Study of buzz phenomenon using visualization of external shock structure

2018 ◽  
Vol 233 (7) ◽  
pp. 2690-2698 ◽  
Author(s):  
M Farahani ◽  
A Jaberi
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Pressure Sensors ◽  
Shock Structure ◽  
The Body ◽  
External Compression ◽  
Mass Flow Rates ◽  
Shock Motion ◽  
Shock Oscillation ◽  
Visual Description

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and shock displacement were measured by inspection of visualization pictures in each test. The obtained data from shadowgraphs were compared with those obtained from pressure measurements, and good agreement was found between them. The results revealed that for a moderate value of mass flow rate, the frequency of shock oscillation decreases as Mach number increases. Further, by increasing angle of attack, the shock displacement of oscillation will increase. At non-zero angles of attack, the displacement and frequency of shock motion show different behaviors on the leeward and windward sides of the body.

A New Micro Turbo-Machinery Test Facility

2010 ◽  
Author(s):  
Chen Xia ◽  
Guoping Huang ◽  
Jie Chen
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Modular Design ◽  
Thermal Protection ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Test Facility ◽  
Inlet Temperature ◽  
Test Bed ◽  
Turbo Machinery

The design and construction of a new test facility of micro turbo-machinery are presented for micro centrifugal compressors and radial turbines. The bed can be used for the full speed compressor test and the long duration hot turbine test. In order to adjust the testing condition rapidly, all the regulations of operating state are completed automatically by the control system. The test bed can be used for testing impeller performance with a series of diameter from 55 to 180 mm as a result of the modular design. A thermal protection system is designed to avoid the heat distortion caused by the high inlet temperature of turbine which may exceeds 1100K and provide a proper experimental environment for the electronic components. A photoelectric torque transducer with an accuracy of 1% is designed to measure the torque of a rigid shaft at a high speed over 120000rpm, and the maximum shaft torque is 7.7 N·m. The pressure and temperature are measured by pressure probes and thermocouples. The dynamic pressure signal of the centrifugal compressor is monitored by dynamic pressure sensors. The V-cone pressure-difference mass-flow meters are used for measuring mass-flow. The maximum rotating speed is 125000rpm, and the mass flow adjusted by the electric control valves varies from 0.1 to 1.0 kg/sec. The maximum inlet total temperature of the turbine is 1180K.

scholarly journals Experimental and Numerical Investigation the Effect of Grooves Impeller on Rotating Stall of High Speed Blower

2018 ◽  
Vol 8 (04) ◽  
Author(s):  
Muna S. Kassim ◽  
Fouad A. Saleh ◽  
Alaa Th. Aliwi
Keyword(s):  
Numerical Investigation ◽  
Mass Flow ◽  
High Speed ◽  
Static Pressure ◽  
Rotating Stall ◽  
High Mass ◽  
Ansys Fluent ◽  
Flow Rates ◽  
Frontal Wall ◽  
Mass Flow Rates

Experimental and numerical investigation to study the influence of add (one groove and two grooves) to the unshroud impeller onto the rotating stall as well fluctuations of pressure at a high speed blower of centrifugal. Experimental test rig which includes blower of centrifugal, transducer of pressure as well measurement instrumentations are constructed and designed for this study. A data acquisition system (hardware) as well its (software) have been developed into transferring the signal than transducer of pressure to the computer. The experimental work has been implemented through measuring the variation of static pressure as well fluctuation of pressure for two cases of the impeller (with one groove and with two grooves). Static pressure has been taken in different points arranged onto the frontal-wall of a volute casing along one track for two cases of the impeller. This track is angular track about the impeller. The results of experimental show that the fluctuations of pressure for different mass flow rates are nature of non-periodical and the mass flow rates decrease with the fluctuations of pressure increase. Also, the results indicate that the impeller with two grooves show high mass flow rates comparison with the impeller with one groove. Simulation of numerical has been implemented onto blower of centrifugal to analysis both field of flow as well fluctuations of pressure through using ANSYS (FLUENT 15). The simulation of numerical has been carried out through solve the continuity as well momentum equations with the moving reference framework technicality inside a blower. The numerical simulation results show good agreement with the results of experimental.

