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The prediction of airfoil characteristics

Description: This report describes and develops methods by which the aerodynamic characteristics of an airfoil may be calculated with sufficient accuracy for use in airplane design. These methods for prediction are based on the present aerodynamic theory and on empirical formulas derived from data obtained in the N. A. C. A. variable density wind tunnel at a Reynolds number corresponding approximately to full scale. (author).
Date: January 1, 1930
Creator: Higgins, George J

Prediction of downwash and dynamic pressure at the tail from free-flight measurements

Description: The present measurements form a continuation of earlier flight tests published in a previous report for predicting the downwash at the tail of an airplane. The method makes use of the tail itself as integrating contact surface to the extent that, beginning from the measurement of the self-alignment of the elevator, the mean downwash angle and dynamic pressure at the tail are determined. The instrumental accuracy is considerably improved if the elevator is completely separate from the controls during the tests, because the effect of friction on the self-alignment of the elevator is then reduced to a minimum and a finer elevator weight balance is rendered possible. The structural design of the push-rod uncoupling mechanism is also described.
Date: July 1, 1942
Creator: Eujen, E

Prediction of flame velocities of hydrocarbon flames

Description: The laminar-flame-velocity data previously reported by the Lewis Laboratory are surveyed with respect to the correspondence between experimental flame velocities and values predicted by semitheoretical and empirical methods. The combustible mixture variables covered are hydrocarbon structure (56 hydrocarbons), equivalence ratio of fuel-air mixture, mole fraction of oxygen in the primary oxygen-nitrogen mixture (0.17 to 0.50), and initial mixture temperature (200 degrees to 615 degrees k). The semitheoretical method of prediction considered are based on three approximate theoretical equations for flame velocity: the Semenov equation, the Tanford-Pease equation, and the Manson equation.
Date: January 1, 1954
Creator: Dugger, Gordon L & Simon, Dorothy M

Prediction of the Critical Heat Flux in Forced Convection Flow

Description: From summary: "A superposition model is developed to predict the critical heat flux in forced convection flow. The model is applied to available experimental results in boiling water flows and good agreement is obtained between the model and test data over the multitude of geometries, flow rates, pressures, and fluid enthalpies tested to-date."
Date: June 20, 1962
Creator: Levy, S.

Prediction of the effects of propeller operation on the static longitudinal stability of single-engine tractor monoplanes with flaps retracted

Description: The effects of propeller operation on the static longitudinal stability of single-engine tractor monoplanes are analyzed, and a simple method is presented for computing power-on pitching-moment curves for flap-retracted flight conditions. The methods evolved are based on the results of powered-model wind-tunnel investigations of 28 model configurations. Correlation curves are presented from which the effects of power on the downwash over the tail and the stabilizer effectiveness can be rapidly predicted. The procedures developed enable prediction of power-on longitudinal stability characteristics that are generally in very good agreement with experiment.
Date: January 1, 1949
Creator: Weil, Joseph & Sleeman, William C , Jr

Prediction of Tube Bundle Instabilities : Case Studies

Description: The concurrent acquisition of flow-induced vibration (FIV) test data for several configurations of an industrial-size shell-and-tube heat exchanger made possible this evaluation of the HXVA method for six cases. Recommendations to improve the prediction capability were made, with priority on the excitation mechanism for dense fluid flows with non-uniform velocity distributions.
Date: November 1986
Creator: Mulcahy, T. M.; Halle, Henry & Wambsganss, M. W.

Preignition characteristics of several fuels under simulated engine conditions

Description: The preignition characteristics of a number of fuels have been studied under conditions similar to those encountered in an engine. These conditions were simulated by suddenly compressing a fuel-air mixture in contact with an electrically heated hot spot in the cylinder head of the NACA combustion apparatus. Schlieren photographs and indicator cards were taken of the burning, and the hot-spot temperatures necessary to cause ignition under various conditions were determined.
Date: January 1, 1941
Creator: Spencer, R C

A preignition indicator for aircraft engines

Description: Report describes an electrical-relay circuit that uses cylinder thermocouples for indicating preignition or misfiring in an aircraft engine. The potential dangers of preignition and the importance of an easy-to-use, practical preignition indicator are provided. The operating principles of the indicator and a description of its functioning, calibration, and installation procedures are also included.
Date: February 1945
Creator: Dallas, Thomas & Harries, Myron L..

