Numerical Investigation of the Aerodynamic Performance Affected by Spiral Inlet and Outlet in a Positive Displacement Blower

The flow in the positive displacement blower is very complex.The existing two-dimensional numerical simulation cannot provide the detailed flow information,especially flow characteristics along the axial direction,which is unfavorable to improve the performance of positive displacement blower.To investigate the effects of spiral inlet and outlet on the aerodynamic performance of positive displacement blower,three-dimensional unsteady flow characteristics in a three-lobe positive displacement blower with and without the spiral inlet and outlet are simulated by solving Navier-Stokes equations coupled with RNG k-ε turbulent model.In the numerical simulation,the dynamic mesh technique and overset mesh updating method are used.The computational results are compared with the experimental measurements on the variation of flow rate with the outlet pressure to verify the validity of the numerical method presented.The results show that the mass flow rate with the change of pressure is slightly affected by the application of spiral inlet and outlet,but the internal flow state is largely affected.In the exhaust region,the fluctuations of pressure,velocity and temperature as well as the average values of velocity are significantly reduced.This illustrates that the spiral outlet can effectively suppress the fluctuations of pressure,thus reducing reflux shock and energy dissipation.In the intake area,the average value of pressure,velocity and temperature are slightly declined,but the fluctuations of them are significantly reduced,indicating that the spiral inlet plays the role in making the flow more stable.The numerical results obtained reveal the three-dimensional flow characteristics of the positive displacement blower with spiral inlet and outlet,and provide useful reference to improve performance and empirical correction in the noise-reduction design of the positive displacement blowers.

Numerical Simulation of Unsteady Discharge Flow with Fluctuation in Positive Discharge Blower

The operating performance of positive discharge blower is markedly influenced by the pulsation of the discharge flow, but difficult to be measured with experimental methods. The internal and discharge flow of positive discharge blower with involute type three-lobe are numerically investigated, both in air cooling and countercurrent cooling conditions by means of computational fluid dynamics （CFD）. The unsteady compressible flow equations are solved using RNG x-ε turbulent model. The finite difference method and the second order upwind difference scheme are applied into discrete equations. In the numerical simulation, the dynamic mesh techniques are used to approach the rotating displacement of cell cubage and the alterability of inlet, outlet flow area. The non-uniform mesh is applied to the rotor-stator coupled area. The reliability of the numerical method is verified by simulating the inner flow and comparing with the semi-empirical theory. The flow flux curves and the distributing of velocity vector showed obvious vortex motion in all the discharge process, both in air cooling and countercurrent cooling conditions. These vortexes with different positions, intension and numbers at different rotating angles have remarkable influences on the discharge flux. For air cooling, the vortex produced a second pulsation with big-amplitude in a cycle, and led to the early appearance of maximum of backflow. For countercurrent cooling, the frequency of pulsation increased due to the pre-inflow, but the backflow at the outlet is prevented, also the pulsation strength has greatly decreased.

Unsteady Flow Simulations in a Three-lobe Positive Displacement Blower

To improve the performance of the positive displacement blower, it is imperative to understand the detailed internal flow characteristics or enable a visualization of flow status. However, the existing two-dimensional unsteady, three-dimensional steady or quasi-unsteady numerical simulation and theoretical analysis cannot provide the detailed flow information, which is unfavorable to improve the performance of positive displacement blower. Therefore, the unsteady flow characteristics in a three-lobe positive displacement blower are numerically investigated by solving the three-dimensional, unsteady, compressible Navier-Stokes equations coupled with RNG k-e turbulent model. In the numerical simulation, the dynamic mesh technique and overset mesh updating method are adopted. Due to the air being compressed in the process of the rotors rotating, the variation of the temperature field in the positive displacement blower is considered. By comparing the experimental measurements and the numerical results on the variation of flow rate with the outlet pressure, the maximum relative error of the flow rate is less than 2.15% even at the maximum outlet pressure condition, which means that the calculation model and numerical computational method used are effective. The numerical results show that in the intake region, the fluctuations of the inlet flow are greatly affected by the direction of the velocity vectors. In the exhaust region, the temperature changes significantly, which leads to the increase of the airflow pulsation. Through analysis on the velocity, pressure and temperature fields obtained from the numerical simulations, three-dimensional unsteady flow characteristics in the positive displacement blower are revealed. The studied results will provide useful reference for improving the performance and empirical correction in the design of the positive displacement blower.

