Influence of exhaust gas recirculation on performance of a turbocharged diesel engine running on biofuels blends.

Thesis (MEng)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Exhaust gas recirculation technology has been implemented with success in the automotive industry in reducing nitrogen oxides in diesel exhaust gas. Given that South Africa’s Clean Fuels programme currently adheres to Euro II fuel and emissions standards, research into the influence of exhaust gas recirculation on a more modern TDI engine running on locally sourced biofuel blends is done for this project. In this research project the existing engine test bench is upgraded by equipping the exhaust gas recirculation system as well as the compressor of the variable geometry turbocharger with various sensors and instrumentation. All the data acquired from the sensors is logged by a graphical user interface program developed in LabVIEW. National Instruments data acquisition devices USB 6351 and USB 4350 are interfaced with LabVIEW to obtain the recorded data. Further improvements include the addition of a water-to-air intercooler developed in-house to control the charge air temperature. An eddy current dynamometer replaces the previous hydraulic dynamometer to improve steady state speed and torque control of the engine. Experiments were performed on two biofuel blends, B20 and E10, using crude derived pump fuel as the base fuel. Both biofuel blends were splash blended and mixed by volume. The B20 blend consists of twenty percent biodiesel, obtained from waste cooking oil, and eighty percent base fuel. The E10 blend consists of ten percent ethanol mixed with the ninety percent base fuel. All fuels are refined locally. The control of the exhaust gas recirculation is maintained as per the original equipment manufacturer. The focus of this study is therefore to determine how exhaust gas recirculation affects a diesel engine optimised to run on ultra-low sulphur diesel and how it responds to running on different biofuel blends in terms of fuel consumption, temperatures and emissions of specifically nitrogen oxides. Results suggest that there is little to no variation in brake specific fuel consumption at the partial loads tested. The emission of nitrogen oxides does not deviate significantly between the fuels, however a marked reduction in soot is noticed for the E10 blend. Carbon monoxide concentrations are also higher for the E10 blend at high speed, low load operating points. As expected, nitrogen oxides are increased with the reduction in exhaust gas recirculation rate.AFRIKAANSE OPSOMMING: Uitlaatgas hersirkulasie word suksesvol deur die motor industrie gebruik om stikstof oksiede in diesel uitlaatgasse te verminder. Suid-Afrika se Skoon Brandstof program voldoen tans aan Euro II brandstof en uitlaatgas standaarde. Hierdie projek fokus dus op navorsing van die invloed van uitlaatgas hersirkulasie op ʼn meer moderne TDI enjin, wat loop op plaaslik vervaardigde biobrandstof mengsels. Die navorsings projek behels die opgradering van die enjin toetsbank deur die uitlaatgas hersirkulasie sisteem sowel as die kompressor van die turboaanjaer, volledig uit te rus met sensors en instrumentasie. Alle data verkry vanaf die sensors word opgeneem deur ʼn grafiese verbruikers koppelvlak program wat ontwikkel is in LabVIEW. Die sensor informasie word deur ˊʼn National Instruments USB 6351 en USB 4350 toestel na die rekenaar herlei deur LabVIEW. Verbeterings aan die toetsbank sluit in die vervanging van die oorpronklike tussen-verkoeler met ʼn water-na-lug tussen-verkoeler om die saamgedrukte lug se temperatuur te beheer. ʼn Nuwe werwelstroom dinamometer, wat die vorige hidrouliese dinamometer vervang, verseker dat die bestendigde toestand van spoed en wringkrag beheer op die toetsbank ook verbeter is. Eksperimente word uitgevoer op twee biobrandstof mengsels, B20 en E10, met ruolie afkomstige pomp diesel as ‘n basis brandstof. Beide mengsels was afgetap en per volume gemeng. Die B20 mengsel beslaan twintig persent biodiesel, afkomstig vanaf ou kookolie, en tagtig persent van die basis brandstof. Die E10 mengsel beslaan tien persent etanol en negentig persent van die basis brandstof. Alle brandstowwe word plaaslik vervaardig. Die beheer van die uitlaatgas hersirkulasie sisteem word bepaal deur die oorspronklike enjin beheereenheid. Die navorsing fokus op die veranderinge wat te weeg gebring word deur die uitlaatgas hersirkulasie sisteem op die enjin karakteristieke insluitend brandstofverbruik, temperature en uitlaatgasse soos stikstof oksiede. Die aanpassing van die enjin beheereenheid met die gebruik van verskillende brandstowwe is ook van belang. Die resultate dui daarop aan dat die spesifieke brandstof verbruik, by laer wringkragte, nie baie varieer tussen die verskillende brandstowwe nie. Die uitlaat van stikstof oksiede varieer nie merkwaardig tussen die verskillende brandstowwe nie, maar die uitlaat van swart roet verminder vir die E10 mengsel. Koolstofmonoksied konsentrasies is hoër vir die E10 mengsel, teen hoë enjin spoed met lae wringkrag. Stikstof oksiede vermeerder hoe minder uitlaat gasse teruggevoer word na die inlaat van die enjin, soos verwag deur die gebruik van uitlaatgas hersirkulasie