Engine Operation Modes Research Articles

Performance studies on homogeneous charge compression ignition (HCCI) engine powered with alternative fuels

Abstract Experiments were carried out on homogeneous charge compression ignition (HCCI) engine to study its performance at different hydrogen fuel energy ratio (HFER) and loads. The engine was powered with two fuels: Hydrogen (H2) as inducted fuel along with air and diesel/Biodiesel fuel (BDF) as injected fuel. Diesel and BDF were injected into the cylinder using common rail direct injection (CRDI) facility developed. Electronic control unit (ECU) was developed to inject the fuel at any required crank angle (CA) for any magnitude of duration. At 80% load, engine operation was associated with severe knocking without exhaust gas recirculation (EGR), however engine operated well only for EGR percentage about 50% and 54% with diesel and BDFs respectively. Beyond this EGR level, HCCI engine showed misfiring and unstable combustion. At this condition, maximum HFER possible was less than 8% in both diesel and biodiesel HCCI operations and misfiring occurred beyond HFER of 8%. The maximum brake thermal efficiency (BTE) of 31.5%, 30.6% and 30.2% were reported with diesel, honge biodiesel (BHO) and cotton seed biodiesel (BCO) respectively in diesel hydrogen HCCI (DHHCCI) and biodiesel hydrogen HCCI (BHHCCI) modes. At 80% load, HCCI engine powered with BDFs showed 65–67% lower smoke, and 98–99% lower NOx emissions with HFER of 7% and EGR of 54% as compared to conventional compression ignition (CI) mode. However this engine operation resulted in nearly 11 times higher HC emissions with HFER of 7% and EGR of 54%. Hence HCCI mode of engine operation could be a feasible technological option to minimize the pollution levels besides improving the fuel economy.

Combustion Model for a Homogeneous Turbocharged Gasoline Direct-Injection Engine

Homogeneous charge is a preferred operation mode of gasoline direct-injection (GDI) engines. However, a limited amount of work exists in the literature for combustion models of this mode of engine operation. Current work describes a model developed to study combustion in a homogeneous charge GDI engine. The model was validated using experimental data from a 1.6 L Ford EcoBoost® engine, tested at the U.S. EPA. The combustion heat release was approximated using a double-Wiebe function, to account for the rapid initial premixed combustion followed by a gradual diffusion-like state of combustion, as observed in this GDI engine. Variables of Wiebe correlations were adjusted into a semipredictive combustion model. The effectiveness of semipredictive combustion model was tested in prediction of in-cylinder pressures. The root-mean-square (RMS) errors between experiments and numerical results were within 2.5% of in-cylinder peak pressures during combustion. The semipredictive combustion model was further studied to develop a predictive combustion model. The performance of predictive combustion model was examined by regenerating the experimental cumulative heat release. The heat release analysis developed for the GDI engine was further applied to a dual mode, turbulent jet ignition (DM-TJI) engine. DM-TJI is a distributed combustion technology with the potential to provide diesel-like efficiencies and minimal engine-out emissions for spark-ignition engines. The DM-TJI engine was observed to offer a faster burn rate and lower in-cylinder heat transfer compared to the GDI engine.

Combustion and emission characteristics of a 2.2L common-rail diesel engine fueled with jatropha oil, soybean oil, and diesel fuel at various EGR-rates

