scholarly journals Experimental Investigation of Stall and Surge in a Multistage Compressor

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Enrico Munari ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Alessio Suman
Keyword(s):  
Mass Flow ◽  
Flow Instability ◽  
Numerical Models ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Test Facility ◽  
Extensive Literature ◽  
Test Rig

Flow instability conditions, in particular during surge and stall phenomena, have always influenced the operational reliability of turbocompressors and have attracted significant interest resulting in extensive literature. Nowadays, this subject is still one of the most investigated because of its high relevance on centrifugal and axial compressor operating flow range, performance, and efficiency. Many researchers approach this important issue by developing numerical models, whereas others approach it through experimental studies specifically carried out in order to better comprehend this phenomenon. The aim of this paper is to experimentally analyze the stable and unstable operating conditions of an aeronautic turboshaft gas turbine axial–centrifugal compressor installed on a brand new test rig properly designed for this purpose. The test facility is set up in order to obtain (i) the compressor performance maps at rotational speeds up to 25,000 rpm and (ii) the compressor transient behavior during surge. By using two different test rig layouts, instabilities occurring in the compressor, beyond the peak of the characteristic curve, are identified and investigated. These two types of analysis are carried out, thanks to pressure, temperature, and mass flow sensors located in strategic positions along the circuit. These measurement sensors are part of a proper control and acquisition system, characterized by an adjustable sampling frequency. Thus, the desired operating conditions of the compressor in terms of mass flow and rotational speed and transient of these two parameters are regulated by this dedicated control system.

scholarly journals Experimental Investigation of Stall and Surge in a Multistage Compressor

2016 ◽  
Author(s):  
Enrico Munari ◽  
Mirko Morini ◽  
Michele Pinelli ◽  
Pier Ruggero Spina ◽  
Alessio Suman
Keyword(s):  
Mass Flow ◽  
Flow Instability ◽  
Numerical Models ◽  
Characteristic Curve ◽  
Experimental Studies ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Test Facility ◽  
Extensive Literature ◽  
Test Rig

Flow instability conditions, in particular during surge and stall phenomena, have always influenced the operational reliability of turbo-compressors and have attracted significant interest resulting in extensive literature. Nowadays, this subject is still one of the most investigated because of its high relevance on centrifugal and axial compressor operating flow range, performance and efficiency. Many researchers approach this important issue by developing numerical models, whereas others approach it through experimental studies specifically carried out in order to better comprehend this phenomenon. The aim of this paper is to experimentally analyze the stable and unstable operating conditions of an aeronautic turbo-shaft gas turbine axial-centrifugal compressor installed on a brand new test-rig properly designed for this purpose. The test facility is set up in order to obtain i) the compressor performance maps at rotational speeds up to 25,000 rpm and ii) the compressor transient behavior during surge. By using two different test rig layouts, instabilities occurring in the compressor, beyond the peak of the characteristic curve, are identified and investigated. These two types of analysis are carried out thanks to pressure, temperature and mass flow sensors located in strategic positions along the circuit. These measurement sensors are part of a proper control and acquisition system, characterized by an adjustable sampling frequency. Thus, the desired operating conditions of the compressor, in terms of mass flow and rotational speed and transient of these two parameters are regulated by this dedicated control system.

Design of a New Experimental Rig for Thermal Cyclic Testing of Combustor Liner Tiles

2008 ◽  
Author(s):  
C. Mende ◽  
O. Liedtke ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Quality Data ◽  
Test Facility ◽  
Test Rig ◽  
Design Data ◽  
High Quality Data ◽  
Damage Models ◽  
Combustor Liner ◽  
Experimental Rig

This paper describes the design and operation of a new test rig, which allows the simulation of real engine operating conditions leading to Low-Cycle Fatigue of combustor liner tiles. The experimental setup will provide high-quality data for the development of damage models. At first the design data of the test rig will be derived from the relevant damage mechanisms in Combustor Liner Tiles (CLT). Then the construction of the test rig and its integration into an existing high temperature high pressure test facility will be elucidated. Finally experimental data of a typical simulated thermal cycle is shown.

