| OCR Text |
Show 3 (5) chemical cornbustion Inay be suitable for this nlaterial because C/C conlposite is protected from direct aging by oxygen. After fuel-rich combustion, the chemical energy relnains in the exhaust gas as H2 and CO that is available for the second gas turbine generation with high efficiency. So this gas turbine using the fuel-rich combustion i named as Chenlical Gas Turbine. Moreover, the boiler efficiency may be higher than conventional combined generation system. This is because the amount of exhaust gas can be decreased in fuel-rich condition to inlprove the efficiency loss due to momentum loss carried out by steam from about 200/0 to less than 100/0. The thermal efficiency of the proposed combined cycle system was calculated under the following conditions: (a) TIT of the first gas turbine is I 500°C, (b) the efficiency of steam turbine is constant at 390/0, (c) the conlposition of exhaust gas from the fuel-rich combustor was determined from chemical equilibrium calculations, (d) turbine efficiency was obtained from the empirical equation that was developed by some gas turbine companies. From the calculations, it was found that the gas turbine efficiency is 440/0 and the thermal efficiency of the combined systenl becomes 660/0. The thermal efficiency of the system is much higher than that of conventional ones. 3. EXPERIMENTS OF FUEL-RICH COMBUSTION UNDER PRESS· URIZED CONDITION 3-1. EXPERIMENTAL APPARATUS AND PROCEDURES Figure 2 is a schematic drawing of lab-scale combustor employed In the present work2).3),4). It consists primarily of an injector, an igniter, a combustion chamber and an exit nozzle. The size of the combustor is 20 mm in inside diameter and 486 mm in length. The combustor is Inade of stainless steel with tungsten liner inside. The injector is a coaxial type. Methane is supplied through the inner nozzle and air is fed through the outer nozzle. In order to achieve easy ignition, special care was paid as follows: the inner tube is set inside the recess of the outer tube because a methane has a low diffusivity. The recess distance between the injection point of methane and that of air is 2 Inm. The inner diameter of the exit nozzle is 4 mm. Produced gas due to combustion is sampled at the point of 419 mm from the injector. The drawing of the experimental setup of gas supply system is shown in Figure 3. Control was made by sequencer. Each experiment begins by supplying air and the igniter is run simultaneously. After 0.2 seconds, methane starts to feed. The nlaxilnUln combustion time was limited to 10 seconds because of the avoidance from overheat of the combustor. In all experiments the igniter worked for 5 seconds. |
