Unburned Hydrocarbon Emissions Research Articles

Analyzing the influence of feedstock selection in pyrolysis on aviation gas turbine engines: A study on performance, combustion efficiency, and emission profiles

Commercial aviation is primarily reliant on fossil fuels, yet the depletion of these sources and the consequences of climate change necessitates the exploration of sustainable alternatives. The pyrolysis process offers a viable method for producing biofuels from various feedstocks. This research examines the combustion, emission, and performance characteristics of biofuels derived from agricultural residues, waste tyres, and plastics using pyrolysis. Pyrolysis oils derived from forestry or agricultural products exhibit high viscosity and moisture content, which impairs combustion efficiency and increases carbon monoxide (CO) from 70 % to 187 % and unburned hydrocarbon (UHC) emissions. Conversely, pyrolysis oils from plastics and waste tyres provide stable combustion with carbon monoxide and total hydrocarbon emissions (THC) comparable to those of commercial jet fuel. However, nitrogen oxide (NOX) emissions are significantly elevated from 57 % to 157 %. Engine performance tests demonstrated that forestry pyrolysis oils result in thrust loss due to their high viscosity value (14.3–113 mm2/s) and low calorific value (17.3–31.7 MJ/kg). In contrast, plastic and tyre pyrolysis oil perform similarly to commercial jet fuels but may potentially cause performance loss due to their high aromatic content (>47.67 %). Overall, upgrading the viscosity, moisture, and aromatic content of pyrolysis oils can enhance their suitability as alternative aviation fuels. These improvements could assist the aviation sector in achieving its carbon-neutral goals by making pyrolysis oils competitive with conventional jet fuels.

Design and Numerical Analysis of an Annular Combustion Chamber

Designing a combustion chamber for gas turbines is considered both a science and an art. This study presents a comprehensive methodology for designing an annular combustion chamber tailored to the operating conditions of a CFM-56 engine, a widely used high bypass ratio turbofan engine. The design process involved calculating the basic criteria and dimensions for the casing, liner, diffuser, and swirl, followed by an analysis of the cooling sections of the liner. Numerical simulations using NUMECA software and the HEXPRESS meshing tool were conducted to predict the combustion chamber’s behavior and performance, employing the κ-ε turbulence model and the Flamelet combustion model. Methane was used as the fuel, and simulations were performed for three fuel injection angles: axial, 45°, and 60°. Results demonstrate that the combustion chamber is properly dimensioned and achieves complete combustion for all configurations. The pressure ratio is 0.96, exceeding the minimum design criteria. Additionally, the emissions of unburned hydrocarbons are zero, while nitrogen oxides and carbon monoxide levels are below regulatory limits. These findings validate the proposed design methodology, ensuring efficient and environmentally compliant combustion chamber performance.

Conjoint impact of modified HHO system, compression ratio variation, and tribological enhancement of steel piston ring substrates on performance and emission characteristics of a spark-ignition engine

