Exhaust Gas Research Articles

The Activation of Oxygen Species on the Pt/CeO2 Catalyst by H2 for NO Oxidation

The Pt/CeO2 catalyst has attracted significant attention due to its exceptional performance in NO oxidation. This study comprehensively examines the effects of calcination temperature and H2 pretreatment on the structure and activity of the Pt/CeO2 catalyst. Experimental findings indicate that the calcination temperature significantly affects the catalyst’s redox performance, thereby modulating its efficacy in NO oxidation reactions. H2 pretreatment facilitates the creation of oxygen vacancies on the catalyst, assisted by the reduction in PtOx to Pt, enhancing the formation of activated oxygen and thereby improving NO oxidation. This study offers valuable insights into the design and optimization of Pt/CeO2 catalysts for environmental applications, particularly in the development of exhaust gas after-treatment technologies.

Air pollution under formal institutions: The role of distrust environment

Formal trust is an important formal institution that may significantly impact the environment. This study uses regional distrust environment as a reverse proxy variable for formal trust and studies the impact of formal trust on corporate sulfur dioxide emissions. This study finds that the environment of distrust significantly increases the sulfur dioxide emission levels of enterprises, which means that formal trust affects the environmental management strategies of enterprises. This study also finds that some other formal institutional factors, which include marketization, the development of intermediate organizations, the legal system environment, and GDP levels, have moderating effects on the impact of distrust environment on corporate sulfur dioxide emissions. In addition, climatic conditions including temperature, humidity, and precedence, as well as the location of the enterprise, have certain moderation effects. Mechanism analysis indicates that distrust environment affects corporate sulfur dioxide emissions through the increase in coal sulfur content in enterprise production, the decrease in exhaust gas processing capacity, the reduction in financing capacity, and the decline in social and environmental responsibilities. Finally, this study finds through further analysis that the local government appears to have noticed this negative impact, and the regions with a distrust environment tend to increase their environmental regulation intensity.

An Ambient Measurement Technique for Vehicle Emission Quantification and Concentration Source Apportionment.

We develop a new technique called plume regression where fast response instruments located at the roadside are used to measure exhaust plumes of passing vehicles. The approach is used to generate highly disaggregated vehicle emissions information by vehicle type, which compares well with traditional vehicle emission remote sensing. Additionally, the technique provides valuable new information on ambient concentration source apportionment by vehicle type. The technique is flexible enough to consider a wide range of air pollutants and be deployed at roadside ambient monitoring locations. The new approach is used to quantify emissions and concentration source apportionment for ammonia (NH3) and nitrogen oxides (NOx). We find that emissions of NH3 are generally very well controlled from diesel vehicles including those with selective catalytic reduction systems that use NH3 to reduce emissions of NOx. By contrast, gasoline passenger cars are shown to be the dominant contributor to NH3 emissions, which increase with vehicle mileage. Average fuel-specific NH3 emission factors for gasoline vehicles range from 0.3 to 1.2 g kg-1, while diesel vehicle emission factors remain below 0.06 g kg-1, with the exception of Euro VI buses with the latest regulatory provisions (0.5 g kg-1).

Revolutionizing urban emission tracking: Enhanced vehicle ratios via remote sensing techniques

This study presents research that examines the use of several remote sensing methods to quantify automobile emissions in China. The research provides a unified data processing technique, using methodologies such as plume chasing (PCH) and point sampling (P-sampling) to measure vehicle emissions accurately. This method accurately calculates the ratios of gaseous combustion, namely NOx/CO2, in different driving scenarios and verifies the technique using controlled vehicle emissions measurements. The results demonstrate the method’s ability to identify variations in emission levels linked to engine operation and alterations in after-treatment systems. This provides significant information for monitoring emissions in metropolitan areas such as Wuhan, China. The suggested method has substantial promise for improving air quality initiatives in China.

