Burner homogeneous

The resulting homogeneous mixture of sample droplets and gases passes to the burner for combustion. With the former method an equilibrium... 

Much can be learned by analyzing the structure of a flame in more detail. Consider, for example, a flame anchored on top of a single Bunsen burner as shown in Fig. 4.3. Recall that the fuel gas entering the burner induces air into the tube from its surroundings. As the fuel and air flow up the tube, they mix and, before the top of the tube is reached, the mixture is completely homogeneous. The flow velocity in the tube is considered to be laminar and the velocity across the tube is parabolic in nature. Thus the flow velocity near the tube wall is very low. This low flow velocity is a major factor, together with heat losses to the burner rim, in stabilizing the flame at the top. 

You want to measure the laminar flame speed at 273 K of a homogeneous gas mixture by the Bunsen burner tube method. If the mixture to be measured is 9% natural gas in air, what size would you make the tube diameter Natural gas is mostly methane. The laminar flame speed of the mixture can be taken as 34cm/s at 298 K. Other required data can be found in standard reference books. 

The catalytic pilot burner processes only a fraction of the fuel and is targeted to retrofitting applications with minor combustor modifications. Test results indicate that to achieve effective stabilization of homogeneous combustion, 18-20% of the fuel-air must be processed in the catalytic pilot, which is a much higher fraction than the typical 2-5% processed in a conventional pilot burner. Under such conditions, test results demonstrated single-digit (<5 ppm at 15% O2) emissions of NO and CO with low acoustics at 50 and 100% load conditions. 

Early studies in this field [35, 36] indicated that a high surface-to-volume ratio, which represents a hurdle for gas-phase combustion, is instead an advantage for catalytic combustion. In fact the small scale enhances considerably the rate of gas-solid mass transfer, which favors the kinetics of the combustion process and compensates for the short residence time. Also, as is well established for large-scale systems, the presence of a catalytic phase allows for stable combustion at significantly lower temperature than traditional homogeneous burners [55, 56]. This makes the design and operation of microcombustors more fiexible. Several recent studies have explored the potential of catalytic microcombustors using H2 [37, 38, 50], methane [37], propane [52,53,57] and mixtures of H2 with propane [57], butane [38,47,52] and dimethyl ether [52]. 

In a 12-1. round-bottom flask are placed 1500 g. of corn cobs (ground to about the size of corn kernels), 5 1. of 10 per cent sulfuric acid and 2 kg. of salt. The flask is shaken in order to secure a homogeneous mixture and is then connected with an upright tube water condenser and return tube as shown in Fig. 4 (p. 50). Heat is applied from a ring burner, the flame being adjusted so that the liquid distils at a rapid rate. 

Figure 5. Plot of the CARS spectrum of Nt gas in the combustion zone of a homogeneous fiat flame burner. Conditions are as noted in the figure.

In the 1940 s a CVD process using a flame to produce homogeneously nucleated (powder) oxides of titanium, zirconium, iron, aluminum, and silicon was reported. A mixture of metal halide vapor and oxygen is injected through the central nozzle of a burner, with fuel gas and supplemental oxygen provided through two concentric outer rings. At 950°C to 1100 C flame temperature, the metal halide vapor decomposes to form very fine oxide powders. 

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