High-speed Engine Research Articles

Power and emission estimation of plastic waste pyrolysis-derived fuel blends in internal combustion engines

Energy, especially from fossil fuels, is essential for everyday life, while plastic waste is an increasing environmental threat. Plastic waste disposal methods such as landfilling and burning cause pollution. Therefore, a process is needed that converts plastic waste into fuel. The object of the study is the engine performance. The problem to be solved is the relationship between the use of a mixture of fossil fuels and pyrolysis fuel on the performance of internal combustion engines. This research uses a systematic data collection process to obtain accurate and reliable results. The necessary equipment, including a dynamometer and gas analyzer, was prepared, and the engine was warmed up to a stable operating temperature of 80 °C. The motorbike is then positioned on the dynamometer with the rear tires aligned and the front tires secured to prevent movement. Data collection was carried out at engine speeds of 2000, 3000, 4000, 5000, and 6000 rpm, using three fuel mixtures: 10 % plastic pyrolysis fuel with 90 % RON 90, 20 % plastic pyrolysis fuel with 80 % 90 RON, and 30 % plastic pyrolysis fuel with 70 % RON 90. Each test was repeated three times, with the output power measured using a dynamometer and exhaust emissions (CO and HC levels) recorded using a gas analyzer. The test results show that the optimal fuel mixture to produce maximum engine power is a PE-RON 90 mixture with a ratio of 20:80, providing the best performance at medium to high engine speeds (3000–6000 rpm) with low CO emissions. The highest power output (1.05) occurs at 4000 rpm, while the PE-RON 90 30:70 alloy produces the best power performance at 6000 rpm (0.78 % CO). Additionally, the pyrolysis fuel blend significantly reduces CO and HC emissions, with the PE-RON 90 30:70 blend showing the lowest CO (0.78 % at 6000 rpm) and consistently reducing HC emissions across the rpm range

Flame kinetics at scramjet-engine-relevant conditions: Role of prompt dissociation of weakly-bound radicals

Combustion in high-speed ram-based propulsion engines occurs under distinct thermodynamic conditions of high reactant temperatures (greater than 1000 K) and relatively low pressures (<5 atm). There is a lack of fundamental flame measurements at such conditions that result in adiabatic flame temperatures (Tad) exceeding 2500 K. In this work, we have measured laminar flame speeds of oxygen-enriched CH4/oxidizer mixtures at sub-atmospheric conditions to probe kinetics at high Tad using the isobaric spherically expanding flame approach. Simulations with recent kinetic models revealed increasing differences between data and model predictions with increasing Tad, reaching up to 25 %. Kinetic analyses reveal that at the thermodynamic conditions in these O2-enriched flames, i.e., lower pressures and higher Tad, the effects of HCO prompt dissociation are accentuated. In addition to HCO, the prompt dissociations of CH2OH and C2H5 are also considered. The prompt dissociations of all three radicals were evaluated and their effects considered in flame speed simulations. Reaction path analysis for the present flames revealed that approximately half of the reaction flux for HCO formation undergoes prompt dissociation to H + CO. Furthermore, these analyses also revealed that the pathways and sensitive reactions are similar between oxygen-enriched fuel/oxidizer mixtures and preheated fuel/air mixtures, if both have similar Tad. Thus, flames of oxygen-enriched mixtures could be a surrogate to probe the flame chemistry of highly preheated mixtures at relatively low pressures that are often encountered in ram-based propulsion engine combustors.

Mixing-controlled compression ignition of ethanol using exhaust rebreathe at a low-load operating condition—Single cylinder experiments in a heavy-duty diesel engine

