed by solving a quadratic equation and the latter is calculated from a classic formulation including the term of spinning. An iterative process is followed to achieve this task. Concerning the obtained results, the aerodynamic characteristics of the Magnus wind turbine, analyzed in this study, provide some elucidation to lead a successful preliminary design of this novel type of machine.

Windmilling Characteristics of a Contra-Rotating Fan

Abstract In the present experimental study, a low aspect ratio, low hub-tip ratio contra-rotating axial fan is investigated to understand its performance under windmilling conditions. Two configurations are tested; in the first configuration (event A), the front rotor of the contra-rotating fan is powered and the rear rotor is allowed to windmill; in the second configuration (event B), the rear rotor of the contra-rotating fan is powered and the front rotor is allowed to windmill. The spanwise distribution of the loading coefficient and the flow angles at different streamwise positions reveal the details of the flow development across the rotors. Though the average total pressure drops across the windmilling rotor for both the events, a small spanwise region behaves as a fan or a stirrer. Thus, a “neutral radius” on the windmilling rotor is identified for both events A and B. The neutral radius appears close to the tip for event A and it appears close to the hub for event B. Thus, the span regions close to the tip behave as a fan for event A and the span regions close to the hub behave as a stirrer for event B. It is also observed that the neutral radius shifts to a lower span location as the flow coefficient reduces. Thus, the flow coefficient is a significant parameter that decides the position of the neutral radius. Further, the unsteady pressure measurements recorded at the casing capture the fundamental phenomena during the stall inception. The paper thus relates the similarities and unveils the contrasting features of the windmilling events A and B. In summary, this paper discusses the performance, flow physics, and stall inception characteristics of a contra-rotating axial fan under windmilling conditions.

Experimental studies into the performance of the lead coolant axial pump wet ends to justify main circulation pumps for the HMLC reactor plant circuits

The paper presents the results of the studies to justify the design solutions for the main circulation pumps of the heavy liquid-metal cooled reactor plant circuits. A substantial difference has been shown in the performance of pumps for the heavy liquid-metal coolant transfer. The studies have confirmed the qualitative difference in the cavitation performance of coolants, the state of the gases and vapors they contain, the influence of supply and discharge devices, and the effects of the impeller blade section performance and geometry and the hub-tip ratio on the pump performance. The studies were performed based on NNSTU’s lead-cooled test facilities with the coolant temperature in a range of 440 to 550 °C and the coolant flow rate of up to 2000 t/h. The outer diameter of the impellers and the straightening devices was about 200 mm, and the thickness of the flat 08Kh18N10T-steel blades was 4.0 mm and that of the airfoil blades was up to 6.0 mm. The pump shaft speed changed in a stepped manner from 600 rpm to 1100 rpm after each 100 rpm. The studies were conducted to justify the engineering and design solutions for pumps as applied to conditions of small and medium plants with fast neutron lead cooled reactors currently under investigation at NNSTU (BRS-GPG). The experimental results can be recommended for use to design other HLMC transfer pumps.

Efficient Method to Predict Rotor Noise Scattered by an Axisymmetric Body

This paper presents an efficient method for predicting noise radiated from rotating sources and scattered by an axisymmetric body, in which a frequency-domain numerical method and a null-field method are employed to compute the acoustic radiation and scattering phenomena, respectively. The novelty of the present research is that an advanced method is proposed to locate fictitious interior observers inside the scattering surface, contributing to that the incident acoustic pressure received by the fictitious interior observers can be efficiently computed. Numerical cases show that the developed method ensures high computational accuracy and significantly improves the computational efficiency compared with existing methods, showing an appealing application potential in efficiently predicting rotor noise scattered by the shaft and casing. Parametric studies are carried out to investigate the effects of the hub–tip ratio and the rotating frequency on a rotor noise scattered by a hub.

Design Work of a Compressor Stage Through High-To-Low Speed Compressor Transformation

Low-speed model testing has advantages such as great accuracy and low cost and risk, so it is widely used in the design procedure of the high pressure compressor (HPC) exit stage. The low-speed model testing project is conducted in Nanjing University of Aeronautics and Astronautics (NUAA) to represent aerodynamic load and flow field structure of the seventh stage of a high-performance ten-stage high-pressure compressor. This paper outlines the design work of the low speed four-stage axial compressor, the third stage of which is the testing stage. The first two stages and the last stage provide the compressor with entrance and exit conditions, respectively. The high-to-low speed transformation process involves both geometric and aerodynamic considerations. Accurate similarities demand the same Mach number and Reynolds number, which will not be maintained due to motor power/size and its low-speed feature. Compromises of constraints are obvious. Modeling principles are presented in high-to-low speed transformation. Design work was carried out based on these principles. Four main procedures were conducted successively in the general design, including establishment of low-speed modeling target, global parameter design of modeling stage, throughflow aerodynamic design, and blading design. In global parameter design procedure, rotational speed, shroud diameter, hub-tip ratio, midspan chord, and axial spacing between stages were determined by geometrical modeling principles. During the throughflow design process, radial distributions of aerodynamic parameters such as D-factor, pressure-rise coefficient, loss coefficients, stage reaction, and other parameters were obtained by determined aerodynamic modeling principles. Finally, rotor and stator blade profiles of the low speed research compressor (LSRC) at seven span locations were adjusted to make sure that blade surface pressure coefficients agree well with that of the HPC. Three-dimensional flow calculations were performed on the low-speed four-stage axial compressor, and the resultant flow field structures agree well with that of the HPC. It is worth noting that a large separation zone appears in both suction surfaces of LSRC and HPC. How to diminish it through 3D blading design in the LSRC test rig is our further work.

