Direct Injection Engine Research Articles

Modeling Ethanol-Blend Fuel Sprays under Direct-Injection Spark-Ignition Engine Conditions

Computational modeling of fuel-injection and fuel-impingement processes was carried out to provide insight into previous experimental results obtained from a direct-injection spark-ignition research engine operated with various ethanol and aromatic fuel blends. Seven model fuels were evaluated using both single- and split-injection strategies. Model results showed that droplet vaporization enriched the concentrations of aromatic species in the liquid phase, especially those with low vapor pressure, and ethanol-containing fuels altered droplet sizes and led to increased liquid-phase mass in the cylinder. For the spray-modeling conditions studied, most of the injected fuel remained in the liquid phase, which would be expected to result in more fuel impingement on cylinder or piston surfaces. Fuel impinging on lower cylinder-temperature surfaces was found to create wall films that could interact with the piston during the compression stroke. Fuel impinging on hotter piston-temperature surfaces vaporized more readily, but for fuels with high ethanol and aromatic content, wall films remained and were highly concentrated with lower vapor pressure and aromatic compounds. These films could lead to pool fires during combustion and therefore significant particulate matter emissions.

Multiple combustion modes switching to realize full-load efficient energy conversion of n-butanol/diesel dual direct injection (DI2) engine

The dual direct injection (DI2) engine system involves the in-cylinder co-direct injections of two fuels with the potential to address the operation limitations of traditional dual-fuel engines at part load conditions. However, for the DI2 engine, its optimal fueling strategies and combustion modes under different load conditions are still unknown. By selecting n-butanol and diesel as the test fuels, this study devotes to identifying the optimal combustion schemes of the DI2 engine at different loads using three-dimensional engine simulation combined with an improved genetic algorithm, and further revealing its optimal fuel stratification and auto-ignition characteristics. The results showed that for low load, the optimal DI2 strategy is to pre-inject a low proportion of diesel (near 20%) into the cylinder early in the compression stroke and then introduce n-butanol into this diesel atmosphere. On the contrary, the fuel injection sequence is reversed at mid load, in which n-butanol is first injected into the combustion chamber to form a partially premixed n-butanol/air mixture, followed by a late diesel injection at −50 to −20 °CA after top dead center (TDC). As for the high-load operation, n-butanol is still preferred to be partially premixed, but the diesel injection event is delayed until after TDC. The main factors driving the ignition under low load are the fuel reactivity and temperature, while at mid load the ignition is primarily initiated by fuel reactivity, however, the effect of temperature is highlighted under high load.

Study and Performance Characteristics of Gasoline Direct Injection Engine Using Alternative Fuels

Abstract: Biogas is the one of the best alternative fuel for IC engines. However some improvements and different techniques are still needed. In this research biogas with petrol fuelled Gasoline Direct Injection (GDI) engine performance was to be studied. The current study shows that biogas with petrol using GDI engine, particularly beneficial to reach interesting conversion efficiencies. It allows a significant boost in energy conversion from biogas compared to existing system.

Combined impact of excess air ratio and injection strategy on performances of a spark-ignition port- plus direct-injection dual-injection gasoline engine at half load

Spark-ignition direct-injection gasoline engine is one of the main power of passenger cars. In this study, combined impact of excess air ratio (λ) and injection strategy on performances of a spark-ignition port- plus direct- injection (PI + DI) dual-injection gasoline engine at half load was investigated experimentally. Experimental results show that the brake mean effective pressure decreased with increasing λ at half load; the brake thermal efficiency first increased, then reached the highest value at approximately λ = 1.1 or 1.2 for different injection strategies, and finally decreased with increasing λ; the maximum cylinder pressure, maximum heat release rate and maximum cylinder temperature decreased with increasing λ, and their corresponding crank angles delayed; the starting of combustion (CA05) increased with increasing λ, the CA05 at PI0DI100 (0 % PI and 100 % DI per cycle), late DI mode and any λ values was the closest to top dead center; for early DI mode, combustion center (CA50) of PI0DI100 was greater or lower than that of PI50DI50 (50 % PI and 50 % DI per cycle) at roughly λ < 1.15 or λ > 1.15, respectively; combustion stability (COVimep) of early DI mode can be controlled within 2 %; the λ had a significant effect on brake-specific carbon monoxide (BSCO) emission at rich mixture and a little effect on BSCO emission at lean mixture; the brake-specific hydrocarbon (BSHC) emission of early DI mode was much higher than that of late DI mode, the injection strategy had an important effect on HC (hydrocarbon) emission; for early DI mode, the brake-specific nitrogen oxides (BSNOX) emissions first increased with increasing λ, then reached the highest value at λ = 1.1, and finally rapidly decreased with further increasing λ; for late DI mode, the BSNOX emissions decreased with increasing λ; the soot emission decreased with increasing λ; the soot emission of late DI mode was much higher than that of early DI mode; at a constant λ, sootPI50DI50,early DI mode ≈ sootPI0DI100, early DI mode ≪ sootPI50DI100, late DI mode < sootPI0DI100, late DI mode.

