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Subsynchronous vibration of high-pressure steam turbine is one of the difficult problems to improve the reliability of power plant. Extensive work has been done to prevent the low frequency vibration of high-capacity steam turbine and most of the problems were practically solved (1). In the future, we must build up theoretical approach to design a new turbine operating under the steam condition of high-temperature and high-pressure. To design such an advanced steam turbine, it is necessary to solve the effect of partial admission on control stage of the steam turbine. This paper describes the experimental results from the scale model of the steam turbine and theoretical analysis of destabilizing forces. In theoretical analysis, destabilizing forces that take partial admission into consideration were analyzed. As a result, it was clarified that large destabilizing force was generated in partial admission condition and the destabilizing force varied periodically by the instant rotor position. In experimental study, we designed the new inlet seal for the prevention against the vibration. From the experimental result that increase of total flow rate leads the system stable, we showed the effectiveness of new inlet seal. And we paid attention to the step-up that is the step between blade and nozzle. As a result, it was experimentally proved that the step-up had a large influence on the rotor stability.

In the seismic design of nuclear power plant, it is recently considered to use probability method in addition to certainty method. The former method is called Seismic Probability Safety Assessment (Seismic PSA). In case of seismic PSA for some components of a nuclear power plant using a shaking table, it is necessary for some limited conditions with high level of accelerations such as actual conditions. However, it might be difficult to achieve the test conditions that a current shaking table based on hydraulic power system is intended for the test facility. Therefore, we have been planning out a test method in which both a current and another shaking table called a booster device are applied. This paper describes the verification test of a synchronized control between a current shaking table and a booster device.

The effectiveness of squeeze-film dampers in controlling vibrations in rotating machinery may be limited by the nonlinear interactions between large rotor imbalance forces with fluid-film forces induced by dampers operating in cavitated conditions. From a practical point of view, the occurrence of nonsynchronous and chaotic motion in rotating machinery is undesirable and should be avoided as they introduce cyclic stresses in the rotor, which in turn may rapidly induce fatigue failure. The bifurcations in the response of a rigid rotor supported by cavitated squeeze-film dampers resulting from such interactions are presented in this paper. The effects of design and operating parameters, namely the bearing parameter (B), gravity parameter (W), spring parameter (S) and unbalance parameter (U), on the bifurcations of the rotor response are investigated. Spring parameter (S) values between 0 and 1 are considered. A spring parameter value of S=0 represents the special case of dampers without centering springs. With the exception of the case S=1, jump phenomena appeared to be a common bifurcation that occurred at certain combinations of B, W and U irrespective of the value of S. Period-doubling and secondary Hopf bifurcations which occurred for low values of S (⩽0.3) were not observed for the higher values S⩾0.5. For very low stiffness values (S

This paper describes an active jiggle control of hung structure using a control moment gyro (CMG) which has two gimbals for one flywheel. The double gimbal CMG enables us to simultaneously control the vibrations for two different dirctions by only one flywheel. Due to the nonlinearlity and interference, it is however difficult to construct the control system for the double gimbal CMG. First, we propose a simple control system design method for the double gimbal CMG based on H2 optimal control theory. In order to improve the gimbal stability, which is necessary for avoiding the interference, we then propose an another design method based on H2/H∞ control using LMI optimization. The performance of all designed control system are evaluated by simulations and experiments.

This paper deals with a rotor balancing method based on influence coefficient method and LMI (Linear Matrix Inequality) optimization technique. The three rotor balancing objectives; (a) minimization of maximum residual vibration, (b) minimization of the least mean square of residual vibration and (c) minimization of the least mean square of correction masses, are considered. Since the conventional influence coefficient method cannot properly treat the objectives (a) and (c), these objectives (a) and (c) have been considered by heuristic trial & error method. In this paper, first, the LMI formulation of the rotor balancing objectives (a)-(c) are derived applying two basic LMI lemmas. Based on these LMI formulation of the objectives, a LMI optimization framework for rotor balancing is then constructed. The proposed method enables us to efficiently achieve the objectives (a)-(c) with the relative weight vector c using LMI optimization technique. Moreover, a reduction algorithm for the number of the correction planes, which is useful in the actual field balancing, is also considered. Finally, the effectiveness of the proposed rotor balancing method is evaluated by numerical simulations and experiments with a model rotor system.

In this paper, the static characteristics of the four-nozzle pintle type servovalve are studies theoretically, under constant supply pressure and constant supply flow conditions.The study is on an eye to the effect of the valve improper configuration, the required pintle driving torque, and the effect of using unsymmetrical loads on the static characteristics.Errors in valve control gaps resulting from inaccurate initial adjustment, wear of else showed to affect slightly the load flow at each load pressure and input displacement.Units driven by unsymmetrical actuators showed to have lower valve flow forces and higher valve efficiency than symmetrical actuators.The minimum flow gain and flow pressure coefficient are obtained when the load is symmetric.The study showed that the flow forces have two instability sources, decentering nature and similar values at different input displacements.The study discussed the selection of the pintle centering spring to overcome the problems of instability.

Recently, according to the enlargement of rotating equipment such as turbines and pumps, the dynamic characteristics of bearings and seals tends to greatly affect the dynamic characteristics of the rotor system. Therefore, numerous researchers have been engaging in developing the hydrodynamically lubricated bearing theory and seal theory. However, it is still difficult to estimate the precise dynamic characteristics of bearings and seals analytically. On the other hand, there are many researcher who have been developing the experimental measurement technique of bearing and seal dynamic characteristics. This paper describes the measurement technique of bearing and seal dynamic characteristics using the random excitation technique.

Water (working fluid) lubricated bearings are used in various pump designs. This type of bearing has many characteristics different from usual oil lubricated bearings. This paper describes the following characteristics of the water lubricated bearings : (1) Turbulent flow (2) Full film due to high ambient pressure (3) Large additional mass effect Theoretical analysis by numerical calculation and model test using a special test system are performed for a cylindrical bearing. As a result, the characteristics of the water lubricated bearing are recognized and good agreement between theoretical and experimental results is confirmed.

This paper describes the vibration analysis technology of MW-701D Gas Turbine which was developed by Mitsubishi Heavy Industries, Ltd. for 50 Hz utilities. MW-701D is the highest performance gas turbine available with a firing temperature of 1,154°C for base load operation. It is employed by the 1,090 MW combined cycle plant, one of the largest of its kind in the world, and the plant began commercial operation at half of the total capacity of 1,090 MW in December, 1984. The plant was designed to supply base load electric power generation by burning imported liquefied natural gas (LNG) fuel. This paper describes the general description of the combined cycle plant and the vibration characteristics of MW-701D Gas Turbine.