Engine Emission Characteristics Research Articles

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.

Modeling the emission characteristics of the hydrogen-enriched natural gas engines by multi-output least-squares support vector regression: Comprehensive statistical and operating analyses

Modeling the emission characteristics of the hydrogen-enriched natural gas engines by multi-output least-squares support vector regression: Comprehensive statistical and operating analyses

Performance and exhaust emission characteristics of a CI engine fuelled with diesel-biodiesel-methane-nitromethane

In reaction to the rising expense of fossil fuels and the rise in the number of pollutants in the environment, professionals are searching for alternative, renewable fuels in order to improve the efficiency of internal combustion engines and decrease the emissions that they create. This is being done in order to improve the efficiency of internal combustion engines and reduce the emissions that they produce. This study was conducted with the intention of determining whether or not alternative fuels, such as mixtures of biodiesel, methanol, and nitro-methane, could be able to effectively replace traditional diesel in an internal combustion engine (1200 r/min to 2100 r/min). Increasing the speed of the engine was helpful in achieving the desired goal of producing a more consistent combustion product. It is possible that the indicator thermal efficiency and economic performance might be improved by increasing both the number of rotations per minute and the number of nitromethane blends that are introduced into the cylinder. It has been shown that the nitro-methane approach has tremendous promise for reducing NOx emissions. However, higher rotations per minute proved beneficial for increasing the pressure and temperature within the cylinders. At a speed of 1500 r/min, this particular engine reached its optimal compression ratio of 18:1. The ratio of nitromethane impact on NOx emissions reached 10%, and the factor that had the most influence on smoke emission for NM3 (85.0% diesel, 10.0% biodiesel, 2.0% methanol, and 3.0% nitromethane) was the engine running condition.

Influence of Mustard Oil Biodiesel Blends in Common Rail Direct Injection Diesel Engine on Its Performance and Emission Characteristics

Almost majority of petroleum produce is utilized for transportation, generation of heat and electricity, and balance used as a raw material in chemical industry. With increasing energy demand, limited fossil fuel sources, study is directed towards alternate renewable fuels. Biodiesel extracted from Vegetable Oil, is becoming a popular alternative propulsion fuel. Experiments were conducted using different blends from Mustard Oil biodiesel mixed with diesel in concentration of 10%, 20%, 30%, 40%, 50%, to determine the properties of these biodiesel blends and evaluate the performance as well as emission characteristics of a CRDI Engine. The trials were conducted for various load conditions viz. 0 kg, 3 kg, 6 kg, 9 kg and 12 kg, for two different compression ratios 16 and 18. The performance assessments indicators like brake power, brake specific fuel consumption, brake thermal efficiency, mechanical efficiency, air-fuel ratio were examined. The highest magnitude of mechanical efficiency observed is 59.14% for Mustard Oil Biodiesel 10% Blend (MuB10) for 12 kg, engine load and compression ratio 16. The emission indicating parameters oxides of nitrogen, hydrocarbon, carbon dioxide, carbon monoxide, and smoke were scrutinized throughout trials. The result of this investigation exposed that blend B10 has given favorable outcomes as compared to pure diesel for CRDI engine performance indicating parameters and has fewer emissions as compared to that of pure diesel.

Effect of Low Heat Rejection on Performance and Emission Characteristics of a 4-Stroke Diesel Engine

Effect of Low Heat Rejection on Performance and Emission Characteristics of a 4-Stroke Diesel Engine

Elman and cascade neural networks with conjugate gradient Polak-Ribière restarts to predict diesel engine performance and emissions fueled by butanol as sustainable biofuel

This study explores the possibility of utilizing green butanol, a promising type of biofuel, in diesel engines to measure its impact on engine performance and emissions. Experimental data were collected on several parameters, including brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature, all of which are influenced by the biofuel type used, in this case, butanol. The study examined emissions such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and smoke opacity. Such emissions have the potential to improve with the use of different biofuels ratios, such as butanol. Advanced machine learning techniques, Elman and Cascade Neural Networks, were employed to predict the performance and emission characteristics of engines using butanol. The models were trained using a Conjugate Gradient Learning Function with Polak-Ribière Restarts to simulate the effects of butanol as biofuel, on diesel engines. Key findings revealed that when incorporating butanol into diesel fuel blends, potential improvements in BTE and fuel efficiency were observed. Notably, using butanol as a biofuel reduced exhaust gas temperatures and CO emissions, demonstrating the potential of this particular biofuel. Conversely, there were observed increases in HC emissions and smoke opacity, signifying the complexities of using biofuels such as butanol. Cascade neural network proved to be highly accurate in predicting engine performance parameters fueled with butanol as biofuel. Overall, the study offers valuable insights into the use of butanol as a biofuel, its potential benefits, and challenges, underscoring the importance of continuous research in sustainable biofuels such as butanol.

