Vaneless Diffuser Advanced Model

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Oleg Dubitsky ◽  
David Japikse
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Zone Model ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Average Flow ◽  
New Model ◽  
Future Design ◽  
The Impact ◽  
Advanced Model

A new vaneless diffuser model is presented. Upon thorough examination of the change in average total pressure, the average static pressure and the average flow angle through a vaneless diffuser, it was discovered that existing models fail to provide useful integrity. Consequently, a new model was built. It was learned that it was necessary to use a two-zone model of the flow entering the vaneless diffuser and to carefully model the two-zone degradation as the flow passes through the vaneless diffuser. The new model is presented with detailed testing. The impact upon future design is outlined, and the expectation is established that various future designs will require the integrity of the new model; old models can be used in limited cases with care.

Vaneless Diffuser Advanced Model (2005D)

2005 ◽  
Author(s):  
Oleg Dubitsky ◽  
David Japikse
Keyword(s):  
Total Pressure ◽  
Static Pressure ◽  
Zone Model ◽  
Vaneless Diffuser ◽  
Flow Angle ◽  
Average Flow ◽  
New Model ◽  
Future Design ◽  
The Impact ◽  
Advanced Model

A new vaneless diffuser model is presented. Upon thorough examination of the change in average total pressure, the average static pressure and the average flow angle through a vaneless diffuser, it was discovered that existing models fail to provide useful integrity. Consequently, a new model was built. It was learned that it was necessary to use a two-zone model of the flow entering the vaneless diffuser and to carefully model the two-zone degradation as the flow passes through the vaneless diffuser. The new model is presented with detailed testing. The impact upon future design is outlined, and the expectation is established that various future designs will require the integrity of the new model; old models can be used in limited cases with care.

scholarly journals Numerical and Experimental Investigations on Optimized 3D Compressor Airfoils

2018 ◽  
Author(s):  
Jan Mihalyovics ◽  
Christian Brück ◽  
Dieter Peitsch ◽  
Ilias Vasilopoulos ◽  
Marcus Meyer
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Experimental Studies ◽  
Total Pressure Loss ◽  
Design Parameters ◽  
Flow Conditions ◽  
Flow Angle ◽  
Flow Phenomena ◽  
The Impact ◽  
Stator Design

The objective of the presented work is to perform numerical and experimental studies on compressor stators. This paper presents the modification of a baseline stator design using numerical optimization resulting in a new 3D stator. The Rolls Royce in-house compressible flow solver HYDRA was employed to predict the 3D flow, solving the steady RANS equations with the Spalart-Allmaras turbulence model, and its corresponding discrete adjoint solver. The performance gradients with respect to the input design parameters were used to optimize the stator blade with respect to the total pressure loss over a prescribed incidence range, while additionally minimizing the flow deviation from the axial direction at the stator exit. Non-uniform profile boundary conditions, being derived from the experimental measurements, have been defined at the inlet of the CFD domain. The presented results show a remarkable decrease in the axial exit flow angle deviation and a minor decrease in the total pressure loss. Experiments were conducted on two compressor blade sets investigating the three-dimensional flow in an annular compressor stator cascade. Comparing the baseline flow of the 42° turning stator shows that the optimized stator design minimizes the secondary flow phenomena. The experimental investigation discusses the impact of steady flow conditions on each stator design while focusing on the comparison of the 3D optimized design to the baseline case. The flow conditions were investigated using five-hole probe pressure measurements in the wake of the blades. Furthermore, oil-flow visualization was applied to characterize flow phenomena. These experimental results are compared with the CFD calculations.

