Common Rail Fuel Injection System Research Articles

Analysis the ECFM-3Z Combustion Model for Simulating the Combustion Process and Emission Characteristics in a HSDI Diesel Engine

An advanced CFD simulation has been performed to analyze the ECFM-3Z (Extended Coherent Flame Model-3Z) combustion model for simulating the combustion process and emission characteristics in a high speed direct injection (HSDI) diesel engine. A four cylinders, HSDI diesel engine based on a Ford production engine with a 2nd generation Delphi common rail fuel injection system has been modeled in this research. 3D CFD simulation was carried out from intake valve closing (IVC) to exhaust valve opening (EVO). A good agreement of calculated and measured in-cylinder pressure trace as well as pollutant formation trends could be observed for all investigated operating points. Based on the confidence gained from validation, the study is extended to evaluate the effect of fuel injection timing on engine performance and emissions. For this purpose, a comprehensive study of the effect of injection timing with respect to performance and emissions has been considered. Three main injection timing, (1) 2.65 BTDC, (2) 0.65 BTDC and (3) 1.35 ATDC, all with 30 crank angle pilot separations has been used to investigate the effect of the injection timing. The results show that the current methodology can be applied as a beneficial tool for analyzing the parameters of the diesel combustion under HSDI operating condition.

An Investigation of Flow in Nozzle Hole of Dimethyl Ether

For over twenty years, DME has shown itself to be a most promising fuel for diesel combustion. DME is produced by simple synthesis of such common sources as coal, natural gas, biomass, and waste feedstock. DME is a flammable, thermally-stable liquid similar to liquefied petroleum gas (LPG) and can be handled like LPG. However, the physical properties of DME such as its low viscosity, lubricity and bulk modulus have negative effects for the fuel injection system, which have both limited the achievable injection pressures to about 500 bar and DME's introduction into the market. To overcome some of these effects, a common rail fuel injection system was adapted to operate with DME and produce injection pressures of up to 1000 bar. To understand the effect of the high injection pressure, tests were carried out using 2D optically accessed nozzles. This allowed the impact of the high vapour pressure of DME on the onset of cavitation in the nozzle hole to be assessed and improve the flow characteristics.

Types of internal Diesel injector deposits and counteracting their formation

The paper attempts to distinguish types of IDID (Internal Diesel Injector Deposits) with regard to the mechanism of formation, factors facilitating their formation and the method of identification. Investigations into their formation mechanism have been discussed in the paper. The results of the investigations into the chemical nature and probable source of these deposits have also been discussed. It has been pointed out that modern common rail fuel injection systems might be less tolerant to deposits due to tighter fitting tolerances, lower mass of parts and sophisticated injection strategies. Various approaches to IDID formation counteracting have also been discussed.

Investigation on the fuel injection quantity fluctuation of a common-rail fuel injection system using response surface methodology

Variations in the parameters affect the injection characteristics of a common-rail injection system and leads to fluctuation in the fuel injection quantity. This paper is aimed at combining the numerical modelling and design of experiments to investigate the significant effects of the interactions between the common-rail injector parameters on the fluctuation in the fuel injection quantity using response surface methodology. A numerical model of a common-rail injector was developed. The model was validated by comparing simulation results with experimental measurements, which showed that it can accurately predict the fuel injection quantity of the system. The design of experiments was performed using a two-level five-factor D-optimal design. The factors studied were the pre-tension of the control valve spring, the diameter of the outlet orifice, the diameter of the inlet orifice, the needle lift and the diameter of the nozzle holes. A quadratic response surface model was suggested by means of partial least-squares regression analysis. The distribution of the standardized residuals, the relation between the predicted fluctuation and the observed fluctuation in the fuel injection quantity, the coefficient R2 of determination and the adjusted coefficient [Formula: see text] of determination for the response surface model were analysed, which demonstrated the significance of the model. Analysis of the F value and the p value for the model terms at the 95% confidence level revealed that the interactions between the control valve spring pre-tension and the nozzle hole diameter, between the outlet orifice diameter and the nozzle hole diameter, between the inlet orifice diameter and the nozzle hole diameter and between the needle lift and the nozzle hole diameter had significant effects on the fluctuation in the fuel injection quantity of the system. Furthermore, the significant effects of the interactions between these parameters were analysed in detail.