Developing an off-site bicarbonation absorber system to promote microalgal fixation of CO2 in exhaust gas from biogas upgrading

In order to address the risk of explosion due to CH4 from exhaust gas produced during biogas upgrading in closed carbon fixation systems employing photosynthetic microalgae, an off-site bicarbonation absorber system was developed to promote microalgal CO2 fixation under atmospheric pressure. The abundant CO2 in the biogas upgrading exhaust gas (≥90 vol.% CO2, ≤10 vol.% CH4) reacted with a Na2CO3 solution in the off-site bicarbonation absorber to produce NaHCO3, which was used as carbon source for microalgal growth in enclosed column photobioreactors. After the reaction, CH4 was discharged outside the bicarbonation absorber because it did not react with the Na2CO3 solution and was extremely difficult to dissolve in water, thereby avoiding the explosion risk due to accumulated CH4 in the enclosed column photobioreactors. The experimental results showed that the Spirulina growth rate first increased 1.7 times, peaking at 0.6g/L/d, and then decreased when the bicarbonation reaction time (optimal 50min), absorber diameter (optimal 10cm), initial Na2CO3 concentration (optimal 173mM), and exhaust gas aeration rate (optimal 100 sccm) increased. The optimal molar ratio of NaHCO3 to total inorganic carbon in the bicarbonation absorber solution reached 79%. The sufficient HCO3- supply and suitable pH of the microalgal solution improved the synthesis of photosynthetic pigments in the microalgal cells and enhanced their photochemical efficiency and carbon sequestration rates.

Emission control in a dual fuel low temperature combustion engine at intermediate loads

Intermediate to high load operation in dual fuel reactivity controlled compression ignition (RCCI) techniques is restricted due to uncontrolled combustion that causes engine knocking. Dual fuel strategies with advanced pilot injection and near-top dead center (TDC) main injection timings are reported to enhance combustion control, albeit with increased soot emissions, reduction of thermal efficiency, and emergence of an intricate trade-off between total hydrocarbon (THC) and oxides of nitrogen (NOx) emissions. In order to address these conflicting issues, an intermediate engine load, corresponding to 6 bar gross indicated mean effective pressure at 1500 and 2200 rev/min engine speeds was investigated in this work. The main objectives of this work are (1) to obtain combination of control parameters to achieve near-zero engine-out NOx and soot emissions and high thermal efficiency while minimizing THC and CO emissions; (2) to understand the effectiveness of diesel oxidation catalysts (DOCs) for the oxidation and reduction of exhaust gas species in the dual fuel mode; and (3) to understand the oxidation characteristics of the soot generated from the dual fuel mode. Optimum dual fuel low temperature combustion strategies, in terms of diesel injection timings, quantity and exhaust gas recirculation levels, were identified using the statistical multi response signal to noise (MRSN) ratio method in which NOx, soot and indicated efficiency were response variables. The performance of commercial DOCs, with different precious metal (Pt and/or Pd) loadings, were also studied at optimum dual fuel strategies for gasoline-diesel dual fuel operations. High DOC outlet temperatures (>∼340°C), due to the exotherm generated by the oxidation of high concentrations of THC and carbon monoxide (CO) emissions from dual fuel operations, resulted in greater than 90% THC conversion efficiency. The exotherm decreased the nitric oxide (NO) oxidation whereas the nitrogen dioxide (NO2) reduction reactions were favored over the DOC in the dual fuel mode at the intermediate load operating condition. Thermogravimetric analysis of the soot showed higher activation energy (177.2 kJ/mol), formed at the dual fuel optimum condition, relative to the activation energy (162.7 kJ/mol) of the soot formed in conventional diesel combustion (CDC).