As pollutant emissions regulations in the heavy-duty sector become further stringent, the energy requirements in this sector continue to increase. Due to the high-power density and operating period requirements within this sector, full electrification is challenging. A viable solution to meet the stringent requirements for criteria pollutant and greenhouse gas (GHG) emissions is the use of low carbon renewable fuels. Low carbon renewable fuels are desirable due to their lower carbon content per unit energy compared to conventional fossil diesel fuel. However, implementing some low carbon renewable fuels in the heavy-duty sector poses challenges due to their low reactivity and the prevalent mixing-controlled compression ignition (MCCI) combustion strategy. Because of this, ignition assistance is needed to ignite low reactive renewable fuels in MCCI. This work investigates the use of a variable valve actuation (VVA) strategy, exhaust rebreathe, as an ignition assistance method to ignite pure fuel grade ethanol (E98) in MCCI. Exhaust rebreathe utilizes the hot combustion products from the previous cycle by reinducing the exhaust back into the cylinder during the intake stroke from a secondary exhaust valve event. The reinduction of exhaust into the cylinder increases the in-cylinder bulk gas temperature aiding in the ignitability of the low reactive fuel. The exhaust rebreathe strategy as an ignition assistance method is investigated in this work by conducting single cylinder engine experiments on a heavy-duty diesel engine fueled with E98. Exhaust pressure is varied for the exhaust rebreathe strategy to achieve combustion characteristics with E98 similar to diesel at a low-load, high engine speed operating condition. Additionally, an elevated intake air temperature strategy is implemented to compare to the exhaust rebreathe strategy as another form of ignition assistance with the objective to induce heat in-cylinder prior to combustion without the presence of diluent. Furthermore, zero-dimensional (0D) constant pressure chemical kinetic simulations are conducted to evaluate the most reactive conditions for ethanol to achieve ignition delay times similar to n-heptane. The experimental results demonstrate that at a high speed, low load condition—the elevated intake air temperature strategy with ethanol requires 120°C intake temperature to yield an ignition delay similar to diesel. When accounting for the energy required to heat the intake air, the brake thermal efficiency is 40% lower than the diesel baseline. On the contrary, the exhaust rebreathe strategy with an exhaust pressure of 1.5 bar-a, is able to achieve the same ignition delay with an MCCI combustion process but maintain a brake thermal efficiency within 5% of the baseline diesel engine.

Experimental investigation of Gyroid recuperator performance integrated with internal combustion engine

The recuperator has the potential to enhance engine performance, reduce fuel consumption, and lower pollutant emissions, making it a promising technology for promoting environmental sustainability. This study investigates the impact of a Gyroid recuperator on the performance of a four-stroke internal combustion engine. Experimental analyses compared engine performance at various set points of rotational speeds before and after recuperator installation. The results validate the effectiveness of the Gyroid recuperator in recovering waste heat, thereby leading to improvements in fuel efficiency. The optimal performance, characterized by an 832.31 J/s increase in recovered combustion heat energy, was observed at 7000 RPM. Additionally, the Gyroid recuperator achieved a maximum overall heat transfer coefficient of 7.9215 W/m2 K at 8000 RPM. The performance of the Gyroid recuperator was further analyzed using the log mean temperature difference method, which yielded a peak value of 114.4 °C at 7000 RPM. The effectiveness-number of transfer units’ method was also employed to assess its effectiveness. These results show that the recuperator can efficiently transmit and recover heat under certain working circumstances. The analysis suggests higher heat energy losses at lower speeds than high speeds, indicating a more efficient energy conversion process at higher engine speeds. The possibilities of the Gyroid recuperator to improve engine performance and its suitability for internal combustion engines are highlighted in this study. This technology offers a promising solution for improving vehicle efficiency and promoting environmental sustainability.

Proteome-scale recombinant standards and a robust high-speed search engine to advance cross-linking MS-based interactomics

Advancing data analysis tools for proteome-wide cross-linking mass spectrometry (XL-MS) requires ground-truth standards that mimic biological complexity. Here we develop well-controlled XL-MS standards comprising hundreds of recombinant proteins that are systematically mixed for cross-linking. We use one standard dataset to guide the development of Scout, a search engine for XL-MS with MS-cleavable cross-linkers. Using other, independent standard datasets and published datasets, we benchmark the performance of Scout and existing XL-MS software. We find that Scout offers an excellent combination of speed, sensitivity and false discovery rate control. The results illustrate how our large recombinant standard can support the development of XL-MS analysis tools and evaluation of XL-MS results.

