Effects of Blade Number on the Propulsion and Vortical Structures of Pre-Swirl Stator Pump-Jet Propulsors

Reducing the noise of the underwater propulsor is gaining more and more attention in the marine industry. The pump-jet propulsor (PJP) is an extraordinary innovation in marine propulsion applications. This paper inspects the effects of blade number on a pre-swirl stator pump-jet propulsor (PJP) quantitatively and qualitatively. The numerical calculations are conducted by IDDES and ELES, where the ELES is only adopted to capture the vortical structures after refining the mesh. The numerical results show good agreement with the experiment. Detailed discussions of the propulsion, the features of thrust fluctuation in time and frequency domains, and the flow field are involved. Based on the ELES results, the vortices in the PJP flow field and the interactions between the vortices of the stator, rotor, and duct are presented. Results suggest that, though changing the blade number under a constant solidity does not affect the propulsion, it has considerable effects on the thrust fluctuation of PJP. The wakes of the stator and rotor are also notably changed. Increasing the stator blade numbers has significantly weakened the high-intensity vortices in the stator wake and, hence, the interaction with the rotor wake vortices. The hub vortices highly depend upon the wake vortices of the rotor. The hub vortices are considerably broken by upstream wake vortices when the load per rotor blade is high. In summary, the blade number is also vital for the further PJP design, particularly when the main concerns are exciting force and noise performance.

A Novel Automatic Algorithm for Estimating the Jet Engine Blade Number of Insufficient JEM Signals

One of the major issues in multifunction radars is time resource allocation to maximize the radar’s ability. If jet engine modulation (JEM) is more efficiently performed in an insufficient dwell-time environment, the remaining time can be allocated for other tasks. This study presents a novel automatic algorithm for estimating the jet engine blade number of insufficient JEM signals. We employed a harmonic selection rule and a modified empirical mode decomposition (EMD) with an adaptive low-pass filtering. For a refined autocorrelation waveform, the analysis focuses on a desirable combination of intrinsic mode functions derived from the modified EMD. The approach is significant because it enables reliable estimation despite the insufficient JEM signal. Also, the proposed algorithm is innovative because it uses only the time-domain method, not the frequency-domain method. The application is expected to enhance the efficiency of radar resource management.

Experimental and Numerical Investigation On the Transient Cavitating Flows in a Mixed Flow Pump with Different Number of Blades At Startup

The objective of this paper is to experimentally and numerically investigate the transient cavitation flow during the startup process of mixed flow pump with emphasis on studying the influence of blade numbers. The transient cavitation simulation was studied based on the improved SST k-ω turbulence model and the Zwart cavitation model. Firstly, in order to obtain the relationship between transient flow rate and the variation of rotational speed at startup, a theoretical analysis based on the fast transients of centrifugal pump was first applied to mixed flow pump and was verified by the current experiment study. Subsequently, the influence of blade number on the cavitation flow in the startup was studied. It is found that the transient cavitation could be classified into four stages regardless of the number of blades: no cavitation stage, the cavitation growth stage, the cavitation reduction stage and the cavitation stabilization stage. However, the blade number does have an impact on the spatial-temporal evolution of cavitation. More specifically, when the blade number increases, the initial cavitation appeared lately, the coverage area of the triangular cavitation cloud and sheet cavitation both decreased, and the increase in blade number has a better inhibitory effect on the sheet cavitation at the cavitation growth stage, and can make sheet cavitation disappear more quickly at the cavitation reduction stage.

Numerical Study the Effect of Blade Number on Archimedes Screw Turbine Utilized in Pico-Hydro in Horizontal Position

Application of Archimedes Screw Turbine (AST) on pico-hydro has been very popular due to its capability to has a high torque with small flow rate and environmentally friendly to biotic of vicinity. This study uses CFD to investigate AST performance when the number of blades is varied. Independency of mesh is conducted to find an efficient number of mesh and it is obtained at 80 thousand mesh. Variation A, B and C respectively has 4,6, and 9 blades varied to analyze the correspondence with torque, pressure loss and velocity contour. The results show that with a higher number of blades would make higher torque. This is because energy extraction from water would be more efficient at higher number blade. However, the side back at such number would arise such as the higher-pressure loss. This is corresponding to energy balance where a high delta pressure is proportional with a generated energy turbine.