Transactions of the Korean Society of Mechanical Engineers B (대한기계학회논문집B)

The Korean Society of Mechanical Engineers (대한기계학회)
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Experimental Study of Discharge Coefficient and Cavitation for Different Nozzle Geometries

노즐 오리피스 형상에 따른 Discharge Coefficient와 Cavitation에 관한 실험적 연구

  • Kim, Sung-Ryoul (Dept. of Mechanical Engineering, Kyungpook Nat'l Univ.) ;
  • Ku, Kun-Woo (Dept. of Mechanical Engineering, Kyungpook Nat'l Univ.) ;
  • Hong, Jung-Goo (Institute of Mechanical Engineering Technology, Kyungpook Nat'l Univ.) ;
  • Lee, Choong-Won (Dept. of Mechanical Engineering, Kyungpook Nat'l Univ.)
  • Received : 2010.07.01
  • Accepted : 2010.08.02
  • Published : 2010.10.01
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Abstract

The purpose of this study is to investigate the generation and development of cavitation in circular and elliptical nozzles. In order to investigate the influence of cavitation, the experiment was conducted with a set of elliptical nozzles that had the same cross-sectional area, different orifice aspect ratios (a/b). Each nozzle was made of acrylic so that visualization was possible. With the injection pressure, the internal flow of the nozzle was classified into the no-cavitation, cavitation, and hydraulic-flip regions. Regardless of the nozzle geometry, with the injection pressure, the flow rate in the no-cavitation and cavitation regions increased and the discharge coefficient decreased. However, the flow rate was constant in the hydraulic-flip region. In the elliptical nozzles, the generation and development of cavitation occurred at higher cavitation number than that in the case of a circular nozzle.

본 연구는 타원형 노즐과 원형 노즐 내부에서 발생되는 cavitation의 발생 및 성장을 실험적으로 관찰하였다. 원형 노즐과 타원형 노즐의 cavitation 특성을 가시화 하기위해 투명한 아크릴로 노즐을 제작하였다. 실험에 사용된 노즐들은 같은 단면적으로 제작되었으며, 타원형 노즐의 경우 형상비(a/b)를 다르게 하였다. 분사압력의 증가에 따라 노즐내부 유동은 no cavitation, cavitation, hydraulic flip 영역으로 나뉘어졌다. 노즐의 형상에 상관없이 no cavitation과 cavitation 영역에서는 분사압력의 증가에 따라 유량은 증가하며, 유출계수는 감소하는 경향을 나타냈다. 그러나 hydraulic flip 영역에서의 유량계수는 일정한 값을 나타냈다. 타원형 노즐은 원형 노즐에 비해 높은 cavitation number에서 cavitation이 성장, 발달하였다. 특히 타원형 노즐에서는 장축의 cavitation length가 단축보다 길게 나타났다.

Keywords

Acknowledgement

Supported by : 한국연구재단

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  2. Numerical Analysis of the Flow Characteristics of High-Pressure Injection Nozzle for Machine Tools vol.35, pp.10, 2011, https://doi.org/10.3795/KSME-B.2011.35.10.1061
  3. Cavitating Flow in Circular and Elliptical Nozzles vol.35, pp.10, 2011, https://doi.org/10.3795/KSME-B.2011.35.10.1005