Patent Description:
An ejector and a vacuum generation device including the ejector are known. For example, a vacuum generation device described in <CIT> circulates a fluid stored in a tank through a pump and an ejector as a first fluid to allow the ejector to generate a suction force, which sucks a second fluid.

The ejector includes a nozzle and a diffuser that are designed to suck the second fluid as intended.

However, the ejector including the nozzle and the diffuser designed as above may fail to suck the second fluid as intended if the ejector malfunctions. The ejector may malfunction when, for example, the pressure of the fluid passing through the diffuser is not raised sufficiently.

<CIT> discloses an ejector, comprising a nozzle configured to eject a first fluid. Furthermore; the ejector is provided with a suction chamber configured to suck a second fluid using a pressure decrease caused by ejection of the first fluid through the nozzle. The ejector further comprises a diffusor configured to discharge the first fluid ejected through the nozzle and the second fluid sucked into the suction chamber while raising a pressure of the first fluid and the second fluid. At least one flow restrictor is located downstream from the diffuser.

<CIT> discloses a chemical dispenser which includes a plurality of eductors for drawing chemical into a diluent to produce an effluent. According to <FIG> a typical eductor is shown having a discharge tube with a flooding ring located below the diffuser in the tube. In operation, water exits the orifice, travels through the diffuser and into the discharge tube where the stream impinges on a bar or other structure of the flooding ring. This causes the fluid to change direction, to back up and to cause a pressure drop. This floods the diffuser section, thus reducing the water diluent velocity. Pressure is reduced and this creates a vacuum at the chemical inlet. Thus, a plurality of flow restrictors formed by the flooding ring located downstream from the diffuser are disclosed. These restrictors are located at the same position in a flow direction.

<CIT> discloses a vacuum generating device, with an ejector unit that has a jet nozzle, a catch nozzle downstream of the blasting nozzle and one in the transition area between the blast nozzle and catch nozzle defined suction zone. Furthermore, a discharge opening is provided which is attached to the discharge opening. The chamber is located adjacent to the catcher nozzle, from which an air outlet channel to the environment diverges. At the of the outlet opening of the catch nozzle axially opposite side of an in the sense of an optional approach or distance relative to the outlet opening adjustable and positionable control element is provided. The flow restrictor is located downstream from a diffuser.

In <CIT> is disclosed an ejector according to the preamble of claim <NUM>.

In response to the above issue, one or more aspects of the invention are directed to an ejector that functions properly.

An ejector according to one aspect of the invention includes a nozzle that ejects a first fluid, a suction chamber that sucks a second fluid using a pressure decrease caused by ejection of the first fluid through the nozzle, a diffuser that discharges the first fluid ejected through the nozzle and the second fluid sucked into the suction chamber while raising a pressure of the first fluid and the second fluid, a pipe having a passage is connected to the downstream end of the diffuser, and at least one flow restrictor located downstream from the diffuser. The flow restrictor comprises a plurality of flow restrictors that include an upstream flow restrictor and a downstream flow restrictor. The upstream and downstream flow restrictors are located inside the pipe. According to the invention the cross-sectional area of the passage in the pipe is uniform from upstream to downstream. The upstream flow restrictor is a disc-shaped flow restrictor orifice plate and the downstream flow restrictor is a downstream disc-shaped flow restrictor orifice plate, each having a circular central opening. The opening in the upstream orifice plate has an area smaller than the cross-sectional area of the passage in the part of the pipe downstream from the orifice plate and the opening in the downstream orifice plate has an area smaller than the cross-sectional area of the passage in the part of the pipe upstream from the orifice plate.

Especially, the ratio of the area of the opening to the cross-sectional area of the passage in the pipe of the upstream orifice plate is equal to the ratio of the area of the opening to the cross-sectional area of the passage in the pipe of the downstream orifice plate.

According to a further embodiment of the invention the downstream orifice plate is located on a downstream end of the pipe, or is located at a joint between the pipe and a tank.

A vacuum generation device according to another aspect of the disclosure includes the above mentioned ejector, the tank that stores the first fluid and the second fluid that have passed through the diffuser, and a pump connected to the tank. The pump pumps a fluid in the tank to the ejector as the first fluid. The pump and the ejector allow the fluid in the tank to circulate through them and suck the second fluid through the ejector.

