Improve Combustion Efficiency Research Articles

On the effects of fractal geometry on reacting and nonreacting flows in a low-swirl burner: A numerical study with large-eddy simulation

Understanding and optimizing turbulence in combustion systems has a profound effect on combustion efficiency, emission reduction, and safety in applications ranging from industrial burners to propulsion systems in aerospace. This paper contributes to this pivotal field by investigating a real-scale low-swirl combustor utilizing a range of turbulence generation plates characterized by different blockage ratios and numbers of fractal pattern iterations. The work encompasses two states, namely nonreacting and premixed reacting modes, utilizing a large-eddy simulation method equipped with a dynamic Smagorinsky sub-grid model and adaptive mesh refinement for high accuracy. Verifying the robustness of the approach, the simulation aligns closely with experimental data, registering a maximum error of less than 0.9% in the swirl number. The research provides an insightful evaluation of the impact of four different fractal geometries on turbulence intensity, a vital element for attaining more complete combustion. Findings indicate a fractal with a 73% blockage ratio and four iteration levels enhances several key parameters including turbulence intensity, flow residence time, vorticity, and velocity gradient in the nonreacting mode. Conversely, a fractal with a 73% blockage ratio and three iteration levels shows the least progress in the reacting mode. Moreover, the paper delves into a comparative analysis of these two cases in the reacting mode, particularly observing the reaction zone. The appropriate fractal geometry unveiled significantly improves combustion efficiency, evidenced by an increased presence of the OH radical and a decrease in NO emission gas, thus demonstrating potential for wider application in enhancing combustion systems.

Parametric analysis on combustion characteristics of hydrocarbon fueled parallel wall-jet inside a supersonic combustor

Using hydrocarbon fuel as cooling film is one of the most promising ways to thermally protect supersonic combustors and it can also be considered as a special combustion process. Parametric analysis is very important for increasing combustion efficiency of this special combustion process which is a parallel fuel wall-jet, and it is numerically investigated in this paper. It is found that, for parallel wall-jet combustion lacking near-field mixing enhancement because of the thermal protection purpose, decreasing equivalence ratio can lead to a significant increase in combustion efficiency since the wall-jet combustion efficiency is only determined by the shear mixing process. Moreover, under the constant equivalence ratio, increasing injection height from 0.67 mm to 2 mm can only slightly increase the combustion efficiency by 1.5% although it can reach a much better cooling performance. It is worth mentioning that, the effects of mainstream parameters on combustion efficiency present a step trend, self-ignition will occur as the mainstream temperature or Mach number reaches a certain value. And afterward, keep increasing mainstream temperature has little effect on the combustion efficiency since the mixing process keeps almost unchanged. Whereas, continuous reduction of mainstream Mach number will improve combustion efficiency by significantly enhancing mixing.

A Novel Experiment Approach for Measurement Breakup Length, Cone Angle, Sheet Velocity, and Film Thickness in Swirl Air-Blast Atomizers

<div>Measuring the dynamic parameters of liquid fragments generated in the near-field of atomizing sprays poses a significant challenge due to the random nature of the fragments, the instability of the spray, and the limitations of current measuring technology. Precise determination of these parameters can aid in improving the control of the atomization process, which is necessary for providing suitable spray structures with appropriate flow rates and droplet size distributions for various applications such as those used in heat engines. In piston and gas turbine engines, controlling spray characteristics such as penetration, cone angle, particle size, and droplet size distribution is crucial to improve combustion efficiency and decrease exhaust emissions. This can be accomplished by adjusting the structural and/or operating parameters of the fuel supply system. This article aims to measure the breakup length, spray cone angle, axial velocity, breakup time, and liquid sheet film thickness for a swirl air-blast atomizer used in a gas-steam engine. The measurement was conducted using a shadowgraph imaging system developed specifically for this study, consisting of a high-speed camera, a lens, and a light source. While lasers are commonly used as light sources in the literature, this study utilized a special LED high-speed pulse light generator, which is cheaper, easier to handle, and provides a more uniform background. Images were processed using a MATLAB code developed for this study. Although the breakup zone is naturally random and the breakup location significantly varies with time, the novel method developed in this study helps quantify critical parameters under different operating conditions.</div>

