combustion characteristics of non-premixed hydrogen micro-jet flame and the influence of bluff body to its extinction limits

Abstract

In this chapter, the simulation results Micro-scale combustion of hydrogen flame in co-flow air are presented. First of all, a validation of maximum flame temperature ranges is performed Using ANSYS program depending on corresponding fuel velocity. Then, a validation of the computed OH concentration of the hydrogen jet diffusion flame, flame height variation obtained at different fuel flow velocities are performed and compared with those obtained experimentally by Jing Zhang. A Study on the effect of a bluff body on the extinction limits of combustion was investigated Using CHEMKIN program, studies are done Using ANSYS18.2 packages to simulate combustion characteristics over these micro reactors. 4.1.1 Validation of ANSYS (Fluent &CFX)

A full scale investigates the s thermal and chemical structure of diffusion flames of laminar hydrogen was performed utilizing nonintrusive UV Raman dissipating combined with the pre- dissociative laser-actuated fluorescence (LIPF) to study the temperature, major species concentrations (O2, N2, H2O, H2) and (OH) radical concentrations. The experiment carried out here was used in testing the validity of ANSYS (Version 18) for modeling laminar hydrogen diffusion flame

4.1.1.1 Experiment layout

With A stainless steel chamber used as the main body, Air stream was fed into a rectangular quartz tube, connected with the stainless-steel chamber. Dimensions of the quartz tube were 10 x 10 cm2, and a wall thickness of 4 mm. air flow uniform velocity was achieved by ceramic beads installed in the camber. The fuel was supplied by a stainless-steel tube, at the chamber center, whose Dimensions were (inner diameter (d) of 800 µm and a thickness of 200 µm).

4.1.1.2 Instruments used by Zhang

The visible flame images were taken using a single lens camera (Nikon 80D) with a macro lens. Adopting a long exposure time (30 s) to take a clear flame image

The distribution of OH was also captured by induced fluorescence planar laser technique (OH- PLIF) based on a ( LaVision) LIF system. The laser system consists of an Nd:YAG laser (Quanta-Ray Pro-230), wavelength of 355 nm, 10 Hz with 10 ns pulse duration and a dye laser (Sirah PSCAN-G-30) with a doubler frequency to excite the Q1(8) line of the A2S)X2P(1, 0) bands of OH at the exact excitation wavelength. The laser make it through the energy monitor and sheet optics to product a laser sheet. Thickness of the laser sheet was not more than 100 mm and the laser height were roughly 60 mm at the location of the flame. The OH fluorescence