Improvement In Thermal Efficiency Research Articles

Investigation of Lips-Guided-Flow Combustion Chamber and Miller Cycle to Improve the Thermal Efficiency of a Highly Intensified Diesel Engine

An investigation into the lips-guided-flow combustion chamber (LGFC) and Miller cycle was conducted on a highly intensified diesel engine under rated power conditions to improve thermal efficiency. The radius and depth of the chamber bowl and lips were optimized to intensify the guided flow and fuel/air mixing. The experimental and simulated results show that the LGFC had a higher fuel/air mixture quality and quicker combustion rate, leading to a higher indicated power and higher thermal efficiency. A late intake valve closing (LIVC) Miller cycle with a higher expansion ratio of 11 and a lower compression ratio of 8.2 was used to control the energy distribution of the thermodynamic cycle and reduce the mechanical and thermal loads. The results show that the maximum combustion temperature was decreased by about 45 K and the thermal efficiency was improved by 2.1%. The research results are useful to guide the improvement in thermal efficiency through combustion chamber design and Miller cycle application for highly intensified diesel engines.

Unveiling the failure mechanism on creep response of a casting Ni-based superalloy in thin-wall thickness

With the improvement of thermal efficiency and the lightweight tendency of engine blades, Ni-based superalloy is widely used owing to its excellent performance in high-temperature atmospheres. This work studied the effects of surface oxidation, internal environmental attack, and matrix damage on the failure mechanism in a thin-walled casting Ni-based superalloy at 980 °C/160 Mpa. At the edge of the fracture, the sample suffered a severe environmental attack, resulting in the oxidation-affected zone forms. However, the loss of effective bear area induced by surface damage could not be the main reason for the sample's failure. At the interior of the matrix, voids were preferably initiated at the interface of MC carbides. As the increase of creep deformation, dynamic recrystallization (DRX) occurred at the tip of the voids, which increased the transverse grain boundaries and promoted crack propagation. Moreover, the DRX provided a short penetration path for the nitrogen, causing internal nitridation with AlN and Ti(Ta)N to precipitate. EBSD analysis confirmed that nitrides induced significant dislocations to accumulate at the boundaries of nitrides/γ, accelerating the failure of the sample.

Fuel consumption and NOx emissions optimization of a marine natural gas engine with lean-burn and reformed exhaust gas recirculation strategies

Marine natural gas (NG) engines have received extensive attention in the shipping industry. To further improve the performance of the lean-burn engine, the reformed exhaust gas recirculation (REGR) technology which can realize hydrogen-rich combustion and exhaust gas recirculation is considered. In the present study, a comprehensive investigation on the performance of the marine NG engine with the exhaust gas-fuel reformer (the closed-loop system) was performed by GT-power software. Firstly, the characteristics of the reformer under different excess air ratios (λ) and reformate addition rates (Rre) were analyzed at specific M/O (the volume ratio of CH4 to O2 in the reformer inlet). Then, effects of the lean-burn strategy (the increase of λ) and REGR strategy (the increase of Rre) on combustion, performance and emission of the engine were studied. Moreover, the multi-objective genetic algorithm was utilized to obtain the optimal operating parameters (λ, Rre and M/O) of the closed-loop system. The results showed that the combustion duration is prolonged, the peak in-cylinder pressure and the NOx emissions are reduced with the increase of λ and Rre, but the brake specific fuel consumption (BSFC) is slightly increased. Despite the energy loss during the reforming process, BSFC of the engine with REGR strategy is lower than that of the lean-burn strategy due to the improvement of the engine thermal efficiency. Taking IMO’s Tier Ⅲ NOx standards and lowest BSFC as the optimization objects, the closed-loop system is recommended to work at λ = 1.41–1.49, Rre = 12–14%, and M/O = 1.0–1.2.

