Impact of Inter-Stage Dynamics on Stalling Stage Identification

2011 ◽  
Author(s):  
Manuj Dhingra ◽  
J. V. R. Prasad ◽  
Prashant Tiwari ◽  
Tsuguji Nakano ◽  
Andy Breeze-Stringfellow
Keyword(s):  
Test Data ◽  
Fluid Dynamic ◽  
Pressure Rise ◽  
State Equation ◽  
Rotating Stall ◽  
Expansion Waves ◽  
Upstream Pressure ◽  
Compression And Expansion ◽  
Suitable Framework ◽  
The Impact

A key objective of compressor rig tests is the identification of compressor stall boundary. A complementary goal is the identification of the stalling stage based on test data. This serves two purposes: 1) Validate the pre-test prediction of the stage loading distribution, and 2) identify the weak stages, should improvements in operating range be desired in subsequent design iterations. Typically the pertinent test data is in the form of static pressure measurements. Many engineers believe that a stalling stage is accompanied by a transient upstream pressure rise coupled with a downstream pressure loss. However, inter-stage dynamics may cloud the identification of the stalling stage. To this end, an analysis of inter-stage dynamics, immediately preceding the stall event, could provide an alternate assessment of the stalling stage. This work reviews existing stall models for studying compressor dynamics. The main focus of this work is to develop ability to capture inter-stage dynamics. A 3-state equation lumped Moore-Greitzer (MG3) model is widely used to study the dynamic compressor response during surge and rotating stall transients. However the evolution of MG3 model may not provide a suitable framework for the investigation of inter-stage dynamics. On the other hand, an unsteady time marching 1-D fluid dynamic model (e.g. similar to the DynTECC formulation which includes body forces), while unable to capture the rotating stall dynamics, is sufficient for this purpose. A numerical simulation has been developed to investigate the impact of stage characteristics, as well as load distribution on the compression and expansion waves that develop prior to a surge event. Through a controlled weakening of selected stages, the time evolution of these waves is related back to the stalling stage. It is found that the weakened stage is not necessarily the stalling stage as identified via the pressure rise and downstream pressure drop pattern.

A Theory of Post-Stall Transients in Axial Compression Systems: Part II—Application

1986 ◽  
Vol 108 (2) ◽  
pp. 231-239 ◽  
Author(s):  
E. M. Greitzer ◽  
F. K. Moore
Keyword(s):  
Axial Compression ◽  
Parametric Study ◽  
Pressure Rise ◽  
Transient Behavior ◽  
Rotating Stall ◽  
Future Research ◽  
System Response ◽  
System Behavior ◽  
Flow Pressure ◽  
The Impact

Using the theory developed in Part I, calculations have been carried out to show the evolution of the mass flow, pressure rise, and rotating-stall cell amplitude during compression system post-stall transients. In particular, it is shown that the unsteady growth or decay of the stall cell can have a significant effect on the instantaneous compressor pumping characteristic and hence on the overall system behavior. A limited parametric study is carried out to illustrate the impact of different system features on transient behavior. It is shown, for example, that the ultimate mode of system response, surge or stable rotating stall, depends not only on the B parameter, but also on the compressor length-to-radius ratio. Small values of the latter quantity tend to favor the occurrence of surge, as do large values of B. Based on the analytical and numerical results, some specific topics are suggested for future research on post-stall transients.

