GB2101293A

GB2101293A - Cooling system for IC engines

Info

Publication number: GB2101293A
Application number: GB08213281A
Authority: GB
Inventors: Rolf Bernhage; Tommy Bjorkovist
Original assignee: NOHAB DIESEL AB
Current assignee: NOHAB DIESEL AB
Priority date: 1981-05-08
Filing date: 1982-05-07
Publication date: 1983-01-12
Also published as: SE425514B; GB2101293B; NO821519L; DE3214855A1; DK153238C; DK206382A; NO156732C; DK153238B; DE3214855C2; NO156732B

Abstract

A process and cooling system are described for regulating the temperature in a water cooling system for a compressor-charged I.C. engine with an air intercooler (9) for a charge of air. The regulation is carried out by the aid of three temperature regulators (T1, T2 and T3) so interconnected with by-pass pipes (7, 11 and 16) that the charge of air of the engine is automatically preheated when the engine is idling and intensely cooled when the load on the engine is high. The adaptation of the cooling system to a multiple engine arrangement is also described. <IMAGE>

Description

SPECIFICATION Cooling system This invention relates to a process for attaining an inverse temperature regulation of a fresh water cooling system for a compressor-charged l.C.

engine provided with an inter-cooler for a charge of air. The invention also relates to a water cooling system for a compressor-charged I.C.

engine, and in a multiple engine arrangement, is concerned with connecting the water cooling system of the cooperating I.C. engines with each other without changing the thermal qualities of the cooling system of each engine in a nondesired direction.

The term "an inverse temperature regulation" means that the actual cooling of the cooling water flowing through the system is reversed when compared with the load on the engine.

With the present cooling system, a strong preheating of the charge of air is automatically attained when the load on the engine is low and an intense cooling of the charge of air is attained when the load on the engine is high, while surplus heat in the cooling water leaving the engine is collected at a certain point where it is available for use for other purposes, this use being facilitated by the fact that the cooling water leaving the engine is kept at a comparatively high and constant temperature independent of the load on the engine.

The requirement to be able to use heavy bodied oils as fuels for diesel engines even under arctic conditions has made it desirable to preheat the charge of air at low loads on the engine. The preheating will improve the ignition of the heavy bodied oils and it will also decrease the fuel consumption when the load on the engine is low, as the heat delivered to the charge air through the cooling water once more will take part in the combustion.

The compressor for charging the l.C. engine, usually a turbo-compressor, will heat the charge of air when the load on the engine is high. It is thus necessary to chill said air when the load on the engine is high. This can be effected in the present cooling system.

A water cooling system for a compressor charged I.C, engine, preferably a medium speed diesel engine, is described in the specification of Swedish Patent No. 78.10997-2 (German Patent Application No. P 29 53 216.9). Said cooling system includes, apart from the cooling jacket of the engine a fresh water cooler and a heat exchanger for intercooling the charge of air.

The cooling system described in this Specification may be considered to be divided into three interconnected temperature circuits consisting of a high temperature circuit, including the cooling jackets of the engine, a circulating pump, flow adjustment devices and a de-airing, expansion, and pressure-maintaining tank, a low temperature circuit including primarily an air inter-cooler and a heat exchanger circuit including a water cooler.

The streams of cooling water and their temperatures in said three temperature circuits are regulated with the aid of two temperature regulators in the form of thermostatic valves arranged at certain crossing points between the different temperature circuits.

The present invention relates to a considerable improvement of this previously described system.

By adding a third temperature regulator and completing the system with new by-pass possibilities, it has been possible to achieve several important advantages when compared with the previously described system without losing any of the good qualities of the system.

