Free Piston Power Pack (FP3)

Free Piston Pack

FP3 design is based on "free pistons" being driven back and forth inside cylinders by controlled internal combustion. Permanent magnets are attached to the pistons. As the magnets move, electric power is generated in coils placed around the magnets. The module represents a fresh approach in free piston engine/generator design. Novel features include passive intake valves, located in the crown of the piston and an integral charge compressor.

These improvements eliminate problems hampering earlier free piston engine designs, such as ported cylinder walls with associated piston ring wear and the need for a bulky, external charge compressor. The result is a significant increase in power density (1kW per kg or 1.93 kW per liters).

Mechanical simplicity (software "replaces" the crankshaft), high pressure direct fuel injection, variable exhaust valve lift and timing as well as variable stroke and compression ratio all contribute to excellent fuel efficiency and low levels of harmful exhaust emissions.

The FP3 is an extremely compact, efficient, clean, low-cost, scaleable electric generator with an output up to 450kW. It can be modified to operate on diesel, ethanol, LPG and hydrogen.

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Passive Intake Valves

Passive Intake Valves Image

Four passive intake valves are located in the crown of each piston. They are seated poppet valves and form the intake ports through which fresh air enters the combustion chamber. The intake valves operate in a completely passive manner, i.e. there are no external controls. The opening and closing of the intake valves is governed by the pressure differential that exists between the compressor and the combustion chamber. The passive intake valves provide three major benefits:

Charge Compressor

Charge Compressor Image

Two compressors, driving the gas exchange process, form an integral part of the FP3. This eliminates the need for a bulky, external charge compressor.

Linear Generator

Linear Generator

The linear generator is highly integrated into the design of the FP3. It consists of eight ring-shaped NeFeB permanent magnets located on the mover assembly and an eight coil stator. The coils are connected to IGBT inverters which convert the generator output to direct current.

The inverters are controlled by a digital signal processor system maximising the efficiency of the power conversion process.

The generator acts as a linear motor when starting the FP3; power is applied to the stator coils in sequence causing the piston to move.

Electro-Pneumatic Exhaust Valve

Electro-Pneumatic Exhaust Valve

The exhaust valve is driven by a high speed, software controlled actuator. The actuator contains two opposing solenoids that open and close the valve. Each solenoid incorporates a gas spring that stores energy required to generate the high forces necessary for rapid operation. The exhaust valve is capable of opening to a stroke of over 7 mm and closing again in 5 ms. The seat diameter of 36 mm provides a large aperture for rapid removal of exhaust gases.

Test Result

Graph of a test result


Mover Bearing

Mover Bearing

The interface between the mover and stator is the only major bearing in the FP3. Because the FP3 is not subjected to dynamic lateral piston forces, the contact pressure in the bearing is less than 0.02 MPa. Since the mover speed is less than 10 m/s there is plenty of scope for the design of a lubrication-free bearing.

Piston Seal

Piston Seal

The FP3 uses an advanced seal rather than conventional piston rings. The main pressure seal is fitted into the inside surface of the bottom of the cylinder. It is subject to relatively low temperatures. Above the main seal is a labyrinth seal that provides a significant pressure reduction, allowing the use of a low-pressure type seal. The prevailing conditions allow for the design of a lubrication-free piston seal.

The FP3 can take advantage of current research in materials and cooling to achieve a minimal crevice volume. This may allow the use of a contact-less piston seal.

Frequency of Operation

Frequency of Operation

The power delivered by the engine and generator can be increased by raising the operating frequency. To achieve this, the mover of the FP3 has been designed for minimum mass (5.2 kg).

A simple analysis shows that the operating frequency can also be increased by around 60% by sub-dividing the unit into four quarter-size sub-modules.

Features

Features

Specifications

Gas Exchange

SwirlScavenging




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Orthodox Internal Combustion Engine Vehicle Technology

Combustion Engine Vehicle Technology

Orthodox Internal Combustion Engine Vehicle Technology

The established internal combustion engine powered vehicle has benefited from over 100 years of research, development, testing and refinement. This has produced designs that have good fuel efficiency, low manufacturing cost and excellent reliability. However, planet earth requires transportation solutions that are more fuel efficient, environmentally responsible and sustainable. It is difficult to further improve existing vehicle design to achieve these goals without recapturing the vehicle's kinetic energy lost when slowing down and braking. It is our opinion that the Series Hybrid Electric Vehicle with the FP3 as a clean and efficient power source will attain these objectives.
 

Series versus Parallel Hybrid Electric Vehicles

Existing and proposed Parallel Hybrid Electric Vehicles are driven, in the main, by an internal combustion engine connected mechanically to the wheels. In parallel is installed an electric motor/generator and battery combination also connected to the wheels, via a separate gear train. With this combination it is difficult to go beyond 25% power regeneration. In contrast, Series Hybrid Electric Vehicles have no mechanical drive. The electric output power of the FP3 is fed directly to a battery and to four electric wheel motors via a power electronic control system. This permits 100% power regeneration of the vehicle's kinetic energy when slowing down or braking. The result is:

When installed in a typical series hybrid family sedan, the following specifications apply:

FP3 versus Fuel Cell Technology

The fuel cell is under development by many automotive manufacturers and has been released on the market in limited numbers. The manufacturing cost of fuel cells is a major obstacle and experts agree that this cost will remain high for many years to come. It has been suggested that it will take at least 10 years for fuel cell vehicle prices to fall below US$100,000. This makes the free-piston concept a much more cost-effective power plant for automobiles.

