GB2470630A

GB2470630A - Internal combustion engine with means to extract power from otherwise wasted heat

Info

Publication number: GB2470630A
Application number: GB1004703A
Authority: GB
Inventors: Richard Lloyd Leslie Daniel
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-04-18
Filing date: 2010-03-22
Publication date: 2010-12-01
Also published as: GB201006091D0; GB0906711D0; GB201004703D0; WO2010119246A1

Abstract

An additional valve 7 in the piston crown, or external to the cylinder, opens as the piston 5 approaches the end of the power stroke to permit the transfer of hot pressurized gases from the cylinder to the sump or another attached pressure chamber. The pressure differential then created when the exhaust valve 6 is opened to vent the exhaust gases to atmosphere drives the piston upwards during what would otherwise be the normal exhaust stroke in the conventional engine cycle. Towards the end of the exhaust stroke the additional valve 7 opens to depressurize the sump/pressure chamber ready for the next cycle. The piston-head valve 7 may be actuated via a cam mechanism 3 by an extension 2 on the small end of the connecting rod 1. A thermal buffer layer 4 may be provided to extract heat from gases passing into the sump/pressure chamber. An inert gas may be injected into the sump/pressure chamber to reduce the risk of explosion. Water may be injected into the cylinder after combustion to convert some heat into increased gas pressure. The engine may be of the four-stroke reciprocating or rotary piston type.

Description

IMPROVED INTERNAL COMBUSTION ENGINE

1. PREAMBLE The invention relates to the modification of an internal combustion engine, to incorporate a means of extracting power from the energy remaining in the extremely hot and/or pressurised gases present in the cylinder, following ignition! burn.

Historically, the industrial revolution was enormously accelerated by the invention of the first steam engine, which utilised only the partial vacuum produced by chilling steam in a cylinder, as the source of mechanical power. i.e. Power was obtained purely from atmospheric pressure. This was enormously wasteful and led to the eventual design of an engine utilising both the "expansion" pressure of the steam plus a separate condenser to extract the "contraction" pressure, without cooling the cylinder. This greatly increased efficiency in a manner that has not been significantly improved to this day. Reports exist of the same power output from an engine, using 66% less coal. In similar manner today, the combined cycle steam-cooled gas turbine returns reported efficiencies approximating 60%.

Conversely, the standard internal combustion engine still utilises only the explosive expansion of ignited gases, to provide propulsive power and fails to exploit the heat and/or pressure energy contained in the resulting hot! pressurised gases remaining in the cylinder following ignition! burn, Generally, this hot gas is merely dumped to atmosphere. This is a major factor in the current poor efficiency [approx. 30%] associated with the internal combustion engine. This fact led to the proposal to extract power from the hot! pressunsed gases to add to the propulsive power already being generated by the engine. It is recognised that some efforts have been made to achieve this by conversion of the 4-stroke cycle to a 6-stroke cycle, however current methods introduce massive changes to engine complexity, not the least of which is in altering valve operating characteristics to align with the longer cycle. Also, advanced proposals exist for introduction of additional [low pressure -hence larger diameter] cylinders within a multi cylinder engine, to exploit residual power in exhaust gases. Again, these demand total re-design of the generic 4-stroke engine and consequentially, also introduce major additional complexities and areas of technical uncertainty.

