ENHANCED WASTE HEAT RECOVERY SYSTEM AND METHOD ALLOWING GLOBAL OPTIMAL CONTROL

Abstract

A waste heat recovery system and control system and method of controlling a waste heat recovery system and control system is provided. The waste heat recovery system and control system comprises a pump, a heat exchanger, an expansion device, a condenser, a plurality of sensors, and a controller. The heat exchanger is in thermal communication with an exhaust of the internal combustion engine. The condenser is in thermal communication with the expansion device and the pump. The plurality of sensors is in communication with the waste heat recovery system. The controller is in communication with the plurality of sensors. In response to information obtained from the plurality of sensors, the controller calculates an efficiency of the waste heat recovery system based on models of the waste heat recovery system and implements a set of control inputs to implement the calculated efficiency on the waste heat recovery system.

Description

CLAIM OF PRIORITY

The present application claims the benefit of priority to U.S. Provisional Application No. 61/968,513 filed on Mar. 21, 2014, which is incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

The present invention relates to energy recovery systems and more specifically to control of waste heat recovery systems used with internal combustion engines.

BACKGROUND OF THE INVENTION

A conventional internal combustion engine typically has a limited brake thermal efficiency (BTE). Energy released during a combustion process utilized by the internal combustion engine is only partially converted to useful work. A large portion of the energy released during the combustion process is rejected as waste heat to an ambient environment of the internal combustion engine. The waste heat is typically dispersed to the ambient environment of the internal combustion engine through the use of a cooling system and an exhaust system of the internal combustion engine. Efficiencies of the internal combustion alone (not accounting for any power transmission losses) typically do not exceed about 50%.

An amount of energy that is rejected as waste heat to the ambient environment is proportional to a fuel consumption of the internal combustion engine. Further, an amount of energy that is rejected as waste heat is inversely proportional to an efficiency of the internal combustion engine. With increasing fuel costs and emission regulations becoming more and more stringent, new technologies to improve an efficiency of internal combustion engines are highly sought after.

FIG. 1 schematically illustrates a waste heat recovery (WHR) system 110 for use with an internal combustion engine 112 that is known in the art. The WHR system 110 is in driving engagement and fluid communication with the internal combustion engine 112. A portion of the WHR system 110 is in driving engagement with a portion of the internal combustion engine 112 through a mechanical connection 114. The WHR system 110 may utilize the organic Rankine cycle; however, it is understood that other thermodynamic cycles may also be used with the WHR system 110. It is understood that the components of the WHR system 110, the components of the internal combustion engine 112, and a working fluid used with the WHR system 110 may be adapted for use with other thermodynamic cycles. The internal combustion engine 112 includes a turbocharger 115. Typically, the internal combustion engine 112 is used as a power source for a vehicle (not shown); however, it is understood that the internal combustion engine 112 may be used in other applications, such as in stationary power generation applications.

The WHR system 110 comprises a pump 116, a heat exchanger 118, an expander 120, a condenser 122, and a plurality of fluid conduits 124. The pump 116 is in fluid communication with the heat exchanger 118 and the condenser 122. The expander 120 is in fluid communication with the condenser 122 and the heat exchanger 118. The WHR system 110 is a closed circuit, thermodynamic device that employs a liquid-vapor phase change to convert heat energy into motive power. It is understood that the WHR system 110 may include additional components not illustrated in FIG. 1, such as, but not limited to, a working fluid reservoir, a plurality of valves, and a plurality of sensors in communication with a control system. The plurality of fluid conduits 124 facilitate fluid communication to occur between each of the components 116, 118, 120, 122 and may comprise a plurality of preformed rigid tubes, flexible conduits, or conduits formed within a portion of each of the components 116, 118, 120, 122.

