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Technical Paper

Tailor-Made Fuels for Future Advanced Diesel Combustion Engines

2009-06-15
2009-01-1811
The finite nature and instability of fossil fuel supply has led to an increasing and enduring investigation demand of alternative and regenerative fuels. The Institute for Combustion Engines at the RWTH Aachen University carried out an investigation program to explore the potential of tailor made fuels to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level. To enable optimum engine performance a range of different hydrocarbons having different fuel properties like cetane number, boiling temperature and different molecular compositions have been investigated. Paraffines and naphthenes were selected in order to better understand the effects of molecular composition and chain length on emissions and performance of an engine that was already optimized for advanced combustion performance. The diesel single-cylinder research engine used in this study will be used to meet Euro 6 emissions limits and beyond.
Technical Paper

Advanced Combustion for Low Emissions and High Efficiency Part 1: Impact of Engine Hardware on HCCI Combustion

2008-10-06
2008-01-2405
Two single-cylinder diesel engines were optimised for advanced combustion performance by means of practical and cumulative hardware enhancements that are likely to be used to meet Euro 5 and 6 emissions limits and beyond. These enhancements included high fuel injection pressures, high EGR levels and charge cooling, increased swirl, and a fixed combustion phasing, providing low engine-out emissions of NOx and PM with engine efficiencies equivalent to today's diesel engines. These combustion conditions approach those of Homogeneous Charge Compression Ignition (HCCI), especially at the lower part-load operating points. Four fuels exhibiting a range of ignition quality, volatility, and aromatics contents were used to evaluate the performance of these hardware enhancements on engine-out emissions, performance, and noise levels.
Technical Paper

Advanced Combustion for Low Emissions and High Efficiency Part 2: Impact of Fuel Properties on HCCI Combustion

2008-10-06
2008-01-2404
A broad range of diesel, kerosene, and gasoline-like fuels has been tested in a single-cylinder diesel engine optimized for advanced combustion performance. These fuels were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions, performance, and noise levels. Low-level biofuel blends, both biodiesel (FAME) and ethanol, were included in the fuel set in order to test for short-term advantages or disadvantages. The diesel engine optimized in Part 1 of this study included cumulative engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under conditions of Homogeneous Charge Compression Ignition (HCCI), at least over some portions of the speed and load map.
Technical Paper

A Parametric Study of the Flammability of Dieseline Blends with and without Ethanol

2019-01-15
2019-01-0020
Low Temperature Combustion using compression ignition may provide high efficiency combined with low emissions of oxides of nitrogen and soot. This process is facilitated by fuels with lower cetane number than standard diesel fuel. Mixtures of gasoline and diesel (“dieseline”) may be one way of achieving this; however, a gasoline/diesel mixture in a fuel tank can result in a flammable headspace, particularly at very cold ambient temperatures. A mathematical model to predict the flammability of dieseline blends, including those containing ethanol, was previously validated. In this paper, that model is used to study the flammability of dieseline blends parametrically. Gasolines used in the simulations had Dry Vapour Pressure Equivalent (DVPE) values of 45, 60, 75, 90 and 110 kPa.
Technical Paper

A Mathematical Model for the Vapour Composition and Flammability of Gasoline - Diesel Mixtures in a Fuel Tank

2017-10-08
2017-01-2407
Low Temperature Combustion using compression ignition may provide high efficiency combined with low emissions of oxides of nitrogen and soot. This process is facilitated by fuels with lower cetane number than standard diesel fuel. Mixtures of gasoline and diesel (“dieseline”) may be one way of achieving this, but a practical concern is the flammability of the headspace vapours in the vehicle fuel tank. Gasoline is much more volatile than diesel so, at most ambient temperatures, the headspace vapours in the tank are too rich to burn. A gasoline/diesel mixture in a fuel tank therefore can result in a flammable headspace, particularly at cold ambient temperatures. A mathematical model is presented that predicts the flammability of the headspace vapours in a tank containing mixtures of gasoline and diesel fuel. Fourteen hydrocarbons and ethanol represent the volatile components. Heavier components are treated as non-volatile diluents in the liquid phase.
Technical Paper

Effect of Octane on the Performance of Two Gasoline Direct Injection Passenger Cars

2015-04-14
2015-01-0767
The performance aspect of gasoline combustion has traditionally been measured using Research Octane Number (RON) and Motor Octane Number (MON) 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, while also helping refiners in the production of gasoline. 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. It has also been suggested that there could be fuel efficiency benefits (on a tank to wheels basis) for specially adapted engines, for example, operating at higher compression ratio, on very high RON (100+). Other workers have advocated the use of an octane index (OI) which incorporates both RON and MON to give an indication of octane quality.
Journal Article

Impact of FAME Content on the Regeneration Frequency of Diesel Particulate Filters (DPFs)

2014-04-01
2014-01-1605
Modern diesel vehicles utilize two technologies, one fuel based and one hardware based, that have been motivated by recent European legislation: diesel fuel blends containing Fatty Acid Methyl Esters (FAME) and Diesel Particulate Filters (DPF). Oxygenates, like FAME, are known to reduce PM formation in the combustion chamber and reduce the amount of soot that must be filtered from the engine exhaust by the DPF. This effect is also expected to lengthen the time between DPF regenerations and reduce the fuel consumption penalty that is associated with soot loading and regeneration. This study investigated the effect of FAME content, up to 50% v/v (B50), in diesel fuel on the DPF regeneration frequency by repeatedly running a Euro 5 multi-cylinder bench engine over the European regulatory cycle (NEDC) until a specified soot loading limit had been reached.
Technical Paper