Energy and exergy analyses of a recompression supercritical CO2 cycle combined with a double-effect parallel absorption refrigeration cycle

In this study, a new cogeneration system is presented that can make optimal use of the waste heat from the sCO2 power cycle using a double-effect parallel absorption refrigeration cycle (DEARC), generating electricity and refrigeration simultaneously. A comparative study between the proposed (sCO2/DEARC) system and the stand-alone sCO2 power system is conducted to show its advantages and potential. The performances of the sCO2 and sCO2/DEARC systems are evaluated from the energetic and exergetic points of view using an in-house developed thermodynamic simulation platform via Engineering Equation Solver (EES) software. Variables such as pressure ratio, turbine inlet temperature, and evaporator temperature are also used for parametric analysis. The results indicate that the proposed system can generate of 132.72 MW cooling capacity. Also, the results show that the proposed sCO2/DEARC system can achieve a 55.8% and 5.2% improvement in thermal efficiency and exergy efficiency, respectively, with a negligible decrease in net power output (Wnet) compared to the stand-alone sCO2 power plant.

Mechanism of the reduction in afterburning and thermal efficiency improvement with highly oxygenated fuels in diesel combustion

Highly oxygenated fuels can effectively reduce afterburning in diesel diffusion combustion and improve the degree of constant volume heat release in spite of increases in injection duration due to smaller heating values. The mechanism of afterburning reduction and the structural differences in the diesel fuel spray with changing the oxygen content in the fuel were investigated in a constant volume vessel and analyzed with 3D CFD simulation. The result showed that the equibalance ratio inside the spray decreased with increases in the oxygen content due to lower theoretical air-fuel ratios, promoting the spray combustion after the end of injection. Further, the combustion characteristics and the exhaust gas emissions of the oxygenated fuels were investigated in an experimental single cylinder diesel engine with modern specifications. With increasing oxygen contents, the degree of constant volume heat release increased with reductions in the afterburning, resulting in higher indicated thermal efficiencies. However, the indicated thermal efficiency showed a maximum at around 27 mass% of the oxygen in fuel and further increases in the oxygen contents resulted in lower indicated thermal efficiencies due to larger cooling losses.

Thermal analysis on the performance of a finned hybrid bi-fluid PVT system

The increase in the temperature of solar panels is a significant issue that leads to low performance of photovoltaic (PV) cells. This numerical investigation aims to perform a transient analysis employing commercial computational fluid dynamics code and improve the electrical energy of the PV panel in a hybrid system by utilizing both water and air and adding fins. The system was cooled from the rear side of the PV/thermal (PVT) module by flowing water at different mass flow rates (ṁw = 0.010 kg/s to 0.020 kg/s) through aluminum tubes adhered to an aluminum absorbent plate. Moreover, the air passes through the channel that contains aluminum fins welded to the absorbent plate and next to the tubes. The objective is to analyze the effects of ṁw and fins on the flow and the thermal efficiency. A comparison was made between two modules of bi-fluid (BF) PVT manifolds: module 1 without fins and module 2 with fins. The effect of the operating temperature rise on the PV panel and the total thermal efficiency was evaluated. The attained results presented a linear decrease in thermal efficiency with the increase of ṁw. The thermal efficiency of modules 1 and 2 at ṁw = 0.010 kg/s is 50% and 60%, respectively. Under the solar irradiance and ṁw = 0.010 kg/s in module 2, an improvement of thermal efficiency of about 5.7% was recorded compared to module 1. The hybrid PVT BF system with fins (module 2) operating with ṁw = 0.010 kg/s has proved that adding fins to the PVT system was very effective in maintaining the system’s thermal efficiency at its highest record.

