Abstract:
A method for optimizing exhaust backpressure of an internal combustion engine, comprising the following steps: 1) arranging a damping component in an exhaust passage of the internal combustion engine, and allowing an exhaust discharged by the internal combustion engine to pass through the damping component; and 2) allowing the exhaust to be cooled prior to passing through the damping component, or allowing the exhaust to be cooled while passing through the damping component. The method allows for relatively high exhaust backpressure when the internal combustion engine has a low load, and for preventing the exhaust pressure from rising excessively rapid when the internal combustion engine has a heavy load. The apparatus and system for optimizing exhaust backpressure of an internal combustion engine is also provided.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention pertains to the technical field of efficiency enhancing of an internal combustion engine, and relates to a method for optimizing exhaust backpressure of an internal combustion engine. The present invention further relates to an apparatus and system for optimizing exhaust backpressure of an internal combustion engine. 
       DESCRIPTION OF THE PRIOR ART 
       [0002]    In this century, the world&#39;s oil resources insufficiency and environmental pollution problems have become increasingly prominent, and there is the need to further improve the economy of the internal combustion engine and exhaust cleaning. The energy efficiency of the internal combustion engine, i.e. fuel efficiency also needs to be further improved, which is the basis and prerequisite of all facilities and equipment powered by internal combustion engines to enhance energy efficiency. 
         [0003]    At present, the main way to increase the energy efficiency of internal combustion engine is to improve the ventilation effect, i.e. intake and exhaust process, of the internal combustion engine. The way of improving intake is ‘pressure boost’, i.e. to increase the intake pressure; the way of improving exhaust is ‘depressurization’, i.e. to reduce the exhaust backpressure, that is, to reduce the resistance of the exhaust. ‘Pressure boost’ and ‘depressurization’, the two complement each other. 
         [0004]    The pressure boost technology developed at the beginning of last century dramatically improves the performances of the power, economy and emission of the internal combustion engine, which has become an important symbol of the internal combustion engine development. Pressure boost model has become the basic model of the internal combustion engine, and in particular, the turbine pressure boost technology that uses the internal combustion engine exhaust gas to drive a turbine, and then a compressor is driven by a turbine to ‘pressure boost’ intake air of an internal combustion engine, and the intercooling technology that is combined with intake air pressure boost, have now developed into a near-perfect and are widely used. But the disadvantage is: the acceleration performance of the internal combustion engine is limited due to the internal combustion engine being sensitive to exhaust backpressure. 
         [0005]    The so-called ‘depressurization’ is to reduce the exhaust backpressure, and the exhaust backpressure is related to the exhaust resistance of the internal combustion engine. With the increase of the load when the engine operates, the mass of the exhaust gas and the temperature of the exhaust gas are also increased. With the double impact of the mass and temperature of the exhaust gas, the volume flow and the flow rate of the exhaust increase even larger, so that the resistance of the exhaust passage, including the resistance of the other components (e.g., a muffler) in the exhaust passage, rises rapidly due to the law of positive pressure being proportional to the square of flow rate. Therefore, the internal combustion engine backpressure also increases rapidly with the engine load. High backpressure means that the exhaust gas flow is encountered with a large resistance, such that the exhaust within the cylinder is difficult to discharge cleanly, thus affecting subsequent combustion quality. Therefore, the exhaust backpressure affects the performance of an internal combustion engine. The increase of the backpressure will lead to decrease of the combustion efficiency, economy and emission performance of the internal combustion engine, and in the meantime the power performance decreases and fuel consumption increases. Data shows that this will cause at least more than 10% loss of energy efficiency to the internal combustion engine. Especially for a turbocharged internal combustion engine rotating at high speed relying on an exhaust gas driven turbine, the increase of the exhaust backpressure leads to a decrease of the pressure drop of the exhaust gas which drives the turbine, causing a decrease of the effect of turbocharging, which in turn makes the intake pressure reduced, so as to result in a further decrease of the energy efficiency of the internal combustion engine. What is even more serious is that, with countries being increasingly strict on international environmental regulations, the requirements for the internal combustion engine exhaust gas treatment are also increasingly higher. 
         [0006]    As the backpressure of a system is the sum of the pressure drops formed by the airflow sequentially passes through each of the elements in the system, and the pressure drop formed by passing through each element is proportional to the square of the flow rate of the airflow passing through. Accordingly, after the installation of the exhaust processing devices and apparatus for muffling, purification or even waste heat recovery for an internal combustion engine, the engine exhaust backpressure is greatly increased, the energy efficiency of an internal combustion engine is reduced, and energy consumption is increased. The rise of the internal combustion engine energy consumption means more fossil fuel consumption, resulting in more pollution, which in turn results in reducing the effects of the environmental protection and energy-saving measures taken earlier. 
         [0007]    So, while people are continuously developing the ‘pressure boost’ technology, they are also seeking for technology of ‘depressurization’, such as the multi-valve technology which enlarges the exhaust gas flow space by using multiple exhaust valves, so that the exhaust backpressure is reduced. For some special competitive occasions, such as racing, the power of an internal combustion engine is required to give full play, even without installing a muffler aiming to reduce backpressure as much as possible. 
         [0008]    However, in a situation where the internal combustion engine is under low load, if the exhaust backpressure is very low, due to the exhaust valve being opened in advance, the fuel gas still having certain pressure will be discharged from the excessively clear exhaust valve before the piston reaches the bottom stop point, such that a portion of power is lost and the torque is reduced. It can be seen that keeping up a certain exhaust backpressure when the internal combustion engine is under low load will instead increase the torque. 
         [0009]    In summary, for the backpressure of an internal combustion engine, it is desired that the backpressure is not too low when the internal combustion engine is under low load, and however, it is desired that the exhaust backpressure is restrained to the greatest extent from increasing too rapidly. Only then the efficiency improvement of the internal combustion engine can only be realized under all working conditions thereof 
       SUMMARY OF THE INVENTION 
       [0010]    In view of the existing desires for the exhaust backpressure of an internal combustion engine, the present invention provides a new method, a new apparatus and a new system for optimizing exhaust backpressure of an internal combustion engine. The present invention is based upon the principle: If the exhaust gas of an internal combustion engine is rapidly cooled, the exhaust backpressure can be greatly reduced. So, when the internal combustion engine is under low load, a certain amount of exhaust resistance is arranged such that the backpressure will not go so far as to be too low; when the internal combustion engine is under high load, the exhaust gas is rapidly cooled so that the backpressure will not go so far as to rise too rapidly. 
         [0011]    A first object of the present invention is to provide a method for optimizing exhaust backpressure of an internal combustion engine, comprising:
       1) providing a damping member in an exhaust passage of an internal combustion engine, and making an exhaust gas discharged from an internal combustion engine passing through said damping member;   2) cooling the exhaust gas before passing through said damping member, or cooling the exhaust gas while passing through said damping member.       
 
         [0014]    By utilizing the method provided by the present invention the following can be achieved: a relatively higher exhaust backpressure when the internal combustion engine is under low load, and the exhaust backpressure will not rise too fast when the internal combustion engine is under high load. Specifically, allowing the exhaust gas discharged by the internal combustion engine to pass through a damping member that is capable of providing a certain amount of exhaust resistance produces a desired relatively high exhaust backpressure, so as to increase the torque of the internal combustion engine when it is under low load. The exhaust gas being rapidly cooled before or when it passes through the damping member can achieve the purpose of increasing gas density of the exhaust gas and decreasing the flow rate of the exhaust gas. The backpressure is restrained from rising to fast when the internal combustion engine is under intermediate, high load, so as to improve the efficiency of the internal combustion engine. 
         [0015]    The present invention also provides an apparatus for optimizing exhaust backpressure of an internal combustion engine, comprising:
       1) a housing;   2) an exhaust gas inlet provided on the housing allowing an exhaust gas to enter into an interior of the housing, an exhaust gas outlet provided thereon allowing an exhaust gas to be discharged out of the housing;   3) a damping member provided in the interior of the housing or on the housing;   4) a cooling member provided in the interior of the housing for cooling an exhaust gas.       
