Improve Engine Efficiency Research Articles

Performance analysis of dual-fuel engines using acetylene and microalgae biodiesel: The role of fuel injection timing

This study evaluates the impact of varying fuel injection timing (FIT) and dual-fuel modes on the performance and emissions of a compression ignition (CI) engine under different load conditions. The biodiesel used was derived from Chlorella protothecoides microalgae through a two-step transesterification process, and its elemental composition was characterized using gas chromatography-mass spectrometry (GC-MS). Acetylene gas was introduced into the engine intake manifold at a rate of 3 L per minute (LPM), while a blend of 20 % methyl ester from Chlorella protothecoides (B20 MEOA) served as the primary injected fuel. To predict engine performance and emission characteristics, advanced machine learning models were employed and evaluated using four statistical criteria, including R-squared, mean absolute error (MAE), and mean squared error (MSE). Experimental results indicated that the optimal configuration involved a dual-fuel mode combining B20 MEOA with acetylene gas and an advanced FIT of 25° before top dead center (bTDC). Performance analysis revealed that under all load conditions, the specific fuel consumption (SFC) decreased by 7.3 %, while brake thermal efficiency (BTE) increased by 1.6 % compared to conventional diesel. Emission testing showed a 7.6 % rise in nitrogen oxide emissions, alongside significant reductions in unburned hydrocarbons (12.5 %), carbon monoxide (25.6 %), and smoke intensity (7.5 %) relative to standard diesel operation. Optimization of the engine parameters ensured that key metrics, such as brake power (BP) and brake-specific fuel consumption (BSFC), remained within acceptable limits. The random forest model outperformed other machine learning models, demonstrating superior accuracy in predicting performance and emissions across all statistical measures. This study underscores the potential of combining advanced biodiesel blends with optimized FIT strategies to improve engine efficiency and emissions control, offering a promising approach for sustainable dual-fuel engine operations.

RSM Hybrid Modeling of a BSFC for a Single Cylinder Four Stroke CI Engine Fueled with Nano-additives Added to Diesel-biodiesel Fuel Blends

Introduction: The expanding need for fossil fuels emphasizes the necessity to comprehend renewable energy sources. Methods: This study examined the performance of a single-cylinder diesel engine using Jatropha biodiesel and aluminum dioxide—the research aimed to evaluate engine reactivity to compression ratio and load variations. The experiment employed with varitaion compression ratios. Results: This study used the Response Surface Methodology to find the best Brake Specific Fuel Consumption performance indicator location. The researchers used a Central Composite Design setup for analysis. A regression model employing the response surface approach was then created to predict fuel phase-out likelihood. Conclusion: This study examines multiple factors' effects. According to studies, Jatropha biodiesel and its blends may improve engine efficiency and lower brake-specific fuel consumption compared to diesel fuel. Minor input parameter modifications are needed to gain these benefits.

Reduction of Emission and Fuel Consumptions based on Mingled Nano Additives in Biodiesel

Using the lipids identified as well as extra residual cooking oil, vegetable, and animal fats, bio-diesel a substitute for fuels derived from petroleum can be produced. Since the 1970s oil crisis, there has been a resurgence of interest in using biodiesel as a fossil fuel substitute due to the fuel's rapidly rising prices, availability uncertainties, and growing environmental and greenhouse gas (GHG) concerns.To produce biodiesel, glycerin and fat or vegetable oil are separated chemically through a process termed transesterification. Glycerin, a valuable byproduct that is typically sold to be used in soaps and other products, and methyl esters, the chemical term for biodiesel, are the two products left over from the process. The industrial term for diesel derived from petroleum, petro diesel, and biodiesel have similar viscosities. Due to the nearly zero sulfur content,it is recommended to be used as an additive in diesel oil formulations to improve the lubricity of pure ultra-low sulfur diesel (ULSD).The current work focuses heavily on reducing emissions and fuel consumption in automobiles. In addition to lowering pollutants and fuel consumption, the transition metal oxide (Copper oxide) additions in nanocrystalline particle form aid in molecular combustion. To create a stable Nano fluid, soap nut biodiesel is combined with metal oxide additive and ultrasonicated. For our experimental investigation, single cylinder, air cooled, constant speed Kirloskar engine is used. The reduction of hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxide (NOx) emissions is investigated. The highest break power of the biodiesel employed in the study is 3.82 KW, greater than the typical diesel's 3.23 KW. The result shows improved engine efficiency, reduced emissions, and better brake thermal efficiency.

