GB2175045A

GB2175045A - Cooling fuel injectors of I.C. engines

Info

Publication number: GB2175045A
Application number: GB08610994A
Authority: GB
Inventors: Karol Galuska
Original assignee: Sulzer AG; Gebrueder Sulzer AG
Current assignee: Sulzer AG
Priority date: 1985-05-03
Filing date: 1986-05-06
Publication date: 1986-11-19
Also published as: IT1191726B; DE3516253A1; NO861728L; IT8620064A0; DK191586A; DK191586D0; JPS61252864A; CN86102587A; CH667698A5; IT8620064A1; GB8610994D0; NO164678B; NO164678C; DK168022B1; JPH0672581B2; CN1006485B; GB2175045B

Abstract

Each cylinder of the engine comprises at least one injector (4) connected to a delivery line (15) of a fuel pump (7) connected by way of an intake line (13) to a feed line (5) and by way of a spill line (20) to a return line (8) of a fuel supply system (2). The injector (4) includes an injection nozzle having a flow channel (51), Figs. 2,4, which extends around a nozzle member (38) and is connected via channels (50),(52) to a supply line (24) and to a return line (25) of a heat exchange system (3). The heat exchange system supply line (24) is connected in parallel with the fuel pump intake line (13) to the fuel supply system feed line (5) while the heat exchange system return line (25) is connected to the fuel supply system return line (8). <IMAGE>

Description

SPECIFICATION Internal combustion engines This invention relates to reciprocating internal combustion engines adapted to be operated on a preheated fuel of relatively high viscosity, more particularly heavy oil.

According to the present invention, such an engine comprises at least one injector per engine cylinder, the injector being connected to a delivery line of a fuel pump connected by way of an intake line to a feed line of a fuel supply system, the injector comprising a fuel injection nozzle connected to a fuel supply channel and directed into an combustion chamber of the cylinder, the injector also comprising a flow channel associated with the nozzle and two connecting channels communicating with the flow channel, the first connecting channel being connectable to a supply line of a heat exchanger and the second connecting channel being connectable to a return line of the heat exchanger, the fuel supply system comprising a return line connected to a spill line of the fuel pump, and the supply line of the heat exchanger being connected in parallel with the fuel pump intake line to the feed line of the fuel supply system, and the return line of the heat exchange system being connected to the return line of the fuel supply system.

It has already been proposed to cool or heat the injectors of heavy oil engines using a heat exchange system which is a circuit compietely separate from the fuel supply system, the heat exchange medium used to cool and heat the injector being water. This system uses an indepedent cooling or heating circuit requiring independent monitoring and control, with correspondingly increased operating costs, both to heat the injector during inoperative times of the engine and to cool the injector when the engine is operating.

The present invention provides a system which is simpler and correspondingly cheaper to produce than the known constructions and which also calls for less outlay on control than the known arrangements.

The arrangement according to the invention leads to a very simple construction of the fuel injection system of the engine since the same medium-i.e., the preheated fuel-flows through the injector in separate channels both when the engine is inoperative and when it is operative. The fuel thus present therefore serves as a very simple means of keeping an inoperative engine in a state ready for operation and the same fuel ensures that the injector nozzle remains at the required operating temperature in operation.

The construction of the injection facility can be greatly simplfied if the second connecting channel, i.e. the channel associated with the return line of the heat exchange system, is connected to an overflow channel disposed in the injector, the overflow channel communicating with a bore extending to the nozzle, the overflow channel being adapted to receive and remove a quantity of fuel issuing from the latter bore and arising from leakages. With this feature, therefore, four injector function s-i.e., fuel supply, leakage removal and the supply and removal of a heat exchange medium-can be provided by just three fuel connections to the injector.

Preferably, the heat exchanger includes a heater and a cooler which are arranged in series with one another in a common branch of the supply line of the heat exchange system. This is a simple arrangement and it has been found that with this arrangement a changeover between heating and cooling of the fuel flowing through the heat exchanger becomes operative in a sufficiently short period of time. In a construction which is compact and which is particularly simple so far as construction and servicing are concerned, the heater and the cooler are disposed in a common casing.

The invention may be carried into practice in various ways but one internal combustion engine embodying the invention will now be described by way of example with reference to the accompanying drawings, jn which: Figure 1 is a simplified diagrammatic view of the fuel injection system of the internal combustion engine, the system relating to a group of injectors; Figure 2 is a view, in section on the line Il-Il of Figure 3 and to an enlarged scale, of one of the injectors of Figure 1; Figure 3 is a plan view of the injector of Figure 2; and Figure 4 is a section on the line IV-IV of Figure 3.

