Improvement In Specific Fuel Consumption Research Articles

The heat transfer potential of compressor vanes on a hydrogen fueled turbofan engine

Hydrogen is a promising fuel for future aviation due to its CO2-free combustion. In addition, its excellent cooling properties as it is heated from cryogenic conditions to the appropriate combustion temperatures provides a multitude of opportunities. This paper investigates the heat transfer potential of stator surfaces in a modern high-speed low-pressure compressor by incorporating cooling channels within the stator vane surfaces, where hydrogen is allowed to flow and cool the engine core air. Computational Fluid Dynamics simulations were carried out to assess the aerothermal performance of this cooled compressor and were compared to heat transfer correlations. A core air temperature drop of 9.5 K was observed for this cooling channel design while being relatively insensitive to the thermal conductivity of the vane and cooling channel wall thickness. The thermal resistance was dominated by the air-side convective heat transfer, and more surface area on the air-side would therefore be required in order to increase overall heat flow. While good agreement with established heat transfer correlations was found for both turbulent and transitional flow, the correlation for the transitional case yielded decent accuracy only as long as the flow remains attached, and while transition was dominated by the bypass mode. A system level analysis, indicated a limited but favorable impact at engine performance level, amounting to a specific fuel consumption improvement of up to 0.8 % in cruise and an estimated reduction of 3.6 % in cruise NOx. The results clearly show that, although it is possible to achieve high heat transfer rate per unit area in compressor vanes, the impact on cycle performance is constrained by the limited available wetted area in the low-pressure compressor.

Experimental investigation of saturated fogging and overspray influence on part-load micro gas turbine performance

• Part-load MGT performance with water spray at the inlet is studied experimentally. • The ambient temperature impact on MGT performance is varied with its load. • The benefits of inlet fogging and overspray systems deceases with loads. • MGT performance is enhanced with water injection with fixed fuel consumption. • Inlet fogging and overspray reduce NO but increase CO concentrations. Micro gas turbines (MGT) are promising power sources for modern industries, especially in the distributed energy generation market, due to their relatively high projected energy densities. Nevertheless, they suffer from lower thermal efficiency due to the inherent constraint of high- exhaust temperature and the relatively high compression work, especially during hot days and partial load operation. Water injection into gas turbine inlet air is a possible route to improve the MGT performance. As a result of the lack of previous experimental studies related to the study of fog and overspray on turbines at partial load operations, the current study aims to evaluate the influence of saturated fogging (inlet fogging) and overspray on the MGT part-load performance experimentally. Two test benches were installed to implement inlet fogging and overspray on a 10 kW MGT. Droplet size and injected water mass flow were measured at varied spraying pressures and nozzle diameters to determine optimum spray conditions. The output power and specific fuel consumption were measured at different overspray ratios for various MGT loads. The results showed that the enhancement in power output due to inlet fogging and overspray varied according to the applied load. After applying saturated fogging, the output power augmentation corresponding to a 14℃-temperature drop was 9.32% at a load of 30%, while this value decreased to 6.86 and 4.91% for loads 50 and 70 %, respectively. It was also observed that a continuous boost in net power output with an increased overspray ratio. Increasing the load from 30 to 70% reduced the power enhancement by about 42 and 39% for overspray ratios of 1 and 2%, respectively. The maximum output power and specific fuel consumption improvement were achieved at a 2% overspray ratio. Inlet fogging and overspray reduced NO concentrations for all loads, and vice versa for CO concentrations, and emission slop decreased with the load.

Performance Improvement of a 43 MW Class Gas Turbine Engine with Inlet Air Cooling

In this study, a process of inlet air cooling was implemented in the intake of a land-based gas turbine engine for electricity generation. The motivation behind the study is to improve the performance of the gas turbine engine in hot climate conditions,which causes a significant decrease in the output power and an increase in specific fuel consumption. For inlet air cooling, a refrigeration cycle was attached to the turbo-shaft gas turbine engine,and power required by the refrigeration is extracted from the mechanical engine power output of the gas turbine. A 43 MWclass gas turbine engine which is similar totheGeneral Electric LM6000 engine was modeled in this study. Considering an average coefficient of performance of 3.0 for a refrigeration system, the inlet cooling provided (by supplying cooled inlet air at 15oC) a 22.21% net power increase anda5.2% power specific fuel consumption improvement at 55oCambient conditions.

