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Technical Paper

Mechanism Analysis on the Effect of Fuel Properties on Knocking Performance at Boosted Conditions

2019-01-15
2019-01-0035
In recent years, boosted and downsized engines have gained much attention as a promising technology to improve fuel economy; however, knocking is a common issue of such engines that requires attention. To understand the knocking phenomenon under downsized and boosted engine conditions deeply, fuels with different Research Octane Number (RON) and Motor Octane Number (MON) were prepared, and the knocking performances of these fuels were evaluated using a single cylinder engine, operated under a variety of conditions. Experimental results showed that the knocking performance at boosted conditions depend on both RON and MON. While higher RON showed better anti-knocking performance, lower MON showed better anti-knocking performance. Furthermore, the tendency for a reduced MON to be beneficial became stronger at lower engine speeds and higher boost pressures, in agreement with previously published modelling work.
Technical Paper

Effect of Octane Number on the Performance of Euro 5 and Euro 6 Gasoline Passenger Cars

2017-03-28
2017-01-0811
Research Octane Number (RON) and Motor Octane Number (MON) are used to describe gasoline combustion which describe antiknock performance under different conditions. Recent literature suggests that MON is less important than RON in modern cars and a relaxation in the MON specification could improve vehicle performance. At the same time, for the same octane number change, increasing RON appears to provide more benefit to engine power and acceleration than reducing MON. Some workers have advocated the use of an octane index (OI) which incorporates both parameters instead of either RON or MON to give an indication of gasoline knock resistance. Previous Concawe work investigated the effect of RON and MON on the power and acceleration performance of two Euro 4 gasoline passenger cars during an especially-designed acceleration test cycle.
Technical Paper

Octane Requirement and Efficiency in a Fleet of Modern Vehicles

2017-03-28
2017-01-0810
In light of increasingly stringent CO2 emission targets, Original Equipment Manufacturers (OEM) have been driven to develop engines which deliver improved combustion efficiency and reduce energy losses. In spark ignition engines one strategy which can be used to reach this goal is the full utilization of fuel octane number. Octane number is the fuel´s knock resistance and is characterized as research octane number (RON) and motor octane number (MON). Engine knock is caused by the undesired self-ignition of the fuel air mixture ahead of the flame front initiated by the spark. It leads to pressure fluctuations that can severely damage the engine. Modern vehicles utilize different strategies to avoid knock. One extreme strategy assumes a weak fuel quality and, to protect the engine, retards the spark timing at the expense of combustion efficiency. The other extreme carefully detects knock in every engine cycle and retards the spark timing only when knock is detected.
Journal Article

An Investigation into the Characteristics of DISI Injector Deposits Using Advanced Analytical Methods

2014-10-13
2014-01-2722
There is an increasing recognition of injector deposit (ID) formation in fuel injection equipment as direct injection spark ignition (DISI) engine technologies advance to meet increasingly stringent emission legislation and fuel economy requirements. While it is known that the phenomena of ID in DISI engines can be influenced by changes in fuel composition, including increasing usage of aliphatic alcohols and additive chemistries to enhance fuel performance, there is however still a great deal of uncertainty regarding the physical and chemical structure of these deposits, and the mechanisms of deposit formation. In this study, a mechanical cracking sample preparation technique was developed to assess the deposits across DISI injectors fuelled with gasoline and blends of 85% ethanol (E85).
Journal Article

Octane Response in a Downsized, Highly Boosted Direct Injection Spark Ignition Engine

2014-04-01
2014-01-1397
Increasingly strict government emissions regulations in combination with consumer demand for high performance vehicles is driving gasoline engine development towards highly downsized, boosted direct injection technologies. In these engines, fuel consumption is improved by reducing pumping, friction and heat losses, yet performance is maintained by operating at higher brake mean effective pressure. However, the in-cylinder conditions of these engines continue to diverge from traditional naturally aspirated technologies, and especially from the Cooperative Fuels Research engine used to define the octane rating scales. Engine concepts are thus key platforms with which to screen the influence of fundamental fuel properties on future engine performance.
Technical Paper

Combustion and Emissions Performance Analysis of Conventional and Future Fuels using Advanced CAE

