Exhaust Gas Research Articles

Research on the modeling technique of infrared radiation scaling law for rocket engine exhaust plumes

The complexity of the rocket motor exhaust plume radiation phenomenon, along with the influence of numerous parameters and implicit propagation, makes the theoretical simulation calculations expensive. This hinders design optimization, parameter identification, and other studies. Hence, it is crucial to establish the direct correlation between thrust, velocity, altitude, detection angle, and plume radiation in engineering.The paper proposes a scaling law modeling approach for predicting plume infrared radiation from liquid oxygen (LOX)/kerosene rocket engines to solve the difficulties of quick prediction and lack of explicit models. An explicit scaling law model with four parameters is developed by utilizing the e-exponential scaling law to relate plume radiance to flight velocity, the power scaling law to relate plume radiance to vacuum thrust, and the sinusoidal scaling law to relate plume radiance to detection angle. This model employs a decoupled modeling approach for plume radiance, flight altitude, flight velocity, vacuum thrust, and detection angle. A fast prediction method for the LOX/kerosene rocket engine plume in the altitude range of 11∼61 km is achieved. The theoretical simulation test shows the relative error of the velocity-scaling law in predicting the radiance of the RD-180 template engine during the Atlas III flight trajectory is less than 20 %. The radiance of the RD-170 and RD-191 rocket engines is predicted using the thrust-scaling law based on the radiance of the RD-180 template engine exhaust plume. The radiance of the exhaust plume from the RD-170 and RD-191 rocket motors is estimated using the thrust-scaling law with an accuracy of under 15 %. Subsequently, the radiance of these two motors at detection angles between 10° and 170° is predicted using the angle-scaling with a relative error of less than 35 %.

Analysis of Operational Control Data and Development of a Predictive Model of the Content of the Target Component in Melting Products

The relevance of this research is due to the need to stabilize the composition of the melting products of copper–nickel sulfide raw materials. Statistical methods of analyzing the historical data of the real technological object and the correlation analysis of process parameters are described. Factors that exert the greatest influence on the main output parameter (the fraction of copper in a matte) and ensure the physical–chemical transformations are revealed: total charge rate, overall blast volume, oxygen content in the blast (degree of oxygen enrichment in the blowing), temperature of exhaust gases in the off-gas duct, temperature of feed in the smelting zone, copper content in the matte. An approach to the processing of real-time data for the development of a mathematical model for control of the melting process is proposed. The stages of processing of the real-time information are considered. The adequacy of the models was assessed by the value of the mean absolute error (MAE) between the calculated and experimental values.

On the Influence of Engine Compression Ratio on Diesel Engine Performance and Emission Fueled with Biodiesel Extracted from Waste Cooking Oil

Despite the extensive research on biodiesels, further investigation is warranted on the impact of compression ratios on emissions and engine performance. This study addresses this gap by evaluating the effects of increasing the engine’s compression ratio on engine performance metrics—brake-specific fuel consumption (BSFC), power, torque, and exhaust gas temperature—and emissions—unburnt hydrocarbons (HCs), carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), and oxygen (O2)—when fueled with a 20% blend of waste cooking oil biodiesel (WCB20) and petroleum diesel (PD) under various operating conditions. The viscosity of the prepared fuels was measured at 25 °C and 40 °C. Experiments were conducted on a single-cylinder diesel engine under wide-open throttle conditions at three different speeds (1400 rpm, 2000 rpm, and 2600 rpm) and two compression ratios (16:1 and 18:1). The results revealed that at a lower compression ratio, both WCB20 and petroleum diesel exhibited reduced BSFC compared to higher compression ratios. However, increasing the compression ratio from 16:1 to 18:1 significantly decreased HC emissions but increased CO2 and NOx emissions. Engine power increased with engine speed for both fuels and compression ratios, with WCB20 initially producing less power than diesel but surpassing it at higher compression ratios. WCB20 demonstrated improved combustion quality with lower unburnt hydrocarbons and carbon monoxide emissions due to its higher oxygen content, promoting complete combustion. This study provides critical insights into optimizing engine performance and emission characteristics by manipulating compression ratios and utilizing biodiesel blends, paving the way for more efficient and environmentally friendly diesel engine operations.

