A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to...A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to the fixed outer casing. Computational models with/without the tip clearance are built and the κ-ω shear stress transport （SST） turbulence model and the unstructured mesh are applied to the numerical simulation for unsteady solutions. The overall performance is measured on a standard experimental bench and the major flow feature of each component inside the centrifugal fan is numerically investigated. In the presence of the tip clearance due to the difference of static pressure between leading and trailing edges of the clearance, i. e. , leading and trailing edges of the impeller, a strong return flow exists inside the clearance passage and re-circulates the main stream inside the impeller passage, and produces the strong flow interaction, thus changing the flow field and influencing the overall performance.展开更多
In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil...In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.展开更多
The fractional volumetric lattice Boltzmann method with much better stability was used to simulate two-chmensional cavity flows. Because the effective viscosity was reduced by the fraction factor, it is very effective...The fractional volumetric lattice Boltzmann method with much better stability was used to simulate two-chmensional cavity flows. Because the effective viscosity was reduced by the fraction factor, it is very effective for simulating high Reynolds number flows. Simulations were carried out on a uniform grids system. The stream lines and the velocity profiles obtained from the simulations agree well with the standard lattice Boltzmann method simulations. Comparisons of detailed flow patterns with other studies via location of vortex centers are also satisfactory.展开更多
The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6....The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6.68 mm.The working fluids are air and water and their superficial velocities range from 0.014 to 8.127 m/s and from 0.0238 to 0.556 m/s,respectively.The void fraction is determined using the flow pattern images captured by a high-speed camera,while quick closing valves are used for verification.Four flow patterns are analyzed in experiments:slug flow,bubbly flow,annular flow and stratified flow.For intermittent flows(bubbly flow and slug flow),the cross-sectional void fraction is in a borderline condition while its probability distribution function(PDF)image displays a bimodal structure.For continuous flows(annular flow and stratified flow)the cross-sectional void fraction behaves as a fluctuating continuous curve while the(PDF)image displays a single peak structure.The volumetric void fraction data are also compared with available predictive formulas,and the results show that the agreement is very good.An effort is also provided to improve the so-called Gregory and Scott model using the available data.展开更多
The proportion and changes of CD4^＋CD25^high regulatory T cells （Trs） in peripheral blood of non-small cell lung cancer （NSCLC） patients were analyzed and their clinical significance explored. The peripheral bloo...The proportion and changes of CD4^＋CD25^high regulatory T cells （Trs） in peripheral blood of non-small cell lung cancer （NSCLC） patients were analyzed and their clinical significance explored. The peripheral blood was collected from 61 patients with NSCLC and 15 healthy controls. By using monoclonal antibodies, the blood samples were evaluated with the flow cytometry for lymphocyte subsets （CD3^＋, CD4^＋ and CD8^＋） and CD4^＋CD25^high Tr cells. The results showed that the proportion of CD4^＋CD25^high Tr cells in NSCLC group was significantly higher than in control group [（4.36 ±2.07） % vs （2.04±1.03） %, P〈0.01]. The proportion of CD4^＋CD25^ high Tr cells in late stage was higher than that in early stage [stages Ⅰ ＋Ⅱ （2.264±0.6） %; stage Ⅲ（3.284± 1.38） %; stage IV （6.06 4±4.08） %] （P〈0.05）. Kaplan-Meier survival analysis revealed that the prognosis of the patients who had higher proportion of CD4^＋CD25^high Tr cells in peripheral blood was worse （P=0.0026）. In conclusion, the relative increase in CD4^＋CD25^high Tr cells in peripheral blood may be related to im- munosuppression and tumor progression in patients with NSCLC. This finding suggests that CD4^＋CD25^high Tr cells in peripheral blood of NSCLC may be positive for prognosis analysis. The use of depletion of the CD4^＋CD25^high Tr cell therapy to treat NSCLC patients may be an effective strategy.展开更多
文摘A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to the fixed outer casing. Computational models with/without the tip clearance are built and the κ-ω shear stress transport （SST） turbulence model and the unstructured mesh are applied to the numerical simulation for unsteady solutions. The overall performance is measured on a standard experimental bench and the major flow feature of each component inside the centrifugal fan is numerically investigated. In the presence of the tip clearance due to the difference of static pressure between leading and trailing edges of the clearance, i. e. , leading and trailing edges of the impeller, a strong return flow exists inside the clearance passage and re-circulates the main stream inside the impeller passage, and produces the strong flow interaction, thus changing the flow field and influencing the overall performance.
