Increasing the Energy and Environmental Efficiency of Fuel Injectors in Diesel Engines

This study comprehensively evaluates the long-term impact of blended diesel fuels containing rapeseed oil on the wear and operational performance of diesel engine fuel systems. A Cummins ISF 2.8 engine equipped with a Common Rail Bosch CP3 injection system was tested over 1,200 hours under conditions simulating real operational cycles. Rapeseed oil used in the blends was cold-pressed, unesterified, straight vegetable oil (SVO) filtered to 5 μm before blending. A brief comparative statistical analysis (one-way ANOVA, α = 0.05) indicated that changes in injector wear metrics were significant for the 20% blend (p < 0.01). In comparison, the 10% blend did not differ significantly from diesel in wear-related parameters but significantly reduced smoke opacity (p<0.01). The experiments demonstrated that a 10% rapeseed oil blend resulted in a moderate increase in injector wear, a 3.1% reduction in injector mass flow, and a minor increase in the spray angle. In contrast, a 20% blend led to a 7.2% decrease in injector performance, significant carbon deposit accumulation of up to 28 µm, and erosion craters reaching 12 µm in depth. Fuel filtration resistance increased by 22% at higher biofuel concentrations, whereas cold-start performance deteriorated markedly, with start times increasing by 3.2 seconds. Despite these drawbacks, blends with up to 10% of rapeseed oil achieved a 14% reduction in exhaust smoke and maintained acceptable durability margins, indicating their practical feasibility for partial replacement of conventional diesel fuel.

ABSTRACT Micro gas turbines (MGTs) fueled with sustainable fuels like biogas can be used for distributed power generation while contributing to the realization of net-zero targets. However, designing MGT systems is fraught with challenges like achieving optimum turbine entry temperature (TET) and meeting the emission limits which depend on several interdependent design parameters. This study investigates the impact of secondary air flow rate and fuel injection strategy on microgas turbine performance under realistic operating conditions. The Finite Volume Method (FVM) is used for numerical investigation of a 20 kW swirl-stabilized tubular combustor for small-scale MGT systems. Turbulence modeling is performed using the realizable k − ε model, while the turbulence-chemistry interaction is simulated through the steady diffusion flamelet (SDF) approach, employing the GRI-3.0 chemical mechanism. The effect of secondary air flow rate variation (0.01, 0.02, and 0.03 kg/s) and different fuel injection strategies, direct injection (DI), swirl injection (SI), and multi-point injection (MPI), are examined. Secondary air flow rate of 0.02 kg/s emerges as the optimum choice based on consideration of outlet temperature, pattern factor, and NOX emissions. Testing different injectors with biogas shows that the MPI injector yields almost 30 % reduction in NOX emissions without compromising outlet temperature uniformity. Using the optimum secondary air flow rate and best injector design in terms of emissions, three fuels, natural gas (CH4), enriched biogas (BG80), and biogas (BG60), are investigated. Combustion efficiency and pressure drop remain similar for all the fuels, and net CO2 emissions are unaffected by fuel composition. Notably, NOX emissions decrease with higher CO2 content, with the lowest observed for BG60 due to the heat absorption by biogas. The findings will support the advancement of biogas-fueled MGTs for clean distributed power generation technologies.

The operation of a diesel engine is greatly affected by the fuel injection process. This process directly impacts fuel atomization and the spray's characteristic parameters, as well as the engine's economic efficiency, technical parameters, and emissions. The present study examines how increasing the fuel injection pressure affects the operating parameters of the 490 QZL diesel engine at maximum torque using a 3D model from the AVL Fire package. The results show that increasing the fuel injection pressure from 500 bar to 3,000 bar increases the power value by 19.7% and decreases the useful fuel consumption rate by 17.6%, with a fuel injection angle of 22 degrees before the Top Dead Center (TDC) remaining constant. Soot emission decreases by 44%, with a more significant decrease observed at injection pressures ranging from 1500 bar to 3000 bar. Nitrogen Οxide (NOx) emissions slowly increase at injection pressures from 1000 bar to 1500 bar, but rapidly increase at injection pressures above 1500 bar. Hydrocarbon (HC) and Carbon Monoxide (CO) emissions decrease most markedly at injection pressures from 1000 bar to 2000 bar; at higher pressure values, the decrease is slower. Additionally, as the injection pressure increases, the length of the fuel spray increases significantly; however, the spray cone angle changes minimally due to the influence of the nozzle hole's geometrical size. Increasing the injection pressure improves the economic efficiency and technical parameters, while reducing the HC, CO, and especially soot emissions. These results form the basis for improving the diesel engine test bed at the Mechanical Laboratory of the University of Transport and Communications in Vietnam.

