Final Report Summary - GENFUEL (Addressing Fundamental Challenges in the Design of new generation fuels.) ER! - A range of refinery based fuels were tested in a constant volume vessel to find the relationship between physical and chemical properties and combustion characteristics, such as ignition delay, burn period, together with the pressure history and the associated heat release analysis to provide information on the combustion modes. Visualisation using chemiluminescence and high-speed imaging provided further information on mixing, ignition and combustion. The fuels tested were diesel like fuels with cetane numbers between 43 and 72, gasoline with 10% Ethanol with different combinations of RON (92/95) and MON (77-87) to vary its octane sensitivity, along with two naphtha type fuels. These were injected in a constant volume vessel with ambient conditions varied between temperatures of 500-590°C, vessel pressures between 28-75 bar, injection pressures between 400-1600 bar and oxygen content between 15%-21%. [1]ER- 2 One aspect of our GENFUEL work focused on the combustion properties of dimethyl ether (DME), which we have been studying for multiple reasons. The first being that it was used as a reactivity booster in our work on the combustion of toluene [4], which is an important component of gasoline fuels and computational surrogates, and hence is of direct relevance to the work being carried out as part of GENFUEL. Our approach to modelling DME combustion is two-tiered. First, high-level quantum chemical methods have been applied to study the elementary reactions of importance in DME low-temperature combustion, with detailed chemical kinetic modelling methods then used to rationalise the broad spectrum of experimental measurements which currently exist in the literature[2] The combustion-related thermodynamic properties of diesel/cetane booster mixtures in order to rationalise endothermic effects observed in the Shell Combustion research unit ( constant volume chamber) [5]In tandem with the above fundamentally focused projects, we have also applied detailed chemical kinetic models to interpret octane effects in highly boosted downsized direct-injection spark-ignition engines, and in CFR engines, in collaboration with global engine manufacturers. These works, contain a wealth of interesting engineering and chemical results which can feed directly into the development of NUI Galway’s chemical kinetics models, Shell’s fuel design process, and the engine design process. [3, 6,7]. Particular focus has been paid to understanding the relative importance of RON and MON in spark ignition enginesER3 - Experimental work was be carried out using a new single cylinder gasoline engine in SHELL(DE) and a multi-cylinder engine at UoB (University of Birmingham).Eight ethanol containing fuels were designed and tested, including four splash blended ethanol fuels (10 vol.%, 20 vol.%, 30 vol.% and 85 vol.% ethanol, referred to as E10, E20, E30 and E85), one match blended fuel (E0-MB) with no ethanol content but the same octane rating as E30, and three fuels (F1-F3) with different combinations of RON and octane sensitivity. The experiments were conducted in a single-cylinder direct-injection spark ignition (DISI) research engine. Load and spark timing sweep tests at 1800 rpm were carried out for E10-E85 to assess the combustion performance of these ethanol blends. In order to investigate the impact of charge cooling on combustion characteristics, the results of the load sweep for E0-MB were compared to those of E30. Load sweep tests were also carried out for F1-F3 to understand the impacts of RON and octane sensitivity on suppressing engine knock. The results showed that at the knock-limited engine loads, splash blended ethanol fuels with a higher ethanol percentage enabled higher engine thermal efficiency through allowing more advanced combustion phasing and less fuel enrichment for limiting the exhaust gas temperature under the upper limit of 850 °C, which was due to the synergic effects of higher RON and octane sensitivity, as well as better charge cooling. In comparison with octane sensitivity, RON was a more significant factor in improving engine thermal efficiency. Charge cooling reduced engine knock tendency through lowering the unburned gas temperature. [8,10]. An overall assessment from a well to wheels perspective has been made of the Greenhouse Gas Benefits of ethanol blending into gasoline [13]Gas-to-liquid (GTL) naphtha can be used as a gasoline blend component, and the challenge of its low octane rating is solved by using ethanol as an octane booster. However, currently there is little knowledge available about the performance of gasolines containing GTL naphtha in spark ignition engines. The objective of this work is to assess full load performance of gasoline fuels containing GTL naphtha in a modern spark ignition engine. In this study, four new gasoline fuels containing up to 23.5 vol.% GTL naphtha, and a standard EN228 gasoline fuel (reference fuel) were tested. These new gasoline fuels all had similar octane rating with that of the standard EN228 gasoline fuel. The experiments were conducted in an AVL single cylinder spark ignition research engine under full load conditions in the engine speed range of 1000–4500 rpm. Two modern engine configurations, a boosted direct injection (DI) and a port fuel injection (PFI), were used. A comprehensive thermodynamic analysis was carried out to correlate experiment data with fuel properties. The results show that, at the full load operating conditions the combustion characteristics and emissions of those gasoline fuels containing GTL naphtha were comparable to those of the standard EN228 gasoline fuel. Volumetric fuel consumption of fuels with high GTL naphtha content was higher due to the need of adding more ethanol to offset the reduced octane rating caused by GTL naphtha. Results also indicate that, compared to the conventional E228 compliant gasoline fuel, lower particulate emissions were observed in gasoline fuels containing up to 15N.4 vol.