Ernst Winklhofer

Monitoring of hydrocarbon fuel-air mixtures by means of a light extinction technique in optically accessed research engines

Light scattering and light absorption of hydrocarbon fuels was utilized to gain information about the presence and the space-time distribution of liquid and vaporized fuel inside the combustion chambers of optically accessed research engines. The design and application of the experimental method is described. Semiquantitative results about the mixing of fuel with in-cylinder air are presented. The conclusions drawn therefrom yield time scales for diesel spray penetration, evaporation, and fuelair mixture formation. In a gasoline engine, different modes of fuel air mixing are identified.

Flame diagnostics by light sheet imaging and by shearing interferometry

Combustion in a propane/air burner is analyzed by means of imaging molecular constituents present in the plane of a laser light sheet and by recording the local refractive index distribution with a shearing interlerometer. The pulsed illumination with a UV light sheet yields an instantaneous image of the distribution of propane by elastic scattering, and of OH and CH radicals by laser-induced fluorescence. Spectral separation allows simultaneous and separate imaging of elastic and inelastic scattering, thus providing a means to analyze the spatial inter-relation of propane, CH, and OH. In a fuel-rich flame, laser-induced incandescence of soot particles is observed. Calibration of propane concentration levels is achieved by the refractive index measurements, which also help to estimate flame temperatures.

Optical access and diagnostic techniques for internal combustion engine development

Methods for optical access to combustion chambers of internal combustion engines are shown. The optical access is either maximised to allow application of complex optical diagnostic techniques whilst maintaining minimum operability of the engine or engine components, or full engine operability is maintained whilst optical access and diagnostic techniques are tailored to the diagnostic demand and the restraints of engine operation. As full optical access allows a wide range of diagnostics to be applied it puts the emphasis on organising and extending realistic engine operation conditions. Full engine operability, however, challenges the optical access and the design of diagnostic systems. The paper gives examples for diagnostic applications for both of these situations.

Mixture Quality Evaluation for Transient Mode Gasoline Engine Calibration

Gasoline engines have perfect emissions quality in stationary part load operation — how to ensure such ideal operation also at engine start, at tip-in tip-out, and at full load conditions? Key to the solution of these issues is the optimum use of components for mixture formation, combustion and exhaust gas aftertreatment with the focus on actuator calibration yielding reliable and low emissions combustion under transient operating conditions. Conventional testing of actuator parameter settings for such transients is evaluated with engine out emissions measurements. Any emissions peaks are well understood to be the result of some specific cycles which suffer from inadequate mixture formation due to limitations of fuel injection, evaporation or air supply. Consequently, improvements are achieved with adaptation of actuator parameters such as fuel injection timing, multiple injections or throttle and boost pressure settings in part load operation. With in-cylinder events being the root cause for emissions related issues, there is demand for diagnostic techniques capable of identifying emissions relevant in-cylinder processes for individual cylinders and on a cycle by cycle basis. This demand is met with the measurement of in-cylinder pressure together with flame radiation intensity. As cylinder pressure signals are evaluated for combustion stability, the simultaneously recorded flame signals provide information on mixture preparation quality. Well premixed charge results in flame radiation signals which are typical for homogeneous turbulent flames. Insufficiently evaporated and partially mixed fuel, especially at engine start, yields flame signals typical for diffusion flames. This simple relation between flame signals and soot formation events provides the basis for measurement techniques enabling mixture formation evaluation for individual cylinders and individual cycles. The application of such in-cylinder pressure and flame measurement techniques to PFI and GDI engines is presented with examples for engine cold start testing. The technique is further applied in the calibration of engine tip-in transients.Copyright

