Compression Ignition Engine Combustion Research Articles

Use of butanol, pentanol and diesel in a compression ignition engine: A review

Using oxygenated alternative fuels in compression ignition (CI) engines is feasible for energy security problems and cli-mate change. Alcohols are regarded as alternative fuels for compression ignition engines because of their excellent physi-cochemical features, emission, and combustion characteristics. Research on alcohols and their additions has progressed significantly in recent years. Several researchers have examined the combined effect of higher alcohol with diesel and their impact and challenged that concentrations of higher alcohol reduce harmful particulate emissions in CI engines. This paper mainly focused on the performance and emissions properties of higher alcohols like butanol and pentanol. Alcohol has a low energy content, typically affecting engine brake-specific fuel consumption (BSFC). Low-temperature combustion (LTC) in compression ignition engines can lower NOx and smoke emissions, and improve the efficiency of the engine. LTC is done by combining higher alcohol with increased exhaust gas recirculation (EGR) rate and retarded fuel injection timing. The higher alcohol, along with the oxygen in the fuel reduces exhaust fumes, improves the air/fuel mixture by providing a longer ignition delay (ID), and can replace the fossil fuel like diesel (partially or whole) to allow efficient and clean combustion in CI engines. Finally, several significant findings and comments are provided regarding potential ave-nues for experimental research and future development. According to thorough analysis, bio-alcohols are considered to be a substitute fuel for CI engines.

The role of charge reactivity in ammonia/diesel dual fuel combustion in compression ignition engine

This study investigates the combustion characteristics of diesel–NH3–air mixture in compression ignition engine. Three different levels of ammonia energy ration (AER) were used for the investigation: 0 % AER (pure diesel), 30 % AER, and 50 % AER. Increasing AER leads to a rise in the initial peak of apparent heat release rate and promotes the prevalence of premixed combustion. Numerical simulations effectively capture the abrupt increase in maximum cylinder pressure (Pmax) from 7.4 to 7.9 MPa as AER increases from 0 to 30 %. Additionally, raising AER from 0 to 30 % extends a high-temperature region externally in the squish zone, attributed to the higher knocking propensity of the 30 % AER premixed charge. The ammonia-assisted diesel accomplish advanced diesel direct injection timing (SOID) at both heavy and medium load conditions. Under light load conditions, an increase in ITE is observed for AER = 50 % as SOID varies from −4 °CA to −10 °CA (ATDC). For medium and high load conditions, ITE monotonically increases with advancing SOID. The maximum ITE of 44.5 % is achieved at SOID = −12 °CA (ATDC) and AER = 30 %.

Influence of hydrogen-assisted combustion in compression ignition engines fueled with fuel blends of pine oil and waste cooking oil biodiesel using toroidal combustion chamber

In this research study, fuel blends of pine oil and waste cooking oil biodiesel (P/WCO) were examined for combustion analysis, engine performance, and emission characteristics tests. Improved combustion and engine performance were achieved using a toroidal re-entrant combustion chamber (TCC) and hydrogen supply as a dual fuel. The combustion behavior of fuel blends and hydrogen fuel was examined by varying the engine load at a constant speed. The results revealed that significant reduction in the specific fuel consumption for rich pine oil. Thus, a slightly lesser energy share from the fuel blends and a higher energy share from the hydrogen fuel was required for the engine to maintain the same brake power. Lower viscosity, higher flash point, and presence of oxygen in the pine oil enhance the combustion rate and brake thermal efficiency. Furthermore, hydrogen induction in the engine improves the flame velocity. A lesser crevice volume in the TCC can trap the unburnt fuel which can further increase the combustion efficiency. Thus, rich pine oil with the support of hydrogen induction in TCC causes advanced ignition, improved combustion, and more heat release during the combustion. The investigation results revealed that hydrogen induction increases the heat release rate and peak pressure by 7.4% and 2.67%, respectively. Similarly, the maximum of 24.55% increase in BTE and 18.22% reduction in BSFC was observed due to a constant 10 lpm hydrogen induction. Furthermore, hydrogen fuel significantly reduces the emissions such as CO, HC, CO2, and smoke. However, more NOx was generated due to more heat release rate during combustion. Thus, pine oil and waste cooking oil biodiesel blends with the support of hydrogen induction in TCC improve the engine performance and mitigate the toxic pollutants and can be a suitable alternative to diesel fuel.

