Support vector machine based emissions modeling using particle swarm optimization for homogeneous charge compression ignition engine

The internal combustion engine faces increasing societal and governmental pressure to improve both efficiency and engine out emissions. Currently, research has moved from traditional combustion methods to new highly efficient combustion strategies such as Homogeneous Charge Compression Ignition (HCCI). However, predicting the exact value of engine out emissions using conventional physics-based or data-driven models is still a challenge for engine researchers due to the complexity the of combustion and emission formation. Research has focused on using Artificial Neural Networks (ANN) for this problem but ANN’s require large training datasets for acceptable accuracy. This work addresses this problem by presenting the development of a simple model for predicting the steady-state emissions of a single cylinder HCCI engine which is created using an metaheuristic optimization based Support Vector Machine (SVM). The selection of input variables to the SVM model is explored using five different feature sets, considering up to seven engine inputs. The best results are achieved with a model combining linear and squared inputs as well as cross correlations and their squares totaling 26 features. In this case the model fit represented by R2 values were between 0.72 and 0.95. The best model fits were achieved for CO and CO2, while HC and NOx models have reduced model performance. Linear and non-linear SVM models were then compared to an ANN model. This comparison showed that SVM based models were more robust to changes in feature selection and better able to avoid local minimums compared to the ANN models leading to a more consistent model prediction when limited training data is available. The proposed machine learning based HCCI emission models and the feature selection approach provide insight into optimizing the model accuracy while minimizing the computational costs.

The research and analysis of Homogeneous Charge Compression Ignition Engine

HCCI represents homogeneous charge compression ignition. It is a cleaner, higher thermal efficiency, and higher fuel efficiency alternative combustion technology. This engine combines the advantages of diesel and gasoline engines so that the compression ratio of diesel engines can be achieved even when gasoline is used as fuel, and there is basically no NOx and soot emissions. However, the HCCI still has some problems such as ignition timing unstable, bad load and speed variation, and cold start capacity. Today, due to the above shortcomings, HCCI is still mainly researched and developed in the laboratory without mass production. The purpose of this paper is discussing the advantage and disadvantage of HCCI technique and analyse the operating principle to provide possible solution that will improve the quality of HCCI engine before the mass production of HCCI.

Research on the Control Mode of Homogeneous Charge Compression Ignition Combustion Working Process and Its Technical Prospect

The homogeneous charge compression ignition (HCCI) engine is considered an advanced technique, a form of internal combustion in which well-mixed fuel and oxidizer (typically air) are compressed to the point of auto-ignition. HCCI engines have higher thermal efficiency and lower emissions than Spark Ignition (SI) and Compression Ignition (CI) engines. The emissions of NOx can be neglected compared to the CI engine. In addition, a wide variety of fuels, combinations of fuels and alternative fuels can be used in this type of internal combustion engine. Moreover, when investigating the heat release rate of a HCCI engine for both single- and two-stage ignition fuels, the results show that for both fuel types, the cycle changes in the ignition and combustion phases increase with the delay of the combustion phase. Also, the cycle change of iso-octane (the single-stage ignition fuel) is higher than that of PRF80 (the two-stage ignition fuel). This paper will first introduce the control mode of the HCCI engine and then review its current status from the perspective of combustion, emissions, and consumption. After presenting the current status, the authors present suggestions about the prospect of further development with respect to the timing of ignition, the expansion of the engine operating range, and the choice of fuel mixture in this new mode of technology.

Investigation of a Combined Refrigeration and Air Conditioning System Based on Two-Phase Ejector Driven by Exhaust Gases of Natural Gas Fueled Homogeneous Charge Compression Ignition Engine

A natural gas-fueled homogeneous charge compression ignition (HCCI) engine is coupled to an exhaust gas operated turbine driven two-phase ejector cycle to generate power and cooling energy, simultaneously. By establishing a thermodynamic model, the simulation of the proposed system and its parametric analyses are conducted. Energetic and exergetic investigations are carried out to study the role of equivalence ratio, engine speed, condenser temperature, refrigeration evaporator temperature, air-conditioning evaporator temperature, and ejector nozzle efficiency on the thermodynamic performance parameters of the combined cycle. The analysis of two-phase ejector cooling cycle using three working fluids including R717, R290, and R600a is conducted. Results reveal that the thermal efficiency of HCCI engine is increased from 47.44% to 49.94%, and for the R600a operated combined cycle it is increased from 60.05% to 63.26% when the equivalence ratio is promoted from 0.3 to 0.6. Distribution of fuel exergy results show that out of 100% exergy input, in case of R717 operated combined cycle, 139.79 kW (38.72%) is the total exergy output, and 164.21 kW (45.49%) and 57 kW (15.79%) are the values for exergy destruction and exergy losses. It is further shown that change in refrigerant minorly influence the percentages of exergy distribution.