EXPERIMENTAL STUDIES ON THE INFLUENCE OF ABRASIVE MATERIALS ON THE WEAR OF HARD-WEARING STEELS

Tribologia ◽  
2018 ◽  
Vol 281 (5) ◽  
pp. 133-141 ◽  
Author(s):  
Andrzej N. WIECZOREK
Keyword(s):  
Experimental Studies ◽  
Structural Steels ◽  
Operating Conditions ◽  
Ring Test ◽  
Test Rig ◽  
Wear Properties ◽  
Aggressive Action ◽  
Low Wear ◽  
Loss Of Mass ◽  
Wear Tests

The paper presents the wear properties of hard-wearing steels and structural steels used in mining and transport machines exposed to the aggressive action of the environment, which have been determined experimentally in the presence of diverse abrasive materials. The wear tests were carried out on a ring-on-ring test rig simulating the operating conditions of elements exposed to abrasive wear. The samples were subjected to tests in conditions of sliding contact, and the main destructive process was micro-cutting of the surface with loose corundum or quartz grain. In the case of the coal abrasive, only slight grinding in of the mating surfaces was observed. The loss of mass in the samples was measured as the parameter characterizing the wear. It was then used to determine the volume loss. Based on the results obtained, it was found that the wear resistance of hard-wearing steels was approximately four times higher as compared to S355J2 structural steel for the corundum and quartz abrasives. In the case of the coal abrasive, there was a relatively low wear for all of the materials examined.

The Experimental Studies of Improving the Aerodynamic Performance of a Turbine Exhaust System

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Stephen Guillot ◽  
Wing F. Ng ◽  
Hans D. Hamm ◽  
Ulrich E. Stang ◽  
Kevin T. Lowe
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Experimental Studies ◽  
Experimental Result ◽  
Test Facility ◽  
Test Rig ◽  
Blow Down ◽  
Recovery Coefficient ◽  
Scale Test ◽  
Turbine Exhaust

Analysis and testing were conducted to optimize an axial diffuser–collector gas turbine exhaust. Two subsonic wind tunnel facilities were designed and built to support this program. A 1/12th scale test rig enabled rapid and efficient evaluation of multiple geometries. This test facility was designed to run continuously at an inlet Mach number of 0.41 and an inlet hydraulic diameter-based Reynolds number of 3.4 × 105. A 1/4th geometric scale test rig was designed and built to validate the data in the 1/12th scale rig. This blow-down rig facilitated testing at a nominally equivalent inlet Mach number, while the Reynolds number was matched to realistic engine conditions via back pressure. Multihole pneumatic pressure probes, particle image velocimetry (PIV), and surface oil flow visualization were deployed in conjunction with computational tools to explore physics-based alterations to the exhaust geometry. The design modifications resulted in a substantial increase in the overall pressure recovery coefficient of +0.07 (experimental result) above the baseline geometry. The optimized performance, first measured at 1/12th scale and obtained using computational fluid dynamics (CFD) was validated at the full scale Reynolds number.

scholarly journals CFD Simulation of Proposed Validation Data for a Flow Problem Reconfigured to Eliminate an Undesirable Flow Instability

2010 ◽  
Author(s):  
Richard W. Johnson ◽  
Hugh M. McIlroy
Keyword(s):  
Mass Flow ◽  
Recirculation Zone ◽  
Cfd Simulation ◽  
Flow Instability ◽  
Index Of Refraction ◽  
Department Of Energy ◽  
Test Facility ◽  
Scaled Model ◽  
Validation Data ◽  
Data Set

The U. S. Department of Energy (DOE) is supporting the development of a next generation nuclear plant (NGNP), which will be based on a very high temperature reactor (VHTR) design. The VHTR is a single-phase helium-cooled reactor wherein the helium will be heated initially to 750 °C and later to temperatures approaching 1000 °C. The high temperatures are desired to increase reactor efficiency and to provide a heat source for the manufacture of hydrogen and other applications. While computational fluid dynamics (CFD) has not been used in the past to design or license nuclear reactors in the U. S., it is expected that CFD will be used in the design and safety analysis of forthcoming designs. This is partly because of the maturity of CFD and partly because detailed information is desired of the flow and heat transfer inside the reactor to avoid hot spots and other conditions that might compromise reactor safety. Numerical computations of turbulent flow should be validated against experimental data for flow conditions that contain some or all of the physics expected in the thermal fluid machinery of interest. To this end, a scaled model of a narrow slice of the lower plenum of the prismatic VHTR was constructed and installed in the Idaho National Laboratory’s (INL) matched index of refraction (MIR) test facility and data were taken. The data were then studied and compared to CFD calculations to help determine their suitability for validation data. One of the main findings was that the inlet data, which were measured and controlled by calibrated mass flow rotameters and were also measured using detailed stereo particle image velocimetry (PIV) showed considerable discrepancies in mass flow rate between the two methods. The other finding was that a randomly unstable recirculation zone occurs in the flow. This instability has a very significant effect on the flow field in the vicinity of the inlet jets. Because its time scale is long and because it is apparently a random instability, it was deemed undesirable for a validation data set. It was predicted using CFD that by eliminating the first of the four jets, the recirculation zone could be stabilized. The present paper reports detailed results for the three-jet case with comparisons to the four-jet data inasmuch as three-jet data are still unavailable. Hence, the present simulations are true or blind predictions.