EFFECT OF ETHANOL ON PERFORMANCE AND DURABILITY OF A DIESEL COMMON RAIL HIGH PRESSURE FUEL PUMP

This paper presents a comparative experimental study for determining the effect of ethanol on functionality of a high pressure pump of the common rail fuel injection system. For experimental durability tests were prepared two identical fuel injection systems, which were mounted on a test bed for a fuel injection pump. One of the fuel injection systems was feed with diesel fuel; other fuel injection system was fuelled with ethanol–diesel fuel blend. A blend with 12% v/v ethanol and 88% v/v diesel fuel and low sulphur diesel fuel as a reference fuel were used in this study. To determine the effect of ethanol on the durability of the high pressure pump total fuel delivery performance and surface roughness of pump element were measured prior and after the test. Results show that the use of the ethanol–diesel blend tested produced a negative effect on the durability of the high pressure fuel pump. The wear of plungers and barrels when using ethanol–diesel fuel blend caused a decrease in fuel delivery up to 30% after 100 h of operation.

Effects of different biofuels blends on performance and emissions of an automotive diesel engine

The impact of blending Ultra Low Sulfur Diesel (ULSD) with different biofuels, obtained from Rapeseed Methyl Ester (RME) and Hydrotreated Vegetable Oil (HVO) respectively, on the performance and emissions of a European passenger car diesel engine was assessed in this paper.First, the hydraulic behavior of the common rail fuel injection system was analyzed in terms of injected volume, injection rate, spray global shape, single jet tip penetration and cone angle with both RME and HVO blends in comparison with neat ULSD.Afterwards, the impact of biofuel blends on engine full load performance was analyzed, both for the standard calibration and for a calibration which was specifically adapted to biofuels characteristics. The effects of biofuel blends on brake specific fuel consumption and on regulated exhaust emissions were then evaluated at different part load operating conditions, representative of the New European Driving Cycle.Finally, the sensitivity of the different fuels to different calibration settings, such as Exhaust Gas Recirculation (EGR) and injection timing, was studied in order to investigate which further emission benefits could be achieved by means of a more extensive engine re-calibration.

커먼레일 시스템용 구동방식에 따른 인젝터별 바이오디젤 분무 특성 연구

Abstract Recently, exhaust gas regulation has been gradually strengthened due to depletion of fossil fuels and environmental prob-lem like a global warming. Due to this global problem, the demand for eco-friendly vehicle development is rapidly increas-ing. A clean diesel vehicle is considered as a realistic alternative. The common-rail fuel injection system, which is the keytechnology of the clean diesel vehicle, has adopted injection strategies such as high pressure injection, multiple injection forbetter atomization of the fuel. In addition, the emission regulations in the future is expected to be more stringent, which aconventional engine is difficult to deal with. One of the way for actively proceeding is the study of alternative fuels. Amongthem, the bio-diesel has been attracted as an alternative of diesel. So, in this study, spray characteristics of bio-diesel wasanalyzed in the common-rail fuel injection system with three injectors driven by different operating mechanism. 1. 서론

Effect of fuel temperature on heavy fuel oil spray characteristics in a common-rail fuel injection system for marine engines

The present study was conducted to investigate the effects of fuel properties on the spray characteristics of a common-rail type marine diesel injector. Spray characteristics are highly influential in determining engine performance and emission characteristics in direct-injection engine systems containing marine diesel engines. Thus, the relationship between the physical properties of HFO fuel and its spray characteristics is investigated via an analysis of HFO and spray experiments. Data from physical property measurements (e.g., fuel density, dynamic viscosity, and surface tension) are used to derive empirical equations between fuel temperatures and physical properties, and the results follow the common tendencies of temperature–property curves for general liquid substances. In spray experiments, injection quantity measurements, injection rate profiles, and spray visualization were conducted under various injection pressures, energizing durations, and ambient pressures. The test temperatures of HFO were set from the results of physical property measurements.Experimental data reveal that spray characteristics are affected by fuel properties in terms of injection delays, injection profiles, and spray development speed. The injection quantity increased proportionally with fuel densities and the onset of injection was delayed with increased dynamic viscosity. Spray tip penetration decreased with increased fuel temperature.

