Stability, Control, and Constraint Enforcement of Piston Motion in a Hydraulic Free-Piston Engine

2017 ◽  
Vol 25 (4) ◽  
pp. 1284-1296 ◽  
Author(s):  
Kevin Zaseck ◽  
Matthew Brusstar ◽  
Ilya Kolmanovsky
Keyword(s):  
Stability Control ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Free Piston Engine ◽  
Constraint Enforcement

scholarly journals Piston motion control of a free-piston engine generator: A new approach using cascade control

2016 ◽  
Vol 179 ◽  
pp. 1166-1175 ◽  
Author(s):  
Boru Jia ◽  
Rikard Mikalsen ◽  
Andrew Smallbone ◽  
Zhengxing Zuo ◽  
Huihua Feng ◽  
...  
Keyword(s):  
Motion Control ◽  
Cascade Control ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
New Approach ◽  
Free Piston Engine

A Virtual-Cam Control Methodology for Free-Piston Engines

2011 ◽  
Author(s):  
Chao Yong ◽  
Eric J. Barth
Keyword(s):  
Internal Combustion Engines ◽  
Control Method ◽  
Piston Engine ◽  
Piston Motion ◽  
Stroke Length ◽  
Free Piston ◽  
Physical Context ◽  
Spark Timing ◽  
Free Piston Engine ◽  
Timing Belt

In conventional internal combustion engines, valves are opened and closed using a cam surface. The cam is kinematically related to the piston positions through the crankshaft and timing belt. In contrast, there is no crankshaft or kinematic cam surface in a free-piston engine to physically realize this mechanism. As a consequence, a free-piston engine has variable stroke lengths, which presents a challenge for active piston motion and precise stroke length control. This paper presents a virtual-cam based approach to relate free-piston motion to actuated engine valve control within a clear and familiar intuitive physical context. The primary functionality of the virtual cam control framework is to create a variable index, which is adjustable from cycle to cycle, for the exhaust/injection valves and spark timing similar to the function of physical cams in conventional engines. Since the cam is virtually created, it can be dynamically rebuilt to comply with cycle-to-cycle variations such as amount of the air/fuel supply, engine load and stroke length. This index rebuilding process is based on a cycle-to-cycle adaptive control method that uses the knowledge obtained from previous cycles to adjust the cam parameters. Preliminary experimental results are presented for a novel liquid-piston free-piston engine intended as a compact and efficient energy source for untethered power dense pneumatic systems such as untethered robots.

Development of free piston engine linear generator system and a resonant pendulum type control method

2020 ◽  
pp. 146808742093124
Author(s):  
Hidemasa Kosaka ◽  
Tomoyuki Akita ◽  
Shigeaki Goto ◽  
Yoshihiro Hotta
Keyword(s):  
Control Method ◽  
Experimental Result ◽  
Piston Engine ◽  
Piston Motion ◽  
Generator System ◽  
Free Piston ◽  
Linear Generator ◽  
Reference Profile ◽  
Cycle Simulation ◽  
Free Piston Engine

A free piston engine linear generator, which has the potential of the compact physique, high brake efficiency and high flexibility for fuel, has been developed. The developed free piston engine linear generator consists of a two-stroke combustion unit, an air-bounce chamber and a linear generator. The key technologies to realize the continuous operation are the control method and lubricating and cooling strategies. The proposed structure is featured as a piston shape with two different diameters coaxially, called a “W-shape” piston, which has an empty space inside for the oil cooling path. The performance of the structure is evaluated by a one-dimensional cycle simulation. The result indicates the possible output power of 10 kW and thermal efficiency of 42% using premixed charge compression ignition combustion strategy. The control method is another challenge of the free piston engine linear generator. This work proposes two strategies of the position feedback control method and the resonant pendulum type control method. The first method has the function of the feedback loops for the piston position and velocity so that the piston motion follows the reference profile calculated in advance. The experimental results show the limited range of operation because the fixed profile does not absorb the deviation of the piston motion due to the combustion deviation. The second method is based on the speed control without a fixed reference profile of the piston motion. The experimental result shows the robustness to the change in operating parameters such as ignition position, amount of fuel and desired power output.