The heat exchanger 118 facilitates thermal communication between an exhaust conduit 126 of the internal combustion engine 112 and a portion of a plurality of fluid conduits 124 facilitating fluid communication between the components. It is understood that the heat exchanger 118 may comprise a plurality of heat exchangers. The heat exchanger 118 is conventional and well known in the art, and may also be referred to as an evaporator. As the working fluid passes through a portion of the heat exchanger 118, the working fluid is heated and evaporated by energy imparted to the working fluid by the exhaust gases passing through the exhaust conduit 126. As a result of the thermal communication between a portion of the plurality of fluid conduits 124 and the exhaust conduit 126, the working fluid leaves the heat exchanger 118 in a gaseous state.

An efficiency of any WHR system, or the WHR system 110 described above, for example, strongly depends on the working conditions employed within the WHR system. The most notable conditions that affect efficiency are temperature and pressure. As most WHR systems are stationary, a source of heat used with the WHR system is typically constant and many of the working conditions the WHR system is exposed to are fixed. In order to maximize an amount of energy recovered from the heat source in mobile applications, such as vehicular applications, the working conditions of the WHR system should constantly be adapted to the heat source, which will exhibit changes in temperature and flow rate.

A proper control strategy must therefore be developed. Each subsystem of the WHR system has its own dynamics and optimal working range and system states and most subsystems have one or more control variables that can be manipulated to drive the subsystem dynamically to a given state. Typically, each subsystem is controlled to obtain a good working condition for that particular subsystem (for example, the feed pump speed is adjusted to control evaporating temperature, and a rotational speed of the expanders is adjusted to change a pressure within the WHR system). However, all of these subsystems are coupled together either due to the working fluid or through mechanical connections. Consequently, most control inputs affect the overall system. A highest efficiency of the total system is thus only reached if all control inputs are correctly set. What such a task requires is global optimization of the system.

The standard practice to optimize WHR systems is to either control only the speed of the feed pump or to control the speed of the feed pump and the expander to adjust an evaporating temperature and a pressure within the WHR system. In instances where the second situation is possible, the expander is typically coupled to a generator, for example, in stationary applications. However, a plurality of set points used for the temperature and pressure are typically determined using trial-and-error methods and operator guesswork.

In a paper titled “Dynamic Modeling and Optimal Control Strategy of Waste Heat recovery Organic Rankine Cycles” by S. Quoilin, R. Aumann, A. Grill, A. Schuster, V. Lemort, H. Spliethoff, from Applied Energy 88 (2011) 2183-2190, the goal was to define a control strategy for a small scale organic Rankine cycles working with a heat source that varies in terms of temperature and mass flow. To that end, the working conditions of the cycle are optimized for a given static heat source. This results in a set point for evaporating temperature and overheating temperature, which in turn is translated to expander speed and pump flow rate setpoints for PI-controllers. This same method is also described in published patent application numbers WO2011137980 and US2011203278. The method is focused on an organic Rankine cycle for stationary applications where the expander is connected to a generator, which in turn is connected to an electrical grid through the use of an inverter.

In published patent application number US2011203278, an optimal efficiency of an organic Rankine cycle is searched by measuring the output power and thus calculating the efficiency while changing control inputs. During operation of the organic Rankine cycle, the optimal efficiency is tracked based on the learned or searched input values. As with the previously mentioned solutions, it is intended for steady-state operation only.

Furthermore, the problem is even more complex if the heat source and/or cooling of the WHR system can be controlled as well. If a total duty cycle for the application is known, or if the future operating conditions of the internal combustion engine can be anticipated, the efficiency over the entire duty cycle should be considered as well.

It would be advantageous to develop a waste heat recovery system for an internal combustion engine and controller that implements a control strategy that increases an efficiency of the internal combustion engine and constantly adapts a control strategy based on fluctuations of an ability to heat and cool the waste heat recovery system.

SUMMARY OF THE INVENTION

Presently provided by the invention, a waste heat recovery system for an internal combustion engine and controller that implements a control strategy that increases an efficiency of the internal combustion engine and constantly adapts a control strategy based on fluctuations of an ability to heat and cool the waste heat recovery system.

