EFFECT OF NOZZLE GEOMETRY ON THE ATOMIZATION AND SPRAY CHARACTERISTICS OF GELLED-PROPELLANT SIMULANTS FORMED BY TWO IMPINGING JETS

2010 ◽  
Vol 20 (12) ◽  
pp. 1033-1046 ◽  
Author(s):  
Jong Guen Lee ◽  
Syed Fakhri ◽  
Richard A. Yetter
Keyword(s):  
Impinging Jets ◽  
Nozzle Geometry ◽  
Spray Characteristics ◽  
Gelled Propellant

Spatially Resolved Gelled Propellant Spray Characteristics of Impinging Jets

2015 ◽  
Author(s):  
Neil S. Rodrigues ◽  
Paul E. Sojka
Keyword(s):  
Drop Size ◽  
Impinging Jets ◽  
Spray Characteristics ◽  
Transverse Axis ◽  
Phase Doppler Anemometry ◽  
Drop Velocity ◽  
Spatially Resolved ◽  
Plane Normal ◽  
Gelled Propellant ◽  
Kappa Carrageenan

The spatially resolved spray characteristics created by the like-on-like impingement of two gelled propellant simulants was experimentally investigated using Phase Doppler Anemometry (PDA). Water based gels of 1.0 wt.-% agar and 1.0 wt.-% kappa carrageenan, which were characterized using the Herschel-Bulkley rheological model, were used as the gel propellant simulants. Spatially resolved measurements for drop size and drop velocity were obtained up to 10 mm away from the centerline along the transverse axis in the plane of the sheet and up to 20 mm away from the centerline along the transverse axis in the plane normal to the sheet. All measurements were obtained at an axial plane 5 cm downstream of the impingement point. Larger D10 and D32 mean diameters and lower mean axial drop velocity Uz-mean were observed for transverse distances away from the centerline of the spray along both the axis in the plane of the sheet and in the plane normal to the sheet.

Towards Primary Breakup Simulation of a Complete Aircraft Nozzle at Realistic Aircraft Conditions

2020 ◽  
Author(s):  
Katharina Warncke ◽  
Amsini Sadiki ◽  
Max Staufer ◽  
Christian Hasse ◽  
Johannes Janicka
Keyword(s):  
Numerical Simulations ◽  
Liquid Fuel ◽  
Fuel Injection ◽  
Operating Conditions ◽  
Nozzle Geometry ◽  
Nozzle Flow ◽  
Spray Characteristics ◽  
Wide Range ◽  
Primary Breakup ◽  
Turbulent Scales

Abstract Predicting details of aircraft engine combustion by means of numerical simulations requires reliable information about spray characteristics from liquid fuel injection. However, details of liquid fuel injection are not well documented. Indeed, standard droplet distributions are usually utilized in Euler-Lagrange simulations of combustion. Typically, airblast injectors are employed to atomize the liquid fuel by feeding a thin liquid film in the shear zone between two swirled air flows. Unfortunately, droplet data for the wide range of operating conditions during a flight is not available. Focusing on numerical simulations, Direct Numerical simulations (DNS) of full nozzle designs are nowadays out of scope. Reducing numerical costs, but still considering the full nozzle flow, the embedded DNS methodology (eDNS) has been introduced within a Volume of Fluid framework (Sauer et al., Atomization and Sprays, vol. 26, pp. 187–215, 2016). Thereby, DNS domain is kept as small as possible by reducing it to the primary breakup zone. It is then embedded in a Large Eddy Simulation (LES) of the turbulent nozzle flow. This way, realistic turbulent scales of the nozzle flow are included, when simulating primary breakup. Previous studies of a generic atomizer configuration proved that turbulence in the gaseous flow has significant impact on liquid disintegration and should be included in primary breakup simulations (Warncke et al., ILASS Europe, Paris, 2019). In this contribution, an industrial airblast atomizer is numerically investigated for the first time using the eDNS approach. The complete nozzle geometry is simulated, considering all relevant features of the flow. Three steps are necessary: 1. LES of the gaseous nozzle flow until a statistically stationary flow is reached. 2. Position and refinement of the DNS domain. Due to the annular nozzle design the DNS domain is chosen as a ring. It comprises the atomizing edge, where the liquid is brought between inner and outer air flow, and the downstream primary breakup zone. 3. Start of liquid fuel injection and primary breakup simulation. Since the simulation of the two-phase DNS and the LES of the surrounding nozzle flow are conducted at the same time, turbulent scales of the gas flow are directly transferred to the DNS domain. The applicability of eDNS to full nozzle designs is demonstrated and details of primary breakup at the nozzle outlet are presented. In particular a discussion of the phenomenological breakup process and spray characteristics is provided.

scholarly journals Effect of Nozzle Geometry and Distance on Cooling Performance of Impinging Jets