In these times of efforts to develop high-efficiency hydrogen-adopted or hydrogen-fueled internal combustion engines (ICEs), and concerns related to electric vehicles such as battery cost, drawbacks in harsh winter climates, low range, etc., it is important to generate original ideas in line with the manufacturing of ICEs with improved efficacy. Accordingly, this study presents a comprehensive experimental investigation to observe the cooperated effects of pulse width modulation (PWM)-controlled hydroxy (HHO) gas introduction and improvement in tribological performance of piston ring-cylinder liner mechanism on performance and emission characteristics of a spark-ignition (SI) engine (co-system). The variation of compression ratio (CR), influence of two electrolyzer types of tube electrolyzer (TE) and plate electrolyzer (PE) for production of HHO gas, and zeta potential (ZP)-based dynamic light scattering (DLS) analysis to specify the optimal catalyst concentration in de-ionized water were also observed. Electron cyclotron resonance-chemical vapor deposition (ECR-CVD) method was utilized to bombard the piston ring substrates with diamond-like carbon (DLC) atoms under high energy plasma to improve the mechanical strength of the friction surface. Using linear tribometer, the uncoated (UPR) and coated piston rings (CPR) underwent friction tests to determine the wear rate (WR), and coefficient of friction (COF) which have substantial contribution to frictional losses. The surfaces of the samples were visualized via scanning electron microscopy (SEM) and atomic force microscopy (AFM) before and after abrasion tests to analyze carbon coating and its effects on tribological performance. The observations depicted that HHO flowrate needs to be varied as the engine load and CR change, and based on these observations, PWM control unit was designed, manufactured and reprogrammed so as to adjust electrical power consumption of HHO system when needed. The aforementioned analyses ensured optimization of the overall system so as to maximize the efficiency of the test engine. The co-system with optimized parameters (CPR + HHO + PWM) yielded an increase in average brake power (Pe) up to 31%, and average reductions in specific fuel consumption (β), carbon monoxide (CO), unburned hydrocarbon (UHC), and nitrogen oxide (NOx) emissions by 17%, 25%, 19%, and 14%, respectively at engine load range from 20% to 100%. It is expected that this study will be a good guide in terms of developing high-efficient ICEs due to promising results provided by the co-system.

Combustion and emission characteristics of distilled waste plastic pyrolysis oil-gasoline blends using single cylinder motorcycle petrol engine

ABSTRACT This study assessed the performance and emissions characteristics of a single cylinder, 2-stroke motorcycle spark ignition engine (Esoo 150 cc) utilising clay-catalytically produced distilled waste plastic pyrolysis oil (DWPPO) fuel. The clay catalyst and fuel properties were analysed using established standard testing procedures. The engine performance and exhaust gas emissions were determined for various fuel blends and compared with those of commercial gasoline at various parameters. Results showed that distilled pyrolysis fuel properties (kinematic-viscosity: 6.4 × 10–7 m2/s; caloric-value: 47.82 MJ/kg) were enhanced compared to kinematic viscosity of 1.92 × 10–6 m2/s and caloric value of 44.41 MJ/kg for Crude Waste Plastic Pyrolysis Oil. Notably, chemical composition of distilled fuel collected within a temperature range of 90°C-180°C closely resembled those of pure gasoline. It was also shown that 50% Distilled Waste Plastic Pyrolysis Oil (D50WPPO) significantly improved the brake power, brake thermal efficiency and reduction in brake specific fuel consumption while operating at full load conditions with various DWPPO-Gasoline blends and pure gasoline. Unburned hydrocarbon emissions reduced by 40% when the engine was fuelled with D50WPPO. The study concluded that DWPPO can potentially be employed as a substitute of conventional gasoline without any engine modifications.

Experimental study of quaternary blends with diesel/palm-oil biodiesel/ethanol/diethyl ether for optimum performance and emissions in a light-duty diesel engine using response surface methodology

Quaternary fuel blend consisting of diesel, palm-oil biodiesel (POB), diethyl ether (DEE), and ethanol is a promising low-carbon fuel solution for diesel engines. In this study, the effects of DEE, ethanol, and engine load on the brake specific fuel consumption (BSFC), nitrogen oxides (NOx), carbon monoxide (CO), and unburned hydrocarbons (UHCs) emissions of a light-duty diesel engine were statistically analyzed using analysis of variance (ANOVA). Desirability-based response surface methodology (RSM) optimization was then employed to determine the optimum quaternary fuel blend. The desired optimum quaternary fuel blend was found to be 6.78 vol% DEE and 20.00 vol% ethanol at an operating engine load and speed of 31.36 % and 2000 rpm, respectively. The engine out responses of BSFC and NOx, CO, and UHCs emissions for the optimal solution were 490.58 g/kWh, 326.84 ppm, 0.300 vol%, and 156.95 ppm, respectively. Validation of the optimized parameters was conducted through actual engine experiments and the errors were less than 5 %. The results suggest that the optimum quaternary blend can be a cleaner alternative for light-duty diesel engine applications.