 
         [0020]    Based on the above principle, mounting the apparatus provided by the present invention in the exhaust passage can not only provide a certain amount of exhaust resistance when the internal combustion engine is under low load, but also makes the exhaust backpressure not rise too fast when the internal combustion engine is under high load. Especially when the existing members having resistance, such as mufflers, in the exhaust passage is replaced with the apparatus of the present invention, the overall performance of the exhaust system can be preferably improved. 
         [0021]    The present invention also provides another apparatus for optimizing exhaust backpressure of an internal combustion engine, comprising:
       1) a housing;   2) an exhaust gas inlet provided on the housing allowing an exhaust gas to enter into an interior of the housing, an exhaust gas outlet provided thereon allowing a exhaust gas to be discharged out of the housing;   3) a damping member provided in the interior of the housing or on the housing;   4) a cooling water inlet provided on the housing allowing cooling water to enter into the housing, a cooling water outlet provided thereon allowing cooling water to be discharged out of the housing;   said cooling water inlet, cooling water outlet, exhaust gas inlet and exhaust gas outlet configured so that cooling water and exhaust gas able to come in to contact with each other in an interior of the housing.       
 
         [0027]    Similarly, installing the apparatus in the exhaust passage can also achieve the purpose of optimizing exhaust backpressure of an internal combustion engine. 
         [0028]    The present invention also provides a system for optimizing exhaust backpressure of an internal combustion engine, comprising an exhaust passage of an internal combustion engine, wherein said system further comprises an apparatus for optimizing exhaust backpressure of an internal combustion engine provided by the present invention, which is mounted in said exhaust passage of an internal combustion engine. Based on the same principle, the present invention provides a system that can achieve the purpose of optimizing exhaust backpressure of an internal combustion engine. 
         [0029]    Utilizing the method, apparatus and system provided by the present invention can simply and efficiently enhance the power of an internal combustion engine, reduce fuel consumption and enhance the specific power of an internal combustion engine, and can be applied to various devices using internal combustion engine as the power. 
         [0030]    The first principle of the present invention is: set a certain amount of exhaust resistance, so that an internal combustion engine has a desired, relatively high exhaust backpressure when under low load. 
         [0031]    The scheme to achieve its purpose is: to provide a damping member in the exhaust passage of an internal combustion engine, and allow the exhaust gas discharged from the internal combustion engine to pass through said damping member. 
         [0032]    Here, the damping member is a member that can provide a certain amount of exhaust resistance, that is, the pressure drop produced before and after exhaust gas passing through the damping member is a desired pressure drop. Forms of the damping member may include: 1) reducing the cross-section of the exhaust passage of the internal combustion engine, or 2) dividing the exhaust gas into small tributaries, or 3) changing the flow direction of the exhaust gas, or 4) other forms that can provide a certain amount of exhaust resistance, or 5) a combination of the above forms. 
         [0033]    The damping member is a member that can reduce the cross-section of the exhaust passage, such as an exhaust pipe with abruptly reduced cross-sections, or a member provided in the exhaust pipe and having pores. It can be provided to abruptly reduce the cross-section of the exhaust passage of an internal combustion engine, so as to provide a certain amount of exhaust resistance. Such as, providing a baffle with pore in the exhaust pipe of an internal combustion engine, such that the exhaust gas can only pass through the pores. It also can be provided such that the exhaust pipe of an internal combustion engine abruptly becomes thinner. In addition, the larger the extent to which the cross-section reduces, the larger the exhaust resistance. 
         [0034]    The damping member may also be a member that can divide the exhaust gas into a plurality of tributaries. Here, the way of the noted ‘divide the exhaust gas into a plurality of tributaries’ may be making the exhaust gas pass through a structure with a plurality of distributed pores, and the exhaust gas is thus dispersed by the pores. The way used may also be making the exhaust gas pass through a structure with a plurality of gaps, and the exhaust gas is thus dispersed by the gaps. By the method of dividing the exhaust gas into small tributaries, a certain amount of exhaust resistance can also be provided. In the method, the degree of the exhaust gas being divided can be adjusted depending on the desired exhaust backpressure: the more the number of small tributaries into which the exhaust gas is divided, the thinner the divided small tributaries, and the greater the exhaust resistance; vice versa. 
         [0035]    The damping member may also be an exhaust pipe that can change the flow direction of the exhaust gas. A certain amount of exhaust resistance can also be provided if the flow direction of the exhaust gas is changed, such as by having a plurality of curved exhaust pipes. 
         [0036]    The damping member referred to in the present invention can also be provided in the interior of a housing, and cools the exhaust gas discharged by the internal combustion engine in the interior of the housing. So, the method provided by the present invention can also include: making the exhaust gas discharged by the internal combustion engine enter into the interior of the housing through an exhaust gas inlet on the housing, then discharge the cooled exhaust gas out of the housing through an exhaust gas outlet on the housing. The damping member may be located in the interior of the housing, such as by providing a pore plate or padding with a large number of gaps in the interior of the housing. In addition, the damping member may also be located on the housing, such as an abrupt reducing of cross-sections existing from the interior of the housing to the exhaust gas outlet on the housing. 
         [0037]    Another principle of the present invention is: the high-temperature exhaust gas of an internal combustion engine being rapidly cooled may greatly reduce the flow rate of the exhaust gas, so that the exhaust backpressure will not rise too fast when the internal combustion engine is under high load. 
         [0038]    It is known in the prior art that: the existing structure of the exhaust passage of the internal combustion engine having a certain amount of exhaust resistance (e.g., an exhaust pipe, muffler, etc.), as the load of the internal combustion engine increases, the gas displacement and the exhaust temperature will rise with it, so that the flow rate rises, and due to the positive pressure, i.e. the resistance being proportional to the square of the flow rate, the exhaust backpressure is thus caused to rise rapidly. 
         [0039]    The applicant has found that before or when the exhaust gas is encountered with a certain amount of resistance, the exhaust backpressure may be reduced if the exhaust gas temperature can be rapidly lowered, thereby improving the efficiency of the internal combustion engine. 
         [0040]    The scheme of rapidly reducing the temperature of the exhaust gas may be: 1) making the exhaust gas and the cooling liquid come into contact with each other; or 2) dividing the exhaust gas into a plurality of small tributaries, and then making the dispersed small tributaries heat exchange with the cooling medium, or 3) a combination of the above two. 
         [0041]    If the high-temperature exhaust gas is made to come into direct contact with a cooling liquid such as cooling water, the purpose of rapid cooling can be achieved. A preferable way is to keep the cooling water flowing, such as the use of spray, discharging the cooling water which has absorbed heat, and the exhaust gas continuously contacting the new cooling water, thus the cooling effect will be better. 
         [0042]    Here, the cooling water source can be determined based on the specific circumstances. 
         [0043]    The cooling water used as the cooling fluid may come from an external independent water system of the immediate natural environment, for example, taken from the natural water body such as seawater or inland freshwater naturally existing. As to the apparatus (such as vessels) that use the internal combustion engine as the power on the ocean or freshwater, the cooling water may be directly extracted from the seawater or freshwater of the immediate nature environment, or, the seawater or freshwater may be firstly stored in a water storing apparatus such as water tank, water tower, the cooling water is obtained from the water storing apparatus. The cooling water which has absorbed heat may be directly discharged to the immediate natural environment; also the cooling water which has absorbed heat may be processed before being discharged to the immediate natural environment. Thus, the method provided by the present invention also includes: extracting cooling water from a natural water body and convey it to the housing. The system provided by the present invention also includes an apparatus, such as a cooling water intake pipe installed with a pump, which is able to extract cooling water from a natural water body and convey it to the housing, the cooling water intake pipe communicating with the cooling water inlet of the housing. 
         [0044]    The cooling water of the internal combustion engine may also be reused to be used as the cooling water for cooling the liquid. Most apparatus that uses internal combustion engine as the power, such as vehicles, vessels, etc., per se, have a set of cooling water system of internal combustion engine. In this case, the cooling water may be taken from the cooling water system of the power apparatus itself. Therefore, the method provided by the present invention also includes conveying the cooling water of an internal combustion engine to a housing. The system provided by the present invention also includes an apparatus that is able to convey the cooling water of an internal combustion engine to a housing. 
