Patent Description:
A conventional power generation system including a fuel cell is known to have a ventilated space inside a housing that accommodates the fuel cell. <CIT> discloses a power generation system provided with a fuel cell unit, a housing and a ventilation passage.

A power generator described in PTL <NUM>, for example, includes a fuel cell and an exhaust pipe. The exhaust pipe is connected to a duct. The duct extends vertically inside a building with an upper end of the duct being located outside the building. The fuel cell is housed in an exterior container. A ventilating pipe that provides air ventilation between the exterior container and the fuel cell is connected to the duct. The exterior container is preferably provided with a ventilation fan.

Described in PTL <NUM> is a fuel cell system that is disposed in a building. This fuel cell system includes a fuel processor, a fuel cell, and a ventilation fan inside a housing. The fuel cell system also includes a merging passage, a ventilation passage, and an exhaust passage.

The merging passage is connected to an external pipe. The ventilation passage is connected to a first junction of the merging passage. Ventilation gas from inside the housing is discharged out of the building by the ventilation fan through the ventilation passage, the merging passage, and the external pipe.

The ventilation passage is provided with a backflow preventer that prevents backflow of the ventilation gas. The exhaust passage is connected to a second junction of the merging passage that is located downstream of the first junction.

An unused oxidant gas of the fuel cell, and a combustion exhaust gas produced by a combustor of the fuel processor are discharged out of the building through the exhaust passage, the merging passage, and the external pipe.

Located between the first junction and the second junction of the merging passage is a passage heading upward from an upstream side to a downstream side for the ventilation gas. In addition, the ventilation passage includes, downstream of the backflow preventer, a passage that is of particular structure to suppress flow of liquids from a downstream end to an upstream end of the ventilation passage.

The technique described in PTL <NUM> is not based on consideration of control of liquids that enter the ventilating pipe, such as condensed water and rainwater. According to the technique described in PTL <NUM>, because of having the particular structure, the ventilation passage suppresses flow of the liquids from its downstream end to its upstream end.

However, the ventilation passage having the particular structure is hardly desirable from a viewpoint of decreasing flow path resistance of the ventilation passage. Accordingly, the present disclosure provides a power generation system that can prevent liquids from entering a ventilator even when a ventilation passage does not have a particular structure.

A power generation system according to the present invention includes a fuel cell unit, a housing, a ventilator, a ventilation passage, and a discharge passage, as defined in claim <NUM>.

The fuel cell unit includes a fuel cell. The housing accommodates the fuel cell unit. The ventilator is disposed in the housing to blow air out of the housing. The ventilation passage is disposed in the housing and allows passage of the air blown by the ventilator and an exhaust gas discharged from the fuel cell unit.

The discharge passage is disposed outside the housing, connects with the ventilation passage and lets the air and the exhaust gas that have passed through the ventilation passage into an atmosphere. An air outlet of the ventilator is located at a higher level than a bottom face of the ventilation passage that is contiguous with the air outlet.

The power generation system according to the present disclosure can prevent liquids from entering the ventilator even when the ventilation passage does not have a particular structure.

In a power generation system including a fuel cell unit, causing air blown by a ventilator and an exhaust gas of the fuel cell unit to merge before being discharged into an atmosphere is conceivable when the ventilator is used to ventilate an interior of a housing.

The exhaust gas includes water vapor, so that when the exhaust gas is cooled, condensed water is generated. If, for example, the condensed water enters the ventilator, there is a possibility that durability of the ventilator will be affected. It is therefore desirable that liquids including the condensed water should not flow upstream along a ventilation passage that the air blown by the ventilator passes through.

In the meantime, a ventilation passage having a particular structure is hardly desirable from a viewpoint of decreasing flow path resistance of the ventilation passage. There is a need for a technique that can prevent the liquids from entering the ventilator even when the ventilation passage does not have a particular structure.

After intensive studies, the present inventors have devised a power generation system that according to the present disclosure, can prevent the liquids from entering a ventilator even when a ventilation passage does not have a particular structure.

A power generation system according to a first aspect of the present disclosure includes a fuel cell unit, a housing, a ventilator, a ventilation passage, and a discharge passage.

According to this aspect, the liquids can be prevented from entering the ventilator even when the ventilation passage does not have a particular structure. Therefore, the power generation system can have increased durability.