To investigate the combustion and emission behavior of straight vegetable oils (SVO), jatropha oil, soybean oil, and diesel fuel were tested. For this research, a 2.2L common-rail engine with a two-stage turbocharging concept was equipped with a cylinder pressure indication system, an exhaust-gas analyzer, an AVL Micro Soot sensor and a Scanning Mobility Particle Sizer 3936 (SMPS) device to detect the particle-size-distribution (PSD). At a low- and mid-load engine-operating point (EOP), the thermodynamic and emissions were investigated under various exhaust gas recirculation (EGR) rates with respect to the PSD. Moreover, the injection behavior of the three test fuels was analyzed separately using an injection rate analyzer. This procedure facilitates the thermodynamic investigations of the engine process and allows the calculation of the hydraulic delay (HD) as well as the ignition delay (ID). The ID of the SVO fuels compared to diesel fuel was found to be lower at all engine-operating modes, while jatropha oil always showed the shortest ID. In the particulate-nitrogen oxide (NOX) trade-off, the SVO fuels showed higher particulate matter (PM) emissions at the low-load EOP, whereas the PM emissions of diesel fuel overtop the SVO fuels at a higher engine load. With increased EGR-rates, a rise in the particle size was observed for all fuels. At the low-load EOP, the SVO fuels showed larger particles for high EGR-rates. This effect also changed by increasing the engine-load to the mid-load EOP, wherein the particle size of the diesel fuel emissions is higher by applying elevated EGR-rates.

Optical Phenomena Observed upon Some Launches of Russian Rockets

In this paper, unusual optical phenomena observed in our country and abroad upon launches of Russian rockets are discussed and interpreted: they are regarded as the aftereffects of sunlight scattering by gas-dust clouds created by rocket fuel combustion products in different modes of engine operation. The results of instrumental observations of the clouds can be used to study physical processes in the upper atmosphere.

Estimation of the flight thrust increment changing the operation mode of the engine

The paper presents a new method for flight test identification of the thrust increment when changing engine operation mode. It is known that the problem of separate estimation of the engine thrust and the aerodynamic drag force from the aircraft flight data belongs to a class of ill-posed. The idea of the presented method is to come out of the ill-posed class by changing the original problem formulation. To achieve this purpose we give up the absolute values of the thrust and proceed to estimating the thrust increment resulting from the change of the aircraft engine operation mode. The accuracy of the solution is improved by introducing the special flight test maneuver. The algorithm requires only a few on-board measured parameters, such as longitudinal and normal overload, airspeed and altitude, and angle of attack. The complimentary use of the engine gas-dynamic model may improve the estimates but is not obligatory. The proposed method also does not require a-priory estimates of the aerodynamic drag force.

Energy and exergy analyses of a combined cycle Kalina and organic Rankine cycles using waste heat

In current research, wasted heat from a reactivity controlled compression ignition (RCCI) engine provides driving energy for organic Rankine cycle (ORC) and Kalina cycle. After developing a numerical model for this system, the effects of some decision variables on the energy and exergy efficiencies are studied. The obtained results show that, by adding ORC and Kalina cycles, energy and exergy efficiency values are increased while, brake specific values of oxides of nitrogen (NOx) and carbon monoxide (CO) emissions are decrease in selected three engine operation modes (4, 9 and 23 bar indicated mean effective pressure) without changing in fuels consumption.

Energy and exergy analyses of a combined cycle Kalina and organic Rankine cycles using waste heat

In current research, wasted heat from a reactivity controlled compression ignition (RCCI) engine provides driving energy for organic Rankine cycle (ORC) and Kalina cycle. After developing a numerical model for this system, the effects of some decision variables on the energy and exergy efficiencies are studied. The obtained results show that, by adding ORC and Kalina cycles, energy and exergy efficiency values are increased while, brake specific values of oxides of nitrogen (NOx) and carbon monoxide (CO) emissions are decrease in selected three engine operation modes (4, 9 and 23 bar indicated mean effective pressure) without changing in fuels consumption.

