Monitoring of the state of electromagnetic fuel injectors of gasoline engines with distributed fuel injection systems

Introduction. Ensuring the trouble-free operation of road transport is one of the priority tasks. The functioning of the internal combustion engine, the most important unit, is impossible without the correct operation of the fuel injectors. A modern electromagnetic nozzle is a fairly reliable element of the engine, however, it can quickly fail when using low-quality fuel. Constant monitoring of the technical condition of the injectors with the help of builtin vehicle diagnostics systems will prevent such negative consequences as fuel overspending, the formation of harmful substances in the exhaust gases, deterioration of the traction and speed characteristics of the vehicle.Materials and methods. The research was carried out by the method of physical modelling, a laboratory stand was developed that simulates the operation of the engine fuel system. As an object, the Bosch 0280 158 996 nozzle was selected, which was controlled using an Arduino-based electronic unit. A series of one-factor experiments was carried out, according to the results of which the dependence of the pressure drop rate on the contamination of the nozzle was constructed.Results. The permissible standard of the pressure drop rate during the operation of the electromagnetic nozzle is determined, which allows unambiguously determining its technical condition (serviceable/not serviceable). An algorithm for checking injectors is proposed, as well as a method for its implementation on modern passenger cars.Discussion and conclusion. The obtained dependence qualitatively coincides with the results of studies by other authors. There is a successful experience of implementing such algorithms on modern cars. The implementation of the research results will allow timely detection of faulty (contaminated) electromagnetic injectors and prevent negative effects on both engine parts and the environment.

Predictions of Vortex Flow in a Diesel Multi-Hole Injector Using the RANS Modelling Approach

The occurrence of vortices in the sac volume of automotive multi-hole fuel injectors plays an important role in the development of vortex cavitation, which directly influences the flow structure and emerging sprays that, in turn, influence the engine performance and emissions. In this study, the RANS-based turbulence modelling approach was used to predict the internal flow in a vertical axis-symmetrical multi-hole (6) diesel fuel injector under non-cavitating conditions. The project aimed to predict the aforementioned vortical structures accurately at two different needle lifts in order to form a correct opinion about their occurrence. The accuracy of the simulations was assessed by comparing the predicted mean axial velocity and RMS velocity of LDV measurements, which showed good agreement. The flow field analysis predicted a complex, 3D, vortical flow structure with the presence of different types of vortices in the sac volume and the nozzle hole. Two main types of vortex were detected: the “hole-to-hole” connecting vortex, and double “counter-rotating” vortices emerging from the needle wall and entering the injector hole facing it. Different flow patterns in the rotational direction of the “hole-to-hole” vortices have been observed at the low needle lift (anticlockwise) and full needle lift (clockwise), due to their different flow passages in the sac, causing a much higher momentum inflow at the lower lift with its much narrower flow passage.

A Comparison of Injection, Spray, and Combustion Characteristics for Non-Eroded and Eroded Multi-Hole Fuel Injectors

It is well known that cavitation erosion in fuel injectors can prevent reliable engine performance after only several thousand hours of operation. However, current simulation tools lack the ability to link flow predictions within the fuel injector to both the efficacy of combustion strategies and lifetime of the injector. Multiphase flow simulation predictions were studied and compared between an informed baseline injector geometry and an x-ray scanned eroded injector geometry. Overall, erosion was found to decrease the fuel mass delivery and injection velocities. A two-stage static coupling approach was employed to link the predicted injection conditions from non-eroded and eroded injectors with the external spray simulations under reacting conditions. Combustion modeling in this coupled approach was carried out using the Unsteady Flamelet Progress Variable approach with a detailed chemical mechanism for n-dodecane, comprising of 2,755 species and 11,173 reactions. Erosion in the injectors led to lower rates of spray penetration in comparison to the baseline configurations. Analysis of the reacting spray simulations revealed an insensitivity of ignition to erosion, yet shorter lift off lengths, higher levels of the soot, and lower levels of NOx were predicted in the eroded injector.

Development of a mathematical model of diesel-generator units with a valve-inductor generator

The paper presents a comprehensive mathematical model of a diesel-generator units with a valve-inductor generator. The calculated data obtained using this model allows optimizing the operation of fuel injectors and adjust the injection characteristics. The electromagnetic part of the model allows taking into account the power losses and efficiency of the generator, calculating the phase windings and their connection schemes, methods for setting the voltage or current of any shape that feeds the windings of the valve-inductor generator, as well as the characteristics of the rotor, stator, and winding materials to obtain the most effective operation parameters of the engine in various operating modes as part of the generator unit.

Gradient-Free Optimization in Thermoacoustics: Application to a Low-Order Model

Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the objective function is provided to the algorithms, this approach might reveal unconventional solutions to complex problems that were out of scope of classical solution strategies. In this study, the potential of these optimization methods on thermoacoustic problems is examined. The optimization algorithms are applied to a generic low-order thermoacoustic can-combustor model with several fuel injectors at different locations. We use three optimization algorithms -- the well established Downhill Simplex Method, the recently proposed Explorative Gradient Method, and an evolutionary algorithm -- to find optimal fuel distributions across the fuel lines while maintaining the amount of consumed fuel constant. The objective is to have minimal pulsation amplitudes. We compare the results and efficiency of the gradient-free algorithms. Additionally, we employ model-based linear stability analysis to calculate the growth rates of the dominant thermoacoustic modes. This allows us to highlight general and thermoacoustic-specific features of the optimization methods and results. The findings of this study show the potential of gradient-free optimization methods on combustor design for tackling thermoacoustic problems, and motivate further research in this direction.

