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Bletchley · 7 January 2010, 06:46 AM

Although Ricardo did not identify his 'reference fuels' by name, only by identification letter, in the published report of his investigations into the properties of the various fuels supplied to him, most of them are readily identifiable by their chemical composition and distillation curves, and from close comparison with the features of named fuels in other contemporary sources. The four lightest of these reference fuels can be identified as the standard WWI aviation fuels - Shell "Sumatra" (C), Shell "Light Borneo" (B), German "Flugbenzin" (E) and US "X" or Export Grade (F). There are also reference fuels that appear to match the published descriptions for Shell 'Super' Borneo (A), Shell 'Heavy' Borneo (H), and a straight run Borneo (D), with a probable but unidentifiable motor gasoline (G) included for purposes of comparison.

Sumatra (C) is listed with a specific gravity of 0.727: 61% paraffins, 8.5% aromatics, 30.5% naphthenes and a 'highest useful compression ratio' of 5.25:1. Distillation curve: 11.5% by 80 deg. C; 47% by 100 deg. C; 79% by 120 deg. C; 92% by 140 deg. C; 98.5% by 160 deg. C. A straight run distillation, the relatively high aromatic content ensured that it would have supported the highest compression ratio used by the Allies (5.3:1) without fear of detonation, but no higher. This was the dominant aviation fuel used by both the British and the French, at least up to early 1918 when the French, in particular, started to supplement this with US "X" grade 'Export' and 'Fighter' grade fuels.

Light Borneo (B) is listed with a specific gravity of 0.723: 62% paraffins, 14.9% aromatics, 23% naphthenes and a 'highest useful compression ratio' of 5.7:1. The distillation curve identifies it as a close-cut fraction: 4% by 60 deg. C; 37.5% by 80 deg. C; 79% by 100 deg. C; 99% by 120 deg. C. Available, apparently, in only relatively small quantities (as compared to the more abundant Sumatra), the very high aromatic content meant that it provided slightly less power (about 1% or 2% less), probably due to a slightly lower calorific value, than Sumatra (above) in all engines with a compression ratio of 5.3:1 or less. It appears to have therefore been regarded as a 'second-grade' aviation fuel, although with a much higher aromatic content it could have been used to support a significantly higher compression aero engine without risk of detonation.

US "X" Grade (F) is listed with a specific gravity of 0.704: 80% Paraffins, 4.3% aromatics, 15.2% naphthenes and a 'highest useful compression ratio' of 5.05:1. Distillation range: 1% by 60 deg. C; 27% by 80 deg. C; 65% by 100 deg. C; 86.5% by 120 deg. C; 94.5 by 140 deg. C (final at 153 deg. C). This paraffinic, very light gasoline is characteristic of the standard US "X" grade 'Export' and 'Fighting' gasolines that were derived mostly from Pennsylvania crude, complying with Specification no.3512 (Export) or no.3513 (Fighting) of the Bureau of Aircraft Production for export aviation gasoline used by the French and the AEF in 1918. The exact chemical composition of this straight run US "X" grade aviation gasoline varied somewhat, depending on the source of the crude oil and distillation, with the 'Fighting' grade being very slightly lighter and having a slightly narrower range of distillation but otherwise being very similar to that of the 'Export' in terms of performance. Tests run by the US Bureau of Standards indicated that, in an engine with a compression ratio of 5.3:1, the US "X" grade aviation gasolines were slightly inferior in their power output to the Shell 'Sumatra', but slightly better than Shell 'Light Borneo' (but only by a difference of 1% or 2%, either way). This can probably be accounted for by the tendency of the US fuels (with a HUCR of just over 5:1) to mild detonation in the highest compression (5.3:1) aero engines then in use by the French and British.

Of the remaining 'reference' fuels detailed by Ricardo, 'H' is a very close match for the 'Heavy' Borneo described by L.J. Simon in the French comparative analysis of Allied and German fuels quoted in NACA Report no.47 Part II. This appears to be a close cut distillation of Borneo crude from Kalimantan, specific gravity 0.767: 10-28% paraffins, 2%-4% aromatics, 70%-85% naphthenes and a 'highest useful compression ratio' of 5.9:1. Distillation range: 7% by 100 deg. C; 55% by 120 deg. C; 83% by 140 deg. C; 94% by 160 deg. C (final at 176 deg. C). This may have been the sample that was tested by Ricardo in 1917, and is probably the heavy, very naphthenic gasoline fraction of the .Borneo crude remaining after the toluene content had been extracted by the Shell refinery in Portishead. From late 1917 onwards this was blended back into other Shell gasolines, although because of the high specific gravity it is very unlikely that it would have been blended back into either the 'Sumatra' or the 'Light Borneo' fractions supplied as aviation fuel. The 'reference' fuel 'A' is very close to the description of the 'Super' Borneo refined by Kewley and Ricardo in 1918, from a straight-run Kalimantan Borneo, a heavy gasoline fraction with a very high aromatic content (39%) and a 'Highest Useful Compression Ratio' of 6:1, whilst 'reference' fuel 'D' , similar but with a much lower aromatic content (14.6%) and HUCR of 5.35:1 is likely to be the straight-run Kalimantan Borneo gasoline fraction that probably forms the base for the close-cut gasolines 'A', 'B', and 'H'. The 'reference' fuel 'E' is a close match for the standard German 'Flugbenzin', and will be examined later, whilst 'reference' fuel 'G' with specific gravity of 0.750 and a 'Highest Useful Compression Ratio' of 4.55:1 is probably a commercial motor gasoline.

