Tlhahlobo ea Phetisetso ea Mocheso Lienjineng tsa Mollo oa Kahare
Pendahuluan
Enjene ea ho chesa ka hare (ICE) ke sesebelisoa sa phetoho ea matla se fetolang matla a lik'hemik'hale a mafura hore e be matla a mechini ka mokhoa oa ho chesa ka phapusing ea ho chesa. Ts'ebetsong ena, phetisetso ea mocheso e bapala karolo ea bohlokoa hobane e khetholla katleho, ts'ebetso, likhase tse tsoang le ts'epo ea enjene. Mocheso o hlahisoang ke ho chesa ha o fetoloe ka botlalo hore e be mosebetsi o thusang ka har'a crankshaft; o mong o lahleha ka lebaka la likhase tsa mosi, o mong o fetisetsoa maboteng a silindara, lipiston le lihlooho tsa silindara, ebe o ntšetsoa lits'ebetsong tsa ho pholisa le ho tlotsa. Ka hona, ho sekaseka phetisetso ea mocheso lienjeneng tsa ho chesa ka hare ke motheo oa bohlokoa oa ho rala lienjene tse bolokang matla haholoanyane, tse matla le tse tšoarellang.
Mehloli le Litsela tsa Phetisetso ea Mocheso
Ka kakaretso, mocheso ka har'a enjene ea ho tuka ka hare o tsoa karabelong ea ho tuka ha motsoako oa moea le mafura. Kamora ho tuka, mocheso oa khase ka har'a silindara o ka fihla ho feta 2000 K maemong a holimo, e leng se etsang hore mocheso o be moholo pakeng tsa khase e chesang le libaka tsa tšepe tse batang haholo. Ka lebaka leo, mocheso o phalla ho tloha khaseng ho ea likarolong tsa enjene ka mekhoa e meraro e meholo: ho tsamaisa motlakase, ho chencha motlakase le mahlaseli.
Litsela tse ka sehloohong tsa phetiso ea mocheso li ka akaretsoa ka tsela e latelang:
1. Khase e chesang → bokaholimo ba kamore e tukang (lebota la silindara, hlooho ea silindara, bokaholimo ba piston) ka har'a convection le mahlaseli.
2. Bokaholimo ba kamore ea ho tuka → bokahare ba thepa ka ho tsamaisa motlakase.
3. Tikoloho ea thepa → ka ho kenella ho ea ho sehatsetsing (radiator) le oli e tlotsang, 'me qetellong moeeng o potolohileng.
Ho utloisisa litsela tsena ho thusa baenjiniere ho fumana libaka tsa bohlokoa tse hlokang ho pholisa ho betere kapa thepa e hanelang mocheso haholoanyane.
Convection ka Silindareng
Convection ke mokhoa o ka sehloohong tlas'a maemo a mangata a ts'ebetso ea enjene. Coefficient ea phetisetso ea mocheso oa convection ka phapusing ea ho tuka e susumetsoa haholo ke pherekano ea phallo ea khase, lebelo la piston, sebopeho sa phapusing ea ho tuka, le maemo a ho tuka.
Nakong ea khatello le ho cha, phallo ea khase e ba le pherekano e kholo ka lebaka la motsamao oa piston le moralo oa kou ea ho kenella, e leng se bakang ho potoloha le ho putlama. Pherekano ena e eketsa coefficient ea phetisetso ea mocheso (h), ka hona e eketsa sekhahla sa phetisetso ea mocheso ho tloha khase ho ea leboteng. Ha re e beha ka bokhutšoanyane, sekhahla sa phetisetso ea mocheso oa convection se ka ngoloa tjena:
\[
\dot{Q}_{conv} = hA(T_g – T_w)
\]
moo \(A\) e leng sebaka sa phetisetso ya mocheso, \(T_g\) mocheso wa kgase, le \(T_w\) mocheso wa lebota. Kaha mocheso wa kgase o fetoha ka potlako nakong ya potoloho, tlhahlobo ya nnete hangata e ba ya nakwana (e fetoha ka nako/lebelo la ho hlanya).
Lithutong tsa enjene, likamano tsa 'mele (mohlala, Woschni) hangata li sebelisoa ho hakanya \(h\) ho latela khatello ea silindara, mocheso oa khase, le lebelo la phallo le ikhethang. Likamano tse joalo li bohlokoa hobane phallo ea ka har'a silindara e rarahane 'me ho thata ho e rarolla ka mokhoa o hlophisitsoeng feela.
