Indicated Mean Effective Pressure Research Articles

Exploration of ultra-low carbon heavy-duty commercial vehicle technology: Liquid ammonia-diesel dual fuel high-pressure direct injection

Ammonia (NH3) has attracted substantial interest as a potential carbon-free fuel source for engine applications. The high-pressure ammonia direct injection is believed a way for higher efficiency. However, only a limited number of experimental studies have been conducted on direct-injection ammonia-fueled engines. In this study, a novel ammonia-diesel dual direct-injection compression-ignition engine was constructed and tested under high-load conditions. The results demonstrated that ammonia fuel combustion was advantageous in high-load situations, achieving a high carbon reduction of 75%. The indicated thermal efficiency (ITE) could be increased to 51.6% at an indicated mean effective pressure (IMEP) of 14 bar by employing a diesel pilot-injection strategy and increasing the pilot-injection ratio to 98%. Moreover, the diesel pilot-injection strategy at high load conditions also decreased unburned ammonia and nitrous oxide emissions. The lowest NH3 and N2O emissions were reduced to 2.1 g/kWh and 0.67 g/kWh. Under high-load conditions of IMEP = 16 bar, employing a diesel pilot-injection strategy increased AER to 73% while maintaining high efficiency. When AER was further increased to 84%, the ITE showed a noticeable decline, and unburned ammonia emissions increased accordingly.

Effects of structural parameters of active pre-chamber on the combustion process of methanol/gasoline TJI rotary engine

The application of Turbulent Jet Ignition (TJI) combustion mode in spark ignition engine can improve combustion efficiency and output power. This paper innovatively proposes the application of active pre-chamber (APC) in rotary engine (RE) to realize this mode. And blending a certain percentage of methanol in gasoline to achieve carbon reduction. A three-dimensional computational model of the APC-RE was developed, and the effects of three APC structural parameters including throat section diameter, throat section length and orifice diameter on the component flow and combustion characteristics were investigated. The results showed that the APC-RE exhibited higher sensitivity to the diameter of the throat section than the length variation under the fixed active fuel injection strategy. The low length or small diameter of the throat section causes insufficient energy in the APC jet, and too high values cause unstable combustion. The optimal APC volume is achieved at a throat length of 8 mm and a diameter of 6 mm, with the highest Indicated mean effective pressure (IMEP) and Indicated thermal efficiency (ITE). Next, The APC volume was fixed and the effect of jet orifice size on RE performance was discussed and the optimal size was determined 1.25 mm, which can further optimize the jet velocity and can continue to increase IMEP and ITE by 1.24 % and 1.46 % respectively.

Experimental investigation on ammonia combustion ignited by methanol-enriched active pre-chamber in an optical engine

To enhance the ignitability and burning rate of ammonia-fueled spark ignition engines, it is an effective way to adopt active pre-chamber (PC) ignition with high-reactivity fuel. Therefore, in this paper, the ammonia combustion characteristics using methanol-enriched active PC ignition were investigated, based on optical engine experiments with simultaneous in-cylinder flame imaging and pressure measurement. Results show that the overall combustion process is characterized by a three-stage heat release: (I) jet flame controlled combustion; (II) ammonia flame propagation; (III) post jet induced combustion. In stage I, methanol active PC jets with high-momentum and high-reactivity are discharged to ignite MC ammonia mixture, contributing to the first peak of heat release rate. In stage II, ammonia turbulent flame propagation dominates the combustion. In stage III, post jets induce the third peak of heat release rate. In this way, with a minimal methanol energy ratio (ER) of lower than 10 %, stable and fast ammonia combustion is achieved under stoichiometric (λMC = 1) and lean-burn (λMC = 1.2) condition, with cyclic variation of indicated mean effective pressure (IMEP) lower than 5 %, flame probability higher than 80 % and maximum global flame speed of about 4 m/s. A highest IEMP of 0.72 MPa and a peak indicated thermal efficiency (ηit) of 30 % is obtained at λMC = 1 and λMC = 1.2, respectively. However, at the rich limit of λMC = 0.9 and lean limit of λMC = 1.4, the quenching of jet flames leads to weak ignition and unstable combustion, which is identified by reduced flame probability distribution and increased cyclic variation of IMEP. In addition, to ensure the cyclic combustion stability, there is also an operating range of methanol ER. At λMC = 1.2, unstable ignition and deteriorated combustion occur below the lower limit of ER = 6 % and above the upper limit of ER = 17 %. This paper can provide data support and operation strategy for the combustion improvements of ammonia-methanol active jet ignition engines.