Fuel consumption assessment of an electrified powertrain with a multi-mode high-efficiency engine in various levels of hybridization

Powertrain electrification including hybridizing advanced combustion engines is a viable cost-effective solution to improve fuel economy of vehicles. This will provide opportunity for narrow-range high-efficiency combustion regimes to be able to operate and consequently improve vehicle’s fuel conversion efficiency, compared to conventional hybrid electric vehicles. Low temperature combustion (LTC) engines offer the highest peak brake thermal efficiency (BTE) reported in literature, but these engines have narrow operating ranges. In addition, LTC engines have ultra-low soot and nitrogen oxides (NOx) emissions, compared to conventional compression ignition and spark ignition (SI) engines. In this study, an experimentally developed multi-mode LTC-SI engine is integrated into a parallel hybrid electric configuration, where the engine operation modes include homogeneous charge compression ignition (HCCI), reactivity controlled compression ignition (RCCI), and conventional SI. The powertrain controller is designed to enable switching among different modes, with minimum fuel penalty for transient engine operations. A pontryagin’s minimum principal (PMP) methodology is used in the energy management supervisory controller to study a multi-mode LTC engine in parallel HEV architecture with various hybridization levels. The amount of torque assist by the e-motor can change the LTC mode operating time, which leads to variation in the vehicle’s fuel consumption. The results for the urban dynamometer driving schedule (UDDS) driving cycle show the maximum benefit of the multi-mode LTC-SI engine is realized in the mild electrification level, where the LTC mode operating time increases dramatically from 5.0% in a plug-in hybrid electric vehicle (PHEV) to 20.5% in a mild HEV.

Interaction of diesel engine soot with NO2 and O2 at diesel exhaust conditions. Effect of fuel and engine operation mode

This work shows a study of the reactivity of twelve different types of soot with either NO2 or O2 under reacting conditions typically present in diesel particulate filters (DPFs). The soot samples were obtained from the combustion of four conventional and alternative fuels (diesel, biodiesel and two paraffinic fuels) in a diesel engine bench operated under three different engine operation modes: a typical urban-driving mode and two variations to this mode to assess the effect of the injection settings. The main objective of the work is to relate the oxidative reactivity of the soot to the nature and the origin of each sample. The possible simultaneous elimination of soot and NOx at typical diesel exhaust conditions is examined, as well. The reactivity tests were performed in a laboratory quartz gas flow reactor, discontinuous for the solid. The soot-NO2 interaction was studied with 200 ppm of NO2 at 500 °C and the soot-O2 interaction was studied with 5% O2 at 500 °C and 600 °C. The experimental results were used to determine the time needed for the complete conversion of carbon (τ) through the use of the equations of the Shrinking Core Model for solid-gas reactions with decreasing size particle and chemical reaction control. In general, the τ values show that the diesel fuel generates a less reactive soot than biodiesel or the alternative paraffinic fuels. In addition, increasing the injection pressure or adding a post-injection to the original injection strategy generates a more reactive soot. These findings point out that there is potential to achieve efficient regeneration processes in DPFs through other fuels than conventional ones and via engine calibration.

Topological development of homogeneous-charge and spray-guided stratified-charge flames in an internal combustion engine

In this work, engine flame topological development was studied to improve the understanding of flame growth in direct-injection engines, in particular when operated under homogeneous-charge and spray-guided stratified-charge combustion conditions. Flame wrinkledness is one of the most important and poorly understood engine combustion phenomena. Generally, a flame may wrinkle for two reasons: (1) its own natural instabilities and/or (2) through interaction with turbulent flow. The relative contribution of these two causes toward flame wrinkledness in the engine environment was unclear, so targeted experiments were performed to provide some clarity. The development of flame wrinkledness within an optically accessible engine was measured with a combination of planar laser–induced fluorescence and stereo particle image velocimetry under homogeneous-charge and stratified-charge conditions. Using the resulting data, equivalence ratio, charge velocities, and flame wrinkledness were quantified and analyzed. For the iso-octane–toluene mixtures studied, flame wrinkling was insensitive to thermo-diffusive flame front instabilities. The relative contribution of wrinkles of various spatial scales toward overall flame wrinkledness was also measured. Homogeneous-charge flames generally had lower wrinkling factors than stratified-charge flames. Overall, flame wrinkledness increased with flame size under both modes of engine operation. Large flames demonstrated an ability to maintain more large-scale wrinkles than small flames, which contributed to their overall higher levels of wrinkledness.

