This paper is a continuation of investigation into the possibilities of industrial application of the modified exhaustheated gas turbine installation with increased thermal efficiency, described in the ASME-Paper 90-GT-369. According to the author’s conception this turbine installation may be very useful when interacting with some chemical processing installations, e.g. by feeding a coal gasifier with pre-heated compressed air. It would then be a turbine system with an air extraction, performing a double duty. The heat contained in the air extracted from the gas turbine system plus the mechanical/electrical power produced create permanent full load conditions yielding the maximum thermal efficiency of the system. It has been found that for some point of extraction from a gas turbine plant of 33 % efficiency (without air extraction) the overall efficiency may raise to some 60 or even 73 %. This is possible due to the fact that the enthalpy increase of the extracted air is calculated with respect to that of the compressor inlet air. Moreover the air supplied to the gasifier does not expand in the turbine and does not perform any mechanical work.
A kind of developed exhaust-heated cycle arrangement comprising two or three reheaters and three intercoolers as well as an extra primary air blower (atmospheric combustion) is proposed. As far as classical exhaust-heated cycle is concerned, its thermal efficiency is quite low (15–20%) and therefore, a conception of a developed system provided with additional heat exchangers and combustion chambers has been worked out. The proposed installation operates on natural gas, which is becoming more and more popular now. A numerical example of calculation of a plant of 5250 kW effective power is presented. The “free-shaft” principle has been adopted. All the compressors are driven by a set of two turbines and the other two turbines are used for driving the electric generator. (Extra power that could be obtained from natural gas expander was not taken into account). In general it may be stated that the modified exhaust-heated cycle arrangement may compete with closed cycle turbine arrangements (e.g. Escher Wyss type). Moreover it may — to some extent — be superior to semi-closed cycle arrangements, since in the system proposed all the turbines are driven by compressed air whereas in the semi-closed cycle two turbines are driven by combustion gases.
Vibration isolators of machines installed on ships are subject to both dynamic forces involved with the working of these machines and inertia forces resulting from the rolling of the ship. In order to illustrate this better, a solution of the vibration equation of a single mass system has been analyzed, the system being excited simultaneously by a dynamic force and a motion of foundation. It has been found that the larger the ratio of rotation speed is to natural frequency of vibration, the larger is the relative displacement of a machine mounted on vibration isolators. To obtain as small as possible a value of this ratio it might be necessary to use “hard” isolators, but such a solution is not one of the best, because forces transmitted to the foundation would then be larger than the dynamic forces causing the vibration of this machine. Thus the author recommends employing “soft” isolators, on condition, however, that the frequency ratio mentioned previously be chosen such that the elastic deformation of the isolators be within allowable limits.
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