GB2365922A

GB2365922A - I.c. engine with variable stroke and constant compression-ratio for use with alternative fuels

Info

Publication number: GB2365922A
Application number: GB0019779A
Authority: GB
Inventors: William May Stott
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-14
Filing date: 2000-08-14
Publication date: 2002-02-27
Also published as: GB0019779D0

Abstract

The engine has a variable stroke, constant compression-ratio mechanism, eg a z-crank. A method of operation and design is disclosed whereby the i.c. engine can continue to be a method of operation and design whereby the internal combustion engine can continue to be operated in a practical and economic manner, to achieve the legislative emission and conservation of diminishing supplies of fossilised fuel and materials now being required world wide by the policy makers, manufacturers, environmentalists and conservationists: - <SL> <LI>a) when petroleum fuelled to develop only the running power required with improvements in fuel economy and reductions in emissions<BR> b) with the use of an alternative fuel allow the ICE to operate with nearly zero emissions<BR> c) the alternative fuel can be produced by off peak times power sources that can be emission free and can be recycled<BR> d) allow minimal changes to vehicle and ICE design, manufacturing, servicing and operating knowledge with minimal retraining and testing of all those concerned with its continuing use. </SL>

Description

<Desc/Clms Page number 1> PATENT APPLICATION SPECIFICATION 1 Subject Reciprocating piston engine 2 Scope An operational method whereby the efficiency emissions and economy of the internal combustion engine ( ICE ) may be improved to meet future ecological and conservation requirements 3 Introduction 3.1 Background If the internal combustion engine is to compete and continue as a power source into the future it will be required to emit none pollutant exhaust emissions i.e. match the performance of all acceptable alternative motive power sources. At present the most probable acceptable alternative sources being hybrid petroleum/electric and electric traction, battery power for city use and fuel cell power for city/out of city use.

If we consider the present design of the petroleum fuelled internal combustion engine (PFICE ) to have nearly reached its limit in efficiency in its present form i.e. all improvements are only yielding small returns. Generally all work is at present being directed to emission control / economy and may be considered to be providing "elegant solutions to problems that should not be there to begin with" Any significant improvements will certainly require a more radical design approach.

The present design of ICE is generally determined by:- 1 maximum power / rpm - engine capacity - say approximately 2% usage 2 maximum compression ratio - full throttle operation - say approx 3% usage 3 part load - by throttling inlet charge - say approx 95% usage Items 1 and 2 produce maximum efficiency, and item 3 decreases this efficiency. This decrease becoming larger as the throttling increases.

Clearly throttling is an extremely inefficient method of engine operation, and is used for the majority of the engine running time.

The decrease in efficiency is caused by the lowering of the achieved compression ratio ( CR ) and the increased pumping losses.

The criteria for improvement is therefore to avoid throttling the inlet charge whilst still maintaining the compression ratio at a suitable high level.

4 Proposal In order to avoid throttling the inlet charge the engine must be run at the full power setting, or open throttle i.e. the engine design specification. To reduce this power to the level required by the vehicle to run in the lower power / speed ranges efficiently, the amount of inlet charge must be reduced. This can be achieved efficiently by reducing the engine capacity in a stepless manner i.e. piston stroke. Providing the C.R. can be maintained at the required figure, this is a very effective method as the engine can now operate at part load in a much improved Specific Fuel Consumption range ( SFC ) running and full power - see figure I - engine power requirement plotted against engine specific fuel consumption and figure 2 - constant speed and full throttle SFC With additional reductions in :a) piston and ring friction b) heat loss to the cylinder wall c) induction and pumping loads d) exhaust gas quantity as these items are approximately proportional to the piston stroke length.

Figure 3 shows the the approximate differences applying this data assuming the power output is proportional to the engine stroke.

However if a more realistic average speed range is considered say 30 to 70 mph the average improvement becomes 60.8% Again the present day engines being more efficient say 60 bhp / litre will require more throttling to reduce the power, but being higher geared will require more throttle. If we assume they cancel each other out the lower improvement average is probably more acceptable.

