Combustion Characteristics Of Engine Research Articles

Impact of produced oxyhydrogen gas (HHO) from dry cell electrolyzer on spark ignition engine characteristics

In the current study, an onboard dry cell electrolyzer was built to produce an oxyhydrogen (HHO) flow rate of 0.5 L/min by water electrolysis. The objective is to show the impact of oxyhydrogen introduction on engine exhaust gases, combustion characteristics, and engine performance related to gasoline. The experiments were carried out in a petrol engine at a fixed engine speed of 3000 rpm and variable engine loading. When comparing HHO gasoline dual fuel to standard gasoline fuel, the maximum improvements in volumetric efficiency, thermal efficiency and air-fuel ratio were determined as 7.5%, 8% and 11%, respectively. In the case of HHO addition, the highest reductions in specific fuel consumption and exhaust gas temperature were 9% and 6.5%, respectively, compared with conventional gasoline fuel. The highest reduction in CO, HC, NOx, and CO2 concentrations was observed as 18%, 9%, 15%, and 11%, respectively, for HHO-gasoline dual-fuel mode compared to gasoline fuel. The peak cylinder pressure and HRR improvements were 1.5% and 4.5%, respectively, at 100% engine load. Oxyhydrogen gas is highly recommended as a substitute fuel since it significantly enhances engine performance and combustion characteristics as well as reducing exhaust pollutants.

Experimental and simulation study of methanol/coal-to-liquid (CTL) reactivity and combustion characteristics of diesel engines in RCCI mode

An experimental and simulation study of the RCCI combustion mode of coal-based fuels (methanol prepared from coke oven gas/coal-to-liquid, Methanol/CTL)) was carried out on a modified dual-fuel compression ignition (CI) engine. The mechanism by which Methanol/CTL, which has a significant difference in reactivity, promotes engine combustion and thermal efficiency is revealed. The results show that with the increasing load (i.e., load recovery ratio (LRR)) supplied by methanol, the reactivity gradient inside the cylinder increased from 28% to 451%, and the area of the ignition region was rapidly enlarged, and the reactivity of the ignition region increased. The HC and CO emissions increase by 1350% and 6866%, while the soot and NOX are reduced by a maximum of 25% and 15%. The reactivity of the ignition region increased by 8% to 26 %. Diffusion combustion forms a strong linear correlation with reactivity, with a maximum reduction of about 30 times in the premixed-to-diffusion combustion ratio. Concentration of the exothermic centre towards the top-dead-centre (TDC) is increased by a maximum of 18%, with an increase in the coefficient of variability (COV) by a maximum of 90%, indicative thermal efficiency (ITE) by a maximum of 22% and brake thermal efficiency (BTE) by a maximum of 17%. The LRR does not exceed 50% while the engine maintains stable operation and 30% while maintaining power and fuel economy.

Effects of E-diesel on the combustion characteristics of a diesel engine operating at different boost pressures

Effects of E-diesel on the combustion characteristics of a diesel engine operating at different boost pressures

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.

Simulation study of N2/Ar dilution gas to improve thermal efficiency and reduce NOX emissions in hydrogen engines

Although N2 dilution is effective in reducing NOX emissions in hydrogen engines, it decreases thermal efficiency. Utilizing Ar with N2 as a dilution gas can improve thermal efficiency while reducing NOX emissions. However, the specific effects and mechanisms of the mixed dilution of Ar and N2 on the combustion and emission characteristics of hydrogen engines remain uncertain. This study examined the influence of Ar and N2 on the combustion and NOX emissions by adding Ar and N2 to the intake gas at various dilution rates. The examined cases were as follows: Case 1 (N2 = 100%), case 2 (N2:Ar = 80%:20%), case 3 (N2: Ar = 50%:50%), case 4 (N2:Ar = 20%:80%), and case 5 (Ar = 100%). The findings indicate that increasing the N2 ratio in the dilution significantly reduces NOX emissions, but it also reduces the combustion rate. In contrast, increasing the Ar proportion enhances combustion, resulting in higher peak values of the in-cylinder pressure, temperature, and heat release rate. In case 1 (N2 = 100%), the NOX emissions decreased from 255 to 3 ppm when the dilution rate increased from 5% to 20%. However, this also caused a significant decrease in the thermal efficiency from 44.4% to 22%. This limitation can be mitigated by appropriately increasing the proportion of Ar. Optimal results, with lower NOX emissions (250–500 ppm) and higher thermal efficiency (47.6%–49.3%), were achieved with a dilution rate of 17%–27% and an Ar proportion of 80%–90%.

