Observed Engine Behavior Research Articles

Performance assessment of classical and fractional controllers for transient operation of gas turbine engines

The nonlinear behaviour of gas turbine engines has motivated the development of advanced controllers for ensuring their safe and reliable operation. In this paper, the problem of controller design for a two-shaft industrial gas turbine is addressed. Specifically, a transient dynamic engine model has been developed in MATLAB/Simulink for assessing the performance behavior of the engine. Observed engine behavior during transient manoeuvres has enabled the development of a PI controller capable of ensuring a smooth gas turbine operation. The performance of the gas turbine engine implementing the developed PI controller has been also compared to a fractional PI controller. Results demonstrate and illustrate the remarkable impact that transient engine simulation has in the development of robust controllers.

Impact of properties of vegetable oil, bio-diesel, ethanol and n -butanol on the combustion and emissions of turbocharged HDDI diesel engine operating under steady and transient conditions

The present work evaluates the impact of properties of four very common bio-fuels, viz. vegetable oil (cottonseed), or its derived (methyl ester) bio-diesel, or ethanol, or n-butanol, in blends of various proportions with diesel fuel, on the combustion and exhaust emissions of a fully instrumented, six-cylinder, four-stroke, heavy-duty direct injection (HDDI), ‘Mercedes-Benz’ bus diesel engine, bearing a waste-gate turbocharger with after-cooler, running under steady and transient conditions. Under steady-state operation, exhaust smoke, nitrogen oxides (NOx), carbon monoxide (CO), and total unburned hydrocarbons (HC) were measured and compared with those of the baseline operation (with neat diesel fuel) and among themselves. Fuel injection, combustion chamber pressure, and heat release rate (HRR) diagrams revealed interesting features of the combustion mechanisms. These results and the different physical and chemical properties of those bio-fuels are used to aid the interpretation of the observed engine behavior. As regards the transient engine operation, measurements for three accelerations tests were examined with the engine fueled on bio-diesel or n-butanol diesel fuel blends. The test bed was complemented with fast response instruments to capture the development of key engine and turbocharger variables, depicted in analytical diagrams, using ultra-fast response instrumentation for the instantaneous measurements of the exhaust NO and smoke opacity. Again, these results and the different physical and chemical properties of bio-fuels are used to aid the interpretation of the engine behavior. Finally, a comparison is made for the influence of bio-fuels properties (bio-diesel and n-butanol) on the NOx and smoke emissions between steady-state and transient operating conditions, under the recognition of the different non-fuel factors affecting the transient operating schedules.

Influence of properties of various common bio-fuels on the combustion and emission characteristics of high-speed DI (direct injection) diesel engine: Vegetable oil, bio-diesel, ethanol, n-butanol, diethyl ether

This work evaluates the influence of properties of various common bio-fuels on the combustion, performance and exhaust emissions of an experimental, single-cylinder, four-stroke, high-speed, DI (direct injection) ‘Hydra’ diesel engine operated at three different loads. Various blends of diesel fuel with either vegetable oil of cottonseed or its derived (methyl ester) bio-diesel, or ethanol, or n-butanol, or diethyl ether were investigated. Fuel consumption, exhaust gas temperature, and exhaust smoke, NOx (nitrogen oxides), CO (carbon monoxide) and total unburned HC (hydrocarbons) were measured. The differences in combustion, performance and exhaust emissions of those bio-fuels blends from the baseline operation of the diesel engine (with neat diesel fuel) and among themselves are compared. Fuel injection, combustion chamber pressure, and HRR (heat release rate) diagrams reveal interesting features of the combustion mechanisms. These results and the different physical and chemical properties of those bio-fuels are used to aid the interpretation of the observed engine behavior. With increasing percentage of all bio-fuels in the blends, significant reduction of smoke opacity is observed with the exception of the vegetable oil case, reduction of NOx, and mixed behavior for the CO and HC emissions against the corresponding neat diesel fuel case.

