Experimental study of filling and emptying of a large-scale pipeline

The ¿lling with liquid of an initially empty pipeline and its counterpart, the draining of an initially liquid-¿lled pipeline, are of great interest due to the many practical applications. Several potential problems may occur, of which water-hammer and slug impact are the most important. To investigate the ¿lling and emptying processes, di¿erent mathematical models have been proposed, in which a common assumption is that the water column evolves with unchanged front and/or tail. This is a reasonable assumption for small-scale systems, particularly in cases with relatively high upstream pressure head and low downstream resistance. However, it is not clear whether this assumption is applicable to large-scale systems. This issue is of high importance for the development of air pockets and gravity currents in pipelines during ¿lling and draining processes. This study presents the experimental results of the ¿ow behaviour during the rapid ¿lling and emptying of a large-scale pipeline. The experimental apparatus was designed and built at Deltares, Delft, The Netherlands, as part of the EC Hydralab III project. Di¿erent from other laboratory studies, the scale of this experiment is close to the practical situation in many industrial plants. The test rig includes a variety of components (e.g. tanks, ¿ow meters, valves, pipes of di¿erent materials) and the operation procedure is rather complex. The ¿ow behaviour is measured by various instruments and hence a thorough hydrodynamic analysis is possible. All these features make the current study particularly useful as a test case for real ¿lling and draining situations. In the ¿lling of an initially empty pipeline, the focus was on the overall behaviour of the lengthening water column and the water-air interface evolution. In the emptying of an initially water-¿lled pipeline, together with the hydrodynamics of the shortening water column, the shape and behaviour of the water tail (air-water interface) was investigated. Thirteen di¿erent combinations of initial upstream driving air pressure and downstream valve resistance were tested. The in¿uence of these two factors on the out¿ow rate is clari¿ed. It was con¿rmed that both the in¿ow front in ¿lling and the out¿ow tail in emptying do not entirely ¿ll the pipe cross section. Shape changes occur at both the water-air and air-water interfaces. Although the ¿ow regime transition is a rather complex phenomenon, certain features of the transition pattern are observed and explained qualitatively and quantitatively

Developments in unsteady pipe flow friction modelling

This paper reviews a number of unsteady friction models for transient pipe flow. Two distinct unsteady friction models, the Zielke and the Brunone models, are investigated in detail. The Zielke model, originally developed for transient laminar flow, has been selected to verify its effectiveness for "low Reynolds number" transient turbulent flow. The Brunone model combines local inertia and wall friction unsteadiness. This model is verified using the Vardy's analytically deduced shear decay coefficient C* to predict the Brunone's friction coefficient k rather than use the traditional trial and error method for estimating k. The two unsteady friction models have been incorporated into the method of characteristics water hammer algorithm. Numerical results from the quasi-steady friction model and the Zielke and the Brunone unsteady friction models are compared with results of laboratory measurements for water hammer cases with laminar and low Reynolds number turbulent flows. Conclusions about the range of validity for the three friction models are drawn. In addition, the convergence and stability of these models are addressed.Anton Bergant, Angus Ross Simpson, John Vìtkovsk

Improving tribological properties of cast Al-Si alloys through application of wear-resistant thermal spray coatings

Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity

Experimental and numerical analysis of laminated carbon fibre-reinforced polymer gears with implicit model for coefficient-of-friction evaluation

Laminated composites have so far received little attention as a potential material for gear drive applications. In the presented study, the thermomechanical performance of a newly developed type of epoxy impregnated, autoclave-cured carbon fibre-reinforced polymer gear—running in pair with a steel pinion—was analysed, using a combination of experimental and numerical approaches. The employed methods enabled the identification of the composite’s mechanical, thermal, and tribological characteristics, as related to the studied gear pair application. A newly proposed, finite-element-analysis-based iterative procedure enabled an implicit evaluation of the analysed material pair’s coefficient of friction (COF), which is a key parameter in determining the gear pair’s thermomechanical characteristics. For the considered material pair, a value of 0.34 was identified for the coefficient in the quasi-steady region. As the coefficient is strongly correlated with frictional heat generation and significantly affects the surface shear stress, it can consequently have a meaningful influence on the composite’s wear rate. The developed COF identification procedure was validated using a reciprocating cylinder-on-flat tribological test method. The composite gear’s service life was additionally tested at various running loads, resulting in pitch contact pressures ranging between 400 and 540 MPa. Lifetime gear test results showed a markedly superior performance compared to the high-temperature thermoplastic polyether ether ketone, which is typically employed in the most demanding polymer gear applications. Several methods are additionally proposed that could further improve the developed composite gears’ performance

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system