Ucwaningo lwe-Thermodynamic ngezinjini zikadizili nezinjini zikaphethiloli
I-Pendahuluan
Injini yokushisa yangaphakathi iwubuchwepheshe obuyinhloko obuguqula amandla amakhemikhali kaphethiloli abe amandla omshini ngokushisa ngaphakathi kwesilinda. Izinhlobo ezimbili ezivame kakhulu ezisetshenziswa ezimotweni kanye nezinhlelo zokusebenza ezahlukahlukene zezimboni yinjini kaphethiloli (i-spark ignition/SI) kanye nenjini kadizili (i-compression ignition/CI). Ngenkathi zombili zithembele emjikelezweni we-four-stroke (emiklamo eminingi) kanye nezimiso eziyisisekelo ze-thermodynamic, kunomehluko obalulekile ekwakhekeni kwengxube, indlela yokushisa, izici zokushisa, kanye nokusebenza kahle. Ucwaningo lwe-thermodynamics lusisiza siqonde ukuthi kungani izinjini zikadizili zivame ukusebenza kahle, ukuthi kungani izinjini zikaphethiloli zinezimpawu zokuphendula ezihlukile kanye ne-rev, nokuthi amapharamitha afana nesilinganiso sokucindezela, izinga lokushisa, ingcindezi, kanye nokulahlekelwa anquma kanjani ukusebenza.
I-Thermodynamics Eyisisekelo Yezinjini Zokushisa Zangaphakathi
Okungcono kakhulu, ukusebenza kwenjini kuvame ukuhlaziywa ngomjikelezo we-thermodynamic olungiselelwe kahle owenza inqubo yangempela ibe lula. Umgomo awukona ukuphinda imininingwane yokusha ngokunembile, kodwa kunalokho ukuhlinzeka ngohlaka lokuhlola ithonya lezinto eziguquguqukayo zomklamo ekusebenzeni kahle. Amanani abalulekile kulolu cwaningo afaka:
1. Isilinganiso sokucindezela (r): isilinganiso somthamo wesilinda lapho i-piston iphansi phakathi nendawo efile nevolumu phezulu phakathi nendawo efile. Isilinganiso sokucindezela sithinta izinga lokushisa lokugcina lokucindezela kanye nengcindezi, ngaleyo ndlela kunquma kakhulu ukusebenza kahle.
2. Okokufaka ukushisa (Q_in) kanye nokukhipha ukushisa (Q_out): emqondweni womjikelezo ofanele, okokufaka ukushisa kwenzeka ngesikhathi sokusha (noma ukwengezwa kokushisa) kanye nokukhipha ukushisa kwenzeka ngesikhathi sokwenqatshwa kokushisa.
3. Umsebenzi we-Net (W_net): umehluko phakathi komsebenzi wokunweba nomsebenzi wokucindezela.
4. Ukusebenza kahle kokushisa (η_th): isilinganiso somsebenzi wenethi kokufakwa kokushisa, okungukuthi η_th = W_net / Q_in.
5. Umthetho Wokuqala We-Thermodynamics: izinguquko zamandla ohlelweni zihlobene nokushisa nomsebenzi. Emjikelezweni ovaliwe ofanele, umsebenzi wenethi ulingana nomehluko phakathi kokufakwa kokushisa nokukhishwa kokushisa.
Empeleni, ukusebenza kahle kwangempela kuhlala kuphansi kunokufanele ngenxa yokungqubuzana, ukudluliselwa kokushisa ezindongeni zesilinda, ukusha okungaphelele, ukulahlekelwa kokupompa, kanye nezici zegesi yokukhipha umoya kanye nesistimu yokupholisa.