Fuel cells use hydrogen as a fuel source. The safe storage of hydrogen in a motor vehicle is a major concern. Another limitation of fuel cells in the short and medium term is the lack of a hydrogen distribution infrastructure. Industry analysts predict that it may take 20 years to establish such an infrastructure. If and when hydrogen starts to replace gasoline and diesel, the FP3 can run on this harmful emissions-free fuel (a low cost, mechanical fuel cell).

It can be argued that the reduction in fossil fuel consumption as well as improvement in air quality will be far greater as a result of the sale of millions of low cost, series hybrid electric vehicles equipped with efficient, clean FP3s, rather than from limited sales of expensive "Zero Emission Vehicles".

Other Applications

Other Applications Image

Proposed Series HEV

Proposed Series HEV

INTERNAL COMBUSTION ENGINE & LINEAR GENERATOR MODULE:

 

 

 

Linear Generator

Power

40 kW

 

Dimensions

225 mm x 225 mm x 520 mm

 

Mass

40 kg

 

 

 

Combustion Engine

Cylinders

8

 

Bore

52 mm

 

Stroke

80 mm

 

Capacity

1.36 l

 

Power

40 kW

 

 

 

Cylinder Heads

2 Exhaust Valves 22 mm bore (one actuator)

 

1 Fuel Injector

 

 

1 Spark Plug

 

 

 

 

Pistons

3 Passive Intake Valves 20 mm bore

 

 

 

Generators

Mover OD

80 mm

 

Mover Length

140 mm

 

Number of Coils

6

 

Stator OD

110 mm

 

Frequency

36 Hz

 

BATTERY ASSEMBLY:

Batteries:

Power

37.5 kW x 3 = 112 kW

 

Dimensions

180 x 590 x 170 mm x 3

 

Mass

23 kg x 3 = 69 kg

 

 

 

 

56 Li-Ion Cells VL7P

 

 

Voltage

200 V

 

Power

37.5 kW

 

Energy

1.4 kWh



WHEEL MOTORS:

Traction Motor:

Power

30 kW x 4 = 120 kW

 

Dimensions

Ø120 x 200 mm

 

Mass

13 kg x 4 = 52 kg

 

Gear ratio

6.75 : 1



PROPOSED SERIES HEV CONFIGURATION:

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Predicted Performance:

Acceleration for a vehicle mass of
1000 kg from 0 to 100 km/h:

6 seconds

Regenerating Capacity for a vehicle mass of 1000 kg:

Vehicle Speed

Retardation

< 43 km/h

10.0 m/s²

50 km/h

8.6 m/s²

60 km/h

7.2 m/s²

80 km/h

5.4 m/s²

100 km/h

4.3 m/s²

120 km/h

3.6 m/s²

 

 

Fuel consumption in city traffic measured in accordance with NEDC: 1.6 l/100 km

PATENTS:

Australia: PQ8065 2000, June

USA: US6,651559B2 2003, November

Europe: 01931200.8 2004, July

Japan: 3607909 2005, January

South Korea: 10-2002-7001442 2005, September

India

Australian Provisional Patent 2006904838

PUBLICATIONS:

pdf Document The Free Piston Power Pack: Sustainable power for Hybrid Electric Vehicles - SAE 2003-01-3277.

pdf Document Hybrid Electric Truck Concept 26-Oct-05

pdf Document Series HEV 31-Oct-05

pdf DocumentParallel versus Series HEV Fuel Consumption

Status Quo:

An intrepid mob of mechanical, electrical, electronic and software engineers has been developing the FP3 at Pempek's R&D facility since February 2001. Prototype electronic control and power modules, sub-systems and engine components have been designed and manufactured. An electro-pneumatic exhaust valve featuring variable valve timing and lift has been developed, successfully tested and patented. A prototype FP3 is currently undergoing test. The design of a 50kW wheel motor has been completed and the first units are currently being constructed. Our senior project engineer has presented a paper on the FP3 (SAE2003-01-3277) at the SAE Powertrain & Fluid Systems conference in Pittsburgh, PA in October 2003.

Click on the image for a larger size viewing:

Engine Under Test

Engine Under Test in our Power Technology Shed:

Engine in it's current state is being tested for field oriented positioning

Engine Controller Setup image Engine Controller Setup:

Rack of multi processor electronics is used in controlling the engine operation.

Exhaust and Inlet Valves

Exhaust and Inlet Valves:

The titanium valves are designed and manufactured for our patented "High speed solenoid valves".

Assembled High-Speed Exhaust Valve

Assembled High-Speed Exhaust Valve:

Comprises the exhaust-valve, solenoid, intake-valve, and gas-springs.

Control Electronics

Control Electronics:

Electronics of the Free Piston Engine Power Pack are customised, designed, and manufactured in Pempek Systems.

High Pressure Fuel Injector Siemens' High Pressure Fuel Injector:

FP3 uses Siemens injectors for high pressure direct injection of fuel into the combustion chamber.

Fuel Pressure Setup Fuel Pressure Setup:

Fuel pressure is being adjusted to 80bar for testing of the fuel injectors.

Fuel Injector Test Setup Fuel Injector Test Setup:

Testing the fuel-injectors and their controllers.  Fuel-injectors are controlled by a DSP for precision operation.

Power Electronics Power Electronics:

High power electronics, which controls the engine and its output, are mounted on a water cooled heat-sink