Exploratory of novel thermal barrier coating on diesel engine performance

This research presents an experimental and theoretical evaluation of the effect of poly-composition thermal barrier coatings on the performance and emission characteristics of the compression ignition engine. This work investigated the thermal and physical behavior of thermal barrier coating. The thermal barrier coating was coated into two layers, and the thermal plasma spray method was used to make the coating. The first layer is AT13, and the top layer is Yttria-stabilized zirconia. The coated and uncoated pistons were analyzed in the Ansys, and it has shown the temperature distribution of the pistons. The experimental report shows that the brake thermal and volumetric efficiency was increased by 7.52% and 1.06%, brake-specific fuel consumption was reduced up to 18.91%, emission of carbon monoxide was reduced by 50%, and hydrocarbon was reduced by 52.38%.

A Comparatively Experimental Study on the Performance and Emission Characteristics of a Diesel Engine Fueled with Tung Oil-Based Biodiesel Blends (B10, B20, B50)

In this paper, the performance and emission characteristics of a diesel engine were investigated with varying ratios of tung oil-based biodiesel blends (B10, B20, and B50) and neat diesel under different operating conditions. The experimental results showed that the addition of biodiesel blends had different effects on engine power and torque depending on the blend ratio. B10 displayed a slight increase in power and torque, which increased by 1.9% and 6.6%. At the same time, B20 and B50 showed declines slightly. The fuel consumption rate increased slightly with an increasing percentage of biodiesel added. In general, all the blends exhibited significantly lower emissions of CO, NOX, HC, and smoke compared to neat diesel. B10 displayed the most notable reduction of CO emissions, with a 42.86% decrease at medium to high loads. NOX emissions of tung oil-based biodiesel blends were reduced at all load conditions except for B50. In addition, HC emissions were all reduced, especially for B20, which led to a 27.54% reduction at 50% load. Among all the tested blends, B50 showed the greatest decrease in smoke emissions of 38.05% compared to neat diesel at 2000 rpm. The research concluded that using biodiesel fuels from renewable resources, such as tung oil, presents a promising environmentally friendly alternative fuel option.

Impact of Biodiesel Blending on Emission Characteristics of One-Cylinder Engine Using Waste Swine Oil

The influence of biodiesel blending on the emission parameters of a one-cylinder engine using waste swine oil was investigated in this research. This research focused on particulate matter, nitrogen oxides, hydrocarbons, carbon monoxide, and carbon dioxide emissions at various engine speeds and biodiesel mixing percentages. According to the results, increasing the amount of biodiesel in diesel blends might result in considerable reductions in particulate matter emissions while potentially raising nitrogen oxide emissions due to biodiesel’s higher oxygen content. Engine speed considerably affects hydrocarbon and carbon monoxide emissions, with biodiesel mixes benefiting more at higher engine speeds. This study also discovered that when the amount of biodiesel in a fuel blend grows, so do carbon dioxide emissions, but brake thermal efficiency drops. These findings indicate that using waste swine oil biodiesel as a fuel source has both advantages and disadvantages in terms of engine emissions, and more study is needed to optimize biodiesel consumption and reduce nitrogen oxide emissions.

Combustion and Emission of Castor Biofuel Blends in a Single-Cylinder Diesel Engine

Fossil fuels confront the problem of strategic resource depletion since they have been continuously utilized for more than 200 years and cause serious damages to the ecological environment of the planet. In this work, the transesterification of castor plant oil was utilized to make biodiesel, and castor biodiesel’s physicochemical qualities were assessed. On a single-cylinder, four-stroke, water-cooled agricultural diesel engine, an experimental study was conducted to compare and analyze the engine performance and emission characteristics of diesel and biodiesel blends in various amounts. The B20, B40, B60, and B80 biodiesel blends were evaluated at different engine speeds (1200, 1400, 1600, and 1800 rpm) with a constant engine load (50%). According to the experimental findings, the brake thermal efficiency (BTE) declines as the engine speed rises, and the biodiesel fuel blend has a lower brake thermal efficiency (BTE) than diesel fuel because of its higher density and viscosity and lower calorific value. The amount of gasoline required to create power increases as the speed does, and the brake-specific fuel consumption (BSFC) trend is upward. Due to their low calorific value and high viscosity properties, biodiesel blends have a greater brake-specific fuel consumption (BSFC) than diesel. The fuel’s exhaust gas temperature (EGT) has an upward trend with an increased rotational speed. The biodiesel blend’s high cetane number shortens the ignition delay and lowers the exhaust gas temperature (EGT) compared to diesel. A fuel with oxygen added, biodiesel enhances combustion, increases the combustion temperature, speeds up the oxidation process, and lowers carbon monoxide (CO) and hydrocarbon emissions. B80 produces the lowest carbon monoxide and hydrocarbon emissions at 1800 rpm, at 0.33%, and 30 ppm, respectively. On the other hand, increased carbon dioxide (CO2) emissions result from a high oxygen concentration. In addition, compared to diesel fuel, biodiesel’s greater combustion temperature causes the creation of increased nitrogen oxide (NOx) emissions. According to the research findings, a castor biodiesel fuel blend is an excellent alternative fuel for engines since it can be utilized directly without modifying the current engine construction and has good engine and exhaust emission performance.

