Increase In Thermal Efficiency Research Articles

Prediction of RCCI combustion fueled with CNG and algal biodiesel to sustain efficient diesel engines using machine learning techniques

This study used microalgae biodiesel as a high-reactive fuel directly injected along with various Compressed Natural Gas (CNG) energy shares (10, 20, 30, and 40%) as low-reactive fuel injected into the intake system. The experiments are performed in a single-cylinder, water-cooled, 1500 rpm, 3.5 kW power Compression Ignition (CI) engine under various loading conditions to examine the effects of CNG energy share on performance and emissions in Reactivity Controlled Compression Ignition (RCCI) combustion mode. The study found that the 30%CNG share decreased Nitrogen oxides (NOx) and smoke by 25 and 31%, as well as an increase in thermal efficiency of 4.35% in comparison to traditional biodiesel combustion. Finally, two machine learning (ML) models, namely the Gradient Boosting Regressor (GBR) and LASSO (Least Absolute Shrinkage and Selection Operator) Regression, were developed for predicting the dependent variables individually from the independent variables. Both the LASSO and GBR models achieved high accuracy with R2 values of 0.98–0.99 and relatively low Root Mean Square Error (RMSE) values.

Experimental Study on the Impact of Hydrogen Injection Strategy on Combustion Performance in Internal Combustion Engines.

Hydrogen is an ideal alternative fuel for internal combustion engines due to its fast combustion rate and near-zero carbon emissions. To further investigate the impact of the injection strategy on combustion performance under various excess air coefficients and loads, experimental methods were employed to systematically study injection timing, injection pressure, and dual injection. The results demonstrate that appropriately delaying hydrogen injection timing can improve the thermal efficiency by up to 2.6% and reduce NOx emissions of equivalent combustion by nearly 88%. While increasing the hydrogen pressure to 8 MPa does not directly enhance the thermal efficiency and emissions, it can reduce the injection pulse width by approximately 75%, allowing for more flexibility in delaying the injection timing. Delaying the secondary end of injection (SEOI) leads to a reduction of over 47% in NOx emissions for λ (excess air coefficient) values of 1.5 and 1.0. The combustion duration and ignition delay initially increase and then decrease with the delay in SEOI, depending on the movement state of the fuel jet. With the increase in secondary injection proportion (SIP), brake thermal efficiency increases by no more than 1%, but NOx is reduced by more than 43% for λ values of 1.5 and 1.0. In the case of ultralean conditions (λ = 2.3), increasing the SIP from 0 to 30% results in a nearly 14% increase in the peak heat release rate (HRR) and a 19% reduction in combustion duration.

Dynamic interdependence of comfortable thermal conditions and energy efficiency increase in a nursery school building for heating and cooling period

The paper studies the influence of building function and orientation, level of thermal insulation on energy efficiency and occupant thermal comfort dynamic interdependence. Energy state dynamic modelling of the typical preschool educational facility (Kyiv, Ukraine) was carried out with different levels of thermal comfort in each of the zones, taking into account occupants' activity, metabolism, clothing, etc. The research was conducted for the heating and cooling periods, taking into account the operational peculiarities of the building. Increasing the thermal resistance from the base version to the Swedish norms reduces energy consumption by 32% for the heating period, compared to the base version. The introduction of intermittent heating leads to a reduction of energy consumption by 14%, compared to the base version. Intermittent heating and ventilation and increased thermal protection to Swedish standards can reduce energy consumption by 42%. The investigation of comfort indicators revealed that during the transition period when the heating is turned off, electric heating of the premises is required to maintain the comfort conditions, which increases the heating energy consumption by 18%. Three different options for children's clothing in the summer period to avoid feeling cold were investigated.