Performance characteristics optimization of CRDI engine fuelled with a blend of sesame oil methyl ester and diesel fuel using response surface methodology approach

The primary aim of this experiment was to use response surface methodology (RSM) to optimize engine operating parameters for optimal performance and emission characteristics of a common rail direct injection (CRDI) diesel engine fuelled with sesame oil methyl ester (SOME)/diesel blends. The experiments were carried out on a water-cooled common rail direct injection engine with a 4-stroke, single-cylinder connected to an eddy current dynamometer. As input variables, the SOME% (0%–20%), fuel injection pressure (FIP) (500–600 bar), EGR rates (0%–14%), and engine load (0–12 kg) were used. The optimization method is utilized to maximize brake thermal efficiency (BTE) while minimizing BSFC, CO, HC, and NOx emissions. Experimental research data were used to create the RSM model through DoE (Design of experiments). The most relevant factors impacting the responses were identified using an ANOVA analysis. According to the optimization findings, the engine’s optimum working parameters were found to be a 20% SOME ratio, 577.5 bar FIP, 5.26% EGR rates, and 5.12 kg engine load. Under these operating circumstances, the optimal responses were determined to be 18.92% BTE, 0.3705 kg/kWh BSFC, 0.03190% vol. CO, 13 ppm HC, and 447.5 ppm NOx emission. At the same time, R2 values were 96.35%, 87.54%, 91.57%, 95.87%, and 93.73% for BTE, BSFC, CO, HC, and NOx respectively.

A Computational Investigation of Engine Heat Transfer with Ducted Fuel Injection

Ducted fuel injection (DFI) is an innovative method that curtails or prevents soot formation in direct-injection compression-ignition engines. DFI uses a simple duct, positioned outside each injector hole, facilitating the fuel/charge gas mixing before ignition. This reduces the equivalence ratio below two, in the autoignition zone, which in turn decreases soot formation. But this method also reduces fuel-conversion efficiency. This study investigates the effects of DFI on in-cylinder heat transfer. Experiments with conventional diesel combustion (CDC) and DFI were performed at four different dilution levels. Computational fluid dynamics (CFD) simulations were carried out at conditions matching those of the experiments, and the simulations were validated by the experimental data. The CFD simulations enabled to examine of in-cylinder heat release and temperature distributions. The heat transfer to the piston, head, and cylinder was investigated. The results show that DFI increased the heat transfer to the walls compared to CDC under the same conditions. This could help explain why DFI has been observed to reduce fuel-conversion efficiency by approximately 1% (absolute) relative to CDC under certain conditions. The efficiency loss typically decreases with dilution, such that DFI can improve fuel-conversion efficiencies relative to CDC at higher dilution levels.

