A Framework of Control-Oriented Reaction-Based Model for Trajectory-Based HCCI Combustion With Variable Fuels

2017 ◽  
Author(s):  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
High Fidelity ◽  
Compression Ignition ◽  
Combustion Control ◽  
Free Piston ◽  
Hcci Combustion ◽  
Least Squares Optimization ◽  
Pure Compression ◽  
Reduce Emissions ◽  
Combustion Processes ◽  
Engine Cycle

A novel combustion control, i.e. the trajectory-based combustion control, was proposed previously. This control is enabled by free piston engines (FPEs) and utilizes the FPE’s controllable piston trajectory to enhance thermal efficiency, reduce emissions and realize variable fuels applications. On top of that, a control-oriented model was also developed aimed to implement the trajectory-based combustion control in real-time. Specifically, a unique phase separation method was proposed in the model, which separates an engine cycle into four phases (pure compression, ignition, heat release and pure expansion) and employs the minimal reaction mechanism accordingly. In this paper, the framework of the previous control-oriented model is extended to variable fuels, such as methane, n-heptane and bio-diesel. Such an extension is reasonable since the separated four phases are representative in typical combustion processes of all fuels within an engine cycle. Besides, a least-squares optimization is formulated to calibrate the chemical kinetics variables for each fuel. At last, simulation results and the related analysis show that all the derived control-oriented models have high fidelity and much lighter computational burdens to represent the HCCI combustion of each fuel along variable piston trajectories.

Optimization of Trajectory-Based HCCI Combustion

2016 ◽  
Author(s):  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
Chemical Kinetics ◽  
Optimization Methods ◽  
Parameters Optimization ◽  
Combustion Control ◽  
Free Piston ◽  
Sqp Method ◽  
Hcci Combustion ◽  
Optimization Study ◽  
Free Piston Engine ◽  
Kinetics Of

Previously, the authors have proposed a novel combustion control enabled by the free piston engine (FPE), e.g. the piston trajectory-based HCCI combustion control. Extensive simulation results show that, by employing specific piston trajectories, the FPE is able to increase the engine thermal efficiency significantly, and reduces the emissions production simultaneously. However, a systematic approach to designing the optimal piston trajectory, according to variable working conditions and versatile fuel properties, still remains elusive. In this paper, the study of this optimization is presented. First, a control-oriented model, which includes thermodynamics of the in-cylinder gas and chemical kinetics of the utilized fuel, is adapted for the optimization study. The unique phase separation method was also implemented into the presented model to sustain sufficient chemical kinetics information and reduce the computational burden at the same time. Two optimization methods are then proposed in this paper: one is converting the original problem to parameters optimization; the other is transforming it to a constrained nonlinear programming and solving it via the sequential quadratic programming (SQP) method. The corresponding optimization results and detailed discussions are followed, which clearly demonstrate the advantage of the trajectory-based HCCI combustion with regard to FPE output work and NOx emission.

Realizing Trajectory-Based Combustion Control in a Hydraulic Free Piston Engine via a Fast-Response Digital Valve

2018 ◽  
Author(s):  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
Chemical Kinetics ◽  
Thermal Efficiency ◽  
Fast Response ◽  
Combustion Control ◽  
Piston Engine ◽  
Free Piston ◽  
Frictional Loss ◽  
Switching Strategy ◽  
Hcci Combustion ◽  
Free Piston Engine

Previously, the authors have proposed the concept of piston trajectory-based combustion control enabled by a free piston engine (FPE) and shown its advantages on both thermal efficiency and emissions performance. The main idea of this control method is to design and implement an optimal piston trajectory into FPE and optimizes the combustion performance accordingly. To realize the combustion control in practice, it is obvious that the design of the optimal trajectory should consider the dynamic behaviors of the FPE’s actuation systems as well as variable load dynamics and fuels’ chemical kinetics. In this paper, a comprehensive model describing the operation of a hydraulic FPE fueled by diesel under HCCI combustion mode is developed. Such a high fidelity model includes four parts, i.e. the piston dynamics, the hydraulic dynamics, the thermodynamics and the fuel’s chemical kinetics. Extensive simulation results are produced, showing that by varying the switching strategy of a fast-response digital valve, the hydraulic FPE can operate at different working loads in a stable manner. Additionally, analysis has been conducted to quantify the thermal efficiency as well as the frictional loss and throttling loss of the FPE. At last, a feedback control is developed to generate optimal switching strategies for the digital valve aimed to achieve the HCCI combustion phasing control. The resulted switching strategy of the digital valve not only increases the thermal efficiency by 0.76%, but also reduces frictional loss by 9.8%, throttling loss by 6.5% as well as NOx emission by 85.6%, which clearly demonstrates the effectiveness of the trajectory-based combustion control.

scholarly journals A Control-Oriented Model for Trajectory-Based HCCI Combustion Control

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
Computational Time ◽  
Combustion Control ◽  
Free Piston ◽  
Motion Patterns ◽  
Practical Applications ◽  
Hcci Combustion ◽  
Free Piston Engine ◽  
One Step ◽  
Chemical Reaction Mechanisms ◽  
Global Reaction

Previously, the authors have proposed the concept of piston trajectory-based homogeneous charge compression ignition (HCCI) combustion control enabled by a free piston engine (FPE) and shown its benefits on both engine thermal efficiency and emissions by implementing various piston trajectories. In order to realize the HCCI trajectory-based combustion control in practical applications, a control-oriented model with sufficient chemical kinetics information has to be developed. In this paper, such a model is proposed and its performance, in terms of computational speed and model fidelity, is compared to three existing models: a simplified model using a one-step global reaction, a reduced-order model using Jones–Lindstedt mechanism, and a complex physics-based model including detailed chemical reaction mechanisms. A unique phase separation method is proposed to significantly reduce the computational time and guarantee the prediction accuracy simultaneously. In addition, the paper also shows that the high fidelity of the proposed model is sustained at multiple working conditions, including different air-fuel ratios (AFR), various compression ratios (CR), and distinct piston motion patterns between the two end positions. Finally, an example is presented showing how the control-oriented model enables real-time optimization of the HCCI combustion phasing by varying the trajectories. The simulation results show that the combustion phasing can be adjusted quickly as desired, which further demonstrates the effectiveness of the piston trajectory-based combustion control.

Emission spectroscopy based sensor developed for engine testing

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Fabian Feldhaus ◽  
Ingo Schmitz ◽  
Thomas Seeger
Keyword(s):  
Emission Spectroscopy ◽  
Internal Combustion Engines ◽  
Combustion Temperature ◽  
Sensor System ◽  
Combustion Engines ◽  
Compression Ignition ◽  
Compression Ignition Engines ◽  
Reduce Emissions ◽  
Engine Testing ◽  
Combustion Processes

AbstractEmissions of internal combustion engines are linked to air pollution, global warming effects and are potentially harmful. In order to reduce emissions, a better understanding of combustion processes is necessary. Therefore, the combustion temperature is an important factor to know, because it has an impact on the amount of exhaust gases like soot and nitrogen oxides. This work presents a complete spectral resolved emission spectroscopy based sensor system for temperature determining in compression ignition engines. The sensor system is developed for series engines and can be used without any modification of the engine.

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