Molecular Structures, Tribological Properties, and Working Mechanisms of Sulfur- and Phosphorus-Free Organic Molybdenum as Additives in Lubricants: A Short Review

Abstract Traditional oil-soluble organic molybdenum (OM) as friction modifiers (FMs) in engine oils contain sulfur and/or phosphorus. Both sulfur and phosphorus are detrimental to the automotive exhaust gas catalysts. Consequently, sulfur and phosphorus in commercial engine oils are limited seriously by laws. Recently, oil-soluble sulfur- and phosphorus-free organic molybdenum (SPFMo) has been developed and measured intensively. This article reviews the molecular structures, tribological properties, and working mechanisms of SPFMo as FM in oils. Some bottlenecks that constrain the wide applications of SPFMo in engine oils are also summarized. In addition, some routes for overcoming the bottlenecks are suggested. Finally, some potential developments of SPFMo in the future are proposed. This review will provide a comprehensive understanding of SPFMo to the researchers in the field of oil additives.

Pore Chemistry and Architecture Control in Anionic Functional Ultramicroporous Materials for Record Dense Packing of Xenon.

Adsorptive separation of Xe and Kr is an industrially promising but challenging process because of their identical shape and similar physicochemical properties. Herein, we demonstrate a strategy through rationally designing the linkers of anionic functional ultramicroporous materials (FUMs) to finely regulate the pore chemistry and architecture, which creates unique stepped channels incorporating dense polar nanotraps to generate a larger effective pore space and enables dense packing of Xe. A new hydrolytically stable FUM (ZUL-530) was prepared, which for the first time achieves a Xe packing density exceeding the liquid Xe density at atmospheric conditions in metal-organic frameworks (MOFs) (based on experimental data), resulting in both excellent Xe uptake (2.55 mmol g-1 at 0.2 bar) and high IAST selectivity (20.5). GCMC and DFT-D calculations reveal the essential role of the stepped traps in the dense packing of Xe. Breakthrough experiments demonstrate remarkable productivities of both high-purity Kr (6.70 mmol g-1) and Xe (1.78 mmol g-1) for the Xe/Kr (20:80) mixture. In a model nuclear industry exhaust gas, ZUL-530 exhibits a top-class Xe dynamic capacity (28.8 mmol kg-1) for trace Xe, which proves it is one of the best candidates for Xe/Kr separation.

Thermal mechanical fatigue cracking of a bladed disk in a turbo engine

After 1221 h of bench testing, linear fluorescent displays were observed on the transition arcs between the blade and the edge plate. Macroscopic and microscopic inspections revealed fatigue cracks originating from cracked grain boundaries on the surface. Metallographic examinations indicated severe oxidation of the crack flank and blunting tip. Finite element thermal stress analysis aligns with the crack distribution. The nature of the cracking is identified as thermal mechanical fatigue, and the elevated temperature gradient induced by the exhaust gas purification device is the main promoter for cracking. Comparative analysis suggests that the root cause lies in the low thermal impact resistance of the material, ultimately resulting in reduced thermal mechanical fatigue resistance. Corresponding remedial methods are proposed to enhance service life and safety.

An experimental study on fuel reforming waste heat recovery engine system fueled with methane

The effects of various operating parameters on a fuel reforming waste heat recovery engine system fueled with methane were experimentally investigated. Steam methane reforming was employed in the system because it is endothermic. Experiments were conducted on the parameters of methane flow rate to reformer and steam-to-carbon ratio to study their effects on the conversion of methane and resulting the overall thermal efficiency of the system. The components of the reformed gas were analyzed, and their effects on the combustion characteristics and thermal efficiency factors of a spark-ignition gas engine were discussed. The effects of engine operating parameters such as spark timing and excess air ratio on the exhaust gas heat recovery effect by fuel reforming and the improvement of system thermal efficiency were also investigated through experiments.

