On the Phenomenon of Pressure Pulses Reflecting Between Blades of Adjacent Blade Rows of Turbomachines

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Jerzy A. Owczarek
Keyword(s):  
Pressure Pulse ◽  
Physical Phenomenon ◽  
Research Work ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Test Results ◽  
Lehigh University ◽  
Pressure Pulses ◽  
Excitation Frequencies ◽  
Asme Paper

The recently revived interest in “acoustic resonances,” whose details are still not well defined or understood, points to a realization that a new look at some previously unrecognized findings is needed to explain problems encountered in operation of compressors and turbines. The purpose of this paper is to call the attention of the turbomachinery community to an important physical phenomenon of pressure waves in form of pulses, which reflect between blades of adjacent blade rows of turbomachines discovered more than 40 years ago, about whose existence and consequences there is little awareness today. The turbine test results which led the author in 1957 to hypothesize the existence of the phenomenon of reflecting pressure pulses are described. Subsequently, his 1966 ASME paper is discussed. In it, the author reported on the photographed observations of pressure pulses reflecting between stationary nozzles and moving blades of a water-table turbine at Lehigh University, on the description of the various types of such waves, and on an explanation of some of the resonant blade excitation frequencies observed by National Advisory Committee for Aeronautics (NACA) in a turbine of turbojet engine. This is followed by a description of his 1984 ASME paper, in which more general formulae were derived for the blade excitation frequencies caused by the reflections of pressure pulses between the rotor blades, and both upstream and downstream stator vanes. These equations were subsequently used to explain the blade excitation frequencies measured in an axial compressor stage. Finally, his 1992 AIAA paper is discussed, in which additional formulae relating to the reflecting pressure pulses were derived, and the process of formation of a pressure pulse was explained. To put this work in perspective, the author provided, in mostly chronological order, excerpts from reports on operational problems encountered with turbomachines in service and brief descriptions, from selected publications, of pertinent research work.

On the Phenomenon of Pressure Pulses Reflecting Between Blades of Adjacent Blade Rows of Turbo-Machines

2009 ◽  
Author(s):  
Jerzy A. Owczarek
Keyword(s):  
Physical Phenomenon ◽  
Research Work ◽  
Axial Compressor ◽  
Rotor Blades ◽  
Lehigh University ◽  
Main Emphasis ◽  
Pressure Pulses ◽  
Excitation Frequencies ◽  
Work Done ◽  
Asme Paper

The main emphasis of the paper is on the work done by the writer between the years 1957 and 1992 on the phenomenon of pressure waves in form of pulses which reflect from blades of adjacent blade rows of turbo-machines. The recently revived interest in “acoustic resonances”, whose details are still not well defined or understood, points to a realization that a new look at some previously unrecognized findings is needed to explain problems encountered in operation of compressors and turbines. The purpose of this paper is to call attention of the turbo-machinery community to an important physical phenomenon discovered more than forty years ago about whose existence and consequences there is little awareness today. The turbine test results which led the writer in 1957 to hypothesize the existence of the phenomenon of reflecting pressure pulses are described. Subsequently, his 1966 ASME paper is discussed. In it the writer reported on the photographed observations of pressure pulses reflecting between stationary nozzles and moving blades of a water-table turbine at Lehigh University, on the description of the various types of such waves, and on an explanation of some of the resonant blade excitation frequencies observed by NACA in a turbine of turbojet engine. This is followed by a description of his 1984 ASME paper in which more general formulae were derived for the blade excitation frequencies caused by reflections of pressure pulses between the rotor blades and both upstream and downstream stator vanes. These equations were subsequently used to explain blade excitation frequencies measured in an axial compressor stage. Finally, his 1992 AIAA paper is discussed in which additional formulae relating to the reflecting pressure pulses were derived and the process of formation of a pressure pulse explained. To put this work in perspective, the writer provided, in mostly chronological order, excerpts from reports on operational problems encountered with turbo-machines in service and brief descriptions, from selected publications, of pertinent research work.

Modelling of Flow Properties of Asphalt Mastics

2013 ◽  
Vol 752 ◽  
pp. 209-216 ◽  
Author(s):  
Róbert Géber ◽  
László A. Gömze
Keyword(s):  
Research Work ◽  
Road Construction ◽  
Test Results ◽  
Flow Properties ◽  
Rheological Models ◽  
Fine Grained ◽  
Mineral Particles ◽  
Asphalt Mastics ◽  
Rheological Modelling ◽  
Mineral Fillers

The present research work deals with the examination and rheological modelling of flow properties of asphalt mastics which are the most important components of asphalt concretes. Asphalt mastics are mixtures of fine grained mineral filler particles (d<0,063 mm) and bitumen, having a stabilizing role in asphalt mixtures and largely determining the cohesion between mineral particles and bitumen. During our examinations two types of mineral fillers – limestone and dolomite – as well as standard bitumen were tested, which are extensively used in Hungarian road construction. Asphalt mastic mixtures were prepared out of these materials and they were tested with dynamic shear rheometer (DSR). According to the test results, rheological models of mastics were determined. It has been established that at different test temperatures and shear rate ranges asphalt mastics behave as Herschel-Bulkley and Bingham-type materials.