Impact of produced oxyhydrogen gas (HHO) from dry cell electrolyzer on spark ignition engine characteristics

In the current study, an onboard dry cell electrolyzer was built to produce an oxyhydrogen (HHO) flow rate of 0.5 L/min by water electrolysis. The objective is to show the impact of oxyhydrogen introduction on engine exhaust gases, combustion characteristics, and engine performance related to gasoline. The experiments were carried out in a petrol engine at a fixed engine speed of 3000 rpm and variable engine loading. When comparing HHO gasoline dual fuel to standard gasoline fuel, the maximum improvements in volumetric efficiency, thermal efficiency and air-fuel ratio were determined as 7.5%, 8% and 11%, respectively. In the case of HHO addition, the highest reductions in specific fuel consumption and exhaust gas temperature were 9% and 6.5%, respectively, compared with conventional gasoline fuel. The highest reduction in CO, HC, NOx, and CO2 concentrations was observed as 18%, 9%, 15%, and 11%, respectively, for HHO-gasoline dual-fuel mode compared to gasoline fuel. The peak cylinder pressure and HRR improvements were 1.5% and 4.5%, respectively, at 100% engine load. Oxyhydrogen gas is highly recommended as a substitute fuel since it significantly enhances engine performance and combustion characteristics as well as reducing exhaust pollutants.

Parametric Analysis and Optimization for Thermal Efficiency Improvement in a Turbocharged Diesel Engine with Peak Cylinder Pressure Constraints

While the original equipment manufacturers are developing engines that can withstand higher PCP, the methodology to maximize the thermal efficiency gain with different PCP limits is still not well-known or documented in the literature. This study aims to provide guidance on how to co-optimize air system parameters, compression ratio, and intake valve closing (IVC) timing of heavy-duty turbocharged diesel engines to enhance thermal efficiency with peak cylinder pressure (PCP) constraints. In this study, a one-dimensional turbocharged engine model is established and validated by experimental data. The effects of turbocharger efficiency, boost pressure, high-pressure exhaust gas recirculation (HP EGR) ratio, compression ratio (CR), and IVC timing on diesel engine efficiency are assessed under PCP constraints through parametric analysis. The results indicate that for enhancing engine thermal efficiency under limited PCP, an increment in boost pressure and CR, and late IVC timing compared to baseline is required. By multiple parameter optimization, the best parameter combination under different PCP constraints is proposed. At a PCP limit of 20 MPa, the combination of a compression ratio of 18.57, boost pressure of 298 kPa, and IVC timing of −95.2 °CA ATDC yields a 1.56% (absolute value) improvement in ITEn over the baseline condition. Raising the PCP limits from 20 MPa to 25 MPa requires increasing the compression ratio to 21.92, boost pressure to 308 kPa, and delaying the intake valve closing timing to −88.7 °CA ATDC, which results in an absolute improvement of 0.86% in ITEn. Baseline engine configuration is updated accordingly to validate the thermal efficiency improvement strategy at a 25 MPa PCP limitation. Experimental results demonstrate a 2.2% (absolute value) improvement in brake thermal efficiency and 1.98% (absolute value) improvement in overall energy efficiency.

Energy and Mass Matching Characteristics of the Heat-Absorbing Side of the Ammonia Energy Storage System under Nonuniform Energy Flow Density.

Ammonia thermochemical energy storage is based on a reversible reaction and realizes energy storage and utilization by absorbing and releasing heat. Under different energy flow densities, the efficiency of an ammonia reactor composed of multiple ammonia reaction tubes is different. Based on the coupling model of light, heat, and chemical energy of an ammonia decomposition reaction system, taking a 20 MW solar thermal power plant as the research object, this paper proposes a new model of ammonia energy storage system, which places the ammonia decomposition side in a low-pressure environment and the ammonia synthesis side in a high-pressure environment. The effects of different inlet temperatures, inlet flow rates, flow distribution, and energy flow density distribution on the ammonia energy storage system were studied. The results show that the increase of inlet temperature and the decrease of inlet flow rate are beneficial to the improvement of thermal efficiency and exergy efficiency of the system to a certain extent, but when the inlet temperature increases or the inlet flow rate decreases to a certain extent, the efficiency of the system will decline. Under the condition of nonuniform energy flow density and nonuniform inlet flow distribution, more ideal system thermal efficiency and exergy efficiency can be obtained.