Analysis of Energy Transfer in the Ignition System for High-Speed Combustion Engines

In order to produce reliable and reproducible ignition of lean fuel–air mixtures and highly stratified mixtures, it is necessary to ensure a high concentration of spark discharge energy and to provide a strong energy impulse for the triggering of chain processes of chemical decomposition of fuel molecules. For this reason, studies have been undertaken on the flow of electrical energy from the ignition system to the spark plug and on the formation of an electric discharge arc with a high concentration of thermal energy. The experimental results were obtained using an ignition coil energy test stand and a constant volume chamber with high-speed spark discharge recording capability. It was confirmed that increasing the charging time of the ignition coil from 0.5 ms to 5.0 ms increases the energy delivered to the coil from 9.5 mJ to 330 mJ. In the same range, the energy generated by the coil was recorded to range from 4.2 mJ to 70 mJ. The coil’s efficiency was found to decrease with increasing charging time from 45% up to 20.5%. Further energy losses were presented when the spark discharge energy was analyzed. In the paper, the results of investigations concerning electric discharge arc development have been presented, illustrated by a few exemplary photos, and discussed. The mathematical interpretation of the electrical energy flux in the ignition system resulting from the energy of the discharge arc has been conducted and illustrated by some functional independences and relationships.

High-speed nonlinear dynamic analysis of dual springs system considering internal structural impact

The significant dynamic responses of helical springs are widely reported as the main reason causing pre-failure in various high-speed conditions. Though the concept of nonlinear springs is proposed to reduce their own dynamic responses, they are found to induce unexpected spike forces during operations. This study presents a dual springs system used within high-speed sports car engines, which aims to mitigate the dynamic responses and spike forces. Analytical models are first developed to calculate the fundamental frequencies of the outer and the inner springs of the system. Then, a transient finite element (FE) model is developed to accurately simulate the dual springs system working at various high engine speeds and validated experimentally by the results of the engine head tests. The simulations reveal that the use of dual springs with different natural frequencies can mitigate the dynamic responses of the whole system to a certain extent. Nevertheless, it is still a compromise as coil clash occurs on each isolated spring though the effects are reduced. The findings of this study indicate that the establishment of direct connections between every component spring would be a promising way to better mitigate the dynamic responses including the effects of coil clash.

Noise monitoring of loud vehicles in four Dutch cities

Excessive noise from loud cars, motorcycles, mopeds, trikes and quads is commonplace in Dutch cities and is a major source of annoyance. In order to assess the sources, causes and potential solutions, TNO has performed a series of noise monitoring campaigns in four major cities including vehicle identification. Sound and vehicle data was acquired at 3 locations in each city for a period of five days. Several steps were applied to separate vehicle noise from other noises, and to attribute the noise to the correct vehicles. The resulting analysis provided insight into the types of vehicles and driving conditions causing most noise. A set of characteristic driving conditions were derived from the measurement data, including high acceleration, engine revving, engine backfire, high engine speed and others. Besides driving behaviour, vehicle modifications such as louder exhausts, removed dB-killers and mechanical or electronic engine modifications are common causes of high noise levels. Also an overview of suggested mitigation options and future outlook is given, based on the findings of the analysis.

Analysis of a High-Speed Airbreathing Research Combustor for JP-7 Fuel-Cooled Design

The continuing maturation of high-speed airbreathing engines has driven an emerging need for a technology transfer from the laboratory into vehicle design. It is now desirable to convert robust, laboratory combustor designs intended for hours of combustion into lightweight, fuel-cooled engines ready for vehicle integration and flight. In a flight-ready combustor, the heat loss of the combustor must be optimized. To understand the heat loss requirement of a laboratory combustor and attempt to optimize it for flight, historical heat loss data of a water-cooled, axisymmetric research combustor are analyzed to inform the conversion of this combustor to a fuel-cooled, flight-like, high-speed airbreathing combustor. Historical data are analyzed at high (0.9) and low (0.3) fuel–air equivalence ratio (ER) values; the analysis shows that the JP-7 cooling flow rate of the combustor can be reduced by 90% (ER 0.3) and 89% (ER 0.9) compared to the baseline research combustor design. This analysis provides an important first look at the cooling design modifications required to convert a research combustor with this internal flow path into a fuel-cooled, flight-ready combustor for use onboard a flight vehicle.

