Patent Application
20180202311
The invention relates to a method for controlling a waste heat utilization system for a motor vehicle driven by an internal combustion engine via a drive train, wherein the waste heat utilization system comprises at least one expander, at least one evaporator and at least one pump for an operating medium, in particular ethanol, and wherein at least the evaporator is disposed in the region of the exhaust gas system of the internal combustion engine, wherein the expander which can be operated in several operating modes delivers work in at least one operating mode and wherein on the basis of at least one input quantity from the group expander speed, gear information, coasting information, pressure and temperature of the operating medium upstream of the expander and/or pressure and temperature downstream of the expander, respectively one operating mode is selected from at least two operating modes of the expander by the control device, and the expander is operated in this operating mode, preferably by triggering at least one bypass valve of the expander disposed in a bypass flow path of the expander.
The invention further relates to a waste heat utilization system for a vehicle driven by an internal combustion engine via a drive train, comprising a control device for controlling the waste heat utilization system, wherein the waste heat utilization system comprises at least one expander which can transmit a torque to the internal combustion engine and which can be bypassed via a bypass flow path, at least one evaporator and at least one pump for an operating means, in particular ethanol, and wherein at least the evaporator is disposed in the region of the exhaust gas system of the internal combustion engine.
It is known to utilize waste heat of internal combustion engines. Such devices known as WHR (waste heat recovery) systems convert the waste heat of the exhaust gas of the internal combustion engine into for example mechanical or electrical energy. Such WHR systems are known, for example, from the publications U.S. Pat. No. 8,635,871 A1, US 2011/0209473 A1 or US 2013/0186087 A1.
US 2009/0071156 A1 discloses a waste heat recovery device with a Rankine cycle which comprises a compressor, a heat exchanger, an expander and a condenser. The expander is drive-connected to an electrical machine and can deliver work to this. The expander can be bypassed via a bypass valve and a bypass flow path, whereby the rotational speed of the expander can be regulated depending on the degree of overheating of the working medium. It is not known from US 2009/071156 A1 that a first operating mode is assigned to a warm-up phase of the expander and a second operating mode is assigned to a normal operating phase of the expander, wherein in the first operating mode the bypass valve is opened and in the second operating mode the bypass valve is closed. Furthermore it is not known from this publication that the second operating mode is selected when the pressure and/or the temperature of the operating medium downstream of the expander exceeds a defined value.
It is the object of the invention to provide an economical, safe and reliable operation of the waste heat utilization system.
According to the invention, this is achieved whereby a first operating mode is assigned to a warm-up phase of the expander and a second operating mode is assigned to a normal operating phase of the expander, and wherein in the first operating mode the bypass flow path is opened and wherein in the second operating mode the bypass flow path is closed, and wherein the second operating mode is selected when the pressure and/or the temperature of the operating means exceeds a defined value downstream of the expander.
In the first operating mode the bypass valve is opened, the starting device is deactivated, The operating medium is thus guided past the expander, with the result that the expander does not generate any torque. In the second operating mode, the bypass valve is closed, the starting device is also deactivated. When the bypass valve is closed, the operating medium flows through the expander with the result that this performs work.
It can further be provided within the framework of the invention that the waste heat utilization system is operated in a fourth operating mode during at least one coasting mode of the vehicle, during at least one warm-up mode of the internal combustion engine and/or at least one engine braking mode of the internal combustion engine. Preferably in the fourth operating mode the bypass flow path is closed in order to deliver torque from the expander to the drive train of the vehicle when the expander is connected to the drive train, whereby the coasting phase of the vehicle can be extended and fuel can be saved. If the expander is connected to an electrical machine, in the fourth operating mode electrical energy can be generated and can be supplied to the electrical system of the vehicle or stored.
Coasting mode is understood as a torque-free mode of the vehicle in which the disengageable clutch between internal combustion engine and transmission is opened to reduce the resistance in the drive train.
Whether a coasting mode of the vehicle is present or not is notified to the control device by the transmission or the disengageable clutch by means of coasting information.
In the first operating mode and/or when the heat utilization system is inactive, the expander is bypassed—with the bypass valve open—via the bypass flow path.
In order to achieve a high efficiency, it is provided within the framework of the invention that the bypass flow path of the expander is only closed when the operating medium of the waste heat utilization system is in an overheated state. When the operating medium of the waste heat utilization system upstream of the expander is in a non-overheated state or when the internal combustion engine is stopped, the bypass flow path is opened.
The invention is described in detail hereinafter with reference to the non-restrictive figures. In the figures schematically:
In the embodiments shown components having the same function are provided with the same reference numbers.
