Fuel cell cathode energy recovery system and control method thereof

Abstract

The invention discloses a fuel cell cathode energy recovery system and a control method thereof, the system comprises a turbine compressor, an intercooler, a humidifier, a water segregator and an electric pile, the turbine compressor comprises an air compression end and a turbine end; the air compression end, the intercooler, the humidifier and the electric pile are sequentially connected, a cathode outlet of the electric pile is connected with a wet side inlet of the humidifier, a wet side outlet of the humidifier is connected with the water segregator, the water segregator is connected with a refrigerant inlet of the intercooler and a turbine end inlet, and a turbine end outlet is connected with the refrigerant inlet of the intercooler. A first flow adjusting assembly is arranged between a cathode outlet of the electric pile and a wet side inlet of the humidifier; a second flow adjusting assembly is arranged between the liquid outlet of the water segregator and the refrigerant inlet of the intercooler. Air entering the system is cooled through turbine end outlet gas, the system design is simplified, and the overall performance and reliability of the electric pile are improved, the service life is prolonged and the system robustness is improved by adjusting the temperature and the humidity of the air entering the electric pile.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a fuel cell cathode energy recovery system and a control method thereof. Background Art

[0002] Fuel cells generate electricity through the electrochemical reaction of air and hydrogen. The air supply end generally uses an air compressor and a back-pressure throttle to meet the flow and pressure operating conditions of the fuel cell stack air inlet (cathode inlet). In order to further reduce the power consumption of accessories, mainly the power consumption of the air compressor, an expander is used to replace a single air compressor and a back-pressure throttle, and the energy of the high-pressure and high-temperature air at the outlet of the stack is recovered and connected to the compressor end through a coaxial connection, thereby reducing the total net power consumption of the compressor, improving the overall system efficiency, and reducing the cost of the compressor motor.

[0003] When the expander turbine is working, the inlet is the high-pressure, high-temperature gas from the fuel cell stack outlet. The gas works on the turbine, and the kinetic energy and potential energy of the gas are converted into mechanical energy of the turbine. The pressure and temperature of the gas at the turbine outlet are significantly reduced, and the temperature can drop from 80°C to room temperature or even close to 0°C. It is directly discharged from the system through the tail pipe and is not effectively recycled. In order to meet the operating conditions such as the temperature and humidity of the fuel cell stack air inlet, a more complex cooling system is usually designed, and there is still the problem of uncontrollable temperature and humidity of the fuel cell stack inlet air.

[0004] Invention patent application CN113809355A discloses a fuel cell circulating water cooling system using cold air at the expander outlet. This patent uses cold air at the expander outlet, but the main body of the invention is a cooling system, and the intercooler is located in front of the expander. The cold air is used as antifreeze in the cooling system and has nothing to do with the air supply system. In addition, the cooling system design of this invention is highly complex, and the gas temperature at the front end of the expander is relatively high, which cannot effectively cool the hot air supply at the air compressor outlet.

[0005] Invention patent application CN117497801A discloses a cathode recirculation regulation system and regulation method for a hydrogen fuel cell. This patent collects and utilizes liquid water at the outlet of the expander, and then passes it into the front end of the compressor to adjust the humidity of the air at the inlet of the stack, which can save the humidifier, reduce costs, simplify the complexity of system design, and achieve the purpose of controllable humidity operating conditions. This patent directly uses the outlet liquid water for humidification, does not simplify the cooling system design, does not effectively reduce the heat dissipation pressure of the cooling system, and passes liquid water into the front end of the compressor, which has the risk of corroding the compressor impeller for a long time and increases the instability of the system. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a fuel cell cathode energy recovery system and a control method thereof. The system design is simplified by using the turbine end outlet gas to cool the air entering the system. By adjusting the air temperature and air humidity entering the fuel cell stack, the overall performance and reliability of the fuel cell stack are improved, the service life is extended, and the system robustness is improved.

[0007] The present invention provides the following technical solutions: In a first aspect, a fuel cell cathode energy recovery system is provided, comprising a turbo compressor, an intercooler, a humidifier, a water separator and a fuel cell stack, wherein the turbo compressor comprises a compressor end and a turbine end connected to each other; The compressed air end outlet is connected to the heat medium inlet of the intercooler, the heat medium outlet of the intercooler is connected to the dry side inlet of the humidifier, the dry side outlet of the humidifier is connected to the cathode inlet of the fuel cell stack, the cathode outlet of the fuel cell stack is connected to the wet side inlet of the humidifier, the wet side outlet of the humidifier is connected to the inlet of the water separator, the liquid outlet of the water separator is connected to the refrigerant inlet of the intercooler, the gas outlet of the water separator is connected to the turbine end inlet, and the turbine end outlet is connected to the refrigerant inlet of the intercooler; A first flow regulating component is provided between the cathode outlet of the fuel cell stack and the wet side inlet of the humidifier, and the first flow regulating component is used to regulate the flow of humid air entering the humidifier to control the humidity of air entering the fuel cell stack; A second flow regulating component is provided between the liquid outlet of the water separator and the refrigerant inlet of the intercooler, and the second flow regulating component is used to regulate the refrigerant flow entering the intercooler to control the temperature of the air entering the fuel cell stack.

[0008] Furthermore, the first flow regulating component includes a first air outlet pipe, a second air outlet pipe and a bypass valve arranged on the second air outlet pipe, which are respectively connected to the cathode outlet of the fuel cell stack; the first air outlet pipe is connected to the wet side inlet of the humidifier; and the second air outlet pipe is connected to a first tail exhaust pipe.

[0009] Furthermore, the second flow regulating component includes a first water distribution pipe and a second water distribution pipe respectively connected to the liquid outlet of the water distributor, and a drain valve arranged on the first water distribution pipe, the first water distribution pipe is connected to the first tail drain pipe, and the second water distribution pipe is connected to the refrigerant inlet of the intercooler.

[0010] Furthermore, an air flow sensor is provided at the compressor end inlet, a first temperature sensor is provided at the compressor end outlet, a second temperature sensor and a pressure sensor are provided at the cathode inlet of the fuel cell stack, a third temperature sensor is provided at the cathode outlet of the fuel cell stack, and a fourth temperature sensor is provided at the turbine end inlet.

[0011] Furthermore, it also includes an air filter, the outlet of the air filter is connected to the inlet of the compressed air end.

[0012] Furthermore, the refrigerant outlet of the intercooler is connected to a second tail exhaust pipe.

[0013] In a second aspect, a control method of the fuel cell cathode energy recovery system according to the first aspect is provided, comprising: Obtain the stack current and the required flow rate, required pressure, required temperature and required humidity of the air entering the stack; Taking the required flow rate and required pressure of the air entering the reactor as the control target, the speed of the turbo compressor and the opening of the turbine blades are adjusted by feedforward and closed loop; Calculate the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier based on the stack current, the required temperature and humidity of the air entering the stack, the cathode outlet temperature, the speed of the turbo compressor and the opening of the turbine blades; The bypass flow at the cathode outlet is calculated according to the flow at the wet side inlet of the humidifier, and the bypass valve opening is calculated according to the bypass flow; The liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler is calculated according to the bypass flow rate and the gas temperature at the dry side inlet of the humidifier, and the drain valve opening is calculated according to the liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler; Control the bypass valve and the drain valve according to the bypass valve opening and the drain valve opening; After the system stabilizes, if the speed of the turbo compressor and the opening of the turbine blades are not within the preset value range compared with the speed of the turbo compressor and the opening of the turbine blades after the initial closed-loop adjustment, the speed of the turbo compressor and the opening of the turbine blades are updated, and the above calculation process is repeated until the changes in the speed of the turbo compressor and the opening of the turbine blades are within the preset value range, and the control is completed.

