Ukubalwa Kokusebenza Kahle Kokushisa Ezinjinini Zesimanje Zomusi
Izinjini zomusi zivame ukubhekwa njengobuchwepheshe "obujwayelekile" obuvela eNguquko Yezimboni. Kodwa-ke, izimiso kanye nentuthuko yazo kusasebenza nanamuhla, ikakhulukazi ezitshalweni zamandla ezisebenzisa amalahle (i-PLTU), ukufakwa kokushisa okuhlanganisiwe namandla (i-CHP), kanye nezinhlelo ze-turbine zomusi embonini yenqubo. "Izinjini zomusi zanamuhla" zibhekisela ezinhlelweni zokukhiqizwa kwamandla ezisekelwe kumjikelezo we-Rankine, ezisebenza kahle kakhulu kunezinjini zomusi ezivamile eziphindaphindayo, zisebenzisa umfutho ophezulu kanye nokushisa, ama-superheater, ama-reheater, kanye nokushisa okuvuselelayo ngama-feedwater heater. Ukuze uqonde ukusebenza kwalezi zinhlelo, ipharamitha eyodwa ebalulekile ehlala ibalwa ukusebenza kahle kokushisa.
1. Umqondo Oyisisekelo Wokusebenza Kahle Kokushisa
Ukusebenza kahle kokushisa kwenjini yomusi kuchaza ukuthi ingakanani yamandla okushisa okufakwayo (kusukela ekushisweni kukaphethiloli noma umthombo wokushisa) eguqulwa ngempumelelo ibe umsebenzi owusizo, ngokuvamile ngesimo samandla omgodi we-turbine noma amandla kagesi ejeneretha. Ngokuvamile, ukusebenza kahle kokushisa kuchazwa ngokuthi:
\[
\eta_{th} = \frac{W_{net}}{Q_{in}}
\]
Di mana:
– \( W_{net} \) umsebenzi we-net womjikelezo (umsebenzi we-turbine ngaphandle komsebenzi wephampu).
– \( Q_{in} \) iwukufaka ukushisa emjikelezweni, ngokuvamile okwenzeka kubhoyila kanye/noma ku-superheater.
Kumjikelezo we-Rankine ofanele, izingxenye eziyinhloko zifaka phakathi ipompo, ibhoyila, i-turbine, kanye ne-condenser. Umusi uphonswa (amanzi okuhambisa) kumfutho ophezulu, ufudunyezwe ube yi-steam (ugcwele noma ushiswe kakhulu), unwetshwe ku-turbine ukuze ukhiqize umsebenzi, bese ugoba ubuye ube uketshezi ku-condenser ngaphambi kokungena kabusha ku-pump. Ukusebenza kahle kokushisa kuyisilinganiso esiyinhloko sokuthi injini ye-steam isebenzisa kanjani amandla okushisa ngempumelelo.
2. Umjikelezo Ofanele vs Wangempela We-Rankine
Ekubaleni kokuqala, onjiniyela bavame ukuqala kusukela kumjikelezo we-Rankine ofanele ukuze bathole umbono womkhawulo ophezulu wokusebenza kahle. Imibono efanele ivame ukuba:
1. Inqubo yephampu ne-turbine ye-Isentropic (engenakulahlekelwa).
2. Akukho ukwehla kwengcindezi kubhoyila, amapayipi, i-superheater, i-reheater, kanye ne-condenser.
3. Akukho ukulahlekelwa ukushisa endaweni ezungezile.
4. Ukuvunda nokushisa kwenzeka ngokucindezela okungaguquki.
Ezimweni zangempela, lokhu kuqagela akuhlangatshezwanga ngokugcwele. Ukulahlekelwa ukungqubuzana, ukulahlekelwa yingcindezi, kanye nokusebenza kahle kwe-isentropic kwamaphampu nama-turbine kungaphansi kuka-100%. Ngakho-ke, ukusebenza kahle kwangempela kokushisa kuhlale kuphansi kunenani elifanele, futhi izibalo kumele zifake amapharamitha anjengalawa:
– Ukusebenza kahle kwe-isentropic ye-turbine (\(\eta_t\))
– Ukusebenza kahle kwephampu ye-Isentropic (\(\eta_p\))
– Ukulahlekelwa ukushisa (ukulahlekelwa ukushisa)
- Ukwehla kwengcindezi
3. Izinyathelo Zokubala Ukusebenza Kahle Kokushisa (Uhlaka Olujwayelekile)
Ukuze ubale ukusebenza kahle kokushisa kwenjini yesimanje yesitimu (esekelwe ku-Rankine), izinyathelo ezijwayelekile yilezi:
a) Nquma Amaphuzu Esifundazwe
Ngokuvamile kumakwa ngokuthi:
1. Indawo yokungenisa i-condenser/ipompo (uketshezi olugcwele ngokucindezela kwe-condenser)
2. Ipayipi lokukhipha amanzi/ibhoyila (amanzi okuhambisa amanzi anomfutho ophezulu)
3. Ibhoyila/indawo yokukhipha i-superheater/indawo yokungena ye-turbine (isisi esomile esigcwele noma esishisayo kakhulu)
4. Indawo yokungena ye-turbine outlet/condenser (ingxube yamanzi anomusi noma umswakama oshisayo kakhulu)
Emijikelezweni enezifudumezi ezivuselelayo kanye nokuvuselelwa, inani lamaphuzu esimo liyakhula. Izinjini zesimanje ze-steam ezitshalweni ezinkulu zamandla ngokuvamile zinezigaba eziningi zokukhipha i-turbine kanye nezifudumezi zamanzi okuhambisa, okwenza ukuhlaziywa kube nzima kakhulu, kodwa isimiso sihlala sifana: ukwenza ibhalansi yamandla engxenyeni ngayinye.
