A single stage transonic centrifugal compressor for a small turbofan engine has been developed. Rig testing has demonstrated 83.2 percents of adiabatic efficiency for 7.5:1 of total to static pressure ratio, using a corrected tip speed of 596 m/sec. This paper mainly presents an impeller blade redesign approach from original blade geometry, based on both experimental and numerical results. An in-housedeveloped Navier-Stokes flow solver has been applied to the impeller redesign process. Taking into a consideration of development schedule, a steady flow solver has been used for the impeller analysis, instead of unsteady stage analysis. As a result, important redesign factors for higher efficiency are leading edge shock control, blade-to-blade loading control and splitter-loading optimization. Also, flow physics on secondary flow mechanism has been captured by the computational analysis and its flow control has been applied to the impeller redesign process. The final stage performance has been achieved using a coupling of a pipe diffuser and an impeller-inducer-bleed system by the rig testing.
Thermally decomposition products from virgin and flame retarded polyesters were investigated by using GC-MS method. Effects of flame retardation on polyester were found to appear at relatively lower temperature. Difference between retardants which contain phosphorus or bromine was shown clearly. Phosphorus-containing polyester emitted more amounts of carbon monoxide, carbon dioxide, and benzene than other polyesters. Bromine-containing polyester emitted less amounts of gaseous products than other polyesters.
Abstract The effect of orientation on the combustion phenomena of a PMMA plate was studied experimentally. A PMMA plate was held by a sample holder made of insulation boards with only one face exposed to the air. Observation of burning inclined plates revealed that flame shape varied with inclination angle. The burning behavior of the upper surface of an inclined plate appeared to differ from that of the lower surface. However, the surface regression rate was found to depend on the inclination angle from the vertical plane. This rate for the upper surface was identical to that of the lower one if the absolute value of the inclination angle was identical, and was found to depend on empirical relationships involving natural convective heat transfer around a heated plate.
Tsunami causes erosion and accretion in a harbor or a bay, which may result in the collapse of structures and the damage of harbors. It is important to calculate the accurate sea bottom changes by Tsunami. The strong pressure gradient transforms the velocity vertical distribution in a strait or a bay mouth where the flow is accelerated and decelerated rapidly. It is necessary to study the propriety of the method that the bottom shear stress is estimated by the mean flow formula.Characteristics of the velocity distribution and the bottom friction velocity of tsunami were carefully investigated by experiments in a narrow strait where the Shields number is more than 10. The velocity distribution becomes uniform in the acceleration phase, and the bottom friction velocity becomes large by the strong velocity gradient near the bottom. Based on the results, the method of evaluation of the bottom sheer stress by the log-wake law is proposed.
There are several flammable gases used in semiconductor industries, and some oxidizing gas such as chlorine trifluoride (ClF3) is also used in the same production apparatus. As knowledge of the combustion characteristics of flammable gases with oxidizing gases other than oxygen are lacking, an experimental study to evaluate combustion characteristics was performed. Chlorine trifluoride, the oxidizing gas used in this study was commercialized recently for etching and cleaning purposes because of its powerful oxidizing ability. As flammable gases, tetraethyl orthosilicate (TEOS: Si (OC2H5)4), hydrogen (H2) and ammonia (NH3) were investigated. These gases are toxic, except for hydrogen, and have high reactivity, so these gases were fist diluted with nitrogen separately. The diluted TEOS and ammonia gases were found to ignite spontaneously while being mixed with the diluted ClF3 gas. On the other hand, the diluted hydrogen gas could be mixed with the diluted ClF3 gas without spontaneous ignition. And a H2/ClF3/N2 mixture could be ignited by an electric spark. Therefore, for TEOS and ammonia, "flammable limit" means the limit of spontaneous combustion, and for hydrogen the flammable limit means the usual limit of ignitability by an external ignition source. The flammability diagrams of TEOS/ClF3/N2, NH [3/CW3/N2 and H2/ClF3/N2 mixtures were determined. And reaction kinetics between them were discussed from observed combustion characteristics.
