Periodic Reporting for period 2 - EDEM (Experimentally Validated DNS and LES Approaches for Fuel Injection, Mixing and Combustion of Dual-Fuel Engines)
Reporting period: 2021-09-01 to 2024-02-29
Energy demand for transportation is increasing globally, driven by developing economies and expansion of urbanisation. Electrification of passenger cars is gradually becoming a reality, while hydrogen fuel cells (FCs) are also playing an increasingly important role. However, due to their limitations in energy density, this results to excess weight/volume for achieving mileage values similar to those of fuel-powered vehicles. Therefore, such powertrains are not suitable for heavy-duty, off-road and marine applications, as these applications require vehicles/vessels with adequate energy stored onboard and ability for high-power operation. Thus, the long-term decarbonisation strategy of these sectors has no alternative but utilisation of near zero CO2 emission (NZE) or carbon-free fuels. These so-called e-fuels are produced from renewable hydrogen (e-H2) reacting with CO2 in chemical processes leading to e-diesel, e-jet, e-gasoline, alcohols, di-methyl ether (DME) etc. Such e-fuels are utilized by the Dual-fuel internal combustion engines (DFICE), which represent the most promising Near Zero Emission alternative for these transportation sectors, satisfying the strictest emission legislations e.g. EURO VI or Tier IV standards, in Europe and in the US, respectively; moreover, they comply with the Tier III limit of the International Maritime Organization (IMO).
In order to allow the relevant industries to design efficient DFICE concepts, computational fluid dynamics (CFD) models have been long utilised. However, existing models fail to predict processes where a variety of fuel mixtures are injected and combust simultaneously. This is due to the simplifications made for the mixing, phase-change and combustion, which all are happening at physical scales typically not resolved by numerical models utilised for industrial design, due to the very long computational time required. The overall objective of the EDEM project was to develop models suitable for flow and chemistry processes taking place at the physically smallest scales realised in the relevant equipment and operating conditions. The developed so-called ‘sub-grid-scale’ models derived with the aid of these models, have been implemented in software utilised by engine and fuel injection equipment manufacturers in order to assist in the design of DFICEs. The EDEM project developed such CFD models and validated them against new experimental data.
DFICEs are relevant to the following, non- exhaustive, list of applications: power generation, cargo ships and tankers, light and heavy-duty trucks, tractors, earth-moving machines and haul trucks. By providing their research findings to the relevant industry and by disseminating their results to the scientific community the EDEM project contributes to the reduction of soot, which is one of the deadliest forms of pollution.
In order to allow the relevant industries to design efficient DFICE concepts, computational fluid dynamics (CFD) models have been long utilised. However, existing models fail to predict processes where a variety of fuel mixtures are injected and combust simultaneously. This is due to the simplifications made for the mixing, phase-change and combustion, which all are happening at physical scales typically not resolved by numerical models utilised for industrial design, due to the very long computational time required. The overall objective of the EDEM project was to develop models suitable for flow and chemistry processes taking place at the physically smallest scales realised in the relevant equipment and operating conditions. The developed so-called ‘sub-grid-scale’ models derived with the aid of these models, have been implemented in software utilised by engine and fuel injection equipment manufacturers in order to assist in the design of DFICEs. The EDEM project developed such CFD models and validated them against new experimental data.
DFICEs are relevant to the following, non- exhaustive, list of applications: power generation, cargo ships and tankers, light and heavy-duty trucks, tractors, earth-moving machines and haul trucks. By providing their research findings to the relevant industry and by disseminating their results to the scientific community the EDEM project contributes to the reduction of soot, which is one of the deadliest forms of pollution.
The EDEM consortium trained the recruited ESRs on a range of scientific modules that have broadened their perspectives in both research and transferable skills. The EDEM ESRs developed models and performed experiments resolving processes realised inside fuel injectors for modern DFICE combustion concepts, including cavitation and induced erosion, primary and secondary atomisation of the injected fuels and tabulated chemistry of fuels utilised in DFICEs. More specifically, the work performed addressed the following activities:
1. Measurements utilising optical/laser diagnostics relevant to dual-fuel injection, mixing & combustion. Measurements have been obtained in transparent injectors and dual-fuel engines and have been used for validation of relevant models.
2. Numerical modelling of processes realised at the smallest spatio-temporal flow scales, referred too as direct numerical simulations (DNS) as well as models of the basic chemical reactions during combustion of the relevant fuels utilising tabulated chemistry. These DNS simulations have resolved cavitation-induced erosion in fuel injectors and fuel atomisation.
3. Large Eddy Simulations (LES) as well as Reynolds Averaged Navier Stokes (RANS) modelling of dual-fuel spray mixing and combustion. These models have also resolved processes related to fuel injection and mixing, while the tabulated chemistry models have been utilised to resolve mixing and combustion at engineering/engine scales of dual-fuel engines but at reduced spatio-temporal resolution. This makes them eligible to resolve processes at computational time scales relevant to industry-design times.
The above experimentally validated models have been integrated to numerical frameworks suitable for simulation of industry-relevant fuel injection system and DFICE designs and they have provided insight to the relevant processes. The research findings have been made publicly available in 22 conferences and 12 journal articles and the findings of the EDEM ESRs have been communicated to the non-academic partners of EDEM, as well as to a wide range of global companies, including Wartsila, Siemens Energy, Toyota, Isuzu, MAN B&W, Volvo, Rolls Royce, Lubrizol and BP. The dissemination of the research findings is still ongoing.
1. Measurements utilising optical/laser diagnostics relevant to dual-fuel injection, mixing & combustion. Measurements have been obtained in transparent injectors and dual-fuel engines and have been used for validation of relevant models.
2. Numerical modelling of processes realised at the smallest spatio-temporal flow scales, referred too as direct numerical simulations (DNS) as well as models of the basic chemical reactions during combustion of the relevant fuels utilising tabulated chemistry. These DNS simulations have resolved cavitation-induced erosion in fuel injectors and fuel atomisation.
3. Large Eddy Simulations (LES) as well as Reynolds Averaged Navier Stokes (RANS) modelling of dual-fuel spray mixing and combustion. These models have also resolved processes related to fuel injection and mixing, while the tabulated chemistry models have been utilised to resolve mixing and combustion at engineering/engine scales of dual-fuel engines but at reduced spatio-temporal resolution. This makes them eligible to resolve processes at computational time scales relevant to industry-design times.
The above experimentally validated models have been integrated to numerical frameworks suitable for simulation of industry-relevant fuel injection system and DFICE designs and they have provided insight to the relevant processes. The research findings have been made publicly available in 22 conferences and 12 journal articles and the findings of the EDEM ESRs have been communicated to the non-academic partners of EDEM, as well as to a wide range of global companies, including Wartsila, Siemens Energy, Toyota, Isuzu, MAN B&W, Volvo, Rolls Royce, Lubrizol and BP. The dissemination of the research findings is still ongoing.
Each ESR has progressed the specific scientific topic of his/her PhD beyond the state-of-the-art, as outlined in the corresponding scientific publications and in their PhD Thesis. Overall, EDEM has developed new computational models for the in-nozzle flow, injection and mixing relevant to DFICE engines that were now available before. These have included real-fluid EoS for various fuel mixtures, cavitation erosion and LES models for such mixtures. Moreover, they have performed experiments that provided new experimental data that were not available before and used for validation of the developed models. The scientific findings of EDEM and the developed models have been adopted in commercial CFD tools widely utilised by global industries. These are expected to enhance design processes and over time, result to products that will contribute to reduced emissions and increased efficiency from DFICEs, contributing this way to the decarbonisation strategy of EU.