DISTRIBUTION LAW OF RANDOM UNBALANCE RESPONSE OF MULTISTAGE BLOWER

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Modelling and verification of a new Roots blower profile based on analysis of performance of different leaf contour

The rotor of a Roots blower is the key component relating to its capability, so the profile design of the rotor in a Roots blower is extremely important. We focused on the modelling and verification for a novel Roots blower tooth profile based on the performance analysis. By comparing the area utilization coefficient and the ratio of several traditional rotor profiles, we proposed a new rotor profile. Then, we further accomplished the mathematical modelling of the proposed rotor profile and the computational fluid dynamics(CFD) simulation, and obtained the Roots blower outlet flow monitoring curves. Finally, we verified the characteristics by a physical experiment.

Theoretical, Experimental and Numerical Investigations of the Effect of Inlet Blade Angle on the Performance of Regenerative Blowers

Regenerative machines allow high heads at small flow rates and present performance curves with very stable features. This research includes a study of the effect of four inlet flow angles (90°, 115°, 125° and 135°) of the blade at outlet flow angle of 90° on the performance of regenerative blower at rotation speed of 3000 rpm and at different flow rates. Investigation and comparison of the experimental results with both one-dimensional theoretical model and numerical CFD technique using CFX-ANSYS 16.1 are done. The numerical CFD analysis show that the flow enters the impeller from the blade side (about 65% of the blade side area) and leaves from the blade tip and blade side (the remaining 35% from the blade side area). According to this observation, a mathematical model that is based on momentum exchange theory to handle one inlet angle and two exit angles for the regenerative blower impeller blades is proposed. Consequently, the experimental work is carried out by two steps. The first step is done by studying the effect of inlet blade angle of 90° and analyzing the results by using the CFD analysis. The CFD results show shock losses and vortices behind each blade at the inlet flow regions. To reduce these losses, an increase of the inlet blade angle in a range between 25° to 45° is proposed. The second step is the splitting of this angle range to three inlet blade angles of 115°, 125° and 135° in order to study and analyze the CFD results for these angels. The CFD analysis shows the disappearance of the shock losses and vortices that are formed behind the blade of angle 90°. The experimental results show that the pressure head and the efficiency depend strongly on the blade inlet and outlet flow angles as well as on the blade geometry. The results also show that the best blower performance can be obtained at an inlet flow angle of 125°, and this is confirmed by CFD simulation analysis. Finally, it is shown that the proposed one-dimensional model yield results that are in a good agreement with the experimental results.

Shape Optimization of a Regenerative Blower Used for Building Fuel Cell System

This paper describes the optimal design of a Cathode blower used for a building fuel cell system. The Cathode air blower has a regenerative blower type. Two design variables, extension angle and number of impeller blade are introduced to enhance the blower performance. Pressure and efficiency of the blower are selected as an object function, and the optimal design is performed by a response surface method. Three-dimensional Navier-Stokes equations are introduced to analyze the performance and internal flow of the blower and to find the value of object function for the training data. Throughout the design optimization, it is found that an extension angle is effective to increase blower efficiency in the blower. The pressure rise for the optimal blower is successfully increased up to 3.17% compared with that of reference one at the design flow rate. It is noted that low velocity region disturbs to make strong recirculation flow in the each blade passage, thus increases local pressure loss. Detailed flow field inside a regenerative blower is also analyzed and compared.

Hydraulically Powered Wood Chip Blower in Test and Its Use Opportunity in Biofuel Supply Chain

Most forest chips are delivered to large-sized, combined heat and power plants in Finland. In this study, we introduce and demonstrate the small-scale delivery of forest wood chips to potential clients, with the wood chips being delivered in a container truck and pneumatically blown into a storage facility. This arrangement of wood chips being blown through a pipe into a storage eliminates the ground handling while requiring a relatively small space. In the demonstration tests, we tested the volumetric flow of biomass in the hose and its noise level while the blower was blowing the material and the flow speed of the material in the hose. This study discusses the test conditions in which the compatibility and suitability of the truck and its hydraulic system were used in conventional chip delivery in Finland and the selected blower type was investigated. According to the results, the biomass volume flow was higher (~0.46 m3/min) when the blower revolution was lower (2392 - 2566 RPM). However, when the RPM was increased to ~3000, the volumetric flow decreased to ~0.24 m3/min. Similarly, the speed of the chips was higher with a lower RPM;29.9 m/s at an RPM of 2400 and 25 m/s at an RPM of 2700. This is potentially due to both the blower and screw conveyer using the same power source. Additional optimization research would be needed to conclusively state the root cause of this phenomenon. On the other hand, chips from pruned stems had better flow than the chips from whole trees, since chips from whole tree have a wider range of chips sizes, including 1.3% of chips being in the range of 31.5 - 40 mm. The larger chips clogged the hose, which hindered the flow. Finally, the noise tests showed that it was louder at 0 degrees, which contrasted with the situation for the blower, with an aside at 90 degrees.

