Fuel Injection Characteristics Research Articles

Optimization design of hydrogen Laval nozzle based on response surface methodology (RSM)

Abstract To conduct an in-depth study of the injection characteristics of gas fuels, the structural parameters of the nozzle are optimized. Utilizing the Response Surface Method (RSM), this study selects an inlet radius R1 , outlet radius R2 , throat straight radius R0 , expansion half angle θ, and contraction half angle α as design parameters. Based on the validated numerical model, a response surface prediction model for outlet velocity v and mass flow rate Q is established. Using the derived expressions, the contribution and interactive effects of design variables on response variables are analyzed. The findings indicate that the outlet radius and throat radius significantly affect the outlet velocity. The outlet radius positively correlates with the outlet velocity, while the throat radius negatively correlates with it. The mass flow rate is most significantly influenced by the throat radius, increasing with its increase. With outlet velocity and mass flow rate as optimization objectives, the MOGA algorithm is applied for multi-objective optimization. The optimization results indicate that the optimized structural parameters increased the centrifugal nozzle’s atomization cone angle and mass flow rate by 1.86% and 27.4%, respectively.

Research on fuel injection characteristics of common rail system based on high pressure pipeline integration and matching

AbstractThe modular prediction model of high pressure common rail system was established to study the influence of high‐pressure pipeline integration matching on the fuel injection characteristics of common rail system. The influence of common rail volume on pressure building and pressure fluctuation in common rail tubes was analyzed. The influence of common rail volume on the matching of fuel injection frequency (number of fuel injectors) and fuel supply frequency (number of plunger pumps) was studied by using the control variable method, and the basic optimal solution of the system was obtained. The influence of the common rail structure on the fuel flow characteristics of the system was also studied. The matching relationship between high pressure tubing and common rail system is studied by introducing dimensionless numbers such as length‐diameter ratio of pipeline. The results demonstrate that the increase of the storage space of the accumulator can effectively reduce the fluctuation in the system, so that the injection volume increases slowly and then decreases rapidly, with a slope of −5.70 × 10−3 mm3. The increase of the diameter of the common rail makes the fuel flow characteristics become good first and then bad, and the increase of the length of the common rail can soothe the pressure fluctuations. The increase of the diameter of the link tube (LT) makes the fuel injection volume of the injector increase first and then decrease. The optimal VR solution for the LT is 0.0249 and the optimal ratio of the length to diameter of a pipeline solution is 55.10. The structure of the distribution tube and its matching to the common rail have little effect on the fuel flow characteristics. When the diameter and length of the injection tube are too large, the influence on the injection pressure of the injector is negatively correlated.

Effect research of fuel injection and pressurization pulse width on injection characteristics of ultra high pressure common rail system

Ultra high pressure common rail system can realize adjustable injection rate by controlling the relationship between fuel injection and pressurization timing, and then affect the fuel injection characteristics of diesel engine. In order to ascertain the effect law and its formation mechanism of the fuel injection and pressurization pulse width on the fuel injection characteristics of ultra high pressure common rail system, on the basis of introducing the mathematical model of the system, the simulation model of ultra high pressure common rail system was established, and the accuracy of the model was verified by performance experiment, the effect of fuel injection and pressurization pulse width on the fuel injection characteristics of the system under different common rail pressure were analyzed. The results show that with the increase of fuel injection pulse width, the shape of fuel injection rate curve is similar to saddle shape and the proportion of large fuel injection rate range in the whole injection process increases gradually. At the same time, the fuel injection opening delay remains unchanged, but the fuel injection closing delay increases significantly when the fuel injection pulse width is small (0.6~1 ms), while it remains basically unchanged when the fuel injection pulse width is large (1~1.4 ms). With the increase of pressurization pulse width, the shape of fuel injection rate curve is similar to saddle shape and remains unchanged under the condition of small injection pulse width, while the fuel injection rate curve shape may appear similar to the "inverted saddle-shaped" under the condition of large injection pulse width, this is due to the rapid decrease of pressurization pressure caused by the closing of the solenoid valve control signal in the pressure-amplifier device before the end of fuel injection.