Simulation of Dual Combustion Cycle in Internal Combustion Engines using MATLAB

The aim of this study is to develop a comprehensive mathematical model to accurately represent the dual combustion cycle in internal combustion engines, with a focus on improving combustion efficiency and reducing emissions. The novelty of this research lies in the integration of advanced combustion models within the mathematical framework to capture the unique characteristics of dual combustion cycles. The model will consider factors such as combustion characteristics, fuel-air mixing, heat transfer, and emissions. By accurately simulating the dual combustion cycle, valuable insights can be gained into the complex interactions occurring within the engine, leading to the development of optimized engine design and control strategies. The proposed model will be implemented using MATLAB, which offers flexibility and computational efficiency. The results obtained from the simulation can be validated against experimental data to ensure the accuracy and reliability of the model. This study is expected to contribute to the advancement of dual combustion cycle technology and provide valuable guidance for the design and optimization of future internal combustion engines.

Effect of shock generator on fuel mixing in an annular single lobe transverse nozzle at the supersonic combustion chamber of a scramjet engine using computational fluid dynamics

This study investigates the influence of a wedge shock generator on hydrogen mixing in an annular single lobe transverse nozzle at the supersonic combustion chamber of a scramjet engine using computational fluid dynamics (CFD). The fuel mixing process is crucial for efficient combustion in scramjet engines, which operate at high speeds and require rapid mixing of fuel and air. The shock generator is a device that generates a shock wave in the flow field, which can enhance mixing by increasing turbulence and promoting the fuel penetration into the air stream. A comparison of three lobe injectors is done to attain the efficient nozzle type for the fuel mixing inside the combustion chamber. CFD simulations were done to analyze the consequence of the shock generator on fuel mixing in the nozzle and assess its potential for improving combustion efficiency. The results show that the usage of shock generator can significantly enhance fuel-air mixing in the nozzle, leading to improved combustion efficiency and reduced emissions. The findings of this study provide valuable insights into the design and optimization of shock generators for scramjet engines, which can contribute to the development of more efficient and sustainable air-breathing propulsion systems.

Custom-Designed Pre-Chamber: Investigating the Effects on Small SI Engine in Active and Passive Modes

This work shows the results of an experimental campaign carried out in two spark ignition engines, a small optical research engine and its commercial counterpart, using a turbulent ignition system (pre-chamber) specifically designed for small engines. Advanced optical techniques and conventional methods were used to study the combustion process under various operating conditions. The pre-chamber operated actively in the research engine and passively in the commercial engine. Results showed that the pre-chamber configuration resulted in an increase in indicated mean effective pressure (IMEP) and a decrease in the coefficient of variation (CoV) of IMEP. These improvements compensated for challenges such as slow methane combustion rate, poor lean burn capability, and air displacement. In addition, the pre-chamber configuration exhibited lower fuel consumption and specific exhaust emissions compared to the standard ignition system. The novelty of this work lies in the successful implementation of the turbulent ignition system as a retrofit solution for SI engines, showing improved combustion efficiency and lower emissions. The study goes beyond previous efforts by demonstrating the benefits of the pre-chamber configuration in small engines without requiring extensive modifications. The results provide valuable insights into the automotive industry’s pursuit of engine optimization and highlight the significance of innovative approaches for spark ignition engines in contributing to sustainable mobility.

Studies into the reduction of domestic fuel burning emissions by means of facile catalytic abatement technology

