With an increase in the number of space transport applications, the need for larger, more powerful and efficient rocket motors are the need of the day. Thus, optimizing the thrust generated by these rocket motors is of great importance, which can be achieved by bell-shaped nozzles with high area ratios. However, the high area ratios result in significant over-expansion at sea level conditions, that cause flow separation inside the nozzle and generate side-loads. Several novel nozzle designs are being developed to overcome the flow separation phenomenon. Characterizing the thrust output from these nozzles in a laboratory is vital for their successful development and implementation. Conventionally, the thrust from a nozzle is measured using load cells on a thrust stand. A thrust stand can provide limited information on the loads generated by the flow through a nozzle, such as the magnitude and direction of time average loads, but the flow features responsible for generating them remain elusive. In the present study, a novel method to estimate thrust from flow-field data, obtained by Particle Image Velocimetry (PIV) experiments and Pitot pressure survey at the nozzle exit, is proposed. The thrust estimated by this method is then validated with the conventional thrust measurements using load cells. A Mach 4 convergent-divergent nozzle with 12.7 mm throat diameter was tested using compressed air at a range of substantially over-expanded operating conditions with Nozzle pressure ratio (NPR) of 4, 5, 6, 7 and 7.5, at two temperature ratios (TR =1.2 and TR =1.5). The flow field at the nozzle exit was surveyed at these conditions using a Pitot tube mounted on a 2-D traverse system and the stereo PIV technique. Using the data obtained from both the flow surveys in the rocket thrust equation, the values of thrust are estimated. The thrust estimated from the flow field data showed identical levels at both temperature ratios. This suggested that temperature ratio has a negligible impact on the thrust measured at respective NPR. Using a load cell, the thrust produced by the nozzle was measured for each NPR at isothermal condition (TR=1). A comparison between the thrust obtained by the two methods verified that PIV and pressure surveys could be used to determine the time-averaged thrust of a nozzle to within 6% of the load cell readings. This experimental study provides a reliable alternative method for rocket nozzle thrust measurements / A Thesis submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2018. / February 2, 2018. / Flow-filed diagnostics, load cell measurements, Over-expanded nozzles, Particle Image Velocimetry (PIV), Rocket Nozzle, Thrust Measurements / Includes bibliographical references. / Rajan Kumar, Professor Directing Thesis; William S. Oates, Committee Member; Neda Yaghoobian, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_653522 |
| Contributors | Vemula, Rohit Chandra (author), Kumar, Rajan (professor directing thesis), Oates, William (committee member), Yaghoobian, Neda (committee member), Florida State University (degree granting institution), College of Engineering (degree granting college), Department of Mechanical Engineering (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, master thesis |
| Format | 1 online resource (79 pages), computer, application/pdf |
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