Part Load Conditions Research Articles

Numerical matching of supercharger for gasoline engine based on three-line working condition method

The traditional study of matching gasoline engine and supercharger mainly focuses on the external characteristic conditions, but the reasonable matching of external characteristic conditions cannot guarantee the reasonable matching of supercharger and gasoline engine in the whole operating range. Therefore, to address the limitation of studying only the external characteristic conditions in the supercharger matching process, a thermodynamic model of a direct injection supercharged gasoline engine was established, based on which the matching between the supercharger and the gasoline engine in the whole operating range was studied by the three-line condition method. The results show that the matching performance of the supercharger in the whole engine operating range can be significantly improved by using the three-line working condition method to match the supercharger. The three-line method takes into account both full-load and part-load engine conditions, and can visually evaluate the operating efficiency of the supercharger over the entire engine operating range, as well as predict the likelihood of surging, blocking and overspeeding of the supercharger over the entire engine operating range, overcoming the limitation of studying only the external characteristic conditions and providing a numerical evaluation method for pre-selection and optimization of the supercharger.

Dynamic Simulation of Partial Load Operation of an Organic Rankine Cycle with Two Parallel Expanders

The parallel expander ORC system is one of the solutions for providing an additional power output by improving the partial-load performance of an ORC. The parallel expander system corresponds to partial-load conditions by switching between various combinations of the expanders. During this process, the dynamic behavior occurs, which have not been characterized well in the open literature according to the best of the authors’ knowledge. In this study, we developed a dynamic modeling of an ORC system using dual expanders (DE-ORC) to study the dynamic responses during its mode changes. System components were simulated using an open-source library of ThermoCycle written in Modelica language. For each component, empirical parameters were implemented based on the experimental results. Furthermore, during the mode change that involved going from dual expander mode to singular expander mode, and to prevent the formation of the droplet in the expanders, a control strategy was proposed and simulated. The strategy involved lowering of the mass flow rate and then shifting the mode. Several timings between flow rate lowering and shifting the mode were analyzed, and the optimum shifting time was found to be in between 40 to 50 s.

Design and calculation of an environmentally friendly carbon-free hybrid plant based on a microgas turbine and a solid oxide fuel cell

This is an overview of a hybrid power plant design and predesign analysis, including a microgas turbine with heat recovery, a high-temperature fuel cell, and a carbon dioxide capture system. A hybrid installation model is presented, taking into account the compatibility and technological limitations of the main components. The material and heat balance calculation of a hybrid power plant is performed depending on the input parameters under partial load conditions. In order to create a decarbonized highly efficient energy production process and in connection with the need to minimize the negative impact of carbon dioxide on the environment, the article presents the developed technologies for carbon dioxide utilization and a carbon adsorption unit as a hybrid power plant part. The hybrid power plant is a carbon-free mini thermal power plant with integrated electricity, steam, and hot water generation and more than 90% total efficiency.

Exergy analysis of a steam power plant at full and partial load conditions

Exergy analysis of a steam power plant at full and partial load conditions

To the substantiation of charge air parameters on different operating modes of diesel engines of diesel locomotives

A numerical method is proposed for quantitative assessment of the specific effective air consumption and the influence of atmospheric air temperature on the working process of a diesel engine, taking into account various modes of its operation. The dynamics of changes in the values of the coefficients of excess air and filling the cylinder with a fresh air charge over the period of the diesel operating process is substantiated depending on the temperature of the outside and charge air, as well as the position of the locomotive driver’s controller, obtained in the form of tabular data and graphical dependencies. The possibilities of increasing the fuel efficiency of operating diesel engines up to 5 - 10 percent through quantitative and qualitative regulation of coolant temperatures or through throttling, heating and cooling of charge air are formulated. It is recommended to continue research to improve the quality of the operating process of supercharged transport diesel engines by substantiating the air characteristics of such diesel engines and their subsequent combination with diesel locomotive and fuel characteristics under partial load conditions and, especially, at low ambient temperatures.

Exergy analysis of a steam power plant at full and partial load conditions

Exergy analysis of a steam power plant at full and partial load conditions

Покращення показників автомобільних дизельних двигунів при додаванні водневої каталітичної добавки