Combustion and emissions of cottonseed oil and its bio-diesel in blends with either n-butanol or diethyl ether in HSDI diesel engine

This experimental investigation evaluates the combustion and exhaust emission characteristics of cottonseed oil and its (methyl ester) bio-diesel in blends with 20% by vol. of either n-butanol or diethyl ether (DEE), fueling a standard, experimental, single-cylinder, four-stroke, high-speed direct injection (HSDI), ‘Hydra’ diesel engine. The tests are conducted using each of the above fuel blends or neat cottonseed oil or its neat bio-diesel, with the engine operating at three different loads. Fuel consumption, exhaust smoke, nitrogen oxides (NOx), carbon monoxide (CO) and total unburned hydrocarbons (HCs) are measured. The differences in the performance and exhaust emissions of these fuel blends from the baseline operation of the diesel engine, i.e. when working with neat cottonseed oil or its neat bio-diesel, are compared. Fuel injection and combustion chamber pressure diagrams are obtained, and heat release rate analysis of the latter ones is performed revealing some interesting features of the combustion mechanisms. These results and the widely differing physical and chemical properties of n-butanol and DEE against those for the cottonseed oil and its bio-diesel are used to aid the correct interpretation of the observed engine behavior. It is revealed that n-butanol and DEE, which can be produced from biomass (bio-butanol and bio-DEE), when added to the vegetable oil or its bio-diesel improve the behavior of diesel engine.

Characteristics of performance and emissions in high-speed direct injection diesel engine fueled with diethyl ether/diesel fuel blends

An experimental study is conducted to evaluate the performance and exhaust emissions characteristics of diesel fuel blends with 8%, 16% and 24% (by vol.) diethyl ether (DEE), in a standard, experimental, single-cylinder, four-stroke, high-speed direct injection (HSDI), ‘Hydra’ diesel engine located at the authors' laboratory. The tests are conducted using each of the fuel blends or neat diesel fuel, with the engine working at three different loads. Fuel consumption, exhaust smoke, and regulated gas emissions such as nitrogen oxides, carbon monoxide and unburned hydrocarbons are measured. The differences in the performance and exhaust emission parameters of the three DEE/diesel fuel blends from the baseline operation of the diesel engine, i.e., when working with neat diesel fuel, are compared. Combustion chamber and fuel injection pressure diagrams are obtained, and heat release rate analysis of the experimentally obtained cylinder pressure diagrams is performed, revealing some interesting features of the combustion mechanisms. These results and the widely differing physical and chemical properties of DEE against those for diesel fuel are used to aid the interpretation of the observed engine behavior. It is revealed that this fuel, which can be produced from biomass (bio-DEE), is a promising one for diesel engines.

Combining experimental and numerical investigations to explore the potential of downsized engines operating with methane/hydrogen blends

Due to the shortening of oil reserves, many research efforts are currently performed to promote alternative fuels for transport. Among them, natural gas, which is mainly composed of methane, offers one of the most promising potential as its large scale production can today be envisaged from biomass or shale. An other advantage of methane is that its high octane rating allows the use of increased compression ratios compared to gasoline, then improving the thermal efficiency of spark ignition engines. This property, combined with its low carbon content makes natural gas one of the best candidates to drastically reduce CO2 emissions from piston engines. However, methane exhibits a low burning velocity, leading to high cycle-to-cycle variations and, in some cases, to increased CH4 emissions, these latter having a huge impact in terms of greenhouse effect. One solution then consists in blending natural gas with hydrogen, a component easily available in refineries. H2 enrichment indeed allows to reach high flame velocities and to limit quenching effects at the combustion chamber walls. Nevertheless, for the specific case of downsized engines, hydrogen may also lead to increase the knock sensitivity. A compromise in terms of blending rate, compression ratio and boost level should then be necessary to reach an optimal configuration. The objective of the present work is to combine experimental and numerical investigations to explore the influence and limits of hydrogen addition in highly downsized engines. The impact of the fuel composition on the combustion velocity and knock occurrence is studied for three compression ratios (9.5, 11.5 and 13). Experiments are conducted with a single-cylinder engine for a wide range of operating conditions in the stoichiometric mode and hydrogen blending rates from 0 to 40%. 3D CFD simulations are then performed using the Extended Coherent Flame Model (Colin et al, Oil & Gas Sci. & Tech., 2003) to describe the turbulent flame propagation, in combination with the Tabulated Kinetics for Ignition model (Colin et al., Proc. Combust. Inst., 2005) for knock prediction. These models require flame velocities as well as auto-ignition delays and reaction rates data, which have to account for the fuel composition. These data are provided using a priori computations of premixed flames and homogenous reactors with the GRI 3.0 and Curran mechanisms. A very good agreement is obtained between engine simulations and experiments, allowing to use CFD to improve the understanding of the observed engine behavior on specific operating points. It is first shown that the effect of hydrogen addition on the combustion velocity is almost linear for the considered blending levels, and that knock can be hardly found even for high load and high compression ratio cases. It is also demonstrated that optimizing an engine for CH4–H2 blends combustion is a challenging task and that a dedicated engine design should be chosen.

