scholarly journals The Specific Fuel Consumption of Aircraft Engines (TSFC versus PSFC)

2021 ◽  
Author(s):  
Dieter Scholz
Keyword(s):  
Fuel Consumption ◽  
Aircraft Engine ◽  
Specific Fuel Consumption ◽  
Flight Performance ◽  
Aircraft Engines ◽  
Minimum Drag ◽  
Extended Approach ◽  
Range Equation ◽  
Performance Calculation ◽  
Fundamental Consideration

From a fundamental consideration of the efficiency (eta = P_out / P_in) it already follows that the power-specific fuel consumption, PSFC or c_P of an aircraft engine should be approximately constant, while c = c_P * V applies to the thrust-specific fuel consumption, TSFC or c in a first approach. Obviously, fuel is consumed already at static thrust (V=0). For this reason the thrust-specific fuel consumption needs an extended approach c = c_a + c_b * V. Breguet's range equation can certainly be described with a constant thrust-specific fuel consumption c, if c is determined for the cruise speed in question. However, this leads to an error if you want to use it to calculate an optimal flight speed in a flight performance calculation. It is recommended (for a first simple consideration) to write Breguet's range equation for jets with a constant power-specific fuel consumption c_P. This then leads to an optimal cruising speed for maximum range at minimum drag (md) V_md instead of 1.316 * V_md as it is determined with the "classic" derivation. For more detailed considerations, the "Herrmann model" should replace the simple equation c = c_a + c_b * V.

Fundamental Differences Between Conventional and Geared Turbofans

2009 ◽  
Author(s):  
Joachim Kurzke
Keyword(s):  
Fuel Consumption ◽  
Real Option ◽  
Pressure Ratio ◽  
Thermodynamic Cycle ◽  
Specific Fuel Consumption ◽  
Thermodynamic Efficiency ◽  
Aircraft Engines ◽  
Direct Drive ◽  
Significant Difference ◽  
Bypass Ratio

The potential for improving the thermodynamic efficiency of aircraft engines is limited because the aerodynamic quality of the turbomachines has already achieved a very high level. While in the past increasing burner exit temperature did contribute to better cycle efficiency, this is no longer the case with today’s temperatures in the range of 1900...2000K. Increasing the cycle pressure ratio above 40 will yield only a small fuel consumption benefit. Therefore the only way to improve the fuel efficiency of aircraft engines significantly is to increase bypass ratio — which yields higher propulsive efficiency. A purely thermodynamic cycle study shows that specific fuel consumption decreases continuously with increasing bypass ratio. However, thermodynamics alone is a too simplistic view of the problem. A conventional direct drive turbofan of bypass ratio 6 looks very different to an engine with bypass ratio 10. Increasing bypass ratio above 10 makes it attractive to design an engine with a gearbox to separate the fan speed from the other low pressure components. Different rules apply for optimizing turbofans of conventional designs and those with a gearbox. This paper describes various criteria to be considered for optimizing the respective engines and their components. For illustrating the main differences between conventional and geared turbofans it is assumed that an existing core of medium pressure ratio with a two stage high pressure turbine is to be used. The design of the engines is done for takeoff rating because this is the mechanically most challenging condition. For each engine the flow annulus is examined and stress calculations for the disks are performed. The result of the integrated aero-thermodynamic and mechanical study allows a comparison of the fundamental differences between conventional and geared turbofans. At the same bypass ratio there will be no significant difference in specific fuel consumption between the alternative designs. The main difference is in the parts count which is much lower for the geared turbofan than for the conventional engine. However, these parts will be mechanically much more challenging than those of a conventional turbofan. If the bypass ratio is increased significantly above 10, then the geared turbofan becomes more and more attractive and the conventional turbofan design is no longer a real option. The maximum practical bypass ratio for ducted fans depends on the nacelle drag and how the installation problems can be solved.

Aircraft Engine Electrical Power Generation With a SOFC Combustor

2014 ◽  
Author(s):  
Rory A. Roberts ◽  
Peter Therkelsen
Keyword(s):  
Power Generation ◽  
Fuel Cell ◽  
Fuel Consumption ◽  
Electrical Power Generation ◽  
Electrical Power ◽  
Aircraft Engine ◽  
Specific Fuel Consumption ◽  
System Level ◽  
Combustion System ◽  
Generation Capacity

