Takashi Ikeguchi

Photodesorption from stainless steel, aluminum alloy and oxygen free copper test chambers

Abstract Photodesorption yields due to synchrotron radiation (SR) from type 316 stainless steel, type A6063 aluminum alloy and high purity oxygen free copper (ASTM Class-1 OFC) test chambers were measured. SR with critical energy of 4 KeV from the 2.5 GeV storage ring of the Photon Factory at KEK was used. The photon beam size is 0.385 mrad in both vertical and horizontal directions. Seven test chambers which have the same shape were tested. The yields of OFC finished with machining is reduced to 9 × 10 −6 molecules photon −1 (N 2 equivalent) which is the lowest value throughout the experiments. Stainless steel treated with electrolytic polishing and 48h prebaking at 450°C shows the second lowest yield. The yield of aluminum alloy is somewhat higher than the others. The yields for other gas species were also measured.

Photoelectron effect of photodesorption in a chamber irradiated by synchrotron radiation

Photodesorption in vacuum chambers exposed to synchrotron radiation were measured at the PF storage ring of KEK. Two types of wire electrodes, one is a cylindrical grid in an axial direction near the inner surface of the test chamber, and the other is a semispherical grid around a surface irradiated by synchrotron radiation, were installed in the test chambers. Desorption and photoelectron currents were measured under conditions of bias voltages applied to the electrodes. Photodesorption caused by synchrotron radiation is greatly influenced by bias voltage. Therefore, electron stimulated desorption due to photoelectron contributes considerably to the photodesorption. Photodesorption can be decreased by a negative electric field around the primary incident surface of the chamber.

Part Load Operation of a Combined Plant Using a Closed Circuit Blade Cooled Gas Turbine

Closed circuit blade cooled gas turbines are drawing attention because of their efficiency compared with that of a conventional air cooled gas turbine. In a closed circuit blade cooled gas turbine, coolant is not discharged into the gas path, so dilution of the hot gas stream, rotor blade pumping loss and pressure loss due to mixing of coolant with the stream are drastically reduced.In this paper, two types of combined cycles, a closed circuit steam cooled gas turbine combined cycle CCSC, and a closed circuit air cooled gas turbine combined cycle CCAC are analyzed to verify the part load performance.The blade temperatures of both combined cycles are lower than at full load, that is, the blades are sufficiently cooled. Under 30% load in the CCSC, the coolant steam pressure is lower than the main gas stream because of a shortage of coolant steam.Copyright

Conceptual Design of the Cooling System for 1700°C-Class Hydrogen-Fueled Combustion Gas Turbines

The effects of three types of cooling systems on the calculated operating performances of a hydrogen-fueled thermal power plant with a 1,700°C-class gas turbine were studied with the goal of attaining a thermal efficiency of greater than 60%. The combination of a closed-circuit water cooling system for the nozzle blades and a steam cooling system for the rotor blades was found to be the most efficient, since it eliminated the penalties of a conventional open-circuit cooling system which ejects coolant into the main hot gas stream.Based on the results, the water cooled first-stage nozzle blade and the steam cooled first-stage rotor blade were designed. The former features array of circular cooling holes close to the surface and uses a copper alloy taking advantage of recent coating technologies such as thermal barrier coatings (TBCs) and metal coatings to decrease the temperature and protect the blade core material. The later has cooling by serpentine cooling passages with V-shaped staggered turbulence promoter ribs which intensify the internal cooling.Copyright

A Method for Analyzing Static Performance at Part Load in a Heat Recovery Steam Generator.

When designing a combined cycle plant, it is essential to estimate performance of the heat recovery steam generator not only at full load but also part load. The method for analyzing the part load performance presented in this paper is based on a full load heat mass balance of the combined cycle plant. Steam turbine inlet pressure, which is the base point of pressure balance, is calculated from a relationship between the pressure ratio and corrected mass flow. Pressure losses of pipes and heat exchangers are corrected by their full load pressure losses. Temperature balance is determined by correcting superheater outlet temperature, pinch point and approach point under the constraints that the area of each heat exchanger is unchangeable. This method is applied to a reheat and triple pressure heat recovery steam generator.