ОСОБЕННОСТИ РАБОТЫ ДИЗЕЛЯ НА РЫЖИКО-МИНЕРАЛЬНОМ ТОПЛИВЕ В РЕЖИМЕ САМОСТОЯТЕЛЬНОГО ХОЛОСТОГО ХОДА

The mode of independent idling, characterized by an impaired process flow, unproductive fuel consumption and increased emissions of harmful substances into the atmosphere, is the most unfavorable mode of the diesel engine operation. Therefore, the aim of the research is to reveal the peculiarities of the tractor diesel engine operation by the camelina-mineral fuel in the mode of independent idling. Camelina-mineral fuel is a mixture of camelina oil and mineral diesel fuel in certain ratio of these components. To assess the possibility of using the camelina oil as biological component of diesel mixed fuel, an experimental study of the D-243 diesel engine in idling mode was carried out, and the degree of influence of the different ratio of the components of the mixed fuel on its parameters was determined. The researches were carried out with the diesel fuel on the L-0.2-62 mineral fuel and the camelina-mineral fuel with a ratio of the biological and mineral components: 25% RyzhM + 75% DT; 50% RyzhM + 50% DT; 75% RyzhM + 25% DT; 90% RyzhM + 10% DT and 90% RyzhM + 10% DT (US). For the parameters of the diesel, the excess air factor, the filling ratio of the diesel cylinder with fresh charge, the maximum cycle pressure, the hourly fuel consumption, smoke and carbon monoxide content in the exhaust gases are taken. It is established that when the diesel engine works on camelina-mineral fuel mode the minimum sustainable speed of the crankshaft idle speed 800 min-1 the values of maximum cycle pressure (6.3 MPa) and the filling ratio of the cylinders of a diesel engine the fresh charge (0,87) remain unchanged. The coefficient of excess air, increasing in mixed fuel shares of camelina oil to 90%, reduced from 7.187 to 4.619, while fuel consumption increases of 1.1 kg/h 2 kg/h. The best environmental indicators are observed when working on red-and-mineral fuel 50% RyzhM + 50% DT. Handling mixed fuel with ultrasound reduces fuel consumption, smoke and content of carbon oxide in the exhaust gas relative to the mixed fuel not treated with ultrasound.

A Study on Reliability Assessment Criteria of Diaphragm-type Accumulator for Intake and Exhaust Valve of Large Ship

A diaphragm type accumulator ("accumulator") is used in a wide range of hydraulic systems, especially the intake valve for fuel injection and the exhaust valve activated after a stroke in the electronic control unit of a ship to reduce shock waves and pulsation pressure and compensate for pressure. In this application, the diaphragm operates in the same manner as in the engine operation mode (240 rev/min : 4 Hz) and is exposed to harsh conditions including abrupt surge pressure (ΔP). Given these such conditions, the diaphragm is physically and structurally vulnerable to recurring faults. While existing local and international assessment standards largely attribute faults in accumulators to damaged diaphragms, screws in the caps and body assemblies break due to structural problems. This leads to loss of functionality and safety issues instead of decreasing performance. This study assumes that the main cause of faults in diaphragm type accumulators are damaged screws and explores the method of assessing reliability using pressure rating testing on a pressurized vessel of NFPA T/2.6.1 dimension. It also looks into a monitoring system to identify any N2 gas leakage during testing.