scholarly journals RESEARCH OF TECHNICAL CHARACTERISTICS OF NEW TYPES OF COUPLINGS

2020 ◽  
pp. 113-121
Author(s):  
Oleksii Tokarchuk ◽  
Yurii Polievoda
Keyword(s):  
Elastic Element ◽  
Rational Design ◽  
Experimental Studies ◽  
Bending Moment ◽  
Operational Reliability ◽  
Modern Technology ◽  
Operating Conditions ◽  
The Moment ◽  
Working Bodies ◽  
Moment Of Resistance

Dynamic loads that occur during the operation of existing couplings cause significant shock loads, which leads to rapid wear of the surfaces of the couplings and shortens the service life. Modern technology faces the task of improving the operational reliability of the working bodies and drives of machines. One way to solve this problem is to develop and use high-precision and low-dynamic safety couplings. In this regard, the question of developing new designs of safety couplings that reduce impact loads and increase the reliability and durability of machinery is relevant. The synthesis of structural and kinematic schemes of ball, cam and planetary safety couplings, the method of their calculation in combination with the nature of the change in the moment of resistance on the working body of the equipment. The article conducts a set of theoretical and experimental studies to determine their rational design, kinematic and dynamic parameters that will satisfy the operating conditions of machines and mechanisms. A force analysis of the elastic element (ring spring) was performed. The scheme of loading of an elastic element by two forces and other settlement schemes are constructed, namely: equivalent system; force diagrams for determining the load torque; force schemes for determining the unit moment; schemes of total bending moment; force schemes to determine the total unit moment. During static experimental studies of the developed ball safety couplings, the nature of their operation was established, the maximum torque at the two stages of operation of the couplings was determined and a comparative analysis between the results of theoretical and experimental studies was performed. The positive results of experimental researches of the developed coupling and theoretical positions which can be applied to a substantiation and a choice of rational parameters of the developed designs of couplings and their engineering designing were confirmed.

scholarly journals Experimental studies and mathematical modeling on the effects of rapid airflow and baking temperature during baking

2020 ◽  
pp. 469
Author(s):  
Mazidah Mior Zakuan Azmi ◽  
Anvarjon Ahmedov ◽  
Farah Saleena Taip
Keyword(s):  
Heat Transfer ◽  
Volume Expansion ◽  
Numerical Models ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Transfer Model ◽  
Temperature Profiles ◽  
Convection Oven ◽  
Baking Process ◽  
Cake Baking

Rapid airflow in oven will influence the heat transfer in baking process therefore the purpose of this study is to experimentally and numerically investigate the effects of operating conditions on the heat transfer mechanism and volume expansion during baking. Cakes are baked in an air fryer and convection oven with constant speed 5.11 m/s and 0.88 m/s respectively at 150, 160, 170 °C in different baking times. A heat transfer model was defined to describe the influence of baking temperature on internal cake temperature by Fourier’s law. It was observed that the presence of rapid airflow (air fryer) and increment in oven temperature yielded an increase in volume expansion but produced a less moist product. Cakes baked in the presence of rapid airflow at 150 °C were moister but with little volume expansion in the cakes compared to convection oven-baked cakes. Significant correlation between the numerical models with experimental temperature profiles were recorded during complete cake baking process.

scholarly journals Estimation peculiarities of external polymer insulation reliability of gas-filled instrument transformers