The Anti-corruption Fights： Perescoping the Whistle Blower Policy in Nigeria

The 2015 elections and swearing of new leadership in Nigeria brought about new promises as well as new policies and strategies. The president elect, Muhammadu Buhari, was quick to indicate his intentions to fight corruption as one of the means through which the government intends to achieve good governance in Nigeria. This intention and follow-up action is like the biblical two-edged sword, cutting off sadness from the lower class while at the same time cutting off happiness from some corrupt people in government. The recent announcement of the whistle blower policy by the Federal Government as another means of fighting corruption in Nigeria brought about an increase in the discovery of hidden/looted money. Relying on primary and secondary findings, based on qualitative and quantitative data the paper examines the potency of the whistle blower policy on corruption. The puzzle： is the policy yielding positive result？ The case provides a strong case to the methodological analysis for both institutional norms to fight corruption and good governance in Nigeria. The thrust of this paper is that, the fight against corruption is a national issue that can be successfully tackled by the citizens. The paper therefore recommends that government and its citizenry come together to fight this malice called corruption.

两代宾利极速赛车 欧陆GT3和BIRKIN“BLOWER”

当2015赛季落下帷幕时,宾利两代战车——欧陆GT3和传奇的4.5L"Blower"汇聚一堂,其同庆祝本赛季的出色表现。现役的GT3和其来自1929年、曾创造辉煌战绩的先辈战车,在位于银石赛道的英国赛车手俱乐部(BRDC)门前欢聚一堂。英国赛车手俱乐部于1928年成立,是由宾利小子、勒芒冠军Dudley Benjafield创立的赛车运动组织。这两台战车年代相差80余年,但是它们身上同样流淌着宾利对创新、竞技以及最重要的速度的满腔热血。

Cycloblower罗茨鼓风机的故障检修和调试

分析了Cycloblower罗茨鼓风机在运行中出现的故障及其原因 ,介绍了机器的修复过程和调试、使用要求。

基于一维和三维CFD方法的四级径流式鼓风机扩压器和回流器设计与优化

Soft In Way Inc. performed the aerodynamic design of a 4 stages high pressure radial blower with vaneless diffusers and deswirlers for DMW Corporation in 2021. The nominal pressure ratio of the machine is near 2.Such a pressure ratio often characterizes what would typically be called a compressor, especially if the compression work is performed in one stage. For the subject machine of the present study, the compression work is split into 4 stages.This paper describes the design procedure for this blower, initially focusing in depth on the tradeoffs between work split,rotor diameter, and rotor vane back-sweep angle. The paper then presents a further design and optimization work of different variants of diffuser and deswirler based on aerodynamic performance for this 4 stages radial blower. The number of deswirler blades in the return channel was reduced from 19 to 10 in consideration of manufacturing requirements. To minimize losses in performance due to reduced blade number, several candidates of varied geometry shape deswirler blades were obtained from an automatic design and optimization workflow combining with 3D CFD calculation. All candidates of deswirler were implemented to the entire 4 stages radial blower to analyze machine performance by 3D CFD calculation and the best 10-blade deswirler geometry was determined. 3D CFD analysis shows that 10 blades of deswirler is unable to provide the same pressure rise and efficiency as the original design with 19 blades when all other parts of the design, such as rotor and diffuser are maintained the same. To further improve the blower performance, the similar automatic workflow was applied to study vaned diffuser influence to the blower performance based on the new blower configuration. The number and geometry of best diffuser blades was obtained from the automatic workflow and entire blower performance with vaned diffuser was analyzed and validated by 3D CFD calculation. After finalizing the aerodynamic flow path geometries and configuration of new blower design,performance for new blower and old one are predicted by 1D method with loss model correction and 3D CFD calculation. 1D and 3D CFD calculation results are compared and good agreement is achieved. Though, small discrepancy between them is noticed and reasons are analyzed. Furthermore, 3D CFD calculations with stall determination method based on several stall-indication metrics were performed to determine surge points of the 2 new blower configurations with vaned and vaneless diffuser. A future publication is intended to show the validation of the design with tested performance data.

