Thermal Efficiency Research Articles

Abstract Conventional large-bore marine engines often suffer from misfire, incomplete combustion, and elevated emissions under lean-burn conditions. This review focuses on the application of prechamber turbulent jet ignition (TJI) systems in internal combustion engines to enable stable and efficient lean-burn. As a significant technological advancement, TJI generates multiple high-energy turbulent flame jets, effectively extending the lean-burn limit and enhancing ignition reliability. Given the increasingly stringent emission regulations and the marine industry’s shift toward zero- and low-carbon fuels-such as H 2 , NH 3 , methane, and methanol—TJI offers a promising solution for clean propulsion. This study systematically reviews the structural design of prechambers and nozzles, the strategies for fuel selection and injection in both the prechamber and main chamber, and their collective influence on combustion performance, emission characteristics, and thermal efficiency. It highlights the potential of TJI to support ultra lean-burn and low-emission operation, offering theoretical insights and technical references for future research and the practical deployment of sustainable marine power systems.

Injection duration is a key parameter affecting in-cylinder mixture formation and combustion in dual-fuel free-piston engines. This study utilizes a coupled numerical model to investigate its impact across a range of 0.05 to 0.25 ms. Simulation results indicate that a short injection duration (0.05 ms) significantly enhances in-cylinder swirl and turbulence, primarily by improving fuel atomization and the mixing rate. The peak turbulent kinetic energy (20 m²/s²) increases by 51% compared to the case with a 0.25 ms injection duration. This optimization promotes more complete combustion, which leads to optimal indicated thermal efficiency and heat release rate. However, it also increases the heat transfer coefficient and heat flux by 16.7% and 33.2%, respectively. Conversely, a longer injection duration enlarges the fuel-rich zone, leading to increased soot emissions. A comprehensive evaluation of performance and emissions identifies 0.05 ms as the optimal injection duration.

Thermal energy, encompassing both heating and cooling demands, accounts for the largest share of global energy consumption. Harvesting thermal energy from the environment, including the Sun and darkness, holds promise for decarbonizing thermal sectors, but suffers from low efficiency and intermittency. Here, inspired by ginkgo leaves featuring wax-coated vertical palisade cells, a 24-h bidirectional thermal energy harvesting approach is developed by integrating spectrally selective aerogels with anisotropic composite phase change materials (CPCMs). During daytime, sunlight is captured, converted into heat, and stored in anisotropic CPCMs with high axial thermal conductivity (24.16 W·m-1·K-1) and an anisotropy ratio of 3.7. Under one-sun irradiation, a high solar thermal energy storage efficiency of 87.5% with a peak temperature of 382.3 K is achieved by leveraging spectrally selective aerogels exhibiting "greenhouse effects". At night, a maximum radiative cooling power of 118.8 W·m-2 is attained, enabling cold energy storage at a temperature 4.0 K below ambient. The proposed leaf-inspired device operates continuously over 24 h, delivering annual thermal energy savings of 5321.4 MJ·m-2·yr-1, outperforming standalone solar thermal and radiative cooling systems by 44.8% and 223.3%, respectively. This bioinspired bidirectional energy harvesting strategy employing both solar and outer space resources, establishes a promising approach toward a carbon-neutral thermal energy supply.

ABSTRACT A novel low-heating-value syngas combustion-biomass pyrolysis and gasification cycle system is introduced in this study, marking a significant advancement in renewable energy conversion. Unlike conventional approaches, the integrated system utilizes Phragmites communis, an aquatic plant as feedstock, and employs a unique coupling of Aspen Plus thermodynamic modeling with reaction kinetics. This integration enables a comprehensive simulation of the entire process, from pyrolysis and gasification to syngas combustion. By optimizing flue gas recirculation, the system’s closed-loop design significantly boosts energy efficiency and substantially reduces pollutant emissions.At a flue gas reflux ratio of 0.2, the system achieves a remarkable thermal efficiency of 69.22%, while maintaining stable combustion even at practical operating conditions with a slightly lower reflux ratio of 0.3, yielding a thermal efficiency of 61.27% and minimal CO and NOX emissions. This research stands out by addressing the limitations of traditional biomass gasification, such as tar formation and low heating value gas combustion instability, through the synergistic integration of flue gas waste heat recovery and internal gasification agents. The proposed system offers a green and low-carbon solution for biomass conversion, providing a robust framework for optimizing energy structures and reducing greenhouse gas emissions.