Umjikelezo Ofanele Wenjini Kaphethiloli: Umjikelezo we-Otto
Injini kaphethiloli efanele imelelwa umjikelezo we-Otto, uma kucatshangwa ukuthi ukwengeza ukushisa kwenzeka ngevolumu engaguquki. Izigaba eziyinhloko zomjikelezo we-Otto efanele yilezi:
1. Ukucindezelwa kwe-Isentropic: ingxube yomoya-kaphethiloli icindezelwa ngaphandle kokudluliselwa kokushisa (okufanelekile).
2. Ukwengezwa kokushisa kwevolumu engaguquki: ukushisa kucatshangwa ukuthi kwenzeka ngokushesha ukuze ivolumu ihlale ingaguquki.
3. Ukwandiswa kwe-Isentropic: igesi yokushisa iyakhula, isunduza i-piston futhi ikhiqize umsebenzi.
4. Ukwenqatshwa kokushisa okunamandla njalo: ukushisa kuyenqatshwa bese umjikelezo ubuyela esimweni sawo sokuqala.
Ukusebenza kahle kokushisa komjikelezo we-Otto ofanele kungabhalwa njengomsebenzi wesilinganiso sokucindezela:
\[
\eta_{Otto} = 1 – \frac{1}{r^{\gamma – 1}}
\]
lapho i-γ iyisilinganiso sokushisa esithile (Cp/Cv). Lesi sibalo sibonisa ukuthi ukwandisa isilinganiso sokucindezela kwandisa ukusebenza kahle. Kodwa-ke, izinjini zikaphethiloli zinqunyelwe ukungqongqoza (ukuqhuma), okuwukushisa okungalawulwa ngenxa yokushisa okuphezulu kanye nokucindezela okubangela ukuthi enye yengxube ivuthe ngaphambi kokuba i-spark plug ikhiqize i-flame front eqinile. Ngakho-ke, isilinganiso sokucindezela sezinjini zikaphethiloli ngokuvamile siphansi kunesezinjini zikadizili.
Umjikelezo Wenjini Kadizili Ofanele: Umjikelezo Kadizili
Injini yedizili efanele imelelwa umjikelezo weDizili, umehluko omkhulu ukuthi ukwengezwa kokushisa kucatshangwa ukuthi kwenzeka ngengcindezi engaguquki (noma ecishe ibe njalo) ngenxa yokujova uphethiloli ngesikhathi sokuqhuma kokuqala. Izigaba zomjikelezo weDizili ofanele yilezi:
1. Ukucindezelwa kwe-Isentropic: umoya wodwa ucindezelwa ekushiseni okuphezulu kakhulu.
2. Ukwengezwa kokushisa okungapheli: uphethiloli uyafakwa futhi ushiswe, okugcina ingcindezi ingaguquki phakathi nengxenye yenqubo.
3. Ukwandiswa kwe-Isentropic: igesi eshisayo iyakhula futhi ikhiqize umsebenzi.
4. Ukushabalaliswa kokushisa okunomthamo oqhubekayo: ukushisa kuyenqatshwa ukuze kubuyele esimweni sokuqala.
Ukusebenza kahle komjikelezo weDizili ofanele kuncike kusilinganiso sokucindezela kanye nesilinganiso sokunqunywa (ρ), okuyisilinganiso sevolumu yokugcina yokwengeza ukushisa kumthamo wokuqala wokwengeza ukushisa. Ngokuvamile, ngesilinganiso esifanayo sokucindezela, ukusebenza kahle kwe-Otto kuvame ukuba phezulu kunokweDizili ofanele. Kodwa-ke, iqiniso liphambene nalokho: izinjini zedizili zivame ukusebenza kahle kakhulu ngoba zingasebenzisa isilinganiso sokucindezela esiphezulu futhi zisebenze ngokulahlekelwa okuncane kwe-throttling.
Ukuqhathaniswa kwe-Thermodynamic: Kungani Udizili Usebenza Kakhulu?
