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Ceramic Industrial centrifugal fans used to guard against noise

Time2014-03-28  


The reason the noise generated

Noise is usually used centrifugal fan zone ceramic industry is divided into mechanical noise generated by the motor noise and aerodynamic noise.

Mechanical noise

Commonly used in the ceramic industry is typically centrifuge impeller is mounted directly on the motor shaft or via a coupling , or coupled together through the fan pulley shaft , the belt shaft and the fan motor shaft and the motor shaft rotates with high speed . Although the design and manufacture of centrifugal fans used the ceramic industry to meet the strength and stiffness requirements, and the fan factory , fan shaft , fan impellers , couplings and pulleys and other rotating parts are rigorously qualified quiet calm before moving flat correction assembled into units . But the ceramic industry used high speed centrifugal fan , harsh production environment, air humidity and dust and so on ; while the main component of the ceramic powder and solid particles such as dust, quartz and still is ( or ) cristobalite , its hardness is particularly high ; apparently ceramics when industrial centrifugal fans used to work , and other rotating fan impeller wear parts can easily generate mechanical noise , etc., and in the following areas:

( 1 ) : fan impeller wear unevenly , and the role of fan pressure , resulting in deformation of the fan impeller , the results of the fan work , but because of the imbalance of the fan impeller produces mechanical noise.

( 2 ) : Due to the fan bearing wear , causing the rolling bearing is formed in contact with the work surface to produce a large gap mechanical noise ; severe, the bearing , the outer ring and the fan shaft , the bearing clearance will form a larger generate mechanical noise .

( 3 ) : Some fans usually work simultaneously a plurality of drive belts , the belt if the length dimension difference is large, the work of the fan , some of the belt tension , the other is not the belt tension , the result of the mechanical noise produced .

( 4 ) : Due to the installation of wind turbine components is not prescriptive work , such as loose coupling bolts caused by mechanical noise.

( 5 ) : Due to the high speed rotation of the fan , the fan causes a resonance component caused by mechanical noise .

Motor noise

Motors are commonly used in the ceramic industry an important part of the centrifugal fan , fan motor manufacturers typically used are provided by professional motor manufacturer , fan manufacturers usually no longer deal with the internal motor , but direct use . In fact, the noise of many types of motors , usually mainly in the following aspects:

( 1 ) due to poor precision motor bearing surface to produce mechanical noise.

( 2 ) radially inside the motor by alternating excitation of the electromagnetic force generated by the electromagnetic noise.

( 3) The friction conductive carbon commutator ring and mechanical noise generated by the commutator itself .

( 4 ) Certain parts of it due to vibration similar to the natural frequency of the resonance frequency of the excitation force , thus forming the noise .

( 5 ) due to the unbalanced axial or axial ( and ) the electromagnetic force generated by the rotor component of the noise caused by a rocky ledge .

( 6 ) due to the aerodynamic shape and size of the motor cooling fan is not reasonable parameters generated noise.

Aerodynamic noise

Aerodynamic noise generated by the ceramic industry centrifuge used is usually divided into rotating noise , eddy noise and impact noise.

Rotation noise

Noise Noise called rotary blade , it is periodic pressure turbine blades rotating at high speed by the gas generated by the pulse noise caused by the gas pressure and velocity changes generated . Specifically , when the fan impeller blades around the fan shaft rotates, the blades of the fan impeller with respect to the air movement , then at the exit of the high-speed rotation of the fan impeller blades gas channel along the circumferential direction of the gas passage smaller volute tongue ( between the diameter of the impeller blades and the minimum distance between the volute Office) at the time , will form a periodic pressure fluctuation and gas velocity fluctuations and velocity fluctuations caused by noise. Furthermore, the fan impeller blades rotate in the free space , with a gas at a fixed location adjacent the fan impeller blades will be induced force of the pressure field , causing the change in gas pressure fluctuation ; Since the fan rotates at high speed , the fan impeller blades frequently individually through the position corresponding to the generated gas pressure pulsation to be formed around the radiation noise.