2017 ◽  
Vol 103 (8) ◽  
pp. 458-467
Author(s):  
Hirokazu Kobayashi ◽  
Kazuhisa Kabeya ◽  
Yukio Takashima ◽  
Hideyuki Takahashi ◽  
Gentaro Takeda
Keyword(s):  
Impinging Jets ◽  
Nozzle Geometry ◽  
Cooling Performance

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics for Different Hole Geometries of a Turbine Casing Impingement Cooling System

2011 ◽  
Author(s):  
F. Ben Ahmed ◽  
R. Tucholke ◽  
B. Weigand ◽  
K. Meier
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling System ◽  
Ambient Air ◽  
Impinging Jets ◽  
Nozzle Geometry ◽  
Impingement Cooling ◽  
Pressure Losses ◽  
Aspect Ratios ◽  
Mach Numbers

A representative part of an active clearance control system for a low pressure turbine has been numerically investigated. The setup consisted of a cylindrical plenum with 20 inline arranged impinging jets at the bottom side discharging on a flat plate. The study focused on the influence of the nozzle geometry on the flow as well as heat transfer characteristics at the impingement plate and the discharge pressure drop. CFD (Computational Fluid Dynamics) simulations were performed for a constant Reynolds number ReD = 7,500 and different mean jet Mach numbers up to 0.7. Different length-to-diameter ratios of the jet holes (L/D) and various hole shapes (cylindrical, elliptic, convergent and divergent conical) were investigated to evaluate the performance of the impingement cooling configurations. The predictions showed a significant influence of the length-to-diameter ratio of the orifice bores on the heat transfer and the pressure losses. For L/D = 2 no suction of the ambient air in the nozzles was observed. In comparison to the configuration with L/D = 0.25 an improvement of the discharge coefficient of 9% for Ma = 0.7 and 20% for Ma = 0.17 was achieved. However, the highest heat transfer was observed for the smallest L/D-ratio of 0.25. The shape variation showed that only the elliptic jet holes with a ratio of AR = 0.5 enhanced the overall heat transfer and simultaneously reduced the pressure losses because of discharging onto the target plate. This result was found to be valid for all investigated jet Mach numbers. Additionally, for both elliptic jet aspect ratios of 0.5 and 2 the axis-switchover phenomenon of the flow was observed.

scholarly journals Heat and mass transfer enhancement strategies by impinging jets: A literature review

2020 ◽  
pp. 227-227
Author(s):  
Florin Bode ◽  
Claudiu Patrascu ◽  
Ilinca Nastase
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Large Scale ◽  
Impinging Jet ◽  
Impinging Jets ◽  
Nozzle Geometry ◽  
Small Scale ◽  
Mixing Enhancement ◽  
Transfer Enhancement

Heat and mass transfer can be greatly increased when using impinging jets, regardless the application. The reason behind this is the complex behavior of the impinging jet flow which is leading to the generation of a multitude of flow phenomena, like: large-scale structures, small scale turbulent mixing, large curvature involving strong normal stresses and strong shear, stagnation, separation and re-attachment of the wall boundary layers, increased heat transfer at the impinged plate. All these phenomena listed above have highly unsteady nature and even though a lot of scientific studies have approached this subject, the impinging jet is not fully understood due to the difficulties of carrying out detailed experimental and numerically investigations. Nevertheless, for heat transfer enhancement in impinging jet applications, both passive and active strategies are employed. The effect of nozzle geometry and the impinging surface macrostructure modification are some of the most prominent passive strategies. On the other side, the most used active strategies utilize acoustical and mechanical oscillations in the exit plane of the flow, which in certain situations favors mixing enhancement. This is favored by the intensification of some instabilities and by the onset of large scale vortices with important levels of energy.

An experimental and theoretical investigation of spray characteristics of impinging jets in impact wave regime

2015 ◽  
Vol 56 (3) ◽  
Author(s):  
N. S. Rodrigues ◽  
V. Kulkarni ◽  
J. Gao ◽  
J. Chen ◽  
P. E. Sojka
Keyword(s):  
Theoretical Investigation ◽  
Impinging Jets ◽  
Spray Characteristics ◽  
Wave Regime ◽  
Impact Wave

Experimental study on the effect of nozzle geometry on string cavitation in real-size optical diesel nozzles and spray characteristics

Fuel ◽  
2018 ◽  
Vol 232 ◽  
pp. 562-571 ◽  
Author(s):  
Zhou Chen ◽  
Zhixia He ◽  
Weiwei Shang ◽  
Lian Duan ◽  
Han Zhou ◽  
...  
Keyword(s):  
Experimental Study ◽  
Nozzle Geometry ◽  
Spray Characteristics ◽  
Real Size
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