scholarly journals A new design way for cylindrical blades with adjustable inlet blade angles

2019 ◽  
Vol 11 (6) ◽  
pp. 168781401983017
Author(s):  
Jing Yan ◽  
Xiaobing Liu ◽  
Li Peng ◽  
Jianan Li
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Design Flow ◽  
Improve Performance ◽  
Plan View ◽  
Pump Design ◽  
New Approach ◽  
Traditional Design ◽  
Inlet Angle ◽  
Blade Leading Edge

A new approach for cylindrical blade design is presented in this article. Authors of this article analyzed the main reasons which are responsible for the low efficiency of untwisted blades and found out that the shock losses along the blade leading edge are much higher than those of twisted blades. Furthermore, based on the analysis, this article proposed a new design approach that is different from the traditional one. This new approach can reduce hydraulic losses at blade leading edge and improve performance and efficiency of cylindrical blades. In the traditional design process, to draw blade projection in plan view, an incidence at intersection of blade leading edge and inner streamline on the meridional section is selected for calculating blade inlet angle accurately. Because the incidence and the blade inlet angle at the intersection of blade leading edge and outer streamline are formed automatically, the blade inlet angles at this point are not suitable for oncoming flow direction, generating noticeable shock losses at this place. In the new design program, blade inlet angles at both intersection points formed by blade leading edge and the outer, inner streamlines are accurately calculated. This makes the shock losses generated by blade leading edge be minimized. Moreover, in conventional design, the projection of blade pressure side into plan view consists of only one plane curve. In the new design way, projection of blade surface in plan view is composed of two curves joined smoothly and continuously. Two impellers with fundamentally identical geometrical parameters were designed and manufactured, and the only difference is that their cylindrical blades were calculated and configured by applying a traditional design method or a the new approach. Test findings from an open loop indicate that in a wide load range from 0.8 to 1.2 times design flow rate, both head and efficiency of the new pump were raised. Over the operating range, efficiency of the new pump increased by 0.5% to 2.7%. Particularly, for higher flow rate, pump performance was improved significantly, and the increase of efficiency at pump design point arrived at 2.7%. The results suggest that the new approach presented in this article offers an effective and useful means to improve performance of low specific speed pumps.

Analysis of Noise Generated by Low Solidity Cascade Diffuser in a Centrifugal Blower

2008 ◽  
Author(s):  
Daisaku Sakaguchi ◽  
Masahiro Ishida ◽  
Hironobu Ueki ◽  
Hiroshi Hayami ◽  
Yasutoshi Senoo
Keyword(s):  
Flow Rate ◽  
Leading Edge ◽  
Broadband Noise ◽  
Frequency Noise ◽  
Centrifugal Blower ◽  
Discrete Frequency ◽  
Edge Location ◽  
Rotating Impeller ◽  
Low Solidity Cascade Diffuser ◽  
Blade Leading Edge

This paper deals with the effect of the blade leading edge location (RLSD) of a low solidity cascade diffuser (LSD) on noise and diffuser performance in a centrifugal blower. The noise of the LSD was measured and analyzed comparing with that of vaneless diffuser (VLD) in view points of overall noise, discrete frequency noise and broadband noise. The numerical flow analysis was conducted in the impeller and the diffuser by using a Navier-Stokes solver. The noise of the VLD varied little in a wide flow rate range, on the other hand, that of the LSD increased remarkably in the small flow rate by about 7 dB. The noise of the LSD did not increase near the design flow and was almost equal to that of the VLD. It was found that the increase in noise due to LSD is dependent mainly on the broadband noise between 600∼1000Hz, which was closely correlated to the lift force of the LSD blade. The two kinds of discrete frequency noise appeared due to an interaction between the rotating impeller and the LSD blade and another interaction between the rotating impeller blades and the reverse flow toward the impeller exit, but their influence on the overall noise were relatively small. By shifting the LSD blade leading edge location downstream from RLSD = 1.1 to 1.2, the noise was reduced by about 3 dB at the maximum without deterioration of the diffuser performance. The maximum lift coefficient of the LSD blade was achieved as high as 1.5 at the high attack angle of 17 degrees even in the case of RLSD = 1.2, resulting in improvement of the diffuser performance by about 40% and in reduction of the unstable flow range by about 11%.

