Microinjection Air/fuel Premixer and Combustor

Gas turbines are being utilized in a variety of applications (electric power production, jet engines, etc.) Modern power turbines have the highest operating efficiencies and turn out the fewest pollutants among major combustion energy converting devices. The power generation industry is faced with increasingly stringent emissions requirements for ozone precursors, such as nitrogen oxides and carbon monoxide [1]. To achieve lower pollutant emissions, gas turbine manufacturers have adopted lean premixed (LP) combustion as a standard technique, particularly for natural gas applications. LP combustion achieves low levels of pollutant emissions without additional hardware for steam injection or selective catalytic reduction. By premixing the fuel and air well, localized regions of near stoichiometric fuel-air mixtures are avoided and a subsequent reduction in thermal NOx can be realized (Lyons, 1982) [2]. Therefore, a high efficiency premixer is required to be designed to produce homogeneous fuel-air mixture distributions. Relative to single-point fuel injection, multi-point fuel injection offers numerous advantages, such as significantly shorter mixing length and time scales [3]. These smaller mixing scales can result in shorter premixer lengths and a significantly lower possibility for flashback and autoignition. In addition, the much smaller premixer helps to decrease a lot on the size and weight of the combustor, which brings a big improvement on aircraft engines. Therefore, a new multi-point injection premixer (figure1) is developed and tested about the mixing improvement in this research. And the combustion performance of the combustor installed with the micro injection premixer is also studied to justify its effect on combustion. With four kinds of mixing method (using the micro injection premixer and the fuel shooting out as the same direction of air, using the micro injection premixer and the fuel shooting out against the air, premixed without the micro injection premixer, and premixed with the miro injection premixer functioning as a screen), we can get the following conclusions about the microinjection premixer based on the combustion experiments and the data processing. • The combustor has a better lean blow out (LBO) range(figure 2).and better instability character(figure 3). • The combustor size can be decreased a lot without worsening the performance of the combustor. Figure 1. Illustration of mixing of the premixer 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.55 0.56 0.57 0.58 0.59 0.60 0.61 0.62 0.63 0.64 0.65 0.66 0.67 premixed w/o plate premixed w plate co-injection counter injection e q u iv a le n c e r a ti o a ir flow rate(kg/s) Figure 2. Lean blow out limit fuel