Numerical optimization of injector hole arrangement for marine methanol/diesel direct dual fuel stratification engines

To investigate the effects of the relative position of injector holes, number of layers, and layer spacing on the performance, combustion, and emission characteristics of a marine methanol/diesel direct dual-fuel stratified (DDFS) engine, numerical optimization of single-layer and multi-layer methanol injector hole arrangement was conducted in this study. Six methanol injector hole positions and three diesel injector hole positions were separately arranged to optimize the relative positions of the injector holes within the single-layer methanol injector hole arrangement scheme. The findings reveal that the interference between methanol spray and premixed flame significantly influences the combustion process. It’s noted that optimizing the methanol injector hole position is more conducive to improving engine efficiency compared to adjusting the diesel injector hole position. When methanol injector holes are positioned between M3 and M5, the engine achieves higher fuel economy. The position of diesel injector holes mainly affects the emissions of HC and CO, whereas the placement of methanol injector holes affects overall emissions simultaneously. When methanol injector holes are arranged in multiple layers, adjusting the number and spacing of injector hole layers only has relatively limited effects on in-cylinder pressure and heat release rate (HRR). Combustion phases are mainly influenced by the contact area between methanol spray and diesel-premixed flame. The preferential combustion of middle-layer methanol provides abundant ignition points for upper and lower-layer methanol sprays, making engine economy under the three-layer methanol injector hole arrangement comparable to that of the optimized single-layer arrangement (D2M3), and superior to the two-layer arrangement. With the optimization of injector hole layer spacing, multi-layer injector hole arrangements demonstrate comprehensive emission performances comparable to those of D2M3. Further research on the circumferential arrangement scheme of multi-layer methanol injector holes indicates that avoiding aligning methanol injector holes with the diesel nozzle axis results in higher fuel economy and better comprehensive emission performance in the methanol/diesel DDFS engine.

Analysis and optimization of energy conversion for an on-board methanol reforming engine with thermochemical recuperation

Methanol steam reforming (MSR) is a promising method to address the storage and safety issues of hydrogen-fueled engines. This method can also significantly improve engine efficiency by recovering exhaust heat. Additionally, low temperature combustion technology can effectively mitigate the issue of excessively high NOx emissions in hydrogen internal combustion engines. However, research on the integration of low temperature combustion technology with methanol steam reforming is limited, and the design of reformers and strategies for methanol reforming remains underdeveloped. Therefore, a one-dimensional model of the methanol steam reforming engine system was established, and methanol reforming strategies were evaluated under varying engine loads. Further a multi-objective optimization of the reformer was conducted to balance system efficiency and economy. The results indicate that complete methanol reforming is unattainable at mid to high loads due to significant turbo work. A partial methanol reforming strategy, where part of the methanol is directly combusted in the cylinder and the rest is reformed to produce hydrogen, achieves the highest system efficiency. After multi-objective optimization of the reformer, this MSR engine yielded a 5.54% increase in average overall system efficiency under three loads, compared to not using thermochemical recuperation.

Increasing the Economic Efficiency of Marine Power Plants Using Waste Heat Boilers with Controlled Flow Separation

Abstract Heat recovery of exhaust gases from main and auxiliary marine diesel engines is an effective way to improve the technical and economic parameters of marine power plants. Improvements in engine efficiency necessitate an increase in the weight-size parameters of the waste heat boilers, which makes it difficult to recover heat. Intensification of the heat transfer process is considered to be an effective way to reduce these indicators. By utilising mathematical modelling, this paper shows the effectiveness of using profiled heating surfaces of waste heat boilers for this purpose. The use of elliptical heating surfaces with a mechanism of controlled flow separation, in the form of a triangular notch, is proposed. This will reduce surface drag and increase the overall thermal-hydraulic efficiency of the heat transfer processes. It is shown that the use of such surfaces in waste heat boilers makes it possible to increase the efficiency of marine power plants in tankers with a deadweight of about 45,500 tons up to 1.5% absolute and container ships with a deadweight of about 122,000 tons up to 2.5% absolute.