Impact of cylinder deactivation on fuel efficiency in off-road heavy-duty diesel engines during high engine speed operation

Off-road heavy-duty diesel engines are equipped with complex aftertreatment systems to meet the stringent EPA Tier 4 emission standards. Traditionally, the thermal management of the aftertreatment system, aimed at efficiently reducing tailpipe emissions, involves controlling engine exhaust flow and temperature. However, this approach often leads to inefficient engine operation, especially in the low to mid-load regions, resulting in higher fuel consumption. Prior studies have highlighted the potential of cylinder deactivation (CDA) in reducing fuel consumption and increasing the exhaust temperature for thermal management in on-road applications. As the significance of controlling greenhouse gas (GHG) emissions from off-road machinery comes into focus, this study aims to experimentally demonstrate the fuel efficiency benefits and efficient aftertreatment thermal management achieved through CDA during high-speed operation on a Tier 4 level off-road heavy-duty diesel engine. In a typical off-road duty cycle, such as Non-Road Transient Cycle (NRTC), about 82.5% of cycle’s energy is produced in the engine speed range of 1750–2200 rpm, prompting investigation into the impact of CDA during high-speed operations. CDA results in airflow reductions and increased exhaust gas temperatures due to lower air–fuel ratio (AFR). The reduced airflow operation minimizes pumping work, allowing for higher open cycle efficiency, and thereby translating into lower fuel consumption. The study reveals a new finding: fuel benefits from CDA extend over a larger load range (up to 8.3 bar BMEP) during high-speed operation in off-road heavy-duty engines compared to findings in on-road heavy-duty engines. This phenomenon can be attributed to sufficient oxygen inducted during CDA operation, resulting from similar turbocharger speeds compared to all-cylinder firing operation, especially at high-loads, thereby maintaining particulate matter (PM) concentration within prescribed constraints. Steady-state test results demonstrate a reduction in fuel consumption from 33.7% at 0.4 bar to 1.4% at 8.3 bar BMEP, at 2100 rpm engine speed.

A numerical model for predicting the wear of a piston ring/cylinder liner at the top dead center

The cylinder liner-piston ring interface is a critical friction pair in diesel engines, and liner wear can significantly affect engine operation. This study proposes a numerical simulation model under variable operating conditions to quantitatively predict wear at the top dead center (TDC) of the liner, and verifies the model's accuracy. It reveals the influence patterns of engine speed, ambient temperature, and ambient pressure on cylinder liner wear. The research demonstrates good qualitative and quantitative agreement between the wear simulation model and experimental data, particularly with high precision near TDC. Further analysis shows that overall TDC wear depth increases with higher engine speeds. Specifically, wear at 1500 r/min is relatively lower compared to 1300 r/min. Moreover, TDC wear depth exhibits a trend of initially decreasing and then increasing with decreasing ambient pressure and increasing ambient temperature, reaching its minimum at 70 kPa pressure and 25°C temperature.

Numerical Study on the Potential of Stratified Mixture to Improve Thermal Efficiency and Reduce Carbon Emissions in High-Speed Gasoline Direct Injection Engine

Abstract Stratified combustion improves the indicated thermal efficiency (ITE) of gasoline direct injection (GDI) engines, but the mechanism of its impact on unregulated emissions remains unclear. In this simulation-based study, double injection strategies were used to create stratified mixtures in the cylinder. The results indicated that as the second fuel injection quantity (FIQ) was increased or as the second fuel injection timing (FIT) was delayed, the oil-film mass increased, leading to an increase in soot emissions. The formation of a large area of stoichiometry (STO) region at the spark plug and at its right side increases the laminar flame velocity and improves the ITE. At 4000 rpm, the ITE of case2-2 (with a second FIT of −220 °CA after top dead center (ATDC) and a second FIQ of 65.5 mg) increased by 1.6% compared to the original scheme. With the increase in STO area, NOx emissions and the content of CH3OH and CH2O increased, while carbon monoxide (CO) and greenhouse gas emissions showed a decreasing trend. Compared to the original scheme, CO and greenhouse gas emissions decreased by 1.97% and 6.7%, respectively, in case2-2. This study provides guidance for the development of GDI engines with high ITE and low carbon emissions.