Performance of single cylinder diesel engine using triple fuel HSD-LPG-Steam

Fuel system modification techniques to improve engine efficiency could be the way to slow down the energy crisis caused by the lack of new fuel inventions. The Compression Ignition (CI) diesel engine is one of the most preferred engines for both in-land and marine transportation motors. The advantages of compact dimensions and large generated power make CI diesel engine superior to other engine types. The large number of single CI diesel engines use in small fishing vessel engines and agricultural machinery will contribute substantially to fuel consumption in a cumulative manner. Previous researchs on the modification of fuel system with bi-fuel system High Speed Diesel (HSD)oil – Liquified Petroleum Gas (LPG) system capable of reducing Brake Specific Fuel Consumption (BSFC) up to 24% and exhaust gas opacity up to 68%. Subsequent studies focused on engines with single fuel HSD oil but were injected with superheated steam in 1 atm (abs) 130 0C by utilizing Heat Recovery Generating System (HRSG) using heat of exhaust gas for a flowrate of 1.5-4.5 kg/hour. It is capable of delivering the performance improvement of Specific Fuel Consumption (SFC), which is reduced by 8.92% compared to diesel engines without steam injection. Recent research combines the above two modification methods so that diesel will adopt two types of fuel- oil-LPG with additional superheated steam injection resulting from exhaust gas heat cogeneration system. Experimental results of the diesel engine with LPG injection maintained at 0.4 kg/h and 3.5 kg/h superheated steam with an engine variation loading of 0.3-0.7 kWh provide an average AFR of 30.09 and SFC improvement up to 37.2% lower than SFC engine standard with a single fuel HSD oil.

Comparative Experimental Studies on Four Stroke Four Cylinder Diesel fuelled Base Line Engine and Low Heat Rejection Engine

The depletion of conventional fuel source at a fast rate and increasing of environment pollution motivated extensive research in energy efficient engine design. In the present work, experimental investigations were carried out on a four-stroke four-cylinder dieselfuelled Base Line Engine (BLE) by conducting a normal load test and measuring the required Brake Thermal Efficiency (BThE) and Specific Fuel Consumption (SFC) in a 100 HP dyno facility. A six-gas Analyser was used for the measurement of Unburnt
 Hydrocarbons (UBHC), Carbon monoxide (CO), Carbon dioxide (CO2), free Oxygen (O2), Nitrogen oxides (NOx), Sulphur oxides (SOx) and a smoke meter was used to measure smoke opacity. Low Heat Rejection (LHR) engine was realized by coating the crown of the aluminium alloy piston with the most popular Thermal Barrier Coating (TBC) material, namely 8%Yttria Partially Stabilized Zirconia (8YPSZ), after coating qualification on research pistons, specifically fabricated to retain the piston material specification, and the geometry of the crown contour. A normal load test was conducted on LHR engine to evaluate the performance as well as to determine the concentration of pollutants. A ~30% improvement in BThE and ~35% improvement in SFC was exhibited by the LHR engine at all loads studied (7 to 64%). While UBHC level showed an increase, the CO, CO2 and O2 contents as revealed in the emission test showed a mixed response (high and low) for an LHR engine. Compared with BLE, NOx and smoke level in LHR engine emission showed an increasing trend with the load. On comparing BLE and LHR engine test results, value addition to the BLE in terms of reduced fuel consumption and pollutants was observed.

Benefits of exhaust gas energy for preheating biodiesel fuel to enhance engine emissions and performance

The need for alternative fuel instead of conventional fossil fuels (diesel or gasoline) has recently increased for several reasons, including the expected shortage of petroleum fossil fuels and the production of pollution by transportation. Consequently, researchers are interested in finding new alternative fuels. At present, the number of studies on biodiesel as a compression ignition engine fuel has increased. Current studies are mainly concerned with studying the use of exhaust gas temperature to preheat biodiesel fuel before it enters the combustion chamber. A heat exchanger is designed to increase the temperature of the biodiesel fuel prior to the combustion process. The performance characteristics of diesel engines and the emission of pollutants resulting from this modification were investigated under different operating conditions, including different engine loads and speeds. The results showed clear improvements in engine performance, including improved output power, specific fuel consumption and pollutant emissions. The engine power and specific fuel consumption improvements as a result of preheating reached up to 1.3 % and 8.27 %, respectively. Pollutant emission also decreased obviously, with carbon monoxide and hydrocarbon emission decreases of 12.95 % and 12.85 %, respectively. However, the emission of nitrogen oxides increased by 4.39 %.

Evaluation of diesel fuel-biodiesel blends with palladium and acetylferrocene based additives in a diesel engine

Influence of biodiesel-diesel fuel blends with acetylferrocene and palladium based additives on diesel engine performance and emissions were studied experimentally. The additives were dosed into the blend fuels as 25 ppm. Bis-[N,N-dimethyl-N′-2-chlorobenzoylthioureato] palladium (II), PdL2 was prepared as palladium based additive. The engine tests were carried out in a single cylinder direct injection diesel engine at 4, 8, 12 and 16 Nm loads. The result of engine test revealed that the blend fuels with additives did not show the considerable effect on variation of cylinder pressure values. Also, specific fuel consumption (SFC) values with Ferrocene based additive showed comparatively better results than those of palladium based additives. Furthermore, CO and PM emissions decreased significantly up to 60.07% and 51.33%, respectively. Besides, at higher loads, NOx emissions values of the blend fuels increased, but decreased at lower loads. Moreover, Sound Pressure Level (SPL) and vibration acceleration values with the blend fuels decreased by 2.76% and 18.26%, respectively. As results, using of the metal based additives with dosage of 25 ppm contributed to improvement of SFC, emissions and vibration values for the diesel engines.

