| The aero-derivative gas turbine(GT)is incorporated with the advantages of solid research base,low research risk,short design cycle,low development cost,and rapid technology upgrade.It can be applied to military and civilian non-aerospace fields,such as power generation,distributed energy,natural gas transmission lines,mechanical drives,armored vehicle power and ship propulsion.After more than half a century of development,its product spectrum has become more and more complete,and its application scope has become increasingly broad.Western developed countries,such as UK,USA,and Russia,rely on their strong aero-engine foundation to gain technology leadership in the field of aero-derivative gas turbines,and their representative models have a high market share.There are a few models of aero-derivative gas turbines in our country,and accordingly,the development of combustion technology started late.Learning from the mature technology of foreign models,absorbing and improving based on this basis have become an effective way to develop new engines relatively quickly and economically.However,at present,the prototypes of a considerable number of aero-derivative gas turbine used both domestically and abroad are the products of the 1960 s and 1970 s.The combustion technology lags behind,and there is space for improvement.Aiming at the above problems,this paper studies the dome structural parameters of the swirl cup annular combustor,which is widely used in aero-derivative gas turbines,to provide a reference for the structural optimization and performance improvement of the swirl cup annular combustor.In this dissertation,firstly,the method of theoretical analysis combined with experimental research was used to optimize the combination of the gas fuel injector and swirl cup venturi in a certain aero-derivative GT combustor,and experiments were conducted to test and verify the performance of the single-head combustor.Subsequently,the similarities and differences of flow fields under wall and periodic swirling flow boundary conditions were revealed,which introduced the problems of interactions between the swirl nozzles and the design of the nozzle spacing.The influences of the inter-nozzle spacing on the performance of the combustor were systematically analyzed.Finally,on the basis of the above-mentioned research of dome structural parameters,such as the optimization of unit nozzle and design of nozzle spacing,a three-head combustor test facility was designed,and the evaluation of its performance parameters were completed.The main research contents and conclusions of this dissertation include:(1)Based on the fuel/air injection unit and single-head model combustor,a series of experiments were carried out under both non-reacting and reacting conditions.For several different dome structures with different fuel injector insertion lengths into the swirl cup venturi,the performances of the model combustor,including the flow resistance characteristics,lean blowout limits,pollutant emission level and flow field structure were studied.The results showed that the depth of the fuel injector embedded in the venturi tube has a significant effect on the total pressure loss coefficient and the lean blowout performance of the combustor.There is an optimal fuel injector position which depends on the geometry of the venturi tube to optimize the above two performances.At the same inlet air flow condition,increasing the flow area of the swirl cup is helpful to reduce the total pressure loss coefficient,improve flame stability and reduce the vibration amplitude of the flame tube wall.However,it is not favorable to promoting the mixing of fuel and air,which results in the increase of pollutant emission concentration.(2)The effects of wall confinement on the flow field structure were then investigated.By comparing the isothermal flow field of a single nozzle with that of multi nozzles,the impacts of the interaction between the nozzles on the swirling flow field were analyzed.As compared to the unconfined flow field,it is found that both the size of the central recirculation zone and the radial velocity of the swirling jet decrease upon confinement.While,the axial velocity and the reflux intensity of the swirling flow increases under the effect of wall constraint.The multi-nozzle flow field exhibits some characteristics different from the single nozzle under the same confinement ratio.In the interacting area between nozzles,the peak axial velocity value increases significantly,and the size of the recirculation zone is changed as well.It can be seen that the interaction between adjacent swirling flow will cause the nozzle performance to change,and it is necessary to study the performance of the multi-nozzle combustor.(3)With respect to the problem of interactions between swirl nozzles and the design of nozzle spacing,both the maximum flame connecting distance and flame propagation dynamic process of the dual-nozzle test facility were experimentally studied under different initial inlet conditions.The effects of nozzle spacing on lean flameout equivalence ratio,non-reacting and reacting flow fields,fluctuating velocity field,and NO emission level were studied as well.It is of great significance to confirm the nozzle spacing in the combustor dome,which makes contribution to the improvement of the combustor performance.The results show that both increasing the air mass flow rate and the initial equivalence ratio help to extend the flame connecting distance.When the equivalence ratio increases by 0.1,the dimensionless maximum flame connecting distance increases by about 0.2.The lean blowout equivalence ratio of all five dual-nozzle structures is smaller than that of a single nozzle at the same air flow rate.As the nozzle spacing decreases,the lean blowout equivalence ratio first reduces and then increases.This change trend is the result of the competition between the heating effects and fluid dynamic effects between nozzles.As the nozzle spacing decreases,the swirling jet gradually merges and the peak velocity of the jet becomes larger;The root mean square velocity in the interacting area between nozzles also increases;The distribution area of main fluctuating velocities becomes wider,and the effect of the adjacent nozzle is significantly enhanced.The NO emission of all five dual-nozzle structures is larger than that of a single nozzle under the same inlet conditions.As the nozzle spacing becomes smaller,the NO emission increases.(4)Based on the optimal fuel/air injection unit and the principle of nozzle spacing design,a new design scheme of three-head combustor test facility was proposed.Then,comprehensive and systematic experiments were conducted to evaluate its performance.The results show that all the parameters,including total pressure recovery coefficient,the outlet temperature distribution factor and the emissions level,meet the requirements or be superior to the prototype combustor except for the combustion efficiency which is due to the inlet air was not preheated.It shows that the optimizing design scheme of the three-head combustor is feasible. |
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