Next generation aircraft will require more onboard electrical power generation capacity as systems previously powered by engine bleed and hydraulics are electrified and new electricity based technologies are integrated. Increasing the amount of electrical power generated from aircraft main engines reduces thrust capacity and thrust specific fuel consumption (TSFC), but could increase specific fuel consumption (SFC). An alternative cycle with very high conversion efficiencies is proposed for electrical power production on aircraft. The unique cycle, termed a SOFC combustor, integrates a Solid Oxide Fuel Cell (SOFC) with existing onboard combustion based engines. The SOFC combustor produces direct current (DC) electrical power and provides high temperature exhaust for use in the expansion process of the aircraft engine. The SOFC combustor utilizes compressed air from the engine’s compressor and vaporized fuel to produce DC current. Fuel and air not utilized by the fuel cell are converted to thermal products by an aerodynamically stabilized combustion system capable of adapting to fuel/air and pressure variations. Hot products from the combustion system are returned to the main engines for use as thrust or mechanical shaft work. System level results will be presented for overall impact to aircraft engine specific fuel consumption.

scholarly journals Comparative study of alternative biofuels on aircraft engine performance

2016 ◽  
Vol 231 (8) ◽  
pp. 1509-1521 ◽  
Author(s):  
Muhammad Hanafi Azami ◽  
Mark Savill
Keyword(s):  
Fuel Consumption ◽  
Engine Performance ◽  
Aircraft Engine ◽  
Specific Fuel Consumption ◽  
Energy Crisis ◽  
Mixing Ratio ◽  
Heating Value ◽  
Fuel Flow ◽  
Lower Heating Value ◽  
Lower Heating

Aviation industries are vulnerable to the energy crisis and simultaneously posed environmental concerns. Proposed engine technology advancements could reduce the environmental impact and energy consumption. Substituting the source of jet fuel from fossil-based fuel to biomass-based fuel will help reduce emissions and minimize the energy crisis. The present paper addresses the analysis of aircraft engine performance in terms of thrust, fuel flow and specific fuel consumption at different mixing ratio percentages (20%, 40%, 50%, 60% and 80%) of alternative biofuel blends already used in flight test (Algae biofuel, Camelina biofuel and Jatropha biofuel) at different flight conditions. In-house computer software codes, PYTHIA and TURBOMATCH, were used for the analysis and modeling of a three-shaft high-bypass-ratio engine which is similar to RB211-524. The engine model was verified and validated with open literature found in the test program of bio-synthetic paraffinic kerosene in commercial aircraft. The results indicated that lower heating value had a significant influence on thrust, fuel flow and specific fuel consumption at every flight condition and at all mixing ratio percentages. Wide lower heating value differences between two fuels give a large variation on the engine performances. Blended Kerosene–Jatropha biofuel and Kerosene–Camelina biofuel showed an improvement on gross thrust, net thrust, reduction of fuel flow and specific fuel consumption at every mixing ratio percentage and at different flight conditions. Moreover, the pure alternative of Jatropha biofuel and Camelina biofuel gave much better engine performances. This was not the case for the Kerosene–Algae blended biofuel. This study is a crucial step in understanding the influence of different blended alternative biofuels on the performance of aircraft engines.

scholarly journals Parameterization of a Conventional and Regenerated UHB Turbofan

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Fábio Oliveira ◽  
Francisco Brójo
Keyword(s):  
Fuel Consumption ◽  
First Generation ◽  
Specific Fuel Consumption ◽  
Aircraft Engines ◽  
Turbofan Engine ◽  
Commercial Aviation ◽  
Technological Developments ◽  
Specific Thrust ◽  
Aero Engines ◽  
Bypass Ratio

AbstractThe attempt to improve aircraft engines efficiency resulted in the evolution from turbojets to the first generation low bypass ratio turbofans. Today, high bypass ratio turbofans are the most traditional type of engine in commercial aviation. Following many years of technological developments and improvements, this type of engine has proved to be the most reliable facing the commercial aviation requirements. In search of more efficiency, the engine manufacturers tend to increase the bypass ratio leading to ultra-high bypass ratio (UHB) engines. Increased bypass ratio has clear benefits in terms of propulsion system like reducing the specific fuel consumption. This study is aimed at a parametric analysis of a UHB turbofan engine focused on short haul flights. Two cycle configurations (conventional and regenerated) were studied, and estimated values of their specific fuel consumption (TSFC) and specific thrust (Fs) were determined. Results demonstrate that the regenerated cycle may contribute towards a more economic and friendly aero engines in a higher range of bypass ratio.

