Fuels From Biomass: An Interdisciplinary Approach

In this study, we investigate oxygenated blends and Diesel surrogate fuels under engine-like conditions in a high-pressure chamber. The investigated surrogate fuels are composed of n-decane and alpha-methylnaphthalene with different compositions according to the reference cetane numbers (CN) 53, 45, 38 and 23. In addition to the two-component surrogate fuel mixtures, we examine a three-component mixtures composed of n-decane, alpha-methylnaphthalene, and di-n-butyl ether with a reference cetane number of 53 to highlight the influence of adding di-n-butyl ether to the surrogate fuel at constant cetane number. Further, four blends with DNBE contents of 0, 10, 20 and 100 % in EN590 Diesel and corresponding cetane numbers of 53, 57.7, 62.4, and 100 were studied. We examine fuel spray characteristics in the liquid and vapor phases and the relationship between ignition quality and lift-off length. Vapor pressure is observed to significantly affect spray characteristics in the liquid phase. Vapor penetration lengths of the different fuels with the same injection pressure are found to be similar, because the differences of fuel density and viscosity in the vapor phase are too small to considerably affect the momentum flux. However, changing the injection pressures affects the vapor penetration lengths. Results show that CN is a good indicator for ignition delay. Furthermore, we discuss the fuel overlap number (OL) to indicate the separation between the liquid spray core and the reaction zone in engine-like conditions. It is found for the surrogate mixtures that OL generally increases with decreasing CN, while for the DNBE/Diesel mixtures, the opposite trend is observed. The OL number is found to be caused by a combination of cetane number and vapor pressure effects, where CN has the stronger effect for the surrogate mixtures, while the vapor pressure effect is dominant for the DNBE/Diesel blends. In the latter case, the high vapor pressure leads to short liquid penetration length and thereby larger OL number.

Biodiversity is defined in the political sphere as an important subject of protection and the extinction of species to be listed here should not only be held in acknowledged protected areas, but rather also in areas used agriculturally. The situation in agriculture is currently strongly changing through influencing factors, such as climate change and restructuring in favour of renewable resources. Since this development on the one hand holds the risk of a loss of biodiversity, and on the other redevelopments also offer opportunities, this is indispensable for a well-founded evaluation to operably forecast the effects of land use change on organisms. Suitable methods for this are currently lacking. These loopholes should be closed by the model worked out here. Based on species collections from earlier studies, autecological organism data from the bibliography, as well as suitable map material, a Geographical Information System will be created which makes it possible to forecast biodiversity in a regional context.

We present a detailed experimental investigation of conditional statistics related to dissipation elements based on the scalar field \( \theta \) and its scalar dissipation rate \( \chi \). Based on high frequency two-dimensional measurements of the mass fraction of propane in a turbulent round jet discharging into surrounding air, we acquire data resolving the Kolmogorov scale in every spatial direction using a high-speed Rayleigh scattering technique and Taylor’s hypothesis. The Reynolds number (based on nozzle diameter and jet exit velocity) varies between 2,000 and 6,700 and the Schmidt number between \( 1.2 \) and \( 1.7 \). The experimental results for the normalized marginal pdf \( \tilde{P}(\tilde{l}) \) of the length of dissipation elements follow closely the theoretical model derived by Wang and Peters (J. Fluid. Mech. 608:113–138, 2008). We also find that the mean linear distance between two extreme points of an element is of the order of the Taylor microscale \( \lambda \). Furthermore, the conditional mean \( \langle\varDelta \theta |l\rangle \) scales with Kolmogorov’s 1/3 power.

The growing energy consumption and the dwindling resources of fossil energy carriers make the exploitation of renewable energy from biomass a key technology for the maintenance of modern industrial societies and lifestyles. Because of the conflict of demand between crops used for first generation biofuels (made from starch) with food production, the development of second generation biofuels from lignocellulose is recognized as preferable system. The recalcitrance of lignocellulose to enzymatic hydrolysis makes the utilization of this renewable feedstock difficult and cost intensive, due to high enzyme loads, pretreatment processes, and the low reactant/product concentrations in lignocellulose hydrolysates. The study outline presented here aims to contribute to the economic efficiency of second generation biofuel production by exploring a cellulolytic system consisting of a minimal set of cellulases, which we expect to optimize for high feed-stock loading. Such systems are provided by nature in the form of proteins secreted into the saliva of plant parasitic nematodes of the genera Meloidogyne, Heterodera and Globodera. These cellulolytic systems typically consist of between two and six cellulases, pectinases and expansin-like proteins. In this article, we review information about root cyst nematodes, their cellulolytic system and provide an experimental outline for achieving insights into the cellulolytic system of the root cyst nematode Globodera tabacum solanacearum.