Performance analysis and comparison of the spark ignition engine fuelled with industrial by-product hydrogen and gasoline

The global push for carbon neutrality in internal combustion engines has driven research into low-carbon or zero-carbon fuels for the transportation sector. Hydrogen, as a carbon-free, high-density, and secondary energy source, can be obtained on large scales during the petroleum refining process as industrial by-product hydrogen (IPH). In this work, the IPH is firstly used and tested in the spark ignition (SI) engine. In, addition, the impacts of operating and controlling parameters on the performances of the SI engine fuelled with IPH are investigated and compared with the engine fuelled with gasoline. The experimental results indicate that the CA 10 and CA50 locations of the SI engine fuelled with IPH initially advance and then retard with increasing load. Meanwhile, its brake specific gas consumption decreases, while the brake thermal efficiency (BTE) increases. The results demonstrate that NOx emissions of the test SI engine fuelled with IPH increase, while the CO and HC emissions reduce with increasing the load and remain relatively low under medium load conditions. The optimum spark timing of the SI engine fuelled with IPH achieves a balance between the BTE and emissions. In addition, the combustion phasing of the SI engine fuelled with IPH advances and its combustion duration shortens compared to the test gasoline engine. Additionally, the SI engine fuelled with IPH outperforms the gasoline engine in terms of fuel economy, and its BTE increases by 15.39% and 11.58% under loads of 2.5 bar and 5 bar, respectively. Compared to the gasoline engine, the NOx emissions of the test SI engine fuelled with IPH slightly increase while its CO and HC emissions are reduced by more than 90%.

A new heat pump-operated solar desalination unit integrated with an air recirculating room

In this paper, a new study was presented studying the effect of coupling a solar still and a heat pump to improve the performance of a solar still. Two setups of solar stills were considered one conventional and one modified using a heat pump coupled with a room containing a Trombe wall to hit two birds with one stone using the effect of cooling and condensing. Besides, some parameters were studied such as the heat pump compressor On and Off duration effect, water depth effect, and the cooling effect for the integrated room. Energy, exergy, and cost analysis were concluded in the manuscript. The findings revealed that, for a water depth of 15 mm and a compressor operation of 55 min. On and5 min. Off, the total amount of water produced was 9.896 L/m2, which represents an improvement of roughly 148.39 % compared to the conventional one. Furthermore, the daily exergy and thermal efficiency increase was evaluated as 49.86 and 82.78 %, respectively. Also, cost decreased by around 4.73 % and was computed as 0.0141 $/L. Finally, the integrated room of the Trombe wall system had a significant benefit since, during the hottest hour (1 P.M.), the cooling effect was 12.8 °C below the ambient, resulting in a temperature drop of over 30.4 %.

Performance characterization of a novel PV/T panel with nanofluids under the climatic conditions of Muscat, Oman

The study presents an experimental analysis of a novel mini channels-based Photovoltaic/Thermal (PV/T) panel with nanofluid flow. The design consists of a PV plate attached to an aluminum substrate absorber plate having minichannels grooved on it to act as a solar collector and cooling mechanism for PV. The proposed design was tested for thermal and electrical efficiencies under the working fluids of water, Al2O3, and SiO2 nanofluids at 0.1% and 0.2% concentrations in water and at a flow rate of 0.005 l/s to 0.045 l/s. The experiments were carried out outdoors in a real environment and the measurements were taken for PV surface and fluid temperatures, incidence solar flux, electrical voltage, and current produced. The PV and PV/T performance was compared, and a noticeable enhancement in electrical efficiency was observed with the proposed design as compared to the bare PV module, and an appreciable augmentation in thermal efficiency was noticed when nanofluids were applied. The maximum electrical and thermal efficiencies of PV/T with 0.2% Al2O3 nanofluid were 19.1% and 73.4%, respectively; whereas for bare PV panels, the electrical efficiency was 18.7%. The Al2O3 nanofluid at 0.2% exhibited more than a 10% increase in thermal efficiency compared to water as a working fluid in PV/T.