Combustion Management of Neat Dimethyl Ether Combustion for Enabling High Efficiency and Low NOx Production

Article Combustion Management of Neat Dimethyl Ether Combustion for Enabling High Efficiency and Low NOx Production Simon LeBlanc, Binghao Cong, Navjot Sandhu, Long Jin, Xiao Yu and Ming Zheng * Department of Mechanical, Automotive and Materials Engineering, University of Windsor, 401 Sunset Avenue, Windsor, ON N9B 3P4, Canada * Correspondence: mzheng@uwindsor.ca Received: 30 June 2024; Revised: 30 September 2024; Accepted: 10 October 2024; Published: 23 October 2024 Abstract: Modern compression ignition engines heavily rely on exhaust gas recirculation to reduce NOx emissions. Despite this, complex and expensive after-treatment systems are still necessary to comply with stringent emission regulations. Conventional diesel combustion operates on a robust and readily controllable mode through which the high-pressure fuel injection and combustion processes are intimately coupled. The heterogeneous nature of direct injection systems is liable to the NOx-soot trade-off inherent to diesel-fueled engines. Dimethyl ether (DME) presents a unique fuel that is reactive, volatile, and oxygenated, offering significant potential to address emission challenges with reduced reliance on aftertreatment systems. In this research, the combustion management of neat DME fuel was investigated using a high-pressure direct injection system. Principally, the suitability of single-shot fuel scheduling as a combustion management technique for DME under low NOx production was explored. The transient high-pressure injection behaviour of DME was characterized with an offline test bench. A single-cylinder research engine platform was employed to study DME combustion characteristics. A wide range of engine conditions was investigated, including injection pressures from 200 bar up to 880 bar and engine loads from 1 bar up to 17 bar indicated mean effective pressure (IMEP). The combustion management of DME as it relates to fuel injection and operating boundary conditions was emphasized throughout the work. To accomplish this, tests were conducted at direct comparison conditions to diesel operation. Most notably, the DME combustion process finished in a shorter period than diesel, albeit with a significantly longer injection duration. At most operating conditions, the soot emissions were below that of upcoming emission regulations without particulate filter exhaust treatment. Even under high engine load operation—17 bar IMEP—of neat DME, the NOx emissions could be readily contained via EGR management to 51 ppm engine-out NOx during which soot reached a maximum of 1.0 FSN. Such operating circumstances of high engine load and low oxygen availability (overall lambda of 1.2) exhibited a deterministic combustion timing control via injection timing while performing with low combustion noise (4.8 bar/°CA) and high burning efficiency (98.5%).

Effect of ethanol content, water injection, and compression ratio on combustion and detailed emissions in an SI-GDI engine