Comparative environmental behavior of bus engine operating on blends of diesel fuel with four straight vegetable oils of Greek origin: Sunflower, cottonseed, corn and olive

An experimental study is conducted to evaluate the use of sunflower, cottonseed, corn and olive straight vegetable oils (SVO) of Greek origin, in blends with diesel fuel at proportions of 10vol.% and 20vol.%, in a fully instrumented, six-cylinder, turbocharged and after-cooled, heavy duty (HD), direct injection (DI), ‘Mercedes-Benz’, mini-bus engine installed at the authors’ laboratory. The series of tests are conducted using each of the above blends, with the engine working at two speeds and three loads. Fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides (NOx), carbon monoxide (CO) and total unburned hydrocarbons (HC) are measured. With reference to the corresponding neat diesel fuel operation, the vegetable oil blends show reduction of emitted smoke with slight increase of NOx and effectively unaffected thermal efficiency. Theoretical aspects of diesel engine combustion, combined with the very widely differing physical and chemical properties of the vegetable oils against those for the diesel fuel, aid to the correct interpretation of the observed engine behavior.

Combustion heat release analysis of ethanol or n-butanol diesel fuel blends in heavy-duty DI diesel engine

An experimental study is conducted to evaluate the effects of using blends of diesel fuel with either ethanol in proportions of 5% and 10% or n-butanol in 8% and 16% (by vol.), on the combustion behavior of a fully-instrumented, six-cylinder, turbocharged and after-cooled, heavy duty, direct injection (DI), ‘Mercedes-Benz’ engine installed at the authors’ laboratory. Combustion chamber and fuel injection pressure diagrams are obtained at two speeds and three loads using a developed, high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams is developed and used. Plots of histories in the combustion chamber of the heat release rate and temperatures reveal some interesting features, which shed light into the combustion mechanism when using these promising bio-fuels that can be derived from biomass (bio-ethanol and bio-butanol). The key results are that with the use of these bio-fuels blends, fuel injection pressure diagrams are very slightly displaced (delayed), ignition delay is increased, maximum cylinder pressures are slightly reduced and cylinder temperatures are reduced during the first part of combustion. These results, combined with the differing physical and chemical properties of the ethanol and n-butanol against those for the diesel fuel, which constitutes the baseline fuel, aid the correct interpretation of the observed engine behavior performance- and emissions-wise.

Investigation of the combustion of neat cottonseed oil or its neat bio-diesel in a HSDI diesel engine by experimental heat release and statistical analyses

An experimental study is conducted to evaluate the effects of using neat cottonseed oil or its neat ME (methyl ester) bio-diesel, on the combustion behavior of a standard, high speed, direct injection (HSDI), ‘Hydra’ diesel engine located at the authors’ laboratory. Combustion chamber and fuel injection pressure diagrams are obtained at medium and high load using a developed, high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams is developed and used. Plots of histories in the combustion chamber of the heat release rate and other related parameters reveal some interesting features, which shed light into the combustion mechanism when using these bio-fuels. These results, combined with the differing physical and chemical properties of the bio-fuels between themselves and against those for the diesel fuel, which constitutes the baseline fuel, aid the correct interpretation of the observed engine behavior performance- and emissions-wise. Moreover, the possible existence of cyclic (combustion) variability is examined as reflected in the pressure indicator diagrams, by analyzing for the maximum pressure and its rate, and the dynamic injection timing and ignition delay, by using statistical analysis for averages, standard deviations and probability density functions. The key results are that with the use of these bio-fuels against the neat diesel fuel case, the ignition delay is hardly affected, the fuel injection pressure diagrams are very slightly advanced accompanied with higher injection pressures, maximum cylinder pressures remain the same with the vegetable oil and slightly increased with the bio-diesel, maximum cylinder pressure rates are increased with the bio-diesel and decreased with the vegetable oil, while the cyclic irregularity is not affected with these bio-fuels remaining at the acceptable neat diesel fuel case levels.