Evaluation of Hydrogen Addition on Combustion and Emission Characteristics of Dual-Fuel Diesel Engines with Different Compression Ratios

In this paper, a computational fluid dynamics (CFD) model was established and verified on the basis of experimental results, and then the effect of hydrogenation addition on combustion and emission characteristics of a diesel–hydrogen dual-fuel engine fueled with hydrogenation addition (0%, 5%, and 10%) under different hydrogenation energy shares (HESs) and compression ratios (CRs) were investigated using CONVERGE3.0 software. And, this work assumed that the hydrogen and air were premixed uniformly. The correctness of the simulation model was verified by experimental data. The values of HES are in the range of 0%, 5%, 10%, and 15%. And, the values of CR are in the range of 14, 16, 18, and 20. The results of this study showed that the addition of hydrogen to diesel fuel has a significant effect on the combustion characteristics and the emission characteristics of diesel engines. When the HES was 15%, the in-cylinder pressure increased by 10.54%. The in-cylinder temperature increased by 15.11%. When the CR was 20, the in-cylinder pressure and the in-cylinder temperature increased by 66.10% and 13.09%, respectively. In all cases, HC, CO, CO2, and soot emissions decreased as the HES increased. But, NOx emission increased.

Emission and in-cylinder combustion characteristics of a spark ignition engine operated on binary mixtures of gas and liquid fuels

In this study, three different gas fuels such as hydrogen, propane, methane and six different liquid fuels such as, benzene, gasoline, toluene, hexane, methanol and ethanol have been combined and combustion characteristics have been simulated for a spark ignition engine (SIE). Variation of in-cylinder temperature, in-cylinder pressure, CO, CO2 and NO has been investigated. The gas fuel ratios in the mixtures were changed between 0 and 100% by mass. It was investigated that how the addition of gaseous fuels to liquid fuels at different ratios affects the combustion characteristics and emission formation. The gas fuel ratios considerably affected emission and combustion specifications of the engine. Increasing liquefied gas fuel ratio in the mixture leads to decrement in the temperature of charge. The maximum pressure first increases with increasing gas fuel ratio and then start to minimize after maximum pressure. The maximum peak pressure values are observed at 50% gasoline and 50% methane, 75% gasoline and 25% propane, 50% gasoline-50% hydrogen as 48.1 bar, 46 bar and 62.4 bar for different gas fuel mixtures. The minimum peak pressure value is displayed at 100% methanol as 44.06 bar. The maximum temperature value is observed at 100% benzene as 2582 K and its minimum value seems at 100% hydrogen as 2059 K. The maximum mass fractions of CO, CO2, NO are observed at 100% benzene as 0.0271, 0.161, 0.0076, the minimum mass fraction of CO2 is observed at 100% methane as 0.095. The minimum mass fraction of CO is observed at 100% methanol as 0.01243. The minimum mass fraction of NO is observed at 100% hydrogen as 0.00085. The fuels are ranked using a multi-criteria decision-making algorithm called AHP after evaluating the values of all performance criteria and their respective sub-criteria, including in-cylinder pressure, in-cylinder temperature, NO, CO2 and CO to get preference rank between fuels.