The negative health and socio-economic impacts of emissions associated with domestic fuel burning are widely recognized. Although there has been much progress in the provision of electricity to households in South Africa, many still rely on solid fuel sources such as wood and coal. While various investigations have been done on reducing household emissions by reducing the use of polluting fuels and improvements in combustion efficiency, comparatively fewer studies have been conducted on the reduction of emissions through emission reduction using abatement technology. Catalytic oxidation could be utilized to oxidize particulate matter precursors such as volatile organic compounds and soot particles to reduce secondary particulate formation. Although catalytic methods have not been effectively utilized in practical domestic applications, studies have shown effective soot reduction during laboratory testing. This study investigated the synthesis and use of a manganese oxide based catalyst to reduce particulate matter from domestic fuel burning stoves. During field testing, the presence of the catalyst increased the mass of particulate matter collected, with Scanning Electron Microscopy (SEM) analysis showing spherical particles in the pores of the catalyst run filters. The baseline runs had very few of these particle clusters. Energy Dispersive X-Ray (EDX) analysis of the catalyst run filters did not detect manganese, revealing that increased particulate concentrations were not as a result of macroscopic particles of the catalyst being dislodged from the support. Dislodgement of very small metal particles from the catalyst could, however serve as nucleation nodes for particle growth which would have a non-metal coating leading to the non-detection of manganese. The increase in particulate matter could also be caused by the impingement of particulate matter precursors on the catalyst followed by particle growth and dislodgement into the flue gas. The testwork showed that an active catalyst can be synthesized onto a mesh catalyst support in a facile and cost effective manner, which can be utilized in domestic fuel burning devices. It is recommended that a range of optimized, potentially active catalysts be tested to improve the oxidation of particulate matter precursors to carbon dioxide.

Machine learning rate constants of hydrogen abstraction reactions between ester and H atom

The rate constants of hydrogen abstraction reactions of alkyl ester by H atom are crucial for optimizing combustion reaction network and improving combustion efficiency of biodiesel. Due to the lack of experimental and theoretical rate coefficients data for some reactions - such as hydrogen abstraction of large biodiesel molecules by free radicals - machine learning provides a viable alternative to predict rate constants. In this study, three different machine learning (ML) methods - feedforward neural network (FNN), extreme gradient boosting (XGB) and XGB-FNN hybrid model - were used to predict rate constants of the reactions between alkyl ester and H atom. The rate constants of 41 reactions between H + CnH2n+1COOCmH2m+1 (n = 0–5, m = 1, 2) were calculated by the Master Equation System Solver (MESS) program over a temperature range of 300–2000 K for model training. The results showed that the XGB-FNN model with 8 descriptors has better overall performance than the other two ML methods. The average deviation of XGB-FNN model on the test set is 33.56% by performing leave one out (LOO) cross validations. The rate constants of the H + methyl decanoate (MD) reactions over a temperature range of 300∼2000 K were predicted by the XGB-FNN model, which follow well the modified three-parameter Arrhenius equation and agree well with theoretical values, indicating that the hybrid XGB-FNN model is robust in predicting the rate constants of alkyl ester and H atom in the temperature range of combustion. The present ML method in this study is supposed to be able to provide accurate and affordable rate constants prediction of larger systems, the molecular sizes of which are comparable to those of the dominant components of real biodiesel. That is important for the development of biodiesel kinetic models.

Effects of Local Mixing Ratios and Mass Flow Rates on Combustion Performance of the Fuel-Rich LOX (Liquid Oxygen)/kerosene Gas Generator in the ATR (Air Turbo Rocket) Engine

This paper presents a numerical simulation analysis of the flow and combustion characteristics of a fuel-rich LOX (liquid oxygen)/kerosene gas generator in an ATR (air turbo rocket) engine, examining the effects of local parameters on the combustion flow field and performance. The analysis considers variations in unit injector mixing ratios and unit mass flow rates. The results indicate that as the mixing ratio in the inner-ring injectors increases (while the mixing ratio in the middle-ring injectors decreases), the oxygen concentration area near the axis zone and the 50% radius zone of the gas generator expands. Conversely, the kerosene concentration area near the axis zone decreases while gradually increasing near the 50% radius zone. In the flow direction section, there is an inverse relationship between the variation trend of local temperature and the oxygen concentration in the local area. As the oxygen concentration increases, the temperature decreases. The temperature distribution across the cross-section of the gas generator exhibits a circular pattern. When the mixing ratio (or mass flow rates) of the unit injector are perfectly balanced, the temperature distribution becomes highly uniform. A larger disparity in flow rate between the inner ring injector and the middle ring injector leads to a lower combustion efficiency. This effect differs from the effect of the mixing ratio difference between the two injector rings. Increasing the mixing ratio in the inner-ring injectors (or decreasing the mixing ratio in the middle-ring injectors) initially leads to a rise in combustion efficiency, followed by a subsequent decline. The maximum combustion efficiency of 89.10% is achieved when the mixing ratio is set to Km-1 = 0.7 and Km-2 = 2.79, respectively. Increasing the flow rate in the inner-ring injectors (or decreasing the flow rate in the middle-ring injectors) initially leads to an improvement in combustion efficiency, followed by a subsequent reduction. The maximum combustion efficiency of 86.13% is achieved when the mass flow rate is set to m-1 = m-2 = 0.1 kg/s.

