The gas turbine engine is a complex assembly of a variety of components that are designed on the basis of aerothermodynamic laws. The design and operation theories of these individual components are complicated. The complexity of aerothermodynamic analysis makes it impossible to mathematically solve the optimization equations involved in various gas turbine cycles. When gas turbine engines were designed during the last century, the need to evaluate the engines performance at both design point and off design conditions became apparent. Manufacturers and designers of gas turbine engines became aware that some tools were needed to predict the performance of gas turbine engines especially at off design conditions where its performance was significantly affected by the load and the operating conditions. Also it was expected that these tools would help in predicting the performance of individual components, such as compressors, turbines, combustion chambers, etc. At the early stage of gas turbine developments, experimental tests of prototypes of either the whole engine or its main components were the only method available to determine the performance of either the engine or of the components. However, this procedure was not only costly, but also time consuming. Therefore, mathematical modelling using computational techniques were considered to be the most economical solution. The first part of this paper presents a discussion about the gas turbine modeling approach. The second part includes the gas turbine component matching between the compressor and the turbine which can be met by superimposing the turbine performance characteristics on the compressor performance characteristics with suitable transformation of the coordinates. The last part includes the gas turbine computer simulation program and its philosophy. The computer program presented in the current work basically satisfies the matching conditions analytically between the various gas turbine components to produce the equilibrium running line. The computer program used to determine the following: the operating range (envelope) and running line of the matched components, the proximity of the operating points to the compressor surge line, and the proximity of the operating points at the allowable maximum turbine inlet temperature. Most importantly, it can be concluded from the output whether the gas turbine engine is operating in a region of adequate compressor and turbine efficiency. Matching technique proposed in the current work used to develop a computer simulation program, which can be served as a valuable tool for investigating the performance of the gas turbine at off-design conditions. Also, this investigation can help in designing an efficient control system for the gas turbine engine of a particular application including being a part of power generation plant.
Several modifications have been made to the simple gas turbine cycle in order to increase its thermal efficiency but within the thermal and mechanical stress constrain, the efficiency still ranges between 38 and 42%. The concept of using combined cycle power or CPP plant would be more attractive in hot countries than the combined heat and power or CHP plant. The current work deals with the performance of different configurations of the gas turbine engine operating as a part of the combined cycle power plant. The results showed that the maximum CPP cycle efficiency would be at a point for which the gas turbine cycle would have neither its maximum efficiency nor its maximum specific work output. It has been shown that supplementary heating or gas turbine reheating would decrease the CPP cycle efficiency; hence, it could only be justified at low gas turbine inlet temperatures. Also it has been shown that although gas turbine intercooling would enhance the performance of the gas turbine cycle, it would have only a slight effect on the CPP cycle performance.
Due to the high impact of the presence of noise in industry, it is mandatory to reduce acoustic noise hazard below the limit where risk to hearing occurs. The first step to achieve this is the identification of acoustic noise sources, which is a complex task that can be achieved using a wide range of techniques that involve different technologies for sound data acquisition, signal processing and study of physical construction. S ound source localization techniques fall into three standard categories: near-field acoustic holography, acoustic beamforming and inverse methods. S electing one method or another depends on the test object, nature of the sound, and the actual environment. In this paper, an intelligent system in the form of a microphone array based on a beam-forming method is proposed for noise detection and localization in porous panel structures through wind tunnel tests. The modification of an already existing experiment by the inclusion of new intelligent entities will increase the scope of these kinds of studies. S trengthening the communication level between the units involves assuring a more accurate identification of the noise sources and consequently assists in undertaking proper action to mitigate them.Keywords-noise, vibrations, wind shields, porous panel shields, wind tunnel tests, "safety, health and environment (SHE)".
In this current work, the design of a single stage centrifugal compressor as part of a complete small gas turbine coupled directly to high speed permanent magnet running at 60000rpm and developing a maximum electrical power of 60kW is presented. The choice of a radial impeller was considered and the design was based on using a non-linear optimisation code to determine the geometric dimensions of the impeller. Also, the optimum axial length and the flow passage of the impeller were found based on prescribed mean stream velocity. The proposed code was verified and showed quite good agreement with the published data in the open literature. The design of a vaneless diffuser and a volute were considered based on satisfying the governing equations of conservation of mass, momentum, and energy conservation simultaneously. Results showed good agreement with the CFD analysis found in the open literature. This work was motivated by the growing interest in micro-gas turbines for electrical power generation, transport and other applications.
Abstract:Gas turbines are often required to operate at different power levels and under varying environmental conditions.But by the nature of the thermodynamic processes in the engine, it is not possible to obtain the same level of efficiency within the entire range of operation. Therefore, depending on the particular application, for example for power generation, the rotational speed would be constant and dictated by the electrical generating machine. Gas turbine engine consists of various components which are linked together in such a way that there exists a mechanical and thermodynamic interdependence among some components. This means that some operational compatibility (matching) between components will be required for a steady state or equilibrium operation. The steady state of gas turbine engine for power generation can be achieved by the matching of its compressor and turbine. The usual approach of matching the compressor and the turbine is usually based on using an iterative procedure to determine the turbine operating points which are then plotted on the compressor characteristics. The draw back of this process is being laborious and time consuming. The new approach developed overcomes this by superimposing the turbine performance characteristics on the compressor performance characteristics while meeting the components matching conditions. This can be done by introducing a new mass flow dimensionless parameter. Superimposing the turbine map on the compressor map cannot be totally accepted until both maps axes (the abscissa and the ordinate) are identical. This paper explains the new approach adopted to a single shaft gas turbine engine. Theoretically, the developed techniques can be applied to other gas turbine engines.
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