Authors:

Marzuk Hasan

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About Paper:

A common thrust stand calibration system for the Rocket-Application Modular RDE (RAMR) and the High-flow Air-breathing Modular RDE (HAMR) test stands at the Maurice J. Zucrow Laboratories at Purdue University is designed to accurately calibrate thrust measurements up to 4000 pounds of force using a ground-truth calibration load cell. When conducting engine testing, it is valuable to understand thrust output in conjunction with combustion data in the RDE to better correlate how properties of combustion affect the engine's efficiency, specific impulse, and other thrust-based performance parameters. However, the force measured by the load cell is an inaccurate representation of thrust. On a voltage - force graph, when no force is applied, the voltage may be non-zero (y-intercept) and the slope of this graph depends upon thrust as well as extraneous factors related to the test stand design, such as thermal expansion of the 1000K air feed system and internal mechanical stresses, all leading to inaccurate force measurements. The calibration system is designed to measure these inaccuracies at a range of force magnitudes representative of possible thrust values and correct hot-fire thrust data for more accurate thrust measurements. This document details the design of a modular calibration system which incorporates considerations for rapid set-up/tear-down, rapid calibration execution, and remote operation. A configurable pneumatic system is selected to provide the most versatility within a compact footprint. Two swappable configurations are used, allowing for any desired force output within 50 lbf accuracy between 188 lbf and 4790 lbf. The system connects to the aft end of the RDE using variable- length turnbuckles attached to the static portion of the test stand, which accommodate a wide range of engine sizes. To calibrate the thrust stand, a range of forces will be applied using the pneumatic cylinders. The force measured by the ground truth load cell will be compared to the measurement load cells, any delta represents force losses from mechanical stresses in the stand. After hot-fire testing, force measurements will be corrected by adding this delta, resulting in more accurate thrust data for RDE performance analysis. Keywords: Calibration; Rocket; Testing; Pneumatic

Source:

Purdue University / 2024

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Co-authors:

Marzuk Hasan