From figure I it can also be seen that the engine full stroke reserve power is retained for acceleration and hill climbing 4.1 Basic principle - e.g. using UK Patent Application GB 2 338 746 A - see figure 4 By fitting a axial moving and Tilting bearing on to a rotary shaft, a variable stroke Z-Crank mechanism is obtained - see figures. Axial movement of the bearing on the shaft, moves the piston axially in the cylinder, and tilts the piston arm. The piston stroke (ps) being the product of the tilt arm radial movement `z'times the ratio of the tilt arm length `wand the piston arm length `b'times two i.e. ps = `z' x `a' / `b' x 2 The C. R. adjustment being controlled by the ratio of the radial tilt to axial movement.. 4.2 Design components, see figures 6 and 7 1 # Engine shaft 2# Axial sliding pivot 3# Tilt bearing 4# Tilt / torque arm 5# Piston arm 6# Piston arm slide bearing - prevents rotation of 5# 7# Engine shaft fixed guide block 8# Axial power actuator ( or alternatively 10# ) 9# Piston 10# Control / power axial actuator rod ( or alternatively 8# )

4.3 Operating arrangement I axial movement of actuator bearing 2# by 8# ( or 10# ), produces two actions a) axial movement of the piston 94, in the cylinder b) annular movement of the tilt arm 4# , in the fixed guide block 2 guide path at the fixed guide block 7# , ratios the tilt arm 4# , axial to radial movement 3 radial movement of the tilt arm 4# , tilts bearing 3# , and piston arm 5# . The radial movement times the ratio of the tilt arm 4# length / piston arm 5# length, moves the piston one half stroke length.

4 one complete revolution of engine shaft 1# , and tilt bearing 3#, moves the piston one complete stroke length.

Note :- piston arm 5# , does not rotate.

5 the difference in the axial movement dimension initiated by action 1 , minus the resultant dimension produced by action 3 , allows the C. R. to be adjusted / maintained.

4.4 Crank Bearing Friction Conventional 4 cylinder engine - plain type - 3 or 5 main - 4 big end - I thrust - 4 little end = 12 or 14 Z-crank 4 cylinder engine - rolling type - 2 main - 2 crank - 1 stabilising - 1 thrust - 8 little end = 14 However the Z-crank bearings whilst being larger in size / diameter will be compensated by reduced bearing oil drag and oil pump power requirement. The increase in little end bearing numbers being compensated by the reduced angular movement required.

Note: - Figure 8 shows the increase in crank power degrees obtained by the Z-crank over the conventional crank and connecting rod arrangement 4.5 Piston and ring friction From figure 9 it can be seen that the piston and rings account for the largest percentage of engine friction. Modern data suggest the piston friction as 44% of the engine total with a ratio of 20% ring to 24% skirt.

In addition to the reduction in piston and piston ring total friction when operating at reduced strokes, further reductions can be achieved by: -.

a) Piston side thrust friction can be reduced significantly by use of a Z-crank type mechanism see figure 1 which allows the piston thrust to act in a direct line.

To reduce ring friction further, again a more radical solution is required which fortunately is also required for the engine valve gear b) Whilst ring friction levels may not be reduced, the total ring friction may be reduced by use of a cylinder sleeve valve where the sleeve movement is partly in phase with the piston movement, even if only at reduced speed, during the compression and power strokes i.e. the most highly loaded ring friction periods. see figure 10. The gain being obtained where the relative piston/ring to sleeve/cylinder movement is reduced

4.6 Valve operation Due to the variable stroke feature conventional poppet valve operation cannot be used at the minimum stroke end due to insufficient clearance for valve lift / overlap.