The transportation sector accounts for 29 % of the total greenhouse gas emissions produced in the US. Steadily tightening criteria emissions and fuel efficiency requirements have led to current research efforts evaluating multiple mixed strategies or extending beyond traditional engine architectures and fuels. Ethanol is used extensively as both a fuel additive and primary fuel replacement for gasoline. Modern engines utilizing boosting or high compression ratios require fuels such as ethanol that are more resistant to pre-ignition to operate efficiently at high load conditions. Water dilution has historically been used for knock reduction and some potential has been found for emissions and efficiency improvements. The studies on these topics, however, often focus on wide-open-throttle (WOT) conditions and neglect part load where engines normally operate. This investigation evaluates the combined effects of fuel ethanol content, compression ratio, and water dilution on the combustion and emissions characteristics A 2.4L 4-cylinder naturally aspirated (NA) gasoline direct injection (GDI) engine at part load conditions.The results indicated that the varied combinations of compression ratio and fuel ethanol content did not change the typical performance or emissions results expected for either parameter alone. Water dilution only significantly degraded stability at conditions with coefficient of variation (CoV) of indicated mean effective pressure (IMEP) values near or above 3 %. Water dilution at 10 % and 20 % W/F rations reduced average oxides of nitrogen (NOx) emissions by 20 % and 40 % respectively. The water dilution effect on unburned hydrocarbons (UHCs) was more mixed with flame ionization detector (FID) results showing mixed positive and negative effects for lower ethanol content fuels and up to a 20 % increase in UHC emissions with the high ethanol fuel (E85). Fourier transform infrared (FTIR) results agreed with the fuel blend UHC sensitivity reported with the FID. Ethanol emissions were found to increase by two to three times more for each level of water dilution than unburned gasoline emissions.

The performance of a spark ignition gasoline engine with hydrogen addition under low-load conditions

With continuously increasing populations and industrialization, more and more green consumers and stringent emission regulations promote low-carbon or zero-carbon alternative fuels in transportation sector. Hydrogen is considered carbon-free when produced using environmentally friendly methods, and could achieve zero carbon emission in the internal combustion engines. This study comprehensively explores the influences of the hydrogen addition on the performance of the gasoline spark ignition (SI) engine operated at low-load conditions. The experimental results showed that the abnormal combustion cycles of the test gasoline engine are greatly reduced with hydrogen enrichment. In addition, the coefficient of variation (COV) of the indicated mean effective pressure (IMEP) of the gasoline engine is 2.66 % under the 1500 rpm and 0.2 Mpa (brake mean effective pressure: BMEP) condition, while the COV of IMEP of the engine fuelled with gasoline and hydrogen is 2.34 % at the same condition. Furthermore, the knocking intensity of the gasoline engine is strengthened by adding hydrogen because the averaged maximum pressure rise rate (MPRR) of the gasoline SI engine is slightly increased. Besides, the indicated thermal efficiency (ITE) of the gasoline engine is increased 0.9 % and its maximum increase rate of the ITE is 4.27 % with hydrogen addition at the 1300 rpm and 0.2 MPa condition. Last, unburned HC, CO, and CO2 of the gasoline engine are reduced while NOx emissions increase with adding hydrogen due to high combustion temperature.

Effect on polytropic index, performance and emission of diesel engine using hydrogen as gaseous fuel with additive di-tert butyl peroxide

Diesel engines are commonly used due to its higher reliability and better fuel conversion efficiency. However, it produces exhaust emissions like carbon dioxide (CO2) and particulate matter (PM). Hydrogen gas is regarded as a clean fuel as it is free from carbon. The addition of hydrogen fuel enhances the burning rates and extends the flammability limits of fossil fuels, and therefore has the potential of reduced exhaust emission in diesel engines operating on dual fuel mode. This paper has investigated the effect of hydrogen addition to the performance and emissions of a single-cylinder diesel engine, working in dual fuel mode with additive di-tert butyl peroxide (DTBP). About 25% hydrogen was introduced into the cylinder on a mass basis via the engine intake manifold with the addition of additive di-tert butyl peroxide up to 5% in diesel fuel. In this experimental study, mean gas temperature, indicated mean effective pressure (IMEP), brake mean effective pressure (BMEP), polytropic index, and exhaust emissions were studied at medium (53%) and high (69%) load conditions. The indicated mean effective and brake mean effective pressure was 9.79 bar with a 3% addition of additive and 4.15 bar with the 5% addition of additive as compared with 8.71 bar and 4.11 bar diesel fuel operation. 16% hydrogen addition with 1% di-tert butyl peroxide, IMEP, and BMEP are 10.92 bar, and 4.14 bar respectively.

