Combustion

Poinsot, Thiérry; Veynante, Denis

doi:10.1002/9781119176817.ecm2067

Cited by 20 publications

(25 citation statements)

References 105 publications

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“…where h s,k is the specific enthalpy of the k th species, p the pressure, τ ki the viscous shear stress, ẇT = | ẇF |H the source term originating from heat release (due to combustion henceforth referred to the heat release rate) with H being the heating value of the fuel, 53 and e = C V T + u k u k / 2 the specific stagnation internal energy. For the current analysis the term…”

Section: Mathematical Backgroundmentioning

confidence: 99%

Effects of fuel Lewis number on the minimum ignition energy and its transition for turbulent homogeneous fuel–air mixtures

Papapostolou

Chakraborty

2023

International Journal of Spray and Combustion Dynamics

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The effects of fuel Lewis number on the minimum ignition energy (MIE) requirements for ensuring successful thermal runaway, and self-sustained flame propagation have been analysed for forced ignition of homogeneous fuel–air mixtures under decaying turbulence for a wide range of initial turbulence intensities using three-dimensional direct numerical simulations. The minimum energy demand for ensuring self-sustained flame propagation has been found to be greater than that for ensuring only thermal runaway irrespective of its outcome for large turbulence intensities, and the minimum ignition energy increases with increasing rms turbulent velocity irrespective of the fuel Lewis number. The MIE values have been found to increase more sharply with increasing turbulence intensity beyond a critical value for all fuel Lewis numbers considered here. The variations of the normalised MIE (MIE normalised by its laminar value) with increasing turbulence intensity beyond the critical point follow a power-law and the power-law exponent has been found to increase with an increase in fuel Lewis number. This behaviour has been explained using a scaling analysis. The stochasticity associated with forced ignition has been demonstrated by using different realisations of statistically similar turbulent flow fields for the energy inputs corresponding to the MIE and successful outcomes are obtained in most instances, justifying the evaluation of the MIE values in this analysis.

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Section: Mathematical Backgroundmentioning

confidence: 99%

Effects of fuel Lewis number on the minimum ignition energy and its transition for turbulent homogeneous fuel–air mixtures

Papapostolou

Chakraborty

2023

International Journal of Spray and Combustion Dynamics

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“…The EDM was introduced by Magnussen and Hjertager ( 12 , 28 ) . It assumes that fuel and oxidiser are carried by separate eddies in diffusion flames.…”

Section: Numerical Modelling Of Scramjetsmentioning

confidence: 99%

“…In the above equation, s is the mass stoichiometric ratio defined as and equals 8 for H 2 –air combustion ( 28 ) , W s is the molar mass in kg/mol and is the mass fraction. In Equation (6), β * is a turbulence model constant with a value of 0.09 and ω (1/s) is the specific dissipation of turbulent kinetic energy obtained through the turbulence model.…”

Section: Numerical Modelling Of Scramjetsmentioning

confidence: 99%

Characterisation of the eddy dissipation model for the analysis of hydrogen-fuelled scramjets

et al. 2019

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The eddy dissipation model (EDM) is analysed with respect to the ability to address the turbulence–combustion interaction process inside hydrogen-fuelled scramjet engines designed to operate at high Mach numbers (≈7–12). The aim is to identify the most appropriate strategy for the use of the model and the calibration of the modelling constants for future design purposes. To this end, three hydrogen-fuelled experimental scramjet configurations with different fuel injection approaches are studied numerically. The first case consists of parallel fuel injection and it is shown that relying on estimates of ignition delay from a 1D kinetics program can greatly improve the effectiveness of the EDM. This was achieved through a proposed zonal approach. The second case considers fuel injection behind a strut. Here the EDM predicts two reacting layers along the domain which is in agreement with experimental temperature profiles close to the point of injection but not the case any more at the downstream end of the test section. The first two scramjet test cases demonstrated that the kinetic limit, which can be applied to the EDM, does not improve the predictions in comparison to experimental data. The last case considered a transverse injection of hydrogen and the EDM approach provided overall good agreement with experimental pressure traces except in the vicinity of the injection location. The EDM appears to be a suitable tool for scramjet combustor analysis incorporating different fuel injection mechanisms with hydrogen. More specifically, the considered test cases demonstrate that the model provides reasonable predictions of pressure, velocity, temperature and composition.

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“…All experiments investigation was founded on the basis of authors [6][7][8][9][10][11][12][13]. Two pellet boilers of different manufacturers of the same heating power (40 kW), equipped with a horizontally feed burners were used to perform the measurements in the present study.…”

Section: Experiments Datamentioning

confidence: 99%

Influence of burner form and pellet type on domestic pellet boiler performance

Rastvorov

Осинцев

Toropov

2017

IOP Conf. Ser.: Earth Environ. Sci.

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Abstract. The study presents combustion and emission results obtained using two serial pellet boilers of the same heating capacity 40 kW. These boilers have been designed by producers for domestic conditions of exploitation. The principal difference between boilers was the type of the burner. The study concerns the efficiency and ecological performance difference between burners of circular and rectangular forms. The features of the combustion process in both types of burners were studied when boiler operated with different sorts of pellets. The results suggest that the burner of circular form excels the rectangular form burner. However, there is some difference of NO x emission between circular and rectangular burners. IntroductionAt present day many economical, technical, ecological, as well as political reasons motivate firms and homeowners to use their own autonomous, independent of central heating pipeline and gas pipeline heat energy sources. The causes of such choice usually are striving for independence of the heat supplying organization pricing policy, avoidance of bureaucratic apparatus cooperation with (in questions of tariff agreement, the correspondence heating pipeline and gas pipeline connection standards, payment for extra project documentation necessary for central pipeline connection), unwillingness to bear expenses for the heat energy losses in a long and, sometimes, not of perfect quality heating pipeline from a relatively distant central heating source. A diesel fuel boiler, a wood boiler, a coal boiler, a heat pump may be used as independent heat energy source, when it is technically possible. A boiler with biomass and a boiler with granules can also be used. The use of boilers with fuel manual load with relatively big heat power is complicated by the need of heavy manual work. Diesel fuel heating is appreciably more expensive that all others named above and causes serious air pollution. The heat pump for relatively big heat power requires sufficiently big electrical power; a pellet or ground biomass boiler is the most suitable option for such decision.In the last 15-20 years pellet boilers have gained serious popularity in Russia and the EU countries and the number of sold pellet boilers keeps growing. The high prevalence of such heat energy sources is reached thanks to several certain factors: easiness of automatization of the fuel feeding process owing to the standardized size of pellets; easy ash removal that can be automatic or manual, because the pellets ash content seldom exceeds 4 %. The exception is pellets made of straw with the ash content from 7 to 10 percent; compactness of all equipment as compared with unstandardized solid fuel boilers; accessibility of pellets in the market, reasonable price for domestic use. In all pellet boilers the fuel-bed firing technology is used. However, prevailing burner and feeding systems in the EU countries and Russia are different.

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Combustion

Cited by 20 publications

References 105 publications

Effects of fuel Lewis number on the minimum ignition energy and its transition for turbulent homogeneous fuel–air mixtures

Effects of fuel Lewis number on the minimum ignition energy and its transition for turbulent homogeneous fuel–air mixtures

Characterisation of the eddy dissipation model for the analysis of hydrogen-fuelled scramjets

Influence of burner form and pellet type on domestic pellet boiler performance

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