Investigation of fuel injection rate identification algorithm based on rail pressure fluctuation characteristics induced by injection

As an important part of the common-rail (CR) fuel system for diesel engines, the injector circulation capacity and the fuel injection mass flow rate vary with carbon deposition and wear, affecting the engine output performance. This study proposes a method to identify the fuel injection rate online, based on the rail pressure fluctuation characteristics induced by fuel injection. The control algorithm uses the signal from the existing rail pressure sensor; the diesel engine does not require modification or additional sensors. A quasi-dimensional model of the CR fuel system was built to analyse the rail pressure wave fluctuation characteristics, and a parameter K was defined as the pressure drop rate. Based on K, a control algorithm was proposed. A high-pressure fuel pump test rig was built to test the fuel injection performance under different operating conditions, and the experimental data were processed by wavelet transform. From the test data, the K of the CR system was analysed using the feedback of the rail pressure sensor. The experimental results show that the value of K increases with an increase in the initial pressure and injection pulse, and is independent of the injection mode. The algorithm is feasible, and works more accurately with a longer injection pulse and a lower pump speed. This method uses the existing rail pressure sensor, does not incur extra cost and has great potential for improving the injection accuracy.

Control Techniques for the Cascaded and Cross-switched Multilevel Inverter - A Comparison

Nowadays, the multilevel inverter has gained huge attention and has become more popularized in high voltage and high-power applications with low harmonics. As the number of output voltage increases, the harmonic content of the output voltage waveform decreases. In this paper, a comparison of cascaded H-bridge and cross-switched multilevel inverters for 7, 9, 15, 21 levels will be carried out. The different control techniques that will be used for carrying out comparisons are space vector pulse width modulation (SPVPWM), sinusoidal pulse width modulation (SPWM), and third harmonic injection pulse width modulation (THI-PWM) respectively. Here, the seven-level inverter is discussed mainly and can be extended to any number of levels.

Modeling of diesel spray tip penetration during start-of-injection transients

Multiple-injection strategy that has been applied widely in diesel engines usually features a short duration for each injection pulse. As a result, the shortened injection makes the needle opening and closing transients increasingly important for spray in an injection event. Owing to the needle movement, the spray development during the transient processes is complex and quite different from the spray at the quasi-steady state. However, so far modeling of the spray development during the transient processes is far from adequate. Particularly, a theoretical zero-dimensional (0-D) spray tip penetration model considering the needle opening and sac pressurization processes as well as ambient and injection conditions during the start-of-injection (SOI) transients is still absent. In this paper, considering the sac pressurization processes, the 0-D model of spray tip penetration during the SOI transients is derived. Then, the model is validated against the experimental spray data using a long-distance microscope together with an ultrahigh speed CMOS camera. The model and experimental results show that the spray tip penetration shows a t3/2 dependence at the initial stage of injection rather than the t dependence suggested by Hiroyasu’s model. Later, the spray tip penetration shows a t3/4 dependence owing to the spray breakup, and a t1/2 dependence with the completion of sac pressurization. The models and analysis are believed to provide new insights into the transient spray behaviors and valuable reference for engineers and researchers who are considering the model-based development of next-generation diesel engines.

Power Management for Plug-in Hybrid Electric Vehicle with Automated Mechanical Transmission using Multiple Dimensional Scaling Method

Background: The study of kerosene fuel for gasoline engines is of great significance to the supply, management, storage and transportation of military fuel, as well as its safety. Small aviation two-stroke kerosene engine fuel injection controller is the key technology of kerosene engines. It is very important to improve the performance of kerosene engine by controlling the air-fuel ratio accurately. Objective: The initial injection pulse spectrum was firstly obtained by numerical calculation in the absence of kerosene injection pulse spectrum, and then the injection controller was designed based on the initial injection pulse spectrum. Methodology: Firstly, a numerical model of the whole engine was established by using BOOST software. The air mass flow data of the inlet was obtained through numerical calculation. The amount of initial engine fuel injection was calculated according to the requirements of air-fuel ratios in each working condition, from which an initial injection pulse spectrum was obtained. Then, based on Free scale 16-bit embedded micro-controller MC9S12DP512, a kerosene engine fuel injection controller was developed, together with the circuit was also designed. According to the initial fuel injection pulse spectrum, a two-dimensional interpolation algorithm was developed by using assembly language and C language mixed programming, and the anti-electromagnetic interference ability of the controller was further enhanced. Finally, the accuracy of the initial injection pulse spectrum and the performance and reliability of the injection controller of the kerosene engine were verified by the kerosene engine bench test. Conclusion: The experimental results show that the numerical model was accurate, and the development time of the injection controller was shortened by using the numerical model to calculate the initial injection pulse spectra. The developed controller was stable and reliable, which can meet the control requirement.

Third harmonic injection pulse-width modulation technique for a five-phase voltage source inverter

<span>Nowadays application of advanced power electronic technology enables producing an AC supply with a phase number higher than three-phase. Five-phase voltage source inverters (5ph-VSI) have been used in advanced power electronic drives to improve the reliability of the drive system and to boost the power capability of the converter as well as to their other inherent merits. This paper shows the mathematical analysis and simulation of the third harmonic injection pulse width modulation (THI-PWM) 5ph-VSI connected with inductive load in three scenarios i.e. star, Pentagon and pentacle. The presented THI-PWM technique for 5ph-VSI aims to increase the inverter fundamental voltage and hence to maximize the utilization of the DC bus without causing over-modulation. The simulation results are compared with typical sinusoidal pulse width modulation (SPWM) and the 10-step mode operation. The proposed scheme may be considered as a compromise case between the two reference cases; as low harmonic components compared with 10-step mode operation and a high utilization factor compared with SPWM.</span>

A phenomenological rate of injection model for predicting fuel injection with application to mixture formation in light-duty diesel engines

Fuel injection rate laws are one of the most important pieces of information needed when modeling engine combustion with computational fluid dynamics. In this study, a simple phenomenological model of a common-rail injector was developed and calibrated for the Bosch CRI2.2 platform. The model requires three tunable parameter fits, making it relatively easy to calibrate and suitable for injector modeling when high-fidelity information about the internal injector’s geometry and electrical circuit details are not available. Each injection pulse is modeled as a sequence of up to four stages: an injection needle mechanical opening transient, a full-lift viscous flow inertial transient, a Bernoulli steady-state stage, and a needle descent transient. Parameters for each stage are obtained as polynomial fits from measured injection rate properties. The model enforces total injected mass, and the intermediate stages are only introduced if the injection pulse duration is long enough. Experimental rates of injection from two separate campaigns on the same injector were used to calibrate the model. The model was first validated against measured injection rate laws featuring pilot injections, short partially premixed combustion pulses, and conventional diesel combustion injection strategies. Then, it was employed as an input to engine computational fluid dynamics simulations, which were run to simulate experiments of mixture formation in an optically accessible light-duty diesel engine. It was found that, though simple, this model is capable of predicting both pilot and main injection pulse mass flow rates well: the simulations yielded accurate predictions of in-cylinder equivalence ratio distributions from injection strategies for both partially premixed combustion and pilot injections. Also, once calibrated, the model produced appropriate results for a wide range of injected mass and rail pressure values. Finally, it was observed that usage of such a relatively simple model can be a good choice when high-fidelity injection rate input and highly detailed information of the injector’s geometry and operation are not available, particularly as noticeable discrepancies can be present also among different experimental campaigns on similar hardware.