A Simple Calculation Method for Ratio of Relative Velocity Within Centrifugal Impeller Channel

A simple but accurate method of calculating ratio of relative velocities within centrifugal impeller channels is proposed using a one-dimensional flow model, whose major parameters are specific speed, non-dimensional root-mean square radius of the inducer inlet, slip factor, flow coefficient and flow angle at impeller exit. After the non dimensional relative velocity at inducer inlet and that at impeller exit are derived, the ratio of relative velocity at impeller exit to that at inducer inlet is obtained. In addition to this, the ratio is divided into two parts: one ratio for the inducer portion and another ratio for the radial portion of the impeller channel. The computations are conducted both for adiabatic inviscid flow and for two conditions assumed for viscous flow, in which one used an empirical relationship between the total pressure ratio and the peripheral speed of impeller and the other used experimental values for the total pressure ratio as a funtion of the flow rate. By the present simple method, the non-dimensional relative velocities as well as the ratios of the relative velocities for the inlets and the exits of an inducer and an impeller channel are calculated accurately.

Experimental Studies on Stall Behavior in a Single Stage Transonic Axial Flow Compressor

ASME 2013 Gas Turbine India Conference ◽

10.1115/gtindia2013-3620 ◽

2013 ◽

Author(s):

Dilipkumar Bhanudasji Alone ◽

Subramani Satish Kumar ◽

Shobhavathy M. Thimmaiah ◽

Janaki Rami Reddy Mudipalli ◽

A. M. Pradeep ◽

...

Keyword(s):

Mach Number ◽

Total Pressure ◽

Pressure Ratio ◽

Tangential Velocity ◽

Axial Flow ◽

Single Stage ◽

Flow Angle ◽

Axial Flow Compressor ◽

Flow Compressor ◽

This paper describes the study of flow behavior of the transonic compressor stage in un-stalled and stalled conditions. Experiments were carried out in an open circuit single stage transonic axial flow compressor test rig. The test compressor was designed for 1.35 total to total pressure ratio at corrected mass flow rate of 22 kg/s. Both steady and unsteady measurements were carried out. The operating envelop of the compressor was experimentally determined to demark the stable and unstable operating range of the compressor at different operating speeds. Variations in the rotor inlet axial and tangential velocity in the tip region were studied using a calibrated single component hot wire probe. The compressor blade element performance was obtained at full flow and near stall conditions using a three hole aerodynamic probe. The variation in flow parameters like absolute flow angle, axial Mach number, absolute Mach number, tangential Mach number, static and total pressure ratio profiles at the rotor exit were obtained and their variations along the blade height were studied at full flow and near stall conditions. Static pressure variation in the tip region along the rotor chord was studied which showed reduction in slope as stall approached. Hotwire measurements showed abrupt variation in the axial velocity as compared to tangential velocity at stalled condition. It was observed that the flow turned in tangential direction at stall, as tangential component of velocity shows more fluctuations at stall in comparison with unstalled condition. The FFT analysis of the raw signals was performed and it was observed that the nature of the rotating stall was abrupt and stall cell travels nearly at half the rotor speed.

A Numerical Investigation of Blade Lean Angle Effects on Flow in a Centrifugal Impeller

Volume 1: Turbomachinery ◽

10.1115/94-gt-149 ◽

1994 ◽

Cited By ~ 3

Author(s):

J. H. G. Howard ◽

M. Ashrafizaadeh

Keyword(s):

Flow Rate ◽

Total Pressure ◽

High Performance ◽

Pressure Ratio ◽

Centrifugal Impeller ◽

Leakage Flow ◽

Lean Angle ◽

Blade Tip ◽

Compressible Turbulent Flow ◽

An established 3-D viscous code (TASCflow3d) for compressible turbulent flow has been used to numerically investigate the effects of lean angle modifications to an existing high performance centrifugal compressor. Numerical results show that an appropriate compound lean can reduce the leakage flow, unload the blade tip and increase the total pressure ratio at a given flow rate while keeping its efficiency at a constant level. They also indicate that a simple lean can marginally improve the impeller efficiency while it lowers the impeller head versus flow curve.

