JPH08218844A - Recovering device for exhaust gas heat out of automobile - Google Patents

Abstract

PURPOSE: To improve engine efficiency by a method wherein a blower and a heat-exchanger are arranged in an exhaust duct, air is fed to the heat- exchanger by a blower, and by cooling exhaust gas, a waste heat is recovered and utilized. CONSTITUTION: Air pressurized by a compressor 1 is heat-exchanged and heated by using engine exhaust gas and a heat-exchanger 2, and by increasing a volume 2-3 times or increasing a pressure 2-3 times, exhaust energy is recovered as high temperature and high pressure air. The high temperature and high pressure air is injected through the divergence nozzle of an ejector 4 and exhaust gas is forcibly discharged. As a result of a pressure reduction effect and an effect to remove remaining combustion gas in an engine being synergistically multiplied, the overall efficiency of an engine 11 is improved. Meanwhile, engine exhaust gas is cooled through heat-exchange with air and simultaneously with contraction, water in combustion gas adsorbs dust, such as soot, and toxic substance, such as SOx and NOx , whereby exhaust gas is purified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle exhaust gas heat recovery apparatus for recovering and utilizing vehicle exhaust gas heat as high-pressure air. Further, the present device is also useful as a device for purifying exhaust gas of automobiles.

[0002]

2. Description of the Related Art In an automobile engine, back pressure is generated due to pressure loss in an exhaust system such as a muffler, so that phenomena such as combustion gas remaining in the engine and reduction in pressure difference between inside and outside of a piston occur, resulting in a decrease in engine efficiency. There is a problem. Further, the thermal efficiency of the engine is as low as 25 to 30%, and there is a problem that a considerable part escapes by the heat of the exhaust gas. As a conventional technology for recovering the energy of exhaust gas, a turbocharger method utilizing an exhaust turbine has been put into practical use as a supercharger for forcibly pushing air to be sent to an engine.
However, the turbocharger uses the energy of the pressure of the exhaust gas and does not actively recover the heat of the exhaust gas. On the other hand, in the exhaust gas,
Soot and other dust generated by combustion of gasoline, SOx,
It contains harmful substances such as NOx, and if it is discharged as it is, it may cause serious air pollution problems. Therefore, conventionally, various exhaust gas purification measures have been taken by using various catalysts. However, the environment of the earth is becoming an increasingly important problem, and further reduction of harmful substances is required, and the method using a catalyst has reached the limit. Further, if the catalyst system is strengthened, the pressure loss of the exhaust gas increases, the efficiency of the engine decreases, and the problem of consuming more fuel occurs.

[0003]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems in the thermal efficiency of an automobile engine, and to recover and utilize the heat discarded by the exhaust gas to significantly improve the engine efficiency. The purpose is to provide the reliable means necessary for. Another object of the invention is to reduce harmful substances in the exhaust gas of motor vehicles.

[0004]

In order to achieve the above object, in the vehicle exhaust gas heat recovery apparatus of the present invention, the heat which is discarded as exhaust gas reaching 800 ° C. is passed through a heat exchanger. We have completed a technology to recover high pressure air and use this air as an energy source for forced exhaust emission. On the other hand, the exhaust gas is cooled by air, its volume is reduced, and water droplets are generated,
We have completed the technology to adsorb harmful substances to water droplets. According to the present invention, there is provided a vehicle exhaust gas heat recovery device having the following configuration. (1) A fan 1 and a heat exchanger 2 are provided in an exhaust duct of an automobile engine, and air is sent to the heat exchanger 2 by the blower 1 to cool the exhaust gas of the engine. Apparatus (2) The vehicle exhaust gas heat recovery apparatus according to (1), wherein the blower is a compressor 1 attached to an engine. (3) An ejector 4 (injection pump) is provided in an exhaust duct of an automobile engine, and high-pressure air is injected from a divergent nozzle 8 incorporated in the ejector 4, and exhaust gas is forcibly discharged. The exhaust gas heat recovery device for an automobile according to (2). (4) Exhaust gas of an automobile according to the above (3), characterized in that an ignition device is provided in the nozzle 8 to supply fuel to the high temperature / high pressure air at the outlet of the heat exchanger 2 for combustion in the nozzle 8. Heat recovery device. (5) The exhaust gas heat recovery device for an automobile according to any one of the above (1) to (4), wherein the drain separator 3 is installed in the exhaust duct of the automobile engine. (6) Install a thermometer 6 on the outlet side air of the heat exchanger 2,
The exhaust gas heat recovery device for an automobile according to any one of (1) to (5) above, wherein the blower 1 is controlled so that the temperature of the outlet air is constant.

