Zongming Yang

Energy saving control algorithms of centrifugal fans/pumps are based on the use of the frequency-controlled induction motor drives and pressure or flow rate sensors, the costs of which are comparable to the cost of the fans/pumps for low-power applications. The paper develops a new and simple estimation approach of the pressure and flow rate, utilising the measured Root Mean Square (RMS) value of the stator current, estimated motor’s input active power, reference stator voltage frequency and feed-forward backpropagation artificial neural network. The error percentage for both flow rate and pressure in experimental and estimated data is within the range of ±5%, which conforms to the ISO 13348 standard. A test rig for the rapid control prototyping of the fan is designed, and necessary design and test procedures are developed. The estimation approach is verified experimentally and demonstrates better estimation accuracy compared to the existing and possible similar simple approaches. The developed algorithm can be easily embedded into the industrial variable frequency drives without any hardware changes.

The enhancement of gas turbine (GT) efficiency through inlet air cooling, known as TIAC, in chillers using the heat of exhaust gas is one of the most attractive tendencies in energetics, particularly in thermal engineering. In reality, any combustion engine with cyclic air cooling using waste heat recovery chillers might be considered as a power plant with in-cycle trigeneration focused on enhancing a basic engine efficiency, which results in additional power output or fuel savings, reducing carbon emissions in all cases. The higher the fuel efficiency of the engine, the more efficient its functioning as a source of emissions. The sustainable operation of a GT at stabilized low intake air temperature is impossible without using rational design to determine the cooling capacity of the chiller and TIAC system as a whole to match current duties without overestimation. The most widespread absorption lithium-bromide chillers (ACh) are unable to reduce the GT intake air temperature below 15 °C in a simple cycle because the temperature of their chilled water is approximately 7 °C. Deeper cooling air would be possible by applying a boiling refrigerant as a coolant in ejector chiller (ECh) as the cheapest and simplest in design. However, the coefficients of performance (COP) of EChs are considerably lower than those of AChs: about 0.3 compared to 0.7 of AChs. Therefore, EChs are applied for subsequent cooling of air to less than 15 °C, whereas the efficient ACh is used for ambient air precooling to 15 °C. The application of an absorption–ejector chiller (AECh) enables deeper inlet air cooling and greater effects accordingly. However, the peculiarities of the subtropical climate, characterized by high temperature and humidity and thermal loads, require extended analyses to reveal the character of thermal load and to modify the methodology of designing TIAC systems. The advanced design methodology that can reveal and thereby forecast the peculiarities of the TIAC system’s thermal loading was developed to match those peculiarities and gain maximum effect without oversizing.

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.

The existence and development of modern society require significant amounts of available energy. Combustion engines are the main sources of heat. Their operation is accompanied by the formation of large volumes of emissions, which have different temperatures and contain harmful substances ejected into the environment. Therefore, the urgent problem today is the reduction in heat emissions. This might be achieved through a reduction in the amount of these pollutants by improving primary heat engines, converting to new, alternative types of fuel, and at the same time, to carbon-free fuel. However, such measures only reduce the temperature level of waste heat but not its volume. Conventional technologies for the utilization of heat emissions are ineffective for using heat with temperatures below 500 K. Thermoacoustic technologies can be used to convert such low-temperature heat emissions into mechanical work or electricity. This article is focused on analyzing the possibilities of improving the thermoacoustic engines of energy-saving systems through the rational organization of thermoacoustic energy conversion processes. An original mathematical model of energy exchange between the internal elements of thermoacoustic engines is developed. It is shown that the use of recuperative heat exchangers in thermoacoustic engines leads to a decrease in their efficiency by 10–30%. From the research results, new methods of increasing the efficiency of low-temperature engines of energy-saving systems are proposed.

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.

Contact cooling using thermopressor technologies is a promising direction for the development of energy-efficient technologies. This technology is based on the implementation of the thermo-gas-dynamic compression effect in special contact heat exchangers that consists of increasing the pressure while decreasing the temperature during the evaporation of a finely dispersed liquid injected into a gas flow moving at a speed close to sound. Upon application of the thermopressor for charge air cooling of the engine, the following result was obtained: an increase in the air pressure after the turbocharger by 340 to 480 kPa. The thermopressor can be used as a boost stage after the turbocharger, resulting in the reduction of a basic turbocharger compression work and the increase of engine power output accordingly. Reducing the work allows for the same air flow rate on the internal combustion engine to reduce the compressor power by 10 to 12%. This increases the temperature of the exhaust gases at the inlet of the exhaust boiler by 10 to 15 °C and boiler steam capacity, resulting in an increase in the power output of the utilization turbine generator with a corresponding reduction in the fuel consumption of the diesel generator of the ship power plant by 2 to 3%.

Gas turbine intake air cooling (TIAC) by exhaust gas heat recovery chillers is a general trend to improve turbine fuel efficiency at increased ambient temperatures. The high efficiency absorption lithium–bromide chillers of a simple cycle are the most widely used, but they are unable to cool inlet air lower than 15 °C. A two-stage hybrid absorption–ejector chillers were developed with absorption chiller as a high temperature stage and ejector chiller as a low temperature stage to subcool air from 15 °C to 10 °C and lower. A novel trend in TIAC by two-stage air cooling in hybrid chillers has been substantiated to provide about 50% higher annual fuel saving in temperate climate as compared with absorption cooling. A new approach to reduce practically twice design cooling capacity of absorption chiller due to its rational distribution with accumulating excessive refrigeration energy at decreased thermal loads to cover the picked demands and advanced design methodology based on it was proposed. The method behind this is issued from comparing a behavior of the characteristic curves of refrigeration energy required for TIAC with its available values according to various design cooling capacities to cover daily fluctuation of thermal loads at reduced by 15 to 20% design cooling capacity and practically maximum annual fuel reduction.

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.