A Comparison of Propeller and Centrifugal Fans for Circulating the Air in a Wind Tunnel

The tests described in this paper afford a direct comparison of the efficiency and smoothness of flow obtained with propeller fan and multiblade centrifugal fan drives in the same wind tunnel. The propeller fan was found to be superior to the centrifugal fan in that the efficiency was about twice as great, and the flow much smoother

Two-Stage Centrifugal Fan

Fan designs are often constrained by envelope, rotational speed, weight, and power. Aerodynamic performance and motor electrical performance are heavily influenced by rotational speed. The fan used in this work is at a practical limit for rotational speed due to motor performance characteristics, and there is no more space available in the packaging for a larger fan. The pressure rise requirements keep growing. The way to ordinarily accommodate a higher DP is to spin faster or grow the fan rotor diameter. The invention is to put two radially oriented stages on a single disk. Flow enters the first stage from the center; energy is imparted to the flow in the first stage blades, the flow is redirected some amount opposite to the direction of rotation in the fixed stators, and more energy is imparted to the flow in the second- stage blades. Without increasing either rotational speed or disk diameter, it is believed that as much as 50 percent more DP can be achieved with this design than with an ordinary, single-stage centrifugal design. This invention is useful primarily for fans having relatively low flow rates with relatively high pressure rise requirements

Pemodelan Kasus Unbalance pada Centrifugal Fan saat Sebelum dan Sesudah Pemasangan DVA

Di dalam operasi permesinan sering kali terjadi getaran. Hal ini disebabkan oleh satu dan berbagai hal, misal: unbalance, misalignment, kerusakan pada gear atau bearing, dst. Salah satu kasus unbalance terjadi pada Centrifugal Fan di PT. PJB Services PLTU Amurang. Kasus unbalance pada Centrifugal Fan ini dapat direduksi dengan beberapa cara, salah satunya yaitu dengan penambahan Dynamic Vibration Absorber (DVA). Tugas akhir ini bertujuan untuk mereduksi getaran dengan penambahan DVA dan mengetahui pengaruh perubahan massa DVA terhadap respon getaran yang dihasilkan dari simulasi Simulink MATLAB. Dengan mengangkat kasus tersebut, hal pertama yang dilakukan untuk mengetahui tipikal DVA yang cocok untuk kasus unbalance ini adalah mensimulasikan getaran yang terjadi ketika Centrifugal Fan dalam keadaan unbalance. Setelah diketahui karakteristik getarannya, dilakukan perancangan DVA teredam dengan variasi massa DVA. Jika massa DVA bervariasi, maka nilai stiffness dan damping DVA akan berubah pula nilainya. Setelah parameter dari DVA dihitung, rancangan DVA tersebut disimulasikan dalam keadaan sudah terpasang pada sistem Centrifugal Fan. Kemudian karaktersitik getaran dari hasil simulasi tersebut dibandingkan, saat sebelum dan sesudah pemasangan DVA. Seluruh parameter sistem Centrifugal Fan yang digunakan diperoleh dari PT. PJB Services PLTU Amurang. Dari data tersebut diperoleh nilai putaran kerja dari Centrifugal Fan sebesar 2840 rpm dan nilai vibrasi tertinggi arah horizontal (sumbu x) sebesar 48.52 mm/sec. Sedangkan untuk massa DVA dihitung dari massa system. Nilai stiffness dan damping DVA pada tiap massa berbeda, tergantung pada tiap rumus perhitungannya. Dari hasil simulasi pemasangan DVA pada Centrifugal Fan didapatkan bahwa getaran yang terjadi pada system tidak berkurang, mulai dari massa pertama hingga massa kelima. Bahkan, saat massa DVA yang dipasang bertambah besar, getaran yang terjadi pada system juga semakin besar. Hal ini dimungkinkan getaran yang terjadi karena kondisi unbalance pada system Centrifugal Fan tersebut tidak dapat direduksi dengan pemasangan DVA. Hal ini juga bertentangan dengan teori dan perumusan bahwa reduksi yang dialami saat system telah dipasang DVA kurang lebih sebesar 90%. =========================================================== Sometimes there is a vibration inside a machine. This vibration caused by one thing and another, such as: unbalanced, misalignment, a damage on the gear or bearing and so on. The unbalanced case happened in Centrifugal Fan at PT. PJB Services PLTU Amurang. The unbalanced case in Centrifugal Fan can be reduced by several methods, one of them is by installing the Dynamic Vibration Absorber (DVA). This final assignment has a purpose to reduce the vibration by installing DVA and understanding the effect of DVA mass changes against vibration respond that is generated by simulation in Simulink MATLAB. By lifting up this case, this final assignment is giving the solution to reduce the vibration which is caused by the unbalanced, by installing the DVA. The first thing to be done is to learn about the DVA type that matches for the unbalanced case and simulate the vibration when the Centrifugal Fan is unbalanced. After the vibration characteristic has been found, the next step is designing the damped DVA with the varied mass. If the DVA masses are varied, the stiffness and damping will change following the amount of the mass. After the parameter of the DVA has been calculated, the designs of the DVA are installed alternately on the Centrifugal Fan and simulate each of them. Then after the vibration characteristics as a result from the simulation have been collected, the vibration of the Centrifugal Fan will be compared on before and after the DVA installation. All of the parameters in the Centrifugal Fan system that is used in this final assignment was obtained from PT. PJB Services PLTU Amurang. In the data, there is a working frequency of the Centrifugal Fan by 2840 rpm and the highest vibration on horizontal direction (X axis) is 48.52 mm/sec. For the value of the DVA mass was calculated from the Centrifugal Fan system mass. The values of the stiffness and damping of the DVA on each mass are different, they depend on the calculations. In the result of the installation of the DVA on Centrifugal Fan was acquired that the vibration inside the system can not be reduced, even with the first until the fifth DVA mass. Moreover, the bigger the DVA mass that was installed on the Centrifugal Fan, the vibration in the system will get larger than before. It is possible that this phenomena happens because the vibration itself can not be reduced by installing the DVA. This phenomena also contradicted with the theories and formulas based on trusted references that the amount of reduced vibration on the system will be about 90% after the DVA installation

