When using modern highly efficient internal combustion engines with lowered potential of exhaust heat the heat recovery systems receive increasing attention. The efficiency of combustion exhaust heat recovery at the low potential level can be enhanced by deep cooling the combustion products below a dew point temperature, which is practically the only possibility for reducing the temperature of boiler exhaust gas, while ensuring the reliability, environmental friendliness and economy of power plant. The aim of research is to investigate the influence of multiplicity of circulation and temperature difference at the exit of exhaust gas boiler heating surfaces, which values are varying as 20?C, 15?C, and 10?C on exhaust gas boiler characteristics. The calculations were performed to compare the constructive and thermal characteristics of the various waste heat recovery circuits and exhaust gas boiler of ship power plant. Their results showed that due to application of condensing heating surfaces in exhaust gas boiler the total heat capacity and steam capacity of exhaust gas boiler increases. The increase of exhaust gas boiler heat capacity is proportional to the growth of its overall dimensions. A direct-flow design of the boiler provides a significant increase in heat efficiency and decrease in dimensions. In addition, a direct-flow boiler circuit does not need steam separator, circulation pump, the capital cost of which is about half (or even more) of heating surface cost.

The fuel efficiency of marine diesel engine as any combustion engine falls with raising the temperature of air at the suction of its turbocharger. Therefore, cooling the engine turbocharger intake air by recovering exhaust gas heat to refrigeration capacity is a very perspective trend in enhancing the fuel efficiency of marine diesel engines. The application of water-fuel emulsion (WFE) combustion enables the reduction of a low-temperature corrosion, and, as a result, provides deeper exhaust gas heat utilization in the exhaust gas boiler (EGB) to the much lower temperature of 90–110 °C during WFE instead of 150–170 °C when combusting conventional fuel oil. This leads to the increment of the heat extracted from exhaust gas that is converted to refrigeration capacity by exhaust heat recovery chiller for cooling engine turbocharger sucked air accordingly. We experimentally investigated the corrosion processes on the condensation surfaces of EGB during WFE combustion to approve their intensity suppression and the possibility of deeper exhaust gas heat utilization. The fuel efficiency of cooling intake air at the suction of engine turbocharger with WFE combustion by exhaust heat recovery chiller was estimated along the voyage line Mariupol–Amsterdam–Mariupol. The values of available refrigeration capacity of exhaust heat recovery chiller, engine turbocharger sacked air temperature drop, and corresponding reduction in specific fuel consumption of the main low-speed diesel engine at varying actual climatic conditions on the voyage line were evaluated.

One of the most effective methods towards improving the environmental safety of combustion engines is the application of specially prepared water-fuel emulsions (WFE). The application of WFE makes it possible to reduce primary sulfur fuel consumption and reveals the possibility of capturing the pollutants from exhaust gases by applying condensing low-temperature heating surfaces (LTHS). In order to realize such a double effect, it is necessary to investigate the pollution processes on condensing LTHS of exhaust gas boilers (EGB), especially the process of low-temperature condensing a sulfuric acid vapor from exhaust gases to investigate the influence of condensing LTHS on the intensity of pollutants captured from the exhaust gases. The aim of this research is to assess the influence of the intensity of pollutants captured from exhaust gases by condensing LTHS in dependence of water content in WFE combustion. Investigations were carried out at a special experimental setup. The processing of the results of the experimental studies was carried out using the computer universal statistical graphic system Statgraphics. Results have shown that in the presence of a condensing heating surface, the degree of capture (purification) of pollutants from the exhaust gas flow is up to 0.5–0.6.

