scholarly journals Influence of Self-Pulsation on Atomization Characteristics of Gas-Centered Swirl Coaxial Injector

2021 ◽  
Vol 9 ◽  
Author(s):  
Chuanjin Jiang ◽  
Yuan Xie ◽  
Yuchao Gao ◽  
Wei Chu ◽  
Yiheng Tong ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
High Speed ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Liquid Ratio ◽  
Feed System ◽  
System A ◽  
Particle Size Analyzer ◽  
Atomization Characteristics ◽  
Coaxial Injector

There is a lack of understanding of the spray characteristics of gas-centered swirl coaxial (GCSC) injectors during self-pulsation occurs. Therefore, the self-pulsation of a GCSC injector was investigated experimentally in this study. Experiments were conducted at atmospheric pressure with filtered water and dried air supplied through a propellant feed system. A back-lighting high-speed photography technique was used to capture unsteady spray features. A laser-based particle size analyzer (LPSA) was used to measure the size of the droplets in the spray. The effects of recess and gas-liquid ratio on spray self-pulsation were analyzed. It was found that the recess of the injector strongly determines the spray pattern. When spray self-pulsation occurs without recess, both the center and periphery of the spray oscillate. With an increase in the mass flow rate of the gas, the boundary between the center and the periphery of the spray becomes more noticeable. Meanwhile, small droplets in the spray center oscillate, with the periphery of the spray being characterized by a periodic “shoulder.” Under the same operating conditions but with a small recess (2 mm), the spray adheres to the injector faceplate. With a larger recess (7 mm), when spray self-pulsation occurs, the spray periodically forms “shoulder” and “neck,” similar to the behavior of self-pulsation in a liquid-centered coaxial injector. Therefore, it can be concluded that spray self-pulsation enhances atomization at the center of the spray to a certain extent. However, atomization becomes worse in the periphery with an oscillating spray.

Forensic Uncertainty Quantification for Experiments on the Explosively Driven Motion of Particles

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Kyle Hughes ◽  
S. Balachandar ◽  
Nam H. Kim ◽  
Chanyoung Park ◽  
Raphael Haftka ◽  
...  
Keyword(s):  
Uncertainty Quantification ◽  
High Speed ◽  
Early Time ◽  
Operating Conditions ◽  
Quality Data ◽  
High Speed Photography ◽  
Particle Array ◽  
X Ray Imaging ◽  
Drag Models ◽  
Air Force Research Laboratory

Six explosive experiments were performed in October 2014 and February of 2015 at the Munitions Directorate of the Air Force Research Laboratory with the goal of providing validation-quality data for particle drag models in the extreme regime of detonation. Three repeated single particle experiments and three particle array experiments were conducted. The time-varying position of the particles was captured within the explosive products by X-ray imaging. The contact front and shock locations were captured by high-speed photography to provide information on the early time gas behavior. Since these experiments were performed in the past and could not be repeated, we faced an interesting challenge of quantifying and reducing uncertainty through a detailed investigation of the experimental setup and operating conditions. This paper presents the results from these unique experiments, which can serve as benchmark for future modeling, and also our effort to reduce uncertainty, which we dub forensic uncertainty quantification (FUQ).

High-Speed Operation of a Gas-Bearing Supported MEMS-Air Turbine

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
C. J. Teo ◽  
L. X. Liu ◽  
H. Q. Li ◽  
L. C. Ho ◽  
S. A. Jacobson ◽  
...  
Keyword(s):  
Gas Turbines ◽  
High Speed ◽  
Journal Bearing ◽  
Operating Conditions ◽  
Feed System ◽  
Coupling Effects ◽  
Leakage Flows ◽  
Aspect Ratios ◽  
Air Turbine ◽  
Gas Bearing

