GB2114655A - Heating i.c. engine intake air - Google Patents

Abstract

Exhaust gas flows between pipes 5 and 6 through an exchanger 3 to heat air flowing from an air filter 4 to a diesel engine intake manifold 2. A bimetal thermostat 12 positions a throttle valve 17 which controls the proportions of the exhaust gas flowing through the exchanger 3 and over a finned heat storage block 10 to the outlet pipe 6a. A swirl device (11A 11B, Fig. 3A) is provided in the exhaust passage at the entry to the exchanger 3. <IMAGE>

Description

SPECIFICATION Improvements in or relating to methods of operating internal combustion engines The present invention relates to adjuncts to internal combustion engines, particularly those designed to improve the efficiency thereof, and is more especially concerned with internal combustion engines operating with self-ignition in mechanically-propelled vehicles.The worst feature of such engines, in their present state of development, is the extremely high overall compression ratios caused by the increasing use of exhaust-driven superchargers, and since it is this ratio which largely governs both the deadliness of the exhaust-borne particulates, and the overall cost of running the engine - i.e. fuel savings resulting from the use of said superchargers, minus any increases in first cost and maintenance charges due to the greatly-increased stresses - it is obviously in the interest of all - users and public alike - that this practice should be stopped and replaced by a more sensible way of obtaining fuel savings.Therefore the following is suggested as a much more suitable way of increasing the power obtainable from a given input of fuel and at the same time avoiding any increase whatever in the stresses developed within the engine for a given duty. Whereas with the exhaust-driven supercharger some of the pressure remaining in the exhaust gases is used to vastly increase the stresses within the engine for a small improvement in efficiency, it is now proposed to use some of the heat energy also remaining in those gases to develop a much greater increase in power from a given fuel input without any increase at all in the internal stresses.

In order to achieve this a heat exchanger is provided between the exhaust gas and the air intake of the engine concerned. This heat exchanger is of suitable capacity and type to exchange sufficient heat to at least double the volume occupied by a given weight of intake air under certain conditions of running.

When the engine is working hard, only a very little heat is absorbed by the intake air, since this has to be near its maximum weight in order to burn near the maximum amount of fuel. But when the engine is working under moderate or light load, as it is in vehicle use for much the greater proportion of the total time, the intake air is absorbing a proportionately greater amount of heat, and the weight of air aspirated by each cylinder per revolution is correspondingly reduced.

We thereby obtain an approximately constant fuel/air mixture for all conditions of load, ensuring (a) the readiest possible ignition with correspondingly reduced particulate formation (b) a longer expansion stroke with lower exhaust pressure at its end, and (c) that the same amount of fuel consumed will produce considerably more power output.

In one embodiment of the invention the inlet manifold of the engine is arranged so that it draws air through the elenents of a heat exchanger, on its way from the air filter. The exhaust manifold of the engine can pass exhaust gases either direct to the exhaust outlet, or by way of the outer casing of said heat exchanger, giving up a portion of the heat contained therein to the air passing within the heat exchanger elements, on their way to the exhaust outlet. The proportion of the gases taking each of these paths is determined by a thermostatically controlled valve which may, for example, be arranged to shut off or progressively to open the direct passage to exhaust outlet according to the temperature of the said exhaust gases on reaching this valve --the alternative way via the heat exchanger remaining fully operf at all times.

The action will now be described by reference to the diagrams on Sheet 1 and Sheet 2, the numbers now used to distinguish the various components being those on said diagrams, viz:- On leaving the engine 1 all the exhaust gases pass to the thermostatically-controlled valve 7 directly from exhaust manifold 5. Assuming now that the engine is under a relatively light load at the time, with correspondingly low demand for power output, and low temperature of the exhaust gases, the valve 7 will be closed or nearly so, and the bulk of the exhaust gases will pass to outlet 6 by way of pipes 8 and 9 and the casing of heat exchanger 3. If, now the load on the engine is increased, and with it the fuel input, the temperature of the gases reaching valve 7 rises, causing said valve to open progressively, diverting more and more of the exhaust gas direct to outlet 6.

In a preferred embodiment of the invention, advantage is taken of the fact that a comparatively large piece of material resistant to high temperatures and of a relatively high specific heat - such as cast iron - will absorb a considerable quantity of heat, by arranging to pass a part of the exhaust gas over the said heat storage material, which is preferably finned or otherwise shaped on the outside for maximum rate of heat absorption. At the same time, inlet air after passing through the heat exchanger elements, continues through the hollow interior of said heat storage material before passing to the engine's inlet manifold.

Thus - when according to the previous embodiment the engine would be discharging all or nearly all of its exhaust gases direct to atmosphere -- and at the same time the gases would be at their hottest - a considerable amount of heat would now be taken up, and stored for future use when the exhaust gases were themselves at lower temperature, while the inlet aire required more heat to be abstracted by it for optimum combustion and efficiency.