Accordingly, one aspect of the present invention provides a process for regulating the temperature in a water cooling system for a compressor-charged l.C. engine provided with an air intercooler for the charge of air and a water cooler for cooling water, wherein the temperature in each of three different temperature circuits into which the cooling system is divided by three, three-branched temperature regulators, is regulated by an associated temperature regulator by controlling the amount of water by-passing the regulator and the amount of water mixed in from an adjacent temperature circuit, and wherein the first of the three temperature regulators is so arranged that it mixes hot water, which had just left cooling jackets of the engine, with the water which is delivered to said cooling jackets in such an amount that the temperature of the resulting cooling water delivered to the engine is never lower than a certain predetermined temperature, the second of said temperature regulators is so arranged that it directs the main part of the cooling water to by-pass the water cooler as long as the temperature of the cooling water is lower than a certain predetermined temperature which is lower than the normal temperature of the cooling water leaving the cooling jackets when the engine is run at an average load, and the third of said temperature regulators is so arranged that it directs the cooling water to by-pass the water cooler in an amount sufficient to avoid overcooling of the cooling water delivered to the air intercooler for the charge of air.

According to another aspect of the present invention there is provided a water cooling system for a compressor-charged I.C. engine, wherein the system includes inter-connected high temperature, low temperature and heat exchange circuits, said high temperature circuit including cooling jackets of the engine, the compressor and means for effecting flow of cooling water through the engine, said low temperature circuit including an air intercooler for a charge of air and the heat exchange circuit including a water cooler and wherein the inlet of the high temperature circuit is connected to a first branch of the three-way temperature regulator the second branch of which is connected to the outlet of the low temperature circuit and the third branch of which is connected via a by-pass pipe to the outlet of said high temperature circuit at a first branched point downstream of the cooling jackets, the temperature regulation of said first temperature regulator being so chosen that the water delivered to the cooling jackets is maintained at a predetermined temperature which is independent of the load on the engine and which temperature is achieved by mixing water taken directly from the outlet of the engine via said bypass pipe with water from the low temperature circuit which has passed through the air intercooler while a second three-way temperature regulator has its inlet connected to the outlet of the high temperature circuit at said first branching point after the engine and has its second and third branches connected respectively to the low temperature circuit before the air intercooler and to the inlet of the heat exchange circuit, the regulating temperature of said second temperature regulator being so chosen that the main part of the cooling water flows through the heat exchanging circuit as long as the temperature of the cooling water at the outlet of the cooling jackets does not exceed a predetermined temperature, which is less than the temperature of the cooling water leaving the cooling jackets with an average load on the engine, said second temperature regulator being in unrestricted connection with the heat exchanging circuit as long as the outlet temperature of the cooling water leaving the engine is higher than said predetermined temperature, said heat exchanging circuit including said water cooler and a by-pass pipe connected to one of the branches of a three-way temperature regulator of which the other two branches are connected to the inlet of the low temperature circuit and the outlet of the water cooler respectively, the regulating temperature of said third temperature regulator being so chosen that the temperature of the cooling water delivered to the low temperature circuit is never less than a predetermined temperature.

The advantages of the present system include the already mentioned preheating of the charge of air when the load on the engine is low and the possibility of using the surplus heat when the load on the engine is high. A comparison between the thermal qualities of the two systems is easily made with the aid of Figure 3 of the above mentioned Patent Specification and Figure 3 of the accompanying drawings and the subsequent description. These Figures have intentionally been designed to simplify a direct comparison between the most important thermal qualities of the two cooling systems. The advantages of the present cooling system will be quite clear after such a comparison.Another important aspect is that the risk of corrosion produced by e.g. the condensation of water on the neck of the valves of the engine is considerably reduced by the fact that the cooling water is given a higher temperature especially when the load on the engine is low. This higher cooling water temperature also simplifies the use of the surplus heat.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings which illustrate diagrammatically any by way of example embodiments thereof and in which: Figure 1 is a diagram of a cooling system for an l.C. engine, Figure 2 is a diagram of a cooling system for a multiple l.C. engine arrangement, and Figures 3 and 4 are graphical representation of relevant data for an engine and its cooling system.