A review of combustion properties, performance, and emission characteristics of diesel engine fueled with Al2O3 nanoparticle-containing biodiesel

A review of combustion properties, performance, and emission characteristics of diesel engine fueled with Al2O3 nanoparticle-containing biodiesel

Effects of multi-walled carbon nanotubes on the combustion, performance, and emission characteristics of a single-cylinder diesel engine fueled with palm-oil biodiesel-diesel blend

Multi-walled carbon nanotubes (MWCNTs) could be an effective fuel additive for 20 vol% palm-oil biodiesel in fossil diesel (B20) owing to its superior thermal conductivity. The effects of MWCNTs on the combustion, performance, and emission characteristics of B20 are investigated at various concentrations by a single-cylinder diesel engine under different engine speeds. The results show that B20 fuels with MWCNTs addition reduced the ignition-delay (ID), advanced the combustion phasing, and shortened the combustion duration by up to 17.6% (−2.6° CA), 12.9% (−1.8° CA), and 18.5% (−4.3° CA), respectively. The addition of MWCNTs in B20 also improved the brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) by up to 15.7% (−47.4 g/kW·h) and 16.3% (+4.6%), respectively. Compared with B20 fuel without MWCNTs, CO and UHCs emissions reduced by up to 34.7% (−8.2 g/kg-fuel) and 16.0% (−3.8 g/kg-fuel), respectively but NOx emissions increased by up to 43.5% (+7.6 g/kg-fuel). Overall, the results suggest that B20 with MWCNTs addition can enhance the combustion, performance, and emission characteristics of a light-duty diesel engine.

Numerical Investigation of Engine Performance and Emission Characteristics of an Ammonia/Hydrogen/n-Heptane Engine Under RCCI Operating Conditions

This paper examines the potential of using ammonia (NH3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_3$$\\end{document}) as a primary fuel in heavy-duty engines for decarbonization, with some challenges yet to be addressed. It presents a numerical study of a Reactivity Controlled Compression Ignition engine, where pilot diesel is used to ignite the premixed ammonia/air mixture. The numerical model and combustion mechanism are validated against engine experimental results using methanol and iso-octane fuels and ignition delay times of ammonia/n-heptane mixtures measured in a rapid compression machine. The findings show that the engine can effectively operate with up to 50% of the total energy supplied by premixed ammonia, albeit with slightly elevated NO emissions compared to a diesel-fueled engine. Increasing ammonia further leads to lower combustion efficiency. Hydrogen can be utilized in the ammonia engine to enhance ammonia combustion; however, NO emissions increase further. Ammonia leakage primarily originates from regions near the cold wall, the center of the cylinder, and the crevice. N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O mainly forms at the ammonia flame front. Emission of N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}O is therefore mainly due to flame front quenching near the wall.

Influence of varying concentrations of TiO2 nanoparticles and engine speed on the performance and emissions of diesel engine operated on waste cooking oil biodiesel blends using response surface methodology