Investigation of the performance and emissions of bus engine operating on butanol/diesel fuel blends

An experimental investigation is conducted to evaluate the effects of using blends of n-butanol (normal butanol) with conventional diesel fuel, with 8% and 16% (by vol.) n-butanol, on the performance and exhaust emissions of a fully instrumented, six-cylinder, water-cooled, turbocharged and after-cooled, heavy duty, direct injection (DI), Mercedes-Benz engine, installed at the authors’ laboratory, which is used to power the mini-bus diesel engines of the Athens Urban Transport Organization sub-fleet. The tests are conducted using each of the above fuel blends, with the engine working at two speeds and three loads. Fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides, carbon monoxide and total unburned hydrocarbons are measured. The differences in the measured performance and exhaust emissions of the two butanol/diesel fuel blends from the baseline operation of the engine, i.e. when working with neat diesel fuel, are determined and compared. It is revealed that this fuel, which can be produced from biomass (bio-butanol), is a very promising bio-fuel for diesel engines. The differing physical and chemical properties of n-butanol against those for the diesel fuel, aided by sample cylinder pressure and heat release rate diagrams, are used to interpret the observed engine behavior.

Effects of butanol–diesel fuel blends on the performance and emissions of a high-speed DI diesel engine

An experimental investigation is conducted to evaluate the effects of using blends of n-butanol (normal butanol) with conventional diesel fuel, with 8%, 16% and 24% (by volume) n-butanol, on the performance and exhaust emissions of a standard, fully instrumented, four-stroke, high-speed, direct injection (DI), Ricardo/Cussons ‘Hydra’ diesel engine located at the authors’ laboratory. The tests are conducted using each of the above fuel blends or neat diesel fuel, with the engine working at a speed of 2000 rpm and at three different loads. In each test, fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides, carbon monoxide and total unburned hydrocarbons are measured. The differences in the measured performance and exhaust emission parameters of the three butanol–diesel fuel blends from the baseline operation of the diesel engine, i.e., when working with neat diesel fuel, are determined and compared. It is revealed that this fuel, which can be produced from biomass (bio-butanol), forms a challenging and promising bio-fuel for diesel engines. The differing physical and chemical properties of butanol against those for the diesel fuel are used to aid the correct interpretation of the observed engine behavior.

Investigation of Mixture Preparation Effects on Gasoline HCCI Combustion Aided by Measurements of Wall Heat Flux

Abstract Expanding the range of HCCI operation will be critical for maximizing the fuel economy benefits in future vehicle applications. The mixture stratification, both thermal and compositional, can have very tangible impact on HCCI combustion, and gaining a deeper insight into these effects is critical for expanding the HCCI range of operation. This paper presents results of the comprehensive experimental investigation of the mixture preparation effects on a single-cylinder gasoline HCCI engine with exhaust reinduction. The effects include the type of mixture preparation (external mixing versus direct injection), charge motion, and injection timing. A combination of pressure-based combustion diagnostics, emission analysis, and heat flux measurements on the combustion chamber wall quantifies the effects on combustion and provides insight into reasons for observed engine behavior. As an example, the instantaneous temperature and heat flux measurements show the fuel impingement locations and allow assessing the fuel film dynamics and their effect on mixture stratification. The effects of direct injection and partial closing of the swirl control valve are relatively small compared with extending the injection timing late into the intake process or completely closing the swirl control valve and allowing charge storage in the intake port.

Effects of ethanol–diesel fuel blends on the performance and exhaust emissions of heavy duty DI diesel engine

An experimental investigation is conducted to evaluate the effects of using blends of ethanol with conventional diesel fuel, with 5% and 10% (by vol.) ethanol, on the performance and exhaust emissions of a fully instrumented, six-cylinder, turbocharged and after-cooled, heavy duty, direct injection (DI), Mercedes–Benz engine, installed at the authors’ laboratory, which is used to power the mini-bus diesel engines of the Athens Urban Transport Organization sub-fleet with a view to using bio-ethanol produced from Greek feedstock. The tests are conducted using each of the above fuel blends, with the engine working at two speeds and three loads. Fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides, carbon monoxide and total unburned hydrocarbons are measured. The differences in the measured performance and exhaust emissions of the two ethanol–diesel fuel blends from the baseline operation of the engine, i.e. when working with neat diesel fuel, are determined and compared. Theoretical aspects of diesel engine combustion combined with the widely differing physical and chemical properties of the ethanol against those for the diesel fuel, are used to aid the correct interpretation of the observed engine behavior.

