In-cylinder Direct Injection Research Articles

Effect of Selective Non-Catalytic Reduction Reaction on the Combustion and Emission Performance of In-Cylinder Direct Injection Diesel/Ammonia Dual Fuel Engines

Ammonia, as a hydrogen carrier and an ideal zero-carbon fuel, can be liquefied and stored under ambient temperature and pressure. Its application in internal combustion engines holds significant potential for promoting low-carbon emissions. However, due to its unique physicochemical properties, ammonia faces challenges in achieving ignition and combustion when used as a single fuel. Additionally, the presence of nitrogen atoms in ammonia results in increased NOx emissions in the exhaust. High-temperature selective non-catalytic reduction (SNCR) is an effective method for controlling flue gas emissions in engineering applications. By injecting ammonia as a NOx-reducing agent into exhaust gases at specific temperatures, NOx can be reduced to N2, thereby directly lowering NOx concentrations within the cylinder. Based on this principle, a numerical simulation study was conducted to investigate two high-pressure injection strategies for sequential diesel/ammonia dual-fuel injection. By varying fuel spray orientations and injection durations, and adjusting the energy ratio between diesel and ammonia under different operating conditions, the combustion and emission characteristics of the engine were numerically analyzed. The results indicate that using in-cylinder high-pressure direct injection can maintain a constant total energy output while significantly reducing NOx emissions under high ammonia substitution ratios. This reduction is primarily attributed to the role of ammonia in forming NH2, NH, and N radicals, which effectively reduce the dominant NO species in NOx. As the ammonia substitution ratio increases, CO2 emissions are further reduced due to the absence of carbon atoms in ammonia. By adjusting the timing and duration of diesel and ammonia injection, tailpipe emissions can be effectively controlled, providing valuable insights into the development of diesel substitution fuels and exhaust emission control strategies.

Experimental study on ignition and flame propagation of premixed ammonia ignited by Direct-Injected diesel in an optical rapid compression Machine

Ammonia (NH3) is considered as one of the most promising zero-carbon fuels for internal combustion engines. Based on diesel engine modification, The ammonia/diesel dual-fuel mode with port injection of ammonia and in-cylinder direct injection of diesel has been proven to be the most feasible strategy. In this paper, the effects of ignition and flame propagation of premixed ammonia ignited by direct-injected diesel were studied based on an optical rapid compression machine (RCM). The results show that the spray and distribution of diesel play the key role in the ignition and flame propagation of NH3/diesel dual fuels combustion. For total excess air ratio (λT) of 1.0, the ignition delay of NH3/diesel with high energy ratio of ammonia (ER of 95 %) was much shorter than ER of 66 % which was mainly due to the low injection pressure of diesel. Under the same injection pressure, with the large nozzle diameter of diesel injector of 0.28 mm, the ignition delay of NH3/diesel will be shortened significantly. When the ER is low, the combustion process presents the characteristics similar to the multi-point compression combustion. When the ER rises to 83 %, the combustion process is mainly dominated by NH3 premixed combustion, and diesel mainly plays the role of ignition. Reducing the background pressure and temperature to 4 MPa and 887 K, respectively, NH3 is not able to be ignited by diesel.

Computational analysis of piston shape effects on in-cylinder gas flow, fuel-charge mixing, and combustion characteristics in a two-stroke rod-less spark ignition opposed-pistons engine

Compared with the traditional in-cylinder direct-injection spark ignition engine, the side-injection and side-spark-ignition characteristics of the two-stroke opposed-piston engine increase the ignition kernel offset and flame propagation distance. Increasing the flame propagation speed can to some extent solve the drawbacks caused by the non-central arrangement of spark plugs. The combustion chamber structure plays a crucial role in gas flow, fuel-charge mixing, and combustion characteristics. Therefore, three pistons were designed and comparatively analyzed in this study. The results show that: The pancake piston is beneficial to maintaining the intake swirl strength due to its simple and smooth spherical arc structure. The swirl strength of the pit and pit-guided piston decreases obviously, and the tumble strength can be maintained well. Compared to pancake and pit-guided pistons, the average TKE for the pit piston increased by approximately 25%, with a more concentrated distribution at the spark timing. The pancake piston exhibits the best scavenging performance, reducing the residual exhaust gas ratio by 2.1% and fresh air loss by 3.3% to the pit piston. A stable ignition core can be formed at the spark timing, but significant differences are observed in the flame propagation process for three pistons. Compared to the pit-guided piston, the pit piston has a 0.3% decrease in the indicated thermal efficiency, but a 13.1% decrease in combustion duration, which reduces knock tendency.