The effect of the properties of porous fillers on the performance of a PCM-based photovoltaic thermal system: A CFD study

In thermal systems, combination of PCMs with porous fillers with high thermal conductivity is a proper method to improve their performance. In photovoltaic thermal (PVT) systems, as porous fillers are introduced to the collector tube and PCM bulk, the thermal efficiency increases. Moreover, since the temperature of the PV unit has dropped, the electrical efficiency has improved too. However, the properties of the porous insertion, i.e., permeability and porosity, might affect the pumping work, and consequently, electrical efficiency. In the present study, the effect of metal foam insertions on thermal and electrical performances is analyzed using a computational fluid dynamics (CFD) method. The results show that installing metal foams with porosities of 0.70–0.94 inside the collector and PCM container of a PVT system improves the thermal efficiency without any considerable decrement in electrical efficiency. When copper foam with a porosity of 0.705 is installed within the collector and PCM tank, the highest thermal efficiency of 66.70% is achieved; while, when copper foam with a porosity of 0.94 is used, the maximum electrical efficiency of 13.24% is resulted.

Solar energy harvesting from the photovoltaic/thermal (PV/T) pavement: Energy performance analyses and comparison considering ground influence

Under the carbon neutrality targets, the easy-installation low-investment photovoltaic (PV) technology is vital, while the limited urban rooftop area and high building façade cost limit the onsite PV installation. Thus, harvesting solar energy from the road, namely pavement-integrated photovoltaic/thermal (PIPV(T)) technology, is promising. The 2D finite element PIPV(T) models are proposed and verified through the field test within 3% (cell temperature) and 7% (PV output) mean absolute percentage error. The parametric analyses on system designs (water tank volume, water velocity, water inlet temperature), weather conditions (solar irradiance, wind velocity), and ground boundary condition influence are conducted. The water inlet temperature acts as a minor factor, while tank volume and fluid velocity are crucial, i.e., a 32.76% thermal efficiency increase for a 125 L tank volume increase. Results show that over 0.2 L/s water flow rate is recommended for a 100 L water tank, and the solar irradiance increase adds to the thermal efficiency to 41.47% under 1000 W/m2 with 11.38% ground influence. The annual system performances for southern and northern metropolises are compared, with water tank variation considered. Results show that a small water tank leads to high temperature and low system thermal efficiency at 9.3% and 12.17% in Hong Kong and Beijing.

Study on the Effects of the Hydrogen Substitution Rate on the Performance of a Hydrogen–Diesel Dual-Fuel Engine under Different Loads

Due to having zero carbon emissions and renewable advantages, hydrogen has great prospects as a renewable form of alternate energy. Engine load and hydrogen substitution rate have a considerable influence on a hydrogen–diesel dual-fuel engine’s efficiency. This experiment’s objective is to study the influence of hydrogen substitution rate on engine combustion and emission under different loads and to study the impact of exhaust gas recirculation (EGR) technology or main injection timing on the engine’s capability under high load and high hydrogen substitution rate. The range of the maximum hydrogen substitution rate was determined under different loads (30%~90%) at 1800 rpm and, then, the effects of the EGR rate (0%~15%) and main injection timing (−8 °CA ATDC~0 °CA ATDC) on the engine performance under 90% high load were studied. The research results show that the larger the load, the smaller the maximum hydrogen substitution rate that can be added to the dual-fuel engine. Under each load, with the increase of the hydrogen substitution rate, the cylinder pressure and the peak heat release rate (HRR) increase, the equivalent brake-specific fuel consumption (BSFCequ) decreases, the thermal efficiency increases, the maximum thermal efficiency is 43.1%, the carbon dioxide (CO2) emission is effectively reduced by 35.2%, and the nitrogen oxide (NOx) emission decreases at medium and low loads, and the maximum increase rate is 20.1% at 90% load. Under high load, with the increase of EGR rate or the delay of main injection timing, the problem of NOx emission increases after hydrogen doping can be effectively solved. As the EGR rate rises from 0% to 15%, the maximum reduction of NOx is 63.1% and, with the delay of main injection timing from −8 °CA ATDC to 0 °CA ATDC, the maximum reduction of NOx is 44.5%.

