SAE J2601:2020 Abbreviations & Symbols 04

4.1 Abbreviations

APRR Average Pressure Ramp Rate (MPa/min)

CD Cold Dispenser

CHSS Compressed Hydrogen Storage System

FC Fueling Command

FCEV Fuel Cell Electric Vehicle

H2 Hydrogen

HSTA Hydrogen Station Test Apparatus

HSV Hydrogen Surface Vehicle

ID Protocol Identifier

IrDA Infrared Data Association

MAWP Maximum Allowable Working Pressure

MOP Maximum Operating Pressure

MP Measured Pressure

MT CHSS Measured Temperature

NIST National Institute of Standards and Technology

NWP Nominal Working Pressure

OD Optional Data

PRV Pressure Relief Valve

RT Receptacle Type

SOC State of Charge

TV Tank Volume

VN Version Number

4.2 Symbols

4.2.1 Table-Based Protocol Symbols

APRR_actual Interpolated value of the average pressure ramp rate (MPa/min) from a look-up table

APRR_target Target average pressure ramp rate (MPa/min)

APRR_sec Prescribed pressure ramp rate at the beginning of the main fueling time (MPa/s)

APRR_final APRR from fallback look-up table (based on ambient temperature and P₀)

ρ(P,T) Gas density, a function of pressure, P, and temperature, T

m_startup Mass dispensed during startup time

P₀ Initial CHSS pressure level prior to fueling

P_target Target fueling pressure

P_station Fueling pressure as measured by station

P_startup Startup pressure

P_vehicle CHSS pressure

t_fueling Main fueling time; does not include intended non-fueling time during the main fueling time

t_end Shutdown time

t_startup Startup time measured in seconds

T_vehicle CHSS temperature data received by station from vehicle during communications fueling

T_fuel Fuel delivery temperature

T_{fuel_inst} Instantaneous fuel delivery temperature

T_fuel-ave The total mass average of the fuel delivery temperature after a total of 30 seconds of mass flow during the main fueling time

T_{fuel-ave-roll} A 30 second rolling mass average of the fuel delivery temperature after a total of 30 seconds of mass flow during the main fueling time

T_amb Ambient temperature as measured by fueling station, not in direct sunlight

SOC_station SOC calculated by using Pstation and MT

SOC_vehicle SOC calculated by using Pvehicle and MT

V_CHSS Volume of the CHSS measured or otherwise determined by the station

V_{station_D} Station volume value to be set between 137 to 174 in liters (for use with CHSS Capacity Category D)

4.2.2 MC Formula-Based Protocol Symbols

a, b, c, d Coefficients utilized in the tfinal equation

AC, BC, GC, KC, JC Five constants utilized in the MC Equation

c_{v_cold} Specific heat capacity of hydrogen at constant volume

CD An optional flag variable that when TRUE, indicates that the “cold dispenser” criteria is met

CHSSC_{apacity_Category} An indicator of the CHSS Capacity Category as defined in Table 8

h The enthalpy measured at the dispenser outlet. A function of Tfuel and Pstation

h_ave The mass average of the dispenser outlet enthalpy calculated from the start of the main fueling time (i.e., from t = 0 seconds)

i A calculation time step counter, which advances every 5 seconds

Indicator Cons RR A flag variable, which when TRUE, indicates that the CHSS Capacity Category is indeterminate

j A calculation time step counter, which advances every second

m The total mass dispensed from the beginning of the main fueling time up to the current time

𝑚̇ The mass flow rate of dispensed hydrogen

m_{init_cold} The initial cold case mass in the 1 kg Type III vessel used in the MC Method ending pressure control option

m_{final_cold} The mass corresponding to 100% SOC of the 1 kg Type III vessel used in the MC Method ending pressure control option

m_add The mass of hydrogen required to be added to the cold case initial mass to achieve mfinal_cold

m_startup Mass dispensed during startup time

MAT_expected The expected mass average of the fuel delivery temperature at the end of the fill

MAT₀ The mass average of Tfuel-inst calculated from the start of the main fueling time (i.e., t = 0 seconds)

MAT₃₀ The mass average of Tfuel-inst calculated starting after a total of 30 seconds of mass flow have elapsed

MAT_C A mathematical combination of MATexpected, MAT30, and MAT0 utilized as the control input for the tfinal equation

MC_cold A parameter representing a lumped heat capacity of the cold case CHSS; used to calculate Tcold

MT The CHSS measured temperature communicated via IRDA according to SAE J2799

MP The CHSS measured pressure communicated via IRDA according to SAE J2799

n A counter which advances at the same frequency as time step counter j, but only if there is mass flow; it is utilized to determine the point in the fill at which the calculation of MAT30 commences

P_control The dispenser outlet pressure which the dispenser control targets throughout the fill

Pfinal The final pressure used in the derivation of the tfinal equation coefficients

P_initial Initial pressure of hydrogen in the CHSS as per the definition in 3.11.3

