Investigation into the transient flow characteristics of noble gas propellants using the pulsed inductive discharge in electric propulsion

To achieve transient flow characteristics at exit of nozzle orifice on gasoline direct injection engine, two phase Euler-Euler schemes was used to simulate the internal flow of the swirl nozzle. Different flow characteristics were calculated in the simulation. Different kinds of nozzle configuration were studied. Cavitaion and swirl flow occured in the nozzles. Injection hole configuration matters more than area variation of swirl tangential slot to discharge coefficient of the studied nozzle. Discharge coefficient changes a little along the injection hole length. The area of the swirl tangrntial slot plays an important throttling action in nozzle internal flow. Smaller area of swirl tangential slot generates larger degree cavitation but smaller mean injection velocity. Turbulence kinetic energy changes with the time of cavitation and swirl field occurring and the nozzle configuration. Before the appearance of cavitation, smaller inclination angle of orifice can generate more turbulence kinetic energy. After that moment, turbulence kinetic energy varies with different configuration. Along injection hole length, turbulence kinetic energy obviously varies. These flow characteristics affect primary atomization and will be as input for next spray simulation. They are also applied to design reference for injection nozzle.

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Investigations on Flow Characteristics in Diffuser-Discharge-Channel of Volute Casing

Volume 3: Fluid Machinery; Erosion, Slurry, Sedimentation; Experimental, Multiscale, and Numerical Methods for Multiphase Flows; Gas-Liquid, Gas-Solid, and Liquid-Solid Flows; Performance of Multiphase Flow Systems; Micro/Nano-Fluidics ◽

10.1115/fedsm2018-83051 ◽

2018 ◽

Author(s):

Yandong Gu ◽

Ji Pei ◽

Shouqi Yuan ◽

Jinfeng Zhang ◽

Ernst Nikolajew ◽

...

Keyword(s):

Cross Sections ◽

Discharge Channel ◽

Transient Flow ◽

Pressure Fluctuations ◽

Flow Characteristics ◽

Centrifugal Pumps ◽

Discharge Pipe ◽

Hydraulic Design ◽

Flow Loss ◽

Two Sides

The volute casing used in centrifugal pumps is efficient for the transformation of kinetic energy into pressure energy, however, its asymmetric hydraulic design makes the flow in diffuser-discharge-channel (DDC) inhomogeneous, resulting in unsatisfactory flow patterns. In this study, the unsteady numerical simulations are carried out to investigate the transient flow characteristics in DDC. The accuracy of numerical results is found to agree well with experimental performance and pressure fluctuations. It is observed that the flow in DDC is significantly uneven. At the elbow of DDC, the static pressure on the volute left side (VL) is larger than the volute right side (VR) due to the flow impact and flow separation respectively. Thereby, this high-pressure gradient induces the secondary flow on the cross sections of DDC. Further, there is an obvious dependency of pressure fluctuations in the discharge pipe on the strong interaction between the impeller and tongue, in which four small peaks and four large peaks can be observed. At each moment, the pressure on VL gradually decreases from the inlet of discharge pipe to the pump outlet, while it increases on VR, finally, two sides tend to be the same. The pressure fluctuation intensity gradually becomes equivalent-distributed. In particular, it should be noticed that the energy loss in the diffuser part is larger than the discharge pipe, which requires a redesign concerning hydraulic performance. This study can help to better understand the transient flow characteristics and provide guidance for reducing flow loss in the volute casing.

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Convective micromixers — design and industrial applications

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1243/09544062jmes717 ◽

2008 ◽

Vol 222 (5) ◽

pp. 807-816 ◽

Cited By ~ 20

Author(s):

N Kockmann

Keyword(s):

Transient Flow ◽

Phase Particle ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Industrial Applications ◽

Particle Generation ◽

Vitamin E Acetate ◽

Mass Flowrate ◽

High Reynolds ◽

20 Nm

Convective static micromixers operate with high Reynolds numbers ( Re from 100 to 1000) in relatively large microchannels (100–1000 μm) for high flowrates and low risk of fouling and blocking. Typical flow characteristics of symmetrical mixing in T-shaped micromixers are presented with transient flow for Re number larger than 240. The simulation results are assisted by experimental data. Parallel mixing elements increase the mass flowrate up to 25 kg/h with 100 kPa pressure loss. The typical flow characteristics are described, which are essential for successful mixing devices. Three dimensionless parameters are introduced to describe the mixing performance and effectiveness of such devices. Particle generation are critical in microchannels due to fouling issues. The gas phase particle generation from homogeneous condensation of vitamin E acetate is described, reaching to particle diameters of 20 nm from temporal temperature gradients of about 1.6×106 K/s. In liquid phase, the reactive precipitation of BaSO4 is investigated, leading to particle diameters below 100 nm.

