A New Design of the Tooth Profile for Single Screw Compressors
The wear of star wheel teeth is an importance issue in the single screw compressor. In order to enhance the wearresistance of star wheel teeth, some new profiles of the meshing pair were proposed to replace the currently used straight line envelope profile, such as single column envelope, multi-straight line (or multi-column) envelope. In this paper, a curved surface of the tooth flank is suggested. The groove flank is the envelope surface corresponding to the curved surface of the tooth flank. Section profile of the new tooth flank is a curved line, which could be elliptical, hyperbolic or involute. During the tooth meshing with the groove, the contact line between the tooth flank and the groove flank could move back and forth in the whole area of the tooth flank. This design is expected to improve the lubricating between the tooth flank and the groove flank, and to prolong the service life of the single screw compressor. Geometric and kinematic investigation of the star wheel and the screw rotor is established. And a new designed tooth flank of the meshing pair is introduced in this paper. Numerical control high-velocity cutting technology is suggested to fabricate the new star-wheel and the screw rotor.
A Multicolumn Envelope Meshing Pair for Single Screw Compressors
This paper introduces a new meshing pair profile envelope by multicolumn in single screw compressors. The screw groove flank of the new meshing pair is a multisegment surface, and the star-wheel tooth flank consisted of multicylindrical surfaces. When the compressor is operating, the position of the contact line on the tooth flank with the screw groove flank uniformly moves in one revolution, which is rather different from the stationary contact position of existing meshing pair profiles. The new meshing pair will result in the improved wear-resistance and longer operation life, lower gas leakage, and higher efficiency of the compressor.
The bradykinin B1 receptor and the central regulation of blood pressure in spontaneously hypertensive rats
We evaluated if the brain bradykinin (BK) B1 receptor is involved in the regulation of blood pressure (BP) in conscious rats. Basal mean BP and HR were 115±2 and 165±3 mmHg and 345±10 and 410±14 beats min−1 in Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR), respectively. Intracerebroventricular (i.c.v.) injection of 1 nmol B1 receptor agonist Lys‐desArg9‐BK significantly increased the BP of WKY and SHR by 7±1 and 19±2 mmHg, respectively. One nmol Sar[D‐Phe8]‐desArg9‐BK, a kininase‐resistant B1 agonist, increased the BP of WKY and SHR by 19±2 and 17±2 mmHg, respectively and reduced HR in both strains. I.c.v. injection of 0.01 nmol B1 antagonists, LysLeu8‐desArg9‐BK or AcLys[D‐βNal7,Ile8]‐desArg9‐BK (R715), significantly decreased mean BP in SHR (by 9±2 mmHg the former and 14±3 mmHg the latter compound), but not in WKY. In SHR, the BP response to R715 was associated to tachycardia. I.c.v. Captopril, a kininase inhibitor, increased the BP of SHR, this response being partially prevented by i.c.v. R715 and reversed into a vasodepressor effect by R715 in combination with the B2 antagonist Icatibant. I.c.v. antisense oligodeoxynucleotides (ODNs) targeted to the B1 receptor mRNA decreased BP in SHR, but not in WKY. HR was not altered in either strain. Distribution of fluorescein‐conjugated ODNs was detected in brain areas surrounding cerebral ventricles. Our results indicate that the brain B1 receptor participates in the regulation of BP. Activation of the B1 receptor by kinin metabolites could participate in the pathogenesis of hypertension in SHR.