High Pressure Common Rail System Research Articles

Real-time estimation of fuel injection rate and injection volume in high-pressure common rail systems

The injection rate and injection volume are essential parameters for the combustion process, which greatly affect the engine efficiency and emission performance. However, at the current time the injection information cannot be obtained in real time during the actual operation of engine. This paper presents a novel real-time estimation method for the injection rate and injection volume based on the measurable rail pressure. A comprehensive dynamic model is derived by considering both the effect of fuel injection and supply process on the pressure fluctuation. Then a linear time-varying state space model is constructed by choosing three appropriate state variables. On this basis, considering the measurement noise and model uncertainty, a Kalman filter-based estimation method of the injection information is investigated. And the noise covariance matrix Q is optimally designed to adapt to a wide range of operating conditions. The proposed estimation method is validated on the different conditions, and the results show the injection rate estimation errors are within 4.5 %, the injection volume estimation errors are within 4 %. And on the situation with overlap of injection and supply process, the injection rate and injection volume estimation errors are all within 4.5 %.

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.

Research on the influential factors related to the fuel leakage rate in the plunger-sleeve clearance of high pressure common rail system

In this study, a numerical model of the fuel leakage rate in the plunger-sleeve clearance of high-pressure common rail system was established based on graph theory. The transient clearance changes caused by the elastic deformation and the physical properties of the fuel along the flow direction within the plunger-sleeve were considered. This model realized the fluid–structure–thermal transient coupling during the leakage, and the accuracy was verified by comparing the calculated fuel leakage rate with the experimental data. Based on the main structural parameters of the plunger-sleeve, a three-level five-factor experimental calculation matrix was proposed using the D-optimal design method. The fuel leakage rates of all groups in the calculation matrix were obtained based on the fuel leakage rate numerical model, and the significant influencing parameters of the fuel leakage rate were determined using analysis of variance (ANOVA). The results indicate that the plunger diameter, sleeve external diameter, plunger-sleeve initial clearance and sealing length are significant parameters that affect the fuel leakage rate. In case of interaction between parameters, the interaction between the plunger diameter and sleeve external diameter, plunger diameter and plunger-sleeve initial clearance, and plunger diameter and plunger-sleeve sealing length contributed to a significant change in the fuel leakage rate. The influencing behavior of significant single parameters and significant interactions between parameters on the fuel leakage rate were revealed. The research outcomes can provide theoretical support for the optimization of the design of plunger-sleeve.

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.

Optimal estimation of injection rate for high-pressure common rail system using the extended Kalman filter

This paper presents an innovative estimation method of the fuel injection rate based on the rail pressure measurement signal for a high-pressure common rail system. A dynamic mathematical model of the injection process is constructed. To meet the requirement of the estimator design, a nonlinear state space model with three state variables is derived. On this basis, an optimal estimation method for the injection rate is proposed based on the extended Kalman filter, and the impact of noise covariance matrices is thoroughly examined. The results demonstrate that the proposed method enables fast convergence of the estimated injection rate. The coefficient R2 values between the estimated and the actual injection rate curves exceed 94%, and the estimated errors of the injection volume are within 5%.

GPIO-based nonsingular terminal sliding mode control for high-pressure common rail systems

The ideal fuel rail pressure is a significant component to keep the high-pressure common rail (HPCR) system work stably. The influence of time-varying fuel injection disturbance of the HPCR system is neither fully considered nor well dealt with in traditional rail pressure control approaches. To this end, the rail pressure tracking problem of an HPCR system is investigated in this paper using a generalized proportional integral observer (GPIO)-based composite control algorithm. A nonlinear model of the HPCR system is first established based on fluid dynamics and mechanics laws. Then, a GPIO is utilized to observe the time-varying fuel injection disturbance. Based on the design of a nonlinear sliding surface using the disturbance estimation, a GPIO-based nonsingular terminal sliding mode control (NTSMC) method is proposed to achieve a better rail pressure tracking control performance and a stronger robustness. Finally, a group of simulations in the MATLAB/Simulink environment and experiments in a more realistic Advanced Modeling Environment for performing Simulation of engineering systems (AMESim) environment are conducted, the results of which demonstrate the advantage and effectiveness of the proposed method.

