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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Three Dimensional Instantaneous Spray Measurements of Additively Manufactured Candidate Injector Schemes at Varying Pressure Drops

Additively manufactured (AM) injectors have the potential to improve upon the combustion performance achieved using traditionally manufactured (TM) injectors. Traditionally manufactured injector combustion performance decreases greatly in off-design conditions. Additively manufactured injectors hold the potential to sustain high combustion performance over a broader range of operating conditions than currently seen in TM injectors. Additively manufactured injectors promise to offer higher resistances to instability and achieve better overall propellant mixing and atomization for all types of combustion devices. This study expands upon previous studies that used 2-D imaging techniques to characterize the injector spray pattern of candidate AM injector elements. In this study, 3-D instantaneous measurements of the injector spray pattern are taken, allowing for deeper insight into the liquid spray breakup, an inherently 3-D phenomena. Stereo imaging is used for three dimensional analysis, which utilizes two cameras at different angles to reconstruct a three dimensional reconstruction. With this information, AM injectors can be designed to improve propellant mixing and atomization and reduce breakup length. As part of this work, a high-pressure, cold flow experimental spray facility was modified to measure each injector’s spray characteristics in terms of 𝑅𝑒 𝐿 and 𝑊𝑒 𝑔 . This facility is operated to capture instantaneous stereo photographic images, mass flow rates, and injector element thrust for pressure drop across the injector face ranging from 100 to 200 psig at a stiffness ratio of 1.0.

Murphy Mitchell↗
NASA NTRS1965

Flow control valve is independent of pressure drop

Remote control of fluid flow in a low-power system is established by a flow control valve with a flapper and nozzle flow control. Constant rates are maintained despite fluctuating pressure across the valve.

Source record↗
NASA NTRS2014

Injector Element which Maintains a Constant Mean Spray Angle and Optimum Pressure Drop During Throttling by Varying the Geometry of Tangential Inlets

A method for determining the optimum inlet geometry of a liquid rocket engine swirl injector includes obtaining a throttleable level phase value, volume flow rate, chamber pressure, liquid propellant density, inlet injector pressure, desired target spray angle and desired target optimum delta pressure value between an inlet and a chamber for a plurality of engine stages. The tangential inlet area for each throttleable stage is calculated. The correlation between the tangential inlet areas and delta pressure values is used to calculate the spring displacement and variable inlet geometry. An injector designed using the method includes a plurality of geometrically calculated tangential inlets in an injection tube; an injection tube cap with a plurality of inlet slots slidably engages the injection tube. A pressure differential across the injector element causes the cap to slide along the injection tube and variably align the inlet slots with the tangential inlets.

Trinh, Huu P.↗
NASA NTRS1972

Comparison of Predicted and Experimental Heat-Transfer and Pressure-Drop Results for an Air-Cooled Plug Nozzle and Supporting Struts

A calculational procedure is presented to analyze the heat-transfer and fluid-flow characteristics of a convectively air -cooled plug-nozzle operating on an afterburning turbojet engine. Anderson's method was used to predict hot-gas static pressures in the supersonic stream with fully expanded flow (high nozzle-pressure ratios); the results were excellent. For low nozzle-pressure ratios, the flow was assumed to expand one-dimensionally and isentropically to the plug back pressure. Wall temperatures predicted using this latter pressure distribution agreed well with the wall temperatures predicted using the measured hot-gas pressures (maximum deviation was about 30 K (54 deg R)). Either an in tegral boundary-layer technique or a simple pipe-flow equation may be used to calculate convective heat transfer from the hot gas to the wall. The simple pipeflow equation results in the prediction of slightly higher wall temperatures than does the integral technique. Experimental wall temperatures were generally in good agreement with the two predicted wall temperature distributions. Excellent agreement was noted b etween measured and predicted coolant static-pressure distributions. The plug-coolant temperature rise was generally overpredicted by about 22.2 K (40 deg R); possible explanations are offered. Although an an alysis of the struts, which support the plug, was purposely kept simple, reasonable results were obtained. Potential flow over an ellipse was used to calculate hot-gas static pressure; the results were satisfactory.

Graber, E. J., Jr.↗
NASA NTRS1993

On the Accuracy of CFD-Based Pressure Drop Predictions for Right-Angle Ducts

The predictive capability of computational fluid dynamics (CFD) codes for turbulent flow through curved ducts is of significant importance to the design and performance analysis of modern rocket engine flowpaths. Code calibration and validation studies for this class of flow are desireable to estimate the performance margin and operating range of components designed using Navier-Stokes methods. Parametric experimental studies such as that of Weske (NACA ARR W-39) provided a wealth of performance data for the design of single- and compound elbow configurations with various cross-sections, curvature and aspect ratios at varying Reynolds numbers. In that work, the majority of data is presented in the form of loss coefficients, characterizing pressure losses due to duct curvature, and including losses due to wall friction. Using measured friction coefficients, losses of equivalent straight lengths of duct are subtracted, resulting in performance curves useful for design computations. These data are currently used in a CFD-based parametric study covering a broad range of operating conditions. Of particular interest for the accuracy of CFD predictions are the effects on pressure loss due to inlet boundary layer thickness (dependent on upstream development length), and the wall treatment for the turbulence equations (conventional wall functions vs. wall integration using a two-layer model). The experimental data are reassessed in the form of an error analysis, and are compared with CFD predictions for 18 computational cases. Grid-independence, grid spacing, and convergence requirements of the cases are discussed. Conclusions regarding the relative importance of the parametric variables will be presented.

Brankovic, Andreja↗