High Pressure Common Rail System Research Articles

Research on a small sample fault diagnosis method for a high-pressure common rail system

In the fault diagnosis of high-pressure common rail diesel engines, it is often necessary to face the problem of insufficient diagnostic training samples due to the high cost of obtaining fault samples or the difficulty of obtaining fault samples, resulting in the inability to diagnose the fault state. To solve the above problem, this paper proposes a small-sample fault diagnosis method for a high-pressure common rail system using a small-sample learning method based on data augmentation and a fault diagnosis method based on a GA_BP neural network. The data synthesis of the training set using Least Squares Generative Adversarial Networks (LSGANs) improves the quality and diversity of the synthesized data. The correct diagnosis rate can reach 100% for the small sample set, and the iteration speed increases by 109% compared with the original BP neural network by initializing the BP neural network with an improved genetic algorithm. The experimental results show that the present fault diagnosis method generates higher quality and more diverse synthetic data, as well as a higher correct rate and faster iteration speed for the fault diagnosis model when solving small sample fault diagnosis problems. Additionally, the overall fault diagnosis correct rate can reach 98.3%.

Experimental study on the performance of ultra high pressure common rail system

In order to overcome the difficulties of high pressure source design and parts integration in the injector, realizing the ultra high pressure injection and controllable fuel injection rate, an ultra high pressure common rail system based on domestic basic materials and manufacturing technology level was proposed and designed. The working principle of this system was first introduced; the performance test bench of ultra high pressure common rail system was built. Then, the influence of pressure-amplifier device structure parameters on the pressurization pressure peak was analyzed quantitatively, and on the basis of selecting the most appropriate combination of parameters, the pressure and fuel injection rate control characteristics were conducted. The results show that ultra high pressure common rail system can magnify fuel pressure to ultra high pressure state (more than 200 MPa) and by changing the control signal timing of pressure-amplifier device and injector solenoid valve, the flexible and controllable fuel injection rate can be achieved. Under the condition of the same pressurization ratio, the peak value of pressurization pressure increases gradually, and with the increase of pressurization ratio, the increasing trend of the pressurization pressure peak value is nonlinear. At the same time, under the same condition of spring preload, the greater of the spring stiffness, the higher of the rail base pressure can bear, that means the pressure-amplifier device can achieve pressurization at a higher base pressure. But if the spring stiffness is too large, the solenoid valve of pressure-amplifier device will not be opened due to insufficient electromagnetic force, so the specific selection should be considered in a compromise.

A calculation method and experiment study of high-pressure common rail injection rate with solenoid injectors.

The high-pressure common rail system has been widely used owing to its precise control of fuel injection rate profile, which plays a decisive role in cylinder combustion, atomization, and emission. The fuel injection rate profile of high-pressure common rail system was studied, and a fuel injection rate profile calculation model is proposed. The model treats the injector as a black box. Some measured data are needed to calculate the parameters in the model. The rise and fall of injection rate is regarded as trigonometric function to reduce the complexity and increase the accuracy. The model was verified using two different types of fuel injectors. The model calculation results were evaluated under various data input conditions. The results show that the model has good applicability to different input data and injectors. In addition, because the model building requires a large amount of experimental data, a comprehensive analysis of various input data was also conducted. The injection profile was analyzed from a new perspective and the regularity of injection rate profile was established.

The effects of natural gas composition on conventional dual-fuel and reactivity-controlled compression ignition combustion in a heavy-duty diesel engine

The use of natural gas (NG) in dual-fuel heavy-duty engines has the potential to reduce pollutant and greenhouse gas (GHG) emissions from the transport sector when compared to the conventional diesel engines. However, NG composition and methane slip are of interest because both can adversely affect the benefits of NG as an alternative fuel, especially when considering GHG emissions. Therefore, this study experimentally investigated the effects of NG fuel properties on the performance and emissions of both conventional dual-fuel and reactivity-controlled compression ignition (RCCI) engine operations. Three different gas mixtures were selected to simulate typical NG compositions available in the world market, with methane numbers (MN) of 80.9, 87.6 and 94.1. These fuels were tested in a single-cylinder compression ignition engine operating at 0.6, 1.2 and 1.8 MPa net indicated mean effective pressure (IMEP). A high-pressure common rail system allowed for the use of various diesel injection strategies while a variable valve actuation system enabled the effective compression ratio to be adjusted via late intake valve closing (LIVC). The RCCI combustion was found to be more sensitive to changes in MN than the conventional NG-diesel dual-fuel operation. The gas mixture with the lowest MN reduced both total unburned hydrocarbons emissions and methane slip at the expense of higher nitrogen oxides (NOx) emissions. The effects of MN on the net indicated efficiency were more significant at 0.6 MPa IMEP, yielding differences of up to 4.9% between the RCCI operations with the lowest and highest MN fuels. Overall, this work revealed that the combination of the RCCI combustion and LIVC can achieve up to 80% lower methane slip and NOx emissions and relatively higher net indicated efficiency than the conventional dual-fuel regime, independent of the NG composition.

