Toshio Takenaka

An investigation of oil column separation in the return line of large free forging press.

In a large free forging press, the high speed operation of a directional control valve often causes an oil column separation in the return line of the valve. This paper deals with the numerical analysis of the pil column separation in the return line of large oil hydraulic systems caused by the valve stroking of linear mode. The relation between the valve closing time and the rejoinder surge pressure following the oil column separation is investigated in detail. The expression of valve characteristic can be simplified by the use of an effective valve stroke. By introducing dimensionless variables for the basic equations, dimensionless parameters are induced. The oil column separation caused by the valve stroking of linear mode is expressed by using the dimensionless parameters.

ON THE EFFECT OF TRAPPED AIR IN A LIQUID CONDUIT ON THE TRANSIENT FLOW RATE.

Trapped air in a liquid conduit has a great influence on the fluid transient. In this paper, especially its effect on the transient flow rate is studied experimentally and analytically. Transient flow velocity, following a quick opening of a valve attached at the downstream end of the test pipeline, was measured experimentally. The experiments showed that the transient flow velocity often exceeds the final steady state flow velocity. The numerical calculation by means of characteristics method showed a good agreement with the experimental results. Maximum value of the transient flow velocity depends on the volume and the position of the trapped air, and the pressure loss of the pipeline and the valve, and the pressure at the downstream side of the valve. Five dimensionless parameters, which represent above-mentioned factors respectively, are derived, and the relations between the maximum flow velocity and these five parameters are expressed graphically.

Study on the High Pressure Generation by Means of Oil Hammer : 2nd Report, Application to a Pressure Intensifier and Lateral Pressure Cutting

Stable hydraulic pressure pulse series can be generated by an appropriate valve operation at a pipe end. The pressure of the pulse series is amplified by a booster piston, consequently the pressure pulse series with a pressure higher than 400 MPa is obtained for a frequency of 15.2 Hz. By a pressure intensifier applying the amplified pressure pulse series, a continuous oil flow with an amplified pressure higher than 300 MPa is obtained for a source pressure of 6.6 MPa, Using this pressure pulse series generator as a lateral pressure cutting device of a ductile material, an aluminum column of 20 mm in diameter with a notch is cut after 580 cycles of the repeating pressure of 204 MPa. Hydraulic pressure pulse series generator discussed in this paper is practical enough to be used as a pressure intensifier and a lateral pressure cutting device.

Flow Measurement by Means of Inlet Nozzles

The authors determined experimentally the discharge coefficients c of inlet nozzles, whose diameters range from one inch to 10.6 inches to measure air, water and oil flow quantity. Experimental formula of c correlated to Reynolds number coincides with the experimental results as shown in Fig. 7.