An Improved Test Facility for Studying Deposit Fouling on Steam Turbine Blades

2016 ◽  
Author(s):  
Alan R. May Estebaranz ◽  
Richard J. Williams ◽  
Simon I. Hogg ◽  
Philip W. Dyer
Keyword(s):  
Turbine Blades ◽  
Steam Pressure ◽  
Reactor Vessel ◽  
Test Facility ◽  
Test Results ◽  
Steam Turbines ◽  
Steam Power ◽  
Scale Test ◽  
Steam Turbine Blades ◽  
Asme Paper

A laboratory scale test facility has been developed to investigate deposition in steam turbines under conditions that are representative of those in steam power generation cycles. The facility is an advanced two-reactor vessel test arrangement, which is a more flexible and more accurately controllable refinement to the single reactor vessel test arrangement described previously in ASME Paper No. GT2014-25517 [1]. The commissioning of the new test facility is described in this paper, together with the results from a series of tests over a range of steam conditions, which show the effect of steam conditions (particularly steam pressure) on the amount and type of deposits obtained. Comparisons are made between the test results and feedback/experience of copper fouling in real machines.

Experimental and analytical investigation on the in-plane dynamic instability of arches owing to parametric resonance

2017 ◽  
Vol 24 (19) ◽  
pp. 4419-4432 ◽  
Author(s):  
Airong Liu ◽  
Zhicheng Yang ◽  
Hanwen Lu ◽  
Jiyang Fu ◽  
Yong-Lin Pi
Keyword(s):  
Parametric Resonance ◽  
Dynamic Instability ◽  
Damping Ratio ◽  
Analytical Investigation ◽  
Engineering Practice ◽  
Test Results ◽  
Periodic Load ◽  
Shallow Arches ◽  
Excitation Frequencies ◽  
Critical Regions

When an arch is subjected to a periodic load, it may lose in-plane stability dynamically owing to parametric resonance. Previous investigations have been concentrated on in-plane dynamic buckling of pin-ended shallow arches. However, in engineering practice, fixed arches with different rise-to-span ratios are often encountered. Little research on in-plane dynamic instability of deep fixed arches has been reported in the literature. This paper is concerned with experimental and analytical investigations for in-plane dynamic instability of fixed circular arches with rise-to-span ratios 1/8–1/2 under a central periodic load owing to parametric resonance. Experiments are carried out to determine the in-plane frequency and damping ratio of arches, to investigate critical regions of frequencies and amplitudes of the periodic load for in-plane dynamic instability of arches, and to explore effects of the rise-to-span ratio and additional weights on dynamic instability. The analytical method for determining the region of excitation frequencies and amplitudes of the periodic load causing in-plane instability of the arch is established using the Hamilton’s principle by accounting for effects of additional concentrated weights. Comparisons of analytical solutions with test results show that they agree with each other quite well. These results show that the rise-to-span ratio significantly influences the bandwidth of regions of critical excitation frequencies for in-plane dynamic instability of arches. The critical frequencies of the periodic load and their bandwidth increase with a decrease of the rise–span ratio of the arch, whereas the corresponding amplitude of the periodic load decreases at the same time. It is also found that the central concentrated weight influences in-plane dynamic instability of arches significantly. As the weight increases, the critical frequencies of excitation and their bandwidth for in-plane dynamic instability of arches decreases, whereas the corresponding amplitude of excitation increases.

