大島 茂:水 圧 ポペ ッ ト弁 内の キ ャ ビテー ショ ンに関 す る実験 的研 究 29 研 究論 文 Experimental Study on Cavitation in Water Hydraulic Poppet Valve Shigeru OSHIMA**, Timo LEINO***, Matti LINJAMA***, Kari T. KOSKINEN***, Matti VILENIUS*** 水 圧 ポ ペ ッ ト弁 内 の キ ャ ビ テ ー シ ョ ン に 関 す る 実 験 的研 究* 大 島 茂**, TimoLEINO***, Matti LINJAMA***, Kari T. KOSKINEN***, Matti VILENIUS*** Cavitation is a common phenomenon in many valves used in water hydraulic systems as well as in oil hydraulic systems. In this paper, the cavitation phenomenon in water hydraulic poppet valve is fundamentally investigated ex- perimentally with a half cut test model. The cavitation appearance processes, the boundary of inception, the effects of cavitation on the characteristics of flow rate and pressuredistributions are investigated. The results are discussed in comparison with the results of the similar tests with oil hydraulic valve in the former study. Key Words: Hydraulics, Water, Cavitation, Poppet valve, Half cut model, Experimental study 1. Introduction In recent years water hydraulic systems have at- tracted attention because of their environmental friend- liness. They have advantages besides the environmental friendliness ; non-flammable, low cost and easy avail- ability of pressure medium etc.1). The amount of appli- cations realized by the water hydraulics has increased in food processing industries, etc., and the trend seems to be upwards2). However, there are still problems to be solved for the water hydraulic systems so that they could be used commonly in industries. One of the impor- tant problems is to get components with longer lifetime. Cavitation is one of the major cause of the life shorten- ing of water hydraulic components as well as the less lu- bricant ability and corrosive properties of water3). Cavitation generally causes undesirable problems in fluid power systems and components, for example; effi- ciency reduction, increase of vibrations and noise, unex- pected change in the characteristics of flow rate and flow force, and erosion of the components in the most violent case. Erosion due to impingement of cavitating water jet has been studied actively4). There have been many studies on cavitation in hydraulic valves up to now, but many of them are with oil hydraulic valves be- cause oil hydraulics has been major in the fluid power systems during this decade. Many experiences gained in the works with oil hy- draulics are valuable and some of them may be applica- ble for water hydraulics. However, it should be known that there are significant differences in the property of oil and water5). The vapor pressure of water is consider- ably higher than that of oil, the viscosity is pretty lower and the density is higher than oil Therefore, the situ- ation of cavitation occurrence and its effects on valve performances are not always equal between the cases of water and oil hydraulic valves. It is very important to reveal fundamentally the cavitation phenomenon in water hydraulic valves and consider the differences be- tween the cases of water and oil hydraulic valves. In this paper, the cavitation phenomenon in water hy- draulic poppet valve is fundamentally investigated ex- perimentally with a half cut test model produced in the same shape and same size as the test apparatus which was used in the former study with oil hydraulic valves6). The cavitation appearance processes, boundary of cavi- tation inception, the effects of cavitation on the charac- teristics of flow rate and pressure distributions are in- vestigated. The results are discussed in comparing with the results by the similar tests in the former study with oil hydraulic valve6)-8). * 平 成13年6月27日 原稿受付 ** NumazuCollege of Technology , Control andComputer EngineeTing depattment (所在 地 〒410-8501沼津 市 大 岡3600) *** Tampere University of Technology , Institute of Hydrau- lics and Automation 第33巻 第2号 1 2002年3月(平成14年)