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Development of a Physically/Chemically Based Approach for 2-Stage Ignition Delay Calculation in Medium Speed Dual-Fuel Engines

Technische Universität Braunschweig-Jelto Frerichs, Peter Eilts
Published 2019-09-09 by SAE International in United States
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 spray model is extended with a mixing controlled evaporation model to derive the temperature distribution inside the spray. A 2-stage ignition delay model with…
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Optical Investigation of Mixture Formation in a Small Bore DISI Engine by Laser Induced Exciplex Fluorescence (LIEF)

Technische Univ. Braunschweig-Alexander Pauls, Peter Eilts
Published 2019-09-09 by SAE International in United States
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. In the previous project “GDI Boundary Bore” the feasibility of an SI engine with direct injection and small bore diameter (60 mm) was shown by the analysis of two different cylinder head concepts (3V and 4V). For the acquirement of deeper understanding of the mixture formation in…
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Optimization of the Exhaust Aftertreatment System of a Heavy Duty Diesel Engine by Means of Variable Valve Timing

Technische Universität Braunschweig-Marius Betz, Peter Eilts
Published 2019-09-09 by SAE International in United States
In view of the current political debate, it can be assumed that the nitrogen oxide limits for commercial vehicles will be further reduced. This is also demonstrated by the currently voluntary certification of the CARB Optional Low NOX legislation, which requires nitrogen oxide emissions of 0.027 g/kWh. This corresponds to a reduction of 93 % compared to the current EU VI standard. Therefore, the optimization of EAT systems represents an essential research focus for future commercial vehicle applications.One way to optimize the EAT system may be the usage of variable valve actuation. Existing investigations show an exhaust gas temperature increase with intake valve timing adjustment, also known as Miller timing. But the authors conclude that it cannot accelerate the warm up process. With regard to the effects on the exhaust aftertreatment system and the resulting tailpipe emissions, only improved HC and CO oxidation could be identified so far. In addition, a potential for improved NOX reduction is expected in the exhaust gas temperature increase.Therefore, further investigations have been carried out. The investigations presented in this…
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Active Control of Cylinder Charge Motion Using Vortex Generating Jets (VGJs) on Generic Intake Port Geometries

SAE International Journal of Engines

Technical University of Braunschweig-Shaowei Sun, Peter Eilts, Peter Scholz, Stefanie Haubold
  • Journal Article
  • 03-11-04-0032
Published 2018-08-08 by SAE International in United States
Swirl is known to have impact on the combustion process and the engine emission performance. Generally the swirl flows are generated on engines by e.g. helical or tangential intake ports. However, such features of intake ports constrict the airflow, resulting in raising pumping losses and thus higher fuel consumption. This article introduces a further possibility to generate and regulate the swirl flow by injecting air directly into the intake ports using Vortex Generating Jets (VGJs). The effect of air injection was studied by means of experimental investigations regarding swirl generation and flow rate improvement. The optimization of VGJ diameters, positions as well as injection airflow rate was carried out with respect to energy efficiency of swirl generation. A new methodology for constructing generic intake ports was developed which specifies realistic intake port geometries with about 20 parameters and enables the derivation of comparable intake ports of desirable characteristics. By using this methodology, one set of generic intake ports was built which has a significant helical form and shows accordingly strong swirl ratios (referred to as…
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WM-LES-Simulation of a Generic Intake Port Geometry

SAE International Journal of Engines

Technische Universität Braunschweig-Peter Scholz, Daniela Gisele François, Stefanie Haubold, Shaowei Sun, Peter Eilts
  • Journal Article
  • 03-11-03-0023
Published 2018-06-18 by SAE International in United States
Fluid mechanical design of the cylinder charge motion is an important part of an engine development. In the present contribution an intake port geometry is proposed that can be used as a test case for intake port flow simulations. The objective is to fill the gap between generic test cases, such as the backward facing step or the sudden expansion, and simulations of proprietary intake ports, which are barely accessible in the community. For the intake geometry measurement data was generated on a flow-through test bench and a wall-modeled LES-simulation using a hybrid RANS/LES approach for near-wall regions was conducted. The objective is to generate and analyze a reference flow case. Since mesh convergence studies are too costly for scale resolving approaches only one simulation was done, but on a very fine and mostly block-structured numerical mesh to achieve minimal numerical dissipation. Also a steady-state RANS was done on the same mesh to identify the significance of the scale-resolving approach. However, to stabilize the RANS on the fine mesh, low-order schemes were required. The results…
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Potentials of Variable Cross Section Compressor Regarding Surge Line and Compressor Efficiency Using Engine Test Bench Measurements and Engine Process Simulation

