System Level Overview of the Hypergolic Gelled Propellant Lab (GPL) Dr. Timothée L. Pourpoint Dr. Steve Heister Dr. William Anderson Dr. Robert Lucht Dr. Steven Son Purdue University Maurice J. Zucrow Laboratories 1
GPL Overview 5 9 1 2 Oxidizer workstation Fuel workstation 1 3 7 4 6 8 2 3 4 5 6 General use fume hood Data acquisition system Ventilation system Workbenches 7 Test stand Dedicated laboratory space for NTO-based and hydrazine-based propellant studies Dedicated ventilation system (0.02" H 2 O P between laboratory and control room) 8 9 LASER Capillary Rheometer 2
Droplet Burning/Vaporization Gelled MMH Droplet Combustion Objective: Improve fundamental understanding of the burning behavior of gelled MMH droplets System Capabilities Variable chamber conditions Inert or oxidizing environment Max pressure: ~10 atm Max temperature: ~450 K Optical access from multiple angles 3
Droplet Burning/Vaporization Results: 1) MMH evaporates from the droplet surface during combustion 2) A semi-rigid shell of HPC is formed 3) The HPC layer blocks diffusion of the fuel vapor 4) A bubble of MMH vapor is formed under the HPC layer (Fig 1-3 ) 5) The pressure of the bubble ruptures the outer layer (Fig 4) 6) A jet of MMH vapor is expelled from the ruptured area (Fig 4-6) MMH Droplet Combustion in a N 2 O 4 Environment t = 0 ms t = 32 ms t = 34 ms 1) 2) 3) t = 35 ms t = 38 ms t = 39 ms 4) 5) 6) Droplet is approximately 2 mm in diameter 4
Droplet Burning/Vaporization Droplets of MMH with 3 wt.% HPC show dependency between mass burning rate and droplet surface area. Mass burning rate mg / s Disturbances to the combustion process caused by accumulation of the solid HPC layer diminish during the combustion process. Droplets with a liquid layer exhibit the opposite behavior with increasing disturbances as combustion progresses. Reduced Volume V/V i 14 12 10 8 6 4 2 1.5 1 0.5 R² = 0.9122 2 4 6 8 10 12 D 2 i mm 2 MMH with 3% HPC MMH with 3% Tetraglyme 0 0 0.2 0.4 0.6 0.8 1 Reduced Time t/t b 5
Droplet Burning/Vaporization High Repetition Rate Laser Diagnostics Objective Obtain insight into dynamics of MMH droplet combustion, flame structure and provide data needed for chemical kinetics modeling System Capabilities Variable chamber conditions Planar Laser Induced Fluorescence (PLIF) imaging at up to 5 khz to observe short duration combustion phenomena Tunable laser wavelength to excite the OH radical High frequency 3-D imaging with rotating mirror 6
Droplet Burning/Vaporization Results OH PLIF images of liquid MMH droplets burning in air 2mm P c = 103.4 kpa 2mm P c = 413.7 kpa Impingement point OH PLIF images of impinging jet test of H 2 O 2 Tetraglyme/NaBH 4 2mm 7
Droplet Burning/Vaporization Hypergolic Droplet Contact Experiment Objective Explore fundamental combustion phenomena for contacting hypergolic propellant droplets in a controlled environment System Capabilities Controlled environment Pressure Temperature Ambient gas composition and velocity Impact velocities Up to 10 m/s Optically accessible PLIF, thin filament pyrometry, absorption spectroscopy, etc. 8
Droplet Burning/Vaporization Results Quantified pre-ignition explosion due to rapid gas production with MMH/RFNA Examined less toxic hypergolic propellants DMAZ, TMEDA, TMEDA/DMAZ, BMIMDCA, etc. MMH contacting RFNA Future Research Explore pre-ignition explosion at higher impact velocities Shift toward less toxic hypergolic propellants 9
Non-Newtonian Propellant Characterization Rheological Characterization of non-newtonian Propellants Objective Investigate and quantify non-newtonian fluid behavior at conditions experienced by propellants during all stages of operation from low shear storage up to high shear injection System Capabilities Low-intermediate shear rotational rheology Propellant yield stress, storage/loss modulus, etc. High shear capillary rheology Safe testing of toxic propellants Controllable shear rate up to 10 6 1/s Remote operation at driving pressures up to 3000 psia 10
Non-Newtonian Propellant Characterization Capillary Assembly Fuel Side of Rheometer Cabinet Loading Tube Linear Encoder Piston Rod Capillary Tube Pressure Transducers Waste Collection Water Flush Tank 11
Non-Newtonian Propellant Characterization Results Dashed lines represent viscosities of liquid MMH and RP-1 Results are very similar for MMH and RP-1 gel Silica properties dominate rheological behavior Viscosity of the gel at high shear is much higher than that of the base fluid Direct impact on modeling efforts for gelled propellants 12
Spray Ignition/Combustion Hypergolic Propellant Spray Ignition/Combustion Objective: Characterize and gain an understanding of the ignition and combustion characteristics of hypergolic propellant sprays System Capabilities 60 Included Angle 360 Optically Accessible Chamber Variable chamber pressure and temperature Variable O/F, R m, injection duration Highly repeatable injection conditions ~3 ms to steady state injection Pulsed operation 13
Spray Ignition/Combustion Results: MMH/RFNA Less Toxic Hypergolic Propellants H 2 O 2 Triglyme/NaBH 4 Pulsed Actuator Response 5 mm Pulse 1 Pulse 2 5 mm 5 mm 14