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Technical Paper

2D Residual Gas Visualization in an Optical Direct Injection Spark Ignition Engine with IR Laser Absorption

2015-04-14
2015-01-1648
The spatial distribution of internal exhaust gas recirculation (EGR) is evaluated in an optically accessible direct injection spark ignition engine using near infrared laser absorption to visualize the distribution of the H2O molecule. The obtained overall internal exhaust gas recirculation compares well to gas-exchange cycle calculations and the spatial distributions are consistent with those measured with inverse LIF. The experimental procedures described in this report are designed to be simple and rapidly implemented without the need to resort to unusual optical components. The necessary spectral data of the selected absorption line is obtained from the HITEMP database and is validated with prior experiments carried out in a reference cell. Laser speckle in the images is effectively reduced using a ballistic diffuser.
Technical Paper

A Thermodynamic Study on Boosted HCCI: Experimental Results

2011-04-12
2011-01-0905
Stricter emissions legislation and growing demands for lower fuel consumption require significant efforts to improve combustion efficiency while satisfying the emission quality demands. Controlled Homogeneous Charge Compression Ignition (HCCI) combined with boosted air systems on gasoline engines provides a particularly promising, yet challenging, approach. Naturally aspirated (NA) HCCI has already shown considerable potential in combustion efficiency gains. Nevertheless, since the volumetric efficiency is limited in the NA HCCI operation range due to the hot residuals required to ignite the mixture and slow down reaction kinetics, only part-load operation is feasible in this combustion mode. Considering the future gasoline engine market with growing potentials identified in downsized gasoline engines, it becomes necessary to investigate the synergies and challenges of controlled, boosted HCCI.
Technical Paper

Analysis of the Combustion Mode Switch Between SI and Gasoline HCCI

2012-04-16
2012-01-1105
The worldwide stricter emission legislation and growing demands for lower fuel consumption require for significant efforts to improve combustion efficiency while satisfying the emission quality demands. Homogeneous Charge Compression Ignition (HCCI) on gasoline engines provides a particularly promising and, at the same time, challenging approach, especially regarding the combustion mode switch between spark-ignited (SI) and gasoline HCCI mode and vice-versa. Naturally aspirated (n.a.) HCCI shows considerable potential, but the operation range is air breathing limited due to hot residuals required for auto-ignition and to slow down reaction kinetics. Therefore it is limited to part-load operation. Considering the future gasoline engine market with growing potentials identified on downsized gasoline engines, it is imperative to investigate the synergies and challenges of boosted HCCI.
Technical Paper

Analysis of the In-Cylinder Flow Field / Spray Injection Interaction within a DISI IC Engine Using High-Speed PIV

2011-04-12
2011-01-1288
This study presents measurements of transient flow field and spray structures inside an optically accessible DISI (direct-injection spark-ignition) internal combustion engine. The flow field has a direct effect upon mixture and combustion processes. Given the need to increase the efficiency and performance of modern IC engines and thus reduce emissions a detailed understanding of the flow field is necessary. The method of choice was high-speed two-component particle image velocimetry (PIV) imaging a large field of view (43 x 44 mm₂). To capture the temporal evolution of the main flow features the repetition rate was set to 6 kHz which resolves one image per 1° crank angle (CA) at 1000 rpm. The crank angle range recorded was the latter half of the compression stroke at various engine speeds as well as various charge motions (neutral, tumble and swirl). Moreover, consecutive cycles were recorded allowing a detailed investigation of cycle-to-cycle variations.
Technical Paper

Challenge Determining a Combustion System Concept for Downsized SI-engines - Comparison and Evaluation of Several Options for a Boosted 2-cylinder SI-engine

2013-04-08
2013-01-1730
To meet future CO₂ emissions limits and satisfy the bounds set by exhaust gas legislation reducing the engine displacement while maintaining the power output ("Downsizing") becomes of more and more importance in the SI engine development process. The total number of cylinders per engine has to be reduced to keep the thermodynamic disadvantages of a small combustion chamber layout as small as possible. Doing so new challenges arise concerning the mechanical design, the design of the combustion system concept as well as strategies maintaining a satisfying transient torque behavior. To address these challenges a turbocharged 2-cylinder SI engine was designed for research purposes by Weber Motor GmbH and Robert Bosch GmbH. The design process was described in detail in last year's paper SAE 2012-01-0832. Since the engine design is very modular it allows for several different engine layouts which can be examined and evaluated.
Technical Paper