Low-NOx study of a 600 MW tangentially fired boiler based on pulverized coal preheating method

Boiler emissions are the primary sources of atmospheric nitrogen oxide (NOx) emissions. Exceeding the NOx emission limit can shut down the boiler, causing financial losses. Herein, a new preheated combustion method is proposed to prevent coal-fired boilers from exceeding the NOx emission limit at low loads. This is a simulation study of internal combustion burners and a 600 MW tangentially fired boiler using a pulverized coal preheating method that explores syngas production patterns after pulverized coal is preheated, the effects of flow characteristics, and variations in NOx and unburned carbon content under different preheating ratios. Our results indicated that the internal combustion burner had a stable preheating effect. The volume fractions of CH4, CO, and H2 at the burner outlet were 0.95%, 12.7%, and 0.8%, respectively. The fuel nitrogen precipitated during the preheating process was converted into N2. High-temperature char and syngas entered the furnace chamber and were mixed with air to accelerate combustion, which enhanced the jet flow intensity and improved the combustion stability at 50% load. The top burner exhibited a more significant nitrogen reduction than the bottom burner. The NO reduction from retrofitting Layers D and E accounted for 53% after retrofitting all five layers. When the preheating ratio was increased from 0 to 100%, NOx concentration was reduced by 63.6% at 6% O2, while unburned carbon content was reduced by 41%, which improved combustion efficiency. By discussing the advantages of internal combustion burners for retrofitting a 600 MW tangentially fired boiler, this study provides theoretical guidance for the application of preheating methods in peaking conditions.

Disclose effect and mechanism of external electric field on RP-1 fuel pyrolysis

To explore the combustion efficiency of aviation fuel in an electric field, a ReaxFF molecular dynamics and density functional theory calculation was performed to study the electric field effect on 3-component RP-1 (methylcyclohexane, n-dodecane, and isododecane) pyrolysis. The electrostatic potential, charge natural population analysis and molecular structure were discussed under electric fields of various directions and strengths. The chemical reaction kinetics and species were analyzed under a wide range of electrostatic fields and temperatures. The key reaction energy of RP-1 components and motion statistics were discussed. The analysis revealed significant changes in molecular charge density and structure, which predicted possible cracking sites. Cyclohexane and chain alkanes exhibited opposite trends of decomposition rates depending on the field strength and temperature. The different trends were detail analyzed by reaction pathways and product distribution. Newly cracking way appeared under electric field. The decomposition reaction barrier was reduced by the electric field overall. While the motion of molecules was inhibited with the field increasing, which decrease the molecular potential energy. This work conducted a comprehensive analysis about effect of external electric field on the RP-1 mixture fuel pyrolysis. offering a potential solution for improving combustion efficiency.

Effects of the swirler on the performance of an advanced vortex combustor

Trapped vortex combustors have garnered significant interest due to the cavity vortex's insensitivity to flow disturbances. Swirling combustion is also highly desirable due to its excellent mixing performance. This study explores the potential of combining vortex combustors with swirling combustion under reacting conditions. Steady-state Reynolds-averaged Navier–Stokes equations are solved through three-dimensional numerical simulations. The results demonstrate a significant improvement in combustion efficiency, from 55% in original vortex combustor to over 99% in swirling vortex combustor, and fuel–air mixing effectiveness. The spatial spiraled vortex structure forms in the cavity and behind the blunt body when the swirler is used. The position of the blunt body influences the shape of the cavity vortex, with a round vortex structure forming when the cavity length to the total combustion chamber length ratio is around 0.2. When the radius of the blunt body to the radius of the combustion chamber, varying from 0.2 to 0.7, is 0.6, two main recirculation zones can be created in the model. Increasing the swirling number results in a larger recirculation zone in the cavity, with an elongated recirculation area appearing behind the blunt body at a blade installation angle of 60°, corresponding to the swirling number is 1.251. However, an excessively high swirling number leads to uneven pressure distribution in the outlet. These findings provide novel insights for advanced vortex combustor research and optimization.

