英語翻译作业,专业英语,工科.docVIP

飞动专业英语阅读大作业 班级：0906102 学号：090610223 姓名：马康康 日期：2012年4月5日 ENERGY TRANSFER FROM GAS FLOW TO TURBINE 6. From the description contained in para. 1, it will be seen that the turbine depends for its operation on the transfer of energy between the combustion gases and the turbine. This transfer is never 100 percent because of thermodynamic and mechanical losses, (para. 11). 7. When the gas is expanded by the combustion process (Part 4), it forces its way into the discharge nozzles of the turbine where, because of their convergent shape, it is accelerated to about the speed of sound which, at the gas temperature, is about 2,500 feet per second. At the same time the gas flow is given a spin or whirl in the direction of rotation of the turbine blades by the nozzle guide vanes. On impact with the blades and during the subsequent reaction through the blades, energy is absorbed, causing the turbine to rotate at high speed and so provide the power for driving the turbine shaft and compressor. 8. The torque or turning power applied to the turbine is governed by the rate of gas flow and the energy change of the gas between the inlet and the outlet of the turbine blades, The design of the turbine is such that the whirl will be removed from the gas stream so that the flow at exit from the turbine will be substantially straightened out to give an axial flow into the exhaust system (Part 6). Excessive residual whirl reduces the efficiency of the exhaust system and also tends to produce jet pipe vibration which has a detrimental effect on the exhaust cone supports and struts. 9. It will be seen that the nozzle guide vanes and blades of the turbine are twisted, the blades having a stagger angle that is greater at the tip than at the root (fig. 5-6). The reason for the twist is to make the gas flow from the combustion system do equal work at all positions along the length of the blade and to ensure that the flow enters the exhaust system with a uniform axial velocity