P_{limit_comm} An upper limit on pressure for communication fills to provide protection against a fault in MT

P_{limit_high} The upper boundary of the pressure corridor which Pstation must stay within

P_{limit_low} The lower boundary of the pressure corridor which Pstation must stay within

ΔP_low An input to the equation for β; it replaces ΔPtol_low in the β equation to reduce excess margin

P_min The initial pressure used in the derivation of the 𝑡_final equation coefficients

ΔP_offset An offset pressure added to Pramp to determine the control pressure Pcontrol

P_ramp The pressure upon which the PRR is based; used to define P_{limit_high}, P_{limit_low}, and Pcontrol

P_station Fueling pressure as measured by station at the dispenser outlet

P_startup Startup pressure

P_{target_non_comm} The target end of fill pressure for non-communication fills

P_{target_comm} The target end of fill pressure for communication fills

ΔP_{tol_high} A delta pressure added to Pramp to define Plimit_high; also used in calculating β

ΔP_{tol_low} A delta pressure subtracted from Pramp to define Plimit_low; also used in calculating β

P_trans A parameter which determines the weighting of MAT₀ and MAT₃₀ in the MATC equation

PRR Pressure ramp rate; this represents the rate of change of Pramp (MPa/s)

PRR_CAP A cap on the PRR to limit the maximum flow rate and to prevent α from becoming too large

PRR_{CAP_Factor} A factor utilized in the equation to calculate PRRCAP which determines the magnitude of PRRCAP

RR_max The maximum calculated pressure ramp rate throughout the fill

RR_min The minimum calculated pressure ramp rate throughout the fill

SOC_target The end of fill target SOC, used in calculating Ptarget_comm; expressed in percentage

t Fueling time, representing the total time elapsed since the initiation of the main fueling time, including the time elapsed during intended non-fueling events

t_final The time required to fill from Pmin to Pfinal under hot case conditions; input to the PRR equation

t_{final_min} The minimum value for tfinal; tfinal_min is a function of Pmin and the CHSSCapacity_Category

t_{final_min_A} The minimum value for tfinal for the CHSSCapacity_Category A

t_{final_min_B} The minimum value for tfinal for the CHSSCapacity_Category B

t_{final_min_C} The minimum value for tfinal for the CHSSCapacity_Category C

t_{final_min_cons} The minimum value for tfinal when the CHSSCapacity_Category is indeterminate

t_{min_cold} A parameter used in MC equation representing the time elapsed after which Δtcold is calculated

t_startup Startup time measured in seconds

Δt_cold The difference between the fueling time t and tmin_cold

t_{tol_low} The time at which ΔPlow is measured to determine if Pstation is less than Pramp

T_{adiabatic_cold} The cold case adiabatic temperature used in the MC Method ending pressure control option calculations

T_amb Ambient temperature as measured by fueling station, not in direct sunlight

T_cold The MC Method ending pressure control option cold case gas temperature; used to determine Ptarget_non_comm and Plimit_comm

T_{fit_1}, T_{fit_2} Regression equations used to calculate Tinit_cold

T_fuel Fuel delivery temperature

T_{fuel_inst} Instantaneous fuel delivery temperature measured at the dispenser outlet

T_{fuel_inst_A}, T_{fuel_inst_B} Two independent measurements of the instantaneous fuel delivery temperature for redundancy

T_{init_cold} The initial gas temperature in the cold case CHSS; Tinit_cold is a function of Tamb and Pinitial

TopOff An optional flag variable that when TRUE, caps PRR at 0.33 MPa/s to reduce the pressure drop

u_{adiabatic_cold} The MC Method ending pressure control option cold case adiabatic specific internal energy

U_{adiabatic_cold} The MC Method ending pressure control option cold case adiabatic internal energy

u_{init_cold} The MC Method ending pressure control option cold case initial specific internal energy

U_{init_cold} The MC Method ending pressure control option cold case initial internal energy

V_CHSS Volume of the CHSS measured or otherwise determined by the station

V_cold The volume of the 1 kg Type III vessel used in the calculation of Tcold in the MC Method ending pressure control option

ρ_{init_cold} The MC Method ending pressure control option cold case initial density calculated based on Pinitial and Tinit_cold

α A parameter which is multiplied by tfinal to compensate for non-linearity in the PRR during the fill

β A parameter which is multiplied by tfinal to allow tolerance on pressure, i.e., the pressure corridor

SAE J 2601 constist of the follow parts :

1. Scope 

2. References

3. Definitons

4. Abbreviations and Symbols

5. General Fueling Protocol Description

6. General Process Requirements for Hydrogen Fueling

7. Key Modeling Assumptions

8. Table-Based Fueling Protocol

9. MC Formula-Based Fueling Protocol

10. Non-standard ,Development Hydrogen Fueling Protocols

11. Notes 

12. Appendix , Figure , Tables