The ejector according to the above aspect includes the flow restrictor located downstream from the diffuser to sufficiently raise the pressure of the fluid passing through the diffuser. The ejector can thus function properly.

The vacuum generation device according to the above aspect includes the flow restrictor located downstream from the diffuser to sufficiently raise the pressure of the fluid passing through the diffuser. The ejector can thus function properly. The vacuum generation device can suck the second fluid properly.

Further advantages, features and potential applications of the present invention may be gathered from the description which follows, in conjunction with the embodiments illustrated in the drawings.

Throughout the description, the claims and the drawings, those terms and associated reference signs will be used as are notable from the enclosed list of reference signs. In the drawings is shown.

Embodiments will be described by way of example with reference to the drawings. The embodiments described below are preferred examples, and do not limit the scope, applications, and uses of the present invention.

<FIG> is a schematic diagram of piping for a vacuum steam heating system <NUM> according to one embodiment.

The vacuum steam heating system (hereafter, the heating system) <NUM> includes a reaction tank <NUM>, which heats an object with steam, a steam supply pipe <NUM>, which supplies steam to the reaction tank <NUM> from a steam generator (not shown), a discharge pipe <NUM>, which discharges a drain generated in the reaction tank <NUM>, and a vacuum generation device <NUM>, which sucks the drain through the discharge pipe <NUM>. The heating system <NUM> includes a fluid circuit <NUM>, which includes the steam supply pipe <NUM>, the reaction tank <NUM>, the discharge pipe <NUM>, and the vacuum generation device <NUM>. The heating system <NUM> heats an object placed in the reaction tank <NUM> with saturated steam at an atmospheric pressure or less.

The reaction tank <NUM> includes a tank body <NUM>, in which an object is placed, and a jacket <NUM>, which extends along substantially the entire periphery of the tank body <NUM>. The steam supply pipe <NUM> is connected to the jacket <NUM>. The steam supply pipe <NUM> includes a supply valve <NUM>, which is an on-off valve. Steam generated in the steam generator is supplied to the jacket <NUM> through the steam supply pipe <NUM>. The steam supplied to the jacket <NUM> indirectly exchanges heat with the object placed in the tank body <NUM> in the reaction tank <NUM> to condense (or liquefy) and heat the object in the tank body <NUM>. More specifically, the object is heated with the condensed latent heat from the steam.

The discharge pipe <NUM> has one end (inlet end) connected to a lower end part of the jacket <NUM>, and the other end (outlet end) connected to the vacuum generation device <NUM>. The discharge pipe <NUM> discharges the drain (condensate) generated from the steam condensed in the jacket <NUM>. The discharge pipe <NUM> includes a steam trap <NUM>, which automatically discharges only the drain flowing into the steam trap <NUM>.

The vacuum generation device <NUM> includes a drain tank <NUM>, which stores the drain, a pump <NUM>, which pumps the drain in the drain tank <NUM>, and an ejector <NUM>, which sucks the drain from the reaction tank <NUM> through the discharge pipe <NUM>. The drain tank <NUM>, the pump <NUM>, and the ejector <NUM> are connected to one another with a pipe <NUM>. This forms a circulation passage including the drain tank <NUM>, the pump <NUM>, and the ejector <NUM>. The vacuum generation device <NUM> circulates the drain stored in the drain tank <NUM> through the pump <NUM> and the ejector <NUM> to cause the ejector <NUM> to generate a suction force, which then sucks the drain from the reaction tank <NUM>.

<FIG> is a schematic diagram of the vacuum generation device <NUM>. The pipe <NUM> includes a first pipe 34a connecting the drain tank <NUM> and the pump <NUM>, a second pipe 34b connecting the pump <NUM> and the ejector <NUM>, and a third pipe 34c connecting the ejector <NUM> and the drain tank <NUM>. The drain tank <NUM> is an example of the tank. The pump <NUM> is driven by a motor <NUM>.

The ejector <NUM> includes a nozzle <NUM> for ejecting a first fluid, a suction chamber <NUM>, which uses a negative pressure generated by the first fluid ejected through the nozzle <NUM> to suck a second fluid, a diffuser <NUM>, which discharges the first fluid ejected through the nozzle <NUM> and the second fluid sucked into the suction chamber <NUM> while raising their pressure, and two orifice plates <NUM> located downstream from the diffuser <NUM>.