Calibration of a V-Cone for Low Mass Flows for Small Core Compressor Research

2020 ◽  
Author(s):  
Julia E. Stephens ◽  
Sameer Kulkarni
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Pressure Ratio ◽  
Axial Compressor ◽  
Flow Rates ◽  
Turbofan Engines ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Mass Flows ◽  
Multistage Axial Compressor

Abstract Advancements in core compressor technologies are necessary for next generation, high Overall Pressure Ratio (OPR) turbofan engines. High pressure compressors (HPCs) for future engines are being designed with exit corrected mass flow rates less than 2.25 kg/s (5 lbm/s). In order to accurately measure the performance of these advanced designs, high accuracy measurements are needed in test facilities. The W7 High Speed Multistage Axial Compressor Facility at NASA Glenn Research Center has been used to acquire data for advanced compressor designs. This facility utilizes an advanced differential pressure flow meter called a V-Cone. The facility has historically tested components with physical mass flow rates in the range of 27 to 45 kg/s (60 to 100 lbm/s). As such, when the V-Cone was calibrated prior to installation, the calibrations focused on higher mass flow rates, and uncertainties in that regime range from 0.5% to 0.85%. However, for low mass flow rates under 9 kg/s (20 lbm/s), expected in tests of advanced high OPR HPCs rear stages, the uncertainties of the V-Cone exceed 2.5%. To address this, using a method similar to that utilized by the National Institute of Standards and Technology, an array of Critical Flow Venturi Nozzles (CFVs) was installed in the W7 test section and used to calibrate the V-Cone in 0.5 kg/s (1 lbm/s) increments up to 10.5 kg/s (23 lbm/s). This effort details the measurements and uncertainties associated with this calibration which resulted in a final uncertainty of the V-Cone measurements under 1%.

Parametric Study of the Frequency of Bubble Formation at a Single Orifice With Liquid Cross-Flow

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Miguel A. Balzan ◽  
Franz Hernandez ◽  
Carlos F. Lange ◽  
Brian A. Fleck
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Liquid Velocity ◽  
Bubble Formation ◽  
Cross Flow ◽  
Average Frequency ◽  
Jet Breakup ◽  
Mass Flow Rates ◽  
Experimental Values ◽  
Processing Techniques

The bubble formation frequency from a single-orifice nozzle subjected to the effects of a crossflowing liquid was investigated using high-speed shadowgraphy, combined with image analysis and signal processing techniques. The effects of the nozzle dimensions, orientation within the conduit, liquid cross-flow velocity, and gas mass flow rate were evaluated. Water and air were the working fluids. Existing expressions in the literature were compared to the experimental values obtained. The expressions showed modest agreement with the experimental mean average frequency magnitude. It was found that increasing the gas injection diameter could decrease the bubbling frequency approximately 12% until reaching a certain value (0.52 mm). Further increasing the nozzle dimensions increase the frequency by around 20%. Bubbling frequency is more sensitive to the liquid velocity where changes up to 63% occurred when the velocity was raised from 3.1 to 4.3 m/s. Increasing gas mass flow rates decreased the gas jet breakup frequency in all cases. This phenomenon was primarily attributed to changes in the bubbling mode from discrete bubbling to pulsating and jetting modes. The nozzle orientation plays a role in modifying the bubbling frequency, having a higher magnitude when oriented against gravity.

Influence of Combustor Geometry on Swirl Stabilized Premixed Methane-Air Flame

2016 ◽  
Author(s):  
Yiheng Tong ◽  
Mao Li ◽  
Jens Klingmann
Keyword(s):  
Cross Section ◽  
Mass Flow ◽  
High Speed ◽  
Total Mass ◽  
Equivalence Ratio ◽  
Circular Cross Section ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Flame Structures ◽  
Co Emission

