Standard ca-platform tso tsheb hlau luam rau BEVs thiab FCEVs siv cov thermoplastic thiab thermoset composites nrog lub cev pob txha tsim uas muab 25% ntau H2 cia.#hydrogen #kev
Tom qab kev koom tes nrog BMW tau pom tias lub cubic tank tuaj yeem xa cov khoom siv hluav taws xob ntau dua li ntau lub tog raj kheej me me, Technical University of Munich tau pib ua ib txoj haujlwm los tsim cov qauv sib xyaw thiab cov txheej txheem tsim ua kom muaj peev xwm rau kev tsim khoom.Duab credit: TU Dresden (sab saum toj) sab laug), Technical University of Munich, Department of Carbon Composites (LCC)
Roj cell electric tsheb (FCEVs) powered los ntawm xoom-emission (H2) hydrogen muab ntxiv txhais tau tias kom ua tiav xoom ib puag ncig lub hom phiaj.Lub tsheb roj ntawm cov neeg caij tsheb nrog lub cav H2 tuaj yeem ua tiav hauv 5-7 feeb thiab muaj qhov sib txawv ntawm 500 km, tab sis tam sim no kim dua vim muaj cov khoom ntim tsawg.Ib txoj hauv kev los txo cov nqi yog siv lub platform rau BEV thiab FCEV qauv.Qhov no tam sim no tsis tuaj yeem ua tau vim tias hom 4 cylindrical tanks siv los khaws cov roj compressed H2 (CGH2) ntawm 700 bar hauv FCEVs tsis haum rau cov roj teeb hauv qab uas tau ua tib zoo tsim rau lub tsheb fais fab.Txawm li cas los xij, cov hlab ntsha siab hauv daim ntawv hauv ncoo thiab lub voos xwmfab tuaj yeem haum rau hauv qhov chaw ntim khoom.
Patent US5577630A rau "Composite Conformal Pressure Vessel", daim ntawv thov ua ntaub ntawv los ntawm Thiokol Corp. hauv 1995 (sab laug) thiab lub nkoj lub siab sib npaug patented los ntawm BMW hauv 2009 (txoj cai).
Lub Department of Carbon Composites (LCC) ntawm Technical University of Munich (TUM, Munich, Lub teb chaws Yelemees) tau koom nrog ob txoj haujlwm los tsim lub tswv yim no.Thawj yog Polymers4Hydrogen (P4H), coj los ntawm Leoben Polymer Competence Center (PCCL, Leoben, Austria).Cov pob khoom ua haujlwm LCC yog coj los ntawm Fellow Elizabeth Glace.
Qhov project thib ob yog Hydrogen Demonstration and Development Environment (HyDDen), qhov twg LCC yog coj los ntawm Researcher Christian Jaeger.Ob lub hom phiaj los tsim ib qho kev nthuav qhia loj ntawm cov txheej txheem tsim khoom rau kev ua kom haum CGH2 tank siv carbon fiber composites.
Muaj kev txwv qhov kev ua tau zoo thaum lub taub me me lub tog raj kheej tau teeb tsa hauv cov roj teeb tiaj tus (sab laug) thiab cov thawv cubic hom 2 siab cov hlab ntsha ua los ntawm cov hlua hlau thiab cov roj carbon fiber ntau / epoxy composite sab nraud (txoj cai).Duab Source: Daim duab 3 thiab 6 yog los ntawm "Numerical Design Approach for Type II Pressure Box Vessel with Internal Tension Legs" los ntawm Ruf thiab Zaremba li al.
P4H tau tsim ib qho kev sim ntsuas lub tank uas siv cov thermoplastic thav duab nrog cov hlua khi / cov hlua qhwv hauv cov pa roj carbon fiber reinforced epoxy.HyDDen yuav siv cov qauv tsim zoo sib xws, tab sis yuav siv cov khoom siv fiber ntau tsis siv neeg (AFP) los tsim tag nrho cov thermoplastic composite tso tsheb hlau luam.
Los ntawm daim ntawv thov patent los ntawm Thiokol Corp. mus rau "Composite Conformal Pressure Vessel" nyob rau hauv 1995 rau German Patent DE19749950C2 nyob rau hauv 1997, compressed gas hlab ntsha "tej zaum yuav muaj tej geometric configuration", tab sis tshwj xeeb tshaj yog cov tiaj tus thiab irregular shapes, nyob rau hauv ib tug kab noj hniav txuas nrog lub plhaub txhawb nqa. .cov ntsiab lus tau siv kom lawv tuaj yeem tiv taus lub zog ntawm kev nthuav dav ntawm cov pa.