A Review on Flame Stabilization Technologies for UAV Engine Micro-Meso Scale Combustors: Progress and Challenges

Unmanned aerial vehicles (UAV)s have unique requirements that demand engines with high power-to-weight ratios, fuel efficiency, and reliability. As such, combustion engines used in UAVs are specialized to meet these requirements. There are several types of combustion engines used in UAVs, including reciprocating engines, turbine engines, and Wankel engines. Recent advancements in engine design, such as the use of ceramic materials and microscale combustion, have the potential to enhance engine performance and durability. This article explores the potential use of combustion-based engines, particularly microjet engines, as an alternative to electrically powered unmanned aerial vehicle (UAV) systems. It provides a review of recent developments in UAV engines and micro combustors, as well as studies on flame stabilization techniques aimed at enhancing engine performance. Heat recirculation methods have been proposed to minimize heat loss to the combustor walls. It has been demonstrated that employing both bluff-body stabilization and heat recirculation methods in narrow channels can significantly improve combustion efficiency. The combination of flame stabilization and heat recirculation methods has been observed to significantly improve the performance of micro and mesoscale combustors. As a result, these technologies hold great promise for enhancing the performance of UAV engines.

Mechanistic understanding of the participation effect of carbon in the combustion of PTFE/n-Al: Combining experimental verification with reactive molecular dynamics simulation

Owing to the high energy density, polytetrafluoroethylene/aluminum nanoparticles (PTFE/n-Al) has been considered as the promising composite in energetic applications, but the limited combustion efficiency restricts its practical uses. Undoubtedly, for the further improvement of combustion efficiency, mechanistic understanding of the combustion of PTFE/n-Al is fundamentally necessary. However, the participation effect of non-fluorine species (i.e., carbon) on combustion has been overlooked, leading to the lack of generalized framework for combustion mechanism. By using a combined experimental verification and reactive molecular dynamics (RMD) simulation approach, this work focuses on the participation effect of carbon and involved reaction mechanism in the combustion of PTFE/n-Al. The thermal reactivity and combustion performance of four PTFE/n-Al composites with F/Al molar ratio of 1.0 (R1), 2.0 (R2), 3.0 (R3) and 4.0 (R4) have been investigated by thermal analyses (TGA-DSC-MS) and combustion experiments (flame images, heat of reaction and condensed combustion products). The heat of reaction decreases in the order of R2 (7.89 kJ/g), R1 (7.67 kJ/g), R3 (7.33 kJ/g) and R4 (6.55 kJ/g), and a similar trend has been found for the flame intensity. Moreover, the carbon deposition percentage (%) in combustion of R1, R2, R3 and R4 reaches 76.5%, 76.4%, 90.2% and 123.3%, which shows a negative effect on combustion performance. Based on experimental results, the RMD simulations for the reactions of n-Al and Al core with trafluoroethylene (TFE) and related fluorocarbon atmospheres have been performed. It is found that, going from R1 to R4, the elevated active fluorocarbon species play a double-edged sword role in combustion. On one side, they exhibit a promoting role in accelerating the crack of Al2O3 shell, the dispersion and heat releasing kinetics of Al core. On the other side, they also result in extensive carbon deposition on unreacted n-Al, showing a hindering role in further reaction and lowering combustion efficiency. Accordingly, in experiments, optimal combustion performance of PTFE/n-Al has been observed with suitable composition (R2). Finally, the generalized reaction mechanism involving participation effects of carbon and fluorine has been proposed for PTFE/n-Al, which is beneficial for perfecting combustion mechanism and improving combustion efficiency of fluorocarbon/metal composites.