Investigation on the electro-magneto-thermoviscoelastic response of multilayer rotating hollow cylinder based on two-temperature theory and fractional-order viscoelastic systems

Hollow cylinder structures play a crucial role in scientific experiment and industrial production, and are widely used in various fields, including pipeline transportation of gases and liquids, high-speed engines, porous combustors, and other engineering equipments. As a result, they have garnered considerable academic interest over the years. However, as science and technology progress, studying hollow cylinders under a single physical field is no longer sufficient for real-world applications. Additionally, the classical viscoelastic model has become inadequate in accurately describing complex materials with properties that fall between elasticity and viscosity. Therefore, this article investigates the electro-magneto-thermoviscoelastic coupling behavior of an infinitely long rotating multilayer homogeneous hollow cylindrical conductor. In this study, based on the fractional-order three-phase lag thermoelasticity theory, the fractional-order viscoelastic system and the two-temperature theory are introduced to further increase the accuracy of the model. To solve the corresponding equations, the Laplace transform technique is employed, resulting in solutions with dimensionless physical quantities. Graphs and tables are used to make relevant comparisons and assess the effects of time, material layering properties, different thermoelastic theoretical models, fractional-order parameters and angular velocity on the considered physical quantities. Finally, the numerical results are discussed to reveal the dynamic response of a homogeneous multilayered hollow cylinder under the complex coupling of multiple physical fields.

Exergy Analysis in Highly Hydrogen-Enriched Methane Fueled Spark-Ignition Engine at Diverse Equivalence Ratios via Two-Zone Quasi-Dimensional Modeling

In the endeavor to accomplish a fully de-carbonized globe, sparkling interest is growing towards using natural gas (NG) having as vastly major component methane (CH4). This has the lowest carbon/hydrogen atom ratio compared to other conventional fossil fuels used in engines and power-plants hence mitigating carbon dioxide (CO2) emissions. Given that using neat hydrogen (H2) containing nil carbon still possesses several issues, blending CH4 with H2 constitutes a stepping-stone towards the ultimate goal of zero producing CO2. In this context, the current work investigates the exergy terms development in high-speed spark-ignition engine (SI) fueled with various hydrogen/methane blends from neat CH4 to 50% vol. fraction H2, at equivalence ratios (EQR) from stoichiometric into the lean region. Experimental data available for that engine were used for validation from the first-law (energy) perspective plus emissions and cycle-by-cycle variations (CCV), using in-house, comprehensive, two-zone (unburned and burned), quasi-dimensional turbulent combustion model tracking tightly the flame-front pathway, developed and reported recently by authors. The latter is expanded to comprise exergy terms accompanying the energy outcomes, affording extra valuable information on judicious energy usage. The development in each zone, over the engine cycle, of various exergy terms accounting too for the reactive and diffusion components making up the chemical exergy is calculated and assessed. The correct calculation of species and temperature histories inside the burned zone subsequent to entrainment of fresh mixture from the unburned zone contributes to more exact computation, especially considering the H2 percentage in the fuel blend modifying temperature-levels, which is key factor when the irreversibility is calculated from a balance comprising all rest exergy terms. Illustrative diagrams of the exergy terms in every zone and whole charge reveal the influence of H2 and EQR values on exergy terms, furnishing thorough information. Concerning the joint content of both zones normalized exergy values over the engine cycle, the heat loss transfer exergy curves acquire higher values the higher the H2 or EQR, the work transfer exergy curves acquire slightly higher values the higher the H2 and slightly higher values the lower the EQR, and the irreversibility curves acquire lower values the higher the H2 or EQR. This exergy approach can offer new reflection for the prospective research to advancing engines performance along judicious use of fully friendly ecological fuel as H2. This extended and in-depth exergy analysis on the use of hydrogen in engines has not appeared in the literature. It can lead to undertaking corrective actions for the irreversibility, exergy losses, and chemical exergy, eventually increasing the knowledge of the SI engines science and technology for building smarter control devices when fueling the IC engines with H2 fuel, which can prove to be game changer to attaining a clean energy environment transition.