A multiphase flow simulation is performed to investigate kerosene liquid fuel injection and breakup characteristics in a cavity-based supersonic combustor with a pylon injector. The homogeneous mixture model, Eulerian-to-Lagrangian transformation method, and adaptive mesh refinement (AMR) method are employed to resolve the breakup process of liquid multi-injections and examine injection phenomena. The large-eddy simulation (LES) model is utilized for turbulence modeling, while the Kelvin–Helmholtz Rayleigh–Taylor (KH–RT) hybrid model and the Abramzon evaporation model simulate secondary breakup and evaporation processes of the liquid fuel. The study analyzes the breakup and mixing efficiency of the liquid fuel under varying injection locations and equivalence ratios. The flow characteristics, droplet distribution, and total pressure loss are evaluated. The fuel distribution considering a specific droplet size is compared with experimental data, showing good agreement. The interactions between the flow around the pylon, the liquid injection location, and the adjacent wall significantly influence fuel distribution and breakup characteristics. In cases of wall-adjacent fuel injection, increased flow stagnation near the wall leads to an extended breakup length, while fuel distribution is further affected by the equivalence ratio and injection positioning. However, the equivalence ratio and fuel injection location have a minimal effect on total pressure loss.

Abstract Exhaust gas recirculation (EGR) can be exploited to increase the CO2 content at the exhaust of gas turbines (GTs), in order to improve the efficiency of carbon capture systems. The lower oxygen level leads to challenging conditions for the combustion process, resulting in high CO and unburned hydrocarbon emissions and the possible onset of thermoacoustic instabilities. To mitigate these effects and expand the combustor's operational range, pilot flames can be employed to stabilize the combustion process, with localized hydrogen injections further enhancing reactivity. In this demanding and complex environment created by EGR, fuel injection strategy is crucial in the flame stabilization mechanism, and many design parameters come into play. The present work illustrates the results of an extensive screening performed in a single-cup atmospheric test rig at the THT Lab of the University of Florence, with EGR conditions simulated with CO2 addition in the combustion air. In particular, six different configurations of a dry low NOx industrial burner have been tested, varying the arrangement and geometry of the pilot jets, and the premix fuel injection mode. Burners' performance has been compared in terms of CO emissions, lean blow-out (LBO) limits, and dynamic behavior, and OH* chemiluminescence imaging has also been employed to investigate the flame structure. The results point out that, for the investigated configuration, the occurrence of thermoacoustic instabilities is, together with CO emissions, the main limiting factor, but benefits have been observed with hydrogen addition, and promising configurations will be further tested in engine-like conditions.

Abstract With gasoline direct injection, fuel injection parameters should be optimally tuned, which is critical in determining the fuel-air mixing and the charge quality during combustion. Fuel injection timing and pressure are two critical parameters considered in this study to examine the role of fuel injection pressures at different fuel injection timings. The resulting air-fuel mixture's sensitivity was investigated concerning ignition timing and engine speed variations based on the engine's combustion and emissions characteristics. The experiments were conducted on a 500-cc, single-cylinder, wall-guided Gasoline Direct Injection engine. All the tests were performed with a fixed fuel injection quantity of ∼22 mg. Three fuel injection pressures, i.e., 100, 150 and 200 bar, and three fuel injection timings indicating different stages of the intake stroke, namely early intake (315° bTDC), mid-intake (270° bTDC) and late-intake (225° bTDC), were considered for the experiments. The degree of complete combustion was maximised with the lowest combustion duration for early fuel injection timing (315° bTDC) due to higher mixture homogeneity and proper charge formation during ignition. . Overall, fuel injection timing of 315° bTDC with 100 bar FIP showed the highest thermal efficiency and lower carbon monoxide and hydrocarbon emissions at all considered engine speeds. In contrast, nitric oxide emissions were significantly higher for these parameters.