The application of water-fuel emulsion (WFE) in internal combustion engines enables to reduce the consumption of sulfurous fuel oils, thereby protecting the environment from emissions of sulfur and nitrogen oxides, as well revealing a great potential for the heat utilization of exhaust gases. The efficiency of utilization of exhaust gas heat in exhaust boilers (EGB) depends on their temperature at the outlet of EGB, id est. the depth of heat utilization. Exhaust gas temperature is limited by the rate of low-temperature corrosion (LTC), which reaches a level of 1.2 mm/year at the wall temperature of about 110 °C for the condensing heat exchange surfaces (HES) and reduces the reliability of the HES operation. Therefore, decreasing the corrosion rate of condensing HES at wall temperature below 110 °C to an acceptable level (about 0.2 mm/year) when undergoing WFE combustion will make it possible to reduce the exhaust gas temperature and, consequently, increase the efficiency of EGB and fuel saving during the operation of the ship power plant. The aim of the research is to assess improvements to the reliability, durability and efficient operation of condensing HES in marine EGB undergoing WFE combustion in a diesel engine based on experimental studies of the LTC process. A special experimental setup was developed for investigation. The use of WFE with a decreased wall temperature of HES below 80 to 70 °C would improve the reliability of the EGB along the accepted service life, increase the lifetime of the HES metal by almost six times as well as the overhaul period, and reduce the cost of repairing condensing HES. Furthermore, due to the reducing corrosion rate under WFE combustion, the application of low-temperature condensing HES makes it possible to enhance the efficiency of deeper exhaust gas heat utilization and provide sustainable efficient operation of a diesel engine plant on the whole at a safe thermal and environmentally friendly level.

Complex gas turbine schemes with air intercooling are usually used to bring the compression process of working fluid in compressor closer to isothermal one. A promising way to realize it is to use an aerothermopressor. The aerothermopressor is a two-phase jet apparatus, in which the highly dispersed liquid (water) is injected into the superheated gas (air) stream accelerated to the speed closed to the sound speed value (Mach number from 0.8 to 0.9). The air pressure at the aerothermopressor outlet (after diffuser) is higher than at the inlet due to instantaneous evaporation of highly dispersed liquid practically without friction losses in mixing chamber and with an increase in pressure of the mixed homogenous flow. The liquid evaporation is conducted by removing the heat from the air flow. In the course of the experimental research, the operation of the aerothermopressor for gas turbine intercooling air was simulated and its characteristics (hydraulic resistance coefficients, pressure increase, and air temperature) were determined. Within contact cooling of air in the aerothermopressor, the values of the total pressure increase in the aerothermopressor were from 1.02 to 1.04 (2–4%). Thus, the aerothermopressor use to provide contact evaporative cooling of cyclic air between the compressor stages will ensure not only compensation for pressure losses but also provides an increase in total air pressure with simultaneous cooling. Injection of liquid in a larger amount than is necessary for evaporation ensures a decrease in pressure losses in the flow path of the aerothermopressor by 15–20%. When the amount of water flow is more than 10–15%, the pressure loss becomes equal to the loss for the “dry” aerothermopressor, and with a further increase in the amount of injected liquid, they are exceeded. The values of errors in the relative increase of air pressure in the aerothermopressor measurements not exceeded 4%. The results obtained can be used in the practice of designing intercooling systems for gas turbines.

A fuel efficiency of a ship engine increases with cooling inlet air. This might be performed by the chillers, which transform the heat of engine exhaust gas and scavenge air for refrigeration. The effect gained due to cooling depends on the intake air temperature drop and the time of engine operation at decreased intake air temperature. Thus, the cooling degree hour (CDH) number, calculated as air temperature depression multiplied by the duration of engine operation at reduced intake air temperature, is used as a primary criterion to estimate the engine fuel efficiency enhancement due to intake air cooling over the ship routes. The engine intake air cooling potential is limited by its value, available according to engine exhaust heat and the efficiency of heat conversion to refrigeration in the chiller, evaluated by the coefficient of performance (COP). Therefore, it should be determined by comparing both the needed and available values of CDH. The ejector chiller (ECh) was chosen for engine exhaust gas heat recovery to refrigeration as the simplest and cheapest, although it has a relatively low COP of about 0.3 to 0.35. However, the ECh generally consists of heat exchanges which are mostly adapted to be placed in free spaces and can be mounted on the transverse and board side bulkheads in the ship engine room. The values of sucked air temperature depression and engine fuel consumption reduction at varying temperatures and humidity of ambient air on the route were evaluated.