Fuel consumption assessment of a multi-mode low temperature combustion engine as range extender for an electric vehicle

Low temperature combustion (LTC) engines, including homogeneous charge compression ignition (HCCI) and reactivity controlled compression ignition (RCCI), are promising to improve powertrain fuel consumption and reduce NOx and soot emissions by improving the in-cylinder combustion process. However, the narrow operating range of LTC engines limits the use of these engines in conventional powertrains. In range extenders, the engine is decoupled from the drivetrain, which allows the engine to operate in a limited operating range; thus, range extenders offer an ideal application for realizing the advantages of LTC engines. In this study, the optimum fuel consumption improvement of an experimentally developed 2-l multi-mode LTC-SI range extender is investigated in a light-duty battery electric vehicle (BEV) platform. In the optimization framework, the mode-switching fuel penalty, exhaust aftertreatment catalyst light-off temperature, and engine noise, vibration, harshness (NVH) are considered. The engine operation modes include HCCI, RCCI, and conventional spark ignition (SI). The simulation results show in the city driving cycle, the single-mode HCCI and RCCI range extenders offer 11.0% and 5.4% fuel consumption improvement, respectively over a single-mode SI range extender. These improvements increase to 12.1% and 9.1% in the highway driving cycles. In the multi-mode operation, up to 1.4% higher fuel economy is achieved over different driving cycles, compared to single-mode HCCI/RCCI operation. As the driving cycle average demanded power increases, the contribution of the RCCI mode predominates the HCCI mode.

Mixed alumina and cobalt containing plasma electrolytic oxide coatings

Principles of plasma electrolytic oxidation of the AL25 aluminum alloy in diphosphate alkali solutions containing cobalt(2+) cations are discussed. It has been established that a variation in the concentration of the electrolyte components provides the formation of mixed-oxide coatings consisting of the basic matrix materials and the cobalt oxides of different content. An increase in the cobalt oxide content in the coating is achieved by the variation in electrolysis current density as well as the treatment time due to both the electrochemical and thermo-chemical reactions at substrate surface and in spark region. Current density intervals that provide micro-globular surface formation and uniform cobalt distribution in the coating are determined. The composition and morphology of the surface causes high catalytic properties of synthesized materials, which confirmed the results of testing in model reaction CO and benzene oxidation as well as fuel combustion for various modes of engine operation.

Dynamic Turbine Clearance Simulation Considering the Influence of Temperature on Mechanical Load–Induced Displacements

AbstractThis paper addresses the problem of precise in-flight simulation of all dynamic engine operational modes, considering the specific features of the control in these modes. One of the dynamic...

Effect of Cooling Parameters on the Thermostressed State of Gas Turbine Nozzle Blades

Numerical simulation results for the material condition of cooled turbine blades at unsteady engine operation modes are presented. The cooling efficiency and relative thermal stresses are linearly related under different heat transfer and fixing conditions. The procedure for the effective assessment of heat transfer parameters that provides the optimum thermal fatigue life of the blade material is proposed.

Characterization of Gas-Phase Organics Using Proton Transfer Reaction Time-of-Flight Mass Spectrometry: Aircraft Turbine Engines

Nonmethane organic gas emissions (NMOGs) from in-service aircraft turbine engines were investigated using a proton transfer reaction time-of-flight mass spectrometer (PTR-ToF-MS) at an engine test facility at Zurich Airport, Switzerland. Experiments consisted of 60 exhaust samples for seven engine types (used in commercial aviation) from two manufacturers at thrust levels ranging from idle to takeoff. Emission indices (EIs) for more than 200 NMOGs were quantified, and the functional group fractions (including acids, carbonyls, aromatics, and aliphatics) were calculated to characterize the exhaust chemical composition at different engine operation modes. Total NMOG emissions were highest at idling with an average EI of 7.8 g/kg fuel and were a factor of ∼40 lower at takeoff thrust. The relative contribution of pure hydrocarbons (particularly aromatics and aliphatics) of the engine exhaust decreased with increasing thrust while the fraction of oxidized compounds, for example, acids and carbonyls increased. Exhaust chemical composition at idle was also affected by engine technology. Older engines emitted a higher fraction of nonoxidized NMOGs compared to newer ones. Idling conditions dominated ground level organic gas emissions. Based on the EI determined here, we estimate that reducing idle emissions could substantially improve air quality near airports.

