Research On The Flow And Heat Transfer Physics Of Novel Film Cooling Structures On The Leading Edge Of Turbine Blade

The leading edge of the turbine blade is directly affected by the impact of the hot gas,it often withstands higher heat loads which may result in material failure due to high temperature and thermal stress.Cooling technology must be used to ensure the turbine blade work safely in high temperature condition.Among the cooling technologies,film cooling technology is one of the widely used method.In the research of the turbine blade leading edge film cooling technology,the study of film-hole row structure and shaped film hole has gradually become the focus of the researchers attention.In the research of novel film cooling structures on the leading edge of the turbine vane,two novel types of film-hole row structures(collinear counter-inclined structure and non-collinear counter-inclined structure)based on the film holes(cylindrical hole and y shaped hole)have been chosen for the study of the film cooling mechanism on the leading edge of the turbine vane with numerical simulation methods.The distributions of the flow and heat transfer characteristics with novel film cooling structures were analyzed at different blowing ratios.The following conclusions can be drawn from the comparison,compared to the cooling configuration with cylindrical hole,the film holes of the cooling configuration with y shaped hole have both spanwise and streamwise inclination,so the film cooling effectiveness is higher and the area of the film coverage is larger,particularly at higher blowing ratio.And the effect of hole shape on the film cooling effectiveness in the region between the film-hole rows is greater than that in the downstream of the second film-hole row.The film-hole row structures have little effect on the leading edge film cooling effectiveness at lower blowing ratio,whereas at higher blowing ratio,the addictive effect of the film jets is more obvious when the film holes are arranged parallel-inclined,so the distribution of the film cooling effectiveness for the parallel-inclined structure with cylindrical hole increases along the spanwise direction,but for the two types of counter-inclined structures with cylindrical hole,the highest film cooling effectiveness region occurs at the counter-inclined position and the lowest film cooling effectiveness region occurs at the two sides of the endwall.At each blowing ratio,the hole shapes and hole structures have little effect on the distribution of the heat transfer coefficient in the downstream of the film hole row.For the four novel types of counter-inclined structures,the interactions between the upstream counter-blowing jets and the downstream jets have a great effect on the film cooling performance in the downstream of the second film-hole row.The interactions weaken the film coverage performance in the downstream of the film hole(z/d=3)in the second row at lower blowing ratio,whereas enhance the film coverage performance in the downstream of the film hole(z/d=3)in the second row at higher blowing ratio.The interactions between the two rows of film jets for the four types of counter-inclined structures weaken the heat transfer intensity in the downstream of the film hole row(z/d=3)in the second row,particularly at higher blowing ratio.In the research of novel film cooling structures on the leading edge of the turbine blade,a detailed numerical simulation of the flow and heat transfer mechanism with a novel type of leading edge film cooling groove structure was carried out in this paper.The effect of groove depth on the flow and heat transfer characteristics of the turbine blade leading edge was analyzed at different blowing ratios.The following conclusions can be drawn from the comparison,the groove structure has a great effect on the film cooling effectiveness of the turbine blade leading edge,particularly at lower blowing ratio,but less on the heat transfer coefficient.At lower blowing ratio,for the structure without groove,the film jet flows to the downstream immediately under the pressing action of the mainstream when it enters the main cavity through the first film-hole row.For the structure with groove,the film jet flows along the spanwise direction in the groove due to the influence of the groove structure and then flows to the downstream under the pressing action of the mainstream when it enters the main cavity through the first film-hole row.Compared to the structure without groove,the film cooling effect is obviously enhanced and the film cooling effectiveness is obviously improved in the whole leading edge region for the structure with groove.The depth of groove has great influence on the leading edge film cooling performance,the film cooling effectiveness decreases with the increase of depth,particularly at higher blowing ratio.For three types of structure with groove,the film cooling effectiveness increases along the spanwise direction,whereas the heat transfer coefficient decreases,particularly at higher blowing ratio.