However sleeve valve design offers the following advantages a) as above 4.5 b) - piston and sleeve move partly in phase, at the most advantageous periods to reduce the overall piston/ring friction b) thermal load and possible distortion more evenly spread i.e. hot spots reduced c) valve actuation desmondromic d) valve drive torque constant i.e. no stab / fluctuating loads e) long service life, no high instantaneous valve cam or seat contact stresses f) produces very little mechanical noise - harmful emission! g) sleeve lubrication distribution good, due to axial and radial movement h) lubrication consumption reduced / avoided as engine intake manifold pressure will not be subjected to high depression (vacuum) i.e. no throttle valve required i) valve area limitations not as restricted as poppet valve layouts j) cylinder head shape free for optimum combustion i.e. ignition and injection layouts 4.7 Basic Concept Summary A mechanical arrangement whereby the stroke of a reciprocating piston engine may be varied in a stepless continueous manner from the maximum stroke to a zero figure, whilst allowing the piston location to be adjusted in the cylinder, thus maintaining the compression ratio at the optimum design figure.

The arrangement also enables the PFICE to operated more efficiently especially in the part load condition, which is generally employed for the maiority of the engine running time. The following part load advantages i.e. reduced stroke being :a) Specific Fuel Consumption improvement - conservation b) Constant Compression Ratio c) Piston and ring friction reduced d) Bearing friction reduction e) Valve service life improvement f) Heat loss to cylinder wall reduced g) Induction and exhaust pumping loads reduced h) Engine starting torque load reduced - minimum stroke to idle, minimum starter power and battery capacity i) Exhaust gas quantity reduced - emissions reduced - ecological k) Exhaust hydrocarbon (lubricating oil ) reduction - no high vacuum / depression in intake an old or cylinder m if

5 Alternative Concept In order that the ICE can compete and continue as a power source into the future, it will be required to produce zero harmful exhaust emissions i.e. match/exceed the performance of all alternative comparable power sources.

5.1 Background At present using fossil fuel we have emissions created by burning fuel and air say Fuel = 86%carbon and 14% hydrogen Air = 76% nitrogen and 21 % oxygen With perfect combustion

Hydrogen + Oxygen = water (steam) = not harmful emission (HE) However see 5.5-3b) Carbon + Oxygen = Carbon dioxide = HE Incomplete combustion = Carbon monoxide = HE = Hydrocarbons = HE High combustion temperature = Nitrogen oxide = HE = Sulphur dioxide = HE To design out these problems we must use an alternative fuel source The fuel should not contain carbon or hydrocarbons or the air source contain nitrogen.

A possible alternative to consider would be hydrogen and oxygen, which is already being considered for fuel cell electrical power production.

5.2 Alternative Technology Examining the alternative power technology being considered we have: a) Battery power with as yet, insufficient power density and high and frequent replacement costs. Together with high power consumption required for vehicle internal heating or cooling, power steering, power braking and lighting. This form of power source however is suitable for short distance journeys especially in town. It is also satisfactory for rapid (contract type hire) fully charged battery pallet type replacement or home/at work/parking recharging. The general vehicle on road running time percentage time scale being low e.g. Assume 100 miles / day = 36,500 miles / year Average overall speed say = 36.5 mph =1000 hours / year Percentage running time =1000 divided by 365 x 24 and x 100 = 11.42 say 12 This allows 88% (7333 hrs) or 33%(if only 8hours/day) available of the year available for onboard fuel regeneration! b) Fuel cell power this appears to require a large amount of onboard equipment and space as well as hydrogen and possible oxygen supply infrastructure.

5.3 Proposed Alternative Fuel Source If we consider that it is possible to produce the hydrogen and oxygen simultaneously by electrolysis using emission free generation power stations (primary fuel?) i.e. hydraulic, wind or fusion (eventually) absorbing surplus power at off peak times. The fuel generated (secondary fuel) may either be supplied direct, as a gas or generated onboard by electrolysis at home or work place, see 5.2 a) above. The fuel sources may therefore be considered acceptable, practical and feasible.