2013-10-14
2013-01-2673
In recent years, there has been rapid progress in characterizing the detailed chemical kinetics associated with the oxidation of liquid hydrocarbons and their blends. However adding these fuel models to the industrial engineer's toolkit has proven a major challenge due to issues associated with high CPU cost and the poor suitability of many of the most promising and well known fuel models to IC engine applications. This paper demonstrates the state-of-the-art in the analysis and modelling of current and future transportation fuels or fuel blends for internal combustion engine applications. First-of-all, a benchmarking of eleven representative fuel models (39 to 1034 species in size) is carried out at engine/engine-like operating conditions by adopting the standard Research Octane and Cetane Number test data for comparison. Next, methods to construct a fuel model for a commercial fuel are outlined using a simple, yet robust surrogate mapping technique.
Technical Paper

Benefits of GTL Fuel in Vehicles Equipped with Diesel Particulate Filters

2009-06-15
2009-01-1934
Synthetic fuels are expected to play an important role for future mobility, because they can be introduced seamlessly alongside conventional fuels without the need for new infrastructure. Thus, understanding the interaction of GTL fuels with modern engines, and aftertreatment systems, is important. The current study investigates potential benefits of GTL fuel in respect of diesel particulate filters (DPF). Experiments were conducted on a Euro 4 TDI engine, comparing the DPF response to two different fuels, normal diesel and GTL fuel. The investigation focused on the accumulation and regeneration behavior of the DPF. Results indicated that GTL fuel reduced particulate formation to such an extent that the regeneration cycle was significantly elongated, by ∼70% compared with conventional diesel. Thus, the engine could operate for this increased time before the DPF reached maximum load and regeneration was needed.
Technical Paper

Impact of Diesel Fuel Composition on Soot Oxidation Characteristics

2009-04-20
2009-01-0286
The regeneration of a Diesel Particulate Filter (DPF) is dependent on both the amount and type of soot present on the filter. The objective of this work is to understand how the fuel can affect this ease with which soot can be oxidized. This soot was produced in a two-cylinder four-stroke direct-injection diesel engine, operated with a matrix of fuels with varying aromatic and sulphur level. Their oxidation behaviour in different environments was determined by Temperature Programmed Oxidation in TGA and a six-flow reactor. Transmission electron microscopy was used to examine the soot morphology. Oxidation with only O2 shows oxidation temperatures strongly dependent on the fuel type. Soot oxidation in the presence of NO and a Pt-catalyst results in a lower oxidation temperature. SO2 has an inhibiting effect leading to higher soot oxidation temperature.
Technical Paper

Exhaust gas fuel reforming for IC Engines using diesel type fuels

2007-07-23
2007-01-2044
Control of NOx and Particulate Matter (PM) emissions from diesel engines remains a significant challenge. One approach to reduce both emissions simultaneously without fuel economy penalty is the reformed exhaust gas recirculation (REGR) technique, where part of the fuel is catalytically reacted with hot engine exhaust gas to produce a hydrogen-rich combustible gas that is then fed to the engine. On the contrary to fuel cell technology where the reforming requirements are to produce a reformate with maximized H2 concentration and minimized (virtually zero) CO concentration, the key requirement of the application of the exhaust gas fuel reforming technique in engines is the efficient on-demand generation of a reformate with only a relatively low concentration of hydrogen (typically up to 20%).
Technical Paper

Particulate and Hydrocarbon Emissions from a Spray Guided Direct Injection Spark Ignition Engine with Oxygenate Fuel Blends

2007-04-16
2007-01-0472
The blending of oxygenated compounds with gasoline is projected to increase because oxygenate fuels can be produced renewably, and because their high octane rating allows them to be used in substitution of the aromatic fraction in gasoline. Blending oxygenates with gasoline changes the fuels' properties and can have a profound affect on the distillation curve, both of which are known to affect engine-out emissions. In this work, the effect of blending methanol and ethanol with gasoline on unburned hydrocarbon and particulate emissions is experimentally determined in a spray guided direct injection engine. Particulate number concentration and size distribution were measured using a Cambustion DMS500. These data are presented for different air fuel ratios, loads, ignition timings and injection timings. In addition, the ASTM D86 distillation curve was modeled using the binary activity coefficients method for the fuel blends used in the experiments.
Technical Paper

