Contents 1 The BSFC calculation (in metric units) 2 The relationship between BSFC numbers and efficiency 3 The use of BSFC numbers as operating values and as a cycle average statistic 4 The significance of BSFC numbers for engine design and class 5 Examples of values of BSFC for shaft engines 6 See also 7 References 8 External links

The BSFC calculation (in metric units) To calculate BSFC, use the formula B S F C = r P {\displaystyle BSFC={\frac {r}{P}}} where: r {\displaystyle r} is the fuel consumption rate in grams per second (g/s) P {\displaystyle P} is the power produced in watts where P = τ ω {\displaystyle P=\tau \omega } ω {\displaystyle \omega } is the engine speed in radians per second (rad/s) τ {\displaystyle \tau } is the engine torque in newton meters (N⋅m) The above values of r, ω {\displaystyle \omega } , and τ {\displaystyle \tau } may be readily measured by instrumentation with an engine mounted in a test stand and a load applied to the running engine. The resulting units of BSFC are grams per joule (g/J) Commonly BSFC is expressed in units of grams per kilowatt-hour (g/(kW⋅h)). The conversion factor is as follows: BSFC [g/(kW⋅h)] = BSFC [g/J] × (3.6 × 106) The conversion between metric and imperial units is: BSFC [g/(kW⋅h)] = BSFC [lb/(hp⋅h)] × 608.277 BSFC [lb/(hp⋅h)] = BSFC [g/(kW⋅h)] × 0.001644

The relationship between BSFC numbers and efficiency To calculate the actual efficiency of an engine requires the energy density of the fuel being used. Different fuels have different energy densities defined by the fuel's heating value. The lower heating value (LHV) is used for internal combustion engine efficiency calculations because the heat at temperatures below 150 °C (300 °F) cannot be put to use. Some examples of lower heating values for vehicle fuels are: Certification gasoline = 18,640 BTU/lb (0.01204 kW⋅h/g) Regular gasoline = 18,917 BTU/lb (0.0122222 kW⋅h/g) Diesel fuel = 18,500 BTU/lb (0.0119531 kW⋅h/g) Thus a diesel engine's efficiency = 1/(BSFC × 0.0119531) and a gasoline engine's efficiency = 1/(BSFC × 0.0122225)

The use of BSFC numbers as operating values and as a cycle average statistic BSFC [g/(kW⋅h)] map Main article: Consumption map Any engine will have different BSFC values at different speeds and loads. For example, a reciprocating engine achieves maximum efficiency when the intake air is unthrottled and the engine is running near its peak torque. The efficiency often reported for a particular engine, however, is not its maximum efficiency but a fuel economy cycle statistical average. For example, the cycle average value of BSFC for a gasoline engine is 322 g/(kW⋅h), translating to an efficiency of 25% (1/(322 × 0.0122225) = 0.2540). Actual efficiency can be lower or higher than the engine’s average due to varying operating conditions. In the case of a production gasoline engine, the most efficient BSFC is approximately 225 g/(kW⋅h), which is equivalent to a thermodynamic efficiency of 36%. An iso-BSFC map (fuel island plot) of a diesel engine is shown. The sweet spot at 206 BSFC has 40.6% efficiency. The x-axis is rpm; y-axis is BMEP in bar (bmep is proportional to torque)

The significance of BSFC numbers for engine design and class BSFC numbers change a lot for different engine design and compression ratio and power rating. Engines of different classes like diesels and gasoline engines will have very different BSFC numbers, ranging from less than 200 g/(kW⋅h) (diesel at low speed and high torque) to more than 1,000 g/(kW⋅h) (turboprop at low power level).