Effect of exhaust gas recirculation(EGR) on combustion and emission of butanol/gasoline combined injection engine

N-butanol is a kind of biomass alcohol which can be produced by fermentation, and it is also a clean alternative fuel. The combustion and emissions characteristics of n-butanol/gasoline SI engine under different combined injection modes with the introduction of EGR was studied. N-butanol inlet injection plus gasoline in-cylinder direct injection is called N-GXDI; Gasoline inlet injection plus n-butanol in-cylinder direct injection is called G-NXDI. Through the analysis of combustion and emission performance under different EGR rates, injection modes and direct injection ratios (DIr), it is found that with the increase of DIr, cylinder temperature, pressure, and IMEP increase first and then decrease. Under the DIr = 50%, the combustion is more complete when the EGR rate is 5%. Under the same DIr, with the increase of EGR rate, CO emission decreased first and then increased, NOx emission opposite, THC emission increased. Under the same EGR rate, the total particle number of the two modes decreases first and then increases with the increase of DIr. The G-NXDI mode has advantages in combustion and primary emissions, while the N-GXDI mode has advantages in particulate emissions, suitable injection mode combined with EGR can greatly improve combustion and emission performance.

Effect of Hydrogen Injection Flow Rate on the Performance of In-Cylinder Direct Injection Hydrogen Engines

Effect of Hydrogen Injection Flow Rate on the Performance of In-Cylinder Direct Injection Hydrogen Engines

Effects of Injection Parameters and EHN Mixing on the Combustion Characteristics of Fueling Pure Methanol in a Compression Ignition Engine

As one of the most ideal alternative fuels for internal combustion engines, methanol can achieve near-zero carbon emissions. The main problem of methanol application in compression combustion engines is the phase lag caused by its poor combustion characteristics, but under low load conditions, the fuel activity can be improved by adding the cetane number improver EHN (Isooctyl nitrate), and the dependence on intake heating can be reduced to a certain extent. Based on a three-dimensional CFD simulation, the effects of methanol injection parameters and the addition of EHN on the combustion characteristics of a four-stroke exhaust turbocharged diesel engine were studied in this paper. With or without EHN, the increase in injection pressure and the advance in injection timing lead to an increase in the peak temperature, pressure, and heat release rate, as well as a shortening of the combustion duration. Adding EHN witnesses reduced requirements for methanol ignition, including a decreased peak temperature, pressure, and heat release rate, a significantly shortened ignition delay period, and an extended combustion duration, which thus results in a reduced indicated thermal efficiency. This study innovatively develops a 3D model of a compression combustion engine applicable to in-cylinder direct injection pure methanol fuel and EHN under small load conditions, which provides a reference for future research and development of small-load pure methanol compression combustion engines and has certain guiding significance.

Study on the Effect of Secondary Injection on the Combustion and Emission of n-Butanol Engines.

