Fuel composition

Abstract

Use of a liquid fuel composition comprising (a) a gasoline base fuel and (b) from 0.5 to 50% v/v of naphtha as a fuel for a spark ignition internal combustion engine, wherein the spark ignition internal combustion engine is comprised within the powertrain of a hybrid electric vehicle.

Claims

1. A method of operating a spark ignition internal combustion engine wherein the spark ignition internal combustion engine is comprised within the powertrain of a hybrid electric vehicle, comprising operating the spark ignition internal combustion engine using a liquid fuel composition comprising (a) from at least 50% m/m of a gasoline base fuel and (b) from 0.5 to 50% v/v of naphtha, wherein the hybrid electric vehicle is a plug-in hybrid electric vehicle.

2. The method of claim 1 wherein the naphtha is Fischer-Tropsch derived naphtha.

3. The method of claim 1 wherein the liquid fuel composition is a gasoline.

4. The method of claim 1 wherein the liquid fuel composition has a Research Octane Number (RON) of 95 or less.

5. The method of claim 1 wherein the liquid fuel composition has a Research Octane Number (RON) of 93 or less.

6. The method of claim 1 wherein the liquid fuel composition comprises from 10 to 50% v/v naphtha.

7. A method of improving the fuel consumption in a spark ignition internal combustion engine comprising operating the spark ignition internal combustion engine using a liquid fuel composition comprising (a) from at least 50% m/m of a gasoline base fuel and (b) from 0.5 to 50% v/v of naphtha, wherein the spark ignition internal combustion engine is comprised within the powertrain of a plug-in hybrid electric vehicle.

8. The method of claim 7 wherein the naphtha is Fischer-Tropsch derived naphtha.

9. A method of improving power output in a spark ignition internal combustion engine comprising operating the spark ignition internal combustion engine using a liquid fuel composition comprising (a) from at least 50% m/m of a gasoline base fuel and (b) from 0.5 to 50% v/v of naphtha, wherein the spark ignition internal combustion engine is comprised within the powertrain of a plug-in hybrid electric vehicle.

10. The method of claim 9 wherein the naphtha is Fischer-Tropsch derived naphtha.

Description

(1) FIG. 1 is a schematic diagram of a plug-in hybrid electric vehicle (PHEV) 100. The PHEV 100 is a type of in hybrid electric vehicle (HEV) that makes use of both electrical energy stored in a battery 102 charged during driving operations by an internal combustion engine (ICE) 104 and mechanical energy converted from fuel via the ICE 104. The PHEV 100 provides the additional benefit of charging the battery 102 via a plug 106 (i.e., electrically connected with the battery 102) while the PHEV 100 is parked. The ICE 104 can include a spark ignition internal combustion engine that is comprised within a powertrain 108 of the PHEV 100. A conventional fuel source 110 supplies fuel via line 112 to a fuel tank 114 where the fuel is used to operate the ICE 104. The fuel via line 112 of the present invention comprises (a) a gasoline base fuel and (b) from 0.5 to 50% v/v of naphtha. The battery 104 stores energy and provides electric power to a motor 116. The motor 116, in turn, converts the electrical energy to mechanical power to move wheels 118 of the PHEV 100. Additionally, the ICE 104 provides mechanical power generated by the fuel via line 112 to move the PHEV 100 via the wheels 118. In this regard, the battery 102, engine 104, or both may provide power to move the wheels 118 so as to operate the PHEV 100.

(2) The invention is further described by reference to the following non-limiting example.

EXAMPLE

(3) The present Example tests cold starting ability, power output performance, CO.sub.2 emissions and fuel consumption in a PHEV compared to a conventional ICE vehicle. The Examples use standard EN 228 compliant gasoline (ComparisonFuel A) versus a test gasoline composition (ExperimentFuel B). The properties of the Comparison and Experiment fuels are set out in Table 1.

(4) TABLE-US-00001 TABLE 1 Fuel Properties EN228 Specification Comparison Experiment Min Max Fuel A Fuel B RON 95 96.5 91.3 MON 85 85.4 82.6 Density @ g/cm.sup.3 0.720 0.775 0.7390 0.7537 15 C. IBP C. 26.0 23.8 FBP C. 210.0 200.9 199.0 E70 % vol 20.0 48.0 33.5 30.9 E100 % vol 46.0 71.0 52.9 51.4 E150 % vol 75.0 84.9 87.8 VP kPa 45.0 110.0 94.9 84.7 GC C 6.48 6.52 H 11.64 12.04 O 0.00 0.00 C % m 87.00 86.66 H % m 13.02 13.34 O % m 2.7 or 0.00 0.00 3.7 Paraffins % vol 12.28 15.81 Isoparaffins % vol 33.52 33.66 Olefins % vol 15.21 13.74 (incl. dienes) Dienes % vol 0.13 0.12 Naphthenes % vol 3.07 4.78 Aromatics % vol 34.62 30.58 Oxygenates % vol 0.00 0.00 Unknowns % vol 1.30 1.43 Total % vol 100.0 100.0 AFR (stoich) 14.46 14.53 Gr. Ent. MJ/kg 43.30 42.489 Com (g) Vol. Ent. MJ/L 31.9987 31.9949 Com. (g) Gr. Ent. MJ/kg 43.000 43.118 Com. (l) Vol. Ent. MJ/L 31.777 31.7219 Com. (l) Heat of MJ/kg 0.371 0.37 vaporisation Cal. H/C 1.796 1.85 ratio Cal. O/C 0.000 0.000 ratio CWF 0.8690 0.8658

