The Role of the Recuperator in High Performance Gas Turbine Applications

With soaring fuel costs and diminishing clean fuel availability, the efficiency of the industrial gas turbine must be improved by utilizing the exhaust waste heat by either incorporating a recuperator or by co-generation, or both. In the future, gas turbines for power generation should be capable of operation on fuels hitherto not exploited in this prime-mover, i.e., coal and nuclear fuel. The recuperative gas turbine can be used for open-cycle, indirect cycle, and closed-cycle applications, the latter now receiving renewed attention because of its adaptability to both fossil (coal) and nuclear (high temperature gas-cooled reactor) heat sources. All of these prime-movers require a viable high temperature heat exchanger for high plant efficiency. In this paper, emphasis is placed on the increasingly important role of the recuperator and the complete spectrum of recuperative gas turbine applications is surveyed, from lightweight propulsion engines, through vehicular and industrial prime-movers, to the large utility size nuclear closed-cycle gas turbine. For each application, the appropriate design criteria, types of recuperator construction (plate-fin or tubular etc.), and heat exchanger material (metal or ceramic) are briefly discussed.

Nonsteady Operational Behavior of Single-Shaft and Two-Shaft Closed-Cycle Gas Turbines

The nonsteady operational behavior of single- and two-shaft closed-cycle gas turbines is investigated on the basis of two reference plants. The behavior in case of a full-load release and after emergency shutdown was calculated. It is proved that these disturbances of operation can be mastered in two-shaft plants as well as in single-shaft plants. Furthermore, the stresses caused by dynamic changes in the circuit and to be considered in designing a closed-cycle gas turbine were investigated.

An Automated Method for the Continuous Determination of Total Sodium in Fuel Oil

Fuel oils are frequently contaminated with sodium salts. Users of gas turbines are concerned with the level of sodium in fuel because of the deleterious effects to the turbine. Until recently, on-line continuous methods of analysis did not reliably measure the total sodium in a given fuel. A method is described for the continuous analysis of total sodium present in fuel oils regardless of its chemical form. A small amount of surfactant, “Liquid G” is added to the fuel, and the total sodium in the resulltant solution is determined by flame photometry. The method described provides for the continuous and reliable measurement of sodium in fuel.

Simulation of Helicopter Powerplant Performance

Programs have been written for a hybrid computer to simulate in real time the dynamic behavior of the engines, airframe, and rotor systems of the Sea King and Lynx helicopters; their purpose is to aid the study of performance and control of helicopter power plants. Since the engines are directly coupled to the lift-producing surface (the rotor), it is important to take proper account of the interactions between the power plant and the rest of the aircraft; however, for this type of work, it is reasonable to limit simulated aircraft maneuvers to three degrees of freedom in a single vertical plane. The method of simulating the major features of the helicopter are discussed, along with their implementation on the hybrid computer. The paper goes on to describe the successful validation of the two models by comparison with specially obtained flight data on a range of rapid maneuvers involving large changes in power demands. Finally, a description is given of an exercise on the Sea King simulation to investigate the effect of an engine or control system failure at a critical flight condition.

Performance Investigations of Large Capacity Centrifugal Compressors

An experimental investigation concerning the optimum relative velocity distribution within impellers, the optimum diffusion ratio of vaned diffusers and the optimum circumferential area distribution, sectional shape of scrolls was carried out using high specific speed shrouded impellers with backward leaning blades. A performance design procedure based on loss analysis and quasi-three-dimensional flow analysis was also developed and modified by introducing experimental results. The design procedure was applied to a 7900-kw four-stage air compressor to demonstrate the usefulness. Field test results of the complete machine showed that the maximum isothermal efficiency was 75 percent with the pressure ratio of 5.96 and the flow rate of 29.3 m3/s.

Recent Developments in Sensors for the Gas Turbine Engine

A review of current technology applied to sensors for the measurement of speed, temperature, and pressure in gas turbine engines. The use of suitable materials and designs to overcome the hostile environments is discussed. The desirability of obtaining a simple interface with control systems is considered.

Analysis of the Flow Field in a Radial Compressor

Using pressure transducers and hot wire anemometers, the flow and pressure field in a subsonic centrifugal compressor is analyzed. Detailed pressure, velocity, and flow angle maps are given for the compressor inlet section, along the shroud, in the outlet section of the rotor, and also in the vaneless diffuser. These measurements show how flow heterogeneities are generated in the compressor and how they decay in the vaneless diffuser.

Cooling Characteristics of Film Cooled Turbine Vane Having Multi-Row of Ejection Holes

Film-cooled turbine vanes having 14 rows of round holes were designed. Two-dimensional cascade tests of two kinds of scaled vanes were carried out and cooling performances were obtained. Coolant flow distributions were controlled by the impingement and plenum chamber configuration. Higher cooling effectiveness than 0.65 was obtained for the coolant flow ratio of 4.5 percent. And it was clarified that the distributions of cooling effectiveness of the vane surface was governed by the configuration of coolant flow distribution to the cooling hole rows, and, that with using relatively greater amount of coolant to the leading edge region, higher cooling performance can be obtained. Also, numerical calculations of cooling performance and prediction for turbine application were presented.

Synthetic Fuels Derived From Coal for Marine Applications

This paper presents a summary of work which is being conducted in the United States in the area of synthetic fuels derived from coal for marine applications, and also gives an overview of the current supply and demand for oil fuels and defines the impact of this picture on the future fuel needs of the maritime and naval communities.

Bypass Control of Closed-Cycle Gas Turbines

The layout of the bypass control system of a closed-cycle gas turbine depends on the steady and nonsteady part-load behavior of the plant. In the paper, the results of investigations into the operating behavior of closed-cycle gas turbines are summarized. From these a method of laying out the bypass valve is deduced. Finally, an advanced bypass control system is described and the control behavior achievable therewith is explained.