n employee assembles a stroller in a factory of baby product company in Kunshan, Jiangsu province. [Photo/Xinhua]
>Economic rebound continues
國民經濟呈恢復性增長
China's economy continued to recover in the first two months of the year, with major economic indicators surging from last year's low base of comparison, the National Bureau of Statistics said on Monday.
據國家統計局3月15日公布的消息，2021年1-2月份我國國民經濟持續穩定恢復。
After deducting the base effect, major indicators grew steadily, with the economy performing within a reasonable range, the NBS said.
受2020年同期基數較低等因素影響，主要指標同比增速較高，扣除基數影響，主要指標增勢平穩，宏觀指數處于合理區間。
The country's industrial output rose 35.1 percent year-on-year in the January-February period, compared with 7.3 percent in December, the NBS said.
1-2月份，全國規模以上工業增加值同比增長35.1%，高于2020年12月份規模以上工業增加值同比增速(7.3%)。
Retail sales grew by 33.8 percent in the first two months on a yearly basis, compared with 4.6 percent in December, the bureau said.
1-2月份，社會消費品零售總額同比增長33.8%，高于2020年12月份社會消費品零售總額同比增速(4.6%)。
Fixed-asset investment rose by 35 percent year-on-year in the January-February period, up from 2.9 percent for the whole year of 2020.
1-2月份，全國固定資產投資(不含農戶)同比增長35%，高于2020年全國固定資產投資增長率(2.9%)。
The surveyed urban jobless rate came in at 5.4 percent in January and 5.5 percent in February, versus the government's annual control target of 5.5 percent, the bureau said.
1月份和2月份，全國城鎮調查失業率分別為5.4%和5.5%，政府要求今年城鎮調查失業率控制在5.5%以內。
Tourists view cherry blossoms at Jimingsi Road in Nanjing, East China's Jiangsu province, March 16, 2021. [Photo/Xinhua]
>Beijing relaxes COVID-19 curbs
低風險區進京無需證明
The city of Beijing will relax COVID-19 restrictions starting Tuesday as the Chinese capital has seen no new locally transmitted cases for over a month, the municipal government said Monday.
北京市人民政府3月15日表示，由于北京市已連續一個多月無新增報告本地確診病例，北京市將自3月16日起有序放開新冠疫情管控措施。
Those from domestic low-risk areas arriving in Beijing do not have to provide negative nucleic acid test results, and taxi and online car-hailing services between Beijing and other cities will resume, said Xu Hejian, the city government spokesperson.
北京市政府新聞發言人徐和建介紹，從3月16日零時起，國內低風險地區人員進返京不再需要持核酸檢測陰性證明，恢復進出北京市跨省出租車、網約車、順風車業務。
Temperature checks will also be unnecessary at community and village entrances, while indoor and outdoor cultural and entertainment venues such as parks, scenic spots, libraries, museums and theaters will be allowed to receive visitors up to 75 percent of capacity, Xu said, adding sales promotion activities will also be allowed.
社區村不再檢測體溫。按75%限流開放公園、景區、圖書館、博物館、影劇院等文化娛樂場所。允許組織開展促消費活動。
Patients with fevers will have to undergo nucleic acid tests, but antibody tests are no longer required for them.
發熱門診所有發熱患者進行核酸檢測，不再進行核酸抗體檢測。
University students outside Beijing can also return to their campuses with a green health code, according to the municipal government.
高校學生可持健康通行碼"綠碼"返校報到。
A Haier employee works at a washing machine production facility in Tianjin in June. [Photo/Xinhua]
>China boosts digital economy
'十四五'繪數字經濟藍圖
The digital economy will become a key ingredient of national strategy during the 14th Five-Year Plan period (2021-25), experts in the technology sector said.
科技行業專家表示，數字經濟將成為"十四五"期間國家發展戰略中的關鍵部分。
Through its newly released outline of the 14th Five-Year Plan, Beijing is expecting the digital economy to account for around 10 percent of its newly added economic output by 2025.
根據中國政府最新公布的"十四五"規劃綱要，2025年我國數字經濟核心產業增加值占GDP比重將提升至10%。
The fact a digital China is singled out as a stand-alone chapter in the latest government directive is a clear indication of the sector's increasing prominence in driving economic growth and empowering all walks of life, said Shao Yu, chief economist at Orient Securities.