Study of the Optimization of Rail Pressure Characteristics in the High-Pressure Common Rail Injection System for Diesel Engines Based on the Response Surface Methodology

This paper establishes a mathematical model of the high-pressure common rail injection system used in diesel engines according to the parameters of its key components, and AMESim 2020 software was used to establish a simulation model of the common rail injection system used in diesel engines. The simulation model mainly includes a high-pressure oil pump model, a common rail pipe model, and a model of four injectors. This paper also describes an experimental analysis of the accuracy of the established simulation model. Through a simulation analysis of the system rail’s pressure fluctuation and pressure characteristics, it was concluded that the length of the common rail pipe, the diameter of the common rail pipe, and the inner diameter of the high-pressure fuel pipes are important influencing parameters for the rail pressure characteristics of the system. In this study, according to the original common rail pipe and high-pressure fuel pipe model, a response surface methodology was used to optimize and analyze the parameters of the common rail pipe and high-pressure fuel pipes, and the optimal size parameters for the common rail pipe and high-pressure fuel pipes were obtained with the minimum rail pressure fluctuations and the average rail pressure setpoint. After the optimization, the pressure for the common rail pipe of the high-pressure common rail system was increased by 0.82%, the pressure fluctuation was reduced by 21.66%, the injection pressure was increased by 1.15%, the single injection volume was increased by 0.86%, and its fuel injection characteristics were significantly improved.

High Quality Multi-Zone and 3D CFD Model of Combustion in Marine Diesel Engine Cylinder

Abstract The paper presents a 3D model of the processes taking place in the cylinder of a large 4-stroke marine engine. The model is based on CFD calculations performed on the moving mesh. The modelling range includes the full duty cycle (720° crankshaft position) and the complete geometry of the cylinder with inlet and exhaust ducts. The input data, boundary conditions and validation data were obtained by direct measurements on the real object. Fuel injection characteristics were obtained by Mie scattering measurements in a fixed-volume chamber. The modelling results have been validated in terms of the pressure characteristics of the engine’s cylinder within the entire range of its loads. The mean error did not exceed 1.42% for the maximum combustion pressure and 1.13% for the MIP (Mean Indicated Pressure). The model was also positively validated in terms of the O2 and NOx content of the exhaust gas. The mean error in this case was 1.2% for NOx fractions in the exhaust gas and 0.4% for O2 fractions. The complete model data has been made available in the research data repository on an open access basis.

A NUMERICAL STUDY OF TRANS-/SUPERCRITICAL FUEL INJECTION BASED ON A GENERALIZED CUBIC EQUATION OF STATE

Trans-/supercritical injection has great potential for improving the formation of combustible gas mixtures and emission performance. In this work, based on the sufficient validation of the current numerical framework, we compared the Peng-Robinson (PR) equation of state (EoS) with the Redlich-Kwong-Peng-Robinson (RK-PR) EoS and applied them to simulate the injection events under trans-/supercritical conditions. The effects of different nozzle diameters and chamber conditions on jet characteristics and pseudo-boiling were investigated. The results indicated that RK-PR EoS has higher prediction accuracy. The fuel injection characteristics are significantly affected by the nozzle diameter and the time required to undergo the pseudo-boiling process becomes longer with increasing nozzle diameter. Compared with chamber temperature, chamber pressure has a greater influence on the fuel injection and mixture formation behavior. The high pseudo-boiling intensity caused by the low supercritical pressure significantly increases the jet length and reduces the mixing layer thickness. Moreover, unlike the single-component case, the mixing effect within a multicomponent fluid influences both pseudo-boiling occurrence and its intensity.

