Linear engine development for series hybrid electric vehicles

Abstract

Linear Engine Development for Series Hybrid Electric Vehicles by Csaba Tóth-Nagy This dissertation argues that diminishing oil reserves, concern over global climate change, and desire to improve ambient air quality all demand the development of environment-friendly personal transportation. In certain applications, series hybrid electric vehicles offer an attractive solution to reducing fuel consumption and emissions. Furthermore, linear engines are emerging as a powerplant suited to series HEV applications. In this dissertation, a linear engine/alternator was considered as the auxiliary power unit of a range extender series hybrid electric vehicle. A prototype linear engine/alternator was developed, constructed and tested at West Virginia University. The engine was a 2-stroke, 2-cylinder, dual piston, direct injection, diesel engine. Experiment on the engine was performed to study its behavior. The study variables included mass of the translator, amount of fuel injected, injection timing, load, and stroke with operating frequency and mechanical efficiency as the basis of comparison. The linear engine was analyzed in detail and a simple simulation model was constructed to compare the trends of simulation with the experimental data and to expand on the area where the experimental data were lacking. The simulation was based on a simple and analytical model, rather than a detailed and intensely numerical one. The experimental and theoretical data showed similar trends. Increasing translator mass decreased the operating frequency and increased compression ratio. Larger mass and increased compression ratio improved the ability of the engine to sustain operation and the engine was able to idle on less fuel injected into the cylinder. Increasing the stroke length caused the operating frequency to drop. Increasing fueling or decreasing the load resulted in increased operating frequency. This projects the possibility of using the operating frequency as an input for feedback control of the engine. Injection timing was varied to investigate two different modes of engine operation experimentally. The two modes were direct injection compression ignition (DICI) and "pseudo" homogeneously charged compression ignition (PHCCI). Simulation was performed to include HCCI operation in the study. The study showed that the HCCI operation resulted in higher peak cylinder pressure than that of DICI operation. A combined genetic algorithm-artificial neural network predictor model was used along with the simulation model to find the combination of engine parameters that yielded the highest engine efficiency. The predictor-simulator model suggested the most efficient combination of engine parameters. I thank Dr. Nigel N. Clark for his guidance during my postgraduate studies. Not only he did provide invaluable input to my research, he also showed the way with his integrity, philosophy, and attitude. I also thank Dr.

Parametric Investigation of Combustion and Heat Transfer Characteristics of Oscillating Linear Engine Alternator

“…Furthermore, the OLEA operates only on a few moving parts, that is, translator rod and mechanical springs. The elimination of crankshaft linkages in the design allows unrestricted piston motion, thereby exhibiting different stroke and variable compression ratio every cycle [4,5].…”

“…Furthermore, the short residence of the piston at the Top Dead Center (TDC) and a faster expansion stroke are beneficial for reducing heat transfer losses, thereby improving the thermal efficiency [7] (v) Minimal vibration: elimination of crankshaft mechanical linkages reduces the associated forces and moments in the OLEA system, thereby cutting back the vibrations in the OLEA system when compared to crankshaft engine. However, of all the OLEA configurations, the opposed piston configuration with equal piston masses enjoys the benefits of minimal vibrations, whereas single cylinder OLEA is more prone to the vibrations [5,7]. The vibrations of the dual cylinder configuration lie in between the single cylinder and opposed piston configuration.…”

Analysis and Optimization of a Dual Free Piston, Spring Assisted, Linear Engine Generator

“…This fed the development of a second generation diesel fueled prototype. In this, a boosted, direct injected, port scavenged, dual cylinder engine operated between 50 and 60 Hz [19]. These research efforts revealed many important insights into the operation of the linear engine.…”

“…Researchers from WVU correlated the model constant ( ) with experimental data gathered from a free piston linear engine and validated the model in ring-down testing [19], showing good success for the model. The same research suggested that the damping coefficient should be dependent on the piston bore and translator mass.…”

Modeling and Simulation of a Free-Piston Engine with Electrical Generator Using HCCI Combustion

“…The prototype represented a diesel fueled, boosted, direct injected, port scavenged and dual cylinder engine. It was operating within a frequency range of 50 to 60 Hz [25]. Another prototype was built in 2007 by Newcastle University.…”