EFFECT OF WET-DRY CYCLING ON BOND BEHAVIOR OF GFRP STRENGTHENED HISTORIC MASONRY STRUCTURES

2016 ◽  
Vol 78 (5-2) ◽  
Author(s):  
Meng Jing ◽  
Werasak Raongjant
Keyword(s):  
Research Work ◽  
Fiber Reinforced Polymer ◽  
Masonry Structures ◽  
Test Results ◽  
Bond Behavior ◽  
Historic Masonry ◽  
Water Permeation ◽  
Reinforced Polymer ◽  
Glass Fiber Reinforced ◽  
Cycling Condition

The objective of this research work is to determine the effect of wet-dry cycling on bond behavior of historic masonry structures strengthened by Glass Fiber Reinforced Polymer (GFRP). Shear bond testing was carried out through total 36 specimens exposed to dry, full moisture or wet-dry cycling conditions.  The selected samples were then tested at 0, 30, 60 and 90 days. Post-ageing test was also preceded on total sixty masonry prisms exposed to dry, full moisture or wet-dry cycling conditions. The compressive strengths of selected samples were then tested at 0, 40, 70 and 100 days. The test results showed an obvious decrease of the bond strength between GFRP sheets and bricks in the wet-dry cycling condition. For masonry prisms with or without GFRP strengthening, in the first 40 days, the compressive strength of GFRP bonded prism decreased quickly to the value near that of prism without GFRP. After 40 days the rate of decrease became slow, which means that, sheets retrofitted outside the masonry prisms helped to improve their durability by reducing water permeation. 

Aerodynamic-Rotordynamic Interaction in Axial Compression Systems—Part I: Modeling and Analysis of Fluid-Induced Forces

2003 ◽  
Vol 125 (3) ◽  
pp. 405-415
Author(s):  
Ammar A. Al-Nahwi ◽  
James D. Paduano ◽  
Samir A. Nayfeh
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Pressure Rise ◽  
Essential Element ◽  
Rotor Blades ◽  
Tip Clearance ◽  
Analytical Models ◽  
Modeling And Analysis ◽  
Equal Importance ◽  
Consistent Treatment

This paper presents a first principles-based model of the fluid-induced forces acting on the rotor of an axial compressor. These forces are primarily associated with the presence of a nonuniform flow field around the rotor, such as that produced by a rotor tip clearance asymmetry. Simple, analytical expressions for the forces as functions of basic flow field quantities are obtained. These expressions allow an intuitive understanding of the nature of the forces and—when combined with a rudimentary model of an axial compressor flow field (the Moore-Greitzer model)—enable computation of the forces as a function of compressor geometry, torque and pressure-rise characteristics, and operating point. The forces predicted by the model are also compared to recently published measurements and more complex analytical models, and are found to be in reasonable agreement. The model elucidates that the fluid-induced forces comprise three main contributions: fluid turning in the rotor blades, pressure distribution around the rotor, and unsteady momentum storage within the rotor. The model also confirms recent efforts in that the orientation of fluid-induced forces is locked to the flow nonuniformity, not to tip clearance asymmetry as is traditionally assumed. The turning and pressure force contributions are shown to be of comparable magnitudes—and therefore of equal importance—for operating points between the design point and the peak of the compressor characteristic. Within this operating range, both “forward” and “backward” rotor whirl tendencies are shown to be possible. This work extends recent efforts by developing a more complete, yet compact, description of fluid-induced forces in that it accounts for all relevant force contributions, both tangential and radial, that may influence the dynamics of the rotor. Hence it constitutes an essential element of a consistent treatment of rotordynamic stability under the action of fluid-induced forces, which is the subject of Part II of this paper.

scholarly journals Design and Build a Multilevel Mace Nutmeg Dryer to Improve the People's Economy

SinkrOn ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 107-112
Author(s):  
Ihsan Ihsan ◽  
Dirja Nur Ilham ◽  
Reza Ade Putra ◽  
Rudi Arif Candra ◽  
Arie Budiansyah
Keyword(s):  
Software Design ◽  
Economic Value ◽  
Research Work ◽  
Test Results ◽  
Drying Process ◽  
Wet Season ◽  
Drying Time ◽  
Agricultural Community ◽  
Design Software

Nutmeg is a source of income for some people in South Aceh, and some types of nutmeg, like mace nutmeg, are of better quality. Mace nutmeg is also an agricultural community with great economic value and benefits for humans, as it can be processed into spices and herbs. A range of products includes nutmeg oil and medicines. The harvesting and drying of mace nutmeg, which is still considered a problem by nutmeg growers, cannot be isolated from the processing of the basic ingredients. The natural process of drying mace nutmeg involves the use of sunshine, which necessitates a considerable drying time. Therefore nutmeg farmers frequently complain of erratic weather, especially during the wet season. The constant rain can cause the mace to rot, causing the nutmeg farming community's revenue to become unstable. Methods and steps of research work starting from the study of literature, determination of design specifications, hardware design, software design, toolmaking, tool testing.Good results were reached with the dryness of the mace nutmeg, which can be adjusted, and without putting into account the weather in the drying process, which is usually done with the heat of the sun, per the results of the testing of the designed tools.The average dryness of mace nutmeg is at a temperature of 45 percent with a time of 4 hours and a capacity of 100 grams; according to the test results of the automatic mace drying machine, it produces 50 grams of dry mace.  