Design Optimization of an Ethanol Heavy-Duty Engine Using Design of Experiments and Bayesian Optimization

Abstract Diesel-fueled engines still hold a large market share in the medium and heavy-duty transportation sector. However, the increase in fossil fuel prices and the strict emission regulations are leading engine manufacturers to seek cleaner alternatives without a compromise in performance. Alcohol-based fuels, such as ethanol, offer a promising alternative to diesel fuel in meeting regulatory demands. Ethanol provides cleaner combustion and lower levels of soot due to its chemical properties, in particular its lower level of carbon content. In addition, the stoichiometric operating conditions of alcohol fueled engines enable the mitigation of NOx emissions in aftertreatment stage. With the promise of retrofitting diesel engines to run on ethanol to reduce emissions, the thermal efficiency of these engines remains the primary optimization target. In order to find the optimal ethanol-fueled engine design that maximizes the thermal efficiency, a large design space needs to be investigated using engineering tools. In this study, previous research by the authors on optimizing the design of a single-cylinder ethanol-fueled engine was extended to explore the design space for a heavy-duty multicylinder engine configuration. A heavy-duty engine setup with multiple operating conditions at different engine speeds and loads was considered. A design optimization analysis was performed to identify the potential designs that maximize the indicated thermal efficiency in an ethanol-fueled compression ignition engine. First, a computational fluid dynamics (CFD) model of the engine was validated using experimental data for four drive cycle points. Using a design of experiments (DoE) approach and a parameterized piston bowl geometry, the model was then exercised to explore the relationship among geometric features of the piston bowl and spray targeting angle and indicated thermal efficiency across all tested operating conditions. After evaluating 165 candidate designs, a piston bowl geometry was identified that yielded an increase between 1.3% and 2.2% points in indicated thermal efficiency for all tested conditions, while satisfying the operational design constraints for peak pressure and maximum pressure rise rate. The increased performance was attributed to enhance mixing that led to the formation of a more homogeneous distribution of in-cylinder temperature and equivalence ratio, higher combustion temperatures, and shorter combustion duration. Finally, a Bayesian optimization (BOpt) analysis was employed to find the optimal piston bowl geometry with a fixed spray injector angle for one of the operating conditions. Using BOpt, a piston candidate was identified that resulted in a 1.9% point increase in thermal efficiency from the baseline design, yet only required 65% of the design samples investigated using the DoE approach.

Experimental study on thermoelectric effect pattern analysis and novel thermoelectric coupling model of BIPV facade system

Electrical and thermal energy are the primary forms of useful energy generated by building integrated photovoltaic façade (BIPV façade) systems, while their interaction during operation remains unclear. This study aims to analyze the energy generation patterns and quantify the impact of thermoelectric coupling in BIPV façade systems. Through long-term outdoor experiment conducted on an actual BIPV façade system, the underlying regularity of thermoelectric coupling was discovered by analyzing the electrical and thermal characteristics. Results showed that under same solar radiation, enlarged air channel spacing led to a 53.22% increase in air channel heat and a 12.27% increase in mean thermal efficiency. Additionally, the heat proportion increased by approximately 15%, while the electricity proportion decreased by 15%. Furthermore, the mathematical relationships of the thermoelectric association factors were determined to quantify the observed thermoelectric generation patterns. A novel thermoelectric coupling model was established and validated with errors below 6.21% for accurate estimation of thermoelectric performance under actual operating conditions. Results emphasized both thermal and electrical energy generation of BIPV façade, which offers a new perspective on the comprehensive utilization of thermoelectric association in BIPV façade design and building applications, opening avenues for enhanced energy efficiency in renewable energy systems.

Preliminary tests of a Diesel engine powered by diesel and hydrogen

This article discusses the possibilities of powering a commonly used diesel engine with renewable fuels. It analyses scientific studies that clearly indicate that the use of hydrogen is a potentially future-proof option due to its potential to reduce specific fuel consumption and improve performance and increase thermal efficiency. The research was carried out on a laboratory bench designed to test a diesel engine fueled by different fuels. A proprietary hydrogen injection system with dedicated control software was used. Hydrogen injection pressures of 1,5, 1,8, 2,0 MPa and hydrogen injector opening times of 2,5, 3,0, 3,5 ms, respectively, were set as control parameters. The rapidly varying engine operating parameters were recorded and the parameters calculated from them were analysed.