CFD Studies on the Performance of a Centrifugal Compressor With Single Wall Rotating Vaneless Diffusers at the Wall Extension Ratios of 1.1 and 1.15

2017 ◽  
Author(s):  
Srinivasa Rao Konakala ◽  
Mukka Govardhan
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Static Pressure ◽  
Substantial Improvement ◽  
Significant Loss ◽  
Vaneless Diffuser ◽  
Shear Forces ◽  
Overall Performance ◽  
Vaneless Diffusers ◽  
And Performance

Efficiency of the centrifugal compressor is affected by non-uniform flow at the exit of the impeller and the losses in the diffuser. This causes a significant loss of total pressure and drop in the performance of a centrifugal compressor. By rotating some portion of stationary vaneless diffuser walls with the speed of the impeller, the shear forces between the flow and diffuser walls are greatly reduced. Thereby improvement in the operating range and performance is achieved. This paper presents CFD studies on the effect of different single wall rotations i.e. hub rotation and shroud rotation of the vaneless diffusers on the overall performance at 10% and 15% extension of impeller walls. It is observed that the performance characteristics of compressors with all RVD models offer higher static pressure recovery and also higher rate of diffusion compared to the base compressor with SVD. It is clear that as extended radius increases from 10% to 15%, substantial improvement of efficiency and reduction of losses are observed for both type of models. Out of two single wall rotation models, SRVD model is able to better mix the jet-wake type of impeller exit flows and minimizes the losses therein and improve the performance of the centrifugal compressor.

Scaling of Incidence Variations With Inlet Distortion for a Transonic Axial Compressor

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
D. J. Hill ◽  
J. J. Defoe
Keyword(s):  
Total Pressure ◽  
Incidence Angle ◽  
Computational Cost ◽  
Force Model ◽  
Flow Angle ◽  
Total Enthalpy ◽  
Transonic Compressor ◽  
Inlet Distortion ◽  
Scaling Relationships ◽  
The Impact

Abstract This paper numerically explores the manner in which blade row inlet incidence variation scales with various distortion patterns and intensities. The objectives are to (1) identify the most appropriate parameter whose circumferential variation can be used to assess scaling relationships of a transonic compressor and (2) use this parameter to evaluate two types of non-uniform inflow patterns, vertically stratified total pressure distortions and radially stratified total enthalpy and total pressure distortions. A body force model of the blade rows is employed to reduce computational cost; the approach has been shown to capture distortion transfer and to be able to predict upstream flow redistribution with inlet distortion. Diffusion factor is shown to be an inadequate proxy for streamline loss generation in non-uniform flow, leading to the choice of incidence angle variations as the metric for which we assess scaling relationships. Posteriori scaling of circumferential flow angle variation based on the maximum incidence excursion for varying distortion intensity yields an accurate method for prediction of the impact for other distortion intensities; linear regression of the maximum variation in incidence around the annulus as a function of distortion intensity had R2 > 0.97 for all spanwise locations examined in both the rotor and stator for both vertically and radially stratified distortions. However, changes to far upstream distortion shape yield highly non-linear incidence variation scaling; the results suggest that the pitchwise gradients of far upstream total pressure govern the degree of linearity for incidence variation scaling.

Flow at the Centrifugal Pump Impeller Exit With Circumferential Distortion of the Outlet Static Pressure

2004 ◽  
Vol 126 (1) ◽  
pp. 81-86 ◽  
Author(s):  
Soon-Sam Hong ◽  
Shin-Hyoung Kang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Total Pressure ◽  
Static Pressure ◽  
Mean Flow ◽  
Simple Method ◽  
Local Flow ◽  
Flow Angle ◽  
Flow Parameters ◽  
Relative Flow

The effects of circumferential outlet distortion of a centrifugal pump diffuser on the impeller exit flow were investigated. A fence with sinusoidal width variation was installed at the vaneless diffuser exit. The flow field was measured at the impeller exit with and without the fence, using a hot film probe and an unsteady pressure sensor. Flow parameters varied with the circumferential position and the mean flow parameters plotted against the local flow rate at each circumferential position showed loops along the quasi-steady curves, which were obtained from the result without the fence. Simple theoretical calculations were used to predict the velocity components at the impeller exit with the relative flow angle or total pressure assumed. Good result was obtained when the relative flow angle was assumed to vary quasi-steadily, not constant with the local flow rate. The radial velocity was also reasonably predicted when the total pressure was assumed to vary quasi-steadily. A simple method is proposed to predict the impeller exit flow with downstream blockage in two-step sequence: the first step deals with the diffuser alone to obtain static pressure distribution at the diffuser inlet, while the second step deals with the impeller alone to obtain velocity components distribution at the impeller exit.

