scholarly journals Strong Azimuthal Combustion Instabilities in a Spray Annular Chamber With Intermittent Partial Blow-Off

2017 ◽  
Author(s):  
Kevin Prieur ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
Light Intensity ◽  
Limit Cycle ◽  
High Speed ◽  
Pressure Sensors ◽  
Nodal Line ◽  
Operating Conditions ◽  
Acoustic Energy ◽  
Transverse Motion ◽  
Fluctuation Analysis ◽  
Lower Amplitude

The present article reports original experiments carried out in the MICCA-Spray combustor developed at EM2C, CNRS and CentraleSupélec. This system comprises 16 swirl spray injectors. Liquid n-heptane is injected by hollow cone simplex atomizers. The combustion chamber is formed by two cylindrical quartz tubes allowing full optical access to the flame region and it is equipped with eight pressure sensors recording signals in the plenum and chamber. A high speed camera provides images of the flames and photomultipliers record the light intensity from different flames. For certain operating conditions, the system exhibits well defined instabilities coupled by the first azimuthal mode of the chamber at a frequency of about 750 Hz. These instabilities occur in the form of bursts with a moderate level of growth. Examination of the pressure and the light intensity signals gives access to the acoustic energy source term. Analysis of the phase between the two signals during the instability bursts (growth, limit cycle, decay) is carried out using cross-spectral analysis. At limit cycle, large amplitude of pressure oscillations are reached with peak values around 5000 Pa (or 5% of the mean pressure in the chamber), and these levels persist over a finite period of time. Detailed analysis of the signals using the spin ratio indicates that the standing mode is predominant. The chamber can exhibit a spinning mode but with a lower amplitude of acoustic fluctuation. Analysis of the flame dynamics at the pressure anti-nodal line reveals a strong longitudinal pulsation with heat release rate oscillations in phase and increasing linearly with the acoustic pressure even at the highest oscillation levels. At the pressure nodal line, the flames are subjected to large transverse velocity fluctuations leading to a transverse motion of the flames and partial blow-off. Scenarios and modeling elements are developed to interpret these features. To the best of our knowledge, this is the first time that azimuthal instabilities are characterized in a well-controlled annular combustor with swirled spray flames.

scholarly journals Strong Azimuthal Combustion Instabilities in a Spray Annular Chamber With Intermittent Partial Blow-Off

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Kevin Prieur ◽  
Daniel Durox ◽  
Thierry Schuller ◽  
Sébastien Candel
Keyword(s):  
Light Intensity ◽  
High Speed ◽  
Transverse Velocity ◽  
Pressure Fluctuations ◽  
Pressure Sensors ◽  
Nodal Line ◽  
Operating Conditions ◽  
Acoustic Energy ◽  
Transverse Motion ◽  
Azimuthal Mode

This article reports experiments carried out in the MICCA-spray combustor developed at EM2C laboratory. This system comprises 16 swirl spray injectors. Liquid n-heptane is injected by simplex atomizers. The combustion chamber is formed by two cylindrical quartz tubes allowing full optical access to the flame region and it is equipped with 12 pressure sensors recording signals in the plenum and chamber. A high-speed camera provides images of the flames and photomultipliers record the light intensity from different flames. For certain operating conditions, the system exhibits well defined instabilities coupled by the first azimuthal mode of the chamber at a frequency of 750 Hz. These instabilities occur in the form of bursts. Examination of the pressure and the light intensity signals gives access to the acoustic energy source term. Analysis of the phase fluctuations between the two signals is carried out using cross-spectral analysis. At limit cycle, large pressure fluctuations of 5000 Pa are reached, and these levels persist over a finite period of time. Analysis of the signals using the spin ratio indicates that the standing mode is predominant. Flame dynamics at the pressure antinodal line reveals a strong longitudinal pulsation with heat release rate oscillations in phase and increasing linearly with the acoustic pressure for every oscillation levels. At the pressure nodal line, the flames are subjected to large transverse velocity fluctuations leading to a transverse motion of the flames and partial blow-off. Scenarios and modeling elements are developed to interpret these features.

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.

Rotating Instability in an Annular Cascade: Detailed Analysis of the Instationary Flow Phenomena

2013 ◽  
Vol 136 (6) ◽  
Author(s):  
Benjamin Pardowitz ◽  
Ulf Tapken ◽  
Robert Sorge ◽  
Paul Uwe Thamsen ◽  
Lars Enghardt
Keyword(s):  
Unsteady Flow ◽  
High Speed ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Pressure Waves ◽  
Flow Profile ◽  
Rotating Instability ◽  
Annular Cascade

Rotating instability (RI) occurs at off-design conditions in compressors, predominantly in configurations with large tip or hub clearance ratios of s* ≥3%. RI is the source of the blade tip vortex noise and a potential indicator for critical operating conditions like rotating stall and surge. The objective of this paper is to give more physical insight into the RI phenomenon using the analysis results of combined near-field measurements with high-speed particle image velocimetry (PIV) and unsteady pressure sensors. The investigation was pursued on an annular cascade with hub clearance. Both the unsteady flow field next to the leading edge as well as the associated rotating pressure waves were captured. A special analysis method illustrates the characteristic pressure wave amplitude distribution, denoted as “modal events” of the RI. Moreover, the slightly adapted method reveals the unsteady flow structures corresponding to the RI. Correlations between the flow profile, the dominant vortex structures, and the rotating pressure waves were found. Results provide evidence to a new hypothesis, implying that shear layer instabilities constitute the basic mechanism of the RI.

