System and method for estimating refrigerant quality at the compressor inlet of an electric vehicle thermal system

Abstract

The present invention relates to a system having a compressor outlet temperature module, a refrigerant quality module, and a correction factor module. The compressor outlet temperature module is configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle. The refrigerant quality module is configured to estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the compressor inlet and an inlet enthalpy correction factor. The refrigerant quality is the ratio of the vapor refrigerant mass to the total refrigerant mass. The correction factor module is configured to determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet.

Description

Technical Field

[0001] The information provided in this section is for the purpose of generally presenting the context of the present disclosure. The work of the currently named inventors within the scope described in this section, as well as aspects that may not conform to the description of the prior art at the time of filing the application, are neither expressly nor impliedly admitted as prior art with respect to the present disclosure.

[0002] The present disclosure relates to a system and method for estimating the quality of refrigerant at the inlet of a compressor in a thermal system of an electric vehicle. Background Art

[0003] A thermal system for a vehicle can be used to heat or cool air circulating through the passenger compartment of the vehicle and can be used to heat or cool coolant circulating through the vehicle's propulsion system. A vehicle thermal system typically has a compressor, a condenser, an expansion valve, an evaporator, and a chiller. The compressor circulates refrigerant through the thermal system. The condenser transfers heat from the refrigerant to ambient air or cabin air. The expansion valve reduces the pressure of the refrigerant. The evaporator transfers heat from the cabin air to the refrigerant. The chiller transfers heat from the coolant to the refrigerant.

[0004] In a thermal system for an electric vehicle, the compressor is typically a scroll voltage compressor. A propulsion system for an electric vehicle typically has an electric motor and a battery pack, which cannot generate enough heat to maintain the cabin air at a target temperature. Therefore, in some cases, a thermal system for an electric vehicle has a coolant electric heater that supplements the heat transferred to the coolant by the propulsion system. Summary of the Invention

[0005] An example of a system according to the present disclosure has a compressor outlet temperature module, a refrigerant quality module, and a correction factor module. The compressor outlet temperature module is configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle. The refrigerant quality module is configured to estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the compressor inlet and an inlet enthalpy correction factor. Refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of refrigerant. The correction factor module is configured to determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet.

[0006] In one aspect, the correction factor module is configured to use a Kalman filter to determine the inlet enthalpy correction factor based on the estimated and measured compressor outlet temperatures.

[0007] In one aspect, the correction factor module is configured to determine the inlet enthalpy correction factor in the current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and measured compressor outlet temperatures.

[0008] In one aspect, the compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model of the work done by the compressor.

[0009] In one aspect, the compressor outlet temperature module is configured to estimate the compressor outlet temperature based on the compressor inlet enthalpy, the enthalpy at the compressor outlet, and the mass flow rate of the refrigerant flowing through the compressor.

[0010] In one aspect, the compressor outlet temperature module is configured to estimate the compressor outlet temperature in the current iteration based on the compressor inlet enthalpy and compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from that previous iteration.

[0011] In one aspect, the system further includes a compressor enthalpy module configured to determine the compressor inlet enthalpy in the current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the compressor inlet, and the pressure measured at the compressor inlet.

[0012] In one aspect, the compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the compressor outlet.

[0013] In one aspect, the system further includes a refrigerant density module, a refrigerant flow rate module, and a compressor power module. The refrigerant density module is configured to determine the refrigerant density at the compressor inlet based on the estimated refrigerant quality. The refrigerant flow rate module is configured to determine the mass flow rate of the refrigerant flowing through the compressor based on the refrigerant density. The compressor power module is configured to determine the power output of the compressor based on the refrigerant mass rate, the compressor inlet enthalpy, and the enthalpy at the compressor outlet.

[0014] In one aspect, the system further includes an actuator control module configured to control at least one of the compressor and the heat exchanger in the thermal system based on at least one of the refrigerant mass flow rate and the compressor power.

[0015] Another example of a system according to the present disclosure has a compressor outlet temperature module and a refrigerant quality module. The compressor outlet temperature module is configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle based on the enthalpy at the inlet of the compressor, the enthalpy at the outlet of the compressor, and the mass flow rate of the refrigerant flowing through the compressor. The refrigerant quality module is configured to determine the quality of the refrigerant at the inlet of the compressor based on the estimated compressor outlet temperature and the temperature measured at the outlet of the compressor. Refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of the refrigerant.

[0016] In one aspect, the compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model that correlates the compressor outlet temperature with the compressor inlet enthalpy, the compressor outlet enthalpy, and the refrigerant mass flow rate.

[0017] In one aspect, the compressor outlet temperature module is configured to estimate the compressor outlet temperature in a current iteration based on the compressor inlet enthalpy and the compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from the previous iteration.

[0018] In one aspect, the system further has a compressor enthalpy module that is configured to determine the compressor inlet enthalpy in a current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the inlet of the compressor, and the pressure measured at the inlet of the compressor.

[0019] In one aspect, the compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the outlet of the compressor.

[0020] In one aspect, the refrigerant quality module is configured to estimate the refrigerant quality based on the difference between the estimated and the measured compressor outlet temperature.

