Sediment wear prediction model of ZG06Cr13Ni4Mo turbine guide vane in sediment-laden hydropower station

The guide vane of a hydraulic turbine in any sediment-laden hydropower station is one of the components most seriously affected by sediment abrasion. Damage to a guide vane can significantly impact stable operation and energy characteristics of the unit, and it is thus essential to address and effectively manage this problem. In this study, the k-ε solid–liquid two-phase turbulence model and sample algorithm were used to numerically simulate the sand-water flow through the entire passage of a hydraulic turbine and sand samples were subsequently collected from the hydropower station to examine the sediment abrasion damage to turbine’s guide vane, which was made of ZG06Cr13Ni4Mo. Thereafter, calculation and test results were used to establish a prediction model for sediment abrasion of hydraulic turbine guide vane. These research findings could provide guidance for improved hydraulic turbine design and could thus contribute to the optimized operation of sediment-laden hydropower stations.

Capillary electroosmosis properties of water lubricants with different electroosmotic additives under a steel-on-steel sliding interface

The process of lubricant penetration into frictional interfaces has not been fully established, hence compromising their tribological performance. In this study, the penetration characteristics of deionized water (DI water) containing an electroosmotic suppressant (cetyltrimethylammonium bromide (CTAB)) and an electroosmotic promoter (sodium lauriminodipropionate (SLI)), were investigated using steel-on-steel friction pairs. The results indicated that the lubricant with electroosmotic promoter reduced the coefficient of friction and wear scar diameter, whereas that with an electroosmotic suppressant exhibited an opposite behavior compared with DI water. The addition of SLI promoted the penetration of the DI water solution, thus resulting in the formation of a thick lubricating film of iron oxide at the sliding surface. This effectively reduced the abrasion damage, leading to a lower coefficient of friction and wear loss.

Assessing the Effect of Curing Conditions, Specimen Type, and Superabsorbent Polymers in Compressive Strength and Abrasion of Pervious Concrete

The effect of curing conditions, specimen type, and the use of super absorbent polymers on the Compressive Strength and Abrasion of Portland Cement Pervious Concrete was evaluated. Five different mixtures, using different water/cement ratios, and the addition of polypromancic based acid and polyacrylate based super absorbent polymers were tested. Half of the specimens were cured in a temperature-controlled room at higher temperature and lower humidity to simulate field conditions. Specimens that were cured in these harsher conditions showed reduced compressive strength in the range of 34% to 35% for cast cylinders, and 27% to 67% for cores when compared to specimens cured under ideal conditions in the lab. These samples also had 3.14 to 3.2 times the abrasion damage compared to laboratory cured samples of similar porosities.

Susceptibility of Avocado Fruit to Scirtothrips aurantii Faure (Thysanoptera: Thripidae) and Wind Scarring Damage in Limpopo and KwaZulu-Natal Provinces of South Africa

In South Africa, the avocado (Persea americana) is an important fruit, grown primarily for export and contributing ZAR 1.75 billion to the gross domestic product of the country. As an export driven industry, optimising exportable avocado fruit volume is a primary concern. Wind induced abrasion and damage by thrips (Thysanoptera: Thripidae), through their feeding on avocado fruit results in corky tissue development (scarring) and making the fruit unsuitable for export. The study aimed to determine the economic losses caused by these agents as well as assess different cultivar responses to scarring damage. Across cultivars, the 1.49% revenue annually due to Scirtothrips aurantii downgrading (3.86% loss factor), translating to ZAR 34.90 million (US$2.39 million). Packhouse study results showed that both thrips and wind abrasion damage accounted for 30% scarring damage, a loss factor of 13.72% and a combined revenue loss of 5.57%. The cultivar ‘Pinkerton’ showed the greatest susceptibility to scarring damage by both wind and S. aurantii whilst the cultivar ‘Carmen®-Hass’ showed a natural predisposition to higher levels of thrips damage. The presence of macadamia trees near avocado trees predisposes avocado fruit to S. aurantii damage.

Post-Harvest Quality of cv. Markies Potatoes Submited to Mechancial Damages

Mechanical damage and storage conditions may alter carbohydrate metabolism and oxidative enzyme activity, causing darkening and impairing the use of tubers in pre-fried potato processing industry. The objective of this study was to evaluate the enzymatic changes and carbohydrate metabolism of ‘Markies’ potato tubers subjected to mechanical damage and exposed to high temperatures before processing. The tubers were stored for 4 months at 8 °C, and further divided into treatment with impact and abrasion damage; and control treatment, in which the tubers were not damaged. Afterwards, they were stored at 28 °C room temperature, evaluated for loss of accumulated fresh mass (FML); total soluble sugar (TSS), reducing sugar (RS) and non-reducing sugar (NRS); color after frying and activity of polyphenoloxidase (PPO) and peroxidase (POD) at 0, 12, 24, 36 and 48 h after placed at room temperature. The mechanical damages incremented FML, RS, PPO and TSS, NRS and POD up to 35.6, 34, and 22 h, respectively. Regardless of the occurrence of mechanical damage and the period of evaluation, the sticks showed a light color after frying and were classified in category 2. The increase in the evaluation time led to the rise in FML and the PPO activity. It is concluded that the mechanical damages increase the FML and cause darkening of the tips of the sticks after frying, however this variety still display qualities that are suitable for industrial processing.