Spray and dynamic heat transfer induced by 2-methylfuran transient spray impingement on piston surface

In the face of increasing air pollution and stricter emission requirements, it is very important to reduce particulate matter emissions in engine exhaust. The presence of the attached liquid film in gasoline direct injection engines produced by spray impingement is an important reason for the increase in engine particulate emissions. The dynamic heat transfer induced by the spray impingement is a key factor affecting the evaporation and existence time of liquid film. In this paper, a single-hole injector was used to carry out 2-methylfuran (MF) spray impingement experiments. The macroscopic morphological characteristics and the dynamic heat transfer of transient spray impingement under different conditions were systematically studied. Spray particle size distribution and spray impact force were also measured to assist in explaining the underlying mechanism responsible for the dynamic heat transfer. The results show that the surface heat flux increases with the rise of initial piston surface temperature. Increasing the injection pressure makes the droplets have a stronger impact force and smaller average diameter, which enhances the heat flux and also produces more bounce and splash of droplets on piston surface. Both the number of small-size droplets and impact force are reduced by the intense evaporation caused by increasing the injection temperature, resulting in the decrease of heat flux and surface temperature reduction. Increasing the distance decreases the droplet diameter and impacting force, as a result, the heat transfer intensity is weakened.

Investigation of injection characteristics for optimization of liquefied petroleum gas applied to a direct-injection engine

With the strengthening of emission regulations for internal combustion engines, studies on alternative fuels that can be immediately adopted are being conducted worldwide. As liquefied petroleum gas (LPG), which is an alternative fuel, emits fewer pollutants, it is considered a practical solution in situations where it is difficult to switch from a conventional engine system to an electric powertrain immediately. Several attempts have been made to convert the fuel in a conventional engine system to LPG for fuel efficiency, but research on optimizing the performance of LPG conversion engine remains insufficient. Since most recent gasoline engines operate with direct-injection fuel supply system, the LPG conversion engine should also consider direct-injection. Injection characteristics such as injection quantity and spray image are used as basic data to optimize engine control parameters. Therefore, in this study, the injection characteristics were analyzed according to fuel type for optimizing the LPG applied to in a gasoline direct-injection engine. According to the analysis results of the spray image acquired with a high-speed camera, the atomization properties of LPG are superior to those of gasoline. And similar to the actual engine condition, the difference is expected to increase as the ambient temperature increases. Since gasoline has a relatively higher density than LPG, the injection quantity of LPG is smaller than that of gasoline fuel. However, it can be calibrated by increasing the injection duration by 2%–5% or increasing the injection pressure by 4%–10% for the LPG conversion engine.

Nano-particle Characteristic Emitted from Gasoline Direct Injection Engine Equipped with Non-Thermal Plasma Device

The impact of non-thermal plasma (NTP) on particulate matter (PM) removal, nitrogen oxide (NOx) reduction, and hydrocarbon species in exhaust gases from gasoline direct injection (GDI) engines using gasoline E20 fuel and a mean effective pressure (IMEP) of 6 bar. The experiments were conducted with an exhaust gas flow rate of 20 L/min, applying high voltage in the range of 0 to 10 kV (2 kV per step) at a frequency of 500 Hz. The results show that NTP reduces PM concentrations, particularly in the nucleation mode (10 nm particles). Maximum PM removal of approximately 83% However, with experimental results, compared to 0 kV, the production of particulate matter Aitken mode increased up to 19 times for a voltage increase of 10 kV, and NOx removal has been at a maximum of about 9.5%, with an energy density of 5 J/L at 10 kV. The effects of NTP on hydrocarbon species such as ethylene, propylene, acetylene, 1.3 butadiene, methane, and ethane have been slightly affected by increased high voltages.

INFLUENCE MECHANISM OF STAGNATION-POINT FLOW ON LIQUID-PHASE SPRAY PENETRATION LENGTH UNDER ENGINE-LIKE CONDITIONS

Formulation of liquid-phase spray penetration length (LPL) is one of the basic research works of direct injection (DI) engines. To predict the spray evolution and LPL in the limited space more accurately, the diffused background-illumination extinction imaging (DBI) technology and highspeed schlieren method were employed to detect the liquid- and vapor-phase spray development in a constant volume combustion chamber (CVCC). The experimental results show that the LPL of the impinging spray is significantly smaller than that of the free spray when the LPL is close to the impinging distance. When the LPL is much smaller than the impinging distance, the LPL of impinging spray is the same as that of free spray. Furthermore, based on the CFD simulation and the stagnation-point flow theory, the spatial distribution of velocity, pressure, and density at the near-wall surface was analyzed in detail. Due to part of the spray kinetic energy was converted into potential energy, creating a sharp increase in pressure and density near the stagnation point, which suppressed the movement of fuel droplets, resulting in a significantly smaller LPL. Moreover, a novel LPL prediction model is introduced, which considering the inhibiting effect of wall on spray penetration and demonstrates enhanced predictive capability of experimental results.