Development of a Large-Scale Integrated Solar-Biomass Thermal Facility for Green Production of Useful Outputs

The present paper develops a new multigeneration plant to produce multiple commodities from two combined renewable energy sources, solar thermal and biomass and considers a specific case study administered for the city of Al Lith in the Kingdom of Saudi Arabia. The plant generates power, heating, refrigeration, hydrogen, chlorine, concentrated sodium hydroxide, ammonia, urea, and fresh water, which are commodities at high demand in the area. The energy efficiency is determined to be 53% with an annual generation of over 1036 GWh of power and cogenerated 858 GWh of heating, nearly 23 GWh of refrigeration effect, over 11,300 tons of ammonia, almost 1800 tons of urea, over 113,000 tons of concentrated sodium hydroxide and over 905,000 m3 of fresh water. The exergy contents of heating, refrigeration, power and commodity products represent a total of 45% of the sources, which leads to a multigeneration platform's exergy efficiency. The system includes an integrated biomass gasification combined cycle with a biomass oxy-gasifier. The Aspen Plus simulations of the oxy-gasifier determined that the oxygen-to-biomass weight fraction should be set to 0.15, whereas the steam-to-biomass weight fraction is around 0.1. The exhaust gas recirculation is applied to enhance power generation rate and efficiency. The recirculation ratio of exhaust gas is found to be 0.21 if power generation efficiency is to be maximized and 0.28 if the power generation rate is to be maximized. The fluctuating and intermittent nature of the solar energy resource causes poor economics when this energy is to be captured in isolation or itself only. The current paper demonstrates that the hybridization of solar and biomass energy together with integrated processes for multiproduct generation enhances the overall competitivity of the renewable energy system. To address this aspect, the objective of the paper is to develop and assess a new integrated flowsheet for hybrid renewable resource multigeneration.

Design and Characterization of a New Quartz Smog Chamber System for Studying the Atmospheric Effects of Vehicle Emissions on Plateaus

Since the 1960s, smog chambers have been an important tool for studying air pollution, and many indoor and outdoor smog chambers have been developed both domestically and internationally. However, all of these chambers are located at altitudes below 1500 meters, only simulating atmospheric conditions in low-altitude plains. Moreover, most are made of polytetrafluoroethylene (PTFE), resulting in a higher wall deposition effect. To simulate the evolution of atmospheric pollution in high-altitude regions, we developed the world's highest-altitude quartz smog chamber, located in Kunming at an elevation of 1900 meters. The chamber is a 3.375m³ cube constructed from 5mm quartz glass and features controlled temperature (0°C to 40°C) and relative humidity (2%-95%). We conducted a comprehensive characterization of the chamber, including tests for temperature and humidity stability, mixing stability, pressure resistance and sealing, light intensity measurement and environmental light matching, and background pollutant and wall loss assessments. The characterization results indicate excellent performance in simulating sunlight and controlling background pollutants. The NO2 photolysis rate is adjustable, ranging from 2.03×10⁻³s⁻1 to 5.87×10⁻³s⁻1. Under dry conditions, after 6 hours of photooxidation, the detected O3 formation rate was approximately 1.05 ppb/h, with a particulate mass concentration around 0.12 μg/m³. The reactor withstands pressures exceeding 1.5 bar, and at this pressure, the leak rate was measured at 1.1‰. Validation using the toluene-NO₂ system showed that indoor mixing reached equilibrium in about four minutes. The wall loss rate for SWFU-HAP particles at 25°C and RH <10% was 0.066 h⁻1, which is 70% lower compared to other chambers, while at RH = 50%, the wall loss rate was 0.137 h⁻1. These results demonstrate the superior performance of our system, meeting the high standards required for high-altitude vehicle exhaust aerosol emissions research and the investigation of the formation mechanisms of vehicle exhaust in high-altitude atmospheric environments.

