Peter Eilts

From the test-tube to the test-engine: assessing the suitability of prospective liquid biofuel compounds

In the recent years, research efforts for the exploitation of biomass for the production of alternative fuels for automotive internal combustion engines has increased tremendously. However, it is still uncertain and a matter of debate what the chemical composition of future biofuels will be. Up to now, the applicability of a prospective biofuel compound can only be analysed using test engine runs. However, as these engine based tests require large quantities of the biofuel candidate (usually at least several litres) and high-cost, specialized equipment alternative strategies for the assessment of small quantities are sought for. However, a multitude of properties has to be considered when assessing the suitability of a chemical substance as seminal biofuel. In this article the selected key properties allowing an initial fuel characterization for diesel-like fuels are discussed, including i) ignition properties: the cetane number, ii) calorific value, iii) greenhouse gas emission, iv) miscibility with a reference substance, v) viscosity and cold-filter-plugging point (CFFP), vi) boiling range and volatility. Thereby, in order to allow an assessment of prospective biofuel compounds already in test tube volumes (i.e. several millilitres), we define a first suggestion for a catalogue of key parameters that can routinely be assessed in chemical laboratories.

Alcoholic biofuels as an admixture component for conventional and alternative diesel combustion processes

Biogenic admixture increases the possible savings in carbon dioxide emissions and reduces the dependency on fossil fuels. In this context especially alcohols not only provide the opportunity to optimize the trade-off between nitrogen oxides and particular matter (NOX/PM trade-off) with conventional combustion processes but they can also support alternative combustion processes by their advantageous properties concerning reaction kinetics. At the Institute of Internal Combustion Engines of the TU Braunschweig investigations on a single-cylinder heavy duty research engine regarding FAME/ethanol and butanol admixtures employing conventional and alternative combustion processes were carried out.

Alkoholische Biokraftstoffe als Beimischungskomponente für konventionelle und alternative Dieselbrennverfahren

Biogene Kraftstoffbeimischungen erhohen das CO2-Einsparpotenzial und reduzieren die Abhangigkeit von fossilen Brennstoffen. Alkohole bieten in diesem Zusammenhang nicht nur die Moglichkeit, den Ausgleich zwischen Ruspartikeln und Stickoxidausstos bei konventioneller Dieselverbrennung zu optimieren, sondern konnen aufgrund gunstiger reaktionskinetischer Eigenschaften alternative Brennverfahren unterstutzen. Am Institut fur Verbrennungskraftmaschinen der TU Braunschweig wurden hierzu Untersuchungen mit RME/Ethanol- und Butanolbeimischungen an einem Nutzfahrzeug-Einzylinderforschungsmotor mit konventionellen und alternativen Dieselbrennverfahren durchgefuhrt.

Potenziale der zweistufigen Aufladung am Großdieselmotor 6L 32/44 CR von MAN

Im Rahmen des europaischen Forschungsvorhabens Hercules wurden bei MAN Diesel SE am Grosdieselmotor 6L 32/44 CR mit einer flexiblen zweistufigen Aufladegruppe sowie variablen Ventilsteuerzeiten Untersuchungen durchgefuhrt, die drastische verbrauchsneutrale Minderung der Stickoxidemissionen bei gleichzeitiger deutlicher Leistungsanhebung zum Ziel hatten.

Anwendbarkeit von Miller-Steuerzeiten bei Kraftstoffen mit unterschiedlicher Zündwilligkeit an einem Nfz-Dieselmotor mit variablem Ventiltrieb

Die immer strenger werdenden Emissionsvorschriften und die Kundenanforderung bezuglich der Kraftstoffverbrauchsreduzierung erfordern weitere Forschungsarbeiten an Nutzfahrzeugmotoren. Durch die innermotorische Senkung der Emissionen konnen die Systemanforderungen an die Abgasnachbehandlung minimiert und dadurch eine Kostenabsenkung erreicht werden. Andererseits ist die Absenkung des Kraftstoffverbrauchs direkt mit dem CO2-Ausstos gekoppelt, weshalb dessen Senkung neben der Betriebskostenreduzierung auch aus Klimaschutzgrunden entscheidend ist.

Verdichtervariabilität zur Reduzierung des Scavenging im Low-End-Torque-Bereich eines einstufig aufgeladenen Ottomotors

Bedingt durch die stetige Verscharfung der Emissionsgrenzwerte durch den Gesetzgeber und den Kundenwunsch nach hoher Dynamik und einem geringen Kraftstoffverbrauch unterliegt der Verbrennungsmotor einer stetigen Weiterentwicklung. Im Bereich des Ottomotors im Pkw-Segment hat sich das Downsizing in Verbindung mit der Abgasturboaufladung als bewahrtes Mittel zur Verschiebung des Betriebsbereiches hin zu hoheren Wirkungsgraden durchgesetzt. Bei einem einstufig aufgeladenen Motorkonzept besteht dabei stets ein Zielkonflikt aus einer hohen Nennleistung und einer guten Performance im Low-End-Torque-Bereich (LET) des Motors. Daraus leitet sich die Anforderung an die Aufladegruppe ab, ein hohes Druckverhaltnis uber eine grose Massenstromspreizung bereitzustellen.

