Showing papers on "Turbine published in 1995"

A general simulation algorithm for the accurate assessment of isolated diesel-wind turbines systems interaction. I. A general multimachine power system model

Abstract: In the first part of this two-part paper, detailed dynamic equations for the power system and wind energy conversion system (WECS) components and their synthesis to a unified model are presented. This model is the basis for creating simulation software able to perform the transient stability analysis of isolated diesel-wind turbine power systems for accurate assessment of their interaction. Approximations in the various component models, when necessary, remain between limits that do not affect the accuracy of the analysis performed. A new general multimachine power system model is also developed which describes the topology and the complexity of wind-diesel power systems in a compact form which is easy to implement in the simulation software. >

Modeling and control of variable-speed wind-turbine drive-system dynamics

Abstract: When designing control for variable-speed wind turbines, one deals with highly resonant, nonlinear dynamic systems subject to random excitation, i.e., wind turbulence. This requires good knowledge of the dynamics to be controlled, particularly when combined with the increasingly common "soft" concept of lightweight, flexible constructional components; it creates cost advantages compared to more material-consuming rigid constructions, but also results in low frequency structural eigenfrequencies, some of which may appear in the bandwidth of closed-loop operation. For this article, system-identification experiments have been performed on an existing 400 kW, variable-speed, horizontal-axis wind turbine using various identification schemes. The identification results have then provided numerical values of the parameters in a physical model of the drive system. The acquired model has been used for design and evaluation of a number of linear and nonlinear control schemes for wind-turbine speed regulation. >

Horizontal axis wind turbine

Abstract: A horizontal axis wind turbine comprises a rotor-supporting framework, a multi-vaned rotor, an electricity-generating stator, and a rotation track. The supporting framework is constructed with a plurality of triangular sub-units. The rotor has a plurality of vanes projecting therefrom. The vanes have adjustable pitch and are encircled by a rim having a plurality of magnets. Wind induces rotation of the rim. The stator is essentially stationary and is mounted on the framework opposite the rim. As magnets on the rotating rim pass by the stator, electricity is generated. The stator uses the pull of the magnets to automatically adjust itself to align with the rotating rim. The framework is mounted on the rotation track so that the framework can continually be adjusted to maximize wind-induced rotation of the rotor.

Fuzzy logic integrated electrical control to improve variable speed wind turbine efficiency and performance

Abstract: A control system utilizing fuzzy logic adaptive control to control the operation of a wind turbine driven electric power generator to control power generator speed and hence power frequency while maximizing the power output of the power generator. Wind turbulence effects are eliminated and airgap magnetic flux of the power generator is controlled.

Distribution of film-cooling effectiveness on a turbine endwall measured using the ammonia and diazo technique

Abstract: The distribution of adiabatic film-cooling effectiveness on the endwall of a large-scale low-speed linear turbine cascade has been measured using a new technique. This technique is based on an established surface-flow visualization technique, and makes use of the reaction between ammonia gas and a diazo surface coating. A new method of calibration has been developed to relate the result of the reaction to surface concentration of coolant. Using the analogy that exists between heat and mass transfer, the distribution of film-cooling effectiveness can then be determined. The complete representation of the film-cooling effectiveness distribution provided by the technique reveals the interaction between the coolant ejected from the endwall and the secondary flow in the turbine blade passage. Over- and undercooled regions on the endwall are identified, illustrating the need to take these interactions into account in the design process. Modifications to the cooling configuration examined in this paper are proposed as a result of the application of the ammonia and diazo technique.

Compressor rotor cooling system for a gas turbine

Abstract: In a gas turbine including a compressor having a bore and a rotor comprised of multiple stages extending between a first stage at a forward end of the compressor and a last stage at an aft end of the compressor, each stage including a rotor disk having a peripheral rim and multiple blades secured to the peripheral rim, a combustion system comprising a plurality of combustors utilizing discharge air from the compressor for combustion, and multiple turbine stages driven by combustion gases from the combustion system, the improvement comprising means for supplying cooling air at least to a peripheral rim of the last stage of the compressor.