Performance and emissions of bus engine using blends of diesel fuel with bio-diesel of sunflower or cottonseed oils derived from Greek feedstock

An experimental investigation is conducted to evaluate the use of sunflower and cottonseed oil methyl esters (bio-diesels) of Greek origin as supplements in the diesel fuel at blend ratios of 10/90 and 20/80, in a fully instrumented, six-cylinder, turbocharged and after-cooled, direct injection (DI), Mercedes-Benz, mini-bus diesel engine installed at the authors’ laboratory. The tests are conducted using each of the above fuel blends, with the engine working at two speeds and three loads. Fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides, carbon monoxide and total unburned hydrocarbons are measured. The differences in the measured performance and exhaust emissions from the baseline operation of the engine, i.e., when working with neat diesel fuel, and the two bio-diesels are determined and compared. Theoretical aspects of diesel engine combustion with the differing physical and chemical properties of these blends, aid the correct interpretation of the observed engine behavior.

Experimental heat release analysis and emissions of a HSDI diesel engine fueled with ethanol–diesel fuel blends

Abstract An experimental study is conducted to evaluate the effects of using blends of ethanol with conventional diesel fuel, with 5%, 10% and 15% (by vol.) ethanol, on the combustion and emissions of a standard, fully instrumented, four-stroke, high-speed, direct injection (HSDI), ‘Hydra’ diesel engine located at the authors’ laboratory. The tests are conducted using each of the above fuel blends or neat diesel fuel, with the engine working at a speed of 2000 rpm and at four different loads. In each test, combustion chamber and fuel injection pressure diagrams are obtained using a specially developed, high-speed, data acquisition and processing system. A heat release analysis of the experimentally obtained cylinder pressure diagrams is developed and used, with the pertinent application of the energy and state equations. From the analysis results, plots of the history in the combustion chamber of the gross heat release rate and other related parameters reveal some very interesting features, which shed light on the combustion mechanism when using these blends. Moreover, for each test, volumetric fuel consumption, exhaust smokiness and exhaust regulated gas emissions are measured. The differences in the performance and exhaust emission parameters from the baseline operation of the diesel engine, i.e., when working with neat diesel fuel, are determined and compared. The heat release analysis results for the relevant combustion mechanism, combined with the widely differing physical and chemical properties of the ethanol against those for the diesel fuel, are used to aid the correct interpretation of the observed engine behavior.

Comparative performance and emissions study of a direct injection Diesel engine using blends of Diesel fuel with vegetable oils or bio-diesels of various origins

An extended experimental study is conducted to evaluate and compare the use of various Diesel fuel supplements at blend ratios of 10/90 and 20/80, in a standard, fully instrumented, four stroke, direct injection (DI), Ricardo/Cussons ‘Hydra’ Diesel engine located at the authors’ laboratory. More specifically, a high variety of vegetable oils or bio-diesels of various origins are tested as supplements, i.e. cottonseed oil, soybean oil, sunflower oil and their corresponding methyl esters, as well as rapeseed oil methyl ester, palm oil methyl ester, corn oil and olive kernel oil. The series of tests are conducted using each of the above fuel blends, with the engine working at a speed of 2000 rpm and at a medium and high load. In each test, volumetric fuel consumption, exhaust smokiness and exhaust regulated gas emissions such as nitrogen oxides (NOx), carbon monoxide (CO) and total unburned hydrocarbons (HC) are measured. From the first measurement, specific fuel consumption and brake thermal efficiency are computed. The differences in the measured performance and exhaust emission parameters from the baseline operation of the engine, i.e. when working with neat Diesel fuel, are determined and compared. This comparison is extended between the use of the vegetable oil blends and the bio-diesel blends. Theoretical aspects of Diesel engine combustion, combined with the widely differing physical and chemical properties of these Diesel fuel supplements against the normal Diesel fuel, are used to aid the correct interpretation of the observed engine behavior.

Interpretation of Gas Turbine Response Due to Dust Ingestion

A measurement program currently underway at Arvin/Calspan Advanced Technology Center has been used in the evaluation of observed engine behavior during dust ingestion. The Pratt and Whitney TF33 turbofan and J57 turbojet were used in the investigation. Solid particle ingestion was found to erode the compressor blades and result in substantial performance deterioration. The engines were found to have increased susceptibility to surge at low power settings. The roles that anti-ice and intercompressor bleed airplay in surge avoidance are discussed. A discussion of the fuel controller behavior in a deteriorated engine and its effect during steady-state engine operation is also presented. Experimental data obtained during testing were compared to a predictive capability developed to describe deteriorated engine response. The effects of tip clearance, blade profile, and secondary flows were taken into account. The results show good agreement with experimentally observed engine behavior.