GM and U Mich receive patent on plug-in series hybrid/extended range electric vehicle powertrain using multiple free piston linear alternator engines
|The GM/U Mich patent envisages using multiple free-piston engines (240A through 240D in the patent drawing). Click to enlarge.|
GM Global Technology Operations LLC and the Regents of the University of Michigan recently were awarded a US patent (Nº 8,261,860) for a plug-in series hybrid or range-extended electric vehicle powertrain using multiple free piston linear alternator (FPLA) engines.
The powertrain system—the patent application for which was filed in 2009—includes an electrical energy storage system—such as a Li-ion battery pack—and an electric traction motor. The covered hybrid powertrain uses the multiple reciprocating free-piston linear alternator engines to generate electric power for the battery pack or the traction motor.
The FPLA units are connected to a power electronics module, which in turn in connected to the electrical energy storage system and the electric motor. A control module determines mechanical and electrical power demands in respond to driver input and a state of charge of the electrical energy storage device. The control module commands operations of the reciprocating free-piston internal combustion engines to generate electric power responsive to the electrical power demands.
|Patent Drawing of an FPLA. Click to enlarge.|
Each FPLA unit includes includes a reciprocating free-piston internal combustion engine having a single cylinder with a double-ended free piston, which forms two variable volume combustion chambers. Each cylinder has a linear electrical alternator, including multiple electrical coils and integrated iron stators, and the double-ended free piston includes multiple permanent magnets.
When the free piston oscillates in the cylinder during operation, electrical energy is generated by the action of the permanent magnets forming and breaking magnetic fields with the iron stators and electrical coils.
Fuels can include gasoline blends, and alcohol blended hydrocarbon fuel grades. Ethanol blended hydrocarbon fuels can include higher ethanol blends (e.g. E80, E85), and neat ethanol (E99). Alternative liquid and gaseous fuels such as neat methanol (M100), natural gas, hydrogen, biogas, various reformates, syngases, and others may also be used.
Each FPLA operates in an engine-on (ON) state and an engine-off (OFF) state. Each FPLA has at least one resonant operating speed corresponding to mass of the piston and length of the cylinder at which it generates a preferred output power—i.e., a maximum output power or an output power achieved at a maximum efficiency point. The preferred output power is referred to as a rated output power at the resonant operating speed.
The use of the FPLAs offers flexibility in terms of power generation. In one embodiment described in the patent, each FPLA operates at a resonant speed and at a fixed output power, e.g., a rated output power of 30 kW. Alternatively, each of the FPLAs has the same rated output power—e.g.30 kW—and operates at one of multiple output powers, e.g., 10 kW, 20 kW, and 30 kW preferably at the resonant speed, the output power controlled by controlling mass of fuel injected each combustion cycle.
In one embodiment, the FPLAs have different rated output powers, and generate different, preferably progressive amounts of output power in the engine-on state.
The FPLAs can be configured to generate different rated output powers by varying engine design factors including bore and stroke of the cylinder, size and mass of the piston, and other factors. Thus, in one embodiment, the first FPLA unit can have a rated output power of 10 kW, the second FPLA unit can have a rated output power of 20 kW, the third FPLA unit can have a rated output power of 30 kW, and the fourth FPLA unit can have a rated output power of 40 kW for a total rated output power of 100 kW of power for the combined operation of the FPLAs. (Numerical values are illustrative and not restrictive.)
US Patent Nº 8,261,860: Hybrid powertrain system using free piston linear alternator engine