Referring now to Figure 1 of the drawings, there is shown an l.C. engine and its cooling system, with cooling jackets of the engine and the turbo charger being shown as a single unit 1. This unit 1 is an integral part of a high temperature circuit which also includes an inlet pipe 2, a fresh water pump 3, an outlet pipe 4, a flow adjustment device 5 and an expansion, de-airing and pressure maintaining tank 6 which is provided with a pressure-maintaining connection 6a. The total flow of water through the cooling jackets of the engine and the turbo charger is controlled by the capacity of the fresh water pump 3 and the flow adjustment device 5. The outlet and inlet pipes 2 and 4 of said high temperature circuit are connected with each other by a by-pass connection 7.A three way temperature regulator T, in the form of a thermostatic valve is arranged at the branching point between said connection 7 and the inlet pipe 2. Two branches of the temperature regulator T, are connected to the inlet pipe 2 and to the connection 7 respectively, while the third branch of said temperature regulatorT, is connected with an intake 8 of a low temperature circuit. A heat exchanger 9 for adjusting the temperature of a charge of air is also connected within said intake. The low temperature circuit is connected to the high temperature circuit via an outlet 10 leading from the branching point between the outlet 4a of the latter and the by-pass pipe 7.The outlet and the inlet of the low temperature circuit are connected with each other by a by-pass pipe 1 A threeway temperature regulator T2 is arranged at the branching point between this by-pass and the outlet of the low temperature circuit, and the third branch of this temperature regulator T2 is connected with the inlet 12 of a heat exchanging circuit. The inlet 12 is connected with a fresh water cooler 1 5 either through a heat exchanger 13 for the use of surplus heat or through a separately regulated by-pass valve 1 4. A by-pass pipe 1 6 also connects the inlet of the heat exchanger 1 5 with its outlet 17.

A three way temperature regulator T3 is arranged at the branching point between the bypass pipe 16 and the outlet 17 from the heat exchanger 1 5. The third branch of the temperature regulator T3 which is the outlet of the regulator, is connected to the branching point between the inlet 8 of the low temperature circuit and the by-pass pipe 11 by an outlet 1 8. Figure 1 shows an arrangement in which the high and the low temperature circuits and their auxiliary systems are assembled directly on the engine while the more spacious parts of the heat exchanging circuits are arranged outside the engine. The engine and the different parts mounted thereon being shown inside a block marked M.

A cold water pipe 1 9 and a cold water pump 20 for cooling the water in fresh water cooler 1 5 are also shown in Figure 1. It will also be seen from Figure 1 that the cooler 1 5 comprises three modules, two modules 1 5a and 1 Sb of the cooler 1 5 being used for the fresh water cooling while the third module 1 sic is used for cooling the lubricating oil. The circuit for the flow of lubricating oil through the cooler 1 sic is designated 0. The circuit 0 includes a temperature regulator To for the regulation of the temperature in the circuit but this regulator To does not form part of the present invention and will therefore not be discussed in further detail.The complete cooler with its different parts is shown inside a block identified with dot-dashed lines and designated K.

A certain amount of cooling water is always flowing through the different by-pass tubes by way of certain side openings through the temperature regulators T1, T2 and T3.

The temperature to which the thermostatic valves of the temperature regulators are regulated are designated t1, t2, and t3 respectively, as indicated in Figure 1 by appropriate control elements t1-t3, there being also a control element to for the temperature regulator T,.

The temperature regulator T1 is responsible for ensuring that the temperature of the cooling water delivered to the engine is substantially independent of the load on the engine.

The regulating temperature and the characteristic of the temperature regulator T2 are chosen so that the main regulation of the jacket cooling and the intermediate cooling of the charge of air are taken over by this regulator when the load on the engine decreases.

That means that the -main part of the cooling water circulating through the system via the bypass line 11 will go back to the low temperature circuit without passing the heat exchanger, when the load on the -engine is so low that the temperature of the cooling water coming from the engine decreases the regulating temperature T2.

This will give an effective preheating of the charge of air.

The regulating temperature t3 of the temperature regulator T3 is so chosen than overcooling of the cooling water delivered to the heat exchanger 1 5 via the temperature regulator T2 cannot occur. Then the load on the engine is normal, the temperature regulator T2 will be kept completely open while the control of the system is taken over by a cooperation between the temperature regulators T, and T3.

As an example, the regulating temperature for the temperature regulators shown in Figure 1 are t1=66*3 CC, t2=7 1 +3 C and t3=38+3 C. These regulating temperatures have proved'to offer a particularly advantagequs temperature distribution in the cooling system for medi-um speed diesel engines which are fueled with heavy bodied oils and which are at least partly used under arctic conditions.

