Control of Magnetoelectric Load to Maintain Stable Compression Ratio for Free Piston Linear Engine Systems

2020 ◽  
pp. 2150017
Author(s):  
Bo Yang ◽  
Chenheng Yuan ◽  
Jiahui Li
Keyword(s):  
Dynamic Model ◽  
Compression Ratio ◽  
Force Balance ◽  
Stable Operation ◽  
Mechanism Analysis ◽  
Connecting Rod ◽  
Nonlinear Dynamic Model ◽  
Piston Motion ◽  
Free Piston ◽  
Linear Engine

The free piston linear engine system (FPLE) is considered as a promising powerplant, which has the advantages such as compact structure, short transfer path and variable compression ratio (CR) because the crank connecting rod is removed. However, the absence of crank-connecting rod inevitably produces uncertainty to the stable operation of the FPLE. A control system of the piston motion regulating for the FPLE is necessary. In this paper, the nonlinear dynamic model simulating the piston motion in a dual-piston FPLE is derived based on energy and force balance. The feasibility of the dynamic model is verified by experiment and simulation results. Based on instability mechanism analysis, a magnetoelectric load controller with motion stroke feedback is designed to maintain the piston position in a predefined CR by regulating the magnetoelectric force. The proposed magnetoelectric load controller is shown to have good control performance for the FPLE. The piston is always stabilized at the predefined position after a short adjustment time. The time of eliminating disturbance for the operation process is less than the start process. Furthermore, the increase in disturbance will result in the increase of time for adjustment.

Simulation Of A Two–Stroke Spark Ignition Free Piston Linear Engine Motion

2012 ◽  
Author(s):  
N. A. N. Mohamed ◽  
A. K. Ariffin ◽  
S. Fonna
Keyword(s):  
Velocity Profile ◽  
Compression Ratio ◽  
Spark Ignition ◽  
Piston Motion ◽  
Piston Velocity ◽  
Stroke Length ◽  
Free Piston ◽  
Linear Engine ◽  
Main Components ◽  
Engine Concept

Enjin linear omboh bebas dua lejang cucuhan bunga api dianalisis dalam kertas kerja ini. Komponen utama daripada enjin adalah kebuk pembakaran, kebuk hapus sisa, kebuk tending balik dan gelangsar–omboh. Model dinamik dan termodinamik bagi gerakan gelangsaromboh dibentangkan. Seterusnya, kesan pelbagai nilai masukan haba dan nisbah mampatan terhadap halaju gelangsar–omboh dan panjang lejang juga diselidik. Dengan menggunakan parameter enjin yang dipilih, pergerakan enjin linear omboh bebas berhasil diselakukan. Hasil penyelakuan menunjukkan bahawa profil gerakan gelangsar omboh jauh dari bentuk sinus. Hasil penyelakuan terhadap pelbagai nilai masukan haba menunjukkan bahawa halaju dan panjang lejang gelangsar–omboh semakin tinggi dengan masukan haba yang semakin tinggi. Dengan semakin tinggi nisbah mampatan menyebabkan halaju gelangsar–omboh semakin tinggi manakala panjang lejang malar. Kata kunci: Enjin linear omboh bebas, dua lejang, nisbah mampatan Two–stroke spark ignition free piston linear engine concept is analyzed in this paper. The main components of the engine are combustion chamber, scavenging chamber, kickback chamber and slider–piston. Dynamic and thermodynamic models of the slider–piston motion are presented. Also, the effect of various heat additions and compression ratio on the slider–piston velocity, time taken for one stroke, and stroke length are explored. By using selected engine variables, the motion of the two–stroke free piston linear engine is successfully simulated. The results show that the velocity profile of slider–piston motion is non–sinusoidal. By varying the amount of heat addition, the velocity and stroke length of slider–piston will increase accordingly. However, by increasing compression ratio, the velocity of slider piston is noted to increase but the stroke length of slider–piston remains constant. Key words: Free piston linear engine, two-stroke, compression ratio

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.

scholarly journals A Review of the Design and Control of Free-Piston Linear Generator

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2179 ◽  
Author(s):  
Xuezhen Wang ◽  
Feixue Chen ◽  
Renfeng Zhu ◽  
Guilin Yang ◽  
Chi Zhang
Keyword(s):  
Motion Control ◽  
Combustion Process ◽  
Integrated Design ◽  
Stable Operation ◽  
Piston Motion ◽  
Free Piston ◽  
Linear Generator ◽  
Advantages And Disadvantages ◽  
Highly Efficient ◽  
Compact Size