For a few decades now fast depleting fossil fuels has been a major challenge. Fast expanding population and increased rate of urbanization has increased energy demand. This makes the current scenario worse. Fossil fuels' emissions are another challenge. Apart from fossil fuel emissions, the untreated disposal of waste cooking oil presents another environment’s sustainability challenge. The treatment of waste cooking oil as fuel presents a tangible solution to challenge. In this research article, impact of the engine speed and the concentration of titanium dioxide (TiO2) nanoparticles (NPs) in diesel-biodiesel blended fuels on the engine’s performance. The emission characteristics of a single-cylinder four-stroke diesel engine has also been examined. TiO2 NPs were produced by a sol-gel methodology. The diesel-biodiesel combination was fortified with TiO2 NPs at 40, 80 and 120 ppm. These mixtures were used to power the diesel engine, which was then run at 1150, 1400, 1650, 1900 and 2150 RPM. Interaction between engine speeds and nanoparticle concentrations and investigation of their combined effect on engine performance and emissions was done using response surface methodology. The minimum BSFC of 0.33994 kg/kWh and maximum BTE of 25.90% were found for B30 + 120 ppm biodiesel blend at 2150 rpm as compared to all other tested fuels. The emissions including CO and HC emissions were recorded as 25.61486 kg/kWh and 0.05289kg/kWh respectively at 2150 rpm for B30 + 120 ppm biodiesel blend while NOx on the contrary side exhibits a slight escalation with increasing engine speed and nanoparticles concentration. The findings of the experiments demonstrated that adding TiO2 nanoparticles to diesel–biodiesel blends is an effective way to enhance the performance of diesel engines while simultaneously reducing the emissions. It was also discovered that the mathematical model that was built can efficiently estimate the performance of the engine and the emission levels.

Combustion and emissions characteristics of a diesel engine fuelled with diesel fuel and different concentrations of amino-functionalized multi-walled carbon nanotube

Nanoparticles have recently been used as fuel additives to enhance diesel engine performance and exhaust gas emissions. Amino-functionalized multiwalled carbon nannotubes (NH2-MWCNTs) are catalysts that can be applied in diesel engines because of their promising properties. This study conducted an experimental investigation to determine the impacts of adding NH2-MWCNTs to diesel fuel using a single-cylinder CI engine running at a constant speed (1500 rpm) and various loads. The NH2-MWCNTs were added to diesel fuel at four concentrations of 25, 50, 75, and 100 ppm. Also, the same doses of pristine multiwalled carbon nanotubes (MWCNTs) were added to diesel to be used as a reference for NH2-MWCNTs. Most NH2-MWCNTs blends were preferred in combustion characteristics, engine performance, and exhaust emissions compared to diesel and MWCNTs blends. Thus, there was a considerable increase in cylinder pressure and heat release rate compared to pure diesel. Also, the brake thermal efficiency was increased, and the brake-specific fuel consumption was decreased compared to diesel. Most NH2-MWCNTs combinations appeared to decrease NOx, soot, and CO levels significantly. The NH2-MWCNTs blends are generally favored over the pristine MWCNTs blends in reducing exhaust emissions.

Environmental adaptability method for improving the cold start performance of the diesel engine based on pilot injection strategy

The deterioration of cold start performance at high altitudes is one of the main problems that restrict the altitude adaptability of diesel engines. In this study, by adapting the pilot injection strategy to improve cold start performance at different altitudes, the effect of the pilot injection ratio and pilot injection timing on the combustion, performance, and emission characteristics of diesel engines are investigated, and suggestions are proposed for optimizing fuel injection according to the altitude. The experimental results indicated that at high altitudes, the cold start performance was worse and more difficult to reach idle speed, NOx emissions increased due to the longer ignition delay. Compared to the single-injection strategy, the pilot injection strategy can effectively improve the combustion environment in the cylinder and thereby improve the cold start performance. As the altitude increase, decreasing the pilot injection mass can shorten the cold start time. The appropriate advance of pilot injection timing could improve mixture formation, which is conducive to improving the cold start performance and emissions at different altitudes. It can be concluded that advancing the pilot injection timing and increasing the pilot mass is a better injection strategy to improve cold start performance at plain. As the altitude increase, the pilot injection mass should decrease.

Investigations on the performance, emission and combustion characteristics of a dual-fuel diesel engine fueled with induced bamboo leaf gaseous fuel and injected mixed biodiesel-diesel blends

The present paper briefly elaborates upon the combination of waste palm and waste sunflower oil methyl ester as post-mixed biodiesel blends being injected into a four-stroke compression ignition engine, which is also fueled with inducted bamboo leaf generated producer gas (BLP.gas) that includes gaseous components of CO (carbon monoxide), H2 (hydrogen), CH4 (methane), and CxHy (hydrocarbons). The objective of the present research is to evaluate the overall performance, emission, and combustion behavior of a Kirloskar TAF1 modified dual-fuel diesel engine fueled with induced bamboo leaf-derived gaseous fuel at a fixed mass flow rate of 21.69 kg/h and injected mixed biodiesel-diesel blends. Initially, diesel fuel and post-mixed methyl ester were examined in dual-fuel mode with a fixed gas flow rate for different loads. It can be seen from the analysis that brake thermal efficiency got reduced by 4.66% and brake-specific fuel consumption increased by 5.26% for PMOME20 (20% post-mixed oil methyl ester + 80% diesel fuel) + BLP. gas with respect to diesel fuel at extreme loading conditions. Moreover, smoke opacity, carbon monoxide, and unburnt hydrocarbons were reduced by 11.22%, 20.44%, and 10.36%, respectively. On the other hand, oxides of nitrogen were reduced by 19.17% at maximum load for PMOME20 + BLP. gas in dual-fuel operation in contrast to that of petroleum diesel. In light of this, the current research concluded that the use of biodiesel and BLP. gas for dual-operative engines may be regarded as an appropriate option for reducing pollutant environment and petroleum fuel scarcity.