Optimization of direct-injection ammonia-diesel dual-fuel combustion under low load and higher ammonia energy ratios

Ammonia (NH3), as a potential zero-carbon fuel, has garnered significant attention for its application in compression ignition (CI) engines. Due to the low reactivity, ammonia is primarily used as dual fuel in CI engines. Therefore, the decarbonization potential is influenced by the ammonia energy ratio (AER). In this study, experimental research was conducted on expanding the AER at low load conditions in a direct-injection ammonia-diesel dual-fuel engine. The ammonia post-injection strategy was explored and significantly improved the suppression effect of high-concentration ammonia on diesel ignition, which could advance ignition timing and increase the peak heat release rate. As a result, coupled with intake heating, it expanded AER to 86 % at an indicated mean effective pressure (IMEP) of 4 bar. This strategy also increased the indicated thermal efficiency (ITE) by 8 % and significantly reduced unburned ammonia emissions. However, the combustion and emission performance was limited by the post-injection ammonia quantity and the injection timing of both diesel and ammonia, especially under high AER conditions.

Combustion characteristics and flame development of ammonia in an optical spark-ignition engine

To meet the ever-increasing serious challenges of global energy shortages and environmental pollution, it is urgent to apply alternative carbon-free fuels in the transportation field to reduce global carbon dioxide emissions. Ammonia is considered a prospective carbon-free fuel for engines due to its advantages in production, storage and transportation. The combustion and flame development characteristics of ammonia at different excess air ratios (λ) were researched in an optical spark ignition (SI) engine employing high-speed natural flame luminosity (NFL) imaging, OH* chemiluminescence imaging and flame spectra measurement. The combustion performance and flame development of ammonia were compared with methane. Results indicate that ammonia has the optimal combustion performance at λ = 0.9, with the most concentrated heat release, the highest power output and the best combustion stability. The peak natural flame luminosity intensity is highest at λ = 0.9, and the flame speed of 13.7 m/s is the fastest among testing cases, which results in the shortest ignition delay and combustion duration. OH* and NH2* spectra intensity of the ammonia flame were quantified and analyzed under different λ. The peak OH* intensity is highest at λ = 0.9, while the largest intensity of NH2* is obtained at the fuel-rich case (λ = 0.8). The maximum overall OH* chemiluminescence intensity at the same crank angles is obtained at λ = 0.9. Finally, despite the delayed spark timing, the combustion performance of methane presents higher indicated mean effective pressure (IMEP) and better combustion stability as well as faster flame propagation speed than ammonia at the same λ. In summary, ammonia shows the best combustion and flame development characteristics at λ = 0.9. The combustion performance of ammonia in SI mode is significantly worse than that of methane.

Controllability of Pre-Chamber Induced Homogeneous Charge Compression Ignition and Performance Comparison with Pre-Chamber Spark Ignition and Homogeneous Charge Compression Ignition

This paper presents an experimental and numerical evaluation of the pre-chamber induced HCCI combustion concept (PC-HCCI) in terms of engine performance, emissions, and controllability. In this concept, a spark-initiated combustion in the pre-chamber is utilized to trigger the kinetically controlled combustion of an ultra-lean mixture in the main combustion chamber. The experimental measurements were performed on a single-cylinder engine with a custom-made active pre-chamber. A high compression ratio of 17.5 was used, which limits the maximum achievable engine load due to high knocking tendency but enables both standard PCSI combustion (flame propagation) at very high dilution levels and HCCI combustion at reasonable intake temperatures. The analysis of combustion characteristics and the resulting performance is performed at indicated mean effective pressures (IMEPs) of 3.5 and 3.0 bars, and three different intake temperatures of 80 °C, 90 °C, and 100 °C. The variation in engine load was achieved by adjusting the excess air ratio in the main chamber. On each combination of intake temperature and engine load, a spark sweep and an injected PC fuel mass sweep were performed to obtain the highest indicated efficiency while satisfying the restrictions in terms of combustion stability and knock intensity. It was shown that, unlike in a conventional HCCI engine, the combustion phasing can be directly and reliably controlled by adjusting either spark timing or the reactivity of the pre-chamber mixture, ensuring adequate combustion stability and eliminating potential misfires. A similar indicated efficiency as with conventional HCCI combustion was obtained, while the NOx emissions, although slightly elevated, are still insignificant. Compared to PCSI combustion at the same engine load, a 4-percentage-point increase in indicated efficiency and two times lower NOx emissions were achieved. Compared to the most efficient PCSI operating point, it was 1 percentage point lower, indicating that efficiency was achieved, but the specific NOx emissions are reduced by approximately 70%. Most importantly, very similar performance was obtained with significant variations in intake temperature, proving the reliability and adaptability of this combustion concept.