A comparative analysis of nylon 610 production: Thermal efficiency and environmental considerations

Enhanced thermal management and efficiency of porous wavy fin using trihybrid nanofluids: A comparative study with hybrid nanofluids and nanofluids

Optimal control-based coordinated operation strategy for fan and air conditioning systems: Balancing individual thermal comfort and energy efficiency

Drag reduction and thermal protection efficiencies of combinational spike and opposing jet with different forebody geometries in hypersonic flows

Enhancing building roof thermal energy efficiency in hot climates: A novel dual-layer design with integrated phase change materials

Thermodynamic analysis and efficiency improvement of a novel wind-hydrogen energy storage system

PINNs and Vieta-Lucas Polynomial Collocation Simulation for Heat Transfer and Thermal Efficiency Analysis in Fully Wetted Semispherical Fins with Temperature-Dependent Thermal Properties: Applications in Air Conditioning Systems

Thermal efficiency impacts of structural and environmental variables in combined cycle plants: A machine learning approach to relocation scenario

Impact of organic carbon concentration on the molecular properties and assembly of riverine dissolved organic matter.

Advancing thermodynamic efficiency by two-stage flashing mixed refrigerant cycle for hydrogen precooling

This study presents a thermodynamic performance analysis of an Intercooled Recuperated Turbofan (IRTF) engine using GasTurb 14 simulation software. The research aims to evaluate the effect of integrating intercooling and recuperation systems on the efficiency, fuel consumption, and energy utilization of a modern turbofan configuration. A baseline turbofan model was established with defined pressure ratios, bypass ratio, and combustion parameters, which served as the reference for subsequent performance evaluation. The simulation results showed that the inclusion of intercooling reduces the compressor work by lowering the inlet temperature of the high-pressure compressor, while the recuperator significantly improves thermal efficiency by recovering exhaust heat to preheat the compressed air before combustion. The T–s and P–v diagrams demonstrated that these modifications optimize the thermodynamic cycle by minimizing irreversible losses and expanding the effective work area. The integrated configuration achieved improvements in thrust-specific fuel consumption (TSFC) and overall thermal efficiency compared to a conventional turbofan. These findings highlight the potential of the intercooled recuperated cycle as a promising solution for enhancing fuel economy and reducing emissions in next-generation aircraft propulsion systems.

This study aims to analyze the performance of a rotary dryer in the grain drying process using an experimental research method. Drying was carried out at an operating temperature of 55 °C for 180 minutes, with temperature and grain moisture content monitored hourly. Observed parameters included hot plate temperature (T_P), drying chamber temperature (T_R), outlet air temperature (T_out), ambient temperature (T_L), and drying efficiency. The results showed that the drying system temperature was stable throughout the process, with TP ranging between 85–95 °C, T_R between 50–60 °C, and Tout slightly lower, indicating effective heat transfer from the heat source to the material. The grain moisture content decreased from 23% to 18.61% in the first hour, 14.01% in the second hour, and 11.45% in the third hour. The highest drying efficiency was achieved at 30% at the 60th minute, then decreased to 20% at the 180th minute as the material moisture content decreased and heat loss increased. Overall, the results of this study indicate that the rotary dryer is effective in reducing the moisture content of grain to a safe storage level (11–14%) with even heat distribution and good thermal efficiency. Therefore, this system has the potential to be applied to small- to medium-scale grain drying.

This study is part of a sustainable construction approach by exploring the mechanical and thermal performance of compressed earth blocks (BTC) made from Dialakoro and Kita clays. BTC measuring 23 x 11 x 8 cm and cylindrical specimens measuring 5 cm in diameter by 10 cm in height were manufactured for the mechanical tests, and rectangular specimens measuring 27 x 27 x 3 cm were used for the measurement of thermal conductivity. The water absorption results by capillary action reveal a low resistance to humidity for the BTC from Kita (caused by rapid degradation in the presence of water) with a coefficient of -8 g/cm²·s¹/², compared to 2 g/cm²·s¹/² for those from Dialakoro, indicating better resistance to humidity. In terms of compressive strength, Dialakoro BTC averaged 6,85 MPa on the 28th day compared to 4,97 MPa for Kita. After 7 days, both types of BTC exceed the minimum permissible compressive strength for BTC, which is 2 MPa according to the NF EN 772-1 standard, with 3,86 MPa for Dialakoro and 2,29 MPa for Kita. Thermal conductivity measurements also show an advantage for Dialakoro’s BTC with 0,86 W/m·K compared to 1,02 W/m·K for Kita’s, suggesting better thermal insulation. These results confirm the superior potential of Dialakoro’s BTC in terms of mechanical performance and thermal efficiency.