Optimizing Separate Exhaust Turbofans for Cruise Specific Fuel Consumption

Cruise specific fuel consumption (SFC) of turbofan engines is a key metric for increasing airline profitability and for reducing CO2 emissions. Although increasing design bypass ratio (BPR) of separate exhaust turbofan configurations improves cruise SFC, further improvements can be obtained with online control actuated variable geometry modulations of bypass nozzle throat area, core nozzle throat area, and compressor variable vanes (CVV/CVG). The scope of this paper is to show only the benefits possible, and the process used in determining those benefits, and not to suggest any particular control algorithm for searching the best combination of the control effectors. A parametric cycle study indicated that the effector modulations could increase the cruise BPR, core efficiency, transmission efficiency, propulsive efficiency, and ideal velocity ratio resulting in a cruise SFC improvement of as much as 2.6% depending upon the engine configuration. The changes in these metrics with control effector variations will be presented. Scheduling of CVV is already possible in legacy digital controls; perturbation to this schedule and modulation of nozzle areas should be explored in light of the low bandwidth requirements at steady-state cruise conditions.

A Study on the Installed Performance Seeking Control for Aero-Propulsion under Supersonic State

AbstractAn integrated model including inlet, engine and nozzle with their internal and external characteristics was built to simulate the propulsion installed performance. With the integrated model, a new performance seeking control scheme under supersonic state is firstly proposed, taking inlet ramp angle as optimizing variable, which is equally important to fuel flow rate, nozzle throat area, guided vane angle of fan and compressor. Specially, engine installed thrust replaces its total thrust as one crucial factor for performance seeking control. Installed performances under supersonic state are significantly improved with the new scheme, as installed thrust increases of up to 4.9% in the maximum thrust mode, installed specific fuel consumption improvements of up to 3.8% in the minimum fuel consumption mode, and turbine temperature decreases of up to 0.6% in the minimum turbine temperature mode. The simulation results also indicates that, the performance seeking control scheme proposed shows superiority in restraining of the increasing of rotational speed and turbine temperature in performance seeking control.

Analyzing the Performance of a Dual Loop Organic Rankine Cycle System for Waste Heat Recovery of a Heavy-Duty Compressed Natural Gas Engine

A dual loop organic Rankine cycle (DORC) system is designed to recover waste heat from a heavy-duty compressed natural gas engine (CNGE), and the performance of the DORC–CNGE combined system is simulated and discussed. The DORC system includes high-temperature (HT) and low-temperature (LT) cycles. The HT cycle recovers energy from the exhaust gas emitted by the engine, whereas the LT cycle recovers energy from intake air, engine coolant, and the HT cycle working fluid in the preheater. The mathematical model of the system is established based on the first and second laws of thermodynamics. The characteristics of waste heat energy from the CNGE are calculated according to engine test data under various operating conditions. Moreover, the performance of the DORC–CNGE combined system is simulated and analyzed using R245fa as the working fluid. Results show that the maximum net power output and the maximum thermal efficiency of the DORC system are 29.37 kW and 10.81%, respectively, under the rated power output condition of the engine. Compared with the original CNG engine, the maximum power output increase ratio and the maximum brake specific fuel consumption improvement ratio are 33.73% and 25%, respectively, in the DORC–CNGE combined system.

Thermodynamic analysis of a Rankine cycle applied on a diesel truck engine using steam and organic medium

A theoretical study is conducted to investigate the potential improvement of the overall efficiency of a heavy-duty truck diesel engine equipped with a Rankine bottoming cycle for recovering heat from the exhaust gas. To this scope, a newly developed thermodynamic simulation model has been used, considering two different working media: water and the refrigerant R245ca. As revealed from the analysis, due to the variation of exhaust gas temperature with engine load it is necessary to modify the Rankine cycle parameters i.e. high pressure and superheated vapor temperature. For this reason, a new calculation procedure is applied for the estimation of the optimum Rankine cycle parameters at each operating condition. The calculation algorithm is conducted by taking certain design criteria into account, such as the exhaust gas heat exchanger size and its pinch point requirement. From the comparative evaluation between the two working media examined, using the optimum configuration of the cycle for each operating condition, it has been revealed that the brake specific fuel consumption improvement ranges from 10.2% (at 25% engine load) to 8.5% (at 100% engine load) for R245ca and 6.1% (at 25% engine load) to 7.5% (at 100% engine load) for water.

Altitude Engine Test of a Turbofan Exhaust Gas Mixer to Conserve Fuel

A comparison of the specific fuel consumption was made with and without an internal mixer installed in a low bypass ratio, confluent flow turbofan engine. Tests were conducted at several Mach numbers and altitudes for core to fan stream total temperature ratios of 2.0 and 2.5 and mixing lengths of L/D = 0.95 and 1.74. For these test conditions, the specific fuel consumption improvement varied from 2.5 to 4.0 percent.