[0021] In one aspect, the refrigerant quality module is configured to estimate the refrigerant quality based on the compressor inlet enthalpy and an inlet enthalpy correction factor.

[0022] In one aspect, the system further has a correction factor module that is configured to determine an inlet enthalpy correction factor using a Kalman filter based on the estimated and the measured compressor outlet temperature.

[0023] In one aspect, the correction factor module is configured to determine the inlet enthalpy correction factor in a current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and the measured compressor outlet temperature.

[0024] The method according to the present disclosure includes: estimating the temperature at the outlet of a compressor in a thermal system of an electric vehicle, estimating the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the inlet of the compressor and an inlet enthalpy correction factor, and determining the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the outlet of the compressor. The refrigerant quality is the ratio of the mass of the vapor refrigerant to the total mass of the refrigerant.

[0025] Through the detailed description, claims, and drawings, other application areas of the present disclosure will become apparent. The detailed description and specific examples are for illustrative purposes only and are not used to limit the scope of the present disclosure.

[0026] Solution 1. A system, the system comprising:

[0027] A compressor outlet temperature module configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle;

[0028] A refrigerant quality module configured to estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the inlet of the compressor and an inlet enthalpy correction factor, wherein the refrigerant quality is the ratio of the mass of the vapor refrigerant to the total mass of the refrigerant; and

[0029] A correction factor module configured to determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the outlet of the compressor.

[0030] Solution 2. The system according to Solution 1, wherein the correction factor module uses a Kalman filter to determine the inlet enthalpy correction factor based on the estimated and measured compressor outlet temperatures.

[0031] Solution 3. The system according to Solution 2, wherein the correction factor module is configured to determine the inlet enthalpy correction factor in the current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and measured compressor outlet temperatures.

[0032] Solution 4. The system according to Solution 1, wherein the compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model of the work done by the compressor.

[0033] Solution 5. The system according to Solution 1, wherein the compressor outlet temperature module is configured to estimate the compressor outlet temperature based on the compressor inlet enthalpy, the enthalpy at the outlet of the compressor, and the mass flow rate of the refrigerant flowing through the compressor.

[0034] Solution 6. The system according to Solution 5, wherein the compressor outlet temperature module is configured to estimate the compressor outlet temperature in the current iteration based on the compressor inlet enthalpy and compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from the previous iteration.

[0035] Solution 7. The system according to Solution 5, the system further having a compressor enthalpy module configured to determine the compressor inlet enthalpy in the current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the compressor inlet, and the pressure measured at the compressor inlet.

[0036] Solution 8. The system according to Solution 7, wherein the compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the compressor outlet.

[0037] Solution 9. The system according to Solution 1, the system further comprising:

[0038] A refrigerant density module configured to determine the refrigerant density at the compressor inlet based on the estimated refrigerant quality;

[0039] A refrigerant flow rate module configured to determine the mass flow rate of the refrigerant flowing through the compressor based on the refrigerant density; and

[0040] A compressor power module configured to determine the power output of the compressor based on the refrigerant mass rate, the compressor inlet enthalpy, and the enthalpy at the compressor outlet.

[0041] Solution 10. The system according to Solution 9, the system further comprising an actuator control module configured to control at least one of the compressor and the heat exchanger in the thermal system based on at least one of the refrigerant mass flow rate and the compressor power.

[0042] Solution 11. A system, the system comprising:

[0043] A compressor outlet temperature module configured to estimate the temperature at the outlet of the compressor in the thermal system of an electric vehicle based on the enthalpy at the inlet of the compressor, the enthalpy at the compression outlet, and the mass flow rate of the refrigerant flowing through the compressor; and

[0044] A refrigerant quality module configured to estimate the quality of the refrigerant at the compressor inlet based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet, wherein the refrigerant quality is the ratio of the vapor refrigerant mass to the total refrigerant mass.

[0045] Solution 12. The system according to Solution 11, wherein the compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model that correlates the compressor outlet temperature with the compressor inlet enthalpy, the compressor outlet enthalpy, and the refrigerant mass flow rate.

[0046] Solution 13. The system according to Solution 11, wherein the compressor outlet temperature module is configured to estimate the compressor outlet temperature in the current iteration based on the compressor inlet enthalpy and compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from the previous iteration.

[0047] Solution 14. The system according to Solution 11, the system further having a compressor enthalpy module configured to determine the compressor inlet enthalpy in the current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the compressor inlet, and the pressure measured at the compressor inlet.

[0048] Solution 15. The system according to Solution 14, wherein the compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the compressor outlet.

[0049] Solution 16. The thermal system according to Solution 11, wherein the refrigerant quality module is configured to estimate the refrigerant quality based on the difference between the estimated and measured compressor outlet temperatures.

[0050] Solution 17. The thermal system according to Solution 11, wherein the refrigerant quality module is configured to estimate the refrigerant quality based on the compressor inlet enthalpy and an inlet enthalpy correction factor.

[0051] Solution 18. The thermal system according to Solution 17, the thermal system further having a correction factor module configured to determine the inlet enthalpy correction factor using a Kalman filter based on the estimated and measured compressor outlet temperatures.