[0014] Furthermore, the method for calculating the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier includes: The saturated vapor pressure P0_sat at the cathode inlet of the stack is calculated as: P0_sat=0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0))), Among them, T0 is the required temperature of the air entering the pile; The water vapor partial pressure P0_H20g at the cathode inlet of the stack is: P0_H20g=P0_sat*RH0, Among them, RH0 is the required humidity of the air entering the pile; The molar flow rate of dry air at the cathode inlet of the stack, n0_air, is: n0_air=M0 / 29, Among them, M0 is the required flow rate of air entering the pile; The molar flow rate of water vapor n0_H2Og at the cathode inlet of the stack is: n0_H2Og=P0_H2O_g / (P0-P0_H2Og)*n0_air, Among them, P0 is the required pressure of air entering the pile; Then the total gas volume flow rate qv_stk at the cathode inlet of the stack is: qv_stk=(n0_air+n0_H2Og)*22.4 / 1000*(T0+273.15) / 273.15*101.325 / P0; The stack current resistance dP_stk is: dP_stk=R0(qv_stk), Among them, R0(*) is the functional relationship between the stack flow resistance and the volume flow rate, which is an inherent characteristic of the stack; The pressure P_stkout at the cathode outlet of the stack is: P_stkout = P0 - dP_stk; The molar flow rate dn0 of dry air consumed by the stack is: dn0=I0 / 96485 / 4*N_stk, Where, I0 is the stack current, N_stk is the number of stack cells; The dry air flow rate n_air_stkout at the cathode outlet of the stack is: n_air_stkout = n0_air - dn0; The gas at the cathode outlet of the stack is saturated water vapor, so the water vapor partial pressure P_stkout_H2Og is equal to the saturated vapor pressure, and the calculation formula is as follows: P_stkout_H2Og=0.61121*exp((18.678-T_stkout / 234.5)*( T_stkout / (257.14+T_stkout))), Wherein, T_stkout is the cathode outlet temperature of the stack; Then the molar flow ratio of water vapor to dry air at the cathode outlet of the stack is: r_out= P_stkout_H2Og / (P_stkout-P_stkout_H2Og); The water transfer rate WRR of the humidifier is: WRR=dn_H2O / n_H20g_wetin, Among them, dn_H2O is the molar rate of water transfer in the humidifier, and n_H2Og_wetin is the molar flow rate of water vapor at the wet measurement inlet of the humidifier; Because n_H2Og_wetin= Mx / 29*r_out, where Mx is the flow rate at the wet side inlet of the humidifier; Therefore, dn_H2O=WRR*Mx / 29*r_out; The required humidity RH0 of the air entering the pile is expressed as: RH0=dn_H2O*(M0 / 29+dn_H2O)*P0 / P0_sat=WRR*Mx / 29*r_out*(M0 / 29+dn_H2O)*P0 / (0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0)))), The only unknown quantity can be calculated: the flow rate Mx at the wet side inlet of the humidifier; The heat exchange capacity of the humidifier Q_HUM is: Q_HUM= *Qmax_HUM, in, is the effectiveness of the humidifier, Qmax_HUM is the theoretical maximum heat exchange capacity of the humidifier; Qmax_HUM=Cmin*(T_stkout-Tx), Where Tx is the gas temperature at the dry side inlet of the humidifier, and Cmin is the smaller of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmin=min[cp_HUM_wetin*M_wetin, cp_air*M0], Among them, cp_HUM_wetin is the constant pressure specific heat capacity of the mixed gas at the wet side inlet of the humidifier, M_wetin is the total mass flow rate of the wet measurement inlet of the humidifier, and cp_air is the heat capacity of the air; The total mass flow rate M_wetin at the wet measurement inlet of the humidifier is: M_wetin=Mx+Mx / 29*r_out*18; The heat capacity of the mixed gas at the wet measurement inlet of the humidifier, cp_HUM_wet, is: cp_HUM_wet=r_out / (r_out+1)*cp_H2Og+1 / (r_out+1)*cp_air, Where cp_H2Og is the heat capacity of water vapor; Therefore: Qmax_HUM= min[cp_HUM_wetin*M_wetin, cp_air*M0]*(T_stkout-Tx); Effectiveness for: =(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))), Among them, Cr is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet on both sides of the humidifier, and NTU is a dimensionless number; Cr=Cmin / Cmax, Among them, Cmax is the larger of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmax= max[cp_HUM_wetin*M_wetin, cp_air*M0]; NTU=U*A / Cmin, Among them, U is the heat transfer coefficient, A is the heat transfer area, and U and A are known quantities; Therefore, the heat exchange Q_HUM of the humidifier is expressed as: Q_HUM=min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)*(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))); The dry side outlet temperature of the humidifier, that is, the required temperature T0 of the air entering the pile is: T0=Tx+Q_HUM / (cp_air*M0); Right now: T0=Tx+min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)*(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))) / (cp_air*M0), The only unknown quantity can be calculated: the gas temperature Tx at the dry side inlet of the humidifier.

[0015] Furthermore, the method for calculating the bypass valve opening includes: The molar flow rate of dry air at the cathode outlet of the stack is n_air_stkout, the molar flow rate of water vapor at the cathode outlet of the stack is r_out*n_air_stkout, the molar flow rate of dry air at the wet side inlet of the humidifier is Mx / 29, and the molar flow rate of water vapor at the wet side inlet of the humidifier is Mx / 29*r_out. The molar flow rate n0_bypass that needs to be bypassed by the bypass valve is: n0_bypass=n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29); The volume flow rate qv_bypass required to bypass the bypass valve is: qv_bypass=(n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29))*22.4 / 1000*101.325 / P_stkout*(273.15+T_stkout) / 273.15; When the cathode outlet of the stack is at atmospheric pressure, the volume flow of the bypass valve is related to the opening and inlet pressure, so the bypass valve opening α_bypass is: α_bypass=F1(qv_bypass,P_stkout), Among them, F1(*) is the functional relationship between the bypass valve opening and the volume flow rate and cathode outlet pressure, and is the performance characteristic of the bypass valve component itself.

