Umphumela Wokushisa Ekusebenzeni Kahle Kwenjini Yokushisa
Injini yokushisa iyithuluzi eliguqula amandla okushisa abe umsebenzi womshini. Izibonelo ziningi: izinjini zomusi ezitshalweni zamandla, izinjini zokushisa zangaphakathi ezimotweni, ama-turbine egesi ezindizeni, ngisho nezinhlelo zamandla zesimanje ezisekelwe kumjikelezo we-thermodynamic. Naphezu kokuhlukahluka kwazo, zonke izinjini zokushisa zisebenza ngesimiso esifanayo: zikhipha ukushisa emthonjeni wokushisa okuphezulu, ziguqule okunye kwakho kube umsebenzi, futhi zenqabe ukushisa okusele ziye endaweni yokushisa okuphansi. Isici esibaluleke kakhulu esinquma ukuthi kungakanani lokhu kushisa okuguqulwa kube umsebenzi izinga lokushisa. Lesi sihloko sihlola ukuthi izinga lokushisa lithinta kanjani ukusebenza kahle kwezinjini zokushisa, kokubili ngokombono wethiyori ye-thermodynamic kanye nomkhuba wobunjiniyela.
Umqondo oyisisekelo wokusebenza kahle kwenjini yokushisa
Ukusebenza kahle kwenjini yokushisa kuvame ukuvezwa njengesilinganiso somsebenzi wenethi okhiqizwa yinjini nokushisa okumuncwa emthonjeni wokushisa. Ngokuvamile:
\[
\eta = \frac{W}{Q_{in}} = 1 – \frac{Q_{out}}{Q_{in}}
\]
no:
– \( \eta \) = ukusebenza kahle kokushisa,
– \( W \) = umsebenzi we-net okhiqizwe,
– \( Q_{in} \) = okokufaka ukushisa (okumuncwa echibini elishisayo),
– \( Q_{out} \) = ukushisa kwenqatshiwe (echibini elibandayo).
Kusukela kulesi sibalo, kungabonakala ukuthi ukusebenza kahle kuzokhula uma ingxenye yokushisa eyenqatshiwe \(Q_{out}\) incane kunokushisa okufakiwe \(Q_{in}\). Yilapho izinga lokushisa lidlala indima ebaluleke kakhulu, ngoba isiqondiso "sokuthambekela" kokudluliselwa kokushisa kanye nomkhawulo wemfundiso wokuguqulwa kokushisa kube umsebenzi kunqunywa umehluko wokushisa phakathi komthombo wokushisa kanye nesinki yokushisa.
Ukusebenza kahle okukhulu: umkhawulo weCarnot kanye nendima yokushisa
Ku-thermodynamics, injini yokushisa efanelekile esebenza kahle kakhulu ezindaweni ezimbili zokushisa ezilinganisiwe ibizwa ngokuthi injini yeCarnot. Ukusebenza kahle kweCarnot kwakhiwe kanje:
\[
\eta_{Carnot} = 1 – \frac{T_c}{T_h}
\]
no:
– \(T_h\) = izinga lokushisa ledamu elishisayo (ku-Kelvin),
– \(T_c\) = izinga lokushisa elibandayo ledamu (ku-Kelvin).
Le fomula inikeza isifundo esibalulekile: ukusebenza kahle kwenjini yokushisa kunqunywa yisilinganiso sokushisa, hhayi umehluko wokushisa wodwa. Kunezindlela ezimbili eziyinhloko zokwandisa ukusebenza kahle okuphezulu ngokusho kweCarnot:
1. Khulisa izinga lokushisa lomthombo wokushisa \(T_h\)
Uma i-\(T_h\) ikhula kuyilapho i-\(T_c\) ihlala ingaguquguquki, khona-ke i-\(T_c/T_h\) iyancipha ukuze ukusebenza kahle kukhuphuke.
2. Ukwehlisa izinga lokushisa ledamu elibandayo \(T_c\)
Uma i-\(T_c\) incipha kuyilapho i-\(T_h\) ihlala ingaguquguquki, ukusebenza kahle kuyakhula ngoba isilinganiso \(T_c/T_h\) siyancipha.
Njengoba izinga lokushisa kumele livezwe ku-Kelvin, ukubala ukusebenza kahle kumele kusebenzise isikali esiphelele. Isibonelo, uma \(T_h = 800 \, K\) kanye \(T_c = 300 \, K\), khona-ke:
\[
\eta_{Carnot} = 1 – \frac{300}{800} = 1 – 0{,}375 = 0{,}625
\]
Ukusebenza kahle okukhulu ngokwethiyori kungu-62,5%. Izinjini zangempela zizohlala ziphansi kunaleli nani ngenxa yokulahlekelwa okuhlukahlukene.
Kungani izinga lokushisa linquma umkhawulo wokusebenza kahle?