Design of High Specific Speed Mixed Flow Micro-Compressor for Co-Flow Jet Actuators

Volume 8: Microturbines, Turbochargers, and Small Turbomachines; Steam Turbines ◽

10.1115/gt2019-90980 ◽

2019 ◽

Cited By ~ 3

Author(s):

Kewei Xu ◽

Gecheng Zha

Keyword(s):

Total Pressure ◽

Static Pressure ◽

Pressure Ratio ◽

Flow Coefficient ◽

High Mass ◽

Aerodynamic Design ◽

Mixed Flow ◽

Work Distribution ◽

Specific Speed ◽

Abstract This paper conducts aerodynamic design of a high specific speed mixed flow micro-compressor used as an actuator for Co-flow Jet (CFJ) Active Flow Control (AFC) airfoil. The aerodynamic design poses several challenges, including: 1) Small size with very low Reynolds number; 2) High specific speed for mixed-flow compressor due to high mass flow rate and low total pressure ratio; 3) Static pressure ratio lower than 1 to match the low pressure of CFJ airfoil leading edge (LE) suction peak. The numerical design approach is validated with a mixed flow micro-compressor with very good agreement between the predicted performance and the measured data. Front loaded rotor blade work distribution is adopted to decrease boundary layer loss at the blade surface. Free vortex work distribution is applied for the rotor span to reduce spanwise mixing loss. The rotor efficiency achieved by the numerical prediction is 91.7%. Significant loss is observed downstream of the rotor when the flow reaches the stator and the outlet guide vane (OGV). For the stator, it is found that an inlet and outlet flow path area ratio of 1.05 achieves a very high total pressure recovery of 99.29%. A very good stage isentropic efficiency of 84.3% is achieved. The final design of micro-compressor achieves a flow coefficient of 0.3 at the design point with a total pressure ratio of 1.117 and a static pressure ratio of 0.987. A structure FEM analysis indicates that the rotor blades satisfy the structure strength and modal frequency requirement.

Investigation Into the Effects of Hub Rotation on the Hub Leakage Flow of Cantilever Stator in a Transonic Axial Compressor

10.1115/gt2020-14324 ◽

2020 ◽

Author(s):

Botao Zhang ◽

Bo Liu ◽

Xin Sun ◽

Hang Zhao

Keyword(s):

Total Pressure ◽

Pressure Ratio ◽

Leading Edge ◽

Tip Clearance ◽

Leakage Flow ◽

Compressor Cascade ◽

Suction Surface ◽

Blade Root ◽

Flow Loss ◽

Abstract In order to explore the similarities and differences between the flow fields of cantilever stator and idealized compressor cascade with tip clearance, and to extend the cascade leakage model to compressors, the influence of stator hub rotation to represent cascade and cantilever stator on hub leakage flow was numerically studied. On this basis, the control strategy and mechanism of blade root suction were discussed. The results show that there is no obvious influence on stall margin of the compressor whether the stator hub is rotating or stationary. For rotating stator hub, the overall efficiency is decreased while the total pressure ratio is increased. At peak efficiency point and near stall point, the efficiency is reduced by about 0.43% and 0.34% individually, while the total pressure ratio is enlarged by about 0.23% and 0.27%, respectively. The gap leakage flow is promoted due to stator hub rotation, and the structure of the leakage vortex is weakened obviously. In addition, the hub leakage flow originating from the blade leading edge of rotating hub may contribute to double leakage near the trailing edge of the adjacent blade. However, the leakage flow directly out of the blade passage with stationary stator hub. The stator root loading and strength of the leakage flow increase with the rotation of the hub, and the leakage vortex is further away from the suction surface of the blade and is stretched to an ellipse closer to the endwall under the shear action. The rotating hub makes the flow loss near the stator gap increase, while the flow loss in the upper part of the blade root is decreased. Meanwhile, the total pressure ratio in the end area is increased. Blade root suction of cantilever stator can effectively control the hub leakage flow, inhibit the development of hub leakage vortex, and improve the flow capacity of the passage, thereby reducing the flow loss and modifying the flow field in the end zone.