Enhancement of Performance by Blade Optimization in Two-Stage Ring Blower

This paper describes the shape optimization of an impeller used for two-stage high pressure ring blower.Two shape variables,which are used to define an impeller shape,are introduced to increase the blower performance.The pressure of a blower is selected as an object function,and the blade optimization is performed by a response surface method.Three-dimensional Navier-Stokes equations are introduced to analyze the internal flow of the blower and to find the value of object function for the training data.Relatively good agreement between experimental measurements and numerical simulation is obtained in the present study.Throughout the shape optimization,it is found that a hub height is effective to increase pressure in the ring blower.The pressure rise for the optimal two-stage ring blower is successfully increased up to 1.86% compared with that of reference at the design flow rate.Local recirculation flow having low velocity is formed in both sides of the impeller outlet by different flow direction of the inlet and outlet of the impeller.Detailed flow field inside the ring blower is also analyzed and discussed.

透平风机与纸机真空系统的匹配设计方法

本课题主要在湿纸幅流阻特性分析的基础上,探讨了透平风机与湿纸幅的气动匹配特性,并以实际生产线技改为例,介绍了应用透平风机改进真空系统的相关设计准则。

挥发窑鼓风管的关键点识别及其摆放位置监测

窑头鼓风管的摆放位置是影响氧化锌挥发窑燃烧状态的重要操作参数之一,现仍由人工看火来手动调节,同时现场没有为挥发窑的运行优化记录完善的鼓风状态数据,也难以及时发现鼓风管被窑内渣块击中等安全隐患.针对上述问题,本文提出一种基于关键点识别的鼓风管位置监测方法.首先,文章对从窑头看火口采集的火焰视频数据集设计一种邻域关键点辅助的数据扩充方法,并构建级联金字塔网络(CPN)来预测鼓风管管口中心点的位置;然后,本文提出一种基于多帧图像的聚类分析算法来消除因烟尘遮挡所产生的异常点,并采用一种量化指标来实现对挥发窑鼓风管摆放位置的实时感知与记录;最后,本文基于现场采集的火焰视频数据进行了对比实验,结果表明所提出的关键点检测模型精度高、鲁棒性强,且鼓风管位置的量化准确率高达92.3%.

Blade optimization design and performance investigations of an ultra-low specific speed centrifugal blower

The ultra-low specific speed centrifugal blower is widely used in energy industries due to its features such as low flow rate,high pressure and low manufacturing cost. However,the width-to-diameter ratio of the above blower becomes relatively small to satisfy the needed operation condition and its performances are considerably degraded as a result of relatively high leakage,disc friction and passage friction loss consequently. The purpose of this paper is to improve its performance through the optimization design of the blade’s profile properly. Based on artificial neural networks (ANN) and hierarchical fair competition genetic algorithms with dynamic niche (HFCDN-GAs),the optimization design approach is established. By conjoining Bezier parameterization and FINE/TURBO solver,the optimized blade is designed by adjusting the profile gradually. An industrial ultra-low specific speed centrifugal blower with parallel hub and shroud has been selected as a reference case for optimization design. The performance investigations of the centrifugal blowers with different types of blades are conducted. The conclusions of the performance improvement of the optimized blade provide positive evidences in the application of the optimization design of the above blower blade.

Optimal Design of Splitters Attached to Turbo Blower Impeller by RSM

This paper describes the optimization of the impeller having splitters for a turbo blower.Two design variables,chord of splitter and pitch of splitter,are introduced to enhance the blower performance.Blower pressure and ef-ficiency are selected as an object function,and the optimization of the blower impeller is performed by a response surface method (RSM).Three-dimensional Navier-Stokes equations are introduced to analyze the internal flow of the blower and to find the value of the object function for each case.Throughout the shape optimization of the splitters attached to the impeller in the turbo blower,pressure and efficiency at the design flow condition are suc-cessively increased by 5.9 percent and 17.9 percent respectively based on the reference blower.The higher blower efficiency obtained by optimization of impeller having splitters is mainly caused by reducing the number of im-peller blades and optimal design of splitters in the blade passage while pressure increase keeps almost the same with the reference blower.For the object function of pressure,pressure increase is obtained at the design and off-design conditions while efficiency keeps higher compared to the reference blower.The enhancement of blow-er performance is due to the reduction of reverse and circulation flows in the blade passage.