Vortex noise

When the vortex noise , also known as vortex noise , on the one hand , the air from the air inlet, shaft drive and front disc into the internal centrifugal fans , due to the rapid changes in the gas flow path , the gas will have a dramatic compression or expansion of a vortex . On the other hand , when the airflow through the fan impeller blade passage , because the gas boundary layer flow separation will form a vortex noise. Specifically , the fan impeller blades when the relative air movement , air flow will be the fan impeller blades to form a barrier around the flow movement , then the fan impeller blades in the back of the line from the air flow along the surface of the rotor blades and the fan impeller the back of the blade without generating a gas flow in a stationary state relative to the gas accumulation region , the accumulation of this gas flow and the boundary region is unstable , viscous force of airflow generated by the entrainment , driving the gas accumulation zone gas movement relatively static state , and the formation of vortex source in the back of the fan impeller blades , expanding vortex source evolved and eventually became a vortex , vortex when expanded to a certain extent , a source from the back of the fan vortex impeller blades from and with the air flow downstream. When the vortex source from just one fan at the back of the impeller blades will form a new vortex source , and repeat the similar process.

Thus, the source of constant vortex formed at the back of the fan impeller blades , and grow out and produce a lot of swirl down the river . Since the center of the vortex pressure at the edge is not the same , so the process of the scroll from the source of the fan impeller blades from the back , the vortex will split disintegration resulting perturbations generated gas , then the fan impeller blades are frequently affected by this alternating disturbance gas forces. According to the principle of action and reaction shows that the fan impeller blades frequently applied to gas cyclical reaction , causing the gas to produce periodic compression and expansion , and to the surrounding acoustic radiation , which produce vortex noise.

Impact noise

Common ceramic industry impact noise generated by the centrifugal fan from the air flow when entering and leaving the centrifugal fan blades , the noise generated by the impact of noise and other components of the whistle when the air flow through the spiral generated by the volute tongue .

The dangers of noise

Noise is usually used ceramic industry generated centrifugal fans will pollute people and different ways of living and working environment , and a serious threat to people 's health through different pathways . Mainly in the following aspects:

( 1 ) : the noise impact on people's psychological and emotional and induce various diseases

The noise of people talking , phone calls , meetings , study, work , rest and sleep , etc., and serious damage to people's health . If people over many years living in noisy environments , people and easily tired , grumpy , etc. Over time, will damage the human ear 's auditory function, leading to hearing loss, severe and even cause noise-induced hearing loss . While clinical experience also shows that the development and progression of heart disease , hypertension , gastrointestinal problems and cancer and other diseases , are associated with the intensity of the noise has a close relationship . In addition, noise can also cause dizziness , headaches , mental fatigue, insomnia, memory loss and reduced fertility and other diseases.

( 2 ) : the effects of noise and reduce the efficiency of production safety

Due to noise , people prone to fatigue, distraction, decreased as a result of lower energy efficiency and decrease the quality of work and so on . And because of the masking effect of noise , people imperceptible sign of the presence of various accidents each alarm signal , can easily cause damage and personal equipment easily casualties occurred , seriously endangering the safety of production .

Ways to Control Noise

Ceramic Industrial noise generated by conventional centrifugal fans , usually through the inlet pipe , inlet , chassis , exhaust pipes, exhaust vents and fans and other space -based communication, and a serious threat to people 's living environment. For this reason our government issued the "industrial enterprises noise hygiene standards (draft ) " and the International Organization for Standardization (ISO) also provides that the noise can not be more than 85 db mining industry (A), public buildings , restaurants, hotels and entertainment venues , etc. noise generated can not be more than 75 db (A). According to the capacity of people to noise from the ceramics industry production plant nearest residential noise during the day and requires no more than 50-60 dB (A), the noise at night requires no more than 40-45 dB (A). In fact, the distance used in the ceramic industry centrifuge around 1-1.5 meters measured over noise typically up to 90-100 dB (A), sometimes even up to 105 db (A). Therefore, we must centrifuges used to noise ceramic industry for effective control and management, its control pathways is as follows:

Ways to control the mechanical noise

( 1 ) fan impeller , fan shafts, pulleys and couplings and other rotating parts are subject to rigorous static equilibrium and balance correction after passing the factory to be assembled into units granted .

( 2 ) regularly check all parts of the fan coupling bolts and anchor bolts are loose , the bearing is abnormal wear and poor lubrication , whether the belt tensioner and so on. If it is found abnormal , should stop immediately ruled out, never with a "sick " work.

( 3 ) When installed, the fan should be between the pad and the reinforced concrete foundation rubber, cork board or felt board and other soft materials , ceramic industry used to transmit vibrations to the centrifugal fan of reinforced concrete foundation to maximize weakened or eliminated, to reduce the purpose of the ceramic industry common centrifugal fan noise.

