Metal-Reinforced Ceramic Composites for Turbine Vanes

Experiments have been performed which indicate the potential of metal-fiber reinforced-ceramic matrix composites for use as a high temperature structural matrix. The results of this work reveal that metal-fiber reinforced ceramics obey compostie theory, and that after cracks occur in the matrix, a pseudo-ductility can be introduced into the composite. This toughness can be predicted from equations of work required to pull the fibers through the matrix. The relationship between strength, toughness, and crack depths, are dependent on the inter-facial bond between the fibers and matrix as well as fiber diameter and length. Based on the results of these experiments, multicomponent materials with superior resistance to failure from oxidation, thermal shock, and high mechanical stresses in air above 2400 F can be postulated. These materials have potential for use as gas turbine engine vanes.

Gas Turbine Recuperator Technology Advancements

Because of intense development in the aircraft gas turbine field over the last 30 years, the fixed boundary recuperator has received much less development attention than the turbomachinery, and is still proving to be the nemesis of the small gas turbine design engineer. For operation on cheap fuel, such as natural gas, the simple cycle-engine is the obvious choice, but where more expensive liquid fuels are to be burned, the economics of gas turbine operation can be substantially improved by incorporating an efficient, reliable recuperator. For many industrial, vehicular, marine, and utility applications it can be shown that the gas turbine is a more attractive prime mover than either the diesel engine or steam turbine. For some military applications the fuel logistics situation shows the recuperative gas turbine to be the most effective power plant. For small nuclear Brayton cycle space power systems the recuperator is an essential component for high overall plant efficiency, and hence reduced thermal rejection to the environment. Data are presented to show that utilization of compact efficient heat transfer surfaces developed primarily for aerospace heat exchangers, can result in a substantial reduction in weight and volume, for industrial, vehicular, marine, and nuclear gas turbine recuperators. With the increase in overall efficiency of the recuperative cycle (depending on the level of thermal effectiveness, and the size and type of plant), the cost of the heat exchanger can often be paid for in fuel savings, after only a few hundred hours of operation. Heat exchanger surface geometries and fabrication techniques, together with specific recuperator sizes for different applications, are presented. Design, performance, structural, manufacturing, and economic aspects of compact heat exchanger technology, as applied to the gas turbine, are discussed in detail, together with projected future trends in this field.

Boundary Layers on Rough Compressor Blades

Blades of axial flow compressors are often roughened by corrosion or erosion. There is only scant information about the influence of this roughening on the boundary layers of the blades and thereby on the compressor efficiency. To obtain detailed information for calculating the efficiency drop due to the roughness, experimental investigations with an enlarged cascade have been executed. The results enabled to develop new formulas for a modified friction coefficient in the laminar region and for the laminar-turbulent transition and the separation points of the boundary layer. Thus, together with the Truckenbrodt theory, it was possible, to get a good reproduction of the experimental results.

Crashworthiness of Safe Fuels

Safety fuels such as emulsified and gelled fuels have been studied over the past several years as one means for reducing the post-crash fire hazard associated with aircraft accidents. However, through the work described herein, only recently has a quantitative evaluation been made to characterize the safety performance of these fuels. The safety performance evaluation program described in this paper includes an initial series of screening tests designed to obtain the characteristics of safe fuels in the aircraft crash environment. The authenticity of the screening tests relative to the full-scale crash environment was evaluated through a second series of experiments designed to simulate a full-scale aircraft crash environment. A crashworthiness evaluation criterion was established in terms of an “ignition susceptibility parameter” to quantitize the relative safety performance of different fuels. The conclusions of this research clearly show that significant savings in lives and equipment can be realized if safe fuels which perform within the non-hazardous envelope of the ignition susceptibility parameter are operationally incorporated in present-day aircraft.