Combustion characteristics of a dual-mode ramjet engine with a supersonic aerodynamic ramp injector

The combustion characteristics of a liquid-hydrocarbon-fueled dual-mode ramjet combustor with a new injector, including a cavity-type flame holder, were investigated under inflow conditions of M 1.8, total pressure of 590 kPa, and total temperature of 930 K. The newly proposed injector uses various injection methods, such as an aerodynamic ramp, pre-mixing chamber, barbotage gas, and supersonic nozzle. The aerodynamic ramp injection method consists of four injectors with inclination angles of 40° and 80° and toe-in angles of 30° and 60°. This was adopted to increase the penetration height of the fuel while minimizing the total pressure loss. A pre-mixing chamber with a barbotage gas injection device was employed to enhance atomization and fuel–air mixing. In addition, a contoured Mach 3 supersonic nozzle was used to obtain a higher momentum through acceleration. For performance comparison, a combustor with a pre-mixing chamber and barbotage gas was used in the same manner, but injected by a cylindrical nozzle with a 15-degree of transverse angle. The ignition was initiated by a torch ignitor installed on the cavity floor with hydrogen pilot fuel. Once combustion stabilized, only the main liquid fuel was supplied. The Mach number was calculated using quasi-one-dimensional analysis based on the measured wall pressures and inlet conditions. The results showed that the model combustor with two types of injectors operated in the ramjet mode, which was subsonic near the flame holder and supersonic at the exit of the combustor. At the combustor outlet, the total pressure according to the equivalence ratio of 0.25 to 0.56, the newly proposed injector case showed a higher pressure level, steep increase, and more uniform pressure distribution than the baseline injector from the measurement result of the pitot pressure rake at the combustor exit.

Impact of hydrogen direct injection on engine combustion and emissions in a GDI engine

The combustion and emission characteristics of a hydrogen engine were investigated through experimental analysis using a GDI engine. To enable hydrogen in-cylinder direct injection, a specialized hydrogen gas injector was employed. A comparative analysis of the combustion performance between gasoline and hydrogen fuels in a spark-ignited engine was conducted. Additionally, the study experimentally explored the thermal efficiency and emission reduction potential of hydrogen engines in lean combustion modes. The results indicated a significant improvement in the combustion rate when hydrogen fuel was utilized in the spark-ignited engine. However, the effective thermal efficiency was found to be lower than that of gasoline fuel due to the delayed MBF50 under stoichiometric conditions. Furthermore, when compared to gasoline fuel, the reduction of CO and THC emissions was accompanied by an increase in NOx emissions. Nevertheless, optimizing the air dilution ratio in hydrogen engines led to an improvement in the effective thermal efficiency. Specifically, under medium load conditions, a Lambda value of 2.7 resulted in an effective thermal efficiency of 43.5%. Additionally, under ultra-lean conditions (Lambda > 2.3), NOx emissions could be reduced to below 50 ppm, reaching as low as 44 ppm. This study highlights the potential of improving combustion efficiency and reducing emissions by utilizing hydrogen fuel, particularly in lean combustion modes. It contributes to the continuous development of hydrogen engine technology and promotes the implementation of cleaner and more efficient energy solutions.

Study on combustion and emission characteristics of a micro‐rotary cam internal combustion engine

AbstractIn this article, the construction principle of rotary engine and sliding vane internal combustion engine is carefully analyzed, and the concept of micro‐rotary cam internal combustion engine is proposed by integrating and innovating on them. Overall design, theoretical analysis, and model making of miniature rotary cam internal combustion engine and its supporting system. The effects of different air intake modes and different ignition advance angles on the combustion and emission characteristics of internal combustion engines were studied. Through the study of the flow field, combustion and emission characteristics of small rotating internal combustion engines, it is found that the intake form has a great influence on the cylinder smoothness of rotating internal combustion engines. The vortex formed by the end cover inlet air in the middle of the combustion chamber can fully mix the fuel and air in the cylinder, and the mixture is evenly distributed in the combustion chamber to effectively promote the spread of flame. Compared with the surrounding air intake structure, the heat release should be increased by 4.3%, and the total amount of HC and CO generated was 26.8% and 15.7% less, respectively. By studying the turbulent kinetic energy, combustion heat release, peak temperature and pressure in the cylinder, fuel consumption rate and emission characteristics of small rotary internal combustion engine, it is found that when the ignition advance angle of the small rotating internal combustion engine is 5°, the peak pressure in the cylinder is increased by 2.3% compared with other schemes, the fuel consumption rate is high, and the combustion is more complete. In addition, in terms of emission characteristics, the amount of CO and HC generated when the ignition advance angle is 5° are reduced by 35% and 35.3%, respectively.

