چكيده به لاتين
This thesis deals with the GT-Power software to modeling and selection single-stage and two-stage series turbochargers for the Rotax914 piston engine for light and ultra-light aircraft, and used two high-pressure turbine and compressor control valves for two-stage turbocharger. The percentage of mass flow rate of control valve (control valve opening percentage) is considered as the design variable as well as the amount of engine power output as the target function (maximization). In optimal choice of turbochargers, the distance between the operating points of turbocharged engines from the surge and the choke lines on the compressor map, the maximum gas pressure inside the cylinder and the maximum gas outlet temperature are considered as constraints. The engine works in 7 steps and in different working conditions, so that along with increasing altitude from zero to 18,000 feet, linearly speed of the engine rises from 3,000 to 5,800. The results show that the one-stage turbocharger can hold up to 3000 feet of brake power and specific fuel consumption in sea-level conditions, while the amount for the series two-stage turbocharger with control valves is up to 9000 feet; So that at altitude of 9000 feet, we are also witnessing 1.23% increase in power. Also, the specific fuel consumption in the highest amount (at 18,000 feet) is reduced by 24.89%. With increasing engine speed and altitude, the two-stage turbocharger has a much better performance than a single stage, so that at a sea-level and engine speed of 3000 rpm, it increases by 28.97% (pressure ratio of 1.27 for one stage to 1.64 for two-stage), while at 18,000 feet and engine speed of 5800 rpm, we see an increase of 111.17 percent (pressure ratio of 1.7 for one stage to 3.59 for two-stage).
The proposed method in this study is faster and less costly than the trial and error method, and it can be used to select and even initial design of the turbochargers of air piston engines in different working conditions (sea level or altitudes).