Crank Angle Resolved Determination of Fuel Concentration and Air/Fuel Ratio in a SI-Internal Combustion Engine Using a Modified Optical Spark Plug

2007-04-16
2007-01-0644
A fiber optical sensor system was used to detect the local fuel concentration in the vicinity of the spark position in a cylinder of a four-stroke SI production engine. The fuel concentration was determined by the infrared absorption method, which allows crank angle resolved fuel concentration measurements during multiple successive engine cycles. The sensor detects the attenuation of infrared radiation in the 3.4 μm wavelength region due to the infrared vibrational-rotational absorption band of hydrocarbons (HC). The absorption path was integrated in a modified spark plug and a tungsten halide lamp was used as an infrared light source. All investigations were carried out on a four-stroke spark ignition engine with fuel injection into the intake manifold. The measurements were made under starting conditions of the engine, which means a low engine speed. The engine operated with common gasoline (Euro Super) at different air/fuel-ratios.
Technical Paper

Design of a Boosted 2-Cylinder SI-Engine with Gasoline Direct Injection to Define the Needs of Future Powertrains

2012-04-16
2012-01-0832
To meet future CO₂ emissions limits and satisfy the bounds set by exhaust gas legislation reducing the engine displacement while maintaining the power output ("Downsizing") becomes of more and more importance to the SI-engine development process. The total number of cylinders per engine has to be reduced to keep the thermodynamic disadvantages of a small combustion chamber layout as small as possible. Doing so leads to new challenges concerning the mechanical design, the design of the combustion system concept as well as strategies maintaining a satisfying transient torque behavior. To address these challenges a turbocharged 2-cylinder SI engine with gasoline direct injection was designed for research purposes by Weber Motor and Bosch. This paper wants to offer an insight in the design process. The mechanical design as well as the combustion system concept process will be discussed.
Technical Paper

Electroformed Multilayer Orifice Plate for Improved Fuel Injection Characteristics

1997-02-24
971070
A new orifice plate (OP) for advanced fuel injection characteristics is presented. The OP is designed to optimize the air-fuel mixture generation and transportation within individually shaped manifold geometries of spark-ignition engines. To generate the suitable spray characteristics, the basic OP design and its flow characteristics have some features originating from the well known turbulence nozzle principle: Turbulence generating flow deflections within the OP are achieved by superimposing layers containing flow cavities, which are displaced from one another. The flow deflections effect atomization and define the spatial spray beam orientation. A great variety and a high volume of precisely structured, low cost OPs can be produced daily by micromachining the layers in electroformed nickel. The flow cavities and outer dimensions of each layer are shaped by photo-resist structures.
Journal Article

Engine Start-Up Optimization using the Transient Burn Rate Analysis

2011-04-12
2011-01-0125
The introduction of CO₂-reduction technologies like Start-Stop or the Hybrid-Powertrain and the future emission legislation require a detailed optimization of the engine start-up. The combustion concept development as well as the calibration of the ECU makes an explicit thermodynamic analysis of the combustion process during the start-up necessary. Initially, the well-known thermodynamic analysis of in-cylinder pressure at stationary condition was transmitted to the highly non-stationary engine start-up. There, the current models for calculation of the transient wall heat fluxes were found to be misleading. Therefore, adaptations to the start-up conditions of the known models by Woschni, Hohenberg and Bargende were introduced for calculation of the wall heat transfer coefficient in SI engines with gasoline direct injection. This paper shows how the indicated values can be measured during the engine start-up.
Journal Article

Estimation of Cylinder-Wise Combustion Features from Engine Speed and Cylinder Pressure

2008-04-14
2008-01-0290
Advanced engine control and diagnosis strategies for internal combustion engines need accurate feedback information from the combustion engine. The feedback information can be utilized to control combustion features which allow the improvement of engine's efficiency through real-time control and diagnosis of the combustion process. This article describes a new method for combustion phase and IMEP estimation using one in-cylinder pressure and engine speed. In order to take torsional deflections of the crankshaft into account a gray-box model of the crankshaft is identified by subspace identification. The modeling accuracy is compared to a stiff physical crankshaft model. For combustion feature estimation, the identified MISO (multiple input single output) system is inverted. Experiments for a four-cylinder spark-ignition engine show the superior performance of the new method for combustion feature estimation compared to a stiff model approach.
Technical Paper