         [0045]    The cooling water used as the cooling liquid may be used combining the above two methods, both using the cooling water from a natural water body and using the cooling water of the internal combustion engine. 
         [0046]    The cooling water used as the cooling liquid may also be recycled. The cooling water discharged from the housing, which has absorbed heat of the high-temperature exhaust gas, may be directly discharge out or discharged after being processed, and may also be recycled. For example, the cooling water absorbing heat after cooling the high-temperature exhaust gas may flow through a heat exchanger, being cooled before entering the housing again as the cooling water. 
         [0047]    The cooling water may be allowed to come into contact with the exhaust gas of an internal combustion engine in an interior of a housing, thereby achieving the purpose of rapidly reducing the temperature of the exhaust gas. Therefore, the method provided by the present invention may also include: making the cooling liquid enter into the interior of the housing through the cooling water inlet of the housing, and discharging the cooling liquid which has absorbed heat from the exhaust gas out of the housing through the cooling water outlet of the housing. 
         [0048]    The exhaust gas of the internal combustion engine may be allowed to enter from the exhaust gas inlet on a housing, and be discharged from the exhaust gas outlet, forming an exhaust gas flow path. In addition, the cooling water may be allowed to enter from the cooling water inlet of the housing, and be discharged from the cooling water outlet, forming a cooling water flow path. The exhaust gas inlet abovementioned refers to any opening that allows fluid enter into the interior of the housing, which may be a direct opening on the wall of the housing, then, through a connecting member, communicates with the pipe for conveying liquid. The housing may also be integrally molded with the conveying pipe. The conveying pipe may also extend into the interior of the housing, so that, the exhaust gas inlet refers to the pipe orifice extending into the interior of the housing. The cooling water inlet, cooling water outlet and the exhaust gas outlet may also use the various forms as abovementioned. 
         [0049]    The housing used by the present invention is a closed housing, that is, except the positions of abovementioned exhaust gas inlet, exhaust gas outlet, cooling water inlet, cooling water outlet, the other parts are all sealed, and the gas or liquid entering the housing can only enter and exit from the abovementioned inlets and outlets. 
         [0050]    In order to achieve the purpose of rapid cooling of the exhaust gas, in the method and apparatus provided by the present invention, the exhaust gas of an internal combustion engine and the cooling water are required to come into contact with each other, that is, the flow path of the exhaust gas of the internal combustion engine and the flow path of the cooling water are made to overlap with each other. 
         [0051]    If a more optimal cooling effect is desired, one preferred embodiment is to make the exhaust gas of the internal combustion engine and the cooling water to contact reversely or/and laterally, that is, the flow direction of the exhaust gas and the flow direction of the cooling water are away from each other or facing each other, or nearly away from each other or facing each other. If the cooling water inlet is made to be located downstream of the exhaust gas flow, and the cooling water outlet is located upstream of the exhaust gas flow, the cooling water and exhaust gas thereby may reversely contact, such that the contact is more adequate. Therefore, in a preferred embodiment, the exhaust gas of the internal combustion engine and the cooling water reversely contact. In a more preferred embodiment, the exhaust gas of the internal combustion engine pass through the interior of the housing from bottom to top, and the cooling water pass through the interior of the housing from top to bottom, allowing them to reversely contact. The advantage thereof is that the exhaust gas of the internal combustion engine may disperse in the interior of the housing more adequately, and the cooling water may flow by fully utilizing the gravity effect, other than applying extra pressure to maintain its flowing. Thus, the cooling water inlet may be configured to be higher than the cooling water outlet in the gravity direction, so that the cooling water entering the housing through the cooling water inlet passes through the interior of the housing from top to bottom; the exhaust gas inlet is lower than the exhaust gas outlet in the gravity direction, so that the exhaust gas entering the housing through the exhaust gas inlet passes through the interior of the housing from bottom to top. Thus, the cooling water and the exhaust gas may reversely contact, thereby the contact is more adequate. 
         [0052]    In order to further enhance the full contact of the cooling water and the exhaust gas, one can think of ways to improve the degree of dispersion of the cooling water entering the housing. For instance, one or more water distributor composed of spraying member with a plurality of pores, arranged uniformly on the upper side of the interior of the housing, spraying the cooling water onto the entire interior of the housing to the best of it, so that the cross-section of the housing can be uniformly distributed with water. Thus, the method provided by the present invention also includes: dispersing the cooling water entering the interior of the housing. The housing of the apparatus provided by the present invention is also provided with a member dispersing the cooling water entering into the interior of the housing, such as a water distributor. 
         [0053]    In a more preferred embodiment, in order to not allow the cooling water from entering the exhaust pipe of the internal combustion engine from the exhaust gas inlet, the cooling water outlet may be configured to be lower than the exhaust gas inlet in the gravity direction. Thus, before the liquid surface of the cooling water flowing to or falling onto the bottom of the housing reaches the position of the exhaust gas inlet, the cooling water is already discharged from the cooling water outlet. 
         [0054]    In addition, the bottom of the casing may also be provided with a water seal, making the liquid surface of the cooling water higher than the cooling water outlet and lower than the exhaust gas inlet. Thus, the exhaust gas will not flow out from the cooling water outlet. Further, providing a water seal makes the cooling water not enter the exhaust gas inlet, even if the angle of inclination of the water seal liquid surface in all direction reaches 22.5 °. 
         [0055]    In a more preferred embodiment, the exhaust gas inlet is located on the lower portion of the side surface of the housing, and the exhaust gas outlet is located at the top of the housing, and the exhaust gas outlet may connect directly to the chimney, discharging directly the exhaust gas into the atmosphere. The cooling water inlet is located on the upper portion of the side surface of the housing, and the cooling water outlet is located on the lower portion of the side surface. Moreover, in the gravity direction, the cooling water outlet is lower than the exhaust gas inlet. In a most preferred embodiment, the exhaust gas inlet is located at the bottom of the housing, and the exhaust gas outlet is located at the top of the housing, so that the exhaust gas inlet may connect directly to the exhaust pipe of the internal combustion engine, and the exhaust gas outlet connects directly to the chimney, discharging the exhaust gas directly into the atmosphere. 
         [0056]    If the exhaust gas is divided into small tributaries, and then the dispersed small tributaries heat exchange with a cooling medium, so that the efficiency of heat exchange between the exhaust gas and the cooling medium can be greatly improved, thereby achieving the purpose of rapidly reducing the exhaust temperature, so that the exhaust backpressure will not rise too face when the internal combustion engine is under high load. Another effect of cooling the exhaust gas in this way is: such that the exhaust backpressure will not be too low when the internal combustion engine is under low load, thereby achieving the effect of optimizing the exhaust backpressure under all working conditions. 
         [0057]    Here, the way of the abovementioned ‘dividing the exhaust gas into small tributaries’ may be making the exhaust gas pass through a structure with pores distributed therein, and the exhaust gas is thus dispersed by the pores. The way used may also be making the exhaust gas pass through a structure having gaps, such as a heat dissipating sheet, and the exhaust gas is thus dissipated by gaps. 
         [0058]    Here, the cooling medium may be gases having endothermic properties, such as air, hydrogen, etc. Then the cooling medium may be made to come into contact with the exhaust gas, which is divided into small tributaries, through the cooling member, so that the exhaust gas is cooled. The cooling member may be a heat dissipating sheet or radiator made of materials having good heat transfer properties, such as a metal material. A part of the cooling member is located in the housing, and a part outside the housing, being able to rapidly transfer the heat of the exhaust gas in the housing to the outside of the housing to be released. In this case, the process of heat exchange between the exhaust gas and the cooling member is at the same time the process of the exhaust gas being divided into small tributaries. Here, the cooling medium may also be in the form of a combination of cooling member and fluid, such as the flowing cooling water being encapsulated in a metal pipe, which can also achieve the purpose of rapid cooling. The benefit of doing so is that the cooling water in the pipe may generate vapor, the heat of which may be conveniently and directly utilized. For example, heat exchange is performed between a heat exchanger of tubular, plate, tube-wall or finned tube, and the exhaust gas. Similarly, when the high-temperature exhaust gas passes through the heat exchanger, it is divided into small tributaries to then perform heat exchange with the heat exchanger as well. 
