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This paper describes a new system for early detection of tripped rollover crashes. The main goal of this system is to improve the protection of restraint devices, such as curtain window bags, in these rollover situations. This is achieved by a new rollover sensing (RoSe) algorithm in the airbag controller which produces a very early and robust deployment decision. Based on the analysis of tripped rollover test data, this paper shows how improved rollover sensing performance can be achieved by considering information about the vehicle's driving state before the rollover occurs. The results of this new approach are discussed in terms of deployment times. Finally a combined active and passive safety system architecture for the realization of the approach is suggested.

Increasing decentralization of production combined with just-in-time delivery of products and components calls for a flexible and reliable transportation system. So far, trucks offer the most versatile and efficient solution to those problems. In consideration of increasingly strict emission standards and customer demands for more engine power and less fuel consumption, further selective developments and optimization of DI-diesel engines are necessary. One step in this direction is the application of 4 valves per cylinder in heavy-duty diesel engines to improve mixture formation of fuel and air to get a cleaner combustion and a higher power output. For visualizing the combustion processes inside the engine, an optically accessible heavy-duty DI-diesel engine was used. This engine is a slightly modified conventional heavy-duty MAN engine based on the D0824 LFL 06 series.

Improved understanding of the active combustion chain “injection - vaporisation - mixture formation - ignition - combustion - exhaust gas emissions” is important for the further development of IC engines with respect to fuel consumption and pollutant emissions. By means of multidimensional optical, mostly laser-based measurement techniques, a modern passenger car common rail system, applied to an optically accessible engine, was investigated. The utilisation of a new optical detection system allowed a simultaneous detection of the liquid phase by Mie scattering, the flame propagation from flame luminosity and the soot formation by laser-induced incandescence inside the combustion bowl of the engine. By such simultaneous measurements, direct dependencies of single combustion phenomena on fuel injection parameters can be resolved, and in particular soot formation and oxidation can be correlated to the actual combustion situation.

A central point for the further development of direct injection engines is the optimization of the mixture formation process, because all subsequent processes as ignition, combustion and pollutant formation are mainly influenced by the local air/fuel-ratio inside the cylinder. Especially for passenger car engines the interaction between the spray and the combustion chamber walls is an important issue for mixture formation. For that reason this interaction was object of the investigation described. The investigations were carried out in a heatable high pressure high temperature chamber under typical diesel engines conditions of 450°C temperature and 50 bar pressure. A passenger car common rail system was used as injection system equipped with a 6 hole nozzle with common rail specific seat geometry, mini-sac hole geometry and double needle guide.

The development of new generations of internal combustion engines requires appropriate measurement techniques for all relevant limited exhaust gas species and particulates. However, because of stricter future emission limits, there is a severe lack especially with respect to soot particles. Conventional methods, like gravimetric sampling, have substantial deficiencies in sensitivity and temporal resolution, which is strongly required for transient tests. Furthermore, artifacts arise from other exhaust components, like sulfuric acid, water vapor and volatile hydrocarbons. In contrast to the state-of-the-art techniques, laser induced incandescence (LII) has been proved to be a favorable technique, which overcomes these deficiencies and offers additional information, which allows new insight into combustion phenomena. Besides soot mass concentration, also the soot primary particle size is accessible by this technique.

This paper presents calibration results of the two excitation laser wavelength fluorescence of acetone for the determination of temperature fields. The calibration was performed under engine relevant conditions and comprises the simultaneous variation of temperature and pressure in the range of 293 K to 750 K and of 0.1 MPa to 2 MPa, respectively. The influence of different gas compositions, e.g., resulting from exhaust gas recirculation, was checked by calibrating for pure nitrogen, synthetic air and carbon dioxide and for a certain extend for water as bath gas. The two excitation wavelengths used were 248 nm and 308 nm.

Road accidents may involve collisions between vehicles of different weights under a variety of circumstances. It is rare for vehicles of equal weight to collide. The range of vehicle curb weights (masses) extends from less than 700 kg (e.g VW Polo) to over 2,000 kg (e.g. Daimler Benz, S-class). In accordance with the impact laws of mechanics, the consequences of collision involving smaller and larger vehicles are mostly more serious for the driver and passengers of the smaller vehicle. In the past, it has not always been possible to completely quantify the seriousness of accidents or the risk of being injured or killed in Germany because there is no direct link between vehicle mass and the seriousness of passenger injuries. All that is available at present is a study by an insurance association based on single accident cases. This analysis covered front-seat passengers using seat belts as well, but not only the drivers.

