kSIST-TP FprCEN/TR 16389:2023
(Main)Automotive fuels - Paraffinic diesel fuel and blends with FAME - Background to the parameters required and their respective limits and determination
Automotive fuels - Paraffinic diesel fuel and blends with FAME - Background to the parameters required and their respective limits and determination
This Technical Report explains the requirements and test methods for marketed and delivered paraffinic diesel from synthesis (XTL) or hydrotreatment (HVO) and of blends thereof with up to 7%(V/V) of fatty acid methyl esters (FAME) according to European fuel specifications. It provides background information to judge the final text of the European Standard EN 15940 and gives guidance and explanations to the producers, blenders, marketers and users of paraffinic automotive diesel.
Paraffinic diesel is a high quality, clean burning fuel with virtually no sulfur and aromatics. Paraffinic diesel fuel can be used in diesel engines, also to reduce regulated emissions. In order to have the greatest possible emissions reduction, a specific calibration may be necessary. Paraffinic diesel fuel can also offer a meaningful contribution to the target of increased non-crude derived and/or renewable content in transportation fuel pool.
For general diesel engine warranty, paraffinic automotive diesel fuel may need a validation step to confirm the compatibility of the fuel with the vehicle, which for some existing engines may still need to be done. The vehicle manufacturer needs to be consulted before use.
NOTE 1 This document is directly related to the development of EN 15940 and will be updated once further publications take place.
NOTE 2 Paraffinic diesel is also used as a blending component in automotive diesel fuel. In that case, composition and properties of the final blends are defined by relevant fuel specification standards.
NOTE 3 For the purposes of this document, the term "% (m/m)" and "% (V/V)" are used to represent the mass fraction, µ, and the volume fraction, φ, respectively.
Kraftstoff für Kraftfahrzeuge - Paraffinischer Dieselkraftstoff und Kraftstoff-Mischungen - Hintergrund zu den erforderlichen Parametern, den entsprechenden Grenzwerten und deren Bestimmung
This document explains the requirements and test methods for paraffinic diesel fuel from synthesis or hydrotreatment. Synthesis refers to XTL processes where X refers to various feedstocks for example Gas (G), Biomass (B) or Coal (C) and TL stands for To-Liquid. Hydrotreatment of vegetable oils and animal fats yield Hydrotreated Vegetable Oil (HVO). Paraffinic diesel fuel can be blended with up to 7,0 % (V/V) fatty acid methyl ester (FAME). It provides background information to the final text of EN 15940 [1] and gives guidance and explanations to the producers, blenders, marketers and users of paraffinic automotive diesel.
Paraffinic diesel fuel is a high quality, clean burning fuel with virtually no sulfur and aromatics. Paraffinic diesel fuel can be used in diesel engines, also to reduce regulated emissions. In order to have the greatest possible emissions reduction, a specific calibration is needed. Some types of paraffinic diesel fuel, at present notably HVO, can also offer a meaningful contribution to the target of increased non-crude derived and/or renewable content in transportation fuel pool.
For general diesel engine operation, durability and warranty, paraffinic automotive diesel fuel needs a validation step to confirm the compatibility of the fuel with the vehicle, which for some existing engines still needs to be done. The vehicle manufacturer needs to be consulted before use.
NOTE 1 This document is directly related to EN 15940 and will be updated once further publications take place.
NOTE 2 Paraffinic diesel fuel is also used as a blending component in automotive diesel fuel. In that case, composition and properties of the final blends are defined by relevant fuel specification standards.
NOTE 3 For the purposes of this document, the terms "% (m/m)" and "% (V/V)" are used to represent respectively the mass fraction and the volume fraction.