Overview of the European “Particulates” Project on the Characterization of Exhaust Particulate Emissions From Road Vehicles: Results for Light-Duty Vehicles

2004-06-08
2004-01-1985
This paper presents an overview of the results on light duty vehicles collected in the “PARTICULATES” project which aimed at the characterization of exhaust particle emissions from road vehicles. A novel measurement protocol, developed to promote the production of nucleation mode particles over transient cycles, has been successfully employed in several labs to evaluate a wide range of particulate properties with a range of light duty vehicles and fuels. The measured properties included particle number, with focus separately on nucleation mode and solid particles, particle active surface and total mass. The vehicle sample consisted of 22 cars, including conventional diesels, particle filter equipped diesels, port fuel injected and direct injection spark ignition cars. Four diesel and three gasoline fuels were used, mainly differentiated with respect to their sulfur content which was ranging from 300 to below 10 mg/kg.
Technical Paper

Relevance of Research and Motor Octane Numbers to the Prediction of Engine Autoignition

2004-06-08
2004-01-1970
Links between the RON, MON and Octane Index (OI) of a gasoline are explored and factors influencing knock severity are discussed. The OI was calculated by considering how the autoignition delay time changes with temperature and pressure. Three fuels were examined: a 65/35% toluene/heptane test fuel, and two primary reference fuels (PRF), one with the RON value of the test fuel and the other with the MON value. PRF autoignition times were taken from Adomeit et al and test fuel autoignition times were generated from mathematical models of RON/MON tests plus two experimental sets of engine autoignition data. The toluene/heptane OI depended strongly on engine conditions and could easily exceed the RON. With a lean mixture at high pressure it was 100.2 whereas the RON was only 83.9. Knock severity is governed by the nature of localized “hot spots”. Severe knock is associated with developing detonations towards the end of the delay time.
Technical Paper

Combustion Imaging and Analysis in a Gasoline Direct Injection Engine

2004-03-08
2004-01-0045
A single cylinder Direct Injection Spark Ignition (DISI) engine with optical access has been used for combustion studies with both early injection and late injection for stratified charge operation. Cylinder pressure records have been used for combustion analysis that has been synchronised with the imaging. A high speed cine camera has been used for imaging combustion within a cycle, while a CCD camera has been used for imaging at fixed crank angles, so as to obtain information on cycle-by-cycle variations. The CCD images have also been analysed to give information on the quantity of soot present during combustion. Tests have been conducted with a reference unleaded gasoline (ULG), and pure fuel components: iso-octane (a representative alkane), and toluene (a representative aromatic). The results show diffusion-controlled combustion occurring in so-called homogeneous combustion with early injection.
Technical Paper

Optimizing Engine Concepts by Using a Simple Model for Knock Prediction

2003-10-27
2003-01-3123
The objective of this paper is to present a simulation model for controlling combustion phasing in order to avoid knock in turbocharged SI engines. An empirically based knock model was integrated in a one-dimensional simulation tool. The empirical knock model was optimized and validated against engine tests for a variety of speeds and λ. This model can be used to optimize control strategies as well as design of new engine concepts. The model is able to predict knock onset with an accuracy of a few crank angle degrees. The phasing of the combustion provides information about optimal engine operating conditions.
Technical Paper

Combustion Chamber Deposit Flaking and Startability Problems in Three Different Engines

2003-10-27
2003-01-3187
A field problem associated with flakes of combustion chamber deposits getting trapped on the exhaust valve seat and causing starting problems has appeared recently. Four fuels have been tested in three different car models using a deposit flaking road test procedure. For each piston top, flaking can be characterised using T1 and T2, the mean deposit thickness on the piston crown before and after flaking respectively. A new measure of deposit flaking, ΔT, the mean of (T1-T2) averaged over all cylinders has been introduced and its variance established for the standard test using one of the models. ΔT quantifies the actual amount of deposits that have flaked and is likely to be a more relevant indicator of flaking for startability problems than Rw, the mean of the ratio of T2 to T1, used in previous work. Deposit flaking is directly related to an increase in valve leakage rates and startability problems.
Technical Paper