In one embodiment, the present invention is directed to a waste heat recovery system and control system and method of controlling a waste heat recovery system and control system. The waste heat recovery system and control system comprises a pump, a heat exchanger, an expansion device, a condenser, a plurality of sensors, and a controller. The heat exchanger is in fluid communication with the pump and thermal communication with an exhaust of the internal combustion engine. The expansion device is in fluid communication with the heat exchanger. The condenser is in thermal communication with the expansion device and the pump. The plurality of sensors is in communication with the waste heat recovery system. The controller is in communication with the plurality of sensors. In response to information obtained from the plurality of sensors, the controller calculates an efficiency of the waste heat recovery system based on models of the waste heat recovery system and implements a set of control inputs to implement the calculated efficiency on the waste heat recovery system.

In another embodiment, the present invention is directed to a method of controlling a waste heat recovery system and control system for use with an internal combustion engine. The method comprises the steps of providing the waste heat recovery system, providing the control system, obtaining information from the plurality of sensors, calculating an efficiency of the waste heat recovery system based on models of the waste heat recovery system using the controller, and implementing a set of control inputs to implement the calculated efficiency on the waste heat recovery system. The waste heat recovery system comprises a pump, a heat exchanger in fluid communication with the pump and thermal communication with an exhaust of the internal combustion engine, an expansion device in fluid communication with the heat exchanger, and a condenser in thermal communication with the expansion device and the pump. The control system comprises a plurality of sensors in communication with the waste heat recovery system and a controller in communication with the plurality of sensors.

Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

FIG. 1 is a schematic illustration of a combined internal combustion engine and waste heat recovery system according to the prior art; and

FIG. 2 is a schematic illustration of a combined internal combustion engine and waste heat recovery system including a controller according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise.

FIG. 2 schematically illustrates a waste heat recovery (WHR) system 200 for use with an internal combustion engine 202. The WHR system 200 and the combustion engine 202 are in communication with a control system 203. The WHR system 200 is in driving engagement and fluid communication with the internal combustion engine 202. A portion of the WHR system 200 is in driving engagement with a portion of the internal combustion engine 202 through a ratio adapting device 204. The WHR system 200 may utilize the organic Rankine cycle; however, it is understood that other thermodynamic cycles may also be used with the WHR system 200. It is understood that the components of the WHR system 200, the components of the internal combustion engine 202, and a working fluid used with the WHR system 200 may be adapted for use with other thermodynamic cycles. The internal combustion engine 202 includes a turbocharger 206. Typically, the internal combustion engine 202 is used as a power source for a vehicle (not shown); however, it is understood that the internal combustion engine 202 may be used in other applications, such as in stationary power generation applications.

The internal combustion engine 202 comprises a primary portion 208, the turbocharger 206, and an engine output 210. The primary portion 208 is in fluid communication with the turbocharger 206 through an intake 212 and an exhaust 214 of the primary portion 208. The primary portion 208 is in driving engagement with the engine output 210. The internal combustion engine 202 may be any type of internal combustion engine which may be fitted with a turbocharger.

The primary portion 208 comprises at least an engine block; however, it is understood that the primary portion 208 may also include components typically used with an internal combustion engine, such as a plurality of valves, a plurality of pistons, at least one crankshaft, a plurality of connecting rods, a clutching device, a ratio adapting device, a fuel delivery system, an ignition system, and a cooling system.

The turbocharger 206 includes a turbine portion 216, a compressor portion 218, and a shaft 220. The turbine portion 216 and the compressor portion 218 are drivingly engaged with the shaft 220. As is known in the art, the turbine portion 216 is driven by exhaust gases via the exhaust 214. The turbine portion 216 is drivingly engaged with the compressor portion 218 to provide compressed air to the intake 212.