         [0059]    As described above, when the internal combustion engine is under high load, the backpressure is desired to be as low as possible. While in the prior art, the exhaust resistance of the structure (such as a muffler) provided in the exhaust passage of the internal combustion engine is relatively small. Therefore, in the case of the internal combustion engine being under low load, the desired exhaust backpressure cannot be achieved. In this way, the process of dividing the exhaust gas into small tributaries is also the process of providing a certain amount of exhaust resistance. The degree of the exhaust gas being divided can be adjusted depending on the desired exhaust backpressure. The more the small tributaries of the exhaust gas divided, the thinner the small tributaries divided, the greater the exhaust resistance; vice versa. 
         [0060]    Accordingly, in this way, the purpose of optimizing exhaust backpressure of an internal combustion engine under all working conditions can be realized. 
         [0061]    For the cooling of the exhaust gas, the most preferred way is to divide the exhaust gas into small tributaries, which is then cooled by way of making which and the cooling liquid (such as cooling water) come into contact with each other. For example, the exhaust gas is made to pass through a member having a large amount of gaps, to be divided into a plurality of small tributaries which in said gaps come into contact with the cooling liquid. In a preferred embodiment of the present invention, the housing is filled with padding which form gaps thereinbetween, thereby forming a padding layer having a large number of gaps which is a member which can divide the exhaust gas into a plurality of small tributaries, i.e. the damping member. Padding containing gaps thereby having a large specific surface area may be included in the housing, for the purpose that a large number of pores are formed in at least a part of the space inside the housing. Thus, the cooling fluid has to be dispersed when passing through the pores between the padding, in which the cooling fluid and the exhaust gas may fully contact. When the cooling liquid is cooling water, the form of padding may be selected to be the common bulk padding as Pall rings, Raschig rings or other saddle rings, also may be selected to be a common structured padding. The padding texture is preferred to be weatherproof materials like metal, ceramics, etc., and also can be selected to be polymer materials, such as polypropylene, polyethylene, or ABS engineering plastics, etc., or there kinds of materials may be used in combination. The high-temperature exhaust gas is divided into small tributaries when passing through this padding having a large specific surface area, preferably making the cooling liquid like cooling water come into direct contact with the high-temperature exhaust gas in said padding, allowing the high-temperature exhaust gas to be cooling rapidly. Therefore, in the method and apparatus provided by the present invention, the housing is filled with padding which can form gaps thereinbetween, forming a padding layer with a large number of gaps. The method provided by the present invention also includes: the exhaust gas is made to pass through a padding layer having a large number of gaps. 
         [0062]    In addition, if the cooling fluid is selected to be cooling gas, such as air, the purpose of rapid cooling may also be achieved. In this case, the padding is preferably selected to be ceramic, enamel and metal materials, and these kinds of materials may be used in combination. 
         [0063]    The method or apparatus provided by the present invention is specially suited for a turbocharged internal combustion engine, where the exhaust gas discharged by the internal combustion engine passes through a turbocharger impeller and works, before entering the housing from the gas inlet of the housing. Accordingly, the method provided by the present invention also includes: the exhaust gas discharged by the internal combustion engine passes through the turbocharger impeller and works before entering the housing. The exhaust passage of the internal combustion engine of the system provided by the present invention may be an exhaust passage of high-temperature exhaust gas, which is connected to the exhaust outlet at the exhaust gas side of the turbocharger. 
         [0064]    Further, as the exhaust passage of current internal combustion engine is normally provided with one or more of a muffler, exhaust gas purification and waste heat recycling apparatus or devices. If these apparatus are arranged in the exhaust passage of the internal combustion engine, a certain amount of exhaust resistance will be provided, providing pressure drop in the exhaust path of the exhaust gas, and these apparatus are the apparatus that can make exhaust gas discharge produce a pressure drop. The more the pressure drop is, the greater the exhaust resistance is, leading to a higher exhaust backpressure. 
         [0065]    According to the apparatus or devices through which the exhaust gas of the internal combustion engine passes before eventually discharged into the atmosphere, and to the different order of passing through these apparatus or devices, the method of the present invention has at least the following several applications: that is, the present method is applied before or after the exhaust gas passing through the above apparatus or devices, or the apparatus for optimizing backpressure according to the present invention is made to achieve the functions of the above apparatus or devices at the same time of optimizing backpressure, so as to replace the above apparatus or devices. 
         [0066]    Thus, the system provided by the present invention may possibly has several ways described as follows, wherein, for convenience of description, in the following content, P 0  is set to be the external atmospheric pressure. In addition, the pressure drop caused by the resistance of the exhaust pipe is ignored, and pressure drop ΔP is used to represent the local pressure drops of one or more other exhaust gas treatment apparatus and devices. As the gas flow passes through the damping member is the apparatus of the present invention, the cooling apparatus per se will bring in a pressure drop ΔP i . Here it should be noted that, when the load of the internal combustion engine rises, the flow rate were to be increased rapidly, but due to the high-temperature exhaust gas being cooled rapidly with increased density and decreased volume, the flow rate thereby is lowered rapidly. Thus, in the case of a relative high-temperature exhaust, the rising range of ΔP i  is small when the load of the internal combustion engine is increasing. In this case, as the flow rate is an exponential relationship with the positive pressure, the positive pressure or resistance caused by the decrease of the flow rate is still decreasing, even taking into consideration of the factor of the increase brought to the positive pressure by the increase of the exhaust gas density. 
         [0067]    When there is no other exhaust gas treatment apparatus and device in the exhaust pipe, the exhaust backpressure of the internal combustion engine then is approximately to be the sum of the external atmospheric pressure P 0  and the pressure drop ΔP i  of the cooling apparatus per se, i.e.: 
         [0000]    
       
      
       P=P 
       0 
       +ΔP 
       i  
      
     
         [0068]    Thus, when the internal combustion engine is under low load, due to the presence of ΔP i , the torque of the internal combustion engine may be improved. When the load of the internal combustion engine is increasing, as described above, the rising range of ΔP i  is small, so the influence on the backpressure P is limited. 
         [0069]    If the exhaust passage is also installed with other apparatus therein which increases the exhaust backpressure, such as a muffler, and is located downstream of the apparatus provided by the present invention, then, the exhaust gas discharged by the internal combustion engine firstly passes through the apparatus provided by the present invention, and then through other apparatus or device for exhaust gas treatment, and after that, passes through the pipe and is discharged into the atmosphere. The exhaust backpressure P is approximately equal to the sum of external atmospheric pressure P 0  and pressure drop ΔP i  of the apparatus per se of the present invention and other apparatus or device for exhaust gas treatment, i.e.: 
         [0000]    
       
      
       P=P 
       0 
       +ΔP+ΔP 
       i  
      
     
         [0070]    Although, in comparison with the case in which the apparatus of the present invention is not used, the newly introduced apparatus of the present invention produces a pressure drop ΔP i , but as the high-temperature exhaust gas when the internal combustion engine is under intermediate and high load is rapidly cooled when passing through the apparatus of the present invention, so that the flow rate is largely decreased. As the pressure drop is proportional to the square of the flow rate, so the pressure drop ΔP when the cooled exhaust gas flow passes through the above described other apparatus or device for exhaust gas treatment is largely decreased in comparison with that when the high-temperature exhaust gas passes through, thereby improving the efficiency of the internal combustion engine. Moreover, in this case, as described above, when the internal combustion engine is under low load, the effect of improving the torque of the internal combustion engine exists, similarly. 
         [0071]    According to the above description, if there is other apparatus for exhaust gas treatment installed in the exhaust passage, the exhaust backpressure will be adversely affected. However, in some cases, for environmental or other objects, it is necessary to install an apparatus for exhaust gas treatment, such as a muffler, in the exhaust passage. Therefore, if multiple functions can be integrated by the apparatus provided by the present invention, for instance, the apparatus is made to simultaneously have the muffling function, thereby the exhaust backpressure can be further optimized. 
