Yuan Shouqi

Numerical analysis of periodic flow unsteadiness in a single-blade centrifugal pump

In this paper, the CFD simulation and new flow unsteadiness analysis for a single-blade centrifugal pump with whole flow passage were carried out. The periodic flow unsteadiness has been quantitatively investigated in detail by defining unsteady intensity and turbulence intensity in both rotor and volute domains under design condition Q=33 L s−1. The results show that the distributions of flow unsteadiness are the functions of impeller rotating angle φ and have complex unsteady characteristics. The obvious Tu fluctuations can be also observed for different impeller positions. In addition, time-averaged unsteady intensity and time-averaged turbulence intensity were calculated by averaging the results of each mesh node for entire impeller revolution period to evaluate the strength distributions of flow unsteadiness directly and comprehensively. The accumulative results of an impeller revolution can directly show the positions and strength of the flow unsteadiness and turbulence intensity in both rotor and stator domains which can be an important aspect to be considered in the single-blade pump optimum design procedure for obtaining more stable inner flow of the pump and decreasing flow-induced vibration and noise. The flow unsteadiness in the side chamber cannot be neglected for an accurate prediction of the inner flow of the pump, and the optimizing design procedure for a single-blade pump impeller will not be accurate using CFD tool if the unsteady flow phenomenon in the side chamber is not considered.

Droplet Size Characterization of the New Type Complete Fluidic Sprinkler

Accurate knowledge of droplet size characteristics of a given sprinkler will aid selection for design of sprinkler irrigation systems. In this paper, the droplet size distribution characteristics of the new type complete fluidic sprinkler have been experimentally determined using a Thiess Clima Laser precipitation monitor under in door conditions. The experimental data were accessed using the RS 48/422 interface of the Laser precipitation monitor. Droplet diameter measurements were performed for three manufacturers recommended operating pressure conditions. Comparisons of the percentage of droplets at the three different operating conditions are presented. The cumulative numeric frequency and cumulative volumetric frequency curves indicate that about 50% of the droplets had diameter less 0.5mm and 50% of the water volume consisted of droplets with diameter less than 2mm at most distances. The results are similar to those obtained by earlier researchers who used different sprinkler-types and droplet size measurement methods and hence proves the validity of the measurements.

Comparative research on hydraulic performance of sprinkler heads in sprinkler irrigation

Sprinkler irrigation has been widely used for agricultural production. Sprinkler head is the key equipment in sprinkler irrigation system, the performance of the sprinkler head play a significant role in irrigation quality. The working theory of sprinkler head typed fluidic sprinkler which was developed by Jiangsu University in China, impact sprinkler, LF types sprinkler in Rainbird Company, R2000 types sprinkler in Nelson Company were introduced. Comparative experiment and analysis of hydraulic performance between these sprinklers were carried out. The parameters included operating pressure, flow rate, rotating speed, wetted radius, application rate, water distribution shape, and droplet size. The combination uniformity of different distance between sprinklers was calculated based on the water distribution. The results show that the new type fluidic sprinkler hydraulic performance was better than others.

Notice of Retraction Numberical simulation of low-specific-speed centrifugal pump cavitation influence of pressure pulsation under different conditions

According to the cavitation of centrifugal pump which produces in the condition of operating at off-design and inhale height exceeds the value of prescribed limit, the cavitation arouse pressure pulsation aggravate, so cause the performance of centrifugal pump that drops. Adopt RNG k - e simulated technology model to study the relation between the pressure pulsation and cavitation of centrifugal pump, the researched operating condition includes design and off- design operating condition, the design point of operating is specified QBET of rate of flow, the off- design points are 0.5 QBET, 0.8 QBET, 1.3 QBET and 1.5 QBET. As the result show, at different operating conditions, duration, location, periodicity and the size of bubble area are changed. At design operation condition the cavitation regional, cavitation duration, pressure pulsation amplitude is minimum; The more deviate the design condition, the cavitation duration grows the more, and in the high rate of flow the cavitation most serious. At low rate of flow of 0.5 QBET cavitation produce mainly in inlet of blade reverse side, pressure pulsation amplitude is the 1.8 times of design operating condition; At high orate of flow of 1.5 QBET, cavitation produce mainly in Inlet of blade pressure side, pressure pulsation amplitude is the 2.6 times of design operating mode.