Direct Injection System Research Articles

Numerical investigation of in-cylinder gas motion dynamics in a heavy-duty direct injection hydrogen internal combustion engine

Mixture homogenization is one of the most important parameter for hydrogen internal combustion engines (H2ICE) to achieve near-zero NOx emissions and stable combustion, especially when premixed combustion strategy is used. On the other hand, inhomogeneities are inevitable due to the limited duration for mixing. This is more prominent in H2ICEs; those adopts low pressure direct injection (LPDI) system. Optimizing an engine to achieve higher level of homogeneity requires profound understanding of in-cylinder gas motion and mixing dynamics.To establish deeper comprehension of gas motion inside the cylinder, a 13-L LPDI H2ICE was modelled, and effect of different parameters were investigated by a holistic 1D-3D simulation methodology. While boundary conditions of operating point were obtained from the 1D simulations, different swirl numbers (SN), piston shapes and injector cap designs were simulated with 3D-CFD. Simulation results were analyzed based on uniquely defined parameters like homogeneity index (HI) and symmetricity of motion (SOM), as well as standard parameters like turbulence kinetic energy (TKE), and 3D visualizations of equivalence ratio iso-surfaces. Analysis showed that, there is a negative correlation between SN and HI under investigated conditions. Moreover, it was found that piston shapes which are promoting the tumble motion, improved average TKE by 31% and HI by 28% over base piston. This study aims to be a reference for the in-cylinder gas motion design of ultra-lean LPDI H2ICEs, where the target is retrofitting an existing diesel engine and attaining the best HI, SOM and TKE values at rated power conditions.

Experimental Study on Performance and Emission of an Electric Turbocharged Hydrogen Direct Injection Engine.

Hydrogen is emerging as a promising zero-carbon emission energy source for vehicle engines. However, the full potential of hydrogen engines and their economic viability remain uncertain. Additionally, comprehensive data on ultralean combustion performance and emissions as well as strategies for improving HC and CO emissions are lacking. This study addresses these gaps by thoroughly examining hydrogen combustion and emissions in a 1.5 L engine. Incorporating a hydrogen direct injection (HDI) system and an electric supercharger, we investigated emissions under various piston ring tensions during lean limit operations. Our findings reveal that hydrogen exhibits a fast combustion speed in the engine within 20 °CA, along with excellent ultralean burn performance, expanding the lambda limit to 3. As the load increases, the thermal efficiency significantly improves, reaching a maximum of 40.8%. NOx emissions peak at a lambda of 1.1 but decrease notably above 2.7, with levels below 10 ppm. At a lambda near 3, NOx emissions hover between 0 and 5 ppm, approaching zero emissions. Additionally, lubricating oil consumption during engine operation yields a minor HC and CO emissions. Higher tension piston rings result in lower HC and CO emissions, typically below 5 ppm, nearing zero emission levels.

Low-pressure gasoline direct injection system development and emissions analysis for a reciprocating two-stroke engine

This study presents the design and construction of an electronic low-pressure gasoline direct injection system for two-stroke engines, with the objective to study engine performance and the emission of exhaust polluting gases, maintaining the expectations of this type of engine. The investigation includes a test bench with an incorporated engine and the required control devices for this, as well as a gas analyzer Class 0, a computerized data acquisition and several tools for displaying and process all the electronic signals from the engine in real time. In order to manage this system, a custom electronic injection control unit has been designed and built, which allows to control the fuel injection timing and duration. This unit uses the signal from an inductive sensor installed in the crankshaft as a reference and synchronization point. Additionally, modifications have been made to the fuel feeder circuit and the electronic of the test engine, as well as to some parts of the mechanism in order to adapt them to this technology. The implementation of the engine tests is described, and the performance and operational points of the original system and those of the new injection system are evaluated.

