Alois Hirsch

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

Das Virtuelle Fahrzeug am Motorprüfstand

Potenziale zur Effizienzsteigerung in der Entwicklung konnen am Motorprufstand nur durch eine realitatsnahe Darstellung des instationaren Motorverhaltens in allen Betriebszustanden erschlossen werden. Durch den Einsatz des neuen Motorprufstands „VVETB“ von AVL wird „Frontloading“ im Entwicklungsprozess moglich. Entwicklungsaufgaben, die normalerweise in spaten Phasen des Entwicklungsprozesses stattfinden, konnen in eine fruhe Phase vorgezogen werden.

The virtual vehicle at the engine test bed

In reality close representation of the installed engine behaviour unlocks the potential for increased efficiency in the development process at the engine test bed. With the utilization of the new engine test bed “VVETB” by AVL “Frontloading” within the development process can be achieved. Development tasks, which are normally done in later phases of the development process, can be performed in early phases.

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.

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.

Emissions formation and exhaust gas aftertreatment

Developing and calibrating engines to meet emissions targets requires the optimum balance of all system components and their effects on mixture formation, combustion as well as gas and heat flux into the aftertreatment system. Composition and temperature of the exhaust gas need to be adapted to the system components behind. This article by AVL List GmbH, Graz, Austria, describes the devices and methods being suited for these requirements.

Emissionsbildung und Abgasnachbehandlung dynamisch messen und zyklusgenau steuern

Die Erfullung der Emissionsgrenzwerte erfordert eine ganzheitliche Abstimmung von Vorgangen der Gemischbildung, Verbrennung und Belieferung des Nachbehandlungssystems. Das Abgas muss in Zusammensetzung und Temperatur an die Erfordernisse der nachgeschalteten Komponenten angepasst sein. Dieser Beitrag der AVL List GmbH beschreibt Gerate und Methoden, die fur diese Anforderungen geeignet sind.

Flame diagnostics for performance and emissions development

Engine series development gets fast and in-time confirmation if a combustion system is as exhaustively exploited as concept design and pre-development have promised. Combustion deficiencies not only compromise performance and emissions, they first of all leave noticeable traces in the signature of the flame. AVL’s Visiolution technology systems enable the series development engineer to read these traces and to use standardised flame analysis tests for fast and precise performance and emissions development.

Flammendiagnostik für die Leistungsund Emissionsentwicklung

Der Serienentwickler verschafft sich rechtzeitig Gewissheit daruber, ob das Potenzial des Brennverfahrens tatsachlich so ausgeschopft wird, wie es Konzept und Zielsetzung verlangen. Weil Verfahrensmangel nicht nur zu schlechten Leistungs- und Emissionsdaten fuhren, sondern zuallererst ihre Spuren in der Art und Weise hinterlassen, wie eine Flamme brennt, haben AVL-Ingenieure Techniken entwickelt, diese Spuren einfach und schnell lesbar zu machen. Die Vorteile, zu erkennen, welche Masnahmen fur die Verfahrensoptimierung besonders geeignet sind, werden sofort nutzbar.