Technologies

Market leading technologies coupled with the highest quality services

Ebara Engineering Review No.206

Reduction of Complex Pressure Fluctuations and Vibrations in a Pump-water Tunnel System (1st Report: Measurement and Understanding of Phenomena)

by Shijie GUO, Yoshiyuki MARUTA, Hidenobu OKAMOTO, Hideki KANNO, & Kiyonori SATO

Significant pressure fluctuations were observed in suction water tunnels when an axial flow pump was operated without an actual head at some blade angles. To identify the causes, investigations were done by measuring acoustic natural frequencies and pressure fluctuations in the tunnels, lateral and torsional vibrations of the pump shaft, and pressure fluctuations of the oil in the hydraulic system to control the blade angle. Measurements were also taken by inserting air into the suction tunnels with a compressor and by setting air bags inside the tunnels. The results showed that acoustic resonance occurred in the tunnels, but it was not a simple resonance. The dominant frequency, which was neither the blade passing frequency nor its higher harmonics, depended on rotating speed in the reverse way: it decreased when rotating speed increased, and vice versa. The pressure fluctuations and vibrations of the pump shaft had a strong relationship. However, they had different dominant frequencies and occurred at different blade angles. Several measurements were made in different seasons and it was found that the phenomena were season-dependent. The causes are discussed. It is believed that the excitation source was vortex shedding from the blades, which locked into the acoustic resonance in the water tunnels via vibration of the blades.

Keywords
Flow-induced-vibration, Pressure fluctuation, Vortex shedding, Acoustic resonance, Turbomachinery, Axial-flow pump, Pump station, Rotordynamics, Hydraulic control, Angle-changable blade

Reduction of Complex Pressure Fluctuations and Vibrations in a Pump-water Tunnel System (2nd Report: Countermeasure by Control of Flow Separation on the Impeller)

by Hidenobu OKAMOTO, Shijie GUO, Hideki KANNO, Shuichiro HONDA, & Kiyonori SATO

This paper describes a vibration reduction countermeasure for a drainage pump station in which axial flow pumps were used. Investigations of vibration phenomena in the station showed that an unsteady fluid force occurred and the force locked into acoustic pressure fluctuations of the suction tunnel or vibration of the impeller. Reducing magnitude or changing frequency of fluctuations of fluid force are ways to remove lock-in phenomena. In the case of an axial type pump, one of the main causes of unsteady fluid force is unsteady vortex shedding on the impeller blade when the pump is operated under the off-design condition. Small lugs like tripping wires are mounted on the blade surface to reduce unsteady vortex shedding and to change its frequency. In this paper, we numerically examine the size and the position of a tripping wire on the blade surface using Vortex Method.

Keywords
Pressure fluctuation, Unsteady fluid force, Vortex shedding, Control of flow separation, Peak frequency, Vortex Method, Small lug, Lock-in, Resonance, Acoustic natural frequency

Static Characteristics of an Absorption Chiller-Heater for Simultaneous Cold and Hot Water Supply

by Naoyuki INOUE, & Tomoyoshi IRIE

A study has been made on the cycles and control method of an absorption chiller-heater, a simultaneous cold and hot water supply type, used for air conditioning systems. Absorption cycles were studied by simulated cycles using an actual machine. Study results revealed that improving the control over the amount of circulated solution in an economizer cycle (cycle in which a condensed refrigerant for heating water shifts to the cooling cycle for chilling the water) had the greatest energy saving effect under all operational conditions.

Keywords
Absorption chiller-heater, Simultaneous supply, Absorption cycle, Economizer, Cycle simulation, Energy saving, Control characteristic

Development of a High-efficiency Phosphorus Recovery Method using a 2-tank type Fluidized-bed MAP Reactor

by Kazuaki SHIMAMURA, Hideyuki ISHIKAWA, & Toshihiro TANAKA

A highly efficient, phosphorus recovery method, featuring the use of a 2-tank type fluidized-bed, MAP (Magnesium, Ammonium, Phosphate) reactor was developed. Standardizing the MAP particle size in the reactor worked to enable high-efficiency recovery. A saving on chemical cost, for treating wastewater containing high concentrations of phosphorus, was achieved by the combined use of low-cost magnesium hydroxide and sulfuric acid. Performance tests were conducted using a pilot plant (treatment capacity:20 m3/day) and an anaerobic digestion supernatant. The phosphorus concentration in the treated water (10 - 25 mg/l) was found to be significantly reduced, compared to that in the supernatant (about 300 mg/l). A phosphorus recovery exceeding 90% was attained.

Keywords
Phosphorus recovery, Crystallization, Fluidized-bed, MAP (Magnesium ammonium phosphate), Anaerobic digestion supernatant, Seed crystal, Particle size

Development of Custom Pump Digital Catalogue

by Toshio HARA, Sinichi SHIGEHARA, Yoko KAKINUMA, & Isao ABE

EBARA's newly developed Custom Pump Digital Catalogue system features a CD by which clients can obtain necessary data on a pump according to desired specifications. This system enables efficient engineering and sales transactions, front-end processing of documents including estimates, and a significant reduction in lead-time. The following outlines the development and details of this system and introduces current trends regarding such digital catalogues.

Keywords
Custom pump, Digital catalogue, BPR, Pump selection, E-market place, Catalogue contents, Pump pre-selection, Pump fine selection, HTML/XML, Selection logic flow, ISO13584

RTC Series Energy-saving Centrifugal Type Refrigerator

by Yuichi SATO, Toru TOKUMARU, & Takahiro SENDA

The RTC series, energy-saving centrifugal type refrigerator, includes a high-efficiency multi-stage compressor,developed for air-conditioning equipment. It features improved aerodynamic performance and minimized mechanical loss enabled by a ball bearing system. The cycle efficiency and system efficiency are also significantly improved compared to those of conventional such machines. In chilled water application, a COP (Coefficient Of Performance) of 6, an energy saving of about 25% compared to that of conventional such machines, while in ice-making application, a COP of 4.6, an energy saving of about 40% compared to the same. The following discusses development concepts, the energy-saving method, compressor features, as well as test results.

Keywords
Energy saving, Coefficient of performance (COP), Centrifugal type refrigerator, High efficiency, Multi-stage compressor, Economizer, Motor direct drive, Ball bearing, Low-pressure refrigerant

Industrial Waste Incinerating Boiler Plant

by Iku SATO, & Koji NOMURA

EBARA's Industrial Waste Incinerating Boiler Plant, incineration capacity of 19.8 tons/day, is now operating at the Amagi Plant of Bridgestone Corporation. This fluidized-bed type boiler system features the use of excess heat from the furnace to generate steam for tire production. Effluent non-combustibles and fly ash are used as material for steel and cement production.

Keywords
Industrial waste, Fludized-bed boiler, Reuse of energy, Reuse of resources