Mahlaseli a Thermal a tsoang Mollong le Likhase tse Chesang
Ntle le convection, mahlaseli a kotsi le ona a kenya letsoho, haholo-holo lienjeneng tsa disele le tlas'a maemo a boima bo phahameng. Lienjeneng tsa disele, ho cha ha motlakase ho hlahisa mosi o mongata, o eketsang ho ntšoa ha khase, e leng se etsang hore mahlaseli a be bohlokoa le ho feta. Mahlaseli a fetisetsoa ho tloha malakabeng le lihlahisoa tsa mollo ho ea maboteng a kamore ea mollo.
Sekhahla sa phetiso ea mocheso o phatsimang hangata se latela molao oa Stefan-Boltzmann:
\[
\dot{Q}_{rad} = \varepsilon \sigma A(T_g^4 – T_w^4)
\]
ka \(\varepsilon\) ho ntša ha khase/lelakabe ka katleho le \(\sigma\) Stefan–Boltzmann constant. Hobane ho itšetlehile ka matla a bone a mocheso, mahlaseli a eketseha haholo ha mocheso o phahameng oa ho tuka o phahame. Leha ho le joalo, ha e le hantle, ho hakanya \(\varepsilon\) ha ho bonolo hobane ho angoa ke sebopeho sa khase, likaroloana tsa soot, le geometry ea kamore ea ho tuka.
Ho Tsamaisa Dikarolo tsa Mochini
Mocheso o monngoang ke bokaholimo ba kamore ea ho tuka o tla tsamaea ho ea ka hare ho thepa ka ho tsamaisa motlakase. Lisebelisoa tsa likarolo hangata ke li-alloy tsa aluminium (li-piston, lihlooho tse ling tsa li-cylinder) kapa tšepe e entsoeng ka tšepe le tšepe (li-cylinder blocks, li-liners, li-valve). Ho tsamaisa motlakase ho hlalosoa ke molao oa Fourier:
\[
\dot{Q}_{cond} = -kA\frac{dT}{dx}
\]
moo \(k\) e leng phetiso ya mocheso wa thepa. Aluminium e na le phetiso e phahameng ho feta tshepe e entsweng ka tshepe, e e dumella ho ntsha mocheso kapele, e fokotsa mocheso o phahameng wa lehae mme e fokotsa kotsi ya dibaka tse chesang. Leha ho le jwalo, aluminium e boetse e na le matla a tlase a mocheso o phahameng ho feta thepa e meng e thehilweng tshepeng, kahoo meralo e hloka ho dumellana pakeng tsa phetiso ya mocheso le ho tshwarella ha sebopeho.
Ho tsamaisa motlakase ho bohlokwa bakeng sa dipiston: mocheso o tswang moqhaka wa piston o lokela ho fetisetswa masaleng a piston, seketeng, mme qetellong maboteng a silindara le oli. Haeba tsela ya ho tsamaisa motlakase e sa lekana, piston e ka ba le katoloso e feteletseng, ho senyeha ka potlako, esita le tshenyo e bakwang ke ho phatloha kapa ho hotetswa pele ho nako.
Phetisetso ea Mocheso ho Mekhoa ea ho Pholisa le ho Lubricate
Mocheso o fihlang maboteng a silindara le hloohong ea silindara o fetisetsoa ho coolant (jakete ea metsi) ka convection. Sistimi ea ho pholisa e boloka mocheso oa ts'ebetso ea enjene o le ka har'a tekanyo e nepahetseng ho netefatsa hore oli e tiile, ho tuka hantle, le ho thibela ho senyeha ha mocheso oa likarolo.
Ka lehlakoreng le leng, oli e tlotsang e boetse e sebetsa e le sebaka sa ho phodisa, haholo-holo bakeng sa lipiston (ka li-jet tsa oli), li-bearing, le libaka tse nang le khohlano e phahameng. Leha bokhoni ba ho phodisa ba oli hangata bo le tlase ho feta ba sephodisang, karolo ea eona ke ea bohlokoa ho laoleng mocheso oa lehae le ho thibela ho hloleha ha tribological (ho tsofala le ho thibana).
Tlhahlobong ea matla a enjene, mocheso ka kakaretso o arotsoe ka: mosebetsi o sebetsang hantle, mocheso ho sesebelisoa se pholileng, mocheso ho oli, le enthalpy ea khase ea mosi. Boholo ba likaroloana tsena bo itšetlehile ka mofuta oa enjene, karolelano ea khatello, leano la ho tuka, le moralo oa sistimi ea ho pholisa.
Phello ea Phetiso ea Mocheso Bokhoning
Tahlehelo ea mocheso leboteng la silindara e fokotsa matla a fumanehang ho hlahisa mosebetsi. Ho ea ka pono ea thermodynamic, lienjine tse fokotsang phetisetso ea mocheso leboteng (ntle le ho hlahisa mathata a mocheso) li na le monyetla oa ho ba le katleho e phahameng ea mocheso. Leha ho le joalo, ho fokotsa phetisetso ea mocheso ha se kamehla ho leng bonolo hobane mocheso oa likarolo o tlameha ho lula o le ka tlase ho meeli ea thepa le ea ho tlotsa.