[0016] Furthermore, the method for calculating the opening of the drain valve includes: The volume flow rate qv_wetin at the wet side inlet of the humidifier is: qv_wetin=Mx / 29*(1+r_out)*22.4 / 1000*101.325 / P_stkout*(T_stkout+273.15) / 273.15; According to the wet flow resistance characteristics of the humidifier: dP_HUMwet=R_HW(qv_wetin), Among them, dP_HUMwet is the wet side flow resistance of the humidifier, R_HW(*) is the functional relationship between the wet side flow resistance of the humidifier and the volume flow rate, which is the inherent characteristic of the humidifier; The pressure P_sepin at the humidifier wet test outlet, i.e. the water separator inlet, is: P_sepin=P_stkout-dP_HUMwet; Since the water separator inlet is saturated water vapor, the water vapor partial pressure P_H2Og_sepin is: P_H2Og_sepin=0.61121*exp((18.678-T_turbin / 234.5)*(T_turbin / (257.14+T_turbin))), Among them, T_turbin is the water separator inlet temperature; The molar flow rate of dry air at the water separator inlet is still Mx / 29, so the total molar flow rate n_sepin at the water separator inlet is: n_sepin=Mx / 29 *(1+P_H2Og_sepin / (P_sepin-P_H2Og_sepin)); Then the volume flow rate qv_sepin at the water distributor inlet is: qv_sepin=n_sepin*22.4 / 1000*101.325 / P_sepin*(T_turbin+273.15) / 273.15; According to the flow resistance characteristics of the water distributor: dP_sep=R_sep(qv_sepin), Among them, dP_sep is the flow resistance of the water divider, R_sep(*) is the functional relationship between the flow resistance of the water divider and the volume flow rate, which is the inherent characteristic of the water divider; The turbine inlet pressure P_turbin is: P_turbin = P_sepin - dP_sep; The mass flow rate M_turbin at the turbine inlet is: M_turbin=Mx+Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)*18; The expansion ratio ER at the turbine end is: ER=F2(P_turbin, T_turbin, M_turbin, N_ACP), Among them, F2(*) is the corresponding functional relationship between the turbine expansion ratio and the inlet temperature, pressure, flow rate, and speed. It is the performance characteristic of the turbine itself and is determined by the turbine performance map. N_ACP is the turbine end speed. Then the turbine outlet pressure P_turbout is: P_turbout=P_turbin / ER The turbine outlet gas temperature T_turbout is: T_turbout=F3(P_turbin,T_turbin,M_turbin,N_ACP), Among them, F3(*) is the corresponding functional relationship between the turbine outlet temperature and the turbine inlet pressure, temperature, flow rate and speed, which is determined by the turbine performance and efficiency map; Since the gas temperature at the turbine outlet is low, the water vapor must be in a saturated state, so the partial pressure of water vapor at the turbine outlet P_H2Og_turbout is: P_H2Og_turbout=0.61121*exp((18.678-T_turbout / 234.5)*(T_turbout / (257.14+T_turbout))); Then the molar flow ratio of water vapor to dry air at the turbine outlet r_turbout is: r_turbout=P_H2Og_turbout / (P_turbout- P_H2Og_turbout); The molar flow rate of gaseous water at the turbine outlet n_H2Og_turbout is: n_H2Og_turbout=Mx / 29*r_turbout; The liquid water flow rate n_H2Ol_turbout at the turbine outlet is: n_H2Ol_turbout=Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)-n_H2Og_turbout; The molar flow rate of liquid water at the refrigerant inlet of the intercooler n_H2Ol_CAClowin is: n_H2Ol_CAClowin=n_H2Ol_turbout+n_H2Ol_add, Wherein, n_H2Ol_add is the molar flow rate of liquid water diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler; The latent heat transfer capacity of the intercooler Q_CAClat is: Q_CAClat= n_H2Ol_CAClowin*18*cp_lat, Where cp_lat is the latent heat per gram of liquid water, which is 2.265 kJ / g; The molar flow rate of water vapor at the outlet of the intercooler refrigerant n_H2Og_CAClow is: n_H2Og_CAClow= n_H2Ol_CAClowin+ n_H2Og_turbout; Then the intercooler heat medium outlet temperature T_CAC_high becomes: T_CAC_high=T_ACPout-Q_CAClat / (M0*cp_air), Among them, T_ACPout is the intercooler heat medium inlet temperature; The heat transfer capacity of the intercooler Q_CACtran is: Q_CACtran= 1*Qmax_CAC, Among them, Qmax_CAC is the theoretical maximum heat exchange capacity of the intercooler, 1 is the intercooler effectiveness; Qmax_CAC=Cmin1*(T_CAC_high -T_turbout), Among them, Cmin1 is the heat capacity of the intercooler refrigerant and heat medium with the lowest heat capacity, that is: Cmin1=min[cp_CAClow*M_CAClow,M0*cp_air] Among them, cp_CAClow is the mixed gas heat capacity of the intercooler refrigerant, M_CAClow is the total mass flow rate of the intercooler refrigerant, and the formula is: M_CAClow= n_H2Og_CAClow *18+Mx; Then the mixed gas heat capacity cp_CAClow of the intercooler refrigerant is: cp_CAClow=n_H2Og_CAClow / (n_H2Og_CAClow + Mx / 29)*cp_H2Og+Mx / 29 / (n_H2Og_CAClow + Mx / 29)*cp_air; Intercooler effectiveness The calculation formula for 1 is: 1=(1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1)))), Among them, NTU1 is a dimensionless number, Cr1 is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet of the refrigerant and the hot medium on both sides of the intercooler, that is: Cr1=Cmin1 / Cmax1, Among them, Cmax1 is the heat capacity of the intercooler refrigerant and heat medium with the highest heat capacity, that is: Cmax1= max[cp_CAClow*M_CAClow, M0*cp_air]; NTU1=U1*A1 / Cmin1, Among them, U1 is the heat transfer coefficient of the intercooler, A1 is the heat transfer area, and both U1 and A1 are known quantities; The total heat exchange capacity of the intercooler Q_CAC is: Q_CAC=Q_CAClat+Q_CACtran; The heat medium outlet temperature of the intercooler, that is, the gas temperature Tx at the dry side inlet of the humidifier is: Tx=T_ACPout-Q_CAC / (cp_air*M0); Further: Tx=T_ACPout-[(n_H2Ol_turbout+n_H2Ol_add)*18*cp_lat+ (1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1))))* Cmin1*(T_CAC_high-T_turbout)] / (cp_air*M0); The only unknown quantity can be calculated: the molar flow rate of liquid water n_H2Ol_add diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler; The total molar flow rate of water produced by the stack reaction n_H2O_pd is: n_H2O_pd=I0 / 96485 / 2*N_stk; The molar flow rate of liquid water flowing out of the liquid outlet of the water separator n_H2Ol_sep is: n_H2Ol_sep=n_H2O_pd-Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin); Then the molar flow rate of water discharged through the drain valve n_H2Ol_valve is: n_H2Ol_valve=n_H2Ol_sep-n_H2Ol_add; The pressure difference dP_valve on both sides of the drain valve is: dP_valve=P_turbin-Pam, Wherein, Pam is the ambient atmospheric pressure; Then the drain valve opening α_valve is: α_valve=F4(dP_valve,n_H2Ol_valve), Among them, F4(*) is the functional relationship between the drain valve opening and the drain valve inlet and outlet pressure difference and liquid water flow rate, which is the performance characteristic of the drain valve itself.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) In the fuel cell cathode energy recovery system provided by the present invention, the turbine end outlet is connected to the refrigerant inlet of the intercooler, so that the intercooler performs air-to-air heat exchange and cools the heat medium entering the intercooler (i.e., the air entering the system), thereby simplifying the design of the cooling system in the prior art, reducing the heat dissipation of the system, thereby reducing costs and improving the overall system efficiency; (2) In the fuel cell cathode energy recovery system provided by the present invention, the liquid outlet of the water separator is connected to the refrigerant inlet of the intercooler, and a second flow regulating component is provided between the liquid outlet of the water separator and the refrigerant inlet of the intercooler, and the second flow regulating component is used to regulate the refrigerant flow entering the intercooler to control the air temperature entering the fuel cell stack; (3) In the fuel cell cathode energy recovery system provided by the present invention, a first flow regulating component is provided between the cathode outlet of the fuel cell stack and the wet side inlet of the humidifier, and the first flow regulating component is used to regulate the flow rate of humid air entering the humidifier to control the humidity of the air entering the fuel cell stack; (4) The control method provided by the present invention calculates the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier, and then calculates the bypass valve opening and the drain valve opening, and controls the bypass valve and the drain valve according to the bypass valve opening and the drain valve opening, thereby achieving adjustable control of the gas temperature and humidity at the cathode inlet of the fuel cell stack, which can cope with more severe environmental conditions, improve the overall performance and reliability of the fuel cell stack, extend its service life, and improve the robustness of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic structural diagram of a fuel cell cathode energy recovery system according to an embodiment of the present invention; Figure 2 It is a flow chart of a control method of a fuel cell cathode energy recovery system in an embodiment of the present invention.

[0019] The markings in the figure are: 1. Air filter; 2. Turbo compressor; 201. Compressor end; 202. Turbine end; 3. Intercooler; 301. Heat medium inlet; 302. Heat medium outlet; 303. Refrigerant inlet; 304. Refrigerant outlet; 4. Humidifier; 401. Dry side inlet; 402. Dry side outlet; 403. Wet side inlet; 404. Wet side outlet; 5. Fuel cell stack; 501. Cathode inlet; 502. Cathode outlet; 6. Bypass valve; 7. Drain valve; 8. Water distributor; 801. Liquid outlet; 802. Gas outlet; 9. Second tail exhaust pipe; 10. First air outlet pipe; 11. Second air outlet pipe; 12. First tail exhaust pipe; 13. First water distribution pipe; 14. Second water distribution pipe. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0021] Example 1

[0022] like Figure 1 As shown, this embodiment provides a fuel cell cathode energy recovery system, including an air filter 1, a turbo compressor 2, an intercooler 3, a humidifier 4, a water separator 8 and a fuel cell stack 5, wherein the turbo compressor 2 includes a compressor end 201 and a turbine end 202 connected to each other.

