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Environmental and economical reasons have led to an increased interest in the usage of alternative fuels for combustion engines. To clarify the influence of these so-called future fuels on engine performance and emissions it is mandatory to understand their effect on spray formation. Usually this is done by performing various spray experiments with potential future fuels which are available for research purposes today. Due to the multitude of possible future fuels and therefore the uncertainty of their properties and their influence on spray formation a more general approach was chosen in the present study. The possible range of physical properties of future fuels for diesel engines was identified and more than twenty different fluids with representative properties, mostly one-component chemicals, were chosen by means of design of experiment (DoE).

The paper demonstrates the potentials of a high speed flap installed upstream of the intake valve of a HSDI diesel engine, to control the amount of fresh mixture and its composition. This switching device will not only enable the impulse charging or Miller-Cycle, but also a new method of external EGR.

Exhaust Gas Recirculation (EGR) is a proven method for in-cylinder NOx reduction. A multitude of scientific work has focused on the temperature-lowering effect of exhaust gases. The disadvantage of a turbocharged heavy duty diesel truck engine is a high positive pressure gradient between intake and exhaust which complicates a High Pressure Exhaust Gas Recirculation (HP-EGR). In this study, a new technology will be presented to introduce EGR in the high pressure loop of a turbocharged HD-Truck engine without penalty of fuel economy caused by the increase of pumping losses.

In this paper, results from conventional, Homogeneous Charge Compression Ignition (HCCI) and Split Combustion (SC) combustion processes in combination with alternative fuels are discussed. First the results of the conventional combustion and Diesel fuel as reference are shown; thereafter the results of a blend of Diesel, Rapeseed Methyl Esther (RME) and ethanol and two blends of Diesel and butanol are described. Second the same fuel and blends are used with the (partially) homogeneous combustion systems to evaluate the possible reduction of emissions and fuel consumption. In addition to the limited emissions some measurements of the particle size distribution are carried out.

Liquefied natural gas (LNG) plays an increasingly important role as a climate-friendly fuel for a sustainable mobility. Compared to diesel, LNG has a CO2 reduction potential of around 20%. There is also the possibility of reducing GHG by adding biogas or synthetic natural gas. The Methane Number (MN) characterizes the knocking properties of gaseous fuels and was defined by AVL. There is no standardized measurement procedure for the MN. Instead, there are some algorithms to calculate the MN from the gas mixture composition. Most of them are based on the original AVL measurement data, e.g. the NPL algorithm. In the AVL study, the different knocking properties of n- and iso-components of the alkanes were not investigated. This paper focuses on the experimental investigation of the knock resistance of different alkanes in LNG mixtures and the improvement of the NPL algorithm based on these results.

A single-stage turbocharger turbine is developed with the objective of enabling a gasoline spark-ignition engine to operate under lean-burn conditions with an air-to-fuel ratio of λ=2 in the range of the Worldwide Harmonized Light-Duty Vehicles Test Cycle. For this purpose, extensive 1-D engine simulations are performed using a combination of a simple compressor and simple turbine model as well as a combination of the stock compressor and a simple turbine model. The results show that an isentropic turbine efficiency of more than 70% over a wide operating range is required for the desired engine operation - especially with regard to the low-end-torque. Based on the crank-angle-resolved engine simulation data, turbine requirements are determined. Their evaluation shows that an axial turbine is a reasonable alternative to conventional radial turbines for this application. Next, a preliminary axial turbine is designed using 1-D/2-D design approaches.

When comparing automotive and large-bore diesel engines, the latter usually show lower specific fuel consumption values, while automotive engines are subject to much stricter emission standards. Within an FVV (Research Association for Combustion Engines) project these differences were identified, quantified and assigned to individual design and operation parameters. The approach was split in three different phases: 1 Comparison of different-sized diesel engines 2 Correlation of differences in fuel consumption to design and operating parameters 3 Further investigations under automotive boundary conditions The comparison in the first phase was made on the basis of operating data and energy balances as well as the separation of losses based on the thermodynamic analysis. To also determine the quantitative effects of each design and operating parameter, a 1D process calculation model of the passenger car engine was transformed gradually to a large-bore engine in the second phase.

