Two stage hot pipe EGR cooler
Technical Field The present invention relates to a gas cooling device, in particular to a kind of exhaust gas recirculation cooler. It can be widely applied to the use of exhaust gas recirculation of the power device. Background Art With the increasingly stringent emission requirements, exhaust gas recirculation technology increasingly application on the power device. The principle is that the 1st to discharge exhaust gas after cooling the part of the return to the engine in order to effectively reduce the generation of nitrogen oxides in exhaust gas. Traditional exhaust gas recirculation (EGR) cooler hours in the process is generally divided into a shell-and-tube type and the plate-fin type two. They mainly has the following disadvantages: 1, the traditional exhaust gas cooling means for cooling the coolant of the engine, because the steam state of the cooling circuit of the engine coolants, cause serious cavitation, the engine total under the working condition of the coolant in liquid form, that is to say waste gas cooling is achieved by way of engine cooling fluid temperature rise take heat away, this way the cooling effect is poor. 2, the conventional EGR cooler shell-and-tube type or plate-fin structure, a more compact structure of simple, will greatly reduce the cooling efficiency of the EGR cooler. 3, the traditional shell-and-tube EGR cooler, the end of the two sides of the tube bundle and has obvious effect heating stress the weld, is easy to leak. 4, the traditional shell-and-tube EGR cooler, the flow direction of the exhaust gas is the same as the coolant flows, the aim is to reduce coolant vaporization level, rather than downstream, however, the cooling effect of the counter-current is good. Content of the invention The present invention is to solve the above-mentioned defect of the prior art, aims to provide a new kind of EGR cooler, which can effectively reduce the temperature of exhaust gas after cooling, the same premise amount of recirculated exhaust gas, the exhaust gas can effectively alleviate the impact of the power of the engine. Can effectively reduce the negative impact of the coking. Also can effectively reduce the leakage of the shell to weld the flange. Solve the above-mentioned problem the technical scheme is:a two-stage heat-pipe EGR cooler, is mainly composed of the two ends are respectively provided with exhaust gas inlet and exhaust gas outlet of the shell, two the heating section is arranged in the interior of the said shell a heat pipe. The heat pipe by the first tail is sequentially communicated with the heating section of the, steam pipe, condensation section, four sections of a pipe body, the heating section of the heat pipe of said two stages of the housing along the flow direction of the exhaust gas the successively arranged, of the stated two-step heat pipe condensing section of the heat-dissipating wind is blown to the overlap. The shell body of the exhaust gas inlet and exhaust gas outlet are respectively through the flange and the engine exhaust pipe and the return pipe is communicated with. Because cooling function of the heat pipe, is composed of a heating section of the heating of the cooling liquid in the heat of vaporization is taken away, this kind of heat exchange means than the heat exchange capacity of the liquid coolant heating mode of the heat-away 100 multiple times. Rejection of the present invention by way of the cooling liquid of the engine, the engine cooling system independent heat exchanging system, its cooling of exhaust air of the engine obviously superior to the traditional effect of the EGR cooler. And, the driving force of the condensate without sur- pump , material can be according to the physical properties of the various States of the self-circulation, effectively saving the energy, and has simplified the structure of the machine. Furthermore, a reasonable combination of the two-stage heat pipes, to further improve the cooling effect of the cooler. In the present invention, the shell is of cylindrical shape, the two ends of the exhaust gas inlet and exhaust gas outlet and the engine exhaust pipe and return pipe is connected through the flange. The said two-stage heat pipe suitable for adopting the same structure as the heating section, this will facilitate production and manufacturing. More preferably, the heating section is the, heating section inside the housing a double column arrangement. The purpose of adopting this kind of structure, on the one hand, the heating section of the pipe is curved, effectively increases the heat exchange working surface area of the heating section; on the other hand, the arrangement of the tube body of the spring occurs when the free expansion and contraction of the pipe, and will not be cracked. And