Prediction of Responses for Simarouba Biodiesel based CRDI Engine using General Regression Neural Network

The evaluation of performance and emission of Common Rail Direct Injection (CRDI) engine fuelled by various biodiesel at different operating conditions is time consuming and expensive. This can be overcome by using prediction techniques like GRNN. The GRNN model is developed using ‘newgrnn’ function in Matlab R2019b software to predict the performance and emission responses of CRDI engine for simarouba biodiesel. A total of 27 experimental dataset of each biodiesel is used for development of model. Out of 27 experimental dataset, 21 datasets are selected randomly for training the model. The remaining 6 datasets are utilized for testing the GRNN model. In this study, 20 different values of spread parameters within the range 0.05 to 1 with step increment of 0.05 are chosen. As a result, 20 simulations are performed and the best predicted results are chosen based on least mean error. The optimum spread parameter for simarouba, pongamia and composite biodiesel GRNN model was found to be 0.1, 0.1 and 0.05 respectively. The Root Mean Square Error (RMSE) values of different responses are found to be acceptable. The results indicated that GRNN model for the prediction of engine responses yields good correlation with experimental values and are acceptable for new predictions.

NUMERICAL STUDY OF DIRECT INJECTION SPRAY BEHAVIOR OF GASOLINE AND METHANOL-GASOLINE BLENDS UNDER SPLIT-INJECTION STRATEGY IN ENGINE-LIKE CONDITIONS

Several studies have shown that the split-injection strategy has improved the shortcomings of the high particulate matter emissions and cycle-to-cycle variations in homogeneous and stratified combustion modes of gasoline direct injection (GDI) engines. However, the spray behavior under the split injection strategy is poorly understood. This study uses computational fluid dynamics (CFD) simulations in Converge software to investigate the spray characteristics of gasoline and methanol-gasoline blends under a split-injection strategy. The simulation studies were performed for a multihole GDI injector in a constant volume spray chamber, replicating the ambient conditions similar to a GDI engine's homogeneous and stratified combustion modes. Appropriate models for simulating different spray phenomena, such as spray breakup, collision, and coalescence, were used. The CFD model was validated using the experimental spray penetration length provided in the engine combustion network database. The results showed that the split-injection reduced the Sauter mean diameter (SMD) of fuel spray droplets and liquid fuel mass content than a single injection case. The dwell time of 2 ms was found suitable for homogeneous mode conditions, while its effect was insignificant in stratified mode conditions. Further, a split ratio of 80:20 resulted in smaller SMD during the injection period and a higher fuel evaporation rate. The effect of methanol addition was also explored under the split-injection mode. M85 showed higher deviations in the liquid spray penetration, SMD, and liquid spray mass content than G100.

Study of Soot Formation in Gasoline Direct Injection Engines by Means of Diffuse Back-Illuminated Extinction Imaging

Study of Soot Formation in Gasoline Direct Injection Engines by Means of Diffuse Back-Illuminated Extinction Imaging

Combined effects of diesel energy ratio and diesel injection nozzle diameter on natural gas high pressure direct injection engine with EGR

Combined effects of diesel energy ratio and diesel injection nozzle diameter on natural gas high pressure direct injection engine with EGR

Comparative Analysis of Injection of Pyrolysis Oil from Plastics and Gasoline into the Engine Cylinder and Atomization by a Direct High-Pressure Injector