         [0072]    When other apparatus or device for exhaust gas treatment can be omitted if their functions are integrated with the apparatus of the present invention, this case is similar to the case in which the apparatus of the present invention is separately installed. Then, the exhaust backpressure of the internal combustion engine is approximately equal to the sum of external atmospheric pressure P 0  and the pressure drop ΔP i  of the apparatus per se of the present invention, i.e.: 
         [0000]    
       
      
       P=P 
       0 
       +ΔP 
       i  
      
     
         [0073]    This means that the pressure drop ΔP brought by other apparatus or device for exhaust gas treatment can be eliminated, and the exhaust backpressure is greatly decreased relative to the original situation, thereby improving the efficiency of the internal combustion engine. Similarly, due to the existence of ΔP i , the torque when the internal combustion engine is under low load is increased. Thus it can be seen that a more preferred scheme is that the apparatus of the present invention can integrate the functions of other apparatus or device for exhaust gas treatment, and then to replace these apparatus or devices for exhaust gas treatment. This replacement is precious for spatial resource, for instance, very important for a floating platform like vessel, etc., equipped with a muffler and a waste heat boiler. 
         [0074]    It should be noted that, from the above description, it can be seen that the principle of the cooling apparatus integrating the waste heat recycling of the waste heat boiler lies in the recycling of the heat absorbed after the heat exchange between the cooling fluid and the high-temperature exhaust gas. The principle of integrating the muffling function of the muffler lies in that the effects of the exhaust gas, passing through the apparatus of the present invention, being divided by cross-section expansion and gas flow alteration, the two of which are theoretically and realistically not contradictory. Therefore, the cooling apparatus of the present invention may simultaneously integrate the functions of waste heat recycling and muffling. 
         [0075]    In order to prevent noise pollution, at present, the exhaust passage of the internal combustion engine is generally mounted with the muffler, which is also a main member causing the rise of the exhaust backpressure of the internal combustion engine. The applicant has found that, if the exhaust gas entering the housing can be rapidly cooled, the function of enhancing the muffling effect can be realized. 
         [0076]    Based on the muffling principle, there are different types of mufflers like resistive muffler, reactive muffler and impedance composite muffler. A resistive muffler mainly uses porous sound-absorbing materials to reduce noises. When sound waves enter the resistive muffler, part of the sound energy is turned into heat by friction in the pores of the porous material to be dissipated, making the sound wave passing through the muffler be weakened. A resistive muffler has good effect on intermediate and high frequency, and poor effect on low frequency. A reactive muffler is combined from chambers and ducts with abrupt interfaces, making use of abrupt expansion or contraction of the cross-section of the pipe to reflect back the sound waves of certain frequencies transmitting along the pipe at the position of sudden change to the direction of the sound source, so as to achieve the purpose of muffling. The reactive muffler is suitable for eliminating noise of low-to-intermediate frequency, and is poor for high-frequency noise. Combining the resistive structure and reactive structure in a certain manner, an impedance composite muffler is formed, which has muffling characteristics of both. 
         [0077]    In order to achieve good muffling effect, the following schemes have been found which facilitate enhancing the muffling effect: 1) multiple changes in the direction of air flow, 2) the air flow repeatedly passing through cross-sections first contracting and then expanding, 3) dividing the air flow into a plurality of small tributaries and flow along a plurality of unsmooth planes, 4) cooling the air flow. 
         [0078]    For an internal combustion engine, on one hand, a muffler is essential, based on the requirements of environmental protection, and on the other hand, the muffling effect is constrained by the result of the rise of the backpressure. Therefore, the existing muffling technology for an internal combustion engine is often not good to meet these expectations. For a resistive muffler, a plurality of pores are needed to be provided in the muffler to change and divide the air flow. The more, longer, more irregular the pores, the better the resistive muffling effect, but the exhaust backpressure caused by the muffler is also greater and the loss of power that the internal combustion engine can withstand is limited. For reactive muffling, the greater the expansion magnification of the cross-section of the exhaust passage, that is, the greater the volume of the muffler, the more favorable for muffling. However, for most occasions, especially for ships etc. which have limited accommodating spaces, the way of cross-section expansion is difficult to apply. As to ‘cooling’ of the air flow, the existing muffling technology is even more difficult to achieve, particularly in the muffler in a dense space of a ship, where not only the cooling cannot be achieved, but to prevent a high-temperature of several hundred ° C. burning the surrounding facilities and personnel, insulation materials have to be used for a tight wrapping up for ‘preserving heat’. 
         [0079]    The method or apparatus provided by the present invention can make use of the principle of reactive muffling to effect muffling. Therefore, in the method or apparatus provided by the present invention, abrupt expansion of cross-section is formed from the exhaust gas inlet to the interior of the housing. Here, the method or apparatus provided by the present invention at least makes use of the principle of reactive muffling. A reactive muffler is combined from chambers and ducts with abrupt interfaces, making use of abrupt expansion or contraction of cross-section of the pipe to reflect back the sound waves of certain frequencies transmitting along the pipe at the position of sudden change to the direction of the sound source, so as to achieve the purpose of muffling. In the method and apparatus provided by the present invention, abrupt expansion of cross-section is formed from the exhaust gas inlet to the interior of the housing. The abrupt expansion of cross-section here refers to reducing noise of the exhaust gas by making use of the reactive muffling principle. 
         [0080]    If the casing is made into a regular shape, e.g. a cylindrical or other regular shape, tested by the applicant, when the cross-sectional area of the exhaust gas inlet is 0.05 to 0.5 times the housing of the cross-sectional area, the muffling effect is very significant. Accordingly, in a preferred embodiment, the exhaust gas inlet cross-sectional area is 0.05 to 0.5 times the cross-sectional area of the housing. The Applicant has also proved that when the housing volume is 3 to 30 times the displacement of the internal combustion engine, the muffling effect of apparatus is more remarkable, therefore, in a more preferred embodiment, the volume of the housing  3  is ˜30 times the displacement of the internal combustion engine. 
         [0081]    The muffling method provided by the present invention may further take advantage of the principle of resistive muffling to enhance the muffling effect. The exhaust gas can be divided into small tributaries. According to the principle of muffling, the exhaust gas is divided into a small tributary to enhance the muffling effect. 
         [0082]    If the housing is filled with padding capable of forming gaps thereinbetween, the muffling effect may be further enhanced. The presence of padding makes the apparatus a resistive muffler. When the exhaust gas enters into the padding, part of the sound is turned into heat by friction in the pores of the porous material to be dissipated, so that the sound waves through the muffler are weakened. The Applicant has also found that a large area of contact of the liquid with the exhaust gas flow, per se, can absorb the energy of sound waves to facilitate muffling. 
         [0083]    Thus, the present invention belongs to the impedance composite muffling, which has muffling characteristics of both resistance and reactance. Further, the present invention cools the high-temperature exhaust gas of hundreds of degrees Celsius down to tens of degrees Celsius, flowing through the muffler, producing the expansion cooling effect while enhancing the effect of the resistance and reactance. A resistive muffler of the present invention mainly makes use of a large number of pores formed in materials such as the padding, since the exhaust gas is cooled, the volume is contracted, and the flow rate is decreased, the resistance generated when flowing through a large number of pores is decreased by a greater range. Therefore, it is possible to use more padding to make up more, longer and more irregular pores, which makes the following of the present invention all higher than existing muffler technology by several orders: frequency of changes in the direction of airflow, the number of the times of repetition of airflow passing through cross-sections first contracting and then expanding, the number of the small tributaries divided from the gas stream, and the area of an unsmooth passage formed. On the other hand, the reactive muffling of the present invention is achieved from abrupt expansion of the cross-sections formed from the exhaust gas inlet to the interior of the housing. Due to the technical solution of the present invention significantly reduces the exhaust gas volume, which is equivalent to increasing the expansion magnification of the cross-section of the exhaust passage, further enhancing the reactive muffling effect. From another perspective, in the occasions where a great expansion ratio is required and the prior art is difficult to achieve by space limitations, the method or apparatus provided by the present invention can achieve that very well. 