b) Thatha idatha yempahla yeThermodynamic
Izakhiwo eziyinhloko ezidingekayo:
– I-Enthalpy (\(h\)) endaweni ngayinye
– I-Entropy (\(s\)) yezinqubo ze-isentropic
– Ingcindezi (\(P\)) kanye nezinga lokushisa (\(T\))
– Ikhwalithi yomusi (\(x\)) uma usesifundeni esinezigaba ezimbili
Le datha ivame ukuthathwa kumathebula e-steam noma isofthiwe (ama-EES, REFPROP, Aspen, noma ama-calculator empahla e-IAPWS/IF97).
c) Bala Umsebenzi Wephampu
Umsebenzi ofanele wokupompa ungalinganiswa kanje:
\[
W_p \cishe v_f (P_2 – P_1)
\]
Lapho \(v_f\) kuyivolumu ethile yoketshezi (m³/kg) endaweni yokungena yepompo. Ngepompo yangempela:
\[
W_{p,actual} = \frac{W_{p,ideal}}{\eta_p}
\]
Bese kuthi i-enthalpy ephuma epompo:
\[
h_2 = h_1 + W_{p,real}
\]
d) Bala Ukufakwa Kokushisa Ku-Boiler
Okokufaka ukushisa ngokuvamile:
\[
Q_{in} = h_3 – h_2
\]
Uma kukhona i-superheater, inani lika-\(h_3\) liyi-enthalpy yesitimu esishisayo kakhulu endaweni yokungena ye-turbine. Uma kukhona i-reheater, kukhona okunye ukufaka ukushisa okwengeziwe:
\[
Q_{in,isamba} = (h_3 – h_2) + (h_5 – h_4)
\]
(kuye ngokuthi amaphuzu angakanani kumdwebo).
e) Bala Umsebenzi We-Turbine
Ukuze uthole i-turbine efanele (isentropic), \(s_3 = s_{4s}\) kanye \(h_{4s}\) kutholakala etafuleni. Ukuze uthole i-turbine yangempela:
\[
\eta_t = \frac{h_3 – h_{4,actual}}{h_3 – h_{4s}}
\Umcibisholo Ongakwesokudla h_{4,wangempela} = h_3 – \eta_t (h_3 – h_{4s})
\]
Ukusebenza kwe-turbine:
\[
W_t = h_3 – h_{4,angempela}
\]
Uma kunezigaba eziningi zokunwetshwa noma zokuvuselela, umsebenzi we-turbine iyonke iyisamba sesigaba ngasinye.
f) Bala Umsebenzi We-Net kanye Nokusebenza Kahle Kokushisa
\[
W_{net} = W_t – W_p
\]
\[
\eta_{th} = \frac{W_{net}}{Q_{in}}
\]
Lokhu kuyisisekelo sokubalwa kokusebenza kahle kokushisa komjikelezo.
4. Isibonelo Esichazayo (Esilula)
Ake sithi umjikelezo wesimanje we-Rankine olula unedatha (ngendlela yama-enthalpies) esivele itholakale kumathebula e-steam futhi icabangela ukusebenza kahle kwezingxenye:
– \(h_1 = 191 \, \text{kJ/kg}\) (uketshezi olugcwele luphuma ku-condenser)
– \(h_2 = 200 \, \text{kJ/kg}\) (ukuphuma kwephampu, okwangempela)
– \(h_3 = 3500 \, \text{kJ/kg}\) (umusi oshisayo kakhulu ungena ku-turbine)
– \(h_4 = 2400 \, \text{kJ/kg}\) (umphumela we-turbine, wangempela)
Ngakho-ke:
– Umsebenzi we-turbine: \(W_t = 3500 – 2400 = 1100 \, \text{kJ/kg}\)
– Umsebenzi wokupompa: \(W_p = 200 – 191 = 9 \, \text{kJ/kg}\)
– Umsebenzi we-Net: \(W_{net} = 1100 – 9 = 1091 \, \text{kJ/kg}\)
– Okokufaka ukushisa: \(Q_{in} = 3500 – 200 = 3300 \, \text{kJ/kg}\)
Ukusebenza kahle kokushisa:
\[
\eta_{th} = \frac{1091}{3300} = 0.331 \cishe kube ngu-33.1\%
\]
Leli nani lifanelekile ngomjikelezo we-Rankine omuhle impela, kodwa izitshalo zamandla zesimanje ezibaluleke kakhulu zingaba phezulu uma zibhekwa njengokusebenza kahle kwesitshalo (yize zisathinteka yi-boiler, i-condenser kanye nokulahlekelwa umthwalo osizayo).
