scholarly journals Influence of the Reshaped Elbow on the Unsteady Pressure Field in a Simplified Geometry of the Draft Tube

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1393
Author(s):  
Raul-Alexandru Szakal ◽  
Alexandru Doman ◽  
Sebastian Muntean
Keyword(s):  
Pressure Field ◽  
Narrow Band ◽  
Draft Tube ◽  
Power Spectra ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Mean Square ◽  
Unsteady Pressure ◽  
Fundamental Frequencies ◽  
Draft Tubes

The paper focuses on the influence of the reshaped elbow geometry of the draft tube on the unsteady pressure field under different operating conditions. The experimental investigations are conducted considering two simplified geometrical configurations of the draft tubes with sharp heel elbow and modified/reshaped elbow, respectively. The discriminated power spectra (rotating and plunging components) of the acquired pressure signals on the wall are determined on five levels for seven operating conditions to quantify the influence of the reshaped elbow. The influence of the reshaped elbow on the fundamental frequencies of both rotating and plunging components and on the amplitude of the rotating component is negligible. In contrast, the equivalent amplitude associated with the root mean square of the plunging power spectrum that propagates along the hydraulic passage is mitigated up to 25% by the reshaped geometry of the elbow. The equivalent amplitude on the narrow band around the fundamental frequency of the plunging component is diminished with 40–50% by reshaping the elbow geometry of the simplified draft tube.

Vibration of Water-Turbine Draft Tubes

1961 ◽  
Vol 83 (1) ◽  
pp. 36-42 ◽  
Author(s):  
Mitsukiyo Murakami
Keyword(s):  
Vortex Core ◽  
Draft Tube ◽  
Experimental Investigations ◽  
Part Load ◽  
Periodic Vibration ◽  
Water Turbine ◽  
Draft Tubes

The vibration in the draft tube of a water turbine is most severe when the turbine is running on part load. This is caused principally by the vortex core of whirling water in the draft tube. The theoretical and experimental investigations of the frequency and force of periodic vibration caused by the vortex core are described, and there is clarification of the draft-tube surge caused by vibration due to the vortex core.

Wake, Shock, and Potential Field Interactions in a 1.5 Stage Turbine—Part I: Vane-Rotor and Rotor-Vane Interaction

2003 ◽  
Vol 125 (1) ◽  
pp. 33-39 ◽  
Author(s):  
R. J. Miller ◽  
R. W. Moss ◽  
R. W. Ainsworth ◽  
N. W. Harvey
Keyword(s):  
High Pressure ◽  
Potential Field ◽  
Pressure Field ◽  
Fast Response ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
The Individual

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers, and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flowfield in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. The paper is split into two parts: the first investigating the effect of the upstream vane on the unsteady pressure field around the rotor (vane-rotor interaction), and the second investigating the effect of the downstream vane on the unsteady pressure field around the rotor (rotor-vane interaction). The paper shows that at typical design operating conditions shock interaction from the upstream blade row is an order of magnitude greater than wake interaction and that with the design vane-rotor inter-blade gap the presence of the rotor causes a periodic increase in the strength of the vane trailing edge shock. The presence of the potential field of the downstream vane is found to affect significantly the rotor pressure field downstream of the Mach one surface within each rotor passage.

Numerical Calculation of Wall Pressure Fluctuations in a Centrifugal Fan

2004 ◽  
Author(s):  
Sandra Velarde-Sua´rez ◽  
Rafael Ballesteros-Tajadura ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Wall Pressure ◽  
Operating Conditions ◽  
Numerical Code ◽  
Experimental Investigations ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Flow Phenomena

In this work, a numerical code has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been contrasted using previous experimental investigations carried out in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been calculated, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. The code has successfully simulated the volute pressure fluctuations due to the aerodynamic field, capturing the main flow phenomena such as the jet-wake effects and the impeller-volute interaction.

Measurement of Unsteady Pressure Field in a Turbocharger Compressor Using Pressure-Sensitive Paint

2018 ◽  
Author(s):  
Takaaki Kitamura ◽  
Masaharu Kameda ◽  
Wataru Watanabe ◽  
Kazutaka Horimoto ◽  
Kenta Akimoto ◽  
...  
Keyword(s):  
Time Series ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Field ◽  
Operating Conditions ◽  
Series Data ◽  
Pressure Sensitive Paint ◽  
Unsteady Pressure ◽  
Pressure Sensitive

It is necessary to quantitatively resolve the flow field generated in compressors at various operating conditions including the surge. In this study, fast-responding pressure-sensitive-paint (PSP) and temperature-sensitive-paint (TSP) was applied to measurement of steady and unsteady pressure and temperature fields in a turbocharger compressor. The surface pressure of a compressor impeller and the diffuser downstream of the impeller was measured under the rotating speed of 133,000 rpm with various mass flow rate of the inlet. Blue LED strobes were used as the excitation light source for PSP/TSP. The luminescence from PSP/TSP were captured by a high-speed camera. These instruments were controlled using the signal synchronized with a fixed rotation angle of the impeller, which was detected using a gap sensor installed near the impeller. The pressure was calculated from the time-series of the PSP signal. The output of PSP/TSP was compared with the signal from semiconductor pressure transducers and the thermal image taken by an infrared camera. For the analysis of the diffuser, the power spectra of the pressure field were obtained using the fast Fourier transform of the time-series data of the pressure fluctuation. The pressure field on the impeller was successfully obtained with the aid of adequate temperature compensation by TSP. It was confirmed that the time-averaged pressure on the impeller blades increased as the inlet mass flow rate was decreased. Large-amplitude points were distributed on the extension line of the impeller blades in the diffuser when the surge occurs.

