Scientific summary
The aim of RADIADE is to enhance capabilities of current Computational Fluid Dynamic (CFD) models. This will increase the possibility for improved prediction of the complex physical phenomena occurring in marine diesel engines and in particular contribute to a more accurate computational prediction of local processes that are directly responsible for formation of harmful emissions.
The results and the developed numerical methodologies may eventually lead to improved design tools that will become important in view of future emission regulations for marine propulsion. Detailed computational modeling of processes inside combustion engines involves modeling of combustion, fluid flow and heat transfer phenomena and their mutual interactions.
Currently, influence of heat radiation from gasses and particles is usually not or at least only in very simplified ways accounted for in state-of-the-art models of in-cylinder flow in combustion engines. This project focuses on improvement of the radiant heat transfer models. The approach will be to adopt large, detailed and computationally demanding modeling of radiation phenomena developed by physicists for engineering purposes.
Since computational resources are limited a compromise must be found between fidelity of the employed model and computation times that are under reasonable limits within an engineering framework. This will be done by systematic sensitivity analysis of model simplifications and thorough validation against experimental results. Those studies are necessary to determine how the computational power is best spent and where the modeling approach is lacking. Different laboratory flames with increasing complexity levels will be used for validation purposes.
This incremental approach is essential to identify where the radiation model becomes deficient. The most complex laboratory flame should comprise the features of a true diesel engine flame as much as possible. However, it must have a simple geometry and be stationary to enable accurate measurements and fast CFD computations. Ultimately the model will be validated against measurements performed in the MAN Diesel & Turbo test engine with optical access.
Objective of the project
The stricter emission regulation for marine diesel engines forces the engine designer to focus on local processes in the combustion chamber, requiring the deployment of a whole range of numerical simulation and modeling tools. One of the most important tools in this context are detailed CFD models on in-cylinder flow, fuel spray, combustion and emission formation. In most cases such models do not account for heat radiation due to the complexity and great numerical cost involved. In particular for large engines it is known that radiation heat transfer plays an important role that lead to decreased gas temperatures and considerable internal heat transfer from hot to cold gases in the cylinder in addition to convective transport of heat.
The social/commercial purpose of this project is to enable more accurate and detailed model prediction of nitrogen oxides (NOx) and soot formation in marine diesel engines. Such model improvements are essential in order to meet future emission regulations without sacrificing the high fuel efficiency of these engines accompanied by increase of carbon dioxide (CO2) emissions.
The scientific purpose of the project is to improve computational tools for modeling of radiant heat transfer and integrate them into existing complex and computationally demanding CFD models of fluid flow. As well as to improve understanding of the complex coupling between the radiant heat transfer, rate of combustion progress and formation of harmful products in combustion processes.
The main results of the project
Main results of interest to society in general will be:
An improved ability to redesign marine diesel engines to comply with future regulations of harmful emissions without sacrificing their high fuel efficiency. Thus, stagnation in CO2 emission levels will decelerate the climate change rate and thereby improve the general public health.
An improved ability to reduce particulate emissions from ships will also reduce the climate change rate, as less deposition of particulates on Arctic ice, will lead to decrease in level of sunlight absorption caused by them - hence reduction in rate of Arctic ice melting.
Main results of interest to the scientific community will be:
An experimental validation of spectral models for relevant gases at high temperatures. The spectral data will be derived from state of the art, line by line, spectral models based on molecular physics.
A sensitivity study applied to different procedures of lumping the detailed data from line by line models into wide band models that can be integrated into complex CFD models.
Development of an experimentally validated procedure that combines continuum spectra from soot and other solids with band spectra from gases.
A sensitivity study applied to different numerical discretization procedures performed in order to integrate numerical treatment of radiation transport into general CFD solution methodology.
An improvement of modeling tools which can expand general understanding of complex coupling between the radiant heat transfer, rate of combustion progress and formation of harmful products in combustion processes.
Economy
The total budget of the project is 20,8 mio DKKR of which The Danish Council for Strategic Research has contributed with 12,3 mio DKKR