[0005]

[Detailed Description] FIG. 1 is a schematic view showing an outline of an automobile exhaust gas heat recovery apparatus of the present invention. The device of the present invention is shown in FIG.
As shown in FIG. 1, it has a compressor 1, a heat exchanger 2, a drain separator 3 and an ejector 4. First, the air pressurized by the compressor 1 ( ² to ²⁰ kg / cm ² ) is heated by exchanging heat with the engine exhaust gas 2 to increase its volume by 2 to 3 times or the pressure by 2 to 3 times. Exhaust energy is recovered as high-temperature, high-pressure air. Next, the air whose volume and pressure have been increased is used as the power for the forced discharge of exhaust gas. That is, by ejecting the increased high temperature / high pressure air from the divergent nozzle 8 of the ejector 4, the exhaust gas is forcibly discharged. The reason why the heat of the exhaust gas can be recovered by the device of the present invention is that the temperature T
_1, n moles of the air to the theoretical power required when compression is -nRT ₁ ln _{(P 1)} to _P 1 kg / cm ^2, the pressure the same, the heated temperature _{T 2} air The energy that can be extracted from the ejector 4 is + nRT for isothermal expansion.
₂ ln (P ₁ ), and eventually the energy acts to be amplified by the ratio of T ₂ / T ₁ . For example, when T ₂ reaches 923 ° K, three times the energy required to compress the air (= 923 ° K / 298 ° K) is obtained, and the compression efficiency of the air and the efficiency loss of the ejector 4 are reduced. Even with consideration, positive energy is recovered by subtraction. However, the energy that can be actually extracted has an amplification effect of about 2.5 times due to adiabatic expansion. Also, if air is sealed and heated, the temperature and pressure can be increased simultaneously under a constant volume,
If this principle is applied, although it is discontinuous, an amplification effect of up to 5 times can be exerted. After all, if exhaust gas is forcibly discharged, the decompression effect and the effect of removing the residual combustion gas in the engine synergize, and even if the power of the compressor 1 is borne, the load of the engine becomes light and the overall efficiency of the engine is reduced. Will be improved. On the other hand, the engine exhaust gas is cooled by heat exchange with air, and its volume is reduced, and at the same time, water in the combustion gas is deposited. This deposited water is dust such as soot and the like generated by combustion of gasoline, S
Exhaust gas is purified because it has a property of easily adsorbing harmful substances such as Ox and NOx.

There are several types of compressors 1, but roots blowers and risholm compressors are well known and are not particularly limited as long as they can efficiently pressurize air. Further, it is rational to take the power directly from the engine rather than a dedicated electric motor, and the lower the air temperature at the time of compression, the smaller the power required, so the compressor 1 should be cooled. The intake of air should be branched from the air cleaner of the engine supply system. Further, in order to operate the compressor 1 without waste, it is preferable to use a pressure regulator and a check valve 5 that are unloaded when a predetermined pressure is reached.

The material of the heat exchanger 2 is made of metal, and the structure thereof is a multi-tube heat exchanger which allows a large contact area between the exhaust gas and the compressed air. However, the structure is not particularly limited as long as it can efficiently transfer the heat of the exhaust gas to the compressed air. For example, a structure in which a finned pipe on the compressed air side is provided in the exhaust duct in a spiral shape may be used. Further, the most efficient heat transfer is to flow the exhaust gas flow and the air flow in opposite directions, and it is preferable to keep the heat-exchanged air so that it does not cool. Further, when energy is recovered as compressed air, efficiency becomes a problem, so air that is insufficient with respect to the amount of heat of exhaust gas is used so that air having a temperature as high as possible can be obtained. Therefore, when purifying the exhaust gas as well, the secondary cooler 7 shown in FIG. 2 is provided to cool the exhaust gas to about 40 ° C. to generate water droplets. Also, the blower does not need to be compressed, so an energy-saving blower fan is used. Conversely, when it is not economical to recover the heat of the exhaust gas, which is mainly in the case of a small engine, the exhaust gas is cooled and water droplets are generated only for purifying the exhaust gas. In that case, it is preferable to omit the heat exchanger 2 and use only the secondary cooler 7. When the catalyst is used together, its position is usually installed before the heat exchanger 2.

