Heat Transmission in High Speed Gas Flow (3rd Report)

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.

Download Full-text

Influence of the Variation of Plasma Torch Parameters on Particle Melting and Solidification

Thermal Spray 1997: Proceedings from the United Thermal Spray Conference ◽

10.31399/asm.cp.itsc1997p0535 ◽

1997 ◽

Author(s):

M. Vardelle ◽

P. Fauchais ◽

A. Vardelle ◽

A.C. Léger

Keyword(s):

Flow Rate ◽

High Speed ◽

Gas Flow ◽

Operating Conditions ◽

Characteristic Parameters ◽

Powder Mass ◽

Arc Current ◽

Plasma Sprayed ◽

Carrier Gas Flow ◽

Melting And Solidification

Abstract A study of the flattening and cooling of particles plasma-sprayed on a substrate is presented. The characteristic parameters of the splats are linked to the parameters of the impacting particles by using an experimental device consisting of a phase Doppler particle analyzer and a high-speed pyrometer. However, during the long experiments required to get reliable correlations, it was observed that variations in plasma spray operating conditions may alter the particles behavior in the plasma jet. Therefore, a simple and easy-to-use system was developed to control in real time the spray jet. In this paper, the effect of carrier gas flow rate, arc current and powder mass flow rate is investigated. The results on zirconia and alumina powders show the capability of the technique to sense the particle spray position and width.

Download Full-text

A Study of High Speed Gas Flow by Hydraulic Analogy : The 4th Report, Flow Around an Airfoil

Bulletin of JSME ◽

10.1299/jsme1958.2.663 ◽

1959 ◽

Vol 2 (8) ◽

pp. 663-669

Author(s):

Yukio TOMITA

Keyword(s):

High Speed ◽

Gas Flow ◽

Hydraulic Analogy

Download Full-text

Analyzing Droplet Size Distributions Inside a Self-Priming Venturi Scrubber for Filtered Containment Venting Systems

Volume 6B: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-82227 ◽

2018 ◽

Author(s):

P. Papadopoulos ◽

T. Lind ◽

H.-M. Prasser

Keyword(s):

Droplet Size ◽

High Speed ◽

Nuclear Power ◽

Power Plants ◽

Gas Flow ◽

Tube Bundle ◽

Droplet Size Distribution ◽

Severe Accident ◽

Design Element ◽

Venturi Scrubber

After the accident in the Fukushima Daiichi nuclear power plant, the interest of adding Filtered Containment Venting Systems (FCVS) on existing nuclear power plants to prevent radioactive releases to the environment during a severe accident has increased. Wet scrubbers are one possible design element which can be part of an FCVS system. The efficiency of this scrubber type is thereby depending, among others, on the thermal-hydraulic characteristics inside the scrubber. The flow structure is mainly established by the design of the gas inlet nozzle. The venturi geometry is one of the nozzle types that can be found in nowadays FCVS. It acts in two different steps on the removal process of the contaminants in the gas stream. Downstream the suction opening in the throat of the venturi, droplets are formed by atomization of the liquid film. The droplets are contributing to the capture of aerosols and volatile gases from the mixture coming from the containment. Studies state that the majority of the contaminants is scrubbed within this misty flow regime. At the top of the venturi, the gas stream is injected into the pool. The pressure drop at the nozzle exit leads to the formation of smaller bubbles, thus increasing the interfacial area concentration in the pool. In this work, the flow inside a full-scale venturi scrubber has been optically analyzed using shadowgraphy with a high-speed camera. The venturi nozzle was installed in the TRISTAN facility at PSI which was originally designed to investigate the flow dynamics of a tube rupture inside a full-length scale steam generator tube bundle. The data analysis was focused on evaluating the droplet size distribution and the Sauter mean diameter under different gas flow rates and operation modes. The scrubber was operated in two different ways, submerged and unsubmerged. The aim was to include the effect on the droplet sizes of using the nozzle in a submerged operation mode.

Download Full-text

Mechanisms Responsible for Arc Cooling in Different Gases in Turbulent Nozzle Flow

Plasma Physics and Technology Journal ◽

10.14311/ppt.2017.3.234 ◽

2017 ◽

Vol 4 (3) ◽

pp. 234-240 ◽

Cited By ~ 1

Author(s):

Y. Guo ◽

H. Zhang ◽

Y. Yao ◽

Q. Zhang ◽

J. D. Yan

Keyword(s):

Material Properties ◽

High Speed ◽

Gas Flow ◽

Ohmic Heating ◽

Circuit Breaker ◽

Fault Current ◽

High Current ◽

Physical Mechanisms ◽

Current Zero ◽

Different Gases

A high voltage gas blast circuit breaker relies on the high speed gas flow in a nozzle to remove the energy due to Ohmic heating at high current and to provide strong arc cooling during the current zero period to interrupt a fault current. The physical mechanisms that are responsible for the hugely different arc cooling capabilities of two gases (SF<sub>6</sub> and air) are studied in the present work and important gas material properties controlling the cooling strength identified.

Download Full-text

Research on collaborative control of double-plunger gas prover based on EtherCAT

Thermal Science ◽

10.2298/tsci191022002x ◽

2020 ◽

Vol 24 (5 Part A) ◽

pp. 2667-2687

Author(s):

Zhipeng Xu ◽

Feipeng Xu ◽

Dailiang Xie

Keyword(s):

Flow Rate ◽

High Speed ◽

Gas Flow ◽

Control Unit ◽

External Diameter ◽

Piston Cylinder ◽

Collaborative Control ◽

Critical Nozzles ◽

Parallel Mode ◽

Working Principle

Piston prover has been widely used as a gas flow standard for its advantages of high accuracy in standard volume, flow stability and repeatability. It has also been employed as the primary gas flow standard in many countries to calibrate meters. However, it is difficult to ensure the uniformity of the inside dimension of the piston, thus the application of conventional piston provers are limited by the maximum calibration flow generated by the piston cylinder volume. In this paper, an improved piston gas prover that mainly consists of two uniform plungers was proposed. Their external diameter constitutes the flow standard. The plungers are driven by servo motor, and the high speed fieldbus EtherCAT has been introduced as the control unit. Hence the two pistons could work collaboratively and operate in three modes: single-piston mode, double-pistons parallel mode, and double-pistons reciprocating mode. Besides generating steady-flow rate, the double-plunger prover can even produce an unsteady-flow rate which could be used to research the dynamic characteristics of flow meters. The structure and working principle of the three modes were carefully introduced. Then experiments for calibrating critical nozzles were carried out, and the results show that the repeatability of the discharge coefficient could be better than 0.06%, and the pressure fluctuation during the process was less than 50 Pa.

Download Full-text