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.

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.

Modeling and Experimental Characterization of a Permanent Magnet Linear Alternator for Free-Piston Engine Applications

2009 ◽  
Author(s):  
Hans T. Aichlmayr ◽  
Peter Van Blarigan
Keyword(s):  
Mathematical Model ◽  
Permanent Magnet ◽  
Experimental Validation ◽  
Experimental Characterization ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Linear Alternator ◽  
The Mathematical Model

Sandia National Laboratories is developing a prototype 30kW free-piston internal-combustion-based linear generator for vehicular applications. This paper describes the development and experimental validation of a mathematical model for the permanent magnet linear alternator that will be used by the prototype. A magnetic-flux versus mover-position function is used to correlate individual coil fluxes to the motion of the mover. This function is derived from a finite element electromagnetic simulation of the linear alternator. The mathematical model of the alternator is compared to experiments with prototype hardware driving 0.5–2kW loads; excellent correspondence to measured voltage and current waveforms is found.

Operation of a turbine-compound free-piston linear alternator

2021 ◽  
pp. 146808742110159
Author(s):  
Chang-Ping Lee ◽  
Claus Borgnakke ◽  
Russell Durrett
Keyword(s):  
Injection Timing ◽  
Actual Behavior ◽  
Piston Engine ◽  
Combustion Chambers ◽  
Free Piston ◽  
Free Piston Engine ◽  
Linear Alternator ◽  
Mechanical Models ◽  
Control Volumes ◽  
Engine Map

A free-piston linear-alternator combined with combustion chambers has been examined in many studies. However, only simplified thermodynamic and mechanical models were developed to mimic the actual behavior of the free-piston engine. The purpose of this study is to establish a fully dynamic model that can calculate the energy transformation under the operation of the free-piston engine. The Matlab/Simulink® model uses non-constant-volume combustion event, the piston transient dynamics, flow, heat losses, and thermodynamics as bridges to connect control volumes. The model successfully captured the behavior and measurements of a GS-34 free-piston engine, based on a thermodynamic calculation calibrated with experimental data. The resulting model is used for a series of parametric studies to understand the very complex system behavior, including low load operation. Operation parameters (injection timing and bounce chamber mass) are optimized to generate the engine map for different alternator sizes. At the end, the advantages of the opposed free-piston engine with a linear alternator are presented through the energy analysis.

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

Study on the Motion Characteristics of a Hydraulic Free-Piston Engine

2014 ◽  
Vol 889-890 ◽  
pp. 390-393
Author(s):  
Shi Yu Li ◽  
Zhao Cheng Yuan ◽  
Jia Yi Ma
Keyword(s):  
Fuel Injection ◽  
Fuel Efficiency ◽  
Injection Timing ◽  
Piston Engine ◽  
Free Piston ◽  
Fuel Injection Timing ◽  
Free Piston Engine ◽  
Center Position ◽  
Working Frequency ◽  
Motion Characteristics

Hydraulic free-piston engines have potential advantages of cost and fuel efficiency. Due to no crankshaft system, it is difficult and important to control the piston motion and working frequency precisely. This paper studies on the motion characteristics for the hydraulic free-piston engine effects of operation parameters, and results are presented. The TDC (Top Dead Center) position and CR (Compression Ration) are great influenced by starting pressure and fuel injection timing, and working frequency is mainly influenced by piston mass, starting pressure and fuel quantity.

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