In the system shown in Figure 1 , these regulating temperatures will give an increase of the temperature of the cooling water over the engine of approximately 100C when there is a normal load on the engine.

When the engine is idling, 95% of the cooling water which is circulating through the system will by-pass the heat exchanging circuit through the temperature regulator T2. When the load on the engine is maximum and the cooling jackets of the engine receives water at a temperature controlled to about 660C through the regulatorT1 and delivers water at a temperature of about 760C to the regulator T2, the latter having a regulating temperature of 71 0C will be kept open.

Substantially 75% of the cooling water circulated through the system will thus pass through the heat exchange 1 5 while the temperature regulator T, will allow about 25% to pass via the by-pass tube 7. When the load on the engine is neither high nor low, the regulators T, and T3 will cooperate while the regulator T2 is more or less wide open and prepared to take over the main regulating function when the load on the engine decreases to zero or a very low value.

Due to the arrangement of the valve 14 and the heat exchanger 13, the surplus heat in the cooling water is always available for use for other purposes.

A combined de-airing expansion and pressuremaintaining tank is described in the specification of the above Swedish Patent No.78.10997-2.

Such a tank is also used for a single system according to the present invention, the tank having a de-airing chamber above a pressure and expansion chamber.

Referring to Figure 2 of the drawings, there is shown a multiple engine system according to the invention in which the high and low temperature circuits mounted on each engine are kept unchanged while the heat exchange circuits of all the engines are connected to a single circuit regulated by a single temperature regulatorT3,. It has also been discovered that it is suitable to connect all de-airing, expansion and pressuremaintaining tanks to a single circuit. The de-airing is done in the same way as in a single engine system but the pressure-maintenance and the expansion is taken over by a joint expansion tank 35. When compared with the pressuremaintaining and expansion tank described in the above mentioned Swedish Specification the following changes had to be carried out at each of the engines in such a multiple engine system.

Water level alarms, water level indication tubes and pressure caps are dispensed with and the upper and lower chambers of each tank are filled with water, while the top openings of the lower chambers, which are closed by the pressure caps in single engine systems, are connected to a central expansion tank. A small pressure of difference between the upper and the lower chambers will give an improved de-airing effect. A small flow of water through the system will continually transport separated gas to the deairing chamber 33 of the central expansion tank 35.

In the multiple engine system shown in Figure 2, the different engines are designated M1-M4.

Parts of which have already been described with reference to Figure 1 have the same reference numerals. Cooling water from the different engines M1-M4 is delivered to the heatexchange circuit through pipes 21-24. The heat exchange circuit adapted for a multiple engine system also includes a heat-exchanger 25 for the use of surplus heat, a fresh water cooler 26, a thermostatic valve T3, with a by-pass pipe 27, connection pipes 29-31 to the different low temperature circuits on each engine and a return pipe 32 through which surplus water can circulate without passing through the engines. The latter is an essential feature especially when one or several of the engines in said circuit are shut off. A circulating pump 36 is also included in the heat exchange circuit of the multiple engine system.

The different engines are also provided with separate oil coolers.

Pressure maintaining and expansion pipes are arranged from the different de-airing tanks 6 to the joint de-airing tank 33 via the expansion tank 35.

The latter is also provided with a pressure maintaining pipe 34.

Current data for a relevant one engine system according to the invention are given on Figures 3 and 4.

Referring to Figure 3, there are shown plotted against the engine load expressed as a percentage of full load various parameters of the system. Starting from the top of Figure 3 there are plotted firstly the effective mean pressure, secondly the rate of flow in kg/sec. and the temperature of the cooling water flowing through the jacket. Thirdly the rates of flow in kg/sec. of water and air through the heat exchanger and their temperatures, and fourthly the rate of flow of water through the engine and water temperature for the fresh water cooling as well as the total amount of heat available for recovery.

Figure 4 shows the control of the temperature of the charge of air as a plot of temperature against load on the engine.

