scholarly journals Investigation on Film Formation Characteristics of Pressure-Swirl Nozzle

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 773
Author(s):  
Dongyun Ma ◽  
Shinan Chang ◽  
Chen Yang
Keyword(s):  
Surface Roughness ◽  
Liquid Film ◽  
Mass Flow ◽  
Film Formation ◽  
Average Thickness ◽  
Flow Zone ◽  
Annular Zone ◽  
Wall Impingement ◽  
Time Average ◽  
Pressure Swirl

The film formation during the spray/wall impingement has attracted more attention. The present study investigated the film formation characteristics of the pressure-swirl nozzle by applying the contact-free optical method. According to experimental results, the impingement distance had a slightly more significant effect on the actual spray angle than the mass flow rate, and the maximum changing value was 34.6°. The bulge at the center of the surface became insignificant with the impingement distance. The liquid film was divided into the raised zone, annular zone, and free flow zone. The maximum time-average thickness at the central position was 2.84 mm, and correlations for predicting the time-average thickness and surface roughness were fitted. The time-average thickness of the annular zone was 0.38–0.59 mm, relatively thinner than other zones. When the impingement distance was lower than 10 mm, the time-average film thickness and surface roughness in the annular zone and free flow zone decreased first and then increased with the impingement distance. However, effects of mass flow rates and impingement distance on the liquid film were negligible when the impingement distance was higher than 10 mm. The experimental findings are helpful to fundamentally understand the film formation during the spray/wall impingement.

scholarly journals Centrifugal Compressor Stall Control by the Application of Engineered Surface Roughness on Diffuser Shroud Using Numerical Simulations

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2033
Author(s):  
Amjid Khan ◽  
Muhammad Irfan ◽  
Usama Muhammad Niazi ◽  
Imran Shah ◽  
Stanislaw Legutko ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Control Method ◽  
Flow Instability ◽  
Passive Flow Control ◽  
Passive Flow ◽  
Low Mass

Downsizing in engine size is pushing the automotive industry to operate compressors at low mass flow rate. However, the operation of turbocharger centrifugal compressor at low mass flow rate leads to fluid flow instabilities such as stall. To reduce flow instability, surface roughness is employed as a passive flow control method. This paper evaluates the effect of surface roughness on a turbocharger centrifugal compressor performance. A realistic validation of SRV2-O compressor stage designed and developed by German Aerospace Center (DLR) is achieved from comparison with the experimental data. In the first part, numerical simulations have been performed from stall to choke to study the overall performance variation at design conditions: 2.55 kg/s mass flow rate and rotational speed of 50,000 rpm. In second part, surface roughness of magnitude range 0–200 μm has been applied on the diffuser shroud to control flow instability. It was found that completely rough regime showed effective quantitative results in controlling stall phenomena, which results in increases of operating range from 16% to 18% and stall margin from 5.62% to 7.98%. Surface roughness as a passive flow control method to reduce flow instability in the diffuser section is the novelty of this research. Keeping in view the effects of surface roughness, it will help the turbocharger manufacturers to reduce the flow instabilities in the compressor with ease and improve the overall performance.

Impingement/Effusion Cooling With Low Coolant Mass Flow

2017 ◽  
Author(s):  
H. I. Oguntade ◽  
G. E. Andrews ◽  
A. D. Burns ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Wall Heat Transfer ◽  
Internal Wall ◽  
Cooling Effectiveness ◽  
Impingement Cooling ◽  
Impingement Heat Transfer ◽  
Design Changes ◽  
Wall Impingement ◽  
The Individual

A low coolant mass flow impingement/effusion design for a low NOx combustor wall cooling application was predicted, using conjugate heat transfer (CHT) computational fluid dynamics (CFD). The effusion geometry had 4306/m2 effusion holes in a square array with a hole diameter of D and pitch of X and X/D of 1.9. It had previously been shown experimentally and using CHT/CFD to have the highest adiabatic and overall cooling effectiveness for this number of effusion holes. The effect of adding an X/D of 4.7 impingement jet wall with a 6.6 mm impingement gap, Z, and Z/D of 2.0, on the overall cooling effectiveness was predicted for several coolant mass flow rates, G kg/sm2bar. At low G the internal wall heat transfer dominated the overall cooling effectiveness. The addition of impingement cooling to effusion cooling gave only a small increase in the overall cooling effectiveness at all G at 127mm downstream of the start of effusion cooling. An overall cooling effectiveness >0.7 was predicted for a low G of 0.30 kg/sm2bar. This represents about 15% of the combustion air for a typical industrial gas turbine combustor and design changes to reduce this further were suggested based on the predictions of this geometry. The main benefit of the impingement cooling was at the start of the effusion cooling, where the overall cooling effectiveness was dominated by the internal wall impingement and effusion cooling. The separate effusion and impingement cooling were also predicted for comparison with their combination. This showed that the combination of impingement and effusion was not the sum of the individual effusion and impingement heat transfer. The predictions showed that the aerodynamic interactions decreased the effusion and impingement internal wall heat transfer.

scholarly journals Impingement characteristics of an early injection gasoline direct injection engine: A numerical study

2016 ◽  
Vol 18 (4) ◽  
pp. 378-393 ◽  
Author(s):  
Nicholas J Beavis ◽  
Salah S Ibrahim ◽  
Weeratunge Malalasekera
Keyword(s):  
Liquid Film ◽  
Film Formation ◽  
Direct Injection ◽  
Cylinder Liner ◽  
Gasoline Direct Injection ◽  
Intake Valve ◽  
Direct Injection Engine ◽  
Gasoline Direct Injection Engine ◽  
Start Of Injection ◽  
Early Injection

