Ufak boy pompalarda tasarım dışı performans ve gürültü üzerine deneysel bir çalışma.

This thesis study is focused on experimentally investigating pump noise at design and off-design operations and its relations with pressure fluctuations. Small size pumps are placed in a semi-anechoic chamber and operated at various system conditions and various rotational pump speeds. Pump operational data, noise data and time dependent pressure data are recorded. Fast Fourier Transform spectra of noise and pressure data are compared. Coherence spectrum between sound pressure level and hydraulic pressures are obtained. Data processing, Fast Fourier Transform and cross correlation are conducted with specific software Soundbook SAMURAI. The experiments have indicated that system characteristics or pump size do not have any influence on the noise of pump. On the other hand, pump characteristics are found to be distinguishable by means of peak frequencies on the sound spectra which are proportional to blade passing frequency. Results of cross correlations also show that, pump outlet pressure is a more significant source of noise than pump inlet pressure.M.S. - Master of Scienc

Dynamic pressure probe response tests for robust measurements in periodic flows close to probe resonating frequency

A single-hole probe was designed to measure steady and periodic flows with high fluctuation amplitudes and with minimal flow intrusion. Because of its high aspect ratio, estimations showed that the probe resonates at a frequency two orders of magnitude lower than the fast response sensor cut-off frequencies. The high fluctuation amplitudes cause a non-linear behavior of the probe and available models are neither adequate for a quantitative estimation of the resonating frequencies nor for predicting the system damping. Instead, a non-linear data correction procedure based on individual transfer functions defined for each harmonic contribution is introduced for pneumatic probes that allows to extend their operating range beyond the resonating frequencies and linear dynamics. This data correction procedure was assessed on a miniature single-hole probe of 0.35 mm inner diameter which was designed to measure flow speed and direction. For the reliable use of such a probe in periodic flows, its frequency response was reproduced with a siren disk, which allows exciting the probe up to 10 kHz with peak-to-peak amplitudes ranging between 20%–170% of the absolute mean pressure. The effect of the probe interior design on the phase lag and amplitude distortion in periodic flow measurements was investigated on probes with similar inner diameters and different lengths or similar aspect ratios (L/D) and different total interior volumes. The results suggest that while the tube length consistently sets the resonance frequency, the internal total volume affects the non-linear dynamic response in terms of varying gain functions. A detailed analysis of the introduced calibration methodology shows that the goodness of the reconstructed data compared to the reference data is above 75% for fundamental frequencies up to twice the probe resonance frequency. The results clearly suggest that the introduced procedure is adequate to capture non-linear pneumatic probe dynamics and to reproduce time-resolved data far above probe resonant frequency

Ufak boyda santrifüj pompa ve fanların gürültü seviyelerinin uygun ortamda ölçülmesi ve gürültüye yönelik tasarım parametrelerinin belirlenmesi

TÜBİTAK MAG31.12.2007Makina mühendisliğinin uygulamalarında fan ile pompalar önemli bir yer oluşturmaktadır. Günümüzde kullanılan fan ve pompaların performanslarına ek olarak bu cihazların aero-akustik özellikleri ve dışarıya yaydıkları gürültü düzeyleri önemli bir problem olarak ortaya çıkmaktadır. Ses düzeyini istenilen seviyelerde tutacak tasarımlar yapabilmeye yönelik bilgi birikimi akışkanlar mekaniği, turbomakinalar, akustik ve mekanik titreşim konuları ile tasarım metodolojilerini biraraya getiren karmaşık bir araştırma konusu olmaktadır. Bu konuda çeşitli standardlar geliştirilmiş olup, analitik tahmin metodları ve ölçüm düzenekleri konusunda çalışmalar devam etmektedir. Proje kapsamında aksiyel ve santrifüj pompa ve fanların gürültü seviyeleri ve akustik özellikleri belirlenmiştir. Çalışma dahilinde Ortadoğu Teknik Üniversitesi Makina Mühendisliği Bölümü Akışkanlar Mekaniği Laboratuarında endüstri desteğiyle bu çalışmaya yönelik olarak yapılmış olan yarı-çınlamalı (semi-anechoic) oda kullanılacaktır. Çalışma üç temel aşamadan oluşmaktadır. İlk aşamada inşa edilen odanın uluslar arası standardlara uygunluğu belirlenecek, ikinci aşamada santrifüj fanların akışkandan (hava) kaynaklanan gürültü ve ses özellikleri belirlenecektir. 3. aşamada gene santrifüj pompaların akışkandan (su) kaynaklanan akustik özellikleri ve gürültü düzeyleri belirlenecektir. Çalışma sonunda akışkan etkisiyle oluşan ses ve gürültü düzeyleri ve buna bağlı bir tahmin metodu belirlenecektir. Projeye kapsamında yapılacak çalışmalar, bir doktora çalışması ile 2 yüksek lisans çalışmasını içermektedir.Fans and pumps are of great importance in Mechanical Engineering applications. In addition to the performance, aero-acoustic properties and noise generation levels of recently utilized fans and pumps become important. Designs keeping the noise in desired levels require the combination of knowledge on fluid mechanics, turbomachines, acoustics, mechanical vibration and design methodology. Standards have been developed on this subject, whereas studies on analytic prediction methods and measurement setups are continuing. This project consists of determination of noise generation levels and acoustic properties of axial and centrifugal pumps and fans. Experimental and numerical analyses are performed in the semi-anechoic room, constructed by an industrial support, is situated in Fluid Mechanics Laboratory in Mechanical Engineering Department in Middle East Technical University. Studies can be divided into three main sections. First of which includes assessment of whether the constructed room is appropriate to the international standards. The acoustic properties and noise generation due to fluid (air) flow through centrifugal fans will be determined in the second phase. The third section includes the determination of acoustic properties and noise generation level in centrifugal pumps due to fluid (water) flow. Analytic prediction method for noise generation level due to fluid flow will be determined at the end of the studies. Studies in the scope of the project include one PhD and two M.Sc. thesis

