Turbulence effects on the vaporization of single droplets
32nd Joint Propulsion Conference and Exhibit, 1996, Florida, Amerika Birleşik Devletleri, 1 - 03 Temmuz 1996, (Tam Metin Bildiri)
- Yayın Türü: Bildiri / Tam Metin Bildiri
- Basıldığı Şehir: Florida
- Basıldığı Ülke: Amerika Birleşik Devletleri
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
Vaporization of single mono and bi-component nalkane droplets in homogeneous, isotropic and zeromean velocity turbulence is investigated. A fan-stirred turbulence chamber produces the required turbulence characteristics. They are fully characterized by twocomponent one and two-point LDA. The vaporization of fiber suspended droplets of five n-alkanes and of their bi-component mixtures subjected to varying turbulence energy levels is investigated by imaging techniques. For all experiments, the energetic turbulence length scales are about 5 times larger than the initial droplet diameter. For mono-component droplets, the D2-law holds for all fuels and turbulence levels. The vaporization rates increase with the turbulence energy, however, the lowest volatility fuels exhibit a larger increase of the relative vaporization rate, which also presents a plateau behavior trend for high turbulence intensities. Bi-component droplets exhibit a sequential vaporization behavior for all mixtures and turbulence levels. The instantaneous vaporization rates increase with increasing turbulence energy levels and increasing volume fraction of the highest volatility component. The experimental results are used to propose a phenomenological model and a global correlation to account for turbulence effects on the vaporization of mono and bi-component droplets. The model explains this effect by emphasizing the contribution of turbulence to disperse/diffuse the fuel vapor away from the droplet surface. This effect is more important for low intensity vaporization processes and when the fuel vapor diffusion coefficient is low. (K/Ks-l)=0.02Rt2/3Sc2 is proposed as a general correlation to account or turbulence effects on mono and bi-component droplets.