Research on Rail Pressure Control of High-Pressure Common Rail System for Marine Diesel Engine Based on Controlled Object Model

The common rail pressure of a marine diesel engine high-pressure common rail system is typically controlled by a PID (Proportional Integral Differential) algorithm, which has problems with both overshoot and response delay. In this paper, the control method based on controlled object model for rail pressure is studied. The control model for a high-pressure common rail system is established within the controller. Through the developed control model and the current actual rail pressure obtained by real-time acquisition, the control variables issued by the controller to the controlled object are predicted and calculated. The fuel supply required in the whole high-pressure common rail system is calculated in advance, with the fuel supply then taken as the input value for the driving model in order to calculate the PWM control signal required by the high-pressure oil pump. A PWM control signal is used to control the proportional valve opening of the high-pressure oil pump, and then control the fuel pressure in the common rail pipe. In order to verify the correctness and control effects of the rail pressure control strategy based on controlled object model, a real-time simulation of the high-pressure common rail system has been developed by combining calculation equations with a MAP data query, which ensures real-time performance. At the same time, the real-time simulation of the high-pressure common rail system shows that the error between the simulation’s calculation and the actual test data is less than 5%, and thus model accuracy is guaranteed. The control method based on controlled object model is combined with the real-time simulation model for the high-pressure common rail system to verify the control strategy function, and the control effect is then compared with that of the PID control. Comprehensive verification shows that the control strategy based on controlled object model can significantly improve the response delay and overshoot of PID control.

Experiment investigation of injection parameters effects on injection stability of a high pressure common rail system.

High pressure common rail system can precisely control the injection time and injection pressure to improve the thermal efficiency of the engine. The injection characteristics of the system can affect the combustion and emission process of the engine. Injection stability is defined as variation characteristics of injection. This could have an unignored influence on combustion and engine output, while few study has been published. The primary objective is to establish evaluation systems and methods for injection stability. Then to study injection stability of the high pressure common rail system. Firstly, several parameters that have an important influence on the emission and combustion are identified. Based on the characteristics data obtained, it is verified that the stability parameters are in accordance with the normal distribution. Then, the five characteristic stability parameters of close speed of injection, cycle injection mass, injection delay, maximum injection rate and open speed of injection were quantitatively analyzed by using range, relative range, kurtosis and variance. It is found that the close speed of injection is greatly depend on injection pressure, the range of close speed varies from 1.8 to 5.1 mg/ms when rail pressure varies from 60 MPa to 160 MPa at 0.6 ms energizing time. The stability of injection mass depends on energizing time, the relative range in short energizing time can be four times than long energizing time. The maximum injection rate has similar characteristics with injection mass, it is also depends on energizing time. The range of maximum injection rate is reduced from the average of 0.6-0.7 mg/ms to 0.3 or even 0.2 mg/ms with the increase of energizing time. The injection delay and open speed of injection seems to be greatly affected by pressure fluctuation, since the observed data present complex rules. Pressure fluctuation in common rail can affect injection stability a lot.

An on-line measurement method of injection rate of high pressure common rail system

This paper presents a new on-line measurement method of injection rate based on the injector inlet pressure. The Riemann wave theory is applied to the fuel system, and the mathematical relationship of injection rate (G) and pressure (P) under single Riemann wave is put forward. The correction algorithm of the interference wave and the decoupling method of the superposition wave are proposed, which improves the accuracy of the algorithm and realizes the calculation of the fuel injection rate during the long injection energizing time. The identification algorithm of the needle maximum upstroke position moment and the needle starting downstroke moment are proposed and taken as the key time characteristics of the injection process. Compared to the experiments, the errors of the injection mass by this method were within 3%, and the fitting goodness of injection rate curve exceeded 0.93, proving quite good precision for the method.