Micro Air Injection and Its Unsteady Response in a Low-Speed Axial Compressor

2002 ◽  
Vol 124 (4) ◽  
pp. 572-579 ◽  
Author(s):  
Chaoqun Nie ◽  
Gang Xu ◽  
Xiaobin Cheng ◽  
Jingyi Chen
Keyword(s):  
Flow Rate ◽  
Axial Compressor ◽  
Leading Edge ◽  
Injection Rate ◽  
Tip Clearance ◽  
Air Injection ◽  
New Approach ◽  
Low Speed ◽  
Flow Disturbances ◽  
The Stability

A new approach, steady micro air injection from the casing, is proposed to improve the stability of a three-stage low-speed axial compression system. Although the injection rate is designated to be only a few ten thousandth of the compressor flow rate, such an injection is able to trigger the unsteady response and thus lower the mass flow rate at stall for up to 5.83%. At the same time, it keeps the steady compressor characteristic with no injection unchanged. In order to verify that the compressor response is indeed unsteady, experiments at various injection configurations are performed, which include different injection angles, axial gaps between injector and blade leading edge, radial penetration of injector and the amount of injected air. Evidences of the unsteady response are further demonstrated through dynamic signal analysis using a wavelet-based method to show the behavior of early flow disturbances under the influence of injection. Numerical analyses performed at near stall condition show that the tip clearance vortices do response to the micro-injection, and thus delay the inception of stall.

Computer-Aided Design and Numerical Flow Analysis of Axial-Flow Pump With Inducer

2006 ◽  
Author(s):  
Yaojun Li ◽  
Fujun Wang
Keyword(s):  
Flow Characteristics ◽  
Axial Flow ◽  
Leading Edge ◽  
Hydraulic Loss ◽  
Trailing Edge ◽  
Impeller Blade ◽  
Pump Design ◽  
Axial Flow Pump ◽  
Flow Pump ◽  
Blade Leading Edge

Axial-flow pump equipped with inducer are widely used in marine propulsion systems. The interaction of inducer and impeller has significant effect on the performance of pump. In this study, a special axial-flow pump is designed and analysed by CAD-CFD approaches to study the interaction of inducer and impeller. The pump includes two main elements, an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. The 3D pump solid model is generated by taking the data file as interface between hydraulic-design and 3D modelling. A computational fluid dynamics code is used to investigate the flow characteristics and performance of the axial-flow pump. Numerical simulation is performed by adopting 3D RANS equations with RNG k-epsilon turbulence model. An unstructured grid system and the finite-volume method are used for the solution procedure of the discretized governing equations for this problem. The rotator-stator interaction is treated with a multiple reference frame (MRF) strategy. Computations are performed in different cases: 7 different relative circumferential angles (Δθ) between the inducer blade trailing edge and the impeller blade leading edge, 3 different axial gaps (G) between the inducer and the impeller. Variation of the hydraulic loss in the rotator is obtained with the change of delta theta. The numerical results show that the pressure generated is minimum in case of (G = 3%D). This indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances are predicted and compared to the experimental measurements. The current investigation leads to a thorough enough understanding of the flow characteristics in axial-flow pumps with complex configurations. Recommendations for future modifications and improvements to the pump design are also given.

Design and Numerical Flow Analysis of a LNG Power Recovery Turbine

2013 ◽  
Author(s):  
Kaiqiang Li ◽  
Jinju Sun ◽  
Juntao Fu ◽  
Peng Song
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Flow Behavior ◽  
Leading Edge ◽  
Cavitating Flow ◽  
Design Flow ◽  
Technical Requirement ◽  
Edge Region ◽  
Flow Rates ◽  
Overall Efficiency