Effects of water direct injection on a combustion phase and performance of six-stroke gasoline homogeneous charge compression ignition engine

An experimental study was conducted to examine how direct water injection (WI) can optimize the combustion phases of a six-stroke gasoline homogenous charge compression ignition (HCCI) engine. With six-stroke HCCI combustion, the limitations of four-stroke HCCI combustion under high loads and the stability of combustion under low loads can be resolved by adding additional compression and expansion stroke. Previous six-stroke HCCI combustion research suggested that the time loss could be reduced by delaying the combustion phase to the top dead center (TDC) with additional cooling. Thus, in this study, the effects of WI on the overall pressure curve, as well as the first and second combustion phases, were studied from a thermal and chemical kinetics perspective. The performance, thermal efficiency, and pressure rise rate were also examined. It was found that WI retarded the first and second combustion. The first and second combustion phases were located after and before TDC, respectively, resulting in a decrease in the first gross mean effective pressure (GMEP) (180–540 CA) and an increase in the second GMEP (540–900 CA). Because the increase of second GMEP was dominant, the indicated thermal efficiency also monotonically increased (2.7–3.5%p). In addition, the maximum pressure rise rate decreased by 23.1% to 65.2%. Thus, the WI can be used to control the combustion characteristics of six-stroke gasoline HCCI engine.

Experimental study on the effect of injection strategies on the combustion and emissions characteristic of gasoline/methanol dual-fuel turbocharged engine under high load

This study aims to investigate the impact of methanol direct injection strategy on the combustion and emission characteristics of a dual-fuel turbocharged engine running under high load of 1500 rpm. Five methanol injection timings ranging from −330° CA (crank angle) to −60° CA ATDC (after top dead center) were tested under four different methanol energy substation ratios. Based on the experimental results, a suitable injection timing was selected to study the effect of methanol energy substation ratio. The results showed that different injection timings had varying effects on engine combustion and emission characteristics. End of injection timing of methanol (EOI) at −180° CA ATDC resulted in fuller atomization of methanol, which delayed combustion and reduced the combustion rate, with the lowest knock intensity and highest indicated mean effective pressure. However, this timing also had the highest emissions of NOx. Further experiments were conducted at EOI = −180° CA ATDC under eight different energy substation ratios. The results demonstrated that adjusting the injection strategy of methanol can effectively change the engine's performance. The optimal injection strategy was found to be EOI = −180° CA ATDC and an energy substation ratio range of 4.6%–8.9%. This research provides valuable insights into the use of methanol as a fuel and its impact on engine characteristics.

An analytical approach to converting vibration signal to combustion characteristics of homogeneous charge compression ignition engines

Homogeneous charge compression ignition (HCCI) is a promising low-temperature combustion technique for low-emission internal combustion engines. Unlike conventional engines, HCCI lacks a direct ignition control mechanism, necessitating closed-loop combustion control. This study proposes a phenomenological-based, cost-effective, and non-intrusive approach using vibration data analysis to determine essential combustion parameters. Experiments were conducted on a single-cylinder research engine with an accelerometer attached to the engine head. The engine operation envelope covered the whole engine’s operating area in naturally aspirated HCCI mode. Wavelet analysis revealed that combustion-related frequencies centered around 500 Hz, independent of operating conditions. The correlation-seeking analysis included peak acceleration amplitude and its crank angle with peak heat release rate (HRR) data. The peak HRR location was accurately identified within one degree when vibration amplitude exceeded the 100 m/s2 threshold. This encompassed 98.5% of the analyzed combustion cycles. The peak HRR prediction accuracy had a maximum error below 21% and was suitable to monitor reaction rates, especially in incomplete combustion and high ringing cycles.

