JPH0152677B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger used in a heat recovery device from exhaust gas of an engine or the like.

Conventional configuration and its problems In recent years, with the trend toward energy conservation, a system as shown in Figure 1 has been devised and put into operation, which aims to improve total energy efficiency by recovering heat from exhaust gas from heat sources such as engines. are doing. This system extracts shaft output from an engine 3 as power, recovers waste heat in a heat exchanger 1, and discharges it through a muffler 2. Conventionally, in such a system, a heat exchanger 1 and a silencer 2 for recovering exhaust heat from the engine 3 are provided separately.
Therefore, the system becomes complicated, and the sound transmitted from the muffler body is large, which has disadvantages such as the need to increase the mass of the muffler.

Furthermore, it is very difficult to attenuate the sound of low frequency components, but as can be seen from the frequency analysis of the explosion sound of engine 3, the explosion cycle (in the case of a 4-cycle, 4-cylinder engine, the engine speed is N rpm) (For example, the explosion cycle is N/60×1/2×4Hz)
A first peak component of sound pressure appears at , and thereafter peak components of sound pressure occur at integral multiples of the explosion cycle. Therefore, a more efficient sound reduction method for low frequency components has been desired. Resonant mufflers have traditionally been used to reduce low-frequency sound, but when the engine speed changes and the sound speed changes, the resonant frequency shifts, causing the sound pressure level at the target frequency to change. It had the disadvantage that it could not be reduced.

OBJECTS OF THE INVENTION In view of the conventional problems, an object of the present invention is to provide a muffler and integrated exhaust gas heat exchanger that is highly efficient and can efficiently reduce low frequency component sound.

Structure of the Invention The present invention divides the space of a water jacket in which a plurality of heat transfer tubes through which a fluid to be heated passes through is divided by a plurality of partition plates, and at least one of the spaces constituted by the partition plates is divided into a so-called resonator. The small hole of the heating fluid passage tube which serves as the mold space and forms the resonance type space is configured to have a variable cross-sectional area, and the means for changing the cross-sectional area includes a hole on the inner wall of the small hole of the heating fluid passage tube. This heat exchanger is constructed using a material that bends toward the inner surface of the tube as the heated fluid rises.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a diagram showing a heat exchanger according to an embodiment of the present invention. 4 is a water jacket, and a plurality of heat exchanger tubes 6 are installed in the space 5 of the water jacket 4.
The partition plates 7 to 10 are inserted and fixed to the heat exchanger tubes 6. A header 11 and a header 12 are provided at both ends of the heat transfer tube 6, the header 12 is provided with a water discharge pipe 13, and the header 11 is provided with a water hole 1.
4 communicates with the water jacket, and the water jacket 4 is further provided with a water inlet pipe 15. Small holes 16 are randomly opened in the partition plates 7 and 10, and spaces 17 to 21 are provided which are divided by each partition plate. An exhaust gas inlet 22 and an exhaust gas outlet 2 are provided in the spaces 21 and 17 at both ends.
3 is provided.

The small holes provided in each partition plate and the space formed by the partition plate are determined taking into account the sound reduction characteristics of the expansion type, and one or more spaces are occupied by the resonance type muffler 19. A heated fluid passage pipe 2 penetrates through an adjacent partition plate and has a small hole 24 around it.
5 is fixed to partition plates 8 and 9. As shown in FIG. 5, the small hole portion 24 of the heated fluid passage pipe 25 has a reed valve 26 fixed to the inner wall of the pipe. The reed valve 26 is made of a material that bends toward the inner surface of the heated fluid passage tube as shown in FIG. 6 as the temperature of the heated fluid increases.

Next, its operation will be explained. First, the fluid to be heated passes through the water jacket 4 from the water introduction pipe 15, enters the header 11 from the water hole 4, and enters each heat transfer pipe 6.
The water is branched into two streams, enters the header 12, and is discharged from the water discharge pipe 13.

On the other hand, exhaust gas from a heat source such as an engine, which is a heating fluid, enters the space 21 through the exhaust gas inlet 22, enters the next space 20 through the small hole in the partition plate 10,
In this embodiment, after passing through the next resonance type muffler 19,
The exhaust gas enters the next space 18, passes through the small hole in the partition plate, enters the next space 17, and is discharged from the exhaust gas outlet 23. While the exhaust gas is flowing in this way, the inner surface of the water jacket 4 and the surface of the heat transfer tube 6 are heat is exchanged.

