Fan Impeller Research Articles

Examining the Effect of Alignment of the Rotor of the Emissions Exhaust Fan on Its Operating Parameters

The paper describes research examining the trends in balancing rotary machines and the application of the sequence of steps in execution of the operational balancing of an impeller of the industrial furnace emissions fan. The balancing process is based on the correction of the weight distribution of the body with the given axis of rotation. In trial operation, vibrations (with the measurement of the oscillation phase) were measured on both emission fan rotor bearings. Since the measured vibration value was higher than recommended, it was necessary to take steps to balance the fan’s impeller. The first step of the operational balancing is to identify the initial vibration vector relative to the reference mark, arbitrarily located on the rotating wheel of the fan. In trial operation, the balancing weight mass was changed in the selected balancing level, resulting in the change of the vibration vector compared to the initial state. The size and the angular position of the balancing weight were determined from the vibration values measured. 15 months into operation after the impeller was balanced, the diagnosis of its current technical condition was performed. Total vibrations of the device were measured in the low- and high-frequency range, at four measuring points on the rotor and the drive engine. The measurement confirmed a satisfactory technical condition of the engine and the fan equipment. The effect of balancing has also been demonstrated in the case observed. Reduced bearing wear, elimination of recurrent defects, foundation damage, etc., have been observed.

The effect of blade slots on flow behaviour in a fan impeller

The use of blade slots is one of the passive methods of controlling flow in a fan impeller. Numerical CFD analyses indicate a possibility of controlling the point of flow separation in the inter-blade space depending on various configurations of the aperture arrangement. Bench studies confirm the possibility of changing the increase of total pressure and internal efficiency. Additionally, the changes affect the noise level during fan operation.

Axial flow fan performance improvement via leading-edge reshaping

Performance improvement in axial flow fans is a popular research topic that is typically explored by changing the blade shape and tip clearance of the leading edge or trailing edge. In this study, the BA©zier curve method was used to reshape the impeller of a typical axial flow fan in effort to improve the vortex structure and minimize noise. Numerical simulations were run to analyze the differences in performance between the original and modified impeller. The performance of impeller B, which was designed with a convexity-preserving structure at the trailing edge, markedly improved with small secondary loss. As expected, the BA©zier curve method as-applied to impeller B facilitated a type-line parametric design in the meridional plane. A noise test was also conducted in a semi-anechoic chamber with 1/3 octave sound pressure in the far field. The noise-reduction effect with convexity-preserving structure at trailing edge was determined by comparing the sound pressure levels at various frequency bands.

The influence of geometry of primary air channels in standard retort burners on dust emission

The article presents the analysis of dust emissions from a low power boiler fired with various solid fuels. The boiler, presented for testing, met the emission conditions for boilers made in the third class in accordance with the PN-EN 303-5: 2012 standard. The solid fuel boiler was equipped with two different retort burners with automatic fuel supply. For the test were used a first generation retort burner with a fixed rim and the next were used second generation retort burner provided with a rotary rim. Both constructions differ in the geometrical model of the primary air supply system to the furnace. During the tests, the work of the burners was controlled using a microprocessor temperature controller. During the research, the rotation time of the screw supplying the fuel through the retort to the furnace was changed, as well as the rotational speed of the blast fan impeller responsible for supplying the combustion air. The purpose of the tests was to check whether the boiler will meet the highest environmental class regardless of the technical parameters of the burner and fuel used. The article describes the research methodology and analysis of the results obtained. The effect of the tests carried out is a comparison of average dust emission values depending on the fuel used and the work settings of a given burner. The test results are a prerequisite for further research work in terms of the impact of primary air supply on the emission of harmful substances.

Theory and Practice of Creation of Modern Air-Cooling Equipment of General Industrial Appointment

The review of the state of the problem of the design of modern air cooling units (AСU) used in the chemical, oil and gas and metallurgical industries is given. The main provisions of the method of establishment and Newton's method for determining the operational parameters of a heat exchanger are generalized. On the basis of a combination of the methods considered, the design of a small-flow condensate condensation condenser has been developed, its technical parameters and the general model of the equipment layout are given. The main parameters of the units of the air cooling device, the type of electric motor, the diameter of the fan impeller and the number of blades in it are determined. The reasons are formulated, in which, under the conditions of the current production, the heat exchanger apparatus is not optimally organized, namely: the intensive failure of several cooling tubes, thereby reducing the heat dissipation area; contamination by foreign objects of fins fins surfaces; increased vibration in the sections of the heat exchangers due to poor assembly of the units of the apparatus or design errors in the design of the project; increased power consumption by the electric drive, which controls the AСU; incorrectly selected angle of adjustment of the cooling medium flow rate on the louvered device.

