WO2012130557A1

WO2012130557A1 - Preheater for high viscosity fuels

Info

Publication number: WO2012130557A1
Application number: PCT/EP2012/053577
Authority: WO
Inventors: Udo Schulz; Henrick Brandes; Dierk Staebler; Silvio Birindelli; Lutz Rauchfuss
Original assignee: Robert Bosch Gmbh
Priority date: 2011-03-29
Filing date: 2012-03-01
Publication date: 2012-10-04
Also published as: DE102011006336A1

Abstract

The invention relates to a preheater (10) for heating high viscosity fuels (22), in particular heavy oil, for operating an internal combustion engine (30). The preheater (10) has a thermally conductive connection to the fuel (22) and comprises at least one heat store (14), wherein the heat store (14) contains a storage medium (16) that gives off heat energy in an exothermal phase change.

Description

Description title

The invention relates to a device for heating highly viscous fuels

Fuels, in particular heavy oil, for operating an internal combustion engine, wherein the device is in heat-conducting connection to the fuel.

For large internal combustion engines, such as those used in particular in the sea, low-quality fuels such as heavy fuel oil and other high-viscosity fuels are used for cost reasons. The fuels used have special physical properties that must be taken into account during operation of the internal combustion engine. One important property is the viscosity of the fuel used for heavy fuel oil

Ambient temperature of 20 ° C is typically in the range of 1 500 to 10 000 mm ² / s. The heavy oil is viscous to puncture resistant under these conditions. In order for the heavy oil to be pumped and supplied to the internal combustion engine via an injection system, the viscosity must be reduced by heating the fuel.

During operation of the internal combustion engine, the waste heat generated is used to heat the high-viscosity fuel, such as heavy oil, so far that it is flowable and can be injected into the internal combustion engine. Typically, the fuel is heated to a temperature of about 100 ° C.

However, if the internal combustion engine is not yet in operation, the fuel must be heated in another way. Only after reaching a certain temperature, and thus a certain viscosity of the fuel, the

Internal combustion engine to be operated with the high-viscosity fuel. From GB 101, 596 it is known that the internal combustion engine initially with another, low-viscosity to operate fuel. The internal combustion engine can later be switched to heavy oil operation when the heavy oil has reached the necessary temperature and thus the required viscosity. Alternatively, the heavy oil over a

Preheater or preheated by an external heat source.

Also known in the art is the use of a starter motor which may be operated with low viscosity fuel such as gasoline or diesel. Initially, only the starting engine is put into operation and the heavy oil is heated with the waste heat of the starter motor until the necessary low viscosity is reached.

Subsequently, the starter motor is switched to the heavy oil-powered internal combustion engine.

High-viscosity fuel remaining in the fuel lines must be flushed from the lines before stopping an internal combustion engine, or kept flowing through heaters. From DE 103 41 708 A1, for example, the arrangement of electric heaters on the fuel lines is known.

Other parts of an internal combustion engine must be brought to operating temperature quickly. From DE 197 38 075 A1, for example, an exhaust manifold embedded in zeolites is known. The zeolites act as latent heat storage and the subsequent catalyst reaches the required operating temperature faster.

DISCLOSURE OF THE INVENTION The inventively proposed device for heating highly viscous

Fuels, in particular heavy oil, for operating an internal combustion engine is in heat-conducting connection to the fuel and comprises at least one heat accumulator, the heat accumulator containing a storage medium which emits heat energy in an exothermic phase change.

The device according to the invention is designed in particular as a preheater for heating highly viscous fuels. The heating of highly viscous fuels with a preheater is necessary to make the fuel flowable. High viscosity is defined as fuels whose viscosity is above 100 mm ² / s at an ambient temperature of 20 ° C., while higher-grade, low-viscosity fuels such as diesel have a viscosity of less than 100 mm ² / s. Are highly viscous fuels such as heavy oil on a

Temperature warmed above 100 ° C, their viscosity decreases to a value below 100 mm ² / s. The energy required for heating the highly viscous fuel is provided in the device according to the invention by a heat accumulator. Of the

Heat storage of the device comprises a storage medium, which of the

Internal combustion engine can absorb heat given off and release again. The heat energy can be absorbed by a temperature increase of the storage medium, as well as by the change of a phase state (solid, liquid, gaseous, crystalline, amorphous) in a different phase state.

