Device for separating fuel components

A device for separating fuel components comprising a separating membrane for separating high-octane fuel components from un-separated fuel and a heat exchanger between first liquid passing through the heat exchanger and second liquid passing through the heat exchanger, is provided. The first liquid is un-separated fuel passing through the heat exchanger before being supplied to the separating membrane. The second liquid is low-octane fuel remaining when the high-octane fuel components are separated from the un-separated fuel, passing through the heat exchanger after changing to an almost liquid phase.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for separating fuel components.

2. Description of the Related Art

For example, in an engine having a high compression ratio, high-octane fuel is needed to restrain knocking. However, in low engine load operations in which knocking rarely occurs, the engine may not be required to use high-octane fuel, but low-octane fuel. Accordingly, it is suggested that the engine not use high-octane fuel (high-octane gasoline) which is expensive, but regular gasoline which is separated into high-octane fuel components and the remaining fuel as low-octane fuel by a device for separating fuel components.

The device for separating fuel components separates aromatic components as high-octane fuel components from fuel by means of a separating membrane and makes the remaining fuel low-octane fuel. In such a device for separating fuel components, un-separated fuel is preferably heated to improve a separating ability of the separating membrane. Therefore, the low-octane fuel remaining when high-octane fuel components are separated from fuel is maintained at a high temperature and may be required to be cooled down before being stored in a low-octane fuel tank. Accordingly, it is suggested that a heat exchanger between the un-separated fuel and the separated low-octane fuel be provided and the separated low-octane fuel be cooled down by the heat exchanger (for example, refer to Japanese Unexamined Patent Publication Nos. 2004-232624 and 2008-095666).

However, a part of the low-octane fuel remaining when high-octane fuel components are separated changes from a liquid phase to a gas phase because the un-separated fuel is heated. Thus, a flow resistance of the low-octane fuel in the heat exchanger is large and a heat transfer coefficient of gas phase is smaller than that of a liquid phase. Therefore, to sufficiently cool down the low-octane fuel including the gas phase, a very large heat exchanger is required, and it is thus difficult for the device for separating fuel components with such a very large heat exchanger to be mounted on a vehicle.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a device for separating fuel components, which can sufficiently cool down the low-octane fuel remaining when high-octane fuel components are separated by means of the separating membrane without a large heat exchanger.

A first device for separating fuel components according to the present invention is characterized in that the first device comprises a separating membrane for separating high-octane fuel components from un-separated fuel and a heat exchanger between first liquid passing through the heat exchanger and second liquid passing through the heat exchanger, wherein the first liquid is un-separated fuel passing through the heat exchanger before being supplied to the separating membrane, and the second liquid is low-octane fuel remaining when the high-octane fuel components are separated from the un-separated fuel, passing through the heat exchanger after changing to an almost liquid phase.

A second device for separating fuel components according to the present invention is characterized in that according to the first device, an air cooling apparatus for cooling down the low-octane fuel is provided to change a gas phase part of the low-octane fuel to an almost liquid phase.

A third device for separating fuel components according to the present invention is characterized in that according to the second device, in a low vehicle speed condition when a speed of the vehicle on which the third device is mounted is lower than a predetermined speed, the un-separated fuel at a set flow rate larger than a set flow rate in an engine idle condition is supplied to the separating membrane to separate high-octane fuel components, and the air cooling apparatus has a cooling ability which can change a gas phase part of the low-octane fuel remaining when the high-octane fuel components are separated from the un-separated fuel at both the set flow rates in the low vehicle speed condition and in the engine idle condition to an almost liquid phase.

According to the first device for separating fuel components of the present invention, the first device comprises the separating membrane for separating high-octane fuel components from un-separated fuel and the heat exchanger between first liquid passing through the heat exchanger and second liquid passing through the heat exchanger. The first liquid is the un-separated fuel passing through the heat exchanger before being supplied to the separating membrane, and the second liquid is low-octane fuel remaining when the high-octane fuel components are separated from the un-separated fuel, passing through the heat exchanger after changing to an almost liquid phase. Such a heat exchanger between the first liquid and the second liquid has a sufficient high heat exchange efficiency to cool down the low octane fuel passing through the heat exchanger as the second liquid even when the heat exchanger is small so as to be easily mounted on the vehicle. To use such a heat exchanger, a gas phase part of the low-octane fuel is changed to an almost liquid phase with pressurization or cooling down and thereafter is made to pass through the heat exchanger.

According to the second device for separating fuel components of the present invention, in the first device, an air cooling apparatus for cooling down is provided to change a gas phase part of the low-octane fuel to an almost liquid phase. Accordingly, with the air cooling apparatus, the low-octane fuel can be made to pass through the heat exchanger as the second liquid.