Numerical investigation of soot formation in methane/n-heptane laminar diffusion flame doped with hydrogen at elevated pressure

The addition of hydrogen in a dual-fuel mode based on natural gas and diesel offers great potential for improving engine efficiency and reducing emissions. Therefore, detailed numerical simulations have been used to explore the effects of soot formation characteristics of natural gas-diesel dual-fuel engines doped by hydrogen at elevated pressure. Numerical simulations are compared with available experimental data, the effects of H2 addition on soot formation in laminar CH4 + n-heptane, H2 + CH4 + n-heptane, FH2 + CH4 + n-heptane diffusion flames at 2, 4, 6 and 8 atm are simulated, FH2 is added to separate the H2 chemical effects. The results show that the dilution and thermal effects of H2 inhibit soot formation, while the chemical effects of H2 promote soot formation under different pressures. The addition of H2 increases the concentration of H and OH radicals, which promotes the formation of C2H2 and benzene (A1). By simplifying the reaction path and analyzing the production rate of A1, the mechanism of H2 addition to promote A1 formation is illustrated. The concentrations of polycyclic aromatic hydrocarbon (PAH) pyrene (A4), benzo(ghi)fluoranthene (BGHIF) and benzo(a)pyrene (BAPYR) are inhibited at higher pressures that result in lower inception and condensation rates. Therefore, the increase of hydrogen abstraction acetylene addition (HACA) rate is the main reason for the increase of soot formation under chemical effects. While the O2 oxidation rate decreases and the OH oxidation rate increases, that is due to the decrease of O2 concentration and the increase of OH concentration in the soot formation area under chemical effects.

Syngas application in various engines

Current engines are not designed to use syngas as fuel, which presents challenges such as differences in air-to-fuel ratio and fuel properties compared to traditional fuels like gasoline and diesel. This research recommends applying dual combustion, regulating pressure rate, using catalysts and employing EGR (exhaust gas recirculation), in order to improve engine efficiencies while reducing emissions. This study concludes that syngas is more effectively utilized in diesel and HCCI engines (homogeneous charge compression ignition) than in gasoline engines due to the cycle variations impacting efficiency. With technological advancements, syngas and other alternative fuels can be developed to reduce emissions and production cost, justifying their implementation.

Study of the Effects of Different Ambient Gases and Buoyancy on Hydrogen Jet Characteristics.

Substituting nitrogen with inert gases in an inert gas cycle engine can not only effectively improve engine efficiency but also eliminate NOX emissions in the combustion products. Owing to the low density of hydrogen, jet development is affected by buoyancy. This study explored the effects of different ambient gases, such as Ar, N2, and He, as well as buoyancy, on the hydrogen jet and mixing characteristics based on Schlieren. The results indicated that as the pressure ratio increases, the penetration length and volume of the hydrogen jet increase, whereas the dispersion angle and entrainment ratio decrease. The penetration capacity of the hydrogen jet is strongest in He, followed by N2, and weakest in Ar. Additionally, in He, the hydrogen jet exhibits the smallest dispersion angle, fastest jet volume growth, and largest entrainment ratio. The entrainment ratio of the H2 jet in He is 2.75-3.84 times that of N2 and 4.72-8.3 times that of Ar. In N2 and Ar, the penetration length of the inverted jet after 2.5 ms is approximately 2-4 mm longer than that of the upright jet, indicating that buoyancy has a certain influence on jet development.