In general, more heat energy can be absorbed by changing the phase state than by a temperature increase of the storage medium.

It is therefore preferred if the storage medium changes its phase state when receiving the waste heat of the internal combustion engine. During the phase change, the volume of the storage medium can increase greatly. In the case of a change in phase from the liquid to the gaseous state, the volume increase may be greater than the factor of 1,000. Therefore, phase changes, such as the transition from the solid to the liquid phase state, in which the volume of the storage medium changes by less than one fifth, are preferred.

The storage medium used is preferably substances whose

Melting temperature and solidification temperature in a temperature suitable for preheating highly viscous fuels temperature range. The temperature range is dictated by the required reduction in the viscosity of the fuel. The viscosity is preferably reduced to such an extent that the heated, highly viscous fuel achieves a viscosity comparable to a low-viscosity fuel. Typically, the temperature required for this is in the range of 100 ° C to 200 ° C. The exact temperature depends on the fuel used and the ambient conditions. Substances which can be present in the liquid phase state even at a temperature below their solidification temperature are particularly preferably used as storage media. This condition is called supercooled melt.

Suitable storage media are aqueous salt solutions, paraffins, salt hydrates,

Sugar alcohols, nitrates, hydroxides, chlorides, carbonates and other substances with a melting temperature in the appropriate range. To the melting temperature of the To be able to set the storage medium more precisely can also be a mixture of several

Substances are used as storage medium.

The stored in the phase transition heat energy of a supercooled melt can be retrieved by the phase transition from the liquid to the solid phase state is deliberately brought about. The supercooled melt solidifies if it contains crystallization nuclei. These crystallization nuclei can have a

Activation device can be added selectively, or can be generated by lowering the temperature or mechanical action in the supercooled melt.

Once the exothermic phase change in the storage medium of the heat accumulator has been activated, the phase change continues until the entire storage medium in the

Heat storage has completed the phase change. The activation device can be triggered for example via a control unit of the internal combustion engine. The released by the exothermic phase change heat energy is on the

highly viscous fuel transmitted, since the device is in heat-conducting connection with the fuel.

When using heavy oil, the fuel is preferably heated to a temperature in the range of 130 ° C to 160 ° C. More preferably, the fuel is heated to a temperature in the range of 140 ° C to 150 ° C to adjust the viscosity of the fuel to 14 to 16 mm ² / s. At this viscosity, the fuel can be injected into the internal combustion engine with a fuel injector, and the internal combustion engine can be started. The time for the start of the internal combustion engine, for example, from one controller via a measurement of the fuel temperature or another

Method can be determined according to the prior art.

The desired temperature of the fuel is after starting the

Internal combustion engine ensures their waste heat. This can be realized, for example, via a heater arranged in the fuel tank, which is connected to the cooling water system of the internal combustion engine. The waste heat of

However, internal combustion engine can also be passed over the warm exhaust gas or another connection to the fuel tank. The thus heated fuel can flow through the device designed as a preheater and the fuel line to the internal combustion engine, and is available for their further operation. As between the device for heating the fuel and the heated fuel, a heat conductive connection exists, the storage medium in the heat accumulator of the device can be regenerated via the heat of the fuel, so transferred to the absorption of heat energy back into the liquid phase state. When the storage medium has been completely regenerated, it is available for a fresh startup as a heat source. The use of the waste heat of the internal combustion engine for regenerating the storage medium is also directly on the cooling water, the exhaust gas, or other connections to the

Internal combustion engine possible.