2021 ◽  
pp. 3-9
Author(s):  
Liudmyla Zhorniak ◽  
Alexej Afanasiev ◽  
Vitaliy Schus ◽  
Olexij Morozov ◽  
Julia Rudenko
Keyword(s):  
High Voltage ◽  
Accurate Determination ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Operational Reliability ◽  
Current Transformer ◽  
Operating Conditions ◽  
Distribution Law ◽  
Instrument Transformers ◽  
And Performance

In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of operational reliability. In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of the operational reliability of a solid insulating structure of high-voltage devices, which is a supporting insulating cover for high voltage instrument transformers filled with gas as an insulating liquid. This technique makes it possible to estimate the parameters of a new distribution law, which is chosen on the condition that it does not contradict the existing distribution law with its known parameters. The developed technique makes it possible to obtain the values of the indicators of the operational reliability of high-voltage equipment by determining the parameters of theoretical distributions, if the developer is the data of experimental studies or statistical information as a result of monitoring the operation of insulating structures, taking into account the actual operating conditions of such high-voltage devices.  This makes it possible to take into account the influence of external factors and performance characteristics inherent in instrument transformers, both current and voltage. In the proposed methodology, as an example, a supporting insulating casing is considered, which is during operation in the most unfavorable conditions, such as external pollution, humidification, overvoltage, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the design of a current transformer of the ТОГ-362 series. A more accurate determination of the effectiveness of the proposed method for predicting the parameters of theoretical distribution laws can be achieved by performing an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that it is possible to use the results obtained to assess the operational reliability of both gas-filled instrument transformers and similar high-voltage equipment.

Delay of Unsteady Flow in a Radial Diffuser

2008 ◽  
Author(s):  
Saad A. Ahmed
Keyword(s):  
Mass Flow ◽  
Flow Rate ◽  
Flow Instability ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Coefficient ◽  
Width Ratio ◽  
Flow Rates ◽  
Lower Flow ◽  
Low Mass

The operation of centrifugal compressor systems is limited at low-mass flow rates by fluid flow instabilities leading to rotating stall or surge. These instabilities limit the flow range in which the compressor can operate. They also lower the performance and efficiency of the compressor. Experiments were conducted to investigate a model of radial vaneless diffuser at stall as well as stall-free operating conditions. The speed of the impeller was kept constant at 2000 RPM, while the mass flow rate was reduced gradually to scan the steady and unsteady operating conditions of the compressor. The flow rate through the compressor was gradually decreased until flow instability is initiated at the diffuser. The flow rate was further reduced to study the characteristics of rotating stall. These measurements were reported for diffuser diameter ratios, Do/Di, of 2.0 with diffuser width ratio, b/Di, of 0.055. At lower flow rates than the critical, the rotating stall pattern with one stall cell was dominant over the pattern with two cells. In addition, the instability in the diffuser was successfully delayed to a lower flow coefficient when rough surfaces were attached to one or both sides of the diffuser with the lowest values achieved by attaching the rough surface to the shroud. Results show that the roughness has no significant effect on stall cell characteristics.

Experimental Characterization of the Flow Instabilities of a Mixed-Flow Multiphase Pump Operating Air and Water Through Local Visualization and Analysis of Dynamic Measurements

2015 ◽  
Author(s):  
Alberto Serena ◽  
Lars E. Bakken
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Operating Conditions ◽  
Test Facility ◽  
Two Phase ◽  
Flow Mechanisms ◽  
Local Measurements ◽  
Specific Geometry ◽  
Promising Development

Part load operation of pumps generates flow and machine instabilities, which are not desirable and should be avoided as they result in premature wear and mechanical problems. Two-phase flow introduces additional challenges, both at the design and operational stages, due to the different phase behavior and mutual interaction. The phenomena involved present an intermittent character and are strongly dependent on the specific geometry and operating conditions. Despite the recent promising development of numerical simulations capabilities, an accurate characterization of the flow mechanisms still relies on real tests, which are needed to validate the numerical models too. An advanced laboratory test facility built at the Norwegian University of Science and Technology provides the required optical access to the pump channels, and high-speed recordings, along with local measurements of the pressure pulsations, allow to describe the flow structures in terms of location, length and time scales, and relate them to overall machine measurements, such as flow, pressure and torque. This provides a wide collection of test data of great value for a further understanding of the surging phenomenon, the development of a surging onset prediction model and a control strategy. Tests are performed covering the whole range of flow rates; a characteristic surging condition is identified and described in the article.

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