[0023] The inlet of the air filter 1 is connected to the atmosphere, the outlet of the air filter 1 is connected to the inlet of the compressor end 201, the outlet of the compressor end 201 is connected to the heat medium inlet 301 of the intercooler 3, the heat medium outlet 302 of the intercooler 3 is connected to the dry side inlet 401 of the humidifier 4, the dry side outlet 402 of the humidifier 4 is connected to the cathode inlet 501 of the fuel cell stack 5, the cathode outlet 502 of the fuel cell stack 5 is connected to the wet side inlet 403 of the humidifier 4, the wet side outlet 404 of the humidifier 4 is connected to the inlet of the water separator 8, the liquid outlet 801 of the water separator 8 is connected to the refrigerant inlet 303 of the intercooler 3, the gas outlet 802 of the water separator 8 is connected to the inlet of the turbine end 202, the outlet of the turbine end 202 is connected to the refrigerant inlet 303 of the intercooler 3, and the refrigerant outlet 304 of the intercooler 3 is connected to the second tail exhaust pipe 9. The air is filtered by the air filter 1 and enters the intercooler 3. After cooling in the intercooler 3, the air enters the humidifier 4 for humidification, and then enters the stack 5 through the cathode inlet 501 to participate in the reaction. The gas-liquid mixture after the reaction is discharged from the cathode outlet 502, enters the wet side of the humidifier 4 to humidify the air entering the stack, and then enters the water separator 8 for gas-liquid separation. The gas enters the turbine end 202 from the gas outlet 802 of the water separator 8, and the turbine end 202 recovers energy from it. The gas temperature is reduced and passed into the intercooler 3 for use as a refrigerant. At the same time, the liquid separated by the water separator 8 also enters the intercooler 3 from the liquid outlet 801 of the water separator 8 as a refrigerant to cool the air entering the stack. The system design is simple, which reduces the heat dissipation of the system, thereby reducing costs and improving the overall system efficiency.

[0024] A first flow regulating component is provided between the cathode outlet 502 of the stack 5 and the wet side inlet of the humidifier 4, and the first flow regulating component is used to regulate the flow of humid air entering the humidifier 4 to control the humidity of the air entering the stack 5. Specifically, the first flow regulating component includes a first air outlet pipe 10, a second air outlet pipe 11, and a bypass valve 6 provided on the second air outlet pipe 11, which are respectively connected to the cathode outlet 502 of the stack 5. The first air outlet pipe 10 is connected to the wet side inlet 403 of the humidifier 4, and the second air outlet pipe 11 is connected to the first tail exhaust pipe 12. That is, by controlling the bypass valve 6, the flow of humid air entering the wet side inlet 403 of the humidifier 4 can be adjusted, thereby controlling the transmembrane water transmission amount in the humidifier 4, and achieving the effect of controlling the air humidity of the cathode inlet 501 of the stack 5.

[0025] A second flow regulating component is provided between the liquid outlet 801 of the water distributor 8 and the refrigerant inlet 303 of the intercooler 3, and the second flow regulating component is used to regulate the refrigerant flow entering the intercooler 3 to control the air temperature entering the fuel cell stack 5. Specifically, the second flow regulating component includes a first water distribution pipe 13 and a second water distribution pipe 14 respectively connected to the liquid outlet 801 of the water distributor 8, and a drain valve 7 provided on the first water distribution pipe 13, the first water distribution pipe 13 is connected to the first tail pipe 12, and the second water distribution pipe 14 is connected to the refrigerant inlet 303 of the intercooler 3. That is, by controlling the drain valve 7, the amount of liquid water flowing from the liquid outlet 801 of the water distributor 8 to the refrigerant inlet 303 of the intercooler 3 can be regulated, thereby controlling the temperature of the heat medium outlet 302 of the intercooler 3, so as to achieve the effect of controlling the air temperature of the cathode inlet 501 of the fuel cell stack 5.

[0026] An air flow sensor is provided at the inlet of the compressor end 201 for detecting the air flow entering the system (i.e., entering the cathode inlet 501 of the fuel cell stack); a first temperature sensor is provided at the outlet of the compressor end 202 for detecting the temperature of the outlet of the compressor end 202 and the heat medium inlet 303 of the intercooler; a second temperature sensor and a pressure sensor are provided at the cathode inlet 501 of the fuel cell stack 5 for detecting the temperature and pressure of the cathode inlet 501 of the fuel cell stack; a third temperature sensor is provided at the cathode outlet 502 of the fuel cell stack 5 for detecting the temperature of the cathode outlet 502 of the fuel cell stack; a fourth temperature sensor is provided at the inlet of the turbine end 202 for detecting the temperature of the inlet of the turbine end 202.

[0027] Example 2

[0028] like Figure 2 As shown, this embodiment provides a control method for the fuel cell cathode energy recovery system described in Embodiment 1, and the steps are as follows: Step 1: Obtain the stack current and the required flow rate, required pressure, required temperature and required humidity of the stack air.

[0029] The stack current I0 can be obtained according to the fuel cell power request, and the required flow rate M0, required pressure P0, required temperature T0 and required relative humidity RH0 of the stack air (the air entering the cathode inlet of the stack) at this time are determined through the stack operating condition table.

[0030] Step 2: Taking the required flow rate and required pressure of the air entering the reactor as the control target, the speed of the turbo compressor and the opening of the turbine blades are adjusted by feedforward and closed-loop.

[0031] Specifically, the feedforward control of the turbo compressor speed N_ACP and the opening degree Duty_turb of the turbine blade is determined by the stack current I0 and the system experimental calibration results, and N_ACP and Duty_turb are regulated with M0 and P0 as closed-loop targets. During the closed-loop regulation process, the real-time air flow and pressure at the cathode inlet of the stack are measured by the air flow sensor set at the compressor end inlet and the pressure sensor set at the cathode inlet of the stack.

[0032] Step 3: Calculate the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier based on the stack current, the required temperature and humidity of the air entering the stack, the cathode outlet temperature, the speed of the turbine compressor and the opening of the turbine blades.

[0033] The steps of the method for calculating the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier are as follows: Step 3.1: Calculation of relevant parameters.

[0034] The saturated vapor pressure P0_sat at the cathode inlet of the stack is calculated as: P0_sat=0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0))), Wherein, T0 is the required temperature of the air entering the pile, and the unit of P0_sat is kPa; The water vapor partial pressure P0_H20g at the cathode inlet of the stack is: P0_H20g=P0_sat*RH0, Among them, RH0 is the required humidity of the air entering the pile, and the unit of P0_H20g is kPa; The molar flow rate of dry air at the cathode inlet of the stack, n0_air, is: n0_air=M0 / 29, Wherein, M0 is the required flow rate of air entering the reactor, and the unit of n0_air is mol / s; The molar flow rate of water vapor n0_H2Og at the cathode inlet of the stack is: n0_H2Og=P0_H2O_g / (P0-P0_H2Og)*n0_air, Where P0 is the required pressure of air entering the reactor, and the unit of n0_H2Og is mol / s; Then the total gas volume flow rate qv_stk at the cathode inlet of the stack is: qv_stk=(n0_air+n0_H2Og)*22.4 / 1000*(T0+273.15) / 273.15*101.325 / P0, Among them, the unit of qv_stk is m 3 / s; The stack resistance characteristics are known, and the stack resistance dP_stk is: dP_stk=R0(qv_stk), Among them, R0(*) is the functional relationship between the stack flow resistance and the volume flow rate, which is an inherent characteristic of the stack; The pressure P_stkout at the cathode outlet of the stack is: P_stkout = P0 - dP_stk; The molar flow rate dn0 of dry air consumed by the stack is: dn0=I0 / 96485 / 4*N_stk, Where, I0 is the stack current, N_stk is the number of stack cells; The dry air flow rate n_air_stkout at the cathode outlet of the stack is: n_air_stkout = n0_air - dn0; The gas at the cathode outlet of the stack is saturated water vapor, so the water vapor partial pressure P_stkout_H2Og is equal to the saturated vapor pressure, and the calculation formula is as follows: P_stkout_H2Og=0.61121*exp((18.678-T_stkout / 234.5)*( T_stkout / (257.14+T_stkout))), Wherein, T_stkout is the cathode outlet temperature of the stack, which is affected by the water temperature. After the water temperature is stable, the temperature changes very little. T_stkout is measured by the third temperature sensor provided at the cathode outlet of the stack. Then the molar flow ratio of water vapor to dry air at the cathode outlet of the stack is: r_out= P_stkout_H2Og / (P_stkout-P_stkout_H2Og).

