Modeling of a Two-Stroke Free-Piston Engine With HCCI Combustion

2010 ◽  
Author(s):  
Ke Li ◽  
Wilson Santiago ◽  
Zongxuan Sun
Keyword(s):  
Internal Combustion Engines ◽  
High Energy ◽  
High Energy Density ◽  
Hydraulic Pump ◽  
Piston Engine ◽  
Free Piston ◽  
Engine Operation ◽  
Hcci Combustion ◽  
Free Piston Engine ◽  
Linear Alternator

This paper describes the modeling of a two-stroke dual chamber free piston engine (FPE) running homogeneous charge compression ignition (HCCI) combustion with an embedded linear alternator and a hydraulic pump. Variable compression ratio of FPE enables multi-fuel operation. Furthermore, the addition of an electric generator and hydraulic pump ensure the engine to have both high energy density and power density. These three concepts combined, will make for a highly efficient and flexible approach for engine operation. However, the characteristic of FPE also brings challenges in engine control. We propose a control oriented model that provides detailed gas exchange processes between intake/exhaust and cylinder volume, and the dynamic interactions between combustion, the linear alternator and the hydraulic pump. Influences of fuel and valve timing on engine performance are studied. Simulated engine dynamics are observed to have significant differences from conventional internal combustion engines.

A Comparative Study of Permanent Magnet Linear Alternator and Hydraulic Free-Piston Engines

2011 ◽  
Author(s):  
Ali Sadighi ◽  
Ke Li ◽  
Zongxuan Sun
Keyword(s):  
Comparative Study ◽  
Permanent Magnet ◽  
Fuel Efficiency ◽  
Hydraulic Pump ◽  
Combustion Chambers ◽  
Free Piston ◽  
Hcci Combustion ◽  
Free Piston Engine ◽  
Linear Alternator ◽  
Homogenous Charge Compression Ignition

This paper presents a comparative study of two possible power-generating units for the free-piston engine (FPE): Permanent-magnet linear alternator (PMLA) and linear hydraulic pump. The FPE discussed in this paper is a linear, opposed-piston, opposed-cylinder (OPOC) engine that operates with a homogenous charge compression ignition (HCCI) combustion. Lack of crankshaft in the FPE allows lower friction loss, variable compression ratio, and higher modularity compared to a conventional engine. Also the OPOC configuration enables high-frequency operation of the FPE, which results in high power density. The FPE is also well suited for HCCI operation, which offers improved fuel efficiency and emissions. The chemical power released in the combustion chambers can be transformed to fluid or electric power. This could be done via a hydraulic pump or a linear alternator. In this paper these two systems are studied and compared as the power-generating device for the FPE.

CFD-Based Optimization of a Diesel-fueled Free Piston Engine Prototype for Conventional and HCCI Combustion

2008 ◽  
Vol 1 (1) ◽  
pp. 1118-1143 ◽  
Author(s):  
Miriam Bergman ◽  
Jakob Fredriksson ◽  
Valeri I. Golovitchev
Keyword(s):  
Piston Engine ◽  
Free Piston ◽  
Hcci Combustion ◽  
Free Piston Engine

Numerical analysis of two-stroke free piston engine operating on HCCI combustion

2011 ◽  
Vol 88 (11) ◽  
pp. 3712-3725 ◽  
Author(s):  
Shuaiqing Xu ◽  
Yang Wang ◽  
Tao Zhu ◽  
Tao Xu ◽  
Chengjun Tao
Keyword(s):  
Numerical Analysis ◽  
Piston Engine ◽  
Free Piston ◽  
Hcci Combustion ◽  
Free Piston Engine

A Virtual-Cam Control Methodology for Free-Piston Engines

2011 ◽  
Author(s):  
Chao Yong ◽  
Eric J. Barth
Keyword(s):  
Internal Combustion Engines ◽  
Control Method ◽  
Piston Engine ◽  
Piston Motion ◽  
Stroke Length ◽  
Free Piston ◽  
Physical Context ◽  
Spark Timing ◽  
Free Piston Engine ◽  
Timing Belt

In conventional internal combustion engines, valves are opened and closed using a cam surface. The cam is kinematically related to the piston positions through the crankshaft and timing belt. In contrast, there is no crankshaft or kinematic cam surface in a free-piston engine to physically realize this mechanism. As a consequence, a free-piston engine has variable stroke lengths, which presents a challenge for active piston motion and precise stroke length control. This paper presents a virtual-cam based approach to relate free-piston motion to actuated engine valve control within a clear and familiar intuitive physical context. The primary functionality of the virtual cam control framework is to create a variable index, which is adjustable from cycle to cycle, for the exhaust/injection valves and spark timing similar to the function of physical cams in conventional engines. Since the cam is virtually created, it can be dynamically rebuilt to comply with cycle-to-cycle variations such as amount of the air/fuel supply, engine load and stroke length. This index rebuilding process is based on a cycle-to-cycle adaptive control method that uses the knowledge obtained from previous cycles to adjust the cam parameters. Preliminary experimental results are presented for a novel liquid-piston free-piston engine intended as a compact and efficient energy source for untethered power dense pneumatic systems such as untethered robots.

scholarly journals Coordination of forces of mechanical and electric subsystems of power plant with free piston engine and electric generator of reciprocating type

2019 ◽  
Vol 64 (3) ◽  
pp. 304-320 ◽  
Author(s):  
A. B. Menzhinski
Keyword(s):  
Power Plant ◽  
Specific Gravity ◽  
High Energy ◽  
Piston Engine ◽  
Free Piston ◽  
Operating Cycle ◽  
Electric Generator ◽  
Free Piston Engine ◽  
Work Cycle ◽  
Electromechanical Energy

Autonomous power supply system of modern mobile special-purpose equipment requires the development of electromechanical energy converters with high energy and minimum weight- and size indicators. In industrialized countries, the system “free piston engine – reciprocating electric generator of transverse type” is considered as a promising power plant. The main feature of this kind of power plant is the lack of crank mechanism in the engine design. This allows: increasing the efficiency of the engine up to 50–60 % and overall power by 2.5–3 times while reducing the specific gravity and metal consumption compared to traditional engines; reducing the specific fuel consumption of the engine up to 30 %; increasing the resource to overhaul by 30–50 thousand hours; implementing a modular structure. The main drawbacks of this kind of power plant are high probability of failure when passing the ignition of the working mixture and instability of work with significant load fluctuations. The noted drawbacks are due to the inconsistency of the forces of the electrical and mechanical subsystems of the power plant throughout the operating cycle. The solution for the problem of matching the forces of the electrical and mechanical subsystems of the power plant in the extreme positions of the piston group of the free piston engine is of particular complexity. In this regard, a method for solving the problem of matching the forces of the mechanical and electrical subsystems of the power plant with a free-piston engine throughout the operating cycle was developed, characterized by the use of an electromechanical reciprocating energy converter with transverse- and longitudinal nonlinear changes in the magnetic flux in the electrical subsystem. Coordination of the forces of mechanical and electrical subsystems of the power plant on the entire operating cycle makes it possible to fulfill the conditions of continuous electromechanical energy conversion at all work cycle and to reduce the specific gravity of the electrical subsystems of the plant while improving efficiency.

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