Characteristics of the Aerodynamics and the Noise of a Dual-cascade Centrifugal Fan (Effects of Bare Ratio and Outlet Angle of Scroll Casing)

Characteristics of the aerodynamics and the noise of dual-cascade centrifugal fan have been experimentally investigated with respect to the effects of the bare ratio and the outlet angle of scroll casing. It was shown that the performance of the fans became best when the bare ratio was around between 9% to 25%, then the characterisitics of the dualcascade centrifugal fan were superior to that of the single-cascade centrifugal fan. The former was little influenced by the different bare ratio and the fans were able to be widely designed in comparison with the latter, the both characterisitics were improved when the outlet angle was 20 degrees

Design of a low-noise aeroacoustic wind tunnel facility at Brunel University

This paper represents the design principle of a quiet, low turbulence and moderately high speed aeroacoustic wind tunnel which was recently commissioned at Brunel University. A new hemi-anechoic chamber was purposely built to facilitate aeroacoustic measurements. The wind tunnel can achieve a maximum speed of about 80 ms-1. The turbulence intensity of the free jet in the potential core is between 0.1–0.2%. The noise characteristic of the aeroacoustic wind tunnel was validated by three case studies. All of which can demonstrate a very low background noise produced by the bare jet in comparison to the noise radiated from the cylinder rod/flat plate/airfoil in the air stream.The constructions of the aeroacoustic wind tunnel and the hemi-anechoic chamber are financially supported by the School of Engineering and Design at Brunel University

Experimental design of a low noise centrifugal fan

The effect of various design parameters on broadband noise generation by centrifugal fans has been studied. The parameters varied included: blade type, radial and axial inlet clearance, scroll development angle, scroll development length and cutoff clearance. Scaling laws for pressure, flow and noise were applied to allow the A-weighted sound power levels of different fans to be compared at the same operating points. That approach has allowed an optimum low noise fan design to be identified. To extend the usefulness of that design, a semi-empirical procedure for predicting the broadband sound power spectrum of any member of a family of geometrically similar centrifugal fans has also been developed. The prediction procedure allows the calculation of 1/3-octave band sound power levels based on a measurement of the sound power radiated by a single member of the fan family. By the use of the prediction procedure, it is straightforward to identify optimally quiet fans that satisfy a range of pumping requirements