[0052] Solution 19. The system according to Solution 18, wherein the correction factor module is configured to determine the inlet enthalpy correction factor in the current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and measured compressor outlet temperatures.

[0053] Solution 20. A method, the method comprising:

[0054] estimating the temperature at the outlet of a compressor in a thermal system of an electric vehicle;

[0055] Estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the inlet of the compressor and an inlet enthalpy correction factor, where the refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of refrigerant; and

[0056] Determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the outlet of the compressor. Description of the Drawings

[0057] The present disclosure will be more fully understood through the detailed description and the drawings, in which:

[0058] Figure 1 is an example of a thermal system for an electric vehicle according to the present disclosure;

[0059] Figure 2 is an exemplary control system according to the present disclosure; and

[0060] Figure 3 is a flowchart illustrating an exemplary control method according to the present disclosure.

[0061] In the drawings, reference numerals may be reused to identify similar and / or identical elements. Detailed Description

[0062] The quality of the refrigerant entering the compressor of the thermal system for an electric vehicle may affect the performance of the thermal system and / or the life of the compressor. Refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of vapor and liquid refrigerant. The density of liquid refrigerant is greater than the density of vapor refrigerant. Therefore, for a given compressor speed, the mass flow rate of the refrigerant flowing through the compressor increases as the refrigerant quality decreases, and vice versa. Thus, changes in refrigerant quality may result in inaccurate calculations of the refrigerant mass flow rate, which can negatively affect the performance and efficiency of the thermal system during cabin cooling, cabin heating, or propulsion system cooling. Additionally, liquid refrigerant entering the compressor can damage the compressor.

[0063] To address this issue, the control system according to the present disclosure determines the quality of the refrigerant at the inlet of the compressor and controls one or more actuators of the thermal system based on the refrigerant quality. For example, when the refrigerant quality decreases, the control system may increase the power supplied to the compressor and / or the blower or fan that blows air over the evaporator or condenser. The refrigerant quality at the inlet of the compressor cannot be accurately measured directly based on the inputs of pressure and temperature sensors, especially in the two-phase region of the pressure-enthalpy diagram. Therefore, the control system according to the present disclosure estimates the refrigerant quality at the inlet of the compressor.

[0064] In one example, the control system estimates the temperature at the compressor outlet using a physics-based linear model and estimates the refrigerant quality based on the estimated compressor outlet temperature and the measured compressor outlet temperature. In one example, the thermal system control module estimates the refrigerant quality based on the enthalpy at the compressor inlet and the inlet enthalpy correction factor. The thermal system control module recursively determines the inlet enthalpy correction factor using a Kalman filter based on the estimated and measured compressor outlet temperatures.

[0065] Now referring to Figure 1 , the thermal system 10 for an electric vehicle is operable to heat or cool the air circulated through the passenger compartment 11 of the electric vehicle. Additionally, the thermal system 10 is operable to heat or cool the coolant circulated through the propulsion system (not shown) of the electric vehicle. The propulsion system has one or more electric motors and one or more battery packs that supply power to the electric motors. In one example, the thermal system 10 absorbs heat from the cabin air into the refrigerant to cool the passenger compartment 11 and discharges the heat from the refrigerant to the ambient air. In another example, the thermal system 10 absorbs heat from the coolant into the refrigerant and discharges the heat from the refrigerant to the cabin air to heat the passenger compartment 11.

[0066] The thermal system 10 has an external condenser 12, a heating condenser 14, an evaporator 16, a cooler 18, a compressor 20, an external condenser flow valve 22, a heating condenser flow valve 24, an evaporator expansion valve 26, and a cooler expansion valve 28. The external condenser 12 is arranged in parallel with the heating condenser 14. The evaporator 16 is arranged in parallel with the cooler 18. The evaporator 16 and the cooler 18 are arranged downstream of the external condenser 12 and the heating condenser 14. The compressor 20 is arranged downstream of the evaporator 16 and the cooler 18 and upstream of the external condenser 12 and the heating condenser 14.

[0067] The external condenser 12 releases heat from the refrigerant flowing therethrough to the ambient air flowing therethrough. The external condenser 12 is arranged outside the passenger compartment 11 of the electric vehicle, for example, near the front end of the electric vehicle. The external condenser flow valve 22 regulates the flow rate of the refrigerant circulated through the external condenser 12. The external condenser flow valve 22 is directly arranged upstream of the external condenser 12. In the example, the thermal system 10 further has an electric fan 30 that forces the ambient air through the external condenser 12.

[0068] The heating condenser 14 releases heat from the refrigerant flowing therethrough to the cabin air flowing therethrough. The heating condenser 14 is arranged inside the passenger compartment 11 of the electric vehicle. The heating condenser flow valve 24 regulates the flow rate of the refrigerant circulated through the heating condenser 14. The heating condenser flow valve 24 is directly arranged upstream of the heating condenser 14.

[0069] Evaporator 16 absorbs heat from the cabin air flowing therethrough into the refrigerant flowing therethrough. The evaporator expansion valve 26 reduces the pressure of the refrigerant flowing therethrough, which lowers the temperature of the refrigerant entering the evaporator 16. In addition, the evaporator expansion valve 26 can be closed to prevent the refrigerant from flowing to the evaporator 16. The evaporator expansion valve 26 is directly disposed upstream of the evaporator 16.

