JPH0332743Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an engine exhaust system structure in which a heat exchanger for exchanging heat between exhaust gas and water is provided to recover exhaust heat.

(Prior art) In a device that recovers engine exhaust heat and uses it as a heat source for heating or a heat pump circuit, the engine exhaust system structure equipped with a heat exchanger for exhaust heat recovery has conventionally been used, for example, in the 1980s.
As shown in Publication No. 1911, the exhaust manifold is surrounded by a water jacket, that is, the exhaust manifold is surrounded by a heat exchange case to form a sealed space without interfering with the flow of gas inside the exhaust manifold. However, there is known a structure in which a heat transfer fluid is allowed to flow into and out of this closed space.

By the way, in order to improve the heat recovery effect, it has been proposed to further install a heat exchanger on the exhaust downstream side of the exhaust manifold. In this case, the exhaust gas is cooled and the moisture in the exhaust gas tends to condense, and in that case, highly acidic condensed water is generated, so the inner walls of the exhaust manifold and heat exchanger are susceptible to corrosion and holes are easily formed in the walls. Also,
In particular, since there is a large temperature gradient as a result of heat recovery at the inlet and outlet sections of the heat exchanger, cracks are likely to occur in the internal heat exchanger core.

If a hole or crack occurs in the wall of the exhaust manifold or heat exchanger, water for heat exchange may flow into the engine through the exhaust manifold, or the exhaust gas may enter the water circuit. .

In addition, in order to increase heat recovery efficiency, it is necessary to reduce the area where the exhaust gas comes into contact with the outside atmosphere and expand the area where the exhaust gas comes into contact with the water that undergoes heat exchange. The heat exchange area with water has not been sufficiently expanded. Furthermore, it is desirable to keep the surface temperatures of the exhaust manifold and heat exchanger as low as possible.

(Purpose of the invention) The present invention was devised in view of the above-mentioned conventional problems. To provide an engine exhaust system structure capable of preventing corrosion of the engine, improving the heat recovery rate, and also improving the flow of water to the exhaust manifold side. With the goal.

(Structure of the invention) The present invention provides a heat exchanger for exchanging heat between the exhaust gas and water in the exhaust passage located downstream of the exhaust manifold of an engine equipped with a heat exchanger for recovering exhaust heat. The exchanger has a three-layer structure consisting of a heat exchanger core through which water circulates, an exhaust passage formed around the outer periphery of this heat exchanger core, and a water passage formed further around the outer periphery of this exhaust passage. At the same time, a water inlet for flowing water into the heat exchanger core is provided on the upstream side of the exhaust gas of the heat exchanger, and a communication section for flowing water from the inside of the heat exchanger core to the water passage is provided on the exhaust gas side of the heat exchanger. A water outlet, which is provided on the downstream side and allows water to flow out from the water passage, is provided on the outer periphery of the upstream end of the heat exchanger toward the outer periphery of the exhaust manifold.

With this configuration, the exhaust gas and water can effectively exchange heat within the heat exchanger, and since cooling water flows through the complex-shaped heat exchanger core, condensed water is is less likely to accumulate, the heat recovery rate is improved, and the surface temperature of the heat exchanger can be kept low.

(Example) First, the overall configuration of the exhaust system structure of an engine in which the present invention is implemented will be described using FIGS. 4, 5, and 6.

Figures 4, 5, and 6 show the rear, top, and side surfaces of the engine, respectively, where 1 is the engine body, and 2 is a configuration in which a water passage is provided above the side of the engine body 1 and surrounds the outer periphery of the exhaust manifold. An exhaust manifold heat exchanger in which the exhaust gas and cooling water flow in countercurrent flow; 3 is a heat exchanger installed on the exhaust downstream side of the exhaust manifold heat exchanger 2 to exchange heat between the exhaust gas and water; The structure of the heat exchanger 3 will be described later, but it is provided on the rear surface of the engine body 1 at a position lower than the height of the exhaust manifold heat exchanger 2. 2 is located above the heat exchanger 3, and the exhaust downstream side portion of the heat exchanger 3 is inclined downward. The connection part 4 is the exhaust manifold heat exchanger 2
and a flange 4 provided on each of the heat exchanger 3
It is constructed by fastening a and 4b with bolts 5. Further, an exhaust pipe 6a extending downward is connected to the exhaust outlet 3c provided at the inclined lower end of the heat exchanger 3, and an exhaust pipe line 6b is further connected to the exhaust pipe 6a branching from the middle of the exhaust pipe 6a. . 7
8 is a condensed water drain mechanism connected to the lower end of the exhaust pipe 6a, and 8 is a silencer provided above the heat exchanger 3 through which exhaust gas flows through the exhaust pipe 6b.

