scholarly journals New Results Regarding Cavitation Behavior of Polymers Modified with Anorganic Substances Coated on Bronze Surfaces

2018 ◽  
Vol 55 (3) ◽  
pp. 460-463 ◽  
Author(s):  
Lavinia Madalina Micu ◽  
Iosif Lazar ◽  
Adrian Circiumaru ◽  
Ilare Bordeasu ◽  
Liviu Daniel Pirvulescu ◽  
...  
Keyword(s):  
Erosion Resistance ◽  
Hydraulic Turbine ◽  
Polymer Layer ◽  
Mechanical Resistance ◽  
Chemical Corrosion ◽  
Modified Polymer ◽  
Hydraulic Machines ◽  
Abrasive Erosion ◽  
Cavitation Behavior ◽  
Ship Propeller

Due to mechanical resistance characteristics, chemical corrosion and abrasive erosion resistance, the polymers are more widely used in equipments and installations that are exploited in different fluid hydrodynamic conditions. Among these applications there is the protection of surfaces of hydromechanic organs stressed by cavitation, like in hydraulic machines rotors and valves. Consequently, the research aimes the extension of using these and protection of other components surfacess hardly streesed by cavitation. The research in this paper points toward the behavior of modified polymer layer, coated on surfaces of bronze used in casting the propellers of maritim and river ships. The tests were performed in standard piezoceramic crystal vibrating equipment within Cavitation Laboratory of Politehnica University of Timisoara. The damaging intensity of equipment is much greater than any cavitational vortex, created by ship propeller, hydraulic turbine or centrifugal pump. The obtained results, compared to both recorded on uncovered surfaces with polymer layer and recorded on surfaces covered with HVOF composite materials layers, show an increased resistance that implies the increased exploiting duration of those surfaces.

Stainless Steels as Erosion Resistant Materials for Hydraulic Machines

2017 ◽  
Vol 750 ◽  
pp. 75-79
Author(s):  
Brandusa Ghiban ◽  
Carmen Anca Safta ◽  
Vlad Motoiu
Keyword(s):  
Steam Turbine ◽  
Geothermal Energy ◽  
Electric Energy ◽  
Heat Energy ◽  
Hydrodynamic Cavitation ◽  
Metallic Surface ◽  
Working Fluid ◽  
Corrosion Mechanism ◽  
Hydraulic Machines ◽  
Abrasive Erosion

The corrosion phenomena lead to serious modifications in the structure of metallic materials from which are manufactured the important active components of hydraulic machines. There are two important types of corrosion: cavitation and silt erosion (abrasive erosion), that are specific to machines which are producing energy [1, 2, 3]. As a corrosion mechanism, in hydrodynamic cavitation [4, 5], when cavitation bubbles implode on the solid surface of hydraulic machine component, the local pressure developed is high and can exceed the fatigue strength, yield point or compression strength of the material. Cavitation phenomenon can be produced in different ways. Four types of cavitation are described in the literature, looking for the method of producing, [6]: hydrodynamic cavitation, particle cavitation, acoustic cavitation, and optic cavitation. Abrasive erosion is the gradual degradation of a structure under the action of solid particles suspended in the working fluid. Impact and sliding erosion are the main categories of abrasive erosion approached in the literature by considering the mechanisms of which the abrasive particles act on the metallic surface, [2]. In the last decades the abrasive erosion phenomenon became a serious problem for the efficient operation of power plants, for instance in hydropower plants [7, 8]. Geothermal energy is the heat energy of the earth given by capturing the springs of heat water. In Romania the geothermal energy is used only for heating because the water has a low temperature and cannot be used to produce electric energy, only heat energy. So, although Romania is the third highest potential geothermal in Europe, practically electric energy from geothermal resource has a low thermal potential, [9]. A steam turbine is working at high rotational speed, high temperatures and using the working fluid which could be steam or wet steam. The working fluid is composed of corrosive chemicals with an aggressive pH. For this reason the common problems of the geothermal steam turbine failures are given by fractures of the blades (rotor blades or stator blades).