In view of the rapidly increasing complexity of conventional as well as hybrid powertrains, a systematic composition platform seeking for the global optimum powertrain is presented in this paper. The platform can be mainly divided into three parts: the synthesis of the transmission, the synthesis of the internal combustion engine (ICE) and the optimization and evaluation of the entire powertrain. In regard to the synthesis of transmission concepts, a systematical and computer-aided tool suitable both for conventional und hybrid transmissions is developed. With this tool, all the potential transmission concepts, which can realize the desired driving modes or ratios, can be synthesized based on the vehicle data and requirements.

Within a project of a research association (Forschungsver-einigung Verbrennungskraftmaschinen e.V.) a DI spark-ignition engine with small engine displacement was designed at the Institute of Internal Combustion Engines of the Technische Universitat Braunschweig. The objective of the project is to investigate the minimum bore diameter which allows the reasonable use of the advantages of gasoline direct injection. This article outlines the preliminary studies to identify suitable geometry variants for lateral and central injector position concerning effective engine operating data. Under consideration of current production possibilities and geometries of available injector and spark plug CAD studies were carried out. All suitable valve concepts, beginning with a two-valve (2V) concept and up to a four-valve (4V) concept, were examined in the CAD studies. The bore diameter was varied in a range from 56 to 62 mm combined with a variation of the stroke/bore ratio from 0.9 to 1.2.

This paper describes the development process and the implementation of an electro-hydraulic variable valve actuation system to a HD single cylinder research Diesel engine. Because of the requirements of this special application the described development process deviates strongly from past publications. These requirements are directly derived from results of the combustion process development on a HD engine and their fulfillment by the VVA is simulated both for the mechanical design and the gas exchange. On the one hand the software AMESim is used on the other hand Ricardo Wave. Finally some experimental results of the prototype system are shown.

This paper presents a newly developed 2-stage ignition delay model for pilot ignited medium speed dual-fuel (DF) engines. This provides the first major step towards a new combustion model for the prediction of the DF combustion in the context of 0D/1D simulation. The combustion models known from literature are based on empirical models of a steady jet. Here in most cases the package model of Hiroyasu is used. Because in a DF engine the injection timing of the diesel fuel is very early and the injection ends before ignition, the spray behavior differs from that of a steady jet. Especially the end-of-injection transients lead to stronger entrainment and therefore affect the ignition delay. In addition, the presence of natural gas in the cylinder extends the ignition delay at the chemical level. In this paper the 1D transient spray model of Musculus and Kattke is used to describe the spray behavior.

The EU recently decided to reduce CO2 emissions of commercial vehicle fleets by 30% until 2030. One possible way to achieve this target is to convert commercial vehicle diesel engines into stoichiometric natural gas engines. Based on this, a commercial vehicle single cylinder diesel engine with variable valve actuation and high-pressure EGR is converted into natural gas operation to increase efficiency and thus reduce CO2. Additionally, a water injection system is integrated. All three technologies are investigated on their own and in combination. To reduce longer combustion durations caused by Miller valve timing and charge dilution, a piston bowl with extra high turbulence generation is designed. Additionally, a swirl variation is carried out. The results show, that high swirl motion and high turbulence can lead to a disadvantage in efficiency despite faster combustion durations due to higher wall heat losses.

Hybrid electric vehicles (HEVs) are facing increased challenges of optimizing the energy flow through a vehicle system, to enhance both the fuel economy and emissions. Energy management of HEVs is a difficult task due to complexity of total system, considering the electrical, mechanical and thermal behavior. Innovative thermal management is one of the solutions for reaching these targets. In this paper, the potential of thermal management for a parallel HEV with a baseline control strategy under different driving cycles and ambient temperatures is presented. The focus of the investigations is on reducing fuel consumption and increasing comfort for passengers. In the first part of this paper, the developed HEV-model including the validation with measurements is presented. In the second part, the combined thermal management measures, for example the recuperation of exhaust-gas energy, engine compartment encapsulation and the effect on the target functions are discussed.

There are numerous methods for accelerated ash loading of particulate traps known from literature. However, it is largely unknown if a combination of these methods is possible and which one generates the most similar ash compared to ash from real particulate filters. Since the influencing variables on the ash formation are not yet fully understood, ashing processes are carried out under carefully controlled laboratory conditions on an engine test bench. The first ashing takes place with low sulfated ash phosphorus and sulfur oil without any methods to increase the quantity of produced ash. The obtained ash is used as a reference and is compared hereinafter with the process examined. Four methods to increase the ash production ratio are investigated. The first one is an increase of the ash content of the lubrication oil through an increase of the additives in the oil. The second one is the additional generation of ash with a burner system where oil is injected into the flame.