2. DESCRIPTION

According to the present invention, a generic internal combustion engine is modified by the introduction of a valve system in the piston head, or external to the cylinder, to permit transfer of hot! high pressure gases in the cylinder, following ignition! burn, to the sump, or another attached pressure chamber. The pressure differential then created, when the exhaust valve is opened to vent spent cylinder gases to atmosphere, drives the piston upward during what would otherwise be the normal exhaust [and! or another] stroke during the conventional engine cycle. Towards the end of this stroke, the valve[s] in the piston head, or external to the cylinder, again open, to de-pressurise the sump/ pressure chamber, and permit entrapped exhaust gases to be released to atmosphere. The sump/ pressure chamber will then attain atmospheric pressure, prior to the next cycle[s]. In its simplest form, this should basically require only modifications to the sump, breather tube, seals and gaskets, plus piston, connector-rod and sump for the piston-head valve arrangement; and exhaust system and/or exhaust valve operating cycle for the external valve arrangement, except in the case of "other pressure chamber" arrangements, which may require complete redesign of the engine. The "other pressure chamber" is intended to include an extended cylinder, forming a second sealed chamber below the conventional piston, the piston then being induced to operate in similar manner to that in a double acting steam engine. This would probably require power output to be extracted via a rhombic drive or similar mechanism in place of a conventional crank arrangement.

In order to minimise possibilities for unplanned ignition of unburned fuel contained in exhaust gases within the sump! pressure chamber, it is proposed that one, or a combination of the following systems, be adopted.

a. Introduction of a "Thermal Buffer" operating in similar fashion to the "Regenerator" in an external combustion [eg Stirling] engine, to extract heat from gases passing into the sump! pressure chamber, and return this heat to gases exhausting from the sump! pressure chamber.

b. Introduction of a buffer to permit pressure transfer from exhaust gases to be transferred to the sump! pressure chamber, but debar exhaust gases from entering the sump/ pressure chamber. This buffer may take the form of a flexible membrane or free-moving piston, within a chamber of suitable dimensions, introduced into the gas flow route between the i.c. engine cylinder and the sump! pressure chamber.

c. Introduction of a means of injecting inert gas [i.e. non-combustible e.g. C02] into the sum p1 pressure chamber at some point in the internal combustion engine cycle, to scourge! expel extant sump! pressure chamber gases [including air], and consequentially minimise! negate explosion hazard within the sump! pressure chamber due to any presence of unburned fuel. The inert gas may be injected at high or low pressure and may be sourced from post-catalytic converter exhaust gases, which largely constitute only CO2 and steam. Unwanted particulate content may be readily removed by existing filtration methodology. The sump breather tube would provide a suitable point for the

introduction of the inert gas.

Perceived benefits include, increased thermal efficiency; reduced fuel usage; reduced atmospheric pollution; reduced need for a flywheel to conserve energy between power strokes to drive ingestion, compression and exhaust strokes and smoother pulsed-power output. Engine dimensions, weight, and moving mass may all be reduced, as is the time required for the engine to reach best operating temperature, from a cold start.

In view of the high temperatures attained within the i.c. engine cylinder, post ignition! burn, it is intended that arrangements may be incorporated [eg introduction of additional injector[s] similar to the fuel injectors], to inject small quantities of water or other liquid! gas into the cylinder[s] at appropriate point[s] in the modified engine's cycle, to convert a proportion of this heat to increased gas pressure. This will provide possibilities for extraction of suitably pressurised gases over a greater range of points during the i.c. engine operating cycle. In addition, it will obviously result in cooling of the cylinder! contained gases, and may permit reduction or elimination of conventional external cooling arrangements [e.g. water jacket! pump! radiator! fan], with commensurate additional mass! moving mass! dimensional and thermal efficiency improvements. To obviate the need to store large volumes of water for injection during extended periods of engine operation, it is proposed that post-catalytic converter steam be condensed to provide a continuous supply during engine operation. This is achievable by use of conventional refrigeration! heat-pump techniques, the quickly available heat removed being available for cabin heating! de-mist! de-frost functions and!or reduction of time for the engine to reach best operating temperature, from a cold start. Note.

When applied to an extant multi-cylinder engine, it may be necessary to segment the sump/ pressure chamber into independently sealed chambers for each cylinder, or group[s] of cylinders. In addition, there may be implications for lubricating oil flow, and measures may be necessary to ensure that reversal of normal oil flow direction due to high.pressure in the sump/ pressure vessel, is eliminated. Although there is some change to the expulsion pattern of exhaust gases, these are deemed unlikely to cause any marked changes in the operation of attached turbocharger[s} since the total mass of gas ejected remains unchanged. In fact, the reduction in pressure pulse levels and addition of steam [additional mass] may prove beneficial in this respect.

