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Technical Paper

Influence of the Alcohol Type and Concentration in Alcohol-Blended Fuels on the Combustion and Emission of Small Two-Stroke SI Engines

2012-10-23
2012-32-0038
The combustion processes optimization is one of the most important factors to enhancing thermal efficiency and reducing exhaust emissions of combustion engines [1; 2]. Future emission regulations for small two-stroke SI engines require that the emissions of gases causing the greenhouse effect, such as carbon dioxide, to be reduced. One possible way to reduce exhaust gas emissions from two-stroke small off-road engines (SORE) is to use biogenic fuels. Because of their nearly closed carbon dioxide circuit, the emissions of carbon dioxide decrease compared to the use of fossil fuels. Also biogenic fuels have a significant influence on the combustion process and thus the emissions of different exhaust gas components may be reduced. Besides greenhouse gases, several other exhaust gas components need to be reduced because of their toxicity to the human health. For example, aromatic hydrocarbons cause dangerous health problems, and can be reduced by using alkylate fuel.
Technical Paper

Experimental Heat Flux Analysis of an Automotive Diesel Engine in Steady-State Operation and During Warm-Up

2011-09-11
2011-24-0067
Advanced thermal management systems in passenger cars present a possibility to increase efficiency of current and future vehicles. However, a vehicle integrated thermal management of the combustion engine is essential to optimize the overall thermal system. This paper shows results of an experimental heat flux analysis of a state-of-the-art automotive diesel engine with common rail injection, map-controlled thermostat and split cooling system. Measurements on a climatic chamber engine test bench were performed to investigate heat fluxes and energy balance in steady-state operation and during engine warm-up from different engine start temperatures. The analysis includes the influence of the operating point and operating parameters like EGR rate, injection strategy and coolant temperature on the engine energy balance.
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

Investigations on Soot Emission Behavior of A Common-Rail Diesel Engine during Steady and Non-Steady Operating Conditions by Means of Several Measuring Techniques

2005-05-11
2005-01-2154
In this work the influence of various engine load changes with different engine speeds on the soot particle concentrations and properties was investigated because these operating modes are well known for short but high soot emissions. To derive specific information on emission behavior of particle matters tests were carried out with the Two-Color-Method and the so called RAYLIX technique in a four-cylinder CR-Diesel engine. The Two-Color-Method (2CM) gives crank angle resolved information about soot formation and oxidation processes inside the combustion chamber of a single cylinder. The RAYLIX technique is a combination of Rayleigh-scattering, Laser-Induced-Incandescence (LII) and extinction measurements which enable simultaneous measurements of temporally and spatially resolved soot concentration, mean primary particle radii and number densities in the exhaust gas manifold of the same cylinder investigated by the Two-Color-Method.
Technical Paper

A New Flame Jet Concept to Improve the Inflammation of Lean Burn Mixtures in SI Engines

2005-10-24
2005-01-3688
Engines with gasoline direct injection promise an increase in efficiency mainly due to the overall lean mixture and reduced pumping losses at part load. But the near stoichiometric combustion of the stratified mixture with high combustion temperature leads to high NOx emissions. The need for expensive lean NOx catalysts in combination with complex operation strategies may reduce the advantages in efficiency significantly. The Bowl-Prechamber-Ignition (BPI) concept with flame jet ignition was developed to ignite premixed lean mixtures in DISI engines. The mainly homogeneous lean mixture leads to low combustion temperatures and subsequently to low NOx emissions. By additional EGR a further reduction of the combustion temperature is achievable. The BPI concept is realized by a prechamber spark plug and a piston bowl. The main feature of the concept is its dual injection strategy.
Technical Paper

Potential of Reducing the NOX Emissions in a Spray Guided DI Gasoline Engine by Stratified Exhaust Gas Recirculation (EGR)

2006-04-03
2006-01-1261
In this paper, results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine are presented. The engine was operated in spray guided direct injection mode. The radial exhaust gas stratification was achieved by a spatial and temporal separated intake of exhaust gas and fresh air. The spatial separation of both fluids was realized by specially shaped baffles in the inlet ports, which prevent an early mixing up to the inlet valves. The temporally separation was performed by impulse charge valves, with one for the fresh air and one for the exhaust gas. From various possible strategies for time-dependent intake of fresh air and exhaust gas, four different strategies for the exhaust gas stratification were examined.
Technical Paper

Influence of Atomization Quality on Mixture Formation, Combustion and Emissions in a MPI-Engine Under Cold-Start Conditions, Part I