Ngokombono we-thermodynamics osetshenziswayo, kunezizathu eziningana eziphoqelelayo:
1. Isilinganiso sokucindezela esiphezulu kudizili
Izinjini zikadizili zicindezela umoya kuphela, ngakho-ke ukugoba akuyona imingcele ebalulekile njengoba kunjalo ngezinjini zikaphethiloli. Izilinganiso zokucindezela kukadizili zingaba phezulu kakhulu, okuholela ekushiseni okuphezulu kokuphela kokucindezela, ukusha okulula, kanye nokusebenza kahle okwandisiwe.
2. Ukusebenza ngaphandle kwe-throttle ngomthwalo oyingxenye
Izinjini eziningi zikaphethiloli zilawula amandla nge-throttle evimbela ukuhamba komoya. Lokhu kudala ukulahlekelwa kokupompa, ikakhulukazi emithwalweni elula. Izinjini zikaphethiloli ngokuvamile zilawula amandla ngenani likaphethiloli elifakwe, kuyilapho zigcina umoya owengeziwe, okuholela ekulahlekelweni okuncane kokupompa kanye nokusebenza kahle okuyingxenye.
3. Izici zokusha kanye nesilinganiso somoya-uphethiloli
Izinjini zikadizili zivame ukusebenza ngengxube engenamafutha amaningi, okuvumela amazinga okushisa aphansi ngaphansi kwezimo ezithile, okunciphisa ukulahlekelwa ukushisa. Kodwa-ke, udizili uphinde ulethe izinselele ngezinto ezincane (umswakamo) kanye nokukhishwa kwe-NOx okudinga ukulawulwa.
4. Inani lama-calorie kanye nobuningi bamandla kaphethiloli
Uphethiloli wedizili unamandla aphezulu kakhulu kunophethiloli. Nakuba ukusebenza kahle kokushisa kusalokhu kungumqondo ohlukile, lesi sici sithinta ukusetshenziswa kukaphethiloli ngekhilomitha kanye nelitha, ngokuvamile okwenza uphethiloli ubonakale "usebenza kahle" kakhudlwana.
Izici Zenqubo Yangempela: Kusukela Kumjikelezo Ofanele Kuya Kumjikelezo Wangempela
Imijikelezo ye-Otto ne-Diesel efanelekile ithatha inqubo ye-isentropic kanye nokwengezwa kokushisa "okuhlelekile". Izinjini zangempela zithola ukuphambuka okukhulu, okuhlanganisa:
– Ukudluliselwa kokushisa odongeni lwesilinda kunciphisa izinga lokushisa legesi elisebenzayo ukuze umsebenzi wokwandisa uncishiswe.
– Ukungqubuzana komshini emasongweni e-piston, amabheringi, kanye nezingxenye ze-valve kunciphisa amandla asebenzayo.
– Isikhathi sokusha: ukusha akusheshi. Ezinjinini zikaphethiloli, ukusha kudinga amazinga amaningana e-angle ye-crankshaft; ezinjinini zikadizili, kukhona ukusha okubambezelekile kanye nokusha kokusabalalisa.
– Igesi esele evela emjikelezweni odlule ishintsha ukwakheka kanye nokushisa kwengxube elandelayo.
– Ukusebenza kahle kwevolumu kuthonywa ukwakheka kokungenisa/ukukhipha umoya kanye nesikhathi se-valve, okunquma ubukhulu bomoya ongena, ngaleyo ndlela kuthinte amandla kanye nokusetshenziswa kwawo.
Ekuhlaziyweni kobunjiniyela, ukusebenza kuvame ukulinganiswa ngengcindezi eqondile esebenzayo (IMEP) kanye nengcindezi eqondile esebenzayo yamabhuleki (BMEP). I-IMEP ibonisa umsebenzi we-thermodynamic owenziwe ku-cylinder, kuyilapho i-BMEP ingumsebenzi otholakala ngempela ku-shaft ngemuva kokususa ukulahlekelwa kwemishini. Umehluko phakathi kwalokhu okubili uhlobene nokusebenza kahle kwemishini.