Effect of the geometrical shapes of the helical-spiral shroud intake valve on swirl generation in cylinder of diesel engine

Improving combustion efficiency for diesel engines is an important requirement to save fuel and lower exhaust gas toxicity. In this study, the effect of the geometric shape of the helical-spiral shroud intake valve (HSSIV) for the swirl generation in a diesel engine cylinder was studied, which has important significance in improving the combustion efficiency in a diesel engine.In this study, helical-spiral shroud (HSS) are classified into convex, flat, and concave types according to the installation angle on the intake valve, and their influence on the swirl generation in the cylinder are comparatively analyzed using the computational fluid dynamics (CFD) method. As a result, it is considered that HSSIV with convex shape generates the best swirl and tumble effect in the engine cylinder. The Model 1 with convex shape has a swirl ratio value of 32.5 which is 3.8 times larger at 80CAD, and the tumble ratio value is 48.2 which is 4.5 times larger at 130CAD, compared to Model 0 with no shroud. The findings and results of this study were applied to the diesel engine, but they can also be applied to gasoline engines, and can also be applied to research subjects that need to generate a swirl in the fluid flow path without additional energy consumption and reduction in the volumetric efficiency of the fluid.

Performance of red mud oxygen carriers in chemical-looping hydrogen production using different components of plastic waste pyrolytic gas

This study proposed plastic waste-fueled Chemical-looping Hydrogen Production (CLHP) based on the concept of three-reactor chemical-looping process for the purposes of sustainable treatment of plastic wastes while producing high purity H2 and separating CO2. Oxygen carrier prepared from red mud wastes (Bauxite residues) was suggested to be circulating materials to improve combustion efficiency and H2 yield. The feasibility of using pelletized oxygen carrier prepared from red mud wastes was experimentally investigated with major components (H2, CH4 and C2H4) of plastics pyrolysis gases as fuels. The red mud oxygen carrier composed of around 38 wt% Fe2O3 and 50 wt% inert materials, and CuO-promoted oxygen carriers composed of 8.0 wt% CuO and 92 wt% red mud wastes were used. The two oxygen carriers were examined by parallel experiments, focusing on the aspects of oxygen transport, stability, hydrogen productivity and carbon deposition. Temperature and different components of plastic pyrolysis gases had significant impacts on oxygen transport behaviors; reduction tests using CH4 or C2H4 fuels suggested that the operation temperature of Fuel Reactor should be higher than 800 °C for deep reduction and high H2 productivity. CuO addition significantly promoted oxygen carrier's reactivity and oxygen transport capacity with various fuel components. The cyclic CLHP experiments, performed over 10 redox cycles with C2H4 as fuels, showed that there was only a limited degradation in oxygen carriers caused by carbon deposition and element migration. The developed oxygen carriers can meet the requirements of long-term operation for CLHP process. Carbon deposition on the oxygen carriers derived from hydrocarbon fuel cracking seemed to be inevitable, which experimentally determined in the range of 0.01–0.043 g g−1 oxygen carriers as C2H4 was used as fuels. However, the reactivity of these carbon deposits was extremely low; their initial steam-gasification temperatures were around 750 °C, much higher than the temperature used for water splitting reaction. This provides the potential opportunities for an industrial CLHP process to produce high purity H2 (>97%) despite of carbon deposits presents in Fuel Reactor.

Theoretical study on the effect of low-temperature reforming on gasoline compression ignition (GCI) at low-load conditions

In this paper, the influence of reforming conditions on the reforming products of gasoline, as well as the effect of main reforming products on GCI combustion at low-load conditions has been studied by experiment and numerical simulation. The results show CO, H2 and CH4 are the major reforming products, and their production is improved by higher reforming temperature, oxygen concentration and reforming time. The production of CO and H2 is mainly determined by the dehydrogenation reaction between fuel molecules and OH, while the one between iC8H18 and O2 is essential for the CH4 generation. The combustion efficiency rises sharply with more CO addition, but increases first and then decreases with increased H2, while the peak value of 96.71% is achieved. Besides, higher combustion efficiency is obtained with more internal exhaust gas recirculation (i-EGR) used. The increased OH and H radicals can be attained by adding CH4, which further improves combustion efficiency.