Pressure Control Strategy and Simulation of High Pressure Common Rail System

Aiming at the control of the pressure wave of the high pressure tubing, considering the different design of the pressure reducing valve, two control strategies of the pressure reducing valve are discussed, and the problems to be noted when designing the control strategy are proposed. First, the actual high pressure common rail system is reasonably simplified as the “pump-nozzle-pipe” system, then based on the relevant theory (fluid flow formula, mass conservation law and relationship between fuel density and pressure), a mathematical model is established to determine the cam angular velocity, opening time and period and threshold of pressure reducing valve, and injection interval of nozzle, these parameters have a great influence on the pressure wave, and finally using the orthogonal test method to explore the influence of these parameters on the pressure wave by computer simulation. The research shows that only the injection interval of nozzle affects the size of the pressure wave range, other parameters only affects the pressure value at the time of stability. The larger the injection interval of nozzle, the smaller the size of pressure wave range. Therefore, when designing the control strategy, the injection interval of nozzle should be increased.

Fuel Pretreatment Systems in Modern CI Engines

The article concerns the possibility of using a fuel pretreatment system in modern compression ignition CI engines, the main task of which is the reduction of toxic emissions in the form of exhaust gases. This fuel pretreatment system consists of a catalytic reactor used in common rail (CR), and a modified fuel atomizer into spiral‒elliptical channels covered with catalytic material. In the system presented here, platinum was the catalyst. The catalyst’s task is to cause the dehydrogenation reaction of paraffin hydrocarbons contained in the fuel to create an olefin form, with the release of a free hydrogen molecule. In the literature, the methods of using catalysts in the exhaust systems of engines, or in combustion chambers, injection pumps, or fuel injectors, are known. However, the use of a catalytic reactor in the CR system in a high-pressure fuel atomizer rail is an innovative project proposed by the authors. Conditions in the high-pressure CR system are favorable for the catalyst’s operation. In addition, the spiral‒elliptical channels made on the inoperative part of the fuel atomizer needle increase the flow turbulence and contact surface for the catalyst.

Gasoline-diesel dual fuel intelligent charge compression ignition (ICCI) combustion: Conceptual model and comparison with other advanced combustion modes

The internal combustion engines can remain the advantage over competitor technologies for automotive driven, especially the engine efficiency, exceeded 50% while maintaining ultra-low emissions. In this paper, a novel combustion mode characterized by dual high-pressure common-rail direct injection systems, denoted as intelligent charge compression ignition (ICCI) combustion, is proposed to realize high efficiency and clean combustion in wide engine operating ranges. Specifically, commercial gasoline and diesel, which are considered to be complementary in physical and chemical properties, are directly injected into the cylinder by the two independent injection systems, respectively. Through this unique design, the in-cylinder air-fuel mixtures can be flexibly adjusted by regulating injection timing and duration of different fuels, consequently obtaining suitable combustion phase and heat release rate. The ICCI mode can widely run from indicated mean effective pressure 2 bar to 16 bar with an utterly controllable cylinder pressure rising rate, around 50% indicated thermal efficiency and low NOx emissions. A series of experiments were carried out to compare the combustion and emissions of ICCI with other combustion modes (including conventional diesel combustion, reactivity-controlled compression ignition, partially premixed combustion, and gasoline compression ignition). The results show that at the medium engine loads, ICCI mode can reach much high indicated thermal efficiency, especially up to 52% along with extremely low NOx emissions. Prospectively, ICCI mode can realize real-time adjustments of in-cylinder mixture stratification and instantaneous combustion mode switch in one cycle at any operating conditions, and has an excellent commercial application prospect for energy conservation and environmental improvement.

Experimental study and optimization in the layouts and the structure of the high-pressure common-rail fuel injection system for a marine diesel engine

The structure and performance of the common-rail system for the marine diesel engine are different from those used for automobile applications, resulting from the larger accumulator volume and the single injection volume. According to the characteristics of the distributed structure of the accumulator volume, a novel optimisation idea to improve the steady-state performance of the high-pressure common-rail fuel injection system designed for a marine engine retrofitting is proposed. The study concentrates on the optimisation in the hydraulic layouts and the structure parameters to manage the energy stored in the pressure waves. First, the test rig was established to study and evaluate the steady-state performance of the high-pressure common-rail system. Second, the experiments of rail orders and injection sequences were carried out to study the influence of different hydraulic layouts on the energy distribution of pressure waves in the system. Meanwhile, a comprehensive and detailed model of the high-pressure common-rail system was built to investigate the structural parameters of a rail-to-injector pipe. Based on the high-pressure common-rail system model, the modified multi-objective genetic algorithm was employed to seek the trade-off between the consistency of the injection volume and the reduction of the rail pressure fluctuation. Results show that a uniform distribution of multiple rails in one cycle contributed to reducing the amplitude of the rail pressure oscillation. In the parameter ranges of this study, a longer length and larger diameter of the rail-to-injector pipe could reduce the standard deviation of the injection volume and the rail pressure fluctuation rate simultaneously.