scholarly journals Valorization of Specially Designed Concrete by Using Sugarcane Bagasse Ash and Inducing the Special Benefits of Waste Tin Fiber Reinforced Concrete

2019 ◽  
Vol 8 (12) ◽  
pp. 220-224
Keyword(s):  
Tensile Strength ◽  
Portland Cement ◽  
Sugarcane Bagasse ◽  
Flexural Rigidity ◽  
Research Work ◽  
Fiber Reinforced Concrete ◽  
Target Strength ◽  
Test Results ◽  
Split Tensile Strength ◽  
Sugarcane Bagasse Ash

This research work has been investigated the agriculture solid waste of sugarcane bagasse ash (SCBA) materials replacing Portland cement and produces the assured quality of concrete. The current research work for various mixes of experimental test results shows the higher compressive strength was 37.51MPa at 28-days, 38.10 MPa at 56-days, the best mix consisting of SCBA (wet sieving method) content up to 15% (by weight of binding materials) along with 1.5% of waste tin fibers and also an excellent improvement trend was noted in flexural rigidity of concrete to addition of tin fibers shows the higher bending stress for all mixes except reference as well as more than 15% of SCBA concrete at different curing days. However, this study focused on the indirect measurement of tensile strength in SCBA concrete obtained the higher split tensile strength was 3.75MPa at 28-days, 3.95MPa at 56-days. It is concluded based on the various test results for different curing days the optimum replacement level of SCBA up to 15% of Portland cement was fixed and achieve the target strength of M25 grade of Portland cement concrete at 28 days.

Rotor Condition Monitoring for Improved Operational Safety of Offshore Wind Energy Converters

2005 ◽  
Vol 127 (2) ◽  
pp. 253-261 ◽  
Author(s):  
Peter Caselitz ◽  
Jochen Giebhardt
Keyword(s):  
Wind Energy ◽  
Condition Monitoring ◽  
Research Work ◽  
Field Tests ◽  
Rotor Blades ◽  
Fault Prediction ◽  
Offshore Wind ◽  
Offshore Wind Energy ◽  
Operational Safety ◽  
Energy Converters

Background: Due to cost effectiveness and operational safety online monitoring of rotor blades is recommended, especially for offshore wind energy converters. Method of Approach: Statistic evaluation of wind speed and power output of a wind energy converter is used to monitor the overall rotor performance including increased blade surface roughness. Nacelle oscillation spectral analysis methods are applied to monitor the rotor faults mass imbalance and aerodynamic asymmetry. Results: Results of ISET’s research work related to online rotor condition monitoring are presented. A description of the fault effects on the rotor, the sensor and data acquisition equipment and a description of the developed signal processing and fault prediction algorithms are given. The paper also presents results from experiments and field tests. Conclusions: The developed algorithms have been verified due to their monitoring capabilities and suitability in commercial online condition monitoring systems.

Cold Blade Profile Generation Methodology for Compressor Rotor Blades Using FSI Approach

2017 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
Sankar Kumar Jeyaraman ◽  
Ajay Pratap ◽  
Kishore Prasad Deshkulkarni
Keyword(s):  
Aspect Ratio ◽  
Rotor Blade ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Blade Profile ◽  
Interaction Technique ◽  
Compressor Rotor ◽  
Blade Shape ◽  
Blade Geometry

This paper describes a methodology for obtaining correct blade geometry of high aspect ratio axial compressor blades during running condition taking into account of blade untwist and bending. It discusses the detailed approach for generating cold blade geometry for axial compressor rotor blades from the design blade geometry using fluid structure interaction technique. Cold blade geometry represents the rotor blade shape at rest, which under running condition deflects and takes a new operating blade shape under centrifugal and aerodynamic loads. Aerodynamic performance of compressor primarily depends on this operating rotor blade shape. At design point it is expected to have the operating blade shape same as the intended design blade geometry and a slight mismatch will result in severe performance deterioration. Starting from design blade profile, an appropriate cold blade profile is generated by applying proper lean and pre-twist calculated using this methodology. Further improvements were carried out to arrive at the cold blade profile to match the stagger of design profile at design operating conditions with lower deflection and stress for first stage rotor blade. In rear stages, thermal effects will contribute more towards blade deflection values. But due to short blade span, deflection and untwist values will be of lower values. Hence difference between cold blade and design blade profile would be small. This methodology can especially be used for front stage compressor rotor blades for which aspect ratio is higher and deflections are large.

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