Nghiên cứu quá trình cháy trong động cơ diesel sử dụng bio diesel

• ;• -IL • l l N CflU-TRAO DOI v.NGHIEN CU'U QUA TRINH CHAY TRONG DONG CO DIESEL SLP DUNG BIO-DIESEL STUDY THE COMBUSTION PROCESS ING DIESEL ENGINE USING BIO-DIESEL TS Nguyen Huy Hao TrUdng Dai hpc Hang hai Viet Nam TOM TAT Nhien lieu sinh hgc Id mgt nhiing nguon nhien lieu thay theco khd nang tdi tao vd thdn thien vdi moi trUdng Bdi bdo gidi thieu ket qud nghien citu ly thuyet vd thiic nghiem qud tr'mh chdy dgng cd diesel sii dung bio-diesel nham ddnh gid khd ndng chuyen do'i sA dung loai nhien lieu ndy cho cdc dgng cd sit dung nhien lieu diesel truyen thong (thUc nghiem diidc trien khai tren dgng cd diesel tdu thuy K657M2-6H12/14 vd 6LU32, tai Trung tdm Nghien ciiu he dgng liic Tdu thuy, TrUdng Dai hgc Hdng hdi Viet Nam) Tflkhda: Diesel sinh hgc, qud trinh chdy, nhien lieu thay the ABSTRACT Bio-fuel is one of the alternative fuels that have rene-wahle and environmentally friendly In this paper was introduced researching result on theory and practice of the combustion process in diesel engines using bio-diesel to avaluate the ability of using this kind of fuel for the traditional diesel engines (Thepractice had been carried out on diesel engines K657M2-6H12/14 and 6LU32 at Reseching center of Marine propulsion system - Vietnam Maritime University) Keyy/ords: Bio-diesel, combustion process, alternative fuel TAP CHi CO KHi V I £ T NAM, '^ Sd nam 2014 www.cokhivietnam.vn NGHIEN ClJfU-TRAO DOI l.DATVANDE 2.1 Mpt so gia thiet Hien nay, nguon nhien heu hda thach dang cang can kiet, dong thdi viec sd dyng ngudn nhien lieu lam cho mdi tnidng bi d nhiem nghiem trgng Chinh vi vay, viec tim nguon nhien lieu thay the cd kha nang tai tao va than thien vdi mdi tnidng la het sdc can thiet va nhien lieu sinh hpe ehinh la mpt nhUng nguon nhien lieu ay De xay dUng md hinh toan hgc qua trinh chay, bai bao sii dung md hinh hai viing d u g e xay dUng b d i V.A Zvonov va G.S Kornilov [1] Md hinh cho phep tinh toan qua trinh chay vdi hai loai nhien lieu ddc lap Day la diem khae biet so vdi cac mo hinh tinh toan khac d chd coi hdn hdp nhien lieu diesel va dau sinh hge la mgt hon hgp ddng nhat va qua trinh chay xay d mpt vung thong nhat O Viet Nam, nhien lieu sinh hpc cd tiem nang ldn nhd cd nguon nguyen lieu phong phu Dau sinh hpc (bio-diesel) ve ed ban cd cac dac tinh ly hda khong khae nhieu so vdi diesel dau md, vay khdng anh hudng nhieu den ehat lypng qua trinh chay xilanh dpng cd, ben canh do, dau sinh hgc khong ehUa phan lUu huynh nen giam phat thai lUu huynh khixa Tuy nhien, de chuyen doi sd dung nhien lieu sinh hpc cho cac dpng cd diesel tau thuy von dypc thiet ke de sU dung nhien Heu co ngudn goc dau md, chiing ta can phai co nhQng nghien eUu danh gia cy the anh hUdng cua nhien lieu sinh hge den cae dac tinh ky thuat cua dgng ed, kha nang giam phat thai dpc hai doi vdi moi trUdng cung nhU can eo nhUng thay doi nhat dinh he thong cung cap nhien lieu cua dgng cd Do pham vi cd han, npi dung bai bao tap trung nghien cdu sy thay doi dac tinh ky thuat cua dpng eo va mUe dp phat thai NOx thong qua cac mo hinh ly thuyet ve qua trinh chay va sy hinh NO^ cung nhu dUa tren eae ket qua thye nghiem dpng eO sif dung nhien lieu bio-diesel MO HINH TOAN H O C QUA TRINH CHAY CUA DONG CO DIESEL SlT DUNG DAU SINH HOC De tinh toan qua trinh chay va qua trinh hinh NOx dpng cP diesel sd dung dau sinh hpc (cu the la hon hdp cua dau diesel va dau sinh hgc tii B5 den B20) vdi cac tinh toan dpc lap eho qua trinh chay dau sinh hgc va dau diesel, ehiing ta can dya mpt s6 giai thiet: - He so dy lypng khdng a sd dung dau sinh hpc va dau diesel la nhU nhau; - Quy luat chay cua nhi^n Heu dugc mo ta bdi cdng thdc Vibe; - Khdng cd sU truyen nhiet giUa san pham chay vdi khdng saeh va nhiet cua hon hpp khong thay doi theo ap suat cua hon hdp Viee tinh toan qua trinh chay dgng cd diesel sd dung nhien lieu sinh hgc dypc dya bdi cac phUdng trinh vi phan can bing the tich bao gom the tich