The use of dimethyl ether (DME) solution in compression ignition engine

The development of compression ignition combustion engines is focused on meeting many challenges, mainly related to growing ecological requirements. Currently, however, due to technological barriers, meeting them is very difficult and requires the use of additional exhaust gas treatment systems. The use of injection of a diesel and gas solution seems to be very promising. The article presents the results of engine tests involving the use of a solution of diesel fuel and dimethyl ether. The tests were performed on a single-cylinder research engine equipped with a common rail fuel system. The obtained results suggest that the use of the solution has a positive effect on the process of creating the fuel-air mixture, resulting in a reduction in the concentration of HC and CO, while increasing the share of NOx, suggesting an improvement in the combustion process, as evidenced by the limiting injection dose.

Laboratory Tests of Electrical Parameters of the Start-Up Process of Single-Cylinder Diesel Engines

Despite continuous work on new power systems for vehicles, machines, and devices, the combustion engine is still the dominant system. The operation of the combustion engine is initiated during the starting process using starting devices. The most common starting system used is the electric starter. The starting process of an internal combustion engine depends on the following factors: the technical condition of the starting system, technical condition of the engine, battery charge level, lubricating properties, engine standstill time, engine and ambient temperature, type of fuel, etc. This article presents the results of laboratory tests of the electrical parameters of the starting process of a single-cylinder compression–ignition engine with variable fuel injection parameters and ambient temperature conditions. It was confirmed that for the increased fuel dose FD2, higher values of the measured electrical parameters (Imax, Pmax, and Pmed) were obtained compared to the series of tests with the nominal fuel dose. Knowledge of the values of the electrical parameters of the starting process is important not only for the user (vehicle driver, agricultural machinery operator, etc.), but above all for designers of modern starting systems for combustion engines and service personnel. The obtained results of testing the electrical parameters of the combustion engine during start-up may be helpful in designing new drive systems supported by a compression–ignition combustion engine.

Nozzle effects on spray combustion and emissions in compression ignition engines using waste cooking oil biodiesel: A computational fluid dynamics analysis at varying injection pressures

AbstractThis study investigates the spray combustion characteristics of waste cooking oil (WCO) in comparison between a swirl nozzle (SN) and a conventional nozzle (CN) of equal cross‐section. n‐Heptane, methyl decanoate, and methyl‐9‐decenoate were used as WCO substitutes in the simulation. The research primarily focuses on multiphase flow using the Lagrangian‐drop Eulerian‐fluid (LDEF) method, employing an equilibrium phase spray model (EP) for droplet behaviour analysis. The model's efficacy was validated through comparisons with experimental works by other engine researchers. At varying injection pressures, the study found that SN slightly reduced evaporative spray tip penetration but increased the cone angle compared to CN. This suggests early fuel jet disintegration and improved air entrainment due to SN. SN also showed a higher heat release rate and temperature, with soot reduction between 3.20 to 6.72% as injection pressure increased from 100 to 300 MPa. This indicates that SN achieves better air‐fuel mixture than CN. Further, the study discovered that the influence of SN becomes more significant as the rheological properties of WCO lessen under ultra‐high injection pressures.

Effect of fuel injection pressure on the performances of a CI engine using water-emulsified diesel (WED) as a fuel