Development of membrane distillation powered by engine exhaust for water desalination

To address water shortage in arid areas and make use of waste heat, an experimental investigation is presented for a novel system of air gap membrane distillation unit driven by an engine exhaust heat source for the development of an on-board car water desalination. The design of the gas-to-water heat exchanger is presented and optimized. The system’s performance, governed by the achieved feed water temperature and measured by the output vapor mass flux, is evaluated with time under varying operational parameters, including engine load, engine speed, and feed water flow rate, with the analysis of production cost for economic viability. Experimental results revealed that higher engine loads and speeds lead to rapid temperature increase of the feed water, enhancing the efficiency of the membrane distillation process and increasing the permeate flux. Notably, a maximum permeate flux of 45 kg/m2h was achieved after 40 min of operation. A minimum production cost of 3.2 $/m3 is estimated at an engine load of 35 N.m. With production costs ranging from 3.2 to 5.8 $/m3, the proposed system emerges as a highly competitive option when compared with other membrane distillation systems driven by waste heat in literature. This study underscores the potential of utilizing waste heat from car engines for cost-effective and sustainable water desalination, paving the way for further development and implementation of the system as a mobile desalination unit for different applications.

Performance of a novel waste heat-powered ionic liquid-based CO2 capture and liquefaction system for large-scale shipping

In this work, we proposed a novel CO2 capture and liquefaction system for large-scale shipping using ionic liquid as capture solvent. By utilizing the waste heat of the exhaust gas and jacket cooling water from the ship’s engine as well as the residual pressure energy of the N2-O2 mixture from the CO2 absorption and desorption process, the system’s net energy consumption has been significantly reduced. We established the thermodynamic model of the system and investigated the effect of 10 primary system operational parameters on system performance with 3 different ionic liquids as CO2 capture solvent. The results demonstrated that the system with [DEME][TF2N] as the CO2 capture solvent had the best system performance. In addition, we performed a multi-parameter optimization of the system using simulated annealing algorithm with net energy consumption as the optimization objective and the minimal net energy consumption is 0.467 GJ/tCO2. Compared to the CO2 capture system that do not utilize waste heat and residual pressure energy, the net energy consumption was reduced by 57.29 % under optimal operational conditions which proves that the novel system significantly reduces the energy consumption of the CO2 capture and liquefaction process.

Technical-economic evaluation of application scenarios of an Organic Rankine Cycle (ORC) as a solution to the cogeneration deficit in a sugar plant

There is currently a cogeneration deficit at a sugar plant near Nepeña, Ancash, Peru, where the exhaust steam from the milling area is at approximately 235°C. The steam should be at a temperature close to 120°C, which is the temperature required by the sugar processing area. However, it should be at a temperature close to 120°C, which is the temperature required by the sugar processing area. Therefore, the heat is dissipated without being utilized or recovered. The low-temperature waste heat can be utilized in an Organic Rankine Cycle (ORC).Three systems are proposed: ORC with exhaust gas system, ORC with unified system and ORC with total unified system. For this reason, six scenarios will be analyzed in which the electrification of the mills and the direct sale of energy to the power grid will be proposed, with the objective of optimizing mill production and determining which are technically and economically feasible. The results obtained are: the increase in plant´s overall efficiency of the plant is between 6.58 and 14.67%, the annual CO2 saving emissions are between 914.65 and 2631.77 Ton CO2/year, the exergy efficiency between 60.93 and 65.4% and the LEC (Levelized Electrical Cost) is between 35.73 and 58.05 $/MW.h.

Impacts of low-temperature heat release on unstretched laminar burning velocity in advanced flex-fuel gasoline-ethanol engines

Improving brake thermal efficiency (BTE) of flex-fuel engines can contribute to decarbonizing conventional and hybridized vehicles running on spark-ignited (SI) engines. High compression ratio (CR) and burning velocity under exhaust gas recirculation (EGR) conditions can improve the engine BTE. Ethanol fuel, which has been attracting increasing attention recently, can improve brake thermal efficiency due to its high-octane number and fast laminar burning velocity (LBV). With higher CRs, low-temperature heat release (LTHR) occurs in the unburned mixture, which affects the compositions, oxidation, and in-cylinder temperature. Such thermodynamic changes on unstretched LBV have not been thoroughly investigated, especially in production-intent next-generation flex-fuel engines. This study aims to clarify the LTHR impacts on LBV under EGR conditions using ethanol-blended gasoline surrogate fuels. The testbed used a single-cylinder SI engine fueled by E0 (gasoline surrogate), E20 (20 % ethanol + 80 % E0 by volume), E40, E60, E85, and E100. Detailed chemical reaction calculations were conducted using the boundary conditions obtained from production-intent, strong-tumble flow, and flex-fuel engine experiments. This work predicted LTHR in an unburned mixture using a zero-dimensional detailed chemical reaction calculation. LBV is predicted by a 1D kinetic laminar flame code. As a result, LTHR proceeds before the main combustion. The results show that the temperature increase associated with LTHR increases the burning velocity, while the partial oxidants decrease the burning velocity. Moreover, this work examined higher CRs using detailed chemical reaction calculations, and the results show that fuels with higher ethanol blending ratios can increase LBV in the late combustion phase.