Effects of hydraulic flow and spray characteristics on diesel combustion in CR direct-injection engine with indirect acting Piezo injector

Recently, the automobile industry has focused on the FIE system of diesel engine with common-rail, EGR, and turbo charger in order to meet a more stringent emission and fuel economy regulations. High-pressure fuel direct injection by using common-rail system is widely accepted because diesel combustion and emission characteristics highly depend on the formation of air-fuel mixture quality. By this fact, an electro-hydraulic injector for common-rail fuel injection system should be designed to have precise and fast response of injector needle’s opening and closing behavior to enhance air-fuel mixing rate. As know, most electro-hydraulic injectors provide its nozzle movement by solenoid coil energy or piezo-actuation. Relatively, servo-hydraulic type piezo injector with bypass-circuit mechanism, which it serve to amplify extension of the piezo stack, is also known for their good efficiency. So the piezo actuator triggers pilot valve for controlling pressure balance, which is accurately regulated by bypass-circuit system. Therefore, main actuation force of piezo injector to move injector needle is hydraulic, which is the key object as it is aimed towards all this research ranges: numerical and experimental approaches. In this study, firstly a full-circuit numerical model of an indirect acting piezo injector with bypass-circuit by using AMESim code has been developed to predict dynamic characteristics of hydraulic components and verified by comparison with experimental data. Also, two experiment schemes were carried out using a constant volume chamber with LED back-illumination system for Mie scattering and a single-cylinder CR direct-injection engine, equipped with a bypass-circuit type piezo and solenoid injector to compare high-speed spray and combustion characteristics in this study because spray penetration and duration are key factor in diesel diffusion combustion. As main results obtained by this study, the injection flow rate and injector internal pressure dynamics calculated by AMESim environment of a bypass type piezo-driven injector reasonably agreed with the experimental result. Also it has better capability in controlling injector needle closing delay and a beneficial effect on diesel diffusion combustion.

Elimination of fuel pressure fluctuation and multi-injection fuel mass deviation of high pressure common-rail fuel injection system

The influence of fuel pressure fluctuation on multi-injection fuel mass deviation has been studied a lot, but the fuel pressure fluctuation at injector inlet is still not eliminated efficiently. In this paper, a new type of hydraulic filter consisting of a damping hole and a chamber is developed for elimination of fuel pressure fluctuation and multi-injection fuel mass deviation. Linear model of the improved high pressure common-rail system(HPCRS) including injector, the pipe connecting common-rail with injector and the hydraulic filter is built. Fuel pressure fluctuation at injector inlet, on which frequency domain analysis is conducted through fast Fourier transformation, is acquired at different target pressure and different damping hole diameter experimentally. The linear model is validated and can predict the natural frequencies of the system. Influence of damping hole diameter on fuel pressure fluctuation is analyzed qualitatively based on the linear model, and it can be inferred that an optimal diameter of the damping hole for elimination of fuel pressure fluctuation exists. Fuel pressure fluctuation and fuel mass deviation under different damping hole diameters are measured experimentally, and it is testified that the amplitude of both fuel pressure fluctuation and fuel mass deviation decreases first and then increases with the increasing of damping hole diameter. The amplitude of main injection fuel mass deviation can be reduced by 73% at most under pilot-main injection mode, and the amplitude of post injection fuel mass deviation can be reduced by 92% at most under main-post injection mode. Fuel mass of a single injection increases with the increasing of the damping hole diameter. The hydraulic filter proposed by this research can be potentially used to eliminate fuel pressure fluctuation at injector inlet and improve the stability of HPCRS fuel injection.

Detailed Dynamic Modeling of Common Rail Piezo Injector

A mathematical model of Bosch 3rd generation Common Rail fuel injection system with piezoelectric injector has been created. The numerical calculations for third different accumulator pressures (30, 80 and 160MPa) and third energizing times ET (0.5, 1 and 2ms) have been carried out. The results of calculations of total injected mass per cycle have been compared with the experiment with good agreement. The maximum error for ET=0.5ms is 10.4% and for ET≥1ms is less than 5%.

Mathematical Model for the Injector of a Common Rail Fuel-Injection System

The paper describes a Diesel fuel injection process. Computer simulation was carried out together with measurement of the Common Rail accumulator fuel-injection system. The computer simulation enables the observation of the phenomena from rail pressure, being the input data for injection parameters calculations, to the injection rate. By means of computer simulation, the pressure values in specific sections of the injection nozzle may be computed, the needle lift, injection rate, total injected fuel, time lag from injector current to first evidence of injection process and other time-lags between various phases of the injection process. The injection rate provides input data for spray computer simulation. Measurements of injection and combustion were carried out within a transparent research engine. This engine is a single-cylinder transparent engine based on the AUDI V6 engine, equipped with a Bosch Common Rail Injection System. The comparison between the computed and measured injection parameters showed good matching.