Since the exhaust gas which has passed through the heat exchanger 2 contains water droplets whose temperature has dropped and which has absorbed harmful substances, the drain separator 3 removes the water droplets. Drain. The structure of the separator 3 is not particularly limited as long as it can separate water droplets, and may be a simple chamber or cyclone shape. However, if possible, it is preferable to have a structure that can further absorb harmful substances in the exhaust gas, such as a structure as shown in FIG. Further, the volume of the exhaust gas is reduced to one third of the original volume by cooling and removing the water droplets, and the piping resistance is reduced, so that the muffler 12 can be miniaturized thereafter. Also, it is better to collect the water drops in a dedicated tank and discard them all together.

Next, regarding the use of high temperature and high pressure air recovered from the exhaust gas, for example, utilization as supercharging air is not possible with the current engine structure, and at present, electricity generated by air expansion turbine power generation is used. It is best used directly as a power source for recovery or forced exhaust emission, in the latter case
It is rational to use the ejector 4. The ejector 4 uses the momentum and kinetic energy of a high-speed fluid,
It is a device that causes the flow of the second fluid and compresses it. The ejector 4 is composed of four parts shown in FIG. 3, and includes a high-pressure nozzle 8 for accelerating the propulsion fluid, a secondary fluid inlet for initial acceleration of the secondary fluid, and a mixing portion for decelerating the primary fluid and accelerating the secondary fluid. And a diffuser for slowing down the mixing flow. The performance of the ejector 4 required in the present invention is designed so that the secondary fluid inlet portion can maintain the low pressure as much as possible. However, for efficient design of the ejector 4,
Experience is a big deal because the relationships involved are complex. The blowing portion of the high-pressure nozzle 8 is preferably a divergent type that is efficient and can obtain a supersonic flow. Further, as described above, when only the air is injected from the nozzle 8, since the temperature is adiabatic expansion, the temperature of the air decreases with the expansion, and the energy utilization efficiency is poor. Therefore, if fuel is supplied to the high-temperature / high-pressure air so that at least isothermal expansion can be maintained and burned in the nozzle 8, the energy utilization efficiency can be remarkably improved. Further, the ejectors 4 may be provided in multiple stages in order to improve the exhaust efficiency.

Since the output of an automobile engine constantly changes, the heat recovery of exhaust gas must be a system capable of coping with the fluctuation. What is important for the system is that the energy of the recovered air is amplified more than the energy required for the original compression, so the temperature of the recovered air must be kept high. Therefore, the control system preferably controls the pressure at the compressor outlet so that the temperature of the air collected by the heat exchanger 2 becomes constant. When the engine has a low output, the pressure becomes low and the air amount decreases, and when the engine has a high output, the pressure becomes high and the air amount automatically increases.
Of course, various sensors and the like may be provided so as to maximize the energy efficiency of the entire system, and more complicated control may be performed, and there is no particular limitation as long as the above conditions are satisfied.

[0011]

The operation of the apparatus of the present invention has been described in the specific description section, but the embodiment will be described with reference to the drawings. It goes without saying that the present embodiment is an example and does not limit the scope of the invention, and that the description of the embodiment does not impose any restrictions. Example 1 An example in which the device of the present invention is applied to a 2000 cc gasoline engine is shown in FIG. 5, which shows operating data of the exhaust gas system during traveling at 70 km / Hr. As shown in the figure, the amount of exhaust gas at the engine outlet is 3370 l / min and the temperature is 79
What was 0 ° C, but the gas amount was 9 at the outlet of the countercurrent heat exchanger 7.
35 l / min, the temperature dropped to 40 ° C. In addition, 117 l / min (5.0 kg / cm ² , 38 ° C.) of compressed air for energy recovery is 355 l / min (5.0 kg / cm ² , 660).
℃) and achieved recovery of waste heat. As a result, the ejector 4 exerts the effect of forcibly discharging the exhaust gas, the fuel efficiency in the engine is improved, and the fuel consumption of the engine is reduced by 3.5% as compared with the case where this device is not installed.
0 g / min was obtained. Drain was also recovered at 2300 g / Hr. Also, dust such as soot in the exhaust gas, SOx, NOx
The harmful substances such as 85%, 40%, and 15% were reduced, respectively, which proves the practicality of the present invention. In this application example, the gasoline engine is shown, but the same effect can be obtained when the diesel engine is used.