Effects of waste cooking oil biodiesel addition on combustion, regulated and unregulated emission characteristics of common-rail diesel engine

The use of waste cooking oil biodiesel as diesel fuel is one of the essential measures to achieve global energy transition and sustainable development. This work aims to explore the influence mechanism of waste cooking oil biodiesel/diesel blended fuel on the combustion and emission characteristics of a common-rail diesel engine. The effects of four fuel blending ratios (0%, 10%, 20%, and 30%) on engine combustion and emission characteristics under different operating conditions were investigated experimentally. The study results showed that adding biodiesel from waste cooking oil prolongs the combustion duration and is also beneficial for combustion at medium and high load conditions (50% and 75%). For the low load condition (25%), the emission concentration showed a decreasing trend with the increase of the blending ratio. In particular, the NOx and CH3CHO emissions increased, and the Soot emission was insensitive to the blending ratio. For medium and high load conditions, as the blending ratio increases, the emission concentration decreases. Moreover, the NOx emission increased slightly. Within the scope of the current work, the addition of waste cooking oil biodiesel improves the combustion and emissions characteristics of a common-rail diesel engine for both 50% and 70% load conditions.

Computational Analysis on Combustion Control of Diesel Engines Fueled with Ester Alcohol Diesel

As the urgency for environmental sustainability escalates globally, the exploration of alternative fuels for diesel engines becomes a crucial endeavor. By combining chemical reaction kinetics and three-dimensional simulation software, the combustion and emission characteristics of a diesel engine fueled with two oxygenated fuels, hydrogenated biodiesel and ethanol, and adopting a multi-stage injection strategy were studied. The combustion mechanism of hydrogenated biodiesel ethanol diesel hybrid fuel was established, and the reaction activity of ester alcohol diesel with different mixing ratios was studied through reaction flow analysis at high and low OH temperatures. The established mechanism was coupled with CFD 2021 three-dimensional simulation software to compare the combustion and emission performance of diesel engines fueled with different ratios of ester alcohol diesel. The results show that as the proportion of ester alcohol mixture increases, at low temperatures, the OH generation rate decreases, the consumption rate increases, and the reaction activity decreases, which is not conducive to the promotion of combustion reaction; at high temperatures, the generation rate of OH increases, the consumption rate decreases, and the reaction activity increases, which is conducive to the promotion of combustion reactions. Compared to diesel, the reaction system activity of mixed fuel is enhanced, and the main peak values of cylinder pressure and instantaneous heat release rate are higher than that of diesel. The diffusion of oil and gas in the cylinder is improved. As the proportion of ester alcohol diesel mixture increases, the oxygen content increases, nitrogen oxides emissions increase compared to diesel, and soot emissions decrease compared to diesel. Soot emissions are mainly distributed in areas with a high equivalence ratio and high temperature, which is consistent with the distribution area of C2H2, the precursor of soot generation.

Effective utilization of waste plastic derived fuel in CI engine using multi objective optimization through RSM

This study provides the prediction that plastic pyrolysis oil (PPO) is equivalent to petroleum diesel in CI engines. The four input parameters have been considered to enhance performance and reduced emissions. The input parameters of engine trials, like fuel blend (PPO and diesel), compression ratio, nanoparticle concentration, and injection timing, were studied with the response surface methodology (RSM) using the central composite rotating design (CCRD) matrix. The main goal is to identify the ideal values of input parameters that will provide the highest achievable brake thermal efficiency (BTE), the lowest possible brake-specific fuel consumption (BSFC), and the lowest possible emission like carbon monoxide (CO), unburnt hydrocarbons (HC) and nitrogen oxides (NOx). The optimal engine output responses for BTE, BSFC, in-cylinder pressure, heat release rate (HRR), and ignition delay, respectively. Along witha composite desirability of 0.89 under optimum operating conditions. After the regression analysis, 16.56% PPO blend ratio, 53.53 ppm Al2O3 nanoparticle concentration, 18.06 compression ratio, and 20.95 °bTDC injection timing were received the optimized engine settings. Optimal engine input parameters were validated through actual engine trials and compared with optimized responses and found satisfactory and acceptable errors (less than 5%). The current study establishes vital input parameters providing the best engine performance, combustion characteristics, and lower emissions during engine trials. So current investigation declared PPO with Al2O3 nanoparticles is potential fuel for the CI engine.