Effect of variation in axial spacing and rotor speed combinations on the performance of a high aspect ratio contra-rotating axial fan stage

This article reports a parametric study on the performance of a high aspect ratio, low speed contra-rotating fan stage. Parameters namely speed ratios of the two rotors and axial spacing between the rotors that play a significant role on the overall performance of the contra-rotating fan stage were evaluated. The rotors have a low hub-tip ratio of 0.35 and chord of 45 mm. The two rotors were designed to develop a pressure rise of 1100 Pa and 900 Pa, respectively, when operating at 2400 r/min and developing a mass flow rate of 6 kg/s. In order to evaluate the performance of the designed rotors, measurements of total pressure at the entry of rotor-1, between the rotors and the exit of rotor-2 were taken using total pressure probe rake, 4-hole probe and a Kiel probe rake. The experiments were conducted for different speed combinations of rotor-1 and rotor-2. All these speed combinations were studied separately for different axial spacing. The performance plots revealed the existence of two stall limits namely, partial stall and full stall. For lower throttle positions, rotor-2 was observed to stall. Further lowering the mass flow rate; reduces the pressure rise capacity of the stage due to stalling of rotor-1 as well as rotor-2. For the design speed operation of rotor-1 in combination with an off-design speed of rotor-2, the flow parameters change significantly. A higher rotational speed of rotor-2 generates a stronger suction effect leading to an overall improvement in the performance of the whole stage. The effect of variation in the axial spacing between the rotors was also studied. The strongest suction effect between the rotors was observed at an axial spacing of 0.9 chord.

축류펌프 안내깃의 성능 향상을 위한 수치해석적 연구

This paper presents a numerical study on the performance improvement of axial-flow pump with guide vanes. Design optimization for guide vanes in an axial-flow pump has been studied through the implementation of a commercial CFD code and DOE (design of experiments). We also discussed how to improve the performance of the axial-flow pump by designing the guide vanes. Geometric design variables were defined by the meridional plane and vane plane development of guide vanes. The effect of hub tip ratio analyzed the meridional plane of guide vanes. The importance of the geometric design variables was analyzed using 2k factorial designs. The objective functions for guide vane geometric variables were defined as the total efficiency and the total head at the design flow rate. From the 2k factorial design results, the important design variables were found and the performance was increased in comparison with the base design model.

초소형 무인기 추진용 프로펠러의 전산해석 및 풍동시험

The MH-75 propeller for the MAV propulsion is designed using a free vortex design method which considers design parameters such as the hub-tip ratio, the twist angle distribution, the maximum camber location and the chord length of the propeller blade. Aerodynamic characteristics of the MH-75 propeller are predicted by changing the flight speed using the frequency domain panel method. And, the thrust characteristics of the MH-75 propeller are measured using the balance system of the subsonic wind tunnel for the validation of numerical results. The performance characteristics of the MH-75 propeller satisfied with design requirements. Numerical results of the MH-75, which are predicted by the frequency domain panel method, are more agree with experimental results compare with XFOIL.

Performance Improvement of High Speed Jet Fan

In this paper, a numerical study has been carried out to investigate the influence of jet fan design variables on the performance of a jet fan. In order to achieve an optimum jet fan design and to explain the interactions between the different geometric configurations in the jet fan, three-dimensional computational fluid dynamics and the DOE method have been applied. Several geometric variables, i.e., hub-tip ratio, meridional shape, rotor stagger angle, number of rotor-stator blades and stator geometry, were employed to improve the performance of the jet fan. The objective functions are defined as the exit velocity and total efficiency at the operating condition. Based on the results of computational analyses, the performance of the jet fan was significantly improved. The performance degradations when the jet fan is operated in the reverse direction are also discussed.

Aerodynamic design and analysis of a propeller for a micro air vehicle

A U-80 propeller and its modified version, U-75 propeller, are used for a micro air vehicle. The performance characteristics of a U-80 propeller and a U-75 propeller have not much known in the published literature. Thus, their aerodynamic characteristics are investigated using a lifting surface numerical method. The lifting surface method is validated by comparing computed results with measured data in a wind tunnel. From the computed results, it is found that the U-75 propeller produces larger thrust with higher efficiency than the U-80 propeller. To enhance the performance of these propellers, a new propeller is designed by following the sequential design procedures with the design parameters such as hub-tip ratio, maximum camber and its position, and chord length distribution along the radial direction. The performance of the designed propeller is shown to be improved much comparing with those of both the U-80 and U-75 propellers.