As described above, according to this embodiment, the exhaust gas led from the engine to the exhaust gas inlet 22 rapidly expands in the first space 21, and then rapidly contracts in the small hole 16 before entering the next space 20. In addition, it exhibits the so-called expansion type noise reduction effect that is rapidly expanded in the next space, and when passing through the resonance type silencer 19, the noise from the engine etc. is significantly reduced due to the resonance type noise reduction effect. be done. Further, since the exhaust gas space is surrounded on the outside by the water jacket 4 having a large mass, transmitted sound can be reduced.

In addition, in the embodiment, the reed valve 26 fixed to the inner wall of the heated fluid passage pipe 25 of the resonance type muffler 19 is directed toward the inner surface of the heated fluid passage pipe as shown in FIG. 6 depending on the temperature of the heated fluid. At this time, the area of the small hole 24 is changed. The temperature of the engine exhaust gas, which is the heated fluid, varies depending on the engine speed, as shown in FIG. 7, and therefore, as the engine speed increases, the small hole area can be increased.

As the engine speed increases, the fundamental frequency, which is proportional to the engine speed, shifts higher. Therefore, in the resonance type muffler, it is necessary to increase the sound reduction effect at that frequency. According to this embodiment, the area of the small hole is increased due to the increase in engine speed for the reason described above, and the resonance frequency expressed by the following equation can be changed in accordance with the engine speed.

Here, the resonance hole (small hole) area S _p , the thickness l _p of the resonance hole portion, the resonance hole constant n, and the resonance volume V _p In this example, as the engine speed increases,
It increases S _p and therefore allows _p to be brought to a higher value. In this way, even if the engine speed changes, the resonance frequency _p can be made to match the explosion cycle, and the sound pressure level of low frequency components can be efficiently reduced.

FIG. 8 shows another possible method for changing the small hole area of the heating fluid passage tube.
This is a method of increasing the cross-sectional area of the small hole by increasing the dynamic pressure due to the increase in the flow velocity passing through the heated fluid passage pipe when the engine speed increases.
An L-shaped fitting 27 protruding inside 4' is fixed at the other end to the heating fluid passage pipe 25' with a spring 29 or the like on the downstream side of the heating fluid 28, and is similar to the first embodiment of the present invention. It is effective.

Furthermore, similar effects can be obtained by using a butterfly valve or the like as a method for changing the small hole area.

Effects of the Invention The heat exchanger of the present invention is a heat exchanger with an integrated muffler, which has an excellent sound reduction effect, and efficiently reduces the sound pressure level of low frequency components even when the engine speed changes. At the same time, it is possible to fully utilize the pulsation of the engine, etc., to improve heat transfer performance.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of an engine system equipped with an exhaust heat recovery heat exchanger, Fig. 2 is a sectional view of a conventional fin type heat exchanger, and Fig. 3 is a sectional view of a conventional plate type heat exchanger. Fig. 4 is a sectional view of a heat exchanger according to an embodiment of the present invention, Fig. 5 is an enlarged sectional view of the heated fluid passage pipe portion of the resonance type muffler shown in Fig. 4, and Fig. 6 is an operation of the reed valve with respect to temperature. FIG. 7 is a diagram showing the relationship between engine speed and exhaust gas temperature, and FIG. 8 is a sectional view of a heated fluid passage pipe portion according to another embodiment of the present invention. 4...water jacket, 6...heat exchanger tube, 8,
9... Partition plate, 24... Small hole, 25... Heated fluid passage pipe, 26... Reed valve.

Claims (1)

[Scope of Claims] 1. A water jacket in which a plurality of heat transfer tubes through which a fluid to be heated passes is divided by a plurality of partition plates disposed in the axial direction of the heat transfer tubes, and the space is constituted by the partition plates. At least one space formed by the heating fluid is a resonant space in which a heated fluid passage tube is fixed to the partition plate, passing through an adjacent partition plate and having a small hole around it, and the small hole is in the state of the heated fluid. A heat exchanger characterized by being configured so that its cross-sectional area can be varied depending on the situation. 2. Claim No. 2, characterized in that the inner wall of the heated fluid passage tube where the small hole is located is provided with a reed valve made of a material that bends toward the inner surface of the tube as the temperature of the heated fluid increases. Heat exchanger according to item 1.