High Octane and Oxygenate test set-up for CFR Octane Engine.

Thesis (MEng)--Stellenbosch University, 2018.ENGLISH ABSTRACT: Petrol blending involves mixing of several refinery fuel streams, each with different properties that contribute to the usability of the final product. The octane rating of a fuel stream is the measure to which auto-ignition can be resisted. Octane properties of fuel streams are measured on a Cooperative Fuels Research (CFR) engine. The typical operating range of a CFR engine does not allow for high octane (Research Octane Number > 100) and oxygenated (Vol % > 25) fuels. While the 100 RON CFR test limit may generally suffice for routine petrol product certification, it results in difficulty characterising the octane properties of the high octane blending components, leading to difficulty in octane prediction and plant planning. Additionally, the impending clean fuels 2 (CF2) legislation gives rise to the significance of research and development of environmentally friendlier fuels, which includes high volume content oxygenated fuels. There are currently no test laboratories in South Africa that are able to provide octane test results above the 100 RON, and 25 % Vol oxygenate limit. In this study, a conventional CFR engine setup at Stellenbosch University was disassembled, inspected, upgraded and modified to allow for research on high octane and oxygenated fuels. The modified setup was calibrated and declared “fit for use”, based on toluene standardised fuels (TSF), and high volume content oxygenated sample tests. The octane properties of previously uncharacterised Sasol refinery stream components, such as TAME, C5 raffinate, and fuel ethanol blends were successfully investigated. TSF test results demonstrated excellent octane continuity, eliminating the need to resort to the American Society for Testing and Materials (ASTM) standard method of using tetraethyl lead (TEL) for bracketing high octane samples. Blending octane number (BON) determinations were investigated, and it was found that, in some cases, similar molecular construction of the base fuel and blending component reduces synergistic intermolecular effects, improving BON results. The modified CFR setup incorporated a chilled fuel float chamber in order to prevent light component evaporation, enabling research on previously untestable highly volatile streams. It was proven that liquid chilling of test samples does not invalidate octane results. A primary reference fuel (PRF) round robin test showed that the modified CFR engine setup at Stellenbosch University produces accurate and repeatable results, on a comparative level with modern, professional and certified octane test laboratories.AFRIKAANSE OPSOMMING: Petrolvermenging behels die vermenging van verskeie raffinaderykomponente met verskillende eienskappe wat bydra tot die bruikbaarheid van die finale produk. Die oktaangetal van ’n brandstofkomponent is die mate waartoe selfontbranding weerstaan kan word. Die oktaangetal van ’n brandstofkomponent word op ‘n “Cooperative Fuels Research”-enjin (CFR Engine) gemeet. Die tipiese bedryfsgrense van ’n CFR-enjin maak nie voorsiening vir hoëoktaanbrandstowwe (Research Octane Number > 100) en hoëkonsentrasie alkoholgebaseerde toetsmonsters (Vol % > 25) nie. Hoewel die 100 RON toetsgrens oor die algemeen voldoende is vir sertifisering van petrolprodukte, veroorsaak dit probleme met die tipering van die oktaaneienskappe van hoëoktaan-mengselkomponente wat weer probleme met oktaanvooruitskatting en aanlegbeplanning tot gevolg het. Die belang van hoë suurstofkonsentrasie brandstoftoetse neem tans toe met die oog op die toekomstige skoon brandstowwe 2 wetgewing (CF2). Daar is tans geen oktaantoetslaboratoria in Suid-Afrika wat oktaantoetsresultate bó die 100 RON- en 25 % perk kan lewer nie. In hierdie studie is ‘n konvensionele CFR-enjinopstelling by die Stellenbosch Universiteit uitmekaargehaal, nagegaan, gerestoureer en aangepas ten einde navorsing op hoëoktaan- en alkoholgebaseerde brandstowwe moontlik te maak. Die aangepaste opstelling is gekalibreer en as geskik vir die bepaalde doel verklaar op grond van tolueen-gestandaardiseerde brandstof toetse, en toetse wat gedoen is op monsters met ’n hoë suurstofkonsentrasie. Die oktaaneienskappe van voorheen ongetipeerde Sasol-raffinaderykomponente, soos TAME, C5-raffinaat en etanolbrandstofmengsels is suksesvol ondersoek. Die TSF-toetsresultate toon uitstekende oktaankontinuïteit wat die behoefte om die American Society for Testing and Materials (ASTM)-standaardmetode van tetraethyl lood (TEL) vir die tipering van hoëoktaanmonsters uitskakel. Vermengde oktaangetalle (BON) is bestudeer en daar is bevind dat soortgelyke molekulêre samestellings van ‘n basisbrandstof en mengselkomponente die sinergistiese uitwerking verminder wat in sekere gevalle BON-uitslae verbeter. Die aangepaste CFR-enjinopstelling het ’n verkoelde brandstoftenk ingesluit wat die verdamping van ligte komponente voorkom en sodoende navorsing op hoogs vlugtige, voorheen ontoetsbare komponente moontlik maak. Daar is bewys dat verkoelde vloeistof-toetsmonsters nie oktaanresultate ongeldig maak nie. ’n “Round robin”-primary reference fuel (PRF)-toets dui daarop dat die gewysigde CFR-enjinopstelling by Stellenbosch Universiteit akkurate en herhaalbare resultate lewer wat kan meeding met moderne, professionele en gesertifiseerde oktaantoets-laboratoria