The nozzle <NUM> is connected to a downstream end of the second pipe 34b. The nozzle <NUM> has an injection hole 41a located at least inside the suction chamber <NUM>.

The suction chamber <NUM> also contains at least an upstream end part of the diffuser <NUM>. The discharge pipe <NUM> has the outlet end connected into the suction chamber <NUM>. In the suction chamber <NUM>, the second fluid is sucked from the discharge pipe <NUM> under a negative pressure (pressure decrease) caused by ejection of the first fluid through the nozzle <NUM>. In the suction chamber <NUM>, the negative pressure resulting from the jet pumping of the first fluid generates a suction force for sucking the second fluid.

The diffuser <NUM> defines a linear passage. The cross-sectional area of the passage defined in the diffuser <NUM> increases from upstream to downstream. A fluid passing through the diffuser <NUM> thus decelerates, and the pressure of the fluid increases the fluid flows from upstream to downstream. The third pipe 34c is connected to the downstream end of the diffuser <NUM>.

The orifice plates <NUM> are disc-shaped, and each have a circular central opening 44a. The orifice plates <NUM> are a flow restrictor. The orifice plates <NUM> are located inside the third pipe 34c. More specifically, the upstream orifice plate <NUM> is located on an upstream end of the third pipe 34c, or is located at a joint between the diffuser <NUM> and the third pipe 34c. The downstream orifice plate <NUM> is located on a downstream end of the third pipe 34c, or is located at a joint between the third pipe 34c and the drain tank <NUM>. The diffuser <NUM> and the third pipe 34c are connected to each other at their flanges. The upstream orifice plate <NUM> is located between the flange of the diffuser <NUM> and the flange of the third pipe 34c. The third pipe 34c and the drain tank <NUM> are connected to each other at their flanges. The downstream orifice plate <NUM> is located between the flange of the third pipe 34c and the flange of the drain tank <NUM>.

The opening 44a in the upstream orifice plate <NUM> has an area smaller than the cross-sectional area of a passage in the part of the third pipe 34c downstream from the orifice plate <NUM>. In the same manner, the opening 44a in the downstream orifice plate <NUM> has an area smaller than the cross-sectional area of a passage in the part of the third pipe 34c upstream from the orifice plate <NUM>. More specifically, the upstream and downstream orifice plates <NUM> function as chokes to narrow the cross-sectional area of the passage downstream from the diffuser <NUM>.

The opening 44a in the upstream orifice plate <NUM> has the same area as the opening 44a in the downstream orifice plate <NUM>. The cross-sectional area of the passage in the third pipe 34c is uniform from upstream to downstream. For the upstream orifice plate <NUM>, the ratio of the area of the opening 44a to the cross-sectional area of the passage in the third pipe 34c (the area of the opening 44a/the cross-sectional area of the passage in the third pipe 34c, or hereafter the aperture ratio) is equal to the aperture ratio of the downstream orifice plate <NUM>.

The vacuum generation device <NUM> with the structure described above supplies the drain inside the drain tank <NUM> with the pressure being raised by the pump <NUM> to the nozzle <NUM> in the ejector <NUM> as the first fluid. The drain is ejected through the nozzle <NUM> into the suction chamber <NUM> to generate a negative pressure around the nozzle <NUM>, which then sucks the drain in the reaction tank <NUM> into the suction chamber <NUM> through the discharge pipe <NUM> as the second fluid. The drain ejected through the nozzle <NUM> and the drain sucked from the discharge pipe <NUM> mix in the suction chamber <NUM>. The resultant drain is then discharged through the diffuser <NUM>. In this state, the drain decelerates and the pressure of the drain increases when flowing downstream through the diffuser <NUM>. The drain finally flows into the drain tank <NUM>. The drain in the reaction tank <NUM> is collected into the drain tank <NUM>.

The orifice plates <NUM> located downstream from the diffuser <NUM> allow the ejector <NUM> to function properly, and the drain to be properly sucked from the reaction tank <NUM>.

