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.

Multi-Dimensional Analysis of NOx and Soot Formation in a Diesel-Fueled Hydraulic Free Piston Engine

2013 ◽  
Vol 690-693 ◽  
pp. 2800-2804
Author(s):  
Ying Xiao Yu ◽  
Zhao Cheng Yuan ◽  
Jia Yi Ma ◽  
Shi Yu Li
Keyword(s):  
Mass Fraction ◽  
Soot Formation ◽  
Combustion Process ◽  
Injection Timing ◽  
Swirl Ratio ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Minor Influence ◽  
A Minor

This paper is aimed at simulating and analyzing emission NOxand Soot formation in the hydraulic free piston engine (HFPE) designed and constructed by Jilin University. The combustion process of HFPE is simulated by using the commercial CFD software AVL FIRE, and the flow field and factors that influence NOxand Soot formation were analyzed. The simulated results indicate that NO is mainly distributed in the burned zone, whereas the distribution of Soot acts in accord with high unburnt equivalence ratio and high temperature burned zone. Injection timing increases, the amount of the formation of NO is reduced, whereas the mass fraction of Soot rises to a peak and descends. And small swirl ratio exerts a minor influence on emission mass fraction of HFPE.

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.

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.

Energy and exergy analysis of hydraulic free-piston engines

2018 ◽  
Vol 233 (12) ◽  
pp. 3074-3087 ◽  
Author(s):  
Lei Wang ◽  
Zhenfeng Zhao ◽  
Chuncun Yu ◽  
Fujun Zhang ◽  
Changlu Zhao
Keyword(s):  
Thermal Efficiency ◽  
Waste Heat ◽  
Energy Utilization ◽  
Injection Timing ◽  
Characteristic Parameters ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

A hydraulic free-piston engine is an unconventional reciprocating piston internal combustion engine in which the piston assembly motion is determined by in-cylinder gas pressure and load force. Fuel combustion energy is directly converted into hydraulic energy. These affect the work process of cylinder and efficiency of energy conversion. In order to study the energy utilization efficiency and to explore the recovery potential of waste heat energy of hydraulic free-piston engine, in this paper, the energy distribution and waste heat energy characteristics of hydraulic free-piston engine have been studied by combining energy and exergy analysis. The thermal efficiency was analyzed by the first law of thermodynamics, and exergy balance was analyzed by the second law. The effect of the characteristic parameters on the thermal and exergy efficiency was studied through the simulation analysis comparing the energy utilization of hydraulic free-piston engine and conventional engines. The results show that control of the injection timing parameter is effective for optimizing efficiency because the cycle characteristic parameters can be controlled by changing the injection timing. The experimental results show that the thermal efficiency is 40.8% and the exergy efficiency is 46.3%. The simulation result show that the thermal efficiency of hydraulic free-piston engine is 38.0% and the conventional diesel engine is 33.0%.

scholarly journals Advanced combustion free-piston engines: A comprehensive review

2018 ◽  
Vol 21 (7) ◽  
pp. 1205-1230 ◽  
Author(s):  
Yingcong Zhou ◽  
Aimilios Sofianopoulos ◽  
Benjamin Lawler ◽  
Sotirios Mamalis
Keyword(s):  
Low Temperature ◽  
Low Temperature Combustion ◽  
Piston Engine ◽  
Free Piston ◽  
Widespread Application ◽  
Comprehensive Review ◽  
Advanced Combustion ◽  
Free Piston Engine ◽  
Linear Alternator ◽  
Temperature Combustion

A reciprocating engine without a crank-slider mechanism is called a free-piston engine. If the piston is directly connected to a linear alternator, it is called a free-piston linear alternator. Free-piston engines and free-piston linear alternators have the potential to offer solutions for future hybrid electric vehicles and stationary power generation, by enabling direct conversion of mechanical energy to electricity. They benefit from reduced friction losses compared to conventional engines and can have variable compression ratio, which enables combustion control and optimization. Their widespread application has been limited by the necessity for high-speed control strategies. However, their operating characteristics can provide high efficiency, especially when used with low temperature combustion strategies. Low temperature combustion combines the high thermal efficiency of diesel engines, with the low soot emissions of spark-ignition engines, and low NO x emissions because of low burned gas temperatures. This article provides a comprehensive review of free-piston engine technology, with a focus on advanced combustion processes and their potential for use in future powertrain systems.

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.

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