In conventional air compressors such as those used on internal combustion engines, exhaust gas energy is used to compress engine intake air. In certain other applications, so called superchargers are driven directly with mechanical engine power or an electric motor to compress air that is then provided pressurized to engine cylinders. In other applications, so called turbochargers are used, which include a turbine that receives pressurized exhaust gas from the engine. The exhaust gas passes through a scrolled passage of the turbine and impinges onto a turbine wheel causing it to turn. The turbine wheel is connected to a shaft, which is connected to a compressor wheel disposed in a compressor housing. The powered rotation of the turbine wheel and shaft operate to turn the compressor wheel, which draws air into a compressor housing having a scrolled shape and compresses it.
Various types, sizes and numbers of turbochargers and/or superchargers have been used on engines in the past. One design consideration when selecting an appropriate compressor for an engine application is the air flow rate and desired pressure ratio of engine intake air that is desired. Further, because air compression increases air temperature, engines typically use heat exchangers, such as air-to-air heat exchangers, to cool the compressed air before it is provided to the engine.
The materials used to construct engine compressor components are selected by consideration of cost and operating parameters. For example, while a forged aluminum compressor wheel is relatively cost beneficial, it may be unsuitable for applications in which the compressed air temperature is or is expected to rise above a threshold value during operation. Other, more expensive, materials that have been used in the past to construct compressor wheels that can withstand higher operating temperatures include Inconel(R), which is a family of alloys for high temperature applications, titanium alloys and the like. Such materials are not only expensive to purchase but are also difficult to form and to machine. However, use of such materials for high temperature applications is common because use of another material, for example, aluminum, in high temperature applications, for example, compressor outlet air temperatures of 220° C. or more, may lead to premature component failures and costly repairs. This is especially true for engine applications operating close to the margins of their operating parameters such as engine applications used at very high altitudes, for example, at 15,000 feet above sea level and/or high ambient temperatures, for example, exceeding about 110° F. (about 43.3° C.).