Silicon based power micro-electro-mechanical system (MEMS) applications require high-speed microrotating machinery operating stably over a large range of operating conditions. The technical barriers to achieving stable high-speed operation with micro-gas-bearings are governed by (1) stringent fabrication tolerance requirements and manufacturing repeatability, (2) structural integrity of the silicon rotors, (3) rotordynamic coupling effects due to leakage flows, (4) bearing losses and power requirements, and (5) transcritical operation and whirl instability issues. To enable high-power density the micro-turbomachinery must be run at tip speeds comparable to conventional scale turbomachinery. The rotors of the micro-gas turbines are supported by hydrostatic gas journal and hydrostatic gas thrust bearings. Dictated by fabrication constraints the location of the gas journal bearings is at the outer periphery of the rotor. The high bearing surface speeds (target nearly 10×106 mm rpm), the very low bearing aspect ratios (L/D<0.1), and the laminar flow regime in the bearing gap (Re<500) place these micro-bearing designs into unexplored regimes in the parameter space. A gas-bearing supported micro-air turbine was developed with the objectives of demonstrating repeatable, stable high-speed gas-bearing operation and verifying the previously developed micro-gas-bearing analytical models. The paper synthesizes and integrates the established micro-gas-bearing theories and insight gained from extensive experimental work. The characteristics of the new micro-air turbine include a four-chamber journal bearing feed system to introduce stiffness anisotropy, labyrinth seals to avoid rotordynamic coupling effects of leakage flows, a reinforced thrust bearing structural design, a redesigned turbine rotor to increase power, a symmetric feed system to avoid flow and force nonuniformity, and a new rotor micro-fabrication methodology for reduced rotor imbalance. A large number of test devices were successfully manufactured demonstrating repeatable bearing geometry. More specifically, three sets of devices with different journal bearing clearances were produced to investigate the dynamic behavior as a function of bearing geometry. Experiments were conducted to characterize the “as-fabricated” bearing geometry, the damping ratio, and the natural frequencies. Repeatable high-speed bearing operation was demonstrated using isotropic and anisotropic bearing settings reaching whirl-ratios between 20 and 40. A rotor speed of 1.7×106 rpm (equivalent to 370 m/s blade tip speed or a bearing DN number of 7×106 mm rpm) was achieved demonstrating the feasibility of MEMS-based micro-scale rotating machinery and validating key aspects of the micro-gas-bearing theory.

scholarly journals Simultaneous Pressure Measurement and High-Speed Photography Study of Cavitation in a Dynamically Loaded Journal Bearing

1993 ◽  
Vol 115 (1) ◽  
pp. 88-95 ◽  
Author(s):  
D. C. Sun ◽  
D. E. Brewe ◽  
P. B. Abel
Keyword(s):  
Pressure Measurement ◽  
Cavitation Bubble ◽  
High Speed ◽  
Journal Bearing ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Pressure Data ◽  
Oil Film ◽  
Dynamically Loaded ◽  
Insight Into

Cavitation of the oil film in a dynamically loaded journal bearing was studied using high-speed photography and pressure measurement simultaneously. Comparison of the visual and pressure data provided considerable insight into the occurrence and non-occurrence of cavitation. It was found that (1), cavitation typically occurred in the form of one bubble with the pressure in the cavitation bubble close to the absolute zero; and (2), for cavitation-producing operating conditions, cavitation did not always occur; with the oil film then supporting a tensile stress.

Investigation of Fuel and Load Flexibility in a SGT-600/700/800 Burner Under Atmospheric Pressure Conditions Using High-Speed Oh-Plif and Oh Chemiluminescence Imaging

2021 ◽  
Author(s):  
Arman Ahamed Subash ◽  
Haisol Kim ◽  
Sven-Inge Möller ◽  
Mattias Richter ◽  
Christian Brackmann ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Gas Turbines ◽  
High Speed ◽  
Recirculation Zone ◽  
Burning Velocity ◽  
Flame Stabilization ◽  
Operating Conditions ◽  
Optical Measurements ◽  
Experimental Investigations ◽  
Pilot Fuel

Abstract Experimental investigations were performed using a standard 3rd generation dry low emission (DLE) burner under atmospheric pressure to study the effect of central and pilot fuel addition, load variations and H2 enrichment in a NG flame. High-speed OH-PLIF and OH-chemiluminescence imaging were employed to investigate the flame stabilization, flame turbulence interactions, and flame dynamics. Along with the optical measurements, combustion emissions were recorded to observe the effect of changing operating conditions on NOX level. The burner is used in Siemens industrial gas turbines SGT-600, SGT-700 and SGT-800 with minor hardware differences. This study thus is a step to characterize fuel and load flexibility for these turbines. Without pilot and central fuel injections in the current burner configuration, the main flame is stabilized creating a central recirculation zone. Addition of the pilot fuel strengthens the outer recirculation zone (ORZ) and moves the flame slightly downstream, whereas the flame moves upstream without affecting the ORZ when central fuel injection is added. The flame was investigated utilizing H2/NG fuel mixtures where the H2 amount was changed from 0 to 100%. The flame becomes more compact, the anchoring position moves closer to the burner exit and the OH signal distribution becomes more distinct for H2 addition due to increased reaction rate, diffusivity, and laminar burning velocity. Changing the load from part to base, similar trends were observed in the flame behavior but in this case due to the higher heat release because of increased turbulence intensity.

scholarly journals Kinematic Analysis of a Clamp-Type Picking Device for an Automatic Pepper Transplanter

