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Ebara Engineering Review No.218

Development of Axial-flow Fan for Cooling Towers Using Inverse Design Method and CFD

by Hidenobu OKAMOTO, & Masashi KITAMURA

A 3D inverse design method and a CFD (Computational Fluid Dynamics) method were applied in the development of an axial-flow fan for cooling towers. These methods were put to use in an attempt to improve the aerodynamic performance of cooling towers. Studies were carried out systematically on blade loading parameters, stacking conditions and rotational speed effects, afterwhich values were optimized according to study results. A fan with a blade featuring the finalized design was installed in an actual cooling tower and tested to verify its aerodynamic performance. Test results revealed that this fan, which featured the inverse design, was able to maintain the amount of rise in static pressure according to specifications, also that its efficiency was more than 20% higher than that of a conventional such fan. All in all, it was proven that the inverse design method could be an advantageous method for the design of axial-flow fans.

Keywords
Inverse design method, Axial flow fan, Cooling tower, Computational fluid dynamics, Blade loading parameter, Verification experiment, Efficiency, Rotational speed

Combustion Characteristics of a CO2 Mixture Methane & a Microturbine Cogeneration System utilizing Sewage Digester Gas

by Tadashi KATAOKA, Teruyuki NAKAJIMA, Takahiro NAKAGAWA, & Saburo YUASA

An attempt has been made to utilize biogas (sewage digester gas) as a fuel for gas turbines. The sewage digester gas utilized had low Btu, constituting 60% methane and 40% carbon dioxide. Conventional attempts necessitate the optimization of combustion systems to improve flame-holding and other characteristics to enable the use of biogas as gas turbine fuel. The novel approach taken here by the authors was to use mass-produced microturbines and peripherals, with minimal modification and without using specially-designed combustors. The regeneration cycle is started up using a high calorific fuel for the microturbine's RQL (Rich-burn, Quick-mix, and Lean-burn) combustor. The fuel is switched to digester gas once the inlet air gets preheated to 600 K or higher. This method has proven itself to enable reliable startup, stable operation (from idling to the rated power output), and to be equivalent in efficiency to that by an operation wherein high calorific fuel is used. This system is looked forward as an energy-efficient, energy-saving cogeneration system with minimal impact on the environment.

Keywords
Microturbine, Biogas, Combustor, Sewage digester gas, Cogeneration

Evaluation on Surface-reaction between Interconnecting Metals and CMP Slurry by In-situ Experiments and Characterization of Surface-layer Mechanical Properties

by Shohei SHIMA, Akira FUKUNAGA, & Manabu TSUJIMURA

An electrochemical polishing experimental apparatus was used to evaluate surface reaction during an actual CMP process. In-situ experiments were conducted to study the electrochemical reaction between interconnecting metals and the CMP slurry. A finding was made that the electrochemical reaction characteristic during polishing and non-polishing differed, also that the characteristic greatly differed depending on the chemical components of the slurry. This evaluation also revealed that it was possible to experimentally determine the effectiveness of a particular slurry and post-treatment agents prior to a particular polishing process, thus realizing a time-saving in the development. Moreover, mechanical properties of metal surface-layers were able to be evaluated from the AFM force curve, revealing a correlation with electrochemical reaction characteristics. This evaluation method suggests a possibility of nano-scale evaluation on the mechanical properties of ultra-thin reaction layers.

Keywords
Chemical Mechanical Planarization, Electrochemistry, Potentiodynamic polarization, Open circuit potential, Slurry, Oxidizer, Chelate agent, Interconnection metal, Atomic Force Microscopy, Spectroscopic ellipsometer

Isopropyl Alcohol (IPA) Drying Effect on Hydrophilic and Hydrophobic Wafer Surfaces

by Kouichi FUKAYA, Shinji KAJITA, Yukiko NISHIOKA, Fumitoshi OIKAWA, Katsuhiko TOKUSHIGE, & Manabu TSUJIMURA

Research had been conducted on precision drying technology for CMP (Chemical Mechanical Polishing) processes, in an effort to minimize damage on the surface of Low-k (low dielectric constant) films. Comparative studies were made on defect (watermark) suppression effects on hydrophilic and hydrophobic films by both the conventional SRD (Spin-Rinse-Dry) and the IPA drying methods. Study results revealed that IPA was optimal for drying hydrophobic film due to its watermark suppressing effect. As for hydrophilic film, although there was no significant difference in the drying performance by both methods, SRD was determined to be more favorable due to faster tact time.