INVESTIGATION ON IMPACTS OF ELLIPTICAL DUCTS ON MACROSCOPIC SPRAY CHARACTERISTICS OF DUCTED FUEL INJECTION

To study the influence of ducts other than circular shapes on spray characteristics of ducted fuel injection (DFI), experimental and simulation methods were used to study the impacts of elliptical ducts on DFI macroscopic spray characteristics. Two elliptical ducts, small and large, were used, with a circular duct for comparison. The small elliptical duct had the same hole cross-sectional area as the circular duct, and the large elliptical duct had a larger cross-sectional area. The DFI spray configuration with the elliptical duct promoted the axial dispersion and weakened the radial dispersion of spray with respect to free spray. Different spray-duct interactions caused differences in spray characteristics, manifested in changes in velocity field and pressure field. The spray velocity field of the circular duct had the best effect on promoting spray dispersion, followed by the small elliptical duct, and finally by the large elliptical duct compared to that of free spray. Furthermore, the pumping effect caused by the pressure differences between inside and outside the duct promoted the thorough mixing of spray and ambient gas inside the duct. From the radial velocity of ambient gas flowing to spray around the duct inlet, the pumping effect of the circular duct was the strongest, followed by the small elliptical duct and finally by the large elliptical duct.

Effect of Fuel Preheating on Engine Characteristics of Waste Animal Fat-Oil Biodiesel in Compression Ignition Engine.

The present study aims at understanding the effects of fuel preheating on engine characteristics of waste animal fat-oil (WAF-O) biodiesel in a single-cylinder CI engine, with the preheating technique proposed as an effective means for enhancing the fuel properties. To understand the effects of the preheated fuel, the WAF-O biodiesel was preheated at 60, 80, 100 and 120 °C and tested along with neat diesel and unheated WAF-O biodiesel. For this purpose, biodiesel was produced from different animal wastes by means of KOH-assisted ethanol-based transesterification, reporting its maximum yield as 96.37 ± 1.8%, with significant distribution of unsaturated oleic acid, saturated palmitic acid and stearic acid. Upon evaluating its fuel characteristics as per ASTM D6751 standards, a rise in preheating temperature by 1 °C reduced the density and kinematic viscosity of WAF-O biodiesel by 0.383 kg/m3 and 0.025 mm2/s, respectively, and was explained by the weakening of intermolecular forces between its fatty acid ester molecules. Preheated samples reported superior combustion characteristics by exhibiting increased in-cylinder pressure (2.24%, on average) and heat release rates in addition to their shortened ignition delay (1–4 °CA). Furthermore, preheating of WAF-O biodiesel reduced its specific fuel consumption and increased its brake thermal efficiency by 7.86% (on average) and 9.23% (on average), respectively. However, higher preheating temperatures (>120 °C) resulted in increased fuel consumption owing to its varied flow characteristics. In addition to the changes in combustion characteristics, preheating WAF-O bio-diesel also resulted in reduced carbon monoxide, nitrous oxide and hydrocarbon emission by 13.88%, 7.21% and 26.94%, respectively, and increased carbon dioxide emission by 7.58%. Summing up, the enhancements in overall engine characteristics of preheated samples were accounted for by their improvised fuel injection characteristics due to their reduced density and viscosity, which ensured for their effective combustion.

Study on Characteristics Optimization of Combustion and Fuel Injection of Marine Diesel Engine

The emission requirements of diesel engines are becoming increasingly strict and reducing emissions has become the key technology. In view of this development trend, the influence law of fuel injection on emission is studied in this paper. Numerical studies were performed to analyze the structural parameters of fuel injection system on combustion and emission characteristics of marine diesel engines. The numerical modelling was validated based on single-cylinder diesel engine tests and fuel injection tests. After investigating the single structural parameters on the fuel injection characteristics, the orthogonal method was used to design the double-parameter structural optimization scheme of the fuel injection system. There are 22 optimized cases selected to further investigate using the CFD method by visualizing scalar distributions in cylinder, which was helpful to explain the reason of pollutant formation. Comprehensively comparing the performance of each fuel injection system’s structural optimization scheme, moderate reduction of the discharge valve chamber volume and high-pressure tubing diameter would increase injection mass, along with faster injection rate and boosted injection pressure, leading to reduced Sauter mean diameter (SMD). Considering pollutant emission characteristics as well as economic and power concerns, case D6 with spray angle enlarging 5° showed best performance. Compared with the original condition, there was no NO deterioration and large reduction of soot emission by 65.4%, along with fuel consumption being lowered by 2.18% and more indicated power, by 2.21%. Therefore, reasonable optimization of spray angle can improve power, economy and emission performance simultaneously.