% GTL naphtha.[9, 12]The anti-knock quality of gasoline fuels is a significant contributing factor to the indicated thermal efficiency (ITE) of spark ignition (SI) engines. Historically, the anti-knock quality of gasoline is characterised by two parameters, research octane number (RON) and motor octane number (MON), which are measured in cooperative fuel research engines (CFR) using iso-octane and n-heptane as the primary reference fuels (PRFs). However, due to significant hardware, operating condition and fuelling differences between the CFR and the modern SI engines, the relevance of RON and MON to modern SI engines needs to be re-assessed. In this study, six fuels were designed with independent control over RON and MON. The other key fuel properties, such as the heat of vaporisation, the oxygen content, the lower heating value and the stoichiometric air-fuel ratio (AFR) were kept similar for all the fuels. Among the six fuels, two fuels represent regular- and premium-grade gasoline fuels with respect to octane quality in the North American market. The objective of this study was to assess the significance of RON and MON to the combustion characteristics of a modern SI engine. A single cylinder 4-stroke direct injection spark ignition (DISI) research engine was used as the experimental tool. The engine tests were conducted at the engine speed of 1800 rpm and the engine load ranging from 4 to 20 bar IMEP. Three market representative engine compression ratios (9.5:1 10.5:1 and 11.5:1) were selected. In addition, the engine K value was calculated at knock-limited engine conditions. The results showed that, under knock-free engine operating conditions and at a fixed engine compression ratio, variation of fuel RON and MON had almost no differential impact on ITE. Under knock-limited operating conditions, increasing MON did not increase ITE, and in contrast, even led to decreased ITE especially when RON was as low as 93 and the compression ratio was high. Under knock-limited operating conditions, when the RON of the fuel was as high as 98, changing the MON up or down only showed combustion phasing benefits/disbenefits without obvious ITE benefit. This is because the octane rating of the fuel was high and in order to differentiate their anti-knock quality, a higher compression ratio than 11.5:1 was needed. The calculated engine K value shows that RON was a more significant influential factor than MON in determining the engine thermal efficiency. RON was found to have a higher impact on ITE at the higher MON of 88 vs. the lower MON of 83 [8,11,14] ER4 - Ignition delay time (IDT) is one of the most important combustion properties of a flammable mixture. It is used as an input for modelling diesel engine combustion, knock modelling, gas turbines and any device where high initial temperature and pressure occur. IDT value was also used to calculate induction zone length in ZND detonation model to assess correlation with detonation cell size or detonability parameters. Example induction zone length calculations in stoichiometric ethane-air mixture with use of different reaction mechanisms: GRI 3.0 Konnov 0.5 and Aramco 2.0 gave the values of 1.9 mm, 1.0 mm and 0.85 mm, respectively. Taking into account the importance of the IDT value in many areas of modelling the proper selection of the chemical reaction mechanism becomes crucial. Up to date there are many chemical reaction mechanisms available of which the majority were validated against limited experimental data. The main aim of the analysis was to quantify the quality of the available chemical reaction mechanisms by comparing numerical IDTs with the experimental ones. The results may be used as a guide for selecting reaction mechanism for modeling combustion of aparticular fuel and for further analyses in the context of mixture detonanability [15-17]Using a modified CFD methodology, simulations have been carried out on detonations in small (20 L tanks) and medium (1 and 6 m3 tanks) scale. [18]ER5 - The consequences of both water usage and greenhouse gas (GHG) emissions and other environmental impacts should be considered over the entire supply chain in order to properly assess the relative environmental impacts of different fuels. However, accounting for water impacts along the supply chain is difficult due to the locality of water use. Existing water accounting methodologies either ignore local water scarcity (e.g. Water Footprint) or aggregate all impacts into one score, meaning that water issues may be hidden (e.g. water life cycle assessment methods). In this study, a methodology has been developed to identify the trade-offs and synergies between GHG emissions, freshwater use, and water pollution (i.e. eutrophication potential) for fuel pathways. The water related impacts are estimated for every stage of the supply chain with a risk matrix where the local water-to-availability (WTA) ratio is plotted against the water intensity allocated to each stage of the supply