Research on Optimization of the Design(Inverse) Issue of S2 Surface of Axial Compressor Based on Genetic Algorithm

10.1115/gt2020-14263 ◽

2020 ◽

Author(s):

Zijing Chen ◽

Bo Liu ◽

Xiaoxiong Wu

Keyword(s):

Genetic Algorithm ◽

Total Pressure ◽

Fitness Function ◽

Pressure Ratio ◽

Axial Compressor ◽

Local Data ◽

Real Coded Genetic Algorithm ◽

Overall Efficiency ◽

Total Pressure Ratio ◽

Peak Value

Abstract In order to further improve the effectiveness of design(inverse) issue of S2 surface of axial compressor, a design method of optimization model based on real-coded genetic algorithm is instructed, with a detailed description of some important points such as the population setting, the fitness function design and the implementation of genetic operator. The method mainly takes the pressure ratio, the circulation as the optimization variables, the total pressure ratio and the overall efficiency of the compressor as the constraint condition and the decreasing of the diffusion factor of the compressor as the optimization target. In addition, for the propose of controlling the peak value of some local data after the optimization, a local optimization strategy is proposed to make the method achieve better results. In the optimization, the streamline curvature method is used to perform the iterative calculation of the aerodynamic parameters of the S2 flow surface, and the polynomial fitting method is used to optimize the dimensionality of the variables. The optimization result of a type of ten-stage axial compressor shows that the pressure ratio and circulation parameters have significant effect on the diffusion factor’s distribution, especially for the rotor pressure ratio. Through the optimization, the smoothness of the mass-average pressure ratio distribution curve of the rotors at all stages of the compressor is improved. The maximum diffusion factors in spanwise of rotor rows at the first, fifth and tenth stage of the compressor are reduced by 1.46%, 12.53% and 8.67%, respectively. Excluding the two calculation points at the root and tip of the blade because of the peak value, the average diffusion factors in spanwise are reduced by 1.28%, 3.46%, and 1.50%, respectively. For the two main constraints, the changes of the total pressure ratio and overall efficiency are less than 0.03% and 0.032%, respectively. In the end, a 3-d CFD numerical result is given to testify the effects of the optimization, which shows that the loss in the compressor is decreased by the optimization algorithm.

Flow Measurements Behind the Inlet Guide Vane of a Centrifugal Compressor

Volume 1: Turbomachinery ◽

10.1115/98-gt-086 ◽

1998 ◽

Cited By ~ 5

Author(s):

I. Kassens ◽

M. Rautenberg

Keyword(s):

Centrifugal Compressor ◽

Total Pressure ◽

Guide Vane ◽

Incidence Angle ◽

Pressure Ratio ◽

Inlet Guide Vane ◽

Flow Measurements ◽

Flow Angle ◽

Partial Load ◽

Measurement Location

In a centrifugal compressor adjustable inlet guide vanes (IGV) in front of the impeller are used to regulate the pressure ratio and the mass flow. The stationary measurement of the velocity profile in front of the impeller with different angles of the IGV displays shock losses at the inlet edge of blade of the impeller. In the partial-load region (e.g. partial-load efficiency) the radial distribution of the flow influences considerably the performance of the impeller. The tested compressor consists of an adjustable IGV with straight vanes, a shrouded impeller and a vaneless, parallel diffuser. In the first measurement location, behind the IGV, total pressure, static pressure and flow angle were measured with a 5-hole cylinder probe. In the second measurement location, in front of the impeller, the measurement of the total pressure was carried out with a Kiel probe and the flow angle with a Cobra probe accordingly the static wall pressure was measured. Taking into consideration the fundamental thermodynamical equations it was possible to determine the velocity profiles because of the measured distributions of the flow angle in these two measurement locations. For different angles of the IGV and with various mass flows the distributions of the deflection defect behind the IGV are described. Starting with the measured distributions of the flow in front of the impeller the flow angles at the impeller inlet are calculated and the distributions of the incidence angle at the impeller inlet are figured out.

