CAJ | 학술논문

为研究不同工况下，叶顶间隙对半开式叶轮离心泵内部流场及外特性的影响，该文对某半开式叶轮离心泵内部三维湍流流场进行数值模拟。揭示了离心泵内不同工况下叶轮流道和叶顶间隙层内的流动规律，对比分析了4种不同流量工况下叶顶间隙泄漏涡的流动特性、叶顶间隙层总压与相对速度分布，以及流量的变化对离心泵外特性的影响。结果表明：在小流量（设计流量为1.5 m3/h）时，间隙层内充满了泄漏涡，随着流量的增加涡核逐渐减少；大流量时涡核几乎消失，但此时流体速度激增，流动冲击损失变大在叶轮出口与间隙层附近存在着大面积回流，小流量时回流几乎占据了整个出口。通过模型泵外特性试验，验证了数值计算的准确性。该文为离心泵叶顶间隙设计及水力优化提供了参考。
위연구불동공황하，협정간극대반개식협륜리심빙내부류장급외특성적영향，해문대모반개식협륜리심빙내부삼유단류류장진행수치모의。게시료리심빙내불동공황하협륜류도화협정간극층내적류동규률，대비분석료4충불동류량공황하협정간극설루와적류동특성、협정간극층총압여상대속도분포，이급류량적변화대리심빙외특성적영향。결과표명：재소류량（설계류량위1.5 m3/h）시，간극층내충만료설루와，수착류량적증가와핵축점감소；대류량시와핵궤호소실，단차시류체속도격증，류동충격손실변대재협륜출구여간극층부근존재착대면적회류，소류량시회류궤호점거료정개출구。통과모형빙외특성시험，험증료수치계산적준학성。해문위리심빙협정간극설계급수력우화제공료삼고。
The centrifugal pumps with semi-open impellers have been widely applied in petrol chemical industry, aerospace industry, power energy, etc. The tip clearance flow is a very complex turbulent flow in which the vortex, secondary flow, and recirculation flow are existent simultaneously, and it plays an important role for internal flow characteristics and external performances. In recent years, lots of numerical and experimental studies have been carried out to investigate the tip clearance flow and improve the performance of the semi-open impeller centrifugal pump. In this paper, numerical simulation and performance test are carried out on the centrifugal pump with a semi-open impeller. Influences of tip clearance on performance and the details of flow in tip clearance layer are studied at four different flow rate conditions. In the numerical simulation, the PRO/E software is used to generate computational geometries. The compatible preprocessor, GAMBIT is used to generate meshes. The commercial CFD software Fluent 6.3 is used to solve the N–S equations. The SIMPLEC algorithm is used to couple pressure and velocity. Second order upwind discretizations have been used for convection terms and the central difference schemes are used for diffusion terms. Three-dimensional viscous incompressible flow field simulations have been performed using multiple reference frame coordinates. The impeller and inducer region is taken as a rotating reference frame with a constant angular speed of 1 450 r/min, and the other surfaces are defined as stationary reference frame. And the boundary conditions are velocity condition at inlet and outflow at outlet of the pump. Also, no-slip wall conditions have been used for the rest surfaces of the pump. Also, the experimental studies are carried out on the tested centrifugal pump with tip clearances of 1.0 mm, and the results are compared with the numerical calculations. Seal gaskets are used to adjust the tip clearance. Tungsten wires (the diameter is 3 mm) are placed in three positions of each blade (the blade tops near the leading edge, trailing edge and middle edge). Once impeller and casing are installed, and bolts are tightened, tungsten wires will be squeezed. Finally, a vernier caliper is used to measure the thicknesses of the squeezed tungsten wires. The tip clearanceΔc is 0.8 mm without any seal gasket and tip clearances are adjusted by increasing the seal gasket (thickness of 0.1 mm, brass gasket). After increasing the seal gasket, the tip clearances will be measured. The results show that there exists strong leakage vortex in the impeller inlet, impeller passage and impeller outlet. Due to the different pressures between suction surface and press surface of blades, the fluid pass through the tip clearance forming a lower pressure area, which leads to the leakage vortex. There exist large vortexes in the tip clearance layer at small flow rate condition. With the increasing of flow rate, vortexes become smaller and the flow state becomes more stable. The vortexes almost disappear at large flow rate condition, whereas the flow speed becomes much higher.