According to the third device for separating fuel components of the present invention, in the second device, in a low vehicle speed condition when a speed of the vehicle on which the third device is mounted is lower than a predetermined speed, the un-separated fuel at the set flow rate larger than the set flow rate in the engine idle condition is supplied to the separating membrane to separate high-octane fuel components, and the air cooling apparatus has the cooling ability which can change a gas phase part of the low-octane fuel remaining when the high-octane fuel components are separated from the un-separated fuel at both set flow rates in the low vehicle speed condition and the engine idle condition to an almost liquid phase. Thus, in both the low vehicle speed condition and the engine idle condition, with the air cooling apparatus, the low-octane fuel can be made to pass through the heat exchanger as the second liquid.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic vertical sectional view showing a device for separating fuel components according to the present invention. InFIG. 1, reference numeral1designates a station for separating fuel components comprising a first section1band a second section1cwhich are divided by a separating membrane1apermeating aromatic components. Un-separated fuel pressurized at a relative high pressure by a fuel pump3is supplied to the first section1bfrom an un-separated fuel tank2for storing the un-separated fuel. Reference numeral4designates a regulator for regulating a flow rate of the un-separated fuel supplied to the first section1b. Reference numeral5designates a heater for heating the pressurized un-separated fuel immediately before supplying to the first section1b. The heater5utilizes, for example, the heat of the exhaust gas. However, the heater5may be an electric heater. Reference numeral6is a temperature sensor for measuring a fuel temperature heated by the heater5immediately upstream of the first section1b.

The separating membrane1ais selectively permeable to aromatic components in the fuel. Therefore, when pressure within the second section1cis maintained at a relatively low pressure, aromatic components of the un-separated fuel in the first section1bpermeate the separating membrane1a, and exude on the surface of the separating membrane1aat the second section1cside. In the present embodiment, a pressure within the second section1cis maintained at a pressure lower than the saturated vapor pressure of the exuded aromatic components and thus the fuel exuded on the surface of the membrane can be vaporized continuously from the surface of the membrane. The vaporized fuel is sent to an air cooling apparatus8by a vacuum pump7and is cooled down in the air cooling apparatus8so as to change to an almost liquid phase.

On the other hand, low-octane fuel remaining when aromatic components permeate the separating membrane1ahas an octane number lower than that of the un-separated fuel. The low-octane fuel is a relative high temperature (for example, about 350 degrees K or 75 degrees C.) because the un-separated fuel is heated by the heater5. Accordingly, when the low-octane fuel flows out from the station1which separates the fuel components, a part of the low-octane fuel becomes a gas phase. Thus, the low-octane fuel is in a mixed gas phase and liquid phase state and is sent to the air cooling apparatus8to be cooled down to an almost liquid phase in the air cooling apparatus8.

The high-octane fuel consisting of aromatic components and the low-octane fuel remaining when a part of the high-octane fuel is separated are cooled down to the liquid phase in the air cooling apparatus8. However, only the air cooling apparatus8cannot cools down the high-octane fuel and the low-octane fuel sufficiently to be stored in the high-octane fuel tank10and in the low-octane fuel tank11.

Therefore, the high-octane fuel in the liquid phase and the low-octane fuel in the liquid phase are made to pass through the heat exchanger9. On the other hand, the un-separated fuel between the regulator4and the heater5, i.e., the un-separated fuel upstream of the heater5is also made to pass through the heat exchanger9. Thus, heat exchange between the un-separated fuel passing through the heat exchanger9and the high-octane fuel passing through the heat exchanger9occurs and heat exchange between the un-separated fuel passing through the heat exchanger9and the low-octane fuel in the liquid phase passing through the heat exchanger9occurs. Therefore, the temperature of the un-separated fuel increases and the temperatures of the high-octane fuel and the low-octane fuel in the liquid phase decrease sufficiently such that they can be stored in the high-octane fuel tank10and in the low-octane fuel tank11.

All of the above mentioned members are mounted on the vehicle. The air cooling apparatus8provides efficient cooling that is exposed to cooling wind when the vehicle on which the air cooling apparatus is mounted is moving. On the other hand, the air cooling apparatus8has heat radiation fins and can provide the cooling while the vehicle is stopped like in the engine idle condition and there is no cooling wind.

The high-octane fuel stored in the high-octane fuel tank10is sent to for example a delivery pipe, and is then injected from the delivery pipe via a fuel injector arranged in the intake port of each cylinder mainly in high engine load operations so as to be supplied to the cylinder from the intake port. On the other hand, the low-octane fuel stored in the low-octane fuel tank11is sent to, for example, another delivery pipe, and is then injected from this delivery pipe via a fuel injector arranged in each cylinder mainly in low engine load operations so as to be supplied to the cylinder directly.