BackgroundThe choice of energy sources is essential for sustainable development to combat different environmental issues caused by the consumption of fossil fuels. Though diesel engines are considered more efficient and reliable than other internal combustion engines, they emit different harmful pollutants which are detrimental to human health and the environment. Researchers are trying to find suitable alternative fuels for diesel engines with lower pollutant emissions and without much compromise in the efficiency of the engine. In this regard, water-emulsified diesel (WED) may be considered to be one of the most suitable alternative fuels. It is expected that the entire world will use electric vehicles in the long term. However, the complete replacement of IC engines in the near future is not feasible. In fact, different European countries have targeted to ban the use of diesel engine cars before the middle of the twenty-first century. Prior to that date, hybrid vehicles will be more popular and diesel engines will continue to play an important role. Hence, research involving improvements in diesel-operated IC engines is still relevant.MethodsAn experimental investigation was carried out using WED containing 10% water by volume as a fuel in a diesel engine at four different fuel injection pressures. The WED was prepared using an ultrasonicator.ResultsWith the increase of injection pressure, peak net heat release rate and in-cylinder pressure are found to have increased. Brake thermal efficiency is also found to have improved at higher injection pressure. The maximum efficiency was recorded when a WED at 210 bar of injection pressure is used, and it is about 3.3% higher than the maximum efficiency achieved when using normal diesel at the same pressure of fuel injection. At a higher load, neat brake-specific fuel consumption is found to be less compared to neat diesel, when only the amount of diesel contained in the emulsion as a fuel is considered. Maximum reduction in both NOx and smoke emission by using WED is recorded at 210 bar, and the average reductions are determined to be 32.6% and 51.9%, respectively.ConclusionsWED can be used as an alternative fuel for existing diesel engines without any retrofitting and with significant reduction in the emissions of pollutants compared to normal diesel fuel. It can also be concluded that at higher injection pressure, the combustion, performance and emission characteristics of compression ignition engines are improved when using emulsified diesel.

Methanol Combustion Characteristics in Compression Ignition Engines: A Critical Review

Methanol has been identified as a transition fuel for the decarbonisation of combustion-based industries, including automotive and maritime. This study aims to conduct a critical review of methanol combustion in compression ignition engines and analyse the reviewed studies’ results to quantify methanol use’s impact on engine performance and emissions characteristics. The diesel and diesel–methanol operation of these engines are comparatively assessed, demonstrating the trade-offs between the methanol fraction, the key engine performance parameters, including brake thermal efficiency, peak in-cylinder pressure, heat release rate, and temperature, as well as the carbon dioxide, carbon monoxide, nitrogen oxides, and particulate matter emissions. The types of the reviewed engines considering the main two combustion methods, namely premixed and diffusion combustion, are discussed. Research gaps are identified, and recommendations for future research directions to address existing challenges for the wider use of methanol as a marine fuel are provided. This comprehensive review provides insights supporting methanol engine operation, and it is expected to lead to further studies towards more efficient use of methanol-fueled marine engines.

Impact of Fuel Hydrogenation and Fuel Additives on Dual Biodiesel Mixture for Improving Combustion and Emission Characteristics in Compression Ignition Engine

Impact of Fuel Hydrogenation and Fuel Additives on Dual Biodiesel Mixture for Improving Combustion and Emission Characteristics in Compression Ignition Engine

Comparative evaluation of different operating parameters on performance, combustion, and emission characteristics in gasoline compression ignition (GCI) engine by using carbon neutrally biofuels

The stringent emission regulations and energy shortage put forward strict requirements for highly efficient and clean combustion for internal combustion engines. The gasoline compression ignition (GCI), which is a new advanced combustion concept, can obtain high efficiency and low emissions simultaneously without many modifications of standard diesel engines. However, little research has been carried out to synergistically optimize the operation parameters in a wide load range, especially fueled with the carbon neutrally biofuels. Therefore, in this paper, the effects of various operating parameters on engine performance, combustion, and emission characteristics of the gasoline compression ignition (GCI) strategy fueled with a blend of butanol and biodiesel were investigated. Specifically, the impact of butanol energy ratio, fuel direct injection timing, and exhaust gas recirculation (EGR) at the indicated mean effective pressure (IMEP) of 4, 8, and 14 bar and the butanol energy ratio of 60%, 70%, and 80% were examined. Result shown that the increase in butanol energy ratio decreased the fuel reactivity and worsen the combustion process, while the lower butanol energy was also disadvantage to the engine performance. The indicated thermal efficiency could achieve 48.5% when the butanol energy ratio was 70% at medium engine load. The earlier fuel injection timing was needed at low engine load, the EGR was necessary to inhibit the in-cylinder pressure rise at high engine load, in which the EGR rates of 20% at the IMEP of 8 bar and 30% at the IMEP of 14 bar could achieve the optimum engine performance, respectively. Meanwhile, the nitrogen oxides emissions shown a greatly decrease with the EGR rates increase, and it was less than 200 ppm at the IMEP of 14 bar when the EGR rates were 50%.