Simultaneous 100-kHz acetone planar laser-induced fluorescence and OH* chemiluminescence in a linear non-premixed detonation channel

Reactant mixing and combustion are investigated in an optically accessible, self-excited linear detonation combustor. The mixing field is captured using 100 kHz planar laser-induced fluorescence (PLIF) imaging of acetone as a tracer in the fuel supply, while 100 kHz chemiluminescence imaging of excited-state hydroxyl (OH*) radicals simultaneously resolves the evolution of the detonation wave. Time sequences are acquired over multiple detonation cycles in each test, with acetone-PLIF images collected along multiple orthogonal planes to reveal the complex three-dimensional topography of the fuel distribution. The instantaneous and phase-averaged acetone-PLIF images enable measurement of key fuel injection characteristics, such as the injector recovery time, fuel jet velocity, and refill height for a range of operating conditions. Instantaneous and phase-averaged measurements of acetone-PLIF with the time-coincident OH* chemiluminescence images also reveal a number of key features, such as fuel stratification and weak detonation in the injector near field, incomplete combustion and deflagration behind the detonation wave, vitiation and deflagration of reactants ahead of the detonation wave, and fuel and oxidizer recovery time mismatch. These measurements significantly enhance the ability to obtain detailed information on the intracycle and intercycle spatiotemporal evolution of the reactant refill process and its coupled effects on the detonation wave structure and propagation.

Experimental study on the effect of post-injection parameters on performance of extra-high pressure common-rail diesel engine

The diesel engine combustion process is mainly controlled by the fuel injection characteristics, which will have a direct impact on the performance of the diesel engine, more flexible injection strategy is the development direction of high pressure common-rail system. In order to obtain the change law of the performance of extra-high pressure common-rail diesel engine under variable injection strategy, and improve the overall performance of diesel engine, the effect of different post-injection parameters on the performance of diesel engine was studied on a self-designed extra-high pressure common-rail diesel engine experiment bench, and the relevant results were discussed and analyzed. The results show that: with the rise of post-injection fuel quantity, NOx concentration and soot concentration decrease gradually, and with the rise of post-injection interval angle, NOx concentration decreases gradually, while soot concentration first decreases and then increases. Therefore, choosing post-injection fuel quantity and post-injection interval angle rationally can achieve lower NOx and soot emission at the same time. Meanwhile, with the rise of post-injection fuel quantity or post-injection interval angle, the fuel consumption rate presents an increasing trend.

Fault detection of industrial large-scale gas turbine for fuel distribution characteristics in start-up procedure using artificial neural network method

In this study, artificial neural network (ANN) based on operating data is adjusted to detect fault operation of large-scale industrial gas turbine. To detect faults, the operating characteristics of gas turbine are first predicted for fuel injection characteristics because, in general, lots of the operating failures are occurred in start-up procedure when fuel distribution characteristics are frequently changed. Data from the GE 7FA gas turbine were used, and the fuel distribution and other operating parameters are set by input and output parameters, respectively, to analysis effect of fuel distribution. The start-up procedure is divided with eight operating process (OP) to detect fault operation by fuel distribution characteristics. An overheating start is detected when turbine exhaust temperature (TET) reaches 110%–120% of the design value with the conventional detecting method; by contrast, the proposed method can detect this problem in advance before OP4. Further, sensitivity analysis of gas turbine operating characteristic parameters for each nozzle was performed to detect not only operation failures but also problems in the fuel supply system. Fault detectability was different with each OP and nozzle, and nozzle system abnormalities can be detected in advance by the results of sensitivity analysis.