Thus, in the engine having a high compression ratio, regular gasoline which has a lower price may be used. In low engine load operations in which knocking rarely occurs, the low-octane fuel separated from the regular gasoline can be mainly used via the fuel injector arranged in the cylinder. On the other hand, in the high engine load operations in which knocking readily occurs, the high-octane fuel separated from the regular gasoline can be mainly used via the fuel injector arranged in the intake port and therefore good operations without knocking can be realized.

In the present embodiment, the heat exchanger9realizes a heat exchange between the first liquid passing through it and the second liquid passing through it. A flow resistance of liquid phase is lower than that of the mixed state of gas phase and liquid phase and a heat transfer coefficient of liquid phase is higher than that of the mixed state of gas phase and liquid phase. Therefore, the heat exchanger9between a first liquid and a second liquid has a very high heat exchange efficiency and can sufficiently cool down the low-octane fuel and the high-octane fuel passing through it as the second liquid with heat exchange between the un-separated fuel passing through it as the first liquid and the second liquid even when the heat exchanger is small so as to be easily mounted on the vehicle.

The un-separated fuel is heated by the heat exchange in the heat exchanger9. Accordingly, a flow rate of the un-separated fuel, which the current heating ability of the heater5can increase to the desired temperature (for example, 355 degrees K or 80 degrees C.), namely, the temperature at which aromatic components can be sufficiently separated by the separating membrane1a, can be increased. The heater5utilizes the heat of exhaust gas and has a different heating ability in every engine operation. For example, heating ability in the engine idle operation is low because a flow rate of the exhaust gas is small and the temperature of the exhaust gas is low. On the other hand, the higher the engine load becomes, the larger the flow rate of the exhaust gas is and the higher the temperature of the exhaust gas is, the higher the heating ability becomes.

Thus, the temperature of the un-separated fuel heated by the heat exchanger9and the heater5is detected by the temperature sensor6and the flow rate of the un-separated fuel supplied to the first section1bof the station1for separating fuel components is regulated by the regulator4such that the detected temperature becomes equal to or higher than the desired temperature. The higher the engine load becomes, the larger the amount of the high-octane fuel is consumed. Therefore, it is desirable that the higher the engine load becomes, the larger the flow rate of the un-separated fuel supplied to the first section1bof the station1for separating fuel components is set.

Thus, because the un-separated fuel is heated at the temperature equal to or higher than the desired temperature at which the separating membrane can separate aromatic components sufficiently, the low-octane fuel remaining when aromatic components are separated is a relatively high temperature. Therefore, when the low-octane fuel flows out from the station1which separates the fuel components, a part of the low-octane fuel becomes a gas phase and the low-octane fuel becomes the mixed gas phase and liquid phase state. The low-octane fuel of the mixed state cannot be cooled down sufficiently by means of the small size heat exchanger9. Therefore, according to the present embodiment, the air-cooling apparatus8cools down the low-octane fuel sufficiently to change to the liquid phase.

However, if the air cooling apparatus8does not cool down the low-octane fuel sufficiently to become the liquid phase, a pressure pump or the like may pressurize the low-octane fuel such that a part of the low-octane fuel does not become the gas phase and thus may send the low-octane fuel of liquid phase to the heat exchanger9.

In the present embodiment, the high-octane fuel is collected from the second section1cof the station1which separates the fuel components as vapor fuel and is cooled down in the air-cooling apparatus8sufficiently to change to the liquid phase. However, a pressure pump may be arranged downstream of the vacuum pump7and may pressurize the high-octane fuel sufficiently to change to the liquid phase. In addition, the high-octane fuel may be collected from the second section1cof the station1for separating the fuel components as liquid fuel and may be supplied to the heat exchanger9.

In the present embodiment, the air-cooling apparatus8does not only cool down the low-octane fuel but also the high-octane fuel simultaneously sufficiently to change to the liquid phase, and the heat exchanger9does not only cool down the low-octane fuel but also the high-octane fuel of liquid phase simultaneously. However, these maters are not limit to the present invention. The high-octane fuel may be cooled down by any cooling means, for example, by another cooling apparatus or another heat exchanger.

In addition, the number and the size of the heat radiation fins of the air-cooling apparatus8are selected such that the cooling ability of the air cooling apparatus8can sufficiently cool down the low-octane fuel remaining when a part of the high-octane fuel is separated from the un-separated fuel at the flow rate set in each of the engine idle condition without the cooling wind when the vehicle is moving and the low vehicle speed condition when the speed of the vehicle on which the device for separating the fuel components is mounted is lower than the predetermined speed and the cooling wind is weak sufficiently to change to the liquid phase. In addition, if the air-cooling apparatus8also cools down the high-octane fuel, the air cooling apparatus8is designed to also have a cooling ability which can cool down the high-octane fuel separated from the un-separated fuel at the flow rate set in each of the engine idle condition and the low vehicle speed condition when the speed of the vehicle is lower than the predetermined speed sufficiently to change to the liquid phase.