Bletchley

Continued:

7 January 2010, 06:46 AM	#4
Bletchley Forum Ace Join Date: Feb 2005 Location: Cowes, England Posts: 634	Although Ricardo did not identify his 'reference fuels' by name, only by identification letter, in the published report of his investigations into the properties of the various fuels supplied to him, most of them are readily identifiable by their chemical composition and distillation curves, and from close comparison with the features of named fuels in other contemporary sources. The four lightest of these reference fuels can be identified as the standard WWI aviation fuels - Shell "Sumatra" (C), Shell "Light Borneo" (B), German "Flugbenzin" (E) and US "X" or Export Grade (F). There are also reference fuels that appear to match the published descriptions for Shell 'Super' Borneo (A), Shell 'Heavy' Borneo (H), and a straight run Borneo (D), with a probable but unidentifiable motor gasoline (G) included for purposes of comparison. Sumatra (C) is listed with a specific gravity of 0.727: 61% paraffins, 8.5% aromatics, 30.5% naphthenes and a 'highest useful compression ratio' of 5.25:1. Distillation curve: 11.5% by 80 deg. C; 47% by 100 deg. C; 79% by 120 deg. C; 92% by 140 deg. C; 98.5% by 160 deg. C. A straight run distillation, the relatively high aromatic content ensured that it would have supported the highest compression ratio used by the Allies (5.3:1) without fear of detonation, but no higher. This was the dominant aviation fuel used by both the British and the French, at least up to early 1918 when the French, in particular, started to supplement this with US "X" grade 'Export' and 'Fighter' grade fuels. Light Borneo (B) is listed with a specific gravity of 0.723: 62% paraffins, 14.9% aromatics, 23% naphthenes and a 'highest useful compression ratio' of 5.7:1. The distillation curve identifies it as a close-cut fraction: 4% by 60 deg. C; 37.5% by 80 deg. C; 79% by 100 deg. C; 99% by 120 deg. C. Available, apparently, in only relatively small quantities (as compared to the more abundant Sumatra), the very high aromatic content meant that it provided slightly less power (about 1% or 2% less), probably due to a slightly lower calorific value, than Sumatra (above) in all engines with a compression ratio of 5.3:1 or less. It appears to have therefore been regarded as a 'second-grade' aviation fuel, although with a much higher aromatic content it could have been used to support a significantly higher compression aero engine without risk of detonation. US "X" Grade (F) is listed with a specific gravity of 0.704: 80% Paraffins, 4.3% aromatics, 15.2% naphthenes and a 'highest useful compression ratio' of 5.05:1. Distillation range: 1% by 60 deg. C; 27% by 80 deg. C; 65% by 100 deg. C; 86.5% by 120 deg. C; 94.5 by 140 deg. C (final at 153 deg. C). This paraffinic, very light gasoline is characteristic of the standard US "X" grade 'Export' and 'Fighting' gasolines that were derived mostly from Pennsylvania crude, complying with Specification no.3512 (Export) or no.3513 (Fighting) of the Bureau of Aircraft Production for export aviation gasoline used by the French and the AEF in 1918. The exact chemical composition of this straight run US "X" grade aviation gasoline varied somewhat, depending on the source of the crude oil and distillation, with the 'Fighting' grade being very slightly lighter and having a slightly narrower range of distillation but otherwise being very similar to that of the 'Export' in terms of performance. Tests run by the US Bureau of Standards indicated that, in an engine with a compression ratio of 5.3:1, the US "X" grade aviation gasolines were slightly inferior in their power output to the Shell 'Sumatra', but slightly better than Shell 'Light Borneo' (but only by a difference of 1% or 2%, either way). This can probably be accounted for by the tendency of the US fuels (with a HUCR of just over 5:1) to mild detonation in the highest compression (5.3:1) aero engines then in use by the French and British. Of the remaining 'reference' fuels detailed by Ricardo, 'H' is a very close match for the 'Heavy' Borneo described by L.J. Simon in the French comparative analysis of Allied and German fuels quoted in NACA Report no.47 Part II. This appears to be a close cut distillation of Borneo crude from Kalimantan, specific gravity 0.767: 10-28% paraffins, 2%-4% aromatics, 70%-85% naphthenes and a 'highest useful compression ratio' of 5.9:1. Distillation range: 7% by 100 deg. C; 55% by 120 deg. C; 83% by 140 deg. C; 94% by 160 deg. C (final at 176 deg. C). This may have been the sample that was tested by Ricardo in 1917, and is probably the heavy, very naphthenic gasoline fraction of the .Borneo crude remaining after the toluene content had been extracted by the Shell refinery in Portishead. From late 1917 onwards this was blended back into other Shell gasolines, although because of the high specific gravity it is very unlikely that it would have been blended back into either the 'Sumatra' or the 'Light Borneo' fractions supplied as aviation fuel. The 'reference' fuel 'A' is very close to the description of the 'Super' Borneo refined by Kewley and Ricardo in 1918, from a straight-run Kalimantan Borneo, a heavy gasoline fraction with a very high aromatic content (39%) and a 'Highest Useful Compression Ratio' of 6:1, whilst 'reference' fuel 'D' , similar but with a much lower aromatic content (14.6%) and HUCR of 5.35:1 is likely to be the straight-run Kalimantan Borneo gasoline fraction that probably forms the base for the close-cut gasolines 'A', 'B', and 'H'. The 'reference' fuel 'E' is a close match for the standard German 'Flugbenzin', and will be examined later, whilst 'reference' fuel 'G' with specific gravity of 0.750 and a 'Highest Useful Compression Ratio' of 4.55:1 is probably a commercial motor gasoline. Bletchley Continued: