magnet piston engin

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Presented by:

Himanshu Sekhar Bal

Reg. No- 1101298386

Mechanical Branch


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The free-piston engine is a linear, 'crankless'combustion engine, in which the piston

motion is not controlled by a crankshaft but

is a result of the interaction of forces from

the combustion cylinder gases, a rebounddevice(e.g., a piston in a closed cylinder)

and a load device(e.g. a gas compressor or a

linear alternator).


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The free-piston diesel engine concept was

developed by Pescara, and engines of various size

were manufactured between 1930-1960 by GM,Ford, Renault, Junker, Sigma and others.

General motor XP-500

It is a combination of reciprocating engine and a

rotary turbine.


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Bounce Chamber Intake Air valve Scavenge Air Box Supercharge pump

Exhaust gas receiverPower turbine


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Specifications

100 kW peak electrical

output power

Four free piston engine

sub-modules 8 cylinders

2.82 litre

displacement

30 Hz operation

(equivalent to 1800rpm in

a two stroke crankshaft

engine)

280x280x660 mm

dimensions


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A cycle starts with the pistonplunger

combination in BDC: most to the right. Theelectronic control opens the frequency control

valve. This increases the pressure in the

compressor cylinder, moving the piston-

plunger to the left. Simultaneously, air is

compressed in the combustion cylinder and oilis sucked into the power cylinder.

When the piston-plunger arrives in TDC fuel is

injected and ignites. The expanding gases will

force the piston plunger to move back to BDC.

Oil is pumped to the high pressure side.

The burned gases are replaced by fresh air

due to the loop scavenging process. In the BDC

the piston-plunger will wait until the

electronic control gives a new starting signal

to the frequency control valve.


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Efficiency-During tests, the free piston engine reached an

indicated efficiency of more than 50%.

Emissions-It was proven that the combination of a high

efficiency combined with low soot and low NOx emissions

is possible.

Power density-The Chiron has an net effective power of

approximately 17kW.Compared with a conventional

diesel engine and pump combination, the number of

parts of the Chiron is reduced to approximately 40%.


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Infinia is a well renowned company that utilizes

free piston technology in three types of machines.

Generators

Cryocoolers Infinias unique stirling design


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1-2: Adiabatic compression

in compressor cylinder

2-a: Adiabatic compression

a-b: Engine combustion

b-3: Adiabatic expansion or

power stroke in dieselcylinder

3-4: Mixing of m2 kg engine

exhaust and m2 kg bypass air

4-5: Adiabatic expansion in

turbine


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LP HP A simple design with high

controllability is the main strength of

the single piston design compared to

the other free-piston engineconfigurations.

The rebound device gives the

opportunity to accurately control the

amount of energy put into the

compression process and thereby

regulating the compression ratio andstroke length.


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LP

HP

Dual piston engine configuration

eliminates the need for a rebound

device, as the (at any time) working

piston provides the work to drive

the compression process in the othercylinder.

It has a simple and more compact

design with higher power to weight

ratio.

The control of piston motion, in

particular stroke length andcompression ratio, has proved

difficult.


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Combustion chamber

Piston synchronization

Bounce chamber

It was exclusively used in theearly free-piston engine designs

(1930-1960).

The perfectly balanced and

vibration- free design is the

exclusive feature of this design.

Due to elimination of cylinderhead, heat transfer losses are

also reduced allowing uniflow

scavenging giving better

efficiency.

The piston synchronization

mechanism and dual set of main

components makes it a bulky and

complicated design.


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Inward compression type

Outward compression type

The basic difference between them is that

inward types compress air during inwardmotion of the piston while the outward types

compress air during the outward motion of the

piston. Furthermore, inward type is simpler,

has less number of working parts and possessbetter accessibility for maintenance than

outward type.


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Two- stroke, since power stroke required

on every cycle.

Though performance gap is decliningbetween 2-stroke and 4-stroke engines

due to recent increase of interest in 2-

stroke engine.


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No motion control and no energy storage.

May lead to less or more compression ratios and

less time for scavenging.

