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Development of a 3D-CFD Model for a Full Optical High-Pressure Dual-Fuel Engine

SAE International Journal of Engines

Technical University of Munich, Germany-Stephanie Frankl, Stephan Gleis
  • Journal Article
  • 03-13-02-0017
Published 2020-01-27 by SAE International in United States
In times of ever stricter exhaust emission regulations, the importance of alternative combustion processes in internal combustion engines continues to grow. One approach to create a combustion progress which produces low CO2, soot, and methane emissions is the “High-Pressure Dual-Fuel” (HPDF)-combustion. Here, the direct-injected methane is ignited by a small amount of pilot-diesel and burns in a diffusive combustion mode. This study describes the development of a three-dimensional computational fluid dynamics (3D-CFD) model for the HPDF-combustion. A Reynolds-Averaged Navier-Stokes (RANS) approach with k-epsilon modelling for turbulence was chosen for the calculation of the flow field. The pilot fuel injection is implemented by using Lagrangian Particle Methods, whereas the gas injection is a mass flow boundary which is derived from measurements of the injector. The model is validated using data from a fully optically accessible single-cylinder research engine. The flow field is compared with particle image velocimetry (PIV) data taken before the start of injection (SOI). Concerning pilot injection, a grid convergence study is conducted and an optimization is developed to reduce computational costs. The penetration…
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Development of a Measuring System for the Visualization of the Oil Film between the Piston and Cylinder Liner of a Gasoline Engine

SAE International Journal of Engines

Technical University of Munich, Germany-Julian Schäffer, Claus Kirner, Martin Härtl, Georg Wachtmeister
  • Journal Article
  • 03-13-02-0013
Published 2019-11-14 by SAE International in United States
The design of cylinder liners, pistons, and piston rings is subject to different conflicting goals. In addition to a loss-free seal of the combustion chamber, sufficient oil must be present between the friction partners. Both the reduction of piston assembly friction and the minimization of oil consumption are crucial to achieve the strictly defined CO2 and emission standards. To master this challenge and find the best compromise requires a lot of system-specific know-how. The automobile and engine manufacturers focus mainly on friction-reducing measures, which are analyzed with different measuring methods such as the floating-liner method, the strip-down method, or the instantaneous indicated mean effective pressure (IMEP) method. However, the interpretation of the results and the development of realistic simulation models lacks information about the oil film behavior and the film thickness. In order to gain this missing knowledge, instruments for oil film visualization and oil film thickness measurement have to be developed. In the FVV-project “Piston ring oil transport - Glassliner”, the two-dimensional laser-induced fluorescence method (2D-LIF) is used to visualize the lubricating oil film…
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Experimental Analysis of Gasoline Direct Injector Tip Wetting

SAE International Journal of Engines

Technical University of Munich, Germany-Fabian Backes, Sebastian Blochum, Martin Härtl, Georg Wachtmeister
  • Journal Article
  • 03-13-01-0006
Published 2019-10-14 by SAE International in United States
At gasoline direct injection, light-duty engines operated with homogeneous, stoichiometric combustion mode, particulate emissions are mainly formed in diffusion flames that result from prior fuel wall wetting. Besides the piston, liner, and intake valves, the injector tip acts as a main particulate source when fuel is adhered to it during an injection. Hence, this injector tip fuel wetting process and influences on this process need to be analyzed and understood to reduce engine-out particulate emissions. The present work analyzes the injector tip wetting process in an experimental way with a high-speed and high-resolution measurement system at an optically accessible pressure chamber. The performed measurements reveal that injector tip wetting can occur during the complete injection event by different mechanisms. Large spray cone angles at start and at end of injection or distortions of the spray result in direct contact of the fuel spray with the step-hole wall. Additionally, fuel accumulates during an injection in the step-hole volume and discharges onto the injector tip surface subsequently. Furthermore, a poor primary breakup at end of injection can…
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Motion Cueing Algorithm for a 9-DoF Driving Simulator: MPC with Linearized Actuator Constraints