The Cavitation Behavior of Fe-Cr-C-Si-Ni Alloys

2006 ◽  
Vol 510-511 ◽  
pp. 274-277
Author(s):  
Ji Hui Kim ◽  
Kwang Su Na ◽  
Seon Jin Kim
Keyword(s):  
Work Hardening ◽  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Hardfacing Alloy ◽  
Ni Alloys ◽  
Ni Addition ◽  
Work Hardening Rate ◽  
Erosion Test ◽  
Cavitation Behavior ◽  
Cavitation Erosion Resistance

The cavitation erosion behavior of Fe-Cr-C-Si-xNi (x = 1, 2 and 3 wt.%) alloys were investigated for 50 hours using a 20 kHz vibratory cavitation erosion test equipment. 1 wt.% Ni added Fe-based hardfacing alloy showed excellent cavitation erosion resistance, comparable to the stellite 6. Above 1 wt.% Ni, however, the erosion resistance deteriorated quickly. It is conjectured that Ni addition above 1 wt.%, which has been shown to increase the stacking fault energy (SFE), resulted in reduction of the work hardening rate during the erosion test. Therefore, the enhanced cavitation erosion resistance of the 1 wt.% Ni alloy over the 2 and 3 wt.% Ni alloys could be explained in terms of the SFE, Ms temperature and work hardening.

scholarly journals The Corrosion Erossion of Ship Propeller Al 7075 Produced by Gravity Sand Casting

2019 ◽  
Vol 2 (2) ◽  
pp. 172-177
Author(s):  
Milka Rante ◽  
Muhammad Syahid ◽  
Onny Sutresman
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloys ◽  
Erosion Resistance ◽  
Aluminum Bronze ◽  
Nickel Aluminum ◽  
Al 7075 ◽  
Slurry Pot Tester ◽  
Mechanical Properties And Corrosion ◽  
Nickel Aluminum Bronze ◽  
Ship Propeller

Propeller is one of the important components of ships and boats that function as motor or boat propulsion. The mechanical properties required in propeller material are high toughness, easy to cast, and good engine capability, as well as good resistance to corrosion and erosion. One of the aluminum alloys that have been widely used in major vessels in propeller systems is the Nickel-aluminum-bronze (NAB) alloy because it has an excellent combination of mechanical properties and corrosion-erosion resistance. Another type of aluminum alloy that is widely used as a machining component is the Al 7075 T651 because it has the highest strength among other aluminum alloys. The mechanical properties of the Al 7075 T651 are directly proportional to the erosion resistance of the propeller which agrees with the pot tester porridge. The higher the value of the erosion propeller failure that occurs also increases with increasing testing rotational speed. For corrosion, a propeller with air testing media at a speed of 1000 rpm which results in significant corrosion products. Keywords: Al 7075 T651, Slurry Pot Tester, Corrosion Erosion

Road Performance of Concrete Incorporating Manganese Slag

2011 ◽  
Vol 402 ◽  
pp. 457-462
Author(s):  
Duo Qiang Liang ◽  
Feng Qin ◽  
Ji Bo Jiang
Keyword(s):  
Ordinary Portland Cement ◽  
Mechanical Tests ◽  
Furnace Process ◽  
Chemical Corrosion ◽  
The Road ◽  
Fundamental Properties ◽  
Abrasive Erosion ◽  
Road Performance ◽  
Manganese Slag ◽  
Chemical Corrosion Resistance

It’s of great importance to innocuity, minimization and reutilization of manganese slag generated in manganese product by electric furnace process. In the paper, ordinary Portland cement was incorporated by manganese slag, and then mechanical tests were performed to obtain the fundamental properties of the cement stabilized material in order to analyze the road performance of cement stabilized layer. The obtained experimental results showed that the manganese slag cement replaced by 2~6%( wt) manganese slag has better road performance such as mechanical properties, hydro-abrasive erosion and chemical corrosion resistance.

Evaluation of a Dynamic Transfer Matrix for a Hydraulic Turbine

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Keita Yamamoto ◽  
Koichi Yonezawa ◽  
Andres Müller ◽  
François Avellan ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Transfer Matrix ◽  
Mass Flow ◽  
Excitation Frequency ◽  
Hydraulic Turbine ◽  
Gain Factor ◽  
System Stability ◽  
Dynamical Response ◽  
Matrix Elements ◽  
Full Load ◽  
Hydraulic Machines