[0070] In the example, the thermal system 10 has a blower 32 and an air door 34. The blower 32 forces the cabin air through the heating condenser 14 and the evaporator 16. The air door 34 adjusts the ratio of the ambient air introduced into the passenger cabin 11 to the cabin air recirculated through the passenger cabin 11. When the air door 34 is fully closed, the air door 34 prevents the ambient air from entering the passenger cabin, and when the air door 34 is fully open, the air door 34 only introduces the ambient air into the passenger cabin 11 (i.e., does not recirculate the cabin air).

[0071] The cooler 18 absorbs heat from the coolant flowing therethrough into the refrigerant flowing therethrough. The coolant circulated through the cooler 18 can absorb heat from the propulsion system or discharge heat to the propulsion system. The cooler expansion valve 28 reduces the pressure of the refrigerant flowing therethrough, which lowers the temperature of the refrigerant entering the cooler 18. In addition, the cooler expansion valve 28 can be closed to prevent the refrigerant from flowing to the cooler 18. The cooler expansion valve 28 is directly disposed upstream of the cooler 18.

[0072] When the compressor 20 is turned on or activated, the compressor 20 circulates the refrigerant through the thermal system 10, which has an external condenser 12, a heating condenser 14, an evaporator 16, and a cooler 18. The speed of the compressor 20 can be adjusted to adjust the flow rate of the refrigerant circulated through the thermal system 10. In Figure 1 the example shown, the thermal system 10 also has a coolant electric heater 36, a compressor inlet temperature sensor 38, a compressor outlet temperature sensor 40, a compressor inlet pressure sensor 42, a compressor outlet pressure sensor 44, a compressor speed sensor 46, and a thermal system control module 48.

[0073] The coolant electric heater 36 heats the coolant flowing therethrough. The coolant flows from the coolant electric heater 36 to the cooler 18. When the coolant electric heater 36 is turned on or activated, the coolant electric heater 36 heats the coolant. When the heat transferred from the propulsion system of the electric vehicle to the coolant is not sufficient to heat the cabin air to the target temperature, or when there is a reason to heat the battery, the coolant electric heater 36 can be activated.

[0074] The compressor inlet temperature sensor 38 measures the refrigerant temperature at the inlet 21 of the compressor 20 and generates a signal indicative of the compressor inlet temperature. The compressor outlet temperature sensor 40 measures the refrigerant temperature at the outlet 23 of the compressor 20 and generates a signal indicative of the compressor outlet temperature. The compressor inlet pressure sensor 42 measures the refrigerant pressure at the compressor inlet 21 and generates a signal indicative of the compressor inlet pressure. The compressor outlet pressure sensor 44 measures the refrigerant pressure at the compressor outlet 23 and generates a signal indicative of the compressor outlet pressure. The compressor speed sensor 46 measures the speed of the compressor 20 and generates a signal indicative of the compressor speed.

[0075] The thermal system control module 48 controls various actuators of the thermal system 10 based on the sensor inputs. When the temperature of the cabin air is less than the target temperature (e.g., the temperature set by the user 49 of the electric vehicle), the thermal system control module adjusts the actuators to transfer heat from the coolant to the cabin air. For example, the thermal system control module 48 opens the heated condenser flow valve 24 and the cooler expansion valve 28 to allow the refrigerant to flow through the heated condenser 14 and the cooler 18. Additionally, the thermal system control module 40 closes the external condenser flow valve 22 and the evaporator expansion valve 26 to prevent the refrigerant from flowing through the external condenser 12 and the evaporator 16.

[0076] When the temperature of the cabin air is greater than the target temperature, the thermal system control module 48 adjusts the actuators to transfer heat from the cabin air to the ambient air through the refrigerant circulated through the thermal system 10. For example, the thermal system control module 40 opens the external condenser flow valve 22 and the evaporator expansion valve 26 to allow the refrigerant to flow through the external condenser 12 and the evaporator 16. Additionally, the thermal system control module 48 closes the heated condenser flow valve 24 and the cooler expansion valve 28 to prevent the refrigerant from flowing through the heated condenser 14 and the cooler 18.

[0077] Additionally, the thermal system control module 48 estimates the quality of the refrigerant at the compressor inlet 21 based on the sensor inputs and controls various actuators of the thermal system 10 based on the estimated refrigerant quality. The refrigerant quality is the ratio of the mass of the vapor refrigerant to the total mass of the vapor refrigerant and the liquid refrigerant. In one example, the thermal system control module 48 estimates the temperature at the compressor outlet 23 using a physics-based linear model and estimates the refrigerant quality based on the estimated and measured compressor outlet temperatures. In one example, the thermal system control module 48 estimates the refrigerant quality based on the enthalpy at the compressor inlet 21 and the inlet enthalpy correction factor. The thermal system control module 48 uses a Kalman filter to determine the inlet enthalpy correction factor based on the estimated and measured compressor outlet temperatures.

