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Commercially available turbocharged internal combustion engines require robust system performance to maintain driveline power output capability. As in-service runtime increases, the accumulation of wear or deposits can adversely affect component performance levels. In a worst-case scenario, the component performance degradation leads to a vicious loop of declining system performance. Endurance testing of a heavy-duty diesel engine revealed performance deterioration over time. Oil deposits, resulting from oil mist associated with the closed crankcase ventilation loop, were observed on the turbocharger compressor and were tied to the deterioration. Cleaning of the compressor recovered initial performance for a short period of time. A different model of turbocharger, when substituted for the original, did not show the same degradation in output.

The prevalence of turbocharged engines in passenger car applications has been increasing rapidly, particularly in the past decade or so. The tightening of emissions requirements and goals for engine downsizing has significantly increased the demand on turbocharger compressor stable operating ranges and efficiency levels, for both diesel and gasoline engines. The operability limits of single-stage turbocharger centrifugal compressors are being severely tested, and customization of some key aerodynamic technologies is required to meet the challenge. This paper addresses some critical design challenges in wide-operability, single-stage turbocharger compressors for advanced automotive diesel engine applications. Starting with a few technological ground rules, a brief exploration of the design space for two notional advanced engine operating lines is presented.

While turbocharging has existed for a full century, its significance has increased very rapidly in the past few decades. At the heart of good turbocharger performance is an excellent compressor stage, or stages, that must be efficient, stable, lightweight, and inexpensive to manufacture. Based on decades of design experience, the performance modeling of these stages is presented, techniques for design optimization are reviewed, and means for rapid machining are explained. The reader will gain insight to some of the most critical aspects of compressor design.