Ngokomzimba, injini yokushisa isebenza ngenxa ye-gradient yokushisa: ukushisa "kugeleza" ngokuzenzakalelayo kusuka ekushiseni okuphezulu kuya ekushiseni okuphansi. Ukuguqula lokhu kugeleza kwamandla okushisa kube umsebenzi oqondisiwe (isb., ukunyakaza kwe-piston noma ukujikeleza kwe-turbine), uhlelo kumele lusebenze phakathi kwamazinga okushisa amabili. Umthetho Wesibili We-Thermodynamics uthi akunakwenzeka ukuguqula konke ukushisa okumuncwe kube umsebenzi ngaphandle kokulahla okunye kwakho kube yi-cooler reservoir. Ngamanye amazwi, ukuba khona kwe-\(T_c\) "kuyintengo" okumele ikhokhwe.
Uma umehluko omkhulu ezimweni zokushisa phakathi komthombo wokushisa kanye nesinki yokushisa (ngokuqondile, uma isilinganiso sincane \(T_c/T_h\)), kulapho ithuba lokuguqula ukushisa okuthile kube ukusebenza ngaphambi kokuba amandla asele alahlwe ekugcineni.
Umphumela wokwandisa izinga lokushisa lomthombo wokushisa (Th) enjinini yangempela
Empeleni, ukwandisa i-\(T_h\) kuvame ukuba isu eliyinhloko lokuthuthukisa ukusebenza kahle kwezitshalo zamandla nezinjini zezimoto. Izibonelo zifaka phakathi ama-turbine egesi kanye nezitshalo zamandla ezishisayo ezibaluleke kakhulu: ukwandisa izinga lokushisa lokungena kwe-turbine ngokuvamile kuthuthukisa ukusebenza kahle komjikelezo.
Noma kunjalo, ukwanda kwe-\(T_h\) kubhekene nemikhawulo yobunjiniyela:
1. Amandla ezinto ezibonakalayo kanye nokumelana nokushisa
Izingxenye ezifana nama-turbine blades, amakamelo okushisa, namapayipi e-boiler kumele zimelane namazinga okushisa aphezulu kakhulu. Emazingeni okushisa aphezulu, izinto zingaba nokukhukhuleka (ukuguquguquka kancane), ukugqwala, ukugqwala okushisayo, kanye nokulahlekelwa amandla omshini.
2. Izidingo zokupholisa izingxenye
Kuma-turbine egesi anamuhla, ama-blade e-turbine apholiswa ngomoya noma uhlelo lokupholisa lwangaphakathi. Lokhu kupholisa kusiza ukuthi izinto zisinde, kodwa kunganciphisa nokusebenza kahle ngoba amandla athile asetshenziselwa uhlelo lokupholisa futhi ukugeleza kuba yinkimbinkimbi kakhulu.
3. Ukwanda kokulahlekelwa kokungalungiseki
Emazingeni okushisa aphezulu, ezinye izinqubo (isib. ukushisa kwangempela, ukuxuba, ukuxokozela, ukudluliselwa kokushisa ngaphezu komehluko omkhulu wokushisa) kungandisa i-entropy futhi kunciphise ukusebenza kahle kwangempela uma kuqhathaniswa nokusebenza kahle okufanele.
Kodwa-ke, izitayela zobuchwepheshe ziyaqhubeka nokuthuthukisa \(T_h\) ngokuthuthukiswa kwezinto (ama-superalloy, izinto zobumba), izembozo ezingashisi ukushisa, kanye nemiklamo yokupholisa eyinkimbinkimbi kakhulu.
Umphumela wokunciphisa izinga lokushisa ledamu elibandayo (Tc)
Ukwehlisa i-\(T_c\) kwandisa nokusebenza kahle, kodwa kuvame ukuba nzima kakhulu kunalokho okubonakala. Ezitshalweni zikagesi, i-\(T_c\) ivame ukuhlotshaniswa nokushisa kwamanzi apholile noma umoya ozungezile. Njengoba indawo ezungezile ingenakukwazi "ukwenziwa ibanda" ngokuthanda kwayo, ukwehla kwe-\(T_c\) kunqunyelwe yi:
1. Isimo sezulu kanye nokushisa kwemvelo
Izitshalo zikagesi ezindaweni ezishisayo ngokuvamile zinezinga eliphezulu (T_c\), ngakho-ke ukusebenza kahle kwehla uma kuqhathaniswa nezitshalo zikagesi ezindaweni ezipholile.
2. Ubuchwepheshe be-Condenser kanye nezinhlelo zokupholisa
Ama-condenser angcono angasondeza izinga lokushisa lokukhipha umoya ekushiseni okuzungezile, kodwa awakwazi ukudlula lowo mkhawulo ngaphandle kwezindleko eziphakeme kanye nobunzima.
3. Imikhawulo ngesilinganiso sokudluliselwa kokushisa
Ukwehlisa i-\(T_c\) esebenzayo kusho ukwandisa umthamo wokususa ukushisa. Lokhu kudinga indawo enkulu yokudlulisa ukushisa, ukugeleza okuphezulu kwe-coolant, noma izindlela ezikhethekile zokupholisa—konke okuthinta izindleko kanye nokusetshenziswa kwamandla abangelwa yizinambuzane (amaphampu, amafeni).