Flame structures, blowout limits and emissions of swirl-stabilized premixed methane-air flames were studied experimentally in a small atmospheric combustor rig. Combustion sections with rectangular cross section (30mm by 40mm) and circular cross section (inner diameter = 39mm) were used to investigate effects of combustor geometry on the flame’s performance. Flame structures and instabilities were obtained from CH* chemiluminescence captured by a high speed intensified CMOS camera. Maps of flame blowout limits (ΦBO) versus total mass flow rates ( ṁ = 70 ∼ 130 standard liter per minute, SLPM) were obtained with the combustor inlet flow temperature (Tin) kept at Tin = 397 ± 5K and a flow swirl number of S = 0.6. Emission data of mole fraction of CO in the exhaust gas versus equivalence ratio was obtained under the conditions of Tin = 293 ± 5K and S = 0.66. It is found that the flame became longer and more unstable with decreasing equivalence ratio or increasing total mass flow rates. A strong high-amplitude and low-frequency oscillation was found to be the reason for the flame blowout. A possible reason for flame instability and blowout is presented in the paper. Within the parameters investigated in this study, the equivalence ratio had the strongest impact on flame stabilities and CO emission. Both in the rectangular and circular combustors, when the flame length increased to a critical value (LIBO, which was approximately the same for these two combustors), flame could not be stabilized anymore and blowout occurred. Compared with the rectangular combustor, the circular one had lower blowout limits and was better in stabilizing the flame. Combustor geometry did not significantly affect CO emission in the current study.

Granular surface flow on an asymmetric conical heap

2019 ◽  
Vol 865 ◽  
pp. 41-59 ◽  
Author(s):  
Sandip Mandal ◽  
D. V. Khakhar
Keyword(s):  
Layer Thickness ◽  
Mass Flow ◽  
High Speed ◽  
Surface Flow ◽  
Operating Conditions ◽  
Angle Of Repose ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Predicted Values ◽  
Granular Surface

We carry out an experimental study of the granular surface flow of nearly monodisperse glass beads on a conical heap formed on a rough circular disc by a narrow stream of the particles from a hopper, with the pouring point displaced from the centre of the disc. During the growth phase, an axisymmetric heap is formed, which grows either by periodic avalanches or by non-periodic avalanches that occur randomly over the azimuthal location of the heap, depending on the operating conditions and system properties. The dynamics of heap growth is characterized by the variation of the heap height, angle of repose and the angular velocity of the periodic avalanche with time, for different mass flow rates from the hopper. When the base of the heap reaches the edge of the disc closest to the pouring point, the heap stops growing and a steady surface flow of particles is developed on the heap surface, with particles flowing over the edge of the disc into a collection tray. The geometry is a unique example of a granular flow on an erodible bed without any bounding side walls. The corresponding steady state geometry of the asymmetric heap is characterized by means of surface contours and angles of repose. The streamwise and transverse surface velocities are measured using high-speed video photography and image analysis for different mass flow rates. The flowing layer thickness is measured by immersing a coated needle in the flow at different positions on the mid-line of the flow. The surface angle of the flowing layer is found to be significantly smaller than the angle of repose and to be independent of the mass flow rate. The velocity profiles at different streamwise positions for different mass flow rates are found to be geometrically similar and are well described by Gaussian functions. The flowing layer thickness is calculated from a model using the measured surface velocities. The predicted values match the measured values quite well.

Experimental Analysis of Altitude Relight Under Realistic Conditions Using Laser and High-Speed Video Techniques

2010 ◽  
Author(s):  
T. Mosbach ◽  
R. Sadanandan ◽  
W. Meier ◽  
R. Eggels
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Frame Rate ◽  
Research Centre ◽  
Oh Radicals ◽  
Fuel Injector ◽  
Flow Rates ◽  
Flame Kernel ◽  
High Speed Video ◽  
Mass Flow Rates

