Atsuo Yamanouchi

Numerical Analysis of Two-Phase Jet Impingement by Homogeneous Flow Model

A two-dimensional homogeneous equilibrium model is developed in order to evaluate impingement load caused by discharge of a two-phase mixture in postulated pipe rupture accidents of light water reactors. The present analysis differs from previous studies mainly in that a backward expansion around the pipe exit is taken into account. As a result: (1) it is confirmed that the backward expansion occurs around the pipe exit in a super-sonic two-phase flow; (2) when the dimensionless position of an impingement wall z/D is larger than 2.0, the present calculations predict the pressure distribution on the impingement wall within an error of 10%, while the previous calculations, which did not take the backward expansion into account, overestimated the pressure by 25%; (3) existence of jet core and occurrence of shock waves in the two-phase jet are obtained and (4) a supersonic state of the jet is illustrated by comparing the velocity with the sonic velocity.

Dimensionless groups of blowdown experiments

In order to clarify the limit of application of the dimensionless groups derived in a former study, numerical analyses were performed on the blowdown with different initial conditions. Dimensionless groups studied were π20 (fractional change rate of residual coolant mass), π30 (fractional change rate of energy due to heat generation), and π0 (= π30/π20). As the reference, the blowdown was considered from the pressure vessel initially filled with saturated water (volumetric fraction of vapor αi = 0) at 6.9 MPa. Numerical analyses based on the lumped model description of blowdown indicated that the dimensionless groups obtained were useful for the blowdowns with not only different volume and discharge area of the vessel, but also different initial pressures (6–8 MPa) and amounts of coolant (αi = 0-0.2). Clarified groups were applied to the comparison of the BWR recirculation line break tests data between two differently scaled facilities. The comparison yielded good agreement in overall trends of both test results and confirmed the validity of the dimensionless groups. Further, the dependence of the major event sequence on the break area during recirculation line break tests was generalized using the dimensionless groups.

A study on applicability of similarity rule to performances of centrifugal pumps driven in two-phase flow

Abstract It is studied in this report whether the similarity rule which is used for pumps in single-phase flow is applicable to those in two-phase flow using fundamental equations by which the hydraulic torques of pumps in two-phase flow are described pretty well. According to the equations, the similarity rule is applicable to pumps driven in two-phase flow if the force acting on the gas-liquid interface per unit length of the flow channel in the impeller is proportional to the pump size, and according to the study of the force it can be said that the force is proportional to the pump size unless the gas velocity is very small or liquid velocity is extremely large in the impeller. Therefore it is concluded that the similarity rule is applicable to pumps in two-phase flow excepting special operating conditions which are not usually realized.