PERFORMANCE ANALYSIS OF AN EFFICIENT NEW-DESIGN SOLAR AIR HEATER BY CFD METHOD

The main contribution of this study is to present a modified V-corrugated grooved absorber plate in the construction of plane solar air heaters for higher performance. The combined effects of extended heat transfer area due to the V-shaped absorber, the suction process by the grooves that maintains the convective flow closed to the heated absorber and the jet impingement enable high efficiency of the proposed solar collector. For simulation purposes, the conduction equation is employed for temperature computations inside the solid elements, while the turbulent airflow equations are solved based on the CFD method using the κε− turbulence model. The present finite element-based analysis is performed using the COMSOL Multi-physic software. To demonstrate the rate of irreversibilities in a solar collector, the entropy generation due to heat transfer and viscous friction and, accordingly, the second law efficiency are computed at different steady operating conditions. The numerical procedure is validated by comparing the obtained numerical findings with the experimental results reported in the literature. From the obtained results, it is found that the proposed absorber plate has a triple-edged sword positive effect on the solar air heater performance, such that the thermal efficiencies up to 80% are computed. Moreover, about 10% improvement in the thermal efficiency of the proposed solar collector compared with its competitor (solar air heater with a simple V-corrugated absorber) reveals the positive impact of the designed absorber plate. Also, the increase in the height of V-shaped absorber from 𝐻𝐻0=2 𝑐𝑐𝑐𝑐 𝑡𝑡𝑡𝑡 𝐻𝐻0=4 𝑐𝑐𝑐𝑐 leads to about 11% improvement in the heater thermal efficiency. The numerical findings can be considered as a good reference to find an alternative for efficient solar collectors.

Impact of hydrogen direct injection on engine combustion and emissions in a GDI engine

The combustion and emission characteristics of a hydrogen engine were investigated through experimental analysis using a GDI engine. To enable hydrogen in-cylinder direct injection, a specialized hydrogen gas injector was employed. A comparative analysis of the combustion performance between gasoline and hydrogen fuels in a spark-ignited engine was conducted. Additionally, the study experimentally explored the thermal efficiency and emission reduction potential of hydrogen engines in lean combustion modes. The results indicated a significant improvement in the combustion rate when hydrogen fuel was utilized in the spark-ignited engine. However, the effective thermal efficiency was found to be lower than that of gasoline fuel due to the delayed MBF50 under stoichiometric conditions. Furthermore, when compared to gasoline fuel, the reduction of CO and THC emissions was accompanied by an increase in NOx emissions. Nevertheless, optimizing the air dilution ratio in hydrogen engines led to an improvement in the effective thermal efficiency. Specifically, under medium load conditions, a Lambda value of 2.7 resulted in an effective thermal efficiency of 43.5%. Additionally, under ultra-lean conditions (Lambda > 2.3), NOx emissions could be reduced to below 50 ppm, reaching as low as 44 ppm. This study highlights the potential of improving combustion efficiency and reducing emissions by utilizing hydrogen fuel, particularly in lean combustion modes. It contributes to the continuous development of hydrogen engine technology and promotes the implementation of cleaner and more efficient energy solutions.

Investigation of the drop-in capabilities of a renewable 1-Octanol based E-fuel for heavy-duty engine applications

This article presents the results of an investigation of neat 1-Octanol and its blends with Diesel, which can be potential drop-in fuels for heavy-duty compression ignition engines. Fuel blends consisting of 10 %, 20 %, and 30 % 1-Octanol by volume in Diesel, including neat 1-Octanol, were investigated for ignition and combustion performances. The ignition behavior was assessed using a constant-volume combustion-chamber-based ignition tester. The experimental investigation was conducted on a heavy-duty single-cylinder engine by varying the combustion center. In addition, injection-rate shaping was performed to understand the effects of various injection-rate shapes, namely square, ramp, and boot rate shapes, on the performance of neat 1-Octanol.The ignition tester results indicated an increased ignition sensitivity of neat 1-Octanol towards the chamber pressure and temperature compared to that of Diesel. At an elevated chamber temperature (650 °C) and pressure (20 bar), the ignition delay of neat 1-Octanol approaches closer to that of Diesel. Engine experiments revealed an improved thermal efficiency with neat 1-Octanol and its blends by up to 1.2 %, owing to their improved mixture homogenization capabilities. Furthermore, neat 1-Octanol and its blend led to a drastic reduction in smoke and carbon monoxide. In addition, it results in the highest peak during the premixed heat release, and with a square injection-rate shape, an additional minor improvement in thermal efficiency was observed. The relative changes in carbon monoxide and hydrocarbon emissions between the injection-rate shapes were negligible. At higher load, the boot-rate shape results in lower NOx formation than the square-rate shape at an almost identical thermal efficiency. Overall, the 10 % 1-Octanol, 20 % 1-Octanol and 30 % 1-Octanol blends, which fulfill the Cetane number requirements for the given fuel norms, can be used as drop-in fuels, as they exhibit a comparable or even better performance than Diesel.