Tailor-Made Fuels: The Potential of Oxygen Content in Fuels for Advanced Diesel Combustion Systems

2009-11-02
2009-01-2765
Fuels derived from biomass will most likely contain oxygen due to the high amount of hydrogen needed to remove oxygen in the production process. Today, alcohol fuels (e. g. ethanol) are well understood for spark ignition engines. The Institute for Combustion Engines at RWTH Aachen University carried out a fuel investigation program to explore the potential of alcohol fuels as candidates for future compression ignition engines to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level. The soot formation and oxidation process when using alcohol fuels in diesel engines is not yet sufficiently understood. Depending on the chain length, alcohol fuels vary in cetane number and boiling temperature. Decanol possesses a diesel-like cetane number and a boiling point in the range of the diesel boiling curve. Thus, decanol was selected as an alcohol representative to investigate the influence of the oxygen content of an alcohol on the combustion performance.
Technical Paper

Modelling a Gasoline Compression Ignition (GCI) Engine Concept

2014-04-01
2014-01-1305
Future engines and vehicles will be required to reduce both regulated and CO2 emissions. To achieve this performance, they will be configured with advanced hardware and engine control technology that will enable their operation on a broader range of fuel properties than today. Previous work has shown that an advanced compression ignition bench engine can operate successfully on a European market gasoline over a range of speed/load conditions while achieving diesel-like engine efficiency and acceptable regulated emissions and noise levels. Stable Gasoline CI (GCI) combustion using a European market gasoline was achieved at high to medium engine loads but combustion at lower loads was very sensitive to EGR rates, leading to longer ignition delays and a steep cylinder pressure rise.
Technical Paper

Impact of Fuel Properties on Advanced Combustion Performance in a Diesel Bench Engine and Demonstrator Vehicle

2010-04-12
2010-01-0334
Six diesel, kerosene, gasoline-like, and naphtha fuels have been tested in a single cylinder diesel engine and a demonstrator vehicle, both equipped with similar engine technology and optimized for advanced combustion performance. This study was completed in order to investigate the potential to reduce engine-out emissions while maintaining engine efficiency and noise levels through changes in both engine hardware and fuel properties. The fuels investigated in this study were selected in order to better understand the effects of ignition quality, volatility, and molecular composition on engine-out emissions and performance. The optimized bench engine used in this study included engine hardware enhancements that are likely to be used to meet Euro 6 emissions limits and beyond, in part by operating under advanced combustion conditions, at least under some speed and load conditions.
Technical Paper

The Impact of Different Biofuel Components in Diesel Blends on Engine Efficiency and Emission Performance

2010-10-25
2010-01-2119
Within the Cluster of Excellence “Tailor-Made Fuels from Biomass” at RWTH Aachen University, the Institute for Combustion Engines carried out an investigation program to explore the potential of future biofuel components in Diesel blends. In this paper, thermodynamic single cylinder engine results of today's and future biofuel components are presented with respect to their engine-out emissions and engine efficiency. The investigations were divided into two phases: In the first phase, investigations were performed with rapeseed oil methyl ester (B100) and an Ethanol-Gasoline blend (E85). In order to analyze the impact of different fuel blends, mixtures with 10 vol-% of B100 or E85 and 90 vol-% of standardized EN590 Diesel were investigated. Due to the low cetane number of E85, it cannot be used purely in a Diesel engine.
Journal Article

Vapour Space Flammability Considerations for Gasoline Compression Ignition Vehicles Operating on “Dieseline” Blends.

2016-10-17
2016-01-2266
Gasoline Compression Ignition (GCI) has been identified as a technology which could give both high efficiency and relatively low engine-out emissions. The introduction of any new vehicle technology requires widespread availability of appropriate fuels. It would be ideal therefore if GCI vehicles were able to operate using the standard grade of gasoline that is available at the pump. However, in spite of recent progress, operation at idle and low loads still remains a formidable challenge, given the relatively low autoignition reactivity of conventional gasoline at these conditions. One conceivable solution would be to use both diesel and gasoline, either in separate tanks or blended as a single fuel (“dieseline”). However, with this latter option, a major concern for dieseline would be whether a flammable mixture could exist in the vapour space in the fuel tank.
Technical Paper

Effect of Diesel Properties on Emissions and Fuel Consumption from Euro 4, 5 and 6 European Passenger Cars

2016-10-17
2016-01-2246
Certain diesel fuel specification properties are considered to be environmental parameters according to the European Fuels Quality Directive (FQD, 2009/EC/30) and previous regulations. These limits included in the EN 590 specification were derived from the European Programme on Emissions, Fuels and Engine Technologies (EPEFE) which was carried out in the 1990’s on diesel vehicles meeting Euro 2 emissions standards. These limits could potentially constrain FAME blending levels higher than 7% v/v. In addition, no significant work has been conducted since to investigate whether relaxing these limits would give rise to performance or emissions debits or fuel consumption benefits in more modern vehicles. The objective of this test programme was to evaluate the impact of specific diesel properties on emissions and fuel consumption in Euro 4, Euro 5 and Euro 6 light-duty diesel vehicle technologies.
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