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The present work is a continuation of the earlier published results by authors on the investigation of Hydrogenated Vegetable Oil (HVO) on a High Efficiency Diesel Combustion System (SAE Int. J. Fuels Lubr. Paper No. 2013-01-1677 and JSAE Paper No. 283-20145128). In order to further validate and interpret the previously published results of soot microstructure and its consequences on oxidation behavior, the test program was extended to analyze the impact of soot composition, optical properties, and physical properties such as size, concentration etc. on the oxidation behavior. The experiments were performed with pure HVO as well as with petroleum based diesel and today's biofuel (i.e. FAME) as baseline fuels. The soot samples for the different analyses were collected under constant engine operating conditions at indicated raw NOx emissions of Euro 6 level using closed loop combustion control methodology.

The main assignment of Controlled Auto Ignition (CAI) operation range expansion is to reduce the burn rate or combustion noise at high load and to minimize misfire at low load. The potential of two principal EGR strategies is well known to initiate CAI in a wide range of operation map by using a variable train system: the Exhaust Port Recirculation (EPR) for higher part load and the Combustion Chamber Recirculation (CCR - also called Negative Valve Overlap) for lower part load. However the detailed comparison of the ignition phenomena with each EGR strategy has not been fully studied yet. In this paper, EPR and CCR were compared with same operational condition (engine speed and load). For the analysis, flame luminescence and Raman scattering method for optical measurement and STAR-CD (CD-adapco) for numerical simulation are used.

While significant progress has been made in recent years to develop hybrid and battery electric vehicles for passenger car and light-duty applications to meet future fuel economy targets, the application of hybrid powertrains to heavy-duty truck applications has been very limited. The relatively lower energy and power density of batteries in comparison to diesel fuel and the operating profiles of most heavy-duty trucks, combine to make the application of hybrid powertrain for these applications more challenging. The high torque and power requirements of heavy-duty trucks over a long operating range, the majority of which is at constant cruise point, along with a high payback period, complexity, cost, weight and range anxiety, make the hybrid and battery electric solution less attractive than a conventional powertrain.

Regulated emissions, CO2-values, comfort, good driveability, high reliability and costs, this is the main frame for all future powertrain developments. In this frame, the diesel powertrain, not only for passenger cars, but also for commercial vehicle applications, faces some challenges in order to fulfil the future European and current US emission legislations while keeping the fuel consumption benefit, good driveability and an acceptable cost frame. One of these challenges is the varying fuel qualities of diesel fuel in different countries including different cetane number, volatility, sulphur content and different molecular composition. In addition to that in the future, more and more alternative fuels with various fuel qualities and properties will be launched into the market for economical and environmental reasons. At present, the control algorithms of the injection system applied in most diesel engines is open loop control.

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.

Measures for reducing engine friction within the powertrain are assessed in this paper. The included measures work in combination with several new technologies such as new combustion technologies, downsizing and alternative fuels. The friction reduction measures are discussed for a typical gasoline vehicle. If powertrain friction could be eliminated completely, a reduction of 15% in CO2 emissions could be achieved. In order to comply with more demanding CO2 legislations, new technologies have to be considered to meet these targets. The additional cost for friction reduction measures are often lower than those of other new technologies. Therefore, these measures are worth following up in detail.

In order to deeply investigate and improve the complete path from biofuel production to combustion, the cluster of excellence “Tailor-Made Fuels from Biomass” was installed at RWTH Aachen University in 2007. Recently, new pathways have been discovered to synthesize octanol [1] and di-n-butylether (DNBE). These molecules are identical in the number of included hydrogen, oxygen and carbon atoms, but differ in the molecular structure: for octanol, the oxygen atom is at the end of the molecule, whereas for DNBE it is located in the middle. In this paper the utilization of octanol and DNBE in a state-of-the-art single cylinder diesel research engine will be discussed. The major interest has been on engine emissions (NOx, PM, HC, CO, noise) compared to conventional diesel fuel.

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.