Absence of crank mechanism andflywheel leads to :-


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Motion is controlled by sum of forces acting on

piston at any time.

Interaction of forces must be arranged in

acceptable limit of motion.

Due to bounce spring nature of combustionchamber and bounce chamber, appropriate load

must be used.

Measures to previous problems :-

< F


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System behaves as a spring-mass system and

have natural frequency given by

= K/m ; where K = F/x

therefore stroke length must be

appropriately chosen to match any of the

natural frequencies.


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No energy storage, as in flywheel, therefore

misfiring may be a problem if engine fails to

build up sufficient compression.

Though practically, misfiring has not been

mentioned in any of the reported

experiments.


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Load must be linear and provide efficient

energy conversion comparable to rotatingloads in conventional engines.

Load is directly connected to mover,

therefore has high mechanical requirements.

Load device may be subjected to heattransfer from engine cylinder.

Generally, Free Piston Engine loads are :-

1. Electric Generators

2. Hydraulic Pumps

3. Air Compressors


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Low frictional losses

Reduced manufacturing cost

Compactness

Low maintenance cost and increased lifetime


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High speed around TDC results in more

turbulence, better mixing of air-fuel and

better combustion.

Rapid expansion due to high piston speedresults in less NOx formation.

Variable compression ratio allows

optimization of combustion process.

Suitable for multi-fuel operation.


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Balancing is a problem but can be sorted out

using mechanical linkages between the

pistons.

Though, using mechanical linkages putconstraint on piston motion and also there is

danger of breaking of linkages at high

speeds.


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Effect of fuel Supply

Effect of Bounce Cylinder Pressure

Effect of Working Pressure


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Simple design with few moving parts reduces

the frictional losses

Compact and low maintenance costs

High power to weight ratio Possible operation on multiple fuels due to

variable compression ratio

Fuel air mixing is enhanced


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Poor fuel economy as specific fuel

consumption is high

Requires a certain quantity of fuel per stroke

that varies according to load causingminimum stability problems

Due to high supercharge rate of combustion

per cylinder volume is high

Reduction Gearing


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Early applicationsa) Widely used as submarine air compressor units

b) Suitable for power generation in mediumpower range

c) They have also been tried in ship propulsion ,road and rail traction

d) High speed centrifugal air compressors andwater pumps can be directly driven by it

e) A mixed gas steam cycle also offers the

possibility of improving the efficiency Modern applications

a) Hydraulic free piston engines

b) Free piston engine generators


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Automotive application is that studied by

most current free-piston engine developers.

The free-piston engine generator is a very

attractive candidate as a prime mover in

series hybrid vehicles or as a range extender

in plug-in hybrids.

It can provide high thermal efficiency

(including high part load efficiency), lowemissions, fuel flexibility, and high power to

weight ratio through a compact design and a

flexible engine layout.


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The piston engine can provide substantial advantages in this

respect, with

Extremely low friction: all frictional losses associated with the

crank system are eliminated and piston friction is reduced due to

no side forces acting on the piston

no load-carrying bearings, allowing operation at high compression

ratios; and

very high piston acceleration around top dead centre, reducing

the time spent in the high-temperature parts of the cycle and

thereby reducing heat transfer losses and emissions formation.


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AIR COMPRESSORS

The first successful application of the free-piston engine

concept was as air compressors. In these engines, air

compressor cylinders were coupled to the moving pistons,

often in a multi-stage configuration. Some of these engines

utilized the air remaining in the compressor cylinders to return

the piston, thereby eliminating the need for a rebound device.Free-piston air compressors were in use among others by the

German Navy, and had the advantages of high efficiency,

compactness and low noise and vibration.


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Besides advantages regarding efficiency,

the free piston compressor offers on-demand start and stop (since there is no

compression stroke in the engine side)

cool operation (given that the

combustion products are greatly dilutedwith air after expanding down below

atmospheric pressure)

quiet operation (given that there is noexhaust of high-pressure gasses)

simple


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efficiency is achieved by matching the dynamic

load of the compressor to the ideal adiabaticexpansion of the hot gas combustion products

The device proposed exploits this fact by

converting thermal energy into kinetic energy ofthe free piston, and then utilizes this stored

kinetic energy to compress and pump air on the

opposite side of the piston toward the end of

the stroke.