東方證券首席經濟學家邵宇指出，"十四五"規劃綱要將建設數字中國作為獨立篇章是一個明確信號，數字經濟的重要性日趨顯著，將驅動經濟增長、賦能各行各業。
"It shows that China regards the transformation and upgrading of the digital economy as a key window of opportunity in the next 10 years, and the digital economy will become the 'core component' fueling economic transformation," Shao said.
邵宇說，這意味著中國將把數字經濟的轉型升級作為未來10年關鍵的機會窗口，數字經濟將成為整個中國經濟轉型的核心部件。
The closed doors of a bar are seen in Paris as part of COVID-19 restrictions measures to fight the coronavirus disease outbreak in France, March 16, 2021. [Photo/Agencies]
>Third COVID wave sweeps EU
歐多國被迫重啟封鎖令
A third wave of the COVID pandemic is now advancing swiftly across much of Europe.
第三輪新冠疫情如今正席卷歐洲大部分國家。
As a result, many nations – bogged down by sluggish vaccination campaigns – are witnessing sharp rises in infection rates and case counts.
隨之而來的是，由于疫苗接種項目停滯不前而陷入困境的多個國家正經歷感染率和確診病例數量的急劇上升。
The infection rate in the EU is now at its highest level since the beginning of February, with the spread of new variants of the COVID-19 virus being blamed for much of the recent increase.
歐盟國家的感染率目前達到了二月初以來的最高水平。近期確診病例的飆升很大程度被歸咎于新冠病毒新變種的傳播。
From this week most of Italy will be placed under lockdown and people will only be allowed to leave their homes for essential errands.
本周起，意大利大部分地區將進入封鎖，人們只有在辦理重要事務時才能出門。
Most shops will be closed, along with bars and restaurants.
大多數商店、酒吧和餐廳都要關閉。
In France, authorities have reported a similar grim situation, with health minister Olivier Véran describing the situation in the greater Paris region as tense and worrying.
法國政府報告了相似的嚴峻形勢，衛生部長奧利維耶?韋蘭稱大巴黎區的局勢緊張而令人不安。
In Germany, 12,674 new infections were reported on Saturday, a rise of 3,117 from the previous week, as the head of the country's infectious disease agency acknowledged the country was now in the grip of a third wave.
3月13日，德國報告了12674例新增病例，比上周增加了3117例。德國傳染病研究中心負責人承認，德國暴發了第三輪新冠疫情。
Several countries are now set to impose strict new lockdown measures in the next few days – in contrast to the UK, which is beginning to emerge slowly from its current bout of shop and school closures and sports bans.