Risk-oriented source apportionment and implications for mitigation strategies of VOCs in industrial parks: Insights from odor pollution and health risks

A typical industrial park in the upper reaches of the Yangtze River Economic Belt, which is 70 km from the Chongqing urban center, was used to investigate the occurrence and exposure of harmful volatile organic compounds (VOCs). An exposure risk method and a risk-oriented source apportionment approach were performed to assess the inhalation risks and apportion VOC sources, respectively. The quantitative relationships between risk factors and pollution sources were established, identifying key pathogenic and odorous VOCs. The quantitative emission reduction strategies were developed based on risk thresholds. Residents within the industrial parks face potential health risks due to pathogenic VOCs and nuisance odors, and workers in specific sectors experience two to six times higher risks than those in residential areas. Six risk sources were identified in the industrial park, ranked according to their contribution to VOC concentrations as follows: industrial sewage treatment (IST) (32.59 %), natural gas chemical industry (NGCI) (27.77 %), diesel vehicle exhaust (DVE) (12.04 %), pharmaceutical manufacturing industry (PMI) (11.14 %), chemical raw materials manufacturing (CRMM) (9.96 %), and iron and steel industry (ISI) (6.5 %). Among these, NGCI, IST, and CRMM were the top contributors to pathogenic risks, with contributions of 32.13 %, 29.71 %, and 21.71 % to non-carcinogenic risks, and 18.15 %, 19.87 %, and 27.99 % to carcinogenic risks, respectively. DVE produced significantly higher odor pollution compared to other sources, with intensities that were 3 to 10 times greater. The key pathogenic and odorous VOCs differ by source, resulting in varying control priorities for different VOC species. Reducing emissions from these six sources for 20 high-risk species (e.g., acrolein, 2-chlorotoluene, 1,2-dibromoethane, dichloromethane, and p-diethylbenzene) will simultaneously lower pathogenic and odor risks, with cumulative reduction rates ranging from 4.11 % to 93.75 %. This study provides quantitative control targets for VOCs from a health risk perspective, offering valuable guidance for developing risk management policies in industrial parks.

Quantification and spatial analysis of gridded (0.1° × 0.1°) emission of indirect GHGs/Air pollutants from anthropogenic sources in India

Indirect greenhouse gases (GHGs) play a key role in modulating both regional and global atmospheric chemistry and act as air pollutants that degrade air quality. The rising number of premature deaths and notable health hazards could be linked to increasing concentration of these air pollutants in the atmosphere. As a developing nation, India is often regarded as one of the most polluting countries due to increasing anthropogenic activities. Therefore, identifying the sources of these indirect GHGs gases such as CO, NOx, VOC and SO2 and quantifying their emissions has become a critical requirement for understanding regional atmospheric chemistry. In this study, we developed a comprehensive, technology-driven gridded emission inventory for India at a high resolution (0.1°×0.1°) for the base year 2020. Using the IPCC bottom-up approach, the study estimated the total emissions of CO (45 Tg/yr), NOx (22.8 Tg/yr), VOC (10.8 Tg/yr) and SO2 (15.1 Tg/yr) from all the dominating sources. Vehicle exhaust contributes the most NOx and VOC whereas the residential and power sectors are the highest emitters of CO and SO2, respectively. This newly reported surface emission data would be an essential tool for policymakers in formulating mitigation strategies and will also serve as a vital input for atmospheric chemistry and climate studies.