While being based on the first aspect, a power generation system according to a second aspect of the present disclosure is as follows. The ventilation passage includes a projection. The projection projects inward from a wall surface that defines the bottom face or a side face of the ventilation passage around the projection. The air outlet is located at a leading end of the projection. According to this aspect, even when the liquids flow along the wall surface surrounding the projection, the liquids can be prevented from entering the ventilator.

While being based on the first aspect, a power generation system according to a third aspect of the present disclosure is such that the air outlet is an upwardly facing opening. According to this aspect, even though the air outlet of the ventilator is the upwardly facing opening, the liquids can be prevented from entering the ventilator.

While being based on the first aspect, a power generation system according to a fourth aspect of the present disclosure is such that the air outlet is horizontally separated from a boundary between the ventilation passage and the discharge passage. According to this aspect, even when the liquids including rainwater drop passing the boundary between the ventilation passage and the discharge passage, these liquids do not enter through the air outlet. Therefore, more reliable prevention of entry of the liquids into the ventilator can be achieved.

While being based on the first aspect, a power generation system according to a fifth aspect of the present disclosure is as follows. The ventilation passage includes a horizontal passage that the air flows horizontally through. The horizontal passage has a cross section with a longer horizontal length. According to this aspect, the horizontal passage can have a decreased height while having an increased cross-sectional area. Thus increase in flow path resistance of the ventilation passage can be suppressed, and another achievement is that the ventilation passage occupies a reduced vertical space in the housing.

While being based on the first aspect, a power generation system according to a sixth aspect of the present disclosure is as follows. The ventilation passage includes a merging portion where the exhaust gas and the air merge. The merging portion is located downstream of the air outlet in a flowing direction of the air.

According to this aspect, the exhaust gas merges at the portion downstream of the air outlet in the flowing direction of the air. Therefore, the exhaust gas including water vapor does not easily pass by the air outlet. Even when the water vapor included in the exhaust gas condenses into water, this liquid can consequently be prevented without fail from entering the ventilator.

While being based on the sixth aspect, a power generation system according to a seventh aspect of the present disclosure is as follows. The ventilation passage includes a horizontal passage that the air flows horizontally through. The horizontal passage includes the merging portion. This aspect enables the horizontally flowing air and the flowing exhaust gas to merge at right angles. Therefore, the exhaust gas is easily diluted with the air. The power generation system thus can have increased safety.

While being based on the seventh aspect, a power generation system according to an eighth aspect of the present disclosure is such that a ceiling of the ventilation passage includes a first segment located above the air outlet, a second segment neighboring the merging portion, and a third segment sloping down between the first segment and the second segment in a direction from the first segment to the second segment.

According to this aspect, even when the ceiling of the ventilation passage has the condensed water as a result of merging of the exhaust gas and the air, the condensed water does not easily come close to the air outlet along the ceiling of the ventilation passage. Accordingly, more reliable prevention of entry of the liquid into the ventilator can be achieved.

While being based on the sixth aspect, a power generation system according to a ninth aspect of the present disclosure also includes a drain outlet in the bottom face of the ventilation passage or in a wall surface connecting with the bottom face. The drain outlet is located at a lower level than the merging portion and a boundary between the ventilation passage and the discharge passage.

The ventilation passage includes a horizontal passage that the air flows horizontally through, and the air outlet is located between the merging portion and the drain outlet in a direction perpendicular to a cross section of the horizontal passage.

According to this aspect, the liquids including the condensed water pass by the air outlet along the bottom face of the ventilation passage, thus being led to the drain outlet. Although the liquids flow upstream along the ventilation passage, the liquids can be prevented thus from entering the ventilator.

While being based on the sixth aspect, a power generation system according to a tenth aspect of the present disclosure is such that the ventilation passage has, at the merging portion, a cross-sectional area that is larger than or equal to an opening area of the air outlet. This aspect provides easy suppression of increase in flow path resistance of the ventilation passage that might be caused by merging of the exhaust gas and the air.

While being based on the first aspect, a power generation system according to an eleventh aspect of the present disclosure is such that the ventilator includes a backflow preventer adjacent to the air outlet. According to this aspect, even when, for example, the exhaust gas flows upstream along the ventilation passage, the backflow preventer can prevent the exhaust gas from entering the ventilator. Therefore, the power generation system can have increased durability.

While being based on the first aspect, a power generation system according to a twelfth aspect of the present disclosure is such that the fuel cell unit also includes a fuel processor that produces a fuel gas to be supplied to the fuel cell. According to this aspect, the fuel gas that is to be supplied to the fuel cell can be produced by the fuel processor.

With reference to the drawings, a description is hereinafter provided of an exemplary embodiment of the present disclosure. The present disclosure is not limited to the following exemplary embodiment.

In each of the accompanying drawings, an xy plane is horizontal, and a positive z-axis direction is vertically upward. An x-axis and a y-axis are perpendicular to each other.

As illustrated in <FIG>, power generation system 1a includes fuel cell unit <NUM>, housing <NUM>, ventilator <NUM>, ventilation passage <NUM>, and discharge passage <NUM>. Fuel cell unit <NUM> includes fuel cell <NUM>. Housing <NUM> accommodates fuel cell unit <NUM>. Ventilator <NUM> is disposed in housing <NUM> to blow air out of housing <NUM>. Ventilation passage <NUM> is disposed in housing <NUM>.

The air blown by ventilator <NUM>, and an exhaust gas discharged from fuel cell unit <NUM> pass through ventilation passage <NUM>. Discharge passage <NUM> is disposed outside housing <NUM> and connects with ventilation passage <NUM>. Discharge passage <NUM> lets the air and the exhaust gas that have passed through ventilation passage <NUM> into an atmosphere.

Air outlet <NUM> of ventilator <NUM> is located at a higher level than bottom face <NUM> of ventilation passage <NUM> that is contiguous with air outlet <NUM>. The exhaust gas of fuel cell unit <NUM> can include water vapor, and there is a possibility that the water vapor condenses to form condensed water. Because of the above configuration, the condensed water can be prevented from entering ventilator <NUM> along bottom face <NUM> of ventilation passage <NUM>. Power generation system 1a thus can have increased durability.

Ventilator <NUM> may be of any structure provided that ventilator <NUM> can suck in air from inside housing <NUM> to blow the air from air outlet <NUM>. Ventilator <NUM> includes, for example, a fan such as a propeller fan, a sirocco fan, or a turbo fan.

Ventilation passage <NUM> is defined, for example, by an interior space of hollow component <NUM> illustrated in <FIG>. Hollow component <NUM> is made of, for example, a synthetic resin such as polypropylene. This makes it easy to form lightweight hollow component <NUM> of a desired shape.

As illustrated in <FIG>, ventilation passage <NUM> includes projection <NUM>. Projection <NUM> projects inward from a wall surface that defines bottom face <NUM> around projection <NUM>. Air outlet <NUM> is located at a leading end of projection <NUM>. Therefore, liquids including the condensed water are prevented from entering ventilator <NUM> even when the liquids flow along the wall surface surrounding projection <NUM>. Projection <NUM> may project inward from a wall surface that defines a side face of ventilation passage <NUM> around projection <NUM>.

As illustrated in <FIG>, air outlet <NUM> is horizontally separated from boundary <NUM> between ventilation passage <NUM> and discharge passage <NUM>. Even when the liquids including rainwater pass boundary <NUM>, the liquids can be more reliably prevented in this case from entering ventilator <NUM> through air outlet <NUM>.

As illustrated in <FIG> and <FIG>, ventilation passage <NUM> includes horizontal passage <NUM>. The air blown by ventilator <NUM> flows horizontally through horizontal passage <NUM>. As <FIG> illustrates, horizontal passage <NUM> has a cross section with a longer horizontal length. The cross-section of horizontal passage <NUM> refers to a section orthogonal to a flowing direction of the air in horizontal passage <NUM>. With its cross section having the longer horizontal length, horizontal passage <NUM> can have a decreased height while having an increased cross-sectional area.

First side face 43a and second side face 43b extend along the direction (a positive y-axis direction) that the air flows through horizontal passage <NUM>. As <FIG> illustrates, it is first side face 43a that is contiguous with air outlet <NUM>. Thus hollow component <NUM> can have a decreased x-axis dimension with air outlet <NUM> keeping a large opening area. As illustrated in <FIG>, air outlet <NUM> may be separated from first side face 43a as well as from second side face 43b in hollow component <NUM>.

As <FIG> and <FIG> illustrate, ventilation passage <NUM> includes merging portion <NUM>. At merging portion <NUM>, the exhaust gas discharged from fuel cell unit <NUM> merges with the air blown by ventilator <NUM>. Merging portion <NUM> is located downstream of air outlet <NUM> in the flowing direction of the air blown by ventilator <NUM>. In this case, the exhaust gas merges at the portion downstream of air outlet <NUM> in the flowing direction of the air. Therefore, the exhaust gas that includes the water vapor does not easily pass by air outlet <NUM>. In this way, the water that results from the condensation of the water vapor included in the exhaust gas can be prevented from entering ventilator <NUM>.