Effect of green fuel and green lubricant with metallic nanoparticles on emissions of HC, CO, NOx, and smoke for a compression ignition engine

The United Nations Sustainable Development Goals (SDGs) are imperative from the point of view of protecting the environment by employing sustainable options. Considerable research has been carried out in the transportation sector to meet this objective. Here, the influence is assessed of epoxidised gingelly oil methyl ester biolubricant with alumina (Al2O3) nanoparticles on the performance and emissions of a single cylinder 0.66-L capacity direct injection compression ignition engine driven by gingelly B20 biodiesel. Engine tests are carried out with gingelly B20 biodiesel as a fuel, and gingelly methyl ester (B100), epoxidised gingelly methyl ester (B100E), and epoxidised gingelly methyl ester (B100E) mixed with 0.5%, 1.0%, and 1.5% w/w alumina (Al2O3) nanoparticles as the lubricant combinations. The results are compared with baseline B20 biodiesel fuel-mineral lubricant operation. The findings indicate that brake thermal efficiency increases by 8.64% for epoxidised gingelly methyl ester (B100E) with 1.0% w/w alumina (Al2O3) nanoparticle biolubricant in comparison to baseline operation. Considerable reductions in emissions are detected; specifically, reductions of 52.4%, 22.0%, 20.0%, and 34.9%, respectively, are observed for CO, NOx, and HC concentrations and smoke opacity for the abovementioned combination as compared to baseline operation. The present work suggests that further research is merited on green fuel-green lubricant combinations. The findings of this study address the United Nations Sustainable Development Goals (SDGs) 7 and 13.

Multi-criteria assessment and optimization of a natural gas-fed solid oxide fuel cell combined heat and power system

Solid oxide fuel cell (SOFC) combined heat and power (CHP) system is a promising candidate for efficient power generation. Due to its complex dynamic characteristics, system performance is still unsatisfied when it operates in variable load conditions. In this study, five improved layouts of a natural gas-fed SOFC-CHP system are proposed using three-fluid heat exchangers innovatively. Performance of the system under different layouts is compared from both energy and exergy perspective and their feasibility in multi-load conditions is evaluated. Sensitivity analysis of four key parameters is conducted to clarify their influences and potential ways for efficiency improvements from both system and component level are explored under different load conditions. Results show that the system with direct combustion of anode off-gas has better adaptability to multi-load conditions. Exergy loss of the combustor always occupies the highest proposition among all the components, at least 30%. Because of the large thermal load and high outlet temperature of the cold fluid, thermal management of the reformer is crucial for the system operation. Changes of the reforming temperature and fuel utilization ratio significantly affect the system performance. As the load increasing, the electric efficiency decreases and the thermal efficiency increases, the total efficiency can always be more than 85% for the SOFC-CHP system.

Evaluation of CI Engine Performance, Emissions, and Combustion Characteristics Using Corn Biofuel Blend with Divergent Cr's and Exhaust Gas Recirculation

This thesis investigates the potential of corn oil biodiesel as a renewable alternative fuel for diesel engines. An experimental study is conducted to enhance the engine characteristics of corn oil blended diesel through various approaches, including adjusting the compression ratio, employing different exhaust gas recirculation (EGR) rates, and incorporating Nano additives into the fuel. Preliminary examinations of corn oil methyl ester (COME) blends at 10%, 20%, and 30% reveal that the COME20 blend outperforms the others, establishing it as the preferred blend for further investigation. Subsequently, the investigation proceeds with COME20 at different load and speed conditions. The experimental results demonstrate notable improvements in engine performance. Specifically, at a compression ratio of 20:1 (CR20:1) compared to 18:1 (CR18:1), brake thermal efficiency increases by 2.72%, and brake-specific fuel consumption (BSFC) decreases by 7.8%. Furthermore, significant reductions in exhaust emissions, including carbon monoxide (17.64%), unburnt hydrocarbons (13.8%), and smoke opacity (3.5%), are observed. However, there is an increase in nitrogen oxides (NOx) emissions. In terms of exhaust gas recirculation (EGR), the addition of 6% and 12% EGR to COME20-CR20 results in reduced NOx emissions compared to diesel. Notably, the 12% EGR exhibits a greater reduction in NOx emissions but compromises engine performance to a greater extent than the 6% EGR. In conclusion, this study highlights the potential of optimizing engine design (compression ratio), control (EGR rate), and fuel reformulation (COME biodiesel blending) to facilitate the efficient utilization of COME biodiesel blended diesel fuel in compression ignition (CI) engines. The findings contribute to the advancement of renewable fuel technologies and offer insights for future developments in the field of sustainable transportation. KEYWORDS: Corn oil biodiesel, Renewable alternative fuel, BSFC (Brake-specific fuel consumption), Compression ratio, Exhaust gas recirculation (EGR), Nano additives, COME20 blend