The article discusses the results of experimental studies on the course of pyrolysis oil injection through the high-pressure injector of a direct-injection engine. The pyrolysis oil used for the tests was derived from waste plastics (mainly high-density polyethylene—HDPE). This oil was then distilled. The article also describes the production technology of this pyrolysis oil on a laboratory scale. It presents the results of the chemical composition of the raw pyrolysis oil and the oil after the distillation process using GC-MS analysis. Fuel injection tests were carried out for the distilled pyrolysis oil and a 91 RON gasoline in order to perform a comparative analysis with the tested pyrolysis oil. In this case, the research was focused on the injected spray cloud analysis. The essential tested parameter was the Sauter Mean Diameter (SMD) of fuel droplets measured at the injection pressure of 400 bar. The analysis showed that the oil after distillation contained a significant proportion of light hydrocarbons similar to gasoline, and that the SMDs for distilled pyrolysis oil and gasoline were similar in the 7–9 µm range. In conclusion, it can be considered that distilled pyrolysis oil from HDPE can be used both as an additive for blending with gasoline in a spark-ignition engine or as a single fuel for a gasoline compression-ignition direct injection engine.

Spark discharge energy effect on in-cylinder characteristics performance of rapid compression and expansion machine with spark ignition direct injection strategy

A spark ignition strategy in compression ignition has been considered to achieve high performance of gasoline direct injection engines. The spark ignition energy depends on the discharge current and the spark discharge duration. However, the respective roles of both on the rapid compression and expansion machine (RCEM) running with spark ignition and gasoline direct injection in-cylinder pressure have not been fully investigated. Both experiments and simulations were carried out in this study to investigate the spark discharge energy’s effect on in-cylinder characteristics performance. Three spark ignition strategy ranging from 50 mA up to 200 mA is applied to enhance the ignition discharge energy according to six selected cases of ignition timing variation (0.7 ms, 1.0 ms, 2.0 ms, 3.0 ms, 4.0 ms, and 5.0 ms). The results show the total released energy at the simultaneous ignition strategy was the largest (around 190 mJ/s), followed in order by the pair ignition strategy and individual ignition strategy. The highest turbulent kinetic energy of gasoline RCEM with spark ignition strategy is 1.43 m2/s2 (an increase 27.96 % from RCEM fueled with diesel). When the start of injection (SOI) of direct injection gasoline was set the same as the SOI of direct injection diesel at 10 oCA BTDC resulted in the thermal efficiency of gasoline RCEM with spark application slightly increased when spark time duration is prolonged at the average of 15.96 %. Finally, the establishment of a compression ignition engine combined with spark energy discharge might contribute to faster plasma formation, as well as expose the kernel development to a wider range of spark duration.

Investigation on combustion characteristics and gas emissions of a high-pressure direct-injection natural gas engine at different combustion modes

In the present study, the potential of natural gas pre-injection, mixing-limited combustion, and slightly premixed combustion modes were evaluated to achieve high thermal efficiency and low nitrogen oxides and carbon monoxide emissions. To this end, a dual direct injection model was established to perform numerical simulations. The obtained results revealed that in the natural gas pre-injection mode, the optimized natural gas pre-injection proportion and injection interval between the end of natural gas pre-injection and the start of diesel injection can significantly reduce carbon monoxide emissions and improve indicated thermal efficiency with a slight increase in nitrogen oxides. In the mixing-limited combustion mode, combustion phasing and indicated thermal efficiency are not sensitive to the variations of the injection interval between diesel and natural gas. Moreover, a larger injection interval between diesel and natural gas is beneficial to reduce carbon monoxide. In the slightly premixed combustion mode, as the injection interval between diesel and natural gas decreases, combustion phasing delays, carbon monoxide emissions reduce, and nitrogen oxides emissions increase first and then decrease. Advancing the start of natural gas injection increases maximum pressure rise rate and nitrogen oxides in both natural gas mixing-limited combustion and slightly premixed combustion modes but decreases carbon monoxide dramatically. The natural gas mixing-limited combustion mode has more potential to meet carbon monoxide limits imposed by the Euro VII standard with no need for extra after-treatment devices while improving thermal efficiency.