Embodiment 2 In the second embodiment, two heat exchangers 7 are provided for the purpose of increasing the output of a 2000 cc gasoline engine.
Compressed air 68 l / min (5.0 kg / cm ² , 38 ° C)
Is introduced into the heat exchanger 7 and the inlet valve is closed to heat it so that the outlet valve is opened at a high temperature and high pressure, and when the pressure drops, the next air is added. By repeating this automatically and alternately, an average of 115 l / min (8.5 kg / cm
^2, high temperature and high pressure air 620 ° C.) is obtained. This was sent to the ejector 4 and 4 g / min of fuel was added thereto, and the fuel was ignited and injected. As a result, the forced exhaust force of the exhaust gas of the ejector 4 is remarkably increased, and when the dynamic characteristics of the engine are measured with a dynamometer, even if the engine shaft horsepower subtracts the load of the compressor 1, the engine without this device is used. This is an increase of 7.5%. As described above, the optimum operating condition required in the present invention is to obtain high-pressure air at a temperature as high as possible.
Consideration should be given to the balance with

[0013]

Since the present invention is configured as described above, it has the following effects. Since the exhaust gas heat recovery device of the present vehicle exchanges heat between high-temperature exhaust gas and air, the exhaust gas is cooled and water droplets are generated. The water droplets adsorb impurities such as soot, SOX, and NOX in the exhaust gas, so that the exhaust gas is purified. The volume of the exhaust gas is significantly reduced because the water content in the exhaust gas is removed and the temperature of the gas is also cooled. For this reason, a sound deadening effect is exerted, piping resistance is reduced, and exhaust is smooth. Energy discarded as exhaust gas from automobiles can be recovered as high-temperature, high-pressure air, and the air is used to power exhaust gas forcibly, so the amount of residual exhaust gas in the cylinder of the engine decreases and the exhaust system The back pressure is also reduced, so the output of the engine is increased. Further, since energy more than three times the energy required for air compression is obtained, positive energy is recovered by subtraction even if the loss of air compression efficiency and nozzle blowing efficiency is taken into consideration, and engine fuel consumption is reduced. Is improved by 3% or more. Not only to improve the fuel economy of the engine,
When fuel is added to the recovered air and ignited and injected, it is also effective as a means for significantly improving the output of the same engine. Further, this device does not require a design change of the existing engine, can be mass-produced, is easy to handle and install, is easy to design freely, and is excellent in economic efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the structure of an exhaust gas heat recovery device according to the present invention.

FIG. 2 is a sectional view schematically showing the structure of another example of the heat exchanger 2 according to the present invention.

FIG. 3 is a sectional view schematically showing a detailed structure of an ejector 4 according to the present invention.

FIG. 4 is a sectional view schematically showing a detailed structure of a drain separator 3 according to the present invention.

FIG. 5 is a diagram schematically showing operation data of Example 1 according to the present invention.

[Explanation of symbols]

 1 ... Compressor 7 ... Secondary cooler 2 ... Heat exchanger 8 ... Suehiro nozzle 3 ... Drain separator 9 ... Adsorber 4 ... Ejector 11 ... Engine 5 ... Check valve 12 ... Muffler 6 ... Temperature sensor 13 ... Catalyst

Claims (6)

[Claims] 1. A blower 1 for an exhaust duct of an automobile engine.
And a heat exchanger 2 are provided, and air is sent to the heat exchanger 2 by the blower 1 to cool the exhaust gas of the engine. 2. The exhaust gas heat recovery apparatus for an automobile according to claim 1, wherein the blower is a compressor 1 attached to the engine. 3. An ejector 4 is provided in an exhaust duct of an automobile engine, and high temperature / high pressure air is injected from a nozzle 8 incorporated in the ejector 4 to forcibly discharge exhaust gas. The exhaust gas heat recovery device of the vehicle described in. 4. The exhaust gas heat recovery device for an automobile according to claim 3, wherein an ignition device is provided in the nozzle 8, and fuel is supplied to the high temperature / high pressure air for combustion in the nozzle 8. 5. A drain for an exhaust duct of an automobile engine
The exhaust gas heat recovery device for an automobile according to claim 1, further comprising a separator 3. 6. The thermometer 6 is provided on the outlet side air of the heat exchanger 2, and the blower 1 is controlled so that the temperature of the outlet air becomes constant. Exhaust gas heat recovery device for automobiles.