A Transonic Mixed Flow Compressor for an Extreme Duty

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Hamid Hazby ◽  
Michael Casey ◽  
Ryusuke Numakura ◽  
Hideaki Tamaki
Keyword(s):  
Test Data ◽  
Pressure Rise ◽  
High Flow ◽  
Flow Coefficient ◽  
Aerodynamic Optimization ◽  
Mixed Flow ◽  
Axial Compressors ◽  
Blade Shape ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Compressor

This paper describes the design of a transonic mixed flow compressor stage for an extreme duty, with an extremely high flow coefficient (φ) of 0.25 and a high isentropic pressure rise coefficient (ψ) of 0.56. The impeller design makes use of modern aerodynamic practice from radial and transonic axial compressors, whereby the aerodynamic blade shape involved arbitrary surfaces on several spanwise sections. Some aspects of the aerodynamic optimization of the design were limited by mechanical considerations, but nevertheless the test data obtained on a prototype stage demonstrates that acceptable performance levels can be achieved at these extreme design conditions, although map width enhancement (MWE) devices were needed to obtain an acceptable operating range. The test data are compared with computational fluid dynamics (CFD) predictions to demonstrate the validity of the design methods used.

A Transonic Mixed Flow Compressor for an Extreme Duty

2014 ◽  
Author(s):  
Hamid Hazby ◽  
Michael Casey ◽  
Ryusuke Numakura ◽  
Hideaki Tamaki
Keyword(s):  
Test Data ◽  
Pressure Rise ◽  
High Flow ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Aerodynamic Optimization ◽  
Mixed Flow ◽  
Axial Compressors ◽  
Blade Shape ◽  
Flow Compressor

This paper describes the design of a transonic mixed flow compressor stage for an extreme duty, with an extremely high flow coefficient (Φ) of 0.25 and a high isentropic pressure rise coefficient (ψ) of 0.56. The impeller design makes use of modern aerodynamic practice from radial and transonic axial compressors, whereby the aerodynamic blade shape involved arbitrary surfaces on several spanwise sections. Some aspects of the aerodynamic optimization of the design were limited by mechanical considerations, but nevertheless the test data obtained on a prototype stage demonstrates that acceptable performance levels can be achieved at these extreme design conditions, although map width enhancement devices were needed to obtain an acceptable operating range. The test data is compared with CFD predictions to demonstrate the validity of the design methods used.

Experimental Study on the Influence of Casing Treatment on Near-Stall Unsteady Behavior of a Mixed-Flow Compressor

2019 ◽  
Author(s):  
Juan Du ◽  
Felix Kauth ◽  
Jichao Li ◽  
Qianfeng Zhang ◽  
Joerg R. Seume
Keyword(s):  
Stability Limit ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Surprising Result ◽  
Mixed Flow ◽  
Stall Inception ◽  
Casing Treatment ◽  
Axial Compressors ◽  
Flow Compressor ◽  
Unsteady Behavior

Abstract This paper aims at experimentally demonstrating the effects of axial slot casing treatment and tip gap variation on compressor performance, unsteady tip clearance flow, and stall inception features in a highly-loaded mixed-flow compressor at partspeed. Two tip gaps (0.32% and 0.64% of rotor blade chord at mid-span) were tested at three rotational speeds. A semicircular axial slot casing treatment improves compressor stability. The experimental results show that this casing treatment significantly moves the stability limit at partial speeds towards lower mass flow for both tip gaps, compared to the reference case without casing treatment. In the case of the compressor with casing treatment, efficiency increases for the large tip gap and decreases for the small tip gap. Dynamic pressure transducers installed in the casing upstream and along the rotor tip chord direction are used to detect the unsteady behavior of tip region flow and stall inception signals of the compressor. The characteristic frequency in the tip region decreases, and the oscillating amplitude first decreases and then increases during the throttling process, regardless of tip gap size or casing treatment. For axial compressors, by contrast, the observation in previous work has been an increase of the oscillating amplitude with decreasing flow coefficient. This is a surprising result of our work. Neither experiment nor CFD so far was able to explain why the trend in this mixed-flow compressor is different from the trend expected from axial compressors. The compressor stalls through the spike stall inception both with and without casing treatment. This observation also differs from recent studies on axial compressors, which demonstrated that casing treatments could change the type of stall inception. The unstable disturbance indicating initial stall inception initially appears in the blade tip region from blade mid-chord to trailing edge, and then propagates upstream towards the leading edge. This disturbance might be generated by the reversed flow separation near mid-chord.

scholarly journals Introduction of an Universal Scale-Up Method for the Efficiency of Axial and Centrifugal Fans

2014 ◽  
Author(s):  
Peter F. Pelz ◽  
Stefan S. Stonjek
Keyword(s):  
Test Data ◽  
Scale Up ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Total Efficiency ◽  
Scaling Method ◽  
Centrifugal Fans ◽  
Axial Fans ◽  
Definition Of ◽  
Acceptance Tests

