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JOURNAL OF SCIENCE & TECHNOLOGY * No 88 2012 MODELLING OF CATALYTIC CONVERSION OF TOXIC GASES IN MOTORCYCLE EXHAUST AFTER TREATMENT SYSTEM MO HiNH HOA QUA TRINH XUC TAC TRUNG H 6 A KHI THAI DOC HAI TR[.]
JOURNAL OF SCIENCE & TECHNOLOGY * No 88 - 2012 MODELLING OF CATALYTIC CONVERSION OF TOXIC GASES IN MOTORCYCLE EXHAUST AFTER-TREATMENT SYSTEM MO HiNH HOA QUA TRINH XUC TAC TRUNG H A KHI THAI DOC HAI TRONG H $ T H N G X I T L Y KHI THAI XE MAY Hoang Dinh Long HanoiUniversity of Science and Technology Received March 8, 2012; accepted May 4, 2012 ABSTRACT The emission contml of motomycles in Vietnam is pariiculariy imporiant due to the high and fast raising number of these means of transpori One of the most effective method sused for emission contml of internal combustion engines is exhaust after-treatment, which has not been used in small capacity motomycles here This paper pmsents the study results on heat transfer and catalytic conversion modelling of the exhaust gas in motorcycle exhaust after-tmatment system equipped with a three-way catalytic converter for optimum design of exhaust emissions contml system The paper considers the chemical conversion of carbon monoxide (CO), unbumed hydrocarbons (HC) and oxide of nitmgen (NO) with detailed heat transfer modelling, which includes conductive, eonveetive and radiative heat transfers The modelling results show that using exhaust after-treatment system equipped with a three-way catalytic converter for emission control of motomycles can reduce exhaust emissions of NO and CO by 99% and HC by 70% after 300s from engine start TOM TAT Vide kiem sodt thdi xe mdy & Vidt Nam cd y nghTa ddc bidt quan vi s6 lugng cdc phuang tidn giao thdng ndy rit l&n vd vin dang ldng nhanh Mdt nhOng cdng nghd kiim sodt thdi hidu qua nhit cue ddng ca ddt tmng Id xi> /y thdi bing bd phan ung xuc tdc nhung edng nghe ndy lai chua dugc s& dqng trdn xe mdy dung tich nhd Bdi bao ndy trinh bdy kit qua nghien ciru md hinh hda qua trinh tmyin nhiet vd xuc tde tmng hda thdi he thdng x(> /y thdi xe mdy trang bj bd xOc tdc tmng hda tlidi ba chirc ndng Idm ca sd di thiet ke tdi uv hd thing xir ly thdi Bai bao di cap din sg biin ddi hda hoc cua d xit cdc bon (CO), hydrd cdc bon chua chay (HC) vd d xit nito (NO) va sg trao ddi nhidt cOa thdi v&i dng thdi vd mdi tru&ng gdm cdc qud trinh trao doi nhidt ddi luv ddn nhidt vd buc xp nhidt Kit qua nghidn ciru chi rang su dung he thing xif /)? thdi trang bi bg xuc tdc tmng hda thdi ba ch&c ndng cho xe mdy cd thi gidm phat thai NO vd CO den 99%, gidm HC din 70% sau 300s tir liic khai ddng ddng ca INTRODUCTION „ , 'n Vietnam, following the socioeconomic development, the number of motorcycles as individual transport means increases very fast By the mid of 2008, the number of these transport means in the country is nearly 22 millions and the expected number for the 2020 will be more than millions [1] This has caused the growing concern on environmental pollution and public health, which has forced the government to be more proactive in emission control of motorcycles as well as ofolher transport vehicles [2], For motor vehicles (cars and trucks), many effective technological advancements have been made to lessen tailpipe emissions which include the improvement of petroleum originated fuel quality, mandatory installation of three-way catalytic converters (TWCs),use of j„,„^,i,e f„e| vehicles such as "plug-in" electric cars, LPG and CNG buses and hybrid ^^^.^|_.^ ^^^ 1,^^^ ^^^ ^^^^ f^^ ^„,^ ^^^^^ ,^^^^ ^^^^^^ „ ^^^j^^ ^ ^ ^ ^ ^ j , ^ j ^ ^ treatment to achieve a significant reduction in ,^^.^ emissions They have been considered to ^^ ^^^ ^^ ,^^ ^^^^ ^fj^^,;^^ technologies of emission control in cars [4] For small capacity motorcycles, however, the design and installation of TWCs have not been of interests The study of emission control ^^ ^^^^^ motorcycles have mainly focussed on _ ^ ^^^ ^^ of alternative fuels [5 6] Nowadays, with more and more stringent JOliRNAL OFSCIENCLiU lECHNOLOGY• No.88-2012 emission standards, it is necessary to further reduce exhaust emissions by applying advanced exhaust after-treatment technologies This paper sludies the conversion efficiency of exhaust gas of the motorcycle exhaust after-treatment system equipped with a TWO The modelling approach is applied for the study of heat transfer and catalytic conversion of exhaust gas in the system for optimum design and installation of a TWC in the system MATHEMATICAL MODELS OF HEAT TRANSFER AND CATALYTIC CONVERSION OF EXHAUST GASES 2.1 Motorcycle system exhaust artcr-lrcalmcnt catalyst material JM of 2200g/m' TWC, catalyst area of ISmVg The size of TWC is primarily chosen and then evaluated and modified accordingly so that it works with conversion efficiency of 70-99% and pressure loss less than 10% In Ibis case the catalyst diameter of 4cm and length of 4cm are primarily determined 2.2 ilcat transfer models In exhaust pipe The heal transfer model simulates thermal response of the exhaust gas and predicts gas temperature along the exhaust pipe It helps to predict accurate gas temperature al the inlet face of the TWC and serves as the input data to Ihe catalyst model.By assuming quasi-steady, incompressible flow, the energy balance equation for Ihe exhaust gas and the exhaust pipe are written as follows: Hi Figure I Motorcycle exhaust system equipped with a TWC (applied lo Honda SuperDream) 1- Flange-joint to engine exhaust port 2- TWC: 3- Exhaust pipe: 4- Muffler Figure I describes a motorcycle exhaust system equipped wilh a TWC for exhaust treatment TWC is installed somewhere at the exhaust pipe between flange I and muffler The appropriate installation position of TWC in the system is experimentally or theoretically detennined dt ' dt u (1) - • dx P.^pn^> D'T ct—f" -9 rod Where T \s temperature;/ - time; x - length coordinate; p- density; c- heat capacity; V- control volume of gas (Ki) or pipe (F;); u- gas velocity; q- transferred heat flux ffrom gas to inner wall of pipe q^, convecdon to ambient q„„ radiation to surroundings^„j); subscripts g for gas, p for pipe.aforambienl q^=h^nd,A.x{T^~T^) ^^Liu.: ^ r - JoanL zinnnP ^nr^ (2) ^r'^/ (3) ã/nô='' T'/:iv(7:^-7;,) (4)