Mekhoa e meng, e kang ho roala litšitiso tsa mocheso holim'a lipiston kapa lihlooho tsa lisilindara, e ka fokotsa phallo ea mocheso ho thepa. Leha ho le joalo, liphetoho tsena li ka eketsa mocheso oa khase, e leng se ka eketsang ho thehoa ha NOx lienjeneng tsa peterole le diesel le ho eketsa kotsi ea ho kokota lienjeneng tsa peterole. Ka hona, ho ntlafatsa phetiso ea mocheso kamehla ho kenyelletsa phapanyetsano pakeng tsa bokhoni, mesi e tsoang le ho tšoarella.
Tlhahlobo ea Nakoana le Kabo ea Mocheso
Lipotoloho tsa enjene li potlakile (mohlala, 2000 rpm e bolela liphetohelo tse 33,3 ka motsotsoana), kahoo mocheso oa khase o fetoha ka potlako ka potoloho e 'ngoe le e 'ngoe. Libaka tsa mabota li na le liphetoho tse nyane tsa mocheso ka lebaka la boima ba mocheso oa thepa. Ka hona, tlhahlobo ea phetisetso ea mocheso lienjeneng hangata e hloka mokhoa oa nakoana: mocheso oa khase e le mosebetsi oa lebelo la crank, li-coefficient tse fetohang tsa convection, le maemo a mahlaseli a feto-fetohang.
Kabo ea mocheso ha e tšoane. Sebaka se haufi le valve ea mosi hangata ke sebaka se chesang ka ho fetisisa hobane likhase tsa mosi li chesa haholo 'me li phalla ka holim'a valve. Sebaka sena se chesang se ka baka ho petsoha ha mocheso hloohong ea silindara kapa valve haeba ho pholisa ho sa lekana. Ka hona, moralo oa jakete ea metsi, khetho ea thepa ea valve, le leano la ho pholisa li bohlokoa haholo.
Litlamorao tsa Moralo le Maano a Taolo
Tlhahlobo ea phetisetso ea mocheso e khanna liqeto tse 'maloa tsa bohlokoa tsa moralo:
1. Sebopeho sa kamore ya ho tuka: se ama sebaka sa bokaholimo, moferefere, le kabo ya mocheso. Dikamore tsa ho tuka tse nang le dibaka tse kgolo tsa bokaholimo di atisa ho eketsa tahlehelo ya mocheso.
2. Lisebelisoa le lipente: khetha conductivity e nepahetseng ea mocheso le khanyetso ea mocheso.
3. Sistimi ea ho pholisa e ikamahanyang le maemo: thermostat, pompo ea motlakase e feto-fetohang, le taolo ea phallo ea coolant ho boloka mocheso o motle ka ho fetisisa meroalong e fapaneng.
4. Taolo ea ho tuka ha mollo: nako ea ho hotetsa/ho kenya, EGR, le leano la motsoako ho leka-lekanya bokhoni le mesi e tsoang.
5. Ntlafatso ea ho tlotsa: jete ea oli ea piston le moralo oa potoloho ea oli ho fokotsa mocheso oa piston le oa bere.
Qetello
Phetisetso ea mocheso enjeneng ea ho tuka ka hare ke ketsahalo e rarahaneng e kenyeletsang phetisetso e matla ea likhase tse ka hare ho silindara, mahlaseli a tsoang malakabeng le likhase tse chesang, le phetisetso ea motlakase ka likarolo tsa enjene ho ea lits'ebetsong tsa ho pholisa le ho tlotsa. Tlhahlobo ea molumo e nolofalletsa baqapi ho utloisisa tahlehelo ea matla, ho laola mocheso oa likarolo, le ho ntlafatsa katleho ha ba ntse ba boloka likhase tse kotsi le botšepehi. Ka likoloi tsa sejoale-joale tse batlang tšebeliso ea mafura le likhase tse kotsi, tsebo ea tlhahlobo ea phetisetso ea mocheso e ntse e eketseha, bakeng sa lienjene tse tloaelehileng le tse nang le mahlale a morao-rao a ho tuka.
Haeba o lakatsa, nka tlatsa sengoloa sena ka: (1) mohlala o bonolo oa palo ea phallo ea mocheso leboteng la silindara, (2) setšoantšo se tloaelehileng sa phallo ea matla (tekanyo ea mocheso) ea enjene ea peterole khahlanong le diesel, kapa (3) lethathamo la litšupiso tsa libuka/koranta ho matlafatsa motheo oa saense.