As illustrated in <FIG> and <FIG>, merging portion <NUM> is included in horizontal passage <NUM>. In this case, the horizontally flowing air and the flowing exhaust gas merge at right angles, so that the exhaust gas is easily diluted with the air.

The exhaust gas is guided to merging portion <NUM> from a direction different from the direction (positive y-axis direction) that the air flows through horizontal passage <NUM>. Preferably, the exhaust gas is guided to merging portion <NUM> perpendicularly to the direction that the air flows through horizontal passage <NUM>. Thus the exhaust gas is reliably diluted with the air. As illustrated in <FIG> and <FIG>, hollow component <NUM> includes first protrusion 41a that is tubular. First protrusion 41a is formed at the side face 43a of hollow component <NUM> to protrude outward from its surrounding wall surface. When guided to merging portion <NUM>, the exhaust gas passes through first protrusion 41a.

Ventilation passage <NUM> has, at merging portion <NUM>, a cross-sectional area that is larger than or equal to the opening area of air outlet <NUM>. This provides easy suppression of increase in flow path resistance of ventilation passage <NUM> that might be caused by merging of the exhaust gas and the air.

As <FIG> and <FIG> illustrate, hollow component <NUM> includes second protrusion 41b that is, for example, tubular. Second protrusion 41b is formed at a top of hollow component <NUM> to protrude outward from its surrounding wall surface. Included in ventilation passage <NUM>, an interior space of second protrusion 41b is located downstream of merging portion <NUM> in the flowing direction of the air. A leading edge of second protrusion 41b defines boundary <NUM>. After merging at merging portion <NUM>, the air and the exhaust gas pass through second protrusion 41b to enter discharge passage <NUM>. Second protrusion 41b is disposed in a through hole formed in a top plate of housing <NUM>. Connected to second protrusion 41b is a pipe including discharge passage <NUM>.

As illustrated in <FIG>, ceiling <NUM> of ventilation passage <NUM> includes first segment 49a, second segment 49b, and third segment 49c. First segment 49a is located above air outlet <NUM>. Second segment 49b neighbors merging portion <NUM>. Third segment 49c slopes down between first segment 49a and second segment 49b in a direction from first segment 49a to second segment 49b.

There is a possibility that the water vapor included in the exhaust gas condenses on second segment 49b into the water when the exhaust gas and the air merge. Because third segment 49c of ceiling <NUM> slopes down in the direction from first segment 49a to second segment 49b, the condensed water on second segment 49a is kept away from first segment <NUM> that is located above air outlet <NUM>. Accordingly, more reliable prevention of entry of the liquids, which include the condensed water, into ventilator <NUM> can be achieved. Third segment 49c may make right angles with the flowing direction of the air.

As <FIG>, <FIG> illustrate, power generation system 1a also includes drain outlet <NUM>. Drain outlet <NUM> is formed in the bottom face <NUM> of ventilation passage <NUM> or in any wall surface connecting with the bottom face <NUM> and is located at a lower level than merging portion <NUM> and boundary <NUM> between ventilation passage <NUM> and discharge passage <NUM>. Air outlet <NUM> is located between merging portion <NUM> and drain outlet <NUM> in a direction perpendicular to the cross section of horizontal passage <NUM>.

Therefore, the water that is formed by condensation of the water vapor included in the exhaust gas when the exhaust gas and the air merge, or water or the like that has passed boundary <NUM> passes by air outlet <NUM> along bottom face <NUM> of ventilation passage <NUM>, thus being led to drain outlet <NUM>.

Although the liquids pass by air outlet <NUM>, the liquid can be prevented thus from entering ventilator <NUM>. Hollow component <NUM> includes third protrusion 41c that is tubular. Drain outlet <NUM> is located at a base of third protrusion 41c. Third protrusion 41c is formed at a bottom of hollow component <NUM> to protrude outward from its surrounding wall surface.

As illustrated in <FIG>, bottom face <NUM> of ventilation passage <NUM> slopes down toward drain outlet <NUM>. Thus the liquids including the condensed water are led to drain outlet <NUM> along bottom face <NUM> of ventilation passage <NUM>.

Inside housing <NUM>, a tank (not illustrated) is disposed below drain outlet <NUM>. Drain outlet <NUM> is connected to this tank via a pipe. A pipe including a drain passage is connected to the tank and extends out of housing <NUM>. After passing through drain outlet <NUM>, the liquids including the condensed water are stored in the tank and are subsequently led out of housing <NUM> through the drain passage.