Effects of using a novel fuel vaporizer on partially premixed charge compression ignition (PPCCI) engine emissions, performance, and combustion characteristics

Environmental concerns of toxic emissions and depleting of fossil fuel supplies due to their excessive usage as the main source of energy have raised interests in the creation of novel combustion modes that result in reduction of combustion temperatures and produce low emissions. In comparison to conventional diesel engines, the partially pre-mixed charged compression ignition (PPCCI) combustion strategy has demonstrated its ability to significantly reduce emissions carbon monoxide (CO), unburned hydrocarbon (HC), oxides of nitrogen (NOX), carbon dioxide (CO2) and smoke opacity. In order to compare the results with those of conventional engines, the current experimental work’s objective is to investigate the combustion, performance, and exhaust emissions characteristics of PPCCI engines. A single-cylinder, air-cooled, 4-stroke, direct-injection diesel engine that had been modified to run in PPCCI mode was used for the experiments. An external mixture formation technique with a fuel vaporizer is added to create the homogeneous mixture for PPCCI combustion. After being heated to the point of vaporization, liquid diesel fuel vapor was mixed with some fresh air and then the mixture directed to the intake manifold, where it was mixed with the remaining fresh air to create an external homogenous mixture that filled the combustion chamber. The tests were conducted at different premixed ratios of diesel fuel proportions of 15%, 20%, and 30% in the intake port. However, the fuel vaporizer chamber was kept at fixed temperature of 100 °C, 105 °C, 110 °C, 115 °C, and 120 °C. The PPCCI engine results were compared with the conventional engine data. Results from the PCCI technique at various premixed ratios indicate a certain decrement for HC, CO, NOX, and smoke emissions, rising in BTE “brake thermal efficiency”. At 30% premixed ratio of the fuel vapour inducted at 110 °C in PCCI mode give the best results as the brake thermal efficiency raised from 28.8% for CDC mode to 34.2% for PCCI mode at full load. Additionally, NOX emissions decreased from 615 PPM to 550 PPM, HC emission decreased to 30 PPM, CO emission decreased from 0.09% to 0.06% and a decrease in smoke opacity from 38% to 19.3%.

Ozone-assisted combustion and emission control in RCCI engines: A comprehensive study

This paper presents an investigation into the combustion and emission characteristics of reactivity-controlled compression ignition (RCCI) engines using ozone seeding, which is known as one of the most highly oxidizing chemical species. The study aims to address challenges pertaining to combustion control and emissions deterioration. Therefore, the current work investigates the RCCI mode of operation in a single-cylinder diesel engine with intake air that has been seeded with ozone by introducing conventional diesel fuel as a high-reactivity fuel using a high-pressure direct injection method and iso-octane as a low reactivity fuel using a low-pressure port injection method. In the experimental study, different ozone concentrations up to 300 ppm and three different energy-based premixed ratios of low reactivity fuel from 0% to 45% with a 15% rise rate were examined under various engine loads and constant engine speed. The methodology used in this research provided for simultaneous decreases in unburned hydrocarbon (HC) emissions and smoke opacity for RCCI engines. According to the experimental findings, simultaneous utilization of RCCI mode and ozone seeding led to a decrease of up to 36% in HC emissions and a reduction of up to 98.7% in smoke opacity. Moreover, nitrogen oxides (NOx) emissions were reduced by up to 39.5% at 20% engine load, whereas carbon monoxide (CO) emissions exhibited a decrease of up to 46% at 60% load. The RCCI mode also yields significant reductions in pollutant emissions and notable increases in brake thermal efficiency (BTE) when compared to the conventional diesel mode (CDM). In conclusion, this experimental study presents a promising solution for addressing emissions deterioration in RCCI engines while simultaneously achieving reductions in pollutant emissions.

Enhancing Performance and Emission Characteristics of Biodiesel-Operated Compression Ignition Engines through Low Heat Rejection Mode and Antioxidant Additives: A Review.