Improvement of diesel combustion with suppression of mutual fuel spray flame interactions with staggered nozzle hole arrangement and a spatially divided combustion chamber

A combination of a fuel injector with staggered nozzle hole arrangement with a combustion chamber divided into upper and lower layers by placing a lip at the middle of the side wall is proposed to improve diesel combustion with suppression of interactions among fuel spray flames. The fuel injector has twelve alternately arranged spray holes ( ϕ0.09 mm), staggered at two injection angles, 79° and 55° from the central axis of the injector. Two ordinary injectors with eight ( ϕ0.113 mm) and twelve ( ϕ0.092 mm) holes with an injection angle of 78° from the central axis with a conventional re-entrant combustion chamber were also examined as references. The experimental results showed that the improvements in thermal efficiencies and the reduction in smoke emissions can be established over a wide IMEP range with the proposed combination of the staggered nozzle hole injector and the divided combustion chamber. The exhaust loss is reduced with the combination of the injector and the combustion chamber while the cooling loss increases slightly. The rate of heat release from the combination of the injector and the combustion chamber has a more active main combustion and smaller afterburning than conventional systems. The three-dimensional CFD simulations showed that the combination of the injector and the combustion chamber can efficiently suppress the interactions among fuel spray flames at the combustion chamber wall after the impingement of fuel spray flames and also suitably distribute the fuel mixture, resulting in reductions in the afterburning and the smoke emissions. The slight increase in cooling loss with the proposed combination may be due to the increase in contact area of hot burned gas on the cylinder head; further improvements in thermal efficiency can be expected with optimization of the design factors related to the fuel injection and the combustion chamber configuration.

Artificial intelligence driven smart operation of large industrial complexes supporting the net-zero goal: Coal power plants

The true potential of artificial intelligence (AI) is to contribute towards the performance enhancement and informed decision making for the operation of the large industrial complexes like coal power plants. In this paper, AI based modelling and optimization framework is developed and deployed for the smart and efficient operation of a 660 MW supercritical coal power plant. The industrial data under various power generation capacity of the plant is collected, visualized, processed and subsequently, utilized to train artificial neural network (ANN) model for predicting the power generation. The ANN model presents good predictability and generalization performance in external validation test with R2 = 0.99 and RMSE =2.69 MW. The partial derivative of the ANN model is taken with respect to the input variable to evaluate the variable’ sensitivity on the power generation. It is found that main steam flow rate is the most significant variable having percentage significance value of 75.3 %. Nonlinear programming (NLP) technique is applied to maximize the power generation. The NLP-simulated optimized values of the input variables are verified on the power generation operation. The plant-level performance indicators are improved under optimum operating mode of power generation: savings in fuel consumption (3 t/h), improvement in thermal efficiency (1.3 %) and reduction in emissions discharge (50.5 kt/y). It is also investigated that maximum power production capacity of the plant is reduced from 660 MW to 635 MW when the emissions discharge limit is changed from 510 t/h to 470 t/h. It is concluded that the improved plant-level performance indicators and informed decision making present the potential of AI based modelling and optimization analysis to reliably contribute to net-zero goal from the coal power plant.