Advantages of the invention

In an internal combustion engine operated with a high-viscosity fuel such as heavy oil, the highly viscous fuel must be heated before starting in order to reduce its viscosity. The inventively proposed

The device utilizes waste heat from the internal combustion engine stored to heat the high viscosity fuel, while prior art solutions require an alternative power supply, either in the form of another, higher quality fuel, or even through the placement of another engine. The inventive device for heating the high-viscosity fuel allows to dispense with an alternative power supply in normal operation. An external supply, for example via a starter motor is only required if no

Regenerated heat storage is available. Since the heat energy stored in the heat accumulator comes from the waste heat of the internal combustion engine, the

Improved energy efficiency compared to internal combustion engines according to the prior art.

Another advantage of the device according to the invention is that most of the heat energy is stored by the transition between two phases of the storage medium, and not by a temperature increase in the heat storage. Since the heat stored in this way is released only during a phase change, and this phase change takes place only when the stored heat energy is needed, can be dispensed with a complex and expensive thermal insulation of the heat storage. Brief description of the drawings Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. FIG. 1 shows an embodiment of the device designed as a preheater. The preheater is disposed between a fuel tank and an internal combustion engine.

Figure 2 shows an embodiment of the invention in which the apparatus for heating high viscosity fuels is housed within a fuel tank.

FIG. 3 shows the device as a preheater arranged on a fuel line.

FIG. 4 shows an embodiment of the device in the case of a fuel line

meandering through the heat storage is performed.

Figure 5 shows an embodiment of the device which includes a plurality of heat storage. Embodiments of the invention

FIG. 1 shows an embodiment of the device for heating highly viscous fuels. The executed as a preheater 10 device is between a fuel tank 20 for

Storage of a high-viscosity fuel 22 and an internal combustion engine 30 arranged on a fuel line 24. The preheater 10 includes a low volume storage bin 12 also filled with the high viscosity fuel 22 and a heat storage 14 surrounding the storage bin 12.

The heat storage 14 and the storage bunker 12 are in heat-conducting

Connection. The heat storage 14 comprises a storage medium 16 for receiving heat energy and an activation device 18. The heat energy is preferably stored not only by an increase in the temperature in the heat storage 14, but by the change of a phase state of the storage medium 16 (solid, liquid, gaseous, crystalline, amorphous) into a different phase state of the storage medium 16. Before fuel 22 is injected into the internal combustion engine 30, the fuel 22 must be heated to reduce its viscosity. For this purpose, a signal is sent to the activation device 18 by a control unit 40. The

Activation device 18 is preferably designed as a Peltier element, and cools the storage medium 16 in its immediate vicinity until the exothermic

Phase change begins. This exothermic process ends only when the phase change in the entire storage medium 16 is complete. The resulting heat Q is delivered to the storage bunker 12 enclosed by the heat accumulator 14 and to the fuel 22 in the interior of the storage bunker 12. After the heating of the fuel 22 in the interior of the storage bunker 12, the internal combustion engine 30 can be started by the control unit 40. With the now available waste heat of

Internal combustion engine 30, the temperature of the fuel 22 in the tank 20 and thus its viscosity, as known from the prior art, further regulated. This can be done for example via a connected to the cooling water system 50 of the internal combustion engine 30 heater 52. The warm fuel 22 flows on its way from the fuel tank 20 via the fuel line 24 to the internal combustion engine 30 through the storage bunker 12. Since the storage bunker 12 is in heat-conducting contact with the heat accumulator 14, the waste heat of the internal combustion engine 30 via the warm fuel 22 can be used as a transport medium to regenerate the storage medium 16. The use of waste heat of the internal combustion engine 30 for

Regeneration of the storage medium 16 is also possible via the cooling water, the warm exhaust gas, or other connections to the internal combustion engine 30.

FIG. 2 shows a further embodiment of the device according to the invention.