[0035] Step 3.2: Calculate the flow rate at the wet side inlet of the humidifier.

[0036] The water transfer rate (WRR) of a humidifier is an inherent characteristic of the humidifier, which reflects the ability of the humidifier to recover water vapor from the wet side. The formula is: WRR=dn_H2O / n_H20g_wetin, Among them, dn_H2O is the molar rate of water transfer in the humidifier, and n_H2Og_wetin is the molar flow rate of water vapor at the wet measurement inlet of the humidifier; Because n_H2Og_wetin= Mx / 29*r_out, where Mx is the flow rate at the wet side inlet of the humidifier; Therefore, dn_H2O=WRR*Mx / 29*r_out; The required humidity RH0 of the air entering the pile is expressed as: RH0=dn_H2O*(M0 / 29+dn_H2O)*P0 / P0_sat=WRR*Mx / 29*r_out*(M0 / 29+dn_H2O)*P0 / (0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0)))), The only unknown quantity can be calculated using the above formula: the flow rate Mx at the wet side inlet of the humidifier.

[0037] Step 3.3: Calculate the gas temperature Tx at the dry side inlet of the humidifier. The humidifier is used as a heat exchanger and the NTU effectiveness method is adopted.

[0038] The heat exchange capacity of the humidifier Q_HUM is: Q_HUM= *Qmax_HUM, in, is the effectiveness of the humidifier, Qmax_HUM is the theoretical maximum heat exchange capacity of the humidifier; Qmax_HUM=Cmin*(T_hot_in-Tx), Among them, T_hot_in is the wet side inlet temperature of the humidifier, which is equivalent to the cathode outlet temperature of the stack T_stkout, that is: Qmax_HUM=Cmin*(T_stkout-Tx), Among them, Cmin is the smaller of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmin=min[cp_HUM_wetin*M_wetin, cp_air*M0], Among them, cp_HUM_wetin is the constant pressure specific heat capacity of the mixed gas at the wet side inlet of the humidifier, M_wetin is the total mass flow rate of the wet measurement inlet of the humidifier, and cp_air is the heat capacity of the air; The total mass flow rate M_wetin at the wet measurement inlet of the humidifier is: M_wetin=Mx+Mx / 29*r_out*18; The heat capacity of the mixed gas at the wet measurement inlet of the humidifier, cp_HUM_wet, is: cp_HUM_wet=r_out / (r_out+1)*cp_H2Og+1 / (r_out+1)*cp_air, Where cp_H2Og is the heat capacity of water vapor; Therefore: Qmax_HUM= min[cp_HUM_wetin*M_wetin, cp_air*M0]*(T_stkout-Tx); Effectiveness for: =(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))), Among them, Cr is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet on both sides of the humidifier, and NTU is a dimensionless number; Cr=Cmin / Cmax, Among them, Cmax is the larger of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmax= max[cp_HUM_wetin*M_wetin, cp_air*M0]; NTU=U*A / Cmin, Among them, U is the heat transfer coefficient, which is the inherent parameter of humidifier heat transfer, A is the heat transfer area, and U and A are known quantities; Therefore, the heat exchange Q_HUM of the humidifier is expressed as: Q_HUM=min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)*(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))); The dry side outlet temperature of the humidifier, that is, the required temperature T0 of the air entering the pile is: T0=Tx+Q_HUM / (cp_air*M0); Right now: T0=Tx+min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)*(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))) / (cp_air*M0), The only unknown quantity can be calculated by the above formula: the gas temperature Tx at the dry side inlet of the humidifier.

[0039] Step 4: Calculate the bypass flow at the cathode outlet according to the flow at the wet side inlet of the humidifier, and calculate the bypass valve opening according to the bypass flow. The specific steps are as follows: The molar flow rate of dry air at the cathode outlet of the stack is n_air_stkout, the molar flow rate of water vapor at the cathode outlet of the stack is r_out*n_air_stkout, the molar flow rate of dry air at the wet side inlet of the humidifier is Mx / 29, and the molar flow rate of water vapor at the wet side inlet of the humidifier is Mx / 29*r_out. The molar flow rate n0_bypass that needs to be bypassed by the bypass valve is: n0_bypass=n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29); The volume flow rate qv_bypass required to bypass the bypass valve is: qv_bypass=(n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29))*22.4 / 1000*101.325 / P_stkout*(273.15+T_stkout) / 273.15; When the cathode outlet of the stack is at atmospheric pressure, the volume flow of the bypass valve is related to the opening and inlet pressure, so the bypass valve opening α_bypass is: α_bypass=F1(qv_bypass,P_stkout), Among them, F1(*) is the functional relationship between the bypass valve opening and the volume flow rate and cathode outlet pressure, and is the performance characteristic of the bypass valve component itself.

[0040] Step 5: Calculate the liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler according to the bypass flow rate and the gas temperature at the dry side inlet of the humidifier, and calculate the drain valve opening according to the liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler. The specific steps are as follows: The wet side inlet temperature of the humidifier is the cathode outlet temperature of the stack T_stkout, the wet side inlet pressure of the humidifier is the cathode outlet pressure of the stack P_stkout, the total molar flow rate of the wet side inlet of the humidifier is Mx / 29*(1+r_out), and the volume flow rate qv_wetin of the wet side inlet of the humidifier is: qv_wetin=Mx / 29*(1+r_out)*22.4 / 1000*101.325 / P_stkout*(T_stkout+273.15) / 273.15; According to the wet flow resistance characteristics of the humidifier: dP_HUMwet=R_HW(qv_wetin), Among them, dP_HUMwet is the wet side flow resistance of the humidifier, R_HW(*) is the functional relationship between the wet side flow resistance of the humidifier and the volume flow rate, which is the inherent characteristic of the humidifier; The pressure P_sepin at the humidifier wet test outlet, i.e. the water separator inlet, is: P_sepin=P_stkout-dP_HUMwet; Since the water separator inlet is saturated water vapor, the water vapor partial pressure P_H2Og_sepin is: P_H2Og_sepin=0.61121*exp((18.678-T_turbin / 234.5)*(T_turbin / (257.14+T_turbin))), Wherein, T_turbin is the water separator inlet temperature, i.e., the turbine end inlet temperature, which is measured by the fourth temperature sensor provided at the turbine end inlet; The molar flow rate of dry air at the water separator inlet is still Mx / 29, so the total molar flow rate n_sepin at the water separator inlet is: n_sepin=Mx / 29 *(1+P_H2Og_sepin / (P_sepin-P_H2Og_sepin)); Then the volume flow rate qv_sepin at the water distributor inlet is: qv_sepin=n_sepin*22.4 / 1000*101.325 / P_sepin*(T_turbin+273.15) / 273.15; According to the flow resistance characteristics of the water distributor: dP_sep=R_sep(qv_sepin), Among them, dP_sep is the flow resistance of the water divider, R_sep(*) is the functional relationship between the flow resistance of the water divider and the volume flow rate, which is the inherent characteristic of the water divider; The turbine inlet pressure P_turbin is: P_turbin = P_sepin - dP_sep; The mass flow rate M_turbin at the turbine inlet is: M_turbin=Mx+Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)*18; The expansion ratio ER at the turbine end is: ER=F2(P_turbin, T_turbin, M_turbin, N_ACP), Among them, F2(*) is the corresponding functional relationship between the turbine expansion ratio and the inlet temperature, pressure, flow rate, and speed. It is the performance characteristic of the turbine itself and is determined by the turbine performance map. N_ACP is the turbine end speed. Then the turbine outlet pressure P_turbout is: P_turbout=P_turbin / ER The turbine outlet gas temperature T_turbout is: T_turbout=F3(P_turbin,T_turbin,M_turbin,N_ACP), Among them, F3(*) is the corresponding functional relationship between the turbine outlet temperature and the turbine inlet pressure, temperature, flow rate and speed, which is determined by the turbine performance and efficiency map; Since the gas temperature at the turbine outlet is low, the water vapor must be in a saturated state, so the partial pressure of water vapor at the turbine outlet P_H2Og_turbout is: P_H2Og_turbout=0.61121*exp((18.678-T_turbout / 234.5)*(T_turbout / (257.14+T_turbout))); Then the molar flow ratio of water vapor to dry air at the turbine outlet r_turbout is: r_turbout=P_H2Og_turbout / (P_turbout- P_H2Og_turbout); The molar flow rate of gaseous water at the turbine outlet n_H2Og_turbout is: n_H2Og_turbout=Mx / 29*r_turbout; The liquid water flow rate n_H2Ol_turbout at the turbine outlet is: n_H2Ol_turbout=Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)-n_H2Og_turbout; The molar flow rate of liquid water at the refrigerant inlet of the intercooler n_H2Ol_CAClowin is: n_H2Ol_CAClowin=n_H2Ol_turbout+n_H2Ol_add, Among them, n_H2Ol_add is the molar flow rate of liquid water diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler.