Optimization of Highly Loaded Fan Rotor Based on Throughflow Model

Volume 6: Turbo Expo 2007, Parts A and B ◽

10.1115/gt2007-27603 ◽

2007 ◽

Cited By ~ 1

Author(s):

Hong Wu ◽

Qiushi Li ◽

Sheng Zhou

Keyword(s):

Mass Flow ◽

Total Pressure ◽

Pressure Ratio ◽

Optimization Method ◽

Design Variables ◽

Adaptive Simulated Annealing ◽

Throughflow Model ◽

Important Design ◽

Total Pressure Ratio ◽

Highly Loaded

This paper presents an optimization method for fan/compressor which couples throughflow model solving axisymmetric Euler equations with adaptive simulated annealing (ASA) algorithm. One of the advantages of this optimization method is that it spends much less time than 3D optimization due to the rapid solving of throughflow model. In addition, the optimization space is quite extensive because more design variables can be adjusted in throughflow phase, such as swirl distribution, hub curve and sweep. To validate this optimization method, a highly loaded fan rotor with pressure ratio of 3.06 as a baseline is optimized. During the optimization process, the objective function is total pressure ratio, moreover, mass flow and efficiency are selected as the constraint conditions. Three important design variables including swirl distribution, hub curve and sweep are parameterized using Bezier curve, and then optimized in throughflow model independently, finally the optimum designs are validated using 3D viscous CFD solver. It is shown that pressure ratio and rotor loading can be improved further through optimizing swirl distribution, however, hub and sweep curves take more effects on mass flow and efficiency respectively. The optimization results demonstrate the advantage and feasibility of this optimization method.

Numerical Investigation on the Effects of Circumferential Coverage of Injection in a Transonic Compressor With Discrete Tip Injection

10.1115/gt2014-25420 ◽

2014 ◽

Cited By ~ 4

Author(s):

Wei Wang ◽

Wuli Chu ◽

Haoguang Zhang ◽

Yanhui Wu

Keyword(s):

Total Pressure ◽

Pressure Ratio ◽

Time Lag ◽

Three Dimensional ◽

Stability Margin ◽

Transonic Compressor ◽

Blade Tip ◽

Tip Injection ◽

The Stability ◽

Discrete tip injection upstream of the rotor tip is an effective technique to extend stability margin for a compressor system in an aeroengine. The current study investigates the effects of injectors’ circumferential coverage on compressor performance and stability using time-accurate three-dimensional numerical simulations for multi passages in a transonic compressor. The percentage of circumferential coverage for all the six injectors ranges from 6% to 87% for the five investigated configurations. Results indicate that circumferential coverage of tip injection can greatly affect compressor stability and total pressure ratio, but has little influence on adiabatic efficiency. The improvement of compressor total pressure ratio is linearly related with the increasing circumferential coverage. The unsteady flow fields show that there exists a non-ignorable time lag of the injection effects between the passage inlet and outlet, and blade tip loading will not decline until the injected flow reaches the passage outlet. Stability improves sharply with the increasing circumferential coverage when the coverage is less than 27%, but increases flatly for the rest. It is proven that the injection efficiency which is a measurement of averaged blockage decrement in the injected region is an effective guideline to predict the stability improvement.