Fluid-solid coupling simulation study on fuel leakage and deformation characteristics of precision coupling component in common rail injector and influence of pressure equalizing structure

In the foreseeable future, the use of fossil energy is still irreplaceable, makes efficient use of fossil energy and reduce emissions became important topics. Diesel engines have a very high share in the transportation field, and high-pressure common rail system has highly improved the performance of diesel engines. As the most important component of common rail system, the performance of common rail injector directly affects the engine. Precision coupling components are composed of moving parts with very precise clearance fit in the injector. With the wear of parts, fuel leakage of precision coupling components may reach the same level as injection quantity, which will seriously affect the injection pressure actually established, and then affect the power, efficiency, and emission performance of diesel engine. Many researchers have studied fuel leakage of precision coupling components, and put forward different methods to reduce fuel leakage, including improving the machining accuracy and machining annular grooves on parts. However, the wear of parts makes it a high-cost and low-effective method to improve machining accuracy. Besides, researchers have not fully considered the deformation of parts. In this work, fluid-solid coupling simulations were performed to analyze deformation and static fuel leakage characteristics, and to investigate effects of pressure equalizing structure on deformation and leakage of precision coupling component in common-rail injector. Different from the previous researches, the influence of machining the annular groove on the plunger sleeve instead of on the plunger, and influence of coexistence of annular groove and deformation were considered. The results show the deformation characteristics of the parts, the fuel flow characteristics in the gap, and the influence of the annular groove on the fuel leakage. The connection between the deformation of parts and fuel leakage, and potential methods to reduce the leakage are also discussed.

Dynamic Modelling of Common Rail Diesel Engines Combined with Amesim and Simulink

The fuel injector of the diesel engine is the core component of the high-pressure common rail system of the diesel engine. The ECU performs flexible control on the fuel injector to realize the precise adjustment of the fuel injection rate and fuel injection quantity of the engine under different working conditions, and achieve the purpose of reducing fuel consumption and noise. The internal structural parameters of the fuel injector have a significant impact on the fuel injection rate, and it is often necessary to make a large number of modifications to the structural parameters of the fuel injector in order to meet the increasingly stringent emission regulations. In this paper, in order to analyze the effect of various structural parameters of fuel injectors on fuel injection rate, increase fuel injection rate, and obtain the best effect, AMESim and simulink software are used to build a simulation model of a common rail fuel injection device and a diesel engine. This model provides a theoretical basis for the structure design of the fuel injector.

GPIO Based Sliding Mode Control for Diesel Engine High Pressure Common Rail System

GPIO Based Sliding Mode Control for Diesel Engine High Pressure Common Rail System

Study on observation method of injection pressure curve in high pressure common rail system

The performance of the diesel engine was determined by the injection pressure of the high pressure common rail system. The observation method of the injection pressure curve was of great value in evaluating the operating conditions of the diesel engine. However, the observation method could make it impossible to directly observe the injection pressure data on a high pressure common rail system in operation. In this paper, common rail pressure signals and control pulse widths, which were easy to collect, were used as the basis for proposing a GRU (Gated Recurrent Unit) based model for the observation of injection pressure curves of high pressure common rail system in order to solve the above problem. The accuracy and precision of the model was verified by the experiments and compared with commonly used simulation models. From the results, it was concluded that the overall accuracy of the injection pressure curve observation was similar to that of the simulation model, but the accuracy was higher around the peak of the injection pressure, as well as the equipment requirement was low and the calculation speed was fast. The mean EMD of the curvilinear observation model of injection pressure of high pressure common rail system is similar to that of the 1D simulation model, with 37.88 and 33.62 respectively. The overall difference in injection pressure between the two models is similar with 53.62 and 54.23 MPa respectively. On the same computing platform, the average computation time of the test set containing five states is 0.0113 s, and the simulation time of each running state is 12951.6 s using AMESim software.

Study on the pressure fluctuation characteristics of the high-pressure common rail system with a distributor

In allusion to the problem of common rail pressure fluctuation when the high-pressure common rail system (CRS) using double rails, a numerical simulation model of a V-type 8-cylinder engine CRS was established by using AMESim software, and the suppression of pressure fluctuation with and without distributor was studied. The optimum structure dimension of the distributor with length of 100 mm and inner diameter of 9 mm was obtained by uniform design method. Then the pressure surge characteristics of CRS was researched. The research results showed that the installation of the distributor cut down the amplitude of the pressure oscillation of the common rail by more than 62.28%. Therefore, the designed distributor can effectively suppress the rail pressure fluctuation and improve CRS stability.