[0041] In the intercooler heat exchange, the refrigerant side first evaporates the heat, and then the NTU effectiveness method is adopted.

[0042] The latent heat transfer capacity of the intercooler Q_CAClat is: Q_CAClat= n_H2Ol_CAClowin*18*cp_lat, Where cp_lat is the latent heat per gram of liquid water, which is 2.265 kJ / g; The molar flow rate of water vapor at the outlet of the intercooler refrigerant n_H2Og_CAClow is: n_H2Og_CAClow= n_H2Ol_CAClowin+ n_H2Og_turbout; Then the intercooler heat medium outlet temperature T_CAC_high becomes: T_CAC_high=T_ACPout-Q_CAClat / (M0*cp_air), Wherein, T_ACPout is the heat medium inlet temperature of the intercooler, that is, the compressor outlet temperature, which is measured by a first temperature sensor provided at the compressor outlet.

[0043] NTU validity method.

[0044] The heat transfer capacity of the intercooler Q_CACtran is: Q_CACtran= 1*Qmax_CAC, Among them, Qmax_CAC is the theoretical maximum heat exchange capacity of the intercooler, 1 is the intercooler effectiveness; Qmax_CAC=Cmin1*(T_CAC_high -T_turbout), Among them, Cmin1 is the heat capacity of the intercooler refrigerant and heat medium with the lowest heat capacity, that is: Cmin1=min[cp_CAClow*M_CAClow,M0*cp_air] Among them, cp_CAClow is the mixed gas heat capacity of the intercooler refrigerant, M_CAClow is the total mass flow rate of the intercooler refrigerant, and the formula is: M_CAClow= n_H2Og_CAClow *18+Mx; Then the mixed gas heat capacity cp_CAClow of the intercooler refrigerant is: cp_CAClow=n_H2Og_CAClow / (n_H2Og_CAClow + Mx / 29)*cp_H2Og+Mx / 29 / (n_H2Og_CAClow + Mx / 29)*cp_air; Intercooler effectiveness The calculation formula for 1 is: 1=(1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1)))), Among them, NTU1 is a dimensionless number, Cr1 is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet of the refrigerant and the hot medium on both sides of the intercooler, that is: Cr1=Cmin1 / Cmax1, Among them, Cmax1 is the heat capacity of the intercooler refrigerant and heat medium with the highest heat capacity, that is: Cmax1= max[cp_CAClow*M_CAClow, M0*cp_air]; NTU1=U1*A1 / Cmin1, Among them, U1 is the heat transfer coefficient of the intercooler, which is the inherent parameter of the intercooler heat transfer, A1 is the heat transfer area, and both U1 and A1 are known quantities; The total heat exchange capacity of the intercooler Q_CAC is: Q_CAC=Q_CAClat+Q_CACtran; The heat medium outlet temperature of the intercooler, that is, the gas temperature Tx at the dry side inlet of the humidifier is: Tx=T_ACPout-Q_CAC / (cp_air*M0); Further: Tx=T_ACPout-[(n_H2Ol_turbout+n_H2Ol_add)*18*cp_lat+ (1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1))))* Cmin1*(T_CAC_high-T_turbout)] / (cp_air*M0); The only unknown quantity can be calculated: the molar flow rate of liquid water n_H2Ol_add diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler; The total molar flow rate of water produced by the stack reaction n_H2O_pd is: n_H2O_pd=I0 / 96485 / 2*N_stk; The molar flow rate of liquid water flowing out of the liquid outlet of the water separator n_H2Ol_sep is: n_H2Ol_sep=n_H2O_pd-Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin); Then the molar flow rate of water discharged through the drain valve n_H2Ol_valve is: n_H2Ol_valve=n_H2Ol_sep-n_H2Ol_add; The pressure difference dP_valve on both sides of the drain valve is: dP_valve=P_turbin-Pam, Wherein, Pam is the ambient atmospheric pressure; Then the drain valve opening α_valve is: α_valve=F4(dP_valve,n_H2Ol_valve), Among them, F4(*) is the functional relationship between the drain valve opening and the drain valve inlet and outlet pressure difference and liquid water flow rate, which is the performance characteristic of the drain valve itself.

[0045] Step 6: Control the bypass valve and the drain valve according to the bypass valve opening and the drain valve opening.

[0046] Step 7: After the system is stable for 5 seconds, if the speed of the turbo compressor and the opening of the turbine blades change from the speed of the turbo compressor and the opening of the turbine blades after the initial closed-loop adjustment within the preset value range (no more than 1%), the control is completed; if the speed of the turbo compressor and the opening of the turbine blades change from the speed of the turbo compressor and the opening of the turbine blades after the initial closed-loop adjustment not within the preset value range (more than 1%), update the speed of the turbo compressor and the opening of the turbine blades, and repeat the above calculation process (steps 3 to 7) until the speed of the turbo compressor and the opening of the turbine blades change within the preset value range (no more than 1%), and the control is completed.

[0047] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0048] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0049] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0050] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fuel cell cathode energy recovery system, characterized in that: It includes a turbo compressor, an intercooler, a humidifier, a water separator and a fuel cell stack, wherein the turbo compressor includes a compressor end and a turbine end connected to each other; The compressed air end outlet is connected to the heat medium inlet of the intercooler, the heat medium outlet of the intercooler is connected to the dry side inlet of the humidifier, the dry side outlet of the humidifier is connected to the cathode inlet of the fuel cell stack, the cathode outlet of the fuel cell stack is connected to the wet side inlet of the humidifier, the wet side outlet of the humidifier is connected to the inlet of the water separator, the liquid outlet of the water separator is connected to the refrigerant inlet of the intercooler, the gas outlet of the water separator is connected to the turbine end inlet, and the turbine end outlet is connected to the refrigerant inlet of the intercooler; A first flow regulating component is provided between the cathode outlet of the fuel cell stack and the wet side inlet of the humidifier, and the first flow regulating component is used to regulate the flow of humid air entering the humidifier to control the humidity of air entering the fuel cell stack; A second flow regulating component is provided between the liquid outlet of the water separator and the refrigerant inlet of the intercooler, and the second flow regulating component is used to regulate the refrigerant flow entering the intercooler to control the temperature of the air entering the fuel cell stack.

2. The fuel cell cathode energy recovery system according to claim 1, characterized in that: The first flow regulating component includes a first air outlet pipe, a second air outlet pipe and a bypass valve arranged on the second air outlet pipe respectively connected to the cathode outlet of the fuel cell stack, the first air outlet pipe is connected to the wet side inlet of the humidifier, and the second air outlet pipe is connected to the first tail exhaust pipe.

3. The fuel cell cathode energy recovery system according to claim 2, characterized in that: The second flow regulating assembly includes a first water distribution pipe and a second water distribution pipe respectively connected to the liquid outlet of the water distributor, and a drain valve arranged on the first water distribution pipe, the first water distribution pipe is connected to the first tail drain pipe, and the second water distribution pipe is connected to the refrigerant inlet of the intercooler.

4. The fuel cell cathode energy recovery system according to claim 3, characterized in that: An air flow sensor is provided at the compressor end inlet, a first temperature sensor is provided at the compressor end outlet, a second temperature sensor and a pressure sensor are provided at the cathode inlet of the fuel cell stack, a third temperature sensor is provided at the cathode outlet of the fuel cell stack, and a fourth temperature sensor is provided at the turbine end inlet.

