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Neat Oxymethylene Ethers: Combustion Performance and Emissions of OME2, OME3, OME4 and OME5 in a Single-Cylinder Diesel Engine

Technical University of Munich-Patrick Dworschak, Vinicius Berger, Martin Härtl, Georg Wachtmeister
  • Technical Paper
  • 2020-01-0805
To be published on 2020-04-14 by SAE International in United States
Diesel engines are arguably the superior device in the ground transportation sector in terms of efficiency and reliability, but suffer from inferior emission performance due to the diffusive nature of diesel combustion. Great research efforts gradually reduced nitrogen oxide (NOX) and particulate matter (PM) emissions, but the PM-NOX trade-off remained to be a problem of major concern and was believed to be inevitable for a long time. In the process of engine development, the modification of fuel properties has lately gained great attention. In particular, the oxygenate fuel oxymethylene ether (OME) has proven potential to not only drastically reduce emissions, but possibly resolve the formerly inevitable trade-off completely. Although intensified investigations with OME were conducted within the past decade, little is known about the specific influence of fuel properties inherent to unimolecular, high chain length OME on combustion characteristics, emission performance and particle size. The latter is of special concern, as studies on oxygenate fuels reported increased formation of nanoparticles, which are known to have adverse effects on human health. In this paper, the authors…
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The Potential of Gasoline Fueled Pre Chamber Ignition Combined with Elevated Compression Ratio

Hitachi Europe GmbH-Henning Sauerland
Technische Universitat Munchen-Andreas Stadler, Martin Härtl, Georg Wachtmeister
  • Technical Paper
  • 2020-01-0279
To be published on 2020-04-14 by SAE International in United States
Pre-chamber ignition is a method to simultaneously increase the thermal efficiency and to meet ever more stringent emission regulations at the same time. In this study, a single cylinder research engine is equipped with a tailored pre-chamber ignition system and operated at two different compression ratios, namely 10.5 and 14.2. While most studies on gasoline pre-chamber ignition employ port fuel injection, in this work, the main fuel quantity is introduced by side direct injection into the combustion chamber to fully exploit the knock mitigation effect. Different pre-chamber design variants are evaluated considering both unfueled and gasoline-fueled operation. As for the latter, the influence of the fuel amount supplied to the pre-chamber is discussed. Due to its principle, the pre-chamber ignition system increases combustion speeds by generating enhanced in-cylinder turbulence and multiple ignition sites. This property proves to be an effective measure to mitigate knocking effects. It is shown that less spark retard compared to conventional spark ignition allows to exploit the efficiency benefit of elevated compression ratios also in high load operation for stoichiometric mixtures.…
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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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Gasoline Fueled Pre-Chamber Ignition System for a Light-Duty Passenger Car Engine with Extended Lean Limit

SAE International Journal of Engines

Technische Universitat München, Germany-Andreas Stadler, Maximilian Wessoly, Sebastian Blochum, Martin Härtl, Georg Wachtmeister
  • Journal Article
  • 03-12-03-0022
Published 2019-06-07 by SAE International in United States
In this work, a light-duty research engine based on a passenger car engine is equipped with an in-house developed pre-chamber (PC) ignition system replacing the conventional spark plug. By using such kind of ignition system, the combustion in the main chamber is enhanced by radical seeding through jets travelling from the pre-chamber to the main chamber. These radicals serve as high-energy ignition sites for the mixture in the main combustion chamber leading to enhanced burn rates and combustion speed. In contrast to conventional spark-ignited combustion starting from the spot of the electrode gap, an extended lean misfire limit and a mitigated knocking tendency are achieved. The presence of a gasoline direct injector inside the PC enables the system to operate in both passive and active mode. The injection of a small fuel amount allows separating the air-to-fuel equivalence ratio of the pre-chamber and the main chamber. By this, an overall lean mixture is ignited by providing a stoichiometric mixture near the PC spark plug. In this study, different orifice nozzles of the PC are investigated…
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A Novel Approach towards Stable and Low Emission Stratified Lean Combustion Employing Two Solenoid Multi-Hole Direct Injectors

SAE International Journal of Engines

Hitachi Europe GmbH-Henning Sauerland
Technical University of Munich-Johann Peer, Andreas Stadler, Thomas Zimmer, Martin Härtl, Georg Wachtmeister
  • Journal Article
  • 03-11-02-0016
Published 2018-04-18 by SAE International in United States
Stratified lean combustion has proven to be a promising approach for further increasing the thermal efficiency of gasoline direct injection engines in low load conditions. In this work, a new injection strategy for stratified operation mode is introduced. A side and a central-mounted solenoid multi-hole injector are simultaneously operated in a single-cylinder engine. Thermodynamic investigations show that this concept leads to improved stability, faster combustion, reduced particle number emissions, and lower fuel consumption levels compared to using only one injector. Experiments at an optical engine and three-dimensional computational fluid dynamics (CFD) simulations explain the improvements by a more compact mixture and reduced piston wetting with two injectors. Finally, the application of external EGR in combination with the above concept allows NOx emissions to be effectively kept at a low level while maintaining a stable operation.
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Development of a High Turbulence, Low Particle Number, High Injection Pressure Gasoline Direct Injection Combustion System

SAE International Journal of Engines

Hitachi Europe GmbH-Henning Sauerland
Technische Universitaet Muenchen-Johann Peer, Fabian Backes, Martin Härtl, Georg Wachtmeister
  • Journal Article
  • 2016-01-9046
Published 2016-11-16 by SAE International in United States
In the present work the benefit of a 50 MPa gasoline direct injection system (GDI) in terms of particle number (PN) emissions as well as fuel consumption is shown on a 0.5 l single cylinder research engine in different engine operating conditions.The investigations show a strong effect of injection timing on combustion duration. As fast combustion can be helpful to reduce fuel consumption, this effect should be investigated more in detail. Subsequent analysis with the method of particle image velocimetry (PIV) at the optical configuration of this engine and three dimensional (3D) computational fluid dynamics (CFD) calculations reveal the influence of injection timing on large scale charge motion (tumble) and the level of turbulent kinetic energy. Especially with delayed injection timing, high combustion velocities can be achieved.At current series injection pressures, the particle number emissions increase at late injection timing. With up to 50 MPa it is possible to overcome this trade off. Higher injection pressures allow faster combustion by delaying injection timing without rising particle number emissions. Especially at high engine loads the enhanced…
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Cetane Number Determination by Advanced Fuel Ignition Delay Analysis in a New Constant Volume Combustion Chamber

ASG Analytik-Service Gesellschaft mbH-Philipp Seidenspinner, Thomas Wilharm
Technische Universität München-Martin Härtl, Georg Wachtmeister
Published 2015-04-14 by SAE International in United States
A new constant volume combustion chamber (CVCC) apparatus is presented that calculates the cetane number (CN) of fuels from their ignition delay by means of a primary reference fuel calibration. It offers the benefits of low fuel consumption, suitability for non-lubricating substances, accurate and fast measurements and a calibration by primary reference fuels (PRF). The injection system is derived from a modern common-rail passenger car engine.The apparatus is capable of fuel injection pressures up to 1200 bar and requires only 40 ml of the test fuel. The constant volume combustion chamber can be heated up to 1000 K and pressurized up to 50 bar. Sample selection is fully automated for independent operation and low levels of operator involvement. Capillary tubes employed in the sampling system can be heated to allow the measurement of highly viscous fuels.For primary reference fuel calibration, ignition delay times of six mixtures with defined CN in the range of 35 to 70 are measured and correlated to their CN using a mathematical best fit curve. First tests showed good correlation with…
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