An Optimal Control Approach to Minimizing Entropy Generation in an Adiabatic Internal Combustion Engine

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Kwee-Yan Teh ◽  
Christopher F. Edwards
Keyword(s):  
Optimal Control ◽  
Entropy Generation ◽  
Combustion Engine ◽  
Combustion Mechanism ◽  
Control Input ◽  
Minimum Entropy ◽  
Piston Engine ◽  
Piston Motion ◽  
Thermodynamic State ◽  
Engine Efficiency

Entropy generation due to combustion destroys as much as a third of the theoretical maximum work that could have been extracted from the fuel supplied to an engine. Yet, there is no fundamental study in the literature that addresses the question of how this quantity can be minimized so as to improve combustion engine efficiency. This paper fills the gap by establishing the minimum entropy generated in an adiabatic, homogeneous combustion piston engine. The minimization problem is cast as a dynamical system optimal control problem, with the piston velocity profile serving as the control input function. The closed-form switching condition for the optimal bang-bang control is determined based on Pontryagin’s maximum principle. The switched control is shown to be a function of the pressure difference between the instantaneous thermodynamic state of the system and its corresponding equilibrium thermodynamic state at the same internal energy and volume. At optimality, the entropy difference between these two thermodynamic states is shown to be a Lyapunov function. In thermodynamic terms, the optimal solution reduces to a strategy of equilibrium entropy minimization. This result is independent of the underlying combustion mechanism. It precludes the possibility of matching the piston motion in some sophisticated fashion to the nonlinear combustion kinetics in order to improve the engine efficiency. For illustration, a series of numerical examples are presented that compare the optimal bang-bang solution with the nonoptimal conventional solution based on slider-crank piston motion. Based on the solution for minimum entropy generation, a bound for the maximum expansion work that the piston engine is capable of producing is also deduced.

An Optimal Control Approach to Minimizing Entropy Generation in an Adiabatic IC Engine With Fixed Compression Ratio

2006 ◽  
Author(s):  
Kwee-Yan Teh ◽  
Christopher F. Edwards
Keyword(s):  
Optimal Control ◽  
Entropy Generation ◽  
Compression Ratio ◽  
Combustion Engine ◽  
Optimal Solution ◽  
Combustion Mechanism ◽  
Control Input ◽  
Piston Velocity ◽  
Ic Engine ◽  
Control Approach

Entropy generation due to combustion destroys as much as a third of the theoretical maximum work that could have been extracted from the fuel supplied to an engine. In this paper, an optimal control problem is set up to minimize the entropy generation in an adiabatic internal combustion engine, with the piston velocity profile serving as the control input function. The compression ratio of the engine is fixed, thereby imposing a constraint on the piston motion. The switching conditions for the optimal bang-off-bang control is determined based on Pontryagin's maximum principle. In thermodynamic terms, the optimal solution reduces to a strategy of equilibrium entropy minimization. This result is independent of the underlying combustion mechanism.

Transient Control of a Hydraulic Free Piston Engine

2013 ◽  
Author(s):  
Ke Li ◽  
Chen Zhang ◽  
Zongxuan Sun
Keyword(s):  
High Efficiency ◽  
Combustion Engine ◽  
Tracking Error ◽  
Control Signal ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Engine Operation ◽  
Free Piston Engine ◽  
Transient Period

The free piston engine (FPE) is a type of internal combustion engine (ICE) with no crankshaft, so that its piston motion is no longer constrained by mechanical linkages. The FPE has a high potential in terms of energy saving given its simple structure, high modularity and high efficiency. One of the technical barriers that prevents the wide spread of the FPE technology, is the lack of precise piston motion control. Previously, a robust repetitive controller is designed and implemented to form a virtual crankshaft that would provide a precise and stable engine operation. The experimental data of engine motoring tests with virtual crankshaft demonstrates the effectiveness of the controller. However, the presence of a transient period after a single combustion event prevents the engine from continuous firing. This paper presents a modified control scheme, which utilizes a reference and control signal shifting technique to modify the tracking error and the control signal to reduce the transient period.

scholarly journals The closed-cycle model numerical analysis of the impact of crank mechanism design on engine efficiency

2017 ◽  
Vol 168 (1) ◽  
pp. 153-160
Author(s):  
Marcin OPALIŃSKI ◽  
Andrzej TEODORCZYK ◽  
Jakub KALKE
Keyword(s):  
Theoretical Models ◽  
Closed Cycle ◽  
Cycle Model ◽  
Piston Engine ◽  
Piston Motion ◽  
Engine Model ◽  
Engine Efficiency ◽  
The Impact ◽  
Crank Mechanism ◽  
Potential Efficiency

The research presents a review and comparison of different engine constructions. Investigated engines included crankshaft engines, barrel engine, opposed-piston engines and theoretical models to present possible variations of piston motion curves. The work comprises also detailed description of a numerical piston engine model which was created to determine the impact of the cycle parameters including described different piston motion curves on the engine efficiency. Developed model was equipped with Wiebe function to reflect a heat release during combustion event and Woschini’s correlation to simulate heat transfer between the gas and engine components.Various scenarios of selected engine constructions and different working conditions have been simulated and compared. Based on the results it was possible to determine the impact of different piston motion curves on the engine cycle process and present potential efficiency benefits.