In-cylinder heat transfer and gas motion of a free-piston diesel engine generator

2017 ◽  
Vol 231 (8) ◽  
pp. 739-752 ◽  
Author(s):  
Chenheng Yuan ◽  
Jing Xu ◽  
Huihua Feng
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Attractive Alternative ◽  
Piston Engine ◽  
Piston Motion ◽  
Compression Process ◽  
Free Piston ◽  
Reciprocating Engine ◽  
Free Piston Engine ◽  
Significant Difference

The free-piston engine generator is an attractive alternative to the conventional reciprocating engine due to the feature that it moves without crankshaft system. This paper presented a simulation for the investigation on the characteristic of in-cylinder gas motion and heat transfer in a compression ignited free-piston engine generator. An operation experiment was performed to obtain the precise piston motion for the modeling of heat transfer and gas flow. The development of the multi-dimensional model was described, and simulation results were presented and showed good similarity with the experimental data. Then, the heat transfer and gas motion in the free-piston engine generator were discussed, on which the influences of piston motion were also investigated compared with a corresponding conventional reciprocating engine. The results indicated that compared with the conventional reciprocating engine, a higher level of squish and reverse squish effect was found for the free-piston engine generator due to its faster motion around top dead center, while its slower piston motion led to weaker gas turbulence in the compression process. Moreover, the free-piston engine generator and conventional reciprocating engine did not show a significant difference in heat transfer during the compression process, however, an obvious advantage of heat transfer was indicated for the free-piston engine generator in combustion and expansion processes due to its lower combustion temperature and the reduced time that is available for heat transfer caused by its faster expansion. The mechanism for such differences is that the free-piston engine generator moves with uneven equivalent speed.

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.

Tribological characteristics of piston rings in a single-piston hydraulic free-piston engine

2017 ◽  
Vol 69 (2) ◽  
pp. 131-141 ◽  
Author(s):  
Zhaoju Qin ◽  
Chenheng Yuan ◽  
Yanpeng Yuan ◽  
Yuanyuan Huang
Keyword(s):  
Numerical Simulation ◽  
Friction Loss ◽  
Piston Engine ◽  
Piston Motion ◽  
Piston Rings ◽  
Free Piston ◽  
Content Type ◽  
Compression Stroke ◽  
Free Piston Engine ◽  
Loss Efficiency

Purpose A free-piston engine (FPE) is an unconventional engine that abandons the crank system. This paper aims to focus on a numerical simulation for the lubricating characteristics of piston rings in a single-piston hydraulic free-piston engine (HFPE). Design/methodology/approach A time-based numerical simulation program was built using Matlab to define the piston motion of the new engine. And a lubrication mode of piston rings was built which is based on the gas flow equation, hydrodynamic lubrication equation and the asperity contact equation. The piston motion and the lubrication model are coupled, and then the finite difference method is used to obtain the piston rings lubrication performances of the FPE. Meanwhile, the lubrication characteristics of the new engine were compared with those of a corresponding conventional crankshaft-driven engine. Findings The study results indicate that compared with the traditional engine, the expansion stroke of the HFPE is longer, and the compression stroke is shorter. Lubrication oil film of the new engine is thicker than the traditional engine during the initial stage of compression stroke and the final stage of the power stroke. The average friction force and power of the hydraulic free piston engine are slightly lower than those of the traditional engine, but the peak friction power of the FPE is significantly greater than that of the traditional engine. With an increase in load, the friction loss power and friction loss efficiency decrease, and with a decrease in equivalence ratio, the friction power loss reduces, but the friction loss efficiency decreases first and then increases. Research limitations/implications In this paper, only qualitative analysis was performed on the tribological difference between conventional crankshaft engine and HFPE, instead of a quantitative one. Practical implications This paper contributes to the tribological design method of HFPE. Social implications No social implications are available now, as the HFPE is under the development phase. However, the authors are positive that their work will be commercialized in the near future. Originality/value The main originality of the paper can be introduced as follows: the lubrication and friction characteristics of the new engine (HFPE) were investigated and revealed, which have not been studied before; the effect of the HFPE’s special piston motion on the tribological characteristics was considered in the lubrication simulation. The results show that compared with the traditional crankshaft engine, the new engine shows a different lubrication performance because of its free piston motion.

Effect of Piston Motion on Combustion of CNG Free Piston Engine (FPE)

2014 ◽  
Vol 889-890 ◽  
pp. 501-506
Author(s):  
Ning Xia Yin ◽  
Zhao Ping Xu ◽  
Si Qin Chang ◽  
Ji Ming Lin
Keyword(s):  
Heat Transfer ◽  
Combustion Process ◽  
Engine Performance ◽  
Expansion Ratio ◽  
Nox Emissions ◽  
Piston Engine ◽  
Piston Motion ◽  
Free Piston ◽  
Beneficial Effects ◽  
Free Piston Engine

CNG is thought to be one of the most promising alternatives to traditional fuels. The multi-fuel ability is another characteristic of the FPE. The piston motion can be controlled to have beneficial effects on the engine performance. This article investigates the effect of piston motion on combustion of four-stroke CNG FPE using a multidimensional simulation model. It is found that the high piston acceleration and velocity at top dead center increases expansion ratio and fasting combustion, reduces the heat transfer losses and decreased NOx emissions formation. At the same time, the turbulent kinetic energy of the gas during the combustion process is added.

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