As illustrated in <FIG>, ventilator <NUM> includes backflow preventer <NUM>. Backflow preventer <NUM> is disposed adjacent to air outlet <NUM>. Backflow preventer <NUM> is, for example, a swing check valve, a lift check valve, or a disc check valve.

Even when the exhaust gas flows upstream along ventilation passage <NUM>, backflow preventer <NUM> can prevent the exhaust gas from entering ventilator <NUM>. Therefore, power generation system 1a can have increased durability.

As <FIG> illustrates, power generation system 1a is installed in building <NUM>. Discharge passage <NUM> extends out of building <NUM>. Discharge passage <NUM> is defined by an interior space of the specified pipe. An inner space of a double walled pipe that extends out of building <NUM> defines a part of discharge passage <NUM>. In this case, air from inside building <NUM> is supplied into power generation system 1a through an outer space of the double walled pipe. Discharge passage <NUM> may be defined by an interior space of a pipe other than the double walled pipe. The double walled pipe may be such that air from outside building <NUM> is supplied into power generation system 1a through the outer space of the double walled pipe.

Power generation system 1a also includes fuel gas supply unit <NUM> and oxidant gas supply unit <NUM>. Fuel gas supply unit <NUM> supplies a fuel gas from a fuel gas supply source (not illustrated) to an anode of fuel cell <NUM>. The fuel gas includes a hydrogen gas. Oxidant gas supply unit <NUM> supplies an oxidant gas, such as air including oxygen, to a cathode of fuel cell <NUM>. Fuel gas supply unit <NUM> is a pump, and oxidant gas supply unit <NUM> is a blower.

In fuel cell <NUM>, the fuel gas supplied to the anode and the oxidant gas supplied to the cathode react, whereby electricity and heat are produced. The electricity produced by fuel cell <NUM> is supplied to an electric power load external to housing <NUM>. The heat produced by fuel cell <NUM> is recovered by a heat medium such as cooling water and is used, for example, to heat water. Fuel cell <NUM> is, for example, a solid polymer fuel cell or a solid oxide fuel cell.

The exhaust gas discharged from fuel cell unit <NUM> includes, for example, an anode off-gas and a cathode off-gas. The anode off-gas includes an unreacted fuel gas and is discharged from the anode of fuel cell <NUM>. The cathode off-gas includes an unreacted oxidant gas and is discharged from the cathode of fuel cell <NUM>.

Power generation system 1a also includes passage <NUM>. Passage <NUM> connects an anode off-gas outlet of the anode of fuel cell <NUM> and a cathode off-gas outlet of the cathode of fuel cell <NUM> with ventilation passage <NUM>.

An interior space of first protrusion 41a defines an end of passage <NUM>. The anode off-gas and the cathode off-gas pass through passage <NUM>, thus being guided to ventilation passage <NUM>. The water vapor is produced by reaction between the fuel gas and the oxidant gas at fuel cell <NUM>. It is for this reason that the gaseous water vapor is also included in the exhaust gas.

Power generation system 1a also includes combustion device <NUM>. Combustion device <NUM> includes combustor <NUM> and air supply unit <NUM>. Supplied to combustor <NUM> are a specified fuel and air which is supplied by air supply unit <NUM>. Accordingly, combustor <NUM> combusts the fuel to produce heat and a combustion exhaust gas. The heat produced is used, for example, to heat water. In other words, combustion device <NUM> is used, for example, as a boiler.

The fuel that is supplied to combustor <NUM> is, for example, an inflammable gas such as natural gas, or a liquid fuel such as kerosene. Air supply unit <NUM> is, for example, a fan or a blower.

Combustion device <NUM> also includes exhaust gas passage <NUM>. Exhaust gas passage <NUM> connects discharge passage <NUM> and a combustion exhaust gas outlet of combustor <NUM>. Inside building <NUM>, discharge passage <NUM> includes merging portion <NUM>. Merging portion <NUM> is where the air and the exhaust gas that are discharged out of housing <NUM> merge with the combustion exhaust gas discharged from combustor <NUM>. These gases pass through discharge passage <NUM>, thus being discharged into the atmosphere.

As stated above, ventilator <NUM> includes backflow preventer <NUM>. Therefore, even when the combustion exhaust gas produced by combustor <NUM> flows upstream along ventilation passage <NUM>, the combustion exhaust gas can be prevented from entering ventilator <NUM>. Consequently, power generation system 1a can have increased durability.