scholarly journals The Model V84.3 Shot Tests: Compressor Flow Field Measurements and Evaluation

1994 ◽  
Author(s):  
M. Janssen ◽  
R. Mönig ◽  
J. Seume ◽  
H. Hönen ◽  
R. Lösch-Schloms ◽  
...  
Keyword(s):  
Flow Field ◽  
Total Pressure ◽  
Static Pressure ◽  
Pressure Rise ◽  
Full Scale ◽  
Test Facility ◽  
Design Calculation ◽  
Flow Measurements ◽  
Flow Angle ◽  
Probe Measurements

Detailed experimental investigations were carried out at the Siemens test-facility in Berlin to validate and develop further the compressor design of the Model V84.3 gas turbine and to generate a comprehensive data base for the verification of the flow calculation programs. The test facility enables Siemens to confirm the design with regard to performance and reliability in the full scale machine under full load and off-design condition. Various measuring techniques well established in the laboratory were applied to the full scale compressor to examine the flow field. Along with rather conventional 5-hole probes for measuring the flow field in the core region, miniaturized 3-hole probes were developed at the Turbomachinery Laboratory of the Technical University of Aachen, tested and finally used for the measurements of endwall boundary layer profiles and their development throughout the compressor. In addition to the probe measurements, wall static-pressure measurements, as well as probed vane measurements, were carried out. The paper briefly describes the test facility, the compressor under investigation, and the instrumentation for the flow measurements. A comparison of the 3-hole and 5-hole probe measurements is presented. The experimental results are compared with calculated results taken from a two-dimensional off-design calculation program with standard loss models. By means of the measured static-pressure rise at the casing wall and the total pressure distributions downstream of the rotor rows, a modification of the loss modeling was performed. The calculated flow field is compared to the results of the 3-hole and 5-hole probe measurements in terms of radial distributions for flow angle. Mach number and total pressure.

Experimental Study of Pinch in Vaneless Diffuser of Centrifugal Compressor

2009 ◽  
Author(s):  
Teemu Turunen-Saaresti ◽  
Aki-Pekka Gro¨nman ◽  
Ahti Jaatinen
Keyword(s):  
Experimental Study ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Compressor Stage ◽  
Vaneless Diffuser ◽  
Moderate Amount ◽  
Flow Angle ◽  
Isentropic Efficiency

A centrifugal compressor is often equipped with a vaneless diffuser because the operation range of a vaneless diffuser is wider than the operation range of vaned diffuser, and the geometry of the vaneless diffuser is simple and inexpensive. The flow field after the centrifugal compressor rotor is highly complicated and the velocity is high. A moderate amount of this velocity should be recovered to the static pressure. It is important to study the flow field in the vaneless diffuser in order to achieve guidelines for design and an optimal performance. In this article, the experimental study of the pinch in the vaneless diffuser is conducted. Five different diffuser heights were used, b/b2 = 1, b/b2 = 0.903, b/b2 = 0.854, b/b2 = 0.806 and b/b2 = 0.903 (shroud). In three of the cases, the pinch was made to both walls of the diffuser, hub and shroud, and in one case, the pinch was made to the shroud wall. The total and the static pressure, the total temperature and the flow angle were measured at the diffuser inlet and outlet by using a cobra-probe, kiel-probes and flush-mounted pressure taps. In addition, the static pressure in the diffuser was measured at three different radius ratios. The overall performance, the mass flow, the pressure ratio and the isentropic efficiency of the compressor stage were also monitored. Detailed flow field measurements were carried out at the design rotational speed and at the three different mass flows (close to the surge, design and close to the choke). The isentropic efficiency and the pressure ratio of the compressor stage was increased with the pinched diffuser. The efficiency of the rotor and the diffuser was increased, whereas the efficiency of the volute/exit cone was decreased. The pinch made to the shroud wall was the most effective. The pinch made the flow angle more radial and increased the velocity at the shroud where the secondary flow (passage wake) from the rotor is present.