Reducing the weight of vehicles could be a strong means of reducing fuel consumption in urban traffic. Published accident and injury statistics however show an inverse correlation of vehicle mass against injury severity in car to car collisions, above all in head-on collisions. This inverse correlation is in part caused by current crash test standards, where compatibility in collisions between cars of different size and weight is not a requirement. Compatibility in frontal collisions demands for significantly different deceleration-time curves in rigid barrier impacts for cars with different weight. Low mass vehicles (LMV) must meet compatibility criteria to comply with current injury criteria in real car to car collisions. Cars designed according to compatibility criteria can change future accident and injury statistics in a way that injury severity in LMVs can be reduced significantly.

A naturally aspirated in-line six-cylinder 2.9-litre Volvo engine is operated in Homogeneous Charge Compression Ignition (HCCI) mode, using camshafts with low lift and short duration generating negative valve overlap. Standard port fuel injection is used and pistons and cylinder head are unchanged from the automotive application. HCCI through negative valve overlap is recognized as one of the possible implementation strategies of HCCI closest to production. It is important to gain knowledge of the constraints and limits on the possible operating region. In this work, the emphasis is on investigating how cycle-to-cycle and cylinder-to-cylinder deviations limit the operating region, how these effects change in different parts of the operating region and how they can be controlled. At low load the cycle-to-cycle phenomena cause periodic behavior in combustion timing; together with cylinder deviations this is found responsible for decreasing the operating regime.

It has been known from multi-zone simulations that HCCI combustion can be significantly affected by temperature stratification of the in-cylinder gas. With the same combustion timing (i.e. crank angles at 50% heat release, denoted as CA50), large temperature stratification tends to prolong the combustion duration and lower down the in-cylinder pressure-rise-rate. With low pressure-rise-rate HCCI engines can be operated at high load, therefore it is of practical importance to look into more details about how temperature stratification affects the auto-ignition process. It has been realized that multi-zone simulations can not account for the effects of spatial structures of the stratified temperature field, i.e. how the size of the hot and cold spots in the temperature field could affect the auto-ignition process. This question is investigated in the present work by large eddy simulation (LES) method which is capable of resolving the in-cylinder turbulence field in space and time.

A 0.5 liter optical HCCI engine firing a mixture of n-heptane (50%) and iso-octane (50%) with air/fuel ratio of 3 is studied using large eddy simulation (LES) and laser diagnostics. Formaldehyde and OH LIF and in-cylinder pressure were measured in the experiments to characterize the ignition process. The LES made use of a detailed chemical kinetic mechanism that consists of 233 species and 2019 reactions. The auto-ignition simulation is coupled with LES by the use of a renormalized reaction progress variable. Systematic LES study on the effect of initial temperature inhomogeneity and turbulence intensity has been carried out to delineate their effect on the ignition process. It was shown that the charge under the present experimental condition would not be ignited without initial temperature inhomogeneity. Increasing temperature inhomogeneity leads to earlier ignition whereas increasing turbulence intensity would retard the ignition.

This paper presents large eddy simulation (LES) and experimental studies of the combustion process of ethanol/air mixture in an experimental optical HCCI engine. The fuel is injected to the intake port manifolds to generate uniform fuel/air mixture in the cylinder. Two different piston shapes, one with a flat disc and one with a square bowl, were employed to generate different in-cylinder turbulence and temperature field prior to auto-ignition. The aim of this study was to scrutinize the effect of in-cylinder turbulence on the temperature field and on the combustion process. The fuel tracer, acetone, is measured using laser induced fluorescence (LIF) to characterize the reaction fronts, and chemiluminescence images were recorded using a high speed camera, with a 0.25 crank angle degree resolution, to further illustrate the combustion process. Pressure in the cylinder is recorded in the experiments.

High-speed laser diagnostics was utilized for single-cycle resolved studies of the formaldehyde distribution in the combustion chamber of an HCCI engine. A multi-YAG laser system consisting of four individual Q-switched, flash lamp-pumped Nd:YAG lasers has previously been developed in order to obtain laser pulses at 355 nm suitable for performing LIF measurements of the formaldehyde molecule. Bursts of up to eight pulses with very short time separation can be produced, allowing capturing of LIF image series with high temporal resolution. The system was used together with a high-speed framing camera employing eight intensified CCD modules, with a frame-rate matching the laser pulse repetition rate. The diagnostic system was used to study the combustion in a truck-size HCCI engine, running at 1200 rpm using n-heptane as fuel. By using laser pulses with time separations as short as 70 μs, cycle-resolved image sequences of the formaldehyde distribution were obtained.