Impact of Diethyl Ether on Performance and Emission Characteristics of a VCR Diesel Engine Fueled by Dual Biodiesel

Biodiesel is widely known as the alternative fuel for the diesel engine, but it comes with its fair share of challenges. To minimize the pertinent drawbacks, fuel additives become an essential tool and help improve renewable fuel’s properties. In this current research, biodiesel is obtained from rice bran oil and cotton seed oil, with diethyl ether as an additive. Diethyl ether is known for good oxygen content, high cetane number, and low viscosity. Experiments were performed on a variable compression ratio engine at a compression ratio of 18:1, and the injection pressure (170 bar, 180 bar, 190 bar and 200 bar) and the injection timing (20, 21, 22 and 23°bTDC) with four different dual biodiesel blends (5%, 10%, 15% and 20% by volume). Different ratios of 1%, 2.5% and 5% of diethyl ether with biodiesel combination were examined in a single-cylinder, four-stroke diesel engine. The engine emission and performance features were discussed at different loads and constant engine speeds. It was observed that using 5% of diethyl ether with biodiesel blends improved brake thermal efficiency, brake-specific fuel consumption and decreased carbon dioxide and oxides of nitrogen emissions. The reduction of oxides of nitrogen emission contributes to biodiesel’s acceptability for the environment’s benefit. This investigation found that diethyl ether, along with dual biodiesel blends, has a better viability in diesel engines.

Effect of synthetic antioxidant doped biodiesel blend with oxy-hydrogen gas on the low heat rejection engine

In this research work, N-Isopropyl-N-Phenyl-p-phenylenediamine (IPPD) and N,N′-Diphenyl-p-phenylenediamine (DPPD) are used as antioxidants for oxides of nitrogen (NOx) mitigation in a biodiesel-diesel blend run in a dual-fuelled compression (CI) engine. Five different antioxidant concentrations are selected for doping JME20, from 0 ppm to 2000 ppm at an interval of 500 ppm. A 4.4 kW rated power at 1500 rpm, four-stroke, single-cylinder, CI engine is modified to operate as a low heat rejection (LHR) engine. The LHR engine is formed by replacing the conventional piston with a YSZ + CeO2 thermal barrier coated (TBC) piston. The combined effects of the antioxidant-doped biodiesel-diesel blend with oxy-hydrogen gas (HHO) gas are experimentally investigated on the LHR engine to study engine combustion, performance, and emission characteristics. The dual-fuelled LHR engine's combustion and performance characteristics are enhanced with the help of hydrogen combustion as compared to diesel data. The results of the engine run on the antioxidant-doped biodiesel-diesel blend reveal that a 3.13%, 6.24%, and 9.8% reduction in BSEC, EGT and NO emissions, respectively are noticed with JME20D4+HHO operation compared to JME20+HHO operation.

Effect of compression ratio and Miller cycle on performance of methanol engine under medium and low loads

Considering the excellent anti-knock property of methanol fuel and the fact that passenger car engines typically operate at medium to low loads, this paper increasing the compression ratio and adopting the Miller cycle to improve the engine's efficiency, based on a methanol engine with compression ratio of 9.5:1. Experimental research is conducted to analyze the engine's combustion and emission characteristics under different operating conditions. The research shows that increasing the compression ratio to 12:1 can effectively reduce methanol consumption under medium to low loads, and applying the Miller cycle on the compression ratio of 12:1 can further improve fuel economy at low loads. Increasing the compression ratio raises the engine's cylinder pressure, maximum pressure rise rate, and cycle-to-cycle variation, thereby enhancing the tendency for knocking. However, the Miller cycle can effectively alleviate this situation while reducing engine pumping losses. From the perspective of emissions at medium and low loads, the high compression ratio reduces CO and HC emissions but increases NOx emissions due to high combustion temperature. The Miller cycle's shorter combustion duration and lower combustion temperature result in higher CO and HC emissions compared to an Otto cycle at the same compression ratio, but NOx emissions are improved.