Ib daim ntawv xyoo 2006 Lawrence Livermore National Laboratory (LLNL) piav txog peb txoj hauv kev: lub filament qhov txhab conformal siab hlab ntsha, lub microlattice siab hlab uas muaj cov qauv hauv orthorhombic lattice (cov hlwb me me ntawm 2 cm lossis tsawg dua), ib puag ncig los ntawm lub thawv H2 nyias, thiab ib lub thawv replicator, uas muaj cov qauv sab hauv uas muaj cov nplaum me me (xws li, hexagonal yas rings) thiab cov khoom sib xyaw ntawm cov tawv nqaij nyias nyias.Cov thawv ntim khoom sib tw yog qhov zoo tshaj plaws rau cov thawv loj uas cov txheej txheem ib txwm siv yuav nyuaj rau kev thov.
Patent DE102009057170A tau foob los ntawm Volkswagen hauv 2009 piav qhia txog lub tsheb-mounted siab nkoj uas yuav muab kev ua haujlwm hnyav thaum txhim kho qhov chaw siv.Rectangular tso tsheb hlau luam siv nro connectors ntawm ob lub voj voog rov qab phab ntsa, thiab cov ces kaum yog sib npaug.
Cov lus saum toj no thiab lwm cov ntsiab lus tau hais los ntawm Gleiss hauv daim ntawv "Txoj Kev Txhim Kho rau Cubic Pressure Vessels nrog Stretch Bars" los ntawm Gleiss li al.ntawm ECCM20 (Lub Rau Hli 26-30, 2022, Lausanne, Switzerland).Nyob rau hauv tsab xov xwm no, nws hais txog TUM txoj kev tshawb fawb luam tawm los ntawm Michael Roof thiab Sven Zaremba, uas pom tias lub cubic siab hlab ntsha nrog nro struts txuas cov duab plaub yog ua tau zoo dua li ob peb lub tog raj kheej me me uas haum rau qhov chaw ntawm lub roj teeb tiaj tus, muab kwv yees li 25. % ntau.qhov chaw cia.
Raws li Gleiss, qhov teeb meem ntawm kev txhim kho ntau yam me me 4 lub tog raj kheej hauv cov ntaub ntawv tiaj tus yog tias "qhov ntim ntawm lub tog raj kheej tau txo qis heev thiab lub kaw lus kuj tseem muaj H2 roj permeation saum npoo loj heev.Zuag qhia tag nrho, lub kaw lus muab lub peev xwm cia tsawg dua li cov thawv ntim. "
Txawm li cas los xij, muaj lwm yam teeb meem nrog lub tank lub cubic tsim.Gleiss tau hais tias "Qhov tseeb, vim yog cov pa roj compressed, koj yuav tsum tiv thaiv lub zog khoov ntawm cov phab ntsa tiaj tus," Gleiss tau hais."Rau qhov no, koj xav tau cov qauv siv zog ntxiv uas txuas sab hauv mus rau phab ntsa ntawm lub tank.Tab sis qhov ntawd nyuaj ua nrog cov khoom sib xyaw. "
Glace thiab nws pab neeg tau sim los koom nrog cov khoom siv zog ntxiv rau hauv lub nkoj siab hauv txoj hauv kev uas yuav tsim nyog rau cov txheej txheem filament winding.Nws piav qhia tias "Qhov no yog qhov tseem ceeb rau kev tsim cov khoom ntim siab," thiab tseem tso cai rau peb tsim cov qauv winding ntawm lub thawv phab ntsa kom ua kom zoo dua cov fiber ntau rau txhua qhov chaw hauv cheeb tsam."
Plaub kauj ruam los ua ib lub cubic composite tank rau P4H project.Duab credit: "Kev txhim kho ntawm cov txheej txheem tsim khoom rau cov hlab ntsha siab nrog kev sib txuas", Technical University of Munich, Polymers4Hydrogen project, ECCM20, Lub Rau Hli 2022.