Leibnitz Universität Hannover-Thorsten Sextro, Joerg Seume
Technische Universität Braunschweig-Jan Flinte, Peter Eilts
Published 2018-05-30 by SAE International in United States
Downsizing of SI engines in combination with turbocharging is state of the art to reach future CO2 emission limits. A single stage turbocharged engine has a conflict of objectives between high rated power and high low-end-torque. To expand the stable map area of the compressor a variable compressor is investigated on an engine test bench supported by the use of engine process simulation. The measurements were carried out on a radial compressor with high trim compressor wheel. The limiting factor of the feasible low end torque is the surge line. Different inlet cross sections are investigated to shift the surge line to lower mass flow. The compressor maps are measured simultaneously on a hot gas and an engine test bench. A combination of both maps provides the input data for a 1D-simulation model of the test engine, which is presented in this paper. A predictive combustion model is validated for full and part load operating points up to 5000 rpm based on the serial production engine. Because a diesel VTG is used with the variable cross…
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Potentials of Miller Cycle on HD Diesel Engines Using a 2-Stage Turbocharging System

Institute of Internal combustion Engines-Peter Eilts
Technische Universitat Braunschweig-David Kovacs
Published 2018-04-03 by SAE International in United States
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. The combustion process and the pollutant emissions are taken over from measurements on a single cylinder test engine equipped with a VVA and…
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Investigations on the Determination of the Service Methane Number of LNG

Technical University of Braunschweig-Peter Eilts, Lennart Klare
Published 2018-04-03 by SAE International in United States
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). It usually shows the same tendencies as the MN…
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Composition Platform for Conventional and Hybrid Powertrains

Institute of Automotive Engineering-Haijun Chen, Lin Li, Mark Schudeleit, Andreas Lange, Ferit Küçükay
Institute of Internal Combustion Engines-Christian Stamme, Peter Eilts
Published 2017-09-04 by SAE International in United States
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. As a result of the transmission synthesis, the detailed information of each transmission concept, including the transmission structure, the shifting logic, the estimated efficiency in each gear, and the estimated space arrangement of the transmission can be given out.The synthesis of transmission concepts is complemented by a comprehensive tool able to synthesize internal combustion engines of gasoline and gasoline/Atkinson type. The ICE synthesis precalculates frictional and thermodynamic…
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Investigation of Engine Processes with Extreme Pressures and Turbocompounding

Technical Univ. of Braunschweig-Peter Eilts
Published 2016-04-05 by SAE International in United States
This work is based on calculations about extreme mean effective and maximum pressures which were published earlier by the author and colleagues. The motivation for the work presented in this paper is to reduce the maximum pressure while keeping a high mep without sacrificing efficiency. It is investigated in a theoretical study in how far this can be accomplished via turbocompounding.The basis is a 320 mm bore four stroke medium speed engine. It is equipped with a state-of-the-art two stage turbocharging system.As a first step turbocompounding is investigated for mean effective pressures from 22 to 80 bar. The bsfc of the turbocharged engine is in the range of 175 to 185 g/kWh depending on mep. With turbocompounding the exhaust pressure before turbine is optimised and figures between 160 and 165 g/kWh are reached. Thermal loading of the engine increases.In the second step strategies to reduce maximum pressure are investigated for an mep of ca. 50 bar. Reduced compression ratio and retarded injection increase the optimum bsfc of the turbocompound engine slightly while a reduced air-fuel-ratio…
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