scholarly journals Wall Heat Transfer Analysis of Internal Combustion Engine with Free Piston Linear Motion

2018 ◽  
Vol 7 (3.17) ◽  
pp. 141
Author(s):  
Mior A. Said ◽  
L K. Mun ◽  
A R. A. Aziz ◽  
. .
Keyword(s):  
Heat Transfer ◽  
Transfer Rate ◽  
Combustion Engine ◽  
Linear Motion ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Free Piston Engine ◽  
Set Up ◽  
Motion Profile

The manuscript should contain an abstract. The abstract should be self-contained and citation-free and should not exceed 200 words. The abstract should state the purpose, approach, results and conclusions of the work.  The author should assume that the reader has some knowledge of the subject but has not read the paper. Thus, the abstract should be intelligible and complete in it-self (no numerical references); it should not cite figures, tables, or sections of the paper. The abstract should be written using third person instead of first person. Intensive researches are being carried out on the main power generator for free piston linear generator(FPLG) by both the academic and industrial research group due to its potential as a high fuel efficiency and low emission engine. The linear generator, which is a coil and a translator positioned to move linearly back and forth relative to each other. The study investigates the heat transfer data of internal combustion engine with free piston linear motion profile and compared with the conventional reciprocating engine for one cycle motion only. Engine simulation software GT-Power is employed which utilize the 1-D thermodynamic modeling. All parameters for both free-piston engine are set-up to be the same except for the piston motion profile and the injection timing. Both conventional and free piston engine models are built, simulation settings are set up, and simulations are launched in GT-ISE.  Once simulation is done, results are viewed in GT-POST, the data collected was analysed and compared to investigate the dictinct effect of piston motion to heat transfer profile and data. The overall trend shows that free piston engine have a lower heat transfer rate throughout majority of the cycle. This finding agrees that due to less time of piston near top dead centre area, heat transfer losses to the wall per cycle are reduced. The heat transfer profile of the free piston also shown distinct feature compared to conventional with rapid increase and decrease of heat transfer rate, followed by a secondary peak of gradual decline of the profile.  

Investigating Trajectory Based Combustion Control Using a Controlled Trajectory Rapid Compression and Expansion Machine (CT-RCEM)

2021 ◽  
pp. 1-23
Author(s):  
Abhinav Tripathi ◽  
Zongxuan Sun
Keyword(s):  
Combustion Engine ◽  
Optimal Operation ◽  
Temperature History ◽  
Control Input ◽  
Combustion Control ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine ◽  
Compression And Expansion ◽  
Rapid Compression

Abstract This work presents a systematic framework for the real time implementation of a new combustion control strategy – trajectory-based combustion control – for the operation of free piston engines. The free piston engine is an alternative architecture of IC engines which does not have a mechanical crankshaft and hence allows extreme operational flexibility in terms of piston trajectory. The key idea of trajectory-based combustion control is to modulate the autoignition dynamics by tailoring the pressure and temperature history of the fuel-air mixture inside the combustion chamber, using the piston trajectory as the control input, for the optimal operation of the free piston engine. Here, we present the experimental investigation of trajectory-based combustion control using a novel instrument called controlled trajectory rapid compression and expansion machine (CT-RCEM) that can be used for studying a single combustion cycle of an internal combustion engine with precisely controlled initial and boundary conditions. The effect of the shape of the piston trajectory on the combustion phasing, combustion efficiency and the indicated thermal efficiency has been found to be significant. The experimental results indicate that the trajectory-based combustion control is an effective strategy for combustion phasing control for FPE operation.

scholarly journals Optimal Control for a Hydraulic Recuperation System Using Endoreversible Thermodynamics

2021 ◽  
Vol 11 (11) ◽  
pp. 5001
Author(s):  
Robin Masser ◽  
Karl Heinz Hoffmann
Keyword(s):  
Optimal Control ◽  
Fuel Consumption ◽  
Energy Savings ◽  
Combustion Engine ◽  
Mechanical Energy ◽  
Hydraulic Systems ◽  
Commercial Vehicles ◽  
Hybrid Drive ◽  
Environmental Considerations ◽  
Onboard System

Energy savings in the traffic sector are of considerable importance for economic and environmental considerations. Recuperation of mechanical energy in commercial vehicles can contribute to this goal. One promising technology rests on hydraulic systems, in particular for trucks which use such system also for other purposes such as lifting cargo or operating a crane. In this work the potential for energy savings is analyzed for commercial vehicles with tipper bodies, as these already have a hydraulic onboard system. The recuperation system is modeled based on endoreversible thermodynamics, thus providing a framework in which realistic driving data can be incorporated. We further used dissipative engine setups for modeling both the hydraulic and combustion engine of the hybrid drive train in order to include realistic efficiency maps. As a result, reduction in fuel consumption of up to 26% as compared to a simple baseline recuperation strategy can be achieved with an optimized recuperation control.

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