An Analysis of Power Characteristics of Oil-Free Scroll Vacuum Pumps

2020 ◽  
pp. 37-43
Author(s):  
A.V. Tyurin ◽  
A.V. Burmistrov ◽  
A.A. Raykov ◽  
S.I. Salikeev
Keyword(s):  
Mathematical Model ◽  
Power Efficiency ◽  
High Speed ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Total Power ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Power Characteristics ◽  
Indicator Power

This paper presents an analysis of the indicator power of an oil-free scroll vacuum pump based on the indicator diagrams obtained through high-speed pressure sensors. These values are compared with the results of calculations using a mathematical model of the pump working process. It is shown that the divergence of the calculated results and experimental values does not exceed 4%, which confirms the adequacy of the developed mathematical model. The total power of the scroll pump exceeds the indicator power by more than 2 times due to the friction losses between the face seals and disks of the reciprocal scroll elements, friction losses in the stuffing box seals and rolling bearings, as well as due to the coefficient of efficiency of the motor. The influence of the radial clearance between the scroll elements on the power consumption is considered. It is shown that at low pressures nearing the ultimate pressure, the power increases with the increased clearance, while at inlet pressures exceeding 40 kPa it decreases. The performed analysis can be used for selecting the optimal geometrical parameters of the scroll elements and increasing power efficiency of the pump depending on specific operating conditions.

Dynamics of cotton textile motion in a domestic tumble dryer and its effect on drying performance

2020 ◽  
pp. 004051752096075
Author(s):  
Xinchen Yu ◽  
Yi Li ◽  
Xuemei Ding
Keyword(s):  
High Speed ◽  
Chemical Engineering ◽  
Video Camera ◽  
Mechanical Action ◽  
Operating Conditions ◽  
Transverse Motion ◽  
Cotton Textile ◽  
High Speed Video Camera ◽  
Tumble Dryer ◽  
The Impact

A high-speed video camera was used to track a tracer textile as it is tumbled among other textiles in a domestic tumble dryer under different operating conditions, with the aim of investigating the mechanisms by which the mechanical action is imposed on textiles and affects drying performance during drying. These mechanisms were first recognized by comparing the clothes drying process to other well-researched chemical engineering processes. From the observation of the recorded motion processes, cotton textile transverse motion can be divided into three categories and a motion index system was derived to characterize the type of motion undergone. The impact of textile transverse motion on drying performance was numerically discussed based on the results of an analysis of variance and regression analysis. Results indicated that textile dynamics with more complexity and flexibility tended to have more mixing, shortened distance of moisture migration inside the fabric layer and fewer wrinkles formed, resulting in higher potential to have a better drying performance.

Exhaust Pressure Estimation and Its Application to Detection and Isolation of Turbocharger System Faults for Internal Combustion Engines

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Yue-Yun Wang ◽  
Ibrahim Haskara
Keyword(s):  
High Speed ◽  
Internal Combustion Engines ◽  
Failure Modes ◽  
Combustion Engine ◽  
Pressure Sensors ◽  
Internal Combustion ◽  
Operating Conditions ◽  
Combustion Engines ◽  
Recirculation Flow ◽  
Model Based

Engine exhaust backpressure is a critical parameter in the calculation of the volumetric efficiency and exhaust gas recirculation flow of an internal combustion engine. The backpressure also needs to be controlled to a presetting limit under high speed and load engine operating conditions to avoid damaging a turbocharger. In this paper, a method is developed to estimate exhaust pressure for internal combustion engines equipped with variable geometry turbochargers. The method uses a model-based approach that applies a coordinate transformation to generate a turbine map for the estimation of exhaust pressure. This estimation can substitute for an expensive pressure sensor, thus saving significant cost for production vehicles. On the other hand, for internal combustion engines that have already installed exhaust pressure sensors, this estimation can be used to generate residual signals for model-based diagnostics. Cumulative sum algorithms are applied to residuals based on multiple sensor fusion, and with the help of signal processing, the algorithms are able to detect and isolate critical failure modes of a turbocharger system.

Experimental Investigations on the Pressure Fluctuations in the Sealing Gap of Dry Gas Seals With Embedded Pressure Sensors

2020 ◽  
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. Even though the non-contacting seal is proved reliable; the ultra-thin gas film can still lead to a host of potential problems due to possible contact. 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 [1], 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.