The turbine portion 216 comprises a plurality of blades (not shown) attached to a rotor (not shown) which is rotatingly disposed in a housing (not shown). The rotor is fixed to the shaft 220. During operation of the internal combustion engine 202, energy present in the exhaust gases leaving the exhaust 214 of the primary portion 208 is imparted to the plurality of blades, and thus to the rotor and the shaft 220. After exiting the turbine portion 216, the exhaust gases continue within an exhaust conduit 222 in fluid communication with the turbine portion 216.

The compressor portion 218 comprises an impeller (not shown) which is rotatingly disposed in a housing (not shown). The impeller is fixed to the shaft 220. During operation of the internal combustion engine 202, energy is imparted to air in the housing through rotation of the impeller, which is driven by the shaft 220, thus increasing a pressure of air at the intake 212 of the primary portion 208.

The engine output 210 is a mechanical component driven by the primary portion 208. The engine output 210 may be a vehicle driveline or a portion of a vehicle driveline, such as a driveshaft, a transmission, or a flywheel. Alternately, it is understood that the engine output 210 may merely facilitate driving engagement between the primary portion 208 and a portion of an electric generator, for example.

The WHR system 200 comprises a pump 224, a heat exchanger 226, an expander 228, a condenser 230, an expander bypass 232, a plurality of fluid conduits 234, and a heat exchanger bypass 235. The pump 224 is in fluid communication with the heat exchanger 226 and the condenser 230. The expander 228 is in fluid communication with the condenser 230 and the heat exchanger 226. The expander bypass 232 allows the expander 228 to be selectively removed from the WHR system 200. The WHR system 200 is a closed circuit, thermodynamic device that employs a liquid-vapor phase change to convert heat energy into motive power. It is understood that the WHR system 200 may include additional components not illustrated in FIG. 2, such as, but not limited to, a working fluid reservoir, a plurality of valves, and additional sensors in communication with the control system 203. The plurality of fluid conduits 234 facilitate fluid communication to occur between each of the components 224, 226, 228, 230, 232, 234 and may comprise a plurality of preformed rigid tubes, flexible conduits, or conduits formed within a portion of each of the components 224, 226, 228, 230, 232, 234.

The pump 224 transfers the working fluid used with the WHR system 200 from the condenser 230 to the heat exchanger 226 through a portion of the plurality of fluid conduits 234. The pump 224 is conventional and well known in the art. The pump 224 may be an electrically operated pump designed to transfer the working fluid in a liquid state. Alternately, it is understood that the pump 224 may be mechanically driven by a rotating component of the primary portion 208, the turbocharger 206, or the expander 228.

The heat exchanger 226 facilitates thermal communication between the exhaust conduit 222 and a portion of the plurality of fluid conduits 234. It is understood that the heat exchanger 226 may comprise a plurality of heat exchangers. The heat exchanger 226 is conventional and well known in the art, and may also be referred to as an evaporator. The heat exchanger 226 includes a heat exchanger bypass 235. As the working fluid passes through a portion of the heat exchanger 226, the working fluid is heated and evaporated by energy imparted to the working fluid by the exhaust gases passing through the exhaust conduit 222. As a result of the thermal communication between a portion of the plurality of fluid conduits 234 and the exhaust conduit 222, the working fluid leaves the heat exchanger 226 in a gaseous state.

The heat exchanger bypass 235 facilitates bypassing the exhaust conduit 22 around the heat exchanger 226. The heat exchanger bypass 235 comprises an exhaust bypass valve 236 and an exhaust bypass conduit 237. The exhaust bypass valve 236 is in communication with the control system 203. In response to a signal received from the control system 203, the exhaust bypass valve 236 is placed in an engaged position. In the engaged position, the exhaust bypass valve 236 removes the heat exchanger 226 from fluid communication with the exhaust conduit 222. It is understood that the exhaust bypass valve 236 may be configured to only direct a portion of the exhaust passing through the heat exchanger 226 through the exhaust bypass conduit 237, and that in response to a signal received from the control system 203, the exhaust bypass valve 236 may be variably engaged.

