This paper outlines the handling of a semi closed cycle gas turbine, its working fluid is carbon dioxide and the fuel is low heating value gas from coal. At startup however, air and natural gas are used. The objective of the machine is to produce clean electricity with the smallest efficiency penalty. Many aspects of the operation of the engine are examined here; these include starting requirements, stator vane and bleed valve scheduling and the working fluid transition from air to carbon dioxide. Other features highlighted are the compressor operating lines and surge margins. The present paper describes the salient features of the three main stages into which the engine operation has been divided. These stages are: startup to synchronous idle, change of working fluid (from air to Carbon Dioxide-Argon) and fuel (from natural gas to coal synthetic gas) at synchronous idle and part load operation. Preliminary findings show that engine handling can be carried out effectively with variable stators. This is possible because of the two shaft gas generator. Another point of interest is the large increase of corrected speed relative to rotational speed experienced when the working fluid changes from air to carbon dioxide. In general the control of the engine does not seem to present any insurmountable problems despite the complexities arising from the need to change working fluid and fuel.

The main performance features of a semiclosed-cycle gas turbine with carbon dioxide–argon working fluid are described here. This machine is designed to employ coal synthetic gas fuel and to produce no emissions. The present paper outlines three tasks carried out. First, the selection of main engine variables, mainly pressure and temperature ratios. Then a sizing exercise is carried out where many details of its physical appearance are outlined. Finally the off-design performance of the engine is predicted. This two-spool gas turbine is purpose built for the working fluid, so its physical characteristics reflect this requirement. The cycle is designed with a turbine entry temperature of 1650 K and the optimum pressure ratio is found to be around 60. Two major alternatives are examined, the simple and the precooled cycle. A large amount of nitrogen is produced by the air separation plant associated with this gas turbine and the coal gasifier. An investigation has been made on how to use this nitrogen to improve the performance of the engine by precooling the compressor, cooling the turbine nozzle guide vanes, and using it to cool the delivery of the low-pressure compressor. The efficiencies of the whole plant have been computed, taking into account the energy requirements of the gasifier and the need to dispose of the excess carbon dioxide. Hence the overall efficiencies indicated here are of the order of 40 percent. This is a low efficiency by current standards, but the fuel employed is coal and no emissions are produced.

This paper describes the performance analysis of a semi closed cycle gas turbine. The working fluid is carbon dioxide and the fuel is low heating value gas synthesised from coal. The objective of the machine is to produce clean electricity with the smallest efficiency penalty. Firstly the thermodynamic properties of the gases in the cycle were obtained as a function of temperature and pressure. Then two performance simulation codes were developed. These have the ability of simulating different configurations of open, closed and semi-closed cycles. The first code was used for cycle optimisation and the second for off-design studies. The design and off-design performance of the machine are predicted. The production of clean electricity will be at the expense of a lower efficiency compared with current equipment. Finally, some critical issues for the development of such a gas turbine are identified.

This paper describes the performance analysis of a semiclosed-cycle gas turbine. The working fluid is carbon dioxide and the fuel is low heating value gas synthesized from coal. The objective of the machine is to produce clean electricity with the smallest efficiency penalty. First, the thermodynamic properties of the gases in the cycle were obtained as a function of temperature and pressure. Then two performance simulation codes were developed. These have the ability of simulating different configurations of open, closed, and semiclosed cycles. The first code was used for cycle optimization and the second for off-design studies. The design and off-design performances of the machine are predicted. The production of clean electricity will be at the expense of a lower efficiency compared with current equipment. Finally, some critical issues for the development of such a gas turbine are identified.

The main performance features of a semiclosed cycle gas turbine with carbon dioxide-argon working fluid are described here. This machine is designed to employ coal synthetic gas fuel and to produce no emissions. The present paper outlines three tasks carried out. Firstly the selection of main engine variables, mainly pressure and temperature ratios. Then a sizing exercise is carried out where many details of its physical appearance are outlined. Finally the off-design performance of the engine is predicted. This two spool gas turbine is purpose built for the working fluid, so its physical characteristics reflect this requirement. The cycle is designed with a turbine entry temperature of 1650 K and the optimum pressure ratio is found to be around 60. Two major alternatives are examined, the simple and the precooled cycle. A large amount of nitrogen is produced by the air separation plant associated with this gas turbine and the coal gasifier. An investigation has been made on how to use this nitrogen to improve the performance of the engine by precooling the compressor, cooling the turbine nozzle guide vanes and using it to cool the delivery of the low pressure compressor. The efficiencies of the whole plant have been computed, taking into account the energy requirements of the gasifier and the need to dispose of the excess carbon dioxide. Hence the overall efficiencies indicated here are of the order of 40 percent. This is a low efficiency by current standards, but the fuel employed is coal and no emissions are produced.