Keywords
Chemical Mechanical Polishing (CMP), IPA drying, Rotagoni drying, Spin rinse drying, Watermark, Hydrophobic film, Hydrophilic film, Low dielectric constant materials, Contact angle

Development of Treatment System for Radioactive Spent Ion Exchange Resins

by Takeshi IZUMI, Masahiro HAGIWARA, Takashi OHTSU, Hirofumi INAGAWA, & Masayuki ARAI

A new ion exchange resin solidification system, featuring the combining of resins with paraffin wax, has been developed. The resulting solid matter, constituting resins and paraffin wax, were able to be easily incinerated at existing incineration plants, Therefore, there is no longer a need to store spent ion exchange resins, as low-level radioactive waste, that had been output from water purification systems at nuclear power plants.

Keywords
Nuclear power plants, Ion exchange resins, Radioactive wastes, Incineration treatment, Solidification, Paraffin wax

Pump Controller for Snow Lasta SP, a Water-Saving Type Snow Thawing System

by Hideji ISOBE, Hiroshi YAMASHITA, & Toshihiro SASAGAWA

The Snow Lasta SP is a snow thawing system developed to cope with land subsidence and groundwater level sinkage in districts of heavy snow. The system's features include automatic shift of operation modes to optimally match particular snowfall conditions and ambient temperature. Pump operation (time and frequency) are constantly monitored by computer, thus enabling an elongation of pump life in the long run. Lowering cost for market competitiveness had been the top priority in the development of previous Snow Lasta models. In comparison, the development of Snow Lasta SP was centered on improvement with considerations made on water and energy saving.

Keywords
Snow thawing system, Snow thawing control, Snow sensor, Snowflake detection, Snowfall pulse, Snowfall intensity, Water saving control, Residual snow prevention, Intermittent operation, Water spray

Development of the System for Cu Oxide Film Removal from Semiconductor Interconnects in Atmosphere pressure

by Hideki TATEISHI, Akira SUSAKI, & Tsutomu NAKADA

A system for removing Cu oxide film grown on the surface of copper semiconductor interconnects has been developed for reducing the resistance of such multi-layered interconnects. This system features a dry process in the atmosphere, and is developed applicable for wet processes such as CMP and plating systems. Formic acid gas, vaporized from liquid form, is efficiently applied on wafer surfaces, resulting in the removal of naturally-oxidized Cu film depositing on 200 mm wafers, in 1 minute under a temperature of 175 ℃. The basic characteristics of a practical system have been proven and a compact system has been realized.

Keywords
Semiconductor, Copper interconnects, Oxide removal, Atmospheric process, Organic acid, Multi-layered interconnects, Low oxygen concentration space, Ellipsometry, Vacuum exhaust means, Plated copper

Development of a SCADA System for Wind Farms

by Takuro WATANABE, Koichi NAOI, Toshiaki MAEZAWA, & Toshimichi MIYASAKA

A SCADA (Supervisory Control And Data Acquisition) system has been developed for totalized monitoring and controlling of wind farms, thus enabling integrated management of both wind turbine and power generator systems. The following discusses the basic geometry, specifications and features of this cost-saving SCADA system.

Keywords
Wind turbine generator, Wind farm, SCADA system, Web server, Database

Reconstruction of Owada Pump Station

by Kenichi UMEMURA

The manufacturing of pump equipment for and construction work at Owada Pump Station, Chiba Prefecture had been undertaken by Ebara between March 2004 and June 2007. This was done as a part of a reconstruction project of this pump station which was getting obsolete after 37 years of service. Ebara's commitment included the modification of pump machinery and control systems, as well as reconstruction of structures by civil engineering. Various technological solutions, beyond the scope of conventional pump facility construction, were put to use, such as designing instrumentations.

Keywords
Drainage pump station, Reconstruction, Vertical axial flow pump, Siphon, Concrete casing, No water system, Silencer, Short schedule, Temporary still water system, Static concrete cutting