Airborne particulate matter and diesel engine exhaust on infrastructure construction sites in the Copenhagen metropolitan area.

Diesel engine exhaust (DEE) is carcinogenic and potentially hazardous for those working in close proximity to diesel-powered machines. This study characterizes workplace exposure to DEE and its associated particulate matter (PM) during outdoor construction activities. We sampled at 4 construction sites in the Copenhagen metropolitan area. We used portable constant-flow pumps and quartz-fiber filters to quantify personal exposure to elemental carbon (EC), and used real-time instruments to collect activity-based information about particle number and size distribution, as well as black carbon (BC) concentration. Full-shift measurements of EC concentration ranged from < 0.3 to 6.4 µg/m3. Geometric mean (GM) EC exposure was highest for ground workers (3.4 µg/m3 EC; geometric standard deviation, GSD = 1.3), followed by drilling rig operators (2.6 µg/m3 EC; GSD = 1.4). Exposure for non-drilling-rig machine operators (1.2 µg/m3 EC; GSD = 2.9) did not differ significantly from background (0.9 µg/m3 EC; GSD = 1.7). The maximum 15-min moving average concentration of BC was 17 µg/m3, and the highest recorded peak concentration was 44 µg/m3. In numbers, the particle size distributions were dominated by ultrafine particles ascribed to DEE and occasional welding activities at the sites. The average total particle number concentrations (PNCs) measured in near-field and far-field positions across all worksites were 10,600 (GSD = 3.0) and 6,000 (GSD = 2.8)/cm3, respectively. Sites with active drilling rigs saw significantly higher average total PNCs at their near-field stations (13,600, 32,000, and 9,700/cm3; GSD = 2.4, 3.4, and 2.4) than sites without (4,700/cm3; GSD = 1.6). Overall, the DEE exposures at these outdoor construction sites were below current occupational exposure limits for EC (10 µg/m3 in Denmark; 50 µg/m3 in the European Union), but extended durations of exposure to the observed DEE levels may still be a health risk.

A Comprehensive Review on the Hydrogen–Natural Gas–Diesel Tri-Fuel Engine Exhaust Emissions

Natural gas (NG) is favored for transportation due to its availability and lower CO2 emissions than fossil fuels, despite drawbacks like poor lean combustion ability and slow burning. According to a few recent studies, using hydrogen (H2) alongside NG and diesel in Tri-fuel mode addresses these drawbacks while enhancing efficiency and reducing emissions, making it a promising option for diesel engines. Due to the importance and novelty of this, the continuation of ongoing research, and insufficient literature studies on HNG–diesel engine emissions that are considered helpful to researchers, this research has been conducted. This review summarizes the recent research on the HNG–diesel Tri-fuel engines utilizing hydrogen-enriched natural gas (HNG). The research methodology involved summarizing the effect of engine design, operating conditions, fuel mixing ratios and supplying techniques on the CO, CO2, NOx and HC emissions separately. Previous studies show that using natural gas with diesel increases CO and HC emissions while decreasing NOx and CO2 compared to pure diesel. However, using hydrogen with diesel reduces CO, CO2, and HC emissions but increases NOx. On the other hand, HNG–diesel fuel mode effectively mitigates the disadvantages of using these fuels separately, resulting in decreased emissions of CO, CO2, HC, and NOx. The inclusion of hydrogen improves combustion efficiency, reduces ignition delay, and enhances heat release and in-cylinder pressure. Additionally, operational parameters such as engine power, speed, load, air–fuel ratio, compression ratio, and injection parameters directly affect emissions in HNG–diesel Tri-fuel engines. Overall, the Tri-fuel approach offers promising emissions benefits compared to using natural gas or hydrogen separately as dual-fuels.