Performance of sCO2 coal-fired power plants at various power capacities

Herein, the effect of the power capacity, Wnet, on the performance of supercritical carbon dioxide (sCO2) coal-fired power plants is investigated, with Wnet in the range of (100–1000) MWe. A comprehensive model was established wherein the sCO2 cycle was coupled with the models of various components. For the sCO2 boiler, the total thermal load was assigned to various heaters, and the pressure drop in each heater was calculated. Owing to the strong penalty effect of the pressure drop, both total flow mode (TFM) and partial flow mode (PFM) were applied to the sCO2 boiler. A fluid network integrating the recuperator units was established for heat recovery in the system. A thermal-hydraulic model was proposed for a single unit and an integration package. Various losses were considered in the prediction of the efficiencies of axial flow turbines and compressors. The thermal efficiency increases, attains a maximum, and then decreases with increase of Wnet. This parabolic distribution results from the tradeoff between the decreased efficiency owing to pressure drops in the heat exchangers and the increased efficiency of the turbomachinery. The maximum thermal efficiency occurred at Wnet of 300 MWe and 200 MWe when using the PFM and TFM, respectively. Based on the results, PFM is found to eliminate the penalty effect of pressure drops. Our study provides guidelines for the design and operation of sCO2 coal-fired power plants.

Superstructure design and optimization on closed Brayton cycle system of fluoride-salt-cooled high-temperature advanced reactor

To exploit the advantages of Fluoride-Salt-cooled high-Temperature Advanced Reactors (FuSTAR) such as high temperature, inherent safety, compact structure, and modularization, an energy conversion system based on a closed Brayton cycle was adopted, and the superstructure design was optimized to attain the best parameters and configuration. To enhance the convergence rate of a single computation, the simultaneous equation method was employed, while the particle swarm method was utilized to prevent local optimality. Irreversible analysis and sensitivity analysis were performed to evaluate the system's performance. The findings demonstrate that thermal efficiency can be significantly enhanced by incorporating reheating into the system. Furthermore, for air and Ar, the recompression intercooling configuration proved effective in reducing the heat transfer temperature difference and enhancing thermal efficiency. For CO2 and Xe, the incorporation of reheating, recompression, and intercooling significantly improved thermal efficiencies beyond 53%, indicating their immense potential for further development. Introducing reheating into the Xe cycle led to a substantial increase in both thermal efficiency and the area of the temperature-entropy graph. The irreversible analysis revealed that for CO2 and SF6, the predominant loss occurred in the cooler and recuperator. In contrast, for the Xe cycle, all kinds of irreversible losses were evenly distributed across each device. Sensitivity analysis indicated that the thermal efficiency of near-critical fluids was more sensitive to the lowest pressure than that of far-critical fluids. Both the near-critical split ratio and the far-critical minimum pressure had a significant impact on the mass flow rate. The design results of this method can guide the selection of the optimal power cycle system configuration for FuSTAR.

