Development of A multichannel data acouisition and analysis software for the experimental investigation of cavitating flows in pumps

Abstract

oz POMPALARDAKİ KAVİTASYONLU AKIŞLARIN DENEYSEL İNCELENMESİ İÇİN ÇOK KANALLI VERİ ALMA VE ANALİZİ YAZILIMIN GELİŞTİRİLMESİ BİLGEN, İsmail Hakkı Yüksek Lisans Tezi, Makina Mühendisliği Ana Bilim Dalı Tez Yöneticisi: Prof. Dr. O. Cahit ERALP Haziran, 1994, 220 sayfa Santrifüj pompalardaki kavitasyon sorununu incelemek için değişik debi ve emme basınçlarında deneysel bir araştırma yapılmıştır. Deneyler sabit debide emme basıncının, dolayısıyla net pozitif emme yüksekliğinin düşürülmesinin etkisi ve bunun farklı debilerde tekrar edilmesi üzerine planlanmıştır. Pompa girişinde farklı noktalara yerleştirilen iki basınç duyargası ile akıştaki basınç değişiklikleri analog veri olarak kaydedilmiştir. Alınan analog verilerin sayısal verilere dönüştürülmesi, 100 kHz kapasiteli PCL-818 Advantech A/D çevrim kartı ve bu kartın programlanması ile gerçekleştirilmiştir. Basınç sinyallerinin analogdan sayısala çevrimi ve izgesel analizi için bir yazılım paketi geliştirilmiştir. Bu yazılımın doğru çalıştığı yapılan denemelerle kanıtlanmıştır. Kavitasyonun başlangıç ve gelişimini incelemek için verilerin güç izgesi araştırılmıştır. Ortaya çıkan sonuçlan desteklemek için iki farklı aralıktaki frekans değerlerinin RMS oranlarını karşılaştırarak, enerji içeriği çözümlemesiABSTRACT DEVELOPMENT OF A MULTICHANNEL DATA ACQUISITION AND ANALYSIS SOFTWARE FOR THE EXPERIMENTAL INVESTIGATION OF CAVITATING FLOWS IN PUMPS BİLGEN, Ismail Hakkı M.S. in Mechanical Engineering Supervisor: Prof. Dr. O. Cahit ERALP June 1994, 220 pages An experimental research for investigating the cavitation problem of centrifugal pumps at different flowrate and suction pressure is performed. Experiments were planned on the effect of decreasing the suction pressure, consequently the net positive suction head, at constant flowrate and repeating this at different flowrates. The pressure changes are recorded as analog data through the pressure transducers located at different places of the pump inlet. The conversion of the acquired analog data into digital data is performed by programming a PCL-818 Advantech A/D converter card of 100 kHz capacity. A software package was developed for the analog to digital conversion and spectral analysis of the pressure signals. It was proved that the developed software run properly after performing several case studies. The power spectra of the data were investigated in order to detect the inception and extent of cavitation. Energy content analysis was also used to support the revealed results by comparing the m

ABSTRACT DEVELOPMENT OF A MULTICHANNEL DATA ACQUISITION AND ANALYSIS SOFTWARE FOR THE EXPERIMENTAL INVESTIGATION OF CAVITATING FLOWS IN PUMPS BİLGEN, Ismail Hakkı M.S. in Mechanical Engineering Supervisor: Prof. Dr. O. Cahit ERALP June 1994, 220 pages An experimental research for investigating the cavitation problem of centrifugal pumps at different flowrate and suction pressure is performed. Experiments were planned on the effect of decreasing the suction pressure, consequently the net positive suction head, at constant flowrate and repeating this at different flowrates. The pressure changes are recorded as analog data through the pressure transducers located at different places of the pump inlet. The conversion of the acquired analog data into digital data is performed by programming a PCL-818 Advantech A/D converter card of 100 kHz capacity. A software package was developed for the analog to digital conversion and spectral analysis of the pressure signals. It was proved that the developed software run properly after performing several case studies. The power spectra of the data were investigated in order to detect the inception and extent of cavitation. Energy content analysis was also used to support the revealed results by comparing the mRMS ratios of the frequency values of two different ranges. As a conclusion, the spectral analysis methods have been found to be useful tools for this purpose and energy content analysis has been shown to be a good supporting comparison method. Keywords: Cavitation, Centrifugal Pumps, Pressure Transducers, A/D Converter Card, Spectral Analysis. Science Code : 625.04.03 IV