Numerical investigation of the hydrogen-enriched ammonia-diesel RCCI combustion engine

Incorporating hydrogen into the fuel blend of ammonia/diesel in reactivity controlled compression combustion (RCCI) engines, while maintaining high indicated mean effective pressure (IMEP) and combustion efficiency (CE), presents a promising approach for mitigating nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), unburnt ammonia emissions and nitrous oxide (N2O) greenhouse gas (GHG)-a pressing challenge in the field. By supplementing ammonia/diesel combustion with hydrogen, potential issues related to incomplete combustion can be mitigated, along with a reduction in intake valve close temperature (TIVC). This study aims to assess the impact of hydrogen enrichment on combustion characteristics in RCCI engines utilizing ammonia and diesel as fuels, employing the kinetic mechanism of combustion reactions within Converge software. The effect of TIVC on key engine parameters, including in-cylinder pressure, heat release rate (HRR), CE, IMEP, and exhaust emissions, are analyzed by considering chemical reaction pathways. The findings reveal that introducing hydrogen into the ammonia /diesel RCCI combustion blend, leads to significant enhancements in CE and IMEP while simultaneously lowering emissions of CO, HC, unburnt ammonia, and N2O greenhouse gas (GHG). Specifically, when utilizing 80 % ammonia energy fraction (AEF) without hydrogen, minimum TIVC of 440 K is necessary to prevent incomplete combustion, increasing NOx emissions by approximately 20 g/kWh. However, by addition of 20 % hydrogen energy fraction (HEF) into the fuel mixture, the TIVC requirement drops to 380 K, thereby reducing NOx emissions to around 13 g/kWh, while maintaining consistent level of N2O GHG (2.7 g/kWh).

Effect of injection and ignition strategy on an ammonia direct injection–Hydrogen jet ignition (ADI-HJI) engine

High-efficiency, low-emission ammonia-hydrogen engines with low hydrogen energy share (XH2) help promote a carbon-neutral transition in heavy-duty, long-distance transportation. In this study, numerical investigations were carried out on a hydrogen jet ignition (HJI) ammonia engine to study the effects of ammonia port fuel injection (PFI) and ammonia direct injection (ADI) on the engine performance, including combustion and emission characteristics, at XH2 = 3 % with varied spark timing (ST). The results show that the ADI mode has higher volumetric efficiency, lower in-cylinder temperature, and lower heat transfer loss compared with the PFI mode, and more retarded injection can further increase the volumetric efficiency and reduce the temperature. ADI mode results in a more inhomogeneous fuel distribution and a lower local equivalence ratio, with hydrogen consumed earlier than ammonia, potentially resulting in more rapid early-stage combustion. ADI mode with multiple injections is more conducive to engine performance than single injection and can achieve the higher indicated mean effective pressure (IMEP) and indicated thermal efficiency (ITE) than PFI mode. By further optimizing ST, the ADI mode improves ITE by 2.8 % and reduces NO emission by 70 % compared with the PFI mode under acceptable NH3 and N2O emission conditions.