現在多個國家正計劃在未來幾天實施嚴格的新封鎖措施，相比之下，英國目前處于關閉狀態的商店和學校正要逐漸開放，并計劃放松體育比賽禁令。
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來源：chinadaily.com.cn
一、風機分類及用途
按作用原理分類
透平式風機--通過旋轉葉片壓縮輸送氣體的風機。
容積式風機—用改變氣體容積的方法壓縮及輸送氣體機械。
分機分類
按氣流運動方向分類：
離心式風機—氣流軸向駛入風機葉輪后，在離心力作用下被壓縮，主要沿徑向流動。
軸流式風機—氣流軸向駛入旋轉葉片通道，由于葉片與氣體相互作用，氣體被壓縮后近似在園柱型表面上沿軸線方向流動。
混流式風機—氣體與主軸成某一角度的方向進入旋轉葉道，近似沿錐面流動。
橫流式風機—氣體橫貫旋轉葉道，而受到葉片作用升高壓力。
按生產壓力的高低分類(以絕對壓力計算)
通風機—排氣壓力低于112700Pa；
鼓風機—排氣壓力在112700Pa~343000Pa之間；
壓縮機—排氣壓力高于343000Pa以上；
通風機高低壓相應分類如下(在標準狀態下)
低壓離心通風機：全壓P≤1000Pa
中壓離心通風機：全壓P=1000~5000Pa
高壓離心通風機：全壓P=5000~30000Pa
低壓軸流通風機：全壓P≤500Pa
高壓軸流通風機：全壓P=500~5000Pa
一般通風機全稱表示方法
一般通風機全稱表示方法
型式和品種組成表示方法
型式和品種組成表示方法
二、風機計算單位
壓力:離心通風機的壓力指升壓（相對于大氣的壓力）,即氣體在風機內壓力的升高值或者該風機進出口處氣體壓力之差。它有靜壓、動壓、全壓之分。性能參數指全壓（等于風機出口與進口總壓之差）,其單位常用Pa、KPa、mmaq、mH2O、mmH2O等。
流量:單位時間內流過風機的氣體容積,又稱風量。常用Q來表示,常用單位是;m3/s、m3/min、m3/h（秒、分、小時）。(有時候也用到“質量流量”即單位時間內流過風機的氣體質量,這個時候需要考慮風機進口的氣體密度,與氣體成份,當地大氣壓,氣體溫度,進口壓力有密切影響,需經換算才能得到習慣的“氣體流量”。
轉速：風機轉子旋轉速度。常以n來表示、其單位用r/min(r表示轉速，min表示分鐘)。
功率：驅動風機所需要的功率。常以N來表示、其單位用Kw。
三、風機常用參數、技術要求
一般通、引風機：全壓P=…Pa、流量Q=…m3/h、海拔高度（當地大氣壓）、傳動方式、輸送介質(空氣可不寫)、葉輪旋向、進出口角度(從電機端正視)、工作溫度T=…℃(常溫可不寫)、電動機型號等。
高溫風機及其它特殊風機：全壓P=…Pa、流量Q=…m3/h、進口氣體密度Kg/m3、傳動方式、輸送介質(空氣可不寫)、葉輪旋向、進出口角度(從電機端正視)、工作溫度T=.....℃、瞬時最高溫度T=…℃、進口氣體密度□Kg/m3、當地大氣壓(或當地海撥高度)、含塵濃度、風機調節門、電動機型號、進出口膨脹節、整體底座、液力偶合器(或變頻器、液體電阻啟動器)、稀油站、慢轉裝置、執行器、啟動柜、控制柜等。
風機常需用的計算公式：
1、軸功率:
軸功率計算
注:0.8是風機效率,是一個變數,0.98是一個機械效率也是一個變數（直連傳動風機為1；聯軸器聯接轉動為0.98；皮帶傳動風機為0.95；）
2、風機全壓：(未在標準情況下修正)
風機全壓計算
式中:P1=工況全壓(Pa)、P2=設計標準壓力(或表中全壓Pa)、B=當地大氣壓(mmHg)、T2=工況介質溫度℃、T1=表中或未修正的設計溫度℃、760mmHg=在海拔0m,空氣在20℃情況下的大氣壓。
2.1海撥高度換算當地大氣壓：
(760mmHg)－(海撥高度÷12.75)=當地大氣壓 (mmHg)
注:海拔高度在300m以下的可不修正。
1mmH2O=9.8073Pa
1mmHg=13.5951 mmH2O
760 mmHg=10332.3117 mmH2O
2.2風機流量0～1000m海撥高度時可不修正；1000～1500M海撥高度時加2%的流量；
1500～2500M海撥高度時加3%的流量；2500M以上海撥高度時加5%的流量。
比轉速:ns
比轉速
注: ρ氣體密度（Kg/m3）;公式:P1=P2×1.2/ρ、ρ=1.2×(273+T2)/(273+20）；
20℃=1.2、50℃=1.089、80℃=0.996、100℃=0.943、150℃=0.813、200℃=0.743、250℃=0.672、280℃=0.636、300℃=0.614、350℃=0.564。
壓力系數:
壓力系數
ψ=壓力系數、P=全壓(Pa)、ρ=氣體密度(Kg/m3)、U=葉輪外緣園周速度(m/s)。
風機最大扭矩:
550×電機功率÷轉速=….Nm(一般是大型電機,或用戶需要的)
風機的動載荷系數:
2900轉是0.5、1450轉是0.25、960轉是0.175、580轉是0.0875
調節門的扭矩:
Tmix=(2～2.5)×10－6×Q3/2×P=….N.m