Impinging stream combustion

In addition, the method of impinging streams can also be used for systems of single phase, such as gas-gas and liquid-liquid impinging streams etc. In fact, single phase impinging streams have great value for practical application in mixing, gas combustion, etc. 

Gas-continuous impinging streams with a liquid as the dispersed phase has wide application, such as in the combustion of liquid fuel droplets, absorption, water-spray cooling of air, etc. [9]. In such systems the dispersity of liquids plays a very important role affecting heat and mass transfer rates, because it influences both the interface area and the mean transfer coefficient. Wu et al. [68] investigated the influence of impinging streams on the dispersity of liquid. 

In principle, gas-continuous impinging streams (GIS) can be applied for the combustion of gases, powdery solids and sprayed liquids. Since gas-combustion is relatively simple and the process is essentially independent of the major feature of GIS, i.e., that it significantly enhances heat and mass transfer between phases, the discussions in this chapter will focus on the combustion of the latter two kinds of fuels. 

From the basic properties of gas-continuous impinging streams and the burning models derived in the last section, impinging streams intensify the combustion processes of atomized liquid and powdery solid fuels by the following mechanisms ... 

Many experimental evidences have been obtained for impinging streams intensifying combustion processes. For example, the results obtained by Enyakin [142] and Enyakin-Dvoretskii [143] from their investigations on the combustion of high sulfur-content oil showed that the oil can burn in impinging streams at a very low excess air factor (as low as 1.02), the number of burners can be decreased, and the length of flame is obviously reduced. The latter result implies that a smaller combustion chamber can be used. 

The content of S03 in the flue gases with a< 1.035 was less than 0.002%. This implies that the boiler of type BKZ-320- 140GM equipped with impinging stream burners provides complete combustion with a negligible corrosion rate of the heated surfaces. 

Figure 8.1 BKZ-320-140GM impinging stream steam boiler. 1 burner 2 combustion space 3 secondary combustion space 4 steam superheating 5 water economizer.

In addition to the two combustors introduced briefly above, researches and development on the application of gas-continuous impinging streams to combustion has been carried out since the 1970s, e.g., the investigations made by Goldberg and Essenhigh [ 146], Ziv etal. [12], Goldman [147-149] and Liu et al. [150]. Mostly, these works involve experimental studies and model analyses, and mainly aimed at the improvements of combustor structure and the arrangement of burners in order to increase combustion efficiency. Most of the experimental combustors employed were very small and their application seems far from practical. 

Cavitation corrosion of cylinder liners is not caused by high velocity water flow, nor by impingement of coolant streams. Rather, it appears that vibratory effects are primarily responsible. Under the tremendous stresses of fuel compression and combustion in the Diesel cycle, these 3/4 inch thick cylinder liners vibrate or "ring" at frequencies estimated to be in the range of 7,000 to 8,000 cycles per second, and higher. 

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