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The regulatory requirements to reduce both greenhouse gases and exhaust gas pollutants from heavy duty engines are driving new perspectives on the interaction between fuels and engines. Fuels that reliefs the burden on engine manufacturers to reach these goals are of particular interest. A low carbon fuel with a higher volatility and heating value than diesel is one such fuel that reduces engine-out emissions and carbon footprint from the entire hydrocarbon lifecycle (well-to-wheel) and improves fuel efficiency, which is a main enabler for gasoline compression ignition (GCI) technology. The present study investigated the potential of GCI technology by evaluating the performance of a low carbon high efficiency, high reactivity gasoline fuel in Doosan’s 6L medium duty diesel engine.

In a regulatory environment for spark ignition (SI) engines where the focus is continuously looking into improvements in fuel economy and reduction in noxious emissions, the challenges to achieve future requirements are utmost. To effectively reduce CO2 emissions on a well-to-wheel basis, future fuels enabling high efficiency SI engines will have to not only satisfy advanced engine requirements, i.e. high knock resistance, but also produce less CO2 emissions in the refinery. This paper describes how to characterize SI combustion's on-demand octane requirement with three different dual fuel configurations. Refinery naphtha was used for low octane component, and three oxygenates were used for high octane knock inhibiting component, such as, Methanol and Methyl tert-butyl ether (MTBE) and Ethyl tert-butyl ether (ETBE). Each low and high octane fuel was introduced via production gasoline direct injector (DI) and port fuel injector (PFI) in both configurations.

Partially premixed combustion (PPC) is an operating mode that lies between the conventional compression ignition (CI) mode and homogeneous charge compression ignition (HCCI) mode. The combustion in this mixed mode is complex as it is neither diffusion-controlled (CI mode) nor governed solely by chemical kinetics (HCCI mode). In this study, CFD simulations were performed to evaluate flame index, which distinguishes between zones having a premixed flame and non-premixed flame. Experiments performed in the optical engine supplied data to validate the model. In order to realize PPC, the start of injection (SOI) was fixed at −40 CAD (aTDC) so that a required ignition delay is created to premix air/fuel mixture. The reference operating point was selected to be with 3 bar IMEP and 1200 rpm. Naphtha with a RON of 77 and its corresponding PRF surrogate were tested. The simulations captured the general trends observed in the experiments well.

In the context of stringent future emission standards as well as the need to reduce emissions of CO2 on a global scale, the cost of manufacturing engines is increasing. Naphtha has been shown to have beneficial properties for its use as a fuel in the transportation sector. Well to tank CO2 emissions from the production of Naphtha are lower than any other fuel produced in the refinery due to its lower processing requisites. Moreover, under current technology trends the demand for diesel is expected to increase leading to a possible surplus of light fuels in the future. Recent research has demonstrated that significant fuel consumption reduction is possible based on a direct injection gasoline engine system, when a low quality gasoline stream such as Naphtha is used in compression ignition mode. With this fuel, the engine will be at least as efficient and clean as current diesel engines but will be more cost effective (lower injection pressure, HC/CO after-treatment rather than NOx).

The present investigation pertains to the development of fast idle catalyst light-off strategy for a light duty gasoline compression ignition (GCI) engine. The engine cold start fast idle operation poses a problem of increased criteria emissions if the catalyst is not activated during the warm up period. Therefore, a control strategy is proposed here to minimize the criteria pollutants during the fast idle phase via enabling fast catalyst light off in a GCI engine and relying on the spark ignition of a globally stoichiometric fuel air mixture. The engine has unique design features such as certain geometry configuration between spark plug and fuel injector arrangement, and the location of spark plug in a high compression ratio (CR) diesel-like combustion chamber. The experiments were performed in a single cylinder GCI engine at cold start fast idle conditions using certification gasoline fuel (RON 91).

The present investigation expands on our previous work on development of fast idle catalyst light-off strategy for a light duty gasoline compression ignition (GCI) engine. In part 1, the steady state experimental investigation in a single cylinder GCI engine indicate an optimum strategy for effective catalyst light off during cold start fast idle operation. According to this strategy, the strategy includes (1) dispersing a first fuel injection during the intake stroke, (2) dispersing a second fuel injection during the expansion stroke, and (3) igniting a spark during the expansion stroke. This strategy increases the exhaust temperature during cold starts thereby assisting in lighting the oxidation catalyst, and reduce emissions and provide greater combustion stability as compared to other injection and spark strategies.

More stringent emissions standards along with higher fuel economy demands have obliged auto makers to develop technical solutions that exploit synergistic features from gasoline and diesel engines. To minimize NOx and soot trade-off, diesel powertrain has been developed to adopt increasingly complex and expensive technology such as extremely high pressure fuel injection systems, low pressure EGR, and variable valve timing. These attempts are associated with promoting Partially Premixed Charge Compression Ignition (PPC-CI) combustion via increasing mixing time and ignition delay. Alternatively, PPC-CI combustion can be achieved easier by using fuels with higher resistance to auto-ignition than conventional diesel fuel. Previous work has demonstrated the possibility of reducing the cost of future diesel after-treatment systems by using gasoline-like fuels.