Photovoltaic thermal system with phase changing materials and MWCNT nanofluids for high thermal efficiency and hydrogen production

The performance and electrical output of photovoltaic/thermal (PV/T) systems are significantly affected by an increase in the PV cell temperature. The integration of nanofluids has been explored as a solution to mitigate cell temperature rise in PV/T modules. However, the use of nanofluids raises environmental concerns. Thus, in this study, the attempt has been made to incorporate both MWCNT nanofluids and phase changing materials to reduce the cell temperature and which apparently improvised the electrical output and thermal efficiency. A series of tests conducted on five different samples at varying mass flow rates of 30 LPM, 40 LPM, and 50 LPM. MWCNT was dispersed in water at volumes of 0.05%, 0.1%, and 0.15% v/v using the sonication method. The proposed PV/T hybrid system effectively reduced panel temperature. Additionally, the integration of PCM and nanofluids resulted in an 8% increase in electrical power and a 12% improvement in thermal efficiency. Furthermore, higher nanofluid mass flow rates led to an enhanced electrical efficiency, ranging from 12.5% to 14.5%. Findings reveal that the incorporation of PCM with nanofluids holds promise for sustainable and improved energy production. Moreover, the possibility of hydrogen production through electrolysis is a viable option that permits further investigation.

Study on performance evaluation framework and design/ selection guidelines of working fluids for subcritical organic Rankine cycle from molecular structure perspective

Organic Rankine cycle (ORC) is a promising power cycle to convert low-grade thermal energy. The quick and easy evaluation of the potential working fluids lacking thermophysical property data is important for the working fluid selection of ORC. This paper proposes a systematic framework of working fluid evaluation from the molecular structure perspective, which couples the quantitative structure property relationship (QSPR) and universal equations of state. The thermodynamic performance of ORC is first correlated with four key thermophysical properties based on universal equations of state. Then, these thermophysical properties are obtained from the corresponding QSPR models based on the molecular structure of working fluids. The influence factors of ORC performance at a micro level are investigated using the QSPR models. Moreover, the effects of molecular characteristics on thermal efficiency are analyzed. The criteria for working fluid design/selection are recommended aiming at the improvement of thermal efficiency. The proposed framework shows sufficient accuracy with the relative errors of −0.41 - 15.85% and mean absolute error of 8.29% compared with the results based on REFPROP. It is found that the cyclization of carbon chain is an ideal method for the working fluid design based on alkanes and alkenes. This work can provide new insights for the evaluation, selection, and design of working fluids on the molecular structure level.

Energy and exergy analysis of VCR engine fueled with rubber-seed oil methyl ester using response surface methodology

This study presents a comprehensive analysis of the thermodynamic performance of a variable compression ratio engine fueled with rubber-seed oil methyl ester blended with diesel. The objective is to evaluate the energy and exergy characteristics according to the first and second laws of thermodynamics for various compression ratios and supercharging pressures. A 3.5 kW engine with compression ratios values ranging from 18:1 to 22:1 and SC pressures of 0, 0.25, and 0.5 bar (g) at 80% load was considered. The inlet manifold pressure was controlled using a centrifugal-type blower (1.5 m3/min, 350 W, 240 V AC) with an adjustable valve. Key fuel energy parameters including shaft energy, cylinder pressure, brake specific energy consumption, thermal efficiency, heat release rate, absorbed energy by cooling water, exhaust gas temperature, exergy efficiency, exergy destruction, exhaust energy, and emissions were analyzed. Results showed significant improvements in shaft energy (35.51%), thermal efficiency (35.37%), and heat release rate (25.17 J/°CA) for compression ratios 20 and supercharging pressure of 0.25 bar, with a reduction in brake specific energy consumption of 2.912 kJ/s kW. The second law efficiency and irreversibility were observed to be 60.31% and 0.0118 kW/K, respectively. Experimental findings demonstrated a reduction in carbon monoxide (25.12%) and hydrocarbon (40%) under the aforementioned conditions. Response surface methodology was employed to predict optimal operating conditions, and the equations were validated using analysis of variance and p-test. The D-optimality test facilitated the determination of optimal operating parameters for different responses through multi-objective optimization techniques. Individual desirability values were combined to obtain a composite desirability of 0.9054. The study identified compression ratios 18 with a supercharging pressure of 1.78 bar as the optimum operating condition for 20% fuel blends in a low-speed agricultural diesel engine, resulting in a remarkable improvement of 41.24% in energy efficiency and 68.45% in exergy efficiency, with minimal emissions.