Carburants pour automobiles - Gazole paraffinique et mélanges d'EMAG - Historique sur la définition des paramètres requis, de leurs limites et de leurs déterminations respectives
Goriva za motorna vozila - Parafinsko dizelsko gorivo in mešanice s FAME - Ozadje zahtevanih parametrov, njihove omejitve ter določevanje
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 16389:2023
01-julij-2023
Goriva za motorna vozila - Parafinsko dizelsko gorivo in mešanice s FAME -
Ozadje zahtevanih parametrov, njihove omejitve ter določevanje
Automotive fuels - Paraffinic diesel fuel and blends with FAME - Background to the
parameters required and their respective limits and determination
Kraftstoff für Kraftfahrzeuge - Paraffinischer Dieselkraftstoff und Kraftstoff-Mischungen -
Hintergrund zu den erforderlichen Parametern, den entsprechenden Grenzwerten und
deren Bestimmung
Carburants pour automobiles - Gazole paraffinique et mélanges d'EMAG - Historique sur
la définition des paramètres requis, de leurs limites et de leurs déterminations
respectives
Ta slovenski standard je istoveten z: FprCEN/TR 16389
ICS:
75.160.20 Tekoča goriva Liquid fuels
kSIST-TP FprCEN/TR 16389:2023 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TP FprCEN/TR 16389:2023
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 16389
RAPPORT TECHNIQUE
TECHNISCHER REPORT
May 2023
ICS 75.160.20 Will supersede CEN/TR 16389:2017
English Version
Automotive fuels - Paraffinic diesel fuel and blends with
FAME - Background to the parameters required and their
respective limits and determination
Carburants pour automobiles - Gazole paraffinique et Kraftstoff für Kraftfahrzeuge - Paraffinischer
mélanges d'EMAG - Historique sur la définition des Dieselkraftstoff und Kraftstoff-Mischungen -
paramètres requis, de leurs limites et de leurs Hintergrund zu den erforderlichen Parametern, den
déterminations respectives entsprechenden Grenzwerten und deren Bestimmung
This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC 19.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2023 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 16389:2023 E
worldwide for CEN national Members.
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Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 EN 15940, Automotive fuels - Paraffinic diesel fuel from synthesis or hydrotreatment -
Requirements and test methods. . 4
4.1 Parameters included . 4
4.2 Considerations on the parameters . 8
4.2.1 Cetane number . 8
4.2.2 Density . 9
4.2.3 Flash point . 11
4.2.4 Viscosity . 11
4.2.5 Distillation characteristics . 14
4.2.6 Lubricity . 16
4.2.7 Total aromatics content . 18
4.2.8 Sulfur content . 21
4.2.9 Contamination . 21
4.2.10 Copper strip corrosion . 23
4.2.11 Oxidation stability . 24
4.2.12 Biodegradability . 24
4.2.13 FAME . 25
4.2.14 Legislation of Sweden . 25
4.2.15 Climate dependence . 26
4.2.16 Additives . 26
4.2.17 Sampling . 27
4.2.18 Pump marking . 27
4.2.19 Housekeeping guidance . 27
4.2.20 Methylcyclopentadienyl manganese tricarbonyl (MMT) . 27
4.2.21 Heating applications . 27
4.3 Parameters considered and not included in the specification . 27
4.3.1 Poly-cyclic aromatic hydrocarbon and olefin content . 27
4.3.2 Elastomer compatibility . 27
5 Acknowledgement . 28
Annex A (informative) SL-BOCLE Lubricity of EN 15940 paraffinic fuels: Summary of Round
Robin test results . 29
Annex B (informative) A meta-analysis of HFRR precision studies . 34
Annex C (informative) Paraffinic diesel fuel Round Robin tests (cetane number) . 38
Annex D (informative) Aromatic Round Robin tests . 43
Annex E (informative) Oxidation stability round robin tests . 45
Annex F (informative) Cloud point and CFPP round robin tests . 46
Bibliography . 48
2
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European foreword
This document (FprCEN/TR 16389:2023) has been prepared by Technical Committee CEN/TC 19
“Gaseous and liquid fuels, lubricants and related products of petroleum, synthetic and biological origin”,
the secretariat of which is held by NEN.