ジャトロファ油／灯油混合燃料を用いたコモンレール式ディーゼル機関の特性

ジャトロファ油／灯油混合燃料を用いたコモンレール式ディーゼル機関の特性

The Effects of Fuel Injection Pressure and Fuel Type on the Combustion Characteristics of a Diesel Engine

In an effort to understand the effects of injection system pressure on alternative fuel performance, a single-cylinder diesel engine was outfit with a modern common rail fuel injection system and piezoelectric injector. As future new fuels will likely be used in both older mechanical injected engines as well as newer high pressure common rail engines, the question as to the sensitivity of a new fuel type across a range of engines is of concern. In this study, conventional diesel fuel (Navy NATO F76) was compared with the new Navy hydroprocessed renewable diesel (HRD) fuel from algal sources, as well as the high cetane reference fuel nC16 (n-hexadecane CN = 100). It was seen that, in general, ignition delay (IGD) was shortened for all fuels with increasing fuel injection pressure and was shortened with higher CN fuels. The combustion duration for all fuels was also significantly reduced with increasing fuel injection pressure, however, longer durations were seen for higher CN fuels at the same fuel pressure due to less premixing before the start of combustion. Companion modeling using the Lawrence Livermore National Lab (LLNL) heavy hydrocarbon and diesel primary reference fuel (PRF) chemical kinetic mechanisms for HRD and nC16 was applied to understand the relative importance of the physical and chemical delay periods of the IGD. It was seen that at low fuel injection pressures, the physical and chemical delay times are of comparable duration. However, as injection pressure increases the importance of the chemical delay times increases significantly (longer), especially with the lower CN fuel.

Development of an electrically driven diesel fuel pump for commercial vehicles using HILS

Common-rail fuel injection systems on modern diesel engines have fuel pumps that are mechanically driven by the crankshaft. The pumps actually house two pumping elements: a low pressure element and a high pressure element. Part of the fuel compressed by the low pressure element returns to the tank in the process of maintaining the pressure in the common-rail at adequate levels for injection. Since the returning fuel represents pumping energy loss, fuel economy improves if the returned fuel can be reduced by using a properly controlled electrical fuel pump. As the first step in developing an electrical fuel pump the fuel supply system on a six-liter diesel engine was modeled with AMESim to analyze the workload and the fuel feed rate of the injection pump; the results served as the basis for selecting a suitable servo-motor to drive the pump. A motor controller was built using a DSP and a program which controls the common-rail pressure using a proportional control method based on the target fuel pressure information from the engine ECU. Test equipment was also fabricated to evaluate the performance of the electrically driven fuel pump. In a simulated vehicle test during the first 200 seconds of the NEDC driving schedule, the electric pump satisfied the fuel pressure and flow demand of the engine, consuming only 48.3% of the energy that an engine-driven pump would require.

English

In this study, the effects of fuel injection discharge curve and injection pressure onpower upgrade of heavy-duty diesel engine by simulation of combustion process in AVL-Fire software are discussed simultaneously. Hence, the fuel injection discharge curve is changed from semi-triangular to rectangular which is usual in common rail fuel injection system. Injection pressure with respect to amount of injected fuel and nozzle hole diameter are changed. Injection pressure is calculated by an experimental equation which is developed for heavy duty diesel engines with common rail fuel injection system. Power upgrade for 1000 and 2000 bar injection pressures are discussed. For 1000 bar injection pressure with 188 mg injected fuel and 3 mm nozzle hole diameter, power is upgraded about 19% in comparison to original state which is semi-triangular discharge curve with 139 mg injected fuel and 3 mm nozzle hole diameter, with no special change in cylinder pressure. On the other hand, both the NOX and the Soot emissions decreased about 30 and 6%, respectively. Compared with the original state, in the case of 2000 bar injection pressure, with injected fuel and nozzle diameter, 196 mg and 2.6 mm respectively, the power is upgraded about 22%, whereas cylinder pressure has been fixed, and the NOX and the Soot emissions are decreased to 36 and 20%, respectively.   Key words: Computational fluid dynamics (CFD) simulation, heavy-duty (HD) diesel engine, upgrading power, injection pressure, fuel injection discharge curve, combustion process.

Effect of di-n-butyl ether blending with soybean-biodiesel on spray and atomization characteristics in a common-rail fuel injection system

In this work, the spray and atomization characteristics of soybean biodiesel, di-n-butyl ether (DBE)/biodiesel blends and 0# diesel were investigated by using a high pressure common-rail injection system. The macroscopic spray characteristics such as the spray tip penetration (STP), the cone angle and the spray projected area were obtained from the spray images captured through high speed schlieren photography. The results show that as DBE is blended into biodiesel, the STP is decreased and the spray cone angle, projected area are increased and when the DBE volume fraction in the DBE/biodiesel blends reaches 30%, the STP, the spray cone angle and the projected area are comparable to that of diesel. For all the tested fuels, the microscopic spray characteristics such as the Sauter Mean Diameter (SMD) and statistical size distributions were measured by particle/droplet image analysis (PDIA) technique. The droplets number density distribution shows that for all the tested fuels, the region near the central of spray has the largest droplets number density and it decreases sharply as the position shifts from the center to the edge of the spray. As DBE is blended into biodiesel, smaller SMD is observed, which indicates that DBE addition can promote the atomization of biodiesel.