Injection duration is a key parameter affecting in-cylinder mixture formation and combustion in dual-fuel free-piston engines. This study utilizes a coupled numerical model to investigate its impact across a range of 0.05 to 0.25 ms. Simulation results indicate that a short injection duration (0.05 ms) significantly enhances in-cylinder swirl and turbulence, primarily by improving fuel atomization and the mixing rate. The peak turbulent kinetic energy (20 m²/s²) increases by 51% compared to the case with a 0.25 ms injection duration. This optimization promotes more complete combustion, which leads to optimal indicated thermal efficiency and heat release rate. However, it also increases the heat transfer coefficient and heat flux by 16.7% and 33.2%, respectively. Conversely, a longer injection duration enlarges the fuel-rich zone, leading to increased soot emissions. A comprehensive evaluation of performance and emissions identifies 0.05 ms as the optimal injection duration.

Investigation of Central and Sidewall Fuel Injection Strategies in a Solid Rocket Scramjet Combustor

Fuel injection prediction for a heavy-duty diesel engine based on deep self-encoder Gaussian process regression

A Comprehensive Research Review on Adaptive Fuel Injection System with AI Optimized Fuel Delivery for Trucks

ABSTRACT Scramjets are advanced air-breathing propulsion systems developed for hypersonic flight, allowing vehicles to reach speeds greater than Mach 5. In these engines, combustion occurs under supersonic conditions, resulting in extremely brief reaction times that challenge the efficiency of air-fuel mixing and combustion. This study looks at how angled fuel injection might improve mingling and combustion capability in a strut-based scramjet engine. The research focuses on varying the angles of fuel injection, both upstream and downstream, through numerical simulations. The simulations employ a 2-D Reynolds-Averaged Navier-Stokes (RANS) equation framework coupled with finite rate/eddy dissipation and the Shear Stress Transport (SST) k-ω turbulence model using a density-based solver with finite volume discretization. When the results are compared, they show that the 30-degree and 60-degree inclined injections slow down the flow by 40% and 60%, respectively, in the strut wake region. This enhances the air-fuel mixing and combustion efficiency by expanding the recirculation area. Overall, the 60-degree injection technique achieves 100% mixing efficiency at a distance of 140 mm, which is 30 mm from a fuel injector. Parallel injection achieves 100% mixing efficiency at a distance of 230 mm, which is 120 mm from a fuel injector. This study shows that angled fuel injection could help improve the performance of scramjet combustor systems when they are operating at hypersonic speeds.

<div>Ducted fuel injection (DFI) was tested for the first time on a production multi-cylinder engine. Design-of-experiments (DoE) testing was carried out for DFI with a baseline ultra-low sulfur diesel (ULSD) fuel as well as three fuels with lower lifecycle carbon dioxide (CO<sub>2</sub>) emissions: renewable diesel, neat biodiesel (from soy), and a 50/50 blend by volume of biodiesel with renewable diesel denoted B50R50. For all fuels tested, DFI enabled simultaneous reductions of engine-out emissions of soot and nitrogen oxides (NOx) with late injection timings. DoE data were used to develop individual calibrations for steady-state testing with each fuel using the ISO 8178 eight-mode off-road test cycle. Over the ISO 8178 test, DFI with a five-duct configuration and B50R50 fuel reduced soot and NOx by 87% and 42%, respectively, relative to the production engine calibration. Soot reductions generally decreased with increasing engine load. Hydrocarbon and carbon monoxide emissions tended to increase with DFI but were not excessive over the ISO 8178 test. Brake-specific energy consumption generally increased with DFI due to the use of retarded injection timings and exhaust-gas recirculation to achieve the desired NOx reductions but was less than or equal to that for conventional diesel combustion with ULSD at a similar NOx level. Significant deposits were encountered on one cylinder when running at idle with the ULSD fuel only, but this was mitigated by replacing the corresponding fuel injector (which showed deformation at the exits of two of its orifices) and using a fuel detergent additive in subsequent testing. In all, the engine was successfully operated for over 300 hours in the DFI configuration. Research areas for improved DFI implementation are identified.</div>