         [0084]    The method of muffling exhaust gas of an internal combustion engine, provided by the present invention, at the same time, has the above-mentioned effect of optimizing the exhaust backpressure of an internal combustion engine. Thus, by using the method provided by the present invention, the effect of optimizing the exhaust backpressure of an internal combustion engine can be achieved as well as muffling effect is achieved by using the same apparatus. In this way, the apparatus of the present invention is mounted to the exhaust passage of an internal combustion engine, so there is no need to install an additional muffler on the ship. Due to the relevant provisions of the existing regulations on the muffling and energy saving, in the existing structure of the ship, the exhaust passage of an internal combustion engine is installed with a waste heat boiler and a muffler. Moreover, in the position of the exhaust path of the internal combustion engine, there is no extra space for installing the apparatus for optimizing the exhaust backpressure of internal combustion engine. By use of the method provided by the present invention, this problem can be well solved, that is, to install the apparatus provided by the present invention in the position of the existing muffler and replace the existing muffler. 
         [0085]    Further, since cooling the exhaust gas itself can achieve the effect of muffling, the present invention also provides a muffling method for exhaust gas of an internal combustion engine, including: making the exhaust gas discharged from the internal combustion engine enter into the interior of the housing through an exhaust gas inlet of the housing, and in addition, said method further including: making the exhaust gas entering into the interior of the housing to come into direct contact with the cooling liquid. 
         [0086]    The present invention also provides a apparatus for muffling the exhaust gas of an internal combustion engine, including: a housing, the housing is provided with an exhaust gas inlet allowing the exhaust gas to enter into the interior of the housing, an exhaust gas outlet allowing the exhaust gas to be discharge out of the housing, a cooling water inlet allowing the cooling liquid to enter into the interior of the housing, a cooling water outlet allowing the cooling liquid to be discharged out of the housing; said cooling water inlet, cooling water outlet, exhaust gas inlet and exhaust outlet are configured so that the cooling liquid and the exhaust gas may come into contact with each other within the housing. 
         [0087]    The present invention also provides a system for muffling exhaust gas of an internal combustion engine, said system comprising an exhaust passage of the internal combustion engine, said system further comprising an apparatus for muffling exhaust gas of an internal combustion engine provided by the present invention, the apparatus is installed in the exhaust passage of the internal combustion engine. 
         [0088]    By using the method, apparatus and system for muffling exhaust gas of an internal combustion engine provided by the present invention, the existing muffler can be replaced, without the need to install other muffler. For an apparatus which can conveniently utilize cooling water, such as vessel sailing on natural water, can be muffled by the method, apparatus or system, provided by the present invention, for muffling exhaust gas of an internal combustion engine. For an apparatus using an internal combustion engine as a power on the land, such as cars, can also use the cooling water of an internal combustion engine as the cooling liquid, so as to proceed muffling of the exhaust gas of an internal combustion engine, by the method, apparatus and system provided by the present invention. 
         [0089]    The method, apparatus and system for muffling exhaust gas of an internal combustion engine can also be functionally combined with existing muffler. For example, an abrupt expansion of cross-section is formed from the exhaust gas inlet to the interior of the housing, thus, rapid cooling of the high-temperature exhaust gas will further enhance the resistance muffling effect. 
         [0090]    In the method, apparatus and system for muffling exhaust gas of an internal combustion engine, provided by present invention, the way of cooling water, contact between cooling water and high-temperature exhaust gas as well as the configuration of inlet and outlet can be the same as or similar to the method, apparatus and system for optimizing exhaust backpressure of an internal combustion engine as described above. 
         [0091]    Data shows that the diesel engine exhaust gas and cooling medium take away heat about 50% of the total fuel heat, most of which is discharged in the form of high-temperature exhaust gas into the atmosphere. The existing shipbuilding regulations, in addition to environmental regulations on muffling, also requires installing waste heat boiler in the exhaust passage of an internal combustion engine. The waste heat boiler, also known as exhaust gas boiler, the role of which is to recycle the heat in the exhaust gas, in order to achieve the purpose of energy saving. The structure of the existing waste heat boiler is a duct encapsulating cooling water, located in the exhaust passage of the internal combustion engine. Thus a contradiction exists: If it is desired to more fully recover waste heat, the pipe encapsulating the cooling water and the exhaust gas of an internal combustion engine is required to fully contact, which would require the pipe encapsulating the cooling water are more densely distributed in the exhaust pipe of the internal combustion engine, which is bound to increase exhaust resistance and the exhaust backpressure, and thereby adversely affect the effectiveness of the internal combustion engine. It is also because of this, the waste heat boiler in the existing vessels does not have high heat recovery efficiency. 
         [0092]    In various embodiments of the method and apparatus provided by the present invention, if the cooling liquid (cooling water) is in direct contact with the exhaust gas for cooling exhaust gas, the cooling water (i.e., hot water) having absorbed heat of the high-temperature exhaust gas can be discharged and utilize the heat therein. Thus, the method and apparatus provided by the present invention can also perform a waste heat recovery function. Accordingly, the method provided by the present invention further comprises: conveying the cooling liquid which has absorbed heat of the high-temperature exhaust gas to the heat utilization apparatus or heat exchanger. The system provided by the present invention further comprises a heat utilization apparatus or heat exchanger, and a duct for conveying fluid to the heat utilization apparatus or heat exchanger. 
         [0093]    Some transportation of goods such as heavy oil, asphalt etc. needs heat source to preserve heat; hot water can be utilized directly; the apparatus using hot water to preserve heat is a heat utilization apparatus. Some transportation of other goods, such as refrigerated transport vessels also need a heat source (specific scheme belonging to the scope of conventional design) is used for cooling, the recovered waste heat by the scheme of the present invention can meet all or part of heat requirements thereof. 
         [0094]    Since the method and apparatus of the present invention make use of a cooling liquid such as cooling water to absorb the large amount of heat that brought by the high-temperature exhaust gas that is originally to be discharged into the atmosphere at the same time of improving the efficiency of the internal combustion engine. The cooling water which has absorbed heat from the exhaust gas becomes the intermediate hot, and can be directly used again, and can also be reused after been transferred into clean hot water by way of a liquid-liquid heat exchange with high heat exchange efficiency. For example, a ton class ship has exhaust emissions of about 1220 kg/h, the temperature of the exhaust gas discharged to the atmosphere exceeds 300° C. under MCR conditions (80% of the rated power), the heat of which is all abandoned. The temperature of the exhaust gas discharged to the atmosphere through the apparatus of the present invention is stabilized at about 50° C. or 30° C. when the ship is under MCR working conditions, allowing the heat of millions of calories per hour that is formerly abandoned to be recycled. Accordingly, the waste heat boiler on the exhaust pipe of the original internal combustion engine may be completely substituted by the present apparatus. Meanwhile, the recycled waste heat is used to produce hot water and/or steam as required. 
         [0095]    For this purpose, the cooling water pump of the apparatus of the present invention is also designed to adjust the size of the flow, by changing the amount of cooling water to achieve temperature adjusting of the hot water produced, so as to better adapt to the need for utilization of waste heat, to further improve the efficiency of waste heat utilization. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0096]      FIG. 1  is a schematic diagram of the apparatus for optimizing exhaust backpressure of an internal combustion engine, according to a first embodiment of the present invention; 
           [0097]      FIG. 2  is a schematic diagram of the system for optimizing exhaust backpressure of an internal combustion engine, according to a first embodiment of the present invention; 
           [0098]      FIG. 3  is a schematic diagram of the correlation between exhaust backpressure and engine load rate, according to a first embodiment of the present invention; 
           [0099]      FIG. 4  is a schematic diagram of the correlation between exhaust temperature and engine load rate, according to a first embodiment of the present invention; 
           [0100]      FIG. 5  is a schematic diagram of the apparatus for optimizing exhaust backpressure of an internal combustion engine, according to a second embodiment of the present invention; 
           [0101]      FIG. 6  is a schematic diagram of the system for optimizing exhaust backpressure of an internal combustion engine, according to a third embodiment of the present invention; 
           [0102]      FIG. 7  is a schematic diagram of the system for optimizing exhaust backpressure of an internal combustion engine, according to a forth embodiment of the present invention; 
           [0103]      FIG. 8  is a schematic diagram of the apparatus for optimizing exhaust backpressure of an internal combustion engine, according to a fifth embodiment of the present invention; 
           [0104]      FIG. 9  is a schematic diagram of the apparatus for optimizing exhaust backpressure of an internal combustion engine, according to a sixth embodiment of the present invention; and 
           [0105]      FIG. 10  is a schematic diagram of the apparatus for optimizing exhaust backpressure of an internal combustion engine, according to a seventh embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0106]      FIG. 1  to  FIG. 4  show the apparatus and system for optimizing exhaust backpressure of an internal combustion engine according to the first embodiment of the present application. 
