Experimental analysis of influence of double-layer bump foils on aerodynamic thrust foil bearings performance

Purpose Gas thrust foil bearings (GTFBs) are used to balance the axial load of engines. However, in some working conditions of large axial force, such as the use of single impeller air compressor, the load capacity of GTFBs is still insufficient. To solve this problem, the load capacity can be improved by increasing the stiffness of bump foil. The purpose of this paper is to explore a scheme to effectively improve the performance of thrust foil bearings. In the paper, the stiffness of bump foil is improved by increasing the thickness of bump foil and using double-layer bump foil. Design/methodology/approach The foil deformation of GTFBs supported by three different types of bump foils, the relationship between friction power consumption and external force and the difference of limited load capacity were measured by experimental method. Findings The variation of the foil deformation, bearing stiffness, friction power consumption with the external force at different speeds and limited load capacity are obtained. Based on experimental results, the selection scheme of bump foil thickness is obtained. Originality/value This paper provides a feasible method for the performance optimization of GTFBs.

Differences between proximal and distal endometrial monolayer thickness in women aged over 50 years undergoing saline infusion sonohysterography

Background Saline infusion sonohysterography (SIS) is a procedure performed to evaluate the endometrium in women with postmenopausal bleeding. Purpose To investigate differences in endometrial monolayer measurements in women aged >50 years undergoing SIS. Material and Methods Retrospective study of women aged >50 undergoing SIS. Endometrial echo (EE) was measured according to the International Endometrial Tumor Analysis (IETA) guidelines. Monolayer thickness was compared between anterior and posterior uterine walls and between the monolayer that was proximal or distal to the ultrasound probe. Presence and location of focal thickening and polyps on each of the monolayers were assessed. Results SIS was performed in 608 patients. Of them, 485 (79.8%) had anteverted, 85 (14%) retroverted, and 38 (6.2%) a midposition uterus. The mean posterior monolayer was thicker than the anterior monolayer (2.14 mm vs. 1.88 mm; P = 0.002). The distal monolayer was thicker than the proximal layer in both anteverted and retroverted uteri (2.18 mm vs. 1.84 mm; P < 0.0001). In 16% of women, the difference between distal and proximal monolayers was ≥1 mm. Focal thickening was seen 3.3 times more frequently in the distal endometrium. Among women with a double layer EE >4 mm, 18.8% had a proximal layer of <2 mm while only 4.6% had a distal EE <2 mm. Conclusion Distal endometrium measures thicker than the proximal endometrium in most SIS cases and in one out of six women, the difference is >1 mm. The distal layer is three times more likely to contain focal thickening. Sonologists should be conscious of possible enhancement artifact when measuring the EE during SIS.