HIGH-PRESSURE BURNING-RATES OF JA2 AND NITROMETHANE PROPELLANTS

Open Access
Author:
Derk, Gregory
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 08, 2019
Committee Members:
  • Richard A Yetter, Thesis Advisor
  • Jacqueline Antonia O'Connor, Committee Member
  • Karen Ann Thole, Committee Member
Keywords:
  • nitromethane
  • JA2
  • supercritical combustion
  • high-pressure combustion
  • monopropellant
Abstract:
A new experimental chamber has been created to directly observe combustion events under ambient temperatures and at constant pressures up to 300 MPa. Several supporting systems were designed and built to operate this chamber including high-pressure gas systems and redundant control systems. To test the data gathering and analysis techniques, the JA2 modified double-base gun propellant was tested at pressures between 14.1 – 207.7 MPa. Experimental burning rates were similar to previously published rates and correlated to: 𝑟𝑏 (𝑚𝑚/𝑠) = 1.659[𝑃(𝑀𝑃𝑎)]^0.91 (for 14.1 < P < 207.7 MPa) By utilizing a windowed chamber, the first direct observations of the quality of JA2 combustion at elevated pressures were obtained. The burning rates of nitromethane, when burned as a monopropellant, were obtained for pressures between 3.6 – 101.7 MPa. Three distinct burning regimes were observed for nitromethane when burned in a 10.6 mm ID glass tube: 1. For pressures between 3.6 – 18.2 MPa, burning rates correlated to: 𝑟𝑏(𝑚𝑚/𝑠) = 0.1829[𝑃(𝑀𝑃𝑎)]^1.15 2. For pressures between 18.2 – 40.8 MPa, burning rates followed a near-linear transition, as a function of pressure, between a burning rate described by a liquid-gas phase interface to a supercritical burning rate that could be described by a freely-propagating flame speed. 3. For pressures between 40.8 – 102 MPa, burning rates correlated to: 𝑟𝑏(𝑚𝑚/𝑠) = 11.04[𝑃(𝑀𝑃𝑎)]^0.679 Nitromethane was also tested using tubes of varying sizes from 1 – 14 mm ID. The size of the tube was found to affect burning rates in the 2nd and 3rd burning regimes with an increasing tube diameter correlating to an increasing burning rate for a given pressure. A set of equations was developed to predict burning rates in the third burning regime for tube sizes within this range. To support the experimental analysis, numerical and analytical predictions for several nitromethane physical properties were developed. These predictions were not experimentally verified during the study.