Effect of shear heat on hydrodynamic lift of brush seals in oil sealing

Importance of hydrodynamic lift clearance has been stated in previous studies [1, 2, 3]. At those studies, derivation of closed form function for oil temperature has been performed and the shear heat dissipation effect has been successfully integrated into the lift force formulation. Oil pressure is successfully derived by tracking three different ways, all of which give very similar results to each other. All these analyses are advanced fluid mechanics and heat transfer analyses, which give consistent results with real-life applications. In this study, function of shear heating effect included in hydrodynamic lift clearance formulation. For a different pressure loads (which is a design parameter and known), change of hydrodynamic lift clearance with rotor surface speed can be found without requiring any experimental leakage data. Furthermore, theoretic lift clearance has consistency with the experimental lift data

A study of brush seal oil pressure profile including temperature-viscosity effects

After proven performance in air applications, brush seals are being considered for oil and oil mist sealing in aero-engines, turbines and generators. The viscous medium between the high speed rotor surface and bearing surfaces formed by brush seal bristle tips generates a hydrodynamic lifting force that determines seal clearance and leakage rate in oil sealing applications. Hydrodynamic lift force and seal clearance have strong dependence on oil temperature and viscosity. In a previous study, short bearing theory has been applied to a single bristle to obtain a solution for hydrodynamic lift force developing at a bristle tip. Rather than individual bristles, this work evaluates pressure for the bristle rows. Applying the Reynolds bearing theory to the control volume between bristle tips and the rotor surface fluid pressure distribution is obtained under each bristle row. Effective temperature and effective viscosity approach has been adopted. Pressure distribution for each bristle row in the rotor axial direction is evaluated. Then, pressure profiles for each bristle row are combined to yield the axial pressure profile under the entire brush pack

NITRIC OXIDE AND LACTATE RESPONSES TO MAXIMAL INTERMITTENT ACUTE EXERCISE

Abstract. Nitric oxide (NO) is a gas with vasodilator and metabolic regulator properties. The present study aimed to examine the relation between NO and lactic acid, and NO difference in acute anaerobic and aerobic loads in aerobic and anaerobic exercise groups. Three groups participated in this study; each group consisted of 11 men with similar physical characteristics. The groups consisted of swimmers as the aerobic group (AeG), volleyball players as the anaerobic group (AnG), and control group (CG). Participants were given 3 acute exercise phases in the scope of lactate minimum speed test (LMSt). NO and lactic acid measurements were taken at particular phases in LMSt. Lactate minimum speed values of AeG (11.5±1.1 km·h-1) were significantly higher than those of the CG (p0.05; 9.2%) than the base NO. Additionally, contrary to the AnG, an increase was observed in ΔNOlevel during active recovery and in NO level after the reloading phase in AeG. Also, lactate elimination level of the aerobic group was higher than the other groups. As a result; these findings show the role of a more active lactate elimination capacity since NO levels in the aerobic group are higher than the other groups following a maximal intermittent exercise.Key words: Nitric oxide, lactate minimum, performance, aerobic, anaerobic

Tenisçilerde performans ile kan nitrit düzeyleri ve toparlanma kapasitesi arasındaki ilişkiler