Influence of structure parameters of pre-chamber on lean combustion of active pre-chamber jet ignition engine

Turbulent jet ignition (TJI) technology has the potential to improve engine efficiency. To elucidate the influence of different factors (diameter and number of holes) affecting the nozzle's total cross-sectional area, internal structure of the pre-chamber, and nozzle angle on the combustion characteristics of the engine. A 3 × 3 orthogonal test was designed and machined. The experiments were carried out on a pre-chamber single-cylinder engine.The results show that the pre-chamber's internal volume ratio has a great effect on the combustion characteristics in the cylinder. While the volume ratio of top of pre-chamber, transition region, and pre-chamber throat is 1:1:1, the engine's peak heat release rate is the highest. The highest Indicated thermal efficiency (ITE) can reach 43.43 %, with an absolute increase of 1.24 %, and the lean burn limit can reach λ = 2.6. Too large or too small nozzle angle will worsen the combustion state in the cylinder. The aperture and Nozzle number, which are the factors influencing the nozzle's total cross-sectional area, have different effects on the ignition delay, CA10-CA50, and CA50-CA90 of the engine. Various factors affecting the nozzle's total cross-sectional area have no apparent influence on the changing trend of ITE, but the aperture greatly influences ITE.

Blade tip clearance measurement technology in gas turbines

Many technologies are used for engine development and testing but no technology has been successfully adopted for long term monitoring over the life of the engine. The challenge is to find a technology that is suitable for long term, high temperature operation but that can also provide accurate and reliable measurement. Blade turbine monitoring is an important area of work for improvements in gas turbine operation. Blade tip clearance measurements offer improvement in engine efficiency by enabling active clearance control. However, this is a difficult measurement because of the harsh turbine environment. The high temperature microwave sensor presented in this paper is one of the most promising candidates for clearance measurement. It has been tested on the high pressure stage of a 25MW gas turbine engine during different operating modes

Impact of Using n-Octanol/Diesel Blends on the Performance and Emissions of a Direct-Injection Diesel Engine

This study evaluates the viability of n-octanol as an alternative fuel in a direct-injection diesel engine, aiming to enhance sustainability and efficiency. Experiments fueled by different blends of n-octanol with pure diesel were conducted to analyze their impacts on engine performance and emissions. The methodology involved testing each blend in a single-cylinder engine, measuring engine performance parameters such as brake torque and brake power under full-load conditions across a range of engine speeds. Comparative assessments of performance and emission characteristics at a constant engine speed were also conducted with varying loads. The results indicated that while n-octanol blends consistently improved brake thermal efficiency, they also increased brake-specific fuel consumption due to the lower energy content of n-octanol. Consequently, while all n-octanol blends reduced nitrogen oxide emissions compared to pure diesel, they also significantly decreased carbon monoxide, hydrocarbons, and smoke opacity, presenting a comprehensive reduction in harmful emissions. However, the benefits came with complex trade-offs: notably, higher concentrations of n-octanol led to a relative increase in nitrogen oxide emissions as the n-octanol ratio increased. The study concludes that n-octanol significantly improves engine efficiency and reduces diesel dependence, but optimizing the blend ratio is crucial to balance performance improvements with comprehensive emission reductions.

Analyzing pyrolysis's effect on the environment and renewable potential of thermochemical plastic recycling

This work uses cerium oxide (CeO2) nanoparticles and purified plastic pyrolysis oil (PPO) to create and evaluate nano fuel for four-stroke diesel engines. The objective is to increase engine performance and decrease emissions without altering the engine. PPO is mixed with conventional diesel fuel to form modified diesel fuel, which is then mixed with surfactant-modified CeO2 nanoparticles to produce a special nano fuel. HR-TEM, SEM, EDS, and XRD characterise the characteristics of the modified nanoparticles. A four-stroke diesel engine is used to test the nano fuel in order to assess emission characteristics and engine efficiency. Comparing the recommended procedure to commercial diesel fuel, the findings demonstrate a 16% reduction in pollutants and a 10% improvement in engine efficiency. This is because the oxygen in the nanoparticles makes the fuel purer and more viscous, which enhances burning efficiency. The performance and emission properties of the nano fuel are evaluated using a four-stroke diesel engine. The results show that, when compared to commercial diesel fuel, the suggested approach increases engine efficiency by 10% and decreases emissions by 16%. It also stresses employing nanoparticle additions to improve diesel engine performance without making substantial engine adjustments.