Research on Pressure Stability Control of High-pressure Common Rail System Based on Differential Equation Optimization Model

To improve the accuracy of fuel injection in high-pressure common rail systems of diesel engine, a mathematical model based on differential equations was established in view of the process of fuel entering and ejecting the common rail pipe, and the pressure variation law under working condition in the common rail tube was simulated in this study. Aiming at reducing the fuel pressure fluctuations in the system, the optimal angular velocity of the cam in high-pressure pump is solved by binary search algorithm, and the optimal control strategies for maintaining the dynamic and stability of pressure are given as well. Numerical simulation results show that with the presented strategies precise control of the pressure can be achieved in the common rail system, helping to improve the efficiency of the diesel engines.

Study on ether spray combustion and its products under sub- and super-critical environments

In order to explore the combustion process of fuel and its products under sub- and super-critical environments, the constant volume combustion bomb system was used. The high-pressure common rail system and single injection instrument were used to supply fuel. Images of spray and combustion processes were recorded by high speed video camera using shadow photographic method, and combustion products were measured with a gas analyzer. The experimental results show that the ether flame presents a bright spherical shape. At the critical pressure point, the spray combustion penetration is the shortest, and the overall flame area is the smallest. The combustion duration of ether increases with increasing ambient pressure, reaches the maximum at the critical pressure, and then decreases with further increasing pressure. The amount of CO emitted from the combustion of the ether continuously decreases with the increase of ambient pressure. The amount of HC changes abruptly at the critical pressure. The differences between combustion characteristics and products formation are mainly due to the differences in fuel physical parameters and its break-up and evaporation mechanisms under sub- and super-critical conditions.

Tribological study of piston–cylinder interface of radial piston pump in high-pressure common rail system considering surface topography effect

Based on the theory of thermal fluid dynamic lubrication, the Reynolds equation and energy equation of the average flow of a piston–cylinder interface of a radial piston pump in a high-pressure common rail system are established, considering the surface topography effect. The tribological properties of the piston–cylinder interface are calculated by solving the Reynolds equation and energy equation. A surface wear model is established and the wear distribution and trend of the piston–cylinder interface are studied. The wear characteristics of the piston–cylinder interface are verified through experiment, and the wear lubrication of the piston–cylinder interface is discussed. The surface topography effect has a considerable influence on the characteristics of the piston–cylinder interface film. Different surface morphologies change the film characteristics of the piston–cylinder interface, yielding different wear behaviors on the mating surface. The wear of the piston–cylinder interface first decreases along the film outlet to the inlet and then rises. The cylinder surface mainly exhibits abrasive, cavitation, and micro-convex scratch wear, whereas the piston surface mainly shows cavitation wear. The results obtained in this study are of considerable significance as they reveal the tribological properties of the piston–cylinder interface under the surface topography effect.

GPIO‐based rail pressure control for diesel high pressure common rail injection system

The rail pressure control in diesel high-pressure common rail (HPCR) system is considered as one of the key issues for precise control of fuel injection. This study investigates the application of generalised proportional integral observer (GPIO)-based control in diesel HPCR system. Firstly, a non-linear mathematical model of HPCR system which uses the metering unit as the actuator is established based on hydromechanics under some proper simplifications. Secondly, a GPIO is developed to estimate the mismatched disturbance caused by the injection process. Then a composite controller combining GPIO and backstepping control method is designed. By introducing the disturbance estimations into the control design process, the disturbance rejection capability of the system is promisingly enhanced. The effectiveness of the proposed control method is validated by the simulation results.

Investigation on the fuel injection stability of high pressure common rail system for diesel engines

High pressure common rail system is the state-of-the art technology for modern diesel engines to achieve energy conservation and emission reduction. The economy and emission performance of the diesel engines are influenced by the fuel injection stability of the high pressure common rail system. In this work, a high pressure common rail injector numerical model based on bond graph theory has been proposed. The comparisons between experimental results and numerical simulations show that the numerical model could reasonably predict the injection characteristics of the system. In order to reveal the essential rules and inherent characteristics of the fuel injection stability for high pressure common rail system, the rank variations of the state matrix at different injection pulse widths during fuel injection are obtained by means of a linear analysis. In addition, the distributions of eigenvalues for the state matrix in complex plane are investigated using Lyapunov method. The results show that the rank is influenced mainly by the movements of control valve and needle. Furthermore, the variation rule of the rank is independent of the injection pulse width before the needle is opened. The needle channel orifice of the injector plays a dominant role in transformation of the system from strong damping oscillation to underdamping oscillation. The opening and closing of control valve have significant effect on the stability of the system because its movement breaks the stability, and the movement of needle has remarkable effect on the oscillating characteristics of the system. High pressure common rail system is a complicated time-variant system with unstable pressure relief and strong oscillation injection.