Method for testing modern common rail piezoelectric fuel injectors

The paper presents the author's own method for testing piezoelectric common rail fuel injectors, which for many years were considered non-repairable components. This was mainly due to the lack of availability of spare parts and dedicated measuring equipment, enabling full diagnostics under test bench conditions. As a result, their workshop and laboratory servicing was very limited, as effective disassembly concerned basicaly only the plunger and barrel assembly (needle with nozzle) for selected reference models. The situation has now improved to such an extent that an author’s own regeneration procedure has been proposed with the replacement of the most important controls and actuators. The tests were carried out on the example of Siemens VDO Continental PCR 2.3 fuel injectors from one engine, listing the most important stages of this process, including the correction of fuel dosage and returns.

Gradient-Free Optimization in Thermoacoustics: Application to A Low-Order Model

Machine learning and automatized routines for parameter optimization have experienced a surge in development in the past years, mostly caused by the increasing availability of computing capacity. Gradient-free optimization can avoid cumbersome theoretical studies as input parameters are purely adapted based on output data. As no knowledge about the objective function is provided to the algorithms, this approach might reveal unconventional solutions to complex problems that were out of scope of classical solution strategies. In this study, the potential of these optimization methods on thermoacoustic problems is examined. The optimization algorithms are applied to a generic low-order thermoacoustic can-combustor model with several fuel injectors at different locations. We use three optimization algorithms — the well established Downhill Simplex Method, the recently proposed Explorative Gradient Method, and an evolutionary algorithm — to find optimal fuel distributions across the fuel lines while maintaining the amount of consumed fuel constant. The objective is to have minimal pulsation amplitudes. We compare the results and efficiency of the gradient-free algorithms. Additionally, we employ model-based linear stability analysis to calculate the growth rates of the dominant thermoacoustic modes. This allows us to highlight general and thermoacoustic-specific features of the optimization methods and results. The findings of this study show the potential of gradient-free optimization methods on combustor design for tackling thermoacoustic problems, and motivate further research in this direction.

Ranking of Aircraft Fuel-Injectors Regarding Low Frequency Thermoacoustics Based on an Energy Balance Method

Many modern low emission combustion systems suffer from thermoacoustic instabilities, which may lead to customer irritation (noise) or engine damages. The prediction of the frequency response of the flame is oftentimes not straightforward, so that it is common practice to measure the flame response in an experiment. The outcome of the measurement is typically a flame transfer-function (FTF), which can be used in low order acoustic network models to represent the flame. This paper applies an alternative criterion to evaluate the potential of the flame to become instable, the flame-amplification factor (FAF). It is based on an energy balance method and can be directly derived from the measured flame-transfer-matrix (FTM). In order to demonstrate this approach two different kerosene-driven aircraft fuel injectors were measured in the Rolls-Royce SCARLET rig in a single-sector RQL-combustor under realistic operating conditions. Here the multi-microphone method has been applied with acoustic forcing from up- and downstream side to determine the FTM. In contrast to the FTF-approach the full FTM data has been post-processed to derive the FAF. The FAF is then successfully used to rank the fuel injectors regarding their low frequency thermo-acoustic behaviour, because it is proportional to amplitudes of self-excited frequencies in FANN-rig (full annular) configuration.

Numerical Investigation of the Low-Swirl Flow in an Aeronautical Combustor With Angular Air Supply

Civil air traffic is predicted to further grow in the near future. Hence, the development of aeronautical combustors will face major challenges to meet future stringent environmental regulations. In the present study, an innovative gas turbine combustor with angular air supply called Short Helical Combustor (SHC) is investigated. The main feature of this concept is the helical arrangement of the fuel injectors around the turbine shaft. Aiming at the implementation of a lean-burn concept, a low-swirl lifted flame is adopted. This flame is lifted off and not anchored to the injector which opens the potential of low NOx emissions due to a high degree of premixing within the combustor. In this work, isothermal flow characteristics of such a generic SHC combustor are studied by use of RANS predictions with special emphasis on the interaction of adjacent low-swirl flows. For evaluating the influence of injector parameters on the flow field, a parametric study based on single sector simulations is performed. It is shown that the asymmetrically confined swirling jet flow is strongly deflected towards the sidewall of the staggered SHC dome. The deflection of the flow is associated with an asymmetric pressure field in the vicinity of the burner which is generally known as Coandă effect. As a consequence of the deflected flow, the angular momentum flux at combustor outlet is increased. The interaction of the low-swirl jet and the SHC sidewall is investigated with regards to backflow momentum and residence time in the recirculation zone. It is concluded that by modifying the momentum of the air flow through the injector, the amount of recirculating air flowing back along combustor walls is strongly affected. The present work establishes an understanding of the underlying aerodynamics of the SHC concept which is essential for matching the requirements of lean lifted flames.

The use of neural network algorithms for modeling injection doses of modern fuel injectors

The article presents the possibilities of using artificial intelligence methods to model the injection doses of a modern Common Rail (CR) fuel injector. The presented neural network solution belongs to the experimental models known as black boxes in mechatronics. The backpropagation algorithm and its Levenberg-Marquardt expansion were used for the simulation. The analysis showed that there is a good match between the measurements and the computational model. The proposed solution can be used in the processes of diagnosing not only elements of the injection equipment, but also the internal combustion engine. The paper presents the construction and operation of fuel injectors and the important role of precision pairs work.