(5) The reference fuel (Fuel A) was a standard unleaded gasoline with an octane quality of RON 96.5 that met the current EN228 specification and was similar to a conventional main grade gasoline fuel. This fuel acted as the baseline for comparison. The Experiment fuel (Fuel B) was a blend of reference fuel (Fuel A) with 10% GTL naphtha. It had a low octane quality of RON 91.3 and both its RON and MON were below the current EN228 specification, otherwise it met it.

(6) Vehicles

(7) A 2008 Toyota Prius 1.5 T4 HEV that was converted by Amberjac to have plug-in charging capability was selected for test as a representative PHEV. This was compared to a standard 2004 Volkswagen Golf 1.6 FSI powered by conventional spark ignition, direct fuel injection, internal combustion engine (ICE) technology. The ICEs in both vehicles operated using a four-stroke cycle with variable valve timing.

(8) Performance Assessment

(9) An important consideration for fuel formulations is the potential for any fuel derived performance benefits or demerits. These are most often determined by operating the vehicle (or engine) at full load during accelerating and/or steady conditions. Fuel A and Fuel B were subjected to power performance testing. The conditions for assessing the power output are set out in Table 2.

(10) TABLE-US-00002 TABLE 2 Performance Testing Test Definition Warm up 100 km/h, road load simulation, 15 min, Tank Fuel Select Fuel Connect test fuel to external fuel lines Purge/Precon Cruise, Drive or Top Gear-1, 90 km/h, road-load, 15 min 5 Wide open throttle (WOT) Acceleration in Drive or Top Gear-1, 50-100 km/h Power Test Wide open throttle (WOT) at 50, 80, 120 km/h in Drive Mode or Top Gear-1: 5 s stabilisation, 5 s measurement Pause: 60 s idle Repeat twice (three measurements at each step) Measurements made: Power (kW), Tractive Force (N), Speed (km/h dynamometer)

(11) Measuring CO.sub.2 Emissions and Fuel Consumption Over NEDC

(12) Both vehicles were used for the CO.sub.2 emissions and fuel consumption test which was conducted on a four-wheel drive chassis dynamometer at a test temperature of 5 C. A standard NEDC (New European Driving Cycle) was used for the emissions measurements. Fuel consumption was calculated using the carbon balance method, which is based on the simple principle of carbon mass continuity through the engine and exhaust system. Hence totalling the measured carbon content of the exhaust gases (CO, CO.sub.2 and total unburned hydrocarbon) and comparing this with the carbon present in the fuel used at the time leading to an accurate determination of fuel consumption. Modern vehicles are equipped with exhaust after-treatment systems that are designed to convert hydrocarbon material in the exhaust into additional water and CO.sub.2. Fuel consumption is therefore generally regarded as being strongly correlated with CO.sub.2 emissions.

(13) The following table (Table 3) outlines the results for cold start New European Driving Cycle (NEDC) alongside a notional prediction based upon the common general knowledge before the tests were run.

(14) TABLE-US-00003 TABLE 3 Fuel consumption compared to Fuel A PHEV ICE Prediction Worse, because of Worse, because of the low octane the low octane quality of Fuel B quality of Fuel B Result NEDC Better by 2.9% Better by 0.6%

(15) The results for % benefit for power output for Fuel B compared to Fuel A are shown in Table 4 below alongside a notional prediction based upon the common general knowledge before the tests were run.

(16) TABLE-US-00004 TABLE 4 Power output compared to Fuel A Fuel B PHEV ICE Prediction Worse, because of Worse, because of the low octane the low octane quality of Fuel B quality of Fuel B Result max power Better by 16.3%* Worse by 8.3%* at 50 km/h Result max power Better by 13.1%* Worse by 5.0%* at 120 km/h *average value for 2 measurements

DISCUSSION

(17) Surprisingly, it was found that Fuel B, despite its low octane quality, was consumed at a lower rate than Fuel A in both cars.

(18) In particular, the results in Table 3 show that using a low octane quality, Fischer-Tropsch naphtha containing fuel, showed benefits in fuel economy, particularly in the PHEV vehicle. Hence, the invention provides for utilisation of fuels containing naphtha, especially GTL naphtha, having low octane quality, in ICEs in general, and more suitably within ICEs comprised within the powertrain of a hybrid electric vehicle.

(19) The results in Table 4 show that Fuel B shows a benefit in power output compared to Fuel A in the hybrid electric vehicle. This benefit is surprising in view of the low octane quality of Fuel B.

(20) Although particular embodiments of the invention have been disclosed herein in detail, this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.