3D CFD Simulation of Water Hammer in High Pressure Common Rail System of Diesel Engine

The water hammer pressure triggered by injection in the high pressure common rail system play a major role in precise controlling of diesel injection. In order to obtain a deep insight into the existing transient three-dimensional effects, a three-dimensional computational fluid dynamics (3D CFD) simulation of water hammer was performed. An adequate mesh and suitable physical model was generated using a commercial code. The transition SST model was applied to simulate the three-dimensional hydrodynamic calculation of the oil supply lines of high-pressure common rail systems. The accuracy of simulation was verified by comparing the results with experimental data. The fluctuation characteristics of pressure and velocity in high pressure oil pipeline and the three-dimensional flow field effect of pipe radial direction were analyzed in the course of water hammer pressure fluctuation propagation in high pressure common rail system. 3D CFD simulation can show more details than traditional methods.

Experimental study of the influence of the fuel and boundary conditions over the soot formation in multi-hole diesel injectors using high-speed color diffused back-illumination technique

Two prototypes multi-hole diesel injector from a high-pressure common rail system were used to operated with diesel and n-Heptane fuels in a high-pressure and high-temperature test rig able to reach 1100 K and 15 MPa under different oxygen concentrations with the goal to study the influence of the boundary conditions on the combustion process evaluating parameters as ignition delay, lift-off length and soot formation. A novel optical set-up was implemented to visualize the soot cloud evolution in the fuel jet between 30 and 85 mm from the nozzle exit using the high-speed color diffused back-illumination technique, it was used as a result of the insertion of a high-pressure window in the injector holder opposite to the frontal window of the vessel allowing an optical arrangement in line-of-sight. The experiments performed in this work used a LED with a wavelength of 460 nm to provide information about physical of the soot properties, the results of varying the operational conditions show the reduction of soot formation with an increase in injection pressure, a reduction in ambient temperature, a reduction in oxygen concentration or a reduction in ambient density. Furthermore, fuel effect on soot formation also has been studied showing a big difference between both fuels, diesel is known to be more prone to produce soot than n-Heptane reducing the ability of the technique implemented, especially in conditions with high temperature and high density.

Simulation of the Effect of Fuel Injection Rate that Matches Fuel Injection Advanced Angle on the Performance of Ultra High Pressure Common Rail Diesel Engine

On the basis of introducing the implementation method of variable fuel injection rate, the calculation model of a single-cylinder ultra high pressure common rail diesel engine was built, and the accuracy of this model was verified with experiments; then the effects of different fuel injection rates and fuel injection advanced angles on the performance of the ultra high pressure common rail diesel engine were analyzed with this model. The results show that the variable fuel injection rate can be realized by adjusting the opening time of electric-controlled pressure amplifier and injector solenoid valve in the ultra high pressure common rail system. With the lagging of pressurization time, the cylinder pressure, cylinder temperature, heat release rate and NOx emissions of the diesel engine decrease, while the soot emission rises. The ultra high pressure rectangle injection rate can make the diesel engine acquire best power and economy performance. With the increasing of fuel injection advanced angle, the cylinder pressure, cylinder temperature, heat release rate and NOx emission of the diesel engine rise, while the soot emission decreases first and then rises, the too small or too large fuel injection advanced angle can both reduce the power and economy performance of the diesel engine. The high fuel injection rate that matches small fuel injection advanced angle can improve power output and reduce fuel consumption of the diesel engine, and there is an optimal fuel injection advanced angle for each fuel injection rate to make the diesel engine performance achieve the best.

Study on Effect of the High Pressure Common Rail System on the HPD Diesel Engine Combustion

The CFD simulation model of the spray and combustion in the cylinder of the diesel engine was built by mean of the FIRE software and was checked through the test; the influence of the common rail pressure and the injection period on the velocity field, fuel-air equivalent ratio distribution and the temperature field were studied when the injection mass was constant; the influence of injection timing on the velocity field, fuel-air equivalent ratio distribution and the temperature field was studied when the common rail pressure and the injection period were constant. The study provided the foundation to match the high pressure common rail system parameters.