Wake, Shock and Potential Field Interactions in a 1.5 Stage Turbine: Part I — Vane-Rotor and Rotor-Vane Interaction

2002 ◽  
Author(s):  
R. J. Miller ◽  
R. W. Moss ◽  
R. W. Ainsworth ◽  
N. W. Harvey
Keyword(s):  
High Pressure ◽  
Potential Field ◽  
Pressure Field ◽  
Fast Response ◽  
Operating Conditions ◽  
Rotor Blades ◽  
Time Resolved ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
The Individual

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows is investigated, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries are considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were conducted at engine-representative Mach and Reynolds numbers, and experimental data was acquired using fast-response pressure transducers mounted on the mid-height streamline of the HP rotor blades. The results are compared to time-resolved computational predictions of the flowfield in order to aid interpretation of experimental results and to determine the accuracy with which the computation predicts blade interaction. The paper is split into two parts, the first investigating the effect of the upstream vane on the unsteady pressure field around the rotor (vane-rotor interaction) and the second investigating the effect of the downstream vane on the unsteady pressure field around the rotor (rotor-vane interaction). The paper shows that at typical design operating conditions shock interaction from the upstream blade row is an order of magnitude greater than wake interaction and that with the design vane-rotor inter-blade gap the presence of the rotor causes a periodic increase in the strength of the vane trailing edge shock. The presence of the potential field of the downstream vane is found to affect significantly the rotor pressure field downstream of the Mach one surface within each rotor passage.

Experimental investigations to predict optimistic biodiesel(s) and its optimistic operating conditions by varying ignition delay period and fuel spray pressures for lower emissions and better performance

2020 ◽  
Vol 234 (19) ◽  
pp. 3890-3902
Author(s):  
Vishal V Patil ◽  
Ranjit S Patil
Keyword(s):  
Methyl Ester ◽  
Ignition Delay ◽  
Seed Oil ◽  
Delay Period ◽  
Operating Conditions ◽  
Experimental Investigations ◽  
Rubber Seed Oil ◽  
Rubber Seed ◽  
Neem Seed Oil ◽  
Ignition Delay Period

In this study, different characteristics of sustainable renewable biodiesels (those have a high potential of their production worldwide and in India) were compared with the characteristics of neat diesel to determine optimistic biodiesel for the diesel engine at 250 bar spray pressure. Optimistic fuel gives a comparatively lower level of emissions and better performance than other selected fuels in the study. Rubber seed oil methyl ester was investigated as an optimistic fuel among the other selected fuels such as sunflower oil methyl ester, neem seed oil methyl ester, and neat diesel. To enhance the performance characteristics and to further decrease the level of emission characteristics of fuel ROME, further experiments were conducted at higher spray (injection) pressures of 500 bar, 625 bar, and 750 bar with varying ignition delay period via varying its spray timings such as 8°, 13°, 18°, 23°, 28°, and 33° before top dead center. Spray pressure 250 bar at 23° before top dead center was investigated as an optimistic operating condition where fuel rubber seed oil methyl ester gives negligible hydrocarbon emissions (0.019 g/kW h) while its nitrogen oxide (NOX) emissions were about 70% lesser than those observed with neat diesel, respectively.

Bifurcation Analysis of Self-Acting Gas Journal Bearings

2001 ◽  
Vol 123 (4) ◽  
pp. 755-767 ◽  
Author(s):  
Cheng-Chi Wang ◽  
Cha’o-Ku`ang Chen
Keyword(s):  
Dynamic Behavior ◽  
Reynolds Equation ◽  
Rotational Velocity ◽  
Power Spectra ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Finite Differences Method ◽  
Subharmonic Response ◽  
Rotor Center ◽  
Rotor Mass

This paper studies the bifurcation of a rigid rotor supported by a gas film bearing. A time-dependent mathematical model for gas journal bearings is presented. The finite differences method and the Successive Over Relation (S.O.R) method are employed to solve the Reynolds’ equation. The system state trajectory, Poincare´ maps, power spectra, and bifurcation diagrams are used to analyze the dynamic behavior of the rotor center in the horizontal and vertical directions under different operating conditions. The analysis shows how the existence of a complex dynamic behavior comprising periodic and subharmonic response of the rotor center. This paper shows how the dynamic behavior of this type of system varies with changes in rotor mass and rotational velocity. The results of this study contribute to a further understanding of the nonlinear dynamics of gas film rotor-bearing systems.

