| OCR Text |
Show 2 well known, to ilnprove the energy conversion efficiency of gas turbine, it is primarily necessary to raise the turbine inlet temperature (TIT) and increase the pressure ratio, of which the first is particularly effecti ve. TIT has been raised during the past three decades by the development of practical heat-resisting metallic Inaterials and cooling techniques. Cooling technology is reaching n1aturity and cooling itself involves energy loss. Therefore further efforts to raise TIT are Inaid to develop better heat -resisting n1aterials. Heat resisting materials include carbon fiber reinforced carbon con1posite (C/C composite). Although ranked high, they have the drawbacks of rapid aging due to oxidation in oxidizing atlnospheres at high ternperature and inclination to react with hot vapor. This discourages the direct application of present technologies to gas turbines for power generation 1). Under these circumstances, Research Center for Advanced Energy Conversion, Nagoya University established in April 1992 is ailning to develop high-temperature gas turbine. As one of break-through technologies of existing gas turbine, a novel gas turbine, named Chemical Cas Turbine, which has been based on promising developments of advanced fuel-rich combustion and C/C composite as turbine blade rotor, has been proposed. As the first step of progralnmed research project to examine the validity of this proposed gas turbine, tits thennal efficiency was estimated and a lab-scale pressurized combustor with methane/air rnixture was designed and operated. Flammability lilnits and elnission characteristics of NOx were observed and compared with chemical equilibriunl calculations. Finally discussions were done based on these results to make further investigations clear. 2. PROPOSAL OF NEW TYPE OF COMBINED CYCLE SYSTEM FOR POWER GENERATION AND ESTIMATION OF ITS THERMAL EFFICIENCY Schematic diagram of the proposed gas turbine/steam turbine combined cycle system is shown in Figure I. The system is composed mainly of a fuel-rich combustor, a fuel-lean combustor, two sets of gas turbine, a steam turbine and heat exchangers. The feature of this system is that the fuel-rich combustion, named Chemical Combustion, is adopted. The reasons why chemical combustion will be adopted in this turbine system are derived from: (1) the exhaust gas through the first gas turbine may still contain chemical energy as H2 and CO. (2) the exhaust gas may be useful for second stage strean1 or gas turbine, or possibly for fuel cell. (3) low NOx combustion may be easily realized in chemical combustion. (4) only possible candidate of materials might be C/C composite that will be used at temperature of more than 1500 C as turbine blade without cooling operations. |