This document is currently submitted to the Vote on TR.
This document will supersede CEN/TR 16389:2017.
The third version of this Technical Report has been updated after the revision of EN 15940:2023. In this
update, several improvements have been made, historical views of task force meetings have been deleted
and the properties of paraffinic diesels are explained in more detail:
— Subclause 4.2.12 on biodegradability was added;
— The requirement in EN 15940 allowing blending of diesel is explained, including subclause 4.2.14
with an additional explanation of the Swedish legislation;
— Subclause 4.2.21 on heating applications was added;
— All available round robin information was included as separate Annexes;
— The information of the latest research was reviewed and updated;
— Summary of the history of XTL-HVO task force was deleted;
— Historical record of the work to date was deleted.
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1 Scope
This document explains the requirements and test methods for paraffinic diesel fuel from synthesis or
hydrotreatment. Synthesis refers to XTL processes where X refers to various feedstocks for example Gas
(G), Biomass (B) or Coal (C) and TL stands for To-Liquid. Hydrotreatment of vegetable oils and animal
fats yield Hydrotreated Vegetable Oil (HVO). Paraffinic diesel fuel can be blended with up to 7,0 % (V/V)
fatty acid methyl ester (FAME). It provides background information to the final text of EN 15940 [1] and
gives guidance and explanations to the producers, blenders, marketers and users of paraffinic automotive
diesel.
Paraffinic diesel fuel is a high quality, clean burning fuel with virtually no sulfur and aromatics. Paraffinic
diesel fuel can be used in diesel engines, also to reduce regulated emissions. In order to have the greatest
possible emissions reduction, a specific calibration is needed. Some types of paraffinic diesel fuel, at
present notably HVO, can also offer a meaningful contribution to the target of increased non-crude
derived and/or renewable content in transportation fuel pool.
For general diesel engine operation, durability and warranty, paraffinic automotive diesel fuel needs a
validation step to confirm the compatibility of the fuel with the vehicle, which for some existing engines
still needs to be done. The vehicle manufacturer needs to be consulted before use.
NOTE 1 This document is directly related to EN 15940 and will be updated once further publications take place.
NOTE 2 Paraffinic diesel fuel is also used as a blending component in automotive diesel fuel. In that case,
composition and properties of the final blends are defined by relevant fuel specification standards.
NOTE 3 For the purposes of this document, the terms “% (m/m)” and “% (V/V)” are used to represent
respectively the mass fraction and the volume fraction.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— IEC Electropedia: available at https://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp/
4 EN 15940, Automotive fuels - Paraffinic diesel fuel from synthesis or
hydrotreatment - Requirements and test methods
4.1 Parameters included
This document gives further detailed information about requirements and parameters as defined in
EN 15940.
All parameters discussed in this document are based on the paraffinic nature of XTL and HVO and the use
of FAME complying with EN 14214 [2] as a blending component. The test methods precisions are
presented in Table 1.