500 kW closed cycle gas turbine unit with different working fluids

This article considers a 500 kW closed cycle gas turbine unit. In contrast to open or semi-closed cycles, a closed cycle implies a working fluid circulating continuously within a closed loop. In other words, a working fluid (any working fluid) with the required initial parameters depending on the properties of the selected working fluid is injected into a closed circuit consisting of a compressor, heat exchangers of various purposes and a turbine. A unit with recirculation of combustion products at high pressure can be created based on existing units with minor modifications. Instead of emission into the atmosphere, the exhaust gases enter the high-temperature heat exchanger, where it gives heat to the closed-cycle gas turbine unit. First of all, the application of such units is relevant at compressor stations in conjunction with the gas turbine drive of the blower. The study involved thermal calculation of a closed-cycle gas turbine unit with different working fluids: carbon dioxide, helium and argon. The main objective is to study the advantages and disadvantages of alternative working fluids with their subsequent comparison. Since the main chemical and physical properties of alternative working fluids differ from the classical ones, there is a possibility of obtaining higher parameters of the unit. According to the results of calculations it is established that the most promising working fluid is carbon dioxide, because this can be used at a wide range of temperatures and pressures. It should also be noted that the consumption of carbon dioxide is the lowest compared to other working fluids. The efficiency of such an installation is 28%, but there is a possibility of improvement if regeneration is added.

Using DPF to Control Particulate Matter Emissions from Ships to Ensure the Sustainable Development of the Shipping Industry

PM (particulate matter) emissions from ships are the main sources of marine atmosphere pollution. Controlling the emissions of particulate matter from ships is related to the sustainable development of the shipping industry. To reduce PM emissions from marine four-stroke diesel engines, DPFs are effective. Our results show that DPF had more than 90% capturing efficiency for both the number and mass emissions of PM, and the capturing efficiency for the accumulation mode was higher than that of the nuclear mode. DPF can also significantly reduce the chemical components of PM in marine diesel exhaust gas. The removal efficiencies for OC and EC were 89.7–91.6% and 84.8–92.8%, respectively, with each particle size range showing over 80% efficiency. SO42− was the ion with the highest content, followed by NH4+, NO3−, Na+, NO2−, and Cl−, with their reduced proportions remaining consistent with the removal efficiency of particulate matter. DPF can also effectively reduce PAH content and toxicity. The use of DPF can greatly improve the impact of ship emissions on the marine atmospheric environment. The appropriate DPF with the best performance can be selected according to the exhaust parameters and particle size distributions with different characteristics.

Collaborative disposal of exhaust gas and waste wind turbine blades: Mechanical properties of recycled glass fibres and economic analysis

The accumulation of waste wind turbine blades poses significant environmental challenges. Pyrolysis offers an industrially viable solution for both disposal and the recycling of valuable glass fibers from these blades. Exhaust gas from industrials with waste heat can be utilized to reduce the process cost. However, for mixed atmosphere of exhaust gas containing both CO2 and O2, its influence on resin matrix decomposition characteristics and fiber mechanical properties are currently unclear. This work provided a solution collaborated with exhaust gas to disposal of waste wind turbine blades, in which operating parameters (atmosphere composition and process procedure) were optimized. Results showed that the early invention at pyrolysis with low concentration of O2 in exhaust gas played a major role in facilitating the formation of surface protection. Atmosphere during oxidation of pyrolytic residual carbon was crucial in maintaining fiber strength. At this stage, the interaction between CO2 (especially at 15% concentration) and O2 could mitigating fiber degradation through promoting the re-oxidization of Si dangling bonds and reducing water corrosion. However, stepwise processing of pyrolysis first and then oxidation under exhaust gas with O2 containing was not recommended due to its little cost-effectiveness. The single step disposal of wind turbine blades collaborated with coal-fired flue gas could increase the strength of recycled glass fiber by over 50% and reduced process costs by 34%.