More specifically, the orifice plates <NUM> located downstream from the diffuser <NUM> increase the flow resistance in the passage downstream from the diffuser <NUM> and increase the fluid pressure in the passage downstream from the diffuser <NUM>. This sufficiently raises the pressure of the fluid passing through the diffuser <NUM>. At a low fluid pressure downstream from the diffuser <NUM>, the pressure of the fluid passing through the diffuser <NUM> may not be raised sufficiently. In the ejector <NUM>, the nozzle <NUM> and the diffuser <NUM> are designed based on the pressure difference between the inlet of the nozzle <NUM> and the outlet of the diffuser <NUM>. If this pressure difference is too small, the ejector <NUM> cannot have an intended negative pressure generated in the suction chamber <NUM>. The orifice plates <NUM> located downstream from the diffuser <NUM> allow a sufficiently large increase in the pressure of the fluid passing through the diffuser <NUM>. This generates an intended negative pressure in the suction chamber <NUM>. The ejector <NUM> can thus function properly.

The diffuser <NUM> may or may not sufficiently raise the pressure of the fluid depending on the temperature of the drain circulating through the vacuum generation device <NUM> (hereafter, the circulating water temperature) in addition to the pressure downstream from the diffuser <NUM>. As the circulating water temperature is higher, the drain has lower viscosity, and thus causes a smaller pressure increase (pressure recovery) in the drain passing through the diffuser <NUM>. In other words, as the circulating water temperature is higher, an intended negative pressure is less likely to be generated in the suction chamber <NUM>.

<FIG> is a graph showing the relationship between the aperture ratio of the orifice plate <NUM> and the circulating water temperature in association with a failure to generate an intended negative pressure in the suction chamber <NUM> (hereafter, a vacuum failure). A solid line in <FIG> indicates a threshold at which a vacuum failure occurs when a single orifice plate <NUM> is used. A vacuum failure can occur in an area defined above the threshold, or an area in which the circulating water temperature is higher than the threshold (a hatched area for the threshold indicated by the solid line in the figure). A broken line in <FIG> indicates a threshold at which a vacuum failure occurs when two orifice plates <NUM> are used.

With no orifice plate <NUM> being used (corresponding to the aperture ratio of <NUM>%), the circulating water temperature at the threshold at which no vacuum failure occurs (hereafter, the threshold water temperature) is T1. As shown in <FIG>, the threshold water temperature can be higher as the opening 44a in the orifice plate <NUM> is smaller. In other words, the circulating water temperature at which no vacuum failure occurs can be higher. With the two orifice plates <NUM> being used, instead of the single orifice plate <NUM>, the threshold water temperature can be still higher (as indicated by the broken line), because the use of more orifice plates <NUM> raises the pressure more in the passage downstream from the diffuser <NUM>.

However, the orifice plate <NUM> having a smaller aperture ratio may have a flow resistance that is too high. This may decrease the flow rate of the drain passing through the third pipe 34c, or the flow rate of the drain passing through the diffuser <NUM>. This lowers the flow rate of the drain to be sucked from the reaction tank <NUM> through the discharge pipe <NUM>.

In contrast, multiple orifice plates <NUM> may be used to increase the flow resistance while retaining the intended flow rate. <FIG> is a graph showing the relationship between the degree of vacuum and the amount of suction by the ejector. In <FIG>, a solid line indicates the structure including a single orifice plate <NUM> with the aperture ratio of <NUM>%, whereas a broken line indicates the structure including two orifice plates <NUM> with the aperture ratio of <NUM>%. When the degree of vacuum is high (e.g., <NUM> kPaG), or specifically when the ejector <NUM> functions properly, the structure including the two orifice plates <NUM> with the aperture ratio of <NUM>% has a larger amount of suction than the structure including the single orifice plate <NUM> with the aperture ratio of <NUM>%. Although the structure including the single orifice plate <NUM> with the aperture ratio of <NUM>% can sufficiently increase the threshold water temperature (refer to <FIG>), the aperture ratio is small and the amount of suction decreases. In contrast, the structure including the two orifice plates <NUM> with the aperture ratio of <NUM>% can retain the intended amount of suction, in addition to sufficiently increasing the threshold water temperature. In other words, the use of more orifice plates <NUM> increases the threshold water temperature, while retaining the intended amount of suction with a greater aperture ratio.

As described above, the ejector <NUM> includes the nozzle <NUM> that ejects the first fluid, the suction chamber <NUM> that sucks the second fluid using a pressure decrease caused by ejection of the first fluid through the nozzle <NUM>, the diffuser <NUM> that discharges the first fluid ejected through the nozzle <NUM> and the second fluid sucked into the suction chamber <NUM> while raising the pressure of the first fluid and the second fluid, and at least one orifice plate <NUM> located downstream from the diffuser <NUM>.