SAE International Journal of Connected and Automated Vehicles

Technical University of Munich, Germany-Felix Ellensohn, Daniel Rixen
BMW Group, Germany-Markus Schwienbacher, Joost Venrooij
  • Journal Article
  • 12-02-03-0010
Published 2019-07-09 by SAE International in United States
In times when automated driving is becoming increasingly relevant, dynamic simulators present an appropriate simulation environment to faithfully reproduce driving scenarios. A realistic replication of driving dynamics is an important criterion to immerse persons in the virtual environments provided by the simulator. Motion Cueing Algorithms (MCAs) compute the simulator’s control input, based on the motions of the simulated vehicle. The technical restrictions of the simulator’s actuators form the main limitation in the execution of these input commands. Typical dynamic simulators consist of a hexapod with six degrees of freedom (DoF) to reproduce the vehicle motion in all dimensions. Since its workspace dimensions are limited, significant improvements in motion capabilities can be achieved by expanding the simulator with redundant DoF by means of additional actuators. This article introduces a global optimization scheme that is able to find an optimal motion for a 9-DoF driving simulator with three redundant DoF. The simulator consists of a tripod with three DoF in longitudinal, lateral and yaw direction as well as a hexapod, which is mounted on top of the…
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A Comprehensive Attack and Defense Model for the Automotive Domain

SAE International Journal of Transportation Cybersecurity and Privacy

Technical University of Munich, Germany-Thomas Hutzelmann, Sebastian Banescu, Alexander Pretschner
  • Journal Article
  • 11-02-01-0001
Published 2019-01-17 by SAE International in United States
In the automotive domain, the overall complexity of technical components has increased enormously. Formerly isolated, purely mechanical cars are now a multitude of cyber-physical systems that are continuously interacting with other IT systems, for example, with the smartphone of their driver or the backend servers of the car manufacturer. This has huge security implications as demonstrated by several recent research papers that document attacks endangering the safety of the car. However, there is, to the best of our knowledge, no holistic overview or structured description of the complex automotive domain. Without such a big picture, distinct security research remains isolated and is lacking interconnections between the different subsystems. Hence, it is difficult to draw conclusions about the overall security of a car or to identify aspects that have not been sufficiently covered by security analyses. In this work, we propose a comprehensive model covering all relevant aspects of the automotive environment and link it with selected attack scenarios and defense strategies already discussed in academic literature. This showcases the capabilities of our model to build…
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Simulative Evaluation of Various Thermodynamic Cycles and the Specification of Their System Components Regarding the Optimization of a Cogeneration Unit

Technical University of Munich, Germany-Sebastian Andreas Zirngibl, Florian Günter, Maximilian Prager, Georg Wachtmeister
Published 2018-09-05 by SAE International in United States
Given the increasing globalization and industrialization, the worldwide demand for energy continuously increases. In the context of modern Smart Grids, especially small and distributed power plants are a key factor. The present article essentially focuses on the investigation of different approaches for waste heat recovery (WHR) in small-scale CHP (combined heat and power) applications with an output range of approximately 20 kW. The engine integrated into the CHP system under investigation applies a lean-burn combustion process generally providing comparatively low exhaust gas temperatures, thus requiring a careful design that is crucial for efficient WHR. Therefore, this article presents the development and use of a simulation environment for the design and optimization of WHR in small-scale CHP applications. The MATLAB-based code allows various combinations of specific components (e.g., heat exchangers and pumps, as well as turbines and compressors) in different thermodynamic cycles. The focus of this article essentially lies on the comparison of the Joule-Brayton and the Clausius-Rankine cycle regarding operating characteristics as well as the selection of specific working fluids. For the Brayton cycle, the…
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Validation of the RAMSIS Force Based Posture Model by Contact Force Measurement

Technical University of Munich, Germany-Heiner Bubb
BMW Group, Germany-Christin Fröhmel, Ernst Assmann
Published 2008-06-17 by SAE International in United States
This paper describes the method for the validation of the RAMSIS force based posture model. For this purpose a variable test setup was adapted and equipped with several force measurement sensors. This experimental setup is explained within this paper as well as some case scenarios and results. The intention of the validation work is the application of this model in the product development process.
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Noise Reduction of Chain-CVTs using Optimisation Techniques

Technical University of Munich, Germany-Lutz Neumann, Heinz Ulbrich, Friedrich Pfeiffer
Published 2006-04-03 by SAE International in United States
Continuous variable chain drives have to satisfy high requirements to compete with common gears and therefore an improvement of certain properties of the CVT (= Continuously Variable Transmission) is desired. In this contribution the important goal to reduce the noise emission of the gear is realised by optimising the geometry of the rocker pin chain. This optimisation is carried out by applying numerical simulation techniques and an optimisation algorithm. For this purpose a detailed dynamical model of the CVT is introduced which includes an exact treatment of the rocker pin kinematics of the chain. The geometry of the rocker pin joints which shall be optimised is defined by the optimisation parameters. A good choice for a measure of the noise emission are the amplitudes of the forces in the bearings in a certain frequency domain. They are used to form the target function. A numerical simulation provides a connection between the optimisation parameters and the objective function, which is not given analytically and takes high simulation effort. Therefore the optimisation algorithm implicit filtering is applied…
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