[0078] Now refer to Figure 2, An exemplary implementation of the thermal system control module 48 has a compressor enthalpy module 50, a compressor outlet temperature module 52, a correction factor module 54, and a refrigerant quality module 56. The compressor enthalpy module 50 determines the compressor inlet enthalpy in the current iteration based on the measured compressor inlet temperature, the measured compressor inlet pressure, and the estimated refrigerant quality from the previous iteration. The compressor enthalpy module 50 makes this determination using a lookup table corresponding to the refrigerant. The compressor enthalpy module 50 receives the measured compressor inlet temperature and the compressor inlet pressure from the compressor inlet temperature sensor and the compressor inlet pressure sensor 38 and 42 respectively.

[0079] The compressor enthalpy module 50 uses a lookup table corresponding to the superheated refrigerant to determine the enthalpy at the compressor outlet 23 under isentropic and non-isentropic conditions based on the measured compressor outlet temperature and the compressor outlet pressure. The compressor enthalpy module 50 receives the measured compressor outlet temperature and the compressor outlet pressure from the compressor outlet temperature sensor and the compressor outlet pressure sensor 40 and 44 respectively. The compressor enthalpy module 50 outputs signals indicating the compressor inlet enthalpy and the compressor outlet enthalpy.

[0080] The compressor outlet temperature module 52 estimates the compressor outlet temperature based on the compressor inlet enthalpy and the compressor outlet enthalpy, using the principle of conservation of energy based on physics for the work done by the compressor 20. For example, the compressor outlet temperature module 52 can estimate the compressor outlet temperature using, for example, the following relationship:

[0081] (1) ,

[0082] where, T CO is the estimated compressor outlet temperature for the current iteration, ṁ c is the mass flow rate of the refrigerant flowing through the compressor 20, h ci is the compressor inlet enthalpy, h co is the non-isentropic compressor outlet enthalpy, h co,isentro is the isentropic compressor outlet enthalpy, η k is the second law efficiency of the compressor 20, m is the mass of the compressor 20, c c is the specific heat of the compressor 20. The compressor efficiency, the compressor mass, and the compressor specific heat can be determined in advance.

[0083] The estimation of the compressor outlet temperature using relationship (1) based on the compressor inlet enthalpy cannot produce accurate results due to inaccuracies in the compressor inlet enthalpy. Therefore, an input enthalpy correction factor can be introduced into relationship (1) to correct for the inaccuracies in the compressor inlet enthalpy. For example, the compressor outlet temperature module 52 can estimate the compressor outlet temperature using, for example, the following relationship:

[0084] (2) ,

[0085] where Δ is the inlet enthalpy correction coefficient.

[0086] The compressor outlet temperature module 52 can estimate the inlet enthalpy correction coefficient in real time using a Kalman filter. However, the relationship (2) is non-linear and may thus be difficult to use for real-time calculations in the thermal system control module 48 to estimate the inlet enthalpy correction coefficient. Therefore, the relationship (2) can be linearized to make it easier to estimate the inlet enthalpy correction coefficient in real time. For example, the compressor outlet temperature module 52 can estimate the compressor outlet temperature using, for example, the following relationship:

[0087] (3) ,

[0088] (4) ,and

[0089] (5) ,

[0090] where T CO is the estimated compressor outlet temperature for the current iteration, T CO1 is the first compressor outlet temperature, T CO2 is the second compressor outlet temperature, is the estimated compressor outlet temperature from the previous iteration, and 273.15 is the conversion coefficient for converting temperature from degrees Celsius to Kelvin.

[0091] The first and second compressor outlet temperatures are variables used to estimate the compressor outlet temperature. The compressor outlet temperature module 52 can use relationships (4) and (5) and a numerical differentiation method to determine the first and second compressor outlet temperatures based on the refrigerant mass flow rate from the previous iteration. Then, the correction coefficient module 54 can determine the inlet enthalpy correction coefficient based on the first and second compressor outlet temperatures and the measured compressor outlet temperature. Then, the compressor outlet temperature module 52 can estimate the compressor outlet temperature using relationship (3) based on the first and second compressor outlet temperatures and the inlet enthalpy correction coefficient. The compressor outlet temperature module 52 outputs a signal indicating the first and second compressor outlet temperatures.

[0092] The correction coefficient module 54 uses a Kalman filter to determine the inlet enthalpy correction coefficient based on the first and second compressor outlet temperatures and the measured compressor outlet temperature from the compressor outlet temperature sensor 40. For example, the correction coefficient module 54 can use, for example, the following relationship to determine the inlet enthalpy correction coefficient:

[0093] (6) ,

[0094] (7) ,

[0095] (8) ,and

[0096] (9) ,

[0097] wherein, is the inlet enthalpy correction coefficient of the current iteration, is the inlet enthalpy correction coefficient of the previous iteration, K k is the Kalman filter gain, y k is the output of the current iteration, is the output of the previous iteration, T in relation (7) CO is the measured compressor outlet temperature, is the state matrix of the previous iteration, R k is the noise covariance matrix of the current iteration. Comparing the combination of relations (6), (7) and (8) with relation (3) reveals that the correction coefficient module 54 determines the inlet enthalpy correction coefficient based on the difference between the measured and estimated compressor outlet temperatures. The correction coefficient module 54 outputs a signal indicating the inlet enthalpy correction coefficient.

