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An intelligent cooling system directly influences the thermal load of high‐temperature components, heat distribution, and fuel economy of a diesel engine. An optimal coolant pump rotational speed map is a key factor in intelligent cooling control strategies. In this study, we designed an experimental variable coolant flow system for a maritime diesel engine. Experiment design and D‐optimal designs were used to optimize the parameters of the diesel engine cooling system. The diesel engine speed, load, and freshwater rotational pump speed were selected as variables. The temperature of the high‐thermal‐load zone of the combustion chamber components, fuel consumption rate, effective power, and peak cylinder pressure were selected as response variables, and the D‐optimal method was used to sample the experimental points. Polynomial response surface models were obtained using a stepwise algorithm. A multiobjective optimization problem was converted into a simple‐objective optimization problem using the ideal point method. A genetic algorithm was used to optimize the single‐objective function globally to obtain the optimal freshwater pump speed map for a diesel engine under all conditions. On average, the optimized cooling system decreased the fuel consumption by 1.901%. Six typical propulsive conditions were selected to confirm the validity of the optimization results. The experimental results indicate that the fuel consumption decreased by 2.35%, the effective power increased by 2.26%, and the power consumption of the water pump decreased by 17.83%. The combination of experiment design and D‐optimal designs offers the advantages of low cost, high efficiency, and high precision in solving multiobjective optimization problems involving strong coupling and nonlinear systems. The results of this research provide data support and a theoretical basis for intelligent cooling control strategies. A multiobjective optimization problem was converted into a simple‐objective optimisation problem using the ideal point method. A genetic algorithm was used to obtain the optimal freshwater pump speed map for a diesel engine under all conditions. The combination of experiment design and D‐optimal designs offers the advantages of low cost, high efficiency, and high precision in solving multiobjective optimization problems involving strong coupling and nonlinear systems.

Improving energy efficiency and reducing environmental impacts have become essential goals in today’s world. Finding ways to utilize waste heat for generating both power and cooling is a meaningful step toward more sustainable energy use and better resource management. In this research, the aim is to enhance the basic efficiency of diesel engines by harnessing the waste heat. By merging the diesel engine cycle with the ORC and the ejector-heat pipe cooling process, we can simultaneously generate power and cooling. This study focuses on tapping into the unused heat from a specific marine diesel engine to produce both power and cooling. The primary motivation is to cut down on fossil fuel usage due to its adverse environmental impact. To put it another way, this research focuses on increasing the base efficiency of diesel engines by recycling waste heat. By systematically integrating the diesel engine cycle with the organic Rankine cycle and the ejector-heat pipe cooling system, we can produce both power and cooling. Ultimately, 2-archive multi-objective cuckoo search algorithm-based optimization (MOCS2arc algorithm) establishes the optimized conceptual design. The system offers an electrical output of 72.01 kW and cooling capabilities of 56.83 kW, achieving an exergy efficiency of 60.4%. Moreover, economic metrics, including the facility’s unit cost of the product ($1259/GJ) and annual exergy destruction costs ($386,670), were ascertained. Under the optimization, exergy efficacy and SUCP of 64.9% and $902.21/GJ are achievable.

Nano-additives are being employed in successive generations of biodiesels to increase the performance characteristics and output of diesel engines. In this study, the impact of mixing carbon nanotubes (CNT) with three different generations of biodiesel in a diesel engine is assessed. With 100 ppm of CNT nanoparticles mixed together, pure biodiesels made from first-generation oil (soybean), second-generation oil (neem), and third-generation oil ( Nannochloropsis oculata microalgae) are used for the analysis. With an engine load ranging from 0 to 100%, a one-cylinder, four-stroke, direct injection diesel engine is employed. The engine has a water-cooling system, a compression ratio of 17.5:1, and a fuel injection angle of 23° before TDC. The evaluated engines’ improved performance and lower emissions serve as proof of the outcomes. The results are evidenced by the lower emissions and higher performance of the tested engines. The biodiesel containing CNT nanoparticles enhanced the cylinder pressure by 0.8–10.69%, the heat release rate (HRR) by 6.38–21.69%, and the brake thermal efficiency (BTE) by 0.32–1.62%. Subsequently, it reduced the brake-specific fuel consumption (BSFC) by 2.53–8.13%, the brake-specific energy consumption (BSEC) by 1.07–3.77%, the smoke opacity (BSN) by 6.26–12.85%, the particulate matter (PM) emissions by 11.04–18.33%, and the carbon dioxide (CO 2 ) emissions by 2.53–8.14% at full engine load. However, an increase in 13.62–18.37% nitrogen emissions (NOx) emissions is also observed with the addition of CNT at 100% load. The investigation supports the use of CNT nano-additives in diesel engines for improved performance and reduced emissions. Graphical Abstract