Numerical study on powder fuel injection characteristics of powder fuel scramjet

Powder fuel injection is an attractive technique for powder fuel scramjets and plays an important role in numerically investigating the particle velocity and concentration distribution in powder fuel injection. In this study, the coupled model of computational fluid dynamics-discrete element method (CFD-DEM) was used to simulate the flow of aluminium powder in the nozzle. Firstly, the flow field characteristics of gas-phase and two-phase gas-particle were compared. The results show that the particle disturbance has a great influence on the convection field, in which the maximum velocity of gas-phase is reduced by 47.15%, the acceleration distance is shortened by 34.18%, and the minimum velocity is reduced by 41.48%. Secondly, particle velocity and concentration distributions under different nozzle convergence angles were compared, and their correlations with the nozzle convergence angle, particle collision, and gas-particle drag force were identified. The results show that as increase in convergence angle of the nozzle, both the number of particle collisions in the nozzle and expansion angle of the particle jet at the nozzle exit have increased, while the particle velocity at the nozzle exit has decreased. The overall simulation results and analyses provide a new reference for the flow mechanism of the fuel injection process and the design of a powder conveying system for a powder fuel scramjet.

Effects of Biodiesel Fuels Produced from Vegetable Oil and Waste Animal Fat on the Characteristics of a TDI Diesel Engine

In this study, four different biodiesel fuels obtained from corn oil, safflower-rapeseed oil mixture (50%-50% v/v), waste chicken fat, and waste fleshing oil were tested in a six-cylinder, water-cooled, TDI diesel engine. Vegetable oil and waste animal fat origin biodiesel fuels’ effects on the performance, injection, combustion and emission characteristics of test engine were compared with each other and petroleum-based diesel fuel as reference fuel. Biodiesel fuels (regardless of their feedstock) increased in-cylinder gas pressure, brake specific fuel consumption, and NOx emissions while decreased THC and CO emissions compared to pure diesel fuel. In comparison to petro-diesel, the start of fuel injection timing advanced but the end of fuel injection timing retarded with biodiesels. In addition, comparatively higher fuel injection pressure values were attained with all biodiesel fuels. Waste animal fat and vegetable oil origin biodiesel fuels showed similar in-cylinder gas pressures, fuel injection characteristics and brake specific fuel consumption values. However, CO emissions of vegetable oil-based biodiesel fuels were lower and NOx emissions were higher than those of waste animal fat-based biodiesels.

Experimental Study on Air-Assisted Injection Characteristics of Different Distillate Fuels

Experimental Study on Air-Assisted Injection Characteristics of Different Distillate Fuels

Effects of Diesel Injector Nozzle Hole Deposit on Fuel Injection and Spray Characteristics

Effects of Diesel Injector Nozzle Hole Deposit on Fuel Injection and Spray Characteristics

Investigation of a method for online measurement of injection rate for a high-pressure common rail diesel engine injector under multiple-injection strategies

As a state-of-the-art injection technology, the high-pressure common rail injection system (HPCRIS) has advantages that include high injection pressure, adjustable injection timing and a flexible injection rate. Nevertheless, the fluctuation of cyclic fuel injection mass (CFIM) in the HPCRIS using a multiple-injection strategy (MIS) reduces the economy of the diesel engine and the stability of vibration and noise control. To realize the precise control of CFIM, the online perception of the injection process is the premise. This paper presents an innovative method for online measurement of injection rate under MIS conditions. According to the evolution characteristics of water hammer pressure oscillation in the fuel system, the rule is that the oscillation form of the water hammer is dependent on the structure of the HPCRIS rather than the injection conditions, and the general applicability of this rule is proved by the hydraulic–electric analog method. Based on this, the method for real-time simulation of the pilot water hammer oscillation wave in the same field is proposed to realize the extraction of the expansion pressure signal components of the main injection. Then, the direct mathematical relationship between the pressure signal and fuel injection rate is established, and the online measurement of fuel injection characteristics under MIS is realized. To improve the robustness of the algorithm a method for real-time calibration of fuel sound velocity is proposed. Finally, when compared with the offline experiment, this method for online measurement of injection rate has relatively high accuracy, the CFIM error is less than 2%, and the goodness of fit of the injection rate curve exceeded 0.91. This measurement method can provide direct feedback to the electronic control unit on the fuel injection system without changing the HPCRIS structure.

