Periodic Reporting for period 1 - EDEM (Experimentally Validated DNS and LES Approaches for Fuel Injection, Mixing and Combustion of Dual-Fuel Engines)
Berichtszeitraum: 2019-09-01 bis 2021-08-31
The constantly increasing energy needs associated with the expansion of urbanisation, population growth and the ever increasingly (road and maritime) transportation needs are/will be met by heavy-duty Diesel internal combustion engines (ICE), for which no foreseen electrification strategy is in place. Despite the immense reduction achieved, soot is one of the deadliest forms of air pollution: such particles inhaled at city centres, are linked to serious health effects, including premature death, heart attacks and strokes, as well as acute bronchitis and aggravated asthma among children. To mitigate the inevitable environmental/health effects, partial substitution of conventional Diesel engines by high-octane liquid or gaseous fuel with lower carbon-to-hydrogen ratio represents the only practical and imminent solution. The so-called dual-fuel internal combustion engines (DFICE) primarily burn a premixed high-octane fuel/air mixture, with a moderate quantity of pilot high-cetane fuel employed only as an ignition agent. DFICE 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.
Utilisation of suitable primary/pilot fuel mixtures enables engine operation to be in compliance with the strictest automotive emissions legislation imposed globally, e.g. EURO VI or Tier IV standards, in Europe and in the US, respectively, as well as with the Tier III limit of the International Maritime Organization (IMO) that dictates further reduction of NOx emitted by marine engines. Utilisation of a high-octane fuel or hydrogen produces virtually no soot. Moreover, it assists the oxidation of soot formed due to the liquid-fuel combustion. The margin for emissions reduction from DFICE has been found to be significant and lying in the range of 20-80% for NOx/PM emissions and 10-50% for CO2 (depending on the degree of biofuel/hydrogen utilisation) without significant penalty in their performance compared to conventional operation.
The high auto-ignition temperature of gaseous fuels requires injection of Diesel fuel as pilot necessary to initiate combustion. Hence, the principle of DFICE operation poses new challenges for the design of injectors that must be capable of handling Diesel fuel in the, so called, ballistic mode, where short injection duration under high pressure must be accomplished. Referring to gaseous fuels, natural gas and hydrogen are widely employed candidates to serve as primary fuels in DFICE. The concept, however, could be extended to an ‘Octane on Demand’ principle, i.e. using the octane number of the primary fuel as a designating factor of the combustion characteristics.
The objectives of the EDEM project are the following:
• OB-1: To obtain measurements in transparent injectors and dual-fuel engines that will guide the development of relevant models.
• OB-2: To perform DNS simulations and develop new physical models suitable for cavitation- induced erosion, primary and secondary atomisation, and tabulated chemistry of dual-fuel engines.
• OB-3: To develop new LES models for fuel injection, mixing and combustion in DFICE, aiming towards the development of new concepts for utilisation of a variety of fuel mixtures.
• OB-4: To develop models assisting the industrial partners in the design of novel DFICE concepts.
• OB-5: To undertake a training programme for the recruited fellows, which covers: individual personalised research projects that lead to their PhDs; specialised training courses offered by the participating institutions; network-wide training activities in the format of seminar, workshop, conference and summer school and knowledge exchange with the members of the network through activities such as secondments.
• OB-6: To manage the proposed programme according to the guidelines of the MCSA actions, including a dissemination and outreach activities plan, aiming to inform the scientific community, industry, and general public of the findings of the network and the benefits of the developed technologies for meeting the C02 and emission directives and for their impact at global environmental, social and economic scales.
Utilisation of suitable primary/pilot fuel mixtures enables engine operation to be in compliance with the strictest automotive emissions legislation imposed globally, e.g. EURO VI or Tier IV standards, in Europe and in the US, respectively, as well as with the Tier III limit of the International Maritime Organization (IMO) that dictates further reduction of NOx emitted by marine engines. Utilisation of a high-octane fuel or hydrogen produces virtually no soot. Moreover, it assists the oxidation of soot formed due to the liquid-fuel combustion. The margin for emissions reduction from DFICE has been found to be significant and lying in the range of 20-80% for NOx/PM emissions and 10-50% for CO2 (depending on the degree of biofuel/hydrogen utilisation) without significant penalty in their performance compared to conventional operation.
The high auto-ignition temperature of gaseous fuels requires injection of Diesel fuel as pilot necessary to initiate combustion. Hence, the principle of DFICE operation poses new challenges for the design of injectors that must be capable of handling Diesel fuel in the, so called, ballistic mode, where short injection duration under high pressure must be accomplished. Referring to gaseous fuels, natural gas and hydrogen are widely employed candidates to serve as primary fuels in DFICE. The concept, however, could be extended to an ‘Octane on Demand’ principle, i.e. using the octane number of the primary fuel as a designating factor of the combustion characteristics.
The objectives of the EDEM project are the following:
• OB-1: To obtain measurements in transparent injectors and dual-fuel engines that will guide the development of relevant models.
• OB-2: To perform DNS simulations and develop new physical models suitable for cavitation- induced erosion, primary and secondary atomisation, and tabulated chemistry of dual-fuel engines.
• OB-3: To develop new LES models for fuel injection, mixing and combustion in DFICE, aiming towards the development of new concepts for utilisation of a variety of fuel mixtures.
• OB-4: To develop models assisting the industrial partners in the design of novel DFICE concepts.
• OB-5: To undertake a training programme for the recruited fellows, which covers: individual personalised research projects that lead to their PhDs; specialised training courses offered by the participating institutions; network-wide training activities in the format of seminar, workshop, conference and summer school and knowledge exchange with the members of the network through activities such as secondments.
• OB-6: To manage the proposed programme according to the guidelines of the MCSA actions, including a dissemination and outreach activities plan, aiming to inform the scientific community, industry, and general public of the findings of the network and the benefits of the developed technologies for meeting the C02 and emission directives and for their impact at global environmental, social and economic scales.
In the first 24 months of the project’s life span, the EDEM consortium has trained the recruited ESRs on a range of unique scientific modules that have broadened their perspectives in both research and classical engineering skills. Equally important, the ESRs have been trained on a range of transferable skills, have started disseminating the work performed and have been engaged to outreach activities.
With regards to the research conducted, experimental facilities have been prepared to record the dual fuel combustion images and multiphase flow. The first recordings for dual fuel combustion without external illumination have already been recorded, and qualitative and quantitative high-speed measurements within the injector orifice and the spray region have been already performed. Some high-resolution simulations related to primary breakup have been tested; highly resolved simulations of n-dodecane liquid droplet phase change have been performed for different ambient temperatures and pressure conditions; 1D dual fuel stratification cases have been simulated with the existing IFPEN combustion model.
With regards to the research conducted, experimental facilities have been prepared to record the dual fuel combustion images and multiphase flow. The first recordings for dual fuel combustion without external illumination have already been recorded, and qualitative and quantitative high-speed measurements within the injector orifice and the spray region have been already performed. Some high-resolution simulations related to primary breakup have been tested; highly resolved simulations of n-dodecane liquid droplet phase change have been performed for different ambient temperatures and pressure conditions; 1D dual fuel stratification cases have been simulated with the existing IFPEN combustion model.
Computational fluid dynamics (CFD) models have been long utilised for the design of efficient ICE. However, existing models fail to predict processes where a variety of fuel mixtures are injected and combust simultaneously. This is due to simplifications made for the mixing, phase- change and combustion, which all are happening at scales not resolved by the grid resolution and require sub-grid scale physical modelling. EDEM is aiming to develop such models, which in turn will be utilised by engine and FIE manufacturers for the design of DFICE.