Investigation On Flow Characteristics And Film-Cooling Mechanism In A 1+1/2 Counter-Rotating Turbine

Counter-Rotating turbine technology is the most important way to increase blade loading,to decrease blade rows and weight,so as to gain higher thrust-weight ratio.In the recent few years,Counter-Rotating turbine has been more and more regarded.At present,1+1 stage Counter-Rotating turbine has been used in some advanced active duty aero-engines.And,Vaneless Counter-Rotating Turbine(VCRT, 1+1/2 stage counter-rotating turbine),which is composed of a highly loaded single stage high pressure turbine and a vaneless counter-rotating single stage low pressure turbine,has been also applied in some up-to-date test engines in Euro-America developed countries.It is obvious that the VCRT will be widely adopted in real aero-engines in the future.However,the research level of the Counter-Rotating turbine in China greatly lags behind developed countries.So,it is very necessary to perform some systemic investigations focusing on Counter-Rotating turbine, especially on the off-design performance of VCRT.In addition,to achieve higher thrust power and thermal efficiency,the inlet temperature of modern gas turbine has increased to 2200K above,which is far beyond the allowable metal temperature.Thus, to maintain acceptable life and safety standards,calls for an efficient cooling technology.It is important to research and improve cooling technology in order to reduce the operating temperature of high-temperature components.Foreign monopolies on gas turbine technologies are mainly concentrated on the high-temperature component in the design and manufacturing technology,including turbine cooling technology.Based on the background,off-design flow characteristics and film cooling mechanisms of VCRT were investigated by means of advanced CFD tools in this paper,film cooling heat transfer characteristics were experimental studied by means of blow-down short duration turbine facility.The blow-down short duration turbine facility is the first and unique in China.The main content in this paper is listed as follows:1.Numerical investigations were performed to study the flow characteristics of VCRT at off-design conditions.Numerical results were compared with experimental data.The operating characteristics of the VCRT are obtained depending on these investigations.The results indicate that the ratio of specific work of the high pressure turbine to that of the low pressure turbine and the efficiency are increased in the VCRT as the rotation speed of the rotor increases under the same expansion ratio.And the research results show that when the rotation speed of the rotor increases,the specific work of the low pressure turbine is decreased,and the effective operation range of the VCRT is reduced.The investigation results also indicate that the numerical code in this paper can qualitatively predict the flow characteristics of the VCRT at off-design conditions.2.Film cooling schemes were designed for the high pressure stator and the high pressure rotor of the VCRT and 3D numerical simulation were performed.The flow characteristic of coolant injection in the VCRT,the interaction between coolant injection and mainstream,the influence of coolant injection on the blade pressure distribution and Relative Ma distribution were investigated.In order to study the film cooling performance for high pressure rotor at off-design conditions,three typical conditions were simulated.The affect of speed,blowing ratio and pressure ratio on the film cooling effectiveness were considered.The coolant injection characteristic on the leading edge,pressure side and suction side of the high pressure rotor were studied. The influences of coolant injection on the pressure distribution and relative Ma distribution of the high pressure rotor blade were given.The affect of coolant injection at different location of pressure side and suction side of high pressure rotor on the complex shock systems were investigated.3.Some preliminarily experimental investigations were performed to study the film cooling heat transfer characteristics of the experimental model which was installed between the high pressure rotor and the low pressure rotor of the VCRT.The experimental data were compared with the 2D unsteady simulation results.And the results show that with film cooling,the heat flux ratio of measured points on the heat transfer experimental model decreased much compared with the data of no film cooling.There are some difference in quantity between the experiment results and 2D numerical simulation data,but the trends are consistent.