Research On Low Emission Combustion Technology With Lean Direct Injcetion

On the background of developing high efficiency and low-emission combustor, the research on low emission combustion technology with lean direct injection(LDI) is carried out in order to control the impact of aircraft engines emissions to the environment. The Mode-ls of single-point, 4-point and 9-point LDI combustors are designed and processed. The effective area and total pressure loss of single-point and 9-point LDI combustors are tested. The Numerical simulation methods are used to research the combustion characteristics of velocity distribution, temperature distribution, component concentrations and pollutant emissions in several LDI combustors. The main research results include:(1)According to the technical requirements of high efficiency and low emission combustor, the designs of single-point, 4-point and 9-point LDI combustors are completed which include the axial swirler with two different swirl angles of 60° and 45°, venturi tubes and array Mode-s of 4-point and 9-point LDI combustors. The experimental parts are processed to preliminary test the total pressure loss and the effective area of single-point and 9-point LDI combustors and result variation of the total pressure loss coefficient and effective area with the inlet flows.(2)The conservation equations needed to the numerical simulation in combustor are described. The characteristics and adaptability of the Realizable k-ε turbulence Mode-l, EDC turbulent combustion Mode-l, PDF Mode-l, discrete Mode-l and NOX Mode-l used in the LDI combustors are analyzed. The experimental Mode-ls of the LDI combustors are simplifized to determine the mesh and boundary conditions.(3)The Mode-ls of single-point LDI combustors with the swirlers whose exit angles are 60 ° and 45 ° clockwise rotation are established respectively. The two kinds of imported conditions with normal temperature and pressure as well as high temperature and pressure are set to research the impact of different imported conditions and exit angles on the combustion characteristics and NO emission characteristics in LDI combustors. The research results show that: The axial velocity under the high temperature and pressure condition of single-point LDI combustors is faster and leads to low NO emission; comparing to the 60° one-pint LDI combustor, the 45° single-point LDI combustor has higher combustion temperature, larger area of high temperature zone and smaller axial velocity which leads to higher NO emission.(4)The three Mode-ls of 4-point LDI combustors with different single element center distance are established to simulate the combustion of H2. The research results show that: For the same equivalence ratio of the combustors, the combustion temperatures of the combustors are substantially the same, but with the center distance decreases, the interaction of adjacent flows is gradually strengthed, the axial velocity is increased, and the NO emission of 4-point combustor with the smallest center distance is significantly reduced, which fully explains that the small center distance has advantage of controlling the NO emission in multi-point LDI combustor.(5)The Mode-ls of 9-point LDI combustors with the swirlers whose exit angles are 60 ° and 45 ° are established respectively. They all have four different forms of arrries. The combustion characteristics in 9-point LDI combustor with four array forms and different exit angles are simulated. The research results show that: The array multi-point LDI combustor can significantly reduce the length of the recirculation zone and the area of high temperature zone, and more conducive to generating lean mixture gas, thus effectively reducing the NO emissions; due to the shear stress direction at the intersection of adjacent flows in the co-swiring array structure is opposite, the mist broken is strengthened which is more conducive to lean combustion and NO emission; the flow interaction of 45° 9-point LDI combustor is weak, so that it cann’t show the advantage of controlling NO emission in multi-point combustor.The research results have laid a solid foundation of the depth reaearch on low emission combustion technology with lean direct injection(LDI), and provid a theoretical basis and technical support for the design and engineering applications of LDI combustor.