David Lejsek

Experimental study on the impact of the jet shape of an outward-opening nozzle on mixture formation with CNG-DI

The energy source natural gas is the most promising alternative to the conventional fuels having beneficial properties like reduced pollutants and CO2 emissions particularly suited for the SI engines. Nevertheless, this environmentally friendly propulsion is met with rejection by the customer due to the deficit in the number of refueling stations and lower power yield compared to gasoline engines. One possibility to raise customers’ acceptance is the improvement of the driveability by increasing the volumetric efficiency with CNG direct injection. However, such a combustion concept puts high demands on the injection system and mixture formation. Among others a much higher flow rate at low injection pressure is necessary which can only be provided by an outward-opening nozzle due to its large cross-section. But this valve concept with a hollow cone jet has a specific propagation behavior with gaseous fuel which completely differs from a liquid one. Thus, the present paper is focused on experimental investigations of the influence of such a jet shape on the mixture formation with CNG-DI. The experiments are performed using a two-cylinder SI engine at stoichiometric homogenous conditions. Additionally, the test-bench results are supported by measurements in a pressure chamber equipped with Schlieren technique and also by numerical 3D-CFD simulations. The last-mentioned ones are presented in a separate paper, named “3D-CFD Analysis on Scavenging and Mixture Formation for CNG-DI with an outward opening Nozzle” from Marlene Wentsch. Nevertheless, the experimental results show a sensitive response of the hollow cone jet to the surrounding combustion chamber walls and thus a significant role of this interaction for the fuel distribution and emissions.

3D-CFD analysis on scavenging and mixture formation for CNG direct injection with an outward-opening nozzle

On the basis of comprehensive experimental measurements, 3D-CFD analyses of CNG direct injection, using an outward-opening nozzle, were performed. Main objective of the presented work was the examination of influencing factors on the hollowcone jet propagation, fuel distribution and therewith directly associated back flow into the intake manifolds.

Einsatz der Brennverlaufsanalyse im Motorhochlauf als Entwicklungs- und Applikationswerkzeug

Mit zunehmend scharfer werdenden Emissionsgrenzwerten wird auch die Optimierung des Startprozesses immer wichtiger. Dieser Beitrag der Robert Bosch GmbH zeigt, wie die Analyse des gemessenen Zylinderdruckverlaufs und die daraus berechneten Brennverlaufe auf den hochgradig instationaren Startvorgang ubertragen werden konnen. Dabei zeigt sich, dass die zyklusaufgeloste Betrachtung der thermodynamischen Vorgange eine effiziente Optimierung des Startprozesses in allen Stufen der Entwicklung ermoglicht.

Vehicle Development for Natural Gas and Renewable Methane

Natural gas vehicles are a mature technology already available today for solving the environmental problems caused by the automobile. The advantage is based on the features of the main fuel content methane. While keeping a minimum fuel quality standard, it is doesn’t matter to the vehicle technology whether the Methane is several million years old or just a few days. There is complete compatibility between fossil and renewable sources for this most simple of all hydrocarbons. Its highest possible ratio between hydrogen and carbon and the resulting features considering production/availability (fossil & renewable), the justifiable effort in the fuel system and the engine and environmental features make methane an ideal vehicle fuel.

Calculation of the wall heat transfer during start-up of SI engines

The introduction of CO2-reduction technologies like the Start-Stop-System and the more stringent future emission limits require a detailed optimization of engine start-up. Thus the thermodynamic analysis of the processes is advantageous for combustion concept development as well as for the calibration of the ECU. In the following article by Bosch is shown how the transient wall heat fluxes can be calculated during engine start-up.

Berechnung des Wandwärmeübergangs im Motorhochlauf von Di-Ottomotoren

Die Einfuhrung von Start-Stopp-Systemen als CO2-Minderungsmasnahme und die zunehmend scharfer werdenden Emissionsgrenzwerte erfordern eine detaillierte Optimierung des Motorstarts. Die thermodynamische Analyse der Vorgange im Brennraum wahrend des Starts ist, sowohl in der Brennverfahrensentwicklung als auch bei der Datenkalibrierung des Motorsteuerungssystems, daher von Vorteil. Dieser Beitrag von Bosch zeigt, auf welche Weise der instationare Wandwarmeubergang wahrend des Motorhochlaufs berechnet werden kann.

Combustion process analysis

As the limits being placed on emissions grow to be more and more stringent, optimizing the start-up process becomes extremely important. This article by Robert Bosch GmbH, Germany, shows how the analysis of the cylinder pressure measurements and the combustion processes calculated from these can be applied to the highly dynamic start-up process. It is shown that the ability to investigate the thermodynamic processes in a cyclic manner is the key to efficient improvement of the start-up process at all stages of development.

Fahrzeugentwicklung für Erdgas und erneuerbares Methan

Erdgasfahrzeuge sind eine bereits heute verfugbare und ausgereifte Technologie zur Losung der durch Automobile verursachten Umweltprobleme. Der Vorteil beruht auf den Eigenschaften des Haupt-Kraftstoffanteils Methan. Bei Einhaltung von Mindest-Kraftstoffstandards ist es fur die Fahrzeugtechnik gleich, ob das Methan viele Millionen Jahre oder erst wenige Tage alt ist. Es besteht vollkommene Kompatibilitat zwischen fossilen und erneuerbaren Quellen fur diesen einfachsten aller Kohlenwasserstoffe. Sein grostmogliches Verhaltnis von Wasserstoff zu Kohlenstoff und die daraus resultierenden Eigenschaften machen Methan uber die Erzeugung/Verfugbarkeit (fossil & regenerativ), den vertretbaren Aufwand im Kraftstoffsystem und die motorischen und Umwelteigenschaften zu einem idealen Kraftstoff.