Regenerative condensing cycle

Abstract: An air cycle environmental control system for an aircraft cabin is disclosed which utilizes cabin exhaust air (200) to power a first stage turbine (108). This provides a significant increase in compressor power which increases the turbine cooling available in a stage turbine (112). The ram air consumption is also reduced due to the cabin exhaust air being ported to the ram air inlet where it merges with the ram air prior to cooling of the bleed air supply in a dual heat exchanger (132).

Integrated power and cooling environmental control system

Abstract: An environmental control system has an air cycle machine that includes a compressor (38), a cooling turbine (34), a motor/generator (36), and a power turbine (40) all mounted on a single shaft (32). The power turbine receives bleed air from the aircraft's engine (12) and has a variable geometry inlet nozzle (42) that adjusts the air flow rate therethrough without significant throttling. Downstream of the nozzle the power turbine extracts the expansion energy from the bleed air while cooling it. This is used to drive the other components of the air cycle machine, and in particular the motor/generator which generates electricity.

A governor/turbine model for a twin-shaft combustion turbine

Abstract: A twin shaft gas turbine unit was tested for the governor response to disturbances. A computer simulation model is presented as well as the test data which was used to derive values for the model parameters. >

A general simulation algorithm for the accurate assessment of isolated diesel-wind turbines systems interaction. Part II: Implementation of the algorithm and case-studies with induction generators

Abstract: In the second part of this two-part paper, a general algorithm to simulate and assess the dynamic behavior of any isolated diesel-wind turbine power system is analyzed and implemented. It is presented how the various power system and wind energy conversion system (WECS) component models described in detail in Part I of the paper can be implemented in order to create integrated simulation software. Case studies for the small size isolated power system on the French island of Desirade are given and analyzed. The algorithm is validated and its usefulness to determine the wind energy penetration level at any disturbed operation conditions is demonstrated. >

Comparative Evaluation of Combined Cycles and Gas Turbine Systems With Water Injection, Steam Injection, and Recuperation

Abstract: Combined cycles have gained widespread acceptance as the most efficient utilization of the gas turbine for power generation, particularly for large plants. A variety of alternatives to the combined cycle that recover exhaust gas heat for re-use within the gas turbine engine have been proposed and some have been commercially successful in small to medium plants. Post notable have been the steam-injected, high-pressure aeroderivatives in sizes up to about 50 MW. Many permutations and combinations of water injection, steam injection, and recuperation, with or without intercooling, have been shown to offer the potential for efficient improvements in certain ranges of gas turbine cycle design parameters. A detailed, general model that represents the gas turbine with turbine cooling has been developed. The model is intended for use in cycle analysis applications. Suitable choice of a few technology description parameters enables the model to represent accurately the performance of actual gas turbine engines of different technology classes. The model is applied to compute the performance of combined cycles as well as that of three alternatives. These include the simple cycle, the steam-injected cycle, and the dual-recuperated intercooled aftercooled steam-injected cycle (DRIASI cycle). The comparisons are based on state-of-the-art gas turbine technology and cycle parameters in four classes: large industrial (123-158 MW), medium industrial (38-60 MW), aeroderivatives (21-41 MW), and small industrial (4-6 MW). The combined cycle's main design parameters for each size range are in the present work selected for computational purposes to conform with practical constraints. For the small posterns, the proposed development of the gas turbine cycle, the DRIASI cycle, are found to provide efficiencies comparable or superior to combined cycles, and superior to steam-injected cycles. For the medium posterns, combined cycles provide the highest efficiencies but can be challenged by the DRIASI cycle. For the largest posterns, the combined cycle was found to be superior to all of the alternative gas turbine based cycles considered in this study

On the performance of a cascade of turbine rotor tip section blading in wet steam Part 2: Surface pressure distributions

