References of "LYBAERT, Paul"
     in
Bookmark and Share    
Peer Reviewed
See detailFeasibility study of the diluted combustion in a domestic heating boiler
SEGGIO, Giovanni; Ngendakumana, Philippe ULg; PESENTI, Barbara et al

in 4th European Combustion Meeting (ECM2009) (2009, April)

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The principle of this type of ... [more ▼]

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The principle of this type of combustion consists in providing a high level of dilution of the reactants with flue gases before combustion reaction occurs, to get a slower reaction in a much larger volume than in classical combustion. The resulting lower local heat release leads to a more homogeneous temperature field in the furnace, without peak values responsible of high thermal NOx formation. There are two requirements for working in diluted combustion: the dilution level of reactants by the flue gases has to be high enough and the temperature level in the combustion chamber has to be above a threshold (the auto-ignition temperature of the mixture). The aim of this work is to assess the technical feasibility and highlight the specific problems of application of diluted combustion in a medium scale boiler. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber. That prevents from getting the minimum level of reactants dilution and temperature needed to reach diluted combustion regime. The idea is to use a natural gas jet-burner (to preheat the combustion chamber) along with a secondary gas injector in order to get a high entrainment of the flue gases by the reactant jets. In fact the air (through the jet-burner) and the gas (through the secondary gas injector) are injected separately in order to get a high dilution of the reactants and a mixture temperature above the auto-ignition threshold. Our test bench consists in a Viessmann hot water boiler whose nominal output power is 370 kW. The combustion chamber of this boiler is cylindrical (length = 1.41 m, diameter = 0.56 m) and is water-cooled. A preliminary CFD study (Fluent ®) has first been performed to select on the market a jet burner and to determine the position of the air and gas injectors able to generate the requirements of diluted combustion. The influence of the operating conditions (firing rate and excess air) has also been studied numerically. The simulation results show the possibility to obtain a temperature field quite homogenous (typical of diluted combustion) but with a light increase of the CO level at the exit of the combustion chamber. These numerical results (obtained with a simple combustion model) have to be validated experimentally. A first experimental study has been carried out in classical combustion on the boiler equipped with the selected jet-burner. The temperature field has been measured in the median plane of the combustion chamber for different excess air and firing rate. These measurements allowed us to verify that the preheating obtained with the jet-burner was important enough for getting a temperature level above the auto-ignition temperature near everywhere in the combustion chamber. A second experimental study in diluted combustion on the combustion chamber equipped with the secondary gas injector will allow the validation the corresponding numerical results. [less ▲]

Detailed reference viewed: 64 (4 ULg)
Peer Reviewed
See detailFeasibility study of the diluted combustion in a semi-industrial boiler at low temperatures
SEGGIO, Giovanni; PESENTI, Barbara; LYBAERT, Paul et al

in 8th European Conference on Industrial Furnaces and Boilers (2008, March)

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess ... [more ▼]

The diluted combustion (called also flameless oxidation) has been already applied in furnaces technology to get high process thermal efficiency with low NOx emissions. The aim of this work is to assess the technical feasibility and highlight the specific problems of application of diluted combustion in a medium scale boiler. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which could prevent from getting the minimum level of reactants dilution and temperature needed to reach diluted combustion regime. The idea is to perform direct injection of the air and the gas in the combustion chamber in order to get a high dilution of the reactants and a mixture temperature above the auto-ignition threshold. Our test bench consists in a Viessmann hot water boiler whose nominal output power is 370 kW. The combustion chamber of this boiler is cylindrical (length = 1.41 m, diameter = 0.56 m) and is watercooled. A preliminary CFD study (Fluent ®) has first been performed to select on the market a jet burner (to be used for the preheating of the combustion chamber) and to determine the position of the air and gas injectors able to generate the requirements of diluted combustion. The selected burner has been purchased and fitted on the boiler. Then, the boiler-burner set has been characterized experimentally in normal combustion regime in order to adapt the boundary conditions to the heat balance. The temperature and the CO concentration will be measured in several locations in the combustion chamber at different firing rate and air excess. In short, the selected burner provides as expected the required preheating and the generated flame doesn’t impact the bottom of the combustion chamber. The results obtained experimentally confirm the simulation results in normal combustion regime. The last part of this work will consist in the determination of the feasibility of the diluted combustion in this boiler. [less ▲]

Detailed reference viewed: 43 (0 ULg)
See detailFeasibility study of the diluted combustion in a semi-industrial boiler at low temperatures
Seggio, Giovanni; Ngendakumana, Philippe ULg; Pesenti, Barbara et al

Conference (2007, September)

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main ... [more ▼]

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which prevents from getting the minimum level of reactants dilution and temperature needed to reach mild combustion regime. Last year, a preliminary CFD study was performed to select a jet burner and secondary gas injector able to generate sufficient dilution and temperature of the air and gas jets before they meet in the combustion chamber of the boiler. In this work, the optimization of the position and the diameter of the gas injector has been performed. Finally, the boundary conditions and the parameters of the combustion model have been investigated. [less ▲]

Detailed reference viewed: 15 (5 ULg)
See detailFeasibility study of the diluted combustion in a semi-industrial domestic heating boiler at low temperatures
SEGGIO, Giovanni; Ngendakumana, Philippe ULg; PESENTI, Barbara et al

Conference (2006, August)

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main ... [more ▼]

The aim of this work is to assess the technical feasibility and highlight the specific problem of application of diluted (or mild) combustion in a medium scale boiler by direct gas injection. The main difficulty is due to the high geometrical confinement and heat losses of a typical boiler combustion chamber, which prevents from getting the minimum level of reactants dilution and temperature needed to reach mild combustion regime. In this work, a preliminary CFD study has been performed to select a jet burner and secondary gas injector able to generate sufficient dilution and temperature of the air and gas jets before they meet in the combustion chamber of the boiler. [less ▲]

Detailed reference viewed: 13 (2 ULg)