Abbreviations, subscripts and symbols
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Statutory Documents - IMO Publications and Documents - International Codes - NOx Technical Code - Technical Code on Control of Emission of Nitrous Oxides from Marine Diesel Engines - Abbreviations, subscripts and symbols

Abbreviations, subscripts and symbols

  Tables 1,2, 3 and 4 below summarize the abbreviations, subscripts and symbols used throughout this Code, including specifications for the analytical instruments in appendix 3, calibration requirements for the analytic instruments contained in appendix 4 and the formulae for calculation of gas mass flow as contained in chapter 5 and appendix 6 of this Code.

  • .1 Table 1: symbols used to represent the chemical components of diesel engine gas emissions addressed throughout this Code;

  • .2 Table 2: abbreviations for the analysers used in the measurement of gas emissions from diesel engines, as specified in appendix 3 of this Code;

  • .3 Table 3: symbols and subscripts of terms and variables used in all formulae for the calculation of exhaust gas mass flow for the test-bed measurement methods, as specified in chapter 5 of this Code; and

  • .4 Table 4: subscripts and descriptions of terms and variables used in all formulae for the calculation of exhaust gas mass flow following the carbon-balance method, as specified in appendix 6 of this Code.

Table 1 Symbols for the Chemical components of diesel engine emissions

Symbol Chemical component Symbol Chemical component
C3H8 Propane NO Nitric oxide
CO Carbon monoxide NO2 Nitrogen dioxide
CO2 Carbon dioxide NOX Oxides of nitrogen
HC Hydrocarbons O2 Oxygen
H2O Water    

Table 2 Abbreviations for analysers in measurement of diesel engine gaseous emissions (refer to appendix 3 of this code)

Abbreviation Term
CFV Critical flow venturi
CLD Chemiluminescent detector
ECS Electrochemical sensor
FID Flame ionization detector
FTIR Fourier-transform infrared analyser
HCLD Heated chemiluminescent detector
HFID Heated flame ionization detector
NDIR Non-dispersive infrared analyser
PDP Positive-displacement pump
PMD Paramagnetic detector
UVD Ultraviolet detector
ZRDO Zirconium dioxide sensor

Table 3 Symbols and subscripts for terms and variables used in the formulae for the test-bed measurement methods (refer to chapter 5 of this code)

Symbol Term Dimension
A T Cross-sectional area of the exhaust pipe m2
C1 Carbon 1 equivalent hydrocarbon -
conc Concentration ppm or Vol%
concc Background corrected concentration ppm or Vol%
EAF Excess air factor (kg dry air per kg fuel) kg/kg
EAFRef Excess air factor (kg dry air per kg fuel) at reference conditions kg/kg
f a Laboratory atmospheric factor (applicable only to an engine family) -
F FCB Fuel-specific factor for the carbon-balance calculation -
F FD Fuel-specific factor for exhaust flow calculation on dry basis -
F FH Fuel-specific factor used for the calculations of wet concentrations from dry concentrations -
F FW Fuel-specific factor for exhaust flow calculation on wet basis -
G AIRW Intake air mass flow rate on wet basis kg/h
G AIRD Intake air mass flow rate on dry basis kg/h
G EXHW Exhaust gas mass flow rate on wet basis kg/h
G FUEL Fuel mass flow rate kg/h
GASX Average weighted NOX emission value g/kW h
H REF Reference value of absolute humidity (10.71 g/kg; for calculation of NOX and particulate humidity correction factors) g/kg
H a Absolute humidity of the intake air g/kg
HTCRAT Hydrogen-to-carbon ratio mol/mol
i Subscripts denoting an individual mode -
K HDIES Humidity correction factor for NOX for diesel engines -
K W,a Dry to wet correction factor for intake air -
K W,r Dry to wet correction factor for the raw exhaust gas -
L Percent torque related to the maximum torque for the test engine speed %
mass Emissions mass flow rate g/h
pa Saturation vapour pressure of the engine intake air (in ISO 3046-1, 1995: psy = PSY, test ambient vapour pressure) kPa
pB Total barometric pressure (in ISO 3046-1, 1995: p x= PX, site ambient total pressure ; p y= PY, test ambient total pressure) kPa
ps Dry atmospheric pressure kPa
P Power, brake-uncorrected kW
P AUX Declared total power absorbed by auxiliaries fitted for the test only, but not required on board the ship kW
P m Maximum measured or declared power at the test engine speed under test conditions kW
r Ratio of cross-sectional areas of isokinetic probe and exhaust pipe -
R a Relative humidity of the intake air %
R f FID response factor -
R fM FID response factor for methanol -
S Dynamometer setting kW
T a Absolute temperature of the intake air K
T Dd Absolute dewpoint temperature K
T SC Temperature of the intercooled air K
T ref. Reference temperature (of combustion air: 298 K) K
T SCRef Intercooled air reference temperature K
V AIRD Intake air volume flow rate on dry basis m3/h
V AIRW Intake air volume flow rate on wet basis m3/h
V EXHD Exhaust gas volume flow rate on dry basis m3/h
V EXHW Exhaust gas volume flow rate on wet basis m3/h
W F Weighting factor -