[0098] The refrigerant quality module 56 determines the quality of the refrigerant at the compressor inlet 21 based on the compressor inlet enthalpy and the inlet enthalpy correction coefficient. For example, the refrigerant quality module 56 can use, for example, the following relation to determine the refrigerant quality:

[0099] (10) ,

[0100] where χ is the refrigerant quality, h SatLiq is the saturated liquid enthalpy of the refrigerant at the compressor inlet 21, h SatVap is the saturated vapor enthalpy of the refrigerant at the compressor inlet 21. The refrigerant quality module 56 can use a look-up table to determine the saturated liquid enthalpy and the saturated vapor enthalpy based on the measured compressor inlet temperature and compressor inlet pressure. The refrigerant quality module 56 outputs a signal indicating the refrigerant quality.

[0101] The exemplary embodiment of the thermal system control module 48 shown in Figure 2 also has a refrigerant density module 58, a refrigerant flow rate module 60, a compressor power module 62, a compressor control module 64, a valve control module 66, and a fan control module 68. The refrigerant density module 58 determines the refrigerant density at the compressor inlet 21 based on the refrigerant quality at the compressor inlet 21. For example, the refrigerant density module 58 can use, for example, the following relation to determine the refrigerant density:

[0102] (11) ,

[0103] where ρ is the refrigerant density, ρ SatLiq is the saturated liquid density of the refrigerant at the compressor inlet 21, and ρ SatVap is the saturated vapor density of the refrigerant at the compressor inlet 21. The refrigerant density module 58 can determine the saturated liquid density and the saturated vapor density using a look-up table based on the measured compressor inlet temperature and compressor inlet pressure. The refrigerant density module 58 outputs a signal indicating the refrigerant density.

[0104] The refrigerant flow rate module 60 determines the mass flow rate of the refrigerant flowing through the compressor 20 based on the refrigerant density and the measured compressor speed. For example, the refrigerant flow rate module 60 can use a relationship such as the following to determine the refrigerant mass flow rate:

[0105] (12) ,

[0106] where rpm c is the measured compressor speed, 60 is a conversion factor for converting the speed from revolutions per minute to revolutions per second, V c is the volume of the compressor 20, and η v is the volumetric efficiency of the compressor 20. The compressor volume and the compressor volumetric efficiency can be determined in advance. The refrigerant flow rate module 60 outputs a signal indicating the refrigerant mass flow rate.

[0107] The compressor power module 62 determines the output power of the compressor 20 based on the refrigerant mass flow rate, the compressor inlet enthalpy, and the compressor outlet enthalpy. For example, the compressor power module 62 can use a relationship such as the following to determine the compressor power:

[0108] (13) ,

[0109] where P c is the compressor power. The compressor power module 62 outputs a signal indicating the compressor power.

[0110] The compressor control module 64 outputs a signal to the compressor 20 to control the speed of the compressor and / or the amount of power supplied to the compressor. The valve control module 66 outputs a signal to the valves 22, 24, 26, 28 to control the position of the valves. The fan control module 68 outputs a signal to the electric fan 30 and the blower 32 to control the speed of the electric fan and the blower and / or the amount of power supplied to the electric fan and the blower. Each of the compressor 20, the valves 22, 24, 26, 28, the electric fan 30, and the blower 32 can be referred to as an actuator. Each of the compressor control module 64, the valve control module 66, and the fan control module 68 can be referred to as an actuator control module.

[0111] The compressor control module 64 controls the speed of the compressor 20 and / or the amount of power supplied to the compressor based on the refrigerant mass flow rate and / or the compressor power. Additionally or alternatively, the valve control module 66 controls the position of one or more of the valves 22, 24, 26, 28 based on the refrigerant mass flow rate and / or the compressor power. Additionally or alternatively, the fan control module 68 controls the speed of one or more of the electric fan 30 and the blower 32 and / or the amount of power supplied to one or more of the electric fan and the blower based on the refrigerant mass flow rate and / or the compressor power.

[0112] In one example, when the compressor power increases or decreases, the compressor control module 64 increases or decreases the amount of power supplied to the compressor 20, respectively. In another example, when the refrigerant mass flow rate is less than or greater than the target mass flow rate, the valve control module 64 increases or decreases the opening amount of one or more of the valves 22, 24, 26, 28, respectively. In another example, when the refrigerant mass flow rate increases or decreases, the fan control module 68 increases or decreases the amount of power supplied to the electric fan 30 and the blower 32, respectively.

[0113] Now refer to Figure 3 , an exemplary method for estimating the quality of the refrigerant at the inlet 21 of the compressor 20 in the thermal system 10 for Figure 1 starts at 70. Figure 3 One or more (e.g., all) steps of the method can be performed by executing instructions stored in a computer-readable medium. At 72, the compressor enthalpy module 50 determines the inlet enthalpy and the outlet enthalpy of the compressor 20. The compressor enthalpy module 50 can determine the compressor outlet enthalpy under isentropic and non-isentropic conditions.