n-Butanol, as a biological alternative fuel containing oxygen, has similar physical and chemical properties to gasoline and has a wide range of sources, which has attracted more and more attention and research. Direct injection technology has been widely used in the field of internal combustion engine due to its advantages of flexibility and control ability. In this paper, the secondary injection of n-butanol engine under the mode of in-cylinder direct injection is discussed to organize stratified combustion of the mixture, optimize combustion to improve the thermal efficiency, and reduce emission. A four-cylinder four-stroke spark ignition (SI) engine was selected to carry out the secondary injection experiment of n-butanol under the excess air ratio (λ) of 1, an engine speed of 1500 r/min, and a low load, and the variables were the second injection ratio and timing. The results show that the secondary injection of n-butanol can achieve stratified combustion of the mixture, but only at a specific second injection timing such as 100°CA before compression top dead center (BTDC) or 125°CA BTDC, the combustion effect is the best. A small second injection ratio can optimize combustion, improve brake thermal efficiency, and reduce hydrocarbon and carbon monoxide emissions. When the second injection ratio is greater than 60%, it results in incomplete fuel combustion, a 3 to 4% reduction in thermal efficiency, and an increase in emissions. Coefficient of variation (COV) was increased by secondary injection, but the effect was insignificant in the small injection ratio, and it will increase with the increase of the second injection ratio. The change of particle number is mainly affected by the nuclear particle number, and with the increase of the second injection ratio, the total particulate number is more affected by the second injection timing. The second injection ratio of 40% can reduce the total particle number under the mixed-gas stratification condition.

Investigation of steam utilization mode on performance and emissions characteristics of gasoline engine

In the present study, the steam utilization mode was discussed based on a gasoline engine. The thermodynamic processes of two steam utilization modes were investigated based on the validated model. And, the effects of in-cylinder direct steam injection (CDSI) and two steam expansion cylinders (TSEC) on engine performance were studied. The results show that the firing cylinder temperature decreases with both CDSI and TSEC engines. However, the in-cylinder pressure increases for the CDSI-engine. The CDSI method can greatly benefit engines from an emissions perspective, as it reduces NOx, HC, and CO by 79.0 %, 2.4 %, and 17.6 % respectively. It is worth noting that the TSEC method cannot improve engine performance through waste heat recovery. The results also demonstrate that the indicated power of the TSEC-engine is higher that the results achieved by using the CDSI method when the steam injection quantity is greater than 0.80 g. All these demonstrate that CDSI approach has great potential for application in gasoline engines. The present results provide strong evidence for the application in gasoline engines.

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.

Numerical investigation of ammonia-rich combustion produces hydrogen to accelerate ammonia combustion in a direct injection SI engine

Ammonia is a carbon-free fuel with significant potential to minimize carbon emissions. However, ammonia has weak combustion properties, necessitating more study to improve its combustion performance in engines. A numerical simulation was conducted to evaluate the impact of fuel composition and injection-ignition synergy strategy on the performance of an ammonia-hydrogen spark ignition engine with liquid ammonia direct injection and hydrogen port injection. Specifically, two distinct injection modes were investigated: injection after intake valve close (IAIVC) and injection before top dead center (IBTDC). The outcomes reveal that the IBTDC mode generates a strong stratification of ammonia near the top dead center, resulting in ammonia-rich combustion, then leading to enriched hydrogen production and finally enhancing ammonia combustion and shorting the combustion duration. Liquid ammonia in-cylinder direct injection reduces the combustion temperature and decreases NO emissions. Optimizing the injection timing and spark timing based on a split injection strategy results in lower fuel consumption and emissions. Specifically, NO emissions decrease from 30.5 g/kWh to 21.7 g/kWh at a similar ITE (≈43.5%), and ITE increased from 43.3% to 44.3% for similar NO emission (≈30.0 g/kWh), respectively, with the reduction in both NH3 and N2O emissions.

Numerical simulation research on the influence of the parameters of water injection on the GDI engine

