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Technical Paper

An Experimental Study of Homogeneous Charge Compression Ignition (HCCI) with Various Compression Ratios, Intake Air Temperatures and Fuels with Port and Direct Fuel Injection

2003-06-23
2003-01-2293
A promising approach for reducing both NOx- and particulate matter emissions with low fuel consumption is the so called homogeneous charge compression ignition (HCCI) combustion process. Single-cylinder engine tests were carried out to assess the influence of several parameters on the HCCI combustion. The experiments were performed both with port fuel injection (PFI) and with direct injection (DI) under various compression ratios, intake air temperatures and EGR-rates. Special emphasis was put on the fuel composition by using different gasoline and diesel fuels as well as n-heptane. Besides engine out emissions (CO2, CO, NO, O2, HC, soot) and in-cylinder pressure indication for burning process analysis, the combustion itself was visualised using an optical probe.
Technical Paper

Experimental Investigations of Two-Stroke SI Combustion with Simultaneous Cycle-Based Fuel Consumption Measurements

2010-09-28
2010-32-0061
Unstable combustion and high cyclic variations of the in-cylinder pressure associated with low engine running smoothness and high emissions are mainly caused by cyclic variations of the fresh charge composition, the variability of the ignition and the fuel mass. These parameters affect the inflammation, the burn rate and thus the whole combustion process. In this paper, the effects of fluctuating fuel mass on the combustion behavior are shown. Small two-stroke engines require special measuring and testing equipment, especially for measuring the fuel consumption at very low fuel flow rates as well as very low fuel supply pressures. To realize a cycle-resolved measurement of the injected fuel mass, fuel consumption measurement with high resolution and high dynamic response is not enough for this application.
Technical Paper

Influence of Injection Nozzle Hole Diameter on Highly Premixed and Low Temperature Diesel Combustion and Full Load Behavior

2010-10-25
2010-01-2109
Diesel engines face difficult challenges with respect to engine-out emissions, efficiency and power density as the legal requirements concerning emissions and fuel consumption are constantly increasing. In general, for a diesel engine to achieve low raw emissions a well-mixed fuel-air mixture, burning at low combustion temperatures, is necessary. Highly premixed diesel combustion is a feasible way to reduce the smoke emissions to very low levels compared to conventional diesel combustion. In order to reach both, very low NOX and soot emissions, high rates of cooled EGR are necessary. With high rates of cooled EGR the NOX formation can be suppressed almost completely. This paper investigates to what extent the trade-off between emissions, fuel consumption and power of a diesel engine can be resolved by highly premixed and low temperature diesel combustion using injection nozzles with reduced injection hole diameters and high pressure fuel injection.
Technical Paper

Use of Ceramic Components in Sliding Systems for High-Pressure Gasoline Fuel Injection Pumps

2010-04-12
2010-01-0600
Spray-guided gasoline direct injection demonstrates great potential to reduce both fuel consumption and pollutant emissions. However, conventional materials used in high-pressure pumps wear severely under fuel injection pressures above 20 MPa as the lubricity and viscosity of gasoline are very low. The use of ceramic components promises to overcome these difficulties and to exploit the full benefits of spray-guided GDI-engines. As part of the Collaborative Research Centre “High performance sliding and friction systems based on advanced ceramics” at Karlsruhe Institute of Technology, a single-piston high-pressure gasoline pump operating at up to 50 MPa has been designed. It consists of 2 fuel-lubricated sliding systems (piston/cylinder and cam/sliding shoe) that are built with ceramic parts. The pump is equipped with force, pressure and temperature sensors in order to assess the behaviour of several material pairs.
Technical Paper

Comparison of the Emission Behaviour and Fuel Consumption of a Small Two-Stroke SI Chainsaw under Test-Bed- and Real In-Use Conditions

2012-10-23
2012-32-0070
The emission behaviour of an internal combustion engine under test-bed conditions shows differences to the emission behaviour under real in-use conditions. Because of this fact, the developers of combustion engines and the legislator are focussing on the measurement and optimization of real in-use emissions. To this day, the research, the adjustment of the carburettor and the legislation of small handheld engines is performed under test bench conditions, especially conditioned fuel pressure and temperature, as well as air temperature. Also the engines are laid out for two operation points: rated speed with full open throttle and idle speed. This test-procedure is used for all kinds of handheld off-road applications and does not consider the load profile of the different power tools. Especially applications with transient load profiles, for example chainsaws, work in more than two operating points in real use.
Technical Paper

A Study of the In-Nozzle Flow Characteristic of Valve Covered Orifice Nozzles for Gasoline Direct Injection

2005-10-24
2005-01-3684
For spark ignition engines, the most effective way to reduce the overall fuel consumption and CO2 emissions respectively is the implementation of gasoline direct injection technology. In comparison to the current wall and air guided systems, the direct injection system of the second generation - the spray guided DI- is the most promising one with respect to fuel economy and emission. In order to exploit its full potential, a thorough combustion process development regarding injector and spark plug design and their positioning within the combustion chamber is essential. Especially multihole injectors offer many degrees of freedom with regard to the nozzle shape and spray pattern. To reduce the development work and costs necessary to identify the ideal nozzle characteristic and spray pattern, reliable CFD models are necessary.
Technical Paper

Comparative Study to Assess the Soot Reduction Potential of Different In-Cylinder Methods and Exhaust Gas Aftertreatment Systems for Direct Injection Diesel Engines

2007-10-29
2007-01-4016
In this study different methods to reduce the soot emissions of Diesel engines were investigated and compared to obtain their soot reduction potential. Apart from investigations on the practically usable engine map area with so called homogeneous charge compression ignition (HCCI) combustion processes a new heterogeneous combustion processes was developed and investigated which offers significantly reduced soot emissions while still applicable in the entire engine map. For the HCCI experiments the emphasis was put on the achievable engine load range when using conventional injector nozzles which still allow a conventional heterogeneous engine operation.
Journal Article

Is a High Pressure Direct Injection System a Solution to Reduce Exhaust Gas Emissions in a Small Two-Stroke Engine?

2013-10-15
2013-32-9143
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. A reduction in hydrocarbon emissions due to scavenging losses can be achieved through inner mixture formation using direct injection (DI). The time frame for fuel vaporization is limited using two-stroke SI engines by the high number of revolutions. A high pressure DI system was used to offer fast and accurate injections. An injection pressure of up to 140 MPa was provided by a common rail system, built out of components normally used in automotive engineering. A standard electromagnetic injector is applied for the fuel injection. This injection unit is dimensioned for multi-point injections in diesel engines.
Journal Article

Investigations on the Effects of the Ignition Spark with Controlled Autoignition (CAI)

2009-06-15
2009-01-1770
Controlled Autoignition (CAI) is a very promising technology for simultaneous reduction of fuel consumption and engine-out emissions [3, 4, 9, 16]. But the operating range of this combustion mode is limited on the one hand by high pressure gradients with the subsequent occurrence of knocking, increasing NOX-emissions and cyclic variations, and on the other hand by limited operating stability due to low mixture temperatures. At higher loads the required amount of internal EGR decrease to reach self-ignition conditions decrease and hence the influence of the ignition spark gain. The timing of the ignition spark highly influence the combustion process at higher loads. With the ignition spark, pre-reactions are initialized with a defined heat release. Thus the location of inflammation and flame propagation can be strongly influenced and cyclic variations at higher loads can be reduced.
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