The popularity and increased usage of insulated gate bipolar transistors (IGBTs) in power control systems have made the problem of cooling them a subject of considerable interest in recent years. In this investigation, a heat flux of 825W∕cm2 at the die was achieved when air-water spray cooling was used to cool IGBTs at high current levels. The junction temperature of the device was measured accurately through voltage-to-temperature characterization. Results from other cooling technologies and other spray cooling experiments were reviewed. A discussion of electrical power losses in IGBTs, due to switching and conduction, is included in this paper. Experiments were conducted on 19 IGBTs, using data collection and software control of the test set. Three types of cooling were explored in this investigation: single-phase convection with water, spray cooling with air-water and spray cooling with steam-water. The results of these experiments show clear advantages of air-water spray cooling IGBTs over other cooling technologies. The applications of spray cooling IGBTs are discussed in open (fixed) and closed (mobile) systems. Current and heat flux levels achieved during this investigation could not have been done using ordinary cooling methods. The techniques used in this investigation clearly demonstrate the superior cooling performance of air-water spray cooling over traditional cooling methods.
The flow fields of two different Siemens-Westinghouse gas turbine mixers were studied experimentally in an effort to better understand fuel-air mixing in confined swirling flows found in industrial applications. The mixers consist of an annular flow region and mixing is achieved using swirl vanes, the pressure side of which is used to inject the fuel. The difference between the two mixers studied is the degree of swirl imparted on the flow by the swirl vanes (45° vs. 55°). Velocity (both axial and azimuthal) and fuel concentration profiles were obtained for non-reacting, atmospheric pressure flows at several axial and radial locations downstream of the swirl vanes by the use of LDV and infrared laser light absorption techniques, respectively. The fuel used in this work was a methane/air mixture, which was injected at a momentum flux ratio comparable to that under operational conditions. Results show that flow uniformity, as evidenced by velocity and fuel concentration profiles, is reached further downstream of the swirl vanes for the 45° mixer than for the 55° mixer. This indicates a lesser mixing performance in the 45° mixer. The axial and azimuthal RMS velocities were consistently higher for the 55° degree mixer and this was a likely contributor to its superior mixing performance. High velocity and fuel concentration gradients are common for both mixers and present in the near-field region close to the swirl vanes. The data obtained indicates that the flow behavior in the region near the swirl vanes strongly influences the mixing of the fuel and air. Frequency analysis of the fuel concentration data shows that some turbulent structures prevail throughout the mixing region in both mixers, revealing that some large scale flow features emanating from the swirl vanes are not dissipated even in the high degree of swirl hardware. Lastly, unmixedness levels in both mixers tested are calculated and compared with a discussion on how they might impact NOx emission levels.
In this investigation, high current levels were applied to an IGBT and, using spray cooling, a heat flux of 825W/cm2 at the die was achieved. Current and heat flux levels achieved during this investigation could not have been done using ordinary cooling methods. The techniques used in this investigation clearly demonstrate the superior cooling performance of spray cooling over traditional cooling methods.
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