Failure of the three-way catalyst (TWC) introduces “super emitters”

Vehicle exhaust is one of the major organic sources in urban areas. Old taxis equipped with failed three-way catalysts (TWCs) have been regarded as “super emitters”. Compressed natural gas (CNG) is a regular substitution fuel for gasoline in taxis. The relative effect of fuel substitution and TWC failure has not been thoroughly investigated. In this work, vehicle exhausts from gasoline and CNG taxis with optimally functioning and malfunctioning TWCs are sampled by Tenax TA tubes and then analyzed by a comprehensive two-dimensional gas chromatography-mass spectrometer (GC×GC–MS). A total of 216 organics are quantified, including 80 volatile organic compounds (VOCs) and 132 intermediate volatility organic compounds (IVOCs). Failure of TWC introduces super emitters with 30 – 70 times emission factors (EFs), 60 – 112 times ozone formation potentials (OFPs), and 34 – 92 times secondary organic aerosols (SOAs) more than normal vehicles. Specifically, for the taxi with failed TWC, the total organic EF of CNG is 16 times that of gasoline, indicating that the failure of TWC exceeds the emission reduction achieved by CNG-gasoline substitution. A significant but unbalanced reduction of ozone and SOA is observed after TWC, whereas a notable “enrichment” in IVOCs was observed. Naphthalene is a typical IVOC component strongly associated with CNG-gasoline substitution and TWC failure, which is lacking in current VOC measurement. We especially emphasize that there is an urgent need to scrap vehicles with failed TWCs in order to significantly reduce air pollution.

Plume and wall temperature impact on the subsonic aft-body flow of a generic space launcher geometry

Experimental and numerical simulation of launcher base flows are crucial for future launcher design. In experiments, exhaust plume simulation is often limited to cold or slightly heated gases. In numerical simulations, multi-species reactive flow is often neglected due to limited resources. The impact of these simplifications on the relevant flow features, compared to real flight scenarios, needs to be characterized in order to enhance the design process. Experimental and numerical investigations were carried out within the framework of the SFB/TRR 40 Collaborative Research Centre to study the impact of plume and wall temperature on the base flow of a generic small-scale launcher configuration. Wind tunnel tests were performed in the Hot Plume Testing Facility (HPTF) at DLR, Cologne, using subsonic ambient flow and pressurized air or hydrogen–oxygen combustion as exhaust gases. The tests were numerically rebuilt using the DLR TAU code employing a scale-resolved IDDES approach, including thermal coupling and detailed chemistry. The paper combines the experimental and numerical findings from the SFB/TRR 40 base flow studies and highlights the most prominent influences on the mean flow field, the pressure field, the dynamic wake flow motion, and the resulting aerodynamic forces on the nozzle. High-frequency pressure measurements, high-speed schlieren recordings, and time-resolved CFD results are evaluated using spectral and modal analysis of the one- and two-dimensional flow field data.

Distribution assessment and source apportionment of particulate bound-PAHs in indoor air of south Asian precinct using IDW and PMF receptor model: A comprehensivestudy