Agriculture ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 627 ◽  
Author(s):  
Md Nafiul Islam ◽  
Md Zafar Iqbal ◽  
Mohammod Ali ◽  
Milon Chowdhury ◽  
Md Shaha Nur Kabir ◽  
...  
Keyword(s):  
Kinematic Analysis ◽  
High Speed ◽  
Model Simulation ◽  
Mechanical Damage ◽  
Maximum Velocity ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Virtual Model ◽  
Significant Difference ◽  
Simulation And Validation

Pepper is one of the most vital agricultural products with high economic value, and pepper production needs to satisfy the growing worldwide population by introducing automatic seedling transplantation techniques. Optimal design and dimensioning of picking device components for an automatic pepper transplanter are crucial for efficient and effective seedling transplantation. Therefore, kinematic analysis, virtual model simulation, and validation testing of a prototype were conducted to propose a best-suited dimension for a clamp-type picking device. The proposed picking device mainly consisted of a manipulator with five grippers and a picking stand. To analyze the influence of design variables through kinematic analysis, 250- to 500-mm length combinations were considered to meet the trajectory requirements and suit the picking workspace. Virtual model simulation and high-speed photography tests were conducted to obtain the kinematic characteristics of the picking device. According to the kinematic analysis, a 350-mm picking stand and a 380-mm manipulator were selected within the range of the considered combinations. The maximum velocity and acceleration of the grippers were recorded as 1.1, 2.2 m/s and 1.3, 23.7 m/s2, along the x- and y-axes, respectively, for 30 to 90 rpm operating conditions. A suitable picking device dimension was identified and validated based on the suitability of the picking device working trajectory, velocity, and acceleration of the grippers, and no significant difference (p ≤ 0.05) occurred between the simulation and validation tests. This study indicated that the picking device under development would increase the pepper seedling picking accuracy and motion safety by reducing the operational time, gripper velocity, acceleration, and mechanical damage.

Characteristics of pulsed nanosecond discharge excited by compact solid-state pulse forming line at atmospheric pressure air

2021 ◽  
Author(s):  
Jie Li ◽  
Yi Liu ◽  
Xi Li ◽  
Pang Dong ◽  
Feixiang Liu ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
High Speed ◽  
Average Energy ◽  
Energy Utilization ◽  
Utilization Efficiency ◽  
High Speed Photography ◽  
Pulsed Plasma ◽  
Streamer Discharge ◽  
Equilibrium Plasma ◽  
Non Equilibrium

Abstract Non-equilibrium plasma is a promising technology for the generation of ozone and removal of exhausted fuel gases. However, applications of non-equilibrium plasma are restricted by energy utilization efficiency in many industry fields. Discharge excited by nanosecond pulsed power is regarded as one of the most efficient methods. In this study, a compact 5 stages stacked blumlein pulse forming line and photoconductive semiconductor switches-based power source was introduced to generate pulsed plasma. This compact source could achieve over 50 kV with 10.1 ns pulse width and 4.8 ns pulse rising time. Coaxial cylindrical reactor was employed to generate a pulsed streamer discharge driven by the nanosecond pulsed source in atmospheric pressure air. Electrical parameters of the streamer discharge have been obtained in this study, the instantaneous power dissipation exceeds 8 MW and the average energy consumption of each pulse exceeds 56 mJ. Experiments of high speed photography have been conducted to observe the evolution process. It can be found that streamer heads start from the central wire electrode and then head to the grounded cylinder electrode in all radial direction of the coaxial electrode. Triple wire-to-cylinder electrodes discharge shows that all the three coaxial discharges develop synchronously and symmetrically, which shows that is capable of generating large volume non-equilibrium diffusive streamer discharge plasma.

Investigations of Arc Behavior and Particle Formation in the Wire Arc Spray Process Using High Speed Photography

2000 ◽  
Author(s):  
N.A. Hussary ◽  
J. Heberlein
Keyword(s):  
Thermal Spray ◽  
High Speed ◽  
Imaging System ◽  
Metal Droplet ◽  
Droplet Formation ◽  
Operating Conditions ◽  
Arc Spraying ◽  
High Speed Photography ◽  
Spray Process ◽  
The Wire

Abstract The wire arc spraying process, one of several thermal spray processes, gained a sizable part of the thermal spray market, however, more control is needed for this process to be used for high precision coatings. This study is aimed at investigating the liquid metal droplet formation process in order to identify methods for droplet trajectory control. A high speed Kodak imaging system has been used to observe the droplet formation for different operating conditions. Decreasing the upstream pressure and the current levels lead to the reduction in the asymmetric melting of both anode and cathode. By decreasing the interactions of the large eddy structures with the formed metal agglomerates one can achieve better control of the particle trajectories and jet divergence. Thus, coatings can be obtained with higher definition and improved reliability.