Depending on the heat content and compression ignition (CI) engine combustion, biodiesel is a viable substitute fuel. Biodiesel is an oxygenated, safe, sulfur-free, biodegradable, and renewable fuel. It may be utilized in CI engines in any combination with diesel fuel without requiring the engine to be significantly modified. Many research studies have been made with several biodiesels as diesel substitutes, including Pongamia pinnata, Jatropha curcas, Mangifera indica, and Madhuca longifolia. The topic of the current review is the potential of renewable fuels to outperform diesel fuel in terms of performance, combustion, and emission characteristics. In the present study, CI engines are fueled with biodiesels made from Man. indica, Mad. longifolia, and pongamia seed oil. Adopting low heat rejection (LHR) mode CI engines and adding an antioxidant agent in addition to the biodiesel blends may resolve the issue of these biodiesels' poorer performance and increased NO emission. Both these additions may provide positive approaches in both performance and emission.

Experimental Investigation of Compression Ignition Engine Combustion, Performance, and Emission Characteristics of Ternary Blends with Higher Alcohols (1-Heptanol and n-Octanol)

Concerns about the depletion of petroleum reserves and rising pollution led researchers to search for alternate and environmentally compatible fuels for compression ignition engines. As an excellent alternative fuel additive to biodiesel–diesel blends, higher alcohol exhibits outstanding fuel properties (such as high energy content and cetane number) and can operate in diesel engines without requiring engine changes. This study focuses on investigating the ternary blends comprising higher alcohols, namely 1-heptanol and n-octanol, in hybrid biodiesel (animal fat oil–rice bran oil–cottonseed oil) and diesel on compression ignition engine characteristics. The performance, combustion, and emissions of a diesel engine fuelled with mono (D100), binary (B20), and ternary fuel blends (B20H10, B20H20, B20O10, and B20O20) were analysed at a constant engine speed of 1500 rpm. The test fuels met the American Society for Testing and Materials standards for fuel properties and exhibited stable behaviour during testing. Experimental results showed that at 100% load, the least brake-specific fuel consumptions for diesel fuel, B20, B20H10, B20H20, B20O10, and B20O20 were 254.1 g/kWh, 302.14 g/kWh, 281.25 g/kWh, 310.94 g/kWh, 292.8 g/kWh, and 313.80 g/kWh, respectively. Meanwhile, the maximum brake thermal efficiency values were obtained as 38.65%, 37.01%, 37.76%, 36.84%, 37.12%, and 36.38%, respectively. At 100% load, the peak heat release rates for diesel, B20, B20H10, B20H20, B20O10, and B20O20 were found to be 64.65 J/deg, 59.07 J/deg, 62.34 J/deg, 56.12 J/deg, 57.95 J/deg, and 51.9 J/deg, respectively. The addition of 1-heptanol and n-octanol as oxygenated additives into the ternary blend resulted in decreased carbon monoxide and unburned hydrocarbon emissions while increasing carbon dioxide and nitrous oxide emissions compared to diesel fuel. Overall, the study concludes that ternary blends with 1-heptanol and n-octanol as additives improve performance and combustion behaviour and reduce exhaust emissions compared to binary blends.

Detailed assessment of exhaust emissions in a diesel engine running with low-carbon fuels via FTIR spectroscopy

Low-carbon fuels have been proposed as alternatives that can help with the transition to a sustainable and decarbonized transport sector. This study examines the potential of four different fuel blends with different renewable content to reduce pollutant emissions by evaluating both regulated and unregulated emissions produced by their combustion in a light-duty compression ignition engine. The study distinguishes between two measurement conditions: drop-in and optimized calibration. The drop-in calibration represents the operation of low-carbon fuels using baseline injection settings, while the optimized calibration involves a specific approach to reduce nitrogen oxide emissions. Unregulated emissions were measured using a Fourier Transform Infrared analyzer, which recorded various substances, including aldehydes (acetaldehyde, formaldehyde), saturated hydrocarbons (ethylene, propylene, 1,3 butadiene, and isobutylene), unsaturated hydrocarbons (methane and ethane), aromatics (benzene and toluene), and the greenhouse gas nitrous oxide (N2O). Results indicated that aldehyde production is not affected at low-load operation for fuels with higher oxygen content, but instead, the use of diesel from vegetable origin in the fuel blend could lead to slight increases in this species. On the other hand, the production of saturated hydrocarbons was impacted by the cylinder temperature and combustion duration, being the oxygenated fuels with longer combustion durations at low-load, which reported reductions, but at mid-load, this effect is mitigated. In addition, the production of aromatics and unsaturated hydrocarbon emissions were assessed as soot precursors. The production rate of these species was higher when the calibration was applied due to the reductions in NOx and increases in soot emissions. Lastly, the results of N2O emissions showed slight decreases in the combustion of oxygenated fuels when using the drop-in calibration, but these emissions returned to similar diesel levels when applying the optimized calibration. Overall, the results of the investigation show the potential of these LCFs to meet the regulations but also not sacrificing the emissions performance of unregulated species.