Table 4 Symbols and descriptions of terms and variables used in the formulae for the carbon balance measurement method (refer to appendix 6 of this code)

Symbol Description Dimension Remark
ALF H content of fuel %m/m  
AWC Atomic weight of C    
AWH Atomic weight of H    
AWN Atomic weight of N    
AWO Atomic weight of O    
AWS Atomic weight of S    
BET C content of fuel %m/m  
CO2D Concentration of CO2 %V/V in dry exhaust
CO2W Concentration of CO2 %V/V (wet) in wet exhaust
COD Concentration of CO ppm in dry exhaust
COW Concentration of CO ppm in wet exhaust
CW Soot mg/m3 in wet exhaust
DEL N content of fuel %m/m  
EAFCDO Excess-air factor based on the complete combustion and the CO2 concentration, l V,CO2 kg/kg  
EAFEXH Excess-air factor based on the exhaust gas concentration of carbon containing components, l V kg/kg  
EPS O content of fuel % m/m  
ETA Nitrogen content of wet combustion air % m/m  
EXHCPN Exhaust gas ratio of components with carbon, c V/V  
EXHDENS Density of wet exhaust kg/m3  
FFCB Fuel-specific factor for the carbon-balance calculation    
FFD Fuel-specific factor for exhaust flow calculation on dry basis   dry basis
FFH Fuel-specific factor used for calculation of wet concentration from dry concentration    
FFW Fuel-specific factor for exhaust flow calculation on wet basis   wet basis
GAIRD Combustion air mass flow kg/h dry combustion air
GAIRW Combustion air mass flow kg/h wet combustion air
GAM S content of fuel % m/m  
GCO Emission of CO g/h  
GCO2 Emission of CO2 g/h  
GEXHD Fuel mass flow kg/h dry exhaust
gexhw Fuel mass flow, claculated by the carbon-balance method, G EXHW kg/h  
GEXHW Fuel mass flow kg/h wet exhaust
GFUEL Fuel mass flow kg/h  
GHC Emission of HC g/h hydrocarbons
GH2O Emision of H2O g/h  
GN2 Emission of N2 g/h  
GNO Emission of NO g/h  
GNO2 Emission of NO2 g/h  
GO2 Emission of O2 g/h  
GSO2 Emission of SO2 g/h  
HCD Hydrocarbons ppm C1 in dry exhaust
HCW Hydrocarbons ppm C1 in wet exhaust
HTCRAT Hydrogen-to-carbon ratio of fuel, a mol/mol  
MV ... Molecular volume of.... 1/mol individual gas
MW ... Molecular weight of.... g/mol individual gas
NO2W Concentration of NO2 ppm in wet exhaust
NOW Concentration of NO ppm in wet exhaust
NUE Water content of combustion air % m/m  
O2D Concentration of O2 %V/V in dry exhaust
O2W Concentration of O2 %V/V(wet) in wet exhaust
STOIAR Stoichiometric air demand for the combustion of 1 kg fuel kg/kg  
TAU Oxygen content of wet combustion air % m/m wet air
TAU1 Oxygen content of wet combustion air that is emitted % m/m wet air
TAU2 Oxygen content of wet combustion air that is combusted % m/m wet air
VCO Volume flow of CO m3/h (exhaust content)
VCO2 Volume flow of CO2 m3/h (exhaust content)
VH2O Volume flow of H2O m3/h (exhaust content)
VHC Volume flow of HC m3/h (exhaust content)
VN2 Volume flow of N2 m3/h (exhaust content)
VNO Volume flow of NO m3/h (exhaust content)
VNO2 Volume flow of NO2 m3/h (exhaust content)
VO2 Volume flow of O2 m3/h (exhaust content)
VSO2 Volume flow of SO2 m3/h (exhaust content)

Note - For STANDARD m3, or STANDARD litre, the dimensions std. m3 and std. l are used. The STANDARD m3 of a gas is related to 273.15 K and 101.3 kPa

Note - Water gas equilibrium constant = 3.5


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