Multi-cycle Direct Numerical Simulations of a Laboratory Scale Engine: Evolution of Boundary Layers and Wall Heat Flux

AbstractMulti-cycle direct numerical simulations (DNS) of a laboratory-scale engine at technically relevant engine speeds (1500 and 2500 rpm) are performed to investigate the transient velocity and thermal boundary layers (BL) as well as the wall heat flux during the compression stroke under motored operation. The time-varying wall-bounded flow is characterized by a large-scale tumble vortex, which generates vortical structures as the flow rolls off the cylinder wall. The bulk flow is found to strongly affect the development of the BL profiles, especially at higher engine speeds. As a result, the large-scale flow structures lead to alternating pressure gradients near the wall, invalidating the flow equilibrium assumptions used in typical wall modeling approaches. The thickness of the velocity BL and of the viscous sublayer was found to scale inversely with engine speed and crank angle. The thermal BL thickness also scales inversely with engine speed but increases with in-cylinder temperature. In contrast, thermal displacement thickness, which is sometimes used as a proxy for thermal BL thickness, was found to decrease with increasing temperature in the bulk. Examination of the heat flux distribution revealed areas of increased heat flux, particularly at places characterized by strong flow directed towards the wall. In addition, significant cyclic variations in the surface-averaged wall heat flux were observed for both engine speeds. An analysis of the cyclic tumble ratio revealed that the cycles with lower tumble ratio values near top dead center (TDC), indicative of an earlier tumble breakdown, also exhibit higher surface averaged wall heat fluxes. These findings extend previous numerical and experimental results for the evolution of BL structure during the compression stroke and serve as an important step for future engine simulations under realistic operating conditions.

Carbon Dioxide Emission Characteristics and Operation Condition Optimization for Slow-Speed and High-Speed Ship Engines

Greenhouse gas emissions from ships are estimated to be approximately 1002 million tons per year; this is the largest carbon dioxide (CO2) emission source among nonroad transportation. Previous studies have generally estimated CO2 emissions using fuel- or power-based emission factors based on fuel consumption or engine power. In this study, CO2 emissions from vessels were measured using a portable emission measurement system. Emission characteristics were analyzed according to the vessel’s operation conditions and compared with the results of other studies. Generally, the higher the rpm value, the more CO2 is emitted, and the emissions at the maximum rpm differ depending on the type and size of the engine. In order to minimize the emissions by ships, those from high seas should be reduced rather than nearby ports. In addition, a method of establishing optimal operating conditions in consideration of economic and environmental perspectives was proposed. Fuel-based emission factors elicited in this study were constant regardless of engine rpm. The fuel-based emission factors of each engine were found to be similar at 3144.22 and 3150.58 kg-CO2/tonne-fuel. Therefore, distinguishing CO2 emission factors according to engine type is not necessary, and additional research is required to understand the emission factors of each fuel type.

Optimization of performance and emission of a diesel engine fueled with isopropyl alcohol Blends: A comparative ANN-GA and RSM-HCO application

This study focuses on optimizing the operating parameters of a diesel engine fueled by diesel-isopropyl alcohol blends, with the aim of enhancing engine performance and minimizing emissions. Using data collected from 144 experimental runs, predictive models were developed utilizing artificial neural networks (ANN) and response surface methodology (RSM). The models exhibited impressive accuracy, with an average absolute percentage error below 2 % for each parameter and an R2 value exceeding 0.99. Subsequently, these models were optimized using genetic algorithm (GA) and hill climbing algorithm (HCO) to identify the optimal engine operating conditions. The results indicate that both ANN-GA and RSM-HCO models exhibit satisfactory accuracy in predicting engine parameters. The ANN-GA model demonstrated an average deviation of 2.9 % from experimental data, while the RSM-HCO model exhibited an average deviation of 5.4 %. Both optimization results indicated that, in an emissions-focused approach, desirability above 0.9 could be achieved with isopropyl alcohol-diesel blends and high engine speeds, such as 2600–2700 rpm, with a 3.5 bar engine load, resulting in low emission values and high engine performance.