The preheater 10, which includes a storage bunker 12 and a heat accumulator 14, is located within a tank 20 for storing highly viscous fuel 22. The internal combustion engine 30 is connected via a fuel line 24 to the preheater 10 in the fuel tank 20. The heat accumulator 14 of the preheater 10 includes a

Storage medium 16 and an activation device 18 and encloses the

Vorratsbunker 12. We in the embodiment just described before the start of the internal combustion engine 30 by a control unit 40, a signal to the

Activation device 18 given. The heat energy Q released during the phase change of the storage medium 16 heats the fuel 22 in the interior of the storage bunker 12. The heated fuel 22 flows via the fuel line 24 to the internal combustion engine 30. After the start of the internal combustion engine 30 by the controller 40, the waste heat of the internal combustion engine 30, the fuel 22 in the fuel tank 20 further heat. This can be done, for example, via a heater 52 arranged in the fuel tank 20, which is connected to the cooling water system 50 of the internal combustion engine 30. As soon as the fuel 22 has been sufficiently heated and its viscosity has been sufficiently reduced, the fuel 22 can flow through the storage bin 12 and the fuel line 24 and be used for the further operation of the internal combustion engine 30.

For the regeneration of the storage medium 16 in the heat storage 14, the waste heat of the internal combustion engine 30 can be used. The waste heat can reach, for example via the heated fuel 22 to the heat accumulator 14, since the fuel flows through the storage bin 12 and this is in heat-conducting connection with the heat accumulator 14. Also conceivable is a regeneration of the heat accumulator 14 via the warm exhaust gas or the cooling water of the internal combustion engine.

FIG. 3 shows a further embodiment of the device according to the invention.

The preheater 10 extends over almost the entire length of a fuel line 24. Only the areas in which no sufficient space available or needed for connection to the tank 20 or the internal combustion engine 30 are not enclosed by the preheater 10. The preheater 10 includes a heat storage 14 that includes a storage medium 16 and an activation device 18. Of the

Heat storage 14 is in heat-conducting connection with the fuel line 24. On the arrangement of an additional storage bunker can be omitted in this embodiment. Before the start of the internal combustion engine 30, the activation device 18 is triggered by a control unit 40 to the exothermic phase change in

Storage medium 16 to start. The heat released is transferred to the fuel line 24 and to the fuel 22 therein. After the fuel 22 is sufficiently heated, and thus its viscosity has been sufficiently reduced, the control unit 40 starts the internal combustion engine 30 and its waste heat heats the

Fuel 22 in the fuel tank 20. This can be done for example with a arranged in the fuel tank 20 heater 52, which is connected to the cooling water system 50 of

Internal combustion engine 30 is connected. Since the heated fuel 22 flows through the fuel line 24 enclosed by the heat accumulator 14, the waste heat of the internal combustion engine 30 can be utilized to supply the storage medium 16 regenerate. The use of the waste heat of the internal combustion engine 30 for the regeneration of the storage medium 16 is also possible via the cooling water, the exhaust gas, or other compounds. FIG. 4 shows a modified embodiment of the device shown in FIG.

As just described, the preheater 10 is disposed on the fuel line 24 between the fuel tank 20 and the internal combustion engine 30. The preheater 10 comprises a heat accumulator 14, a storage medium 16 and a

Activation device 18 includes. To make the preheater 10 more compact and thus space-saving, the fuel line 24 is meandering through the heat accumulator 14. Other ways to lead the fuel line 24 through the heat storage 14 are conceivable, such as a helical guide.

