摘要：Automotive turbochargers require small dimen-sion stages able to supply the engine fresh mixture or airinquire over a wide speed and load range, McCutcheon andBrown [1], Capobianco and Gambarotta [2]. Radial tur-bines with nozzle guide vanes have found a wide applica-tion in diesel engine turbochargers and a lesser extent insmall gas turbine engines. Matching the turbocharger ge-ometry to engine operating conditions normally ensuresgood engine performances. The benefits of variable ge-ometry turbochargers are described by McCutcheon andBrown [1] and Okazaki et al. [3]. Several configurationswere tested and evaluated such as movable side walls vo-lute and variable geometry stators, Capobianco and Gam-barotta [2]. One of the most efficient configurations con-sists in pivoting the turbine stator blades to modify theflow incidence and therefore the nozzle section area. Theinfluence of a variable guide vane nozzle on the designparameters of a radial turbine stage is studied by Binder etal. [4]. The authors found that an important variationaround the nominal operating design geometry disturbs theperformance characteristics and the initial design parame-ters are not conserved. Consequently, the nominal operat-ing design approach is clearly not sufficient to get anadapted geometry for a large operating range. They sug-gest extending this approach to a new concept which takesinto account a large operating range of the turbine. But it isstill difficult for the designer to take into account the com-plexity of variable geometry stages from the very firststeps of the design.
