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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.

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 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.

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.

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.

Small natural gas cogeneration engines usually operate with lean mixture and late combustion phasing to comply with NOx emission standards, leading to significant losses in engine efficiency. Owing to water evaporation heat and high specific heat capacity of the water vapor, leads the water injection to cooling the combustion chamber charge, which enables earlier combustion phasing, higher compression ratio and thus higher engine efficiency. Therefore, water injection enables mitigating the tradeoff between NOx emissions and engine performance, without loss in engine efficiency. The intake port injection represents, because of the low required injection pressure and the simple injector integration, a cost-effective way to introduce water into the engine. Hence, the purpose of this work is to adapt the intake port water injection timing to the charge mixture flow conditions in the intake port.

Hybrid electric vehicles (HEV's) are facing increasing challenges in optimizing the energy flow through a vehicle system, in order to improve both fuel economy and vehicle emissions. Energy management of HEV's is a difficult task due to the complexity of the total system in terms of electrical, mechanical and thermal behavior. In this paper, an advanced control strategy for a parallel hybrid vehicle is developed. Four main steps are presented, particularly to achieve a reduction in fuel consumption. The first step is the development of a highly complex HEV model, including dynamic and thermal behavior. Second, a heuristical control strategy is developed to determine the HEV modes and third, a State of Charge (SoC) leveling is developed with the interaction of a fuzzy logic controller. It is proposed to calculate the load point shifting of the Internal Combustion Engine (ICE) and the desired battery SoC.

The current level of mean effective pressure (mep) of automotive diesel engines is 20 to 30 bar. Maximum pressure (pmax) is about 180 to 200 bar. In special applications even higher figures have been achieved in the past. This led the authors to investigate what can be expected when operating at much higher pressures. In a theoretical study the mep of a passenger car engine was increased up to 80 bar. A zero-dimensional cycle simulation program was used for the calculations. Rate of heat release, valve timing and mechanical efficiency were kept constant. Several strategies concerning turbocharging and thermal loading were investigated. Some results for mep = 80 bar: - The specific fuel oil consumption is reduced by some 5%, if certain prerequisites are given. - Further reductions are possible depending on mechanical efficiency, which was set constant in this study. - Charge air pressure increases to approximately 10 bar.

LNG is a fuel that is under increasing discussion for transport purposes. It differs from CNG because it often has a higher concentration of hydrocarbons > C4. This affects knocking in a negative way. The knocking properties of a gaseous fuel are characterized by the Methane Number (MN) which is defined as the methane content in a mixture of methane and hydrogen which has the same knocking properties as the gas under investigation. It was defined by AVL in the late 1960s. In contrast to the Octane or Cetane Number there is no standardized measurement procedure for the MN, because the equipment AVL used was unique and does not exist anymore. But AVL created a calculation methodology based on the large amount of data they had measured. There are several software implementations of this methodology. Further there are other algorithms which are not based on the AVL data. If an MN is measured on an arbitrary engine the result is called a Service Methane Number (SMN).

Legislative and customer demands in terms of fuel consumption and emissions are an enormous challenge for the development of modern combustion engines. Downsizing in combination with turbocharging and direct injection is one way to increase efficiency and therefore meet the requirements. This results in a reduction of the displacement and thus the bore diameter. The emerging trends towards long-stroke engine design and hybridization make the use of small bore diameters in future gasoline engines a realistic scenario. The application of direct injection with small cylinder dimensions increases the probability of the interaction of liquid fuel with the cylinder walls, which may result in disadvantages concerning especially particulate emissions. This leads to the question which bore diameter is feasible without drawbacks concerning emissions as a result of wall wetting.

The paper presents laser optical investigations of mixture formation at negative pressure conditions, typical for throttle-controlled SI engines. A high pressure injector as well as a low pressure injector is used to estimate the behavior of different fuels (premium gasoline and ethanol) at different negative ambient pressures. The objective is to show the potential of combining the better evaporation due to less ambient pressure with a heat loading effect due to variable inlet timing especially for the use of ethanol.

The transportation sector, and commercial vehicles in particular, play an important role in global CO2 emissions. For this reason, the EU recently decided to reduce CO2 emissions from commercial vehicles by 30% until 2030. One alternative to conventional diesel propulsion is the usage of stoichiometric natural gas combustion. Due to the lowered C/H ratio and the cost effective exhaust after treatment (EAT) in form of a three way catalyst (TWC), less CO2 is emitted and it is possible to comply even with most stringent NOX legislations. However, the stoichiometric combustion of natural gas has also disadvantages. In particular, the throttling and retarded 50 % mass fuel burned (MFB50) positions due to knocking lead to efficiency losses. One way to minimize these is the usage of exhaust gas re-circulation (EGR), Miller cycle and water injection. The reduced knocking tendency allows the geometric compression ratio to be increased further, which leads to an additional efficiency advantage.

Variable valve trains offer the opportunity to apply advanced combustion process strategies such as the Miller cycle. As is well known, applying Miller timing for CI engines is an effective way to reduce NOX emissions and can lead to an increase in engine efficiency. Because of the intended future NOX and GHG limits for on-road HD CI engines, the use of variable valve trains become more and more inevitable. Previous studies of the authors have shown that the improvement potential highly depends on the achievable cylinder charge level. Increasing this (through additional increase in boost pressure) results in a significant decrease in ISFC as well as in an improved NOX-PM trade-off. However, in these considerations the pressure difference of the charge air and the exhaust back pressure was kept on the same level. The present paper investigates the improvement potentials for heavy duty CI engines taking a two-stage turbocharging group into account.

A variable air path on diesel engines offers further potentials to manage the challenges of engine development - such as reduction of emissions and fuel consumption, as well as performance increase. The Miller cycle is one of the possibilities, which is well known as an effective way to reduce process temperatures and so NOX emissions. The present paper discusses the potentials of this strategy for heavy duty diesel engines by identifying and analyzing the effects caused. The investigations were carried out in the upper load range. First the isolated effect of the Miller cycle was analyzed. The results show reduced NOX emissions, although increased PM and CO emissions were measured. Further, the Miller cycle caused a reduction in peak cylinder pressure. This pressure reserve can be used to combine the Miller cycle with further measures while maintaining the maximum cylinder pressure of the reference operation point. On the one hand, a performance increase of about 10% was achieved.