The aim of the study is to present a new proposed method for improving the efficiency of transportation diesel engines. Considering the rising cost of transportation, where 80% of the expenses are attributed to fuel costs, there is a necessity to develop methods for reducing fuel consumption. Among the main approaches are the use of alternative fuels or fuel additives. One of the most effective and promising options is the utilization of hydrogen, both as an alternative fuel and a fuel additive. Among the crucial factors significantly influencing the efficiency of hydrogen additives is the method of their delivery to the internal combustion engine. Injecting hydrogen during the engine's intake stroke, although a simple method, faces challenges in achieving precise engine control and poses risks due to the potential formation of an explosive mixture in the intake tract and subsequent ignition. A proposed solution involves introducing small hydrogen additives into the high-pressure fuel line, between the fuel pump and the injector. After the completion of the injection process in the high-pressure line, a "rarefaction wave" is generated. Utilizing this effect allows introducing a small amount of hydrogen into the diesel fuel. Hydrogen delivery is ensured by a special device equipped with a check valve that reacts to changes in pressure in the fuel line. Hydrogen, when introduced into the fuel, promotes improved combustion and increased engine efficiency. This results in a reduction in fuel consumption by 0.4 to 3.5% compared to nominal values, with particularly high fuel efficiency observed at partial load conditions, as well as during acceleration and maneuvers. It is worth noting the positive environmental impact of this technology. When adding hydrogen in a proportion of 0.1% of the fuel mass, a decrease in hydrocarbon emissions by 40–50% and carbon monoxide by 15–25% is observed. However, an increase in nitrogen oxide emissions by 3–7% has been identified, which is associated with a certain elevation of the maximum cycle temperature. Nevertheless, NOx emissions increase can be mitigated by implementing appropriate adjustments to the engine's operating parameters.

To the study of 10D100 diesel engines of operating diesel locomotives by the fuel supply advance angle

The results of the justification for the distribution of diesel engines 10D100 are presented, taking into account the value of the actual advance angle of fuel supply at the nominal operating mode of the diesel generator set of operating diesel locomotives. A methodology for studying the dynamics of changes in the empirical and theoretical distribution of quantities is proposed, lean on the basic principles of probability theory and mathematical statistics, taking into account the criteria of agreement of Pearson and A. N. Kolmogorov's. It has been proven that the distribution of the studied diesel locomotive diesel engines according to the actual fuel supply advance angle corresponds to the law of normal distribution. It is recommended to continue these studies for partial load conditions, covering a larger number of operating diesel locomotives on railway sections of different complexity.

Numerical analysis of vorticity transport and energy dissipation of inner-blade vortex in Francis turbine

The inner-blade vortex results in flow instability when Francis turbines operates at off-design conditions. The numerical method was conducted versus Francis turbine to study the inner-blade vortex characteristics. Firstly, the potential rothalpy gradient (PRG) is applied to analyze the inner-blade vortex evolution innovatively. The PRG is the main power which drives the inner-blade vortex develop in radial direction. The difference of potential rothalpy between hub and shroud curve occurs at 1/3 distance from blade inlet to outlet for deep load condition and 1/4 distance for part load condition. Then, the inner-blade vortex evolution is deeply analyzed based on the vorticity transport equation in cylindrical coordinate system. It indicates that the vorticity transport in radial and axial direction was mainly affected by stretching term and the Coriolis force term makes major contribution to vorticity in circumferential direction. Finally, the energy loss was calculated in Francis turbine by entropy production theory. The relative error was 3.51% and 3.07% for guide vane opening 8.28° and 10.85° between entropy production method and pressure drop method for efficiency calculation. And the interaction characteristics between inner-blade vortex and the energy dissipation was revealed by vorticity transport equation and entropy production method.

Low-temperature waste heat recovery from internal combustion engines and power output improvement through dual-expander organic Rankine cycle technology

Energy, being the driving force behind the economic development, there has been continued efforts to develop alternative energy-utilisation strategies. Due to lower heat utilisation efficiency of internal combustion engines, they provide a huge potential of waste heat recovery by organic Rankine cycle technology. The present work is devoted towards the waste heat recovery from engine coolant. This study provides the complete thermodynamic analyses, cycle configuration, system size design and selection of working fluid for the development of the stand-alone engine-coolant based ORC. The system performance at fluctuating flow of jacket cooling water with engine speed and load is investigated. The effect of changing mass flow rate of heat source, which leads to varying heat input available to be recovered from the engine coolant is considered with fixed temperature of 90°C. Methodology has been presented to enhance the cycle thermal efficiency with the use of dual expander at part load conditions, by parallelising the flow to attain the favourable input conditions for the expanders over wider variation of heat input. R245fa showed the highest performance characteristics giving cycle efficiency and work output of 4.72% and 0.97 kW, respectively at dual expander operating mode. The control strategy to switch to the dual expander is based upon its evaluation of actual isentropic efficiency and optimum working range. The present study establishes the importance of considering the continually varying heat-input conditions and its effect on the key components, unlikely assuming its performance to be constant. And to capture their varying characteristics and integrate its effect on the overall system to provide operational controlling at off-design conditions to attain flatter efficiency at wider operating conditions for system optimisation.

