Improvement of charge air cooling for marine diesel engines

The relevance of improving charge air cooling in marine diesel engines as a means of improving their technical and economic performance in accordance with the Strategy for the Development of the Shipbuilding Industry of the Russian Federation until 2050 is substantiated. It is shown that traditional recuperative coolers (air-to-air and water-to-air) have limited thermal efficiency and considerable weight and dimensions, which do not fully ensure the required degree of boosting in terms of mean effective pressure (2.5–3.0 MPa) and a reduction in nitrogen oxide emissions. As a promising alternative to recuperative heat exchangers, evaporative cooling technology based on in-channel injection of finely atomized water directly into the flow path of a centrifugal compressor is proposed. The main physical limitations associated with the extremely short residence time of droplets in the compressor (0.002–0.005 s) and the need to ensure a Sauter mean droplet diameter of no more than 20 μm are identified. Based on a review of scientific and technical literature on centrifugal compressor gas dynamics, two-phase flows, film evaporation, and moisture separation, it has been established that there is currently no comprehensive computational and experimental methodology covering the entire sequence of interrelated processes: from the generation of a gas–droplet flow to droplet evaporation, film formation on the blades, secondary breakup, and final separation of residual moisture. The scientific and technical task of developing system-engineering principles and design recommendations that ensure complete moisture evaporation and prevent liquid water from entering the engine cylinders is formulated. The study defines directions for further theoretical research and numerical modeling of inchannel water injection into marine centrifugal compressors .