Micro-scale Catalytic Ignition And Combustion Of N-Butane

In recent decades, the trend of device miniaturization has led to a rapid growth inthe demand for high energy density power sources. The weight specific energy ofhydrocarbons is two orders higher than that of conventional chemical power sources. So,miniaturized energy conversion from hydrocarbon fuels to electricity through acombustion-based thermoelectric system is one of reasonable paths to expectedalternative battery with high energy density. n-Butane is a kind of liquid-gas fuel and iseasily to be storage because of its low liquefaction pressure (only0.21Mpa). And thecatalytic combustion of n-butane can be stable at very low temperature. Theseadvantages make n-butane be favorable for micro power source based onmicro-combustion. However, it is lack of studies on the micro-combustion of n-butane.Therefore characteristics of micro-scale catalytic ignition and combustion of n-butaneare studied in this work. The main work and conclusions of this thesis can besummarized as follows:Firstly, the effects of catalyst Pt on the pyrolysis and combustion of n-butane werestudied in a Pt-coated monolith catalytic reactor with external heating. The comparisonbetween experiments with and without Pt under various temperatures indicates that Pthas no effect on the pyrolysis of n-butane, but can strengthen the combustion ofn-butane under low temperature. Catalytic ignition temperatures of n-butane undervarious equivalence ratio and Reynolds number were measured. The results indicate thatthe catalytic ignition temperature of n-butane is obviously lower than the gas phaseignition temperature.Secondly, characteristics of hydrogen-assisted ignition of n-butane were studied ina Pt-coated monolith catalytic reactor. Hydrogen-assisted catalytic ignition can start thereaction of n-butane/air mixtures under room temperature, and cancel the ignitor orother device for ignition. The results of experiments and numerical simulations indicatethat, during the hydrogen-assisted ignition process, hydrogen has not only thermal effectof heating the mixture, but also chemical effect of lowering the catalytic ignitiontemperature of n-butane. Simulation manifests that the surface coverage before theignition of n-butane is changed since the hydrogen catalytic combustion. In this part of work, effects of hydrogen fraction, startup method and thermal insulation onhydrogen-assisted catalytic ignition were discussed.Then, a catalytic Swiss-roll combustor with0.9mm character length wasfabricated. Stable combustion was achieved by placing a Pt-coated porous ceramics inthe chamber. In this part of work, hydrogen-assisted ignition was employed in thecomplex combustor, and the ignitor was cancelled.At last, for improving the combustor performance and enlarge the flammable range,two combustor improvement methods were studied: adjusting catalyst arrangement andhydrogen addition combustion. Results of experiments indicates that, improvement ofcatalyst arrangement can improve the combustor performance to a certain extent, but thelower limits are not lowered to the fule-lean condition; hydrogen addition can notableenlarge the n-butane flammable range, especially the lower limits can be lower than thecondition that equivalence ratio is0.5. Thus, the utilization of fuel increases remarkably.Analysis on exhaust gases shows that the conversion of n-butane increase with theimprovement of catalyst arrangement or the hydrogen addition.