Means are provided whereby, in order still further to increase efficiency, the exhaust gases after leaving the engine may be given a degree of violent turbulence by passing rhrough a vortex device on their way to the heat exchanger-heat storage complex. In the case of a static type of heat exchanger, such as is specified for the reasons set out below, this turbulence will greatly increase the rate at which heat is imparted through its elements into the cold air flowing within them.The combined effects of heat storage, and turbulence of the incoming exhaust gases on entering the heat exchanger, are intended to allow a compact but static type of heat exchanger to do all that is required in supplying heat to the inlet air at all times, in accordance with the engine's needs for optimum functioning in varying conditions of load, thus enabling a type of heat exchanger which does not suffer from the disadvantages of the regenerative type for this purpose, to be used.

The said disadvantages of the regenerative type of heat exchanger, when used for such a purpose as outlined here, are (a) dilution of the inlet air by exhaust gases and particulates carried through by the moving element from the portion of the heat exchanger occupied by said exhaust gases, to the portion occupied by inlet air (b) the requirement of a power source to operate the heat exchanger.

This preferred embodiment of the invention is shown in Figures 3, 3A and 4 on Sheet 3 of the diagrams herewith, in which Figure 3 is a sectional view of the heat exchanger-heat storage complex, Figure 3A is a cross-sectional view and end view of a suitable form of vortex device, and Figure 4 a perspective view of the heat exchanger-heat storage complex showing its manner of connection to the engine in a convenient way.The numbers on said diagrams refer to the various parts and components as follow viz:- 1 - diesel engine, inlet manifold, 5 exhaust manifold, 3 - heat exchanger, 4 - air filter, 6, 6A - exhaust outlets to atmosphere, 1 0 - heat storage block, 1 - vortex device, having curved vanes 1 A and solid central core 11 B, 1 2 - thermostat, whose moving element may be connected directly or indirectly to butterfly valve 17, 13/1 3A - internal baffles within the heat exchanger, 14 - passage connecting exhaust-gas-occupied portions of heat exchanger 3 and heat storage chamber 15, 1 6 - bypass connection enabling inlet air or a portion thereof to avoid passing through heat exchanger-heat storage complex.

The action is as follows: Air enters through air filter 4 and passes through the tube-elements of heat exchanger 3, thence through the central bore of the heat storage block 10 and thence through a pipe-connection to engine's air-inlet manifold 2.

Exhaust gas leaves engine's exhaust-manifold 5 and passes to the vortex-device 11, there having turbulence imparted to it before entering the outer casing of heat exchanger 3 and passing over thermostat 12 (this latter may take the form of a bimetal strip) on its way into the nest of tubes in contact with their exteriors, or alternatively by way of passage 14 into heat-storage chamber 1 5. The first-mentioned portion of exhaust gas passes straight across the tubes in a direction normal to them, then is forced by baffle 1 3 to re-pass across them, and again by baffle 1 3A to make a further re-pass, before leaving by way of exhaust outlet 6.

The second-mentioned portion of exhaust gas imparts heat to storage block 10 thus raising its temperature, before leaving by way of outlet 6A.

Summarising, with the preferred embodiment the volume of preheated air will be maintained at its maximum in relation to its weight while the load is light by withdrawing heat from heat exchanger and/or heat storage block, giving an optimum mixture for instant ignition and good combustion combined with maximum expansion stroke efficiency. At the same time exhaust pressure to atmosphere will be at its lowest possible. Only when the load on the engine demands it will something approaching the more normal relatively high exhaust pressure apply, and even then heat, and pressure, of exhaust gases will still be being reduced by the heat storage arrangements.

Thus the usual expensive and extensive silencing arrangements customary with these engines may not be considered so necessary, with further reduction in back-pressure and increased engine efficiency.

Claims (6)

1. Means whereby the exhaust of an internal combustion engine is used to heat and expand the incoming air for use by the said engine.

2. Means whereby the amount or proportion of the total exhaust so used is regulated according to (a) the amount of load being overcome by the said engine, and (b) the amountsof fuel being injected into the cylinders of the said engine per revolution of its crankshaft.

3. Means whereby heat may be extracted from any part of the said exhaust not being used directly as above, and stored temporarily in order that it may be withdrawn and added to that already in the incoming air if and when conditions require it.

4. Means as described above whereby the efficiency of the said engine may be increased due to the amount of incoming air being increased in volume by virtue of the heat passed to it, and thus the weight of the said air entering the cylinders per charge may be decreased, in order that the weight of air may more closely approximate the amount needed by the weight of fuel being injected into the cylinders per charge at the time, in order to provide for the most efficient combustion possible.

5. Means as described above whereby the temperature of the air charge at the moment of injection of fuel into the cylinders may be as high as possible thus ensuring quicker and more complete combustion as well as greater efficiency.

6. Means as described above whereby the particles of fuel as they are injected into the cylinders may combine with air molecules and combustion take place as rapidly as possible -- in order that the minimum amount of fuel particles shall be left over, and available to be coagulated into carcinogenic particulates by the pressure and temperature conditions obtaining within the engine cylinders -- and thus be thrown out into the atmosphere with the engine's exhaust.