WATER AND WATER-ALCOHOL INJECTION IN A SUPERCHARGED JAGUAR AIRCRAFT ENGINE

1938 ◽  
Vol 16a (8) ◽  
pp. 149-176 ◽  
Author(s):  
M. S. Kuhring
Keyword(s):  
Fuel Consumption ◽  
Water Injection ◽  
Aircraft Engine ◽  
Full Scale ◽  
Specific Fuel Consumption ◽  
Alcohol Injection ◽  
Effect Of Water ◽  
Fuel Charge ◽  
Rich Mixtures ◽  
Water Alcohol

Tests have been carried out in order to determine the effect of water injection on the operation of a full-scale aircraft engine. A Jaguar Mk IV supercharged aircraft engine was used and quantities of water as great as 83 lb. per 100 lb. of fuel were injected. As would be expected, the use of water permitted large gains in power without increase in cylinder temperature and apparent detonation. An increase of approximately 90 b.hp. was obtained. Quite appreciable cooling of the air-fuel charge was noted. The specific fuel consumption remained the same or slightly better with injection. From the results it would appear that alcohol does not improve the operation of the engine appreciably, although tests were conducted only at full rich mixtures.

Exergy analysis of a turboprop engine at different flight altitude and speeds using novel consideration

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Dinc ◽  
Yousef Gharbia
Keyword(s):  
Fuel Consumption ◽  
Thermal Efficiency ◽  
Exergy Efficiency ◽  
Specific Fuel Consumption ◽  
Flight Altitude ◽  
Fuel Flow ◽  
Turboprop Engine ◽  
Shaft Power ◽  
Two Parameters ◽  
The Relationship

Abstract In this study, exergy efficiency calculations of a turboprop engine were performed together with main performance parameters such as shaft power, specific fuel consumption, fuel flow, thermal efficiency etc., for a range of flight altitude (0–14 km) and flight speeds (0–0.6 Mach). A novel exergy efficiency formula was derived in terms of specific fuel consumption and it is shown that these two parameters are inversely proportional to each other. Moreover, a novel exergy efficiency and thermal efficiency relation was also derived. The relationship showed that these two parameters are linearly proportional to each other. Exergy efficiency of the turboprop engine was found to be in the range of 23–33%. Thermal efficiency of the turboprop engine was found to be around 25–35%. Exergy efficiency is higher at higher speeds and altitude where the specific fuel consumption is lower. Conversely, exergy efficiency of the engine is lower for lower speeds and altitude where the specific fuel consumption is higher.

Two-Stroke Marine Diesel Engine Variable Injection Timing System Performance Evaluation and Optimum Setting for Minimum Fuel Consumption at Acceptable NOx Levels

2014 ◽  
Author(s):  
Dimitrios T. Hountalas ◽  
Spiridon Raptotasios ◽  
Antonis Antonopoulos ◽  
Stavros Daniolos ◽  
Iosif Dolaptzis ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Fuel Consumption ◽  
Engine Performance ◽  
Operating Conditions ◽  
Specific Fuel Consumption ◽  
Injection Timing ◽  
Nox Emissions ◽  
Pressure Measurements ◽  
Cylinder Pressure ◽  
Start Of Injection

Currently the most promising solution for marine propulsion is the two-stroke low-speed diesel engine. Start of Injection (SOI) is of significant importance for these engines due to its effect on firing pressure and specific fuel consumption. Therefore these engines are usually equipped with Variable Injection Timing (VIT) systems for variation of SOI with load. Proper operation of these systems is essential for both safe engine operation and performance since they are also used to control peak firing pressure. However, it is rather difficult to evaluate the operation of VIT system and determine the required rack settings for a specific SOI angle without using experimental techniques, which are extremely expensive and time consuming. For this reason in the present work it is examined the use of on-board monitoring and diagnosis techniques to overcome this difficulty. The application is conducted on a commercial vessel equipped with a two-stroke engine from which cylinder pressure measurements were acquired. From the processing of measurements acquired at various operating conditions it is determined the relation between VIT rack position and start of injection angle. This is used to evaluate the VIT system condition and determine the required settings to achieve the desired SOI angle. After VIT system tuning, new measurements were acquired from the processing of which results were derived for various operating parameters, i.e. brake power, specific fuel consumption, heat release rate, start of combustion etc. From the comparative evaluation of results before and after VIT adjustment it is revealed an improvement of specific fuel consumption while firing pressure remains within limits. It is thus revealed that the proposed method has the potential to overcome the disadvantages of purely experimental trial and error methods and that its use can result to fuel saving with minimum effort and time. To evaluate the corresponding effect on NOx emissions, as required by Marpol Annex-VI regulation a theoretical investigation is conducted using a multi-zone combustion model. Shop-test and NOx-file data are used to evaluate its ability to predict engine performance and NOx emissions before conducting the investigation. Moreover, the results derived from the on-board cylinder pressure measurements, after VIT system tuning, are used to evaluate the model’s ability to predict the effect of SOI variation on engine performance. Then the simulation model is applied to estimate the impact of SOI advance on NOx emissions. As revealed NOx emissions remain within limits despite the SOI variation (increase).