THE STUDY OF HEAT TRANSFER INTENSITY AND AERODYNAMIC DRAG INSIDE A FLAT PIPE

It is know that a heat exchange tube with a flat-oval profile has excellent thermal and aerodynamic characteristics in contrast to a round tube. Thus, with the same planes, a flat tube has a significant increase in thermal and aerodynamic efficiency compared to a round tube, which is widely used in industry. However, at present, there are a limited number of publications on the study of heat transfer and aerodynamics inside a flat pipe.
 In this paper, we present the methodology and results of the study of heat transfer and aerodynamic drag in a pipe, and describe the experimental stand for such studies.
 The experiments performed in a flowing wind tunnel with an internal diameter of 36 mm, operating in an open-loop circuit. The working medium is air drawn from the laboratory room. The prototype was a steel pipe with a flat-oval profile, 320 mm long, 30x15 mm cross section, and 2 mm wall thickness.
 The created experimental stand allows us to study the heat transfer and aerodynamic drag of a flat pipe under the boundary condition q=const. An electric heater ensured this condition, which is a nichrome wire with a diameter of 0.6 mm wound along the entire length of the pipe and insulated from the external environment.
 The experiments were carried out in the range of Reynolds numbers (10.5 - 55.0) 103 and dissipated powers (50 - 150) W. The average air temperature in the pipe was set in the range (20 - 55) 0C, and the average temperature of the pipe wall was set in the range (24 - 140) 0C in accordance with the electric power supplied to the heater.
 Empirical correlations proposed for determining the intensity of heat transfer and aerodynamic drag inside a flat pipe. The data had compared with a round tube. The results had analyzed, and it had shown for the first time that the intensity of heat transfer and aerodynamic drag in a flat-oval pipe is 1.1 to 1.2 times and 1.4 to 1.7 times higher, respectively.

Effects of ammonia addition on the performance and emissions for a spark-ignition marine natural gas engine

The application of natural gas (NG) and ammonia in internal combustion engines contributes to reducing greenhouse gas (GHG) emissions. The present study aims to discuss the optimization direction and evaluate the GHG emission reduction potentials of NG engines blending with ammonia. In the present study, the effects of ammonia volume fraction (XNH3) and excess air ratio (λ) on the performance and emission characteristics of a spark-ignition marine NG engine were experimentally and numerically investigated. The in-cylinder pressure, heat release rate, brake thermal efficiency, and emissions (e.g. CH4, NH3, NOx, CO, CO2, N2O) were analyzed. Results show that the peak values of the in-cylinder pressure and heat release rate decrease with the increase of XNH3 and the optimum brake thermal efficiency increases by 1% compared with the pure NG engine. As for emission characteristics, it is found that NOx emissions increase first and then decrease with ammonia addition and the main NOx is produced from ammonia. With the increase of XNH3, CH4 emissions fluctuate, NH3 and N2O emissions monotonously increase. Moreover, the addition of ammonia can reduce CO2 emissions and the maximum reduction of CO2 emissions is approximately 44.1%.

Magnetic photo-thermal evaporator with joule-assisted heating for stable vapour generation

Solar energy has the potential to be applied in the production of vapour that relies on high-temperature liquids in conventional ways because it is one of the reproducible energy sources. In this work, a magnetic photo-thermal evaporator (MPE) based on nickel foam coated with reduced-graphene-oxide is used to produce vapour. The increase of thermal conversion efficiency can be implemented by a solar absorbed structure that promotes the vaporization of generated water. MPE has its optimal energy conversion efficiency of 98 %. Due to the coupling joule heat and solar thermal processes, the efficient and stable interfacial evaporated performance could be controlled, which is to optimize the multi-process coupling and multi-energy complementary process and promote the actual applications of MPE. Under the solar power of 1000 W·m−2, the evaporation rates obtained were 1.75 kg·m−2·h−1 and 1.81 kg·m−2·h−1 for the coupled continuous and segmented magnetic fields for the 90 s, which are much higher than the theoretical evaporation rate limit for two-dimensional interfacial photo-thermal evaporator. In case of extreme water shortage, the magnetic field can be used to assist in the rapid extraction of fresh water. The advantages of rapid fabrication and lower cost of the MPE have made the developments of solar evaporator applications possible such as desalination and wastewater treatment.