The expander 228 extracts work from the working fluid in the gaseous state. The expander 228 is conventional and well known in the art, and may also be referred to as a turbine. The expander 228 comprises a plurality of blades (not shown) attached to a rotor (not shown) which is rotatingly disposed in a housing (not shown). The rotor is fixed to a shaft 238, which is in driving engagement with the ratio adapting device 204. The ratio adapting device 204 is drivingly engaged with the engine output 210 to deliver additional work thereto.

The expander bypass 232 facilitates fluid communication of the working fluid between a portion of the plurality of fluid conduits 234 between the heat exchanger 226 and the expander 228 and a portion of the plurality of fluid conduits 234 between the condenser 230 and the expander 228. The expander bypass 232 comprises a bypass valve 239 and a bypass conduit 240. The bypass valve 239 is in communication with the control system 203. In response to a signal received from the control system 203, the bypass valve 239 is placed in an engaged position. In the engaged position, the bypass valve 239 places the heat exchanger 226 in fluid communication with the condenser 230. It is understood that the bypass valve 239 may be configured to only direct a portion of the working fluid passing through the heat exchanger 226 through the bypass conduit 240, and that in response to a signal received from the control system 203, the bypass valve 239 may be variably engaged.

During normal operation of the WHR system 200, the working fluid leaving the heat exchanger 226 is expanded in the expander 228, imparting work to the plurality of blades, and thus to the rotor and the shaft 238. During expansion of the working fluid, the working fluid drives the expander 228 and the pressure and temperature of the working fluid are reduced. After exiting the expander 228, the working fluid continues within a portion of the plurality of fluid conduits 234 to the condenser 230.

The condenser 230 facilitates thermal communication between the working fluid in the gaseous state and an ambient environment of the WHR system 200. The condenser 230 is a heat exchanging device and is conventional and well known in the art. The condenser 230 may be a liquid to air type heat exchanger or a liquid to liquid type heat exchanger. As the working fluid passes through a portion of the condenser 230, the working fluid is cooled as the energy within the working fluid is distributed by the condenser 230 to the ambient environment of the WHR system 200. The condenser 230 provides further cooling for the working fluid, in addition to the temperature drop that occurs as the working fluid passes through the expander 228. As a result of the thermal communication between the working fluid and the condenser 230, the working fluid condenses and leaves the condenser 230 in a liquid state. After passing through the condenser 230, the working fluid (now in a fully liquid state) flows to the working fluid reservoir (not shown) and is then pumped to an increased pressure by the pump 224 so that the cycle may be repeated.

The ratio adapting device 204 is a continuously variable transmission that is drivingly engaged with the shaft 238 and the engine output 210. Further, it is understood that the ratio adapting device 204 may be drivingly engaged with a portion of the expander 228 or a portion of the turbocharger 206. The ratio adapting device 204 facilitates driving engagement between the shaft 238 and the engine output 210, despite a difference and a variability of a rotational speed of each of the shaft 238 and the engine output 210. The ratio adapting device 204 may include a clutching device (not shown) for drivingly disengaging the expander 228 from the engine output 210. As a non-limiting example, the ratio adapting device 204 may be a pulley-belt style continuously variable transmission. The pulley-belt style continuously variable transmission comprises of a pair of variable-diameter pulleys, each shaped like a pair of opposing cones, with a belt running between them. The pulley-belt style continuously variable transmission is conventional and well known in the art. Alternately, the ratio adapting device 204 may comprise another type of ratio adapting device, such as a belted connection, a fixed ratio transmission; or a fixed ratio transmission paired with a slipping clutch, for example.

The control system 203 is in communication with the WHR system 200 and the internal combustion engine 202. The control system 203 comprises a plurality of sensors 242 and actuators 244 in communication with a controller 246. The plurality of sensors 242 and actuators 244 are incorporated into the WHR system 200 and the internal combustion engine 202 to facilitate enhanced control over the WHR system 200 using the controller 246.