The altitude relight performance of a lean fuel injector and combustor was investigated at the altitude relight test rig at the Rolls-Royce Strategic Research Centre (SRC) in Derby. The studies were performed for different mass flow rates of air and kerosene, a combustor temperature and pressure of 278 K and 0.5 bar, respectively. Good optical access to the combustion chamber enabled the application of optical and laser measuring techniques. High-speed video imaging in the UV and visible wavelength range at a frame rate of 3.5 kHz was used to visualize the temporal development of the flame kernel. The observed differences between the UV and visible flame emissions demonstrate the different origins of the luminosity, i.e. OH* chemiluminescence and soot radiation. Further, laser-induced fluorescence of kerosene and OH radicals was applied at a frame rate of 5 Hz to visualize the fuel distribution and regions of hot and reacting mixtures. For two exemplary flames with different mass flow rates and fuel-to-air ratios, the steady burning flames after successful ignition are characterized in this paper by the distributions of kerosene, OH*, OH and soot luminosity. An example of the flame kernel development for a successful ignition is given by an image sequence from a high-speed video recording of the chemiluminescence. The importance of the upstream movement of the flame kernel as a condition preceding successful flame stabilization is identified.

scholarly journals Experimental Study of Primary Atomization Characteristics of Sonic Air-Assist Atomizers

2021 ◽  
Vol 11 (21) ◽  
pp. 10444
Author(s):  
Raghav Sikka ◽  
Knut Vågsæther ◽  
Dag Bjerketvedt ◽  
Joachim Lundberg
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Water Pressure ◽  
Research Work ◽  
Spray Angle ◽  
Flow Rates ◽  
Breakup Length ◽  
Mass Flow Rates ◽  
Sheet Breakup ◽  
Atomization Characteristics

The present study compares two twin-fluid atomizer concepts based on the airflow (shock waves) pattern obtained through shadowgraph imaging for atomization of water with a low air/water pressure supply. The research work was conducted using the backlight imaging technique for converging (sonic) and converging–diverging (supersonic) air-assist atomizers with a 3.0 mm (throat) diameter. An annular sheet of thicknesses 70 µm and 280 µm with a high-speed air-core was employed to study the breakup dynamics for different water mass flow rates (100–350 kg/h) and air mass flow rates (5–35 kg/h). Different sheet breakup patterns were identified as the function of the ALR ratio (air-to-liquid mass flow), liquid Weber number (WeL), and Reynolds number (Reg). Different breakup modes extend from canonical Rayleigh bubble breakup, ligament-type breakup, to the pure pulsating breakup via annular sheet disintegration. The sheet breakup dynamics were studied in terms of spray angle and breakup length. With higher ALR values, breakup length showed a decreasing trend, while spray angle showed an increasing trend in the converging and converging–diverging (CD) air-assist atomizers, respectively, owing to the drastic difference in the jet flow dynamics.

Bleed Slot Benefits on Turbocharger Centrifugal Compressor Stability

2014 ◽  
Author(s):  
Matthieu Gancedo ◽  
Erwann Guillou ◽  
Ephraim Gutmark
Keyword(s):  
Mass Flow ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Broad Band ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Low Mass ◽  
Response Pressure ◽  
Compressor Map ◽  
Speed Response

Bleed slots located in the inducer region of centrifugal compressors have been demonstrated to extend the surge margin with minimal negative impact on performance. This paper describes the investigation of the effect of a bleed slot on map width enhancement of a turbocharger centrifugal compressor used for heavy duty diesel engine application. The goal is to evaluate the overall pressure instabilities on the compressor map and to study the dynamic phenomena occurring at low mass flow rates to better understand the benefits of the bleed slot on the compressor stability and surge line. The obstruction of the bleed slot permitted to compare the compressor behavior with the recirculation feature and without it. The pressure instability levels were measured along the accessible compressor map for the two cases using a high speed response pressure transducer at the compressor outlet. In addition, static and dynamic pressure measurements were conducted within the diffuser using respectively pressure taps and high speed response pressure transducers. The compressor with open bleed slot proved to have lower instability levels at low mass flow rates when not experiencing deep surge. Frequency responses at low mass flow rates showed that the implementation of the bleed slot suppresses broad band frequencies below the rpm frequency, which improves the overall stability. These frequencies are associated with rotating instabilities (RIs) with changing propagation speed depending on the rotational speed. At lower speeds, RIs are propagated with the wheel rotation whereas at higher speeds, they tend to propagate with the speed associated with their characteristic frequency.

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