Enhanced Heat Transfer Mechanism And Performance Study On Composite Cooling Structure At Leading Edge Of A Gas Turbine Vane

Gas turbine is broadly applied in the fields of aviation,power,ship,industrial drive,vehicle drive and so on,which is important power equipment in the fields of aviation,energy and national defense.The temperature improvement of turbine inlet is one of the main methods to enhance the performance of gas turbine.However,along with the improvement of inlet temperature,the blade surface,especially the temperature at the front edge brushed directly by gas is risen,which exceeds 2,200 K.The researchers have been devoted to the cooling research on the blade of gas turbine in order to ensure its safety.However,the single cooling technology can’t meet higher cooling requirements,the composite cooling technology is the hotspot in the current research of blade cooling field,and it’s also the future direction.Composite cooling technology includes multiple composite cooling technology and internal/external composite cooling technology.Simplified model is mostly adopted for the current composite cooling research,but the influence of blade’s geometry is neglected,the influence of solid heat conduction and gas heat transfer has not been considered in the research of multiple internal composite cooling technology,so the intensified heat transfer mechanism and performance of composite cooling structure used in gas turbine blade can’t be accurately analyzed.Therefore,the blade is taken as research subject and fluid-thermal-solid interaction model method is adopted to perform research on the intensified heat transfer mechanism and performance research of multiple internal composite cooling and internal/external composite cooling structure and optimize composite cooling structure,which has important academic and engineering value.The research work in the paper is as follows:Aiming to the research on heat transfer mechanism and performance of blade’s multiple internal composite cooling structure,the C3X blade is taken as research subject to design and introduce impingement-dimples composite cooling structure into the cooling research of gas turbine blade and the arrangement method of impingement structure and dimple structure as well as the influence of cooling working medium and gas mass flow rate on the multiple internal composite cooling performance is analyzed.It’s shown in the research that the impingement cooling is mutually affected with dimple turbulent flow cooling,dimple structure make the wall-attached jet area of impingement cooling compacted and negative influence is produced on the impingement cooling performance;however,the composite cooling efficiency is higher than single impingement cooling efficiency under the coupling function of two structures;the cooling efficiency on the suction surface is improved when the dimple structure is in literal arrangement with the impingement structure;the cooling efficiency at all the area of the blade’s front edge is obviously improved when dimple structure is in literal crossing and arrangement with the impingement structure.The average cooling efficiency at blade’s front edge is improved along with the increase of mass flow rate when the single impingement cooling structure and impingement-dimple composite cooling structure is adopted,and the trend of increasing is gradually reduced;compared to single impingement cooling structure,the cooling working medium flow consumption is less if impingement-dimple composite cooling structure is adopted when the blade’s front edge reaches the same cooling effect,so it’s more energy-saving.Aiming to the research on heat transfer mechanism and performance of blade’s internal/external composite cooling structure,the C3X blade is taken as research subject to firstly introduce swirl-film composite cooling structure and two kinds of cyclone-type cooling cavity structures are designed,the “cooling contribution coefficient” is defined,the quantitative evaluation is performed on the weight and cooling effectiveness of swirl cooling and film cooling in internal/external composite cooling coupling function and the influence of swirl cooling cavity structure and mass flow rate on internal/external composite cooling performance is analyzed.It’s shown in the research results that the cooling cavity structure has obvious influence on the film cooling;By calculating the cooling contribution coefficient,it is found that the contribution coefficient of internal cooling mode is more than 0.71,which means that the internal cooling is in leading role in internal/ external composite cooling;both of the two designed cyclone cooling cavity structures obviously improve the internal cooling amount and composite cooling amount;the swirl-film composite cooling structure is adopted,the average composite cooling efficiency and composite cooling amount at the blade’s front edge is increased along with the rising of mass flow rate and the trend of increasing is gradually reduced;compared to non-swirl-film composite cooling structure,the adoption of swirl-film composite cooling structure can save more than 50% of cooling working medium flow amount when the blade’s front edge reaches the same cooling effect,so it’s more energy-saving.Compared with the non-interval channel swirl cooling cavity,the internal cooling performance of composite cooling structure and composite cooling performance is stronger by adopting interval channel swirl cooling cavity structure.Aiming to the optimized design of composite cooling structure,based on stronger heat transfer performance of the interval channel swirl cooling cavity,the average composite cooling efficiency of the blade’s front edge is taken as index,the septum thickness(b),channel width(d)and interval channel height(l)are taken as factors and the orthogonal analysis method is adopted to optimize swirl-film composite cooling structure,present the best plan,arrange the influential weight on factors and analyze the influential mechanism of the factor with the largest weight.It’s shown in the research results that the optimum program is b=3mm,d=1mm,l=3mm;the geometric parameters influence weight of interval channel is arranged as:channel width > interval channel height > septum thickness;thereinto,the channel width and interval channel height has obvious influence on the average composite cooling efficiency of the blade’s front edge.The channel width is reduced when the interval channel is certain,the flow rate of cooling working medium into the front cavity is increased,the vortex system is strengthened,the internal cooling performance is improved,the internal cooling amount is increased and the composite cooling amount is enhanced.The research achievements in the paper produce a new idea on the heat transfer mechanism,performance and optimization of composite cooling structure of gas turbine vanes.