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Table 1 — Precision of the methods to paraffinic diesel fuel and conventional diesel
Property Unit Test method Paraffinic diesel fuel EN 590 [3] Precision
Precision
Cetane number EN ISO 5165 [4] Average cetane number Repeatability Reproducibility
a
level
(R = 0,125*CN - 2,2)
40 0,8 2,8
44 0,9 3,3
48 0,9 3,8
52 0,9 4,3
56 1,0 4,8
EN 15195 [5] r=0,01380 X
R=0,04682 X
EN 16906 [6] r = 1,474 2 + 0,004 3 X
R = −1,054 2+ 0,069 2 X
EN 17155 [7] r = 0,002 931(ICN)1.47
R = 0,006407 (ICN)1.47
3 3
Density at 15 °C EN ISO 3675 [8]
kg/m r= 0,5 kg/m
3
R=1,2 kg/m
3
EN ISO 12185
r=0,2 kg/m
[9]
3
R=0,5 kg/m
Flash point °C EN ISO 2719 r=0,029 X
[10]
R=0,071X
2
Viscosity at EN ISO 3104 Repeatability
mm /s
40 °C [11]
0,0043 * (X + 1)
Reproducibility
0,0082 * (X + 1)
ISO 23581 [12] r = 0,01 05 – 0,000 3 X
R = 0,034 6 + 0,005 X
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Property Unit Test method Paraffinic diesel fuel EN 590 [3] Precision
Precision
Distillation °C or EN ISO 3405 Percentage evaporated Repeatability °C Reproducibility °C
% recovered [13]
IPB 3,3 5,6
5 r1+0,66 R1+1,11
10 r1 R1
20 r1 R1
30 to 70 r1 R1
80 r1 R1
90 r1 R1-1,22
95 r1 R1-0,94
FBP 3,9 7,2
Each of the variables r1
and R1 is a constant
function of the slope,
ΔC/ΔV, at each
distillation point in
question, with values
calculated from: r1 =
0,864 (ΔC/ΔV) + 1,214;
R1 = 1,736 (ΔC/ΔV) +
1,994.
EN ISO 3924 Percent recovered Repeatability °C Reproducibility °C
[14]
b b
IBP
0,011 x 0,066x
5 %
0,0032(x+100) 0,015 (x+100)
10 % to 40 %
0,8 0,013 (x+100)
50 % to 90 %
1,0 4,3
95%
1,2 5,0
FBP
3,2 11,8
EN 17306 [15] Repeatability Reproducibility Valid range
IBP r = 3,9 R = 6,0 145 °C – 195 °C
T5 r = T * 0,011 94 R= T * 0,017 2 175 °C – 250 °C
T10 r = T * 0,009 54 R = T * 0,017 7 160 °C – 265 °C
T20 r = T * 0,009 32 R = T * 0,011 7 180 °C – 275 °C
T30 r = T * 0,007 82 R = T * 0,012 2 190 °C – 285 °C
T40 r = T * 0,008 22 R = T * 0,012 2 200 °C – 290 °C
T50 r = T * 0,006 14 R = T * 0,010 3 170 °C – 295 °C
T60 r = T * 0,005 34 R = T * 0,009 2 220 °C – 305 °C
T70 r = T * 0,004 05 R = T * 0,008 4 230 °C – 315 °C
T80 r = T * 0,004 41 R = T * 0,008 4 240 °C – 325 °C
T90 r = T * 0,004 1 R = T * 0,008 1 180 °C – 340 °C
T95 r = 2,03 R = 3,23 260 °C – 360 °C
FBP r = 3,93 R = 7,7 195 °C – 365 °C
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Property Unit Test method Paraffinic diesel fuel EN 590 [3] Precision
Precision
Method A (camera)
Lubricity, µm EN ISO 12156-1
corrected wear [16]
r= 50µm
scar diameter
R=80 µm
(wsd 1,4) at
Method B (visual)
60 °C
r=70 µm
R=90 µm
FAME content % (V/V) EN 14078 [17] Overall repeatability is between 0,1 – 0,5 %
Overall reproducibility is between 0,5 – 1,5 %
Total aromatics
% (m/m) EN 12916 [18] range 0,2 to 2,0 wt % range 7 to 42 wt %
content
total aromatic r=0,0391x + 0,00722 r=0,040 X -0,070
R=0,1713X + 0,3469 R=0,172 X – 1,094
Sulfur content mg/kg EN ISO 20846 range 3 to 60 mg/kg
[19]
r = 0,0553 X + 0,55
R=0,1120X + 1,12
EN ISO 20884 range 5 to 60 mg/kg
[20]
r=1,7 + 0,0248X
R= 1,9 + 0,1201x
2/3
Carbon residue EN ISO 10370
% (m/m)
r=0,077∗X
(on 10 % [21]
2/3
R=0,2451∗X
distillation
residue)
Ash content % (m/m) EN ISO 6245 Ash content r R
[22]
0,001-0,079 0,003 0,005
0,08-0,180 0,007 0,024
range 0,003 % (m/m) to 0,100 %
Water content mg/kg EN ISO 12937