Experiment investigation on Momordica Charantia biodiesel in CRDI engine with cerium oxide (CeO2) nanoadditives

Most of the transportation fuel is diesel. This type of fuel is widely used and helps the economy by providing high combustion efficiency and affordability. The goal of this study was to analyse the performance and characteristics of a multi-cylinder diesel engine utilising a rail direct injection system and fuel that's composed of 20% momordica. The addition of cerium oxide nanoparticles in the fuel mass fractions of 20 and 40 ppm was performed using an ultrasonicator and a mechanical homogeniser. These small particles help improve fuel stability and prevent injector blockages. By adding cerium oxide nanoparticles to the biodiesel–diesel blend, brake thermal efficiency and heat release rate were also improved. At full load, the MC20 emits 12.341 g/kW h of HC and 84 HSU of smoke, compared to 9.021 g/kW h and 52 HSU for the CONP 40 blended MC20. It is recommended to use cerium oxide nanoparticles at a concentration of 40 ppm for optimal performance, emission combustion, and characteristic enhancement.

Effects of PODE substitution rate and fuel injection timing on combustion, emission characteristic and energy balance in PODE-gasoline dual direct-injection engine

Dual direct injection (DDI) mode allows two kinds of different reactivity fuels to be flexibly injected into the cylinders and offers lower pressure rise rate (PRR), CO and HC emissions than Reactivity Controlled Compression Ignition (RCCI) mode. Thus, a single-cylinder engine was modified to adopt two direct-injection systems to inject PODE and gasoline respectively in this paper. Due to high oxygen content and high cetane number, PODE was selected as a high reactivity fuel to replace diesel in the experiments. The effects of different PODE substitution rates(PSR), PODE injection timing(injP) and gasoline injection timing(injG) on the combustion, emission characteristics and energy balance were studied. The results concluded the using PODE-gasoline mode could increase the indicated thermal efficiency(ITE) and reduce exhaust losses compared to the diesel-gasoline mode. As PSR increased, it led to the increased ITE and effective power, decreased CO, HC emissions. Compared to the PODE late injection mode, the effective power and ITE were higher, and CO, HC emissions were lower in the PODE early injection mode. The coefficient of variation of IMEP(COVIMEP) for the DDI combustion was also in an acceptable range. Furthermore, an early injG could lead to higher ITE, lower COVIMEP, CO and HC.

A Complete Assessment of the Emission Performance of an SI Engine Fueled with Methanol, Methane and Hydrogen

This study explores the potentiality of low/zero carbon fuels such as methanol, methane and hydrogen for motor applications to pursue the goal of energy security and environmental sustainability. An experimental investigation was performed on a spark ignition engine equipped with both a port fuel and a direct injection system. Liquid fuels were injected into the intake manifold to benefit from a homogeneous charge formation. Gaseous fuels were injected in direct mode to enhance the efficiency and prevent abnormal combustion. Tests were realized at a fixed indicated mean effective pressure and at three different engine speeds. The experimental results highlighted the reduction of CO and CO2 emissions for the alternative fuels to an extent depending on their properties. Methanol exhibited high THC and low NOx emissions compared to gasoline. Methane and, even more so, hydrogen, allowed for a reduction in THC emissions. With regard to the impact of gaseous fuels on the NOx emissions, this was strongly related to the operating conditions. A surprising result concerns the particle emissions that were affected not only by the fuel characteristics and the engine test point but also by the lubricating oil. The oil contribution was particularly evident for hydrogen fuel, which showed high particle emissions, although they did not contain carbon atoms.

Experimental analysis of the near-nozzle direct injection spray for gasoline and ethanol-gasoline blended fuels

The current work analyses the spray during the early stage of development in the near-nozzle region using a single-hole gasoline direct injection system for gasoline (G100) and ethanol-gasoline (E85) blended fuels. The present work combined a Galilean-type beam expander with an achromatic lens, using an LED light and a high-speed camera to visualize a magnified view of the near-nozzle microscopic aspect of the emerged jet. Three different shapes, spheroids, cylindrical, and steeple, were visualized experimentally during the evolution of the fuel jet under different fuel injection and chamber pressures. A transition in shape from the steeple-to-spheroid shape was detected. It was observed that the velocity of the emerged jet is affected by its evolved shapes, attributing to differences in the initial breakup characteristics and shot-to-shot variation in the spray at a given condition. The velocity of the cylindrical-shaped jet was 14% and 42% higher than the steeple and spheroid-shaped jets, respectively. The Rayleigh-Plesset equation describes the reason for an increase in the spheroidal-shaped jet velocity by 84% when the chamber pressure is reduced from 0.6 to 0.1 MPa. The Ohnesorge and Reynolds number of the emerged liquid jets were estimated to describe the breakup regime of the jet during the initial stage. It was observed that the cylindrical and the steeple-shaped jets pertain to a higher tendency to atomize during the initial stage of evolution compared to the spheroidal jet. The average jet velocities and liquid penetrations in the near-nozzle region for E85 and G100 were estimated.