The liquefaction process of natural gas often operates at high pressure level, thus the LNG product is of very high pressure and must be reduced to satisfy the technical requirement for storage and transportation. Traditionally, the high-pressure LNG is expanded isenthalpically by means of J-T valves but this introduces an unexpected temperature rise, leading to vaporization of LNG product and subsequently a reduced delivery. An efficient alternative is using the LNG expanders to replace the J-T valves and achieve a near-isentropic expansion and subsequently suppress the cavitation. In the present study, a single stage LNG turbine expander is developed as a replacement of J-T valve for the purpose of cavitation suppression. The cavitating flow behavior is investigated by using a multiphase cavitation model. The effect of impeller geometric parameters on the turbine flow and performance has been identified through sensitivity studies. The following are demonstrated: (1) The predicted turbine overall efficiency is 91.34%, shaft power delivery is 81.16kW, temperature drop is 0.84 K; and the overall vaporization rate is less than a percentage. (2) Cavitation is encountered in the impeller leading edge region and half stream-wise region, resulting respectively from the viscous dissipation and flow separation. (3) At larger than design flow rates, the predicted turbine overall efficiency decreases nonlinearly with the flow rate due to cavitation zone growth in the leading edge region; at lower than design flow rates, the overall efficiency increases with the flow rate, due to cavitation zone decrease in the half streamwise region. (4) Cavitating flow behavior is sensitive to impeller geometry tuning. Variation of the impeller inducer twist angle reduces the trialing edge cavitation and subsequently improves the turbine overall performance. (5) Cavitation flow behavior is also sensitive to the radial gap size of the nozzle and impeller.

Micro Air Injection and Its Unsteady Response in a Low-Speed Axial Compressor

2002 ◽  
Author(s):  
Chaoqun Nie ◽  
Gang Xu ◽  
Xiaobin Cheng ◽  
Jingyi Chen
Keyword(s):  
Flow Rate ◽  
Axial Compressor ◽  
Leading Edge ◽  
Injection Rate ◽  
Tip Clearance ◽  
Air Injection ◽  
New Approach ◽  
Low Speed ◽  
Flow Disturbances ◽  
The Stability

A new approach, steady micro air injection from the casing, is proposed to improve the stability of a three-stage low-speed axial compression system. Although the injection rate is designated to be only a few ten thousandth of the compressor flow rate, such an injection is able to trigger the unsteady response and thus lower the mass flow rate at stall for up to 5.83%. At the same time, it keeps the steady compressor characteristic with no injection unchanged. In order to verify that the compressor response is indeed unsteady, experiments at various injection configurations are performed, which include different injection angles, axial gaps between injector and blade leading edge, radial penetration of injector and the amount of injected air. Evidences of the unsteady response are further demonstrated through dynamic signal analysis using a wavelet-based method to show the behavior of early flow disturbances under the influence of injection. Numerical analyses performed at near stall condition show that the tip clearance vortices do response to the micro injection and thus delay the inception of stall.

Multi-Point Optimization of Recirculation Flow Type Casing Treatment in Centrifugal Compressors

2016 ◽  
Author(s):  
Min Thaw Tun ◽  
Daisaku Sakaguchi ◽  
Ryusuke Numakura ◽  
Baotong Wang
Keyword(s):  
Flow Rate ◽  
Flow Separation ◽  
Optimization Design ◽  
Leading Edge ◽  
Design Flow ◽  
Centrifugal Compressors ◽  
Rate Condition ◽  
Recirculation Flow ◽  
Casing Treatment ◽  
Flow Type

In this paper, an optimization design approach to recirculation flow type casing treatment for centrifugal compressors of turbochargers has been performed. The optimization code is a global exploring system based on a metamodel assisted evolutionary algorithm. In this study, the objective functions of the optimization are adiabatic efficiency at design flow rate and near surge flow rate condition. Several optimized shapes on a “Pareto front” are selected in order to discuss the effect of casing treatment at the point of view of suppression of flow separation and a reduction of leading edge flow separation. The influence of optimized recirculation flow rate on the optimization output is also discussed. Increase in adiabatic efficiency of optimized casing treatment at near surge flow rate is discussed by the streamwise relative velocity distribution, reversed flow zone, static entropy distribution and flow incidence at impeller inlet. Detailed sensitivity of design variables on the adiabatic efficiency at design and off-design conditions was carried out.

