This award is partially funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)." PI: Li, Xianchang Proposal Number: 0927376 Overall Research Proposed: Gas turbine engines have been widely used in power generation and aircraft propulsion. Any increase of the gas turbine efficiency can lead to a significant saving of energy. To improve the efficiency, the turbine inlet temperature is usually elevated to be higher than the metal melting point. Therefore, effective cooling of gas turbine is a critical task for engines? efficiency as well as safety and lifetime. Film cooling has been used in gas turbine engines for many years. In film cooling, air drawn from the compressor is discharged through small holes in the blade walls, after passing the turbine blade internal channel. The relatively cold air blankets the blade surface so that heat transfer between the hot working gas flow and blades is reduced. The main issues related to film cooling are its poor coverage, aerodynamic loss, and increase of heat transfer coefficient due to strong mixing. To overcome these problems, film cooling with backward injection is proposed in this research. Preliminary data evidence the advantage of the proposed concept. The main objective of this study is to explore the fundamental mechanism of film cooling with backward coolant injection, including the optimum design conditions. Both experimental test and numerical simulation are proposed. Experiments will be conducted to evaluate the cooling performance by measuring flow velocity and temperature with a Particle Imaging Velocimetry (PIV) and an infrared (IR) camera together with other instruments. The test data will also be applied to validate numerical results. Intellectual Merit: The proposed research is to investigate the fundamental phenomena of fluid flow and heat transfer of film cooling with backward injection. The intellectual merit lies in: (1) This research envisions a new concept in film cooling design. The research will lead to a comprehensive understanding of the impact of backward injecting flow on the boundary layer or the near-wall region of the main flow. The backward injection does potentially have a larger pressure loss when compared to its counterpart, forward injection. The proposed research will explore the impact on both pressure drop and heat transfer, especially the lateral distribution. A compromise between pressure drop and heat transfer will lead to an improved cooling effectiveness without scarifying the overall engine efficiency. (2) The proposed study can result in data/correlation highly realistic to industrial applications by both numerical simulation and experimental test. While the experimental test can validate the numerical simulation under laboratory conditions, cases at gas turbine operating conditions can be investigated with numerical simulation. (3) The mechanism of backward injection explored in this study can also provide an opportunity for related applications such as aerodynamic flow control. Broader Impact: (1) This fundamental research has a strong background in industrial applications. Its success will directly benefit many related industrial companies, and eventually benefit even more gas turbine end-users such as power generation and aircraft companies. (2) This research will benefit the academic community and general public through data/result dissemination. It can also benefit college-level education through integrating the research into thesis work, course work, and student recruiting. Plans are made to broaden the impact to K-12 education and inspire the interest in engineering among young students. Collaboration with researchers from other institutes will also broaden the impact. (3) Special effort will be made to achieve the goals of this NSF BRIGE program. More than 50% of population is African American in the area where the PI?s university is located, but less than 10% of the students are from this group in the College of Engineering. For broader participation of individuals from underrepresented groups in the engineering disciplines, the PI plans to offer presentations to high-school students from general engineering concepts to advanced technologies as addressed in this proposal. Furthermore, it is also planned to host an engineering seminar per semester to high-school science teachers so that the teachers can take engineering concepts to their classes. In this way, more students will be introduced to engineering fields.