scholarly journals Optimization Study of the Dump Diffuser in Gas Turbine to Reduce Pressure Loss

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Fei Xing ◽  
Hao Su ◽  
Shining Chan ◽  
Leilei Xu ◽  
Xinyi Yu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Method ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Test Model ◽  
Gap Ratio ◽  
Efficient Combustion ◽  
The Impact

As a key component-connecting compressor and the entrance of combustion chamber, the diffuser is able to increase the pressure and slow down the airflow in order to promote efficient combustion as well as avoid a large amount of pressure loss. In this paper, experimental investigation and numerical studies have been carried out to understand the effects of air bleeding from dump region and dump gap ratio on the total pressure loss and static pressure recovery of the dump diffusers. The ultimate objective is optimizing the dump diffuser design to get the maximum static pressure recovery and minimum total pressure loss. A simplified test model is used to study the effect of the air bleeding from the outer dump region and the dump gap ratio on the total pressure loss and static pressure recovery in the dump diffuser. The impact of the dump gap ratio in the performance of the dump diffusers has also been discussed. Nearly all the pressure raise occurs in the prediffuser, and most of the total pressure loss occurs in the dump region. For the recirculating area in the dump region, the controllable vortex can be introduced. Bleeding air from the outer dump region can improve the velocity distribution near the flame tube. The results show that when 0.4% of the air is bled from outer dump region, the performance of the dump diffuser is optimal. Hence, the controllable vortex method is effective for improving the performance of the dump diffuser.

The Impact of Centre Body Alignment to Flow Through an Annular Diffuser

2013 ◽  
Author(s):  
D. J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Order Statistics ◽  
Total Pressure ◽  
Static Pressure ◽  
Pressure Coefficient ◽  
Reynolds Numbers ◽  
Uniformity Coefficient ◽  
First Order ◽  
Annular Diffuser ◽  
Flow Through ◽  
The Impact

Cold air-flow testing was completed over a range of inlet Reynolds numbers of 0.8–3.5 × 105 on several annular diffuser designs to quantify the variation in first order statistics due to misalignment. The procedure involved in attaching the outer duct wall caused a maximum 5% axis shift with respect to the outlet diameter at the diffuser outlet relative to the centre body axis and translated to an approximate inlet variation in height of 2%. This shift was sufficient to distort the flow whereby the quadrant with the greater area at the annular diffuser inlet corresponded to higher total pressure at the outlet. Results showed that static pressure coefficient never varied by more than 3.8% and the outlet velocity uniformity coefficient stayed within 2.4% from reference configurations; however, total pressure coefficient had a larger variation in some cases greater than 10%.

Thickness and Blade Angle Distribution for Design of Centrifugal Compressor Stage Return Channel Vane

2015 ◽  
Author(s):  
Arindam Bera ◽  
N. K. Singh
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Thickness Distribution ◽  
Angle Distribution ◽  
Compressor Stage ◽  
Blade Angle ◽  
Flow Angle ◽  
Return Channel

Return channel de-swirl vanes form an integral part of a centrifugal compressor stage for multi-stage configuration. In this paper, a few configurations of return channel vanes (RCV) are arrived at by modifying the blade angle and thickness distribution from leading edge to the trailing edge. Influence of these two parameters on the overall performance of return channel in terms of total pressure loss co-efficient and static pressure recovery co-efficient along with stage exit flow angle are evaluated through CFD analysis. CFD results show that, proper thickness distribution after maximum thickness point to the trailing edge improves the stage exit flow angle but not the total pressure loss co-efficient and static pressure recovery co-efficient. Whereas, by suitably modifying the blade angle distribution, all the three performance parameters can be improved considerably.

Sign in / Sign up

Export Citation Format

Share Document