Patterns in change and balancing of aerodynamic imbalance of the low­pressure axial fan impeller

We have studied patterns in the change and balancing of aerodynamic imbalance of the impeller for the axial fan of type VO-06-300 (Ukraine). We have found the aerodynamic imbalance of the impeller caused by mounting one blade: – at a different angle of attack; – with a violation in the step uniformity; – not perpendicularly to the longitudinal axis of the impeller; – with all three of the above-mentioned errors present at once. We have estimated a change in the aerodynamic imbalance due to change in air density. We estimated the influence of air temperature, altitude above sea level, atmospheric pressure, on air density and aerodynamic imbalance. It was established that a different angle of attack and a violation of the perpendicularity give rise to the dynamic imbalance in which the moment component is an order of magnitude larger than the static component. A violation of the step uniformity gives rise only to the static component, which is in the plane of the impeller. Among the errors considered, the most undesirable one relates to mounting a blade at a different angle of attack. At such an error, aerodynamic imbalance is 6‒8 times larger than that due to other errors. A ±4-degree change in the angle of attack of a single blade in the impeller can degrade the accuracy of balancing of the impeller to the accuracy class G 6.3 at a frequency of 1,500 rpm, or G 16 ‒ at 3,000 rpm. It was established that the ordinary and aerodynamic imbalances can be balanced at the same time. It is appropriate to carry out dynamic balancing in two correction planes. It is possible to conduct balancing by rotor mass correction or using passive auto-balancers. A specific example is used to demonstrate the procedure for taking into consideration the aerodynamic imbalance in differential equations of motion of the axial fan. In accordance with the procedure, the aerodynamic imbalance components are added to the respective components of the ordinary imbalance. The results obtained are applicable when designing and manufacturing low-pressure axial fans. Employing them would improve vibration characteristics of the specified fans.

Centrifugal fan with inclined blades for vacuum cleaner motor

Centrifugal fans have several technical applications. Their aerodynamic performance is well-optimized nowadays, but the same does not apply to their acoustic performance. Noise control studies of centrifugal fans are often focused on designed operating conditions or operating conditions close to the onset of instability. This paper seeks to find an alternative geometry of the centrifugal fan impeller which would improve noise control of centrifugal fans in a wide range of operating conditions. In this paper, the term noise control refers to noise level reduction and additionally to manipulating the psychoacoustic properties of noise.The experimental work and numerical calculations focus on the centrifugal fan in vacuum cleaners. The experimental work, based on numerical simulations, is described to investigate the influence of the triangular cross section on the flow channel, formed by two inclined blades in opposite directions, on aerodynamic properties and the psychoacoustic performance of the impeller. The study demonstrates that impellers with a triangular flow channel achieve an aerodynamic performance which is comparable to that of standard impellers. The results also show that impellers with inclined blades deliver superior results in psychoacoustic metrics compared to impellers with upright blades.

Analyses on uniformity of particles under HPGR finished grinding system

In order to deal with the disadvantages of excessive grinding and non-uniformity in finished particle under high-pressure grinding rolls (HPGR) finished grinding system, four aspects were investigated, including evaluating indicators, effects of operating factors, effect of particle uniformity on the flotation and formation mechanism of particle uniformity. Experiment of HPGR finished grinding system, cationic reverse flotation experiment and simulation test of particle bed comminution under the condition of quasi-static were carried out. Theoretical analyses indicated that both of uniformity coefficient and average particle size should be included in the uniformity analysis of the mineral particles. The results show that the effect of circulation fan impeller speed on particle uniformity is the most evident, HPGR working pressure and roll gap are second and HPGR roller speed is the last. Average particle size has a more obvious effect on the grade of flotation concentrate while uniformity coefficient has a more obvious effect on the flotation recovery. Considering the two aspects of grade and recovery, the optimal uniformity coefficient for flotation is 1.1–1.2 and the optimal average particle size for flotation is 50–55 μm. The operating factors which promote the shielding effect and compact effect in the HPGR finished grinding system should be strengthened based on the uniformity of particles.

