Engine Knock Intensity Modelling for Future Fuels
| Project supported by The Research Association for Combustion Engines (FVV) | |
| Duration ► | 24 months |
| Start ► | May 2022 |
| FVV funding ► | 636 k€ |
Context
Future scenarios to effectively lower the man-made greenhouse gas emissions on a global scale still include the subsequent use of internal combustion engines in various mobility and industrial sectors. However, climate neutrality can realistically only be achieved if a consequent defossilisation policy is pursued.
Thereby, alternative liquid or gaseous energy carriers as ammonia, hydrogen or methanol come to the fore of this research project. As the production of these alternative fuels is quite energy demanding, an efficient combustion process has the highest priority, aiming at brake thermal efficiencies of ~ 50%.
In order to reach this ambitious goal, further technological steps as extreme mixture enleanment and high compression ratios are necessary. On the other hand, one of the main limiting factors for achieving this goal is the knock phenomenon, which is mainly examined in the planned project. By now, research projects on knock phenomena focussed on gasoline fuel.
The knowledge base regarding the knock behaviour of (synthetic) alternative fuels is quite poor. With the combined approach including experimental investigations and simulation tool development, new corner stones for future ICE development can be laid.
Objectives
With the shift towards a carbon neutral society, development of internal combustion engines faces great challenges for the use of renewable fuels, which will also demand SME to adapt their modelling techniques. Depending on the application, which can vary from land and sea transport to construction equipment as well as generators, a variation of different fuels can prove to be the ideal substitute for the fossil energy carrier.
This project focusses on the modelling of engine knock as one key limiting factor for peak efficiencies for the use of gasoline-like fuels. Knock modelling has proven to be extremely difficult to predict and has been a challenge for the past decades of engine development. State of the art knock modelling approaches will be applied and enhanced for three synthetic fuel candidates: Ammonia, Hydrogen and Methanol, which all strongly differ in their combustion properties and application range.
Partners
FVV is the German Member organisation for Combustion Engine research. In the case of the proposed project, FVV will be responsible for the project management of the German side and is the coordinating association for this project.
IFS will perform virtual investigations, including 0D/1D simulations.IFS will use its modelling experience to adapt the existing knock occurrence prediction models to (synthetic) alternative fuels as ammonia and hydrogen and develop a detailed knock intensity and frequency prediction model.
PRISME will be responsible of providing different data set about ammonia combustion, support the selection of accurate reaction mechanisms to carry over the test data to simulation and improve commercial CFD code as Converge.
VKA will carry out 3D-CFD analysis for selected operating points with Ammonia, Hydrogen and Methanol.
Work Plan
PRISME of University of Orléans will carry out dedicated studies for Ammonia (incl. Hydrogen dosing) using thermodynamic testing on a single cylinder engine with a focus on knocking combustion. At the same time, the experimental database is expanded for measurements of Methanol and Hydrogen, which VKA has available from previous FVV projects. This project will feature a documentation of thermodynamic investigations at knock limit for a very broad application range, which itself will provide great insights for SMEs and enable them for validation of their own models based on this data.
VKA of RWTH Aachen University will develop, validate and document a model to predict knock frequency and intensity using a CFD-approach, which represents the mean engine cycle by making use of a probability density function based method.
IFS will develop two new 0D/1D knock model extensions. First, the existing knock boundary model is adapted to the renewable fuels in order to predict the knock occurrence for averaged working cycles. Therefore, the auto-ignition integral calculations are adapted to the physical properties of the respective fuels. The second model extension includes the prediction of statistical values regarding knock phenomena. The knock frequency and the knock intensity of an operating point are simulated based on a predictive cycle-to-cycle variations model.
Expected Results
The first practical result consists of two new 0D/1D models that include validated knock occurance prediction for alternative fuels (WP3). Furthermore, a second model is able to predict statistical values of the knock event as knock frequency and knock intensity (WP4).
The second practical result is the delivery of a validated approach, which allows for prediction of the aforementioned knock quantities within a mean-cycle-based 3D-CFD (WP2). That result comes along with the selection of suitable reaction mechanisms and tabulated data for ignition delay times, which also can be utilized for other applications by SMEs.
Another benefit for SMEs is the comprehensive validation of the delivered models. These results are a useful basis for a first assessment which boundaries are imposed for new engine in terms of efficiency enhancement potential.
The measurements methods developed within the course of this project provide further information about rapid compression machine and test bench setup, including measurement methodology (WP1).
Finally, publications and literature evolving from this project will extend the knowledge from various knock phenomena projects conducted with gasoline fuel and create a basis for the deeper understanding of alternative fuels. Having this literature at their disposal, cost-efficient development by SMEs is supported.
Contact : Christine ROUSSELLE ⇒ christine.rousselle@univ-orleans.fr