Power generation system 1a also includes controller <NUM>. Controller <NUM> is, for example, a digital computer storing an executable program that operates power generation system 1a. Controller <NUM> obtains information indicative of results measured by measuring devices that are included in power generation system 1a, such as a temperature sensor and a flowmeter. Moreover, controller <NUM> transmits control signals to fuel gas supply unit <NUM>, oxidant gas supply unit <NUM>, ventilator <NUM>, the fan, the blower, a pump, a heater, the valve, or the like.

Power generation system 1a can be modified in various respects. For example, power generation system 1a may be replaced with power generation system 1b illustrated in <FIG>.

Those constituent elements of <FIG> power generation system 1b that are identical or correspond to the constituent elements of <FIG> power generation system 1a have the same reference marks and are not described in detail.

As illustrated in <FIG>, fuel cell unit <NUM> of power generation system 1b includes fuel processor <NUM>. Fuel processor <NUM> produces a fuel gas that is to be supplied to fuel cell <NUM>.

Fuel processor <NUM> includes reformer 15a and combustor 15b. Reformer 15a produces hydrogen by reforming reaction such as steam reforming reaction (CH4 + H2O -> CO + <NUM><NUM>). A reforming catalyst is housed in reformer 15a for the purpose of promoting the reforming reaction. Also housed in reformer 15a are catalysts that remove carbon monoxide (CO).

The catalysts that remove carbon monoxide include a CO shifting catalyst and a CO selective oxidation removal catalyst. A source gas to be supplied to reformer 15a is, for example, a hydrocarbon gas such as city gas or liquefied petroleum (LP) gas. Including hydrogen produced by reformer 15a, the fuel gas is supplied to fuel cell <NUM>.

Combustor 15b is connected to an anode off-gas outlet of fuel cell <NUM>. An anode off-gas is supplied to combustor 15b as a gas to be used for combustion. Power generation system 1b includes air supply unit <NUM> that supplies air to combustor 15b. Air supply unit <NUM> is, for example, a pump or a blower.

Combustor 15b combusts the anode off-gas and the air, thus producing heat and a combustion exhaust gas. Because of the heat produced by combustor 15b, reformer 15a is heated, and the reforming reaction is promoted accordingly.

Passage <NUM> is connected to a combustion exhaust gas outlet of combustor 15b. Therefore, the combustion exhaust gas produced by combustor 15b passes through passage <NUM> and is guided to ventilation passage <NUM> together with a cathode off-gas, thus being included in an exhaust gas. Not only the anode off-gas but also the cathode off-gas may be supplied to combustor 15b.

Claim 1:
A power generation system comprising:
a fuel cell unit (<NUM>) including a fuel cell (<NUM>);
a housing (<NUM>) accommodating the fuel cell unit (<NUM>);
a ventilator (<NUM>) disposed in the housing (<NUM>) and blowing air out of the housing (<NUM>);
a ventilation passage (<NUM>) disposed in the housing (<NUM>), the ventilation passage (<NUM>) allowing passage of the air blown by the ventilator (<NUM>) and an exhaust gas discharged from the fuel cell unit (<NUM>); and
a discharge passage (<NUM>) that lets the air and the exhaust gas that have passed through the ventilation passage (<NUM>) into an atmosphere, the discharge passage (<NUM>) being disposed outside the housing (<NUM>) and connecting with the ventilation passage (<NUM>),
wherein an air outlet (<NUM>) of the ventilator (<NUM>) is located at a higher level than a bottom face (<NUM>) of the ventilation passage (<NUM>) that is contiguous with the air outlet (<NUM>),
characterized in that:
the ventilation passage (<NUM>) includes a projection (<NUM>), the projection (<NUM>) projecting inward from a wall surface that defines one of the bottom face (<NUM>) and a side face (43a, 43b) of the ventilation passage (<NUM>) around the projection (<NUM>);
a drain outlet (<NUM>) in one of the bottom face (<NUM>) of the ventilation passage (<NUM>) and a wall surface connecting with the bottom face (<NUM>), the drain outlet (<NUM>) being located at a lower level than a merging portion (<NUM>) where the exhaust gas and the air merge and a boundary (<NUM>) between the ventilation passage (<NUM>) and the discharge passage (<NUM>);
the bottom face (<NUM>) of the ventilation passage (<NUM>) slopes down toward the drain outlet (<NUM>); and
the air outlet (<NUM>) is located at a leading end of the projection (<NUM>).