Evaluating Ignition and Combustion Performance with Al-Metal- Organic Frameworks and Nano-Aluminum in HTPB Fuel

Incorporating aluminum metal-organic frameworks(Al-MOFs)as energetic additives for solid fuels presents a promising avenue for enhancing combustion performance.This study explores the potential benefits of Al-MOF(MIL-53(Al))energetic additive on the combustion performance of hydroxyl-terminated polybutadiene(HTPB)fuel.The HTPB-MOF fuel samples were manufactured using the vacuum-casting technique,followed by a comprehensive evaluation of their ignition and combustion properties using an opposed flow burner(OFB)setup utilizing gaseous oxygen as an oxidizer.To gauge the effectiveness of Al-MOFs as fuel additives,their impact is compared with that of nano-aluminum(nAl),another traditional additive in HTPB fuel.The results indicate that the addition of 15%(mass fraction)nAl into HTPB resulted in the shortest ignition delay time(136 ms),demonstrating improved ignition performance compared to pure HTPB(273 ms).The incorporation of Al-MOF in HTPB also reduced ignition delay times to 227 ms and 189 ms,respectively.Moreover,under high oxidizer mass flux conditions(79—81 kg/(m^(2)s)),HTPB fuel with 15%nAl exhibited a substantial 83.2%increase in regression rate compared to the baseline HTPB fuel,highlighting the positive influence of nAl on combustion behavior.In contrast,HTPB-MOF with a 15%Al-MOF additive showed a 32.7%increase in regression rate compared to pure HTPB.These results suggest that HTPB-nAl outperforms HTPB-MOF in terms of regression rates,indicating a more vigorous and rapid burning behavior.

Heat Transfer and Energy Analysis of a Pusher Type Reheating Furnace Using Oxygen Enhanced Air for Combustion

Oxy-fuel firing is more energy efficient and environmental friendly than conventional air-fuel firing and its application to reheating furnaces has begun since 1990s. A computational method was presented to predict the steady heat transfer to the billets and temperature distribution in a continuous pusher type reheating furnace in which combustion air was enhanced by oxygen. Radiation heat flux calculated from the radiation heat exchange within the furnace was modeled using the FVM considering the effects of furnace walls and billets. Energy consumption per ton of steel, production rate and thermal efficiency of furnace, and trend of NOx emission in various levels of oxygen enrichment were investigated by comparing with baseline furnace （21% of O2 in air）. The results showed that the best range of oxygen enrichments was between 21% and 45% by volume, as the higher slope of flame temperature and production increase occur in this range. The reduction of energy consumption can be obtained up to 18% per ton of steel for oxygen enrichment of 60 % by volume.

Experimental investigation for temperature and emissivity by flame emission spectrum in a cavity of rocket based combined cycle combustor chamber

Flame temperature and spectral emissivity were the important parameters characterizing the sufficient degree of fuel combustion and the particle radiative characteristics in the Rocket Based Combined Cycle(RBCC)combustor.To investigate the combustion characteristics of the complex supersonic flame in the RBCC combustor,a new radiation thermometry combined with Levenberg-Marquardt(LM)algorithm and the least squares method was proposed to measure the temperature,emissivity and spectral radiative properties based on the flame emission spectrum.In-situ measurements of the flame temperature,emissivity and spectral radiative properties were carried out in the RBCC direct-connected test bench with laser-induced plasma combustion enhancement(LIPCE)and without LIPCE.The flame average temperatures at fuel global equivalence ratio(a)of 1.0b and 0.6 with LIPCE were 4.51%and 2.08%higher than those without LIPCE.The flame combustion oscillation of kerosene tended to be stable in the recirculation zone of cavity with the thermal and chemical effects of laser induced plasma.The differences of flame temperature at a=1.0b and 0.6 were 503 K and 523 K with LIPCE,which were 20.07%and42.64%lower than those without LIPCE.The flame emissivity with methane assisted ignition was 80.46%lower than that without methane assisted ignition,due to the carbon-hydrogen ratio of kerosene was higher than that of methane.The spectral emissivities at 600 nm with LIPCE were 1.25%,22.2%,and 4.22%lower than those without LIPCE at a=1.0a(with methane assisted ignition),1.0b(without methane assisted ignition)and 0.6.The effect of concentration in the emissivity was removed by normalization to analyze the flame radiative properties in the RBCC combustor chamber.The maximum differences of flame normalized emissivity were 50.91%without LIPCE and 27.53%with LIPCE.The flame radiative properties were stabilized under the thermal and chemical effects of laser induced plasma at a=0.6.

Enhancements of Impinging Flame by Pulsation

Experimental investigations on the pulsating jet-impinging diffusion flame were executed. A solenoid valve was aligned upstream of tile jet orifice and the methane fuel was controlled in open-closed cycles from 0 Hz to 20 Hz. Results show that the open-closed cycles indeed increase the fluctuations of the methane fuel obviously. The evolutions of pulsating flame therefore develop faster than the continuous impinging flame. The optimized pulsating frequencies are near 9 to 11 Hz from the Re = 170 to 283. The temperature differences between that under optimized pulsating rate and full open condition (no pulsation) are ranging from 100 to 150 degree. The pulsating effect is more significant at low Reynolds number. The cross section of continuous impinging flame behaves as elliptic shape with axial ratio equals to 2/3. The tip of the impinging flame obviously crosses at 42 mm above the impinging point. Because of the phenomenon of pulsation flame, the flame sheet or flame front may not be identified clearly in the averaged temperature contours. Results show that the averaged end-contour of pulsation flame rears at 38 mm above the impinging point. By observation and experiment, the pulsating flame behaves more stable and efficient than the continuous impinging flame.