Waste plastic oil as an alternative fuel: A review

Today, with the high population density of the world, the energy demand is increasing continuously. Global dependency on fossil fuels is very strong and there is a compelling need to reduce our energy consumption in order to offset greenhouse gas emissions. Due to regularly increasing prices of fossil fuels alternative fuels are needed to fulfill the requirements of developing countries like India. Plastics in today's world have become crucial. They are excessively used in industry, as well as in households and other fields due to their lightweight, durability, and design flexibility. Plastic demand is growing day by day, which now poses a huge environmental threat. The current study summarizes the use of WPO (waste plastic oil) in the diesel engine and also concludes the combustion, performance, and emission parameters. After an exhaustive literature search, some interesting results have been found. The study reveals that when using WPO as an alternative source in a diesel engine, the combustion, performance, and emissions are similar to those using conventional diesel fuel. An enhanced BTE (brake thermal efficiency) and reduced emissions of unburned hydrocarbons (UBHC) and carbon monoxide (CO) are reported.

Experimental investigations of CI engine performance using ternary blends of n-butanol/biodiesel/diesel and n-octanol/biodiesel/diesel

This study explored the ternary blends of biodiesel-diesel-n-butanol and biodiesel-diesel-n-octanol on common rail direct injec-tion (CRDI) diesel engines. The compositions of fuels, which varied from 0% to 100%, were altered by up to 5%. On the basis of their properties, these blends were chosen, with various concentrations of alcohol at 5% and 10%, 5% diesel, and the remainder being biodiesel. Two ternary fuel blends of waste cooking oil biodiesel (90–85%), diesel (5%), and butanol (5–10%), namely BD90D5B5 and BD85D5B10, and subsequently, another two ternary similar blends of waste cooking oil biodiesel (90–85%), diesel (5%), and octanol (5–10%), namely BD90D5O5 and BD85D5O10, were used to conduct the experiments. The experiments were done with varying injection pressure from 17° to 29° crank angle (CA) before top dead centre (bTDC). The optimum con-dition for the blends is achieved at 26°CA bTDC for 80% loading. So, the engine trials were conducted on 26°CA bTDC to attain the results. The BD90D5O10 blend achieved the lowest brake specific fuel consumption (BSFC) reading of 0.308 kg/kWh while operating at full load. The maximum brake thermal efficiency (BTE) was 31.46% for BD90D5B5. The maximum heat release rate (HRR) achieved with BD85D5O5 fuel blend was 58.54 J/°CA. The quantity of carbon monoxide that BD85D5B10 created was the lowest (25.86 g/kWh). BD85D5B10 had a minimal unburned hydrocarbon emission of 0.157 g/kWh while operating at full load. Oxides of nitrogen (NOx) were emitted in the maximum quantity by BD85D5O10, which was equal to 6.01 g/kWh. This study establishes the viability of blends of biodiesel and alcohol as an alternative for petro-diesel in the future to meet the growing global energy demand.

Experimental and numerical study on flow/flame interactions and pollutant emissions of premixed methane-air flames with enhanced lean blowout hydrogen injection

This study investigates experimentally and numerically the stability, combustion, and emissions characteristics of premixed swirl-stabilized methane/air flames with enhanced lean blowout (ELBO) injection of hydrogen in the non-premixed mode for higher turndown ratio gas turbines. The study analyzed the effects of hydrogen fraction (HF: volumetric percentage of H2 in the total fuel) ranging from 0 to 25% and equivalence ratio (φ) ranging from 0.5 to 0.893 on flow/flame interactions and flame stability, structure, and emissions. The introduction of non-premixed H2 yields two conflicting outcomes, with enhancements in reaction kinetics and flame speed yet counteracted by increased hydrogen jet momentum dispersing the flame. The combustor lean blowout (LBO) limit remains relatively unaffected (φoverall≈ 0.5) by H2 injection. Flame temperature is primarily influenced by φ and minorly by HF. Increasing HF resulted in localized temperature rises around H2 jets without an overall increase in flame temperature, offering a promising strategy for reduction of NOx emissions. Nevertheless, using H2 as a pilot fuel leads to an increase in intermediate species like OH, H, and O, contributing to flame stabilization. However, this practice also results in higher CO and unburned hydrocarbons emissions due to the inherent characteristics and heightened reactivity of H2.