High-speed laser diagnostics was utilized for single-cycle resolved studies of the fuel distribution in the combustion chamber of a truck-size HCCI engine. A multi-YAG laser system consisting of four individual Nd:YAG lasers was used for planar laser-induced fluorescence (PLIF) imaging of the fuel distribution. The fundamental beam from the lasers at 1064 nm was frequency quadrupled in order to obtain laser pulses at 266 nm suitable for excitation of acetone that was used as fuel tracer. Bursts of up to eight pulses with very short time separation were produced, allowing PLIF images with high temporal resolution to be captured within one single cycle event. The system was used together with a high-speed framing camera employing eight ICCD modules, with a frame-rate matching the laser pulse repetition rate.

Hydrogen has been proposed as a possible fuel for automotive applications. This paper reports an experimental investigation of hydrogen as HCCI engine fuel. The aim of the experimental study is to investigate the possibility to run an HCCI engine on an extremely fast burning fuel such as hydrogen as well as to study the efficiency, the combustion phasing and the formation of emissions. The experiments were conducted on a single-cylinder research engine with a displacement volume of 1.6 litres and pancake combustion chamber geometry. Variation of lambda, engine speed, compression ratio and intake temperature were parts of the experimental setting. The engine was operated in Homogenous Charge Compression Ignition (HCCI) mode and as comparison also in Spark Ignition (SI) mode. Hydrogen was found to be a possible fuel for an HCCI engine. The heat release rate was extremely high and the interval of possible start of combustion crank angles was found to be narrow.

The linear Raman scattering has been applied for the investigation of the influence of fuel properties on the mixture formation of high pressure swirl injectors. The measurements have been performed in an optically accessible high pressure high temperature chamber with a multi-component fuel consisting of benzene and n-decane. The local air/fuel-ratio and the composition of the fuel vapor phase were detected simultaneously with high spatial and local resolution along a line inside the spray region of the injector. In addition to the measurements performed with this two-component fuel mixture formation of the injector has also been studied by the separate use of the fuel components alone. Furthermore the influence of injector cooling on mixture formation has been investigated.

The application of exhaust gas aftertreatment systems is currently discussed to be the most suitable solution to significantly reduce soot and nitrogen oxide emissions of modern diesel engines. Nevertheless, an improvement of the engine combustion process reducing the raw emissions must be seen in combination with such systems or as a replacement. In this study, the influence of nozzle geometry, rail pressure and pre-injection on injection, vaporisation and combustion was analysed in a transparent single-cylinder diesel engine equipped with a common rail injection system by means of optical measurement techniques. The results show that a high-speed fuel intake into the combustion bowl, in combination with high rail pressures, forces the injection jets to break-up close to the wall of the combustion bowl. The engine swirl and the influence of the wall improve the mixture formation.

A five-cylinder diesel engine, converted to a single cylinder operated optical engine is run in Homogeneous Charge Compression Ignition (HCCI) mode. A blend of iso-octane and n-heptane is used as fuel. An experimental study of the horizontal boundary layer between the main combustion and the non-reacting surface of the combustion chamber is conducted as a function of speed, load, swirl and injection strategy. The combustion behaviour is monitored by chemiluminescence measurements. For all cases an interval from -10 to 16 crank angles after top dead center (CAD ATDC) in steps of one CAD are studied. One image-intensified camera observes the boundary layer up close from the side through a quartz cylinder liner while a second camera has a more global view from below to see more large scale structure of the combustion. The averaged chemiluminescence intensity from the HCCI combustion is seen to scale well with the rate of heat release.

Two-dimensional images of fuel distributions have been recorded in the intake of a fired 6-cylinder-4-valve spark ignition engine. As markers for the fuel a new exciplex-seed combination of triethylamine (TEA) and benzene was developed. Mixture formation and fuel evaporation of two different types of fuel injectors were compared inside the intake. The images were coupled with measurements of unburnt hydrocarbons (UHC) emissions of the two injectors in the exhaust gas. The behaviour of the fuel vapour distribution was examined at different times during the engine cycle. Instantaneous and averaged fuel distributions are shown and discussed in their influence on mixture formation.

Auto-ignition with SI-compression ratio can be achieved by replacing some of the fresh charge by hot residuals. In this work an engine is run with a negative valve overlap (NVO) trapping hot residuals. By increasing the NVO, thus raising the initial charge temperature it is possible to investigate the intermediate zone between SI and HCCI as the amount of residuals is increased. Recent research has shown the potential of using spark assistance to aid gasoline HCCI combustion at some operating conditions, and even extend the operating regime into regions where unsupported HCCI combustion is impossible. In this work the influence of the spark is studied in a single cylinder operated engine with optical access. Combustion is monitored by in-cylinder pressure and simultaneous high speed chemiluminescence imaging. It is seen that even for large NVO and thus high residual fractions it is a growing SI flame that interacts with, and governs the subsequent HCCI combustion.