The control system 203 may incorporate the following sensors 242:

• • A temperature sensor 242 located in the exhaust conduit 222
  • A mass flow sensor 242 located in the exhaust conduit 222
  • A temperature sensor 242 configured to measure a temperature of an ambient environment of the WHR system 200
  • A pressure sensor 242 configured to measure an air pressure of an ambient environment of the WHR system 200
  • A sensor 242 configured to measure a rotational speed of the expander 228 or a pressure at an inlet or an outlet of the expander 228
  • A sensor 242 configured to measure a rotational speed of the pump 224
  • A sensor 242 configured to measure a speed ratio of the ratio adapting device 204
  • A sensor 242 configured to measure a state of operation of the internal combustion engine 202 through an engine control unit 246
  • A sensor 242 configured to measure a state of operation of a portion of a driveline associated with the internal combustion engine 202 through a gearbox controller 248

The control system 203 may incorporate the following actuators 244:

• • An actuator 244 engaged with the bypass valve 239 to adjust a position thereof
  • An actuator 244 engaged with the exhaust bypass valve 236 to adjust a position thereof
  • An actuator 244 configured to actuate a cooling fan 250 to facilitate dissipation of heat using the condenser 230

The controller 246 is a programmable logic controller and/or a computer based system including computer-readable media containing at least one programmatic algorithm to facilitate enhanced control over the WHR system 200 using a plurality of steps, which are described hereinbelow. It is understood that the following steps may be performed in any order, and may be rearranged by the controller 246 as needed.

First, the controller 246, using the plurality of sensors, measures the various states of operation of the WHR system 200. The various states of operation of the WHR system 200 that may be measured by the sensors 242 are described above. In addition to the use of the sensor 242 for mass flow in the exhaust conduit 222, it is understood that the mass flow can also be estimated based on a throttle position and a rotational speed of the internal combustion engine 202.

Next, based on models of the WHR system 200, an efficiency is calculated by the controller 246 for the possible control inputs, based on information collected from the sensors 242. The models may be such as static or dynamic models where the modeling effort is focused on the parts of the WHR system 200 with the slowest dynamics. Non-limiting examples of static models may include, but are not limited to, look up tables or formulae, both of which may provide some parameters on the actual conditions. Non-limiting examples of dynamic models may include, but are not limited to, models that take into account a history of the WHR system 200. For example, a dynamic model might take into account past performance of the WHR system 200 before and/or after a particular modeled event to determine the most efficient way to proceed in the current circumstance. The heat exchanger 226 is one of the parts of the WHR system 200 that is more likely to have slow dynamics. Rotating elements of the WHR system 200, such as the expander 228, may also have slow dynamics because of their rotational inertia. Thus, the models may be focused on the heat exchanger 226 and/or the rotating elements because of their slow dynamics compared to other components of the WHR system 200. The possible control inputs of the models may be discrete control inputs of the WHR system 200, such as enabling the expander bypass 232 or enabling the cooling fan 250, as well as continuous control inputs, such as a rotational speed of the pump 224 or a ratio of the ratio adapting device 204.

Next, a maximum efficiency of the WHR system 200 is searched and applied by the controller 246. In the preceding step, the maximum efficiency of the WHR system 200 was determined using the aforementioned models. Once the maximum efficiency is determined by the models, the efficiency of the WHR system 200 is set, and the control inputs are known. The controller 246 then implements the control inputs.

Next, in addition to the objective of maximizing the energy recovered using the WHR system 200, several other goals have to be met as well. In particular, constraints on the states of the WHR system 200 need to be maintained. These constraints include, but are not limited to, a minimal rotational speed and a maximal rotational speed of the pump 224 and the expander 228, a minimal pressure and a maximal pressure of the components of the WHR system 200, temperature limits of the components of the WHR system 200, and a presence of positive superheating, which must always be maintained by the controller 246 to avoid damage to the expander 228. It can be appreciated that controlled superheating ensures condensation of the working fluid does not occur in the expander 228, or damage of the expander 228 may result.

