To improve acoustic performance of an air cleaner system,both experimental and theoretical studies were carried out.The air cleaner＇s acoustic numerical model was built by finite element methods（FEM）.Acoustic param...To improve acoustic performance of an air cleaner system,both experimental and theoretical studies were carried out.The air cleaner＇s acoustic numerical model was built by finite element methods（FEM）.Acoustic parameters of filter paper imported in the FEM model were calculated according to experiential formulas.Based on the models,the cleaner＇s acoustic character of transmission loss（TL） was computed.To verify the numerical results,TL results of the real air cleaner with or without filter paper were tested by four-microphone transferring function method.The experimental results show that the filter paper influence acoustic performance of the air cleaner significantly,especially in mid and high frequency band,and should be considered in numerical simulation.Comparisons between experimental and numerical results show that the numerical model is accurate enough to be used in multi-scheme acoustic optimization.Based on our study,TL results of two schemes were calculated and analyzed,which is useful to the air cleaner＇s final design decision.展开更多
This paper reports results of the authors’ studies on the virtual design method used in the development of low noise intake system of I.C. engine. The resulting high pass-by noise at level above the legislative targe...This paper reports results of the authors’ studies on the virtual design method used in the development of low noise intake system of I.C. engine. The resulting high pass-by noise at level above the legislative target at full throttle when engine speed was around 5200 r/min necessitated a BEM-aided redesign task, following the typical process of design and development of an intake system. During the initial design, based on the acoustic theory and the requirements (1. The air flux of the redesigned should equal to or exceed the value of the original flux; 2. The filtering area must not be degraded), and considering the constraint of space in the engine compartment, total volume and rough internal dimensions were determined. During the detailed design, the exact internal dimensions of the air cleaner were determined, and an effective method was applied to improve the acoustic performance at low frequency. The predicted sound power of the intake system indicated that the objective of reducing the overall engine noise by minimizing intake system noise was achieved.展开更多
Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is pollut...Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.展开更多
This study assessed six commercially available in-duct air cleaning devices which are designed to be mounted in the central ventilation system of offices or commercial buildings.The selected devices use different air ...This study assessed six commercially available in-duct air cleaning devices which are designed to be mounted in the central ventilation system of offices or commercial buildings.The selected devices use different air cleaning technologies:mechanical filtration,electrostatic precipitation,gas filtration,ionization/cold plasma,photocatalytic oxidation(PCO)and catalysis under UV light.They were tested against particles,a mixture of volatile organic compounds containing acetone,acetaldehyde,toluene,heptane and formaldehyde,and two bio-contaminants:Aspergillus brasiliensis(fungus)and Staphylococcus epidermidis(bacteria).Two different test rigs were used.The single pass efficiency of each device was determined for three airflow rates,corresponding to face velocities ranging from 0.9 to 2.7 m/s,and two sets of temperature and humidity that are representative of indoor air conditions in wintertime and summertime.The concentration of the chal-lenge volatile organic compounds was also varied in the 30 to 100μg/m^(3)range as a way to characterize their influence on efficiency at realistic concentration levels for non-industrial buildings.Measurements of ozone and formaldehyde concentration downstream of the air cleaners were carried out to determine the emission rate of by-products into the air stream.Finally,the energy issue was addressed by measuring the electric power drawn and pressure loss of the devices.The results showed that two devices,namely a radiant catalytic ionizer and a plasma ionizer,had a very low single pass efficiency against all the challenge pollutants.The association of the plasma ionizer and the electrostatic precipitator did not produce a synergetic effect between the two technologies either,contrary to what their manufacturer claims.Finally,three of the six devices tested were effective in terms of pollutant removal,but only two had an acceptable energy effectiveness in view of their use in low or zero energy buildings.Their energy effectiveness ranged from a few thousand m^(3)/kWh for VOCs at the highest airflow rate(3600 m^(3)/h),to more than 60000 m^(3)/kWh for particles and bio-contaminants at 1200 or 1600 m^(3)/h.These results are at least one order of magnitude higher than the majority of stand-alone air cleaners.Moreover,they suggest that optimal IAQ and energy conditions can be achieved if variable air volume control methods are used to maintain indoor temperature and humidity.展开更多
A novel air-cleaner with a coil-shape photocatalysis-plasma synergistic reactor was developed. The air-cleaner showed 95% ± 1% reduction of a TVOCs concentration in tobacco smoke at “single-pass” condition. Air...A novel air-cleaner with a coil-shape photocatalysis-plasma synergistic reactor was developed. The air-cleaner showed 95% ± 1% reduction of a TVOCs concentration in tobacco smoke at “single-pass” condition. Air-purification activity of the air-cleaner was stably-maintained after the treatment of 12,000 cigarettes of tobacco smoke.展开更多
基金Supported by Ministerial Level Advanced Research Foundation(1030021200706)
文摘To improve acoustic performance of an air cleaner system,both experimental and theoretical studies were carried out.The air cleaner＇s acoustic numerical model was built by finite element methods（FEM）.Acoustic parameters of filter paper imported in the FEM model were calculated according to experiential formulas.Based on the models,the cleaner＇s acoustic character of transmission loss（TL） was computed.To verify the numerical results,TL results of the real air cleaner with or without filter paper were tested by four-microphone transferring function method.The experimental results show that the filter paper influence acoustic performance of the air cleaner significantly,especially in mid and high frequency band,and should be considered in numerical simulation.Comparisons between experimental and numerical results show that the numerical model is accurate enough to be used in multi-scheme acoustic optimization.Based on our study,TL results of two schemes were calculated and analyzed,which is useful to the air cleaner＇s final design decision.