Exhaust Induction Device for the Improvement of Combustion Efficiency of Internal Combustion Engine : Carbon and Particulate Matter Footprint Reduction Analysis

Objectives : The purpose of this study is to introduce an exhaust induction device (EID) for the improvement of combustion efficiency of internal combustion engines and to analyze fuel consumption savings with the installation of EID. To show the effectiveness of EID, The carbon footprint (CF) and particulate matter footprint (PMF) were calculated and compared before and after the EID installation and utilization.Methods : Firstly, the EIDs were installed in 39 Taxi vehicles that use LPG fuel. The monthly fuel consumption data were collected before installation and compared with three months after the EID installation. With the fuel consumption data, CF and PMF were calculated and compared.Results and Discussion : There were a few differences between EID installation Taxi vehicles. The results show that CF was 2.12E+00 kgCO<sub>2</sub> eqv., and PMF was 4.54E-03 kgPM2.5 eqv. per 1 km vehicle driving before EID installation. After EID installation, the three-month CF and PMF were reduced to 7%, 4%, and 8%, respectively. The CF and PMF result in each Taxi vehicle reduced from 1% to 27%. The overall results show that the EID installation can improve the combustion efficiency of internal combustion engines and reduce CF and PMF.Conclusion : The carbon and particulate matter footprint should be studied and reduced continuously in the transportation sector. In this study, a new EID for the improvement of the combustion efficiency of internal combustion engines was introduced. Also, CF and PMF were calculated using LPG fuel consumption before and after the EID installation. The results show that the EID installation can reduce fuel consumption, CF and PMF. The EID can significantly reduce fuel consumption, CF, and PMF in gasoline and diesel vehicles, fishing boats etc., producing more emissions. Further studies are needed considering drivers’ driving patterns, weather conditions, etc.

Numerical study to improve the combustion and thermal efficiencies of off-gas/synthesis gas-fueled HCCI-engine at different loads: Piston-shape and crevice design

This numerical work aims to improve combustion efficiency and thermal efficiency by modifying the piston shape and crevice volume ratio of the HCCI engine operated under excessively lean air-fuel mixture conditions for power generation employment. The baseline piston, optimized for the diesel engine, gives strong reverse squish flow during the expansion stroke, causing a reduction in the efficiency of the engine. Therefore, the flow field in the squish area of the piston bowl should be weakened to facilitate auto-ignition at different points to boost the burning rate. Hence, the baseline piston shape was modified by bringing down the piston bowl depth and reducing the squish area ratio from 34% to 5% with a constant compression ratio. Crevice volume ratio Vcrevice/VTDC is also optimized for the HCCI engine to achieve high performance. All calculations are executed at MBT conditions by changing the inlet temperature of the mixture. Finally, the computational model results are validated with literature data. The results indicate that combustion phasing advances by changing the piston shape, and it also reports that the highest engine combustion efficiency of about 96%, 97%, and 99% are achieved by changing the piston shape and reducing the 40% crevice volume ratio of the engine, at low load, medium load, and high loads, respectively. The results also show that thermal efficiency is improved from 40% to 46% at low load while enhancing from 36 to 38.5% at 10 bar IMEP, respectively.

Effect of gas injection holes on mixing and combustion in solid propellant ducted rockets

Combustion efficiency is an important parameter of the combustion chamber. Gas injection holes have an important influence on the mixing and combustion in solid propellant ducted rockets, but there is currently little research on gas injection holes. This paper describes numerical simulations of solid propellant ducted rocket combustion chambers, with the numerical method verified through a direct-connected experiment. We investigate the effect of adding injection holes to the gas generator nozzle on the mixing and combustion performance, and examine the mixing degree, combustion efficiency, and flow field characteristics. This paper focuses on the number and the position of the gas injection holes. The results show that, when the total mass flow rate is constant, the mixing effect becomes better as the dispersion degree of gas injection increases and the mass flow rate of each hole decreases. For this study, the 5-hole scheme has the best performance, and when the total mass flow rate and the number of injection holes are fixed, a smaller mass flow rate of gas injected toward the outlet of each air inlet is more conducive to better mixing and combustion effects. When the total mass flow rate is constant and the shape of the injection holes are complete circles, increasing the number of holes is more effective than decreasing the mass flow rate of gas injected toward the outlet of the air inlets in improving combustion efficiency.