The fuel injection system shown in Figure 1 comprises a tank 1 for a high-viscosity fuel, such as heavy oil, which is prepared and preheated in a manner known and not shown, a fuel supply system 2 and a heat exchange system 3 for a group of-in this illustration-four injectors 4 of a cylinder (not shown) of a reciprocating internal combustion engine. Depending upon engine construction, the number of injectors per cylinder can be other than shown and there can be, for example, just a single injector. The fuel supply system 2 comprises a feed line 5 which is connected to the tank 1 and in which a circulating pump 6 is disposed, a fuel pump (injection pump) 7 and a return line 8 which returns to the tank 1 and which can have a pressure gauge 9 and a restrictor valve 19 adjustable to a predetermined fuel pressure.The pump 7 comprises a piston 11 which is guided sealingly in a cylinder 10 and which drive means (not shown) reciprocate vertically as seen in Figure 1 in dependence upon the speed of the engine crankshaft.

As can be seen in Figure 1, a cylinder chamber 10a of the fuel pump 7 is connected by way of an intake valve 12 and intake line 13 to the feed line 5 and by way of a delivery valve 14 and a heated delivery line 15 to a distributor 16 from which delivery lines 15a extend each to a fuel connection nipple 17 of one of the injectors 4. Chamber 1 0a also communicates by way of a spill valve 18 and a spill line 19 with the return line 8.

Stop valves 21 are disposed in the intake line 13 and in the spill line 20. The intake valve 12 and the spill valve 18 are each controllable between a throughflow position and a shutoff position. With the valve 12 open and the valve 18-closed, a descent of the piston 11 draws in a corresponding quantity of fuel, and with the valves 12, 18 closed an ascent of the piston 11 delivers such quantity of fuel through the lines 15, 15a to the injectors 4.

Opening of the valve 18 terminates fuel delivery to the injectors 4. A bypass 22 in the fuel pump 7 interconnects the intake line 13 and spill line 20 and enables the fuel to circulate when the valves 12, 14, 18 are in the closed state.

The injectors 4 are also connected in parallel with one another to a branch line 24a of a second supply line 24 for the fuel which in this arrangement serves as heat exchange medium, the branch line 24a having a stop valve 21, and the connectors 4 are connected to a branch line 25a, which has a check valve 30, of a corresponding return line 25 of the heat exchange system 3. The supply line 24 is connected in parallel with the intake line 13 to feed line 5 of the fuel supply system 2 and includes a heater 26 and a cooler 27. The heater 26 and the cooler 27 are connected in series with one another and can be received in a common casing 28 as shown in Figure 1.

Further branch lines 24b, 24c, 24d... extend from the supply line 24 and each leads to an additional group (not shown) of injectors, the groups being respectively associated with further cylinders and connected by way of corresponding branch lines 25b, 25c, 25d... to the return line 25. Each additional group of injectors can be connected by way of its own fuel pump 7 to the feed line 5. The return line 25 is connected in parallel with the spill line 20 to the fuel supply system return line 8.

The heater 26 can be connected to an existing steam heating system (not shown) of a fuel preparation facility. The cooler 27 can be connected to an appropriate water or oil cooling system which is inoperative for the engine to cool the pistons, cylinders and/or charging air.

As shown in Figures 2-4, each injector 4 has a body 31 secured by screws 32 in a cylinder head 33 operative as the top closure of a combustion chamber 34 of the diesel engine not shown in further detail. The body 31 comprises a top part 35, a bottom part 36 and a union nut 37 interconnecting the parts 35 and 36. The bottom part 36 has a nozzle member 38 which extends into the combustion chamber 34 and which has a valve seat 38a co-operating with a conical seat surface of a barrel 40, the member 38 being formed with a number of nozzle orifices 41 which are directed into the combustion chamber 34 and through which the fuel is injected.

The barrel 40 is guided for axial movement in a central bore 39 in the bottom part 36 and bears by way of a tappet 40a and a cup 42 on a compression spring 43 operative to press the bottom end of the barrel 40 on to the valve seat 38a.

The connection nipple 17 of the delivery line 15a is screwed into a bore 44 in the valve body 31 extending parallel to the central bore 39, a narrowed headpart 1 7a on the nipple being pressed on to the base surface of the bore 44 in sealing-tight manner. The end face of the part 17a extends around the orifice of a fuel supply channel 45 extending substantially lengthwise of the valve body 31 to an annular chamber 46 around the barrel 40, the chamber 46 being bounded towards the chamber 34 by the co-operating seat surfaces of the nozzle member 38 and barrel 40.