Simultaneous prediction of CO2, CO, and NOx emissions of biodiesel-hydrogen blend combustion in compression ignition engines by supervised machine learning tools

This study mathematically inspects the effects of engine speed/load and biodiesel–hydrogen fuel blend composition on CO2, CO, and NOx emissions. Since this modeling task requires a basic knowledge of mechanics, chemistry, and combustion, the literature suggests no approach to anticipate these emissions. This multi-input and multi-output (MIMO) problem is so complex that can only be simulated by special types of machine-learning tools. Consequently, this study utilizes the multi-output least-squares support vector regression (MLS-SVR) and two efficient artificial neural networks (cascade feedforward and multilayer perceptron) to handle this complicated MIMO regression. These intelligent models are constructed and tested using 307 × 3 experimental emissions related to the combustion of different biodiesel–hydrogen blends at various engine speeds and loads. Extensive numerical analyses and ranking tests are conducted to confirm that MLS-SVR is the best approach to simultaneously predict the actual CO2, CO, and NOx emissions with the mean absolute relative error of 2.75%, 7.00%, and 2.62%, and regression coefficient of 0.9966, 0.9947, and 0.9979, respectively. The applicability domain inspection approves that only seven emission measurements may be problematic samples and all other 300 samples are reliable.

Sustainable nano-added biofuel production from borassus flabellifer oil for conventional internal combustion engines

The source of biodiesel production is significant as the demand for diesel is very high. Sustainable fuel development is the prime aim of meeting the demand. Drought-tolerant trees are widely available and can cultivate more to increase the feedstock capacity. Hence, this experimental research investigates the potential for deriving an alternative fuel from borassus flabellifer. Accordingly, this research employed biodiesel production from borassus flabellifer oil through the transesterification technique with methanol at 65 °C of temperature for 3 h with 300 rpm of magnetic stirrer speed. The blends by volume of 20% biodiesel of borassus flabellifer (20BOPP) and 80% of diesel (80D) were used to create the Biodiesel of borassus flabellifer blend (20BOPP+80D). Then it is enhanced by mixing 100 ppm of aluminium oxide nanoparticles (AONP) in that fuel to produce the nano-fuel of 20BOPP+80D + AONP. The base fuel (20BOPP) is enhanced by preparing a new blend of 20% ethanol (20 E) and 60% diesel added with 20BOPP to produce 20BOPP+20E+60D and then the new class of fuel enhanced by AONP to produce 20BOPP+20E+60D + AONP. The nano-fuel was prepared with the help of an ultrasonicator. The prepared blends and conventional diesel fuel were tested at varying engine loads, and the results revealed that the enhanced nonfuel of 20BOPP+20E+60D + AONP produced equivalent brake thermal efficiency (BTE) of 31.94% like diesel fuel, reducing the emission nitrogen oxides (NOx) by 29.2% and emission of Carbon Monoxide (CO) emission by 11.4% to pure diesel fuel. The enhanced nano-fuel of 20BOPP+20E+60D + AONP reduced smoke opacity by 35.3% more than pure diesel. Hence the mixing of both alcohol and nanoparticles in the biodiesel blend produces better results at maximum load conditions than their performance mixing individually in the biodiesel blend due to the alcohol's higher volatility and nanoparticles catalytic reaction during combustion in the Direct-Injection Compression Ignition (DICI) engine due to the alcohol's higher volatility and nanoparticles catalytic reaction during combustion stage.