Biomass represents a major renewable carbon source and thus is increasingly important as a feedstock for the synthesis of fuels and chemicals. To achieve sustainable conversion of biogenic resources in the future, it is important to develop new selective catalytic reaction pathways. Olefin metathesis is one important tool in organic synthesis to convert unsaturated compounds while maintaining their functionalities. While classical heterogeneous catalysts are not capable of the transformation of such compounds, homogeneous ruthenium based catalysts seem suitable because of their high tolerance towards functional groups. In the following article we describe our investigations for the valorization of oleic acid methyl esters. Beyond the use as bio fuel there is an interest in adding the compounds value by conversion to base and fine chemicals. Therefore sustainable reaction paths have to be developed, in which innovative reaction media like supercritical fluids and ionic liquids are used for the establishment of a multiphase reaction system.

The effective activation of (hetero)aromatic compounds is of particular interest for the production of tailor made compounds that can serve as key intermediates in the development of alternative combustion fuels. As a sustainable alternative for late transition metals, organocalcium complexes are studied in the context of activation of carbon dioxide and aromatic N- and O-heterocycles. Highly regioselective C–H bond activation and carbometalation reactions have been observed for conversions with pyridine derivatives. Rapid insertion of CO₂ into calcium carbon bonds of the obtained products is observed. Furan derivatives are found more inert and the formation of polymeric products is described. Slow isomerization of 2,5-dihydrofuran (2,5-DHF) to 2,3-dihydrofuran (2,3-DHF) is reported.

Due to the increasing demand for alternative energy carriers, biomass is in the focus of research and industry as raw material for fuels and base chemicals. This has led to an increased use of feedstock for biofuel production and to conflict between using this feedstock for either food or for fuel generation. To avoid this problem, lignocellulose is seen as a promising raw material, as it is not used for food or feed production and harbors high amounts of sugars in form of cellulose and hemicellulose. Currently, the enzymes used for cellulose degradation are mainly produced directly in their natural hosts (e.g. Trichoderma reesei) or in genetically altered microorganisms. The high costs for the production of these enzymes make them a major obstacle for the economically feasible use of lignocellulose as a renewable raw material. As an alternative production platform, plants could be used to express these enzymes cheaply and directly in the raw material to be used for conversion. To alleviate the skepticism towards genetically altered plants, especially prevalent in Germany and Europe, chloroplast transformation offers the opportunity to combine efficient production of a set of cellulases within a single plant, while reducing the risk of releasing altered genetic information into the environment. This approach is used in this project to express seven cellulolytic enzymes, derived from the bacterium Thermobifida fusca, in the chloroplasts of Nicotiana tabacum and to analyze their activity on cellulosic substrates as well as their influence on plant growth.

A short and convenient synthetic pathway affording diastereomerically pure 1,3-dilignols in both their erythro and threo form has been developed. Additionally, H₂Ru(CO)(PPh₃)₃ has been identified as a promising catalyst for the cleavage of lignin model compounds. The greater accessibility of 1,3-dilignols will facilitate future lignin cleavage studies of ruthenium catalysts and other transition metal systems, employing model compounds that closely resemble the β-O-4 linkage within lignin.

Biogas is easily transportable, storable and CO₂ neutral. The scope of this work is to show the feasibility of H₂ production through Auto Thermal Reforming (ATR) of biogas and its utilisation in High Temperature Proton Exchange Membrane Fuel Cell (HT-PEM FC) application. In this study, a fuel cell system was modelled and simulated using MATLAB/Simulink to find the feasibility of biogas reforming for High Temperature Proton Exchange Membrane (HT PEM) Fuel Cell Application. The main criteria considered are high yield of H₂ and lowest possible CO. The optimum temperature, Steam to Carbon Ratio (SCR), Air-Fuel Ratio (AFR), and reforming temperature were found out with the help of simulation. A test reference 5 kWth Auto Thermal Reformer (ATR) with Water Gas Shift (WGS) reactor was built according to the simulation guidelines in order to produce H₂ to feed a 1 kW_el HT-PEM Fuel Cell with anode gas. The reliability and the durability of the system were tested with a start-and-stop strategy and a continuous mode respectively. The electrical efficiency of the whole Fuel Cell system was simulated to around 30 %. The experimental work validated the simulation results within acceptable margins. The experimental study shows that it is not only feasible to produce on-board H₂ with biogas but also that the start-and-stop mode of operation does not damage the fuel cell which makes it even suitable for automotive application.