Paper 4: Development of High-Pressure Boiler Feed Pumps in Britain during the Last Decade

1966 ◽  
Vol 181 (14) ◽  
pp. 6-16 ◽  
Author(s):  
G. F. Arkless
Keyword(s):  
High Pressure ◽  
High Speed ◽  
Material Selection ◽  
Operating Conditions ◽  
Feed Water ◽  
Feed Pump ◽  
Feed System ◽  
Axial Thrust ◽  
Advantages And Disadvantages ◽  
Component Design

This paper traces the evolution of the high-pressure feed pump in this country over the last decade, concentrating on its application in land-based, steam power plant. The influence of the choice of feed system and the effect of mounting feed water flow rates, pressure, and temperature on the design of the feed pump is discussed. Advantages and disadvantages of the various methods of driving a feed pump are enumerated and attention given to the reasons for the adoption of higher running speeds, and the means whereby high-speed pumps have been accommodated in view of their higher net positive suction head requirements. Material selection and component design is also considered in the light of the changing requirements brought about by larger size, more onerous operating conditions, and higher running speed. Glands, axial thrust balancing devices, impeller mountings, controls, and high-pressure joints, are each briefly discussed.

Random Behavior of Kerosene Spray Autoignition in Crossflow

2016 ◽  
Author(s):  
Yongsheng Zhao ◽  
Chi Zhang ◽  
Yuzhen Lin
Keyword(s):  
High Speed ◽  
Flow Reactor ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
High Speed Photography ◽  
Primary Analysis ◽  
Photoelectric Detection ◽  
Random Behavior ◽  
Gauss Distribution ◽  
Autoignition Delay

Based on the flow reactor with rectangle cross-section, this paper studies the spray autoignition characteristics of liquid kerosene injected into air crossflow under high temperature and high pressure conditions. Millisecond-level kerosene injection, millisecond-level photoelectric detection, and high speed photography record experiment techniques are adopted in this research. The operating conditions of this research are as follows: 2.3MPa inlet pressure, 917K inlet temperature, fuel/ air momentum ratio of 52, and Weber number of 355. Photoelectric sensor and photomultiplier equipped with CH filter are used to get the autoignition delay time (ADT). A total of 320 experiments are conducted under the same operating conditions in order to obtain the random ADT probability distribution. The high speed photography is utilized to observe and record the developing process of spray autoignition of kerosene. The results show that the ADT varies from 2.5–5.5millisecond (ms) in the above operating conditions, and confirm the existence of the random behavior of kerosene spray autoignition in the crossflow. These random behaviors of ADT can be correlated well with Gauss distribution. The primary analysis shows that the random behavior stems from the random distributions in the diameter and dispersion due to intrinsic turbulence breakup and transportation which dominate the characteristics of spray autoignition.

Determination of Void Fraction, Incipient Point of Boiling, and Initial Point of Net Vapor Generation in Sodium-Heated Helically Coiled Steam Generator Tubes

1978 ◽  
Vol 100 (2) ◽  
pp. 268-274 ◽  
Author(s):  
H. C. U¨nal
Keyword(s):  
Heat Flux ◽  
Mass Velocity ◽  
High Speed ◽  
Initial Point ◽  
Operating Conditions ◽  
High Speed Photography ◽  
Centrifugal Forces ◽  
Vapor Generation ◽  
Volumetric Rate ◽  
Rate Ratios

Void fraction was measured with high-speed photography in a 26.7 m and a 40.1 m long, sodium-heated helically coiled steam generator tube of 0.018 m ID. The ratio of coil diameter to tube diameter was 38.9. The operating conditions for the tests were as follows: Pressure: 4–18 MN/m2, mass velocity: 429–1518 kg/m2s, heat flux: 0.013–0.42 MW/m2, outlet subcooling: 0.3–12.5 K, outlet steam quality: 0.000032–0.075. For vapor volumetric rate ratios greater than 0.4, the so-called distribution parameter is not affected by centrifugal forces, and is equal to 0.875. For vapor volumetric rate ratios smaller than 0.4, this parameter is affected by centrifugal forces and the aforesaid ratio. The incipient point of boiling and initial point of net vapor generation were determined with high-speed photography in the aforementioned 26.7 m long helical coil for the following range of operating conditions: Pressure: 4–18 MN/m2, mass velocity 757–1518 kg/m2s, heat flux: 0.082–0.413 MW/m2, outlet subcooling: 4.4–12.5 K. The data were correlated by using both the average and local values of the operating conditions.

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