Simulation study on pressure fluctuation characteristics of a high-pressure common rail system

Pressure fluctuations in the high-pressure common rail systems have a significant impact on the fuel injection and engine performance. In this study, the pressure fluctuation in a high-pressure common rail system was investigated using simulations. The fluctuation can be caused by hydraulic structures and control factors. The degree of influence of those two causes was evaluated and discussed in this work. First, the hydraulic and control factors that dominate the models of injection systems were established. Then, the mechanism of pressure fluctuation on high-pressure common rail systems was highlighted. A dimensionless parameter was defined to quantitatively describe the effects of control factors and hydraulic structures on pressure fluctuation. Finally, the developed model was used to study the effects of injection conditions and structural parameters on pressure fluctuation. The results show that the injection frequency has a limited effect on the system pressure fluctuation. In addition, the increase in the injection energizing time and the injection pressure will increase the hydraulic pressure fluctuations of the system, thus increasing the total pressure fluctuations of the system. Moreover, the increase in the volume by increasing the diameter was found to decrease the pressure fluctuations more effectively compared to the impact of the length, but there is a marginal diminishing effect. The results demonstrated that the effect of a 20 bar signal error and a 160 mm common rail length is almost the same on decreasing pressure fluctuations. It can be concluded that the improvements in the electronic part of the high-pressure common rail system have more potential than the mechanical part.

Control Strategy Based on Flow Conservation Equation for High-pressure Common Rail System

Control Strategy Based on Flow Conservation Equation for High-pressure Common Rail System

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.

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.

Establishment of a Real-Time Simulation of a Marine High-Pressure Common Rail System

In this paper, the high-pressure common rail system of the marine diesel engine is taken as case study to establish a real-time simulation model of the high-pressure common rail system that can be used as the controlled object of the control system. On the premise of ensuring accuracy, the real-time simulation should also respond quickly to instructions issued by the control system. The development of the real-time simulation is based on the modular modeling method, and the high-pressure common rail system is divided into submodels, including the high-pressure oil pump, common rail tube, injector, and mass conversion. The submodels are built using the “surrogate model” method, which is mainly composed of MAP data and empirical formulas. The data used to establish the real-time simulation are not only from the empirical research into the high-pressure common rail system, but also from simulations of the high-pressure common rail system undertaken in AEMSim. The data obtained from this real-time simulation were compared with the experimental data to verify the model. The error in fuel injection quality is less than 5%, under different pressures and injection durations. In order to carry out dynamic verification, the PID control strategy, the model-based control strategy, and the established real-time simulation are all closed-loop tested. The results show that the developed real-time simulation can simulate the rail pressure wave caused by cyclic injection according to the control signal, and can feedback the control effect of different control strategies. Through verification, it is clear that the real-time simulation of the high-pressure common rail system can depict the rail pressure fluctuation caused by each cycle of fuel injection, while ensuring the accuracy and responsiveness of the simulation, which provides the ideal conditions for the study of a rail pressure control strategy.

Radial development of pentanol–biodiesel fuel spray in a high-pressure common-rail system

Pentanol is a potential alternative fuel. The effect of blending pentanol on the radial diffusion of biodiesel spray was studied. There are seldom eyes on the comprehensive study on the radial development of spray. For evaluating the radial development ability, the spray characteristic parameters such as the maximum width, the actual distance from the widest part to the nozzle, the cone angle, and the spray mean width were chosen for study. The influences of ambient pressure and injection pressure were also analyzed. The radial diffusion ability of biodiesel spray could be improved by adding pentanol, and it would also be affected by the varying of ambient and injection pressures. With the addition of pentanol, the maximum width of spray increased, the distance from the nozzle to the widest range shortened, the spray cone angle increased, and the average spray width increased, which means the maximum radial diffusivity and average radial diffusivity of the spray were enhanced. When the ambient pressure increased, the distance from the nozzle to the widest range was shortened, the spray cone angle increased, and the average spray width increased. When the injection pressure increased, the maximum spray width of the blended fuel containing a small amount of pentanol increased, the distance from the nozzle to the widest width increased, and the average spray width increased. The maximum radial diffusivity of spray was only affected by ambient pressure, and the average radial diffusion capacity was affected by both ambient pressure and injection pressure.

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.