350MW燃用贫煤锅炉改烧强结渣沾污烟煤的调整及改造技术研究

国内某电厂2×350 MW机组锅炉原设计煤为贵州贫煤,属于中等结渣特性煤种。在掺烧靖边烟煤过程中出现了燃烧器烧损和严重结渣、沾污问题,为了解靖边烟煤的燃烧特性、结渣特性、沾污特性,以及锅炉设备对煤种的适应性,进行了一维火焰炉燃烧试验和煤灰烧结试验。靖边烟煤属于极易着火、燃尽煤种,是优质的动力用煤,但其灰分中钙、铁、钠等金属氧化物含量较高,灰熔点较低,具有严重结渣沾污倾向。靖边烟煤和原设计煤相比,燃用煤着火、燃尽特性更好,但结渣、沾污特性增强了。改造过程中根据煤质特性对燃烧器进行了调整,在炉膛区域增加20支短程吹灰器,水平烟道增加10支长伸缩式吹灰器,竖井增加24支长伸缩式吹灰器,并在改造后进行了燃烧优化调整试验。结果表明:改造后锅炉结渣明显改善,靖边烟煤掺烧比例由12.5%提高至75%,空预器入口烟气温度降低30.4℃,空预器出口烟气温度降低25.5℃,灰渣含碳量基本不变,脱硝入口NO_(x)浓度由705 mg/m^(3)降至384 mg/m^(3),锅炉效率升高1.49%,预计年节约燃料成本约280万元,改造后锅炉汽水系统和风烟系统对掺烧75%靖边烟煤具有良好的适应性。因此,可以通过设备改造增强锅炉对燃料的适应性,大幅拓宽锅炉煤种适应能力,缓解电厂购煤困难的问题。

VPSA制氧系统中离心鼓风机变工况调节规律研究

为提升离心鼓风机的变工况性能,以某真空变压吸附(VPSA)制氧系统中的离心鼓风机为研究对象,采用数值计算的方法分别对转速、扩压器角度单独调节以及二者联合调节时离心鼓风机的性能变化规律进行了研究。结果表明,相较于固定式,联合调节的工作压比范围扩大42%,可以使离心鼓风机在全压比范围内保持高效稳定运行;通过建立效率与转速、扩压器角度、压比之间的函数模型,采用内点法寻优得出了联合调节的最佳控制方案,为离心鼓风机的高效运行提供了依据。最后为验证寻优结果的可靠性,结合离心鼓风机的实际工作压比变化规律,按照最佳控制方案对试验模型的转速与扩压器角度进行联合调节,经测量可使离心鼓风机保持效率为87%以上持续运行。

Noise Characteristics of Centrifugal Blower with Low Solidity Cascade Diffuser(Noise Reduction by means of Small Groove Located at LSD Blade Leading Tip)

This paper deals with the effect of the blade tip-groove of the low solidity cascade diffuser (LSD) on the blowercharacteristic and the noise generated by the LSD. The small grooves were set up at the root and/or tip near theleading edge of the LSD blade. In order to clarify the mechanism of noise increase due to LSD and also to reducethe noise, the relationships between the noise increase based on the LSD, the LSD performance and the secondaryflow formed additionally by the tip-groove were investigated experimentally as well as numerically, especiallyanalyzing flow behaviors in the LSD in view points of flow separation on the suction surface of the LSD bladeand the secondary flow on the side walls. By reducing the stagnation region smaller near the root and/or tip of theLSD blade leading edge, the secondary flow behavior changes remarkably around the LSD blade, as a result, thenoise level and the blower characteristics vary. It can be concluded that, by means of a small tip-groove locatedonly at the shroud side near the LSD blade leading edge, the noise generated by the LSD can be reduced withoutdeteriorations of the LSD performance and the blower characteristics as well.