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Current swirl combustion technology with faulty coal lacks flexibility for peak shaving without aids, necessitating a novel low–load stable combustion technology. This paper presented such a technology, developed from gas–particle experiments, that did not require major modifications to the burner secondary air structure. The new technology was applied to a low NO x axial swirl burner (LNASB) in a 350 MW boiler and a vortex swirl burner (VSB) in a 700 MW boiler. Comparative analysis at 20 % boiler load showed both prototypes lacked recirculation zones, characterized by high primary air axial velocities and low turbulence intensity. After modification, LNASB became stable combustion LNASB (SLNSB), and VSB became stable combustion VSB (SVSB). SLNASB had a central recirculation zone, while SVSB had a large annular recirculation zone. The relative length and diameter of SLNASB's recirculation zone were 0.7 and 0.472, while for SVSB, they were 1.5 and 0.477. LNASB had a diffusion angle of 4.7° and a swirl number of 0.511; SLNASB had 29.7° and 0.695; VSB had 11.4° and 0.445; SVSB had 33.3° and 0.784. The turbulence intensity of SLNASB and SVSB were notably higher than their prototypes. High–concentration particles accumulated at the center of SLNASB and SVSB, then entered the recirculation zone. • A universal low–load stable combustion technology has been developed. • New technology significantly reduces both modification and operational costs. • Combining swirling primary air with blunt body is not ideal for low–load. • Post–modification, new burner can operate stably at a 20 % boiler load. [ABSTRACT FROM AUTHOR]

There is growing interest in combustion-driven thermophotovolataic (TPV) power generation. Previous investigations have shown that inadequate conversion of fuel energy to photon-convertible radiation restrained combustion-driven TPV power systems from achieving high efficiency. In this paper, A TPV power system integrating a composite radiant burner and cells with different low bandgaps was proposed and constructed. The composite radiant burner consists of two thermal radiators in tandem. They emit two streams of radiation. GaSb cells and InGaAsSb cells were installed in the TPV power system, and were illuminated by the two radiators, respectively. The radiations were matched correspondingly to the sensitivities of GaSb and InGaAsSb cells. The combustion performance of the composite radiant burner and the electric output characteristics of the TPV cells in the integrated natural gas-fired TPV system were investigated under various conditions. The proposed cascaded utilization of heat released during the combustion and the effective thermal management successfully increased the TPV system efficiency. [ABSTRACT FROM AUTHOR]

This paper investigates the geometric parameters related to thermal efficiency and pollution emission of a multi-hole flat flame burner. Recent experimental studies indicate that such burners are significantly influenced by both the use of distribution mesh and the size of the diameter of the main and retention holes. The present study numerically simulated methane-air premixed combustion using a two-step mechanism and constant mass diffusivity for all species. The results indicate that the addition of distribution mesh leads to uniform flow and maximum temperature that will reduce NOx emissions. An increase in the diameter of the main holes increased the mass flow which increased the temperature, thermal efficiency and NOx emissions. The size of the retention holes should be considered to decrease the total flow velocity and bring the flame closer to the burner surface, although a diameter change did not considerably improve temperature and thermal efficiency. Ultimately, under temperature and pollutant emission constraints, the optimum diameters of the main and retention holes were determined to be 5 and 1.25 mm, respectively. [ABSTRACT FROM AUTHOR]

In this paper we report an experimental investigation of the dynamical features of a propagating partially premixed flame established on a concentric coflow burner. The variation regulation about the propagation and structure characteristics in different inflow condition is analyzed basing on high-speed photography. The results show that 1)In condition of large center jet velocity, transition from turbulent to laminar combustion is exhibited in the process of attaching, reverse transition is observed in the process of blowing out. 2)A stronger rich-premixed center flow mainly enhances the flame propagation in an attaching flame and the local flow velocity in a blowing out flame. 3)The displacement of the flame base and tip accounts for the major change and small-scale oscillation in the flame length, respectively. 4)The flicker of the flame slacks when the propagation state transitions to lifted-off or blowing out from attaching. [ABSTRACT FROM AUTHOR]

Abstract: Combustion of pulverized coal in oxy-combustion technology is one of the effective ways to reduce the emission of greenhouse gases into the atmosphere. The process of transition from conventional combustion in air to the oxy-combustion technology, however, requires a thorough investigations of the phenomena occurring during the combustion process, that can be greatly supported by numerical modeling. The paper presents the results of numerical simulations of pulverized coal combustion process in swirl burner using RANS (Reynolds-averaged Navier–Stokes equations) and LES (large Eddy simulation) methods for turbulent flow. Numerical simulations have been performed for the oxyfuel test facility located at the Institute of Heat and Mass Transfer at RWTH Aachen University. Detailed analysis of the flow field inside the combustion chamber for cold flow and for the flow with combustion using different numerical methods for turbulent flows have been done. Comparison of the air and oxy-coal combustion process for pulverized coal shows significant differences in temperature, especially close to the burner exit. Additionally the influence of the combustion model on the results has been shown for oxy-combustion test case. [Copyright &y& Elsevier]