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The unsteady inlet guide vane (IGV)–impeller–diffuser interaction in a centrifugal compressor is investigated numerically and experimentally under different IGV prewhirl angles. The influence of IGV prewhirl angle on the flowfield and the unsteadiness of the impeller and diffuser are studied, and the mechanism of the unsteady IGV–impeller–diffuser interaction is explored. Results show that quite fair quantitative agreements are achieved between the predicted and measured flowfield. The IGV wake can decrease the unsteadiness on the impeller and diffuser, and the reduction of the unsteadiness caused by the IGV is a function of the IGV prewhirl angle. The unsteadiness in the diffuser with negative IGV angles is larger than that for positive prewhirl angles. The low-frequency oscillations inside the flowfield are induced by the IGV. When IGV prewhirl occurs, the basic frequency of the unsteady flow in the vaneless diffuser is mainly half of the blade passing frequency of the impeller. In practice, the IGV prewhirl angle can be adjusted to avoid unsteady vibrations in some off-design conditions, with reliability and performance improved simultaneously.

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It is very important for rapeseed hybrid production to develop and utilize a novel cytoplasmic male sterility (CMS) system concerning the possible risk because of a narrow cytoplasm background. Here the anatomy of anther development in the CMS system, named NCa, was observed using light microscope and transmission electron microscope, and the restriction fragment length polymorphism (RFLP) analyses of mitochondrial DNA of NCa sterile line were also performed in comparison with the other rapeseed sterile lines, such as pol, nap, ogura, and tour. The anther abortion of this CMS line occurred at the later uninucleate microspore stage, and the anatomic aborting characteristics were obviously different from all the other rapeseed CMS lines reported before. The RFLP analyses revealed that five probe/ enzyme combinations could distinguish the five CMS lines. The results of anatomic observations and mitochondrial DNA polymorphism indicated that the NCa CMS system is a novel one which differs from the pol, nap, ogura, and tour systems.