Abstract: In the course of expansion in turbines steam nucleates to become a two-phase mixture, the liquid consisting of a very large number of extremely small droplets carried by the vapour. Formation and subsequent behaviour of the liquid lowers the performance of turbine wet stages. To produce turbine nucleating and wet flow conditions realistically requires a supply of supercooled steam which can be achieved under blow-down conditions by the equipment employed. To obtain wet steam, the supercooled vapour generated is passed through a venturi before admission to the cascade. To evaluate the influence of droplet size two separate Venturis have been used in the investigation. The performance of a cascade of rotor tip section blading in wet steam has been studied. This paper is the second of a set and describes the results of the surface pressure measurements.

Closed-circuit air cooled turbine

Abstract: A gas turbine engine includes a compressor, combustor, and turbine, and a cooling air closed-circuit having an extraction line from the compressor to a hot turbine component such as vanes, blades, or shrouds, and a return line to the compressor The extraction line may be joined to any suitable compressor stage for extracting air at a suitable pressure for flow to the turbine, with the return line being joined to any suitable injection stage of the compressor having a lower pressure than the extraction stage for driving the cooling air through the closed-circuit The compressor itself therefore drives the closed-circuit and is self regulated

An assessment of the thermodynamic performance of mixed gas-steam cycles. Part A: Intercooled and steam-injected cycles

Abstract: This paper discusses the thermodynamics of power cycles where steam or water are mixed with air (or combustion gases) to improve the performance of stationary gas turbine cycles fired on clean fuels. In particular, we consider cycles based on modified versions of modem, high-performance, high-efficiency aeroderivative engines. The paper is divided into two parts. After a brief description of the calculation method, in Part A we review the implications of intercooling and analyze cycles with steam injection (STIG and ISTIG). In Part B we examine cycles with water injection (RWI and HAT). Due to lower coolant temperatures, intercooling enables us to reduce turbine cooling flows and/or to increase the turbine inlet temperature. Results show that this can provide significant power and efficiency improvements for both simple cycle and combined cycle systems based on aero-engines ; systems based on heavy-duty machines also experience power output augmentation, but almost no efficiency improvement. Mainly due to the irreversibilities of steam/air mixing, intercooled steam injected cycles cannot achieve efficiencies beyond the 52-53 percent range even at turbine inlet temperatures of 1500°C. On the other hand, by accomplishing more reversible water-air mixing, the cycles analyzed in Part B can reach efficiencies comparable (RWI cycles) or even superior (HAT cycles) to those of conventional unmixed combined cycles.

Gas turbine generator set

Abstract: A small gas turbine generator set (100) comprising a rotating group and combustor contained within a circumferential recuperator (110). The rotating group comprises an alternator rotor (222) on a common shaft with a turbine wheel (400) and compressor impeller (312), supported by double acting compliant foil thrust bearings and a radial compliant foil bearing. The circumferential recuperator consists of a plurality of apertured boundary foils (122) having embossments for structurally spacing the foils apart, arranged to provide the flow channels, manifolds, and structure to permit the existence of differential pressure between each surface of the foil. The circumferential recuperator (110) is unitarily constructed surrounding the rotating group and combustor (700) wherein the inflowing air is heated by the recuperator (110) before entering the combustor. Due to the intercompatibility and modularity of the components, the air flow path associated with the compressor discharge and the turbine inlet is formed upon installation of the rotating group and the recuperator and by final assembly of the combustor unit (700) which forms a final enclosure for the turbine inlet air.

