Wyniki wyszukiwania - BazTech

1

On the energy efficiency in the heatproof nozzle of the pneumatic pulsator system during supersonic airflow

Wołosz K. J., Wernik J.

Journal of Mechanical and Energy Engineering

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2018

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Vol. 2, No 2

155--161

EN

In this article, a study of supersonic airflow through a channel with various cross-section is presented. The channel is namely a heatproof nozzle which is used in a pneumatic pulsator system. The system utilizes a pneumatic impact to destructor to avoid of the creation of unfavourable phenomena which comes from cohesion forces. The pneumatic pulsator system is driven by compressed air and a high-velocity airflow is induced by the difference between internal and external air pressure. This flow changes its characteristics during a work cycle of the pulsator from subsonic to supersonic conditions. It causes a very dynamic gas conversion and may produce additional heat inside the pulsator and its nozzle. The article presents a method for calculating the value of the heat which can be generated inside the heatproof nozzle. The results of the study shows that the small amount of energy is lost during the airflow which can generate an increment of heatproof nozzle wall temperature.

2

Design of Acoustic Tubes Array and Application to Measuring Acoustic Loads in Supersonic Airflow

Wei L., Li M., Fu Q., Fan Y., Yang D.

Archives of Acoustics

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2014

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Vol. 39, No. 3

395--402

EN

In the acoustic fatigue experiment for hypersonic vehicle in simulated harsh service environment on ground, acoustic loads on the surface of test pieces of the vehicle need to be measured. However, for the normal microphones without high temperature resistance ability, the near field sound measurement cannot be achieved. In this work, on the basis of previous researches, an acoustic tubes array is designed to achieve the near field measurement of acoustic loads on the surface of the test piece in the supersonic airflow with high temperature achieved by coherent jet oxygen lance. Firstly, the process of designing this acoustic tubes array is introduced. Secondly, the equality of phase differences at the front and at the end of the tubes is stated and proved using a phase differences test with an acoustic tubes array whose design is presented in this text; therefore, the phase differences of signals acquired by microphones can be directly applied to beamforming algorithm to determine the acoustic load source. Finally, using above mentioned acoustic tubes array, measurement of acoustic load, with and without a test piece in the supersonic airflow made by the coherent jet oxygen lance, is conducted respectively, and the measurements results are analyzed.

3

The Nonwovens Formation in the Melt - blown Process

Lewandowski Z., Ziabicki A., Jarecki L.

Fibres & Textiles in Eastern Europe

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2007

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Vol. 15, no. 5-6 (64)

77--81

EN

Melt-blowing is an industrial method for the rapid production of nonwoven fibres. In melt-blowing a polymer is melted and extruded through a capillary while heated air is blown through an air nozzle. The aerodynamic drag of the air jets on the polymer provides the attenuation force that draws the polymer streams into fine diameter fibres. In this paper, the following factors are presented: a modified mathematical model of melt spinning for a pneumatic process accounting for the effects of structural transformation in the viscoelastic behavior of the spun polymer; the application of mathematical modelling to the melt-blown process; a novel method for nonwoven formation in airflow with supersonic velocity.

PL

Pneumatyczne przędzenie włókien ze stopu stanowi podstawę przemysłowej metody szybkiej produkcji włóknin. W procesie tym stopiony polimer, wytłaczany przez kapilarne dysze, poddany jest rozciąganiu aerodynamicznemu przez strumień gorącego powietrza wydmuchiwany współosiowo z dysz umieszczonych po obu stronach belki przędzalniczej. Siła tarcia pomiędzy strumieniem powietrza a strugami polimeru prowadzi do ich szybkiego zwężania się wzdłuż osi przędzenia i otrzymywania cienkich włókien. Przedstawiono wyniki obliczeń dynamiki procesu przeprowadzone w szerokim zakresie szybkości nadmuchu powietrza z zastosowaniem matematycznego modelu dynamiki strumienia powietrza oraz modelu przędzenia włókien ze stopu w strumieniu aerodynamicznym z uwzględnieniem przemiany struktury polimeru i efektów lepkosprężystych. Zaprezentowano nową metodę aerodynamicznego przędzenia włóknin ze stopu w naddźwiękowym strumieniu powietrza.