Txhawm rau ua tiav ntawm cov saw hlau, pab pawg tau tsim lub tswv yim tshiab uas muaj plaub kauj ruam tseem ceeb, raws li qhia saum toj no.Lub nro struts, pom nyob rau hauv dub ntawm cov kauj ruam, yog ib tug prefabricated thav duab qauv fabricated siv txoj kev coj los ntawm MAI Skelett project.Rau txoj haujlwm no, BMW tau tsim lub tshuab ua cua sov "lub hauv paus" siv plaub fiber ntau ntxiv pultrusion rods, uas tau muab molded rau hauv ib lub thav duab yas.
Lub thav duab ntawm kev sim cubic tank.Hexagonal skeletal seem 3D luam tawm los ntawm TUM siv unreinforced PLA filament (sab saum toj), ntxig CF / PA6 pultrusion rods raws li nro braces (nruab nrab) thiab ces qhwv lub filament nyob ib ncig ntawm lub braces (hauv qab).Duab credit: Technical University of Munich LCC.
Glace tau hais tias "Lub tswv yim yog tias koj tuaj yeem tsim lub thav duab ntawm lub cubic tank raws li tus qauv qauv," Glace hais."Cov qauv no tom qab ntawd muab tso rau hauv cov cuab yeej molding, qhov nro struts tau muab tso rau hauv cov thav duab modules, thiab tom qab ntawd MAI Skelett txoj kev siv nyob ib ncig ntawm cov struts los ua ke nrog cov ncej."Cov txheej txheem ntau lawm, uas ua rau muaj cov qauv uas tom qab ntawd siv los ua ib lub mandrel los yog cov tub ntxhais los qhwv lub tank sib xyaw plhaub.
TUM tsim lub tank thav duab raws li lub cubic "cushion" nrog cov khoom sab, cov ces kaum sib npaug thiab cov qauv hexagonal nyob rau sab saum toj thiab hauv qab los ntawm kev sib txuas tuaj yeem ntxig thiab txuas.Lub qhov rau cov racks no kuj tau luam 3D."Rau peb lub tank sim thawj zaug, peb 3D luam tawm hexagonal thav duab seem siv polylactic acid [PLA, bio-based thermoplastic] vim tias nws yooj yim thiab pheej yig," Glace hais.
Pab neeg no tau yuav 68 pultruded carbon fiber reinforced polyamide 6 (PA6) rods los ntawm SGL Carbon (Meitingen, Lub teb chaws Yelemees) siv los ua kev sib raug zoo.Gleiss hais tias, "Kom sim lub tswv yim, peb tsis tau ua ib qho molding," tab sis tsuas yog ntxig spacers rau hauv 3D luam ntawv honeycomb core thav duab thiab glued lawv nrog epoxy kua nplaum.Qhov no ces muab ib lub mandrel rau winding lub tank. "Nws sau tseg tias txawm hais tias cov pas nrig no yooj yim rau cua, muaj qee qhov teeb meem tseem ceeb uas yuav piav qhia tom qab.
"Thaum thawj theem, peb lub hom phiaj yog los ua kom pom kev tsim khoom tsim thiab txheeb xyuas cov teeb meem hauv lub tswv yim tsim khoom," piav qhia Gleiss."Yog li qhov nro struts protrude los ntawm sab nrauv ntawm lub cev pob txha, thiab peb txuas cov carbon fibers rau cov tub ntxhais no siv cov ntaub ntub dej ntub dej.Tom qab ntawd, nyob rau theem peb, peb khoov lub taub hau ntawm txhua txoj hlua khi.thermoplastic, yog li peb tsuas yog siv cov cua sov los hloov lub taub hau kom nws flattens thiab xauv rau hauv thawj txheej ntawm qhwv.Peb mam li mus qhwv cov qauv dua kom lub taub hau tiaj tiaj yog geometrically nyob rau hauv lub tank.laminate rau ntawm phab ntsa.
Spacer cap rau winding.TUM siv lub kaus mom yas ntawm qhov kawg ntawm qhov nro rods los tiv thaiv cov fibers los ntawm tangling thaum filament winding.Duab credit: Technical University of Munich LCC.