Design Optimization of Aerofoil Radial Fan Impeller

Design Optimization of Aerofoil Radial Fan Impeller

On the limited accuracy of balancing the axial fan impeller by automatic ball balancers

The study explores the process of dynamic balancing of the impeller of an axial fan VО 06-300 (Ukraine) by two automatic ball balancers. The computer simulation of the dynamics of the fan in the absence and presence of automatic balancers has confirmed the qualitative results of a previously conducted field full-scale experiment. Thus, the presence of automatic balancers reduces the following: – the mean square value of the vibration velocity in the segment from the rotor start to the beginning of automatic balancing, – the vibration velocity values at two resonant peaks when the rotor is running down, and – the peaks of the vibration velocities in the section of the start of automatic balancing (74 times in the 3D modelling; 5.4 times in the field experiment). The computer simulation of the dynamics of the axial fan with the «on» and «off» gravity forces has allowed determining the following: – the effect of gravity on the accuracy of balancing the impeller decreases rapidly with increasing the cruising speed of the impeller, – when increasing the forces of viscous resistance to the motion of the balls, the effect of gravity on the accuracy of the rotor balancing increases; – at low speeds of rotation (15 r/s), the impeller can be balanced not better than by accuracy class G 2.5, but at the rated speed of 25 r/s, it is balanced according to accuracy class G 1. Herewith, the residual vibration velocities that are caused only by gravity decrease with increasing the rotor speed. The residual vibration velocities that are caused only by the eccentricities of the raceways increase directly proportionally to the rotor speed. Therefore, fast-turning rotors need a more precise installation of automatic balancers. It is recommended to reduce the eccentricity of the raceway of the automatic balancer at least 2.5 times in relation to the maximum permissible value. Residual vibration velocities in the automatic balancing mode (up to 3 mm/s) on the test fan are mostly caused by gravity. The probable causes of residual vibration velocities are eccentricities of the raceways of the automatic balancers, standstill of the balls (lack of reaction to small unbalances), etc. Therefore, residual vibration velocities can be reduced at the stages of manufacturing and installing automatic balancers into a fan.

СОКРАЩЕНИЕ ВРЕМЕНИ ПРОСТОЕВ В РЕМОНТЕ ОДНОКОВШОВЫХ ЭКСКАВАТОРОВ НА РАЗРЕЗЕ "БОРОДИНСКИЙ" ПОСРЕДСТВОМ МОДЕРНИЗАЦИИ СТУПИЦЫ РАБОЧЕГО КОЛЕСА ВЕНТИЛЯТОРА

СОКРАЩЕНИЕ ВРЕМЕНИ ПРОСТОЕВ В РЕМОНТЕ ОДНОКОВШОВЫХ ЭКСКАВАТОРОВ НА РАЗРЕЗЕ "БОРОДИНСКИЙ" ПОСРЕДСТВОМ МОДЕРНИЗАЦИИ СТУПИЦЫ РАБОЧЕГО КОЛЕСА ВЕНТИЛЯТОРА

Effect of innovative circular shroud fences on a centrifugal fan for augmented performance - A numerical analysis

This paper presents the influence of circular front and back shroud fences on the performance of a backward swept centrifugal fan impeller handling air. The analysis is carried out to determine the main characteristics of the fan i.e. the variation of head and theoretical efficiency for various flow coefficients. The circular fence size is optimized parametrically by varying its diameter and the location on the shroud surface. The effect of the shroud fences on the flow field was analyzed for the fences placed on both front and back shroud surfaces of the impeller separately. The numerical simulation is carried out using an appropriate k - e turbulence model. The relative flow inside the impeller passages is modeled using the standard sliding mesh technique. The numerical results for the base model (i.e. without the fence) are validated against experimental results obtained from the test rig built specially for validation study and are found to have good agreement. It is found from the analysis that the average percentage increase in head coefficient is significant and is about 2 % higher as compared to the base model for the optimized geometrical configuration of diameter ratio and radial fence location as determined in the study. The optimized geometrical configuration also yields a higher theoretical efficiency of about 2.3 % corroborating the improvement in head coefficient with respect to the base model. Hence the efficacy of optimally placed circular fence on the performance of centrifugal fan is established in this numerical study.