As stringent emission regulations and safety standards for explosion-proof diesel engines become more critical, the demand for efficient exhaust cooling systems has increased. Traditional cooling systems, typically relying on cooling and purification water tanks, have limitations in terms of safety, performance, and emissions control. To address these challenges, a novel dry exhaust gas cooling system was developed, incorporating a heat exchanger and exhaust dilution cooling device, replacing the conventional water-based cooling systems. This study explores the performance of the dry exhaust gas cooling system through a series of experiments including explosion-proof testing of the exhaust system, whole machine explosion-proof testing, exhaust temperature measurements, surface temperature evaluations, and exhaust gas composition analysis. The system’s performance was compared to both wet and combined dry + wet exhaust gas cooling systems. Results showed that the dry exhaust cooling system maintained its explosion-proof integrity during all tests, with the highest exhaust temperature at 68.5 °C and a surface temperature of 130.8 °C—both of which comply with safety standards. Notably, the dry exhaust system also demonstrated improved power output and reduced fuel consumption by over 4% compared to the other systems. Furthermore, it significantly lowered harmful exhaust emissions, reducing CO, HC, NOX, and CO2 levels by 55%, 71%, 68%, and 82%, respectively, when compared to the wet exhaust cooling system. In comparison to the dry + wet system, these reductions were even more pronounced—63%, 75%, 66%, and 94%, respectively. The findings suggest that the dry exhaust gas cooling system offers a safer, more efficient, and environmentally friendly alternative to conventional exhaust cooling systems in explosion-proof diesel engines.

This study was aimed to evaluate the effect of diesel fuel temperature on engine performance and emissions.  A 4-cylinder 4-stroke water cooled direct injection (DI) diesel engine was tested at three fuel temperatures (50, 60 and 70( °C. The fuel temperatures were controlled by A thermoelectric cooling system (TEC) fixed on the fuel supply line before the injection pump. The engine was run with two speed levels, included 1200 and 1500 rpm, with constant load (full load). An electric dynamometer was connected to the engine to make load by electric heaters. Gas emission was measured using gas analyzer type AirRex - HG540 and Texa gas box. Results obtained from the experiment were statistical analyzed using the factorial experiment system. The experiment design is (CRD), the averages of the results were tested using the least significant difference (LSD) at the probability level (0.05) using the (Genstat) program and showed that the fuel temperatures (50 °C) detected a sharp reduction in each of the brake specific fuel consumption (BSFC) by )6.95,4.34%) , Exhaust Gas Temperature(EGT) by (4.98,2.38%), Nitric Oxide (NOx) by )29.09,27.08%), and Particulate matter (PM) by (46.25,31.25%) and registered a slight increase brake thermal efficiency (BTE) of )7.12,4.40%) respectively, compared to the fuel temperature of (60,70) °C.