Glace rov hais dua tias thawj lub tank no yog qhov pov thawj ntawm lub tswv yim."Kev siv 3D luam ntawv thiab kua nplaum tsuas yog rau kev sim thawj zaug thiab muab peb lub tswv yim ntawm qee qhov teeb meem uas peb ntsib.Piv txwv li, thaum lub sij hawm winding, cov filaments raug ntes los ntawm qhov kawg ntawm qhov nro rods, ua rau fiber ntau tawg, fiber ntau puas, thiab txo cov fiber ntau los tiv thaiv qhov no.peb siv ob peb lub kaus mom yas ua cov khoom siv uas tau muab tso rau ntawm tus ncej ua ntej thawj kauj ruam winding.Tom qab ntawd, thaum cov laminates sab hauv tau tsim, peb tshem cov kaus mom tiv thaiv no thiab kho qhov kawg ntawm tus ncej ua ntej kawg qhwv. "
Pab neeg no tau sim nrog ntau yam kev tsim kho dua tshiab.Grace hais tias "Cov neeg uas saib ib puag ncig ua haujlwm zoo tshaj plaws," Grace hais."Tsis tas li ntawd, thaum lub sij hawm prototyping, peb siv cov cuab yeej hloov kho los siv cov cua sov thiab kho cov hlua khi xaus.Nyob rau hauv lub tswv yim ntau lawm, koj yuav muaj ib lub cuab yeej loj uas tuaj yeem tsim thiab tsim txhua qhov kawg ntawm cov struts rau hauv ib lub laminate tha xim sab hauv tib lub sijhawm..”
Drawbar taub hau reshaped.TUM tau sim nrog cov tswv yim sib txawv thiab hloov kho cov welds los kho qhov kawg ntawm cov kev sib txuas sib txuas rau txuas rau lub tank phab ntsa laminate.Duab credit: "Kev txhim kho ntawm cov txheej txheem tsim khoom rau cov hlab ntsha siab nrog kev sib txuas", Technical University of Munich, Polymers4Hydrogen project, ECCM20, Lub Rau Hli 2022.
Yog li, lub laminate yog kho tom qab thawj kauj ruam winding, cov ncej yog hloov dua siab tshiab, TUM ua tiav qhov thib ob winding ntawm filaments, thiab tom qab ntawd lub tank sab nrauv laminate yog kho dua zaum ob.Thov nco ntsoov tias qhov no yog hom 5 lub tank tsim, uas txhais tau hais tias nws tsis muaj cov yas liner li cov roj barrier.Saib cov kev sib tham hauv Cov Kauj Ruam Tom ntej hauv qab no.
Glace tau hais tias "Peb tau txiav thawj qhov kev ua yeeb yam rau hauv ntu ntu thiab kos duab thaj chaw sib txuas," Glace tau hais."Ib qho ze ze qhia tau tias peb muaj qee qhov teeb meem zoo nrog lub laminate, nrog lub taub hau strut tsis nteg ncaj nraim rau sab hauv laminate."
Kev daws teeb meem nrog qhov khoob ntawm lub laminate ntawm sab hauv thiab sab nrauv ntawm lub tank.Hloov khi hlua lub taub hau tsim qhov sib txawv ntawm thawj thiab thib ob lem ntawm lub tank sim.Duab credit: Technical University of Munich LCC.
Qhov thawj zaug 450 x 290 x 80mm tank tau ua tiav lub caij ntuj sov dhau los.Glace tau hais tias "Peb tau ua tiav ntau yam txij li ntawd los, tab sis peb tseem muaj qhov sib txawv ntawm sab hauv thiab sab nrauv laminate," Glace hais."Yog li peb tau sim ua kom tiav cov qhov khoob no nrog cov dej huv, siab viscosity resin.Qhov no ua tau zoo txhim kho kev sib txuas ntawm cov studs thiab laminate, uas ua rau muaj kev ntxhov siab heev. "
Pab neeg no txuas ntxiv txhim kho lub tank tsim thiab txheej txheem, suav nrog kev daws teeb meem rau qhov xav tau winding qauv.Glace piav qhia tias "Lub sab ntawm lub tank sim tsis tau curled tag nrho vim tias nws nyuaj rau qhov geometry no los tsim txoj kev winding," Glace piav qhia."Peb lub kaum sab xis pib winding yog 75 °, tab sis peb paub tias ntau lub voj voog yuav tsum tau ua kom tau raws li lub nra ntawm lub nkoj siab no.Peb tseem tab tom nrhiav kev daws teeb meem rau qhov teeb meem no, tab sis nws tsis yooj yim nrog software tam sim no ntawm kev ua lag luam.Tej zaum nws yuav dhau los ua ib txoj haujlwm taug qab.