Control of Deep-Hysteresis Aeroengine Compressors1

1996 ◽  
Vol 122 (1) ◽  
pp. 140-152 ◽  
Author(s):  
Hsin-Hsiung Wang ◽  
Miroslav Krstic´ ◽  
Michael Larsen
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Dynamic ◽  
Convex Combination ◽  
Pressure Rise ◽  
Open Loop ◽  
Rotating Stall ◽  
Qualitative Description ◽  
Entire Family

Frequencies of higher-order modes of fluid dynamic phenomena participating in aeroengine compressor instabilities far exceed the bandwidth of available (affordable) actuators. For this reason, most of the heretofore experimentally validated control designs for aeroengine compressors have been via low-order models—specifically, via the famous Moore-Greitzer cubic model (MG3). While MG3 provides a good qualitative description of open-loop dynamic behavior, it does not capture the main difficulties for control design. In particular, it fails to exhibit the so-called “right-skew” property which distinguishes the deep hysteresis observed on high-performance axial compressors from a small hysteresis present in the MG3 model. In this paper we study fundamental feedback control problems associated with deep-hysteresis compressors. We first derive a parametrization of the MG3 model which exhibits the right skew property. Our approach is based on representing the compressor characteristic as a convex combination of a usual cubic polynomial and a nonpolynomial term carefully chosen so that an entire family of right-skew compressors can be spanned using a single parameter ε. Then we develop a family of controllers which are applicable not only to the particular parametrization, but to general Moore-Greitzer type models with arbitrary compressor characteristics. For each of our controllers we show that it achieves a supercritical (soft) bifurcation, that is, instead of an abrupt drop into rotating stall, it guarantees a gentle descent with a small stall amplitude. Two of the controllers have novel, simple, sensing requirements: one employs only the measurement of pressure rise and rotating stall amplitude, while the other uses only pressure rise and the mass flow rate (1D sensing). Some of the controllers which show excellent results for the MG3 model fail on the deep-hysteresis compressor model, thus justifying our focus on deep-hysteresis compressors. Our results also confirm experimentally observed difficulties for control of compressors that have a high value of Greitzer’s B parameter. We address another key issue for control of rotating stall and surge—the limited actuator bandwidth—which is critical because even the fastest control valves are often too slow compared to the rates of compressor instabilities. Our conditions show an interesting trade-off: as the actuator bandwidth decreases, the sensing requirements become more demanding. Finally, we go on to disprove a general conjecture in the compressor control community that the feedback of mass flow rate, known to be beneficial for shallow-hysteresis compressors, is also beneficial for deep-hysteresis compressors. [S0022-0434(00)03101-4]

Dense Particulate Flow in a Cold Gas Dynamic Spray System

2008 ◽  
Vol 130 (8) ◽  
Author(s):  
B. Samareh ◽  
A. Dolatabadi
Keyword(s):  
Volume Fraction ◽  
Stagnation Pressure ◽  
Bow Shock ◽  
Particulate Flow ◽  
Normal Velocity ◽  
Particle Interactions ◽  
Expansion Waves ◽  
Large Particles ◽  
Compression And Expansion ◽  
The Impact

The effect of particle-gas and particle-particle interactions in a cold spray process is studied when the particle loading is high. To examine the effect of the presence of a dense particulate flow on the supersonic gas, an Eulerian-Eulerian approach is used. It is found that when the volume fraction of the injected particles is increased, the turbulence of the gas phase will be augmented by the motion of particles and consequently, the shape, the strength, and the location of the compression and expansion waves will be altered. Shock-particle interactions are demonstrated for various volume fractions. Another important parameter, which will affect the spraying deposition efficiency, is the substrate stand-off distance. It is found that the stagnation pressure alternates for different stand-off distances because of the formation of compression and expansion waves outside the nozzle exit. The particle normal velocity on impact is a strong function of the stagnation pressure on the substrate as particles must pierce through the bow shock formed on that region. The effect of the particle size and number density are also studied for different loading conditions. It is found that small and large particles behave differently as they pass through shock diamonds and the bow shock, i.e., in the case of very small particles, as the loading increases, the impact velocity increases, while, for the large particles, the trend is reversed.

scholarly journals Vibro-Acoustical Sensitivities of Stiffened Aircraft Structures Due to Attached Mass-Spring-Dampers with Uncertain Parameters