PAHs have been recognised as a major menace to living-beings as well as environment. Several researchers have extensively claimed regarding death-defying nature of PAHs and its derivatives. However, these studies have only considered the ambient air which is a composition of automobile exhausts, industrial emissions etc. as major source of harmful air pollutants. Indoor air quality (IAQ) is an overlooked area since, although many researchers in recent times have been working on the chemistry and composition of IAQ, yet, source determination and nature of pollutants is still a comprehensive area to be explored. With the above stated objective, the present study emphases on 16 USEPA specified PAHs which are allied with particulate matter. Both PM as well as PAHs are some very common and treacherous chemical contaminant accountable for more than a million death globally. PAHs are organic compound which are either attached to PM of various sizes or can exist in gaseous form. Current work precises the concentration of PAHs associated with fine PM i.e., PM2.5 in indoor environment of south Asian precinct, further, using receptor modelling technique for determination indoor sources responsible for the emanation of specific PAHs. The toxicity equivalent quotient i.e., TEQ evaluated in the study demonstrations that the highest toxicity among all PAHs is exhibited by BaP followed by InP, BKF, BbF. Seasonal variations in the concentration of PAHs and their respective sources were also established using PMF models, which depicted the domination of 3-ring PAHs in winter with 42% contribution in outdoors, whereas, four-ring PAHs dominion in indoors. Similarly, in summer two-ring accounted for 35% in outdoors, and three-ring PAHs contributed highest with 26.8% in indoors. In monsoon PAHs with two-ring contributed highest with 45.2% in outdoors, whereas, 2-ring PAHs contributed 38.3% in indoors. Also, IDW mapping and molecular diagnostic ratio were assessed for an intense study on distribution of PAHs in the locality and the source apportionment purpose respectively. To the best of our knowledge, the study is first of its kind in this part of the world where, majority of the countries are either developing or under-developed and hence at greater risk to the noxious effects which are often overlooked. The study will provide a clear picture regarding the indoor sources of the PAHs and further help the further professionals to build a credible and pragmatic mitigation technique accordingly.

Design of multi-component gas measurement system based on STM32

Abstract To detect the concentration of toxic and harmful gases in the environment in a timely and effective manner, this article designs a multi-component gas measurement system based on the STM32 processor, which can effectively detect three toxic and harmful gases (CO, NO2, and SO2), a gas detection terminal for the concentration of two greenhouse gases (CO2 and CH4) and an inhalable particulate matter (PM2.5), and a handheld display terminal that can display the measured gas concentration in real-time. A practical application circuit for electrochemical sensors has been designed, simplifying the design of driving amplification circuits. Finally, the feasibility of the system was verified through automobile exhaust experiments.

Comparison of high mileage LPG cars in different technical condition in Czechia: Particle-bound PAHs

Liquefied petroleum gas (LPG) is represented in the literature as a transport fuel with lower regulated and non-regulated emissions compared to petrol. For the purpose of this paper, real-world emissions measurements were performed on a random sample of four commonly operated passenger vehicles with higher mileage (over 200 thousand km) and on a new one. The aim is to compare the emission factors of particle-bound polycyclic aromatic hydrocarbons (PAHs) in dual-fuelled passenger cars running on LPG and petrol, or rather to compare the emission factors of the two fuel types. PAH concentrations are determined by gas chromatography based on the analysis of particles captured on a filter during isokinetic sampling of the exhaust gas during driving in real traffic. In terms of the sum of the 8 most hazardous PAHs analysed, LPG fuelling reduced the total (summary) emission factor of only two of the vehicles analysed, by 22% and 26% respectively compared to petrol. For the remaining vehicles, there was an increase in the total emission factor ranging from 4.4 to 68.8%. The results show that in terms of particle-bound PAHs, the benefit of LPG fuel in terms of vehicle emissions may not be so clear-cut in real-world tests and it depends very much on whether a suitable propulsion system is fitted to the vehicle, how it is set up and how the vehicle is serviced (i.e. the vehicle overall condition).

Pengaruh Modifikasi Permukaan Piston terhadap Emisi Gas Buang Motor Bakar Kapasitas 100 cc

Technological advances in motorized transportation are progressing rapidly, making motorized vehicles the main mode of transportation. The increasing number of motorized vehicles in society results in a significant increase in exhaust emissions. Combustion in vehicle engines is not always perfect, producing exhaust gases containing compounds harmful to human health, such as carbon monoxide (CO), hydrocarbons (HC), carbon dioxide (CO2), and nitrogen oxides (NOx). This study investigates the effect of variations in piston dome shape on exhaust emissions in a 100cc internal combustion engine using RON 90 fuel. The goal is to find the optimal compression ratio to produce cleaner exhaust emissions. The research data are presented in tabular form and analyzed using one-way ANOVA and graphs. The results showed a significant reduction in CO and HC emissions at all engine speeds (1000, 2000, 4000, and 5000 rpm) with variations in piston dome shape. The reduction in CO emissions ranged from 55.07% to 85.73%, while the reduction in HC emissions ranged from 54.14% to 86.10%. These results suggest that variations in piston dome shape can be an effective solution to minimize harmful exhaust emissions in internal combustion engines.

