Search Results

The introduction of alternative fuels is crucial to limit greenhouse gases. CNG is regarded as one of the most promising clean fuels given its worldwide availability, its low price and its intrinsic properties (high knocking resistance, low carbon content...). One way to optimize dedicated natural gas engines is to improve the CNG slow burning velocity compared to gasoline fuel and allow lean burn combustion mode. Besides optimization of the combustion chamber design, hydrogen addition to CNG is a promising solution to boost the combustion thanks to its fast burning rate, its wide flammability limits and its low quenching gap. This paper presents an investigation of different methane/hydrogen blends between 0% and 40 vol. % hydrogen ratio for three different combustion modes: stoichiometric, lean-burn and stoichiometric with EGR.

To meet LEV and EU Stage III emission requirements, it is necessary for new catalytic converters to be designed which exceed light-off temperature as quickly as possible. The technical solutions are secondary air injection, active heating systems such as the electrically heated catalytic converter, and the close coupled catalytic converter. Engine control functions are extensively used to heat the converter and will to play a significant role in the future. The concept of relocating the converter to a position close to the engine in an existing vehicle involves new conflicts. Examples include the space requirements, the thermal resistance of the catalytic coating and high temperature loads in the engine compartment.

The study of oil emission is of essential interest for the engine development of modern cars, as well as for the understanding of hydrocarbon emissions especially during cold start conditions. A laser mass spectrometer has been used to measure single aromatic hydrocarbons in unconditioned exhaust gas of a H2-fueled engine at stationary and transient motor operation. These compounds represent unburned oil constituents. The measurements were accompanied by FID and GC-FID measurements of hydrocarbons which represent the burned oil constituents. The total oil consumption has been determined by measuring the oil sampled by freezing and weighing. It has been concluded that only 10 % of the oil consumption via exhaust gas has burned in the cylinders. A correlation of the emission of single oil-based components at ppb level detected with the laser mass spectrometer to the total motor oil emission has been found.

Nowadays, due to the high competitiveness in the automotive market, the car manufacturers and the engine developers are concentrating as many efforts as possible in order to diminish the lead-time to production and to promote cost reductions of their engine developments. As a consequence, many systems and component tests are being substituted by numerical simulations, allowing a significant reduction in the amount of engine and bench tests. The integration of individual numerical simulation tools generates the philosophy of Virtual Engine Development, which is based on the concept of simulating as much as possible the entire engine as well as its components behaviors. This paper presents the application of Virtual Engine Development (VED) in a PSA 1.4l SI engine development. Theoretical results of engine performance as well as powercell components behavior such as piston, rings, conrod, bearings, liner, engine block and cylinder head, among others, are presented and discussed.

A new phenomenological model of injection and auto-ignition is established in a 4-cylinder DI diesel engine of the production size class equipped with an inclined 5 holes injector. Measurements are performed at representative engine conditions for partial load. The penetration of the liquid phases is visualized in the whole combustion chamber by simultaneous Laser-Induced Fluorescence (LIF) and Mie scattering techniques. The autoignition and combustion are analyzed by a time-resolved direct imaging of the chemiluminescence process. Experiments based on the correlation of two separated images of the combustion phenomena in a single cycle have allowed a detailed comprehension of spatial and temporal description of the autoignition and reaction zones development. Several autoignition sites are revealed in the vicinity of the injector nozzle. The reaction zone is shown to develop independently and then to merge to a unique one in the whole combustion chamber.

To simultaneously reduce wear and friction in automotive valve train systems, a technique for measuring the rotational speed of tappets by placing radionuclide markers in their surfaces has been developed. Using an electrically driven test rig, counting rate variation during camshaft rotation is traced, allowing a mean value of the tappet's rotational speed to be determined. Measurements were performed on a V6 Peugeot engine cylinder head for various geometrical combinations of the cam-to-tappet contact (crown radius of the tappet, cam taper angle), and the dependence of the tappet's rotational speed upon functional parameters (lubricant pressure and temperature, angular speed of the camshaft) was determined. Tappet rotation was found to be strongly affected by camshaft operating speed and the design of the cam-to-tappet contact, and less by lubrication conditions (off pressure and temperature).

Particle Image Velocimetry (PIV) technique was used to study the in-cylinder flow motion in a single cylinder transparent spark ignition (SI) engine, with 4 valves pent-roof cylinder-head. Experiments have been firstly performed using classical PIV technique in the symmetrical plane of the combustion chamber. The instantaneous two-dimensional velocity fields show that during intake stroke, the flow has strong relatively stable structures with low cycle by cycle (CBC) variations, whereas during compression stroke, the flow consists of large unstable eddies with high CBC variations. In all cases, no large tumble-like motion was observed on instantaneous fields in the measurement plane during the intake stroke. Therefore, Stereoscopic Particle Image Velocimetry (SPIV) technique was adapted to complete the classical two-dimensional measurements and in order to have a better understanding of the in-cylinder flow during compression stroke.

The optimization of fuel efficiency and the minimization of the residual gas fraction require individual cylinder control of the amounts of inducted air mass and injected fuel mass. Determination of an individual cylinder air/fuel ratio (AFR) regulator is based on the measured AFR for each cylinder, using 4 proportional UEGO sensors. The innovative character of this study describes a unified and robust individual cylinder AFR estimator, using a single measuring point: a proportional oxygen sensor located in the exhaust manifold. The model used for the estimator is a state model such that the dimension of the state and measurement matrices are unique, whatever the manifold configuration and the sensor position (confluence point or exhaust manifold: unified model), the engine speed (robust model).

For development of new engines a ‘general purpose ECU’ for spark ignition engines with up to 12 cylinders has been developed. As part of this ECU a DSP (Digital Signal Processor)-based measurement unit for high frequency combustion analysis has been integrated. In this paper, details about this signal processing platform are given. The DSP-unit has 24 analog input channels. 12 channels are used for cylinder pressure measurement; the other 12 channels are general purpose ones. For example, they can be used for ionic current analysis. Additional digital inputs allow measurement of crank speed and crank speed variations. This is an important topic for misfire detection as part of the OBD regulations.

Synthetic fuels for internal combustion engines offer CO2-neutral mobility if produced in a closed carbon cycle using renewable energies. C1-based synthetic fuels can offer high knock resistance as well as soot free combustion due to their molecular structure containing oxygen and no direct C-C bonds. Such fuels as, for example, dimethyl carbonate (DMC) and methyl formate (MeFo) have great potential to replace gasoline in spark-ignition (SI) engines. In this study, a mixture of 65% DMC and 35% MeFo (C65F35) was used in a single-cylinder research engine to determine friction losses in the piston group using the floating-liner method. The results were benchmarked against gasoline (G100). Compared to gasoline, the density of C65F35 is almost 40% higher, but its mass-based lower heating value (LHV) is 2.8 times lower. Hence, more fuel must be injected to reach the same engine load as in a conventional gasoline engine, leading to an increased cooling effect.