Energy efficiency optimization of water pump based on heuristic algorithm and computational fluid dynamics

Abstract To reduce the energy consumption of large centrifugal pumps, modified heuristic intelligent algorithms are used to directly optimize the diffuser of centrifugal pumps. Considering the hydraulic efficiency under the design condition as the optimization target, in this study, 14 geometric parameters such as the inlet diameter, outlet diameter, and leading and trailing vane angles of the diffuser are selected as design variables, and the modified particle swam optimization and gravitational search algorithm are used to directly search for optimization in the design space. The performance and loss of internal entropy production of the different models before and after optimization are compared and analyzed in detail. The results show that the global optimization ability of the modified algorithm is improved. The diffuser model changes from cylindrical to twisted, the vane wrap angle increases, and the thickness of the leading edge decreases. Under the design condition, the efficiency of modified particle swarm optimization algorithm solution is increased by 2.75% and modified gravitational search algorithm solution by 2.21%, while the power remains unchanged. Furthermore, the optimization solution has the largest lift efficiency improvement under part-load conditions. After optimization, the unstable flow in the model is improved and internal entropy production loss is reduced significantly. The interior of the diffuser is dominated by turbulent entropy production and direct entropy production under different operating conditions, and the wall entropy production accounts for the smallest proportion.

The Impact of Fuel Injection Timing and Charge Dilution Rate on Low Temperature Combustion in a Compression Ignition Engine

Using high charge dilution low temperature combustion (LTC) strategies in a diesel engine offers low emissions of nitrogen oxides (NOx). These strategies are limited to part-load conditions and involve high levels of charge dilution, typically achieved through the use of recirculated exhaust gases (EGR). The slow response of the gas handling system, compared to load demand and fuelling, can lead to conditions where dilution levels are higher or lower than expected, impacting emissions and combustion stability. This article reports on the sensitivity of high-dilution LTC to variations in EGR rate and fuel injection timing. Impacts on engine efficiency, combustion stability and emissions are assessed in a single-cylinder engine and compared to in-cylinder flame temperatures measured using a borescope-based two-colour pyrometer. The work focuses on low-load conditions (300 kPa gross indicated mean effective pressure) and includes an EGR sweep from conventional diesel mode to high-dilution LTC, and sensitivity studies investigating the effects of variations in charge dilution and fuel injection timing at the high-dilution LTC condition. Key findings from the study include that the peak flame temperature decreased from ~2580 K in conventional diesel combustion with no EGR to 1800 K in LTC with low-NOx, low-soot operation and an EGR rate of 57%. Increasing the EGR to 64% reduced flame temperatures to 1400 K but increased total hydrocarbon (THC) and carbon monoxide (CO) emissions by 30–50% and increased fuel consumption by 5–7%. Charge dilution was found to have a stronger effect on the combustion process than the diesel injection timing under these LTC conditions. Advancing fuel injection timings at increasing dilution kept combustion instability below 2.5%. Peak in-cylinder temperatures were maintained in the 2000–2100 K range, while THC and CO emissions were controlled by delaying the onset of bulk quenching. Very early injection (earlier than 24 °CA before top-dead-centre) resulted in spray impingement on the piston crown, resulting in degraded efficiency and higher emissions. The results of this study demonstrate the potential of fuel injection timing modification to accommodate variations in charge dilution rates while maintaining low NOx and PM emissions in a diesel engine using low-temperature combustion strategies at part loads.

An investigation of optimum control of injection timing/injection pressure for a multicylinder common rail direct injection engine fueled with AB20 blend

A multicylinder turbocharged common rail direct injection engine was tested at part load (62.4 Nm) and high load (156 Nm) to determine the optimum combination of injection pressure (IP) and injection timing (IT) for AB20 blended fuel. IP and IT were varied from default settings, that is, 9.2° before top dead center (BTDC), 45 MPa at part load; 9.8° BTDC, 95 MPa at high load, as specified in the calibration map of the engine. As a result of the experimental results, brake thermal efficiency (BTE) increased up to 5.36% when IP increased from 35 MPa to 45 MPa and 0.72% when IP increased from 45 MPa to 55 MPa under the part load condition. At high load, the maximum BTE of 38.22% was attained at 105 MPa IP and 9.8° BTDC IT. At this condition, nitrogen oxide (NOx) emission was noted as 1353 ppm, which is 12.28% higher than the NOx noted for diesel fuel at the default IP and IT conditions. When IP increases from 35 to 55 MPa at part load and 85–105 MPa at high load, cylinder pressure, heat release rate, and rate of pressure rise increase at all tested ITs. At high load, the condition of retarded IT (8.8° BTDC) and default IP (95 MPa) shows (a) 2.35% higher BTE and (b) almost similar NOx and improved HC, CO, and smoke emissions for the AB20 blend. Moreover, at the same experimental conditions, premixed heat release for the AB20 blend was noted to be 70.16 J/Deg./C.A, with heat release rate peak at 6° ATDC.

