【作者】 翟明；

【导师】 夏新林； 董芃；

【作者基本信息】 哈尔滨工业大学 ， 动力工程及工程热物理， 2010， 博士

【摘要】 脉动燃烧作为一种先进的燃烧方式具有燃烧效率高、低污染排放等优点。然而脉动燃烧机理复杂,传统的Helmholtz型机械阀或气动阀脉动燃烧器由于受到其自吸供气方式的限制,其热负荷低、调节范围窄,这也成为该设备大型化的主要瓶颈。本文提出了Helmholtz型无阀自激脉动燃烧器的设计思想,采用连续强制供气方式,直接利用燃烧器的声学结构产生脉动燃烧,具有自主调节平衡压力,运行可靠性强,容积热负荷高,负荷调节范围宽,并可实现大功率化等优点。本文以Helmholtz型无阀自激脉动燃烧器为研究对象,对燃烧器的频率特性、压力特性、传热特性、运行稳定性及调节方法进行了实验研究和理论分析,得到如下研究结果:(1)研制了Helmholtz型无阀自激燃气脉动燃烧器实验系统,通过连续供气、供燃料的方式,直接利用燃烧器的Helmholtz型共振声学结构来实现脉动燃烧,可自主调节燃烧器的热负荷。实验运行结果表明本文设计的Helmholtz型无阀自激燃气脉动燃烧器不仅能够产生稳定的脉动燃烧,且脉动的压力幅度明显高于相同条件下的传统Helmholtz型脉动燃烧器。(2)对上述Helmholtz型无阀自激脉动燃烧器的频率特性、压力特性、传热特性进行了理论分析和实验研究,得到了燃烧器几何结构、过量空气系数、放热量与频率、压力之间的关系,并通过实验研究单尾管及多尾管条件下的燃烧器运行特性,验证了理论分析的正确性;定量地比较了单尾管及多尾管条件下脉动流与相同雷诺数下稳定流的传热系数,得到脉动流的传热系数是稳定流传热系数的2~5倍;通过实验测量和计算,以及在实验工况条件下对尾管内脉动流动进行数值模拟,阐述了尾管内脉动流动特性,解释了脉动燃烧强化传热的原因。(3)建立了Helmholtz型无阀自激脉动燃烧器稳定性数学模型。该模型考虑了反应物的供给方式、燃烧室内的化学反应、燃烧室壁面辐射与对流传热损失以及尾管内流体的密度变化对脉动燃烧稳定运行的影响。在实验条件范围内对实验结果与理论计算结果进行比较,得到了Helmholtz型无阀自激脉动燃烧器能够稳定运行的条件。(4)提出了在不改变燃烧器结构的条件下调节脉动燃烧的方法。在脉动燃烧器尾部建立去耦室压力调节系统,实验研究了去耦室压力变化对脉动燃烧器运行特性的影响,并根据声学理论分析了各参数之间的关系,提出了能够增强脉动燃烧强度及增强传热的方法。针对Helmholtz型无阀自激脉动燃烧器运行过程中可能出现的频率跳变现象进行了实验研究,得到了脉动燃烧器的运行频率随热负荷、当量比跳变的规律,并运用瑞利准则分析了产生这一现象的原因,提出了调节脉动燃烧器频率跳变的有效方法。更多还原

【Abstract】 Pulse combustion as an advanced combustion has many advantages over conventional combustion, such as high combustion efficiency, low pollution emissions. However, pulse combustion mechanism is very complex, the major bottleneck for popularization and application of conventional pulse combustors of the Helmholtz-type with mechanical or aerodynamic valves is the self-priming mode of gas supply, which results in low power operation and low load regulation. In this paper, the idea of a valveless self-excited pulse combustor of the Helmholtz-type, using continuously forced air and fuel supply, which makes use of the combustion chamber acoustic structure directly, was presented. The advantages of this pulse combustor are self-adjusted for the equilibrium pressure, operation reliability, high volumetric heat load, wide range of heat load regulation which may realize in large scale pulse combustors. The main objective of the paper is to experimentally and theoretically study the operational characteristics of the valveless self-excited pulse combustor of the Helmholtz-type, such as frequency, pressure, heat transfer, operation stabilization and adjusting methods. The main results are as follows:(1) The experimental system of a valveless self-excited pulse combustor of the Helmholtz-type which can produce pulse combustion with continuously air and fuel supply and directly making use of the Helmholtz resonant acoustic structure of the combustor was developed. Self-adjusted for the heat load of the combustor can be achieved by this method of air and fuel supply. Experimental results show that the pulse combustor designed in this paper can produce stable pulse combustion, and the pressure amplitude of pulse combustion is higher than that of conventional pulse combustor at the same conditions.(2) The operational characteristics of the valveless self-excited pulse combustor of the Helmholtz-type, such as frequency, pressure and heat transfer were theoretically and experimentally investigated. The relations of the structure of the combustor, excess air coefficient, heat release with pressure and frequency were obtained. The validity of the theoretical analysis was confirmed by experimental investigation on the operational characteristics of the pulse combustor with single tailpipe and multiple tailpipes. The heat transfer coefficient of pulsating flow is about 2-5 times of that of stable flow according to the quantitative comparison of pulsating flow and stable flow in single tailpipe and multiple tailpipes at the same Re number. The pulsating flow characteristics in tailpipe were described and the reason of the enhancement in heat transfer was explained by the simulation results of pulsating flow in tailpipe based on the experimental working condition.(3) A mathematical model for the stability of the valveless self-excited pulse combustor of the Helmholtz-type was established. The model considered the influences of the mode of reactants supply, the chemical reaction in the combustion chamber, radiation and convection heat loss of the combustion chamber wall, as well as fluid density changes in the tailpipe on stable operation of pulse combustion. The calculation results of the model within the range of experimental condition were compared with the experimental data and the conditions for stable operation of the valveless self-excited pulse combustor of the Helmholtz-type were obtained(4) Adjusting methods for pulse combustion without changing the structure of the combustor were presented. A decoupling chamber pressure adjusting system was set up at the end of the self-excited pulse combustor tailpipe. The effects of the decoupling chamber pressure variation on the operational characteristics of the pulse combustor were experimental studied. The regulations between each parameter were analyzed by acoustic theory. The method for enhancing heat transfer of the pulse combustor was proposed. Frequency hopping phenomena that may occur during the operation in the self-excited pulse combustor was experimentally studied. The regulation of operating frequency with power and equivalence ratio was measured; the mechanism of the phenomenon was explained by Rayleigh criteria. The effective methods for adjusting the pulse frequency hopping were presented.更多还原