This paper analyzes the feasibility of applying model predictive control strategies for mit-igation of the auto-ignition phenomenon, which affects the performance of spark-ignition internal combustion engines. The first part of this paper... more
This paper analyzes the feasibility of applying model predictive control strategies for mit-igation of the auto-ignition phenomenon, which affects the performance of spark-ignition internal combustion engines. The first part of this paper shows the implementation and experimental validation of a two-dimensional model, based on thermodynamic equations, to simulate operating conditions in engines fueled with natural gas. Over this validated model, several control strategies are studied in order to evaluate, through simulation analysis, which of these offer the best handling capacity of the auto-ignition phenomenon. In order to achieve this goal, multivariate control strategies are implemented for a simultaneous manipulation of the fuel/air ratio, the crank angle at ignition, and the inlet pressure. The controlled variable in this research is the temperature at the ignition point. This temperature is obtained through an estimation based on pressure in the combustion chamber at that point, which is located toward the end zone of the compression stroke. If the ignition temperature of the fuel–air mixture is reached during the compression process , then auto-ignition takes place. Proposed control strategies consist of maintaining the temperature in the ignition point below the fuel–air mixture auto-ignition temperature. The results show that auto-ignition is difficult to avoid using a single input–single output (SISO) strategy. However, a multiple input–single output (MISO) approach avoids the influence of the phenomenon without a significant impact over the engine's performance. Among the developed strategies, an approach based on model predictive control and feedforward control strategy shows the best performance, measured through the integral absolute error (IAE) index. These results open the possibility of new ways for improving the control capacity of auto-ignition phenomenon in engines compared to currently available feedback control systems.
Control strategies for auto-ignition control in turbocharged internal combustion engines operating with gaseous fuels are presented. Ambient temperature and ambient pressure are considered as the disturbing variables. A thermodynamic... more
Control strategies for auto-ignition control in turbocharged internal combustion engines operating with gaseous fuels are presented. Ambient temperature and ambient pressure are considered as the disturbing variables. A thermodynamic model for predicting temperature at the ignition point is developed, adjusted and validated with a large experimental data-set from high power turbocharged engines. Based on this model, the performance of feedback and feedforward auto-ignition control strategies is explored. A robustness and fragility analysis for the Feedback control strategies is presented. The feedforward control strategy showed the best performance however its implementation entails adding a sensor and new control logic. The proposed control strategies and the proposed thermodynamic model are useful tools for increasing the range of application of gaseous fuels with low methane number while ensuring a safe running in internal combustion engines.
N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the autoignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the... more
N umerous studies have attributed pre-ignition events in turbocharged spark ignited engines to the autoignition of lubricant oil-fuel mixture droplets. These droplets result from the interaction of the directly injected fuel spray on the lubricant oil film on the cylinder walls, causing fuel splashing to pull oil off the walls, forming droplets. The dilution of the oil by the fuel also changes lubricant oil droplet properties. Therefore, it is important to understand lubricating oils, with and without fuel dilution, as a possible ignition source in pre-ignition and super knock events. In this work, a constant volume (4 L) combustion chamber (CVCC) that allows the introduction of a single droplet of lubricating oil has been built. It is capable of operation at elevated pressures and temperatures. To simulate the droplet-induced pre-ignition event, a droplet injection system was incorporated into the vessel. The oil droplet was suspended on the junction of a thermocouple where the instantaneous internal droplet temperature was measured throughout the oil droplet lifetime. The experiments were carried out in an air atmosphere heated to 300 °C. The ambient pressure was varied from 2-15 bar. In the present work, the effect of pressure on droplet ignition of conventional engine oil (SAE 15 W-40), its surrogate hexadecane (C 16 H 34), and hexadecane mixed with lubricant oil additives has been investigated to understand the fundamental physics of droplet-induced ignition. The objective of this study is to determine the probability that an oil droplet will ignite at temperatures and pressures relevant to modern turbocharged GDI engines.
Extracting the knocks characteristics is the key of ignition control in auto-ignition compression engines, especially those severely suffered from abnormal consumption in the engine chamber. Most of the advanced detecting methods of... more
Extracting the knocks characteristics is the key of ignition control in auto-ignition compression engines, especially those severely suffered from abnormal consumption in the engine chamber. Most of the advanced detecting methods of knocking are generally related to the two main variables, including engine cylinder pressure signals and the engine cylinder block vibration signals, commonly measured using piezoelectric accelerometer sensors. Being familiar with different approaches capable of determining the engine knocking occurrence probability as well as providing suitable methods for knock intensity evaluation is significantly helpful to propose a comprehensive predicting model for measuring the level of oscillation pressure waves frequencies originated by the knocks. Following by predicting the knock intensity and extracting the knock feature, optimizing the engine operation in terms of fuel consumption, thermal efficiencies, and lifetime duration would be possible. For this aim, the current paper is addressed with overviewing upon the researches performed in the regard of developing high accurate models and optimized knock detection approaches.