Frequency of juvenile idiopathic arthritis and associated uveitis in pediatric rheumatology clinics in Turkey: A retrospective study, JUPITER

Background Juvenile idiopathic arthritis (JIA), is the most common pediatric rheumatologic disorder with unknown etiology. Currently, no population-based data are available regarding the distribution of categories and frequency of uveitis in patients with JIA in Turkey. The purpose of this study was to evaluate the frequency of JIA-associated uveitis (JIAU) and distribution of JIA categories in a Turkish JIA cohort. Methods This was a retrospective study of 500 randomized patients in four pediatric rheumatology clinics in Turkey. Results Oligoarticular JIA (oJIA) was the most common JIA disease category in this study cohort (38.8%). The frequencies of the other categories were as follows: enthesitis-related arthritis (ERA), 23.2%; rheumatoid factor (RF)-negative polyarthritis, 15.6%; systemic arthritis, 12.2%; juvenile psoriatic arthritis, 5.2%; undifferentiated arthritis, 2.8%; and RF-positive polyarthritis, 2.2%. JIA-associated uveitis was observed in 6.8% of patients at a mean (Standard Deviation, SD) age of 9.1 (3.8) years over a mean JIA disease duration of 4 (1.9) years. Uveitis developed after joint disease, with a mean (SD) duration of 1.8 (1.9) years. Patients with oJIA had the highest rate of uveitis (12.9%) followed by patients with ERA (5.2%) and polyarticular RF-negative disease (3.8%). Compared with persistent oJIA, the extended oJIA category had a > 3-fold higher risk of uveitis (11.3% vs 27.7%; odds ratio, 3.38 [95% Confidence Interval, 1.09-10.4]). The most frequently administered drug after development of uveitis was tumor necrosis factor-alpha inhibitors (38.2%). Five patients (14.7%) had uveitis-related complications that required surgical intervention. Conclusions Turkish pediatric patients with JIA experience a lower frequency of oJIA and higher frequency of ERA than their white European counterparts; the occurrence of uveitis is also somewhat lower than expected. Geographic and ethnic factors may affect these differences and need further investigation

Prognostic factors for survival in children who relapsed after allogeneic hematopoietic stem cell transplantation for acute leukemia

Background Post-transplant relapse has a dismal prognosis in children with acute leukemia undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Data on risk factors, treatment options, and outcomes are limited. Procedure In this retrospective multicenter study in which a questionnaire was sent to all pediatric transplant centers reporting relapse after allo-HSCT for a cohort of 938 children with acute leukemia, we analyzed 255 children with relapse of acute leukemia after their first allo-HSCT. Results The median interval from transplantation to relapse was 180 days, and the median follow-up from relapse to the last follow-up was 1844 days. The 3-year overall survival (OS) rate was 12.0%. The main cause of death was disease progression or subsequent relapse (82.6%). The majority of children received salvage treatment with curative intent without a second HSCT (67.8%), 22.0% of children underwent a second allo-HSCT, and 10.2% received palliative therapy. Isolated extramedullary relapse (hazard ratio (HR): 0.607, P = .011) and relapse earlier than 365 days post-transplantation (HR: 2.101, P < .001 for 0-180 days; HR: 1.522, P = .041 for 181-365 days) were found in multivariate analysis to be significant prognostic factors for outcome. The type of salvage therapy in chemosensitive relapse was identified as a significant prognostic factor for OS. Conclusion A salvage approach with curative intent may be considered for patients with post-transplant relapse, even if they relapse in the first year post-transplantation. For sustainable remission, a second allo-HSCT may be recommended for patients who achieve complete remission after reinduction treatment

Relapse after allogeneic hematopoietic stem cell transplantation for acute leukemia in children: A survey by the Turkish Pediatric Bone Marrow Study Group of 255 cases

...European Society for Blood and Marrow Transplantatio