         [0107]    As shown in  FIG. 1 , in this embodiment, the apparatus for optimizing exhaust of an internal combustion engine comprises housing  6  provided with a cooling water inlet  10  and a cooling water outlet  11 . Wherein, cooling water inlet  10  is located on the upper portion of the side surface of the housing, and cooling water outlet  11  is located on the lower portion of the side surface of the housing. Under the effect of gravity, cooling water entering the housing from cooling water inlet  10  pass through from top to bottom, and is discharged through cooling water outlet  11 . 
         [0108]    The housing  6  is also provided with an exhaust gas intake pipe  8  and an exhaust gas outlet  9 . Wherein, the exhaust gas intake pipe  8  extends into the interior of the housing, the pipe orifice extending into the interior of the housing being an exhaust gas inlet  7 . The exhaust gas inlet  7  is located at the bottom of the housing, and the exhaust gas outlet  9  is located at the top of the housing. The exhaust gas entering housing  6  from exhaust gas inlet  7  passes through in the interior of the housing from bottom to top and is discharged through exhaust gas outlet  9 . 
         [0109]    Wherein, the cooling water outlet  11  is located below the exhaust gas inlet  7  in the direction of gravity, so that the cooling water flowing to or falling onto the bottom of the housing does not enter exhaust gas intake pipe  8  through exhaust gas inlet  7  under the effect of gravity. 
         [0110]    Padding which forms gaps thereinbetween is filled within the housing  6 , form padding layer  12 . A water distributor  14  is provided above padding layer  12 . 
         [0111]    Further, in order to prevent the cooling water from entering exhaust gas intake pipe  8  from exhaust gas inlet  7 , a water baffle  13  is also provided between exhaust gas inlet  7  and padding layer  12 . Water baffle  13  is located right above exhaust gas inlet  7 , completely blocking the liquid from top to bottom in the vertical direction to not allow the liquid into exhaust gas inlet  7 . The edge part of the upper surface of water baffle  13  is lower than the central part, so that the rinsing water flowing to or falling onto water baffle  13  further flows to or falls onto the bottom of the housing, which further prevents the rinsing water from entering exhaust gas inlet  7 . 
         [0112]    Hereby exhaust gas intake pipe  8  and exhaust gas inlet  7  are configured to make exhaust gas smoothly reaches inlet  7 , and avoiding water baffle  13 , and then enters into the housing, in order that the high-temperature and high velocity exhaust gas discharged from an internal combustion engine does not turn direction suddenly before reaching exhaust gas inlet  7  due to the obstruction of water baffle  13 , causing a large exhaust resistance. 
         [0113]    As shown in  FIGS. 1 and 2 , in use, apparatus  5  for optimizing exhaust backpressure is mounted in the exhaust passage of an internal combustion engine of a ship, the apparatus together with the exhaust passage of an internal combustion engine constituting a system for optimizing exhaust backpressure of an internal combustion engine. The internal combustion engine of the ship is equipped with a turbocharger  2  thereon. In the existing structure of a ship, an exhaust passage of an internal combustion engine is installed with a waste heat boiler and a muffler according to the relevant provisions of the existing regulations on muffling and energy efficiency; moreover, there is no surplus space for further installation of device with large dimensions in the place where the exhaust passage of the exhaust gas from an internal combustion engine. In the present embodiment, apparatus  5  for optimizing exhaust backpressure of an internal combustion engine is mounted in a muffler&#39;s position in an existing ship, replacing the original muffler and waster heat boiler. Exhaust gas intake pipe  8  communicates with exhaust pipe  3  of an internal combustion engine, and chimney  4  communicates with exhaust gas outlet  9 . Further, in the present embodiment, the system for optimizing exhaust backpressure of an internal combustion engine may also include cooling water inlet pipe  16 , cooling water outlet pipe  17 , pump  18 , control valve  19 , heat exchanger  20 , and heat utilization apparatus  21 , wherein cooling water inlet pipe  16 , apparatus  5  for optimizing exhaust backpressure of an internal combustion engine, cooling water drain pipe  17  constitutes a flow path of cooling water. Heat exchanger  20  is mounted on the cooling water drain pipe  17  for transferring the heat of the cooling water having absorbed heat to another fluid, and for further transferring to heat utilization apparatus  21  for utilization. 
         [0114]    The apparatus and system of the present embodiment is used by the following method: when the ship is sailing in the ocean, the internal combustion engine works to produce high-temperature exhaust gas (approximately 500° C. or so), which is discharged through exhaust pipe of the internal combustion engine and then enters the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine through exhaust gas inlet pipe; cooling water inlet pipe extracts sea water directly from its immediate natural environment, and sea water is conveyed into the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine via pump. Under the effect of exhaust pressure and natural diffusion, exhaust gas flows by in the interior of the housing from bottom to top; under the effect of gravity, sea water flows by in the interior of the housing from top to bottom. High-temperature exhaust gas is divided into small tributaries in padding layer, and comes into contact with sea water to be quickly cooled. The cooled exhaust gas (approximately 30° C. to 80° C. after passing through padding layer) is discharged into the atmosphere through the chimney. Sea water having absorbed heat is drained from the cooling water outlet, and then flows through the cooling water drain pipe to transfer heat to another fluid via heat exchanger, and then is discharged into the ocean. Another fluid that has absorbed heat in the heat exchanger is conveyed to heat utilization apparatus to be utilized. 
         [0115]    The above embodiment utilizes padding layer having large gaps to divide high-temperature exhaust gas into a plurality of small tributaries so as to provide certain amount of exhaust resistance and rapidly cool the high-temperature exhaust gas in padding layer. The cooled high-temperature exhaust gas has a sudden extraction in its volume and the quantity and rate of flow thereof declined, and the resistance caused thereby is decreased by a larger extent. The exhaust backpressure of the internal combustion engine is relatively lowered, so that not only the working condition of ventilation of the internal combustion engine is improved, but also pressure boost efficiency of the turbocharger is enhanced. In the present embodiment, the exhaust backpressure relatively decreases with the increase of the load, thus completely eliminating the factors sensitive to exhaust backpressure. In addition, as the present embodiment also provides a certain amount of backpressure when the internal combustion engine is under low load, the torque of the internal combustion engine is thus increased. 
         [0116]    In the present embodiment, apparatus  5  for optimizing exhaust backpressure of an internal combustion engine also plays a role of a muffler. The principle of muffling pertains to the impedance composite muffling, having both muffling characteristics of resistance and reactance. As the high-temperature exhaust gas of hundreds of degrees Celsius is cooled down to several tens of degrees Celsius, producing a cooling expansion effect of simultaneously enhancing muffling effect of resistance and reactance, thus a better muffling effect is obtained than prior art. 
         [0117]    A ton class vessel is installed with the system for optimizing exhaust backpressure of an internal combustion engine provided by the embodiment. The main pushing diesel engine displacement thereof is P=336 liters, combusting heavy oil with sulfur content of 2% to 3% mm. According to the spatial conditions along the path of the exhaust passage of the internal combustion engine, the volume of the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine is selected in the scope of 3-30 times of exhaust amount of the internal combustion engine. According to size of the exhaust gas intake pipe  3 , cross-sectional area of the exhaust gas intake pipe is 0.3 m 2 , and cross-section area of housing is selected according to 0.05-0.5 time thereof, then the volume of the housing is selected as 5.3 m 3 , cross-sectional area selected as 1.8 m 2 . An apparatus for optimizing exhaust backpressure of an internal combustion engine is installed on the exhaust passage of the main pushing diesel internal combustion engine, and the main pushing internal combustion engine of that ship is no longer configured with muffler and waste heat boiler. 
