Pulsation Analysis in Positive Displacement Pump Systems Using Waterhammer, Modal and Animation Software
James M. Blanding, Ph.D., DuPont Company; Trey Walters, P.E., Applied Flow Technology - Presented at the 45th Turbomachinery & 32nd Pump Symposia Conference, September 13, 2016
High-pressure and flow metering systems often include a positive displacement (PD) pump and a network of piping and process equipment. Steady state pressure and flow dynamics (pulsation) is a common problem in PD pump systems, which can cause high vibration, fatigue failures, frequent maintenance outages, and flow uniformity or product quality problems.
A number of engineering consulting firms have developed computational capabilities in pulsation, which they offer in the form of client services, but these are expensive. So too is the limited amount of commercial pulsation-specific software.
This paper describes a methodology to computer model pulsation using a combination of general-purpose and readily available, widely used software, such as AFT Impulse. Waterhammer Software – Normally used to simulate transients, if periodic flow forcing is modeled, the transients die out, and leave only the steady-state pulsation Modal Software – Frequency analysis of high-speed digital time history data can be done with many software platforms, including those for Experimental Modal Analysis (EMA), Data Acquisition, or general-purpose Statistical/Mathematical modeling Animation Software – Typically included with EMA software, animation is not necessary, but is useful to visually show pressure and flow response across the system at acoustic natural frequencies and for PD pump flow forcing An example problem shows how to efficiently model complex systems to determine acoustic natural frequencies, mode shapes, and pulsation response to PD pump forcing. Fundamentals of waterhammer and important modeling techniques are discussed. An introduction to EMA and digital signal processing is also provided.