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Combustion Analysis with Residual Gas as a Design Parameter for Two-Stroke Engines

Andreas Stihl AG & Co KG-Florian Schumann
Graz University of Technology-Pascal Richard Piecha, Stephan Jandl, Stefan Sturm, Stephan Schmidt, Roland Kirchberger
Published 2018-10-30 by SAE International in United States
In a variety of applications, two-stroke engines assert their usage as a propulsion unit, for examples in off-road vehicles, scooters, hand-held power tools and others. The outstanding power to weight ratio is the key advantage for two-stroke engines. Furthermore, two-stroke engines convince with high durability and low maintenance demand. However, an increasing environmental awareness, the protection of health and the shortage of fossil resources are the driving factors to further enhance the internal combustion process of two-stroke engines. The reduction of emissions and fuel consumption with a constant power level is focused on.Developments deal with the optimization of the combustion process itself or the enhancement of the exhaust gas aftertreatment. Especially in very small two-stroke engines an exhaust gas aftertreatment system is rarely applied, due to disadvantages regarding component temperatures and product costs. Beside different parameters, the exhaust gas back pressure mainly influences the residual gas content as well as the gas exchange in two stroke engines. Both are essential for the combustion process quality, which can be determined by values of 50% MFB, COV,…
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Practicability and Influencing Factors of a Lean Burn Mode for Two-Stroke Engines in Hand-Held Powertools

Andreas Stihl AG & Co KG-Florian Schumann, Tim Gegg
Graz University of Technology-Pascal Piecha, Christoph Ninaus, Stephan Schmidt, Roland Kirchberger
  • Technical Paper
  • 2017-32-0043
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
For many applications, such as scooters, hand-held power tools and many off-road vehicles, two-stroke engines are used as a preferred propulsion unit. These engines convince by a good power to weight ratio, a high durability and low maintenance technology and are therefore the first choice in this field of application. In general, already much development effort has been expended to improve those systems. However, an increasing environmental awareness, the protection of health and the shortage of fossil resources are the driving factors to further enhance the internal combustion process of those adapted two-stroke engines. The current focus here is on the reduction of emissions and fuel consumption with an at least constant power output.An approach to address an improvement of engine efficiency can be covered by applying a lean combustion burn mode. In almost all combustion technology sectors, including furnaces, gas turbines and many internal combustion engines, a lean combustion is utilized. Possible advantages of a combustion process under lean conditions are low pollutant emissions and high efficiencies, because flame temperatures are typically low. Nevertheless,…
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Optical Analysis on the Mixture Preparation and Combustion Behavior of Small Two-Stroke SI Engines Fueled with Alcohol-Blends

ANDREAS STIHL AG & Co. KG-Tilman Seidel, Stefan Schweiger, Florian Schumann, Tim Gegg
MOT GmbH-Justus Weßling, Fabian Rauber, Fabian Titus, Kai W. Beck
  • Technical Paper
  • 2017-32-0078
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
Small gasoline engines are used in motorcycles and handheld machinery, because of their high power density, low cost and compact design. The reduction of hydrocarbon emissions and fuel consumption is an important factor regarding the upcoming emission standards and operational expenses. The scavenging process of the two-stroke engine causes scavenging losses [1]. A reduction in hydrocarbon emissions due to scavenging losses can be achieved through a better understanding of the inner mixture formation. The time frame for fuel vaporization is limited using two-stroke SI engines by the high number of revolutions. With crank angle resolved optical methods it is possible to analyze the mixture formation behavior and combustion. A topic of these investigations is the use of alternative fuels such as alcohol- or butanol-blends and the analysis of their impact on the engine behavior. These fuels show high potential for further reduction of exhaust emissions while simultaneously increasing the engine power output.
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Investigations and Analysis of Working Processes of Two-Stroke Engines with the Focus on Wall Heat Flux

SAE International Journal of Engines

Andreas Stihl AG & Co KG-Florian Schumann, Stephan Meyer, Tim Gegg
BRP-Powertrain GmbH & Co KG-Stefan Leiber
  • Journal Article
  • 2016-32-0028
Published 2016-11-08 by SAE International in United States
Small displacement two-stroke engines are widely used as affordable and low-maintenance propulsion systems for motorcycles, scooters, hand-held power tools and others. In recent years, considerable progress regarding emission reduction has been reached. Nevertheless, a further improvement of two-stroke engines is necessary to cover protection of health and environment. In addition, the shortage of fossil fuel resources and the anthropogenic climate change call for a sensual use of natural resources and therefore, the fuel consumption and engine efficiency needs to be improved.With the application of suitable analyses methods it is possible to find improving potential of the working processes of these engines. The thermodynamic loss analysis is a frequently applied method to examine the working process and is universally adaptable. Within this paper, a series production small displacement two-stroke engine is experimentally investigated on the test bench and adapted with measuring equipment in order to analyze the working process with focus on the wall heat flux. Due to high speed and vibrations, these investigations are complex. This publication considers an assessment of correlation predictability of heat…
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Investigations on the Heat Transfer in HCCI Gasoline Engines

SAE International Journal of Engines

Institut für Kolbenmaschinen (Institute for Reciprocating Engines), Universität Karlsruhe (TH)-Sebastian Hensel, Fatih Sarikoc, Florian Schumann, Heiko Kubach, Ulrich Spicher
  • Journal Article
  • 2009-01-1804
Published 2009-06-15 by SAE International in United States
In this work, heat loss was investigated in two different HCCI single cylinder engines. Thermocouples were adapted to the surfaces of the cylinder heads and the temperature oscillations were detected in a wide range of the engine operation conditions. The local heat transfer is analyzed with port fuel and direct injection, for different engine parameters and operating points. It is shown that the spatially averaged measured heat loss in HCCI operation represents the global heat loss well. The spatial variations are small in the operation map presuming stable operating points with low cyclic variations and good engine performance.Furthermore, the heat loss measured in HCCI operation is compared to the heat loss detected in homogeneous and stratified DI-SI operation in the same engine. It is shown that the local heat losses in stratified DI-SI operation show large variations, depending on the direction of the flame propagation. A comparison with the averaged measured heat loss is not valid for this operation mode.Finally the measured heat losses in HCCI operation are compared with the predictions of existing heat…
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A New Model to Describe the Heat Transfer in HCCI Gasoline Engines

SAE International Journal of Engines

Institute for Reciprocating Engines, Universität Karlsruhe (TH)-Sebastian Hensel, Fatih Sarikoc, Florian Schumann, Heiko Kubach, Amin Velji, Ulrich Spicher
  • Journal Article
  • 2009-01-0129
Published 2009-04-20 by SAE International in United States
In this work, heat loss was investigated in two different HCCI single cylinder engines. Thermocouples were adapted to the surfaces of the cylinder heads and the temperature oscillations were detected in a wide range of the engine operation maps. The resultant heat transfer profiles were compared to the heat losses predicted by existing models. As major discrepancies were stated, a new phenomenological model was developed that is well-manageable and describes the heat loss in HCCI mode more precisely than existing models.To analyze the insulating effect of deposits, the heat transfer equation was solved analytically by an approach that allows consideration of multiple layers with different material properties and thickness. This approach was used for the first time in conjunction with engines to calculate the heat flux at the surface of deposits and the deposit thickness. Additionally, the heat loss measured in HCCI operation was compared to the heat loss detected in homogeneous SI operation in the same engine. The differences in the heat transfer characteristics are demonstrated.
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