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Laser-induced fluorescence (LIF) is frequently used for the investigation of mixing processes in internal engine combustion. Toluene is one of the main fluorescing compounds of commercial gasoline. Understanding its fluorescence properties is therefore crucial for the correct interpretation of signal intensities observed under engine (i.e. high temperature and high pressure) conditions. Toluene LIF signal has been investigated as a function of temperature and oxygen concentration in order to enable quantitative fuel tracer imaging. Signal behavior and interpretation for engine-related conditions is demonstrated based on a semi-empirical fluorescence model. Toluene as well as gasoline-LIF is strongly quenched by oxygen. It has therefore been suggested for a direct measurement of fuel/air equivalence ratios. Contrary to this frequently used FARLIF assumption, oxygen quenching is not dominant at elevated temperatures and thus the toluene signal is not proportional to the fuel/air ratio under all the pressure and temperatures conditions in the compression stroke of IC engines. The correct signal interpretation is demonstrated for various practical cases.

In future automotive collision avoidance systems (CAS) collision-free path planning will be required. For this reason, two possible path planning techniques are compared. The first method is based on the mathematical theory of differential games, the second method focuses on so-called elastic bands. However, the method of elastic bands is essentially modified to provide solutions in complex driving situations. Furthermore, it is shown how path planning, path following control and driving condition estimation can be embedded in a possible overall CAS-setup. Therein, driving conditions are estimated based on the characteristic velocity. Finally, simulation results for an emergency maneuver are presented.

The improvement of the exhaust gas contents of diesel engines with respect to particles and gaseous emissions is still a very important engineering topic. In this work two different direct injection methods into the combustion chamber of a diesel engine have been investigated and compared. The first system involves the separate injection of H 2 O 2 /water solutions using a second nozzle, while the other is the injection of H 2 O 2 /water/diesel emulsions by a single injection system. It is known that H 2 O 2 forms OH radicals at higher temperatures, whose probability for the oxidation of diesel soot is much higher than that of molecular oxygen [1]. The H 2 O 2 injection into the combustion chamber [2] and the exhaust pipe of diesel engines [3] has proved to be an effective measure towards the reduction of diesel soot. A Differential Mobility Analyzer (DMA) is applied to detect the change in particle diameter as function of H 2 O 2 /water addition. The injected H 2 O 2 concentration in relation to injected diesel fuel was varied from 1 to 10 %, and the injection pressure was also varied between 200 and 500 bars. By constant injection pressure and injection timing, it was found that H 2 O 2 /water/diesel emulsion leads to a higher reduction of unburned hydrocarbons and particulates. Correspondingly, an increase in the NO x emission is observed in comparison to separate injection of H 2 O 2 /water solution. The highest reduction of diesel particles was observed at higher injection pressures, and during delay injection timing of H 2 O 2 /water.

In direct-injection gasoline (GDI) engines with charge stratification, minimizing engine-out nitrogen oxide (NO x ) emission is crucial since exh ust-gas aftertreatment tolerates only limited amounts of NO x . Reduced NO x production directly lowers the frequency of energy-inefficient catalyst regeneration cycles. In this paper we investigate NO formation in a realistic GDI engine. Quantitative in-cylinder measurements of NO concentrations are carried out via laser-induced fluorescence imaging with excitation of NO (A-X(0,2) band at 248 nm), and subsequent fluorescence detection at 220-240 nm. Engine modifications were kept to a minimum in order to provide results that are representative of practical operating conditions. Optical access via a sapphire ring enabled identical engine geometry as a production line engine. The engine is operated with commercial gasoline (Super-Plus, RON 98). Recent high-pressure spectroscopic studies of NO, O 2 and CO 2 are utilized to select an appropriate detection scheme for quantitative NO measurements under realistic conditions. CO 2 UV light absorption data is used to correct for laser and signal attenuation. NO-LIF concentrations are compared to extractive measurements using a fast gas sampling valve (GSV). NO formation is investigated at different operating conditions such as variable exhaust gas recirculation (egr).