expansion of the pipe body to be fall off the carbon deposit of the outlet. In order to increase the condensation effect, the condensation of a suitable ventilating ducts is provided. In the heat pipe of each stage, in order to make the coolant realize good directional circulation, the condensing section and the interface of the steam pipe with the condenser should be higher than the interface. As the further improvement of this invention, said two-stage heat pipe circulation of the cooling liquid in the direction opposite to the flow direction of the exhaust gas in the shell. The reverse flow of the exhaust gas and the cooling of the design of the intersection line, conducive to the full heat exchange. Its specific mode can be realized, the steam tube and said heating section interface is located in the direction of exhaust air inlet of the casing, the condenser tube and the heating section of the interface is located in the direction of the waste gas outlet of the shell. Because the shell close to the exhaust gas inlet and the section of a section close to the exhaust gas outlet temperature difference is large, this arrangement is favorable for the heat medium in natural circulation. As the further improvement of this invention, the 1st-stage heat pipe, the heating section is arranged in the shell to one side of the exhaust gas inlet, 2nd-stage heat pipe, the heating section is arranged in the shell to one side of the waste gas outlet. The 1st-stage heat pipe and the use of water as a cooling medium, and the 2nd-stage heat pipes use methanol as the cooling medium. Because the shell in a high-temperature exhaust gas at the inlet, it can be very apt to water vaporization, the boiling point of the higher specific heat is used for water as a cooling medium, more heat can be absorbed. The export of the relatively low temperature of the exhaust gas, if the 2nd-stage heat pipes used in water as the cooling medium, then in the working process, there will be only a small amount of water is at a relatively low temperature waste gas vaporization, not play a role. The low boiling point of methanol, is used in the waste gas outlet of the relatively low temperature of the more appropriate. By adopting this kind of two-stage design of the different heat dissipation medium, can effectively play a two-stage double cooling, the cooling performance of the structure. On the basis of the above-mentioned improvements, as improved goes a step further again of the invention, the 1st stage cooling section of the heat pipe is arranged on the heat-dissipating wind to be blown to the cooling section before 2nd-stage heat pipe, in other words the 2nd-stage heat pipe cooling section of the cooling section than the 1st-stage heat pipes closer to the heat dissipation fan. This kind of structure is set up according to two-stage heat pipe of the cold medium determine the different boiling points. Methanol will be used as a cooling medium to the cooling section of the heat dissipation fan, can, firstly the cooling. Because of its low boiling point, the heat-dissipating wind after cooling will not be very hot, and then to the water as a cooling medium for cooling of the cooling section, can still achieve good effect. On the contrary, used as a heat radiating medium of the methanol will be very difficult to realize cooling. EGR cooler the heat pipe of this invention has the following advantages: 1, the latent heat of vaporization of the coolant used for cooling, the heat exchange capacity of the conventional cooling liquid phase than 100 times or more, that is to say, of the present invention after the cooler cools the exhaust gas temperature is low, in this context, the present invention of the same cooler cools the exhaust gas to return to the engine after a smaller space occupation, this will effectively reduce the exhaust gas recirculation to the engine the impact of the power per liter. 2, with the traditional cooling the fluid walks the shell regulation manner on the contrary, in the present invention no longer waste gas in the narrow of the heat exchanging pipe to the pipeline, but rather from the housing through the inner cavity. The method of exhaust gas to the shell, since the heating of the structure of the spring, the more easily the heat expansion and cold contraction of the tube surface is attached to the carbon deposit breaking, falling off, with automatic transferring function, can greatly reduce the negative impact of the coking. 3, the heating section heat pipe of the present invention structure design of the spiral spring, its transverse free flexibility is relatively strong, can be effectively used for cushioning the impact of thermal stress. 4, the form is more favorable for countercurrent flow to perform heat exchange between the exhaust gas and the coolant. 