Lastly, in addition to the optimization of the control inputs to obtain the maximum efficiency instantaneously and/or in the near future, the controller 246 can use the dynamic models of the WHR system 200, or parts of the WHR system 200, and knowledge about the duty cycle of the WHR system 200 to predict a future state of the WHR system 200 and to optimize the efficiency, or power take-off, over a longer period of time.

The calculations performed by the controller 246 to obtain the maximum efficiency can also be executed offline or by another computer system than the controller 246 of the WHR system 200. The results of the optimization can be stored in tables or functions that subsequently are stored on a computer-readable medium and be used by the controller 246 of the WHR system 200.

The controller 246 can also be equipped with additional connections and communication methods to other controllers including, but not limited to, global positioning system information, radio based information, among others when the controller 246 is configured for mobile applications. The data obtained from these devices can be used by the controller 246 to optimize the efficiency of the WHR system 200, as described above. Furthermore, the controller 246 can issue commands to other controllers, such as the engine control unit 246 or the gearbox controller 248, to regulate their respective controlled systems. As a non-limiting example, commands may be issued by the controller 246 to the engine control unit 246 regarding exhaust gas recirculation. Such communication forms an integral part of the WHR system 200 and it is understood that additional subsystems can be instructed by the controller 246 in an effort at optimizing global control of the WHR system 200 and the internal combustion engine 202.

The control system 203 and WHR system 200 for use with an internal combustion engine 202 have many advantages over control strategies used with WHR systems known in the art.

Currently, control strategies used with WHR systems known in the art control only utilize control of a speed of a feed pump or control of the speed of a feed pump and an expander to set an evaporating temperature and a pressure of the WHR system. A plurality of set points used for the temperature and pressure used with these control strategies are typically determined using trial-and-error methods and operator guesswork. In the known art described above, only the optimal set points for temperature and pressure are presented. Consequently, the WHR system in total is not optimized, but rather just the above-mentioned set points.

The known art also suffers from other disadvantages compared to the control system 203 and WHR system 200 for use with an internal combustion engine 202 and control strategy described hereinabove. The known art suffers from the following disadvantages:

• • Not all the basic input variables are used in the known art. For example, in the known art, either only the evaporating temperature or the overheating temperature is used as variables in the optimization of the WHR system. The control system 203, the WHR system 200, and the control strategy contemplates optimizing the WHR system 200 in its entirety, not just two basic input variables for the WHR system 200.
  • No attention is given to possible auxiliary control inputs in the known art. Whereas in the control system 203, the WHR system 200, and the control strategy, attention is given at least to the exhaust bypass valve 236 for the exhaust and/or the bypass valve 239 for the working fluid to provide possible auxiliary control inputs.
  • The known art does not take into account constraints of WHR systems to facilitate optimization as currently known. These constraints such as a pressure and a temperature of the working fluid and the minimum and maximum speed of components such as the pump 224 and the expander 228 are taken into account during the optimization process of the control system 203 and the control strategy described hereinabove.
  • The known art systems typically utilize a search method in an effort to optimize the WHR system. The search method may be generally described as making a change to a control strategy and then measuring a resulting output of the WHR system. The known art systems thus seek a desired optimization based on changes made to an input. In the control system 203 and the control strategy described hereinabove, the various possible conditions are simulated in real time to determine the control inputs most likely to result in optimization based on predictive behavior. In other words, the control inputs are not changed until the optimized control inputs have been calculated using the models described hereinabove.
  • The known art does not take into account a future efficiency of the WHR system, any future operating conditions for the WHR system, a duty cycle of the WHR system, or dynamics of the WHR system. In the control system 203 and the control strategy described hereinabove, each of these items are taken into account.

The control system 203, the WHR system 200, and the control strategy is able to perform a globalized optimal control of the WHR system 200 by using all possible control inputs in the optimization, while also taking the interactions of the subsystems into account. This means that instead of locally optimizing the subsystems, the overall efficiency of the WHR system 200 is maximized while considering the constraints of the subsystems. Moreover, the dynamics of the WHR system are explicitly used to optimize the efficiency and future efficiency is optimized by using the dynamics of the WHR system and knowledge about the duty cycle and expected operating conditions.