Gleiss hais tias, "Peb tau ua kom pom qhov ua tau ntawm lub tswv yim tsim khoom no," tab sis peb yuav tsum ua haujlwm ntxiv los txhim kho kev sib txuas ntawm laminate thiab kho cov hlua khi.“Kev kuaj sab nraud ntawm lub tshuab kuaj.Koj rub cov spacers tawm ntawm lub laminate thiab sim cov khoom siv kho tshuab uas cov pob qij txha tuaj yeem tiv taus. "
Qhov no ntawm Polymers4Hydrogen qhov project yuav ua tiav thaum kawg ntawm 2023, los ntawm lub sijhawm ntawd Gleis vam tias yuav ua tiav qhov kev ua yeeb yam thib ob.Interestingly, cov qauv tsim niaj hnub no siv cov thermoplastics zoo zoo hauv cov ncej thiab cov thermoset sib xyaw hauv cov phab ntsa tank.Puas yog txoj hauv kev no hybrid yuav siv rau hauv qhov kev ua yeeb yam zaum kawg?"Yog," Grace hais."Peb cov koom tes hauv Polymers4Hydrogen project tab tom tsim epoxy resins thiab lwm cov ntaub ntawv sib xyaw matrix nrog cov khoom siv hydrogen zoo dua."Nws teev ob tus neeg koom tes ua haujlwm rau txoj haujlwm no, PCCL thiab University of Tampere (Tampere, Finland).
Gleiss thiab nws pab neeg kuj tau sib pauv ntaub ntawv thiab sib tham tswv yim nrog Jaeger ntawm qhov thib ob HyDDen qhov project los ntawm LCC conformal composite tank.
Jaeger hais tias "Peb yuav tsim lub nkoj sib xyaw ua ke rau kev tshawb fawb drones," Jaeger hais."Qhov no yog kev sib koom tes ntawm ob lub tuam tsev ntawm Aerospace thiab Geodetic Department ntawm TUM - LCC thiab Department of Helicopter Technology (HT).Qhov project yuav ua tiav thaum kawg ntawm 2024 thiab tam sim no peb tab tom ua tiav lub nkoj siab.ib tug tsim uas yog ntau ntawm aerospace thiab automotive mus kom ze.Tom qab lub tswv yim pib theem no, cov kauj ruam tom ntej yog ua kom paub cov qauv qauv thiab kwv yees qhov kev ua tau zoo ntawm cov txheej txheem phab ntsa. "
"Lub tswv yim tag nrho yog los tsim ib qho kev tshawb nrhiav drone nrog hybrid roj cell thiab roj teeb propulsion system," nws hais ntxiv.Nws yuav siv lub roj teeb thaum lub sij hawm muaj zog loads (piv txwv li takeoff thiab landing) thiab ces hloov mus rau lub roj cell thaum lub teeb load cruising."Cov pab pawg HT twb muaj kev tshawb fawb drone thiab rov tsim lub zog tsheb ciav hlau siv ob lub roj teeb thiab roj hlwb," Yeager tau hais."Lawv kuj tau yuav lub tank CGH2 los kuaj qhov kis no."
"Kuv pab neeg tau ua haujlwm los tsim lub tank siab tus qauv uas yuav haum, tab sis tsis yog vim muaj teeb meem ntim khoom uas lub tank cylindrical yuav tsim," nws piav qhia.“Lub tank flatter tsis muaj cua tiv taus ntau npaum li cas.Yog li koj tau txais kev ua haujlwm dav hlau zoo dua. "Tank qhov ntev approx.830 x 350 x 173 mm.
Tag nrho cov thermoplastic AFP raws tank.Rau HyDDen qhov project, LCC pab pawg ntawm TUM tau pib tshawb nrhiav qhov zoo sib xws rau qhov uas siv los ntawm Glace (saum toj no), tab sis tom qab ntawd tsiv mus rau txoj hauv kev uas siv kev sib xyaw ua ke ntawm ntau cov qauv qauv, uas tau dhau los siv AFP (hauv qab).Duab credit: Technical University of Munich LCC.