[0114] At 74, the compressor outlet temperature module 52 determines the first and second compressor outlet temperatures based on the refrigerant mass flow rate, the compressor inlet enthalpy, and the compressor outlet enthalpy from a previous iteration. At 76, the correction factor module 54 determines the inlet enthalpy correction factor using a Kalman filter based on the first and second compressor outlet temperatures. At 78, the refrigerant quality module 56 determines the quality of the refrigerant at the compressor inlet 21 based on the inlet enthalpy correction factor and the compressor inlet enthalpy.

[0115] At 80, a refrigerant density module 58 determines a density at a compressor inlet 21 based on a refrigerant quality at the compressor inlet 21. At 82, a refrigerant mass flow rate module 60 determines a mass flow rate of the refrigerant at the compressor inlet 21 based on the refrigerant density at the compressor inlet 21. At 84, a compressor power module 62 determines a power output of a compressor 20 based on the refrigerant mass flow rate at the compressor inlet 21. At 86, one or more actuator control modules in an actuator control module in a thermal system control module 48 control one or more actuators in a thermal system 10 based on the refrigerant mass flow rate and / or the compressor power. Then, the method returns to 72. Each completion from 72 to 86 can be referred to as an iteration.

[0116] As described above, variations in the quality of the refrigerant circulating through the thermal system of an electric vehicle can result in inaccurate calculations of the refrigerant mass flow rate, which can adversely affect the performance and efficiency of the thermal system. Additionally, liquid refrigerant entering the compressor of the thermal system can damage the compressor. To address these issues, the systems, methods, and computer-readable media according to the present disclosure are configured to estimate the refrigerant quality at the compressor inlet based on the compressor inlet enthalpy and an inlet enthalpy correction factor. The systems, methods, and computer-readable media are configured to determine the inlet enthalpy correction factor based on the estimated temperature at the compressor outlet and the measured temperature at the compressor outlet. The systems, methods, and computer-readable media are configured to determine the refrigerant mass flow rate based on the refrigerant quality, which improves the performance and efficiency of the thermal system and prevents compressor damage.

[0117] The foregoing description is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses. The broad teachings of the present disclosure can be implemented in a variety of forms. Thus, while the present disclosure has specific examples, the true scope of the present disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method can be executed in a different order (or concurrently) without altering the principles of the present disclosure. Additionally, while each embodiment above is described as having certain features, any one or more of those features described with respect to any embodiment of the present disclosure can be implemented in and / or combined with the features of any other embodiment, even if such a combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and the arrangement of one or more embodiments with respect to each other is still within the scope of the present disclosure.

[0118] The spatial and functional relationships between elements (e.g., between modules, between circuit elements, between semiconductor layers, etc.) are described using various terms, including "connected", "joined", "coupled", "adjacent", "next to", "on top of", "above", "below", and "disposed". Unless explicitly described as "direct", when the relationship between a first and a second element is described in the foregoing disclosure, the relationship can be a direct relationship in which no other intervening elements exist between the first and second elements, but can also be an indirect relationship in which one or more intervening elements (spatially or functionally) exist between the first and second elements. As used herein, the phrase "at least one of A, B, and C" shall be interpreted to mean a logical (A or B or C), using non-exclusive logical OR, and shall not be interpreted to mean "at least one of A, at least one of B, and at least one of C".

[0119] In the figures, as indicated by the arrows, the direction of the arrows generally shows the flow of information (such as data or instructions) of interest to the illustration. For example, when elements A and B exchange various information, but the information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This one-way arrow does not mean that no other information is transmitted from element B to element A. In addition, for the information sent from element A to element B, element B may send a request for the information or receive an acknowledgement to element A.

[0120] In this application, including the following definitions, the term "module" or the term "controller" may be replaced with the term "circuit". The term "module" may refer to, belong to, or include: an application specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

[0121] A module may include one or more interface circuits. In some examples, the interface circuit may include a wired or wireless interface connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules connected via the interface circuit. For example, multiple modules may allow load balancing. In another example, a server (also referred to as remote or cloud) module may perform certain functions on behalf of a client module.

[0122] The term code, as used above, may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term shared processor circuit includes a single processor circuit that executes some or all of the code from multiple modules. The term group processor circuit includes a processor circuit that, in combination with additional processor circuits, executes some or all of the code from one or more modules. References to multiple processor circuits include multiple processor circuits on discrete die, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or a combination of the above. The term shared memory circuit includes a single memory circuit that stores some or all of the code from multiple modules. The term group memory circuit includes a memory circuit that, in combination with additional memory, stores some or all of the code from one or more modules.

[0123] The term memory circuit is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not include transitory electrical or electromagnetic signals propagated through a medium (such as on a carrier wave); thus, the term computer-readable medium can be considered tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0124] The devices and methods described in this application may be implemented in part or in whole by a special purpose computer created by configuring a general purpose computer to execute one or more specific functions included in a computer program. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into a computer program by the routine work of a skilled technician or programmer.

[0125] A computer program includes processor-executable instructions stored on at least one non-transitory tangible computer-readable medium. A computer program may also include or rely on stored data. A computer program may include a basic input / output system (BIOS) that interacts with the hardware of the special purpose computer, device drivers that interact with specific devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, and the like.