A study on the spray and engine combustion characteristics of diesel–dimethyl ether fuel blends

The purpose of this study was to compare the spray characteristics, the combustion characteristics and the emissions (nitrogen oxides, carbon monoxide, hydrocarbon and smoke) of typical fuels (100% diesel and 100% dimethyl ether) and diesel–dimethyl ether fuel blends in a constant-volume chamber and a single-cylinder direct-injection diesel engine. The spray characteristics were investigated by varying the ambient pressure and the fuel injection pressure using a common-rail fuel injection system with various fuel mixture ratios. The spray characteristic research parameters were the spray shape, the penetration length and the spray angle at the seven-hole injector. Common types of injector were used (Bosch). Two types of fuel blended by mass fraction were employed. Typical fuels (100% diesel and 100% dimethyl ether) and fuel blends with diesel:dimethyl ether mixture ratios of 95:5 and 90:10 were used. The injection pressure was fixed at 70 MPa while the ambient pressure was varied (0 MPa, 2.5 MPa and 5 MPa). The combustion experiments were conducted in a single-cylinder engine equipped with a common rail. The injection pressure was 700 bar at 1200 r/min. The amount of injected fuel was adjusted to obtain a fixed input calorific value of 972.2 J/cycle in order to make a comparison between the fuel types. The results showed that the injection quantity was greater with diesel fuel but not for dimethyl ether fuel and for the fuel blend with the higher mixing ratio. The spray penetration length increased with increasing ambient pressure for diesel but decreased for dimethyl ether with a larger spray angle. The ignition delay and the heat release rate decreased with increasing dimethyl ether which led to a higher indicated mean effective pressure and higher thermal efficiency because there was less negative work in the expansion. The total hydrocarbon emissions and the carbon monoxide emissions decreased with increasing dimethyl ether, but the nitrogen oxide emissions generated were greater owing to the increased combustion temperature.

Theoretical analysis and mathematical modelling of a high-pressure pump in the common rail injection system for diesel engines

In this paper, a study on the performance of a high-pressure pump of the common rail fuel injection system is presented. The mathematical models established include: (i) the fluid model for the pump chamber and rail which takes the structural deformation and interface leakage into consideration; (ii) the nonisothermal fluid–structure interaction model for the leakage at the piston/cylinder interface; and (iii) the unified model for the physical properties of the fuel such as dynamic viscosity, density and isobaric specific heat capacity versus pressure and temperature relationships. The factors leading to the loss of the pump volumetric efficiency during the four phases of the pump working cycle are theoretically analysed. Both differential and iterative methods are applied in the numerical solution of the model. The leakage model was validated against the measured leakage rates, and showed satisfactory results. A parametric study is carried out to analyze the effects the piston diameter has on the establishment process of the chamber pressure, the piston/cylinder interface leakage and the compression stroke. Results show that the impacts of the leakage, the compression stroke and the suction loss on the volumetric efficiency loss of the pump all increase with the nominal rail pressure.

Effects of injection timing on performance and emissions of a HD diesel engine with DMCC

Experiments were conducted on a 6-cylinder turbocharged intercooled heavy duty (HD) diesel engine with diesel/methanol compound combustion (DMCC) mode. The baseline engine was equipped with a common rail fuel injection system and had been modified to run under DMCC mode. In DMCC mode, methanol is fumigated into the intake manifold to form lean air/methanol homogeneous mixture, and then ignited by the direct-injected diesel fuel in cylinder. This study is aimed to investigate the effects of injection timing on performance and exhaust emissions of the engine with DMCC mode. Experimental results showed that under DMCC mode both increasing methanol substitution ratio and advancing injection timing could increase the peak cylinder pressure and the maximum heat release rate. The brake specific energy consumption (BSEC) and exhaust temperature of DMCC engine decreased with advancing injection timing. NOX was increased and soot was decreased as the diesel injection timing was advanced. Compared with the diesel fuel mode, the DMCC mode had benefits in reduction of intake air temperature, NOX and soot emissions, while there was an obvious increase in NO2, HC and CO emissions. In addition, the HC and CO emissions of DMCC mode exhibited a decreasing trend according to an advance in the injection timing.