Uma kubhekwa injini yokushisa yangaphakathi yemoto, "idamu elibandayo" lingaqondwa njengohlelo lokupholisa lwenjini kanye nendawo ezungezile. Isimo sezulu esishisayo sivame ukubangela amazinga okushisa okusebenza akhuphuke, okunganciphisa ukusebenza kahle futhi kwandise ingozi yokushayisa noma ukushisa ngokweqile.
Ukusebenza kahle okufanelekile uma kuqhathaniswa nokusebenza kahle kwangempela: umphumela wokushisa ekulahlekelweni
Nakuba iCarnot inikeza imikhawulo ephezulu, imishini yangempela ibhekene nezinkinga ezengeziwe:
– Ukungqubuzana komshini (amashafu, amapistoni, amabheringi) okuguqula umsebenzi ube ukushisa.
– Ukulahlekelwa kokudluliselwa kokushisa okungafuneki endaweni ezungezile.
– Ukusha okungaphelele ezinjinini zokushisa zangaphakathi, ngakho-ke akuwona wonke amandla amakhemikhali aguqulwa abe ukushisa okuwusizo.
– Ukulahlekelwa ukugeleza koketshezi (ukwehla kwengcindezi) emapayipini, kumavalvu, kuma-heat exchanger.
– Ukungaguquki ngenxa yezinqubo ezingashintshi, ukuphazamiseka, kanye nokuxubana.
Izinga lokushisa lihlobene eduze nalokhu kulahlekelwa. Isibonelo, umehluko omkhulu wokushisa ku-heat exchanger ungasheshisa ukudluliselwa kokushisa, kodwa lokhu kuvame ukwandisa ukungabi khona ngenxa yokukhiqizwa okukhulu kwe-entropy. Lokhu kusho ukuthi ukwakheka kokushisa kumele kulinganise izidingo zokusebenza nokunciphisa ukungabi khona.
Izibonelo zokusetshenziswa: Imijikelezo yeRankine neBrayton
Esitshalweni samandla esinomusi (umjikelezo we-Rankine), ukwandisa izinga lokushisa kanye nengcindezi yesitimu yokungena kwe-turbine (isb., ukushisa kakhulu noma okubaluleke kakhulu) kuvame ukwandisa ukusebenza kahle. Ngokuphambene nalokho, ukusebenzisa i-condenser ephumelelayo ukwehlisa ingcindezi/izinga lokushisa lesitimu sokukhipha umoya nakho kwandisa ukusebenza kahle, yize kunemikhawulo yemvelo.
Kuma-gas turbine (umjikelezo waseBrayton), ukusebenza kahle kuyanda njengoba izinga lokushisa lokungena kwe-turbine likhuphuka. Ngaphezu kwalokho, amasu anjengokuvuselela, ukupholisa, kanye nokuvuselela alawula iphrofayili yokushisa ukuze kuncishiswe imfucuza futhi kwandiswe umsebenzi wenethi. Umjikelezo ohlangene, osebenzisa ukushisa kokukhipha kwe-gas turbine ukukhiqiza umusi emjikelezweni we-Rankine, uyisibonelo esicacile sesu lokuthuthukisa izinga lokushisa: ukushisa emazingeni okushisa aphakathi okwakuchithwa ngaphambilini manje sekusetshenziselwa ukukhiqiza umsebenzi owengeziwe.
Isiphetho
Izinga lokushisa liyinguquko ebalulekile enquma ukusebenza kahle kwenjini yokushisa. Ngokwethiyori, ukusebenza kahle okuphezulu kunqunyelwe ukusebenza kahle kweCarnot, \(\eta = 1 – T_c/T_h\), okubonisa ukuthi ukusebenza kahle kuyanda njengoba izinga lokushisa lomthombo wokushisa likhuphuka kanye/noma izinga lokushisa ledamu elibandayo lincipha. Empeleni, ukwandisa \(T_h\) kunqunyelwe amakhono ezinto ezibonakalayo, izidingo zokupholisa, kanye nokulahlekelwa okungenakulungiseka; kuyilapho ukunciphisa \(T_c\) kunqunyelwe izinga lokushisa elizungezile kanye nekhono lesistimu lokwenqaba ukushisa. Ngakho-ke, ukuthuthukisa ukusebenza kahle kwenjini yokushisa akuyona nje indaba "yokuyenza ishise kakhulu" noma "yokuyenza ibanda kakhulu," kodwa kunalokho kuyindaba yokwenza ngcono uhlelo lokushisa luphelele - ukukhetha izinto, ukuklama ama-heat exchanger, ukulawula ukulahlekelwa, nokusebenzisa ukushisa emazingeni ahlukahlukene okushisa. Ngokuqonda ubudlelwano phakathi kwezinga lokushisa nokusebenza kahle, singaklama izinjini zokushisa ezisebenzisa amandla kahle, ezithembeke kakhulu, futhi ezinobungane kakhulu nemvelo.
Uma ufisa, ngingaguqula lesi sihloko sibe yinguqulo: (1) ezemfundo kakhulu enezinkomba ezengeziwe kanye nezibalo, (2) ethandwa kakhulu ngabafundi besikole samabanga aphezulu, noma (3) egxile ezibonelweni zezinjini zezimoto noma iziteshi zikagesi.