Recent research [21] has shown that the compression ignition concept where very low cetane fuels (RON between 70 and 85) are run in compression ignition (CI) mode has several advantages. The engine will be at least as efficient and clean as the current diesel engines but will have a less complicated after-treatment system. The optimum fuel will be less processed and therefore simpler to make compared to current gasoline or diesel fuels. Naphtha, which is a product of the initial distillation of petroleum, is one such fuel. It provides a path to mitigate the global demand imbalance between heavier and lighter fuels that is otherwise projected. Since naphtha requires much less processing in the refinery than either gasoline or diesel [23], there is an additional benefit in terms of well-to-wheel CO2 emissions and overall energy consumed. Partially premixed charge compression ignition combustion with such a low cetane fuel has usually been investigated with a diesel engine base.

This paper is the second of a two part study which investigates the use of advanced combustion modes as a means of improving the efficiency and environmental impact of conventional light-duty vehicles. This second study focuses on drive cycle simulations and Life Cycle Assessment (LCA) for vehicles equipped with Octane-on-Demand combustion. Methanol is utilized as the high octane fuel, while three alternative petroleum-derived fuels with Research octane numbers (RONs) ranging from 61 to 90 are examined as candidates for the lower octane fuel. The experimental engine calibration maps developed in the previous study are first provided as inputs to a drive cycle simulation tool. This is used to quantify the total fuel consumption, octane requirement and tank-to-wheel CO2 emissions for a light-duty vehicle equipped with two alternative powertrain configurations. The properties of the lower octane fuel are shown to affect the vehicle fuel consumption and CO2 emissions significantly.

An experimental study has been carried out to provide qualitative and quantitative insight into gas to wall heat transfer in a gasoline fueled Homogeneous Charge Compression Ignition (HCCI) engine. Fast response thermocouples are embedded in the piston top and cylinder head surface to measure instantaneous wall temperature and heat flux. Heat flux measurements obtained at multiple locations show small spatial variations, thus confirming relative uniformity of in-cylinder conditions in a HCCI engine operating with premixed charge. Consequently, the spatially-averaged heat flux represents well the global heat transfer from the gas to the combustion chamber walls in the premixed HCCI engine, as confirmed through the gross heat release analysis. Heat flux measurements were used for assessing several existing heat transfer correlations. One of the most popular models, the Woschni expression, was shown to be inadequate for the HCCI engine.

Pre-chamber combustion (PCC) is a promising engine combustion concept capable of extending the lean limit at part load. The engine experiments in the literature showed that the PCC could achieve higher engine thermal efficiency and much lower NOx emission than the spark-ignition engine. Improved understanding of the detailed flow and combustion physics of PCC is important for optimizing the PCC combustion. In this study, we investigated the gas exchange and flame jet from a narrow throat pre-chamber (PC) by only fueling the PC with methane in an optical engine. Simultaneous negative acetone planar laser-induced fluorescence (PLIF) imaging and OH* chemiluminescence imaging were applied to visualize the PC jet and flame jet from the PC, respectively. Results indicate a delay of the PC gas exchange relative to the built-up of the pressure difference (△ P) between PC and the main chamber (MC). This should be due to the gas inertia inside the PC and the resistance of the PC nozzle.

Pre-chamber combustion (PCC) enables leaner air-fuel ratio operation by improving its ignitability and extending flammability limit, and consequently, offers better thermal efficiency than conventional spark ignition operation. The geometry and fuel concentration of the pre-chamber (PC) is one of the major parameters that affect overall performance. To understand the dynamics of the PCC in practical engine conditions, this study focused on (i) correlation of the events in the main chamber (MC) with the measured in-cylinder pressure traces and, (ii) the effect of fuel concentration on the MC combustion characteristics using laser diagnostics. We performed simultaneous acetone planar laser-induced fluorescence (PLIF) from the side, and OH* chemiluminescence imaging from the bottom in a heavy-duty optical engine. Two different PC Fueling Ratios (PCFR, the ratio of PC fuel to the total fuel), 7%, and 13%, were investigated.

The current work utilizes computational fluid dynamics (CFD) simulations to assess the effects of different piston geometries in an active-type pre-chamber combustion engine fueled with methane. Previous works identified that the interaction of the jets with the main chamber flow and piston wall are key aspects for the local turbulent flame speed and overall burning duration. The combustion process is simulated with the G-equation model for flame propagation combined with the MZ-WSR model to determine the post-flame composition and to predict possible auto-ignition of the reactant mixture. Four setups were considered: two bowl-shaped and one flat piston, and one additional case of the flat piston with jets at wider jet angles to the cylinder axis. The results show that premature jet-wall interaction impacts the main chamber pressure build-up, turbulence, and burn rate.