The internal combustion engine 10 further has a waste heat utilization system 20 for utilizing the exhaust gas values of the exhaust gas system 11 of the internal combustion engine 10. The waste heat utilization system 20 has an evaporator 21 which—in relation to the exhaust gas flow in the exhaust gas system 11—is arranged downstream of the exhaust gas after-treatment device 12 in the region of the exhaust gas system 11. The waste heat utilization system 20 which functions for example according to the organic Rankine cycle (ORC) comprises, downstream of the evaporator 21 in the operating medium circuit, an expander 22 and a condenser 23, as well as a pump 24 for the operating medium. For example, ethanol can be used as operating medium. In order to bypass the expander 22, a bypass line 25 with a bypass valve 26 is provided. The evaporator 21 can be bypassed on the exhaust gas side via a bypass line 36 and a bypass valve 37 if the exhaust gas heat is too high for the evaporator 21 or the system pressure exceeds a defined value or the cooling system is excessively loaded or the waste heat utilization system 20 is in an error mode or in pure engine mode, without engine braking, The bypass valve 37 is triggered depending on at least one of the operating parameters from the group fan power, system pressure, system temperature and mass flow of the operating medium.
A control device 30 is provided for controlling the waste heat utilization system 20, which has a program logic 31 which is configured to select the most suitable operating mode from the plurality of operating modes 1, 2 or 1, 2, 4, 5 for operation of the waste heat utilization system 20. The selection of the most suitable operating mode is made on the basis of at least one of the input variables of the control device 30, namely: expander rotational speed n, gear information GI, coasting information CI, pressure p1 temperature T1 of the operating medium upstream of the expander 22 as well as the pressure p2 and the temperature T2 of the operating medium downstream of the expander 22. Pressure sensors 32, 33 and temperature sensors 34, 35 are provided upstream and downstream of the expander 22 in the operating medium circuit of the waste heat utilization system 20 to record the parameters pressures p1, p2 and temperatures T1, T2. The pressure sensors 32, 33 and temperature sensors 34, 35 are connected to the control device 30. The gear information GI and coasting information CI are provided, for example by suitable sensors in the transmission 16 of the control device 30.
In the simple first embodiment shown in
The operating modes of this first embodiment are shown in
First operating mode 1 is executed during the warm-up phase of the expander 22; in the operating mode 1 the bypass valve 26 is opened so that the operating medium is guided past the expander 22.
Second operating mode 2: this operating mode 2 is assigned to the normal operation of the expander 22. As soon as the pressure p2 and/or the temperature T2 of the operating medium downstream of the expander 22 exceed a defined value or defined values, the operating mode 2 is activated.
Optionally a fourth operating mode can also be driven during coasting operation of the vehicle, wherein electrical energy can be generated by the electrical machine and supplied to the on-board network.
The second embodiment shown in
The operating modes of this first embodiment are shown in
First operating mode 1 is executed during the warm-up phase of the expander 22; in the operating mode 1 the bypass valve 26 is opened so that the operating medium is guided past the expander 22.
Second operating mode 2: this operating mode 2 is assigned to the normal operation of the expander 22. As soon as the pressure p2 and/or the temperature T2 of the operating medium downstream of the expander 22 exceed a defined value or defined values, the operating mode 2 is activated.
Fourth operating mode 4: this operating mode 4 is used during the coasting mode, the warm-up mode and/or the engine braking mode of the internal combustion engine 10. In the coasting mode the vehicle travels without transmission of torque between internal combustion engine 10 and drive wheels 18, generally with the disengageable clutch 15 open. The bypass valve 26 is closed in the operating mode 4 in order to transmit torque from the expander 22 to the internal combustion engine 10. As a result—in particular when the disengageable clutch 15 is open—the fuel consumption during idling is reduced and/or the coasting phase of the vehicle is lengthened. If the expander 22 is connected to an electrical machine 40, electrical energy can be generated in the fourth operating mode and supplied to the electrical system of the vehicle or stored.
Fifth operating mode 5: this operating mode 5 is used for starting the expander 22 via an internal or external starting device 27.
Alternatively to this, starting can also take place via a self-starting mechanism of the expander 22 (without the fifth operating mode 5).
In order to avoid the expander 22 being operated at excessive rotational speed and thereby being damaged, the control device 30 provides special safety measures. Thus, the bypass valve 26 is only closed when the operating medium is in an overheated state, i.e. for example when the operating medium ethanol is in the gas phase.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 50609/2015 | Jul 2015 | AT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AT2016/050248 | 7/11/2016 | WO | 00 |