5, a reasonable combination of the two-stage heat pipes, two cooling medium and with the effective, greatly improve the cooling effect of the cooler. Description of drawings Figure 1 is a schematic diagram of conventional shell-and-tube EGR cooler. Figure 2 is a structure diagram of the two-stage heat pipe EGR cooler of the invention. Figure 3 is a schematic diagram of 2nd-stage heat pipe assembly relations between the shell. Figure 4 is the cooling medium flow direction 2nd-stage heat pipe a schematic diagram. Figure 5 is a schematic diagram the flow direction of the exhaust gas in the shell. Figure 6 is the two-stage heat pipes of this invention position relationship of the cooling section of a schematic diagram. Figure 7 is a left view of fig. 6. Mode of execution With reference to Figure 1, shown in this Figure is a kind of shell-and-tube conventional EGR cooler, which comprises a lateral surface thereof is provided with a cooling fluid inlet 3 and outlet 4 of the housing 2, in the shell 2 and are arranged in parallel in a group with a clearance between the heat exchange tube 1. The heat-exchange tube 1 through the inlet flange 5 and an outlet flange 6 is connected to the engine in the exhaust gas recirculation loop. And the engine cooling liquid from the pipe after the coolant inlet 3 into the housing 2 inner cavity, then from the cooling liquid outlet 4 flows out, then the pipeline is returned to the engine cooling system. In this structure, in order to achieve better heat exchange effect, the heat-exchange tube 1 are generally many and very fine, in the heat exchange tube in the narrow pipe, the inner wall of the tube can be easily made, and it is difficult to automatically remove carbon deposition, thus greatly reducing the cooling efficiency of the EGR cooler. With reference to Figure 2, 3, the present invention relates to EGR cooler the heat pipe by the two-stage heat pipe and shell of three parts. Wherein said shell is composed of two sections of groups of cylindrical tube 23, 11 form, its two ends are respectively provided with exhaust gas inlet 10 and the exhaust gas outlet 13. The same structure said two-stage heat pipe, comprises a heating section, a steam pipe 22, 8, the cooling section 21, 7 and a condenser 24, 9 ; the heating section is arranged in the inner cavity of the housing. The steam pipe 22, 8 and a condenser 24, 9 are respectively connected to the two ends of the heating section, and then from the housing 23, 11 to the surface side. Re-are respectively connected to the cooling section 21, 7 of the two end. The cooling section 21, 7 is arranged in the upper part of the shell. Because the heat pipe heating section and the cooling section 21, 7 between the shell only through the steam pipe 22, 8 and a condenser 24, 9 is connected, and the heating section and the cooling section are suspended free end, therefore, the generated stress can be automatically eliminated. Said two-stage heat pipe heating section of the exhaust-gas flow direction in the inner edge of shell successively arranged, its 1st-stage heat pipe heating section close to the exhaust gas inlet. The two-stage cooling sections of the heat pipe is heat dissipation fan blows to overlap. Figure 4 in the heat pipe structure of the present invention, here to 2nd-stage heat pipe, for example, 1st-stage heat pipe in the shell structure of the end is the same as 2nd-stage heat pipe. Building decoration can be seen, the heating section of the heat pipe 12 bent into a double-layer spring, the steam tube 8 is connected at the left end thereof, the condensation duct 9 is connected with the right end thereof. The cooling section 7 bent into a ventilating ducts, the steam tube 8 and its junction 16 is located in the most above the left end of, the condenser tube 9 and its junction 17 is located in the lowest part of the right end. From this it can be seen, the coolant within the heat pipe to the direction of circulation of the heating section-steam pipe-cooling section-condenser-heating section. Here, the heat pipe heating section 12 form the three flow, the cooling blades can be fully brought into contact with the exhaust gases, to better absorb the heat in the exhaust gas, in order to protect to fully vaporize the medium in the heat pipe. With reference to Figure 5, the shell is a cylindrical straight cylindrical, its left and right ends respectively through the inlet flange 14 and an outlet flange 15 of the engine is communicated with an exhaust pipe and a return pipe. The exhaust gas in the shell is to the direction of flow from left to right. Combined with Figure 4 and Figure 5 can be known, in the present invention the two-stage heat pipes of the EGR cooler in the flow direction of the exhaust gas in the shell at two levels