2002-10-21
2002-01-2807
The study presented in this two part paper was focused on the influence of primary mixture formation on engine running behavior covering the areas combustion and raw emissions. Two different concepts for primary fuel atomization were utilized and compared, the standard production injector and a flash boiling injector. The spray generated by the flash boiling injector was characterized by a significant reduction in droplet size and a partial direct vaporization during the injection process by preheating the fuel inside the injector. In this study special emphasis was put on the transient process of engine start between typical cooling water temperatures of -7°C and 85°C. Various measurements and visualization techniques were applied to investigate the mixture preparation, the deposition of liquid fuel on the walls, the start of combustion, and in-cylinder and engine-out UHC emissions.
Technical Paper

Influence of Atomization Quality on Mixture Formation, Combustion and Emissions in a MPI-Engine Under Cold-Start Conditions, Part II

2002-10-21
2002-01-2806
The intention of the study presented in this two part paper is to investigate the influence oalf primary mixture formation on engine running behavior, covering the areas of combustion and raw emissions. Two different concepts for primary fuel atomization were utilized and compared, the standard production injector and a flash boiling injector. The flash boiling injector is characterized by a significant reduction in droplet size and a partial direct vaporization during the injection process by preheating the fuel inside the injector. In this study special emphasis was laid on the transient process of engine start between typical cooling water temperatures of -7°C and 85°C. Various measurements and visualization techniques had been applied to investigate mixture preparation, deposition of liquid fuel on the walls, start of combustion, and in-cylinder as well as engine-out UHC emissions.
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

Spectroscopic Measurements in Small Two-Stroke SI Engines

2009-11-03
2009-32-0030
This paper demonstrates the potential of optical sensors in the combustion chamber of a small two-stroke SI engine to detect conditions that hinder an optimal combustion process using emission bands and/or emission lines. The primary focus is on the spectroscopic examination of the combustion radiation emissions cycle-by-cycle. For this purpose, spark-ignition type combustion events, as well as the influence of both the air-fuel-ratio and the fuel type, are investigated on a crank angle resolved basis. Furthermore, an assessment of the radiation emissions of the OH, CH and C2 radicals is made. As a next step, the calculation of a temperature profile inside the combustion chamber is attempted by means of the line-emission-method regarding the thermally excited alkaline metals sodium and potassium. These data enable recognition of diffusion combustion and the detection of inadequate mixture quality.
Technical Paper

Influence of High Frequency Ignition on the Combustion and Emission Behaviour of Small Two-Stroke Spark Ignition Engines

2013-10-15
2013-32-9144
The two-stroke SI engine is the predominant driving unit in applications that require a high power-to-weight ratio, such as handheld power tools. Regarding the latest regulations in emission limits the main development area is clearly a further reduction of the exhaust emissions. The emissions are directly linked to the combustion processes and the scavenging losses. The optimization of the combustion processes, which represents one of the most challenging fields of research, is still one of the most important keys to enhance the thermal efficiency and reduce exhaust emissions. Regarding future emission regulations for small two-stroke SI engines it is inevitable that the emissions of gases causing the greenhouse effect, like carbon dioxide, need to be reduced. As most small SI engines are carburetted and operate open loop, the mixture formation and the amount of residual gas differs from cycle to cycle [1].
Technical Paper

67 Analysis of Mixture Conditions in a Small Two Stroke Engine Using a Gas Sampling Valve

2002-10-29
2002-32-1836
The quality of mixture formation and the combustion process is of significant importance for reducing the hydrocarbon emissions of small two stroke engines. The scope of this work was to investigate the mixture conditions after the exhaust closes and after the end of combustion depending on various engine operating points. For this experimental investigation a Gas Sampling Valve (GSV) was combined with a flame ionisation detector (FID) and a CO2-analyser. Using this technique, it was possible to measure the hydrocarbon concentration after end of combustion. Furthermore the local residual gas concentration after exhaust closes was determined. To allow for a comparison of the experimental results with calculations with CFD codes, in cylinder pressure measurement and exhaust gas measurements are done additionally.
Technical Paper

Application of Multifiber Optics in Handheld Power Tools with High Speed Two-Stroke Gasoline Engines

2006-11-13
2006-32-0060
When developing effective exhaust emission reduction measures, a better understanding of the complex working cycle in crankcase scavenged two-stroke gasoline engines. However, in a two-stroke gasoline engine detailed measurement and analysis of combustion data requires significantly more effort, when compared to a lower speed four-stroke engine. Particularly demanding are the requirements regarding the high speed (>10,000 rpm) which inevitably goes along with heavy vibrations and high temperatures of the air cooled cylinders. Another major challenge to the measuring equipment is the increased cleaning demand of the optical sensor surface due to the two-stroke gasoline mixture. In addition, the measuring equipment has to be adapted to the small size engines. Therefore, only a fiber optical approach can deliver insight into the cylinder for analyzing the combustion performance.
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.
Technical Paper

Application of Particle Image Velocimetry for Investigation of Spray Characteristics of an Outward Opening Nozzle for Gasoline Direct Injection