chay cua dau diesel va the tich chay cua dau sinh hpc [I] Ddng thdi, buong dot thi khdi lUpng eua san pham chay khdng thay doi va nhiet buong ddt la nhiet eua hdn hgp san pham chay, cac thdng so khae phue vu chd viec tinh toan nong dp NO^ thi da dupc xac dinh ro TAP CHi C O KHi VIET NAM, Sd nam 2014 www.cokhivietnam.vn NGHIEN CUfU-TRAOeOl 2.2 Md hinh toan hoc qua trinh chay Phypng trinh vi phan can bang the tieh san pham chay buong dot dUde xac dinh theo cdng thdc sau [1]: dV„ + dV,=dV^ + dV+dV, (1) phan phan tram theo khdi lypng eua hidro, oxy cd dau diesel va dau sinh hgc; L^P la lupng khdng ly thuyet de dot chay het kg dau diesel; L^^ la lUgng khong ly thuyet de dot chay het kg dau sinh hpc; q^ lUpng dau sinh hpc cd kg hon hpp nhien lieu Lugng nhiet nhan dUpc ddt chay Trong dd: dV^yla the tieh san pham chay kg dau sinh hpe [1]: cua hon hgp nhien heu diesel [m^];dVglk the tich san pham chay cua hdn hpp nhien lieu sinh hpc [m^]; dV^^ la sy thay doi doan nhiet cua the tich chay budng dot [m^], dypc xae dinh theo cdng thdc sau: dK.„ kp (2) dp t/K„ la sy thay doi the tich sy thay doi so phan tii nhien Heu d the qua trinh chay [m^], va dypc xac dinh theo cdng thdc sau: dV (3) ^—dM M Vdi: V la the tich xilanh d thdi diem ket thue qua trinh chay [m^]; p la ap suat xilanh d thdi diem ket thuc qua trinh chay [Mpa]; M la so moi san pham chay, M dUde xac dinh theo cdng thdc sau: 32 ' (1-9,; (4) M = ^ ^ + — + a L „ , q, (5) M=M„+Mj (6) 32 Vdi: Q^p la nhiet tri thap cua dau diesel [J/kg]; Qj^g nhiet tri thap cua dau sinh hoe [J/ kg]; ton that nhiet qua vach xilanh [J]; ton that nhiet sU phan tan va nhien lieu khdng chay [J], "' Nhiet lugng ton that qua vach xilanh dupc tinh theo cong thUc Woschi [3]: dQ.- - ,.{T = 1,151.^;?' r (2,45 + 0,185c„,) (8) (9) Trong do: a,,,, la he so toa nhiet cua chay tdi vach xilanh [w/mlK]; F^, la dien tich be mat chay vdi vach xilanh [m^]; T^, p la nhiet va ap suat cua chay; n toe quay ciia true khuyu [v/pj; c^^ toe dp chuyen dong tinh tien trung binh cua piston [m/sj; la goc quay ciia true khuyu Ton that nhiet phan tan va nhien lieu khong chay duoc xac dinh theo cong thUc (21: dQ^=(Q„/uydM Trong do: H„, O^, H,, O,, tuong ilng la -TJ.F^.^ + Q,„.M.di-,„) (10) Trong do: r ^ o '^ ty le CO san pham chay; Qco=264000kJ/mol "^ TAP CHI' CO KHi VIET NAM, So nam 2014 www.cokhivietnam.vn NGHIEN cufu - TRAO D | Nhiet va ap suat buong dot duoc xac dinh til phuong trinh trang thai cua chat [3]: r, P^ ^R + T 8,314M C, ' (11) Trong do: Q la luong nhiet nhan duoc til chay [J/kg]; C^: Ap suat chay xilanh [Mpa]; Cp la ty nhiet dang ap trung binh cua chay [J/kg.K]; V the tich san pham chay [m'l; T^ la nhiet moi chat cuoi qua trmh nen [K], duoc xac dinh theo cong thiic sau [2]: r=r.ô"'-' NjO + H ã N , + O H Xac dinh nong NOx * « " '^" '^^^ Zeldovich: Phuong trinh xac dinh toe hinh NO duoc the hien cong thiJc sau day [1]: (13) •10%, + dT ' i (12) Vcfi: T^ la nhiet xilanh cuoi qua trinh nap [K]; £ la ty so nen cua dong cO; n^ la chi so nen da bien cua dpng co Trong do: r^o,/-^^, r^, v l ^ ^ ^ h phan the tich cua NO, N,, O, O^ K,^ K,^, K,, la cac he so phan ilng dUpc xac dinh bang cac cong thdc [2]: MO HINH TINH TOAN QUA TRINH HINH THANH N O x NOx '^^^'^ l^l"!' dpng ca ducfi dang: ni-to tac dung vdi hydrocarbon khong chay (HC), tao cac goc oxit ni-tO; ni-tO nguyen til nhien lieu tac dung vdi 6-xi qua trinh chay, ni-to khong nap tac dung vdi 6-xi phan Ung chay d nhiet dp ldn hdn 1700 °K tao cac 6-xit ni-to 37985 A:,^=1.3610"( (14) K:,=3.l2\0"e (15) = 1.33-10'"r.,e K: La he so can bang phan dng N^ + O^ = N 0);; Dudi day la cac phan dng hda hoc ciia qua trinh hinh NO^: Xet phUdng trinh tong quat [2]: v„A + Vi^B^vC l.O-l-N, N0 + d[C]_ C O K H i V I £ T NAM, (17) K,j[AY-[BT K„lAY-[B]" (18) Vdi gia thiet nong cua cac chat 0,0j, H, OH, Nj d trang thai can bang va ndng dp N,NO dupe khong che bdi dgng hoc phan Ung N,0 + H ^- NH + NO CHi + v,D Toe tao mpt chat d ve phai, vi du chat C dUdc tinh nhu sau [1]: N -I- O H