An overview of the Common Rail (CR) diesel engine challenges and of the promising state-of-the-art solutions for addressing them is provided. The different CR injector driving technologies have been compared, based on hydraulic, spray and engine performance for conventional diesel combustion. Various injection patterns, high injection pressures and nozzle design features are analyzed with reference to their advantages and disadvantages in addressing engine issues. The benefits of the statistically optimized engine calibrations have also been examined. With regard to the combustion strategy, the role of a CR engine in the implementation of low-temperature combustion (LTC) is reviewed, and the effect of the ECU calibration parameters of the injection on LTC steady-state and transition modes, as well as on an LTC domain, is illustrated. Moreover, the exploitation of LTC in the last generation of CR engines is discussed. The CR apparatus offers flexibility to optimize the engine calibration even for biofuels and e-fuels, which has gained interest in the last decade. The impact of the injection strategy on spray, ignition and combustion is discussed with reference to fuel consumption and emissions for both biodiesel and green diesel. Finally, the electrification of CR diesel engines is reviewed: the effects of electrically heated catalysts, electric supercharging, start and stop functionality and electrical auxiliaries on NOx, CO2, consumption and torque are analyzed. The feasibility of mild hybrid, strong hybrid and plug-in CR diesel powertrains is discussed. For the future, based on life cycle and manufacturing cost analyses, a roadmap for the automotive sector is outlined, highlighting the perspectives of the CR diesel engine for different applications.

This experimental research test was conducted on DTSI (Digital Three Spark Ignition) fueled with an EFI (Electronic Fuel Injection) system. This engine is high speed. single-cylinder, high-compression-ratio, and multi-valve (4 valves per cylinder). The engine was modified for testing on hydrogen gaseous fuel. Two different injectors for gasoline and hydrogen fuel were used. All tests are conducted from 3000 rpm to 6000 rpm with intervals of 1000 rpm at Wide Open Throttle (WOT) conditions. Initially the engine was tested with gasoline fuel and on hydrogen with λ status of 1.6,2.0 and 3.0. From the results, the maximum brake thermal efficiency achieved is 39.5% with hydrogen fuel; this is an 8.5 % improvement over gasoline. From this experiment, it can be concluded that the existing spark ignition engine can be easily converted to a hydrogen port fuel injection system with few modifications to meet the future stringent emission norms. Keywords: Emissions, PFI Engine, Hydrogen, Gasoline, Alternative Fuels, Co2, DTSI, fuel injection, Internal Combustion Engine, Fuel properties

Abnormalities in cardiac function arise irregularly and typically involve multimodal electrical, mechanical vibrations, and acoustics alterations. This article proposes an Electro-Mechano-Acoustic (EMA) activity model for mapping the complete macroscopic cardiac function to refine the systematic interpretation of cardiac multimodal assessment. We abstract this activity pattern and build the mapping system by analyzing the functional comparison of the heart pump and Electronic Fuel Injection (EFI) system from the multimodal characteristics of the heart. Electrocardiogram (ECG), seismocardiogram (SCG) & Ultra-Low Frequency seismocardiogram (ULF-SCG), and Phonocardiogram (PCG) are selected to implement the EMA mapping respectively. First, a novel low-frequency cardiograph compound sensor capable of extracting both SCG and ULF-SCG is proposed, which is integrated with ECG and PCG modules on a single hardware device for portable dynamic acquisition. Afterward, a multimodal signal processing chain further analyses the acquired synchronized signals, and the extracted ULF-SCG is shown to indicate changes in heart volume. In particular, the proposed method based on waveform curvature is used to extract 9 feature points of the SCG signal, and the overall recognition accuracy reaches over 90% in the data collected by EMA portable device. Ultimately, we integrate the portable device and signal processing chains to form the EMA cardiovascular mapping system (EMACMS). As a next-generation system solution for cardiac daily dynamic monitoring, which can map the mechanical coupling and electromechanical coupling process, extract multi-characteristic heart rate variability (HRV), and enable extraction of important time intervals of cardiac activity to assess cardiac function.

