Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
  • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
  • F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
  • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
  • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
  • F01K23/065—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle the combustion taking place in an internal combustion piston engine, e.g. a diesel engine
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N5/00—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy
  • F01N5/02—Exhaust or silencing apparatus combined or associated with devices profiting by exhaust energy the devices using heat
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the present invention relates to a method for operating an exhaust gas heat recovery cycle in a motor vehicle, having the features of the preamble of claim 1. Furthermore, the invention relates to an exhaust heat utilization device, a motor vehicle. Furthermore, the invention relates to a fluid for use as working fluid in an exhaust heat utilization device.
• water is vaporized as the working fluid of the Rankine cycle system, by the waste heat of the exhaust gas in an evaporator through which the exhaust gas flows.
• the temperature of the steam exiting the evaporator is measured and regulated by means of this steam temperature, the evaporator supplied amount of water.
• a Rankine circuit system Described in a Rankine circuit system according to DE 20 2007 002 602 U1, with an organic compound as the working fluid, such.
• the organic working fluid As methylcyclohexane or octane or heptane, the organic working fluid is vaporized by the exhaust heat.
• a safety temperature limiter is arranged on the exhaust side of the evaporator after the flow through it with exhaust gas, which spends the system by means of switching signal in a safe state when a temperature threshold is exceeded.
• other safety equipment such.
• B account for a flow monitoring in the working fluid circuit of the Rankine circle system. A low temperature indicates a flooded and flowed evaporator.
• a temperature control device for an evaporator is described in EP 1 431 523 A1, wherein the evaporator can be part of a Rankine circuit system with which an exhaust heat of an internal combustion engine in a motor vehicle can be used.
• water is evaporated as working fluid in the heat exchanger of the Rankine circular system by the waste heat of the exhaust gas.
• the steam temperature is adjusted by means of the temperature control device by regulating the amount of water fed into the evaporator, based on the flow rate of the exhaust gas, the temperature of the exhaust gas, the temperature of the water and the steam temperature.
• Rankine circuit systems can be operated with organic or non-organic media.
• Rankine circular systems that are operated with organic working fluid are also referred to as Organic RC or ORC.
• Rankine cycles operated with organic media are often referred to as Clausius-Rankine circular systems or CRCs.
• a disadvantage of Rankine circular systems with an organic working fluid is the limited to relatively low temperatures thermal stability of the organic working fluid.
• the present invention deals with the problem for an operating method or for an exhaust heat utilization device or for a working fluid to provide an improved or at least another embodiment, which is particularly characterized in that the thermal stability of the working fluid is better taken into account. In particular, a higher efficiency is sought.
• the invention is based on the general idea, when operating an exhaust heat utilization cycle in a motor vehicle, to control a working temperature of a working fluid of the exhaust heat recovery cycle by adjusting a mass flow of the working fluid flowing through the heat exchanger of the exhaust heat recovery cycle. It should be avoided by regulating the working temperature that the working fluid exceeds a maximum allowable working temperature. Especially in the case of using organic working fluids, the exhaust gas temperature can be well above the chemical decomposition temperature of the working fluid. Therefore, it is expedient to regulate the maximum permissible operating temperature of the working fluid only slightly below the chemical decomposition temperature. Preferably, the process temperature of the working fluid should fall below the decomposition temperature by the tolerance range of the temperature control quality. As a result, decomposition of the particular organic working fluid can be prevented or at least reduced or delayed.
• the decomposition temperature is preferably the lowest of the chemical decomposition temperatures of the components of the working fluid. This is also referred to below as the lowest chemical decomposition temperature of the working fluid.
• Exhaust gas heat recovery cycle processes that are equipped with, in particular, organic, working fluids and are operated so that the operating temperature is regulated by adjusting a mass flow of the working fluid flowing through a heat exchanger of the exhaust gas heat recovery cycle can be used in exhaust heat utilization devices of a motor vehicle.
• an organic fluid may be used in such exhaust heat utilization device of a motor vehicle having an exhaust heat utilization cycle.
• the fluid is vaporizable and condensable, an organic compound or a mixture of organic compounds and has at least methanol, ethanol, N-propanol, iso-propanol, dimethyl ether, ethyl methyl ether, diethyl ether or an alkane.
• At least one of the organic compounds or a compound mixture containing at least methanol when used in a waste heat utilization device, causes the waste heat utilization device to have a higher efficiency than with water as the working fluid.
• the exhaust heat utilization may utilize the heat of the exhaust gases in the exhaust system and / or the heat of the recirculated exhaust gas recirculation gases.
• Fig. 1 a via a heat exchanger with the exhaust stream of a
• FIG. 2 shows an efficiency behavior of different working fluids.
• an exhaust heat utilization device 1 for use in automobiles an exhaust heat utilization cycle 2 and an internal combustion engine 3, which are connected to each other via an exhaust gas supply line 4.
