Flow Structure Around the Intake of a Vertical Pump

The flow structure around the intake of a vertical pump is investigated experimentally and numerically in order to obtain a guideline in designing the optimum shape of the intake of vertical pumps, in which their installation area is demanded to be minimum without losing the high performance. We concentrate our attention on the expansion ratio of the intake as a representative characteristic of the shape of the pumps and investigate the effect of the expansion ratio on pump performance. It is concluded that the optimum expansion ratio ranges in 1.1-1.2 if we take into consideration that the area needed for the installation of the pump should be minimum.

Vibration Control of Vertical Turbine Pump by Optimization of Vane Pitch Tolerances of an Impeller Using Statistical Techniques

The objective of the study is to find the tolerance on vane pitch dimensions of a Vertical Turbine(VT)pump impeller.For this purpose,the study is divided into two parts viz.to find the critical hydraulic eccentricity of a VT pump impeller by way of numerical simulations and design of experiments to find the vane pitch tolerance using critical hydraulic eccentricity.The effect of impeller vane pitch deviations on hydraulic unbalance is examined for a vertical turbine pump using Design of Experiments(DOE).A suitable orthogonal matrix has been selected with vane pitch at different axial locations of an impeller as the control factors.Hydraulic eccentricity,which is the output of the DOE experiments is analyzed using S/N ratio,ANOM and regression analysis to find the significant control factor effecting the hydraulic unbalance and hence vibrations.The vane pitch deviation at outlet and inlet of impeller shroud geometry are found to be the most critical factor affecting the pump vibrations.

Submesoscale activity over the shelf of the northern South China Sea in summer:simulation with an embedded model

We applied a primitive equation ocean model to simulate submesoscale activities and processes over the shelf of the northern South China Sea(NSCS) with a one-way nesting technology for downscaling.The temperature and density fields showed that submesoscale activities were ubiquitous in the NSCS shelf.The vertical velocity was considerably enhanced in submesoscale processes and could reach an average of 58 m per day in the subsurface.At this point,the mixed layer depth also was deepened along the front,and the surface kinetic energy also increased with the intense vertical movement induced by submesoscale activity.Thus,submesoscale stirring/mixing is important for tracers,such as temperature,salinity,nutrients,dissolved organic,and inorganic carbon.This result may have implication for climate and biogeochemical investigations.

一种采用直井井组细分层压裂注热水开采天然气水合物的工艺方案

在海底的沉积物或冻土中,赋存有大量的天然气水合物,这是一种适于未来开发利用的能源,具有优质、洁净、资源量大等优势。由于开采对象的复杂性,在世界范围内,开采技术整体上尚无成熟配套,面临着单井产量低、连续时间短、经济效益差等缺陷,因此需要针对天然气水合物储层研究高效开采的工艺方法。本研究针对有一定渗流能力的水合物储层,提出了一种采用直井井组细分层压裂注热水开采的工艺技术:(1)依据地质资料,对目标储层布置直井井组,直井分为注水井与生产井,通过井组注入热水开采提高采收率;(2)采用套管射孔完井,套管内下入筛管防砂;(3)对注水井进行不加砂细分层压裂,采出井不压裂;(4)至生产效果变差时,开始通过注水井注入热水激发,从生产井生产天然气;(5)采用海水源热泵技术提供热水,就地取材,经济高效;(6)对采出井进行注入固结剂作业,采用系统防砂技术;(7)建立数学模型进行模拟,结果表明,细分层压裂注热水开发方案能大幅提高产量。该工艺能够提高储层的加热效率与受热体积,减少出砂的可能性,大幅提高储层生产天然气的产量与持续时间,进而提高经济效益。

Numerical investigations on performance improvement mechanism of a high-power vertical centrifugal pump with special emphasis on hydraulic component matching

The purpose of this paper is to investigate the performance improvement mechanism of a high power vertical centrifugal pump by using numerical calculations.Therefore,a comparative study of energy losses and internal flow characteristics in the original and optimized models was carried out with special attention to the hydraulic component matching.The optimized model(model B)was obtained by optimizing the vaned diffuser and volute based on the original model(model A),mainly the diffuser inlet diameter,diffuser inlet vane angle,volute channel inlet width and volute throat area were changed.Firstly,the comparative results on performance and energy losses of two models showed that the efficiency and head of model B was significantly increased under design and part-load conditions.It is mainly due to the dramatic reduction of energy loss PL in the diffuser and volute.Then,the comparisons of PL and flow patterns in the vaned diffuser showed that the matching optimization between the model B impeller outlet flow angle and diffuser inlet vane angle resulted in a better flow pattern in both the circumferential and axial directions of the diffuser,which leads to the PL3 reduction.The meridian velocity Vm of model B was significantly increased at diffuser inlet regions and resulted in improvements of flow patterns at diffuser middle and outlet regions as well as pressure expansion capacity.Finally,the comparisons of PL and flow characteristics in the volute showed that the turbulence loss reduction in the model B volute was due to the flow pattern improvement at diffuser outlet regions which provided better flow conditions at volute inlet regions.The matching optimization between the diffuser and volute significantly reduced the turbulence loss in volute sections 1–4 and enhanced the pressure expansion capacity in sections 8–10.