Experimental investigation of diethyl ether (DEE) blended jack fruit peel oil (JFP) with hydrogen as a secondary fuel in dual-fuel compression ignition engines.

Jack fruit peel oil (JFPO) exhibits passive chemical characteristics; thereby, dual-fuel mode frequently involves hydrogen to address its combustion difficulties. This strategy has been gaining prominence nowadays. The present investigation investigates on the performance, emission, and combustion characteristics of a direct injected compression ignition dual-fuel engine operating on a binary fuel blend of jack fruit peel oil (JFPO) and diethyl ether with hydrogen induction. The engine was operated by inducing hydrogen gas into the intake manifold of the engine at 8 and 10 LPM with the applied load ranging from 25 to 100%. The test fuel was prepared by blending jack fruit peel oil and diethyl ether in the volumetric ratio of 90:10. JFP brake thermal efficiency was 16% lower than diesel at full load but enhanced by 9% with direct hydrogen induction at a knock limit of 10 LPM and 23% with JFP + H2 + 10% DEE at maximum load. At maximum load, JFP + 10 LPM of hydrogen gas + 10% DEE produces 916ppm of NOx, which is 44.46% less than diesel. Furthermore, adding hydrogen gas and DEE to air fuel mixture decreased emissions of carbon monoxide and unburned hydrocarbon by 0.702% and 28.30% opa, respectively.

A comprehensive phenomenological model for unburned fuel emission simulation applied to natural gas engines

The development of lean-burn concepts for internal combustion engines, utilizing a homogeneous air/fuel charge, aims to improve multiple aspects simultaneously, including thermal efficiency, fuel consumption, nitric oxide, and carbon monoxide emissions. However, the adoption of this technology may result in a notable increase in the emission of unburned hydrocarbons (uHC) compared to stoichiometric engines. The sources of uHC are diverse and their relative significance depends on fuel characteristics, engine operating conditions, and geometric features of the combustion chamber. This concern becomes more pronounced when considering engines fueled with natural gas, as methane has a high global warming potential compared to other pollutant emissions. This research proposes an enhancement to an existing simulation model that describes the primary mechanisms involved in uHC formation, which are filling/emptying of the piston top-land crevice volume and the flame wall quenching, with subsequent uHC post-oxidation. The improvements include the calculation of flame penetration into crevice volumes, the description of uHC production from non-piston crevices, and the introduction of a novel scavenging model. The uHC model is integrated into commercial software (GT-Power) as a “user routine”. Validation of the model is conducted with reference to three large bore engines (W31DF, W31SG, and W46SG) with bore sizes of 31 cm and 46 cm, fueled with natural gas, and operated under lean mixtures (λ > 2), employing different ignition methods (dual fuel mode or pre-chamber device). The uHC model is validated against engine-out measurements, exhibiting an average error of 10.0 % for W31DF, 19.4 % for W31SG, and 14.0 % for W46SG engines, respectively. The reliability of the uHC model is demonstrated by the absence of case-specific adjustments to its tuning constants, even when there are significant variations in engine load and geometric design of the crevice volumes.

