Süpersonik Ejektörlerde Karışım Artırımı ile Momentum Korunumu Arasındaki Dengenin Sağlanması: Sinüzoidal Karışma Odası Geometrisi Üzerine Sayısal Bir İnceleme

Abstract

Bu çalışma, R134a akışkanlı bir süpersonik ejektörde, karışma odası içerisindeki sinüzoidal duvar yapılarının akış fiziği ve sistem performansı üzerindeki etkilerini kapsamlı bir üç boyutlu Hesaplamalı Akışkanlar Dinamiği (HAD) analiziyle ele almaktadır. Araştırmada "eşit alan" kısıtlaması uygulanarak, boyutsuz genlik ve dalga boyunun iç gaz dinamiği üzerindeki etkileri birbirinden ayrıştırılmış; böylece performans değişimlerinin doğrudan duvar kaynaklı akış fenomenlerinden kaynaklanması sağlanmıştır. Sayısal modelleme stratejisi kapsamında; şok dalgaları, kayma tabakaları ve türbülanslı dalgalanmalar arasındaki karmaşık etkileşimleri hassasiyetle çözümleyebilmek adına NIST REFPROP veri tabanından alınan gerçek gaz hal denklemi, k-omega Shear Stress Transport (SST) türbülans modeli ile entegre edilmiştir. Elde edilen sayısal bulgular, sinüzoidal modülasyonun güçlü akış yönlü girdapları ve şok-sınır tabakası etkileşimlerini tetikleyerek iç akış alanını temelden yeniden şekillendirdiğini ve süpersonik potansiyel çekirdeğin sönümlenmesini hızlandırdığını göstermektedir. 1,5 değerindeki sabit boyutsuz dalga boyunda, genliğin 0,01'den 0,03'e çıkarılmasının türbülans kinetik enerjisi üretimini sistematik olarak artırdığı; ancak birincil jet momentumunun türbülanslı dalgalanmalara harcanması nedeniyle bu yoğun karışımın sürükleme oranında bir düşüşe yol açtığı tespit edilmiştir. Buna karşın, 0,02 sabit genlikte dalga boyunun artırılması, türbülans enerjisinin daha geniş bir eksenel alana yayılmasını sağlayarak karışım iyileştirme ile momentum korunumu arasında daha verimli bir dengenin kurulmasına olanak tanımıştır. Analizler sonucunda tanımlanan boyutsuz zorlama parametresi aracılığıyla, aşırı verim kaybı yaşanmadan kontrollü karışım sağlayan en uygun konfigürasyon “Vaka 6” olarak belirlenmiştir. Bu bulgular, yüksek performanslı süpersonik ejektörlerde karışma odalarının pasif optimizasyonu için ölçeklenebilir bir tasarım çerçevesi sunmaktadır.

Keywords

• Süpersonik Ejektör
• Sinüzoidal Karışma Odası
• HAD (Hesaplamalı Akışkanlar Dinamiği)
• Türbülans Kinetik Enerjisi (TKE)
• R134a Gerçek Gaz Modeli
• Şok-Girdap Etkileşimi

Balancing Mixing Enhancement and Momentum Conservation in Supersonic Ejectors: A Numerical Investigation of Sinusoidal Mixing Chamber Geometry

Abstract

This study presents a comprehensive three-dimensional Computational Fluid Dynamics investigation into the impact of sinusoidal wall structures within the mixing chamber on the flow physics and performance of an R134a-driven supersonic ejector. By imposing an equal-area constraint, the study disentangles the influence of dimensionless amplitude and wavelength on internal gas dynamics, ensuring that performance variations are strictly attributable to wall-induced flow phenomena. The numerical framework integrates a real-gas equation of state derived from the NIST REFPROP database with the k-omega Shear Stress Transport turbulence model to accurately resolve the intricate interactions between shocks, shear layers, and turbulent fluctuations. Numerical results demonstrate that sinusoidal modulation fundamentally reshapes the internal flow field by triggering potent streamwise vortices and shock-boundary layer interactions, which accelerate the collapse of the supersonic potential core. At a constant dimensionless wavelength of 1.5, increasing the amplitude from 0.01 to 0.03 was found to systematically amplify turbulence kinetic energy production; however, this intensified mixing led to a decline in the entrainment ratio as primary jet momentum was dissipated into turbulent fluctuations. Conversely, increasing the wavelength at a fixed amplitude of 0.02 redistributed turbulence energy over a broader axial extent, facilitating a more efficient balance between mixing enhancement and momentum conservation. The analysis introduces a dimensionless forcing parameter, identifying Case 6 as the optimal configuration for achieving controlled mixing without excessive efficiency loss. These findings establish a scalable design framework for the passive optimization of mixing chambers in high-performance supersonic ejectors.

Keywords

• Supersonic Ejector
• Sinusoidal Mixing Chamber
• CFD
• Turbulent Kinetic Energy (TKE)
• R134a Real-Gas Model
• Shock–Vortex Interaction.

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