In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.

Claims

1. A waste heat recovery system and control system for use with an internal combustion engine, the waste heat recovery system and control system comprising:

a pump;

a heat exchanger in fluid communication with the pump and thermal communication with an exhaust of the internal combustion engine;

an expansion device in fluid communication with the heat exchanger;

a condenser in thermal communication with the expansion device and the pump;

a plurality of sensors in communication with the waste heat recovery system; and

a controller in communication with the plurality of sensors, wherein in response to information obtained from the plurality of sensors, the controller calculates an efficiency of the waste heat recovery system based on models of the waste heat recovery system and implements a set of control inputs to implement the calculated efficiency on the waste heat recovery system.

2. The waste heat recovery system and control system according to claim 1, further comprising an expander bypass and bypass valve, the bypass valve in communication with the controller.

3. The waste heat recovery system and control system according to claim 1, further comprising a heat exchanger bypass and exhaust bypass valve, the exhaust bypass valve in communication with the controller.

4. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a temperature sensor and a mass flow sensor in the exhaust of the internal combustion engine.

5. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a temperature sensor and a pressure sensor configured to measure an air pressure of an ambient environment of the waste heat recovery system.

6. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a sensor configured to measure a pressure at an inlet or an outlet of the expander.

7. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a sensor configured to measure a pressure at an inlet or an outlet of the expander.

8. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a sensor configured to measure at least one of a rotational speed of the expander and a rotational speed of the pump.

9. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a sensor configured to measure a state of operation of the internal combustion engine through an engine control unit.

10. The waste heat recovery system and control system according to claim 1, wherein the plurality of sensors include a sensor configured to measure a state of operation of a portion of a driveline associated with the internal combustion engine through a gearbox controller.

11. A method of controlling a waste heat recovery system and control system for use with an internal combustion engine, the method comprising the steps of:

providing the waste heat recovery system comprising: a pump; a heat exchanger in fluid communication with the pump and thermal communication with an exhaust of the internal combustion engine; an expansion device in fluid communication with the heat exchanger; and a condenser in thermal communication with the expansion device and the pump;

providing the control system comprising: a plurality of sensors in communication with the waste heat recovery system; and a controller in communication with the plurality of sensors;

obtaining information from the plurality of sensors;

calculating an efficiency of the waste heat recovery system based on models of the waste heat recovery system using the controller; and

implementing a set of control inputs to implement the calculated efficiency on the waste heat recovery system.

12. The method of controlling a waste heat recovery system and control system according to claim 11, wherein the step of calculating an efficiency of the waste heat recovery system is performed using static or dynamic models.

13. The method of controlling a waste heat recovery system and control system according to claim 12, wherein the models used in calculating the efficiency of the waste heat recovery system are focused on components of the waste heat recovery system that have slow dynamics.

14. The method of controlling a waste heat recovery system and control system according to claim 12, wherein when the step of calculating an efficiency of the waste heat recovery system is performed using a dynamic model, the controller takes into account a past performance of the waste heat recovery system before and/or after a particular modeled event to determine a most efficient way to proceed.

15. The method of controlling a waste heat recovery system and control system according to claim 11, further comprising the step of maintaining constraints on the states of the waste heat recovery system.

16. The method of controlling a waste heat recovery system and control system according to claim 15, wherein the constraints include at least maintaining a minimal rotational speed and a maximal rotational speed of the pump and the expander, maintaining a minimal pressure and a maximal pressure within the waste heat recovery system, maintaining temperature limits within the waste heat recovery system, and maintaining a presence of positive superheating within the expander.

17. The method of controlling a waste heat recovery system and control system according to claim 11, further comprising the step of using the dynamic models of the waste heat recovery system to predict a future state of the waste heat recovery system.