FIELD OF THE INVENTION

The invention relates to Waste Heat Recovery (WHR) systems coupled with internal combustion engines and, more specifically, to an apparatus and method for improved containment and detection of leaks in a waste heat recovery boiler.

BACKGROUND AND SUMMARY OF THE INVENTION

Waste heat recovery systems can make available for use energy in internal combustion engine exhaust gases and other heat sources that would otherwise be lost. For example, and not by limitation, the waste heat recovery system can be designed to recover heat from the EGR (exhaust gas recirculation) system or the engine coolant system, which reduces the cooling load on the engine cooling system. In addition, a waste heat recovery system can extract useful energy from the exhaust gas exiting the tail pipe or exhaust stack, which would otherwise be lost to the environment.

Typically, a waste heat recovery boiler is connected to receive heated fluid from the internal combustion engine (for example, exhaust gas) and transfer the heat to a working fluid (for example, ethanol) without mixing the fluids. A typical boiler structure includes separate flow paths for the fluids that are sealed to prevent leaking of fluids from one flow path to the other.

A failure in the boiler structure, for example a seal failure, may result in a leak of working fluid into the exhaust gas stream. Leaking working fluid can result in damage to the boiler. If the boiler is connected to the EGR (exhaust gas recirculation) system, leaking working fluid can be carried into the engine, which may result in damage to the engine or runaway combustion (if the working fluid is combustible). It is important to contain leaks to prevent damage to the engine. It is known in the art to provide leakage passageways in boilers so that internal leaks, as for example from a brazing failure in a plate heat exchanger, do not result in mixing of the fluids. Various structures exist for conducting fluid from a leak site to exit the boiler to the outside of the boiler where the leaking fluid may be seen. For example, FR 2 454 075 discloses a double walled plate heat exchanger with a leak passageway defined between parallel plates. US 4,976,313 to Dahlgren et al discloses a plate heat exchanger with partially sealed ports carrying fluid between plates. US 5,913,361 to Engstrom et al discloses a plate heat exchanger that includes an annular leak passage surrounding the ports connecting inter-plate spaces with a weep hole communicating from the leak passage to the environment. US Patent Application Publication No. 2012/267084 by Crawford discloses a plate heat exchanger with a weep hole that channels leaking fluid from leak spaces built in the plates to a location outside the exchanger.

It is important to detect leaks as soon as possible to allow protective measures to be taken, for example, closing a working fluid inlet valve to the boiler, bypassing the exhaust around the boiler, or other measures to prevent the mixing of working fluid and the heat source fluid.

Current technology to detect leak failures includes sensing pressure loss in the working fluid and monitoring the engine for runaway combustion. Detecting leaks visually, as done currently, depends on the heat exchanger and weep hole being visibly accessible to an operator and on the operator performing regular inspections. For waste heat recovery apparatuses associated with internal combustion engines on vehicles such as trucks, visually detecting a leaking boiler may be difficult.

The present invention provides a method and apparatus for improved containment and detection of boiler leak failures in a waste heat recovery apparatus. A waste heat recovery apparatus for an internal combustion engine may include a working fluid circuit on which are connected an expander for converting heat energy to mechanical or electrical energy, a condenser, a pump for moving the working fluid through the circuit, and a heat exchanger for transferring heat from the internal combustion engine exhaust to the working fluid. The heat exchanger is also known in the art as a boiler or vaporizer. In the following description the term "boiler" will be used.

The boiler may be coupled to an exhaust line, an exhaust gas recirculation line as an EGR cooler, on an engine coolant line, or to any other heat source of engine generated waste heat. The boiler is configured to transfer heat from the waste heat fluid to the working fluid of the waste heat recovery apparatus without mixing the fluids.

According to one embodiment of the present invention, a waste heat recovery system includes a boiler having a flow path for carrying leaking working fluid connected to a containment vessel to receive working fluid that escapes the boiler. The containment vessel may be a container connected to receive leaking fluid from the flow path. Alternatively, the containment vessel may be a shell or jacket that surrounds the boiler.