Changes in Clay Hollow Block Geometry for Energy Efficiency Benefits—Thermal Simulation for Brazil

Masonry, which constitutes a large area of many buildings’ envelopes, represents important thermal performance and energy consumption functions. Clay hollow block geometry can influence these results. In this sense, this work aims to numerically evaluate the thermal properties and energy efficiency improvement provided by new geometries of clay blocks in the Brazilian context. Two commercial block geometries were selected, and new internal void geometries were proposed, maintaining approximately the same percentage of voids. The new formats were submitted to numerical simulation using Abaqus/CAE 2020 software, to obtain their thermal resistance. Finally, an energy simulation study was carried out in three housing typologies located in two Brazilian cities, Curitiba and Fortaleza, using EnergyPlus 9.2 software. Geometric changes resulted in reductions in thermal transmittance values of greater than 30% for the blocks and 20% for the walls. Regarding possible energy reduction, the study demonstrated that there is a non-significant reduction in values for periods of higher temperature (hottest month), in the evaluated schedule use, as well as a potential for savings (34% in the apartment typology for the coldest month) at lower temperatures. Findings of this study serve as a reference to discuss improvements in clay hollow brick geometry regarding energy efficiency and thermal comfort in the Brazilian context.

Experimental and numerical investigation of an innovative complex piston with enhanced free spray length for the heavy-duty engine applications

The combustion and emission formation process in heavy-duty compression ignition engines are strongly influenced by the design of the piston bowl, the cylinder charge motion and the performance of the injection system. This paper proposes an innovative complex piston bowl design approach called as ’flower piston’ to improve the combustion process. It can be manufactured using the conventional machining approaches without use of still expensive additive manufacturing techniques. The flower piston features a scooped cavity with an intention of increasing the free fuel spray penetration. The potential of this innovative flower piston is evaluated using a validated 3D CFD model and compared with the results of single cylinder engine experiments at operating points with minimum fuel consumption. The results of the experimental investigations with the flower piston show an improvement in thermal efficiency in comparison to the conventional piston by up to 0.5%. This is due to a faster initial heat release and increased high pressure cycle work. However, the smoke emissions increased threefold due to fuel entrapment into the flower cavities, leading to formation of fuel-rich pockets. Also, the wall heat losses increased twofold with an increase in NOx raw emissions. With increased spray targeting angle, there was a drastic reduction in smoke emissions and an additional improvement in the thermal efficiency.

Numerical and experimental study for a modified LPG cooking burner

A new modification of the LPG burner (NB-5) is proposed in this study. The modification combines the advantageous features that originated from three Thai commercial burners: KB-5, S-5, and EB-5. CFD techniques were used to investigate and prove the benefits each burner’s features. Combining features increase the mixing intensity and primary aeration, generates a swirling central flame, reduces heat loss, and increases secondary aeration. These enhancements cause an increase in combustion temperature and flow velocity, which significantly improves the net heat flux of the NB-5. The simulation results indicated that the NB-5 produced the highest average temperature of 929.35 K, and the highest heat flux of 58.01 kW/m2. This leads directly to an enhancement in thermal efficiency. The new modification burner (NB-5) was built and tested experimentally based on CFD results. The NB-5 burner obtained significant improvements in thermal efficiency and a reduction in CO and NOx emissions over the three commercial burners. In comparison with the traditional KB-5 burner, it was found that the NB-5, EB-5, and S-5 burners provided average energy savings of 22.37%, 8.46%, and 1.69%, respectively. This study shows the benefit of utilizing the CFD simulations to assist in designing and modifying LPG burners. This allows manufacturers to design and optimize burners more effectively at a much lower cost than the traditional water boiling tests.