Impact of medium-pressure direct injection in a spark-ignition engine fueled by hydrogen

In the automotive sector, hydrogen is being increasingly explored as an alternative fuel to replace conventional carbon-based fuels. Its combustion characteristics make it well-suited for adaptation to internal combustion engines. The wide flammability range of hydrogen allows for higher dilution conditions, resulting in enhanced combustion efficiency. When combined with lean combustion strategies, hydrogen significantly reduces environmental impact, virtually eliminating carbon dioxide and nitrogen oxide emissions while maintaining high thermal efficiency. This paper aims to assess the potential of using an outwardly opening poppet valve hydrogen direct injection (DI) system in a small engine for light-duty applications. To achieve this, a comparison of performance, emission levels, and combustion parameters is conducted on a single-cylinder spark-ignition (SI) research engine fueled by hydrogen, using both port fuel injection (PFI) and this new direct injection system. Two different engine loads are measured at multiple air dilution and injection timing conditions. The results demonstrate notable efficiency improvements, ranging from 0.6% to 1.1% when transitioning from PFI to DI. Accurate control of injection timing is essential for achieving optimal performance and low emissions. Delaying the start of injection results in a 7.6% reduction in compression work at low load and a 3.9% reduction at high load. This results in a 3.1-3.2% improvement in ISFC in both load conditions considered.

Effects of hydrogen peroxide on the combustion and emissions of an ethanol/gasoline combined injection engine under different excess air ratios

Hydrogen peroxide (H2O2) can prompt hydroxyl radicals and chain reactions in the combustion process. Compared with the research on compression ignition engines, the effects of H2O2 were less studied in spark ignition (SI) engines. In this paper, 30 % laboratory-grade H2O2 (H2O2-30 %) was utilized to obtain the H2O2-ethanol blend, which was applied to a direct injection system in a combined injection SI engine. Gasoline was used for the port injection system. The effects of H2O2-30 % ratio (H2O2r) = 0 %, 5 %, 10 %, 15 % and 20 % on combustion and emission performance of an ethanol/gasoline engine were explored at three excess air ratios (λ = 0.9, 1 and 1.2). Engine operating condition was set at engine speed = 1500 rpm and intake manifold pressure = 49.5 kPa. The results showed that H2O2-30 % could reduce the Tmax and Pmax, and extend CA0-10, CA50 and CA10-90. The inhibition effects of water on combustion performance can be alleviated due to the hyperactive H2O2 at the H2O2r > 5 %. Optimal H2O2r increased engine IMEP by 0.14 bar, 0.11 bar and 0.05 bar, and reduced BSHC and BSCO by 30.5 %, 36.6 %, 31.6 % and 17.9 %, 32.1 % and 40.8 %, respectively. BSNOx were reduced by an average of 38.0 %, 28.8 % and 42.2 % at λ = 0.9, 1 and 1.2, respectively.