Increasing shortages of energy resources as well as emission legislation development is increasing the pressure to develop more efficient, environmentally friendly propulsion systems for vehicles. Alternatives such as fuel cell systems or hybrid propulsion are in discussion or have already been introduced. This paper gives a survey on the present technical status of internal combustion engines, hybrid concepts and current fuel cell vehicles. Different solutions will be presented, so that an evaluation of advantages and drawbacks can be given. The further potentials of each concept, as well as combinations of different systems are discussed, and an outlook into the future is given.

High levels of exhaust temperature or rich mixtures are necessary for the regeneration of today's diesel particulate filters or NOx catalysts. Therefore, late main injection or post injection is an effective strategy but leads to the well-known problem of lubricating oil dilution depending on the geometry, rail pressure and injection strategy. In this paper a method is developed to simulate fuel entrainment into the lubricating oil wall film in the diesel combustion chamber to predict oil dilution in an early design stage prior to hardware availability for durability testing. The simulation method integrates a newly developed droplet-film interaction model and is compared to results of an optical single-cylinder diesel engine and a similar thermodynamic single-cylinder test engine. Phenomena of diesel post injection like igniting early post injection or split post injections with short energizing times are considered in this paper.

In this paper a new approach is presented to evaluate the combustion behaviour of homogeneous gasoline engines by predicting burn delay and -duration in a way which can be obtained under the time constraints of the development process. This is accomplished by means of pure in-cylinder flow simulations without a classical combustion model. The burn delay model is based on the local distribution of the turbulent flow near the spark plug. It features also a methodology to compare different designs regarding combustion stability. The correlation for burn duration uses a turbulent characteristic number that is obtained from the turbulent flow in the combustion chamber together with a model for the turbulent burning velocity. The results show good agreement with the combustion process of the analyzed engines.

Pre-ignition in a boosted spark-ignition engine can be triggered by several mechanisms, including oil-fuel droplets, deposits, overheated engine components and gas-phase autoignition of the fuel-air mixture. A high pre-ignition resistance of the fuel used mitigates the risk of engine damage, since pre-ignition can evolve into super-knock. This paper presents the pre-ignition propensities of 11 RON 89-100+ gasoline fuel blends in a single-cylinder research engine. Albeit the addition of two high-octane components (methanol and reformate) to a toluene primary reference fuel improved the pre-ignition resistance, one high-RON fuel experienced runaway pre-ignition at relatively low boost pressure levels. A comparison of RON 96 blends showed that the fuel composition can affect pre-ignition resistance at constant RON.

Based on the TurboDISI engine presented earlier [1], [2], a new Spray Guided Turbo (SGT) concept with enhanced engine performance was developed. The turbocharged engine was modified towards utilizing a spray-guided combustion system with a central piezo injector location. Higher specific power and torque levels were achieved by applying specific design and cooling solutions. The engine was developed utilizing a state-of-the-art newly developed charge motion design (CMD) process in combination with single cylinder investigations. The engine control unit has a modular basis and is realized using rapid prototyping hardware. Additional fuel consumption potentials can be achieved with high load EGR, use of alternative fuels and a hybrid powertrain. The CO2 targets of the EU (120 g/km by 2012 in the NEDC) can be obtained with a mid-size vehicle applying the technologies presented within this paper.

In view of limited crude oil resources, alternative fuels for internal combustion engines are currently being intensively researched. Synthetic fuels from natural gas offer a promising interim option before the development of CO2-neutral fuels. Up to a certain degree, these fuels can be tailored to the demands of modern engines, thus allowing a concurrent optimization of both the engine and the fuel. This paper summarizes investigations of a Gas-To-Liquid (GTL) diesel fuel in a modern, post-EURO 4 compliant diesel engine. The focus of the investigations was on power output, emissions performance and fuel economy, as well as acoustic performance, in comparison to a commercial EU diesel fuel. The engine investigations were accompanied by injection laboratory studies in order to assist in the performance analyses.

Today's biofuels require large amounts of energy in the production process for the conversion from biomass into fuels with conventional properties. To reduce the amounts of energy needed, future fuels derived from biomass will have a molecular structure which is more similar to the respective feedstock. Butyl levulinate can be gained easily from levulinic acid which is produced by acid hydrolysis of cellulose. Thus, the Institute for Combustion Engines at RWTH Aachen University carried out a fuel investigation program to explore the potential of this biofuel compound, as a candidate for future compression ignition engines to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level. Previous investigations identified most desirable fuel properties like a reduced cetane number, an increased amount of oxygen content and a low boiling temperature for compression ignition engine conditions.