Claims

1. A process for regulating the temperature in a water cooling system for a compressor-charged l.C. engine provided with an air intercooler for a charge of air and a water cooler for cooling water, wherein the temperature in each of three different temperature circuits into which the cooling system is divided by three, three-branched temperature regulators, is regulated by an associated temperature regulator by controlling the amount of water by-passing the regulator and the amount of water mixed in from an adjacent temperature circuit, and wherein the first of the three temperature regulators is so arranged that it mixes hot water, which has just left cooling jackets of the engine, with the water which is delivered to said cooling jackets in such an amount that the temperature of the resulting cooling water delivered to the engine is never lower than a certain predetermined temperature, the second of said temperature regulators is so arranged that it directs the main part of the cooling water to by-pass the water cooler as long as the temperature of the cooling water is lower than a certain predetermined temperature which is lower than the normal temperature of the cooling water leaving the cooling jackets when the engine is run at an average load, and the third of said temperature regulators is so arranged that it directs the cooling water to by-pass the water cooler in an amount sufficient to avoid overcooling of the cooling water delivered to the air intercooler for the charge of air.

2. A water cooling system for a compressorcharged l.C. engine, wherein the system includes interconnected high temperature, low temperature and heat exchange circuits, said high temperature circuit including cooling jackets of the engine, the compressor and means for effecting flow of cooling water through the engine, said low temperature circuit including an air intercooler for a charge of air and the heat exchange circuit including a water cooler and wherein the inlet of the high temperature circuit is connected to a first branch of a three-way temperature regulator the second branch of which is connected to the outlet of the low temperature circuit and the third branch of which is connected via a by-pass pipe to the outlet of said high temperature circuit at a first branching point downstream of the cooling jackets, the temperature regulation of said first temperature regulator being so chosen that the water delivered to the cooling jackets is maintained at a predetermined temperature which is independent of the load on the engine and which temperature is achieved by mixing water taken directly from the outlet of the engine via said by-pass pipe with water from the low temperature circuit which has passed through the air inter cooler, while the second three-way temperature regulator has its inlet connected to the outlet of the high temperature circuit at said first branched point after the engine and has its second and third branches connected respectively to the low temperature circuit before the air intercooler and to the inlet of the heat exchange circuit, the regulating temperature of said second temperature regulator being so chosen that the main part of the cooling water flows through the heat exchanging circuit as long as the temperature of the cooling water at the outlet of the cooling jackets does not exceed a predetermined temperature, which is less than the temperature of the cooling water leaving the cooling jackets with an average load on the engine, said second temperature regulator being in unrestricted connection with the heat exchanging circuit as long as the outlet temperature of the cooling water leaving the engine is higher than said predetermined temperature, said heat exchanging circuit including said water cooler and a by-pass pipe connected to one of the branches of a three-way temperature regulator of which the other two branches are connected to the inlet of the low temperature circuit and the outlet of the water cooler respectively, the regulating temperature of said third temperature regulator being so chosen that the temperature of the cooling water delivered to the low temperature circuit is never less than a predetermined temperature.

3. A water cooling system as claimed in Claim 2, wherein the heat exchange circuit is completed with a device for using excess heat on the cooling water and wherein said device is provided with a by-pass pipe and regulating valve.

4. A water cooling system as claimed in Claim 2 or 3, wherein the temperature regulators are set so that the regulating temperatures are respectively 66+30C, 71+30C and 38+30C.

5. A water cooling system as claimed in any one of claims 2 to 4, wherein the high and low temperature circuits including the air intercooler and the first and the second temperature regulators are mounted on the engine while the heat exchange circuit and the water cooler is mounted outside the engine.

6. A water cooling system as claimed in Claim 5 for a multiple engine arrangement, wherein each engine in the arrangement has an associated high temperature circuit and low temperature circuit, and wherein the all heat exchange circuits for the different engines are combined with each other to form a single heat exchange circuit directed by a temperature regulator so that the excess heat from every engine is collected to a single point at the inlet to the heat exchange circuit.

7. A water cooling system as claimed in Claim 6, wherein the system is provided with a by-pass pipe for the recirculation of excess water to the water cooler.

8. A process for regulating the temperature in a water cooling system for a compressor charged l.C. engine substantially as hereinbefore described with reference to Figures 1, 3 and 4 or Figure 2 of the accompanying drawings.

9. A water cooling system for a compressorcharged l.C. engine substantially as hereinbefore described with reference to Figures 1, 3 and 4 or Figure 2 of the accompanying drawings.