As a rule, the highest permissible sulfur content in the marine fuel must drop below 0.5% from 1 January 2020 for global fleets. As such, ships operating in emission control areas must use low sulfur or non-sulfur fuel to limit sulfur emissions as a source of acid rain. However, that fact has revealed two challenges for the operating fleet: the very high cost of ultra-low sulfur diesel (ULSD) and the installation of the fuel conversion system and the ULSD cooling system. Therefore, a solution that blends ULSD and biodiesel (BO) into a homogeneous fuel with properties equivalent to that of mineral fuels is considered to be significantly effective. In the current work, an advanced ultrasonic energy blending technology has been applied to assist in the production of homogeneous ULSD-BO blends (ULSD, B10, B20, B30, and B50 with blends of coconut oil methyl ester with ULSD of 10%, 20%, 30% and 50% by volume) which is supplied to a small marine diesel engine on a dynamo test bench to evaluate the power and torque characteristics, also to consider the effect of BO fuel on specific fuel consumption exhaust gas temperature and brake thermal efficiency. The use of the ultrasonic mixing system has yielded impressive results for the homogeneous blend of ULSD and BO, which has contributed to improved combustion quality and thermal efficiency. The results have shown that the power, torque, and the exhaust gas temperature, decrease by approximately 9%, 2%, and 4% respectively with regarding the increase of the blended biodiesel rate while the specific fuel consumption and brake thermal efficiency tends to increase of around 6% and 11% with those blending ratios.

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.

This manuscript investigates the utilization of waste heat from automobiles, such as exhaust gas and engine coolant water, to run a lithium bromide water Absorption Cooling System (ACS). This study proposed adding a secondary heat exchanger located between the primary heat exchanger and generator. It takes heat from engine coolant water to reduce thermal load on the generator and to enhance the Coefficient of Performance (COP) of the system. The effect of concentration solution, primary heat exchanger effectiveness, and the temperature of main component (generator, condenser, evaporator and absorber) are studied. The results show a COP of 0.79 with a cooling capacity of 5 kW at generator, condenser, evaporator, and absorber temperatures of (90, 40, 10, and 35), respectively. The COP increases as the evaporator temperature increases, and it decreases as the condenser and absorber temperature increases. Also, any increase in the heat exchanger effectiveness will be led to increase the COP. The results show that the addition of a secondary heat exchanger led to reduce the load on the generator by 4% to 7%, and that depends on the operating conditions and the system. In addition, the results examine a significant reduction in CO 2 emissions by 1.58 kg/hr. These findings point out to a substantial possibility for lowering thermal emissions and increasing energy efficiency, and that provides a long-term way to use waste energy in automobiles.

Addressing the engineering challenges of high thermal load, limited engine compartment space, and complex cooling conditions in high-power-density diesel engines, this study establishes a multi-domain coupled simulation model integrating a turbocharged diesel engine with its cooling system. The cooling component modeling innovatively combines thermal balance equations with ε-NTU heat exchanger theory, significantly enhancing computational efficiency. Model validation is performed against dynamometer test data. Furthermore, the Specific Heat Dissipation Rate (SHDR) is introduced as an evaluation metric for cooling efficiency. Simulation studies reveal the impacts of synergistic optimization between the Miller cycle and the Geometric Compression Ratio (GCR) on engine performance. Results demonstrate that under 3800 r/min operation, employing an intake valve closing advance of 40° CA combined with increasing the GCR from 14 to 17 led to 1.9% improvement in brake efficiency, 12g/(kW·h) reduction in brake specific fuel consumption (BSFC), and 8.73% decrease in SHDR. This approach enhances both power performance and fuel economy while significantly alleviating thermal management pressure.

For the benefit of solving the problem of absoluteness of conditional probability distribution and difficulty in obtaining basic event probability in Bayesian networks, this paper studies the reliability of diesel engine cooling systems through leakage noise or gate intuitionistic fuzzy Bayesian network. Firstly, the leakage noise or gate is introduced into the intuitionistic fuzzy Bayesian network, which makes the results more realistic. Secondly, prior probability in the Bayesian network is obtained based on the similarity aggregation method of triangular intuitionistic fuzzy numbers. The results show that the introduction of leakage noise or gate, intuitionistic fuzzy set, and Bayesian network can solve the problem that the probability of basic events in a Bayesian network is difficult to obtain. The conditional probability table corrected by leakage noise or gate is more realistic and greatly reduces the workload. It is determined that the two weakest components of the cooling system are the thermostat and the water pump. The results show that the way in this paper can provide support for the reliability analysis of the complex system.