Rotating Instability in an Annular Cascade: Detailed Analysis of the Instationary Flow Phenomena

2013 ◽  
Author(s):  
Benjamin Pardowitz ◽  
Ulf Tapken ◽  
Robert Sorge ◽  
Paul Uwe Thamsen ◽  
Lars Enghardt
Keyword(s):  
Unsteady Flow ◽  
High Speed ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Tip Vortex ◽  
Pressure Waves ◽  
Flow Profile ◽  
Rotating Instability ◽  
Annular Cascade

Rotating instability (RI) occurs at off-design conditions in compressors, predominantly in configurations with large tip or hub clearance ratios of s* ≥ 3% [1]. RI is the source of the blade tip vortex noise and a potential indicator for critical operating conditions like rotating stall and surge. The objective of this paper is to give more physical insight into the RI phenomenon using the analysis results of combined near-field measurements with High-Speed PIV and unsteady pressure sensors. The investigation was pursued on an annular cascade with hub clearance. Both the unsteady flow field next to the leading edge as well as the associated rotating pressure waves were captured. A special analysis method illustrates the characteristic pressure wave amplitude distribution, denoted as ‘Modal Events’ of the RI. Moreover, the slightly adapted method reveals the unsteady flow structures corresponding to the RI. Correlations between the flow profile, the dominant vortex structures and the rotating pressure waves were found. Results provide evidence to a new hypothesis, implying that shear layer instabilities constitute the basic mechanism of the RI.

Setup of a High-Speed Optical System for the Characterization of Flow Instabilities Generated by Cavitation

2007 ◽  
Vol 129 (7) ◽  
pp. 877-885 ◽  
Author(s):  
Angelo Cervone ◽  
Cristina Bramanti ◽  
Lucio Torre ◽  
Domenico Fotino ◽  
Luca d’Agostino
Keyword(s):  
High Speed ◽  
Cavity Length ◽  
Fluid Dynamic ◽  
Pressure Oscillation ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Flow Instabilities ◽  
Test Facility ◽  
Fluctuation Analysis ◽  
Oscillation Analysis

The present paper illustrates the setup and the preliminary results of an experimental investigation of cavitation flow instabilities carried out by means of a high-speed camera on a three-bladed inducer in the cavitating pump rotordynamic test facility (CPRTF) at Alta S.p.A. The brightness thresholding technique adopted for cavitation recognition is described and implemented in a semi-automatic algorithm. In order to test the capabilities of the algorithm, the mean frontal cavitating area has been computed under different operating conditions. The tip cavity length has also been evaluated as a function of time. Inlet pressure signal and video acquisitions have been synchronized in order to analyze possible cavitation fluid-dynamic instabilities both optically and by means of pressure fluctuation analysis. Fourier analysis showed the occurrence of a cavity length oscillation at a frequency of 14.7Hz, which corresponds to the frequency of the rotating stall instability detected by means of pressure oscillation analysis.

scholarly journals Stochastic Uncertainty in a Dam-Break Experiment with Varying Gate Speeds

2021 ◽  
Vol 9 (1) ◽  
pp. 67
Author(s):  
Hiroshi Takagi ◽  
Fumitaka Furukawa
Keyword(s):  
High Speed ◽  
Pressure Sensors ◽  
Dam Break ◽  
Maximum Pressure ◽  
Vertical Acceleration ◽  
Ship Wakes ◽  
Dam Break Flow ◽  
Statistical Relationships ◽  
Flow Propagation ◽  
Impulsive Pressure

Uncertainties inherent in gate-opening speeds are rarely studied in dam-break flow experiments due to the laborious experimental procedures required. For the stochastic analysis of these mechanisms, this study involved 290 flow tests performed in a dam-break flume via varying gate speeds between 0.20 and 2.50 m/s; four pressure sensors embedded in the flume bed recorded high-frequency bottom pressures. The obtained data were processed to determine the statistical relationships between gate speed and maximum pressure. The correlations between them were found to be particularly significant at the sensors nearest to the gate (Ch1) and farthest from the gate (Ch4), with a Pearson’s coefficient r of 0.671 and −0.524, respectively. The interquartile range (IQR) suggests that the statistical variability of maximum pressure is the largest at Ch1 and smallest at Ch4. When the gate is opened faster, a higher pressure with greater uncertainty occurs near the gate. However, both the pressure magnitude and the uncertainty decrease as the dam-break flow propagates downstream. The maximum pressure appears within long-period surge-pressure phases; however, instances considered as statistical outliers appear within short and impulsive pressure phases. A few unique phenomena, which could cause significant bottom pressure variability, were also identified through visual analyses using high-speed camera images. For example, an explosive water jet increases the vertical acceleration immediately after the gate is lifted, thereby retarding dam-break flow propagation. Owing to the existence of sidewalls, two edge waves were generated, which behaved similarly to ship wakes, causing a strong horizontal mixture of the water flow.

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