Propagating Stall in Compressors With Porous Walls

A modification is presented to the Emmons/Stenning analysis for predicting stall propagation, taking into account the unsteady flow through the end wall of a cascade row of compressor blades. It is shown that if radial flow from the blade channels is permitted, then the condition for flow instability is changed. The expression obtained for the flow coefficient at which stall occurs indicates an improvement in operating range, with virtually no effect on stall cell speed. Experimental evidence suggests that a mechanism such as that described may be the reason for the delay in stall onset produced by porous wall treatment of axial compressors.

Early Experience With a 31,050-Hp Regenerative Cycle Gas Turbine

To gain the economic advantages of size, the trend has been to use larger and larger compressor/driver units in many types of service. Coupled with this “economy of size” trend, the recent sharp increase in the cost of fuel has made driver efficiency a major consideration. This paper describes the application, and discusses the early experience, of a recent installation of a very large, efficient gas turbine driven compressor unit in a natural gas transmission pipeline station. The task of the compressor/driver unit and the station arrangement are described and details of the turbine and compressor are presented. Then a brief account of the operating history is given.

The Vorbix Burner: A New Approach to Gas Turbine Combustors

The vorbix burner (acronym for Vortex Burning and Mixing) represents a new approach to a practical gas turbine combustor design. The concept exploits the Rayleigh instability of swirling flows to enhance the mixing and combustion rates. The combination of a two-stage fuel system with a piloted combustor leads to a unique high rate technique for fuel prevaporization within the combustor proper. This paper presents the fundamental concepts in the definition of the vorbix combustor and the results of exploratory tests conducted on can (tubular) and annular vorbix combustors. The results indicate that this type of combustor has unique performance characteristics that include excellent stability and high combustion efficiency over wide excursions in operating fuel air ratios in addition to substantially reduced emission levels during high power operation.

The Refracting Inlet: A New Concept for Aircraft Inlet Noise Suppression

Observations of wave refraction in flowfields containing large transverse velocity gradients have suggested a means by which refraction effects could be used to aid suppression of the noise propagating forward through aircraft gas turbine inlets. The first part of this paper describes an experiment using a schlieren apparatus to observe waves passing through inlet-type flowfields. The second part describes a test program using model inlets to examine the feasibility of the refracting inlet concept.

Recuperator Development Trends for Future High Temperature Gas Turbines

The current energy crisis and substantial increases in the costs of liquid and gaseous fuels, combined with reduced pollutant emission requirements, make the higher efficiency recuperative gas turbine cycle economically attractive for industrial and vehicular application. For future low cost, high temperature, small gas turbines, with improved cycle efficiencies, it is postulated that the complete hot section of the engine (combustor, ducts, turbine nozzle and rotor) will be all ceramic and may include a ceramic heat exchanger. Few of the answers are available today in the areas of ceramic recuperator performance, cost and structural integrity and concentrated development efforts are required to demonstrate the viability of a fixed boundary ceramic gas turbine heat exchanger. This paper briefly outlines possible design and development trends in the areas of exchanger configuration, surface geometry and materials, and it includes specific sizes and economic aspects of ceramic recuperators for future advanced low SFC gas turbines.

Recent Application of Multistage Centrifugal Compressors for Gas Transmission

Multistage compressor parameters are related to recent gas transmission applications having a diversity of requirements, ranging from large flows to high pressure.

Cascade Research on a Small, Axial, High-Work, Cooled Turbine

This paper presents the results of an experimental cascade investigation of the aerodynamic performance of a 1.524-cm (0.6-in.) blade height, low aspect ratio, highly loaded, cooled turbine. The experimental program was performed with a cold flow annual sector cascade with various geometric and aerodynamic perturbations. The perturbation included nozzle endwall contour, inlet turbulence and velocity distortion, stator and rotor solidity, rotor loading and nozzle cooling flow and point of injection. The turbine design evolved through a parametric analysis considering a turboshaft engine configuration required to have a 750-hr life at design power output and satisfy realistic mechanical constraints. The gas generator turbine configuration selected for investigation was a single-stage turbine with a turbine inlet temperature of 1316 C (2400 F) and an actual work output of 418.68 kJ/kg, (180 Btu/lb). The baseline turbine was sized for a stage work coefficient of 5.0 at the hub radius and an average flow coefficient of 0.675 for a best mechanical-aerothermodynamic compromise to meet realistic engine constraints.

A Study on the Flow Mechanism Within Centrifugal Impeller Channels

Investigations concerning the flow patterns within centrifugal impeller channels have been made for many years. However, many of the problems remain unresolved about the secondary flow and the loss production mechanism within impeller channels. In the present study, measurements of the flow mechanism within impeller channels under the off-design conditions were performed by employing yaw probes to compare the results with those at the design point. The impellers with straight radial blades employed in the present study were of the same configuration except the shroud profiles which made diffusion ratios different from each other. From the present results, it became clear that the loss production mechanisms and the flow patterns within impeller channels were essentially unvaried both under design and off-design operations. The results thus obtained by the present study were furthermore compared with the others to examine the reliability of these results.

Industrial Gas Turbine Materials and Some Service Experiences

After discussion of the design and materials of construction of the RUSTON TA series gas turbines, information relating to applications and lifetimes is given. The main portion of the paper deals with a variety of interesting material problems and their solutions, that have arisen over the years. These have been reported under the headings of: Influence of atmosphere; influence of fuel; influence of temperature; influence of material; and influence of lubricating oil. Finally, reference is made to specific installations and their operating data in order to re-affirm the suitability of the industrial gas turbine as a power source in a very wide variety of demanding applications and environments.

Isothermal Shape Rolling of Airfoil Sections for Gas Turbines

Isothermal Shape Rolling is a new hot metal shaping process developed by the Solar Division of International Harvester. The process is unique in that it uses refractory metal rolls with closed loop control of forming temperature. Heating is achieved by passage of electric current through the workpiece from the electrically conductive shaping rolls. The process eliminates much of the processing costs encountered in the more conventional rolling of airfoil sections in corrosion or heat resistant alloys. Cost reduction is made possible by single pass rolling to the finished airfoil, freedom from surface contamination of the rolled surface and the fine surface finish of the as-rolled section. The general characteristics of the process are described and examples of application to gas turbine components are presented.