[0126] A computer program may include: (i) descriptive text to be parsed, such as HTML (HyperText Markup Language), XML (eXtensible Markup Language), or JSON (JavaScript Object Notation); (ii) assembly code; (iii) object code generated from source code by a compiler; (iv) source code executed by an interpreter; (v) source code compiled and executed by a just-in-time compiler, etc. By way of example only, the source code may be written using the syntax of the following languages, including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, JavaScript®, HTML5 (HyperText Markup Language, Fifth Edition), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB, SIMULINK, and Python®.

Claims

1. System, the system comprising: A compressor outlet temperature module configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle; A refrigerant quality module configured to estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the compressor inlet and an inlet enthalpy correction factor, wherein the refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of refrigerant; and A correction factor module configured to determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet.

2. The system according to claim 1, wherein, The correction factor module uses a Kalman filter to determine the inlet enthalpy correction factor based on the estimated and measured compressor outlet temperatures.

3. The system according to claim 2, wherein, The correction factor module is configured to determine the inlet enthalpy correction factor in the current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and measured compressor outlet temperatures.

4. The system according to claim 1, wherein, The compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model of the work done by the compressor.

5. The system according to claim 1, wherein, The compressor outlet temperature module is configured to estimate the compressor outlet temperature based on the compressor inlet enthalpy, the enthalpy at the compressor outlet, and the mass flow rate of the refrigerant flowing through the compressor.

6. The system according to claim 5, wherein, The compressor outlet temperature module is configured to estimate the compressor outlet temperature in the current iteration based on the compressor inlet enthalpy and compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from the previous iteration.

7. The system according to claim 5, the system further having a compressor enthalpy module configured to determine the compressor inlet enthalpy in the current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the compressor inlet, and the pressure measured at the compressor inlet.

8. The system according to claim 7, wherein, The compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the compressor outlet.

9. The system according to claim 1, the system further comprising: A refrigerant density module configured to determine the refrigerant density at the compressor inlet based on the estimated refrigerant quality; A refrigerant flow rate module configured to determine the mass flow rate of the refrigerant flowing through the compressor based on the refrigerant density; and A compressor power module configured to determine the power output of the compressor based on the refrigerant mass rate, the compressor inlet enthalpy, and the enthalpy at the compressor outlet.

10. The system according to claim 9, the system further comprising an actuator control module configured to control at least one of the compressor and the heat exchanger in the thermal system based on at least one of the refrigerant mass flow rate and the compressor power.

11. System, the system comprising: A compressor outlet temperature module, the compressor outlet temperature module configured to estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle based on the enthalpy at the inlet of the compressor, the enthalpy at the compression outlet, and the mass flow rate of the refrigerant flowing through the compressor; and A refrigerant quality module, the refrigerant quality module configured to estimate the quality of the refrigerant at the inlet of the compressor based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet, wherein the refrigerant quality is the ratio of the mass of vapor refrigerant to the total mass of refrigerant.

12. The system according to claim 11, wherein, The compressor outlet temperature module is configured to estimate the compressor outlet temperature using a linear model that correlates the compressor outlet temperature with the compressor inlet enthalpy, the compressor outlet enthalpy, and the refrigerant mass flow rate.

13. The system according to claim 11, wherein, The compressor outlet temperature module is configured to estimate the compressor outlet temperature in the current iteration based on the compressor inlet enthalpy and compressor outlet enthalpy from a previous iteration and the refrigerant mass flow rate from the previous iteration.

14. The system according to claim 11, wherein the system further has a compressor enthalpy module configured to determine the compressor inlet enthalpy in the current iteration based on the estimated refrigerant quality from a previous iteration, the temperature measured at the compressor inlet, and the pressure measured at the compressor inlet.

15. The system according to claim 14, wherein The compressor enthalpy module is configured to determine the compressor outlet enthalpy based on the measured compressor outlet temperature and the pressure measured at the compressor outlet.

16. The thermal system according to claim 11, wherein The refrigerant quality module is configured to estimate the refrigerant quality based on the difference between the estimated and measured compressor outlet temperatures.

17. The thermal system according to claim 11, wherein The refrigerant quality module is configured to estimate the refrigerant quality based on the compressor inlet enthalpy and the inlet enthalpy correction factor.

18. The thermal system according to claim 17, wherein The thermal system further has a correction factor module configured to determine the inlet enthalpy correction factor using a Kalman filter based on the estimated and measured compressor outlet temperatures.

19. The system according to claim 18, wherein The correction factor module is configured to determine the inlet enthalpy correction factor in the current iteration based on the inlet enthalpy correction factor from a previous iteration, the Kalman filter gain, and the estimated and measured compressor outlet temperatures.

20. A method, the method comprising: Estimate the temperature at the outlet of a compressor in a thermal system of an electric vehicle; Estimate the quality of the refrigerant at the inlet of the compressor based on the enthalpy at the compressor inlet and the inlet enthalpy correction factor, where the refrigerant quality is the ratio of the vapor refrigerant mass to the total refrigerant mass; and Determine the inlet enthalpy correction factor based on the estimated compressor outlet temperature and the temperature measured at the compressor outlet.

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