Experimental and chemical-kinetic evaluation of a heavy-duty methanol PFI engine with direct water injection

Internal combustion engines are still widely used for propulsion in modern vehicles. Upcoming emission legislation imposes stricter limits on exhaust emissions. One method to achieve emission compliance is by using a three-way catalyst (TWC), which offers excellent emission reduction if the mixture is stoichiometric. However, stoichiometric mixtures in spark-ignited engines have the drawback of increased knock propensity. Knock can be mitigated by using water injection, which serves as both a diluent and utilizes latent heat to reduce the temperature, thereby reducing the reactivity of the unburned mixture. Methanol as a fuel has received more attention thanks to its high research octane number (RON) and its potential to contribute to decarbonization when produced as e- or bio-methanol. In the current study, Direct Water Injection (DWI) was evaluated on a Heavy-Duty (HD) single-cylinder research engine fueled by methanol. This work aims to fill a research gap on methanol-fueled engines with water injection. A direct injection system of water was chosen as it offers the freedom to inject during the closed cycle. Furthermore, a chemical kinetic study on the oxidation of stoichiometric methanol–water mixtures was conducted based on findings in the literature suggesting that, under certain conditions, water mixed with alcohol (in this case, ethanol) can reduce the ignition delay. The experimental results demonstrate that DWI effectively suppresses knock and reduced Nitrogen Oxides (NOx), albeit with deteriorated combustion efficiency. The chemical kinetic study suggested that at lower to intermediate temperatures, water acts as an efficient third-body collider, which lowers the ignition delay. However, this effect is not significant for the typical timescales encountered in HD engines.

Transient and altitude performance analysis of hydrogen fuelled internal combustion engines with different charging concepts

In the internal combustion engine industry, there is a significant shift towards alternative fuels to accomplish zero net carbon dioxide emissions as well as the legislation requirements. According to former studies, in addition to its advantages of being carbon-free and having appropriate combustion characteristics, low nitrogen oxide engine-out emission levels are achieved at lean burn combustion of hydrogen. Lean combustion leads to a turbocharging system requirement. Which is then utilized to generate the expected power output at high altitudes and during transient maneuvers.This study aims to determine the ideal air-charging vessel which can meet the objectives of high altitude. Which is 0 % torque derate and transient response time with respect to 0 %–90 % of maximum torque which is typically ∼3–4 s for diesel engines, while keeping the lean combustion to release ultra-low NOX emissions. Different charging concepts have been investigated by applying 1-D thermodynamic modeling on a H2ICE with a direct injection system which is for heavy-duty vehicles.

Laser ignition and flame propagation of methanol-air mixture in a constant volume combustion chamber

ABSTRACT The combustion performance of laser-ignited methanol-air mixture in a constant volume combustion chamber was investigated using the Schlieren photography technique. The experimentation was conducted at 5, 7, 9, and 11 MPa fuel injection pressure and 363 K initial chamber temperature using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser of 1064 nm wavelength. The gasoline direct injection (GDI) system was used for injecting the fuel at different pressures inside the chamber. The laser beam is focused into the chamber using a 150 mm focal length lens, and laser energy of 200 mJ was used for all experimentation. The Schlieren system was used for capturing flame propagation of methanol-air mixture for different equivalence ratios. The pressure-time history for equivalence ratio (ϕ) of 0.8, 0.9, and 1.0 was plotted and analyzed at different chamber filling pressures. Flame propagation was found faster for ϕ of 1.0 due to higher laminar velocity than 0.8 and 0.9. Flame visualization showed that the flame attains the ellipsoid shape during the early stage of ignition. It generates two lobes in the vertical direction and then again expands in a horizontal direction toward the ignition source. For all equivalence ratios, the flame propagation toward the incoming laser source (X-) was observed faster compared to the flame propagation in the direction and perpendicular to the laser beam direction. For all equivalence ratios, higher laminar flame speed was observed at 5 MPa injection pressure; however, it decreases as the injection pressure increases. At ϕ of 1.0 and 11 MPa injection pressure, the maximum peak pressure of 0.67 MPa and combustion duration of 19.3 ms were noted. At 9 MPa injection pressure and ϕ of 1.0, the peak pressure and combustion duration was found as 0.61 MPa and 19.4 ms, respectively. At ϕ of 0.8, the peak pressure and combustion duration were observed 0.27 MPa with 34.6 ms duration and 0.47 MPa with 36.9 ms duration at 5 MPa and 11 MPa injection pressures, respectively.