文摘This paper reports results of the authors’ studies on the virtual design method used in the development of low noise intake system of I.C. engine. The resulting high pass-by noise at level above the legislative target at full throttle when engine speed was around 5200 r/min necessitated a BEM-aided redesign task, following the typical process of design and development of an intake system. During the initial design, based on the acoustic theory and the requirements (1. The air flux of the redesigned should equal to or exceed the value of the original flux; 2. The filtering area must not be degraded), and considering the constraint of space in the engine compartment, total volume and rough internal dimensions were determined. During the detailed design, the exact internal dimensions of the air cleaner were determined, and an effective method was applied to improve the acoustic performance at low frequency. The predicted sound power of the intake system indicated that the objective of reducing the overall engine noise by minimizing intake system noise was achieved.
基金This study was jointly funded by the National Key Research and Development Program of China(No.2016YFC0700500)the Opening Fund of Key Laboratory of Plateau Green Building and Ecological Community in Qinghai Province(No.KLKF-2020-005).
文摘Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.
文摘This study assessed six commercially available in-duct air cleaning devices which are designed to be mounted in the central ventilation system of offices or commercial buildings.The selected devices use different air cleaning technologies:mechanical filtration,electrostatic precipitation,gas filtration,ionization/cold plasma,photocatalytic oxidation(PCO)and catalysis under UV light.They were tested against particles,a mixture of volatile organic compounds containing acetone,acetaldehyde,toluene,heptane and formaldehyde,and two bio-contaminants:Aspergillus brasiliensis(fungus)and Staphylococcus epidermidis(bacteria).Two different test rigs were used.The single pass efficiency of each device was determined for three airflow rates,corresponding to face velocities ranging from 0.9 to 2.7 m/s,and two sets of temperature and humidity that are representative of indoor air conditions in wintertime and summertime.The concentration of the chal-lenge volatile organic compounds was also varied in the 30 to 100μg/m^(3)range as a way to characterize their influence on efficiency at realistic concentration levels for non-industrial buildings.Measurements of ozone and formaldehyde concentration downstream of the air cleaners were carried out to determine the emission rate of by-products into the air stream.Finally,the energy issue was addressed by measuring the electric power drawn and pressure loss of the devices.The results showed that two devices,namely a radiant catalytic ionizer and a plasma ionizer,had a very low single pass efficiency against all the challenge pollutants.The association of the plasma ionizer and the electrostatic precipitator did not produce a synergetic effect between the two technologies either,contrary to what their manufacturer claims.Finally,three of the six devices tested were effective in terms of pollutant removal,but only two had an acceptable energy effectiveness in view of their use in low or zero energy buildings.Their energy effectiveness ranged from a few thousand m^(3)/kWh for VOCs at the highest airflow rate(3600 m^(3)/h),to more than 60000 m^(3)/kWh for particles and bio-contaminants at 1200 or 1600 m^(3)/h.These results are at least one order of magnitude higher than the majority of stand-alone air cleaners.Moreover,they suggest that optimal IAQ and energy conditions can be achieved if variable air volume control methods are used to maintain indoor temperature and humidity.
文摘A novel air-cleaner with a coil-shape photocatalysis-plasma synergistic reactor was developed. The air-cleaner showed 95% ± 1% reduction of a TVOCs concentration in tobacco smoke at “single-pass” condition. Air-purification activity of the air-cleaner was stably-maintained after the treatment of 12,000 cigarettes of tobacco smoke.