The impact of scavenging air state on the combustion and emission performance of marine two-stroke dual-fuel engine

The scavenging process significantly affects the combustion and emission performance of marine low-speed two-stroke dual-fuel engines. Optimizing scavenging air pressure and temperature can enhance the engine's combustion efficiency and emission control performance, thereby achieving more environmentally friendly and efficient operation of dual-fuel engines. This study focuses on marine low-speed two-stroke dual-fuel engines, analyzing the effects of scavenging air pressure (3.0 bar, 3.25 bar, 3.5 bar, and 3.75 bar) and scavenging air temperature (293 K, 303 K, and 313 K) on engine performance and emission products. The results indicate that scavenging air pressure has a greater impact on engine performance than scavenging air temperature. An increase in scavenging air pressure leads to higher thermal efficiency and power. As the scavenging air pressure increases from 3 to 3.75 bar, the indicated thermal efficiency (ITE) increases from 44.02 to 53.26%, and indicated mean effective pressure (IMEP) increases by approximately 0.35 MPa. Increased scavenging air pressure improves nitrogen oxide (NOx) and hydrocarbons (HC) emissions. For every 0.25 bar increase in scavenging air pressure, NOx emissions decrease by 3.53%, HC emissions decrease by 33.35%, while carbon dioxide (CO2) emissions increase by 0.71%. An increase in scavenging air temperature leads to lower ITE and IMEP. As the air temperature changes from 293 to 313 K, the ITE decreases by approximately 1%, and IMEP decreases by about 0.04 MPa. Increased scavenging air temperature improves CO2 emissions. For every 10 K increase in the air temperature, the CO2 emissions decrease by 0.02%, while NOx emissions increase by 4.84%, HC emissions increase by 34.39%. Therefore, controlling scavenging air pressure is more important than scavenging air temperature in the operational management of marine two-stroke engines. Higher power and lower NOx and HC emissions can be achieved by increasing the scavenging air pressure.

Optical study on the effect of ozone addition on a diesel/ammonia dual fuel engine with pilot injection

Influenced by the concept of carbon neutrality, ammonia is gaining widespread attention in the transport sector as a zero-carbon fuel. Diesel/ammonia dual fuel engines can achieve stable combustion of ammonia and reduce carbon emissions. To further enhance the low load combustion performance of a diesel/ammonia dual fuel engine, the effect of ozone addition on in-cylinder combustion and flame development was investigated based on an optical engine. Beyond that, ozone addition on pure diesel was also tested to understand the effect of ozone addition on diesel combustion enhancement in diesel/ammonia reactivity controlled compression ignition (RCCI) mode. The results show that the addition of ozone significantly advances the ignition phase, increases the flame area and brightness, and results in a growth in flame luminescence intensity along the radial length and closer to the center of the view field for diesel/ammonia RCCI combustion. In addition, chemical kinetic analysis shows that diesel/ammonia combustion requires higher ozone concentrations to overcome the inhibitory effect of ammonia to reach the upper limit of the promotional effect on the ignition phase and indicated mean effective pressure (IMEP), due to the large amount of OH consumed by ammonia compared to pure diesel. The promotional effect of added ozone on IMEP is similar for different pilot injection ratios (PIRs). At a low PIR and high ozone concentration, the diesel/ammonia RCCI engine achieves the highest IMEP, indicating that ozone addition combined with optimization of diesel injection parameters contributes to improve the performance of the diesel/ammonia RCCI engine at low loads.

Experimental study on the effects of pilot injection strategy on combustion and emission characteristics of ammonia/diesel dual fuel engine under low load