0,5
[23]
r=0,01874 x
0,5
R=0,06877 X
r=0,0644X +1,6099
Total mg/kg EN 12662 [24]
contamination
R=0,1644 X + 4,1110
Copper strip rating EN ISO 2160 no generally acceptable method for determining precision
corrosion [25]
(3 h at 50 °C)
3
0,25
Oxidation g/m EN ISO 12205
r=5,4x(X/10)
stability [26]
0,25
R = 10,6x(X/10)
where C is total insoluble matter:
Insoluble matter (C), Repeatability (r) Reproducibility (R)
3
g/m
1 3,0 6,0
5 4,5 8,9
10 5,4 10,6
15 6,0 11,7
20 6,4 12,6
25 6,8 13,3
30 7,1 14,0
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Property Unit Test method Paraffinic diesel fuel EN 590 [3] Precision
Precision
h EN 15751 [27] r = 0,22027 + 0,04344X
R = 0,37269 + 0,19038X
where X represents the average of the two results in minutes
min EN 16091 [28] r = 0,0288X + 0,4965
R = 0,0863X + 1,3772
where X represents the average of the two results in minutes
CFPP °C EN 116 [29] r = 1,7282 - 0,017X r = 1,2-0,027X
R = 2,0677 - 0,0291X R = 3,0-0,060X
EN 16329 [30] r = 0,9863 - 0,0401X r = 3
R = 0,949 - 0,2231X R = 7
Cloud point °C EN ISO 3015 r = 1,4339 - 0,0071X
[31]
R = 3,9585 + 0,0661X
where X is the mean of two results being compared
Manual method: r and R reported for distilled oils:
r = 2
R = 4
EN ISO 22995 r= 1,1 °C
[32]
R= 2,5 °C
Manganese mg/kg EN 16576 [33] r = 0,035 2 X + 0,0290
content
R = 0,1147 X + 0,0944
where X represents the mean of the two results expressed in mg/l
a
Values for CNs intermediate to those listed above can be obtained by linear interpolation.
b
Where X is the average of the two results in degrees Celsius.
4.2 Considerations on the parameters
4.2.1 Cetane number
The cetane number is a measure of the compression ignition behaviour of a fuel. It influences cold
startability, exhaust emissions and combustion noise. The cetane number is measured on a test engine or
a Derived Cetane Number (DCN) is determined from a correlation with ignition delay as measured in a
constant volume combustion chamber. The cetane number reflects the combination of the natural self-
ignition properties and the effects of cetane improver additives.
The choice of two different classes originates from the differences between the processes which results
in different chemical composition. The processes are the low-temperature and high-temperature Fischer-
Tropsch (LTFT and HTFT) and Hydrogenated Vegetable Oils (HVO). Because a higher cetane number is
an advantage for some applications, the specific distinction between automotive diesel complying with
EN 590 class (minimum cetane of 51) and a high-cetane fuel (minimum 70) has been incorporated in
EN 15940.
GTL and HVO are highly paraffinic. LTFT GTL and HVO consist of linear and branched paraffins and have
very high cetane numbers in excess of 70. Generally, a high cetane number leads to a reduction in white
smoke, noise, engine misfire, emissions and improved cold starting in some engines, especially in engines
without pilot injection. HTFT GTL will in general be produced with a cetane between 52 and 65, as this
paraffinic fuel also contains significant quantities of cyclo-paraffins. In earlier discussions, a maximum
cetane number would be desirable by the OEMs, but it was not introduced in the standard. It is difficult
to adjust the production process to limit high cetane number in paraffinic fuels.