An Assessment of the Thermodynamic Performance of Mixed Gas-Steam Cycles: Part B—Water-Injected and HAT Cycles

Abstract: Part B of this paper 1 focuses on intercooled recuperated cycles where water is injected to improve both efficiency and power output. This concept is investigated for two basic cycle configurations : a Recuperated Water Injected (RWI) cycle, where water is simply injected downstream of the HP compressor, and a Humid Air Turbine (HAT) cycle, where air/water mixing is accomplished in a countercurrent heat/mass transfer column called saturator. For both configurations we discuss the selection and the optimization of the main cycle parameters, and track the variations of efficiency and specific work with overall gas turbine pressure ratio and turbine inlet temperature (TIT). TIT can vary to take advantage of lower gas turbine coolant temperatures, but only within the capabilities of current technology. For HAT cycles we also address the modelization of the saturator and the sensitivity to the most crucial characteristics of novel components (temperature differences and pressure drops in heat/mass transfer equipment). The efficiency penalties associated with each process are evaluated by a second-law analysis, which also includes the cycles considered in Part A. For any given TIT in the range considered (1250 to 1500°C), the more reversible air/water mixing mechanism realized in the saturator allows HAT cycles to achieve efficiencies about 2 percentage points higher than those of RWI cycles : At the TIT of 1500°C made possible by intercooling, state-of-the-art aero-engines embodying the above-mentioned cycle modifications can reach net electrical efficiencies of about 57 and 55 percent, respectively. This compares to efficiencies slightly below 56 percent achievable by combined cycles based upon large-scale heavy-duty machines with TIT = 1280°C.

Injector for turbine engines

Abstract: An injector for turbine engines which includes a shaped injector core fitted with an eccentric spinner inlet communicating with a cylindrical, annular fuel spinner chamber and a preheater or evaporator for preheating and vaporizing fuel, wherein the vaporized fuel is eccentrically injected into the fuel spinner chamber to effect a spinning fuel sequence around a fuel guidance pin extending through the center of the fuel spinner chamber. Compressed air from the turbine compressors flows through the primary nozzle of an air guidance nozzle surrounding the injector core into a shaped secondary nozzle, where the air mixes with the spinning fuel at a selected air flow angle to facilitate thorough mixing of the fuel and air as the combustible mixture is channeled into the annular turbine combustor. The unique spinning component applied to the preheated, vaporized fuel and manner of introducing the compressed air into the spinning fuel using multiple, spaced injectors and corresponding air guidance nozzles effects exceptionally good air-fuel mixing and facilitates increased turbine operating efficiency and reduction of NOX emissions in the turbine exhaust gases.

Method and apparatus for turbine cooling

Abstract: A method and apparatus provide cooling air from a compressor to hot components in a gas turbine engine. Compressed air discharged from an exit of the compressor is stratified into a main flow channeled to a combustor, and a separate bleed flow channeled to a heat exchanger. The bleed flow has an above average pressure whereas the main flow has a below average pressure. The bleed flow is cooled in the heat exchanger and channeled to hot components of the engine for cooling thereof.

Arrangement for return of exhaust gases in supercharged engines with turbines in series

Abstract: In supercharged engines it is difficult to return exhaust gases from the exhaust side to the inlet side during operating situations in which the pressure is greater on the inlet side than on the exhaust side. To overcome this, an EGR turbine (6) is incorporated in the exhaust gas flow in series after the turbine (4) of the supercharger and is thus driven by the exhaust gases which have already passed through the turbine of the supercharger. The EGR turbine (6) is used for driving an EGR compressor (7) which delivers the partial gas flow which is to be returned to the inlet manifold (2) of the combustion engine. The partial gas flow intended for return to the inlet side is tapped from the exhaust manifold (3, 3') and is pressurised in the compressor stage (7). The EGR turbine (6) may be controlled by a waste-gate valve (15).

An Investigation of nucleating flows of steam in a cascade of turbine blading-theoretical treatment

Abstract: This paper describes the theoretical part of an investigation into nucleating flows of steam in a cascade turbine nozzle blading. The main flow field is regarded as in viscid and treated by the time-marching technique. The viscous effects are assumed to be concentrated in boundary layers which are treated by the integral method. The agreement obtained with the observed surface pressure distributions and overall efficiency measurements is very good.