This article describes the use of a Lagrangian discrete droplet model to evaluate the liquid fuel impingement characteristics on the internal surfaces of an early injection gasoline direct injection engine. This study focuses on fuel impingement on the intake valve and cylinder liner between start of injection and 20° after start of injection using both a single- and a multi-component fuels. The single-component fuel used was iso-octane and the multi-component fuel contained fractions of iso-pentane, iso-octane and n-decane to represent the light, medium and heavy fuel fractions of gasoline, respectively. A detailed description of the impingement and liquid film modelling approach is also provided. Fuel properties, wall surface temperature and droplet Weber number and Laplace number were used to quantify the impingement regime for different fuel fractions and correlated well with the predicted onset of liquid film formation. Evidence of film stripping was seen from the liquid film formed on the side of the intake valve head with subsequent ejected droplets being a likely source of unburned hydrocarbons and particulate matter emissions. Differences in impingement location and subsequent location of liquid film formation were also observed between single- and multi-component fuels. A qualitative comparison with experimental cylinder liner impingement data showed the model to well predict the timing and positioning of the liner fuel impingement.

Numerical Investigation of Condensation Heat Transfer Characteristics of R134A in Rectangular Minichannel

2019 ◽  
Author(s):  
Di Lv ◽  
Wei Li ◽  
Jingzhi Zhang
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Liquid Film ◽  
Mass Flow ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Condensation Process ◽  
Vapor Quality ◽  
Vof Model ◽  
Friction Pressure

Abstract This study numerically investigated the condensation heat transfer and flow characteristics of refrigerants R134a in rectangular minichannels. Three-dimensional simulations were carried out at different mass flux values, vapor qualities and gravity conditions through using the VOF model, the turbulence model and the phase transition model. The effects of various parameters on the surface heat transfer coefficient and the friction pressure gradient is clarified. The condensation process is found to be enhanced due to the increase of vapor quality and mass flow, while the friction pressure gradient decreases with the decrease of vapor quality and mass flow. According to the data obtained from the simulation, the liquid film tends to accumulate along the corner of the cross section in retangular minichannel. And the thickness of liquid film increased with the decrease of mass flux and vapor quality.

Effect of surface roughness on the mass flow rate predictions for adiabatic capillary tubes

2020 ◽  
Vol 118 ◽  
pp. 269-278 ◽  
Author(s):  
Thiago Torres Martins Rocha ◽  
Cleison Henrique de Paula ◽  
Vinícius Melo Cangussu ◽  
Antônio Augusto Torres Maia ◽  
Raphael Nunes de Oliveira
Keyword(s):  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Capillary Tubes ◽  
Effect Of Surface

Effect of Process Parameters on Depth of Penetration & Surface Roughness in Abrasive Waterjet Cutting of Copper

2019 ◽  
Vol 895 ◽  
pp. 301-306
Author(s):  
Keshav Kashyap ◽  
S. Srinivas
Keyword(s):  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Process Parameters ◽  
Flow Rate ◽  
Traverse Speed ◽  
High Water ◽  
Water Jet ◽  
Abrasive Waterjet ◽  
Depth Of Penetration

This study evaluates the effect of process parameters on depth of penetration and surface roughness in abrasive waterjet (AWJ) cutting of copper. Full factorial experiments are carried out on trapezoidal blocks for each of the three abrasive particle sizes used. Experimental parameters - abrasive mass flow rate, water jet pressure and traverse speed are varied at three levels. Main effects and contributions of process parameters to depth of penetration and surface roughness is calculated. From the data, it is observed that, high abrasive mass flow rate, high water jet pressure and low traverse speed resulted in higher depth of penetration and a high abrasive mass flow rate, high water jet pressure and low traverse speed resulted in lesser Ra value. Using experimental data a statistical model for predicting depth of penetration & surface roughness is developed. Error between experimental and statistical values are compared to validate the statistical model. The maximum DOP of 49.32mm was observed at AMFR=405.4 g/min, P=300 MPa, TS=60 mm/min, MS=60 Mesh and minimum DOP of 4.27mm was observed at AMFR=200 g/min, P=100 MPa, TS=90 mm/min, MS=80 Mesh.

Experimental investigations on atomization characteristics of dual-orifice atomizers part II: Optimization method application

2020 ◽  
pp. 095765092095996
Author(s):  
Xiongjie Fan ◽  
Cunxi Liu ◽  
Fuqiang Liu ◽  
Qianpeng Zhao ◽  
Jinhu Yang ◽  
...  
Keyword(s):  
Liquid Film ◽  
Mass Flow ◽  
Cone Angle ◽  
Optimization Method ◽  
Experimental Investigations ◽  
Structure Parameters ◽  
Spray Cone Angle ◽  
Spray Cone ◽  
Design And Optimization ◽  
Expansion Angle

In this paper, the optimization method we obtained from dual-orifice atomizers previously is used to design and optimize new dual-orifice atomizers, whereas there are some differences between the new dual-orifice atomizer and dual-orifice atomizer used in Part I. For example, the mass flow is much smaller, there is an expansion angle at pilot nozzle to regulate pilot stage spray cone angle, and there is no recess length between main nozzle and pilot nozzle. Influences of structure parameters on mass flow, spray cone angle and liquid film fusion and separation are investigated, which are consistent with the expectation. Structure parameters that meet performance requirements of dual-orifice atomizer are analyzed. In addition, a new phenomenon has been found is that liquid film oscillation appears with the increase of Δ P, which should be avoided during the design and optimization of new atomizers. Pilot liquid film oscillation will influence the development of dual-orifice liquid film. Pilot swirling groove depth and expansion angle of pilot nozzle are key parameters that influence liquid film oscillation. Conclusions in this paper can be used to guide the design and optimization of new dual-orifice atomizers.

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