Experimental Measurement Techniques to Optimize Design of Gasoline Injection Valves

1992-02-01
920520
In order to reduce the spark-ignition engine exhaust-gas emission and fuel consumption, it is essential that the required air/fuel ratio is maintained under all operating conditions. An important contribution to this claim is delivered by the injection valve by metering the fuel precisely and producing fine atomization. In this report experimental methods to get specific measuring information and methods for optimizing flow in injection valves are described. Original valves as well as large-scale models were used for the investigations concerning the steady and unsteady-flow characteristics, and were equipped with a number of different sensors. Holograms of the short-time recording of the spray cone are generated and used for the quantification of the atomization quality when injecting into atmospheric pressure and into vacuum, thus complying with the conditions encountered in the engine intake-manifold.
Technical Paper

FEM Approximation of Internal Combustion Chambers for Knock Investigations

2002-03-04
2002-01-0237
The resonances of SI engine combustion chambers are slightly excited during normal combustion but strongly excited by knock. In order to avoid knocking combustions extensive knowledge about knock and its effects is necessary. In this paper the combustion chamber of a serial production engine is modeled by finite elements. Modal analyses are performed in order to gain information about the resonances, their frequencies, and their frequency and amplitude modulations. Simulation results are compared to measured data using a high-resolution time-frequency method. Furthermore, a connection between knock origin and the excitation of the resonances is postulated applying transient analyses.
Technical Paper

Impact of Oil Aging on Wear of Piston Ring and Cylinder Liner System

2010-09-28
2010-32-0124
The piston ring and cylinder liner tribosystem is very sensitive. It is a heavily loaded system with high temperature and force exposure. High demands are made on the components in this area. These facts concern not only system components, but also the engine oil which can reach up to 300°C at the inner cylinder walls. High temperatures and force cause oil aging. As a part of the combustion chamber, the piston ring-cylinder liner tribosystem is in close contact with combustion constituents. If alternative fuels like ethanol are used, the influences to this tribosystem have to be investigated. In particular, the impacts of oil aging have to be considered to avoid higher wear and damage to the engine, to assure low fuel consumption, and to extend oil change intervals. Research work on abrasion of the ring-cylinder system was aimed to gain detailed information about the effects on this tribosystem.
Technical Paper

Impact of the Injection and Gas Exchange on the Particle Emission of a Spark Ignited Engine with Port Fuel Injection

2017-03-28
2017-01-0652
This study presents a methodology to predict particle number (PN) generation on a naturally aspirated 4-cylinder gasoline engine with port fuel injection (PFI) from wall wetting, employing numerical CFD simulation and fuel film analysis. Various engine parameters concerning spray pattern, injection timing, intake valve timing, as well as engine load/speed were varied and their impact on wall film and PN was evaluated. The engine, which was driven at wide open throttle (WOT), was equipped with soot particle sampling technology and optical access to the combustion chamber of cylinder 1 in order to visualise non-premixed combustion. High-speed imaging revealed a notable presence of diffusion flames, which were typically initiated between the valve seats and cylinder head. Their size was found to match qualitatively with particulate number measurements. A validated CFD model was employed to simulate spray propagation, film transport and droplet impingement.
Technical Paper

Impact of the Wall Film Formation on the Full Load Performance of an Engine Operated with the Ethanol Blend E85

2011-11-08
2011-32-0535
A naturally aspirated SI engine with port fuel injection was investigated at the Institute for Powertrains and Automotive Technology of the Vienna University of Technology to analyze the impact of the ethanol blend E85 on the full load performance. Measurements and numerical studies with a predictive wall film model have been carried out to explain the mixture cooling, the calorific fluid properties after inlet valve closing and the volumetric efficiency with conventional fuel and E85. It could be shown that only with a detailed modelling of the wall film formation in the inlet port an accurate prediction of the engine's full load performance is possible when studying different fuels with varying fluid properties. Anyway, an integrated approach that includes measurements and numerical investigations is necessary to analyse the mixture preparation and the engine process correctly.
Journal Article