Examples of values of BSFC for shaft engines The following table takes values as an example for the specific fuel consumption of several types of engines. For specific engines values can and often do differ from the table values shown below. Energy efficiency is based on a lower heating value of 42.7 MJ/kg (84.3 g/(kW⋅h)) for diesel fuel and jet fuel, 43.9 MJ/kg (82 g/(kW⋅h)) for gasoline. Power (kW) Year Engine type Application SFC (lb/(hp⋅h)) SFC (g/(kW⋅h)) Energy efficiency 93 1942 Lycoming O-235 piston, gasoline General aviation 0.43 262[1] 31.4% 63 1991 GM Saturn I4 engine, gasoline Saturn S-Series cars 0.411 250[2] 32.5% 150 2011 Ford EcoBoost gasoline, turbo Ford cars 0.403 245[3] 33.5% 1,305 1973 General Electric CT7 turboprop Let L-610G airliner 0.413 251[4] 33.6% 300 1961 Lycoming IO-720 piston, gasoline General aviation 0.4 243[5] 34.2% 2,000 1945 Wright R-3350 Duplex-Cyclone gasoline, turbo-compound Bombers, airliners 0.380 231[6] 35.5% 57 2003 Toyota 1NZ-FXE, gasoline Toyota Prius car 0.370 225[7] 36.4% 550 1931 Junkers Jumo 204 two-stroke diesel, turbo Bombers, airliners 0.347 211[8] 40% 36,000 2002 Rolls-Royce Marine Trent turboshaft Combat ships 0.340 207[9] 40.7% 2,340 1949 Napier Nomad Diesel-compound planned (aircraft intended) 0.340 207[10] 40.7% 165 2000 Volkswagen 3.3 V8 TDI Audi A8 car 0.337 205[11] 41.1% 2,013 1940 Klöckner-Humboldt-Deutz DZ 710 Diesel two stroke none (aircraft intended) 0.330 201[12] 41.9% 42,428 1993 General Electric LM6000 turboshaft Ship, electricity 0.329 200.1[13] 42.1% 130 2007 BMW N47 2L turbodiesel BMW cars 0.326 198[14] 42.6% 88 1990 Audi 2.5L TDI Audi 100 car 0.326 198[15] 42.6% 3,600 MAN Diesel 6L32/44CR four-stroke Ship, electricity 0.283 172[16] 49% 4,200 2015 Wärtsilä W31 four-stroke Ship, electricity 0.271 165[17] 51.1% 34,320 1998 Wärtsilä-Sulzer RTA96-C two-stroke Ship, electricity 0.263 160[18] 52.7% 27,060 MAN Diesel S80ME-C9.4-TII two-stroke Ship, electricity 0.254 154.5[19] 54.6% 34,350 MAN Diesel 12G95ME-C9 two-stroke Ship 0.254 154.5[20] 54.6% 605,000 2016 General Electric 9HA combined cycle gas turbine electricity generation 0.223 135.5 (eq.) 62.2%[21] Turboprop efficiency is only good at high power; SFC increases dramatically for approach at low power (30% Pmax) and especially at idle (7% Pmax) : 2,050 kW Pratt & Whitney Canada PW127 turboprop (1996)[22] Mode Power fuel flow SFC Energy efficiency Nominal idle (7%) 192 hp (143 kW) 3.06 kg/min (405 lb/h) 1,282 g/(kW⋅h) (2.108 lb/(hp⋅h)) 6.6% Approach (30%) 825 hp (615 kW) 5.15 kg/min (681 lb/h) 502 g/(kW⋅h) (0.825 lb/(hp⋅h)) 16.8% Max cruise (78%) 2,132 hp (1,590 kW) 8.28 kg/min (1,095 lb/h) 312 g/(kW⋅h) (0.513 lb/(hp⋅h)) 27% Max climb (80%) 2,192 hp (1,635 kW) 8.38 kg/min (1,108 lb/h) 308 g/(kW⋅h) (0.506 lb/(hp⋅h)) 27.4% Max contin. (90%) 2,475 hp (1,846 kW) 9.22 kg/min (1,220 lb/h) 300 g/(kW⋅h) (0.493 lb/(hp⋅h)) 28.1% Take-off (100%) 2,750 hp (2,050 kW) 9.9 kg/min (1,310 lb/h) 290 g/(kW⋅h) (0.477 lb/(hp⋅h)) 29.1%

