شبيه سازي عددي اجكتورهاي راه انداز مافوق صوت هوا در نيروگاه هاي بخار

In today’s world, where the deman‎d for sustainable an‎d efficient energy continues to grow, steam power plants remain one of the cornerstones of electricity generation. However, operational challenges—particularly the need for effective initial vacuum priming of the condenser for safe an‎d efficient startup—have consistently driven engineers to seek innovative solutions. Prior to initiating the main cycle, the condenser must be evacuated of air an‎d non-condensable gases to reduce internal pressure to the required low levels, thereby maximizing the efficiency of the Rankine cycle. This initial vacuum priming process not only shortens startup time but also prevents potential equipment damage an‎d optimizes energy consumption. Traditional methods, such as conventional steam ejectors, suffer from limitations including high motive steam consumption an‎d significant noise generation. The emergence of supersonic air ejectors opens new horizons: these devices utilize instrument air at pressures between 6 an‎d 8 bar to generate the required vacuum. This approach, grounded in the principles of compressible flow an‎d two-fluid mixing, enables energy savings of 10–15%, reduces maintenance costs due to the absence of moving parts, an‎d offers high durability. This research presents a numerical simulation of the flow inside a supersonic air ejector using air as the working fluid to investigate its behavior under realistic power plant operating conditions. The modeling is based on the governing equations for turbulent compressible flows. Operating conditions include motive pressures in the specified range (6–8 bar) for the primary fluid an‎d low suction pressures (5–10 kPa) for the secondary fluid. The core of the study focuses on the influence of key geometric parameters, including the secondary nozzle inlet diameter, primary nozzle exit position, primary nozzle exit diameter, an‎d the constant-area mixing section diameter. The results demonstrate that proper optimization of these parameters—for instance, optimal selec‎tion of the secondary nozzle inlet diameter—can improve the entrainment ratio by up to approximately 20% while ensuring flow stability. The optimized configuration achieves a significant vacuum level down to 10 kPa, sufficient for the initial condenser priming requirements of steam power plants, an‎d maintains stable performance at higher discharge pressures. Validation against experimental data shows an error of less than 10% at critical operating points. Ultimately, this work introduces a novel pathway for optimizing vacuum systems in steam power plants without reliance on large auxiliary boilers an‎d highlights the potential for broader applications across related industries.

رامين كوهي كمالي

احمدرضا پيشه وراصفهاني , مهدي نيلي احمدآبادي