Acceptance tests on large fans to prove the performance (efficiency and total pressure rise) to the customer are expensive and sometimes even impossible to perform. Hence there is a need for the manufacturer to reliably predict the performance of fans from measurements on down-scaled test fans. The commonly used scale-up formulas give satisfactorily results only near the design point, where inertia losses are small in comparison to frictional losses. At part- and overload the inertia losses are dominant and the scale-up formulas used so far fail. In 2013 Pelz and Stonjek introduced a new scaling method which fullfills the demands ( [1], [2]). This method considers the influence of surface roughness and geometric variations on the performance. It consists basically of two steps: Initially, the efficiency is scaled. Efficiency scaling is derived analytically from the definition of the total efficiency. With the total derivative it can be shown that the change of friction coefficient is inversely proportional to the change of efficiency of a fan. The second step is shifting the performance characteristic to a higher value of flow coefficient. It is the task of this work to improve the scaling method which was previously introduced by Pelz and Stonjek by treating the rotor/impeller and volute/stator separately. The validation of the improved scale-up method is performed with test data from two axial fans with a diameter of 1000 mm/250mm and three centrifugal fans with 2240mm/896mm/224mm diameter. The predicted performance characteristics show a good agreement to test data.

Assessment of a Novel Non-Axial Counter-Rotating Compressor Concept for Aero-Engines

2018 ◽  
Author(s):  
Quentin Dejour ◽  
Huu Duc Vo
Keyword(s):  
Pressure Rise ◽  
Axial Direction ◽  
Boundary Layer Separation ◽  
Low Flow ◽  
Compressor Stage ◽  
Mixed Flow ◽  
Stall Margin ◽  
High Loss ◽  
Multi Stage ◽  
Flow Compressor

This paper presents the first assessment of a new non-axial counter-rotating compressor concept. This concept consists of replacing the stator of a mixed-flow compressor stage or the diffuser of a centrifugal compressor stage with a counter-rotating rotor that will turn the flow back to the axial direction with much lower diffusion factor, while providing the equivalent in work of the upstream mixed-flow rotor or impeller. This concept has two advantages. First, the very high stage pressure rise means that only a single counter-rotating rotor may be required, making mechanical implementation simpler than for multi-stage axial counter-rotating compressors. Second, the replacement of the high flow turning (high loss) stator/diffuser in a non-axial stage with a low flow turning counter-rotating rotor gives the new concept potential for achieving higher efficiency than conventional non-axial compressors. As a first proof of concept, a subsonic counter-rotating mixed-flow compressor and its conventional (i.e. rotor-stator) equivalent have been designed with the intent of being implemented in a test rig. CFD simulations have been carried out for a comparative evaluation of both configurations. Results show that the counter-rotating mixed-flow compressor produces more than double the pressure rise of its conventional version with a slightly higher peak-efficiency while having a smaller axial length. Moreover, the counter-rotating configuration has a better stall margin than its conventional counterpart, for which the boundary layer separation from excessive flow turning in the stator causes early stall.

Influence of distorted inflows on the performance of a contra-rotating fan

2020 ◽  
pp. 1-18
Author(s):  
M.P. Manas ◽  
A.M. Pradeep
Keyword(s):  
Pressure Rise ◽  
Aircraft Engine ◽  
High Flow ◽  
Flow Coefficient ◽  
Potential Candidate ◽  
Blade Surface ◽  
Axial Fan ◽  
Stall Inception ◽  
Relative Contribution ◽  
Inflow Conditions

ABSTRACT A contra-rotating fan offers several aerodynamic advantages that make it a potential candidate for future aircraft engine configurations. Stall in a contra-rotating axial fan is interesting since instabilities could arise from either or both of the rotors. In this experimental study, a contra-rotating axial fan is analysed under clean or distorted inflow conditions to understand its performance and stall inception characteristics. The steady and unsteady measurements identified the relative contribution of each rotor towards the performance of the stage. The tip of rotor-1 is identified to be the most critical region of the contra-rotating fan. The contribution of rotor-2 to the overall loading of the stage is observed to be relatively less than rotor-1. The penalty due to distortion in the stage pressure rise is mostly felt by rotor-1, while rotor-2 also shows a reduction in performance for distorted inflows. Rotor-2 stalls at a high flow coefficient marking the initiation of partial stall of the stage, and the stall of the whole stage occurs once rotor-1 stalls. A fluid phenomenon that is attached to the blade surface marks the stall of rotor-1, and this fluid phenomenon initially rotates at a speed close to the speed of rotation of the blade. As the stage moves towards the fully developed stall, this fluid phenomenon sheds from the blade surface. The fluid phenomenon thus propagates at a speed much lower than the rotational speed of the blade during fully developed stall.