with cooling liquid in the adverse direction of circulation of the heat, this is more convenient for the full realization of heat exchange. With reference to Figure 6, 7, the two-stage the cooling section of heat pipe 21, 7 overlapping arranged on the heat dissipation fan 25, 26 rear, and 2nd-stage heat pipe cooling section 7 is arranged in the closer to the cooling fan 25, 26 one side of. It should be understood is: the above-mentioned embodiment is only a description of this invention, and is not limiting of the present invention, any not exceed the spirit of the invention within the scope of the invention, all fall into the scope of protection of this invention. The invention discloses a two-stage thermotube type EGR cooler. The two-stage thermotube type EGR cooler mainly consists of a shell with an exhaust gas inlet and an exhaust gas outlet respectively arranged on two ends of the cooler and a two-stage thermotube with heating sections arranged inside the shell. The thermotube is communicated with four pipe sections of a heating section, a steam tube, a condensation section and a condensation tube in turn from beginning to end; the heating sections of the two-stage thermotube are arranged along the exhaust gas flow direction in order; and the condensation sections of the two-stage thermotube are overlapped and arranged along the radiation wind blowing direction. In the two-stage thermotube, a first stage thermotube and a second stage thermotube respectively adopt water and methanol as cooling mediums. The two-stage thermotube type EGR cooler adopts the principle of cooling exhaust gas by the thermotube technology and has good cooling effect. In addition, the reasonable combination of the two-stage thermotube and the cross matching of two radiating mediums further improve the temperature reduction effect of the cooler. 1, a two-stage heat-pipe EGR cooler, the exhaust gas inlet are respectively arranged at the two ends (10) and exhaust gas outlet (13) of the housing and two levels of the heating section is arranged in a heat pipe in the shell, are the stated two-step heat pipe is connected in turn by the first end of the heating section (12), a steam pipe (22, 8), a condensation section (21, 7), a condenser (24, 9) of a four-section of the pipe, the two heat pipe, the heating section (12) of the housing along the flow direction of the exhaust gas the successively arranged, the condensation sections of the two heat pipes (21, 7) is arranged along the radiating wind blows to overlap. 2, two-stage heat pipe EGR cooler according to Claim 1, characterized in that the shell is of cylindrical shape, the two ends of the waste gas inlet (10) and exhaust gas outlet (13) connected with an engine exhaust pipe and the return-air duct through a flange (14, 15) is connected. 3, two-stage heat pipe EGR cooler according to Claim 1, characterized in that said two-stage heat pipe, the heating section (12) is double-layer cylindrical spiral shape within the housing. 4, two-stage heat pipe EGR cooler according to Claim 1, characterized in that the steam pipe (22, 8) and a condenser (24, 9) penetrates out from the side of the shell, and is fixed to it. 5, two-stage heat pipe EGR cooler according to Claim 1, characterized in that the cooling section (21, 7) above is disposed in the housing. 6, any one of the EGR cooler according to Claim 1-5 the two-stage heat pipes, characterized in that the cooling section (21, 7) with said steam pipe (22, 8) with the condenser is higher than the interface of (24, 9) of the interface. 7, two-stage heat pipe EGR cooler according to Claim 6, characterized in that the said two-stage heat pipe the direction of circulation of the cooling liquid in the shell opposite the flow direction of the exhaust gas. 8, two-stage heat pipe EGR cooler according to Claim 7, characterized in that the steam pipe (22, 8) with the heating section (12) located in the interface of the exhaust gas inlet side of the casing, the condenser tube (24, 9) with the heating section (12) located in the interface of the exhaust-gas outlet of the shell side. 9, two-stage heat pipe EGR cooler according to Claim 8, characterized in that 1st-stage heat pipe, the heating section is arranged in the shell near the exhaust gas inlet (10) to one side of, the heating of the 2nd-stage heat pipe (12) is arranged in the shell near the exhaust gas outlet (13) at one side of, and the 1st stage cooling section of the heat pipe (21) compared, 2nd stage the cooling section of heat pipe (7) is arranged in the closer to the heat dissipation fan (25, 26) on one side of the. 10, two-stage heat pipe EGR cooler according to Claim 9, characterized in that 1st-stage heat pipe using water as the cooling medium, the 2nd-stage heat pipe using methanol as a cooling medium.