With the rise of the concept of carbon neutrality, carbon-free fuel ammonia has attracted widespread attention from internal combustion engine researchers. Ammonia/diesel dual fuel mode can effectively overcome the ignition difficulty of ammonia in the engine and is an effective measure to promote ammonia combustion. Based on a single-cylinder engine, diesel-ignited ammonia combustion experiments were conducted under conditions of 1200 rpm and 30 % load to systematically study the impact of ammonia energy ratio (AER), pilot injection ratio/timing on the combustion and emission characteristics of the ammonia/diesel dual fuel engine. This study finds that the pilot injection improves the upper limit of AER, reduces the cyclic coefficient of variation (COV). The rapid combustion fraction has been defined to understand the dual fuel combustion process. With the AER increases, the rapid combustion fraction of the single injection increases while the trends of the pilot injection strategy are the opposite. Both NOx emissions of the pilot injection strategies decrease while CO emissions increase. The reduction of NOx emissions may be caused by a decline in in-cylinder temperature. At a 35 % AER,Medium-low pilot injection ratios can increase the indicated mean effective pressure (IMEP), which is because as the pilot injection ratio exceeds 35 %, the growth rate in the effective expansion efficiency (EEE) is lower than that of heat transfer loss. When the pilot injection ratio is 35 %, the highest IMEP is achieved, CO and NOx emissions are cut down by 23 % and 20 %, respectively, compared to the single injection.

Effect of excess air ratio and ignition timing on the combustion and emission characteristics of the ammonia-hydrogen Wankel rotary engine

As a hydrogen carrier, ammonia can suppress knock and enhance thermal efficiency of the hydrogen-fueled Wankel rotary engine (WRE), and achieve zero carbon emissions. This research established a three-dimensional fluid dynamics model coupled with detailed reaction kinetics of ammonia and hydrogen and verified it based on experiments. Incorporating 10% volume fraction of ammonia into the hydrogen-fueled WRE eliminates knock and decreases the excess air ratio (λ) from 1.8 to 1.4, effectively improving the indicated mean effective pressure (IMEP). The results indicate that when λ exceeds 1.4, flame propagation accelerates with higher concentration of the mixture. This enhances peak in-cylinder pressure and heat release rate, but it results higher NOx emissions. As λ varies from 1.8 to 1.4, NOx emission levels rise by 47.4%. At λ ≤ 1.2, the rapid flame propagation leads to short combustion duration, diminishing the power output. At this stage, the NO formation is dominated by H radicals, and the NOx production reaches its minimum value at λ of 1.0. In summary, the ammonia-hydrogen WRE achieves optimal performance at λ of 1.4 and ignition timing of −5 °CA after top dead center, the indicated thermal efficiency reaches 36.9% and the IMEP achieves 0.683 MPa.

Influence of baffle height on the in-cylinder mixing and performance characteristics of a gasoline direct injection engine - a CFD investigation

In modern GDI engines, in-cylinder flows play a crucial role in the performance and emission characteristics. Adding baffles to the cylinder head is one way to enhance these flows, as baffle effectiveness is linked to its height. This study aims to investigate the influence of baffle height on the in-cylinder flows and its impact on the performance and emission characteristics of a four-stroke, four-valve, spray-guided GDI engine using computational fluid dynamics (CFD) analysis. The maximum baffle height is determined based on the geometry of the engine. Throughout the analysis, the engine operates at a constant speed of 1000 rev/min., under part-load conditions. From the results, the baffle heights of 2 mm and 3 mm significantly improve mixture stratification compared to the base engine. Furthermore, the indicated mean effective pressure (IMEP) for the engine with 2 mm and 3 mm baffle height improves by about 3% and 4%, respectively, compared to the base engine. In addition, with the increase in the baffle height, there is a significant reduction in the HC emissions with a marginal increase in NOX emissions.

Investigation on efficient and clean combustion pre-injection strategy of a diesel/methanol dual direct-injection marine engine under full load