2006-10-16
2006-01-3377
The hollow cone spray from a high pressure outward opening nozzle was investigated inside a pressure vessel by means of particle image velocimetry (PIV). The flow velocities of the air outside the spray were measured via PIV in combination with fluorescent seeding particles and optical filters. The high pressure piezo electric injector has an annular nozzle to provide a hollow cone spray with an angle of about 90°. During injection a very strong and stable vortex structure is induced by the fuel spray. Besides the general spray/air interaction, the investigation of double and triple fuel injections was the main focus of this study.
Technical Paper

Investigations of the Formation and Oxidation of Soot Inside a Direct Injection Spark Ignition Engine Using Advanced Laser-Techniques

2010-04-12
2010-01-0352
In this work the formation and oxidation of soot inside a direct injection spark ignition engine at different injection and ignition timing was investigated. In order to get two-dimensional data during the expansion stroke, the RAYLIX-technique was applied in the combustion chamber of an optical accessible single cylinder engine. This technique is a combination of Rayleigh-scattering, laser-induced incandescence (LII) and extinction which enables simultaneous measurements of temporally and spatially resolved soot concentration, mean particle radii and number densities. These first investigations show that the most important source for soot formation during combustion are pool fires, i.e. liquid fuel burning on the top of the piston. These pool fires were observed under almost all experimental conditions.
Technical Paper

Influence of Mixture Preparation on Combustion and Emissions Inside an SI Engine by Means of Visualization, PIV and IR Thermography During Cold Operating Conditions

1999-10-25
1999-01-3644
The focus of this work was to determine the influence of spray targeting on temperature distributions, combustion progress and unburned hydrocarbon (HC) emissions at cold operating conditions, and to show the capability of model and full engine tests adapted for different measurement techniques. A comprehensive study applying endoscopic visualization, infrared thermography, combustion and emission measurements was carried out in a 4-stroke 4-cylinder 16-valve production engine with intake port injection during different engine operating conditions including injection angle and timing. In addition 2D visualization and PIV measurements were performed in a back-to-back model test section with good optical access to the intake manifold and the combustion chamber. The measurements in both set ups were in good agreement and show that model tests could lead to useful findings for a real engine.
Technical Paper

A Study of the Thermochemical Conditions in the Exhaust Manifold Using Secondary Air in a 2.0 L Engine

2002-05-06
2002-01-1676
The California LEV1 II program will be introduced in the year 2003 and requires a further reduction of the exhaust emissions of passenger cars. The cold start emissions represent the main part of the total emissions of the FTP2-Cycle. Cold start emissions can be efficiently reduced by injecting secondary air (SA) in the exhaust port making compliance with the most stringent standards possible. The thermochemical conditions (mixing rate and temperature of secondary air and exhaust gas, exhaust gas composition, etc) prevailing in the exhaust system are described in this paper. This provides knowledge of the conditions for auto ignition of the mixture within the exhaust manifold. The thus established exothermal reaction (exhaust gas post-combustion) results in a shorter time to light-off temperature of the catalyst. The mechanisms of this combustion are studied at different engine idle conditions.
Technical Paper

Investigations of Mixture Formation and Combustion in Gasoline Direct Injection Engines

2001-09-24
2001-01-3647
The spray propagation and disintegration is investigated in a pressure chamber. With Particle Image Velocimetry the direction and velocity of both, fuel droplets and induced gas flow are detected. By means of shadow photographs the spray cone geometry is visualized. To verify the predictions made of the measurements mentioned above and to rate the quality of the tuning of the parameters in-cylinder gas flow, injection pressure, position of Injector and position of spark plug under real engine conditions, a fast gas sampling valve is used in three different engines. The in-cylinder gas temperature and the soot concentration are measured crank angle resolved by means of the Two-Colour-Method in a 1-cylinder GDI-engine. The soot concentration and temperature show the influence of the injection pressure on emissions like soot and nitric oxide.
Journal Article

Experimental Investigations of a DISI Engine in Transient Operation with Regard to Particle and Gaseous Engine-out Emissions

2015-09-01
2015-01-1990
The investigation of transient engine operation plays a key role of the future challenges for individual mobility in terms of real driving emissions (RDE). A fundamental investigation of the transient engine operation requires the simultaneous application of measurement technologies for an integrated study of mixture formation, combustion process and emission formation. The major prerequisite is the combustion cycle and crank angle resolved analysis of the process for at least several individual consecutive combustion cycles during transient operation. The investigations are performed with a multi cylinder DISI engine at an Engine-in-the-Loop test bench, able to operate the engine in driving cycles as well as within target profiles (e.g. speed and torque profiles). The research project describes the methodology of analyzing elementary transient operational phases, (e.g. different variants of load steps).
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