Integral and statistical characteristics of the turbulent swirl flow in a straight conical diffuser

The results of the experimental investigations of the turbulent swirl flow in a straight conical diffuser with inlet diameter 0.4m and total divergence angle 8.6? are presented in this paper. The incompressible swirl flow field is generated by the axial fan with outer diameter 0.397m. The measurements were performed in one measuring section downstream the axial fan impeller in the conical diffuser in position (z/R0 = 1) with original classical probes and an one-component laser Doppler anemometry (LDA) system, for four flow regimes. The comparative measurements of axial and circumferential velocities are presented. The Reynolds number, calculated on the basis of the average velocity, ranges from 149857 to 216916. Integral parameters, such as volume flow rate, average circulation and swirl number, are determined. Statistical characteristics, such as level of turbulence, skewness and flatness factors, are calculated. The highest levels of turbulence for axial velocity are reached in region 0.4 < r/R < 0.6, where D = 2R. The highest levels of turbulence for circumferential velocity are reached for the regimes with lower circulation in r/R ? 0.4, i.e., in the vortex core region for the cases with higher circulation.

Effect of inlet guide vanes on the performance of small axial flow fan

Effects of the inlet guide vanes on the static characteristics, aerodynamic noise and internal flow characteristics of a small axial flow fan are studied in this work. The inlet guide vanes with different outlet angle are designed, which are mounted on the casing and located at the upstream of the impeller of the prototype fan. Both steady and unsteady flow simulations are performed. The steady flow is simulated by the calculations of Navier-Stokes equations coupled with RNG k-epsilon turbulence model, while the unsteady flow is computed with large eddy simulation. According to the theoretical analysis, the inlet guide vanes with outlet angle of 60° are regarded as the optimal inlet guide vanes. The static characteristic experiment is carried out in a standard test rig and the aerodynamic noise is tested in a semi-anechoic room. Then, performances of the fan with optimal inlet guide vanes are compared with those of the prototype fan. The results show that there is reasonable agreement between the simulation results and the experimental data. It is found that the static characteristics of small axial flow fan is improved obviously after installing the optimal inlet guide vanes. Meanwhile, the optimal inlet guide vanes have effect on reducing noise at the near field, but have little effect on the noise at the far field.

Effect of meridional shape on performance of axial-flow fan

In this study, the effect of impeller meridional shape on the performance of axial-flow fan is investigated by CFD method. Three axialflow fan impellers with different meridional shapes are designed. The blade angle, blade stacking condition and other structure factors of the impellers are all remained consistent. The performance curves of the three impellers are calculated and compared. In almost all the interested flowrate range, the impeller W3 with an inverted-isosceles-trapezoid meridional shape and the longer blade camber achieves both the higher pressure rise and the higher efficiency than the other two impellers. A two-stage axial-flow fan designed on basis of W3 is manufactured and tested. Test results show good agreement with the calculated performance curves. Further, analyses of the CFD results are conducted to reveal the reasons for the different performance. A newly-defined Local Euler head (LEH) is introduced to represent the distribution of the major Euler work in the axial-flow fan. And the LEH distributions in the three impellers are obtained. W3 achieves the highest LEH at blade Trailing edge (TE), because it could perform the most Euler work to the fluid with the longest blade camber. Then losses in the impellers are analyzed by means of the entropy generation. Among the losses in impeller, the tip leakage loss and endwall friction loss are dominated at design flowrate. The generation condition of the tip leakage loss shows significant differences among the three impellers. And the whole power loss in impeller of W3 is slightly higher than those of the other two models. However, the power loss difference among the three impellers is negligible. And due to the highest shaft power, the efficiency loss of W3 is the lowest of all.

