Single-cylinder research engine for gas combustion process development

Today, the use of renewable fuels is becoming more and more important. However, the main focus is on the stringent emission regulations and fuel efficiency. To meet these requirements, the combustion process must be fundamentally adapted. A special case is the combustion process of gas engines, which are examined at the institute.

For this purpose, a single-cylinder research engine based on the Mercedes Benz 500 series with a typical truck-specific displacement of two liters is available. For operation in a dual-fuel mode, a modern common-rail injection system was adapted and the combustion chamber geometry was modified. The gas is injected into the intake manifold during the intake stroke and ignited towards the end of the compression stroke by a diesel pilot injection.

All operating media are externally conditioned, which ensures optimal reproducibility of the engine boundary conditions. Both the fuel path and the air and exhaust gas lines are designed for maximum variability. In order to be able to control these process variables simultaneously and with high precision, a control unit network is used, which represents a flexible engine management system. This provides an optimal measurement environment, and also allows a rapid adaptation of new measuring instruments or changed engine parameters.

Currently, as part of a publicly funded research project of the FNR (Fachagentur für Nachwachsende Rohstoffe) at the ITV in cooperation with the Öl-Wärme-Institut Herzogenraht a new dual-fuel combustion process is developed, which aims to use unrefined biofuels in supercharged engines and simultaneously reduce pollutant emissions. The technical approach to achieve these goals is to first vaporize the fuel into a homogeneous mixture in a reactor upstream of the engine and then ignite it in the combustion chamber with a small amount of diesel fuel (Diesel Pilot Injection). For the injection of the gas into the combustion chamber, various concepts are developed and tested.

In the future, this engine test bench can also be used for other gas engine combustion process developments, for example mixing processes or dual-fuel concepts.
At the institute, a nearly identical, optically accessible research single-cylinder engine is available. This opens the possibility to investigate spatially and temporally resolved processes of mixture formation, ignition and combustion with optical measurement techniques.