scholarly journals Impact of Combustion Variance on Sustainability of Free-Piston Linear Generator during Steady-State Generation

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4081
Author(s):  
Ahsan Bashir ◽  
Saiful A. Zulkifli ◽  
Abd Rashid Abd Aziz ◽  
Ezrann ZZ Abidin
Keyword(s):  
Steady State ◽  
Combustion Engine ◽  
Fundamental Problem ◽  
Control Measure ◽  
Weight Ratio ◽  
Attractive Alternative ◽  
Free Piston ◽  
Linear Generator ◽  
Linear Engine ◽  
The Impact

A free-piston linear generator (FPLG) has a number of advantages compared to a traditional crank-slider internal combustion engine, including better thermal and mechanical efficiencies, different fuel compatibility, and a higher power-to-weight ratio. For electric vehicle propulsion and generation of portable power, an FPLG is a very attractive alternative source of energy. This paper presents the development of an FPLG simulation model using MATLAB-Simulink and investigates the impact of combustion variance on its operation. Results provided insight into various characteristics of system behavior through variation of structural dimension and operational parameters. In steady-state operation with fixed electrical load and fixed ignition for combustion, it was found that consecutively low combustion pressures can easily lead to engine stoppage, pointing to the significance of control for continuous operation. Due to the absence of the moment of inertia and flywheel character of the rotating engine, a linear engine-generator is subject to ceased operation even after two consecutively low combustions under 10% variance. This will not be a fundamental problem in an ordinary crank-slider engine-generator, but in a linear engine-generator, control measure will be necessary to ensure sustained operation.

The Effect of Spring System Design on Scavenging of Two Stroke Single Cylinder Spark Ignition Free Piston Linear Engine

2017 ◽  
Vol 862 ◽  
pp. 326-331
Author(s):  
Aguk Zuhdi Muhammad Fathallah ◽  
Ahmad Rizki Firdaus
Keyword(s):  
Fluid Flow ◽  
Combustion Chamber ◽  
Combustion Engine ◽  
Spark Ignition ◽  
Average Pressure ◽  
Free Piston ◽  
Single Cylinder ◽  
Average Value ◽  
Spring System ◽  
Linear Engine

To increasing the efficiency research a single cylinder linear engine with spring system has been done. Issues raised in the study was the analysis of air flow into the combustion chamber in a single cylinder linear engine, with a spring system for its return cycle. Solidworks has been used to design and simulation as well. This study compared the fluid flow in the combustion chamber between the conventional engine and linear combustion engine. The parameters used are the engine speeds 1000 rpm, 4000 rpm and 4500 rpm. The speeds is chosen because has been predicted that the inlet port on the linear engine can not work properly. Results of analysis that has been done appears average pressure of conventional has a higher value than the linear combustion engine. The same thing happened in velocity, in the average value of the conventional engine is higher than the linear combustion engine.

Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices

2014 ◽  
Author(s):  
Matthew C. Robinson ◽  
Nigel N. Clark
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Combustion Engine ◽  
System Stability ◽  
Otto Cycle ◽  
Restoring Force ◽  
Free Piston ◽  
Mass System ◽  
Heat Addition ◽  
Linear Engine

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress towards new ones. The free piston linear engine (FPLE) is a device with the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Meanwhile, naturally variable compression ratio provides a unique platform to employ advanced combustion regimes. Possibly high variations in stroke length also result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability. Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form non-dimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modelling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to top dead center is allowed causing the compression ratio to decrease towards stable, Otto operation. And, a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.

Modeling and Simulation of a Moving-Coil Linear Generator

2011 ◽  
Vol 110-116 ◽  
pp. 2458-2463
Author(s):  
Imran Fazal ◽  
K.S. Rama Rao ◽  
Mohd Noh Karsiti
Keyword(s):  
Finite Element Method ◽  
Permanent Magnet ◽  
Electromotive Force ◽  
Flux Distribution ◽  
Impact Force ◽  
Combustion Engine ◽  
Control Strategies ◽  
Prime Mover ◽  
Free Piston ◽  
Linear Generator

This paper presents the analysis on flux and electromotive force (EMF) developed by moving coil and moving iron linear generators using finite element method (FEM). A 6 pole moving coil and 6/4 moving iron linear generator are used to analyze and compare the flux distribution in the air gap. These generators will be used for free piston linear engine. A moving permanent-magnet linear generator has drawbacks of thermal and impact force demagnetization, in addition to requiring complex control strategies. To overcome these limitations, one of the solutions is to place magnets on the stator instead on the translator. Based on the analysis it is proposed to replace the moving permanent-magnet by a moving-coil for a linear generator whose prime mover is a free-piston linear combustion engine.