The small enhanced technology that synergizes in-cylinder direct injection and turbocharging has good power and fuel economy, and has become a trend in the development of gasoline direct injection engines. However, the enhanced technology has sharply increased the thermal load in the cylinder. It is easy to cause engine knocks, which is currently one of the main limiting factors in improving the performance of direct injection gasoline engines. This paper discusses the influence of direct injection of water into the cylinder on the combustion of gasoline direct injection engines through numerical simulation. The gasoline engine is induced to knock by increasing the compression ratio and advancing the ignition timing. The influence of the water injector (six nozzle holes) layouts (direct water injection in the cylinder) and the water temperatures on the water movement in the cylinder and on the combustion and knock is explored. The in-cylinder water injector and the fuel injector are injected with two nozzles. Results show that when the water injector is arranged in the center of the cylinder head, the water evaporation in the cylinder before ignition is faster. Most of the water is located near the cylinder wall surface, which can reduce the temperature near the wall surface as much as possible and suppress the knock. Therefore, the effect of suppressing knocks is better. The injecting water is advantageous to make the mixed gas distribution uniform and the turbulent kinetic energy high when its temperature is low.

Effects of EGR combined with DOC on emission characteristics of a two-stage injected Fischer-Tropsch diesel/methanol dual-fuel engine

Fischer-Tropsch (F-T) diesel and methanol are widely regarded as promising clean alternative fuels for engines. The emergence of reactivity controlled compression ignition (RCCI) combustion mode provides new approaches to the application of F-T diesel and methanol in diesel engines, but there is a pressing need to further reduce engine emissions. To this end, a dual-fuel engine test bench was built based on a high-pressure common rail diesel engine with a methanol injection system at the intake manifold combined with a two-stage in-cylinder direct injection (pre-injection + main injection) F-T diesel. The combined effects of methanol substitution ratio (MSR), exhaust gas recirculation (EGR) and diesel oxidation catalyst (DOC) on the combustion and emission characteristics of the dual-fuel engine was investigated at 2000 rpm and 75 % load. The results show that EGR improves the combustion characteristics of the F-T diesel/methanol dual-fuel engine while adding a DOC significantly reduces engine gaseous emissions. However, as the MSR and EGR rate increase, NOx emissions decrease, but other emissions increase. NOx emissions were reduced by 73 % compared to the original engine emissions for an MSR of 30 % and an EGR rate of 15 % without a DOC. When the MSR is 0 %, the DOC promotes the conversion of NO to NO2. While, when the MSR greater than 0, the DOC promotes the conversion of NO2 to NO. When equipped with a DOC, CO, NO, NO2, NOx, MeOH, and HCHO emissions decrease as the EGR rate increases, with the reduction of CO and MeOH emissions being greater than 99.5 % and 93 %, respectively, and the maximum conversion efficiency for HCHO emissions being 82 %. The present study showcases the key challenges as well as advantages in the use of EGR combined with a DOC assisting the application of coal-based alternative fuels in dual-fuel engines.

A Hybrid Taguchi-Regression Algorithm for a Fuel Injection Control System.

The fuel injection system is one of the key components of an in-cylinder direct injection engine. Its performance directly affects the economy, power and emission of the engine. Previous research found that the Taguchi method can be used to optimize the fuel injection map and operation parameters of the injection system. The electronic control injector was able to steadily control the operation performance of a high-pressure fuel injection system, but its control was not accurate enough. This paper conducts an experimental analysis for the fuel injection quantity of DI injectors using the Taguchi-Regression approach, and provides a decision-making analysis to improve the design of electronic elements for the driving circuit. In order to develop a more stable and energy-saving driver, a functional experiment was carried out. The hybrid Taguchi-regression algorithm for injection quantity of a direct injection injector was examined to verify the feasibility of the proposed algorithm. This paper also introduces the development of a high-pressure fuel injection system and provides a new theoretical basis for optimizing the performance of an in-cylinder gasoline direct injection engine. Finally, a simulation study for the fuel injection control system was carried out under the environment of MATLAB/Simulink to validate the theoretical concepts.

