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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

High Energy Cutting and Stripping Utilizing Liquid Nitrogen

The Aerospace Industry has endeavored for decades to develop hybrid materials that withstand the rigors of mechanized flight both within our atmosphere and beyond. The development of these high performance materials has led to the need for environmentally friendly technologies for material re-work and removal. The NitroJet(TM) is a fluid jet technology that represents an evolution of the widely used, large-scale water jet fluid jet technology. It involves the amalgamation of fluid jet technology and cryogenics technology to create a new capability that is applicable where water jet or abrasive jet (water jet plus entrained abrasive) are not suitable or acceptable because of technical constraints such as process or materials compatibility, environmental concerns and aesthetic or legal requirements. The NitroJet(TM) uses ultra high-pressure nitrogen to cut materials, strip numerous types of coatings such as paint or powder coating, clean surfaces and profile metals. Liquid nitrogen (LN2) is used as the feed stream and is pressurized in two stages. The first stage pressurizes sub cooled LN2 to an intermediate pressure of between 15,000 and 20,000 psi at which point the temperature of the LN2 is about -250 F. The discharge from this stage is then introduced as feed to a dual intensifier system, which boosts the pressure from 15,000 - 20,000 psi up to the maximum operating pressure of 55,000 psi. A temperature of about -220 F is achieved at which point the nitrogen is supercritical. In this condition the nitrogen cuts, strips and abrades much like ultra high-pressure water would but without any residual liquid to collect, remove or be contaminated. Once the nitrogen has performed its function it harmlessly flashes back into the atmosphere as pure nitrogen gas. The system uses heat exchangers to control and modify the temperature of the various intake and discharge nitrogen streams. Since the system is hydraulically operated, discharge pressures can be easily varied over a very wide range providing considerable flexibility for various operations. The NitroJet(TM) is an advance on the nitrogen fluid jet technology initially developed at the Idaho National Engineering Laboratory in Idaho Falls, Idaho. NitroCision(R) first introduced the NitroJet(TM) into a commercial setting in 2003 and there has been considerable interest from many diverse sectors of government and industry since then. While the current system is an industrial system with the size and mass normally associated with industrial applications, a smaller system that is much more compact is being contemplated for those applications that do not need the full capabilities of the larger system. The NitroJet(TM) can be deployed as a fixed or mobile system with multiple end effectors capable of cutting, stripping, cleaning, and surface profiling either in robotic or manual applications.

Hume, Howard↗
NASA NTRS1981

Mass and Momentum Turbulent Transport Experiments with Confined Coaxial Jets

Downstream mixing of coaxial jets discharging in an expanded duct was studied to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the propulsion community for combustor flow modeling. Flow visualization studies showed four major shear regions occurring; a wake region immediately downstream of the inlet jet inlet duct; a shear region further downstream between the inner and annular jets; a recirculation zone; and a reattachment zone. A combination of turbulent momentum transport rate and two velocity component data were obtained from simultaneous measurements with a two color laser velocimeter (LV) system. Axial, radial and azimuthal velocities and turbulent momentum transport rate measurements in the r-z and r-theta planes were used to determine the mean value, second central moment (or rms fluctuation from mean), skewness and kurtosis for each data set probability density function (p.d.f.). A combination of turbulent mass transport rate, concentration and velocity data were obtained system. Velocity and mass transport in all three directions as well as concentration distributions were used to obtain the mean, second central moments, skewness and kurtosis for each p.d.f. These LV/LIF measurements also exposed the existence of a large region of countergradient turbulent axial mass transport in the region where the annular jet fluid was accelerating the inner jet fluid.

Johnson, B. V.↗
NASA NTRS1983

Statistical characteristics of velocity, concentration, mass transport, and momentum transport for coaxial jet mixing in a confined duct

An experimental study of mixing downstream of coaxial jets discharging into an expanded circular duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used for combustor flow modeling. A combination of turbulent momentum transport rate and two velocity component data was obtained from simultaneous measurements with a two-color LV system. A combination of turbulent mass transport rate, concentration and velocity data was obtained from simultaneous measurements with laser velocimeter (LV) and laser induced fluorescence (LIF) systems. These measurements were used to obtain mean, second central moment, skewness and kurtosis values for three velocity components and the concentration. These measurements showed the existence of countergradient turbulent axial mass transport where the annular jet fluid was accelerating the inner jet fluid. Results from the study are related to the assumptions employed in the current mass and momentum turbulent transport models.

Johnson, B. V.↗
NASA NTRS1981

Flow through axially aligned sequential apertures of the orifice and Borda types

Choked flow rate and pressure profile data were obtained and studied for two axially aligned sequential configurations consisting of four Borda type inlets of 1.9 1/D with two separation distances of 0.8 and 30 diameters and four orifice type inlets of 0.5 1/D with two separation distances of 0.66 and 32 diameters. Data were obtained using fluid nitrogen over the reduced inlet temperature and pressure range 0.68 T/T sub c gas and P/P sub c to 2. A flow coefficient reduced temperature plot can be used to represent the flow rate data for each geometry. At the larger separation distances, the pressure profiles dropped sharply at the entrance and partially recovered within each of the Borda and orifice inlet configurations; the exception being the last inlet where at low entrance temperatures, fluid jetting could occur. For the smaller spacings fluid jetting was prevalent throughout each of the inlet configurations at lower inlet temperatures. These results are in qualitative agreement with data of tubes with single Borda or sharp edge orifice type inlets to 105 1/D and water flow visualization studies.

Hendricks, R. C.↗
NASA NTRS1981

Flow through axially aligned sequential apertures of the orifice and Borda types

Choked flow rate and pressure profile data were taken and studied for two axially aligned sequential configurations consisting of: (1) Four Borda type inlets of 1.9 1/D with two separation distances of 0.8 and 30 diameters. (2) Four orifice type inlets of 0.5 1/D with two separation distances of 0.66 and 32 diameters. A flow-coefficient reduced-temperature plot can be used to represent the flow rate data for each geometry. At the larger separation distances, the pressure profiles dropped sharply at the entrance and partially recovered within each of the Borda and orifice inlet configurations; the exception being the last inlet where at low entrance temperatures, fluid jetting could occur. For the smaller spacings fluid jetting was prevalent throughout each of the inlet configurations at lower inlet temperatures. These results are in qualitative agreement with data of tubes with single Borda or sharp-edge orifice type inlets to 105 1/D and water flow visualization studies.

Hendricks, R. C.↗
NASA NTRS2006

Excavation of Regolith by Impinging Jets of Gas

There are many situations in nature and technology where particulate matter is excavated by a fluid jet. Such a process is often used to excavate soil or to dig wells. Air jets are often used to transport particulate matter such as powders in various industrial processes. Similar situations occur in nature, as when waterfalls scour holes in sand. In other cases, the excavation is unwanted such as when a rocket lands on the sandy or dusty surface of a planet or moon. Recent research into regolith excavation by gas jets has obtained new insights into the physical processes of that excavation, and these may lead to new advances in technology for more efficient fluid-jet excavation processes and for better control of the unwanted excavation effects of landing rockets. This talk will explain the new insights and point to future work supporting lunar exploration.

Metzger, Philip T.↗