Next, the structure of the heat exchanger 3 will be explained with reference to FIGS. 1 to 3.

The heat exchanger 3 includes an exhaust inlet 3a as an exhaust passage;
It has an exhaust passage 3b, an exhaust outlet 3c, a water inlet 3d as a cooling water passage, a heat exchanger core 3e through which water flows, a return water passage 3f, and a water outlet 3g.
has. Then, an exhaust passage 3b is formed around the outer periphery of the heat exchanger core 3e, and a return water passage 3f is formed further around the outer periphery of the exhaust passage 3b, so that the exhaust gas and water are separated into three layers. The structure allows for heat exchange. Heat exchanger core 3
e The water inlet 3d that allows water to flow into the interior is provided on the side near the end on the upstream side of the exhaust gas of the heat exchanger 3, and is connected to the return water passage (water passage on the outer periphery of the exhaust passage) from the inside of the heat exchanger core 3. A communication section that allows water to flow to 3f is provided on the exhaust downstream side of the heat exchanger 3, and the water outlet 3g that allows water to flow out from the return water passage 3f.
is provided on the outer periphery of the upstream end of the heat exchanger 3 toward the outer periphery of the exhaust manifold. Stainless steel is suitable as the material for the heat exchanger core 3e, and aluminum is suitable as the material for the outer case constituting the return water passage 6f. Further, both the exhaust inlet 3a and the water outlet 3g are provided on the flange 4b and connected to the flange 4a on the exhaust manifold heat exchanger 2 side.

Then, the flow of exhaust gas passes from the exhaust manifold heat exchanger 2 through the connection part 4, through the exhaust inlet 3a, exhaust passage 3b, and exhaust outlet 3c of the heat exchanger 3, and then through the exhaust pipe 6a and exhaust pipe line 6b, The silencer 8 extends from the inlet 8a to the exhaust port 8b. In addition, the cooling water passes through the heat exchange core e from the water inlet 3d located on the exhaust upstream side of the heat exchanger 3, flows into the return water passage 3f on the exhaust downstream side, and heads toward the exhaust upstream side,
From the water outlet 3g at the upstream end of the heat exchanger 3, it flows into the exhaust manifold heat exchanger 2 via the connection part 4. Furthermore, it flows from the exhaust manifold heat exchanger 2 through the water pipe 9a (FIG. 6) and the water pump 10 into the water jacket inside the engine body 1, and further flows into the thermostat and the water pipe 9b.
and then reaches the water outlet 9c.

Next, the operation of the above configuration will be explained.

Cooling water flows in from the water inlet 3d of the heat exchanger 3,
The heat exchanger 3 and the exhaust manifold heat exchanger 2 exchange heat with the exhaust gas and recover the exhaust heat,
The water flows into the water jacket in the engine body 1 to cool the engine, and the high-temperature water flows out from the water outlet 9c. This hot water is sent to a radiator installed separately from the engine and used as a heat source for indoor heating, or, although not shown, is used in a compressor for pressurizing refrigerant in a heat pump refrigerant circuit driven by the output shaft of the engine body 1. It is used as a heat source for the outdoor heat exchanger in this heat pump refrigerant circuit. In this way, the hot water is used as a heat source, and the cooled water flows into the water inlet 3d of the heat exchanger 3 again.