Study on the effects of intake valve timing and lift on the combustion and emission performance of ethanol, N-butanol, and gasoline engine under stoichiometric combustion and lean burn conditions

To achieve carbon neutrality goals, renewable alcohols and new technologies are receiving increased attention. Variable valve technology can effectively improve engine efficiency. However, there is limited research on valve strategies suitable for alcohol. To further promote the efficient and clean application of alcohol, this article studies the effects of intake valve timing and lift on performance of ethanol, n-butanol, and gasoline engines under stoichiometric combustion and lean burn. It is found that the combustion process of ethanol and n-butanol is prolonged by advancing intake valve timing, while gasoline is the opposite. Meanwhile, the improvement of equivalent brake-specific fuel consumption (ESFC) is the most significant when fueled with gasoline, improving by 6.9 %. The improvement of BSNOx is the highest when fueled with ethanol, improving by 42.07 %. Adjusting intake valve lift has a weaker impact on economy than valve timing. However, when adjusting the combination of throttle, valve lift and timing, the ESFC of ethanol, n-butanol, and gasoline can be reduced by 6.79 %, 4.35 %, and 10.98 %. Furthermore, combining valve timing and lean burn can further improve economy and emissions. The ESFC of ethanol, n-butanol, and gasoline can be decreased by 12.73 %, 6.87 %, and 11.96 %, while BSNOx decrease by 93.69 %, 74.86 % and 61.65 %.

An optical investigation on macro spray characteristics of convergent-divergent ducted fuel injection under high ambient pressures

The fuel-air mixing process can be improved via straight (ST) ducted fuel injection along with the risk of greater heat transfer loss due to prolonged spray tip penetration (STP) and spray impingement. We proposed the convergent-divergent (CD) duct spray in this study to produce acceptable STP and wider spray cone angle (SCA) for improving engine efficiency. STP and SCA are closely related to ambient pressure. This paper aims to explore the influence of ambient pressure on the macro spray characteristics of CD duct spray for better fuel-air mixing with the analysis of spray air entrainment (SAE). The Schlieren system was used to record the spray morphology of different duct sprays under ambient pressures of 20, 30, 40, and 50 bar. The results showed that compared with free spray, with the increase of ambient pressure, the application of CD duct can more effectively improve the SCA increase rate of free spray. With the ambient pressure changes from 20 to 50 bar, the SCA increase rate is up to 20.17% for free spray, and the SCA increase rate increased more than three times to 76.96% with ST3 duct and more than eight times to 173.06% with CD 4.5 duct compared with free spray respectively. The SAE of CD3 and ST3 duct sprays is higher than that of other sprays. CD4.5 and CD6 duct sprays reduce the probability of spray-wall impingement but along with a certain reduced amount of SAE.

Experimental Investigation of Glycerol Derivatives and C1–C4 Alcohols as Gasoline Oxygenates

Certain oxygenated compounds, when blended with gasoline, have the ability to inhibit the occurrence and decrease the intensity of engine knock, helping improve engine efficiency. Although ethanol has had widespread use as an oxygenate, higher alcohols, such as butanol, exhibit superior properties in some respects. Besides alcohols, glycerol derivatives such as glycerol tert-butyl ether (GTBE), among others, also have the potential to be used as gasoline oxygenates. This work provides a direct comparison, performed on a modified Waukesha CFR engine, of C1–C4 alcohols and the glycerol derivatives GTBE, solketal, and triacetin, all blended with a gasoline surrogate in different concentrations. The tests focused on how these oxygenated compounds affected the knocking behavior of the fuel blends, since it directly impacts engine efficiency. The test matrices comprised spark-timing sweeps at two different compression ratios, at stoichiometric conditions and constant engine speed. The results showed that, in general, the C1–C4 alcohols and the glycerol derivatives were effective in decreasing knock intensity. n-Butanol and solketal were the noteworthy exceptions, due to their demonstrated inferior knock-inhibiting abilities. On the other hand, isopropanol, isobutanol, and GTBE performed particularly well, indicating their potential to be used as gasoline oxygenates for future engines, as alternatives to ethanol.