Amplified Pressure Waves During Autoignition: Relevance to CAI Engines

2002-10-21
2002-01-2868
Controlled autoignition (CAI) engines ideally operate at very lean stoichiometries to achieve low NOx emissions. But at high loads, when combustion approaches stoichiometric, they become noisy and severe engine knock develops. A possible cause is the development of amplifying pressure waves near the hot spots that inevitably occur in the autoigniting gas. This paper presents the results from numerical solutions at realistic engine conditions of the detailed chemical kinetic equations with acoustic wave propagation. Those calculations that involve hot spots must include a spatial dimension. Because of this, they are much more time-consuming than for the homogeneous case. A model system of mixtures of 0.5 H2-0.5 CO with air for equivalence ratios, ϕ, between 0.45 and 1.0 has been used at engine-like temperatures and pressures. These calculations investigate the behaviour for various values of ϕ, hot spot size and temperature elevation.
Technical Paper

Safety Considerations in Retailing Hydrogen

2002-06-03
2002-01-1928
To be used in public, untrained people must be able to handle hydrogen with the same degree of confidence and with no more risk than conventional liquid and gaseous fuels. Physical properties relevant to the safety of hydrogen as a fuel are reviewed and compared to gasoline, LPG and methane. The key parameters are flammability, detonability, ignition energy, materials compatibility, buoyancy and toxicity. For many years, Shell has conducted an experimental programme on gas safety, which has recently been extended to include hydrogen. A selection of results from this programme is presented.
Technical Paper

The Volumetric Efficiency of Direct and Port Injection Gasoline Engines with Different Fuels

2002-03-04
2002-01-0839
A study has been undertaken with a single-cylinder engine, based on the Mitsubishi GDi combustion system, that has the option of either port injection or direct injection. Tests have been undertaken with pure fuel components (methane, iso-octane, toluene and methanol), and a representative gasoline that has also been tested with the addition of 10% methanol and 10% ethanol. The volumetric efficiency depends both on the fuel and its time and place of injection. For stoichiometric operation with unleaded gasoline, changing from port injection to direct injection led to a 9% increase in volumetric efficiency, which was improved by a further 3% when 10% methanol was blended with the gasoline. The improvements in volumetric efficiency will be used to quantify the extent of charge cooling by fuel evaporation, and these will be compared with predictions assuming the maximum possible level of fuel evaporation.
Technical Paper

Fuel Anti-Knock Quality - Part I. Engine Studies

2001-09-24
2001-01-3584
This is the first part of a two-part study on how to define the anti-knock quality of practical fuels. Knock intensity is measured in two single-cylinder research engines using different fuels at different mixture strengths, throttle settings and two compression ratios. The anti-knock quality of a fuel in a given engine operating condition is defined by its octane index OI = RON - KS where K is a constant for that condition and S is the sensitivity, (RON-MON), and RON and MON are the Research and Motor Octane numbers respectively. The higher the octane index, the better the anti-knock quality of the fuel. K is often assumed to be 0.5 so that OI=(RON+MON)/2. However, it is found that K depends on engine operating conditions and in some cases, K is negative so that for a given RON, a fuel with higher sensitivity (lower MON) has better anti-knock quality. The value of K decreases as the engine becomes more prone to knock i.e. as its octane requirement increases.
Technical Paper

Well-to-Wheel Energy Use and Greenhouse Gas Emissions for Various Vehicle Technologies

2001-03-05
2001-01-1343
The well-to-wheel greenhouse gas (GHG) emissions and energy use of selected alternative vehicles are compared to those of a conventional gasoline vehicle. The vehicle technologies investigated are internal combustion engine, hybrid and fuel cell technology. The fuels are assumed to be produced from either crude oil or natural gas. Wherever possible real data has been used. The study shows that hybrid vehicles emit a similar amount of greenhouse gas as fuel cell vehicles. The diesel hybrid uses the least primary energy. The least greenhouse gas emissions are produced by natural gas and hydrogen hybrid and fuel cell vehicles.
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