scholarly journals Unsteady pressure measurement and numerical simulations in an end-wall region of a linear blade cascade

2021 ◽  
Vol 3 (8) ◽  
Author(s):  
Erik Flídr ◽  
Petr Straka ◽  
Milan Kladrubský ◽  
Tomáš Jelínek
Keyword(s):  
Numerical Simulations ◽  
Pressure Measurement ◽  
Power Spectra ◽  
Surface Flow ◽  
Wall Region ◽  
Suction Surface ◽  
Flow Angle ◽  
Unsteady Pressure ◽  
Flow Visualizations ◽  
End Wall

AbstractThis contribution describes experimental and numerical research of an unsteady behaviour of a flow in an end-wall region of a linear nozzle cascade. Effects of compressibility ($$M_\mathrm {2,is}$$ M 2 , is ) and inlet flow angle ($$\alpha _1$$ α 1 ) were investigated. Reynolds number ($$Re_\mathrm {2,is}$$ R e 2 , is $$=8.5\times 10^5$$ = 8.5 × 10 5 ) was held constant for all tested cases. Unsteady pressure measurement was performed at the blade mid-span in the identical position $${\mathfrak {s}}$$ s to obtain reference data. Surface flow visualizations were performed as well as the steady pressure measurement to support conclusions obtained from the unsteady measurements. Comparison of the surface Mach number distributions obtained from the experiments and from the numerical simulations are presented. Flow visualizations are then compared with calculated limiting streamlines on the blade suction surface. It was shown, that the flow structures in the end-wall region were not affected by the primary flow at the blade mid-span, even when the shock wave formed. This conclusion was made from the experimental, numerical, steady as well as unsteady points of view. Three significant frequencies in the power spectra suggested that there was a periodical interaction between the vortex structures in the end-wall region. Based on the data analyses, anisotropic turbulence was observed in the cascade.

Experimental Investigation on the Rubbing Process of Labyrinth Seals Considering the Material Combination

2020 ◽  
Author(s):  
Lisa Hühn ◽  
Oliver Munz ◽  
Corina Schwitzke ◽  
Hans-Jörg Bauer
Keyword(s):  
Turbine Blades ◽  
Design Guidelines ◽  
Operating Conditions ◽  
Contact Forces ◽  
Experimental Investigations ◽  
Process Data ◽  
Labyrinth Seals ◽  
Material Combination ◽  
Higher Temperature ◽  
And Control

Abstract Labyrinth seals are used to prevent and control the mass flow rate between rotating components. Due to thermally and mechanically induced expansions during operation and transient flight maneuvers, a contact, the so-called rubbing process, between rotor and stator cannot be excluded. A large amount of rubbing process data concerning numerical and experimental investigations is available in public literature as well as at the Institute of Thermal Turbomachinery (ITS). The investigations were carried out for different operating conditions, material combinations, and component geometries. In combination with the experiments presented in this paper, the effects of the different variables on load due to rubbing are compared, and discussed with the focus lying on the material combination. The influence of the material on the loads can be identified as detailed as never before. For example, the contact forces in the current experiments are higher due to a higher temperature resistance of Young’s modulus. The analysis will also be based on the rubbing of turbine blades. Design guidelines are derived for labyrinth seals with improved properties regarding tolerance of rub events. Based on the knowledge obtained, guidelines for designing reliable labyrinth seals for future engines are discussed.

Experimental Inverstigations On the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals with Embedded Pressure Sensors

2021 ◽  
Author(s):  
Jingjing Luo ◽  
Dieter Brillert
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Static Pressure ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Test Facility ◽  
Experimental Investigations ◽  
Mechanical Seals ◽  
Process Gas ◽  
Sealing Gap

Abstract Dry gas lubricated non-contacting mechanical seals (DGS), most commonly found in centrifugal compressors, prevent the process gas flow into the atmosphere. Especially when high speed is combined with high pressure, DGS is the preferred choice over other sealing alternatives. In order to investigate the flow field in the sealing gap and to facilitate the numerical prediction of the seal performance, a dedicated test facility is developed to carry out the measurement of key parameters in the gas film. Gas in the sealing film varies according to the seal inlet pressure, and the thickness of gas film depends on this fluctuated pressure. In this paper, the test facility, measurement methods and the first results of static pressure measurements in the sealing gap of the DGS obtained in the described test facility are presented. An industry DGS with three-dimensional grooves on the surface of the rotating ring, where experimental investigations take place, is used. The static pressure in the gas film is measured, up to 20 bar and 8,100 rpm, by several high frequency ultraminiature pressure transducers embedded into the stationary ring. The experimental results are discussed and compared with the numerical model programmed in MATLAB, the characteristic and magnitude of which have a good agreement with the numerical simulations. It suggests the feasibility of measuring pressure profiles of the standard industry DGS under pressurized dynamic operating conditions without altering the key components of the seal and thereby affecting the seal performance.

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