The structure including the orifice plate <NUM> located downstream from the diffuser <NUM> can raise the pressure of the passage downstream from the diffuser <NUM>. This structure thus sufficiently raises the pressure of the fluid passing through the diffuser <NUM>, and enables the ejector <NUM> to function properly.

For example, the pipe <NUM> (in particular, the third pipe 34c) may be short to downsize the ejector <NUM> and thus the vacuum generation device <NUM>. In this case, the pressure downstream from the diffuser <NUM> tends to be lower. The pressure of the fluid passing through the diffuser <NUM> may not be raised sufficiently. The orifice plate <NUM> used in this structure can sufficiently raise the pressure of the fluid passing through the diffuser <NUM>. In other words, the structure including the orifice plate <NUM> is particularly effective for the ejector <NUM> and the vacuum generation device <NUM> that are compact.

The orifice plate <NUM> narrows the cross-sectional area of the passage from its peripheral portion, and thus allows the fluid to have an appropriate pressure decrease without excessively disturbing the outwardly diverging flow of the fluid.

The at least one orifice plate <NUM> includes a plurality of orifice plates <NUM>. This structure can raise the pressure in the passage downstream from the diffuser <NUM> without excessively reducing the flow rate of the fluid passing through the diffuser <NUM>.

Further, the at least one orifice plate <NUM> has the opening 44a with a smaller cross-sectional area than passages upstream and downstream from the orifice plate <NUM> as the restrictor.

The orifice plate <NUM> narrows the passage to increase the flow resistance.

The vacuum generation device <NUM> includes the ejector <NUM>, the drain tank <NUM> that stores the first fluid and the second fluid that have passed through the diffuser <NUM>, and the pump <NUM> connected to the drain tank <NUM>. The pump <NUM> pumps the fluid in the drain tank <NUM> to the ejector <NUM> as the first fluid. The pump <NUM> and the ejector <NUM> allow the fluid in the drain tank <NUM> to circulate through them and suck the second fluid through the ejector <NUM>.

In this structure, the ejector <NUM> can function properly as described above, and the second fluid can be sucked through the ejector <NUM> properly.

The ejector <NUM> and the vacuum generation device <NUM> are usable for systems other than the vacuum steam heating system <NUM>. For example, the ejector <NUM> and the vacuum generation device <NUM> may be used for a system that performs cooling in addition to heating with steam. The steam used in such systems may not be steam at an atmospheric pressure or less.

Although the ejector <NUM> circulates water in the above embodiments, the ejector <NUM> may not be a liquid ejector. The ejector <NUM> may circulate a gas.

Claim 1:
An ejector (<NUM>), comprising:
a nozzle (<NUM>) configured to eject a first fluid;
a suction chamber (<NUM>) configured to suck a second fluid using a pressure decrease caused by ejection of the first fluid through the nozzle (<NUM>);
a diffuser (<NUM>) configured to discharge the first fluid ejected through the nozzle (<NUM>) and the second fluid sucked into the suction chamber (<NUM>) while raising a pressure of the first fluid and the second fluid;
a pipe (34c) having a passage is connected to the downstream end of the diffuser (<NUM>);
and at least one flow restrictor (<NUM>) located downstream from the diffuser (<NUM>), the flow restrictor (<NUM>) comprises a plurality of flow restrictors (<NUM>) that include an upstream flow restrictor (<NUM>) and a downstream flow restrictor (<NUM>),
the upstream and downstream flow restrictors (<NUM>) are located inside the pipe (34c),
characterized in that
the cross-sectional area of the passage in the pipe (34c) is uniform from upstream to downstream;
the upstream flow restrictor (<NUM>) is a disc-shaped orifice plate and the downstream flow restrictor (<NUM>) is a disc-shaped orifice plate, each having a circular central opening (44a);
the opening (44a) in the upstream orifice plate (<NUM>) has an area smaller than the cross-sectional area of the passage in the part of the pipe (34c) downstream from the orifice plate (<NUM>) and the opening (44a) in the downstream orifice plate (<NUM>) has an area smaller than the cross-sectional area of the passage in the part of the pipe (34c) upstream from the orifice plate (<NUM>).