Influence of TiO2 nano-additive and compression ratio on the performance parameters in a VCR diesel engine using microalgae biodiesel

The current study emphasizes effect of TiO2 nanoparticle dissemination in microalgae biodiesel blend to enhance the characteristics of fuel MAB20 and boost VCR CI engine features. The TiO2 nanoparticle was mixed with microalgae biodiesel at three distinct levels, i.e. (25ppm, 50ppm, and 75ppm) with surfactant (Span80) by ultrasonication. The compression ratio (17, 19, and 21) used at varying braking load. Current research confirms the use of 75 ppm TiO2 nanoparticle in MAB 20 at CR 21 has reduced the unburned hydrocarbon emission by 22.36% and 41.58%, smoke opacity emission by 35.66% and 65.67%, CO emission by 18.60% and 30.69%, NOx emission by 14.58 and 5.62% as compared to MAB20 and Diesel respectively. The TiO2 nanoparticle concentration increases from 25 ppm to 75 ppm. It shows lowered HC emission by 14.49%, CO emission by 13.28%, NOx emission by 9.05%, and smoke emission by 28.42%. In contrast, Brake thermal efficiency has increased by 5.06%, specific fuel consumption reduces to 10.19%, and Exhaust gas temperature has declined by 9.58% as compared to MAB20 and with an increase in nanoparticle concentration from 25ppm to 75ppm BTE has reduced by 0.95%, BSFC has increased by 1.66%, and EGT has lowered by 5.86%. Also, CPmax was increased by 11.75%, and NHRR was increased by 10.84% compared to MAB20. Increase in nanoparticle concentration increases CPmax and NHRR by 7.43% and 6.76%.

Effect of excitation Strouhal number on a backward-inclined jet flame in crossflow

Combustion is often accompanied by environmental pollution due to incomplete reaction. A non-excited flame usually exhibits poor combustion performance with features of diffusion flame such as dual-peak temperature distributions and large combustion product concentrations. Efficient fuel-air mixing has been identified as a key factor in mitigating this issue. The present study investigated the effects of the acoustic excitation Strouhal number on the combustion performance of a backward-inclined jet flame in crossflow. A loudspeaker was used to induce jet pulsations with excitation Strouhal numbers ranging from 0.47 to 1.54 at a pulsation intensity of 0.90. Time-averaged and instantaneous flame images were captured using digital cameras. A customized R-type thermocouple and a commercial gas analyzer were employed to analyze the thermochemical structures. A critical excitation Strouhal number of approximately 0.9, distinguishing two characteristic flame modes: strongly affected flame (SA flame) and weakly affected flame (WA flame), was found. At excitation Strouhal numbers lower than the critical value, the SA flame featured single-peak temperature profiles and low unburned hydrocarbon, carbon monoxide, and nitric oxide emissions. The combustion performance was significantly improved due to the strong mixing effect induced by the acoustic excitation. The WA flame appeared at excitation Strouhal numbers higher than the critical value. It exhibited dual-peak temperature distributions and slightly improved combustion performance. The dynamic behavior and emissions of acoustically excited jet flames offered a fascinating insight into the influence of excitation Strouhal numbers on combustion characteristics. More excitation conditions were expected for future research.

The effects of limonene and eugenol additives in n-heptane and low-octane gasoline on the emission characteristics and fuel consumption of single-cylinder gasoline engine

This study investigated the effects of two additive polarities: polar (eugenol) and nonpolar (limonene) additives blended into n-heptane and low-octane gasoline. These compounds were chosen due to their unique molecular structure characteristics which influences the exhaust emissions. The physicochemical properties, fuel consumption, and exhaust gas emissions of a single-cylinder gasoline engine were measured. Four fuel blends were created by blending eugenol and limonene on a volumetric basis, n-heptane-eugenol (NHE), n-heptane-limonene (NHL), low-octane gasoline-eugenol (GE), and low-octane gasoline-limonene (GL). Tests were conducted on a single-cylinder gasoline engine. The exhaust gas emissions were analyzed using gas chromatography, and the role of each additive substance in the formation of carbon monoxide (CO), unburned hydrocarbon (HC), residual oxygen (O2), and carbon dioxide (CO2) emissions was validated using Hyperchem simulation and gas chromatography mass spectrometry. Owing to differences in the molecular structure and energy content of the two additives, the fuel consumption of NHE-fueled vehicles increased by 19.69% compared to NHL, whereas GE decreased by 32.15% compared to GL. Owing to the presence of oxygen atoms and low binding energy, blending eugenol with n-heptane and low-octane gasoline significantly reduced CO by 1.87% higher than limonene. However, eugenol’s aromatic structure can only reduce 14.45% of HC emission, while limonene, with its dynamically moving electrons and nonpolar properties can reduce up to 18.24%. It was discovered that the two additives could improve the quality of exhaust gas emissions.