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Transient flow characteristics and performance of a solid rocket motor with a pintle valve

Chinese Journal of Aeronautics ◽

10.1016/j.cja.2020.04.023 ◽

2020 ◽

Author(s):

Anchen SONG ◽

Ningfei WANG ◽

Junwei LI ◽

Baoyin MA ◽

Xinjian CHEN

Keyword(s):

Transient Flow ◽

Flow Characteristics ◽

Rocket Motor ◽

Solid Rocket Motor ◽

And Performance ◽

Solid Rocket

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On the Measurement and Modeling of High-Pressure Flows in Poppet Valves Under Steady-State and Transient Conditions

Journal of Fluids Engineering ◽

10.1115/1.4036150 ◽

2017 ◽

Vol 139 (7) ◽

Cited By ~ 3

Author(s):

Stephan Mohr ◽

Henry Clarke ◽

Colin P. Garner ◽

Neville Rebelo ◽

Andrew M. Williams ◽

...

Keyword(s):

Steady State ◽

Transient Flow ◽

Three Dimensional ◽

Flow Characteristics ◽

Valve Lift ◽

Transient Pressure ◽

Dynamic Flow ◽

Steady State Flow ◽

State Flow ◽

Piston Cylinder

Flow coefficients of intake valves and port combinations were determined experimentally for a compressed nitrogen engine under steady-state and dynamic flow conditions for inlet pressures up to 3.2 MPa. Variable valve timing was combined with an indexed parked piston cylinder unit for testing valve flows at different cylinder volumes while maintaining realistic in-cylinder transient pressure profiles by simply using a fixed area outlet orifice. A one-dimensional modeling approach describing three-dimensional valve flow characteristics has been developed by the use of variable flow coefficients that take into account the propagation of flow jets and their boundaries as a function of downstream/upstream pressure ratios. The results obtained for the dynamic flow cases were compared with steady-state results for the cylinder to inlet port pressure ratios ranges from 0.18 to 0.83. The deviation of flow coefficients for both cases is discussed using pulsatile flow theory. The key findings include the followings: (1) for a given valve lift, the steady-state flow coefficients fall by up to 21% with increasing cylinder/manifold pressure ratios within the measured range given above and (2) transient flow coefficients deviated from those measured for the steady-state flow as the valve lift increases beyond a critical value of approximately 0.5 mm. The deviation can be due to the insufficient time of the development of steady-state boundary layers, which can be quantified by the instantaneous Womersley number defined by using the transient hydraulic diameter. We show that it is possible to predict deviations of the transient valve flow from the steady-state measurements alone.

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Numerical Study of Thermal and Flow Characteristics of Plate-Fin Heat Sink with Longitudinal Vortex Generator Installed on the Ground

Mathematical Problems in Engineering ◽

10.1155/2014/245759 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9

Author(s):

Yen-Tso Chang ◽

Han-Ching Lin ◽

Chi-Jui Huang ◽

Go-Long Tsai ◽

Jinn-Feng Jiang

Keyword(s):

Heat Sink ◽

Transient Flow ◽

Numerical Study ◽

Thermal Flux ◽

Flow Characteristics ◽

Vortex Generator ◽

Attack Angle ◽

Longitudinal Vortex ◽

Coolant Fluid ◽

Transverse Distance

This study applied the commercial software ANSYS CFD (FLUENT), for simulating the transient flow field and investigating the influence of each parameter of longitudinal vortex generators (LVGs) on the thermal flux of a plate-fin heat sink. Vortex generator was set in front of plate-fin heat sink and under the channel, which was in common-flow-down (CFD) and common-flow-up (CFU) conditions, which have the result of vortex generator of delta winglet pair (DWP). In this study the parameters were varied, such as the minimum transverse distance between winglet pair, the attack angle of the vortex generator, fins number, the fin height, and the distance between the vortex generator and plate-fin. The coolant fluid flew into the fin-to-fin channel and pushed the vortex from different geometry toward the bottom. This phenomenon took off the heat from the plate to enhance the heat transfer. The numerical results indicated that the LVGs located close to the plate-fin heat sink are zero with the attack angle being 30°, presenting optimal overall conditions.

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