chain. As a next step, the scores of the risk matrix, the GHG savings and eutrophication potential of various fuel pathways are plotted in a radar diagram to compare their environmental impacts. The methodology is demonstrated with case studies of biodiesel from rain-fed or irrigated soybean from Nebraska and a conventional fossil diesel from California. The results show water related risks may arise during oil refining and oil production, mainly due to the high water stress in California (WTA = 0.49). Water related risks may also arise during soybean cultivation if irrigation is taking place, mainly due to the large water volumes. For rain-fed soybean diesel production, no water related risks are expected due to low water stress and modest water volumes. However, the rain-fed case leads to slightly lower GHG savings (58% versus 61%) and higher eutrophication potentials (0.09 versus 0.11 kg PO43--e/GJfuel) than the irrigated case. Using this methodology, it is possible to clearly visualize that both irrigated and rain-fed cases. [19,20]Publications1. Hardalupas, Y; Hong, C; Taylor, AMPK, “Ignition delay and burn duration of refinery based fuels in a constant volume vessel at diesel engine conditions”. FISITA Conference, 2016, Busan, Korea.2. K. P. Somers, U. Burke, B. Parjuli, G. Mittal, R.F. Cracknell, H.J. Curran “A Quantum Chemical, Detailed Chemical Kinetic Modelling and Rapid Compressions Machine Study on the Combustion of Dimethyl Ether Proceedings of the European Combustion Meeting”, 2017, Dubrovnik, Croatia3. K.P Somers, Roger F Cracknell, Henry J Curran “Simulating the Octane Appetite of SI Engines”: The Influence of Chemical Mechanisms”, Proceedings of the European Combustion Meeting, 2015, Budapest, Hungary4. Yingjia Zhang , K. P. Somers,, Marco Mehl, William J. Pitz, Roger F. Cracknell, Henry J. Curran “Probing the antagonistic effect of toluene as a component in surrogate fuel models at low temperatures and high pressures. A case study of toluene/dimethyl ether mixtures” Proceedings of the Combustion Institute, 36,, 2017, 413–4215. K.P Somers, H J Curran, U Burke, C Banyon, H M Hakka, Ph.D; F Battin-Leclerc, P-A Glaude,; S Wakefield; R F Cracknell “The Importance of Endothermic Pyrolysis Reactions in the Understanding of Diesel Spray Combustion” Accepted for publication in Fuel6. K.P. Somers, Roger F. Cracknell, H.J. Curran “A Chemical Kinetic Interpretation of the Octane Appetite of Gasoline Engines” Submitted to International Combustion Symposium 20187. Cracknell R.F. Prakash A., Somers K.P. Wang C ”Impact of Detailed Fuel Chemistry on Knocking Behaviour in Engines”. In: Günther M., Sens M. (ed.s) Knocking in Gasoline Engines. Proceedings of the 5th International Congerence on Knocking in Gasoline, Engines, Berlin, Germany December 12-13 2017. Springer, Cham https://doi.org/10.1007/978-3-319-69760-4_148. Wang CM, Zeraati-Rezaei S, Xiang L, Xu H. “Ethanol blends in spark ignition engines: RON, octane-added value, cooling effect, compression ratio, and potential engine efficiency gain”. Applied Energy. 2017;191:603-19.9. Wang CM, Chahal J, Janssen A, Cracknell R, Xu H. “Investigation of gasoline containing GTL naphtha in a spark ignition engine at full load conditions. Fuel. 2017;194:436-47. in 10. Wang CM, Janssen A, Prakash A, Cracknell R, Xu H. “Splash blended ethanol a spark ignition engine – Effect of RON, octane sensitivity and charge cooling”. Fuel. 2017;196:21-31.11. Prakash, A., Wang, C., Janssen, A., Aradi, A. et al., "Impact of fuel sensitivity (RON-MON) on engine efficiency," SAE Int. J. Fuels Lubr. 10(1):2017, doi:10.4271/2017-01-0799.12. Wang CM, Chahal J, Janssen A, Cracknell R, Xu H. Evaluation of GTL naphtha as a gasoline blend component for modern spark ignition engines-part load study. FISITA Conference, 2016, Busan, Korean.13. Warnecke, W, Cadu, J, Janssen, A., Balthasar, F, Balzer, C, Wang CM, Wilbrand K, “The Role of High Octane Fuels in Future Mobility” - A Technical Review, 25th Aachen Colloquium Automobile and Engine Technology14. R F Cracknell, V Pellicciari, A Prakash, A Aradi, C Wang, “The impact of fuel octane sensitivity and research octane number on the efficiency of a direct injection spark ignition engine” Proceeding of IMechE Internal Combustion Engines, 2017, Birmingham, UK December 6th-7th 2017 15. A. Jach*, I. Cieślak, W. Rudy, A. Pękalski, A. Teodorczyk “Comparison of the Performance of Several Hydrocarbon Combustion Mechanisms in Reproduction of Ignition Delay Times of C1-C4 Hydrocarbons” Proceedings of the European Combustion Meeting, 2017, Dubrovnik, Croatia 16. Jach A., Rudy W., Pekalski A., Teodorczyk A., “Validation of detailed chemical kinetics mechanisms for combustion of C2-C5 alkenes” Proceedings of 26th ICDERS meeting, Boston, USA 30th July – 4th August 201717. Rudy W., Jach A., Pekalski A., Teodorczyk A., “Chemical reaction mechanisms validation based on ignition delay time of C1-C5 hydrocarbons” Proceedings of 26th ICDERS meeting, Boston, USA 30th July – 4th August 201718. Rudy W., Pekalski A., Makarov D., Teodorczyk A., Molkov V. “Modelling and simulations of gaseous deflagrations in closed vessels“ In preparation19. M.M.J. Knoope, C.H. Balzer, C.L. Price, F.G.M. Niele, E. Worrell “Developing an integrated approach to account for water and greenhouse gases” Journal for cleaner production and is under review.20. M.M.J. Knoope, C.H. Balzer, E. Worrell “Critical review of existing LCA water methodologies” Presented at Life Cycle Management (LCM2017) conference, 3-6 September 2017, Luxembourg.