3. EXAMPLE

A specific application, by modifications to a generic 4-stroke internal combustion engine will now be described by way of example, with reference to the accompanying drawings and diagrams.

The following example refers to the incorporation of the basic concept in a conventional single cylinder reciprocal 4-stroke piston engine, with a piston-head valve installed. Following ignition! burn, the piston head valve is opened by a lever-extension on the upper end [small end] of the connector rod. Post-burn gases are then diverted to the engine sump, as a source of power to drive/ assist the piston movement during the following exhaust stroke.

The figures depict a sectional view through a piston, cylinder and cylinder head. Although only one cylinder is depicted, the concept also applies to multi-cylinder arrangements.

Figure 1 of 6 Piston 5 is at the top-dead-centre position. Inlet valve 9 in cylinder head 8, is open at the start of the conventional ingestion stroke. Piston-head valve 7 is closed. The Connecting Rod [Con-Rod] 1 is vertical, hence the con-rod lever 2 is at the mid-point of its travel relative to the cam mechanism 3, as determined by the instantaneous crankshaft position.

A conventional ingestion of air! gases ensues.

Figure 2 of 6 Having completed a conventional ingestion stroke, the inlet valve 9 is now closed as the piston 4 has commenced to pass up the cylinder to produce a conventional compression stroke. The cam mechanism 3 has been moved by the Con-Rod lever 2, without opening the piston head valve 7.

Figure 3 of 6 Having completed a conventional compression stroke and fuel injection! ignition cycle, the piston 5 has commenced to move down the cylinder in a conventional power stroke. The cam assembly 3 has again been moved by the Con-Rod lever 2, without opening the piston head valve 7. [i.e. The cam mechanism 3 is being stepped through a cycle by the rocking movements of the connecting rod 1.] Figure 4 of 6 As the piston 5 approaches the end of a conventional power stroke, the cam mechanism 3 has again been moved by the Con-Rod lever 2 causing the Piston-head valve 7 to open momentarily. A small quantity of water is injected directly into the cylinder through an installed additional injector, similar to the fuel injector [Both not illustrated] This permits high pressure, high temperature gases, present at that point in the cycle, to enter and pressurise the sump This reduces the temperature, but not the pressure, of the gases in the sump, relative to the gases in the cylinder at this point in the cycle. The temperatures of the cylinder! piston and contained gases are reduced by extraction of heat in converting injected water to high pressure superheated steam. . Heat in the transferred gas is removed in passing through Thermal Buffer Layer 4, where a portion of this heat is retained.

Figure 5 of 6 Once the piston 5 nears the bottom of the cylinder, the continued oscillation of Con-Rod lever 2 causes the Piston-head valve 7 to close under the action of its closure spring and the cam mechanism 3. Exhaust valve 6 then opens to permit spent gases now remaining in the cylinder, to escape to atmosphere as in a conventional exhaust stroke. However, due to the high pressure retained in the sump the pressure differential between this and [approximately atmospheric] pressure on the upper side of the piston 5, forces the piston upwards, hence producing a second power stroke.

Figure 6 of 6 As the piston 5 approaches the top of the exhaust stroke, the Piston-head valve 7 is opened under the action of the cam mechanism 3, driven by continued oscillation of the Con-Rod lever 2. This permits de-pressurisation of the sump. As gases pass through the Piston-head valve 7, retained heat in the thermal buffer 4, is recovered and deposited to atmosphere through the conventional exhaust valve, which is still in the open position.

The four strokes then continue repetitively until the engine is stopped.

[i.e. Ingestion, Compression, IgnitionlPower, Exhaust/Power.]