Analyse und Effizienzoptimierung von Ottomotoren in Hybridantrieben mithilfe der Gesamtfahrzeugsimulation

Die CO2-Flottengrenzwerte fur Pkw verscharfen sich weltweit [1]. Daher mussen Automobilhersteller in noch starkerem Mase Technologien entwickeln, die die CO2-Emissionen von Pkw effektiv reduzieren [2]. Die Entwicklung von Hybridfahrzeugen (HEV) ist eine von vielen Moglichkeiten die CO2-Emissionen deutlich zu reduzieren und ein moglicher Pfad zu einer nachhaltigen Mobilitat [3].

Advanced Optimization of Hybrid-Electric-Vehicle Drivelines using Engine-in-the-Loop Simulation

At the Institute of Internal Combustion Engines of Technische Universität Braunschweig (ivb) a modular real-time longitudinal vehicle simulation model has been developed. The main goal of the vehicle model is the calculation of boundary conditions for the virtual development process of internal combustion engines (ICE). Especially in hybrid electric vehicle (HEV) development an efficient tool is necessary to solve the nearly unmanageable task to find the optimum configuration of hybrid topology, degree of hybridization and efficient operation strategy. To achieve optimal results several ICE models with different levels of detail, depending on the state of development, were used. By coupling a real-time vehicle model and a hardware-inthe-loop (HiL) test bench engine characteristics like fuel consumption and exhaust gas emissions can be analysed. The use of engine-in-the-loop (EiL) provides the opportunity to integrate hard to simulate parameters in hybrid strategies. By using identical vehicle models for the power train design process and experimental studies at the test bench systematic errors can be avoided. Additionally the development time decreases. Furthermore the EiL method enables the development of any kind of hybrid power train and helps to design intelligent and unconventional hybrid strategies online. Introduction Increasing oil prices, limited fossil resources and growing environmental requirements are a huge challenge in a world of rising demand for individual mobility. The aim of reducing fossil energy consumption and the greenhouse gas emission production demands alternative, innovative and efficient power train solutions. Beside the optimization of ICE’s efficiency the combination with an electric motor in an HEV is a possibility to reach these targets. Between conventional and electric vehicles almost all interim solutions are possible by combining ICE, EM and battery in hybrid structures as well as different degrees of hybridization. Figure 1 shows conceivable types of HEV power trains. To find the optimal combination in this parameter space an intelligent engineering method is obligatory. Because of the wide range of solutions a strategic method must be used to handle the almost unmanageable task of finding an optimal HEV configuration in minimum development time. Based on the preliminary studies at the ivb [1], [2] a combined method of real-time simulation and experimental engine testing has been developed to manage this challenge. Figure 1. Overview of HEV power trains. SNE Simulation Notes Europe – Print ISSN 2305-9974 | Online ISSN 2306-0271 SNE 22(3-4), 2012, 157-167 | doi: 10.11128/sne.22.tn.10149 B Tilch et al. Advanced Optimization of Hybrid-Electric-Vehicle Drivelines 158 SNE 22(3-4) – 12/2012 TN Besides different ICE models with different levels of detail a co-simulation with an engine test bench is possible. By replacing the simulated ICE by hardware at the EiL test bench research on the real engine behaviour for example considering thermal influences in engine friction or exhaust gas emissions can be done. 1 Vehicle Simulation Model and Engine-in-the-Loop test bench 1.1 Vehicle Simulation Model For the experimental studies a longitudinal HEV drive train was modelled in Matlab/Simulink. An overview of the simulation model for a parallel HEV gives Figure 2. The model is built up as a forward-looking-model and is divided in driver-, power train and vehicle model. In addition to the physical models of ICE, electrical motor (EM), battery, gearbox and axle drive, electronic control units (ECU) for ICE, EM and gearbox are necessary. Supervisory an HEV operating ECU manages the interaction of the other component-ECUs. The HEV-ECU splits the target torque between the ICE and the EM depending on the operation strategy. Furthermore the HEV-ECU triggers the two clutches between ICE and EM and between EM and gearbox. The driver model acts as a PID controller. Due to comparison the current vehicle speed and the target speed the driver actuates the accelerator or brake pedal based on the control deviation. In the power train model the traction force is calculated from the accelerator position. The power train model depends on the HEV structure and considers the losses, inertias and transmissions. A tyre model transforms the brake pedal position into a brake force. In the vehicle model the available traction or brake force is balanced with the vehicle driving resistances. In the model vehicle the longitudinal forces are balanced (Eq. 1). The resulting traction force depends on the driving resistances: rolling, air, gradient and acceleration resistant (Eqs. 2-6).

Primary methods to reduce NO x emissions of medium-speed large-bore diesel engines

Due to its economy the large-bore diesel engine dominates the market for propulsion and auxiliary drives of merchant ships. The medium-speed main engine is the preferred choice especially for cruise liners, passenger ships, product tankers and feeder ships. Currently there is a discussion about a decrease in the IMO NOx limits of 2 to 3 g/kWh from the beginning of 2011. Against this background the possibilities and limits of primary methods for NOx reduction were considered within a FVV research program, which was carried out by the Hamburg University of Technology.