Proposed Gas Turbine Procurement Standard

This paper describes the specific procurement information required from the purchaser and corresponding information required from the gas turbine manufacturer in the various phases of procurement. Through the guidelines presented the preparation of procurement specifications and manufacturer’s response will be facilitated and mutual understanding promoted. In sequence, the paper deals with: (a) the purchaser’s inquiry, (b) the manufacturer’s proposal or bid tendering and (c) required after order information: Specimen data sheets are included to illustrate in detail the material presented. This paper is one of a series of ASME papers which present a Proposed Gas Turbine Procurement Standard.

Actuator Disc Flow Calculated by Relaxation: An Approach to the Analysis Problem of Turbomachinery

When dealing with axisymmetric rotating flow through turbomachines of a given geometry, the existence of discontinuities, due to incidence at the leading edges of the blades, has to be accepted as a logical consequence of axisymmetry. By introducing special conditions resulting from dynamical equilibrium considerations, a relaxation method has been enabled to cope with these discontinuities.

A Comparison of Calculated Flows in Radial Turbines With Experiment

The flow in the rotors of three radial turbines, of differing peak efficiency, is analyzed using a streamline curvature method. The turbine of greatest efficiency is analyzed at both on- and off-design conditions; the other two turbines at the design point only. Comparison is made between the predictions of the calculation and the experimental determination of two features of the flow — the shroud static pressure distribution and the outlet velocity profile. Fair agreement with the shroud pressure is obtained at on-design conditions, but correlation with the exit velocity distribution is poor. Some improvement in the calculation of the exit profile is achieved when the analysis is modifed so as to allow for the experimentally observed angle of deviation at the blade trailing edge. Consideration is given to the ability of the analytical method to discriminate between turbines which prove experimentally to have high or low peak efficiency.

Modification of Jet Fuels to Decrease the Fire Hazard in Survivable Aircraft Crashes

This paper is directed to the modification of jet fuels to reduce the inherent fire hazard of such fuels. Some of the problems and compromises involved in this development program are discussed. The theoretical concept pursued is outlined and some of the physical properties of the final compromise modified fuel are shown.

Noise and Other Environmental Considerations in the Design and Planning of Gas Compressor Stations in the U.K.

This paper briefly outlines some of the considerations taken into account in the design and planning of gas compressor stations for the UK Natural Gas Transmission System. Environmental considerations, and in particular the aspects of noise, play a large part in the design of these stations. The requirements for silencing to meet very low ambient noise levels and the development of gas turbine compressor unit enclosures is dealt with in some detail. The need for acoustically efficient and aesthetically pleasing structures is emphasized. The paper compares some representative alternative designs for individual enclosures with the design of an equivalent building and concludes that for small numbers of units, the individual enclosure is the economic solution. Other aspects of noise, including venting of gas are discussed and future design trends indicated. In the consideration of future designs, ease of maintenance and security are fundamental considerations, together with the need to ensure that noise emitted will not pollute the environment.

Design Study of an Advanced Concept Simple Gas Turbine for Possible Use in Low Emission Automobiles

United Aircraft Corporation studied the potential costs of various possible gas turbine engines which might be used to reduce automobile exhaust emissions. As part of that study, United Aircraft of Canada undertook the preliminary design and performance analysis of high-pressure-ratio nonregenerated (simple cycle) gas turbine engines. For the first time, high levels of single-stage component efficiency are available extending from a pressure ratio less than 4 up to 10 or 12 to 1. As a result, the study showed that the simple-cycle engine may provide satisfactory running costs with significantly lower manufacturing costs and NOx emissions than a regenerated engine. In this paper some features of the preliminary design of both single-shaft and a free power turbine version of this engine are examined. The major component technology assumptions, in particular the high pressure ratio centrifugal compressor, employed for performance extrapolation are explained and compared with current technology. The potential low NOx emissions of the simple-cycle gas turbine compared to regenerative or recuperative gas turbines is discussed. Finally, some of the problems which might be encountered in using this totally different power plant for the conventional automobile are identified.