Umthelela we-Thermodynamic ekukhishweni kwegesi
Ucwaningo lwe-thermodynamics alunakuhlukaniswa nokwakheka kokukhishwa kwegesi ngoba izinga lokushisa, ingcindezi, kanye nokwakheka kwengxube kunquma ukusabela kwamakhemikhali.
– Izinjini zikaphethiloli zivame ukukhiqiza i-CO kanye ne-HC uma ukusha kungaphelele, kodwa ama-catalyst anezindlela ezintathu ayasebenza uma ingxube iseduze ne-stoichiometric.
– Izinjini zikadizili zivame ukukhiqiza i-NOx (ngenxa yokushisa okuphezulu kanye nomoya-mpilo oweqile) kanye nezinhlayiya/umswalo (ngenxa yezindawo ezicebile zendawo ekushiseni okusabalele). Amasu afana ne-EGR (ukujikeleza kabusha kwegesi ekhipha umoya), i-turbocharging, kanye nokwelashwa ngemva kokusebenzisa umoya (i-SCR/DPF) asetshenziswa ukulinganisela ukusebenza kahle kanye nokukhishwa komoya.
Intuthuko Yanamuhla: I-Turbocharging, Injection Eqondile, kanye ne-Mixed Cycle
Intuthuko yezobuchwepheshe ifiphaza imingcele phakathi "kwezici zephethiloli" kanye "nezici zedizili." Izinjini zephethiloli zesimanje zivame ukusebenzisa i-direct injection kanye ne-turbocharging ukuthuthukisa ukusebenza kahle nokunciphisa ukusetshenziswa kukaphethiloli, yize lokhu kungandisa izinto ezincane futhi kudinge izihlungi. Okwamanje, izinjini zephethiloli zesimanje zisebenzisa i-multi-stage injection control kanye ne-variable turbocharging ukuze kuthuthukiswe ukusha.
Ezifundweni ze-thermodynamic, izinjini zanamuhla zivame ukuhlaziywa njengomjikelezo ophindwe kabili: ukwengezwa kokushisa kwenzeka ngokwengxenye ngevolumu engaguquki kanye nengxenye ngengcindezi engaguquki. Lo modeli unengqondo kakhulu ekuchazeni ukushisa kwangempela okungahlangabezani ngokugcwele nokucatshangwa kwe-Otto noma i-Diesel.
Isiphetho
Izifundo ze-thermodynamic zezinjini zedizili nephethiloli zibonisa ukuthi izindlela ezahlukene zokushisa nokwakheka kwengxube ziholela emijikelezweni ehlukene efanele: i-Otto (ivolumu eqhubekayo) kaphethiloli kanye neDizili (ingcindezi eqhubekayo) kaphethiloli. Ngenkathi umjikelezo we-Otto ofanele ungasebenza kahle kakhulu ngesilinganiso esifanayo sokucindezela, izinjini zedizili ezisebenza kahle zivame ukuba ngcono ekusebenzeni kahle ngenxa yekhono lazo lokusebenzisa izilinganiso zokucindezela eziphakeme futhi zinciphise ukulahlekelwa kokupompa emithwalweni engaphelele. Kodwa-ke, ukusebenza kahle akuyona inkinga yodwa: ukukhishwa kwegesi, izici ze-torque, izindleko zesistimu, kanye nezidingo zokulungisa konke kuyizinto ezinquma ukusetshenziswa. Ngobuchwepheshe besimanje njengokufakwa ngqo, i-turbocharging, i-EGR, kanye nokwelashwa ngemuva, zombili izinhlobo zezinjini ziyaqhubeka nokuthuthuka ziye emaphuzu amasha afanele - ukuthuthukisa ukusebenza kahle kokushisa ngenkathi kunciphisa ukukhishwa kwegesi - ngakho ukuqonda i-thermodynamics kuhlala kuyisisekelo esibalulekile sokuklama nokuhlola ukusebenza kwezinjini zokushisa zangaphakathi.