Prediction of combustion, performance, and emission parameters of ethanol powered spark ignition engine using ensemble Least Squares boosting machine learning algorithms

This research concentrates on the application of machine learning techniques to predict combustion, performance, and emission parameters in a dual-fuel spark ignition (SI) engine powered by neat gasoline and E20 ethanol dual fuel. The goal is to overcome the limitations posed by repeated engine experiments and nonlinear test results. In order to optimise engine parameters, the research seeks to develop efficient machine learning models with high generalizability and employ an optimisation strategy to determine the optimal engine settings. Input for training and evaluating machine learning algorithms, such as Artificial Neural Networks (ANN), and Ensemble LS Boosting was derived from experimental data from a combustion test engine, which includes Neat gasoline, and Ethanol dual fuel blend E20 at various load conditions. The dataset includes engine combustion, performance, and emission indices such as brake thermal efficiency (BTE), Exhaust Gas Temperature (EGT), Hydrocarbons (HC), Carbon monoxide (CO), Carbon dioxide (CO2), and Nitrogen oxides (NOx), under various operating conditions. Load and brake-specific fuel consumption (BSFC) were training input attributes. Using a comprehensive experimental database of input-output engine parameters, the Artificial Neural Network (ANN) and Ensemble LS Boosting were constructed. The training data points were resampled to generate multiple training datasets for training different models. 50 test samples were used to evaluate the generalisation capability of the machine learning models, while BTE, EGT, CO, CO2, HC and NOx, were the primary parameters subject to prediction. The optimal machine learning method was determined by comparing R-squared (R2) values, root mean square error (RMSE), mean square error (MSE), and mean absolute error (MAE). Using multiple hyperparameter tuning iterations, the agreement between actual and predicted values for diverse Ensemble LS Boost algorithms was evaluated. The Ensemble LS Boost model exhibits the maximum level of agreement between predicted and experimental engine parameters across all datasets when compared to the other ANN models. This finding was corroborated by additional research based on test datasets, specifically the test sample interpolation data, which measures generalisation ability. The study also focuses on developing and applying two unique, interactive Simulink models for the Spark Ignition (SI) engine that are tailored for Neat Gasoline and Ethanol E20 test fuels under all loads. The key component of the model-based development technique in MATLAB and Simulink was the incorporation of sophisticated machine learning algorithms, i.e., Ensemble Least-Squares (LS) Boosting, to the model-based development workflow which produced reliable results. Implementing an Ensemble LS Boost machine learning framework is therefore highly recommended as an efficient method for predicting and optimising the combustion, performance, and emission characteristics of dual-fuel gasoline engines utilising Ethanol-based dual-fuel blends.

Effect of injection parameters on the hydrogen enriched dual-fuel CRDI diesel engine

ABSTRACT To maximize the performance of the diesel engine run with alternative renewable fuels, operational parameters such as injection time (IT) and injection pressure (IP) must be fine-tuned. Meanwhile, hydrogen has come out as a one of the best alternative fuel for dual-fuel mode of operation, since it minimizes the drawback that use of biodiesel alone possesses like low calorific value, high viscosity etc. Based on the above findings, the objective of the current study is set as “to evaluate the impact of varying injection parameters on the engine characteristics of hydrogen-enriched palm fueled CRDI diesel engine.” In this research work, a hydrogen-enriched (7 lpm and 10 lpm) palm biodiesel blend (P20) with diesel fuel was used to examine how changing injection pressure (IP) and injection time (IT) affected CRDI diesel engine performance, combustion, and emission characteristics. Three different IPs (240 bar, 420 bar, and 600 bar) and ITs (23°CA bTDC, 25°CA bTDC, and 27°CA bTDC) are used at a steady speed of 1500 rpm under full load circumstances. The results showed a maximum BTE of 31.09% for P20 + 10 H2 at 25°CA bTDC IT and 600 bar IP. Better fuel atomization is responsible for the improvement in BTE (17.94%) and BSFC (15.15%) with increased IP (600 bar). Advancement in IT (25°CA bTDC) leads to superior performance in terms of HC (32%) and CO (8.33%) emissions reduction for P20 + 10 H2 because more time is available for optimal air-fuel mixing. However, NOX emission increases significantly because of the rise in temperature within the cylinder with hydrogen enrichment. This can be attributed to the high calorific value of hydrogen which is almost three times to that of diesel. A maximum increase in NOX emission of 45.65% is obtained for P20 + 10 H2 w.r.t. diesel. With an increase in IP, ICP and HRR improve by 28.04% and 22.70%, respectively, due to improved fuel atomization, resulting in the greatest amount of fuel being burned during the pre-mixed combustion stage. It can be concluded that the 25°CA bTDC IT and 600 bar IP is the optimum condition when the engine performs at its peak.