Bleed-Induced Distortion in Axial Compressors

2014 ◽  
Author(s):  
S. D. Grimshaw ◽  
G. Pullan ◽  
T. Walker
Keyword(s):  
Axial Flow ◽  
Flow Coefficient ◽  
Axial Compressors ◽  
Swirl Angle ◽  
Geometric Factors ◽  
Circumferential Distribution ◽  
Flow Compressor ◽  
The Stability ◽  
Chamber Size ◽  
Distribution Of Flow

In this paper, the influence of non-uniform bleed extraction on the stability of an axial flow compressor is quantified. Non-uniformity can be caused by several geometric factors (for example, plenum chamber size or number of off-take ducts) and a range of configurations is examined experimentally in a single stage compressor. It is shown that non-uniform bleed leads to a circumferential distribution of flow coefficient and swirl angle at inlet to the downstream stage. The resultant distribution of rotor incidence causes stall to occur at a higher flow coefficient than if the same total bleed rate had been extracted uniformly around the circumference. The loss of operating range caused by the non-uniform inlet flow correlates with the peak sector-averaged bleed non-uniformity for all the bleed configurations tested. A connection is made between the analysis of non-uniform bleed extraction and the familiar “DCθ” criterion used to characterize inlet total pressure distortion.

Effect of a Recirculation Device on the Performance of Transonic Mixed Flow Compressors

2014 ◽  
Author(s):  
Ryusuke Numakura ◽  
Hideaki Tamaki ◽  
Hamid Hazby ◽  
Michael Casey
Keyword(s):  
Measurement Data ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Suction Surface ◽  
Mixed Flow ◽  
Recirculation Flow ◽  
Stable Operating ◽  
Compressor Performance ◽  
The Stability ◽  
Stability Enhancement

Two transonic mixed flow compressors with an extremely high flow coefficient of ϕ = 0.25 and pressure ratios of 2.5 and 2.65 have been designed and tested. CFD simulations indicated that both impellers operate with a suction surface relative Mach number of above 1.5 at their design conditions. Both compressors achieved a narrow stable operating range when tested without recirculation devices. The effects of two different recirculation devices on the compressor performance maps were investigated both experimentally and numerically. The first type is a widely used recirculation device which consists of an upstream slot, bleed slot and an annular cavity which connects both slots. The other has vanes installed in the cavity which were designed to provide a recirculation flow with negative swirl at the impeller inlet. Measurement data demonstrated the effect of the recirculation devices on increasing the range of these two transonic mixed flow compressors and showed the superiority of the recirculation device with vanes. The effects of the recirculation devices on the impeller flow field at near surge conditions are studied using steady state 3D CFD calculations. Both measurements and simulations showed that the stability enhancement is partly caused by a steeper pressure rise characteristic.

Effects of Impeller Squealer Tip on Centrifugal Compressor Performance

2016 ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Lorenzo Toni ◽  
Dante Tommaso Rubino
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Flow ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Performance Improvements ◽  
Positive Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Performance ◽  
Load Conditions

This paper summarizes the main results sorted out from a Design of Experiment (DoE) based on a validated Computational Fluid Dynamics (CFD). Several tip recessed geometries applied to an unshrouded impeller were considered in conjunction with two tip clearance levels. The computations show that recessed tip geometries have positive effects when considering high flow coefficient values while in part-load conditions the gain is reduced. Starting from the results obtained when studying tip cavities, a single rim tip squealer geometry was then analysed: the proposed geometry leads to performance improvements for all the tested conditions considered in this work.

A Theory of Rotating Stall of Multistage Axial Compressors: Part I—Small Disturbances

1984 ◽  
Vol 106 (2) ◽  
pp. 313-320 ◽  
Author(s):  
F. K. Moore
Keyword(s):  
Pressure Rise ◽  
Propagation Speed ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Fluid Inertia ◽  
Flow Distortion ◽  
Axial Compressors ◽  
Experimental Values ◽  
Stagger Angle ◽  
Small Disturbances

An analysis is made of rotating stall in compressors of many stages, finding conditions under which a flow distortion can occur which is steady in a traveling reference frame, even though upstream total and downstream static pressure are constant. In the compressor, a pressure-rise hysteresis is assumed. Flow in entrance and exit ducts yield additional lags. These lags balance to give a formula for stall propagation speed. For small disturbances, it is required that the compressor characteristics be flat in the neighborhood of average flow coefficient. Results are compared with the experiments of Day and Cumpsty. If a compressor lag of about twice that due only to fluid inertia is used, predicted propagation speeds agree almost exactly with experimental values, taking into account changes of number of stages, stagger angle, row spacing, and number of stall zones. The agreement obtained gives encouragement for the extension of the theory to account for large amplitudes.

Effects of Impeller Squealer Tip on Centrifugal Compressor Performance

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Dante Tommaso Rubino ◽  
Lorenzo Toni
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Flow ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Performance Improvements ◽  
Positive Effects ◽  
Computational Fluid Dynamics Cfd ◽  
Compressor Performance ◽  
Load Conditions

This paper summarizes the main results sorted out from a design of experiment (DoE) based on a validated computational fluid dynamics (CFD). Several tip recessed geometries applied to an unshrouded impeller were considered in conjunction with two tip clearance levels. The computations show that recessed tip geometries have positive effects when considering high-flow coefficient values, while in part-load conditions the gain is reduced. Starting from the results obtained when studying tip cavities, a single rim tip squealer geometry was then analyzed: the proposed geometry leads to performance improvements for all the tested conditions considered in this work.

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