Abstract It is well known that hydraulic machines experience various types of flow instabilities causing a negative influence on the system under off-design operations. The transfer matrix method correlating the flow properties in upstream and downstream of hydraulic machines is widely adopted as a first step to investigate dynamical characteristics of flow. Transfer matrix elements are the key to understand hydraulic system stability. This study focuses on measurements of transfer matrix elements for a hydraulic turbine. The oscillations of the flowrate are produced by two flow exciters located in upstream and downstream of the turbine, and evaluated from the fluctuations of the pressure difference across two streamwise locations. It is shown that the transfer matrices are successfully evaluated at part load and full load operations in the presence and absence of cavitation. In particular, cavitation compliance and mass flow gain factor, which determine the dynamical response of cavitation to the change of pressure and flowrate, are calculated from the measured transfer matrix elements. The absolute value of both cavitation compliance and mass flow gain factor is found to increase with respect to the decrease of the cavitation number. The phase of the mass flow gain factor is delayed as the excitation frequency increases. This suggests that hydraulic systems may be stabilized when the oscillation frequency increases. As a result of stability analyses, it is demonstrated that the mass flow gain factor plays a crucial role, especially in the full load cavitation surge.

scholarly journals Effect of Surface Treatment of Polypropylene (PP) Fiber on the Sulfate Corrosion Resistance of Cement Mortar

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3690
Author(s):  
Yanyan Hu ◽  
Linlin Ma
Keyword(s):  
Corrosion Resistance ◽  
Silane Coupling Agent ◽  
Erosion Resistance ◽  
Cement Mortar ◽  
Fiber Surface ◽  
Cement Matrix ◽  
Chemical Corrosion ◽  
Silane Coupling ◽  
Cement Based Materials ◽  
Treated Fiber

Sulfate erosion is one of the most complex and harmful chemical corrosion actions. Following sulfate erosion, concrete expands, cracks, dissolves, peels off, and decreases in strength, which affects the durability of structures. Polypropylene fiber (PP) is widely used in various concrete structures because of its good mechanical properties and chemical corrosion resistance. However, PP fiber has a number of shortcomings, such as a smooth surface, poor hydrophilicity, lack of active groups in the molecular chain, and agglomeration and poor dispersion in cement-based materials. These issues limit its application in cement-based materials. Although the use of a silane coupling agent to modify the surface of PP fiber is effective, the influence of treated PP fiber on the sulfate resistance of cement-based materials is not significant. In this study, a PP fiber treated with a silane coupling agent was used to examine effects of different cement-to-sand ratios (C/S) and dosages of the treated PP fiber on the sulfate erosion resistance of cement mortar. Furthermore, the apparent morphology, mass loss rate, flexural strength, corrosion resistance coefficient, and microstructure of the concrete were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the PP fiber became rough after modification. Active groups were introduced on the fiber surface, which were well dispersed in the mortar and formed a good network distribution structure in the cement mortar, thereby slowing the erosion rate of the PP fiber mortar in a sodium sulfate solution. At a C/S ratio of 1:1 and a treated fiber dosage of 0.6%, the treated fiber mortar has exhibited good sulfate resistance. In addition, the monofilament fiber immersion test revealed that a layer of sodium sulfate crystals was deposited on the fiber surface, thereby increasing the roughness of the fiber surface and the pull-out force of the fiber from the cement matrix, this result indicated that the interfacial adhesion between the treated PP fiber and cement matrix was improved, which in turn led to the improvement in the sulfate erosion resistance of the treated PP fiber.

The Influence of Cooling Rate from High Temperature upon the Cavitation Erosion Resistance of the Duplex Stainless Steel X2CrNiMoN22-5-3

2015 ◽  
Vol 1111 ◽  
pp. 145-150
Author(s):  
Lavinia Madalina Micu ◽  
Ion Mitelea ◽  
Ilare Bordeaşu ◽  
Corneliu Marius Crăciunescu ◽  
Mihaela Popescu
Keyword(s):  
High Temperature ◽  
Cooling Rate ◽  
Stainless Steels ◽  
Cavitation Erosion ◽  
Erosion Resistance ◽  
Cold Plastic Deformation ◽  
Final Heat Treatment ◽  
Slow Cooling ◽  
Cavitation Behavior ◽  
Cavitation Erosion Resistance

Duplex stainless steels are processed by a process of hot or cold plastic deformation and welding operations. Their properties of the use depend on the type of product (deformed, welded) and to the final heat treatment. The proportion of the basic structural constituents (austenite and ferrite) essentially depends on the chemical composition and cooling rate from high temperatures. This paper shows the that slow cooling in the furnace at the high temperature (1060 ° C) lead to a predominantly austenitic microstructure (cca.75%) while that cooling in the water sudden limited the transformation austenite → ferrite, so that the microstructure will be composed of cca.52% F + 48% A.These modifications by structure justify the changes the occurring with respec ultrasonic erosion cavitation behavior.

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