Optische Verbrennungsdiagnostik mit einfach applizierbarer Sensorik

In der Entwicklung anspruchsvoller Verbrennungssysteme werden in zunehmendem Ausmas Visualisierungsmethoden eingesetzt, um die theoretisch moglichen Potenziale eines virtuell voroptimierten Brennverfahrens auch zielstrebig im Motorenversuch realisieren zu konnen. In speziell adaptierten Versuchsmotoren haben sich dafur eine Reihe von optischen Mess- und Visualisierungsverfahren durchgesetzt. Um die Aussagekraft solcher Methoden jedoch optimal nutzen zu konnen, darf der Motor oft nur unter eingeschrankten Bedingungen betrieben werden. Bei derartigen Aufgaben tritt der Bedarf nach Visualisierungsverfahren auf, die ahnlich wie die Druckindizierung den Motorbetrieb nicht beeintrachtigen, dabei aber die Ergebnisse der Druckindizierung durch Information uber die ortlichen Ablaufe im Brennraum vertiefen, wie folgender Beitrag der AVL GmbH zeigt.

Kombinierte Fluid- und Strukturberechnung zur thermischen Analyse in Zylinderköpfen von Verbrennungskraftmaschinen

Die effektive Auslegung der Kuhlung ist ein Arbeitsschwerpunkt der AVL List GmbH, um wichtige Ecksteine einer Motorenentwicklung wie Abgasemissionen, Kraftstoffverbrauch und Komponentenhaltbarkeit zu unterstutzen und zu verbessern. Nicht zuletzt die immer hoheren spezifischen Leistungen von Motoren, bei gleichzeitiger Forderung eines niedrigeren Verbrauchs und Reduzierung der Emissionen, stellen besondere Anforderungen dar, die den Einsatz immer schnellerer und genauerer Entwicklungsmethoden erfordern. Als Werkzeuge dienen numerische Verfahren, welche die Optimierung von virtuellen Prototypen ermoglichen.

Irregular Combustion Events in RDE Test Situations Diagnostics – Analysis – Improvements

The paper describes a method to identify and analyze pre-ignition (PI) events appearing in engine and vehicle RDE drive cycle tests or similar transient and stationary test schedules. A specific requirement in such long duration drive cycles is the large amount of data to be recorded for each combustion cycle and the data processing during and after a test procedure. Identification of PI events is accomplished with measurement of ignition delay time, i.e. spark discharge timing and the instant when flame growth is detected. PI events show up with negative ignition delay. How this simple concept is implemented in a combustion measurement procedure with many thousand cycles is explained in some detail. Classification of PI events and root cause analysis is then supported with evaluation of the optical signals of the tests. Specific evaluation procedures to accomplish such task have been described in earlier publications.

Verbrennungsdiagnostik - Indizieren und Visualisieren in der Verbrennungsentwicklung

Verbrennungsdiagnostik wird in der Motorenentwicklung immer dann eingesetzt, wenn bei Messungen von Verbrauch, Leistung und Emissionen ungenutztes Potenzial im Vergleich zu thermodynamisch moglichen Zielwerten festgestellt wird. Bei den hohen Zielanforderungen, die an moderne Motoren gestellt werden, ist zumindest eine thermodynamische Verbrennungsanalyse durch Messen des Zylinderdrucks immer ein fester Bestandteil im Entwicklungsablauf.

Transient Mode Calibration — Mixture Quality Evaluation

AVL List GmbH presents a measurement technique which enables evaluation of mixture formation quality in order to support calibration of emissions relevant SI engine operation. The method is especially suited to identify individual cycles’ particulate emissions contributions at engine start and in transient operation. Sensors, signal recorders and signal evaluation are part of standard test bed and on-board analysis systems.

Transientkalibrierung — Bewerten der Gemischqualität

Dieser Beitrag der AVL List GmbH beschreibt eine Messtechnik, mit der die Gemischqualitat in jedem Zyklus und in jedem Zylinder eines Ottomotors bewertet wird. Emissionsrelevante Kalibrieraufgaben an Ottomotoren werden damit schnell und prazise durchgefuhrt. Die dafur verwendeten Sensoren, die Mess- und Bewertungsmethoden reihen sich in den vertrauten Ablauf einer Motorindizierung am Prufstand und im Fahrzeug.