Research on transmission and coupling characteristics of multi-frequency pressure fluctuation of high pressure common rail fuel system

To analyze the coupling characteristics of system-level fuel supply and injection and the mechanism of multi-frequency pressure fluctuations affecting system stability, a prediction model of the high-pressure common rail system was established. The effects of common rail pressure, control pulse width and engine speed on pressure fluctuations were analyzed. Simultaneously, the influence of different hydraulic components such as pumps, rails, and injectors on pressure fluctuations was analyzed by employing hydraulic decoupling method. The influence of pressure fluctuations caused by fuel supply characteristics of pump, filtering effect of rail and fuel injection characteristics of injector on the entire system was studied. The result demonstrates that adjusting target rail pressure and control pulse width alters the fuel supply ability and fuel injection level respectively. During the fluctuation process, the pressure fluctuation overshoot is about 7.7%, and the steady state fluctuation is about ± 1.5%. The adjustment of engine speed influences the overall trend of pressure fluctuations apparently. Additionally, the pressure fluctuations in the system are mainly induced by the coupling of high and low frequency pressure waves. Among them, low-frequency fluctuations everywhere are highly consistent, whereas high-frequency fluctuations are affected significantly by working properties of hydraulic components. Through decoupling analysis, it is illustrated that the fuel pump fluctuations affect the entire fluctuation trend to a great extent. The volume of common rail pipe has an effect on the fluctuation degree and filtering capability. The transient motions of fuel inlet valve, fuel delivery valve and needle valve are the main source of high-frequency fluctuations.

The Effect of the Structure and Parameters of Diesel Injector on Atomization Characteristics

The quality of the fuel injection system mainly depends on the fuel injection characteristics and atomization characteristics of the system. The structural parameters of the fuel injector play an important role in the flow condition of fuel injection, thus affecting the atomization characteristics of fuel injection. The atomization characteristics of the fuel injection system are seriously affected by the nozzle structure. In this paper, the influence of the nozzle diameter and the chamfering at the nozzle entrance on the atomization characteristics of the system is analyzed. The results show that the diameter of the jet hole increases, the area of the negative pressure increases, the cavitation intensity decreases, the flow coefficient of the nozzle relatively decreases, and the fuel injection speed decreases, but the range of the oil beam and the spray cone angle increase. With the increase of the chamfer angle at the entrance of the nozzle, the area of the negative pressure decreases, the cavitation intensity relatively decreases, but the uniformity of fuel injection speed increases, the flow coefficient of the nozzle increases, the average fuel injection speed increases, and the fuel oil range and the spray cone angle increase. The back pressure has no obvious effect on the internal flow and overall atomization of the nozzle. The response surface method (RSM) is used to obtain the response surface function of the mass flow and the chamber pressure. The analysis shows that in order to increase the mass flow rate, it is necessary to increase the spray hole diameter as much as possible. In order to increase the chamber pressure and reduce the cavitation, it is necessary to reduce the diameter of the spray hole, the top radius of the valve core and the diameter of the pressure chamber ball as much as possible. It provides theoretical and practical guidance for the structural optimization design of fuel injection system.

Research on Working Process and Stability of Hydraulic Free Piston Engine

This paper studies the working principle of the hydraulic free piston engine, and details the related contents of the working process of the hydraulic free piston engine. The related contents include the analysis of working state, the analysis of fuel injection characteristics, the analysis of the air exchange system, the analysis of the operating parameters, the working process in the cylinder, etc. The stability of the hydraulic free piston engine is studied by establishing a nonlinear model. Based on this, the stability control strategy is developed, which aims to accumulate reliable experimental data and lay a good application foundation for developing the dynamic control of hydraulic free piston engine in working process.