Aerospace ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 174
Author(s):  
Johannes Seidel ◽  
Stephan Lippert ◽  
Otto von Estorff
Keyword(s):  
System Response ◽  
Fuzzy Arithmetic ◽  
Parameter Uncertainties ◽  
Excitation Spectra ◽  
Radiated Noise ◽  
Linking Elements ◽  
Manufacturing Tolerances ◽  
Suitable Framework ◽  
Mass Spring ◽  
The Impact

The slightest manufacturing tolerances and variances of material properties can indeed have a significant impact on structural modes. An unintentional shift of eigenfrequencies towards dominant excitation frequencies may lead to increased vibration amplitudes of the structure resulting in radiated noise, e.g., reducing passenger comfort inside an aircraft’s cabin. This paper focuses on so-called non-structural masses of an aircraft, also known as the secondary structure that are attached to the primary structure via clips, brackets, and shock mounts and constitute a significant part of the overall mass of an aircraft’s structure. Using the example of a simplified fuselage panel, the vibro-acoustical consequences of parameter uncertainties in linking elements are studied. Here, the fuzzy arithmetic provides a suitable framework to describe uncertainties, create combination matrices, and evaluate the simulation results regarding target quantities and the impact of each parameter on the overall system response. To assess the vibrations of the fuzzy structure and by taking into account the excitation spectra of engine noise, modal and frequency response analyses are conducted.

scholarly journals Determination of Zero Dimensional, Apparent Devolatilization Kinetics for Biomass Particles at Suspension Firing Conditions

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1018
Author(s):  
Anna Espekvist ◽  
Tian Li ◽  
Peter Glarborg ◽  
Terese Løvås ◽  
Peter Arendt Jensen
Keyword(s):  
Aspect Ratio ◽  
Particle Density ◽  
Fluid Dynamic ◽  
Particle Radius ◽  
Biomass Combustion ◽  
Least Squares Regression ◽  
Gas Temperature ◽  
Density Maximum ◽  
Parameter Ranges ◽  
The Impact

As part of the strive for a carbon neutral energy production, biomass combustion has been widely implemented in retrofitted coal burners. Modeling aids substantially in prediction of biomass flame behavior and thus in boiler chamber conditions. In this work, a simple model for devolatilization of biomass at conditions relevant for suspension firing is presented. It employs Arrhenius parameters in a single first order (SFOR) devolatilization reaction, where the effects of kinetics and heat transfer limitations are lumped together. In this way, a biomass particle can be modeled as a zero dimensional, isothermal particle, facilitating computational fluid dynamic calculations of boiler chambers. The zero dimensional model includes the effects of particle aspect ratio, particle density, maximum gas temperature, and particle radius. It is developed using the multivariate data analysis method, partial least squares regression, and is validated against a more rigorous semi-2D devolatilization model. The model has the capability to predict devolatilization time for conditions in the parameter ranges; radius (39–1569 μμm), density (700–1300 kg/m3), gas temperature (1300–1900 K), aspect ratio (1.01–8). Results show that the particle radius and gas phase temperature have a large influence on the devolatilization rate, and the aspect ratio has a comparatively smaller effect, which, however, cannot be neglected. The impact of aspect ratio levels off as it increases. The model is suitable for use as stand alone or as a submodel for biomass particle devolatilization in CFD models.

scholarly journals Impact of partial slip and lateral walls on peristaltic transport of a couple stress fluid in a rectangular duct

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110136
Author(s):  
Safia Akram ◽  
Najma Saleem ◽  
Mir Yasir Umair ◽  
Sufian Munawar
Keyword(s):  
Couple Stress ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Partial Slip ◽  
Couple Stress Fluid ◽  
Rectangular Duct ◽  
Peristaltic Pumping ◽  
Current Article ◽  
The Impact ◽  
Lateral Walls

The impact of lateral walls and partial slip with different waveforms on peristaltic pumping of couple stress fluid in a rectangular duct with different waveforms has been discussed in the current article. By means of a wave frame of reference the flow is explored travelling away from a fixed frame with velocity c. Peristaltic waves generated on horizontal surface walls of rectangular duct are considered using lubrication technique. Mathematical modelling of couple fluid for three-dimensional flow are first discussed in detail. Lubrication approaches are used to simplify the proposed problem. Exact solutions of pressure gradient, pressure rise, velocity and stream function have been calculated. Numerical and graphical descriptions are displayed to look at the behaviour of diverse emerging parameters.