Synthesis and carbon monoxide purification performance of ZSM-5 molecular sieve Co-doped Mn/V catalytic material

Trackless, rubber-tired, diesel-powered vehicles are widely used in the mining industry. In recent years, the use of high-performance catalysts to remove carbon monoxide (CO) from diesel vehicle exhaust has attracted much attention. In this paper, a series of manganese-vanadium doped ZSM-5 molecular sieve catalysts were prepared by an impregnation method. The structures of the catalysts were characterized and experiments were conducted to evaluate their performance. The CO catalytic oxidation performance experiments revealed that Mn0.6-V0.4-ZSM-5 had the best performance, with a conversion rate of 97.5 % at 300 °C. The catalyst was also tested for water resistance and stability. Kinetic measurements were performed and the fitted activation energy was 22.68 kJ/mol. Characterization studies revealed that the surface defects formed by Mn and V doping provided a large number of active sites and oxygen vacancies for CO oxidation, increased the number of adsorbed oxygen species on the surface, and enhanced the redox capacity through the interaction of Mn4+ and V5+ to improve the catalytic oxidation performance of the catalyst. The adsorption configurations, adsorption energy (Ebin), and formation energy of oxygen vacancies of CO at different adsorption sites and different active fractions were calculated with density functional theory. The Ebin of CO on Mn2V2O7, the active fraction of Mn0.6-V0.4-ZSM-5, was −1.29 eV, which was the most stable adsorption configuration. This configuration had good oxygen mobility, and was conducive to CO catalysis, confirming the characterization and performance experiments.

Effect of modified Fe2O3/activated carbon catalysts for low-temperature CO selective catalytic reduction of NOx in underground diesel vehicle exhaust

The elimination of CO and NOx has practical significance for the control of exhaust pollutants from underground diesel vehicles. Catalytic reduction of NO by CO (CO-SCR) using activated carbon (AC) catalysts is considered a cost-effective and environmentally friendly denitrification method. In this study, Fe2O3/AC-based catalysts were prepared using an impregnation method and modified with different metals to investigate their impact on catalyst performance. The results demonstrated that the catalyst exhibited the highest denitrification efficiency when loaded with 10% Fe. The Mn-doped 10Fe/AC catalyst exhibited the best catalytic performance, with the highest NO conversion of 97.5% and CO removal rate of 83.3% at 240 °C. The effects of loading Mn, Ce, and La on the physical and chemical properties of the catalysts were analyzed using various characterization tools, and the reaction mechanism of the catalysts was investigated by in situ DRIFTS technique. The findings revealed that the strong synergistic interaction occurring between Mn and Fe led to an increase in the surface-adsorbed oxygen (Oα) and Fe3+, which produced more oxygen vacancies on the catalyst, thus improving the redox properties. The in-situ DRIFT results indicated that the addition of Mn enhanced the adsorption capacity of active NO and CO. For the CO-SCR reaction on Fe-Mn/AC catalyst, the E-R mechanism was followed at low temperature and the L-H mechanism was followed at high temperature.

Utilization of Palm Frond Waste as Fuel for Co-Firing Coal and Biomass in a Tangentially Pulverized Coal Boiler Using Computational Fluid Dynamic Analysis

Renewable energy sources are becoming increasingly crucial in the global energy industry and are acknowledged as a significant substitute for fossil fuels. Oil palm fronds are a type of biomass fuel that can be utilized as a substitute for fossil fuels in the combustion process of boilers. Co-firing (HT-FRD) is a beneficial technology for reducing exhaust gas emissions generated by coal-burning power stations. By utilizing computational fluid dynamics (CFD), this study has modeled and evaluated co-firing palm frond residue (HT-FRD) with hydrothermal treatment into a 315 MWe boiler. In the simulation, six different HT-FRD co-firing ratios, 0%, 5%, 15%, 25%, 35%, and 50%, were used to demonstrate the differences in combustion characteristics and emissions in the combustion chamber. The data indicate that HT-FRD co-firing can enhance temperature distribution, velocity, and unburned particles. All in all, co-firing conditions with 5–15% HT-FRD ratios appear to have the most favorable combustion temperature, velocity, and exhaust gas characteristics.