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The OEMs wished to have a certain band in order to tune the engine where possible. The original band
was 55 to 70. Because 55 was really borderline for the HTFT producers, the minimum was lowered to 51
and the maximum to 66 in order to preserve the band width. With this decision it left a four-point gap
(66 to 70), so it was decided to delete maximum on class B. There are two classes Class A with minimum
cetane number 70 and Class B with minimum cetane number 51 either of classes do not have maximum
limit for cetane number.
For a European Standard, all referenced test methods need to be applicable to paraffinic fuels and have
valid precision statements.
EN 15940 referenced four different test methods for cetane number test methods; EN ISO 5165 (CRF
engine) [4], EN 15195 (IQT) [5], EN 16906 (BASF engine) [6] and EN 17155 (ICN) [7].
EN ISO 5165 is the method using the CFR cetane engine and EN 16906 is the method using the BASF
engine. EN 15195 is derived cetane by combustion in a constant volume chamber and, specifically using
the Ignition Quality Tester or IQT apparatus, EN 15195 directly measures the ignition delay under
prescribed conditions from which a derived cetane number (DCN) is calculated from a correlation to
cetane number. EN 17155 is a test method for the quantitative determination of the indicated cetane
number (ICN) intended for use in compression ignition engines.
All four cetane number methods cover conventional and paraffinic diesel fuels.
CEN/TC 19 decided that EN 15195 is the method to be used in cases of dispute due to the significantly
better precision of EN 15195 over the other methods at the higher cetane numbers. This was agreed to
even though this is a derived test method and not a direct measurement in an engine.
During the update process of EN 15940 in 2022 it was agreed to remove subclause 5.6.3 and Annex A
(precision statement), because EN 15195 was also under an update process and it was agreed that an
optional equation in the annex was removed in 2023 [34].
Cetane index is a calculated value that approximates the ‘natural’ cetane of a fuel. Cetane index is linked
to arctic climate requirements of automotive diesel fuel. However, the cetane index as it stands now,
cannot be applied to paraffinic diesel fuels since XTL and HVO fuels were not part of the database
underpinning the empirical correlation. Cetane index has not been incorporated in EN 15940.
4.2.2 Density
Generally, paraffins have a lower density than aromatic hydrocarbons and consequently, the density of
3 3
highly paraffinic XTL/HVO diesel is lower than that of conventional diesel (765 kg/m to 810 kg/m
3 3
compared to 820 kg/m to 845 kg/m for petroleum diesel fuels). The presence of aromatics in
conventional diesel results in a higher density fuel.
The diesel fuel injection is controlled volumetrically or by timing of the solenoid valve. Variations in fuel
density (and viscosity) result in variations in engine power and, consequently, in engine emissions and
fuel consumption. Therefore, in order to optimize engine performance and tailpipe emissions, OEMs
prefers both minimum and maximum density limits to be defined in a fairly narrow range. Moreover, the
(volumetric) injection quantity is a control parameter for other emission control systems like the exhaust
gas recirculation (EGR). Variations in fuel density therefore result in non-optimal EGR-rates for a given
load and speed point in the engine map and, as a consequence, influence the exhaust emission
characteristics.
Engine and vehicle manufacturers prefer a narrow range of density for good driveability not exceeding
3
40 kg/m . For durability, a minimum density limit, and for optimized exhaust emission characteristics, a
maximum density limit, is important. Diesel fuel categories 3, 4 and 5 of the WWFC 2019 which are
defined for markets with more stringent emission requirements restrict the density range from
3 3 3
815 kg/m to 840 kg/m , with the option to relax the lower density limit to 800 kg/m for fuel used under
low temperature conditions (cloud point below -10 °C).