A key technology for further improving the efficiency of gasoline engines lies in downsizing in combination with turbocharging. Decreasing the engine displacement greatly increases the demands on the turbocharging system. The charging of the engine with a single-stage turbocharger leads to a compromise to fulfill the requirements of the nominal power of the engine and the low-end torque. To avoid the use of complex two-stage boosting systems, it is necessary to increase the pressure ratio and the air flow rate at the same time. The wide speed and airflow range of gasoline engines intensify this trade-off. The use of a variable geometry turbine (VGT), additionally equipped with a wastegate bypass, offers great potential to meet the requirements on the turbine side. The range of stable operation of the compressor is limited by choke at high mass flow rates and surge at low mass flow rates. The variable geometry compressor (VGC) is one promising approach to extend the compressor map.

Individual transport plays a considerable role in global greenhouse gas emissions. Hence, worldwide legislation increases the demands on the automotive industry with regard to emissions. Because internal combustion engines will likely play an important role in the future transport, particularly in hybrid propulsion systems, further improvement of the combustion system is necessary. Therefore, the potential of lean burn combustion in combination with other technologies is investigated. The primary focus is on the improvement of SI engine efficiency. For the investigations conducted, an extremely downsized SI single cylinder research engine is upgraded with various engine technologies. The stroke-to-bore ratio is increased to 1.5, leading to higher piston speeds. The resulting increase in tumble and hence turbulent flame speed supports the combustion performance of highly diluted mixtures.

This study investigates the technical feasibility of onboard carbon capture in vehicles. In fact there are two different main concepts of hybrid electric vehicles with batteries and range extenders proposed. The first concept uses an Internal Combustion Engine as range extender. Carbon dioxide is separated from the flue gas of this Internal Combustion Engine by chemical or physical absorption. In the second concept a solid oxide fuel cell (SOFC) is used as a range extender. The CO remaining in the anode exhaust gas is not combusted as usual by mixing anode and cathode exhaust gases but shifted with water vapor, sufficient available in the anode exhaust gas flow, to H₂ and CO₂. The H₂ is separated by a membrane permeable only for H₂ and recycled by the methane flow to the SOFC stack. Carbon dioxide can then be separated by simply condensing the water vapor of the anode exhaust gas of the SOFC.

A model for the calculation of heat release in direct injection Diesel engines is presented. It needs only one engine-specific experimental parameter. In the form the model is presented here it is limited to the medium and upper load range, where Diesel combustion is mainly mixing controlled. The development of the model is based on data from medium speed engines. The applicability to automotive engines is shown in some examples. The model is based on the theory of single phase turbulent jets. Starting from the balance of momentum and fuel mass flow the stationary part of the jet can be calculated. The propagation of the front of the unsteady jet is determined from a continuity consideration. Heat release is calculated based on the assumptions of the Simple Chemically Reacting System (SCRS). Fuel that is mixed with air is assumed to be burnt instantaneously.

A vehicle thermal management system is required to increase the operating efficiency of components, to transfer the heat efficiently and to reduce the energy required for the vehicle. Vehicle thermal management technologies, such as engine compartment encapsulation together with grille shutter control, enable energy efficiency improvements through utilizing waste heat in the engine compartment for heating powertrain components as well as cabin heating and reducing the aerodynamic drag . In this work, a significant effort is put on recovering waste heat from the engine compartment to provide additional efficiency to the components using a motor compartment insulation technique and grille shutter. The tests are accelerated and the cost is reduced using a co-simulation tool based on high resolution, complex thermal and kinematics models. The results are validated with experimental values measured in a thermal wind tunnel, which provided satisfactory accuracy.

Internal combustion engines fall under increased environmental and social pressure. However, they will still play an important role in future transport, especially in hybrid propulsion systems. As a consequence, efficiency of SI engines has to be further increased. Lean burn operation provides a promising way to reach this target. An extremely downsized SI single cylinder research engine is used for the investigations. The engine features a stroke-to-bore ratio of 1.5, leading to higher piston speeds and hence increased tumble motion. The resulting increase in turbulent flame speed supports sufficient combustion performance of diluted mixtures. Although the mentioned provisions increase combustion stability for lean burn operation the reachable relative air/fuel ratio is limited. In order to extend the lean burn capabilities of the engine (λ ≥ 2.0) and further exploit the efficiency advantages of this combustion process the engine is upgraded with a hydrogen port fuel injection.