See also Fuel economy in automobiles Fuel economy-maximizing behaviors Fuel management systems Marine fuel management Thrust specific fuel consumption

References Notes ^ O-235 and O-290 Operator's Manual (PDF), Lycoming, Jan 2007, p. 3-8  ^ Michael Soroka (March 26, 2014). "Are Airplane Engines Inefficient?".  ^ "Advanced Gasoline Turbocharged Direct Injection (GTDI) Engine Development" (PDF). Ford Research and Advanced Engineering. May 13, 2011.  ^ "General Electric CT7". AAE Propulsion. Purdue.  ^ IO-720 Operator's Manual (PDF), Lycoming, October 2006, p. 3-8  ^ Kimble D. McCutcheon (27 October 2014). "Wright R-3350 "Cyclone 18"" (PDF). Archived from the original (PDF) on 1 August 2016.  ^ "Development of New-Generation Hybrid System THS II - Drastic Improvement of Power Performance and Fuel Economy". Society of Automotive Engineers. 8 March 2004.  ^ inter-action association, 1987 ^ "Marine Trent". Civil Engineering Handbook. 19 Mar 2015.  ^ "Napier Nomad". Flight. 30 April 1954.  ^ "The new Audi A8 3.3 TDI quattro: Top TDI for the luxury class" (Press release). Audi AG. July 10, 2000.  ^ "Jane's Fighting Aircraft of World War II". London, UK: Bracken Books. 1989.  ^ "LM6000 Marine Gas Turbine" (PDF). General Electric. 2016. Archived from the original (PDF) on 2016-11-19.  ^ "BMW 2.0d (N47)" (in French). Auto-innovations. June 2007.  ^ "The New Audi 5-Cylinder Turbo Diesel Engine: The First Passenger Car Diesel Engine with Second Generation Direct Injection". Society of Automotive Engineers. 1 February 1990.  ^ "Four-Stroke Propulsion Engines" (PDF). Man Diesel. 2015. Archived from the original (PDF) on 2016-04-17.  ^ "The new Wärtsilä 31 engine". Wärtsilä Technical Journal. 20 October 2015.  ^ "RTA-C Technology Review" (PDF). Wärtsilä. 2004. Archived from the original on December 26, 2005. CS1 maint: Unfit url (link) ^ "MAN B&W S80ME-C9.4-TII Project Guide" (PDF). Man Diesel. May 2014.  ^ "MAN B&W G95ME-C9.2-TII Project Guide" (PDF). Man Diesel. May 2014. p. 16.  ^ Tomas Kellner (17 Jun 2016). "Here's Why The Latest Guinness World Record Will Keep France Lit Up Long After Soccer Fans Leave" (Press release). General Electric.  ^ "ATR: The Optimum Choice for a Friendly Environment" (PDF). Avions de Transport Regional. June 2001. p. PW127F engine gaseous emissions. Archived from the original (PDF) on 2016-08-08.  Bibliography Reciprocating engine types HowStuffWorks: How Car Engines Work Reciprocating Engines at infoplease Piston Engines US Centennial of Flight Commission Effect of EGR on the exhaust gas temperature and exhaust opacity in compression ignition engines Heywood J B 1988 Pollutant formation and control. Internal combustion engine fundamentals Int. edn (New York: Mc-Graw Hill) pp 572–577 Well-to-Wheel Studies, Heating Values, and the Energy Conservation Principle

External links Exemplary maps for commercial car engines collected by ecomodder forum users Retrieved from "https://en.wikipedia.org/w/index.php?title=Brake_specific_fuel_consumption&oldid=824071394" Categories: Engine technologyPower (physics)Hidden categories: CS1 French-language sources (fr)CS1 maint: Unfit url