Predicting the effects of direct-injected fuels co-powered by high-CO2 biogas on RCCI engine emissions using kinetic mechanisms and multi-objective optimization

High inert gas content in biogas resulted in poor burning and emissions attributes, though scarcely investigated in reactivity controlled compression ignition (RCCI). Established kinetic mechanisms were combined with multi-objective optimization to investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The work examined the impact of direct-injected high reactivity fuels (HRF) and port-injected Biogas at various inert gas (carbon dioxide, CO2) rates (25 – 45% vol), biogas fractions (40 – 70%), speeds (1600 – 2000 rpm), and loads (4.5 – 6.5 bar IMEP) on emissions of RCCI engine, experimentally. The findings revealed that while engine speeds greatly decreased CO (carbon monoxide) and NOx (nitrate oxide) emissions with rising unburned hydrocarbon (UHC) regardless of HRF employed, higher engine load significantly reduced UHC emissions. Diesel-biogas reduces NOx emissions and performs better in reducing CO and UHC emissions at lower speeds than B5-biogas, except in low-level loads. Although increasing CO2 impact led to a reduction in UHC and CO emissions, the biogas proportion was the most significant variable. The main factor influencing increased NOx emissions was engine load, which is inversely correlated with reduced NOx and increased particulate emissions owing to high CO2 content and biogas proportion. The premixed mode's optimisation outcome confirms the trade-off reduction at 5.5 bar IMEP, 35.586% CO2, and 50% fraction. As a result, running the RCCI engine with direct-injected diesel co-powered in equal proportion with high-CO2 biogas cuts the emissions trade-off dramatically, limiting the environmental repercussions of the emissions.

Biogas intake pressure and port air swirl optimization to enhance the diesel RCCI engine characteristics for low environmental emissions

Exhaust emission and combustion control in RCCI (reactivity-controlled compression ignition) focused mainly on the direct-injected fuel parameters, urging to investigate the advantages of port-fuel intake parameters. The engine was modified for port injection of Biogas at the valve and RCCI mode. The influence of port swirl ratio (PSR, 0 – 80%) and biogas injection pressure (BIP, 1 – 4 bar) on the diesel RCCI combustion and emissions was tested and optimized at varied loads and 1600 rpm in a port injection at the valve (PIVE) approach. Established kinetic mechanisms were combined with multi-objective optimization to further investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The results show that the radiation absorption triggered by increased CO2 lowers combustion temperature, resulting in prolonged ignition. Setting the airflow to swirl lowers the in-cylinder pressure at elevated BIP while raising the heat generated across the BIPs. Increasing the PSR slows the combustion while BIP speeds up the process. BIP and PSR show great trade-off reduction ability among all emission parameters. The optimum unburned hydrocarbon, nitrogen oxide, particulate, and carbon monoxide emissions for the injection at the valve were found to be 109.58, 0.577, and 2.336 ppm, and 0.103%, respectively, at low-load, low-BIP, and high-PSR. The emissions were lowered by 6.58, 91.26, 80.65, and 13.45% compared to the premixed RCCI mode, respectively. Therefore, introducing low-pressure biogas amid high swirling air at the valve elevates the in-cylinder condition while lowering the emissions, mitigating their environmental implications.

