Seiichi Tanabe

Discharge Coefficient of Poppet Intake Valve with Rotating Flow.

An intake valve flow discharge coefficient was investigated in the case of air swirling around the valve, as seen in the helical-type intake port of an IC engine. A cylindrical intake port, poppet intake valve of enlarged model and suction tank were constructed to be coaxial, and a honeycomb swirler was installed at the port entrance and rotated around the valve shaft at high speed. The valve angle was 30 degrees, and pressure distributions on the valve and valve seat surfaces were measured. The discharge coefficients were determined by changing the swirler speed and valve lift. Theoretical air flow was induced by taking account of swirling air. The effect of swirl intensity on the discharge coefficient becomes more significant at higher valve lifts, i. e., the higher swirl the lower the coefficient. At lower valve lift, the swirl effect is more suppressed.

The Effects of a Wall Boundary Layer on Local Heat Transfer from a Circular Cylinder in Cross Flow.

Heat transfer from a circular cylinder in cross flow, in particular, from its rear region is enhanced in the neighborhood of a wind wall on which a turbulent boundary layer is developed. At two stations where the boundary-layer thicknesses are 0.75 and 2.4 times as large as the cylinder diameter, the local heat transfer was measured in the spanwise and circumferential directions by means of a small heat-flux measuring probe devised by the authors utilizing a thermistor. Circumferentially averaged heat transfer is enhanced in the neighborhood of the tunnel wall by 1.6 [approximately] 1.8 times as much as that in the uniform cross-flow region. The local heat transfer in the neighborhood of the wall is more enhanced at the rear stagnation point than that at the front stagnation point. The enhancement in the larger thickness of the boundary layer is greater and appears nearer the wall than that in the smaller thickness, which is due to the strong vortex generated adjacent to the wall just behind the cylinder.

Turbulent Velocity Measurement Errors due to Signal Noise in Laser Doppler Counter Processor.

Cycle-to-cycle variations in the time period of a Doppler signal cycle on which higher frequency noise is superimposed give rise to velocity turbulence errors in a commercially available counter processor. The errors simulated and measured by the dual-beam LDV are found to increase in lower turbulent flows at lower count-cycle numbers and higher shift frequencies. The measured turbulence was corrected to some extent by the simulation described in this study.

Turbulent folw analysis in water turbine draft tube.

A new finite-element technique for three-dimensional turbulent flow analysis based on the two-equation turbulence model was applied using a supercomputer, to internal flows in a water turbine draft tube. Predicted results were compared with the experimental flow pattern from the oil film method, and the total loss was measured by a pitot tube. Compared with the oil film, the occurrence of reverse flow, the main flow behaviour, and the secondary flow direction, were adequately predicted, but the flow pattern at the reverse flow section did not have good agreement. Using a finer mesh improved the flow pattern for the reverse flow. Regarding the total loss, the predicted loss was about twice the measured loss, and use of the finer mesh improved the predicted loss.

Experimental Study of Unsteady Flow Behind a Francis Turbine Runner Exit

The flows behind the runner exit of a high specific speed Francis turbine were studied by using a probe for unsteady water flow. A 5-hole pitot probe was used along with pressure transducers, set near the holes, to measure the flows. The mean velocity and total head distributions behind the runner exit between one pitch of the runner vanes from the crown to the band, were examined under five operating conditions. Especially, flows near the vane wake and flows when a reverse flow occurred on the suction surface were examined. And, some comparisons were made with flow pattern obtained by the oil film method.

Effects of Air Swirl on Diesel Combustion

This paper describes about the effects of air swirl on the exhaust smoke, the nitrogen oxides emissions and the combustion efficiency of a direct-injection diesel engine. Using a 1.35 ltr singlecylinder engine with a disc-type combustion chamber, the investigations were made, by means of the exhaust gas analysis, into the influences of the swirl ratio (swirl speed/engine speed), SR, the numbers of holes of fuel injection nozzle, Nh, and the oxygen concentration in intake air on the concentration of soot and nitrogen oxides and the combustion efficiency.The results of experiments are as follows:(1) The effects of the swirl on the diesel combustion varies with the numbers of the holes of fuel injection nozzle. The sooting ratio, the nitrogen oxides concentration and the combustion efficiency are able to be put in order of SR Nh values.(2) In the condition of small value of the excess air ratio, the over swirl phenomenon clealy occurs at SR Nh>about 15.(3) The effect of swirl on the exhaust smoke and combustion efficiency becomes remarkable with the decreases in the excess air ratio and the oxygen concentration in intake air.(4) The effects of oxygen concentration in intake air, νS (O2), on the soot concentration, SWV, and the combustion efficiency, ηu, are expressed as follows:SWV=SWV(0.21){νS(O2)/0.21}-α, ηu=1-{1-ηu(0.21)}{νS(O2)/0.21}-β, where the values of α and β vary with SR and Nh.