Diesel ignition in-cylinder direct-injection methanol marine engine has shown enormous application potential due to its superior fuel economy and lower carbon emission. However, with high vaporization latent heat in methanol and increasingly strict emission regulations, new injection strategy urgently need to be studied to further improve the engine performance. To explore the feasibility of achieving high-efficiency and low-emission combustion by using pre-injection strategy in a diesel/methanol dual direct-injection marine engine, a numerical investigation is conducted to understand the combustion development, the mechanism of forming unregulated emissions, and the influence of methanol pre-injection timing (SOMIpre) and methanol pre-injection ratio (MPR) on engine performance. The results reveal that too early SOMIpre leads to a wet wall, while too late SOMIpre leads to insufficient mixing, thereby deteriorating combustion stability. The optimal fuel economy characterizing an indicated thermal efficiency (ITE) of 49.58% can be achieved when methanol is pre-injected at 35° crank angle (CA) before the top dead center (BTDC). As SOMIpre advances, the peak in-cylinder pressure (Pmax), peak heat release rate (HRRmax), and indicated mean effective pressure (IMEP) are decreased, along with increased soot, CO, and HC emissions, while the emissions of NOX and CO2 remain essentially unchanged. Additionally, the optimal methanol pre-injection strategy is yielded with an SOMIpre of 35°CA BTDC and an MPR of 15% when adopting a diesel injection timing (SODI) of 20°CA BTDC, increasing ITE by 19.9% and 2.7% and cutting CO2 emissions by 19.4% and 2.9% compared to the prototype (pure-diesel mode) and single-injection strategy. The results of this study provide new direction and data support for the research and development of efficient and clean combustion marine methanol engines.

Performance and Emission Analysis of Ethanol-Petrol Blends in Single-Cylinder Engines: A Sustainability Perspective

This study investigates the blending of ethanol and petrol in the Indian subcontinent, addressing the urgent need for sustainable fuel alternatives amid rising energy demands and environmental concerns. Ethanol, as a renewable biofuel, presents a viable option for enhancing the efficiency of internal combustion engines while reducing harmful emissions. Given the significant air pollution issues prevalent in urban areas of India, optimizing fuel blends can substantially improve engine performance and contribute to cleaner air. The primary objectives of this research include analyzing the impact of different ethanol-petrol blends on the performance of a single-cylinder petrol engine, assessing key performance metrics such as brake power, Indicated Mean Effective Pressure (IMEP), Brake Mean Effective Pressure (BMEP), and Brake Thermal Efficiency (BTHE). Emission analysis was conducted to measure hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO₂), oxygen (O₂), and nitrogen oxides (NOₓ) across various blends, quantifying the environmental impact of each. Grey Relation Analysis (GRA) was employed to rank the fuel blends based on their performance and emissions, helping identify the most effective blend for optimal engine operation. Additionally, the sustainability of ethanol blending as an alternative fuel solution in the Indian automotive sector was assessed. The study recorded key performance indicators and emissions using standardized techniques, with GRA calculating Grey relational coefficients to measure the degree of similarity between observed data and desired outcomes. This approach facilitated the ranking of blends, ultimately identifying the optimal ethanol-petrol blend. The findings revealed significant variations in both performance and emissions across different blends, indicating that ethanol blending holds substantial promise as a sustainable solution for the Indian automotive sector. These insights align with recent studies on the benefits of biofuels in enhancing engine performance and reducing emissions, providing valuable guidance for optimizing ethanol-petrol blends to improve sustainability in energy consumption.

Combustion Analysis of Active Pre-Chamber Design for Ultra-Lean Engine Operation

<div>In this article, the effects of mixture dilution using EGR or excessive air on adiabatic flame temperature, laminar flame speed, and minimum ignition energy are studied to illustrate the fundamental benefits of lean combustion. An ignition system developing a new active pre-chamber (APC) design was assessed, aimed at improving the indicated thermal efficiency (ITE) of a 1.5 L four-cylinder gasoline direct injection (GDI) engine. The engine combustion process was simulated with the SAGE detailed chemistry model within the CONVERGE CFD tool, assuming the primary reference fuel (PRF) to be a volumetric mixture of 93% iso-octane and 7% n-heptane. The effects of design parameters, such as APC volume, nozzle diameter, and nozzle orientations, on ITE were studied. It was found that the ignition jet velocity from the pre-chamber to the main chamber had a significant impact on the boundary heat losses and combustion phasing. The simulation showed that, under 16.46 compression ratio (CR) and 8.93 bar indicated mean effective pressure (IMEP) condition, it is possible to achieve the peak ITE of 49.85% with λ = 2.23.</div>