Nitrik oksit (NO) vazodilatör, antioksidan özelliklere sahip ayrıca kan glikoz (GL) ve laktat (LA) metabolizmasında da rolü olan bir gazdır. Tenisteki performans, “groundstroke” dediğimiz forehand/backhand vuruşları, servisin hızları ve isabet başarı yüzdesi ile tenise özgü hareketleri tekrarlı olarak gerçekleştirebilme kapasitesine bağlıdır. Literatürde NO’ nun tenis performansı, LA düzeyleri ve LA eliminasyonu ile ilişkilerini birlikte inceleyen bir çalışmaya rastlanmadı. Bu nedenle bu çalışmada; düzenli olarak antrenman yapan 20-30 yas arası elit erkek tenis oyuncularında (n=20), kortta bir egzersiz modeli geliştirerek; performans yüzdesi, NO, LA ve GL parametreleri arasındaki ilişkilerin araştırılması amaçlandı. Bu modelde; şiddeti top atış hızı ile belirlenen ve gittikçe artarak maksimale kadar süren ve aralıklı 4 periyottan oluşan ve toplam 14 dk. süren bir forehand/backhand vurusu gerçekleştirilmiş olup isabet yüzdesi de performans olarak tanımlanmıştır. Bu maksimal egzersiz periyodundan hemen sonra da 20 dk.’lık pasif toparlanma periyodu başlatılmıştır. Her bir periyot ve toparlanma sonrasında alınan parmak ucu kanlarından belirlenen parametreler ile performans arasındaki ilişkiler incelenmiştir. Sporcuların fiziksel ve fizyolojik (Anaerobik esik) ölçümleri yapılmıştır. Verilerin analizlerinde SPSS 12.0 istatistik programı kullanılmıştır ve anlamlılık değerleri p<0.05 olarak belirlenmiştir. Her bir periyot sonunda: Kan NO, LA, GL ve KAH parametreleri lineer bir artış gösterirken performans yüzdesi ise bunların tersine bir düşüş gösterdi. Yine her bir periyot sonrasındaki performans, kan NO (3.periyot hariç), LA ve GL değerleri, KAH ve LA eliminasyonu ve anaerobik esik değerleri arasında anlamlı bir ilişki bulunmadı. Sadece 3. periyotta, performans ve kan NO değeri arasında (r = 0.494; p<0.05) ve toparlanma periyodu esnasındaki NO ve glikozun düşme hızları (oranları) arasında anlamlı bir ilişki bulundu. Sonuç olarak: Bu çalışmada egzersizin kan NO düzeyleri artırıcı yönde olumlu bir etkisi görüldü. Toparlanma esnasındaki NO ve GL metabolizmalarının birbiriyle ilişkili olması dikkat çekicidir. Elit tenis sporcularında 3. periyottakine benzer submaksimal bir antrenman modeli performans açısından daha yararlı olabilir. Ayrıca bu egzersizle NO’ da görülen artış sağlık açısından da önem taşımaktadır

Brush seal performance measurement system

Brush seals are rapidly replacing conventional labyrinth seals in turbomachinery applications. Upon pressure application, seal stiffness increases drastically due to frictional bristle interlocking. Operating stiffness is critical to determine seal wear life. Typically, seal stiffness is measured by pressing a curved shoe to brush bore. The static-unpressurized measurement is extrapolated to pressurized and high speed operating conditions. This work presents a seal stiffness measurement system that is capable of measuring brush seal stiffness under engine operating pressure and speed condition which is not available in open literature. Stiffness measurement system design, testing methodology and calibration procedure are discussed

The Relationship Between the Force Production in the Isometric Squat and Bench Press Exercises and the Lower and Upper Body Anaerobic Power Parameters

The primary aim of this study was to investigate relationships between the muscular force in the isometric bench press and squat movements and the Wingate anaerobic test (WanT) results for the upper and lower body. Secondary purpose was to investigate possible correlations between the WanT and the explosive isometric force. Eighteen healthy male volunteer athletes (age: 23.37 ± 1.65, height: 178.37 ± 5.67, body mass; 76.69 ± 3.73) with at least 2 years of strength training participated in the study. During the two test sessions, one-repetition maximum (1-RM), isometric squat and isometric bench press tests and anaerobic power tests with Wingate anaerobic power and arm ergometer were performed. Results of the study showed a high degree of correlation between isometric squat (Squatiso) and lower body Peak Power and Average Power (r (14) = 0.766, p ;lt; 0.001 and r (14) = 0.690, p ;lt; 0.003 respectively). However, there was no significant relationship between Squatiso and Fatigue Index (FI) (p ;gt; 0.05). In isometric bench press, there was also a high level of correlation between upper body peak power and average power (r (14) = 0.620, p ;lt; 0.01 and r (14) = 0.749, p ;lt; 0.001 respectively). These data can be used to classify the power capabilities of the athletes and determining the training loads to be used in achieving the training goals. In addition, periodic measurements of the maximum power and strength performances of the athletes with field tests and laboratory test batteries according to the characteristics of the sports branch can also provide significant contributions to the coaches and researchers