5. The fuel cell cathode energy recovery system according to claim 3, characterized in that: It also includes an air filter, the outlet of which is connected to the air compression end inlet.

6. The fuel cell cathode energy recovery system according to claim 3, characterized in that: The refrigerant outlet of the intercooler is connected with a second tail exhaust pipe.

7. A control method for a fuel cell cathode energy recovery system according to any one of claims 3 to 6, characterized in that: include: Obtain the stack current and the required flow rate, required pressure, required temperature and required humidity of the air entering the stack; Taking the required flow rate and required pressure of the air entering the reactor as the control target, the speed of the turbo compressor and the opening of the turbine blades are adjusted by feedforward and closed loop; Calculate the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier based on the stack current, the required temperature and humidity of the air entering the stack, the cathode outlet temperature, the speed of the turbo compressor and the opening of the turbine blades; The bypass flow at the cathode outlet is calculated according to the flow at the wet side inlet of the humidifier, and the bypass valve opening is calculated according to the bypass flow; The liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler is calculated according to the bypass flow rate and the gas temperature at the dry side inlet of the humidifier, and the drain valve opening is calculated according to the liquid water flow rate from the liquid outlet of the water manifold to the refrigerant inlet of the intercooler; Control the bypass valve and the drain valve according to the bypass valve opening and the drain valve opening; After the system stabilizes, if the speed of the turbo compressor and the opening of the turbine blades are not within the preset value range compared with the speed of the turbo compressor and the opening of the turbine blades after the initial closed-loop adjustment, the speed of the turbo compressor and the opening of the turbine blades are updated, and the above calculation process is repeated until the changes in the speed of the turbo compressor and the opening of the turbine blades are within the preset value range, and the control is completed.

8. The control method of the fuel cell cathode energy recovery system according to claim 7, characterized in that: The calculation method of the gas temperature at the dry side inlet and the flow rate at the wet side inlet of the humidifier includes: The saturated vapor pressure P0_sat at the cathode inlet of the stack is calculated as: P0_sat=0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0))), Among them, T0 is the required temperature of the air entering the pile; The water vapor partial pressure P0_H20g at the cathode inlet of the stack is: P0_H20g=P0_sat*RH0, Among them, RH0 is the required humidity of the air entering the pile; The molar flow rate of dry air at the cathode inlet of the stack, n0_air, is: n0_air=M0 / 29, Among them, M0 is the required flow rate of air entering the pile; The molar flow rate of water vapor n0_H2Og at the cathode inlet of the stack is: n0_H2Og=P0_H2O_g / (P0-P0_H2Og)*n0_air, Among them, P0 is the required pressure of air entering the pile; Then the total gas volume flow rate qv_stk at the cathode inlet of the stack is: qv_stk=(n0_air+n0_H2Og)*22.4 / 1000*(T0+273.15) / 273.15*101.325 / P0; The stack current resistance dP_stk is: dP_stk=R0(qv_stk), Among them, R0(*) is the functional relationship between the stack flow resistance and the volume flow rate, which is an inherent characteristic of the stack; The pressure P_stkout at the cathode outlet of the stack is: P_stkout = P0 - dP_stk; The molar flow rate dn0 of dry air consumed by the stack is: dn0=I0 / 96485 / 4*N_stk, Where, I0 is the stack current, N_stk is the number of stack cells; The dry air flow rate n_air_stkout at the cathode outlet of the stack is: n_air_stkout = n0_air - dn0; The gas at the cathode outlet of the stack is saturated water vapor, so the water vapor partial pressure P_stkout_H2Og is equal to the saturated vapor pressure, and the calculation formula is as follows: P_stkout_H2Og=0.61121*exp((18.678-T_stkout / 234.5)*( T_stkout / (257.14+T_stkout))), Wherein, T_stkout is the cathode outlet temperature of the stack; Then the molar flow ratio of water vapor to dry air at the cathode outlet of the stack is: r_out= P_stkout_H2Og / (P_stkout-P_stkout_H2Og); The water transfer rate WRR of the humidifier is: WRR=dn_H2O / n_H20g_wetin, Among them, dn_H2O is the molar rate of water transfer in the humidifier, and n_H2Og_wetin is the molar flow rate of water vapor at the wet measurement inlet of the humidifier; Because n_H2Og_wetin= Mx / 29*r_out, where Mx is the flow rate at the wet side inlet of the humidifier; Therefore, dn_H2O=WRR*Mx / 29*r_out; The required humidity RH0 of the air entering the pile is expressed as: RH0=dn_H2O*(M0 / 29+dn_H2O)*P0 / P0_sat=WRR*Mx / 29*r_out*(M0 / 29+dn_H2O)*P0 / (0.61121*exp((18.678-T0 / 234.5)*(T0 / (257.14+T0)))), The only unknown quantity can be calculated: the flow rate Mx at the wet side inlet of the humidifier; The heat exchange capacity of the humidifier Q_HUM is: Q_HUM= *Qmax_HUM, in, is the effectiveness of the humidifier, Qmax_HUM is the theoretical maximum heat exchange capacity of the humidifier; Qmax_HUM=Cmin*(T_stkout-Tx), Where Tx is the gas temperature at the dry side inlet of the humidifier, and Cmin is the smaller of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmin=min[cp_HUM_wetin*M_wetin, cp_air*M0], Among them, cp_HUM_wetin is the constant pressure specific heat capacity of the mixed gas at the wet side inlet of the humidifier, M_wetin is the total mass flow rate of the wet measurement inlet of the humidifier, and cp_air is the heat capacity of the air; The total mass flow rate M_wetin at the wet measurement inlet of the humidifier is: M_wetin=Mx+Mx / 29*r_out*18; The heat capacity of the mixed gas at the wet measurement inlet of the humidifier, cp_HUM_wet, is: cp_HUM_wet=r_out / (r_out+1)*cp_H2Og+1 / (r_out+1)*cp_air, Where cp_H2Og is the heat capacity of water vapor; Therefore: Qmax_HUM= min[cp_HUM_wetin*M_wetin, cp_air*M0]*(T_stkout-Tx); Effectiveness for: =(1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))), Among them, Cr is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet on both sides of the humidifier, and NTU is a dimensionless number; Cr=Cmin / Cmax, Among them, Cmax is the larger of the total heat capacity of the dry side inlet and the wet side inlet of the humidifier, that is: Cmax= max[cp_HUM_wetin*M_wetin, cp_air*M0]; NTU=U*A / Cmin, Among them, U is the heat transfer coefficient, A is the heat transfer area, and U and A are known quantities; Therefore, the heat exchange Q_HUM of the humidifier is expressed as: Q_HUM=min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)* (1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))); The dry side outlet temperature of the humidifier, that is, the required temperature T0 of the air entering the pile is: T0=Tx+Q_HUM / (cp_air*M0); Right now: T0=Tx+min[cp_HUM_wetin*(Mx+Mx / 29*r_out*18),cp_air*M0]*(T_stkout-Tx)* (1-exp(-NTU*(1-Cr))) / (1-(Cr*exp(-NTU*(1-Cr)))) / (cp_air*M0), The only unknown quantity can be calculated: the gas temperature Tx at the dry side inlet of the humidifier.

9. The control method of the fuel cell cathode energy recovery system according to claim 8, characterized in that: The calculation method of the bypass valve opening includes: The molar flow rate of dry air at the cathode outlet of the stack is n_air_stkout, the molar flow rate of water vapor at the cathode outlet of the stack is r_out*n_air_stkout, the molar flow rate of dry air at the wet side inlet of the humidifier is Mx / 29, and the molar flow rate of water vapor at the wet side inlet of the humidifier is Mx / 29*r_out. The molar flow rate n0_bypass that needs to be bypassed by the bypass valve is: n0_bypass=n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29); The volume flow rate qv_bypass required to bypass the bypass valve is: qv_bypass=(n_air_stkout*(1+r_out)-Mx(1 / 29-r_out / 29))*22.4 / 1000*101.325 / P_stkout*(273.15+T_stkout) / 273.15; When the cathode outlet of the stack is at atmospheric pressure, the volume flow of the bypass valve is related to the opening and inlet pressure, so the bypass valve opening α_bypass is: α_bypass=F1(qv_bypass,P_stkout), Among them, F1(*) is the functional relationship between the bypass valve opening and the volume flow rate and cathode outlet pressure, and is the performance characteristic of the bypass valve component itself.