Investigations on the Transient Wall Heat Transfer at Start-Up for SI Engines with Gasoline Direct Injection

2009-04-20
2009-01-0613
The introduction of CO2-reduction technologies like Start-Stop or the Hybrid-Powertrain and the future emissions regulations require a detailed optimization of the engine start-up. The combustion concept development as well as the calibration of the ECU makes it necessary to carry out an explicit thermodynamic analysis of the combustion process during the start-up. As of today, the well-known thermodynamic analysis using in-cylinder pressure traces at stationary condition is transmitted to the highly dynamic engine start-up. Due to this approximation the current models for calculation of the transient wall heat fluxes by Woschni, Hohenberg and Bargende do not lead to desired results. But with a fraction of approximately 40 % of the burnt fuel energy, the wall heat is very important for the calculation of energy balance and for the combustion process analysis during start-up.
Journal Article

Model Guided Application for Investigating Particle Number (PN) Emissions in GDI Spark Ignition Engines

2019-01-09
2019-26-0062
Model guided application (MGA) combining physico-chemical internal combustion engine simulation with advanced analytics offers a robust framework to develop and test particle number (PN) emissions reduction strategies. The digital engineering workflow presented in this paper integrates the kinetics & SRM Engine Suite with parameter estimation techniques applicable to the simulation of particle formation and dynamics in gasoline direct injection (GDI) spark ignition (SI) engines. The evolution of the particle population characteristics at engine-out and through the sampling system is investigated. The particle population balance model is extended beyond soot to include sulphates and soluble organic fractions (SOF). This particle model is coupled with the gas phase chemistry precursors and is solved using a sectional method. The combustion chamber is divided into a wall zone and a bulk zone and the fuel impingement on the cylinder wall is simulated.
Journal Article

Novel Transient Wall Heat Transfer Approach for the Start-up of SI Engines with Gasoline Direct Injection

2010-04-12
2010-01-1270
The introduction of CO₂-reduction technologies like Start-Stop or the Hybrid-Powertrain and the future emissions limits require a detailed optimization of the engine start-up. The combustion concept development as well as the calibration of the ECU makes an explicit thermodynamic analysis of the combustion process during the start-up necessary. Initially, the well-known thermodynamic analysis of in-cylinder pressure at stationary condition was transmitted to the highly non-stationary engine start-up. There, the current models for calculation of the transient wall heat fluxes were found to be misleading. But with a fraction of nearly 45% of the burned fuel energy, the wall heat is very important for the calculation of energy balance and for the combustion process analysis.
Technical Paper

Numerical and Experimental Studies on Mixture Formation with an Outward-Opening Nozzle in a SI Engine with CNG-DI

2016-04-05
2016-01-0801
CNG direct injection is a promising technology to promote the acceptance of natural gas engines. Among the beneficial properties of CNG, like reduced pollutants and CO2 emissions, the direct injection contributes to a higher volumetric efficiency and thus to a better driveability, one of the most limiting drawbacks of today’s CNG vehicles. But such a combustion concept increases the demands on the injection system and mixture formation. Among other things it requires a much higher flow rate at low injection pressure. This can be only provided by an outward-opening nozzle due to its large cross-section. Nevertheless its hollow cone jet with a specific propagation behavior leads to an adverse fuel-air distribution especially at higher loads under scavenging conditions. This paper covers numerical and experimental analysis of CNG direct injection to understand its mixture formation.
Journal Article

Optical Investigations of the Ignition-Relevant Spray Characteristics from a Piezo-Injector for Spray-Guided Spark-Ignited Engines

2015-01-01
2014-01-9053
The spray-guided combustion process offers a high potential for fuel savings in gasoline engines in the part load range. In this connection, the injector and spark plug are arranged in close proximity to one another, as a result of which mixture formation is primarily shaped by the dynamics of the fuel spray. The mixture formation time is very short, so that at the time of ignition the velocity of flow is high and the fuel is still largely present in liquid form. The quality of mixture formation thus constitutes a key aspect of reliable ignition. In this article, the spray characteristics of an outward-opening piezo injector are examined using optical testing methods under pressure chamber conditions and the results obtained are correlated with ignition behaviour in-engine. The global spray formation is examined using high-speed visualisation methods, particularly with regard to cyclical fluctuations.
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