Flow analysis and structural optimization for centrifugal fan impeller used to throw snow

Flow analysis and structural optimization for centrifugal fan impeller used to throw snow

Analysis and research on time-dependent reliability of fan impeller structure based on the pneumatic elasticity

Because of the working in the bad environment, the fan of rail train is greatly influenced by the environment, especially with the increase of the year. Impeller structure often fails in the design life cycle. According to the uncertainty and self-dependence of structure size, material and load, the time variant reliability analysis of the impeller structure is carried out. Based on the time-dependent reliability analysis technique, an efficient method for analyzing the time-dependent reliability of fan blade structure is presented, which the time varying reliability is converted to the traditional static reliability problem, and the random process is discretized in time. Based on the analysis of the Pneumatic Elasticity, the reliability index and failure probability of the impeller structure under different damping coefficients are obtained, which can provide reference for the practical engineering application. Compared with the analysis results of without considering the aeroelasticity, the conclusion is that the reliability index of aerodynamic elasticity is much smaller than that without considering the aeroelastic reliability index. Without consideration of aeroelastic analysis, the reliability and safety of the impeller structure can be easily overestimated. By analyzing the influence of aerodynamic elasticity on the structure reliability of the impeller, it is very important and necessary to analyze the dynamic elasticity of the impeller.

Experimental study of the process of the static and dynamic balancing of the axial fan impeller by ball auto-balancers

The process of the static and dynamic balancing of the impeller of the axial fan by ball auto-balancers is experimentally investigated. The influence of auto-balancers on sections of the racing and the run-out of the fan and the efficiency of the auto-balancers in the cruising sections are studied. It is shown that the vibrations of the impeller occur with the frequency of its rotation. This means that the usual and aerodynamic unbalances are the main sources of vibrations and they are similar to each other; both unbalances give rise to vibrations with the rotor frequency. It is shown that the impeller has two resonant frequencies (although the impeller itself is a short rotor and has one resonant frequency). This is because the impeller is mounted into a massive corps and dynamically it behaves like a long rotor. The larger resonant frequency of the impeller is almost 2 times lower than its operating frequency. Therefore, it falls into the area of the beginning of balancing with a margin. It is shown that the presence of one auto-balancer does not worsen the racing process of the fan. It is shown that in the run-out when the rotor passes through the resonant velocities, the value of the vibration accelerations and the duration of the passage of the velocities: – in the presence of one auto-balancer are decreased insignificantly by 20–40 %; – in the presence of two auto-balancers are decreased significantly by 60–80 %. These are explained by the following: in auto-balancers at the run-out there is retention of the balls and balls are retained in the balancing positions almost until the rotor stops. It is shown that dynamic balancing occurs faster than static balancing. It is shown that on the cruising steady motion: – one auto-balancer, mounted from the side of the impeller (the shank), significantly reduces vibration accelerations in its plane and almost does not reduce vibration accelerations from the side of the shank (the impeller); – two auto-balancers significantly reduce the vibration accelerations of the impeller in all planes. It is shown that the attachment of additional masses to the fan protective casing reduces its vibrations, but does not reduce the loads on the bearings.

Experimental investigations of the turbulent swirl flow in straight conical diffusers with various angles

Results of experimental investigations of the turbulent swirl flow in three straight conical diffusers with various diffuser total angles are presented in this paper. All three diffusers have the inlet diameter 0.4 m and total divergence angles 8.6?, 10.5?, and 12.6?. The incompressible swirl flow field is generated by the axial fan impeller, and for each diffuser several regimes were achieved by changing rotation number. Original classical probes were used for measurements. The distributions of the average main swirl flow characteristics along the diffuser are shown. Distributions of the inlet Boussinesq number, outlet Coriolis coefficient, ratio of the swirl and completely axial flow loss coefficients at conical diffuser on the inlet swirl flow parameter are also presented.

On the Variation of the Polytropic Exponent in a High Pressure Fan Impeller

Fan impellers are usually designed considering that the pumped air is incompressible and homogeneous, i.e. its density remains constant. When the incompressibility hypothesis can lead to significant errors, as in the case of high pressure fans, the analysis of the air flow can be made by considering that the air undergoes a polytropic process of constant polytropic exponent. In this paper, the concept of polytropic process of variable exponent depending on impeller radius is introduced, in order to better approximate the phenomena that take place inside blade passages. Numerical results obtained for an impeller of a high pressure fan without spiral casing suggest that the pumped air undergoes two different processes: an expansion in the first part of the impeller and the usual compression in the second part. The two processes are reflected in the strong variation of the polytropic exponent, which shows a vertical asymptote where the change of the process takes place. The results also suggest that high pressure fan impellers could consist of two stages, each stage being designed according to the process that takes place inside it: expansion or compression.