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“Low piston's speed allows piston rings getting stucked in grooves.”
Piston speed is not one of the reasons rings get stuck. Blowby, poor combustion, failure of scraper rings, excessive cylinder lube, and faulty injection can all contribute to sticking rings but not piston speed.
”Injection's timing instability.”
You’ll have to explain that one in a bit more detail.
” Charge air temperature. Of course it's low at low load... and this affects combustion dramatically for all groups. There are a lot of marine applications, where charge air is even preheated up to 60-70 deg C during running at lower rate.”
Please list the engines and applications where that is the case.
The only reason to ever heat charge air is to aid in starting of small high-speed engines (and very few do that), or in the case of extremely low inlet air conditions where condensation might become an issue. In the latter case, coolant flow through the charge air cooler is reduced to maintain temperatures that do no exceed around 40 degrees C.
You will find that most engines with turbochargers and aftercoolers aim for a charge air temperature of about 12 degrees C above the temperature of the cooling medium. In the case of seawater cooled aftercoolers that is around 38 C. No engine manufacturer looks for charge air temps much above 50 at maximum and most are rated at under 40. Lowering charge air temperature increases charge density and increases power, it also decreases NOx production and allows engines to meet the EPA and IMO emissions limits. For EPA rated engines you must refer to the engine manufacturer’s technical file, as approved by class to determine the maximum charge air temperature.
“This improves quality of combustion.”
In some cases higher charge air temperatures may reduce soot production, but, at the cost of increased NOx and higher fuel consumption, both of which are not acceptable and may be illegal. No good comes from having high charge air temperatures and the marine propulsion industry is working overtime to reduce them on all engines.
”Injection timing.”
This is not a problem with modern engines, even mechanical engines do not suffer from this problem as at low rpm there is more time available over a given crank angle. Electronically controlled engines, especially common rail completely eliminates any of the problems we normally associate with antique engines.
”Fuel atomization.”
See above
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