Experimental investigation on n-butanol/methyl oleate dual fuel RCCI combustion in a single cylinder engine at high-load condition

Reactivity controlled compression ignition (RCCI) engines have a high thermal efficiency as well as low emissions of soot and nitrogen oxides (NOx). However, there is a conflict between combustion stability and harmful emissions at high engine load. Therefore, this work presented a novel approach for regulating n-butanol/methyl oleate dual fuel RCCI at high engine load in attaining lower pollutant emissions while maintaining stable combustion and avoiding excessive in-cylinder pressure. The tests were conducted on a single cylinder engine under rated speed and 90% full load. In this study, n-butanol was selected as a low-reactivity fuel for port injection, and n-butanol/methyl oleate blended fuel was used for in-cylinder direct injection. Combustion and emission characteristics of the engine were first investigated with varied ratios of n-butanol port injection (PFI) and direct injection (DI). Results showed that as the ratio of n-butanol PFI and DI rose, the peak cylinder pressure and heat release rate increased, while NOx and soot emissions reduced, and carbon monoxide (CO) and hydrocarbon (HC) emissions increased under most test conditions. When RNBPI = 40% and RNBDI = 20%, the soot and NOx emissions of the engine were near the lowest values of all test conditions, yet the peak in-cylinder pressure and fuel consumption could not increase significantly. Therefore, the possibility of optimizing the combustion process and lowering emissions by adjusting the pilot injection strategy was investigated utilizing these fuel injection ratios. The results revealed that with an appropriate pilot injection ratio and interval, the peak in-cylinder pressure and NOx emission were definitely reduced, while soot, CO, and HC emissions did not significantly increase.

Brownian coagulation of particles in the gasoline engine exhaust system: Experimental measurement and Monte Carlo simulation

In this article, Brownian coagulation of particles in the exhaust system of a gasoline engine were investigated by measuring particle size distribution (PSD) at different sampling points and Monte Carlo simulation. The measurement results show that the particle size distributions of nucleation mode (NM) change remarkably after the exhaust gas passes through the exhaust plenum chamber. The constructed coagulation model based on the classic coagulation theory can well catch the measured PSDs, particle number (PN) concentrations, and count median diameters (CMDs) along the exhaust system under both the in-cylinder direct injection and port fuel injection modes, indicating that the particle process in the exhaust system is dominated by coagulation. The NM PN concentration decreases, and the NM CMD increases in the downstream exhaust gas, and the changes are more significant at higher accumulation mode (AM) PN concentration conditions. The coagulation history provided by modelling shows that coagulation mainly occurs between two NM particles (NM-NM) or one NM and one AM particles (NM-AM). At higher AM PN concentration conditions, the NM-AM coagulation dominates and quickly eliminates NM particles, resulting in more significant NM particle reduction. The PN concentration variation as a function of time indicates that PN concentration decreases quickly at first and then the decreasing rate slows down.

ANALYSIS OF CRANKSHAFT MECHANISM OF AGRICULTURAL ENGINE UNDER THE APPLICATION OF COMPOUND SUPERCHARGING TECHNOLOGY

With the development of engine supercharging technology and the application of in-cylinder direct injection technology, engines with high power and torque have become a trend. Crankshaft, as one of the most important and expensive parts in tractor engine, plays the role of transforming linear motion into circular rotation. The damage and destruction of crankshaft will lead to the damage of other parts of the engine, which makes the engine unable to work normally, and its stability affects the reliability of the whole engine to a great extent. The main failure form of tractor engine crankshaft is bending fatigue failure, so alternating bending stress occurs in crankshaft, which may cause fatigue failure of crankshaft. Crankshaft is one of the important components of tractor engine, and its stress is complex, which is the key and difficult point of engine design. In this paper, the crankshaft of tractor engine is analysed and studied based on compound supercharging technology, so that the dynamic characteristics of the engine are deeply understood, the action law of dynamic working load is mastered, the response analysis and evaluation of the system are carried out, and the optimization method of crankshaft mechanism of agricultural tractor engine is found out.

Simulation study on effect of late-intake-valve-closing Atkinson cycle on the performance of a direct injection engine based on fuel economy

Given the wide application of hybrid engines, how to improve hybrid engine fuel economy is being more and more studied, and using the Atkinson cycle to improve fuel economy is considered effective. In this study, the in-cylinder direct injection engine model was established with the data obtained from a benchmarking test using the GT-POWER simulation software. The working process of this engine was simulated after using Atkinson cycle. This simulation primarily focused on the research of the impact on engine fuel economy with different late intake valve closing strategies. The simulation results were calculated under the partial load conditions which are typically used in hybrid engines. The results indicated that engine fuel economy improved and fuel consumption decreased by using the Atkinson cycle. However, the Atkinson cycle would cause a decrease in power.