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After the success of the free-piston aircompressor, a number of industrial researchgroups started the development of free-pistongas generators. In these engines there is no loaddevice coupled to the engine itself, but the

power is extracted from an exhaust turbine.(The only load for the engine is thesupercharging of the inlet air.)

A number of free-piston gas generators weredeveloped, and such units were in widespread

use in large-scale applications such as stationaryand marine powerplants [3]. Attempts were madeto use free-piston gas generators for vehiclepropulsion (e.g. in gas turbine locomotives) butwithout success.
http://dictionary.sensagent.com/free-piston+engine/en-en/http://dictionary.sensagent.com/Gas_turbine_locomotive/en-en/http://dictionary.sensagent.com/Gas_turbine_locomotive/en-en/http://dictionary.sensagent.com/Gas_turbine_locomotive/en-en/http://dictionary.sensagent.com/free-piston+engine/en-en/


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Free-piston engines could be used togenerate electricity as efficiently as, and lessexpensively than, fuel cells.

It could be used to generate electricity as

efficiently as fuel cells yet cost less.Having a cheap and efficient way to generate

electricity is becoming more important asautomakers develop electric vehicles with

onboard generators for recharging thebattery pack and extending range. Suchvehicles, called series plug-in hybrids orextended-range electric vehicles


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Automakers such as GM, Lotus, and Volvo have

started to investigate the possibility of using

such engines in future vehicles.

To generate electricity, the pistons could be

equipped with rows of magnets that shuttle past

metal coils to create an electrical current.

The free-piston design can also allow the engine

to be instantly optimized for different fuels,

such as hydrogen, natural gas, ethanol, gasoline,

and diesel. Ideally, drivers could use whatever

fuel is cheap and readily available.


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Sound of the engines: the fast explosions are

very loud and will be difficult to muffle.

The biggest issue is control: it makes

necessary some sort of active controlmechanism to ensure that each cycle is the

same, variations could cause poor

performance and increased emissions.


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These engines are commonly of the single

piston type, with the hydraulic cylinder

acting as both load and rebound device using

a hydraulic control system. This gives the

unit high operational flexibility, and

excellent part load performance has been

reported for such engines .


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The Chironfree piston engine is an integratedcombination of an internal combustion engineand a hydraulic pump.

The core of this engine is a combustion piston

directly coupled to a hydraulic plunger. The piston is not connected to any mechanism

but is free to move within the limitations of thecylinders. In this way the energy of thecombustion process is almost directly converted

into hydraulic energy. Compared to a conventional combination of a

pump and a combustion engine, the number ofparts is reduced to approximately 40%.
http://www.innas.com/Chiron.htmlhttp://www.innas.com/Chiron.html


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The HyDrid is a hydraulic hybrid drive train forroad vehicles. In this new concept, the completemechanical transmission of a car is replaced by afull hydrostatic transmission, allowing energyrecuperation and an efficient operation.

The concept requires extremely efficienthydrostatic pumps, motors and transformers,which have been developed recently.

Simulation by the German Institute for FluidPower Drives and Controls (IFAS) at RWTH Aachen

University proved that an average fuelconsumption of 3.1 liter per 100 km (or 77 MPG)is possible for a mid-sized (1450 kg) passengercar.


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TWO CARS: SAME

WEIGHT, SAME SIZE,

SAME ENGINE,SAME TRACTION, SAME

PERFORMANCE


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This can be achieved with a series hydraulic

hybrid drivetrain, called the Hydrid, which

is developed by the Dutch company INNAS.

In this new concept, the complete

mechanical transmission of a car is replaced

by a full hydrostatic transmission, allowing

energy recuperation and an efficient engine

operation.

The concept requires extremely efficient

hydrostatic pumps, motors and transformers,

which have been developed recently.


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Engine control problem which is fully solved

only in single piston hydraulic engine

Influence of cycle to cycle variations in the

combustion process


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