Performance, Emissions, and Combustion Characteristics of a Hydrogen-Fueled Spark-Ignited Engine at Different Compression Ratios: Experimental and Numerical Investigation

This paper investigates the performance of hydrogen-fueled, spark-ignited, single-cylinder Cooperative Fuel Research using experimental and numerical approaches. This study examines the effect of the air–fuel ratio on engine performance, emissions, and knock behaviour across different compression ratios. The results indicate that λ significantly affects both engine performance and emissions, with a λ value of 2 yielding the highest efficiency and lowest emissions for all the tested compression ratios. Combustion analysis reveals normal combustion at λ ≥ 2, while knocking combustion occurs at λ < 2, irrespective of the tested compression ratios. The Livenwood–Wu integral approach was evaluated to assess the likelihood of end-gas autoignition based on fuel reactivity, demonstrating that both normal and knocking combustion possibilities are consistent with experimental investigations. Combustion analysis at the ignition timing for maximum brake torque conditions demonstrates knock-free stable combustion up to λ = 3, with increased end-gas autoignition at lower λ values. To achieve knock-free combustion at those low λs, the spark timings are significantly retarded to after top dead center crank angle position. Engine-out NOx emissions consistently increase in trend with a decrease in the air–fuel ratio of up to λ = 3, after which a distinct variation in NOx is observed with an increase in the compression ratio.

Effect of green synthesized zinc oxide nanoadditives and rice bran oil biodiesel blend on performance and combustion characteristics of a variable compression ratio diesel engine: an experimental study

AbstractThe aim of this research was to investigate experimentally the performance and combustion characteristics of a four‐stroke, single‐cylinder, water‐cooled variable compression ratio diesel engine using rice bran oil biodiesel blends with zinc oxide nanoparticles. Rice bran oil biodiesel was prepared using a transesterification reaction with a 6:1 methanol‐oil molar ratio and 1% w/w potassium hydroxide as catalyst. Zinc oxide nanoparticles were synthesized using a green method incorporating Psidium guajava leaf extract as a capping agent to reduce precursor use and to reduce the toxicity of the nanomaterial. The synthesized zinc oxide nanoparticles were characterized by using X‐ray diffraction and Fourier‐transform infrared spectroscopy to confirm the formation of highly crystalline pure zinc oxide nanoparticles with a hexagonal wurtzite crystal structure with an average diameter of 20.963 nm. Rice bran‐oil biodiesel‐diesel blend was prepared by volumetrically mixing 20% biodiesel and 80% mineral diesel and was considered as a base fuel for comparison. Zinc oxide nanoparticles were diffused in the base fuel at dosage levels of 25, 50, and 75 ppm, with the aid of ultrasonication. Measurement of the major physicochemical properties of test fuels showed an increase in the cetane number and calorific value and a reduction in viscosity with an increase in the zinc oxide concentration. The overall properties of all the test fuels were found to be similar in comparison with commercial diesel. An experimental engine test was carried out under different loading conditions with a constant speed of 1500 RPM and two different compression ratios – that is, 17.5:1 and 15:1. Among all the test fuels at both compression ratios, engine performance and combustion properties improved with an increase in the zinc oxide concentration. Test fuel with 75 ppm of zinc oxide additive at 17.5 compression ratio resulted in an overall improvement at full load: brake thermal efficiency increased by 2.45%, brake specific fuel consumption reduced by 5.45%, cylinder peak pressure increased by 3.27% and net heat release increased by 10.32% in comparison with base fuel.