Performance of Motorcycle Fueled with Pertalite‒LDPE Pyrolytic Oil Blendings

Plastic use has expanded substantially, and its waste is primarily disposed of in landfills, which further harm ecosystems owing to inadequate waste management. Pyrolysis, which converts plastic waste into liquid fuel, is one of the potential chemical recycling alternatives for plastic. The purpose of this study is to determine the viability of using pyrolytic oil from an LDPE grocery bag as an alternative fuel for a four-stroke spark ignition motorcycle engine. The LDPE grocery bag was pyrolyzed at 500 oC at a heating rate of 3 oC/min, and the condensed pyrolytic vapor's characteristics were determined. Torque, power, and fuel consumption were investigated using a four-stroke spark ignition motorbike powered by pertalite‒LDPE pyrolytic oil blends. The results reveal that the properties of LDPE pyrolytic oil and pertalite were considerably different; hence, when the blending fuel was applied to the motorcycle, the engine torque and power decreased at low engine speed (2000‒3500 rpm), about equal at medium speed (3500‒5500 rpm), and increased at high engine speed (5500‒8500 rpm). Furthermore, the greater blending fuel greatly reduced fuel usage due to the high viscosity of the LDPE pyrolytic oil.

Extraction and characterization of Cucumis melon seeds (Muskmelon seed oil) biodiesel and studying its blends impact on performance, combustion, and emission characteristics in an internal combustion engine

This study examines the performance, combustion, and emissions characteristics of a single-cylinder internal combustion diesel engine when fueled with a blend of diesel and biodiesel derived from muskmelon seeds. The kinematic viscosity of the extracted muskmelon seed oil was 6.1 cSt at 40 °C, which is higher than the kinematic viscosity of petroleum diesel of 2.6 cSt. Muskmelon biodiesel was further analyzed using thin-layer chromatography (TLC) and high-voltage separator tests. A comparison of the fuel properties of muskmelon biodiesel with conventional diesel fuel revealed that muskmelon biodiesel could be used alone or in a diesel–biodiesel blend to fuel compression diesel engines. In this study, muskmelon seed biodiesel was blended with diesel fuel at proportions of 10 %, 20 %, and 50 % (BD10, BD20, and BD50, respectively). At a relatively low rotational speed of 1200 rpm, the brake thermal efficiency (BTE) of the engine operated with BD10 and BD20 blends were 36.1 % and 36.0 %, respectively, while the brake-specific fuel consumption (BSFC) of the two blends were 0.260 kg/kWh, and 0.262 kg/kWh, respectively. These values closely resemble those typically observed in diesel fuel engines. Indeed, the average BTE of the BD20 blend was only 3.24 % less than the average BTE of diesel fuel. Diesel fuel generates less NOx and SO2 emissions compared to biodiesel blends: BD100 emitted the most NOx pollution of all fuels tested. In addition, BD10 released significantly more SO2 emissions compared to the other fuels tested. However, the BD20 blend outperformed all other blends in terms of CO, NOx, and SO2 emissions at high engine speeds. The only exception was H2S emissions, which were higher than BD50 and BD100. BD20 also exhibited significantly reduced CO emissions compared to diesel fuel, while BD10 emitted significantly more CO emissions than the other biodiesel blends. Our findings revealed that BD20 exhibited the best engine performance and lower emissions among all fuels tested. In other words, BD20 is the ideal fuel blend for use in diesel engines and does not require any alterations to the engine. Muskmelon waste seeds represent a non-edible waste stream that can be exploited in the production of biodiesel fuel, allowing for the upcycling of a potentially problematic thermochemical conversion feedstock. This potentially valuable use for waste muskmelon seeds in the energy sector could address the wastefulness associated with this particular waste stream.

Modelling of high-speed engine flows using a space-marching method

A computationally efficient mathematical model was developed to analyze high-speed engine flows. The inlet and nozzle flows were modelled using the space-marching method to automatically solve the shock reflection and nozzle plume flow. The combustor flow was treated using a quasi-one-dimensional model that considered the rise in pressure of the isolator owing to the shock train. The resulting model was compared with the experimental results. Three test cases were used to validate the model's accuracy: 1) a hydrogen-fuelled combustor experiment, 2) an integrated inlet/combustor configuration experiment, and 3) a single-expansion-ramp nozzle flow experiment. The results showed that the space-marching method predicted the pressure profiles of the inlet flow and nozzle plume flow with reasonable accuracy. The computational time for the inlet and nozzle flows merely takes several minutes on a CPU with 3.6 GHz. The quasi-one-dimensional model calculated the fuel ignition and pressure rise in the combustor with a high computational efficiency of several seconds. The integration of the space-marching method and quasi-one-dimensional method can be developed as a powerful tool for fast evaluations of high-speed engine performance.