The NO distribution in a directly-injected Diesel engine with realistic combustion chamber geometry was investigated with laser-induced fluorescence (LIF) imaging with KrF excimer laser excitation. The highest possible level of selectivity has been ensured using spectrally resolved LIF investigations inside the Diesel engine. To minimize interference from both, oxygen and polycyclic aromatic hydrocarbon (PAH) LIF the NO signal was detected around 237 nm, blue-shifted compared to the excitation wavelength resulting in a background contribution below 10% at the earliest detection timing possible in the engine under study (20°ca after top dead center, TDC). The in-cylinder NO LIF intensities were compared for different injection systems and operating conditions and correlated to variations in pressure traces and soot temperature measurements. Laser and signal attenuation were assessed in separate experiments using spectrally resolved O2 LIF detection with the same optical path as in the imaging measurements. Attenuation is then measured using the FranckCondon pattern of the emission spectrum of excited oxygen. A comparison with model calculations shows that the main contribution to the observed attenuation effects is absorption by hot, vibrationally excited CO2. Using these absorption data and an external calibration source the LIF intensities of a selected data series are quantified.

The influence of exhaust gas recirculation (EGR) on the formation of nitric oxide (NO) was studied experimentally in a transparent gasoline direct injection engine by quantitative laser-induced fluorescence imaging. Spectral properties of the excited transition within the NO A2S+-X2P(0,2) band are well known from previous studies. The excitation scheme allows quantitative NO concentration measurements without detailed knowledge of the gas phase temperature. Good agreement was found with exhaust gas NOx chemiluminescence (CLD) measurements. The experiments were carried out in an optically accessible gasoline engine featuring a direct injection cylinder head (BMW) and a Bosch injection system, based on a serial inline six-cylinder engine with an enlarged crankcase. The measurements were performed in the pent-roof section of the combustion chamber. Various concentrations (0, 10 and 16%) and compositions (pure nitrogen, nitrogen / carbon dioxide and nitrogen / carbon dioxide / water) of synthetic exhaust gas were investigated. NO formation could be significantly reduced by EGR, from an average of about 1200 ppm (without EGR) to about 200 ppm (16% EGR-rate). The NO formation decreased steadily with increasing heat capacity of the inert gases present, independent of their chemical composition. In the temporal evolution of the NO formation, a retarded onset of up to 5° CA was found with 16% EGR. The two-dimensional NO concentration fields appeared to be very homogeneous when adding 16% EGR, whereas without EGR, strong inhomogeneities with local NO peak concentrations of up to 3400 ppm were detected.

Transient two-dimensional temperature distributions in the compression stroke and in the unburned end-gas of an SI engine were measured employing laser-induced fluorescence (LIF) of a fuel marker that possesses strongly temperature-dependent spectroscopic properties. The use of two different excitation wavelengths simplifies the otherwise complicated relation between LIF signal intensity and system parameters. The temperature fields obtained in this manner can be used to correct measured tracer-LIF maps and thus help to determine fuel distributions. Averaged temperature fields are compared to model calculations based on a homogeneous reactor assumption.

Various fluorescence tracers were assessed for their applicability for simultaneously measuring fuel distributions of different volatility classes. Tracers were chosen to show significantly different boiling behaviour representing three volatility classes of non-fluorescing multi-component fuels. Fluorescence properties of the markers were investigated using a heated static high-pressure cell with respect to emission behaviour, temperature and pressure dependence and quenching influences. A combination of ketonic and aromatic tracers appeared to be ideal for simultaneous imaging purposes since fluorescence is emitted in separate spectral regions with little overlap. Simultaneous measurements of the fuel distribution of two volatility classes were performed in a port fuel injected engine showing significant differences in the fuel distributions of low and mid boiling fractions in early stages of compression. The results obtained from fluorescence imaging are compared to fuel spatial distributions gained via tomographic line-of-sight measurements using near infrared absorption which allows the application to commercial fuels without requiring additional marker components.

The present paper reports on measurements of particles emitted by a 6.3 kW, single-cylinder two-stroke engine. The engine exhaust gas was diluted in a mini-dilution tunnel. Particle size classification was performed by means of differential mobility particle sizer (DMPS) system. Measurements of the number distribution of the particle diameter and the related mass concentration were made under different engine operating conditions. It was found that the use of neither mineral nor synthetic lubrication oil had any detrimental influence on the emission characteristics of the engine. On the contrary: a considerable decrease in the particle number distribution was obtained by reducing the mixing ratio of lubrication oil and fuel. Also, the impact of an electrostatic precipitator was tested behind the engine's silencer. It could be shown that a significant reduction of particle emission of 70% in mass was obtained by removing nearly all naturally charged particles from the exhaust gas.