5.3 Proposed Alternative Engine Operation By direct timed injection into the cylinder of an ICE we have: Hydrogen + oxygen + ignition source? = Heat + steam = power Thus the ICE now becomes an IC steam engine (ICSE) As no air is required for combustion the engine cycle can now be a much improved two stroke as there is no need for: a) an intake valve or port b) an induction stroke c) a compression stroke d) Or complete exhaustion of the steam produced, as it does not effect the volumetric efficiency or retained an additional expansion media for the next cycle. Should any increase in quantity be required the exhaust back pressure may be increased.

These features will also increase the power to weight output by having double the number of power strokes compared with the normal covenentional four-stroke engine, improving the efficiencies. 5.4 Basic alternative design changes Whilst the above alternative fuel principle can be applied to the conventional ICE further increases in efficiencies can be gained by using the basic design principles described previously. The major difference in design being to the valve operation, porting (exhaust only) and frequency i.e. now two stroke operating cycle. 5.5 Further advantages In addition to those previously stated in 5.3 1) the engine overall design temperature may be lowered sufficient to allow self /reduced oil lubrication of the piston and rings 2) engine crankcase oil can be contaminated by water, which can be safely and readily removed / recycled 3) engine cooling system may be replaced with a exhaust steam condensing system enabling a) lowering the engine exhaust back pressure from the cylinder b) prevent any exhaust steam plume which may be a visibility hazard to following traffic c) allow the recycling of the exhaust condensate by retaining for onboard electrolysis, disposal or recycling d) provide a safe heat source for the conventional vehicle internal heating system 4) allow surplus exhaust energy for turbo electrical generation plus additional possible direct to turbo fuel supply/combustion to be used-reduced battery capacity / weight 5) reduce exhaust noise significantly - harmful emission!

5.6 Alternative Fuel Concept Summary In addition to those previously stated in 5.3 and 5.5 1) Allow the ICE in a modified form ICSE to achieve the practical legislation and economical requirements, which will ultimately be demanded i.e. nearly, zero em,asions including noise and fuel source economy 2) Fuel source renewable, can be recycled and capable of being produced by zero/ low harmful emission power sources 3) Fuel source may be considered common with fuel cell technology 4) Fuel network and system can be similar to that at present being employed by LPG 5) Fuel generation (future) may be possible with onboard / home based plug in electrolysis 6) Existing vehicle design and manufacturing technology and capacities can be retained 7) Minimal changes required to vehicle servicing, operator and existing driver know-how 8) Vehicle power train sizing and layouts can be similar to existing conventional systems 9) Vehicle internal space retained 10) Exhaust energy may be used for vehicle internal heating 11) Fuel supply protection enhance by use of pressurised cylinders i.e. strong construction not thin steel or plastic shells which also allows rapid cylinder recharging/refuelling if required 12) Engine and vehicle development can still progress along with petroleum fuelled vehicles 13) As the H and 0 will be required to be stored at pressure for transportation and storage this feature may also enable the vehicle onboard fuel to be self pressurised direct injected into the engine 14) No carbon to contaminate exhaust or engine oil thus oil and filter life may be prolonged indefinitely and further pollution sources avoided.

15) Water contamination of engine oil easily removable, disposable or recycled 16) Engine lubricating oil engine containment from exhaust improved by positive cylinder and exhaust pressures 17) Engine design may allow starting by self pressurised electronic controlled (timing adjustable) direct fuel injection / combustion i.e. no starter motor required 18) Gearbox the number of forward ratios may be reduced as maximum torque available at zero RPM

Claims

Claims A practical and economic overall method whereby the ICE can continue to provide an acceptable solution to the present ever increasing transportation legislative emission reduction requirements and the diminishing supply of non renewable fossil fuel sources now being required by the policy makers, environmentalists and conservationists by: a) Altering the conventional fixed stroke petroleum fuelled ICE to a variable stroke and constant CR with improvements in fuel economy and reductions in emission b) By the use of an alternative fuel(s) allowing the ICE to become nearly totally emission free c) The fuel(s) can be produced at off peak times by emission free power sources and is readily renewable/ recycled d) Allowing minimal changes to the present vehicle and ICE design, manufacturing, servicing / testing, operating knowledge and equipment (including vehicle drivers)