Improving the performance of gasoline fuels by adding methanol and methyl tertiary-butyl ether along with metal oxides titanium oxide and magnesium oxide

These variables include the type of nanoparticle additives integrated into the fuel blend and the operational engine speed. The focus is on two specific oxygenated additives, methanol and isobutanol, in conjunction with Methyl Tertiary-Butyl Ether (MTBE) and two metal oxide nanoparticles, namely magnesium oxide and titanium oxide. The experimental framework entails testing these new fuel blends in a controlled environment, utilizing a four-stroke engine linked to a dynamometer and a speed analyzer. The tests are conducted at rotational speeds of 750 and 1250 rpm. The comprehensive data collected encompass a range of parameters, including engine power and torque, as well as the emissions of carbon dioxide (CO2), nitrogen oxides (NOx), unburned hydrocarbons (HC), and carbon monoxide (CO). The study meticulously analyzes data to build a robust model, significantly enhancing engine performance while substantially lowering emissions. It finds that adding specific additives to gasoline notably reduces carbon monoxide and hydrocarbons. Testing gasoline with methanol, MTBE, and titanium oxide at 750 RPM showed a notable shift in emissions: nitrogen oxide increased by 40.5%, while hydrocarbons, CO, and CO2 saw reductions of 17.5%, and from 2.4% to 7.8%–1.197% and 7.661%, respectively, underlining the need for careful fuel composition management for environmental benefits.

A relative comparison of HCCI, PCCI, and RCCI combustion strategies: an alternative fuels perspective

Low temperature combustion (LTC) strategies have the potential for simultaneous reduction in oxides of nitrogen (NOx) and soot emissions while achieving higher thermal efficiency. Commercial widespread implementation of LTC strategies demands addressing several challenges, including narrow operating load range, lack of ignition timing control, and reducing high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. These challenges could be because the conventional engine design and fuels cannot adapt well to LTC modes. Thus, replacing conventional diesel fuel with suitable alternative fuels for LTC strategies is essential. In the present work, three LTC strategies, Homogenous Charge Compression Ignition (HCCI), Premixed Charge Compression Ignition (PCCI), and Reactivity Controlled Compression Ignition (RCCI), are compared with conventional diesel combustion in a production, light-duty diesel engine from an alternative fuel perspective to come up with a befitting strategy and fuel to achieve wider operating range and lower emissions. The fuel selection strategy based on the fundamental fuel property requirements of the three LTC strategies has been discussed in detail. The baseline reference data is fixed by comparing three LTC strategies with conventional diesel combustion using diesel and gasoline as reference fuel at 40% load, the maximum common achievable load among the three LTC strategies. This is followed by an investigation of the effect of alternative fuels across three LTC strategies to address the shortcomings of the LTC strategies. The results show that the engine operating load range could be extended, and HC and CO emissions are reduced significantly with alternative fuels in the three LTC strategies.

Synergistic effects of nano-enhanced waste transformer oil and hydrogen premixing on CI engine performance and emissions

Waste materials possess untapped potential when harnessed effectively. One such resource is waste transformer oil, derived from electrical transformers, which can be converted into a valuable fuel source for compression-ignition (CI) engines using pyrolysis techniques. In this study, we explored the utilization of a 50 % blend of waste transformer oil with diesel, augmented with Titanium dioxide nanoparticles (referred to as “nano fuel of waste transformer oil”), in an unmodified CI engine. To further enhance the performance of this nano fuel, we introduced hydrogen (at flow rates of 2.5 LPM, 5.0 LPM, and 7.5 LPM) into the inlet section during the suction phase, promoting premixing within the cylinder. Hydrogen premixing significantly improved combustion dynamics. Notably, when 7.5 LPM of hydrogen was introduced alongside waste transformer oil-derived nano fuel, a remarkable 37.30 % increase in brake thermal efficiency was achieved. Moreover, this configuration exhibited a 15.33 % reduction in brake-specific fuel consumption (BSFC), a 27.09 % decrease in carbon monoxide (CO) emissions, a 37.50 % decrease in unburned hydrocarbon (UHC) emissions, and a 28.53 % reduction in smoke opacity compared to traditional diesel operation. These results highlight the potential for enhanced CI engine performance and reduced emissions through the strategic combination of waste transformer oil-based nano-fuel and hydrogen premixing. Consequently, we recommend further exploration of hydrogen premixing in conjunction with nano-enhanced waste transformer oil for superior CI engine performance.