         [0118]    The cooling water conveyed to the apparatus for optimizing exhaust backpressure of an internal combustion engine is extracted from sea water by pump, the amount of cooling water being controlled to be 20-100 m 3 /h. 
         [0119]    Tested by the applicant, after the above vessel applied with this embodiment, the exhaust noise of the vessel is reduced by 23 db. 
         [0120]      FIG. 3  is a schematic diagram showing the relationship between the exhaust backpressure of the vessel and load rate of the internal combustion engine that are tested by the applicant in the first embodiment, wherein the data of the prior art is obtained by testing the vessel (other configuration are the same as the configuration of the vessel of the present embodiment) mounted with muffler and waste heat boiler. The exhaust backpressure data is collected from exhaust gas inlet, with unit of Pa. It can be seen from the result in the figure that after installing the apparatus of the present invention, the exhaust backpressure of the present embodiment is a little larger than that of the prior apparatus (muffler) when the internal combustion engine is under low load. With the increase of the load of an internal combustion engine, the exhaust backpressure of the prior art increases rapidly, while the exhaust backpressure of the present embodiment increases with a velocity and extent much smaller than that of the prior art. 
         [0121]      FIG. 4  is a schematic diagram showing the relationship between exhaust gas temperature of the vessel and the load rate of the internal combustion engine that are practically tested by the applicant in the first embodiment, wherein the data of the prior art is obtained by testing the vessel (other configuration are the same as the configuration of the vessel of the present embodiment) mounted with muffler and waste heat boiler. The data of temperature is collected at the discharge port of the chimney. It can be seen from the result in the figure that in a vessel of the prior art, the temperature of the exhaust gas discharged is increased with the increase of the load of an internal combustion engine, maximum to about 350° C. Obviously, there is a lot of waste heat in the exhaust gas that is not utilized yet. While after installing the apparatus of the present embodiment, the exhaust temperature has been stable at about 30° C. 
         [0122]      FIG. 5  shows an apparatus for optimizing exhaust backpressure of an internal combustion engine according to the second embodiment of the present invention. 
         [0123]    In this embodiment, different from the apparatus for optimizing exhaust backpressure of an internal combustion engine in the first embodiment, exhaust gas inlet  7  of the apparatus for optimizing exhaust backpressure of an internal combustion engine is located on the lower portion of the side surface of housing  6 ; in the direction of gravity, the position of exhaust gas inlet  7  is higher than that of rinsing water outlet  11 . In this case, the exhaust passage of the internal combustion engine communicates with the side surface of the housing through exhaust gas inlet  8 . As the exhaust gas enters from the side surface of the housing, there is no need for a water baffle. 
         [0124]    The exhaust passage of the internal combustion engine communicates with the side surface of the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine. In the present embodiment, the displacement of the internal combustion engine is P=33 liter, housing volume is 0.2 m 3 , cross-sectional area is 0.3 m 2 , cross-sectional area of exhaust gas intake pipe is 0.06 m 2 . 
         [0125]      FIG. 6  illustrates a system for optimizing exhaust backpressure of an internal combustion engine according to the third embodiment of the present invention. 
         [0126]    Different from the system for optimizing exhaust backpressure of an internal combustion engine in the first embodiment, in this embodiment, the cooling water in the system for optimizing exhaust backpressure of an internal combustion engine is taken from the cooling water of the internal combustion engine, the cooling water which has absorbed heat can be directed drained in the same way as the cooling water of the internal combustion engine. 
         [0127]      FIG. 7  illustrates a system for optimizing exhaust backpressure of an internal combustion engine according to the forth embodiment of the present invention. 
         [0128]    Different from the system for optimizing exhaust backpressure of an internal combustion engine according to the first embodiment, in this embodiment, the system for optimizing exhaust backpressure of an internal combustion engine, in addition to including a pipe conveying the fluid of the housing to heat exchanger  20 , also includes a pipe conveying the fluid of heat exchanger  20  to the housing. 
         [0129]    In this kind of system for optimizing exhaust backpressure of an internal combustion engine, the cooling water that has absorbed heat from high-temperature exhaust gas is conveyed to the housing to act as cooling water again after passing through heat exchanger  20 , so as to realize recycling utilization. 
         [0130]    Further, the system for optimizing exhaust backpressure of an internal combustion engine in this embodiment also includes impurity separator  22  installed in the cooling water drain pipe for filtering the impurities in the cooling water, discharging the impurities from impurity discharge pipe  24 , so as to prevent particles brought by the cooling water from accumulating too much. Impurity separator  22  has the function of adding cooling water at the same time, supplementing through cooling water supplementing pipe  23  the cooling water decreased due to evaporation. 
         [0131]      FIG. 8  illustrates the apparatus for optimizing exhaust backpressure of an internal combustion engine according to the fifth embodiment. 
         [0132]    In this embodiment, heat dissipating member  25  is provided in the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine, i.e. cooling member. Heat dissipating member  25  is composed of heat pipe  26 , heat absorbing sheet  27  and heat dissipating sheet  28 . Heat absorbing sheet  27  is located in the interior of the housing, made of good heat conductor, for dividing the exhaust gas into small tributaries and absorbing the heat in the exhaust gas. Heat dissipating sheet  28  is located outside of the housing, made of good heat conductor, for releasing heat into the environment. Heat pipe  26  connects heat absorbing sheet  27  and heat dissipating sheet  28 , made of good heat conductor, for transferring the heat absorbed by the heat absorbing sheet to the heat dissipating sheet. 
         [0133]    When the high-temperature exhaust gas discharged from the internal combustion engine passes through the apparatus in this embodiment, it is divided by heat absorbing sheet  27  into small tributaries, and is cooled at the same time through heat exchanging with heat dissipating member  25 . 
         [0134]    The apparatus for optimizing exhaust backpressure of an internal combustion engine in this embodiment may also be directly installed in device using internal combustion engine as the power on the land, such as automobiles. 
         [0135]      FIG. 9  illustrates the apparatus for optimizing exhaust backpressure of an internal combustion engine according to the sixth embodiment of the present invention. 
         [0136]    Cooling pipe  29  allowing cooling water flowing therein is provided in the housing of the apparatus for optimizing exhaust backpressure of an internal combustion engine in this embodiment, i.e. cooling member. Cooling pipe  29  is densely distributed in the housing, and thus may acts to divide the exhaust gas into small tributaries. 
         [0137]    In use, cooling water is kept flowing in the cooling pipe, and the exhaust gas is rapidly cooled during the process of being divided into small tributaries. The cooling water forms vapor after absorbing the heat from the high-temperature exhaust gas, and the vapor formed may be conveyed to heat utilization apparatus to be directly utilized. 
         [0138]    The apparatus in this embodiment may be installed on the ship, the cooling water being taken from the sea water, river water or lake water from a natural water body. Cooling water may also use the cooling water of the internal combustion engine. The apparatus may also be installed in an automobile, and the cooling water may also use the cooling water of the internal combustion engine. 
         [0139]      FIG. 10  illustrates the apparatus for optimizing exhaust backpressure of an internal combustion engine according to the seventh embodiment of the present invention. 
         [0140]    The apparatus for optimizing exhaust backpressure of an internal combustion engine in this embodiment includes housing  6  provided with exhaust gas inlet  7  and exhaust gas outlet  9 . Different from above, no abrupt expansion of cross-sections is formed from exhaust gas inlet  7  to the interior of the housing, wherein the existence of exhaust gas inlet  9  reduces the cross-section of the exhaust passage so as to provide a certain amount of exhaust resistance. 
         [0141]    The apparatus in this embodiment also includes sprayer  15 , for spraying cooling water to the interior of the housing, thereby rapidly reducing the temperature of the high-temperature exhaust gas. The cooling water which has absorbed heat is discharged from cooling water outlet  11 .