5. Izici Ezandisa Ukusebenza Kahle Kwezinjini Zesimanje Zomusi
a) Khulisa izinga lokushisa kanye nokucindezela komusi ongena ku-turbine
Uma izinga lokushisa elimaphakathi lokwengeza ukushisa liphakeme, kulapho kusebenza kahle khona (ngokuvumelana nesimiso sikaCarnot). Ubuchwepheshe obuphezulu kakhulu kanye nobuphezulu kakhulu buvumela ukusebenza ezingcindezini ezingaphezu kwephuzu elibalulekile lamanzi (22,1 MPa), kunciphisa ukulahleka okuhlobene nokushintsha kwesigaba kanye nokwandisa ukusebenza kahle.
b) Ukwehlisa Umfutho We-Condenser (Umshini Ongcono Wokushaja)
Ukwehlisa ingcindezi ye-condenser kwandisa ububanzi bokukhula kwe-turbine, ngaleyo ndlela kwandisa ukusebenza kwe-turbine. Kodwa-ke, lokhu kunqunyelwe izinga lokushisa lamanzi apholile, usayizi we-condenser, kanye nengozi yamazinga aphezulu omswakama ezigabeni zokugcina ze-turbine.
c) Umjikelezo Wokushisa Kabusha
Isifudumezi sifudumeza umusi ngemva kokunwetshwa kancane, bese siwukhulisa kabusha. Umphumela uba ukusebenza kahle okukhulu kanye nezinga eliphansi lomswakama endaweni yokukhipha i-turbine (kuphephile kakhulu kuma-blade e-turbine).
d) Ukuvuselelwa (Ukushisa Amanzi Okudla)
Ngokuthatha umusi othile ovela ku-turbine ukuze ufudumale amanzi okuhambisa amanzi, ibhoyila ayidingi ukunikeza ukushisa okuningi ukuze ifinyelele endaweni yokubila. Ukuvuselelwa kabusha kwandisa ukusebenza kahle komjikelezo, yize kunciphisa umthwalo womsebenzi we-turbine ngoba umusi othile awukhiqizi umsebenzi ngokucindezela okuphansi.
6. Umehluko phakathi kokusebenza kahle kokushisa komjikelezo vs. ukusebenza kahle kokukhiqiza
Kubalulekile ukuhlukanisa:
– Ukusebenza kahle kokushisa komjikelezo we-Rankine: kusekelwe ku-\(W_{net}/Q_{in}\) ezingxenyeni zomjikelezo.
– Ukusebenza kahle kokukhiqiza: kucatshangelwa ukulahlekelwa kokushisa, ukusebenza kahle kwebhoyila, ukulahlekelwa yijeneretha, imithwalo yokusiza (amaphampu, amafeni, ama-conveyor), kanye nokulahlekelwa kokudluliselwa kwangaphakathi.
Ezitshalweni zamandla ezisebenzisa amalahle, ukusebenza kahle kwebhoyila kanye nokulahlekelwa yisistimu kungaba yinto ebalulekile. Ngakho-ke, noma ngabe ukusebenza kahle kokushisa komjikelezo kubonakala kuphezulu, ukusebenza kahle okuphelele kungaba ngaphansi.
7. Isiphetho
Ukubalwa kokusebenza kahle kokushisa ezinjinini zesimanje ze-steam kusekelwe kakhulu ebhalansini yamandla omjikelezo we-Rankine: ukubala umsebenzi we-turbine, umsebenzi wepompo, kanye nokufakwa kokushisa ku-boiler (kanye ne-reheater, uma ikhona). Isihluthulelo sokunemba ukunqunywa okunembile kwamaphuzu esimo kanye nezakhiwo ze-thermodynamic (i-enthalpy, i-entropy, ikhwalithi ye-steam), kanye nokufakwa kwezimo zangempela ezifana nokusebenza kahle kwe-isentropic kanye nokwehla kwengcindezi. Ukusebenza kahle kokushisa kuyisibonakaliso esiyinhloko sokusebenza kwesistimu kanye nesisekelo sokuhlola ukulungiswa njengokwenyuka kwezinga lokushisa/ingcindezi, ukufudumala kabusha, ukuvuselelwa kabusha, kanye nokuthuthukiswa kwe-condenser.
Uma ufisa, ngingangeza isibonelo sokubala "sesimanje" (isb. umjikelezo wokushisa kabusha + ama-feedwater heater angu-1-2) agcwele amathebula e-state point kanye nemidwebo ye-Ts ukuze kulinganiswe ucwaningo lwe-PLTU lwangempela.