10. The control method of the fuel cell cathode energy recovery system according to claim 9, characterized in that: The method for calculating the drain valve opening includes: The volume flow rate qv_wetin at the wet side inlet of the humidifier is: qv_wetin=Mx / 29*(1+r_out)*22.4 / 1000*101.325 / P_stkout*(T_stkout+273.15) / 273.15; According to the wet flow resistance characteristics of the humidifier: dP_HUMwet=R_HW(qv_wetin), Among them, dP_HUMwet is the wet side flow resistance of the humidifier, R_HW(*) is the functional relationship between the wet side flow resistance of the humidifier and the volume flow rate, which is the inherent characteristic of the humidifier; The pressure P_sepin at the humidifier wet test outlet, i.e. the water separator inlet, is: P_sepin=P_stkout-dP_HUMwet; Since the water separator inlet is saturated water vapor, the water vapor partial pressure P_H2Og_sepin is: P_H2Og_sepin=0.61121*exp((18.678-T_turbin / 234.5)*(T_turbin / (257.14+T_turbin))), Among them, T_turbin is the water separator inlet temperature; The molar flow rate of dry air at the water separator inlet is still Mx / 29, so the total molar flow rate n_sepin at the water separator inlet is: n_sepin=Mx / 29 *(1+P_H2Og_sepin / (P_sepin-P_H2Og_sepin)); Then the volume flow rate qv_sepin at the water distributor inlet is: qv_sepin=n_sepin*22.4 / 1000*101.325 / P_sepin*(T_turbin+273.15) / 273.15; According to the flow resistance characteristics of the water distributor: dP_sep=R_sep(qv_sepin), Among them, dP_sep is the flow resistance of the water divider, R_sep(*) is the functional relationship between the flow resistance of the water divider and the volume flow rate, which is the inherent characteristic of the water divider; The turbine inlet pressure P_turbin is: P_turbin = P_sepin - dP_sep; The mass flow rate M_turbin at the turbine inlet is: M_turbin=Mx+Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)*18; The expansion ratio ER at the turbine end is: ER=F2(P_turbin, T_turbin, M_turbin, N_ACP), Among them, F2(*) is the corresponding functional relationship between the turbine expansion ratio and the inlet temperature, pressure, flow rate, and speed, which is the performance characteristic of the turbine itself, and N_ACP is the turbine end speed; Then the turbine outlet pressure P_turbout is: P_turbout=P_turbin / ER The turbine outlet gas temperature T_turbout is: T_turbout=F3(P_turbin,T_turbin,M_turbin,N_ACP), Among them, F3(*) is the corresponding functional relationship between the turbine outlet temperature and the turbine inlet pressure, temperature, flow rate and speed; Since the gas temperature at the turbine outlet is low, the water vapor must be in a saturated state, so the partial pressure of water vapor at the turbine outlet P_H2Og_turbout is: P_H2Og_turbout=0.61121*exp((18.678-T_turbout / 234.5)*(T_turbout / (257.14+T_turbout))); Then the molar flow ratio of water vapor to dry air at the turbine outlet r_turbout is: r_turbout=P_H2Og_turbout / (P_turbout- P_H2Og_turbout); The molar flow rate of gaseous water at the turbine outlet n_H2Og_turbout is: n_H2Og_turbout=Mx / 29*r_turbout; The liquid water flow rate n_H2Ol_turbout at the turbine outlet is: n_H2Ol_turbout=Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin)-n_H2Og_turbout; The molar flow rate of liquid water at the refrigerant inlet of the intercooler n_H2Ol_CAClowin is: n_H2Ol_CAClowin=n_H2Ol_turbout+n_H2Ol_add, Wherein, n_H2Ol_add is the molar flow rate of liquid water diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler; The latent heat transfer capacity of the intercooler Q_CAClat is: Q_CAClat= n_H2Ol_CAClowin*18*cp_lat, Where cp_lat is the latent heat per gram of liquid water, which is 2.265 kJ / g; The molar flow rate of water vapor at the outlet of the intercooler refrigerant n_H2Og_CAClow is: n_H2Og_CAClow= n_H2Ol_CAClowin+ n_H2Og_turbout; Then the intercooler heat medium outlet temperature T_CAC_high becomes: T_CAC_high=T_ACPout-Q_CAClat / (M0*cp_air), Among them, T_ACPout is the intercooler heat medium inlet temperature; The heat transfer capacity of the intercooler Q_CACtran is: Q_CACtran= 1*Qmax_CAC, Among them, Qmax_CAC is the theoretical maximum heat exchange capacity of the intercooler, 1 is the intercooler effectiveness; Qmax_CAC=Cmin1*(T_CAC_high -T_turbout), Among them, Cmin1 is the heat capacity of the intercooler refrigerant and heat medium with the lowest heat capacity, that is: Cmin1=min[cp_CAClow*M_CAClow,M0*cp_air] Among them, cp_CAClow is the mixed gas heat capacity of the intercooler refrigerant, M_CAClow is the total mass flow rate of the intercooler refrigerant, and the formula is: M_CAClow= n_H2Og_CAClow *18+Mx; Then the mixed gas heat capacity cp_CAClow of the intercooler refrigerant is: cp_CAClow=n_H2Og_CAClow / (n_H2Og_CAClow + Mx / 29)*cp_H2Og+Mx / 29 / (n_H2Og_CAClow + Mx / 29)*cp_air; Intercooler effectiveness The calculation formula for 1 is: 1=(1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1)))), Among them, NTU1 is a dimensionless number, Cr1 is the ratio of the maximum heat capacity to the minimum heat capacity at the inlet of the refrigerant and the hot medium on both sides of the intercooler, that is: Cr1=Cmin1 / Cmax1, Among them, Cmax1 is the heat capacity of the intercooler refrigerant and heat medium with the highest heat capacity, that is: Cmax1= max[cp_CAClow*M_CAClow, M0*cp_air]; NTU1=U1*A1 / Cmin1, Among them, U1 is the heat transfer coefficient of the intercooler, A1 is the heat transfer area, and both U1 and A1 are known quantities; The total heat exchange capacity of the intercooler Q_CAC is: Q_CAC=Q_CAClat+Q_CACtran; The heat medium outlet temperature of the intercooler, that is, the gas temperature Tx at the dry side inlet of the humidifier is: Tx=T_ACPout-Q_CAC / (cp_air*M0); Further: Tx=T_ACPout-[(n_H2Ol_turbout+n_H2Ol_add)*18*cp_lat+ (1-exp(-NTU1*(1-Cr1))) / (1-(Cr1*exp(-NTU1*(1-Cr1))))* Cmin1*(T_CAC_high-T_turbout)] / (cp_air*M0); The only unknown quantity can be calculated: the molar flow rate of liquid water n_H2Ol_add diverted from the liquid outlet of the water distributor to the refrigerant inlet of the intercooler; The total molar flow rate of water produced by the stack reaction n_H2O_pd is: n_H2O_pd=I0 / 96485 / 2*N_stk; The molar flow rate of liquid water flowing out of the liquid outlet of the water separator n_H2Ol_sep is: n_H2Ol_sep=n_H2O_pd-Mx / 29*P_H2Og_sepin / (P_sepin-P_H2Og_sepin); Then the molar flow rate of water discharged through the drain valve n_H2Ol_valve is: n_H2Ol_valve=n_H2Ol_sep-n_H2Ol_add; The pressure difference dP_valve on both sides of the drain valve is: dP_valve=P_turbin-Pam, Wherein, Pam is the ambient atmospheric pressure; Then the drain valve opening α_valve is: α_valve=F4(dP_valve,n_H2Ol_valve), Among them, F4(*) is the functional relationship between the drain valve opening and the drain valve inlet and outlet pressure difference and liquid water flow rate, which is the performance characteristic of the drain valve itself.

Images