Corrosion behavior and mechanism of NiCrAl–NiC abradable sealing coating system in NaCl solution

As an important component of aviation turbine engines, abradable sealing coatings have the function of protecting turbine blades and improving engine efficiency. However, Abradable Sealing Coating systems (ASCs) are often damaged by corrosion in their applications, which may cause safety accidents. This article uses atmospheric plasma spraying technology to prepare NiCrAl–NiC ASC system, which is divided into three layers with a porous structure on the top. In order to fully explore the corrosion behavior of NiCrAl–NiC ASC system, corrosion tests were conducted on the ASC system using immersion method. The corrosion potential of this coating system is −0.96V, and a low corrosion potential indicates that the coating is more prone to corrosion. On the other hand, its current density is 51.64 × 10−6 A cm−2, indicating a slower corrosion rate of the coating. After immersion for 600 h, the corrosive medium Penetrated into the interior of the coating, forming interlayer corrosion. The electrochemical impedance results showed that the corrosion process of the coating was divided into three stages, and the impedance fitting results were consistent with the changes in coating porosity during the immersion process. The corrosion products of the coating are oxygen-containing compounds of various metal elements, including Al2O3, Al (OH)3, NiO, Ni(OH)2, and Cr2O3. The porous, multi-layered, and multiphase characteristics of coatings result in their unique corrosion behavior.

An experimental apparatus for the study of high-temperature degradation and solid-deposit formation of lubricants.

When exposed to high surface temperatures, engine lubricating oils degrade and may form solid deposits, which cause operational issues and increase shutdown time and maintenance costs. Despite its being a common issue in engine operation, the information available on the mechanics of this phenomenon is still lacking, and the experimental data and conditions must be updated to match the improvements in both lubricant stability and engine efficiency. To this end, an experimental apparatus has been developed to study the mechanisms that lead to the degradation and deposit formation of lubricants at high temperatures. The apparatus is designed to operate at pressures up to 69 bar, surface temperatures up to 650 °C, oil bulk temperatures up to 550 °C, and flow rates of <14 mL/min. In this apparatus, the oil is cycled through a heated test section, and deposits accumulate on the heated surface. The time required for deposits to start accumulating under the test conditions is determined based on the recorded temperature traces, and collected oil and deposit samples may be analyzed to determine changes in composition over time due to high-temperature exposure. The removable test section can be modified to accommodate different geometries, surface materials, and flow paths to adapt the instrument to a range of potential research directions. This paper presents the technical details of the new apparatus and the steps taken to characterize the experimental conditions. In addition, sample data are provided to show the unique capabilities of the new instrument, and an Arrhenius plot for Castrol Perfecto X 32 in the surface temperature range of 445-475 °C is presented as a demonstration of its use for quantifying the coking delay time. The new instrument detailed herein is the first such device to demonstrate a reliable, lab-scale technique for studying lube oil coke formation and deposition at temperatures and pressures of interest to power generation gas turbines.

Efforts to Improve Engine Efficiency and Ensure Engine Safety

Efforts to Improve Engine Efficiency and Ensure Engine Safety

Wear behavior of novel abradable porous Yb2Si2O7-CaF2-PHB coatings fabricated by atmospheric plasma spraying

The abradable sealing coatings (ASCs) matched with ceramic matrix composites (CMCs) can improve engine efficiency and reduce fuel consumption. A study of plasma-sprayed porous Yb2Si2O7-20 vol% CaF2 with various contents of poly-p-hydroxybenzoate (PHB) as ASCs compatible with CMCs is reported. The microstructure and phase composition, Rockwell hardness, wear behaviors and abradability of the coatings were comparatively studied. The results show that the porosity increased and the hardness decreased as the PHB content was increased, and the coating containing 20 vol% PHB had a minimum hardness of about 65.2 HR45Y and a maximum porosity of about 39.2%. The friction coefficients and IDR values decreased, wear depth and volume wear rates of the coatings effectively improved with the increase of porosity. The wear mechanisms were analyzed based on the observation of the worn surfaces. This work might provide some guidance for the design and application of ASCs for CMCs.