Investigation into shock-to-shock interactions induced by flash boiling and the impact on spray behaviors

Through recent numerical studies, the shock-to-shock interactions between flash-boiling jets are believed to be the reason for multi-jet spray collapse in gasoline direct injection (GDI) engines. But this sort of interaction was not well understood through the experimental investigation. In the present study, a two-hole GDI injector was used to examine this process via optical diagnostics and CFD simulations. With the increase in superheat level (Rp), the shock waves (primary cells) in individual jets became observable. Further increase in Rp could cause shock-to-shock interactions, and a secondary cell could be formulated between two primary cells. The different intensity of shock-to-shock interactions would result in different jet-to-jet interaction behaviors. In the moderate interaction region, the secondary jet appeared inside and downstream of the secondary cell, but the sprays did not collapse. In the highly interaction region, both the secondary jet and spray collapse could be observed, where the secondary jet would laterally develop perpendicular with the plane of the two jets. The detailed numerical results showed that the secondary cell was small in the moderate interaction region, but became much larger in the highly interaction region. The occurrence of secondary cell directed the fuel from primary cells into the secondary cell, contributing to the generation of secondary jet. After flowing out of the secondary cell, the incipient secondary jet could subsequently entrain the nearby low-velocity fuel. Further, the strong shock-to-shock interactions would alter the shape of primary cells, reducing the transverse velocity component of jets and promoting collapse. Based on the experimental and numerical results, the existence of shock-to-shock interactions and its important role in jet-to-jet interactions and spray collapse were fully illustrated, and this understanding would be of help in nozzle optimization.

The Impact of Thermochemical Exhaust Energy Recovery Using Ethanol-Gasoline Blend on Gasoline Direct Injection Engine Performance

Thermochemical exhaust energy recovery in a modern gasoline direct injection engine is investigated using ethanol-gasoline blend (E25) and gasoline, as base fuel. The primary objectives of this research are focused on reducing carbonaceous emissions as well as improving thermal efficiency and fuel economy in combustion engines. These are consistent with the global commitment to lessen carbon emissions and meet environmental regulations and agreements.The possibility of hydrogen production through catalytic reforming of mentioned fuels using actual exhaust composition is investigated on full-scale Rh (Rhodium)—Pt (Platinum) catalysts. ANSYS-Chemkin is utilized for thermodynamic equilibrium analyses based on the Gibbs energy minimization method to explore the key reaction pathways for E25 reforming. Main reforming parameters including steam to carbon molar ratios and reforming temperatures are selected to investigate the feasibility of ethanol-gasoline blend reforming as well as to identify the reformate composition and evaluate the whole process efficiency. The results revealed that the presence of ethanol in reforming fuel mixture facilitates endothermic reactions and improves hydrogen-rich mixture, particularly at high engine load conditions where maximum heat recovery is obtained. Furthermore, E25 fuel reforming helped achieving up to 16% greater CO2 compared to gasoline fuel reforming under the same engine condition. Overall, the experimental results of full-scale reforming tests using E25 can be accredited for effective implementation of the reforming technique in practical application.

An investigation of optimum control of injection timing/injection pressure for a multicylinder common rail direct injection engine fueled with AB20 blend

A multicylinder turbocharged common rail direct injection engine was tested at part load (62.4 Nm) and high load (156 Nm) to determine the optimum combination of injection pressure (IP) and injection timing (IT) for AB20 blended fuel. IP and IT were varied from default settings, that is, 9.2° before top dead center (BTDC), 45 MPa at part load; 9.8° BTDC, 95 MPa at high load, as specified in the calibration map of the engine. As a result of the experimental results, brake thermal efficiency (BTE) increased up to 5.36% when IP increased from 35 MPa to 45 MPa and 0.72% when IP increased from 45 MPa to 55 MPa under the part load condition. At high load, the maximum BTE of 38.22% was attained at 105 MPa IP and 9.8° BTDC IT. At this condition, nitrogen oxide (NOx) emission was noted as 1353 ppm, which is 12.28% higher than the NOx noted for diesel fuel at the default IP and IT conditions. When IP increases from 35 to 55 MPa at part load and 85–105 MPa at high load, cylinder pressure, heat release rate, and rate of pressure rise increase at all tested ITs. At high load, the condition of retarded IT (8.8° BTDC) and default IP (95 MPa) shows (a) 2.35% higher BTE and (b) almost similar NOx and improved HC, CO, and smoke emissions for the AB20 blend. Moreover, at the same experimental conditions, premixed heat release for the AB20 blend was noted to be 70.16 J/Deg./C.A, with heat release rate peak at 6° ATDC.