• the exhaust heat utilization cycle 2 which is formed in this embodiment as a Clausius-Rankine cycle, has a heat exchanger 5, a turbine 6 with a power converter 7, a capacitor 8 and a pump 9.
• a pressure P 1 and a temperature T 1 prevails between the condenser 8 and the pump 9, a pressure p 2 between the pump 9 and the heat exchanger 5 and a temperature T 2 , between the heat exchanger 5 and turbine 6, the pressure p 2 and a temperature T 3 and between the turbine 6 and condenser 8, the pressure P 1 and the temperature T 1 , wherein the pressure p 2 is greater than the pressure P 1 and the temperature T 3 is greater than the temperature T 2 and greater than the temperature T 1 .
• the exhaust heat utilization cycle 2 can also be operated according to other cycles, such. B. after the Carnot cycle, the Stirling cycle or the Joule cycle or the like. In this case, possibly other pressure and temperature conditions occur in the working fluid.
• the expanded working fluid is subsequently liquefied in the condenser 8 and pumped through the heat exchanger 5 for receiving waste heat 11 by means of the pump 9 at elevated pressure p 2 .
• the exhaust heat utilization cycle 2 can be operated by a method in which the working temperature of the working fluid is controlled by adjusting a mass flow of the working fluid flowing through the heat exchanger 5 so that a maximum allowable working temperature of the working fluid is not exceeded.
• organic working fluids such as methanol, diethyl ether, dimethyl ether or the like or organic compound mixtures
• the regulation of the working temperature T 1 , T 2 of the working fluid is essential for the proper functioning of the exhaust heat recovery cycle 2, since due to the hot exhaust gases, for example, the temperatures of 700 0 C can reach, a decomposition temperature of a working fluid of z. B. 350 0 C is far exceeded.
• the hot exhaust gas flowing through the heat exchanger 5 would at least partially decompose the organic working fluid also flowing through the heat exchanger 5 in opposite directions. Since this should be prevented, it is expedient to select the maximum permissible operating temperature of the working fluid so that it is, for example, at least 20 0 C less than the chemical decomposition temperature of the working fluid.
• the working temperature of the working fluid can be regulated by cooling it prior to entry into the heat exchanger 5.
• the operating temperature may be affected by limiting the waste heat fluid mass flow passing through the heat exchanger 5 and by admixing cold fluids to the waste heat fluid before entering the heat exchanger 5.
• Such measures are advantageous if in the circulation line 10, a maximum possible working fluid mass flow is reached and this can not be increased. If, in this case, a temperature increase continues after the heat exchanger 5 in the direction of the turbine 6, and there is the danger that the maximum permissible operating temperature of the working fluid is exceeded, the waste heat 11 which is present in the heat exchanger 5 can be removed by the above-described measures is supplied by the waste heat, limited and thus the working temperature of the working fluid can be controlled.
• the waste heat 11 transferred in the heat exchanger 5 are determined in particular in time dependence due to the detection signals and thus the working temperature are kept constant regardless of peak loads below the chemical decomposition temperature.
• a waste heat utilization device 1 in which the efficiency of the waste heat recovery device 1 is greater than using water as the working fluid.
• methanol should be mentioned here, as can be seen from FIG. According to FIG. 2, several efficiency curves of n-octane 13, n-heptane 14, toluene 15, n-hexane 16, cyclohexane 17, benzene 18 and ethanol 19 show a poorer efficiency behavior than the efficiency curve of water 20. In the examples given alone the efficiency curve of methanol 21 is superior to water 20 in terms of efficiency. Also suitable as working fluid are alkanes.
• a change in the mass flow of the working fluid changes the temperature T3 of the working fluid.
• Increasing the mass flow reduces the heat input per mass and lowers the working medium temperature T3.
• a reduction of the mass flow can increase the heat input per mass and thus the working medium temperature T3. In this way, a regulation of the operating temperature T3 by means of adaptation of the working fluid mass flow can be displayed.
• the decomposition temperature of such a working fluid can be taken into account by regulating the working temperature by adjusting the working fluid mass flow in such a way that the working temperature in each case remains below the decomposition temperature of the working fluid during operation of the exhaust heat utilization device.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Engine Equipment That Uses Special Cycles (AREA)
• Air-Conditioning For Vehicles (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2009
  • 2009-05-09 DE DE102009020615A patent/DE102009020615A1/de not_active Withdrawn
• 2010
  • 2010-03-24 CN CN201080020310XA patent/CN102422007A/zh active Pending
  • 2010-03-24 WO PCT/EP2010/001834 patent/WO2010130317A2/de active Application Filing
  • 2010-03-24 JP JP2012508921A patent/JP2012526224A/ja active Pending
  • 2010-03-24 EP EP10712331A patent/EP2411652A2/de not_active Withdrawn
• 2011
  • 2011-11-09 US US13/373,279 patent/US20120090321A1/en not_active Abandoned

Non-Patent Citations (1)

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