Impellers of vortex pumps with peripheral channels

Abstract

UDC 621.515-253.001.5 Nowadays dynamic machines are used widely in many industrial fields for compression of gases. In some cases vortex pumps having peripheral channels can be used successfully for these purposes. In vortex pumps of the referred type, the gas stream in the frontal part of the intervane channel of the impeller moves against centrifugal forces. Therefore, regulated steady circulatory gas flow in the meridional plane of the flow-through part of the vanes with peripheral channel is of decisive importance for efficient energy transfer from the impeller to the medium under compression. Operating efficiency of vortex treads dependsonthe degree of compatibility between the regulated gas flow and the geometry of the flow-through part of the operating channel and the tread impeller. The effect of the basic geometric parameters of impellers on the functioning of vortex treads with peripheral channels was investigated at the N. ~. Bauman Moscow Higher Technical School. Efficiency of such treads depends on the angle of inclination of the impeller vanes Bv (6v is the angle between the vane axis and the tangent to the outer diameter of the impeller) and the angle of mounting of the vanes 6_. In impellers of this type the vanes are turned by an angle ~ relative to the axis ofmimpeller rotation.* The operation of the vane m is also dependent on the geometry of the intervane channels and the inner edges of the impeller vanes. The effect of ~ was investigated on a multichannel model of vortex tread having peripheral channels. ImPellers differing in angle of vane inclination (B v = 90, 125, 135, and 145~ were used. The geometry of the operating channels and the end clearance remained constant. Tests were conducted in the open. As evident from Fig. i, the coefficient of tread pressure depends markedly on the angle of vane mounting. The maximum pressure coefficient corresponds to the vane inclination angle 140-130 ~ . It is known that vortex pumps having peripheral channels develop maximum pressure when the vane inclination angle 5v is 125 ~ Tests showed that the efficiency of vortex treads having peripheral channels depends much on the vane mounting angle ~m" The effect of the angle ~m was investigated on a single-channel model of vortex tread. Four impellers with the vane mounting angles 0, i0, 20, and 30 ~ were tested. The test results are shown in Fig. 2. Change of ~m to ~i0 ~ significantly elevates the coefficient of tread pressure (more than twice) with nearly 15% rise in efficiency in comparison with the usual vortex tread whose operating vanes are mounted along the rotational axis of the impeller. It should be noted that in a system with ~m = 0 the flow in the frontal part of the operating channel is randomly meridional and is not sufficiently intense along the operating channel in the course of the gas compression. Circulatory flow in any direction is possible in this type of symmetric tread with radial entry and exit of gas from the operating channel. Such meridional flow is not so steady, especially when consumption is low. Mounting of impeller vanes at a certain angle B ensures steady meridional flow all along the m flow-through part and fixed direction of the meridional vortex, The vortex tread with optimum Bm creates significant pressure differential between the discharge and suction pipings (as compared to the tread witb ~_ = O) because no part of the active area of the operating channel is wasted in regulating ~e meridional flow.