Synergistic approaches to NOx reduction: Fuel innovations and engine modifications in biomass waste-fueled CI engines

Achieving low nitric oxide emissions in biomass fuel combustion remains a challenge. This study aims at enhancement of NOx reduction by employing a sequence of strategies to arrive at the optimal combination of techniques. This work explores the role of nano particle emulsion, change in profile of combustion chamber geometry, exhaust gas recirculation rates and contribution of selective catalytic reduction (SCR) in the combustion and emission phenomena of CI engine. Cerium oxide and zinc oxide nanoparticles are added in emulsion form at 50 ppm and 100 ppm dosage to grapeseed oil biodiesel. Furthermore, combustion chamber geometry is modified to shallow depth and toroidal shape and tested with ZnO 100 nano blend of grapeseed oil biodiesel (GSBD). EGR at 5 %, 10 %, 15 % and 20 % rates are included in the toroidal shape after concluding that profile as the best performing geometry. A customized model of SCR is implemented to the above combination of ZnO fuel blend, toroidal combustion chamber geometry and 5 % EGR to further reduce NOx emission. SCR device is fabricated with suitable flow and injection parameters with dual type mixers to enhance its NOx conversion efficiency. Overall, this research work gives useful insights for development of NOx reduction strategies in biomass fuel combustion in CI engines. A comprehensive reduction of NOx from 9.3 g/kWh to 2.05 g/kWh is noticed at the end of cumulative set of experiments.

The influence of exhaust gas recirculation on combustion and emission characteristics of ammonia-diesel dual-fuel engines: Heat capacity, dilution and chemical effects

As the greenhouse effect intensifies, ammonia is garnering increasing attention as a carbon-free fuel. In the transport sector, ammonia-diesel dual-fuel (ADDF) engines are regarded as an effective means of reducing carbon emissions. The objective of this study is to investigate the combustion and emission optimization of an ADDF engine under high load conditions. To this end, an experimental optimization study of different start of diesel injection timing (SODI) and exhaust gas recirculation (EGR) rates was conducted at a load of 18 bar and an ammonia energy ratio of 80 %. The mechanism of heat capacity, dilution, and chemical effects of EGR was also revealed by numerical simulation based on the separated variables method. It was demonstrated that advancing SODI is effective in enhancing combustion efficiency. However, this approach is limited by the upper limit of in-cylinder pressure and results in higher nitrogen oxides (NOx) emissions, which can be mitigated by the EGR. The heat capacity effect of EGR increases the specific heat capacity and decreases the average temperature. The suppression of the combustion process leads to a reduction in thermal and fuel NOx, but an increase in nitrous oxide (N2O) emissions. The dilution effect of EGR results in insufficient oxygen, which decreases the heat release rate and combustion efficiency. Additionally, the NOx and N2O are significantly reduced. The chemical effect of EGR affects reactive groups and unburned components that accelerate heat release rate and increase accumulated heat release, resulting in significantly higher NOx. The comprehensive effect of EGR results in a decrease in N2O emissions and a significant reduction in thermal and fuel NOx. The EGR and further optimization of SODI enabled the ADDF engine to achieve a gross indicated thermal efficiency of 48.5 % with a load of 18 bar and an ammonia energy ratio of 80 %. In addition, NO emissions were reduced by 32.8 percent and greenhouse gas emissions by 63.3 percent.