Research On Capacity-increase Technique Of Gas Turbine Combustor

Intercooled cycle(IC)could enhance the power of gas turbine.But with the intervening of IC,it will lead to some problems:such as fuel-injection quantity and volumetric heat intensity increase significantly,length of flame extends,outlet temperature homogeneity worsens and then affect the life of turbine.Therefore,systematic research should be done on capacity-increase condition to provide technical support for IC gas turbine.How to increase heat intensity under the condition of not changing gas turbine combustor global size is very important.At the same time,the combustion performance on capacity-increase condition should approached or even exceed design condition of prototype.It is a huge challenge and urgent mission.This dissertation investigated a type of annular gas turbine combustor,researched the effect of droplets characteristic and structure parameter of swirler on combustion flow field by numerical simulation.Then a new method named Feature-Section-criterion(FSC)for predicting LBO of annular combustor and combined vortex induced scheme were put forward in the present work.These researches provide theoretical basis for capacity-increase and design of gas turbine combustor.The main contents are as follows:(1)The transport equations for combustion flow field were established and best grid number and turbulent combustion model were confirmed at first.Numerical simulation on the annular combustor of gas turbine working with cold fluid field and combustion field were carried out under design condition and capacity-increase condition.The problems which are brought by capacity-increase are:pressure loss increases 135%,form of flame is irregular,high-temperature region is eccentric,combustion efficiency decreases 1.5%and outlet temperature homogeneity is worsening.(2)Lean blowout characteristic were analyzed about prototype and a new method named Feature-Section-criterion were put forward in this dissertation.The effects of inlet air velocity,inlet air temperature,droplet averaged-diameter,rotation direction of swirler and flow split among swirlers and primary holes on the LBO of aero-engine combustor have been discussed by using of FSC.The result shows that the predictions of Feature-Section-criterion are in agreement with corresponding experimental data and the error is lower than current model.And the range of application is wider(it could be used in gas turbine combustor and bluff body burner).This method is reliable for engineering applications and could provide theoretical reference for gas turbine design.(3)Effect of droplets characteristic and structure parameter of swirler on combustion performance(combustion efficiency,length of flame and OTDF)were researched in this dissertation.The detail structure parameters are:initial average diameter,initial spray angle,oblique-hole eccentricity,oblique-hole angle,oblique-hole diameter,oblique-hole number,swirl-vane angle and vane number.(4)Combined vortex induced scheme were put forward in the present work.The results show that:outlet perimeter is longer than original swirler;this could extend contacting area between air and fuel.Besides central recirculation zone,there are radial and axial recirculation zone behind each lobe.These recirculation zones form a kind of special combined vortex flow field,and they could quicken up the mixing rate between air and fuel.At the same time,they could make the burning quickly and form pilot flame;these flames could increase the capacity to resist blowout.(5)Effect of aspect ratio,number and length of lobe on combustion efficiency,outlet average temperature,total pressure loss and NOx emission were shown in this dissertation.The results show that:aspect ratio,number and length of lobe could influence combustion efficiency,outlet average temperature and NOx emission.Total pressure loss only affected by lobe number.(6)The best parameters of droplet characteristic,swirler and combined vortex induced scheme were confirmed by comprehensive parameter optimization method.With these parameters,a new gas turbine combustor was designed and the performance on cold fluid field and combustion field were researched.The results show that:under capacity-increase condition,the combustion efficiency,OTDF,length of flame,combustion heat intensity and volumetric heat intensity are both obtained major improvement,and these parameters accord with the design standard of gas turbine combustor.