FIG. 5 shows a further embodiment of the device according to the invention, in which the preheater 10 comprises a storage bunker 12 and a plurality of heat stores 14 that are separate from one another. Each heat storage device comprises a storage medium 16 and an activation device 18. The heat energy of the individual heat storage devices 14, which are independent of each other, can be selectively retrieved by a control device 40. This makes it possible to dose the retrieved amount of heat energy Q. The exothermic phase change in the

Although storage medium 16 in one of the heat accumulators 14 can only ever be completely carried out, the control unit 40 may depend on the required one

Heat energy Q only a certain number of heat storage 14 activate. On the other hand, a redundancy is achieved by the arrangement of a plurality of heat accumulators 14. The highly viscous fuel 22 contained in the storage bunker 12 can still be heated and liquefied thereby, if one of the heat storage 14 is not responsive to the signal of the controller 40, or the regeneration of a heat storage 14 was not completed. Furthermore, it is possible to fill the heat accumulators 14 with different storage media 16, whose melting temperatures are different. Upon activation of a heat accumulator 14, this heats up to the

Melting temperature of the contained storage medium 16. The temperature of the fuel 22 can be adjusted by a specific activation of certain heat storage 14. This makes it possible to keep the viscosity within the required range, even with 22 different temperature requirements, depending on the tanked fuel. It is particularly preferred if both concepts are combined and in the preheater 10 several groups of

Heat storage 14 can be used, wherein in each group another storage medium 16 is used with a different melting temperature.

In addition to the embodiments shown in the figures, further embodiments of the device according to the invention are conceivable. Thus, for example, the shape of the preheater 10 and the heat accumulator 14 contained therein vary in order to adapt them to the available space. It is also not necessary that the heat accumulator 14 completely encloses the storage bin 12. However, preferred are molds that offer the largest possible contact surface for a good heat conduction between the preheater 10 and the fuel 22.

It is also possible to further improve the redundancy of the

Device according to the invention to provide a known from the prior art starting system such as a starter motor, an electric heating element or a system for alternative operation with low-viscosity fuel to the side. The starter motor or the low-viscosity fuel can be used if no regenerated heat storage is available. Furthermore, it is conceivable to use the starter motor and the preheater according to the invention at the same time in order to accelerate the heating of the high-viscosity fuel.

Claims

Claims 1. A device for heating highly viscous fuels (22), in particular heavy fuel oil, for operating an internal combustion engine (30), wherein the device is in heat-conducting connection to the fuel (22), characterized in that the device comprises at least one heat accumulator (14) containing a storage medium (16) which releases heat energy in an exothermic phase change.

2. Apparatus according to claim 1, characterized in that the exothermic

Phase change from a supercooled liquid state of the storage medium (16) in a solid state of the storage medium (16) extends.

3. Device according to one of the preceding claims, wherein the heat accumulator (14) comprises an activation device (18) to the exothermic phase change in

To trigger storage medium (16).

4. Apparatus according to claim 3, characterized in that the activation device (18), the phase change mechanically, in particular by pressure waves through

Temperature change, in particular via a Peltier element, or by the addition of crystallization nuclei triggers.

5. Device according to one of the preceding claims, characterized in that the exothermic phase change in the storage medium (16) at a temperature in the range of

100 ° C to 200 ° C, preferably in the range of 130 ° C to 160 ° C and more preferably in the range of 140 ° C to 150 ° C.

6. Device according to one of the preceding claims, characterized in that the storage medium (16) in the heat storage (14) is an aqueous salt solution, a paraffin, a

Salt hydrate, a sugar alcohol, a nitrate, a hydroxide, a chloride, a carbonate or a mixture of substances of said substance groups is.

7. Device according to one of the preceding claims, characterized in that the heat accumulator (14) is regenerable via the waste heat of the internal combustion engine.

8. Device according to one of the preceding claims, characterized in that the heat accumulator (16) via warm fuel (22), the cooling water or warm exhaust gas is regenerated.

9. Device according to one of the preceding claims, characterized in that the heat accumulator (16) is housed within a fuel tank (20).

10. Device according to one of the preceding claims, characterized in that the heat accumulator (16) on the fuel line (24) between the fuel tank (20) and

Internal combustion engine (30) is arranged.

1 1. Device according to one of the preceding claims, characterized in that the device comprises a plurality of heat storage (14), wherein each heat storage device has its own activation device (18) and a separate storage medium (16).

12. The device according to claim 11, characterized in that the heat storage (14) may have different storage media (16) with different melting temperatures.