Overall Effectiveness for a Film Cooled Turbine Blade Leading Edge With Varying Hole Pitch

2010 ◽  
Author(s):  
Thomas E. Dyson ◽  
Dave G. Bogard ◽  
Justin D. Piggush ◽  
Atul Kohli
Keyword(s):  
Turbine Blade ◽  
Hot Spots ◽  
Leading Edge ◽  
Stagnation Line ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Blowing Ratio ◽  
Cylindrical Holes ◽  
Overall Effectiveness ◽  
Blade Leading Edge

Overall effectiveness, φ, for a simulated turbine blade leading edge was experimentally measured using a model constructed with a relatively high conductivity material selected so that the Biot number of the model matched engine conditions. The model incorporated three rows of cylindrical holes with the center row positioned on the stagnation line. Internally the model used an impingement cooling configuration. Overall effectiveness was measured for pitch variation from 7.6d to 9.6d for blowing ratios ranging from 0.5 to 3.0, and angle of attack from −7.7° to +7.7°. Performance was evaluated for operation with a constant overall mass flow rate of coolant. Consequently when increasing the pitch, the blowing ratio was increased proportionally. The increased blowing ratio resulted in increased impingement cooling internally and increased convective cooling through the holes. The increased internal and convective cooling compensated, to a degree, for the decreased coolant coverage with increased pitch. Performance was evaluated in terms of laterally averaged φ, but also in terms of the minimum φ. The minimum φ evaluation revealed localized hot spots which are arguably more critical to turbine blade durability than the laterally averaged results. For small increases in pitch there was negligible decrease in performance.

scholarly journals Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

2001 ◽  
Vol 7 (3) ◽  
pp. 173-181
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen
Keyword(s):  
Flow Rate ◽  
Turbulence Intensity ◽  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Flow Region ◽  
Design Flow ◽  
Laser Doppler ◽  
Centrifugal Fan ◽  
Doppler Velocimetry ◽  
Flow Rates

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Hydraulic Design of Inlet Guide Vane and its Full Flow Passage Numerical Simulation on Centrifugal Pump

2014 ◽  
Author(s):  
Hucan Hou ◽  
Yongxue Zhang ◽  
Zhenlin Li ◽  
Xin Zhou ◽  
Zizhe Wang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Guide Vane ◽  
Hydraulic Performance ◽  
Design Flow ◽  
Inlet Guide Vane ◽  
Hydraulic Efficiency ◽  
Flow Passage ◽  
Setting Angle ◽  
Hydraulic Design

In order to effectively improve hydraulic performance of centrifugal pump on off-conditions, the hydraulic design of inlet guide vane (IGV) was completed by adopting two dimensional theory in-house code based on one kind of IS series of centrifugal pump, which can achieve pre-whirl regulation of centrifugal pump. During design process the trailing edge of vane is assumed as equal velocity moment condition, and the distribution of vane setting angle along meridional streamline is also given as a quartic function firstly, the camber line is then drawn by point-by-point integration method and thickened at both sides along circumferential direction. With local vortex dynamics diagnosis theory, the optimal improvement of vane space shape can be finished by adjusting the design parameters of vane setting angle distribution coefficient ap. The full flow passage numerical simulations of centrifugal pump with IGV device are completed to analyze the influence of pre-whirl regulation on hydraulic performance of centrifugal pump under various pre-whirl angles. The results show that the pre-whirl regulation can improve the hydraulic performance of centrifugal pump on off-conditions. Under the positive pre-whirl regulation conditions, the best efficient point shift to small flow rate zone, and under the negative pre-whirl regulation conditions it moves to large flow rate zone. Compared with the pump without IGV device at the same flow rate condition of 0.8Q (Q the design flow rate), the hydraulic efficiency of centrifugal pump with IGV device improves obviously and reaches up to 1.43%. Meanwhile compared with that installed with the straight vanes designed based on the traditional theory, the inner flow field of centrifugal pump with the designed vanes improves and the overall hydraulic efficiency of centrifugal pump is somewhat increased.

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