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Ebara Engineering Review No.246

Measurement of Stress Distribution for Rotating Shaft Using Thermography

by Keisuke HAYABUSA, Dai KUDO, Kikuo KISHIMOTO, & Tadaharu ADACHI

A rotating shaft is designed by comparing calculated stress for expected load with material strength. Because unexpected force is often applied to the shaft in an actual machine, the generated stress can be larger than the calculated one. Strain gauge method is generally applied rotating shafts by using a slip ring or telemetry. However measurement accuracy is decreased by electrical noise generated from motors in the machine. In the paper, the method of two-dimensional thermoelastic stress measurement was developed to determine fluctuating distribution of stress in the rotating shaft. Bending stress in the rotating shaft could be accurately identified by using inverse analysis with images taken from multiple positions of a thermographic camera. Validity and efficiency of the method were confirmed on the basis of numerical and the experimental results and the accuracy of the stress was also found to depend on reference temperature in the measurement.

Keywords
Stress analysis, Nondestructive inspection, Shaft, Inverse problem, Thermography, Rotary bending, Temperature change

Optimal Control Method for Ground Source Heat Pump System

by Mitsuteru FURUYA, & Tomomichi ISHIYAMA

Spreading and expanding a heat pump system utilizing ground thermal energy, which is one of the renewable energies, require an understanding of the characteristics of the system and the establishment of an optimal control method according to conditions.
East Japan Railway Company and Ebara Refrigeration Equipment & Systems Co., Ltd. jointly conducted a demonstration experiment with the aim of establishing a control method to make the most efficient use of ground thermal energy. Experimental equipment for a ground source heat pump (GSHP) system was installed on the premises of East Japan Railway Company in Saitama City, Saitama Prefecture, and test operations were conducted for 8 months from July 2013 to February 2014 to grasp the operating characteristics of borehole type GSHP. Furthermore, an optimal control method was devised based on the observed data.

Keywords
Renewable energy, Ground source heat pump (GSHP), Optimal control method, Ground heat exchanger (GHE), Ground thermal energy usage, Visualization, Time required for recovering underground temp.,Radiant panel

Basic Knowledge about Pump Cavitation Phenomenon [Part 2]

by Motohiko NOHMI

This paper explains vibration and noise problems caused by pump cavitation. The compression property of cavitation bubbles provides a spring factor in the fluid. The behavior of a single bubble is described by Rayleigh-Plesset equation. As for the whole of the bubbles in the pump, the continuity equation, cavitation compliance, mass flow gain factor and a lumped constant model of piping systems are combined to analyze their behaviors. Vibration of cavitation bubbles in various frequencies causes broadband cavitation noise. The phenomenon in which all the cavitation bubbles in the pump vibrate at a low frequency is a one-dimensional unstable phenomenon called cavitation surge. Three-dimensional unstable phenomena include rotating cavitation and alternate blade cavitation. Many studies have been conducted regarding the cavitation instability in inducers.

Keywords
Cavitation, Cavitation noise, Vibration, Cavitation surge, Rotating cavitation, Alternate blade cavitation, Cavitation instability, Inducer, Cavitation compliance, Mass flow gain factor

Water Supply Equipment: Introduction of Product Technologies
− Part 2: Selection, Installation, Piping and Wiring of Water Supply Equipment −

by Hirokazu HAMADA

Water supply equipment, which is used to supply water to facilities such as collective housing and office buildings, has some series corresponding to several water supply systems. Each series has its own model lineup covering different kinds of pump bore and motor output. This paper explains how to calculate the water supply capacity and pressure to choose an appropriate model from the various types of water supply equipment, as well as the installation, piping and wiring of the equipment.

Keywords
Water supply equipment, Calculation of water supply capacity, Calculation of water supply pressure, Installation method, Outdoor installation, Suction piping, Discharge piping, Power supply specifications, Electrode control of the reception tank, Electric noise