tailieunhanh - GasTurbine Engineering HandbookSecond Edition phần 6

khu bên trong một buồng đốt ``''thông thường. Thiết kế này cố tình bị đốt cháy tất cả các nhiên liệu trong một loạt các khu vực giàu nhiên liệu nhiên liệu nạc để cung cấp ổn định và hiệu quả đốt cháy trên toàn bộ phạm vi quyền lực. Sự phụ thuộc của sự hình thành NOx trên nhiệt độ cho thấy ảnh hưởng trực tiếp của nước hoặc phun hơi nước giảm NOx. | Combustors 395 zones inside a conventional combustor. This design deliberately burned all of the fuel in a series of zones going from fuel-rich to fuel-lean to provide good stability and combustion efficiency over the entire power range. The great dependence of NOX formation on temperature reveals the direct effect of water or steam injection on NOX reduction. Recent research showed an 85 reduction of NOX by steam or water injection with optimizing combustor aerodynamics. In a typical combustor as shown in Figure 10-19 the flow entering the primary zone is limited to about 10 . The rest of the flow is used for mixing the combusted air and cooling the combustor can. The Maximum temperature is reached in the primary or stoichiometric zone of about 4040 F 2230 C and after the mixing of the combustion process with the cooling air the temperature drops down to a low of 2500 F 1370 C . Basis for NOX Prevention. Emissions from turbines are a function of temperature and thus a function of the F A ratio. Figure 10-20 shows that as the temperature is increased the amount of NOX emissions are increased and the co and the unburnt hydrocarbons are decreased. The principal mechanism for NOX formation is the oxidation of nitrogen in air when exposed to high temperatures in the combustion process the amount of NOX is thus dependent on the temperature of the combustion gases and also to a lesser amount on the time the nitrogen is exposed to these high temperatures. Figure 10-20. The effect of flame temperature on emissions. 396 Gas Turbine Engineering Handbook The challenge in these designs is to lower the NOX without degradation in unit stability. In the combustion of fuels that do not contain nitrogen compounds NOX compounds primarily NO are formed by two main mechanisms thermal mechanism and the prompt mechanism. In the thermal mechanism NO is formed by the oxidation of molecular nitrogen through the following reactions NOX is primarily formed through high temperature reaction .