Preignition-limited performance of several fuels

Description: Preignition-limited performance data were obtained on a supercharged CFR engine at two sets of operating conditions over a wide range of fuel-air ratios to determine the preignition characteristics for the following five fuels: s-3 reference fuel, s-3 plus 4 ml. tel per gallon, afd-33(140-p), benzene, and diisobutylene. Maximum thermal-plug temperatures at constant intake-air pressures were also determined to correlate the preignition characteristics of each fuel with its ability to increase general engine-temperature levels. Additional runs were made to compare the preignition-limited performance of triptane, triptane plus 4 ml. tel per gallon, and an-f-28r fuel.
Date: January 1, 1945
Creator: Male, Donald W & Evvard, John C

Preimpoundment Water Quality in the Tioga River Basin, Pennsylvania and New York

Description: Introduction: The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, and aided by the Susquehanna River Basin Commission, investigated the water quality of the Tioga River basin, Pennsylvania. The study, made from September 1973 to September 1978, was designed to evaluate water quality at various sites prior to impoundment. Results of the investigation will aid the Corps of Engineers in designing the operation of three reservoirs that were in the final stages of construction in late 1979.
Date: March 1981
Creator: Ward, Janice R.

Preimpoundment Water Quality of Raystown Branch Juniata River and Six Tributary Streams, South-Central Pennsylvania

Description: Abstract: The Raystown Branch Juniata River watershed, which is the main water source for Raystown Lake, is a 960-square-mile (2,490 square kilometers) drainage basin in south-central Pennsylvania. Preimpoundment water-quality data were collected on the Raystown Branch and six tributary streams in the basin. Specific conductance values varied inversely with water discharge. The pH values were extremely low only at the Shoup Run site. Dissolved oxygen concentrations observed at all sites indicated a relatively high oxygen saturation level throughout the year. Seasonal variations in nitrate-N and orthophosphate-P levels were measured at the main inflow station at Saxton, Pa. The highest concentrations of nitrate-N and orthophosphate-P occurred in the winter and spring months and the lowest concentrations were measured during the summer and fall. Bacteriological data indicated no excessive amounts of fecal matter present at the in-flows. Soil samples collected at four sites in the impoundment area were predominantly of the Barbour, Philo, and Basher series, which are considered to be highly fertile soils with silt-loam and sandy-loam textures. Morphological features of the lake basin and lo~ nutrient levels at the ·inflows should prevent excessive weed growth around the lake perimeter.
Date: June 1976
Creator: Williams, Donald R.

Preknock vibrations in a spark-ignition engine cylinder as revealed by high-speed photography

Description: The high-speed photographic investigation of the mechanics of spark-ignition engine knock recorded in three previous reports has been extended with use of the NACA high-speed camera and combustion apparatus with a piezoelectric pressure pickup in the combustion chamber. The motion pictures of knocking combustion were taken at the rate of 40,000 frames per second. Existence of the preknock vibrations in the engine cylinder suggested in Technical Report no.727 has been definitely proved and the vibrations have been analyzed both in the high-speed motion pictures and the pressure traces. Data are also included to show that the preknock vibrations do not progressively build up to cause knock. The effect of tetraethyl lead on the preknock vibrations has been studied and results of the tests are presented. Photographs are presented which in some cases clearly show evidence of autoignition in the end zone a considerable length of time before knock occurs.
Date: January 1, 1944
Creator: Miller, Cearcy D & Logan, Walter O , Jr

Preliminary Aerodynamic Data Pertinent to Manned Satellite Reentry Configurations

Description: Report presenting some experimental data and calculations for a variety of aerodynamic shapes considered for use as manned reentry vehicles. Three types of vehicles were tested: non-lifting bodies, lifting bodies, and airplane-like vehicles. All of the configuration types were found to be suitable for use as manned reentry vehicles with certain fin and flap modifications for certain shapes.
Date: July 21, 1958
Creator: Penland, Jim A. & Armstrong, William O.