Yager hais tias, "Ib lub tswv yim zoo ib yam li Elisabeth [Gleiss] txoj hauv kev," Yager hais tias, "kom siv cov hlua khi rau ntawm phab ntsa ntawm lub nkoj kom them nyiaj rau lub zog khoov siab.Txawm li cas los xij, tsis txhob siv cov txheej txheem winding los ua lub tank, peb siv AFP.Yog li ntawd, peb xav txog kev tsim ib qho kev sib cais ntawm cov hlab ntsha siab, uas cov racks twb tau ua ke.Txoj hauv kev no tso cai rau kuv los ua ke ob peb ntawm cov kev sib koom ua ke no thiab tom qab ntawd siv lub hau kawg kom kaw txhua yam ua ntej qhov kawg AFP winding. "
"Peb tab tom sim ua kom tiav lub tswv yim zoo li no," nws hais ntxiv, "thiab tseem pib sim xaiv cov khoom siv, uas yog qhov tseem ceeb heev los xyuas kom meej qhov tsim nyog tiv thaiv H2 roj nkag mus.Rau qhov no, peb tsuas yog siv cov ntaub ntawv thermoplastic thiab tab tom ua haujlwm ntawm ntau yam khoom siv yuav cuam tshuam li cas rau tus cwj pwm permeation thiab kev ua haujlwm hauv AFP tshuab.Nws yog ib qho tseem ceeb kom nkag siab tias kev kho mob puas yuav muaj txiaj ntsig thiab yog tias yuav tsum tau ua tom qab ua tiav.Peb kuj xav paub seb cov pawg sib txawv yuav cuam tshuam li cas hydrogen permeation los ntawm lub nkoj siab. "
Lub tank yuav ua los ntawm cov thermoplastic nkaus thiab cov strips yuav muab los ntawm Teijin Carbon Europe GmbH (Wuppertal, Lub teb chaws Yelemees)."Peb yuav siv lawv cov PPS [polyphenylene sulfide], PEEK [polyether ketone] thiab LM PAEK [tsawg melting polyaryl ketone] cov ntaub ntawv," Yager hais."Kev sib piv yog ua kom pom qhov twg yog qhov zoo tshaj plaws rau kev tiv thaiv kev nkag mus thiab tsim cov khoom nrog kev ua tau zoo dua."Nws vam tias yuav ua kom tiav cov kev sim, kev tsim qauv thiab kev ua qauv thiab kev ua qauv qhia thawj zaug hauv xyoo tom ntej.
Kev tshawb fawb ua haujlwm tau ua nyob rau hauv COMET module "Polymers4Hydrogen" (ID 21647053) nyob rau hauv COMET qhov kev pab cuam ntawm Tsoom Fwv Teb Chaws Kev Nyab Xeeb Kev Nyab Xeeb, Ib puag ncig, Zog, Mobility, Innovation thiab Technology thiab Tsoom Fwv Teb Chaws Ministry rau Digital Technology thiab Economics..Cov kws sau ntawv ua tsaug rau cov koom tes nrog Polymer Competence Center Leoben GmbH (PCCL, Austria), Montanuniversitaet Leoben (Faculty of Polymer Engineering thiab Science, Department of Chemistry of Polymer Materials, Department of Materials Science thiab Polymer Testing), University of Tampere (Faculty of Engineering thiab Science) Khoom siv).) Science), Peak Technology thiab Faurecia pab txhawb rau txoj haujlwm tshawb fawb no.COMET-Modul yog nyiaj txiag los ntawm tsoomfwv Austria thiab tsoomfwv ntawm lub xeev Styria.
Cov ntawv ua ntej siv rau cov khoom thauj khoom muaj cov fibers txuas ntxiv - tsis yog los ntawm iav, tab sis kuj los ntawm carbon thiab aramid.
Muaj ntau txoj hauv kev los ua cov khoom sib xyaw.Yog li ntawd, kev xaiv ntawm txoj kev rau ib feem yuav nyob ntawm seb cov khoom siv, qhov tsim ntawm ib feem, thiab qhov kawg siv los yog daim ntawv thov.Ntawm no yog ib daim ntawv qhia kev xaiv.
Shocker Composites thiab R&M International tab tom tsim cov khoom siv hluav taws xob siv hluav taws xob uas muab xoom tua, tus nqi qis dua li nkauj xwb fiber ntau thiab nws thiaj li yuav muab qhov ntev uas txuas mus ntxiv fiber ntau hauv cov khoom siv.
Post lub sij hawm: Mar-15-2023