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The impact of the lower density of paraffinic fuels on the gravimetric injection amount depends on the
injection principle. For passenger cars, many injectors are designed according to the servo principle with
a full ballistic behaviour. In such applications, the gravimetric injection amount is only marginally
reduced despite density of paraffinic fuels is 6 % to 7 % lower. For energising times up to 1 000 µsec, i.e.
before the lift stop of the nozzle needle is reached, lower density affects fuel flow through the injector
orifices and results in a faster and slightly stronger lift of the nozzle needle (Bernoulli equation).
Consequently, the distance that the needle needs to travel for closing is increased. For a given injection
timing, changed needle opening and closing behaviour allows a slightly higher volume of fuel to be
injected. Under ballistic operating conditions, the increased volumetric injection amount is inversely
proportional to fuel density. For paraffinic fuels, the volume injected is approximately increased by 6 %
to 7 %, fairly compensating for the lower density and thus corresponding to a gravimetric injection
amount of ±1 % compared to standard diesel fuel. Considering the higher inferior heating value of
paraffinic fuels (around 44,1 MJ/kg compared to 42,9 MJ/kg for standard diesel) the same gravimetric
injection amount results in an approx. 2,8 % higher engine power for paraffinic fuels under part load
conditions (see Figure 1).
In the non-ballistic operating area of diesel injectors, typically above injection timings of 1 000 µsec, the
increase of the volumetric injection amount is smaller and does usually not exceed 3 %, thus not fully
compensating for the lower density of paraffinic fuels. Such conditions are more typical of full power
operation, as might be found on heavy duty vehicle applications. The higher injected volume compensates
for approximately half of the density related loss in fuel energy only. Considering again the higher inferior
heating value of paraffinic fuels, the injected energy is only slightly reduced and engine performance
remains largely unchanged. Older mechanical fuel injection system designs are frequently volume (piston
stroke) metered, so will lose gravimetric injection quantity in proportion to density.
a) b)
c) d)
Key
solid line conventional diesel fuel EN 590
dotted line paraffinic diesel fuel EN 15940
Figure 1 — Volumetric (1a) and gravimetric (1b) injection quantity at different pressure levels
(p1 to p3) as a function of the energising time, volumetric (1c) and gravimetric injection rate
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kSIST-TP FprCEN/TR 16389:2023
FprCEN/TR 16389:2023 (E)
(1d) at maximum pressure (p3), presented by the example of the Bosch passenger car injector
CRI2.25
The Task Force investigated the effect of temperature on density, based on work done by the PTB
(Physical Technical Institute) Braunschweig, Germany. The work is summarized in Annex B of
EN 15940:2023.
4.2.3 Flash point
Flash point of a diesel fuel is defined as the lowest temperature at which fuel vapours above the liquid
will ignite upon exposure to an ignition source. It is used to classify fuels for transport and storage
according to hazard level; minimum flash point temperatures are (legally) required for proper safety and
handling of the fuel. Flash point varies inversely with the fuel’s volatility.
Flashpoint is a legal requirement for diesel grade fuels. As the flash point of a diesel fuel is associated with
the light (lower boiling) material, a diesel fuel with too much light material (shorter carbon chain length
molecules) will have a low flash point and it will be hazardous to handle.
Generally, the flash point of neat FAME (soya, rapeseed and palm) fuels is higher than that of paraffinic
diesel and conventional crude-derived diesel fuels.
The flash point in EN 15940 has been defined as “Above 55 °C” as in EN 590. Most of the paraffinic diesel
1
fuels have a flashpoint above 60 °C and as such are not required to be labelled as flammable . The higher
flashpoint allows for the use of such fuels in marine applications. More data is given in the chapter on IBP
and cavitation.
4.2.4 Viscosity
Viscosity is a measure of a fuel’s resistance to flow and affects the performance of diesel fuel pumps and
injection systems. Low viscosity also has an influence on sliding by changing hydrodynamic contacts, e.g.
bearings of camshafts, rollers, etc. Also, mixed contacts, e.g. piston in cylinder, can be adversely affected.
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