Application of Particle-Size Analysis Data for the Determination of Air/Cleaner Performance

A general purpose centrifuge method for measuring particle-size distribution of air-filter inlet, outlet and catch dust samples is demonstrated. Treatment and analysis of data to determine air-cleaner performance based on size distribution is shown for two types of air filters, a louver and a glass-fiber media filter. The advantages and limitations of the method and interpretations of results associated with the application of these procedures for arriving at efficiency versus particle-size performance curves, and for predicting filter efficiency for any given dust are discussed.

Sea Experience With Pratt and Whitney Aircraft FT12 Gas Turbine in LCM-8

The design features of the FT12 gas turbine are described. The development background of the gas turbine is reviewed along with service-experience background which, with appropriate marinizing treatments, prompted evaluating the gas turbine in a sea-borne environment. The program conducted in an LCM-8 landing craft, its highlights and results are discussed.

Development of a High-Speed Reverse Gear for Marine Gas Turbine

This paper describes the operation and salient design features of a high-speed reversing gear used with the Solar 1100-hp Saturn gas-turbine Engine. Development history leading to successful marine applications is reviewed.

Use of Scale-Model Aids in Solution of Complex Air-Flow Design Problem

This paper describes a method used to design the inlet section of a jet-engine test cell. Calculations, accomplished with the use of standard, tabulated flow formulas and coefficients which can be found in basic fluid-flow texts, are shown. The step-by-step procedure enables the reader to use the methods and formulas in this paper as a guide for solving similar problems. Selection of an optimum turning-vane configuration is described herein by the use of tufts of cotton in the air stream of the model. A table is included which compares the model data with actual full-scale construction at various stages.

The Effect of Reynolds Number on the Performance of Partial Admission and Re-Entry Axial Turbines

In turbines designed for open-cycle auxiliary power systems for orbital and reentry vehicles, turbine blade Reynolds numbers of less than 1000 are not uncommon. An investigation of the effect of Reynolds number in this range on the performance of partial admission and reentry axial turbines, which are the predominant types of turbine used in this class of power system, was recently conducted. This paper describes the test program carried out, the results of the investigation, and examines the implications of the results on the design of turbines for this application. In general, it was found that the drop in efficiency with reduced Reynolds number was not so rapid with the types of turbine studied as with the full-admission turbine. The optimum pressure-ratio split was also found to be significantly affected by the Reynolds numbers encountered in the turbine stages.

Evaluation of Air Filter Test Methods

There are three generally accepted test methods in current use for determining the effectiveness of air filters used for the collection of atmospheric dust. These three methods are (a) weight, (b) dust spot, and (c) DOP, which uses dioctyl-phylate as the aerosol. These test methods are discussed briefly and illustrations are used to assist the reader in visualizing the concentration of dust which will remain in the clean-air stream for efficiency values reported by each test method.

The Effect of Reynolds Number on the Performance of a Tangential-Flow Turbine

The tangential-flow turbine, which was developed from the drag turbine in an effort to take advantage of the circulatory flow in the drag-turbine passages, frequently has been proposed for use in power systems characterized by low specific speeds. Since such systems often operate with low exhaust pressures which lead to low Reynolds numbers in turbine passages, it is of interest to determine the effect of Reynolds number on the performance of this type of machine. Theoretical determination of the effect is made difficult by the complex three-dimensional nature of the flow in this type of turbine. This paper describes a program of tests which was run on a tangential-flow turbine to investigate the effect of Reynolds number, and presents a simplified theoretical approach to the Reynolds-number effect which is shown to give a reasonable prediction of the trend of the effect.

The Pulsating-Flow Performance of Inward Radial-Flow Turbines

The study of the pulsating-flow behavior of small inward radial-flow turbines as used in automotive type turbosuperchargers is of great importance in relation to the mode of operation of such units in conjunction with internal-combustion engines. In complete engine-turbocharger systems detailed analysis of turbine behavior is handicapped by the complex interaction of engine and turbocharger, with resultant interdependence of operating variables. In the present investigation the use of a rotary valve driven at various predetermined speeds and discharging cold air under critical conditions ensures close control of the pressure pulses constituting the turbine-energy input. It has therefore been possible to investigate systematically the influence of the most important parameters, viz., (a) pulse frequency, (b) pulse form, (c) pulse amplitude, (d) pipe length, (e) pipe diameter, and (f) turbine speed.

Thermal-Stress and Low-Cycle Fatigue Data on Typical Materials

This paper presents the results of low-cycle-fatigue tests wherein either thermal strain or mechanical strain was the independent variable. The materials investigated were primarily ferrous alloys for use in nuclear reactors. The analysis of results was based on plastic-strain-range measurements which could be made reproducibly in the 2 × 10−5 range. Graphs of plastic strain range versus cycles to failure were often found to be independent of large variations in temperature and cycle time. The results from thermal-fatigue and constant-temperature-fatigue tests were usually indistinguishable on these graphs, suggesting that identical metallurgical phenomena occurred in each type of test.

Effects of Surface Imperfections on the Thermal-Fatigue Life of Metals

The effects of surface defects on the low-cycle, thermal-fatigue life of two steels and two superalloys were determined. Thermal fatigue was induced by cyclic self-resistance heating of the specimens in a restraining fixture that converted the thermal strains to mechanical strains. Although the results were quite erratic, they indicate statistically that surface roughness and defects are detrimental to the thermal-fatigue life. Thermal-fatigue is much more adversely affected by transverse shallow sharp notches and cracks than by point-type notches or general surface roughness.