The Free-piston linear generator (FPLG) is a novel energy converter which can generate electrical energy and is regarded as a potential technology for solving the restriction of the short driving range of electric vehicles. Getting rid of the crank and flywheel mechanism, FPLG obtains some advantages of a variable compression ratio, compact size, and highly-efficient power generation. Linear electric machine (LEM) design and piston motion control are two key technologies of FPLG. However, they are currently the main obstacles to the favorable performance of FPLG. LEM being used to drive the piston motion or generate electric energy is an integrated design including a motor/generator. Various types of LEMs are investigated, and suitable application scenarios based on advantages and disadvantages are discussed. The FPLG’s controller is used to ensure stable operation and highly-efficient output. However, cycle-to-cycle variations of the combustion process and motor/generator switching make it difficult to improve the performance of the piston motion control. Comments on the advantages and disadvantages of different piston motion control methods are also given in this paper.

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.

DYNAMIC MODEL FOR GRANULAR ASSEMBLY

1993 ◽  
Vol 07 (09n10) ◽  
pp. 1929-1947 ◽  
Author(s):  
DANIEL C. HONG
Keyword(s):  
Dynamic Model ◽  
Dynamic Equation ◽  
Nonlinear Dynamic ◽  
Numerical Solutions ◽  
Mass Term ◽  
Two Dimensions ◽  
Force Balance ◽  
Nonlocal Interaction ◽  
Nonlinear Dynamic Model ◽  
Granular Pile

In this paper, we investigate in detail the complex dynamics and flow patterns of granular materials based on two simple yet quite realistic models: the diffusing void model and the nonlinear dynamic model. We first show how the diffusing void model describes some of the unusual and unique features of granular flows in a confined geometry such as the deformation of the free surface, the formation of dead zones, the flow around obstacles, the shock front with its companion void regions, and the front profile of the propagating density waves. We then provide theoretical framework for the diffusing void model by deriving it from the continuity equation and the microscopic force balance equation. This approach shows how the nonlinear term arises naturally, leading to the nonlinear dynamic equation, whose numerical solutions do exhibit the features shown by the diffusing void model and the experiment. When nonlocal interaction between grains is taken into account, the mass term appears in the dynamic equation in the thermodynamic limit, leading to exponential decay of the granular pile. This might account fot the different behaviors for large and small granular piles. We also present exact results of the stress distribution of a hexagonally packed granular pile in two dimensions and show that the load acting on each grain at the bottom layer is identical. We also present the results of molecular dynamics simulations which show that the speed of the outgoing grains in a hopper is independent of the depth. We then outline a few outstanding problems that are technologically important, yet can be handled by the models proposed and developed in this paper.

Analysis of Tourism Ecology Capacity Based on the Nonlinear Dynamic Model

2009 ◽  
Vol 11 (2) ◽  
pp. 163-168
Author(s):  
Long LV ◽  
Zhenfang HUANG ◽  
Jiang WU
Keyword(s):  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Model

scholarly journals Development, Modeling and Control of a Dual Tilt-Wing UAV in Vertical Flight

Drones ◽  
2020 ◽  
Vol 4 (4) ◽  
pp. 71
Author(s):  
Luz M. Sanchez-Rivera ◽  
Rogelio Lozano ◽  
Alfredo Arias-Montano
Keyword(s):  
Dynamic Model ◽  
Attitude Control ◽  
Test Bench ◽  
Aerodynamic Coefficients ◽  
Nonlinear Dynamic Model ◽  
Modeling And Control ◽  
Drag And Lift ◽  
And Control ◽  
Dynamics Method ◽  
Indoor And Outdoor

Hybrid Unmanned Aerial Vehicles (H-UAVs) are currently a very interesting field of research in the modern scientific community due to their ability to perform Vertical Take-Off and Landing (VTOL) and Conventional Take-Off and Landing (CTOL). This paper focuses on the Dual Tilt-wing UAV, a vehicle capable of performing both flight modes (VTOL and CTOL). The UAV complete dynamic model is obtained using the Newton–Euler formulation, which includes aerodynamic effects, as the drag and lift forces of the wings, which are a function of airstream generated by the rotors, the cruise speed, tilt-wing angle and angle of attack. The airstream velocity generated by the rotors is studied in a test bench. The projected area on the UAV wing that is affected by the airstream generated by the rotors is specified and 3D aerodynamic analysis is performed for this region. In addition, aerodynamic coefficients of the UAV in VTOL mode are calculated by using Computational Fluid Dynamics method (CFD) and are embedded into the nonlinear dynamic model. To validate the complete dynamic model, PD controllers are adopted for altitude and attitude control of the vehicle in VTOL mode, the controllers are simulated and implemented in the vehicle for indoor and outdoor flight experiments.

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