Roles of vanes in diffuser on stability of centrifugal compressor

2019 ◽  
Vol 233 (14) ◽  
pp. 5380-5392
Author(s):  
Wangzhi Zou ◽  
Xiao He ◽  
Wenchao Zhang ◽  
Zitian Niu ◽  
Xinqian Zheng
Keyword(s):  
High Pressure ◽  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Centrifugal Compressors ◽  
Compression System ◽  
The Stability ◽  
Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

Computational Fluid Dynamic Applications for Jet Propulsion System Integration

1991 ◽  
Vol 113 (1) ◽  
pp. 40-50 ◽  
Author(s):  
R. H. Tindell
Keyword(s):  
System Integration ◽  
Fluid Dynamic ◽  
Low Cost ◽  
Separated Flow ◽  
Propulsion System ◽  
Navier Stokes ◽  
Aerospace Vehicles ◽  
Design Engineers ◽  
Flow Phenomena ◽  
The Impact

The impact of computational fluid dynamics (CFD) methods on the development of advanced aerospace vehicles is growing stronger year by year. Design engineers are now becoming familiar with CFD tools and are developing productive methods and techniques for their applications. This paper presents and discusses applications of CFD methods used at Grumman to design and predict the performance of propulsion system elements such as inlets and nozzles. The paper demonstrates techniques for applying various CFD codes and shows several interesting and unique results. A novel application of a supersonic Euler analysis of an inlet approach flow field, to clarify a wind tunnel-to-flight data conflict, is presented. In another example, calculations and measurements of low-speed inlet performance at angle of attack are compared. This is highlighted by employing a simplistic and low-cost computational model. More complex inlet flow phenomena at high angles of attack, calculated using an approach that combines a panel method with a Navier-Stokes (N-S) code, is also reviewed. The inlet fluid mechanics picture is rounded out by describing an N-S calculation and a comparison with test data of an offset diffuser having massively separated flow on one wall. Finally, the propulsion integration picture is completed by a discussion of the results of nozzle-afterbody calculations, using both a complete aircraft simulation in a N-S code, and a more economical calculation using an equivalent body of revolution technique.

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.

Theoretical Investigation of a Peristaltic Magneto-Fluid Dynamic Induction Compressor-2

1965 ◽  
Vol 9 (02) ◽  
pp. 56-65
Author(s):  
Joseph L. Neuringer ◽  
Eugene Migotsky ◽  
James H. Turner ◽  
Robert M. Haag
Keyword(s):  
Scaling Laws ◽  
Electromechanical Coupling ◽  
Constant Pressure ◽  
Fluid Dynamic ◽  
Pressure Rise ◽  
Magnetic Reynolds Number ◽  
Design Parameters ◽  
Propulsion Systems ◽  
Geometric Scaling ◽  
Axial Mass

In Part 3, the nature of the electromechanically induced motions inside the compressor both of the fluid conductor and of the pumped fluid when the electromechanical coupling is weak, i.e., in the limit of small magnetic Reynolds number, is investigated. The analysis predicts the development of a constant pressure gradient in the pumped fluid when the condition is imposed that the time-average axial mass flow across the conducting fluid annulus is zero. In Part 4, a preliminary feasibility study is made to determine whether the induction compressor has the potential to provide the pressure rise required to propel large and small undersea craft by means of jet propulsion systems for reasonable power and current-sheet inputs. Also determined here are the geometric scaling laws for the appropriate operating and design parameters.

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