The current direction for Diesel combustion system development is towards homogenization, in order to reduce particulate and NOx emissions. However, a strong increase of carbon monoxide emissions (CO) is frequently noted in combination with enhanced homogenization. Therefore, the current investigation focuses on a detailed analysis of the particulate - CO trade-off using a laser-optical and multidimensional CFD investigation of the combustion process of a swirl HSDI system. The CFD methodology involves reduced kinetics for soot formation and oxidation and a three-step CO model. These models are validated by a detailed comparison to optical measurements of flow, spray penetration and the spatial distribution of soot, temperature and oxygen concentration. The results obtained show that high concentrations of CO occur as an intermediate combustion reaction product. Subsequently, CO and soot are oxidized in large areas of the combustion chamber.

Lignocellulosic biomass consists of (hemi-) cellulose and lignin. Accordingly, an integrated biorefinery will seek to valorize both streams into higher value fuels and chemicals. To this end, this study evaluated the overall combustion performance of both cellulose- and lignin derivatives, namely the high cetane number (CN) di-n-butyl ether (DnBE) and low CN anisole, respectively. Said compounds were blended both separately and together with EN590 diesel. Experiments were conducted in a single cylinder compression ignition engine, which has been optimized for improved combustion characteristics with respect to low emission levels and at the same time high fuel efficiency. The selected operating conditions have been adopted from previous “Tailor-Made Fuels from Biomass (TMFB)” work.

In order to thoroughly investigate and improve the path from biofuel production to combustion, the Cluster of Excellence “Tailor-Made Fuels from Biomass” was installed at RWTH Aachen University in 2007. Since then, a variety of fuel candidates have been investigated. In particular, 2-methyl tetrahydrofurane (2-MTHF) has shown excellent performance w.r.t. the particulate (PM) / NOx trade-off [1]. Unfortunately, the long ignition delay results in increased HC-, CO- and noise emissions. To overcome this problem, the addition of di-n-butylether (DNBE, CN ∼ 100) to 2-MTHF was analyzed. By blending these two in different volumetric shares, the effects of the different mixture formation and combustion characteristics, especially on the HC-, CO- and noise emissions, have been carefully analyzed. In addition, the overall emission performance has been compared to EN590 diesel.

Modern biofuels offer the potential to decrease engine out emissions while at the same time contributing to a reduction of greenhouse gases produced from individual mobility. In order to deeply investigate and improve the complete path from biofuel production to combustion, in 2007 the cluster of excellence “Tailor-Made Fuels from Biomass” was installed at RWTH Aachen University. Since then, a whole variety of possible fuel candidates have been identified and investigated. In particular oxygenated fuels (e.g. alcohols, furans) have proven to be beneficial regarding the particulate matter (PM)/ NOx trade-off [1, 2, 3] in diesel-type combustion. Alcohols that provide a longer ignition delay than diesel might behave even better with regard to this trade-off due to higher homogenization of the mixture. Recent studies carried out within the Cluster of Excellence have discovered new pathways to derive 1-octanol from biomass [4], which features a derived cetane number (DCN) of 39.

The finite nature and instability of fossil fuel supply has led to an increasing and enduring investigation demand of alternative and regenerative fuels. An investigation program is carried out to explore the potential of tailor made fuels to reduce engine-out emissions while maintaining engine efficiency and an acceptable noise level. In this paper, fundamental results of the Diesel engine relevant combustion are presented. To enable optimum engine performance a range of different reference fuels have been investigated. The fundamental effects of different physical and chemical properties on emission formation and engine performance are investigated using a thermodynamic diesel single cylinder research engine and an optically-accessible combustion vessel. Depending on the chain length and molecular structure, fuel compounds vary in cetane number, boiling temperature etc. Therefore, different hydrocarbons including n-heptane, n-dodecane, and l-decanol were investigated.