基金financially supported by the National Natural Science Foundation of China (Grant No.51674281)the Opening Fund of Shandong Provincial Key Laboratory of Oil&Gas Storage (Study on low temperature flow characteristics of oil and water in gathering pipeline)the Transportation Safety and the Fundamental Research Funds for the Central Universities
文摘In order to ensure the safety of the non-heating gathering and transportation processes for high water fraction crude oil,the effect of temperature,water fraction,and flow rate on the flow characteristics of crude oil with high water fraction was studied in a flow experimental system of the X Oilfield.Four distinct flow patterns were identified by the photographic and local sampling techniques.Especially,three new flow patterns were found to occur below the pour point of crude oil,including EW/O&W stratified flow with gel deposition,EW/O&W intermittent flow with gel deposition,and water single-phase flow with gel deposition.Moreover,two characteristic temperatures,at which the change rate of pressure drop had changed obviously,were found during the change of pressure drop.The characteristic temperature of the first congestion of gel deposition in the pipeline was determined to be the safe temperature for the non-heating gathering and transportation of high water cut crude oil,while the pressure drop reached the peak at this temperature.An empirical formula for the safe temperature was established for oil-water flow with high water fraction/low fluid production rate.The results can serve as a guide for the safe operation of the non-heating gathering and transportation of crude oil in high water fraction oilfields.
文摘The fractional volumetric lattice Boltzmann method with much better stability was used to simulate two-chmensional cavity flows. Because the effective viscosity was reduced by the fraction factor, it is very effective for simulating high Reynolds number flows. Simulations were carried out on a uniform grids system. The stream lines and the velocity profiles obtained from the simulations agree well with the standard lattice Boltzmann method simulations. Comparisons of detailed flow patterns with other studies via location of vortex centers are also satisfactory.
基金This work was supported by the Guangdong Basic and Applied Basic Research Foundation(2019A1515111116)Key R&D Program of Shandong Province(Nos.2019GSF109051,2019GGX101030)+1 种基金Shandong Provincial Postdoctoral Innovation Project(No.201902002)Foundation of Shandong University for Young Scholar’s Future Plans.
文摘The flow patterns and the void fraction related to a gas-liquid two-phase flow in a small channel are experimentally studied.The test channel is a transparent quartz glass circular channel with an inner diameter of 6.68 mm.The working fluids are air and water and their superficial velocities range from 0.014 to 8.127 m/s and from 0.0238 to 0.556 m/s,respectively.The void fraction is determined using the flow pattern images captured by a high-speed camera,while quick closing valves are used for verification.Four flow patterns are analyzed in experiments:slug flow,bubbly flow,annular flow and stratified flow.For intermittent flows(bubbly flow and slug flow),the cross-sectional void fraction is in a borderline condition while its probability distribution function(PDF)image displays a bimodal structure.For continuous flows(annular flow and stratified flow)the cross-sectional void fraction behaves as a fluctuating continuous curve while the(PDF)image displays a single peak structure.The volumetric void fraction data are also compared with available predictive formulas,and the results show that the agreement is very good.An effort is also provided to improve the so-called Gregory and Scott model using the available data.
基金This project was supported by grants from National Science Fundation for Distinguished Young Scholars (No. 30225038) The National Basic Research Program(No.2001CB5101).
文摘The proportion and changes of CD4^＋CD25^high regulatory T cells （Trs） in peripheral blood of non-small cell lung cancer （NSCLC） patients were analyzed and their clinical significance explored. The peripheral blood was collected from 61 patients with NSCLC and 15 healthy controls. By using monoclonal antibodies, the blood samples were evaluated with the flow cytometry for lymphocyte subsets （CD3^＋, CD4^＋ and CD8^＋） and CD4^＋CD25^high Tr cells. The results showed that the proportion of CD4^＋CD25^high Tr cells in NSCLC group was significantly higher than in control group [（4.36 ±2.07） % vs （2.04±1.03） %, P〈0.01]. The proportion of CD4^＋CD25^ high Tr cells in late stage was higher than that in early stage [stages Ⅰ ＋Ⅱ （2.264±0.6） %; stage Ⅲ（3.284± 1.38） %; stage IV （6.06 4±4.08） %] （P〈0.05）. Kaplan-Meier survival analysis revealed that the prognosis of the patients who had higher proportion of CD4^＋CD25^high Tr cells in peripheral blood was worse （P=0.0026）. In conclusion, the relative increase in CD4^＋CD25^high Tr cells in peripheral blood may be related to im- munosuppression and tumor progression in patients with NSCLC. This finding suggests that CD4^＋CD25^high Tr cells in peripheral blood of NSCLC may be positive for prognosis analysis. The use of depletion of the CD4^＋CD25^high Tr cell therapy to treat NSCLC patients may be an effective strategy.