Characteristics of Water-in-Diesel Emulsions in a Single Cylinder Compression Ignition Engine

2014 ◽  
Author(s):  
Teja Gonguntla ◽  
Robert Raine ◽  
Leigh Ramsey ◽  
Thomas Houlihan
Keyword(s):  
Fuel Consumption ◽  
Direct Injection ◽  
Engine Performance ◽  
Operating Conditions ◽  
Specific Fuel Consumption ◽  
Brake Specific Fuel Consumption ◽  
Compression Ignition Engine ◽  
Oil Emulsion ◽  
Single Cylinder ◽  
Performance And Emission

The objective of this project was to develop both engine performance and emission profiles for two test fuels — a 6% water-in-diesel oil emulsion (DOE-6) fuel and a neat diesel (D100) fuel. The testing was performed on a single cylinder, direct-injection, water-cooled diesel engine coupled to an eddy current dynamometer. Output parameters of the engine were used to calculate Brake Specific Fuel Consumption (BSFC) and Engine Efficiency (η) for each test fuel. DOE-6 fuels generated a 24% reduction in NOX and a 42% reduction in Carbon Monoxide emissions over the tested operating conditions. DOE-6 fuels presented higher ignition delays — between 1°-4°, yielded 1%–12% lower peak cylinder pressures and produced up to 5.5% lower exhaust temperatures. Brake Specific Fuel consumption increased by 6.6% for the DOE-6 fuels as compared to the D100 fuels. This project is the first research done by a New Zealand academic institution on water-in-diesel emulsion fuels.

An Improvement of Part Load Performance of Diesel Engines Operating at Constant Speed Conditions

1994 ◽  
Vol 208 (1) ◽  
pp. 21-25 ◽  
Author(s):  
A A Abdel-Rahman ◽  
M K Ibrahim ◽  
A A Said
Keyword(s):  
Fuel Consumption ◽  
Diesel Engines ◽  
Petroleum Refining ◽  
Specific Fuel Consumption ◽  
Constant Speed ◽  
Maximum Pressure ◽  
Brake Specific Fuel Consumption ◽  
Part Load ◽  
Generating Sets ◽  
In Series

This paper discusses the possibility of improving the part load performance of diesel electric turbocharged engines operating at constant speed conditions. A sequential turbocharged system is proposed, where the compressors are connected In series. The study focused on two turbocharged diesel–electric generating sets existing at Ameria Petroleum Refining Company in Alexandria, Egypt. The results of the prediction showed that, at part load, both the maximum pressure and temperature were increased, and the brake specific fuel consumption was reduced considerably (by about 10 per cent).

Three-dimensional predator–prey interactions: a computer simulation of bird flocks and aircraft

1986 ◽  
Vol 64 (11) ◽  
pp. 2624-2633 ◽  
Author(s):  
Peter F. Major ◽  
Lawrence M. Dill ◽  
David M. Eaves
Keyword(s):  
Computer Simulation ◽  
Prey Species ◽  
Three Dimensional ◽  
Aircraft Engine ◽  
Aquatic Environments ◽  
Aircraft Engines ◽  
Predator Prey ◽  
Simulation Techniques ◽  
Computer Simulation Techniques ◽  
Individual Prey

Three-dimensional interactions between grouped aerial predators (frontal discs of aircraft engines), either linearly arrayed or clustered, and flocks of small birds were studied using interactive computer simulation techniques. Each predator modelled was orders of magnitude larger than an individual prey, but the prey flock was larger than each predator. Expected numbers of individual prey captured from flocks were determined for various predator speeds and trajectories, flock–predator initial distances and angles, and flock sizes, shapes, densities, trajectories, and speeds. Generally, larger predators and clustered predators caught more prey. The simulation techniques employed in this study may also prove useful in studies of predator–prey interactions between schools or swarms of small aquatic prey species and their much larger vertebrate predators, such as mysticete cetaceans.The study also provides a method to study problems associated with turbine aircraft engine damage caused by the ingestion of small flocking birds, as well as net sampling of organisms in open aquatic environments.

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