Rudolf Maly

Emissions Performance of GTL Diesel Fuel and Blends with Optimized Engine Calibrations

The results of a comprehensive experimental investigation into the exhaust emission performance and combustion properties of neat and blended Gas-To-Liquids (GTL) diesel fuel are presented. A sulphur-free European diesel fuel was used as the reference fuel, and two blends of the GTL diesel fuel with the reference fuel, containing 20% and 50% GTL diesel fuel respectively, were investigated. The study was based on a Mercedes Benz 2.2 liter passenger car diesel engine and presents emission data for both the standard engine calibration settings, as well as settings which were optimized to match the characteristics of each fuel. Vehicle emission tests showed that the GTL diesel fuel results in reductions in HC and CO emissions of greater than 90%, while PM is reduced by 30%, and NOx remains approximately unchanged. Engine bench dynamometer tests showed reductions in soot of between 30% and 60%, and NOx reductions of up to 10% with the GTL diesel fuel, depending on the operating point. Results with the GTL diesel blends showed a pronounced non-linear response, with reductions in emissions generally being larger than indicated by the blending ratio, to the extent that the emission performance of the 50% blend was similar to that of the neat GTL diesel fuel. Optical engine tests were carried out to investigate the combustion properties of the neat GTL diesel fuel in more detail. In addition to reflecting the better ignition quality of the GTL diesel, these tests also showed that it has better vaporization characteristics and a more uniformly distributed flame structure. A design of experiments (DOE) approach was used to optimize the injection settings and EGR rates for each fuel in order to obtain the most favourable NOx-soot trade-off. By this means it was estimated that simultaneous reductions of 35% in both NOx and PM could be obtained in the vehicle emission test with GTL diesel fuel, with an optimized engine calibration. The corresponding estimated reductions with the 50% and 20% blends of GTL diesel are 30% and 15% respectively, again reflecting the non-linear exhaust emission response of the blended fuels.

Unsteady vaporization and ignition of a three-dimensional droplet array

Abstract A detailed numerical simulation has been carried on a stationary three-dimensional array of heptane droplets at intermediate Reynolds numbers (Re). A goal of the simulation is to understand and quantify the interactions between droplets in the array, and to determine the change in the flow physics and chemistry caused by the droplets interactions. The flow equations solved were the low Mach number Navier-Stokes equations with variable liquid and gas, properties. In order to treat the geometry of interacting droplets the overset or Chimera grid method has been employed, and this method has accurately and efficiently simulated the droplet arrays. Simulations have been carried out at two intermediate Re and the lower Re results exhibited stronger array interactions. At higher Re there are droplet blockages, and this interaction can be quite strong. For droplets inside the array there are significant differences in droplet drag, heat transfer, and mass transfer, and the results depend on the droplet array configuration. The array geometry also has a strong influence on chemical reactions, and this is clearly seen in the ignition results. The results show clearly that groups of droplets behave differently than single droplets, and this difference is quantified with both local and global calculations of the droplet flow, heat, and mass transfer processes.

Cycle-Resolved Two-Dimensional Flame Visualization in a Spark-Ignition Engine

A cycle-resolved two-dimensional flame visualization technique using Mie-scattering from submicron sized smoke particles added to the homogeneous charge mixture of a spark-ignition engine has been developed. This diagnostic technique was applied to a square piston engine with four windows. Pulsed laser sheets were generated by a copper vapor laser at a frequencies of 6 kHz. The light scattered by the smoke particles was collected by a drum camera on high sensitivity photographic film.

A group combustion model for treating reactive sprays in I.C. engines

A model is presented and discussed treating the complex interactions between the fluid dynamics, the size, space, and time distributions of droplets as well as the combustion chemistry in a Diesel spray. The three-dimensional droplet characteristics are modeled with an overset gridding scheme, CHIMERA, and time dependent solutions of the Navier-Stokes equations have been carried out with the digital computer. The chemistry is treated with global and detailed reaction kinetics in a two-stage model. The global kinetics were used with the detailed Navier-Stokes equations, and the detailed kinetics were employed with a time dependent one-dimensional model that used information from the detailed model. The typical thermodynamic conditions of a modern truck engine have been used to provide insight into the details of ignition, combustion, and pollutant formation in spray commbustion. The study has considered droplet groups that have both uniform and different size droplets, and different groupings of the droplets have been investigated. The present model allows the droplets to move and vaporize in time, and the time development of ignition has been studied. The results indicate that group combustion effects have a dominant influence on all aspects of spray combustion.

Die Zukunft der Funkenzündung

An Zundsysteme fur kunftige Ottomotoren werden noch hohere Anforderungen bezuglich Zuverlassigkeit, Leistungsfahigkeit und Wartungsfreiheit gestellt, als sie heute schon ublich sind. Die dafur notwendigen Entwicklungsrichtungen und deren Nutzpotentiale konnen aus den Grundeigenschaften der elektrischen Funkenentladung abgeleitet werden. Trotz uber 140 Jahren Entwicklungszeit sind erhebliche Verbesserungspotentiale noch ungenutzt. Durch konsequente Grundlagenforschung und Komponentenentwicklung im Schulterschlus zwischen Anwender und Zulieferer konnen wesentliche Produktverbesserungen realisiert werden.

Fuel Effects on Engine Combustion and Emissions

The Energy Information Administration (EIA) estimates indicate that 90% of the energy consumed worldwide is fossil fuel based, and a large fraction of this is derived from petroleum. Figure 8.1 shows the world energy fuel consumption historically, and projected through 2030. It is clear that past, present, and most current future projections indicate that the world energy needs will in large part be based on petroleum. Petroleum composition is widely variable, depending on the source, but in general the composition includes several hundred hydrocarbons, with boiling points ranging from –68◦C to 900◦C, and molecular weights ranging from 44 to well over 1000. Historically, petroleum processing consisted of a relatively simple separation process using distillation to take advantage of the range of boiling points and molecular weights. As a general rule, the lighter hydrocarbon components have a higher resistance to autoignition, i.e. a higher autoignition temperature. This makes them ideally suited for flame propagation engines, where the boiling point distribution is also nearly ideal. Over time, the ignition characteristics and the boiling point distributions have been additionally tailored through refinery processing for use in premixed flame propagation engines. The first flame propagation engines were fueled using straight run gasoline, or basically the first fraction of hydrocarbons distilled from the early petroleum sources. The heavier fractions, on the other hand, generally have lower autoignition temperatures making them more ideal for use in compression ignition engines. In addition, the boiling point distribution and viscosity characteristics of the heavier

Numerical simulation of reactive flow on the IBM ES/3090 Vector Multiprocessor

Prohibiting knock damage in internal combustion engines presents severe restrictions for engineers. Laboratory experiments are expensive or even impossible; nevertheless, numerical attempts that employ supercomputers have been rarely undertaken. The numerical approach described in this paper combines a recent shock-capturing finite-volume scheme for the compressible Navier Stokes equations, with semi-implicit treatment of the chemical source terms. An algorithm is described and validated by experiment that is optimaliy adapted to vector and parallel computersT. he algorithm has been implemented on the IBM Enterprise System/3090™ (ES/3090™) Vecto Multiprocessor. Performance measurements are discussed. The potential of the codeis illustrated by an example: formation of pseudos hock waves due to interaction of a shock wave with turbulent boundary layer flow.