According to another aspect of the invention, a sensor is provided in the containment vessel to detect the presence of working fluid and provide a signal responsive thereto to a controller. The sensor may be a pressure sensor, a fluid detecting sensor, a temperature sensor, or some other suitable sensing device. The controller acts in response to the signal from the sensor to close a working fluid inlet to the boiler, close a heat source fluid inlet to the boiler, or take another measure to prevent damage to the waste heat recovery apparatus and/or the internal combustion engine. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a typical waste heat recovery apparatus;

FIG. 2 is a side sectioned view of a plate type boiler according to the invention;

FIG. 3 shows a detail of the boiler of FIG. 2;

FIG. 4 shows an embodiment of the invention in schematic view. DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts schematically a waste heat recovery system as may be used in conjunction with an internal combustion engine. The waste heat recovery system as shown includes a working fluid circuit 12, formed as a closed loop through which a working fluid is circulated. Connected on the working fluid circuit 12 are a boiler 10, an expander 14, a condenser 16 and a pump 18.

The boiler 10 is connected to a waste heat fluid flow 20 and is configured to transfer the waste heat from the waste heat fluid to the working fluid. The source of waste heat may be the engine exhaust flow or the exhaust gas recirculation flow, engine coolant, or another waste heat source.

The boiler 10 must provide for heat exchange contact between the waste heat fluid flow 20 and the working fluid without mixing of the fluids.

One type of boiler 100, illustrated by way of example in FIG. 2, well suited to this function comprises a stack of spaced, hollow plates 102 interconnected by a common inlet port tube 104 and a common outlet port tube 106 to allow working fluid to flow through the plates from an inlet port to an outlet port. The plates 102 are contained in a housing 1 10 having an inlet 1 12 and an outlet 114 for the waste heat fluid. The waste heat fluid flows through the spaces 120 between the hollow plates, which allows heat from the waste heat fluid to transfer to the cooler working fluid.

As illustrated in a simplified view in FIG. 3, which shows the inlet port side, for each of the plates 102, the connection between the inlet port 104 and the outlet port 106 on each plate 102 includes a primary seal 130 formed by a connection such as brazing the respective port to the plate. A secondary seal 132, also formed by a connection such as brazing, is formed spaced from the primary seal to contain working fluid in event the primary seal fails. The primary seal and secondary seal define a leak passagewayl40 to carry leaking working fluid out of the boiler. In heat exchangers of the current art, the leak passageway, sometimes called a vent, opens to the atmosphere. Also known in the art are boilers without a secondary connection defining a leak passageway (e.g., brazing 132), in which case a leak in the primary connection may allow working fluid to pass into the waste heat flow path 20.

According to the invention, shown schematically in FIG. 4, a boiler 30 includes a containment vessel 32 connected to the outlet or outlets of the leak passageway (not shown in FIG.4), which may be a weep hole or other aperture formed on the outer surface of the boiler and connected to the leak passageway, to receive working fluid that has escaped the boiler. The containment vessel 32 may be connected to leak passageway outlets in any convenient manner, for example, by threaded fittings. For boilers having a plurality of leak passageway outlets a manifold may be connected to collect working fluid exiting the leak passageway outlets and conducts it to the containment vessel. Alternatively, each leak passageway may be extended by a conduit to connect to the containment vessel. Other devices for connecting the leak passageway outlet or outlets to the containment vessel are also possible. According to another alternative, the containment vessel may be a jacket or shell that surrounds the boiler.

A sensor 40 is installed in the containment vessel 32 to detect the presence of working fluid in the containment vessel, and may be a pressure sensor, fluid sensor, a temperature sensor, or other device capable of detecting working fluid medium. The sensor 40 is connected to a controller 42 and is adapted to send a signal to the controller responsive to the presence of working fluid in the containment vessel 32. The controller is connected to control a valve 50 on the inlet port 104 of the boiler 30 controlling the flow of working fluid into the boiler and to a second valve 52 on the heat source fluid inlet 112 controlling the flow of heat source fluid (e.g., exhaust or recirculated exhaust gas in the EGR system) to the boiler.

The controller 42 is configured to implement a shut-down procedure in the event working fluid is detected in the containment vessel 32 which may include closing the valve 50 on the inlet port and the valve 52 on the heat source inlet 112, stopping the pump 18, or otherwise stopping the flow of working fluid. In the present application, the use of terms such as "including" is open-ended and is intended to have the same meaning as terms such as "comprising" and not preclude the presence of other structure, material, or acts. Similarly, though the use of terms such as "can" or "may" is intended to be open-ended and to reflect that structure, material, or acts are not necessary, the failure to use such terms is not intended to reflect that structure, material, or acts are essential. To the extent that structure, material, or acts are presently considered to be essential, they are identified as such.

While this invention has been illustrated and described in accordance with a preferred embodiment, it is recognized that variations and changes may be made therein without departing from the invention as set forth in the claims.