Experimental study on the effects of injection pressure on the combustion in a SI aviation piston engine fueled with kerosene

Kerosene becomes an alternative to gasoline in aviation piston engines for its safety and easy replenishment on some special occasions. However, the low octane number of kerosene tends to cause the knock of SI engine, as a result, most of the current SI kerosene engines run in an operation mode of two-stroke, which has the disadvantage of a low compression ratio and high fuel consumption. This study conducted a series of experiments on a two-stroke SI kerosene engine equipped with an air-assisted direct injection system to improve engine performance and fuel economy by increasing injection pressure and combining it with control strategy optimization. First, the effects of injection pressure on the combustion of kerosene engines were studied, including cylinder pressure, combustion rate, and the stability of combustion. The results show that increasing the injection pressure shortens the ignition delay, accelerates the combustion, and substantially improves the combustion stability. Then, the effects of increasing the injection pressure on the control strategies of injection advance angle, ignition advance angle, and fuel injection duration were investigated. Ultimately, based on the investigation of the effects of injection pressure on the control strategies, two optimizations of control strategies were obtained to reduce fuel consumption and increase power, respectively, with the former reducing fuel consumption by 14.9% and the latter increasing power by 6%.

Comparative study of hybrid architectures integrated with dual-fuel intelligent charge compression ignition engine: A commercial powertrain solution towards carbon neutrality

The dual-fuel intelligent charge compression ignition (ICCI) engine, equipped with double direct injection systems, can simultaneously improve fuel consumption and gaseous emissions by substituting low-carbon fuels for conventional fuels. This work investigates the optimal application of the ICCI engine on hybrid powertrains under various standard driving conditions. The purpose is to evaluate the profit of combining the advantages of hybrid powertrains with the advanced engine. Dynamic programming (DP) is applied to the energy management control, realizing the global optimization in the design phase. Three typical hybrid configurations are compared, including series (SHEV), parallel (PHEV), and power-split (PSHEV) hybrid electric vehicles. Except for the charging sustaining stage, the optimal state of charge trajectories are also researched to verify the reasonable parameters in the charging stage. Considering multiple objectives, a non-dominated sorting genetic algorithm (NSGA-II) is coupled to optimize fuel consumption, gaseous emissions, and battery cost. The ICCI engine is mapped by the test bench results, while the involved hybrid configurations are modeled in Matlab/Simulink. The results illustrate that PSHEV achieves the best fuel economy and emission purification among the involved structures. With the ideal solution provided by DP, fuel consumption and gaseous emissions for PSHEV are reduced by 10% and 50%, and the low-carbon fuel utilization ratio has tripled, contributing to carbon neutrality. The engine was operated in several working conditions for SHEV, achieving the cleanest gaseous emissions. For PHEV, the engine performance was rarely improved compared with the engine without the assistance of hybrid systems. The optimization provided by NSGA-II indicates that the minimum values of multiple objectives cannot be reached simultaneously. A further 50% reduction in emissions would cause fuel consumption to double the original.

Model-Free Control for High Pressure in a Direct Injection System

Model-Free Control for High Pressure in a Direct Injection System

Energy and exergy analysis for a turbocharged direct-injection hydrogen engine to achieve efficient and high-economy performances

Hydrogen is a potential alternative fuel for combustion engines with its higher renewability, near zero emission, and excellent combustion performance. The direct-injection (DI) engine provides favorable brake thermal efficiency (BTE), less dependence on the hydrogen purity but sacrificing the production cost. This study explores both effects of turbocharging and DI on the energy and exergy balances, as well as the cost-effective analysis on a spark ignition engine. Results reveal the exergy efficiencies are related to the engine speeds and loads, while its maximum is 58.8% with 3500 rpm and 1.4 MPa of brake mean effective pressure. The DI system increases 2.6% maximum BTE from the port fuel injection. However, the exhaust energy proportions exceed 32.8% and 18.9% at the maximum power and BTE. An organic Rankine cycle is utilized to improve the exergy to the maximum of 58.9%. The valuable experience can be widely applied for hydrogen engine design.

