Abstract
For low speed diesel engines under severe ocean conditions, high efficiency air–water separators must be equipped to separate excess moisture contained in the air and reduce the corrosion. Optimal design of air–water separator is an indispensable part in the development of marine main engines. In view of the complex gas–liquid two-phase turbulent motion within an air–water separator with corrugated plates, a mathematical model is established and numerical simulations of flow field, droplet trajectory and secondary transport are realized. The separation efficiency and pressure drop of the air–water separator under different structure parameters and different working conditions are studied. The results show that reducing the spacing of corrugated plate is helpful to improve the separation efficiency. The bending and hydrophobic hooks of the corrugated channel are important to improve the separation efficiency. The separation of droplet is mainly concentrated on the first two stages of the air–water separator, and the separation efficiency at the third stage is significantly reduced. Research results will further support corrugated plate theory, experimental research and optimization design of similar separators.
Highlights
When air entering the marine diesel engine passes through the supercharger and the air cooler of the diesel engine, the moisture contained in the air condenses together to form water droplets.The water droplets are brought into the scavenging box and cylinder of the diesel engine by the pressurized air, causing the damage to the oil film on the cylinder and aggravating the corrosion and wear of the cylinder, exhaust valve and piston ring, which results in the decline of the power and economic performance of the diesel engine
For large marine diesel engines providing power propulsion for large vessels, an air–water separator with corrugated plates must be arranged to separate excess moisture contained in the air and reduce the corrosion
After a period of aggregation, the droplets flow down the wall to the lowest point of the structure of the air separator and separate out. It is the existence of the baffle that makes the airflow velocity behind the baffle very low, which reduces the possibility of the droplet being carried twice and improves the separation efficiency
Summary
When air entering the marine diesel engine passes through the supercharger and the air cooler of the diesel engine, the moisture contained in the air condenses together to form water droplets. Chen et al [7] numerically studied the effects of parameters such as air velocity, droplet size, folding plate form, spacing and installation mode on the separation efficiency and pressure drop of a folded plate air-liquid separator and achieved good comparison numerical results with the cold state experimental results. Zhang et al [11] studied the flow field and separation efficiency of a high gravity rotary gas–liquid separator by CFD techniques and compared the numerical results with the available experimental data. In order to evaluate the separation performance of air–water separators with different corrugated plates and to select the most appropriate separator for the studied marine diesel engine, a numerical procedure is proposed and expected to present valuable data for performance parameters. The separation efficiency and pressure drop of the air–water separator under different structure parameters and different working conditions are studied by calculating and analyzing the flow of two phases inside the air–water separator
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