To improve the flexibility of injection rate control, this study developed a set of drive current timing strategies for a dual-solenoid-valve injector (DSVCI) featuring (NCV-1) and (NCV-2). These strategies enabled operation in single-valve rectangular, dual-valve rectangular, and ramp injection modes. The corresponding injection characteristics, including injection rate profiles, injection delay, duration, and fuel quantity, were systematically examined across a wide range of conditions. Results show that the ramp mode initiates with a gradual increase in injection rate driven by NCV-1, followed by a sharp acceleration upon NCV-2 activation. The opening delay in ramp mode closely matches that of the single-valve rectangular mode, while its injection onset occurs 0.23 ms later than in dual-valve operation. In contrast, the closing delay in ramp mode aligns with the dual-valve rectangular mode and exceeds that of the single-valve mode. Both ramp and dual-valve modes exhibit reduced injection durations with increasing pressure, whereas the single-valve mode maintains a nearly constant duration at low pressures. Under long-duration injections, the fuel quantity increases linearly in rectangular modes but displays an accelerating growth trend in the ramp mode as NCV-2 activation time increases. These findings provide new insights into the dynamic behavior of the dual-solenoid-valve control injector and highlight the potential of ramp shaping for advanced injection rate control.

The paper discusses issues related to wear phenomena occurring in modern compression-ignition engine fuel supply equipment. The paper examines how non-efficient injectors affect the operating and environmental performance of a common-rail diesel engine. Engine and laboratory tests were carried out. During the engine tests, power, torque, specific fuel consumption (SFC) and environmental parameters were measured on a bench for the engine running on non-efficient and efficient fuel injectors. Wear of injectors resulted in a decrease in engine power of up to 9% and a decrease in engine torque of up to 2%. In contrast, SFC increased for the worn injectors by more than 9%. The non-efficient injectors were then examined on an STPiW-3 test bench with a thermal imaging camera to determine their degree of wear. They were then disassembled into their component parts and examined with a stereoscopic and an electron microscope. The examinations showed that there was contamination inside the fuel injectors tested, both from outside and generated by the high-pressure pump. It is discussed how the inadequacies of the injection apparatus affect the combustion process of the combustible mixture in the cylinder headspace and the overall operation of the engine.

Abstract This study investigates nitrogen oxide emissions (NO $$_x$$ x ) in a heavy-duty hydrogen engine by comparing Port Fuel Injection (PFI) with two Direct Injection (DI) configurations under various load conditions. A fast chemiluminescence detector (CLD) enables cycle-resolved nitrogen monoxide emission (NO) measurements, providing detailed insights into the emission characteristics of each injection strategy. The findings reveal that the PFI configuration consistently results in the lowest NO $$_x$$ x emissions due to superior air–fuel mixture homogenization. Additionally, it exhibits minimal cycle-to-cycle variations in both pressure traces and NO emissions. The indicated efficiency of the PFI setup is also higher compared to DI, likely due to the higher charge air pressures required to maintain a constant air–fuel ratio and reduced wall-heat losses. Conversely, the DI configurations, especially the 4-hole cap design, produce significantly higher NO $$_x$$ x emissions and show considerable variability between cycles. A strong exponential correlation between NO emissions and peak cylinder pressure (p $$_{max}$$ max ), which directly influences in-cylinder temperature, is observed across all configurations. The DI setups exhibit faster combustion, driven by increased turbulent kinetic energy from the hydrogen jet, leading to higher in-cylinder pressures and temperatures. This rapid combustion process complicates emission control by increasing NO $$_x$$ x formation. Despite similar combustion behavior and efficiency between the 1-hole and 4-hole DI setups, the latter generates much higher NO $$_x$$ x emissions, highlighting the crucial role of mixture homogenization. Cycle-based analysis further indicates that DI configurations, particularly the 4-hole cap design, experience single-cycle NO emissions spikes, making consistent emission control more challenging. While PFI presents clear advantages in emission reduction and efficiency, DI setups provide comparable power output with lower charge air pressure requirements. However, challenges in mixture formation must be addressed to optimize DI strategies for hydrogen engines. Overall, the study underscores the significance of optimizing mixture formation to mitigate NO $$_x$$ x emissions in hydrogen engines.

Optimization of Fuel Injection Parameters for Enhanced Performance and Emission Reduction in a Diesel Engine Using Animal Fat–Based Biodiesel Blends