The behavior of tip vortex in an axial fan without casing wall (called open axial fan) was discussed and analyzed. The velocity measurement was performed by using two-compon ents Laser Doppler Velocimetry (LDV) system. The detailed velocity and vorticity distribution inside blade passage and downstream of rotor were obtained. Thus the structure of tip vortex and its behavior were graphically visualized by experimental fluid dynamics (EFD). The tip vortex flow trace was indicated with the calculation of vorticity. As a result, it was found that tip vortex was generated at blade tip region near leading edge and it extended to downstream of blade exit with its core tending inward to hub direction. In addition, leading edge vortex was also found at the forepart of the experimental open fan.

Regulations in fuel consumption and emission become more and more strict, it is required to give more research on finding methods of saving energy and reducing emissions, also, reducing energy loss of engine attachments is an effective method. Oil pump play a key role in engine lubrication system, it provides power to make oil flow for lubrication and cooling of moving parts in engine. Due to discharge effect of the pressure relief valve in oil pump, thus, traditional oil pump loses a lot of energy as engine works in a high speed period. On the contrary, variable displacement oil pump has a certain effect on energy-saving by reducing oil pump displacement directly when an engine is running in a high speed period. This article gives research on the structural characters and energy-saving effect on both rotor type and vane type of variable displacement oil pump.

We carried out investigations for the purpose of clarifying the rotor outlet flow fields with rotating stall cell in a diagonal-flow fan. The test fan was a high-specific-speed (n s = 1620) type of diagonal-flow fan that had 6 rotor blades and 11 stator blades. It has been shown that the number of the stall cell is 1, and its propagating speed is approximately 80% of its rotor speed, although little has been known about the behavior of the stall cell because a flow field with a rotating stall cell is essentially unsteady. In order to capture the behavior of the stall cell at the rotor outlet flow fields, hot-wire surveys were performed using a single-slant hotwire probe. The data obtained by these surveys were processed by means of a double phase-locked averaging technique, which enabled us to capture the flow field with the rotating stall cell in the reference coordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the three-dimensional velocity components at the rotor outlet flow fields were obtained. The behavior of the stall cell was shown for each velocity component, and the flow patterns on the meridional planes were illustrated.Keywords Fan, Internal flow, Rotating stall, Stall cell, Unsteady flow A diagonal-flow fan has relatively high efficiency, a low noise level, and a wide operating range. However, when its specific speed becomes high, its pressure/flow-rate curve tends to indicate unstability by a positive gradient in the low flow range that is similar to that of an axial-flow fan. It is well known that the rotating stall is the main cause of this unstable characteristic, and a flow field with a rotating stall indicates remarkable un- , 1999;Moore and Greitzer, 1986;Poensgen and Gallus, 1996; SaxerFelice et al., 1998) have investigated the flow field with a rotating stall cell. However, there are very few studies of unsteady flow fields in diagonal-flow fans. Kaneko and colleagues (1993, 1995, 1997) tried to measure an unsteady flow field with a rotating stall in a high-specific-speed diagonal-flow fan using hot-wire and pressure probes. From that series of studies the unsteady flow characteristics of a rotating stall cell were clarified to some extent. Since then, Shiomi and colleagues (2000) have reported the behavior of a stall cell in a pressure field using a total pressure probe in a high-specific-speed diagonal-flow fan, but the detailed flow pattern has been unknown.Most surveys of the internal flow fields of turbomachines have been performed using a phase-locked averaging technique, because the flow field includes the periodical fluctuations caused by the rotor blades' passing. Under rotating stall conditions, however, another fluctuation caused by the stall cell's propagating at a speed different from that of the rotor is superimposed on the flow field. Therefore, it is impossible to analyze a flow field with a rotating stall cell by using the ordinary phase-locked averaging technique. In order to clarify a flow field with a rotating stall cell and the beh...

An Unsteady flow field with rotating stall cells in a high specific-speed diagonal flow fan has been investigated experimentally. Although a general feature of stall cells has already indicated, i.e., the number of stall cells is one and its propagating speed is approximately 80 percent of rotor speed, little has been known about the flow field when a rotating stall occurs because of its unsteadiness. In order to capture the behavior of the rotating stall cell, measurements of the flow field at the rotor inlet were carried out with a single slant hot-wire. Those data were processed by a so-called "double phase-locked averaging" (DPLA) technique, which enabled to capture the flow field of the cell in the reference coordinate system fixed to the rotor. As a result, time-dependent ensemble averages of the threedimensional velocity components at the rotor inlet have been obtained and the behavior of the rotating stall cell has been illustrated with each velocity component.

An experimental investigation was carried out to clarify unsteady flow fields with rotating stall cell, especially behavior of stall cell, in a high specific-speed diagonal flow fan. As its specific-speed is very high for a diagonal flow fan, its pressure-flow rate curve tends to indicate unstable characteristics caused by rotating stall similar to axial flow fan. Although for an axial flow fan many researchers have investigated such the flow field, for a diagonal flow fan little study has been done. In this study, velocity fields at rotor inlet in a high specific-speed diagonal flow fan were measured by use of a single slant hot-wire probe. These data were processed by using the "Double Phase-Locked Averaging" (DPLA) technique, i. e. phases of both the rotor blade and the stall cell were taken into account. The behaviors of stall cell at rotor inlet were visualized for the meridional, tangential and radial velocity.