Effect of Spark Ignition Timing and Water Injection Temperature on the Knock Combustion of a GDI Engine

A turbocharged downsizing spark ignition (SI) engine cooperating with an in-cylinder direct injection technology is one of the most effective ways to improve the power and economy of gasoline engines. However, engine knock has limited the application and development of the downsizing of gasoline engines. Water injection technology can effectively suppress the knock. In this study, a method of numerical simulation was used to explore the effect of the water injection temperature on the combustion and suppression of the knock. First of all, the knock of the gasoline engine was induced by advancing the spark timing. Then, when the other conditions were the same, different water injection temperatures were set. The results show that lowering the water injection temperature reduced the knock intensity in the cylinder, but increasing the water injection temperature made the water distribution more uniform, and the peak values of each monitoring point were more consistent. The circulating work power increased with the increase of the water injection temperature. For emissions, as the temperature of the water injection increased, the emissions of soot and unburned hydrocarbons (UHCs) decreased, and NOx slightly increased.

Biodiesels powered in-cylinder common rail direct injection (CRDi) Assisted Homogeneous Charge Compression Ignition (HCCI) engine

ABSTRACT Experimental tests were performed on homogeneous charge compression ignition (HCCI) with in-cylinder direct injection (DI) of diesel, biodiesel of Ceiba Pentandra oil methyl ester (CPOME) and biodiesel of Acid oil methyl ester (ACOME). Initially some trial experiments were conducted at different fuel injection timing (IT) to distinguish the HCCI operation from common rail direct injection (CRDI) operation. For this, heat release rate (HRR) analysis, trial experiments were conducted for 40 % Load. The cool flame always started at about 20° before top dead centre (bTDC) showing HCCI operation started with fuel IT advancement of 50° bTDC and more. HCCI engine showed lowered peak HRR and retarded one. Higher injection pressure (IP) lowered oxides of nitrogen (NOx) due to lower HRR. NOx of 42 ppm, 36 ppm and 34 ppm were achieved with diesel, ACOME and CPOME respectively at IP 900 bar and IT of 80° bTDC in HCCI mode. Lower smoke of 9 HSU, 15 HSU and 17 HSU was achieved with diesel, ACOME and CPOME respectively at the same operating conditions. Overall, it could be concluded that, IP 900 bar and IT of 80° bTDC are the best operating conditions to reduce NOx and smoke with slightly lower brake thermal efficiency (BTE) in HCCI mode.

Effect of water injection on the knock, combustion, and emissions of a direct injection gasoline engine

A turbocharged downsizing spark ignition (SI) engine cooperating with in-cylinder direct injection technology is one of the most effective ways to improve the fuel economy and to reduce the emissions of gasoline engines, but knock combustion limits the application and development of downsizing of SI engines in practice. In this research, a numerical simulation method was used to study the feasibility of in-cylinder direct water injection technology to weaken the knock tendency of a turbocharged direct injection gasoline (GDI) engine and improve its combustion emission performance. First, the knock of a certain type of turbocharged direct injection gasoline engine was induced by increasing the spark timing, thereby determining the position at which the end mixture was spontaneously ignited. Then, at a given water injection moment, the influence of the amount of water injection on the knock and emissions of the turbocharged direct injection gasoline engine was investigated. The results show that the knock intensity gradually decreased with the increase of the water injection quality. For the cyclic work, the amount of circulating work decreased with the increase of the water injection quality. Water injection is beneficial for reducing the emissions of nitrogen oxides (NOX), carbon monoxide (CO), and unburned hydrocarbons (UHC). However, the soot emissions will increase as the amount of water injection increases.