( 4 ) Installation section of rubber hose in the mouth of the inlet and exhaust fan can be used ceramic industry centrifugal fan duct vibration transmitted to maximize weakened or eliminated at the rubber hose , used to reduce the ceramic industry centrifuge noise.

Ways to control the motor noise

( 1 ) motor cooling fan blades are subject to rigorous static balance and dynamic balance correction after passing the factory to be assembled into units granted . Should also be a reasonable choice gap motor cooling fan blades and inlet ring between , etc., to effectively reduce the motor cooling fan blade rotation noise.

( 2 ) a reasonable selection of motor cooling fan blade shape and size and the size of the diameter of the fan blades and other parameters , to effectively reduce eddy current motor cooling fan noise .

( 3 ) If the low-frequency electromagnetic noise generated by the motor , the stator showed eccentric , uneven air gap , we can eliminate low-frequency electromagnetic noise generated by the motor through the motor stator repair or replacement ; If the motor generates high frequency electromagnetic noise , indicating that the rotor has defects by repair or replacement of the rotor can eliminate the high-frequency electromagnetic noise generated by the motor .

( 4 ) should be regularly checked various components inside the motor coupling bolts are loose, the motor bearings are abnormal wear and poor lubrication . If it is found abnormal , should stop immediately ruled out, never with a "sick " work.

Ways to control the aerodynamic noise

( 1 ) fan inlet and exhaust muffler installed at the mouth

Muffler is the use of porous sound-absorbing material to absorb sound energy , when sound waves through the air inlet and exhaust stickers lining the mouth of the porous sound-absorbing material , porous sound-absorbing acoustic materials will inspire countless holes in a dramatic air molecules moved , to overcome some of the acoustic energy and the viscous frictional resistance and resistance to heat and consumed converted , so as to achieve the purpose of reducing the aerodynamic noise generated by the ceramic industry for the centrifuge used . Practical experience shows that installing the muffler inlet and exhaust ports in the ceramic industry at common centrifugal fan , usually to reduce aerodynamic noise intake vents and exhaust vents generated at about 20-30 dB (A).

( 2 ) Set the fan inlet fairing

The exhaust port by the impeller blades commonly used industrial sizes of ceramic is generally greater than the centrifugal fan at the inlet of the front disk size, the air flow of the fan , the vortex formed in many parts of the inlet arc segment ( Figure 1 ) , eddy current will be generated and fan inlet volute and several parts frequently collide to form aerodynamic noise. If the fan is located at the periphery of the internal spiral design in place to prevent the fan inlet fairing generates eddy currents ( Figure 1 ) , namely the creation of the rectifier baffle ring and can effectively prevent the formation of air flow at the fan inlet vortex , so as to achieve the purpose of reducing the aerodynamic noise generated by the ceramic industry of centrifuges used .

( 3 ) improve the structure of the fan volute form

The role of the ceramic industry is a collection of commonly used centrifuge volute outflows from high-speed air turbine impeller and guide high-speed airflow to the air vents , in the process , will hit the fan scroll speed airflow and aerodynamic noise generated . Scroll through the optimization and improvement of production processes, and streamlined production of precision logarithmic spiral volute scroll fan curve , we can effectively reduce aerodynamic noise generated by the ceramic industry of centrifuges used .

( 4 ) to improve gas flow fan impeller

Ceramic Industrial centrifuges used to reduce the impeller inlet wind speed , which can effectively reduce the flow rate of the gas turbine impeller flow channel , to achieve the purpose of reducing the aerodynamic noise generated by the ceramic industry used a centrifuge . If the fan impeller design the blade design made ??into a swept- twisted blades, that is, the fan impeller blades moderately tilted forward at the exhaust port , and in the air inlet and moderately tilted backwards , so you can avoid the gas flow path when dramatic changes to prevent gas swirl , so as to achieve the purpose of reducing aerodynamic noise centrifugal fan used ceramic industry generated .

Other ways to control noise

Usually sound when passing through the wall material uniformly dense , sound can be reduced or eliminated, the sound can weaken the more noise the better then . If using a sound-absorbing material between acoustic cover or insulation , ceramic industrial centrifuges used in this small enclosed space , will be able to prevent its spread to the outside noise , thus reducing the noise common purpose ceramic industry generated centrifugal fans .

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