Understanding hydrogen jet dynamics for direct injection hydrogen engines

The energy paradigm is shifting toward carbon-free and low-emission alternative fuels. Among the many candidates, hydrogen is considered a promising option thanks to its favorable fuel properties, including zero carbon content, high gravimetric energy density, and fast flame speed, despite its technical fuel production and storage challenges. Direct injection technology has been identified as the best approach for applying hydrogen in combustion engines to overcome the accompanying issues, such as backfire and low energy density. However, studies have yet to be conducted on hydrogen jet behavior in direct injection systems, specifically, studies that elucidate engine design and injection parameter optimization in the combustion system. Therefore, we aimed to assess hydrogen jet behavior through experiments and computational approaches comprehensively. Hydrogen was injected at 10 MPa using the direct injection method into a constant volume chamber under a quasi-steady ambient condition. Z-type high-speed Schlieren imaging was performed using a high-speed camera to visualize the hydrogen jet structure, which depicted the hydrogen jet’s vapor intermittency and vortex structure. We also performed a computational fluid dynamics (CFD) simulation to understand the aerodynamics of the jet. The results showed the formation of vortical flow in the inner core region, where the pressure was comparatively lower than that on the outer side of the jet. Our further investigation of the injection strategy showed that multiple injections were more beneficial in forming a favorable hydrogen-air mixture near the spark plug than a single injection case.

The study of fuel accumulation in the oil of a gasoline engine with direct fuel injection

BACKGROUND: The worldwide powertrain engineering tendency is reduction of mass and dimension properties of an engine with simultaneous increase of its specific power and power-to-weight ratio. It can be achieved with compression ratio increase, engine cycle improvement, implementation of supercharging system and direct fuel injection. With the direct injection systems implementation, the issue of fuel accumulation in oil became relevant.
 AIMS: The article addresses general issues related to fuel accumulation in the motor oil.
 METHODS: Analysis of the published data addressing this issue.
 RESULTS: The reasons of fuel entry into oil were formulated, the possible acceptable limits of fuel concentration in oil were defined, and the data of vehicle fleet observation performed by specialists during several years was given.
 CONCLUSIONS: There is rather considerable range of opinions and recommendations regarding acceptable fuel concentration in oil. Therefore, it may be concluded that the value of fuel concentration in itself makes little difference, and, in order to define the maximal acceptable level of fuel concentration in oil, it is reasonable to carry out studies of determination acceptable limits of particular motor oil properties, primarily viscosity.

The effect of different charging concepts on hydrogen fuelled internal combustion engines

Hydrogen has been widely acknowledged as a potential fuel for internal combustion engines, owing to its unique chemical properties, environmental friendliness, and the ability to be produced from a variety of sources. The carbon-free nature of hydrogen is of particular significance as it is considered to be a key contributor to achieving stringent emissions regulations. However, one of the challenges associated with hydrogen as a fuel is the requirement for high air flow during combustion, which is necessary to meet the stoichiometry of the combustion process. The failure to achieve this high air flow can result in elevated emissions of Nitrogen Oxides (NOx), a phenomenon that is of concern for engine manufacturers.Turbocharging increases the power and efficiency of internal combustion engines by forcing more air into the combustion chamber. This can be particularly beneficial for hydrogen-fuelled engines as hydrogen has a lower energy density compared to traditional fossil fuels. This study aims to establish the most efficient boosting strategy for hydrogen-fuelled internal combustion engines with the goal of achieving a combination of fuel economy, high power density, and low emissions of NOx. To achieve this objective, a model of a hydrogen-fuelled internal combustion engine, specifically tailored for heavy-duty vehicle applications and featuring a direct injection system, has been developed. The validity of the model has been evaluated through a comparison of the results obtained from the model with those obtained from dynamometer testing. The study employs a model-based approach to examine a variety of charging concepts.

Effect of Excessive Air Ratio on Hydrogen-fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System toward Higher Brake Power and Thermal Efficiency

Effect of Excessive Air Ratio on Hydrogen-fueled Spark Ignition Engine with High Compression Ratio Using Direct Injection System toward Higher Brake Power and Thermal Efficiency