| 摘要: | 研究期間：10108~10207;This three-year proposal investigates experimentally and analytically high-pressure, high-efficiency lean-burn natural gas combustion with hydrogen addition based on the already established technology for natural gas doping with hydrogen under atmospheric pressure (“Effects of Hydrogen or CO2 Additions, Equivalence Ratio, and Turbulent Straining on Turbulent Burning Velocities for Lean Premixed Methane Combustion”, Combustion and Flame, Vol. 153, No. 4, pp. 510-524). High-pressure lean premixed turbulent combustion mode is used to achieve the aforesaid high-efficiency and low NOx emission goals, which should be very useful to gas turbine engines and spark ignition engines, having great potential in further improving fuel efficiency, reducing NOx emission, and increasing thermal efficiency. However, there are two problems when applying this lean-burn technique: (1) There are a substantial decrease of burning velocities; (2) a large increase in misfires, especially when the premixtures become too lean (the equivalence ratio ψ~ 0.6, which is near the lean flammability limit of natural gas). To solve these two problems, several attempts have been made, such as for instance, increasing the ignition energy or stratifying premixtures (stratified combustion). Though these attempts can indeed improve lean premixed combustion performance to some extent, however, to burn even leaner mixtures at even higher burning velocities and at even lower pollutions requires other methods. In this research, a different approach other than the above two attempts is employed. By adding a small amount of hydrogen into the natural gas under elevated pressure conditions, we expect to improve the high-pressure lean premixed combustion performance. This is because the hydrogen has very low fuel/air equivalence ratio of lean flammability limit and very high burning velocities. We will conduct a series of high-pressure turbulent premixed combustion experiments using lean natural gases with hydrogen addition in a high-pressure, double-chamber turbulent premixed combustor, as schematically shown on the previous page. The present key working items which differ with our previous studies under atmospheric pressure are listed as follows. (1) Under elevated pressure varying from p = 0.1~1.0 MPa (1~10 atm), we measure high-pressure turbulent burning velocities of lean natural gas (methane) with various hydrogen additions from 10% to 50% in volume and at different equivalence ratios varying fromψ=0.45~0.8 over a wide range of turbulent intensities which are higher than hitherto. (2) To confirm the relations of high-pressure turbulent burning velocities with hydrogen addition as a function of turbulent intensities. (3) To find the lean flammability limit of high-pressure natural gas (methane) with hydrogen addition. (4) To explore the influential factors of hydrogen diffusive reactions at elevated pressure turbulent environment. (5) Emissions of NOx will be also measured by gas analyzers and thus their concentrations as a function of adding hydrogen volume percentage and/or turbulent intensities can be found. The goal of this three-year proposal is to establish sufficient knowledge and technology for solving these aforementioned problems and developing high-pressure, high-efficiency lean-burn natural gas combustion technique. Finally, the results expecting to obtain from this proposal should be very useful to natural gas fire power plant and spark ignition engines for further increasing efficiency, saving fuel usage, and reducing pollution. |
