The overall goal of the research is to improve the efficiency of large industrial gas turbines through improvement of compressor performance. Specifically, the research focuses on two important aspects of compressor science and technology. The first aspect addresses loss and flow blockage generation in high-speed multistage axial compressors to establish a design philosophy for high efficiency and for broadening the island of peak efficiency. The second aspect seeks to quantify the variation of efficiency as blade (rotor tip and stator hub) clearance approaches zero and its implication on peak efficiency in a multistage environment. The overall framework of the approach consists of using computational analyses to first establish the traceability of flow features as they impact compressor performance changes; this is then to be followed by experimental assessments.