Here, in the heat exchanger 3, high-temperature exhaust gas flows in from the exhaust inlet 3a, passes through the exhaust passage 3b,
Heat exchange is performed with water flowing through the heat exchanger core 3e and the return water passage 3f. At this time, condensed water is likely to be generated as the exhaust gas is cooled by the cooling water passing through the heat exchanger core 3e, but in the present invention, the cooling water is not allowed to flow inside the heat exchanger core 3e, which has a complicated passage shape. Since the exhaust gas is passed through the simple passage 3b on the outside, it is difficult for condensed water to accumulate. Therefore,
This prevents the heat exchanger core 3e from corroding and forming holes due to the generation of acidic condensed water, thereby preventing cooling water from leaking into the exhaust passage 3b or exhaust gas from flowing into the water circuit. In addition, in this embodiment, the connection part 4 between the heat exchanger 3 and the exhaust manifold heat exchanger 2 is located above the engine body 1, and the heat exchanger 3 is positioned so that the downstream side of the exhaust gas, that is, the side of the exhaust outlet 3c, is positioned downward. Since the cooling water is installed at an angle, even if cooling water were to leak into the exhaust passage 3b, this cooling water would flow into the exhaust manifold heat exchanger 2 side and enter the combustion chamber of the engine. It is designed to prevent backflow.

In addition, in the present invention, the heat exchanger 3 has a three-layer structure of exhaust gas and cooling water, and the cooling water flows from the water inlet 3d on the upstream side of the exhaust gas, to the heat exchanger core 3e, to the communication part on the downstream side of the exhaust gas, and to the return water. Since the heat reaches the water outlet 3g after passing through the passage 3f and reciprocating almost the entire heat exchanger 3, the heat recovery efficiency becomes high. Moreover, since the water outlet 3g is provided on the outer periphery of the upstream end of the heat exchanger toward the outer periphery of the exhaust manifold, the cooling water that has passed through the heat exchanger 3 can smoothly flow to the exhaust manifold heat exchanger 2.
This improves water circulation. Further, since the outer periphery of the exhaust passage 3b is surrounded by the return water passage 3f, the surface temperature of the heat exchanger can be lowered.

(Effects of the invention) As described above, according to the invention, a heat exchanger for exchanging heat between the exhaust gas and water provided in the exhaust system of an engine is connected to a heat exchanger core through which water flows, and a heat exchanger core through which water flows, By adopting a three-layer structure consisting of an exhaust passage formed around the outer periphery of the core and a water passage formed further surrounding the outer periphery of this exhaust passage, a decrease in the temperature of the exhaust gas inside the heat exchanger is suppressed. Corrosion of the heat exchanger core etc. due to accumulation of condensed water can therefore be reduced. In addition to the above-mentioned three-layer structure, the cooling water reciprocates almost the entire length of the heat exchanger, greatly increasing the heat recovery rate. By providing it toward the outer periphery of the exhaust manifold, the flow of cooling water toward the exhaust manifold through this heat exchanger can be made smooth. Moreover, it is a reasonable structure for improving the heat recovery rate and cooling water circulation, and can be a simple and compact structure. Furthermore, the surface temperature of the heat exchanger can be lowered, contributing to improved safety.

[Brief explanation of the drawing]

FIG. 1 is a top view showing an embodiment of a heat exchanger in the exhaust system structure of an engine according to the present invention, FIG. 2 is a cross-sectional view taken along the line - FIG. FIG. 4 is a rear view of an engine implementing the exhaust system structure of the present invention, FIG. 5 is a top view of the same engine, and FIG. 6 is a side view of the same engine. 1...Engine body, 2...Exhaust manifold heat exchanger, 3...Heat exchanger, 3b...Exhaust passage,
3e... Heat exchanger core, 3f... Return water passage.

Claims (1)

[Scope of utility model registration request] In an engine exhaust system structure that is equipped with a heat exchanger that recovers exhaust heat, a heat exchanger that exchanges heat between the exhaust gas and water is installed in the exhaust passage located downstream of the exhaust manifold of the engine, and this heat exchanger a heat exchanger core through which water circulates; an exhaust passage formed around the outer periphery of the heat exchanger core;
It has a three-layer structure consisting of a water passage formed by further surrounding the outer periphery of this exhaust passage, and a water inlet for flowing water into the heat exchanger core is provided on the exhaust upstream side of the heat exchanger. A communication part for flowing water from inside the core to the water passage is provided on the downstream side of the exhaust gas of the heat exchanger, and a water outlet for flowing water from the water passage is provided on the outer periphery of the upstream end of the exhaust gas of the heat exchanger and to the outer periphery of the exhaust manifold. An engine exhaust system structure characterized by being provided towards the engine.