Investigation of material wear on centrifugal fan impellers

M.Tech. (Mechanical Engineering)Abstract: Material wear formation on centrifugal fan impeller has been a major problem to many process plants in the whole world and this has been regarded as a grey area to many of OEM of extraction fans. TLT ACTOM has designed and manufactured an ID centrifugal fan for Sugar plant situated in Swaziland. The ID fan after a few months of operation the impeller was found to be subjected to wear. Wear initially took place such that the impeller could not last a season which is made of 9 months. The research was conducted to study the behaviour of wear taking place on the impeller material used in sugar mill plant. Establish the uncertainty of what type of wear is taking place and what cause this wear. The study focused on the formation particle flow pattern and minimization of wear to give a solution to fan manufacturers and end-user of the extraction fans. A visit to the plant in Swaziland was organized and during that site visit, bagasse and coal ash samples together with water samples were collected from inside of the venturi wet scrubber after the scrubber has been switched off for over a month for maintenance purposes. These samples were sent to a laboratory to analyse chemical compositions. The test aimed to determine particles sizes, a composition of mass in percentage, elements and mass of a chemical or contaminate per unit volume of water. A physical inspection has been performed on the wet scrubber to inspect if there were any trace that can lead to wear resulting from wet scrubber failing to perform what is expected from it. A correlation on how wear might have taken place on the impeller was conducted by using a CFD simulation. CFD simulation was conducted by using SolidWorks CAD software. Before conducting the simulation, calculations were made to determine parameters to be used as boundary conditions in the simulation software. Calculations were based on the actual centrifugal fan duties provided by the consultant company that was responsible for designing the entire plant system..

Intelligent Method for Diagnosing Structural Faults of Rotating Machinery Using Ant Colony Optimization

Structural faults, such as unbalance, misalignment and looseness, etc., often occur in the shafts of rotating machinery. These faults may cause serious machine accidents and lead to great production losses. This paper proposes an intelligent method for diagnosing structural faults of rotating machinery using ant colony optimization (ACO) and relative ratio symptom parameters (RRSPs) in order to detect faults and distinguish fault types at an early stage. New symptom parameters called “relative ratio symptom parameters” are defined for reflecting the features of vibration signals measured in each state. Synthetic detection index (SDI) using statistical theory has also been defined to evaluate the applicability of the RRSPs. The SDI can be used to indicate the fitness of a RRSP for ACO. Lastly, this paper also compares the proposed method with the conventional neural networks (NN) method. Practical examples of fault diagnosis for a centrifugal fan are provided to verify the effectiveness of the proposed method. The verification results show that the structural faults often occurring in the centrifugal fan, such as unbalance, misalignment and looseness states are effectively identified by the proposed method, while these faults are difficult to detect using conventional neural networks

Investigation of material wear formation on centrifugal fan impeller

Abstract: This paper reports the investigation of wear formation on centrifugal fan impeller which was exposed to bagasse ash particles in the sugar process plant and to simulate what took place as particles impact on the impeller surface. Computational Fluid Dynamics has been used as a tool to simulate impaction of flow around the impeller to determine the impingement angles and velocity particles. After performing simulation using SolidWorks, angle of impingement was found to be low at the impeller inlet and gradually increase angle toward 90°, in reference to the blade root. The lowest angle found after simulation was 23°. This angle correlate with the theory mentioned for ductile material, stating that ductile material is susceptible to wear formation when the impact angle is between 15° and 45° with a peak at 25°. Computational Fluid Dynamics using SolidWorks has been verified by using a third‐party company that worked on Creo 3.0 simulation. Research has revealed that material selection based on particles impingement angle, is key as when applied to centrifugal fans and related applications

Test stand for measurement and sampling of brake wear particle emissions

The thesis deals with the practical design of an airtight enclosure around the braking mechanism with the filtered air has drawn into the chamber and provides cooling to the braking mechanism. This flow scavenges the wear particle produced by brake wear. The air is drawn into the designed pipe system with dilution tunnel and multiple sampling points for the isokinetic sampling process, then it is directed to the exhaust system by a variable speed centrifugal fan. This thesis includes the literature survey, description of two different design variants with pressure drop calculations, technical drawings and part lists.The thesis deals with the practical design of an airtight enclosure around the braking mechanism with the filtered air has drawn into the chamber and provides cooling to the braking mechanism. This flow scavenges the wear particle produced by brake wear. The air is drawn into the designed pipe system with dilution tunnel and multiple sampling points for the isokinetic sampling process, then it is directed to the exhaust system by a variable speed centrifugal fan. This thesis includes the literature survey, description of two different design variants with pressure drop calculations, technical drawings and part lists