On the Optimal Location and Number of Intercoolers in a Real Compression Process

In this paper the optimal location and number of intercoolers in a real compression process, including pressure losses, is derived by minimizing the compression specific work. Consequently the series of intermediate pressure values where the system intercoolers should be located is evaluated. As a result a solution different from the classical-isothermal compression process is obtained. The ideal process is evaluated and verified as a particular case by assuming no pressure losses. In reality, minimizing the compression work is only a partial criterion of optimization and the final decision regarding the optimal number of intercoolers should be obtained by using techno-economic criteria.

A Procedure to Reduce the Effects of Variable Fluid Temperatures in the Flow Direction: Application to the Design of a Rotary Regenerator

The purpose of this paper is to present results of an analytical procedure which accounts for variations in temperature dependent fluid properties in the flow direction of a heat exchanger. The procedure is called the multi-element method and is used in the performance calculations of a rotary regenerator subject to axial temperature variations greater than 2:1. The multi-element method partitions the flow length and evaluates the heat exchanger by combining the performances of each length. The results show graphically the differences between using the multi-element method and a more commonly used single-element method. The differences presented are between the predicted regenerator disk thickness and between the predicted core pressure drop for a variety of operating conditions.

Gas Turbine Heat Recovery Steam Generators for Combined Cycles Natural or Forced Circulation Considerations

In recent years the combined cycle has become a very attractive power plant arrangement because of its high cycle efficiency, short order-to-on-line time and flexibility in the sizing when compared to conventional steam power plants. However, optimization of the cycle and selection of combined cycle equipment has become more complex because the three major components, Gas Turbine, Heat Recovery Steam Generator and Steam Turbine, are often designed and built by different manufacturers. Heat Recovery Steam Generators are classified into two major categories — 1) Natural Circulation and 2) Forced Circulation. Both circulation designs have certain advantages, disadvantages and limitations. This paper analyzes various factors including; availability, start-up, gas turbine exhaust conditions, reliability, space requirements, etc., which are affected by the type of circulation and which in turn affect the design, price and performance of the Heat Recovery Steam Generator. Modern trends around the world are discussed and conclusions are drawn as to the best type of circulation for a Heat Recovery Steam Generator for combined cycle application.

An Indirectly Fired Gas Turbine Cogeneration Plant Utilizing Sawdust as a Fuel

A technical and economic assessment of an indirectly fired gas turbine cogeneration system is presented. The plant is designed for use in a sawmill, burning sawdust to generate both electricity and process heat to dry the lumber. After being dried, the sawdust is burned in a specially designed combustor which incorporates both radiant and convective heat transfer sections to generate a supply of air heated to 760 C (1400). This hot air drives the gas turbine and then the exhaust stream is utilized as a heat source for drying lumber in the dry-kilns. A materials and energy balance is presented which shows that there is more than enough sawdust available in a typical sawmill to supply all of the process heat requirements and to generate most of the electricity required to operate the mill machinery. This site-specific feasibility study indicates that an indirectly-fired gas turbine cogeneration system should be both technically and economically viable for application in a sawmill producing dried softwood lumber.

Developmental Testing of a Heat Recovery Module for Industrial Cogeneration

The initial developmental testing of a Heat Recovery Module (HRM) for cogeneration applications is described. The HRM is a prepackaged, pretested, skid-mounted system sized for the 500 to 1000 kW class of industrial gas turbine. Key features of the module include: • a highly compact, once-through boiler fabricated using finned Incoloy 800 tubing • a gas-fired supplementary burner capable of 1256 K (1800°F) refiring for greater system operating flexibility • a “spill-over” mode of boiler operation that allows feedwater softening rather than deionization • a fully integrated microprocessor-based control system System design and performance data are presented.

Impingement/Effusion Cooling: Overall Wall Heat Transfer

Experimental results are presented for the overall heat transfer coefficient within an impingement/effusion wall, using a transient cooling technique. This was previously used for determining the effusion hole heat transfer alone. Two impingement/effusion geometries were used with an 8 mm gap and the same impingement wall with an X/D of 11. The separate impingement and effusion short hole heat transfer coefficients were also determined. The impingement/effusion overall heat transfer was 45% and 30% higher than the impingement heat transfer alone for the two test geometries. The greater increase was for the higher pressure loss effusion wall. It was shown that the combined heat transfer was predominantly the addition of the impingement and effusion heat transfer coefficients but the interaction effects were significant and resulted in an approximately 15% deterioration in the combined heat transfer coefficient. Overall film cooling effectiveness was obtained that showed a significant improvement with the addition of the impingement cooling, but still had a major effusion film cooling contribution.

Review of Design Parameters in Gas Turbines for the Prospective User

This paper is based on five selected areas of gas turbine design that should be reviewed by prospective purchasers of gas turbines in the specification and procurement phase, in view of adverse industry experience associated with them. The details that should be requested and reviewed, and the criteria that should be met, are discussed. Case histories of adverse industry experience are provided for substantiation of the recommendations. The design areas discussed are: 1. Compressor-blade resonance diagrams 2. Compressor performance maps 3. Turbine-blade resonance diagrams 4. Temperature profiles in turbine flowpath 5. Response to combustor flameout

Development of a Thermal and Structural Analysis Procedure for Cooled Radial Turbines

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.

Decentralized Control and Automation of Gas Turbine and Combined-Cycle Power Plants

Unfired combined-cycle power plants of Siemens/KWU design each comprise five different package-engineered functional areas of mechanical and associated electrical equipment which are matched to different fuels, site conditions and operating requirements in order to achieve optimum power generation with each application. A modular programmable microprocessor-based automation station allocated to each functional area sequentially controls and protects all the equipment therein. By means of a redundant bus system all the functionally distributed automation stations are connected to one another and to a central control room where VDU screens provide operators with an in-depth insight into the running performance status of the entire combined-cycle block at all times. Function keyboards and back-up conventional hardwired controls permit operators to intervene in the automatic operation of the station whenever desired.

The Effects of an Excited Impinging Jet on the Local Heat Transfer Coefficient of Aircraft Turbine Blades

The primary objective of this paper is to present the results of research into the effects of periodic excitation upon the local heat transfer characteristics of a turbine blade cooled by an impinging jet of air. A curved plate (used to simulate the inner leading edge of a turbine blade) was subjected to a two-dimensional jet flow field (Re = 10,000) with a superimposed periodic acoustic disturbance. When compared to the naturally disturbed flow, the excited flow field was found to reduce the local Nusselt number and cool the blade less efficiently (by as much as ten percent in the extreme cases). The results of the study appear to indicate that harmonic disturbances present a serious controlling factor in the quest for optimization of turbine blade cooling techniques. By isolating dominant frequencies in gas turbine engines and working to suppress them, the authors believe it possible to make significant contributions towards the desired increase in turbine inlet temperature.