Comparative analysis of performance of dual fuel (DF) and homogeneous charge compression ignition (HCCI) engines fuelled with honne oil methyl ester (HOME) and compressed natural gas (CNG)

Experiments were conducted at different compressed natural gas energy ratio (CNGER), brake mean effective pressure (BMEP) and charge temperatures to perform the comparative analysis of homogeneous charge compression ignition (HCCI) and dual fuel (DF) engines. Compressed natural gas (CNG) was inducted along with air and diesel/honne oil methyl ester (HOME) was injected into the intake air to control the start of combustion. The engine could not run at BMEP below 2.5bar in the HCCI mode as the intake charge temperature could not be raised beyond 145°C due to system limitations and beyond a BMEP of 4bar, combustion rate became very high and very careful control over the charge temperature and CNG flow rate was needed. In DF mode the liquid fuel was injected into the cylinder and CNG was inducted along the intake air. Brake thermal efficiency (BTE) of compressed natural gas diesel homogeneous charge compression ignition (CNGDHCCI) and compressed natural gas biodiesel homogeneous charge compression ignition (CNGBHCCI) as well as the compressed natural gas diesel dual fuel (CNGDDF) and compressed natural gas biodiesel dual fuel (CNGBDF) modes are lower than that of neat diesel powered compression ignition (CI) mode of engine operation. However, the BTE of CNGDHCCI and CNGBHCCI is always better than that of CNGDDF and CNGBDF modes. Nitrogen oxide (NOx) and smoke emission drastically reduced in HCCI mode of engine operation but carbon monoxide (CO) and hydrocarbon (HC) emissions are higher.

Measurement of exhaust gas emissions from miniature turbojet engine

This paper presents a methodology developed to measure exhaust gas emissions during operation of a miniature turbojet engine, using a laboratory test rig. The rig has been built for research and development works aimed at modelling and investigating processes and phenomena occurring in jet engines. The miniature jet engines, similarly to full–scale ones used commonly in air transport, are characterized by variable exhaust gas emissions, depending on engine operating parameters. For this reason, an attempt has been made to determine the characteristic features of miniature engine operation modes and to define the variability of operation parameters and exhaust gas emissions as a function of time. According to the authors, the preliminary tests allowed for defining specific profile of engine test, which enables proper measurement regarding exhaust gas emissions using the miniature jet engine. The paper also presents test results for Jet A-1 fuel, according to the used methodology.

Formaldehyde, acetaldehyde and other aldehyde emissions from HCCI/SI gasoline engine equipped with prototype catalyst

In this study a qualitative and quantitative analysis of carbonyl compound emissions from exhaust gas of homogeneous charge compression ignition (HCCI) and spark ignition (SI) engines, trapped on dinitrophenylhydrazine (DNPH) solution, were investigated. The hydrazine formed were analysed by means of HPLC and detected with ultraviolet (UV) detector. 15 standards of carbonyl – DNPH derivatives were identified and compared with engine emissions before and after catalyst. Emissions compounds such as formaldehyde (HCHO), acetaldehyde (CH3CHO), and acrolein (H2CHCHO) are of interest to the scientific and regulatory communities due to their suspected or likely impacts on human health. The frequent exhaust products of the two engine operation modes were, acetaldehyde followed by acrolein, m-tolualdehyde, benzaldehyde (C6H5CHO) and formaldehyde; other aldehydes in the exhaust gas were observed to be very small. The percentage contribution of carbonyl compounds to the total hydrocarbon (THC) emissions in this study lies between 2.6–4.5% for HCCI stoichiometric and 5.5–8.4% for HCCI lean operation. These results indicate that engine-operating conditions appear to exert a strong influence on the total mass emissions of carbonyls measured before catalyst. The prototype catalytic converter eliminates most of the carbonyls species in the exhaust in both combustion modes except for acetaldehyde species, a negative conversion presented for all engine conditions. A prototype catalyst showed high efficient conversion on aromatic and unsaturated aldehyde for both engine modes.