A comparative study of the influence of different means of turbine cooling on the thermodynamic efficiency and specific work of gas turbines is presented. A common general model of a simple open cycle gas turbine is used to compare the performance of turbines using different types of cooling; internal convection and impingement by air, film cooling by air, internal convection and impingement by steam, film cooling by steam and closed loop cooling by water. The results are also compared to the previously published results of the analysis of open loop water cooled gas turbines. The model evaluates the efficiency and specific work of simple cycle gas turbines as it is influenced by mixing losses of coolant with combustion gases, pumping work of coolant and heat transfer from the expanding gas. The study is performed in terms of dimensionless variables in order to achieve generality and to provide useful design guidelines and insights. Blades internally cooled by convection and impingement are treated as heat exchangers operating at constant metal temperature and the coolant exit temperature is simply expressed as a function of a heat exchanger effectiveness, an independent parameter which is normally a function of the intricacy of the layout of the cooling passages. The coolant requirements and heat transfer with film cooling are determined using a dimensionless correlation derived experimentally at M.I.T. Sample calculations give the optimum turbine inlet temperature of thermodynamic efficiency and specific work for different pressure ratios and typical dimensionless numbers. The data on specific work are significant because they can be readily used in evaluations of a given type of gas turbine in a combined cycle. The sensitivity of the efficiency and specific work to each key input parameter is reported.
The use of superheated steam as a coolant can provide some performance advantages since the steam raised in a waste heat boiler expands with the combustion gases, increases the turbine mass flow and also provides a certain amount of heat regeneration. Performance results are also reported for this steam cooled gas turbine operating with mixed working fluid.
In this investigation, experimental results on combustion control systems to suppress the pressure oscillation and combustion noise were indicated using laboratory scale rigs of premixed gas turbine combustors. As for the way of controlling, two different control approaches were examined. One was a thermoacoustic approach using minute secondary flames. The control system had a simple time-delay algorithm and equipped a microphone as a sensor. The minute secondary flames as an actuator were formed with pulsing supply of the secondary fuel using a piezo valve. The other was a fluid mechanical approach using a secondary injection method. In that case, both fuel and air injections as the secondary jet from the center of nozzle were examined to clarify the control factor to reduce the pressure oscillation and NOx emissions. As the results, combustion noise caused by pressure oscillation was reduced successfully with the suppression of about 10 dB by the thermoacoustic approach. Furthermore, it was found that secondary air injection was effective to suppress the NOx emissions based on thermal NO.
Concept of solar-hydrogen-methanol energy system for the transportation sector in Japan is outlined. In the system, methanol is produced with CO2 recycled and H2 produced by electrolysis with photovoltaic power.Concerning CO2 recovery from the exhaust gas of a 10,000 kW diesel engine to be used in the methanol energy system, the effects of CO2 recovery parameters such as gas and liquid flow rates, liquid concentration, and stripping temperature on the engine performance and the attainable CO2 recovery ratio are analyzed on the basis of a mass transfer calculation model for a packed column with aqueous monoethanolamine solution.Heat rejected from the engine is used for CO2 recovery, but reduction in the engine output power is not avoidable, which is mainly caused by the shortage in power of turbocharger and the supplemental supercharging power. Both the maximum attainable CO2 recovery ratio and the reduction in the engine output power depend on the ratio of the stripping steam feed rate to the flow rate of the exhaust gas.
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