Fuel Density Distribution Research Articles

Revealing Three-Dimensional Variations in Fuel Structures in Subtropical Forests through Backpack Laser Scanning

Wildfire hazard is a prominent issue in subtropical forests as climate change and extreme drought events increase in frequency. Stand-level fuel load and forest structure are determinants of forest fire occurrence and spread. However, current fuel management often lacks detailed vertical fuel distribution, limiting accurate fire risk assessment and effective fuel policy implementation. In this study, backpack laser scanning (BLS) is used to estimate several 3D structural parameters, including canopy height, crown base height, canopy volume, stand density, vegetation area index (VAI), and vegetation coverage, to characterize the fuel structure characteristics and vertical density distribution variation in different stands of subtropical forests in China. Through standard measurement using BLS point cloud data, we found that canopy height, crown base height, stand density, and VAI in the lower and middle-height strata differed significantly among stand types. Compared to vegetation coverage, the LiDAR-derived VAI can better show significant stratified changes in fuel density in the vertical direction among stand types. Among stand types, conifer-broadleaf mixed forest and C. lanceolata had a higher VAI in surface strata than other stand types, while P. massoniana and conifer-broadleaf mixed forests were particularly unique in having a higher VAI in the lower and middle-height strata, corresponding to the higher surface fuel and ladder fuel in the stand, respectively. To provide more informative support for forest fuel management, BLS LiDAR data combined with other remote sensing data were advocated to facilitate the visualization of fuel density distribution and the development of fire risk assessment.

Limited-view tomography reconstructs fuel density distribution during fusion reactions

Using images of the primary neutron signals, researchers were able to determine the deuterium-tritium fuel density distribution during fusion ignition – an important step for optimizing fusion processes.

Effect of Fuel Distribution on the Onset of Detonation in Gaseous Octane Air Mixture

Formation of detonation waves in a tube is a complex phenomenon and depends upon many factors like ignition energy, presence of a deflagration to detonation transition (DDT) enhancement device and spatial distribution of fuel, etc. In present study, gaseous octane-air mixtures have been examined by varying the equivalence ratio linearly along the axial direction of the detonation tube though the overall stoichiometry was maintained in the tube. Three different conditions have been modelled and studied, which includes small, moderate and large, fuel density gradient in axial direction with equivalence ratio ranging from 1 to 2 near the ignition zone. A series of simulation study have been conducted and the analysis of simulation results reveal that the DDT onset is significantly affected by the initial fuel distribution at the ignition zone as well as on fuel density gradient in a detonation tube. It has been observed thata moderate gradient in the fuel density distribution is favorable for onset of detonations. From the study of pressure plots for above mentioned conditions it has been found that the presence of large gradients in fuel density has adverse effect on the stability of detonation wave.

Development of a Coupled Code for Steady-State Analysis of the Graphite-Moderated Channel Type Molten Salt Reactor

The molten salt reactor (MSR) is one of the six advanced reactor concepts selected by Generation IV International Forum (GIF) because of its inherent safety and the promising capabilities of TRU transmutation and Th-U breeding. In this study, a three-dimensional thermal-hydraulic model (3DTH) is developed for evaluating the steady-state performance of the graphite-moderated channel type MSR. The coupled code is developed by exchanging the power distribution, temperature, and fuel density distribution between SCALE and 3DTH. Firstly, the thermal-hydraulic model of the coupled code is validated by RELAP5 code. Then, the mass flow distribution, temperature field, keff, and power density distribution for a conceptual design of the 2MWt experimental molten salt reactor are calculated and analyzed by the coupled code under both normal operating situation and the central fuel assembly partly blocked situation. The simulated results are conductive to facilitate the understanding of the steady behavior of the graphite-moderated channel type MSR.

Fast ignition of inertial fusion targets by laser-driven carbon beams

Two-dimensional simulations of ion beam driven fast ignition are presented. Ignition energies of protons with Maxwellian spectrum and carbon ions with quasimonoenergetic and Maxwellian energy distributions are evaluated. The effect of the coronal plasma surrounding the compressed deuterium-tritium is studied for three different fuel density distributions. It is found that quasimonoenergetic ions have better coupling with the compressed deuterium-tritium and substantially lower ignition energies. Comparison of quasimonoenergetic carbon ions and relativistic electrons as ignitor beams shows similar laser energy requirements, provided that a laser to quasimonoenergetic carbon ion conversion efficiency around 10% can be achieved.

Flat flux in a slab reactor with natural uranium

On the basis of two-group theory as non-linear differential equation for fuel distribution is formulated which generates a flat thermal flux in a slab reactor with resonance escape probability depending on the density of fuel. An iterative procedure for solving this equation is described which was employed for numerical calculation of fuel density distribution in a homogeneous slab reactor with D 2O and natural uranium.