The Optimization of a Centrifugal Impeller Based on a New Multi-Objective Evolutionary Strategy

Volume 2C: Turbomachinery ◽

10.1115/gt2016-56592 ◽

2016 ◽

Cited By ~ 1

Author(s):

Xiaojian Li ◽

Yijia Zhao ◽

Zhengxian Liu ◽

Hua Chen

Keyword(s):

Pressure Ratio ◽

Aerodynamic Performance ◽

Evolutionary Strategy ◽

Centrifugal Impeller ◽

Nsga Ii ◽

Multi Objective ◽

Compressor Performance ◽

Aero Engines ◽

Total Pressure Ratio ◽

Petrochemical Engineering

Centrifugal compressors with high aerodynamic performance are widely used in turbochargers, aero-engines and petrochemical engineering. The impeller is the core component and plays a key role in determining the compressor performance. This paper reports the optimisation of the aerodynamic performance of an industrial centrifugal impeller by a multi-objective evolutionary strategy. Firstly the 3-D modeling method for parameterisation of impeller’s geometry was described. Secondly the traditional NSGA-II method was modified to improve its ability and efficiency. Employed CFD code was first validated using the experimental data of an existing impeller. The optimisation was applied to the industrial centrifugal impeller through a two-step optimization process to allow for significant variations of the impeller geometry and speedy finding of the optimum. The optimisation was completed within 53 hours on a workstation with two 24-core processors (Xeon(R) E5-2670 v3 2.3GHz). The results indicated that the isentropic efficiency of the impeller increased by 5.3 percents and the total pressure ratio by 20.5 percents at design condition.

Experimental Investigation of Aspiration in a Multi-Stage High-Speed Axial-Compressor

10.1115/gt2016-56440 ◽

2016 ◽

Cited By ~ 3

Author(s):

Jan Siemann ◽

Ingolf Krenz ◽

Joerg R. Seume

Keyword(s):

Flow Field ◽

Total Pressure ◽

High Speed ◽

Pressure Ratio ◽

Axial Compressor ◽

Reference Configuration ◽

Corner Separation ◽

Part Load ◽

Total Pressure Ratio ◽

Isentropic Efficiency

Reducing the fuel consumption is a main objective in the development of modern aircraft engines. Focusing on aircraft for mid-range flight distances, a significant potential to increase the engines overall efficiency at off-design conditions exists in reducing secondary flow losses of the compressor. For this purpose, Active Flow Control (AFC) by aspiration or injection of fluid at near wall regions is a promising approach. To experimentally investigate the aerodynamic benefits of AFC by aspiration, a 4½-stage high-speed axial-compressor at the Leibniz Universitaet Hannover was equipped with one AFC stator row. The numerical design of the AFC-stator showed significant hub corner separations in the first and second stator for the reference configuration at the 80% part-load speed-line near stall. Through the application of aspiration at the first stator, the numerical simulations predict the complete suppression of the corner separation not only in the first, but also in the second stator. This leads to a relative increase in overall isentropic efficiency of 1.47% and in overall total pressure ratio of 4.16% compared to the reference configuration. To put aspiration into practice, the high-speed axial-compressor was then equipped with a secondary air system and the AFC stator row in the first stage. All experiments with AFC were performed for a relative aspiration mass flow of less than 0.5% of the main flow. Besides the part-load speed-lines of 55% and 80%, the flow field downstream of each blade row was measured at the AFC design point. Experimental results are in good agreement with the numerical predictions. The use of AFC leads to an increase in operating range at the 55% part-load speed-line of at least 19%, whereas at the 80% part-load speed-line no extension of operating range occurs. Both speed-lines, however, do show a gain in total pressure ratio and isentropic efficiency for the AFC configuration compared to the reference configuration. Compared to the AFC design point, the isentropic efficiency ηis rises by 1.45%, whereas the total pressure ratio Πtot increases by 1.47%. The analysis of local flow field data shows that the hub corner separation in the first stator is reduced by aspiration, whereas in the second stator the hub corner separation slightly increases. The application of AFC in the first stage further changes the stage loading in all downstream stages. While the first and third stage become unloaded by application of AFC, the loading in terms of the De-Haller number increases in the second and especially in the fourth stage. Furthermore, in the reference as well as in the AFC configuration, the fourth stator performs significantly better than predicted by numerical results.