This study used a Homogeneous Charge Compression Ignition-Direct Injection (HCCI-DI) engine to test the combustion, performance, and emissions of neem oil biodiesel blends. Analysis of engine behaviour was conducted based on the biodiesel blending ratio, combustion mode, and addition of aluminium oxide (Al2O3) nano additive. It has been found that peak in-cylinder pressures (Pmax) and heat release rates decreased with increasing biodiesel content, both in Direct Injection (DI) and HCCI-DI. Compared to DI, the HCCI-DI improved combustion characteristics, while the nano Al2O3 provided further improvements. In DI and HCCI-DI, pure biodiesel reduced brake thermal efficiency (BTE) by 2.01% and 1.68%, respectively. However, diesel and biodiesel BTE increased when HCCI-DI was used, as well as Al2O3 nano additive. Nitrogen oxide (NOx) emissions from biodiesel increased by 18.3% in DI mode but decreased by 4.3% in HCCI-DI mode when nano additives were used. Hydrocarbon (HC) emissions are reduced by 52.17% by biodiesel, however they are increased by HCCI-DI mode. On the other hand, HC emissions are reduced by up to 19.51% by nano additives. Carbon monoxide (CO) emissions were reduced by up to 55.56%, and smoke emissions decreased by 22.7% in DI mode and 39.1% in HCCI-DI mode due to using biodiesel, HCCI-DI mode, and the nano additive. Combining biodiesel and HCCI-DI combustion in engines with Al2O3 nano additive enhances performance and reduces emissions.

Using fossil fuels in compression ignition (CI) engines is still a challenge today due to concerns over environmental pollution and the long-term sustainability of fuel sources. Addressing these difficulties necessitates the development of alternate fuel methods that can boost engine performance while simultaneously lowering emissions. The current study focusses on employing a 20% blend of lemongrass (Cymbopogon Citratus) biodiesel and diesel supplemented with MWCNTs at 40 ppm (also known as “nano fuel of Lemongrass oil”) and investigating the usage of this mixture in an unmodified CI engine. To improve the performance of the nano-fuel, 5LPM hydrogen was premixed through intake manifold. This led to significantly better combustion, thanks to improved mixing inside the cylinder and quicker flame spread. Notably, adding 5 LPM hydrogen to the nano additive biodiesel made from lemongrass biodiesel resulted in a 12.6% boost in brake thermal efficiency. When compared to the LG20 blend operation, these studies revealed a 15.34% reduction in brake-specific fuel consumption (BSFC), a 19.6% decrease in carbon monoxide (CO) pollutants, a 5.35% decrease in unburned hydrocarbon (UHC) pollutants, and an 8.33% reduction in smoke opacity. As a result, we propose further research into hydrogen premixing in conjunction with nano-enhanced Lemongrass biodiesel to increase CI engine performance. It has been noticed that LG20 + MC + H2 fuel increases BTE by 12.6% and reduces BSFC by 15.33% when compared to LG20 fuel. These findings demonstrate the synergistic effect of hydrogen premixing and nanoparticle-enriched biodiesel in increasing CI engine performance and lowering emissions, indicating a possible path towards cleaner and more efficient engine operation.

Industrial waste-based catalysts provide a sustainable and cost-efficient solution for biodiesel production, improving yield, quality, and environmental impact. When this biodiesel is used in advanced reactivity-controlled compression ignition (RCCI) mode, it enhances the combustion process within direct injection (DI) diesel engines. These strategies effectively reduce nitrogen oxide (NOx) emissions and smoke without compromising engine performance. This study used cottonseed (Gossypium arboreum) methyl ester (CSME) as the pilot injection fuel. It was produced under optimal conditions of 2 wt% industrial waste dolomite catalyst, an 8:1 methanol-to-oil molar ratio, and heating at 55 °C for 45 min during transesterification through the response surface methodology (RSM) with central composite design (CCD). The catalytic potential of the industrial waste dolomite catalyst is validated through X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) analyses. Next, the n-butanol was injected into the intake manifold of the diesel engine at different energy shares of 10%, 20%, and 30% using an electronic primary fuel injection (EPFI) system in the RCCI mode. The fuel blends of diesel, CSME10 (10% CSME + 90% diesel), CSME20 (20% CSME + 80% diesel), and CSME100 (100% CSME) were tested as single-fuel in conventional mode, and CSME100 + 10% n-butanol, CSME100 + 20% n-butanol, and CSME100 + 30% n-butanol were tested in RCCI mode under variable load settings. Compared to the single-fuel operation, the RCCI combustion mode improved the performance and reduced emissions characteristics for all n-butanol energy shares. Especially, the CSME100 + 30% n-butanol mixture boosts brake thermal efficiency (BTE) by 22.25% and lowers brake specific fuel consumption (BSFC) by 23.33%. The unburnt hydrocarbon (HC) and carbon monoxide (CO) emissions were slightly increased by 28.13% and 27.37%, respectively. Also, the RCCI mode could simultaneously reduce smoke opacity (up to 58.07%) and NOx emission (up to 41%) through lower peak cylinder pressure and heat release rate (HRR) at 18 kg in 100% engine load operation. Based on these analyses, it is suggested that the RCCI mode with n-butanol injection by the EPFI system shows efficient fuel combustion and significantly reduced tailpipe emissions in DI diesel engine applications.