Based on local extreme points of the absolute value \( u \) of the velocity field \( u_{i} \), streamlines are partitioned into segments as proposed by Wang (J. Fluid. Mech. 648:183–203, 2010). The temporal evolution of the arc length l of streamline segments is analyzed and associated with the motion of the isosurface defined by all points on which the gradient in streamline direction \( \partial u/\partial s \) vanishes. This motion is diffusion controlled for small segments, while large segments are mainly subject to strain and pressure influences. Due to the non-locality of streamline segments, their temporal evolution is not only a result of slow but also of fast changes, which differ by the magnitude of the jump \( \varDelta l \) that occurs within a small time step \( \varDelta t \). The separation of the dynamics into slow and fast changes allows the derivation of a transport equation for the probability density function (pdf) P(l) of the arc length l of streamline segments. While slow changes in the pdf transport equation translate into a convection and a diffusion term when terms up to second order are included, the dynamics of the fast changes yield integral terms. The convection velocity corresponds to the first order jump moment, while the diffusion term includes the second order jump moment. It is theoretically and from DNS data of homogeneous isotropic decaying turbulence at two different Reynolds numbers concluded that the normalized first order jump moment is quasi-universal, while the second order one is proportional to the inverse of the square root of the Taylor based Reynolds number \( Re_{\lambda }^{ - 1/2} \). It’s inclusion thus represents a small correction in the limit of large Reynolds numbers. Numerical solutions of the pdf equation yield a good agreement with the pdf obtained from the DNS data. It is also concluded on theoretical grounds that the mean length of streamline segments scales with the Taylor microscale rather than with any other turbulent length scale, a finding that can be confirmed from the DNS.

The experimental analysis of the highly unsteady three-dimensional flow in internal combustion (IC) engines requires measurement techniques that are able to capture the velocity field with high temporal and spatial resolution. Among other techniques, particle-image velocimetry (PIV) is used to measure the flow in combustion engines. Depending on the specific goal of a measurement series, either standard 2D-2C PIV, stereoscopic PIV (2D/3C) or fully three-dimensional PIV methods (3D/3C) can be used. In this study, the fundamentals of particle-image velocimetry (PIV) are explained in detail, with a special focus on the application of this measurement technique to internal combustion engines. As far as the generation of the particle images is concerned, this paper describes the special characteristics of seeding particles for use in IC engines including the generation process followed by a short introduction into different light sources and light-sheet generation methods. With regard to image acquisition and processing, digital imaging devices and image evaluation methods are described. Moreover, three component two dimensional and three dimensional PIV measurement techniques, namely stereoscopic-PIV and holographic-PIV, are concisely explained. Hereafter, two-component PIV measurements in several planes, three-component-PIV measurements in a set of planes and holographic-PIV measurements in the whole volume of the intake flow of a four valve piston engine at 160° crank angle are analyzed. The results of the stereoscopic PIV measurements show the highly three-dimensional propagation of the engine flow. Furthermore, the feasibility of holographic PIV for the analysis of engine flows is confirmed.

In face of the continuous depletion of fossil carbon resources alternative liquid energy carriers have to be identified to guarantee sustainable future mobile propulsion. In this context, the Cluster of Excellence (CoE) “Tailor-Made Fuels from Biomass” (TMFB) at RWTH Aachen University aims at identifying sustainable fossil fuel surrogates from biomass by means of a holistic approach from biomass supply to engine combustion. As the fuel identification process requires the screening of a tremendous number of possible fuel candidates, solely experimental methodologies cannot be applied. To this end, a research team at AVT.PT contributes to a model-based fuel design (MBFD) methodology which is based on an integrated product and process design approach, considering aspects of both fuel combustion and fuel production. It aims at identifying possible fossil fuel surrogates from a database of rigorously generated molecular structures. These fuel surrogates have to comply with a set of pre-defined constraints, which has been elaborated by interdisciplinary collaboration within the CoE. The present contribution illustrates the status quo and future perspectives of model-based fuel design and its integration into the research context of the TMFB cluster.

The requirements on the development of combustion engines have dramatically changed in the past decade. This includes strict emission laws, CO₂ emission reduction, different propulsion concepts including powertrain electrification and a reduced time to market with an increased number of engine variants. One alternative to mitigate both the need for fossil burnings and the CO₂ emission reduction is the use of alternative fuels from biomass. Thus, different legislation authorities aim for higher proportions of alternative fuels on the market. However, this strategy involves changes on different development domains for combustion engines. This paper presents ongoing research taking place within the interdisciplinary activities at the Institute for Combustion Engines. The effects on the control system as one enabler of further investigations are presented from the perspective of variant management and complexity handling. Proceedings of the research on innovative control algorithms for fuel adaption are outlined. At third, we discuss the impact of direct injection of alternative fuels on liner wetting and piston ring development. At last, the combustion of fuels from biomass with regards to the emissions formation is investigated from two points of view: for gasoline combustion methods, the characteristics of gaseous emission are presented. For Diesel combustion, we show the different formation of particles by applying diverse measurement methods.