Fundamental Explorations of Spring-Varied, Free Piston Linear Engine Devices

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Matthew C. Robinson ◽  
Nigel N. Clark
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Combustion Engine ◽  
System Stability ◽  
Otto Cycle ◽  
Restoring Force ◽  
Free Piston ◽  
Mass System ◽  
Heat Addition ◽  
Linear Engine

The conventional crank-based internal combustion engine faces many challenges to remain a viable option for electric power generation. Limitations in mechanical, thermal, and combustion efficiencies must be overcome by innovations in existing technologies and progress toward new ones. The free piston linear engine (FPLE) has the potential to meet these challenges. Friction losses are reduced by avoiding rotational motion and linkages. Instead, electrical power is generated by the oscillation of the translator through a stator. Naturally, variable compression ratio provides a unique platform to employ advanced combustion regimes. However, possibly high variations in stroke length result in unknown dead center piston positions and greater difficulties in compression control as compared to conventional engines. Without control, adverse occurrences such as misfire, stall, over-fueling, and rapid load changes pose greater complications for stable system operation. Based on previous research, it is believed that incorporating springs will advance former designs by both increasing system frequency and providing a restoring force to improve cycle-to-cycle stability. Despite growing interest in the FPLE, current literature does not address the use of springs within a dual, opposed piston design. This investigation is an extension of recent efforts in the fundamental analysis of such a device. Previous work by the authors combined the dynamics of a damped, spring mass system with in-cylinder thermodynamic expressions to produce a closed-form nondimensional model. Simulations of this model were used to describe ideal Otto cycle as the equilibrium operating point. The present work demonstrates more realistic modeling of the device in three distinct areas. In the previous model, the work term was a constant coefficient over the length of the stroke, instantaneous heat addition (representing combustion) was only seen at top dead center (TDC) positions, and the use of the Otto cycle included no mechanism for heat transfer except at dead center positions. Instead, a position based sinusoid is employed for the work coefficient causing changes to the velocity and acceleration profiles. Instantaneous heat addition prior to TDC is allowed causing the compression ratio to decrease toward stable, Otto operation, and a simple heat transfer scheme is used to permit cylinder gas heat exchange throughout the stroke resulting in deviation from Otto operation. Regardless, simulations show that natural system stability arises under the right conditions. Highest efficiencies are achieved at a high compression ratio with minimal heat transfer and near-TDC combustion.

Review of recent advances of free-piston internal combustion engine linear generator

2020 ◽  
Vol 269 ◽  
pp. 115084 ◽  
Author(s):  
Chendong Guo ◽  
Zhengxing Zuo ◽  
Huihua Feng ◽  
Boru Jia ◽  
Tony Roskilly
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Internal Combustion ◽  
Free Piston ◽  
Linear Generator ◽  
Recent Advances

Design of an External Combustion Engine and its Application in a Free Piston Compressor

2007 ◽  
Vol 3 ◽  
Author(s):  
Jonathan Hogan Webb
Keyword(s):  
Combustion Engine ◽  
Piston Compressor ◽  
Dead Volume ◽  
Transfer Energy ◽  
Free Piston ◽  
Combustion Gases ◽  
Intermediate Chamber ◽  
Fuel Mixtures ◽  
External Combustion ◽  
External Combustion Engine

The design of a free piston compressor and an analysis on integrating an external combustion engine into the compressor design are presented in this article. A free piston compressor is a device which converts chemical energy to work on a volume of air through the kinetic energy of an inertia driven piston, which is not rigidly attached to a ground. An external combustion engine serves as in intermediate chamber which transfers combustion gases to a device to perform some work. The following discusses the design and experiments on an external combustion engine, with a focus on eliminating an injection holding force on a free piston compressor’s elastomeric membranes. The efficiency of the external combustion engine to transfer energy without significant losses due to heat, dead volume, air/fuel mixtures, and actuated valve speed are also presented.

Characterizing the effectiveness of COVID-19 mitigation measures: A data-centric approach (Preprint)

2020 ◽  
Author(s):  
Lukman Olagoke ◽  
Ahmet E. Topcu
Keyword(s):  
Control Measure ◽  
Control Measures ◽  
World Health ◽  
Mitigation Measures ◽  
Effective Control ◽  
The World ◽  
Decision Making Processes ◽  
And Performance ◽  
Health Organization ◽  
The Impact

BACKGROUND COVID-19 represents a serious threat to both national health and economic systems. To curb this pandemic, the World Health Organization (WHO) issued a series of COVID-19 public safety guidelines. Different countries around the world initiated different measures in line with the WHO guidelines to mitigate and investigate the spread of COVID-19 in their territories. OBJECTIVE The aim of this paper is to quantitatively evaluate the effectiveness of these control measures using a data-centric approach. METHODS We begin with a simple text analysis of coronavirus-related articles and show that reports on similar outbreaks in the past strongly proposed similar control measures. This reaffirms the fact that these control measures are in order. Subsequently, we propose a simple performance statistic that quantifies general performance and performance under the different measures that were initiated. A density based clustering of based on performance statistic was carried out to group countries based on performance. RESULTS The performance statistic helps evaluate quantitatively the impact of COVID-19 control measures. Countries tend show variability in performance under different control measures. The performance statistic has negative correlation with cases of death which is a useful characteristics for COVID-19 control measure performance analysis. A web-based time-line visualization that enables comparison of performances and cases across continents and subregions is presented. CONCLUSIONS The performance metric is relevant for the analysis of the impact of COVID-19 control measures. This can help caregivers and policymakers identify effective control measures and reduce cases of death due to COVID-19. The interactive web visualizer provides easily digested and quick feedback to augment decision-making processes in the COVID-19 response measures evaluation. CLINICALTRIAL Not Applicable

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

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