Each of the branch lines 24a of the heat exchange system supply line 24 leads to a connector 47 which is screwed into a bore 48 in the top part 35 of the particular valve body 31 concerned. The bore 48 extends into the annular chamber present between the nipple head part 1 7a and the wall of the bore 44 and sealed off from the fuel supply channel 45. A communicating channel 50 is connected to the last-mentioned annular chamber and continues substantially lengthwise of the valve body 31 as far as an annular flow channel 51 around the nozzle member 38.By way of a connecting channel 52 which extends substantially parallel to the central bore 39, the channel 51 communicates with a widened part 39a of the central bore 39, the part 39a extending around the top end of the tappet 40a and around the compression spring 43, and a substantially radial bore 53 in the top part 35 extends from the widened part 39a of the central bore 39. A connector 54 to which the branch line 25a of the heat exchange system return line 25 is connected is screwed into the bore 53.

In operation the prepared and preheated fuel is delivered by way of the fuel pump 7 in timed fashion and at a pressure of, for example, 1 000 bar through the heater delivery line 15 into the annular channels 46 of the injectors 4, the barrel 40 lifting off the seat 38a against the force of the compression spring 43 and fuel being injected through the orifices 41 into the combustion chamber 34.

Opening of the spill valve 18 interrups injection due to the decreasing fuel pressure causing the barrel to be pressed on to the valve seat 38a. Because of the high fuel pressure and of the clearance between the barrel 40 and the wall of the bore 39 by which the barrel is guided a small amount of fuel (leakage) may be forced from the bottom part 36 into the top part 35 of the valve body 31.

The leakage fuel can return to the tank 1 by way of the branch line 25a connected to the widened part 39a of the bore 39.

In operation fuel is supplied at a pressure of, for example, 5 bar through the supply line 24 and connecting channel 50 and removed through the connecting channel 52 and return line 25 to cool the nozzle member 38; the fuel, preheated to the required injection temperature- of, for example, 140"C may be cooled as it flows through the cooler 27 to a temperature t = approximately 100"--120"C and heated in the injector 4 to a temperature t2 = approximately 110"--130"C. As indicated in Figure 1, the temperature of the nozzle member 38 can be influenced by an adjusting or control valve 21a which, by means of a load-dependent adjustment of the rate of flow of coolant through the cooler 27, can produce an adjustment of the corresponding temperature tl of the fuel issuing from the cooler 27. In appropriate conditions of operation the cooler 27 can be shut down and the fuel circulating in the heat exchange system 3 can be used uncooled to cool the nozzle member 38.

To ensure permanent readiness for operation and manoeuvre at times when the engine is inoperative, for example when a ship is in harbour, the preheated fuel circulating in the heat exchange system 3 can keep the injectors 4 permanently heated to the required fuel injection temperature. The fuel can be preheated in known manner, for example in the tank 1 and/or by bringing the heater 26 into operation.

Claims

1. A reciprocating internal combustion engine adapted to be operated on a preheated fuel of relatively high viscosity and comprising at least one injector per engine cylinder, the injector being connected to a delivery line of a fuel pump connected by way of an intake line to a feed line of a fuel supply system, the injector comprising a fuel injection nozzle connected to a fuel supply channel and directed into a combustion chamber of the cylinder, the injector also comprising a flow channel associated with the nozzle and two connecting channels communicating with the flow channel, the first connecting channel being connectable to a supply line of a heat exchanger and the second connecting channel being connectable to a return line of the heat exchanger, the fuel supply system comprising a return line connected to a spill line of the fuel pump, and the supply line of the heat exchanger being connected in parallel with the fuel pump intake line to the feed line of the fuel supply system, and the return line of the heat exchange system being connected to the return line of the fuel supply system.

2. An engine as claimed in Claim 1 in which the second connecting channel is connected to an overflow channel in the injector, the overflow channel communicating with a bore extending to the nozzle, the overflow channel being adapted to receive and remove a quantity of fuel issuing from the latter bore and arising from leakages.

3. An engine as claimed in Claim 1 or Claim 2 in which the heat exchanger includes a heater and a cooler which are arranged in series with one another in a common branch of the supply line of the heat exchange system.

4. An engine as claimed in Claim 3 in which the heater and the cooler are disposed in a common casing.

5. A reciprocating internal combustion engine substantially as described herein with reference to the accompanying drawings.