Wind energy conversion system

Abstract: A wind energy conversion system employs a wind turbine means mounted on a frame, said wind turbine having a venturi configured shroud with a core and a plurality of blades fixedly mounted between the core and the throat of the venturi. The blades have an air foil design consisting essentially of an inverted pan-shaped, cross-sectional configuration to create high torque at low air speed.

Fuel cell powered propulsion system

Abstract: Apparatus for powering an electric motor (4) comprising a solid oxide fuel cell (SOFC) (8) having a controlled fuel input (22) and a controlled oxidizer input (24). This apparatus may be combined with a turbine (104) driven by the exhaust gases of the fuel cell (8). The turbine (104) drives a generator whose power output (102) supplements the fuel cell power output (96) to power the electric motor (4). The oxidizer may be compressed by a compressor (98) driven by the turbine (104). The electric motor (4) may be a DC unipolar motor with controlled field excitation current. A controller (40') may control the fuel input (90), the compressor oxidizer input (108) or the field excitation current.

Hybrid two-phase turbine

Abstract: A rotary separator turbine having inlet structure (25, 26) for mixtures of gas and liquid, rotary shaft structure (29) comprising separator structure (28, 28a) to receive the mixture of gas and liquid and to separate the mixture into a stream of gas (32) and a stream of liquid (30); first structure (31) to receive the streamof gas for generating torque exerted on the shaft structure, and second structure (36a) to receive the stream of liquid for generating torque exerted on the shaft structure; whereby the first and second structure separately operate to generate shaft power.

System to assess the starting performance of a turbine

Abstract: An apparatus and method to assess the performance of a start of a turbine is described. The apparatus includes an accumulator to compare a set of on-line data signals corresponding to the starting performance of the turbine to a set of normative starting parameters so as to identify a set of comparison signals. The comparison signals may also be identified by comparing the set of on-line data signals with a database of historical information relating to starts and design profiles of the turbine. In addition, the comparison signals may be identified by comparing the set of on-line data signals with information in an expert system defining fault conditions in previous starts of the turbine. The comparison signals are processed by an analyzer to identify those comparison signals that exceed predetermined thresholds. Those comparison signals that exceed the predetermined thresholds are processed by a risk factor assessor, which generates quality-of-start predication signals corresponding to the likelihood of success of future starts of the turbine. An anticipator then processes the quality-of-start prediction signals and generates output signals that are used to improve the starting performance of the turbine.

Turbine shroud segment with serpentine cooling channels having a bend passage

Abstract: A turbine shroud segment for use in a gas turbine engine includes a serpentine channel along at least one axial edge of the segment. Various construction details are developed that disclose a channel for efficiently flowing cooling fluid through an axial edge of a shroud segment. In a particular embodiment, a turbine shroud segment includes a leading edge serpentine channel having a bend passage which includes a purge hole to avoid separating flow in the bend passage.

Preliminary Investigation of the Use of Air Injection to Mitigate Cavitation Erosion

Abstract: This project was initiated as part of a new research and development focus to improve hydropower generation. One aspect of the problem is severe cavitation erosion which is experienced when hydroturbines are operated at best power or in spinning reserve. Air injection has been used successfully to minimize or eliminate cavitation erosion in other applications. Thus, an investigation was initiated to determine whether or not air injection would be an effective solution for turbine erosion problems. A specially instrumented hydrofoil of elliptic planform and a NACA 0015 cross section was tested at flow velocities up to 20 m s{sup {minus}1}, at various values of cavitation index. Although pit sizes were measured on a soft aluminum insert, pitting rate was not measured directly but was inferred from direct measurement of impulsive pressures on the surface of the hydrofoil and by monitoring accelerometers mounted at the base of the hydrofoil. Cavitation noise was also measured by a hydrophone positioned in the water tunnel test section. Air was injected through small holes in the leading edge of the foil. Air injection was found to be very effective in minimizing erosion as inferred from all three cavitation erosion detection techniques.