Theoretical model for sound radiation from annular jet pipes: far- and near-field solutions

An analytical model is presented for sound radiation from a semi-infinite unflanged annular duct. The duct carries a jet which issues into a uniform mean flow while an inner cylindrical centre body extends downstream from the duct exit. This geometrical arrangement forms an idealized representation of a turbofan exhaust where noise propagates along the annular bypass duct, refracts through the external bypass stream and radiates to the far field. The instability wave of the vortex sheet and its interaction with the acoustic field are accounted for in an exact way in the current solution. Efficient numerical procedures are presented for evaluating near-field and far-field solutions, and these are used as the basis for a parametric study to illustrate the effect of varying the hub–tip ratio, and the ratio of jet velocity to external flow velocity. Since the ‘Kutta’ condition can be turned on and off in the current solution, this capability is used to assess the effect of vortex shedding on noise radiation. Far-field directivity patterns are presented for single modes and also for a multi-mode ‘broadband’ source model in which all cut-on modes are assumed to be present with equal modal power. Good agreement is found between analytical solutions and experimental data. Near-field pressure maps of the acoustic and instability portions of the solution are generated for selected tones.

Application of casing treatment to an industrial axial-flow fan

This paper deals with an experimental investigation into the influence of a vaned recess casing treatment on the performance of an industrial-type axial-flow fan with a hub-tip ratio of 0.4. The treatment has been tested in a variety of configurations relative to the fan, with an emphasis on the amount of fan blade tip exposure to the treatment. Two sets of blading, one of which is of the fully reversible type, have been investigated. Detailed flow measurements have been carried out with a slanted hot wire probe to provide an insight into the operation of the device and into the nature of the rotating stall in the solid casing configuration. Strain gauges have been employed to enable blade stresses to be recorded and an in-duct microphone to enable comparative tests on fan noise has also been used.

Performance of straight-walled annular diffusers with swirling flow

AbstractPerformance data are presented for eight annular diffuser families, a family being defined by the inner and outer cone angles and the inlet hub-tip ratio. These results include profiles of velocity and total pressure across the inlet and outlet lanes as well as overall pressure recovery coefficients. Diffuser outer cone angles range from 10° to 60° and inner cone angles from 59° to -19°. Swirl angles were varied from 0° up to 44°. Each diffuser family was tested over a range of lengths and swirl angles resulting in over ninety different tests. A procedure for extending the non-swirling definition of effectiveness to swirling flows is presented and used to evaluate a limiting swirl angle for separation for free-vortex-type inlet swirl. Comparisons are made to several measured values of flow separation. Some experimental diffusers exhibited a violently unsteady hub stall which apparently consisted of rotating reverse flow regions.

A Study of Stall in a Low Hub–Tip Ratio Fan

An investigation has been carried out in order to define the process of rotating stall inception in a low-speed, low hub–tip ratio fan. Based on elementary cascade analysis, the fan would be expected to stall from the root. However, considerable experimental evidence indicates that tip stall is more frequently incurred. Although the analysis has been undertaken for a specific fan, it is considered to be representative of a broad range of machines. The analysis has involved two primary considerations, first the effect of streamtube contraction, which has been studied theoretically, and second, real flow effects (those not contained in the theoretical model), which have been studied experimentally. The study of streamtube contraction indicates that the root rematches to a more stable operating point, thus alleviating some of the problems in that region. The experimental investigation was undertaken on an isolated rotor, with successive build modifications to increase the likelihood of rotating stall inception at the root. It was apparent that real fluid effects tended to steepen the root pressure rise characteristic, thus enhancing the stability in that region. The performance of the fan at the tip tended to be poor, providing a pressure characteristic with a lower negative gradient than anticipated, indicating less stability than simple flow models would suggest. Hot-wire flow mapping at the rotor exit supported the overall conclusion that the rotor showed a strong reluctance to stall at the root apparently due to “centrifuging” of the boundary layer toward the tip.

Discussion: “A Study of Stall in a Low Hub–Tip Ratio Fan” (Soundranayagam, M., and Elder, R. L., 1993, ASME J. Turbomach., 115, pp. 10–16)

Discussion: “A Study of Stall in a Low Hub–Tip Ratio Fan” (Soundranayagam, M., and Elder, R. L., 1993, ASME J. Turbomach., 115, pp. 10–16)

Closure to “Discussions of ‘A Study of Stall in a Low Hub–Tip Ratio Fan’” (1993, ASME J. Turbomach., 115, p. 17)

Closure to “Discussions of ‘A Study of Stall in a Low Hub–Tip Ratio Fan’” (1993, ASME J. Turbomach., 115, p. 17)