Simulations of ammonia spray evaporation, cooling, mixture formation and combustion in a direct injection compression ignition engine

This study investigates the novel approach of direct liquid ammonia injection into the combustion chamber of a compression ignition engine. Unlike traditional gaseous ammonia port injection, this method shows promise in reducing ammonia slip and emissions. To simulate and analyze the behavior of the liquid ammonia spray, we employed numerical models based on existing literature on flashing and non-flashing spray simulations, as well as recent experimental studies on ammonia spray characteristics using a gasoline direct injection (GDI) injector. Our approach utilized a Lagrangian discrete phase modelling technique to perform a series of three-dimensional computational fluid dynamics (CFD) simulations. The primary objectives of this research were to evaluate the evaporation process of ammonia and its cooling effect, as well as to gain insights into mixture formation within the engine cylinder under different operating conditions. The simulations encompassed the entire engine cycle, considering a multi-hole GDI ammonia spray in conjunction with pilot n-heptane, a diesel surrogate, in equal proportions on an energy basis. Three distinct injection timings for ammonia were examined, leading to varying thermodynamic conditions within the combustion chamber during each spray formation. Consequently, different modelling parameters and initial conditions were necessary to accurately replicate the spray behavior. To address this, we proposed a systematic procedure for assigning pre-defined spray angles. The non-reacting, evaporating spray simulations yielded valuable insights into the mixture formation process, which guided our analysis. Finally, reacting conditions were considered to evaluate engine performance and resulting exhaust gas emissions. This study provides a comprehensive overview of critical aspects related to direct ammonia injection in internal combustion engine (ICE) systems. Moreover, it uncovers performance trends that can serve as a foundation for future investigations in this field.

Experimental and numerical investigation of an innovative complex piston with enhanced free spray length for the heavy-duty engine applications

The combustion and emission formation process in heavy-duty compression ignition engines are strongly influenced by the design of the piston bowl, the cylinder charge motion and the performance of the injection system. This paper proposes an innovative complex piston bowl design approach called as ’flower piston’ to improve the combustion process. It can be manufactured using the conventional machining approaches without use of still expensive additive manufacturing techniques. The flower piston features a scooped cavity with an intention of increasing the free fuel spray penetration. The potential of this innovative flower piston is evaluated using a validated 3D CFD model and compared with the results of single cylinder engine experiments at operating points with minimum fuel consumption. The results of the experimental investigations with the flower piston show an improvement in thermal efficiency in comparison to the conventional piston by up to 0.5%. This is due to a faster initial heat release and increased high pressure cycle work. However, the smoke emissions increased threefold due to fuel entrapment into the flower cavities, leading to formation of fuel-rich pockets. Also, the wall heat losses increased twofold with an increase in NOx raw emissions. With increased spray targeting angle, there was a drastic reduction in smoke emissions and an additional improvement in the thermal efficiency.

Parametric evaluation of neat methanol combustion in a light-duty compression ignition engine

Methanol is currently considered a promising alternative fuel for energy de-fossilization due to its simplicity and adequacy for renewable production. This study investigates the feasibility of using neat methanol in high-efficiency compression ignition engines, with a focus on its potential to reduce CO2 emissions compared to conventional diesel. However, achieving efficient combustion of neat methanol in compression ignition engines presents challenges due to its low ignition capability, requiring higher compression ratios, intake temperatures, and pressures than diesel for autoignition. Furthermore, the high latent heat of vaporization contributes to significant cycle-to-cycle combustion variability. This work evaluates the combustion characteristics of neat methanol in a light-duty multi-cylinder compression ignition engine with a 19:1 compression ratio, examining its suitability for commercial applications. Performance indicators such as engine efficiency, fuel consumption, and engine-out pollutant emissions are assessed. The findings contribute to advancing research and implementation of methanol fuel as an energy source for internal combustion engine vehicles, addressing both the advantages of the fuel and the challenges that need to be overcome, particularly with respect to its low auto-ignition characteristics. Notably, despite methanol's lower energy density compared to diesel, the achieved combustion efficiency is comparable, with remarkable improvements in NOx and soot emissions trade-off.The study reveals that neat methanol combustion poses difficulties, especially at low loads, speeds, and during engine startup, due to its high ignition energy requirement and long ignition delay. Even with modifications such as increased compression ratio, and the addition of intake heaters and glow plugs, sustaining combustion at low load conditions remains a challenge. However, once the engine is warmed up, methanol combustion can be sustained at medium to high loads without additional heating accessories, although the use of such accessories improves combustion stability.