Effective Air Pollution Monitoring System for Eco Balance

Air pollution in urban areas is increasingly driven by vehicle emissions, which release harmful gases include such things as carbon monoxide (CO), nitrogen oxides (NOx), hydrocarbons (HC), and particulate matter (PM). These pollutants pose significant risks to both environmental quality and public health, highlighting the urgent need for effective monitoring and control systems. This project presents the development of an automated Effective Air Pollution Monitoring System for Eco Balance, designed to detect exhaust gas levels in real-time as vehicles pass designated points. The system employs advanced sensors to monitor pollutant concentrations and utilizes a camera- based recognition system to capture the number plates of vehicles that exceed permissible emission levels. The collected data, including pollution metrics and vehicle details, is transmitted to the Regional Transport Office (RTO) for necessary enforcement actions. By promoting compliance with emission standards, this automated system aims to significantly reduce vehicle-related air pollution, fostering a cleaner and healthier urban environment

High‐Temperature Oxidation Response of 444 Ferritic Stainless Steel in a Synthetic Automotive Exhaust Gas

The high‐temperature oxidation behavior of 444 ferritic stainless steel has been studied in cyclic oxidation experiments using synthetic automotive exhaust gas atmospheres at 950 and 1050 °C. The weight gain per unit area of the 444 ferritic stainless steel following oxidation at 950 °C for 100 h iss 85.7% lower than recorded at 1050 °C. The oxide scale at both temperatures consisted of Fe–Cr and Mn–Cr spinels in the outer layer and Cr2O3 in the inner layer. Nodule formation and spallation of the oxide scale are identified as the main causes of breakaway oxidation. The depth of the internal oxides gradually increases with the oxidation time. The nucleation and growth of internal SiO2 result in the formation of metal protrusions, which are eventually consumed in the formation of a SiO2 layer. The SiO2 layer is formed at the interface between the oxide scale and the substrate at 1050 °C. The nucleation and growth of internal SiO2, in combination with lateral growth of SiO2 at the Cr2O3 layer/substrate interface contributed to the formation of the SiO2 layer.

Research on Carbon Footprint Reduction During Hydrogen Co-Combustion in a Turbojet Engine

The paper presents experimental studies on the effect of co-combustion of aviation kerosene with hydrogen in the GTM400 turbojet engine on the change in the carbon footprint generated by the engine in relation to its standard operation without hydrogen in the fuel. This research is in line with current research and development trends carried out in the EU, linking them to the issues of the European Green Deal, the Fit for 55 directive and current environmental trends in aviation and energy. The main objective of the research was to check the effect of hydrogen co-combustion in a turbojet engine on the change of the carbon footprint, while a secondary objective was to verify the impact of higher exhaust gas temperatures generated by the new, high-calorific fuel on the secondary generation of nitrogen oxides (NOx), especially in the thermal mechanism, as an undesirable effect. The research shows that the co-combustion of hydrogen with aviation kerosene in a turbojet engine reduces the carbon footprint (reduction of CO2 maximum of 15% and CO emissions maximum of 24%), but also increases the emission of nitrogen oxides (NOx) maximum of 58%, including those generated in the thermal mechanism (significant increase in the temperature of exhaust gases), moreover, the increase in nitrogen oxide emissions is proportional to the amount of co-combusted hydrogen, which is directly related to the stoichiometry of the combustion process. The main conclusion of the research is that technologies for the combustion or co-combustion of hydrogen in turbojet engines require further research and development, mainly on the side of the use of excess exhaust gas temperature generated during combustion and methods of reducing secondary nitrogen oxides.