Emission characteristics of cellulosic jet biofuel blend under laminar and turbulent combustion

Alternative biofuels have the potential to reduce greenhouse gas emissions and particulate matter due to free of aromatics compared to traditional petroleum-based aviation fuel. The potential mitigating emission of hydrothermal-condensation-hydrotreating jet biofuel (HCHJ) derived from agriculture residue was investigated. The effects of aviation biofuel components, blend ratio and equivalent ratio on emission characteristics were conducted by Premixed Pre-evaporated Bunsen burner (PPBB) for laminar combustion and ZF850 jet engine for turbulent combustion. In compositions, HCHJ had a higher concentration of cycloparaffins (mostly in C8–C10) while petroleum-based aviation fuel (RP-3) had a higher concentration of alkylbenzenes (mostly in C8–C11). In laminar combustion, HCHJ and both 50% blend HCHJ appear no unburned hydrocarbon (UHC) due to low aromatics content and no sulfur in the biofuel. Moreover, there were no significant differences in NO and NO2 concentration for HCHJ and HCHJ blends. In turbulent combustion, HCHJ blends and RP-3 were compared engine emissions at various state points. Considering all complex effects of fuel and combustion environment, HCHJ blend had a noticeable reduction in PM2.5 emissions in comparison with RP-3 due to their lower aromatics and sulfur content. As HCHJ is similar to RP-3 in C/H ratio, density and heat value and the different aromatics contents have different tendencies to generate PM2.5 at different condition, PM2.5 emission is not only related with the total aromatic content and individual aromatic structure but also the combustion environment at thrust setting and coexisting pollutants including NOx and UHC emissions. CO and NOx emission indicated that both of turbulent state and fuel type influence emissions. HCHJ blend can be benefit for PM2.5 reduction and combustion efficiency growth. PM2.5 reduction can be obtained 77.5% at 10% HCHJ blend and 9.5% at 5% HCHJ blend while combustion efficiency can be obtained 0.05% at 5% HCHJ blend and 0.36% at 10% HCHJ blend through all thrust output.

Operational condition and furnace geometry for premixed C3H8/Air MILD combustion of high thermal-intensity and low emissions

MILD combustion is usually operated at relatively low thermal intensity to achieve uniform temperature field and low pollutant emissions, further understanding of its emission characteristics at high thermal intensity condition is required to widen its application. In the present numerical study of premixed C3H8/air MILD combustion, different operational conditions (equivalence ratio Φ and thermal input Pinput) and furnace geometries (side wall angle α and aspect ratio AR) are considered to reveal their correlations with pollutant emissions including CO, NOx and unburned hydrocarbon (UHC) at thermal intensities up to 1.06 MW/m3. By adopting reactor network calculation with detailed combustion chemistry, it is found that AR plays a notable role in controlling CO, NOx and UHC emissions, while NOx emission is insensitive to the variation of side wall angle. Both the CO and UHC emissions are related to the location of the internal recirculating vortex. Moreover, following the parametric study and NOx formation analysis, the optimized furnace geometry and operating condition of AR = 5, α = 0° and Φ = 0.6 are obtained to significantly reduce the pollutant emissions by 90 % for both C3H8 and CH4 fuels. The present investigation offers valuable insights into the high thermal intensity MILD combustion.