Carbon Capture Performance Assessment Applied to Combined Cycle Gas Turbine Under Part-Load Operation

Abstract The growing share of renewable energies in our electricity production, together with the still lacking storage capacity, strongly reinforces the need for more flexible electricity production units. In this context, combined cycle gas turbines (CCGTs) have a role to play, both in the current and future electricity production system due to their high efficiency, high load flexibility, and low CO2 emissions compared to other conventional thermal power plants. Nevertheless, bearing in mind our current challenges concerning climate change, the CO2 emissions of these CCGTs need to be reduced drastically. The amine-based absorption carbon capture (CC) process is currently the most mature and applicable CC technology. This process is known to require a considerable amount of thermal energy, degrading plant performance. However, to back-up renewable production, CCGTs will operate most of the time under part-load conditions. The impact of these part-load operations on the CC is still relatively unknown. Within this framework, this study aims to assess the performance of the CC process applied to a typical CCGT under part-load operation using specific simulation models. The CC plant model has been successfully validated against experimental data from a pilot-scale capture facility. Then, the CC plant has been scaled-up to the CCGT scale and the process has been optimized for each operating condition. The simulation results show that the specific reboiler duty increases for part-load operation, while the specific cooling requirements decrease. Moreover, the analysis of the yearly CCGT operation highlights a relative increase in CC energy penalty of 21% for an annual CCGT load factor of 0.5, impacting significantly plant performance. The next step will involve reducing this energy penalty.

Demonstration of Natural Gas and Hydrogen Cocombustion in an Industrial Gas Turbine

Abstract Hydrogen cofiring in a gas turbine is believed to cover an energy transition pathway with green hydrogen as a driver to lower the carbon footprint of existing thermal power generation or cogeneration plants through the gradual increase of hydrogen injection in the existing natural gas grid. Today there is limited operational experience on cocombustion of hydrogen and natural gas in an existing gas turbine in an industrial environment. The ENGIE owned Siemens SGT-600 (Alstom legacy GT10B) 24 MW industrial gas turbine in the port of Antwerp (Belgium) was selected as a demonstrator for cofiring natural gas with hydrogen as it enables ENGIE to perform tests at higher H2 contents (up to 25 vol. %) on a representative turbine with limited hydrogen volume flow (one truck load at a time). Several challenges like increasing risk of flame flashback due to the enhanced turbulent flame speed, avoiding higher NOx emissions due to an increase of local flame temperature, supply and homogeneous mixing of hydrogen with natural gas as well as safety aspects have to be addressed when dealing with hydrogen fuel blends. In order to limit the risks of the industrial gas turbine testing a dual step approach was taken. ENGIE teamed up with the German Aerospace Center (DLR), Institute of Combustion Technology in Stuttgart to perform in a first step scaled-burner tests at gas turbine relevant operating conditions in their high-pressure combustor rig. In these tests the onset of flashback as well as the combustor characteristics with respect to burner wall temperatures, emissions and combustion dynamics were investigated for base load and part load conditions, both for pure natural gas and various natural gas and hydrogen blends. For H2 < 30 vol. % only minor effects on flame position and flame shape (analyzed based on OH* chemiluminescence images) and NOx emission were found. For higher hydrogen contents the flame position moved upstream and a more compact shape was observed. For the investigated H2 contents no flashback event was observed. However, thermo acoustics are strongly affected by hydrogen addition. In general, the scaled-burner tests were encouraging and enabled the second step, the exploration of hydrogen limits of the second generation dry low emissions burner installed in the engine in Antwerp. To inject the hydrogen into the industrial gas turbine, a hydrogen supply line was developed and installed next to the gas turbine. All tests were performed on the existing gas turbine hardware without any modification. A test campaign of several operational tests at base and part load with hydrogen variation up to 25 vol. % has been successfully performed where the gas composition, emissions, combustion dynamics and operational parameters are actively monitored in order to assess the impact of hydrogen on performance. Moreover, the impact of the hydrogen addition on the flame stability has been further assessed through the combustion tuning. The whole test campaign has been executed while the gas turbine stayed online, with no impact to the industrial steam customer. It has been proved that cofiring of up to 10% could be achieved with no adverse effects on the performance of the machine. Stable operation has been observed up to 25 vol. % hydrogen cocombustion, but with trespassing the local emission limits.

Experimental and simulation assessment of an adaptable cooling coil in the tropics

Overcooling or too high humidity issues may occur when the cooling coil in the central air-conditioning system is inadequate to meet both room temperature and humidity requirements, which might affect indoor thermal comfort, air quality, and building energy efficiency. Developing more advanced cooling coils to adapt to cooling load changes is one of the promising solutions to overcome these issues. This paper presents both experimental and detailed simulation results for an “adaptable coil”, in which the coil row number is changed based on the building cooling load. Theoretically, when fewer rows are activated at part-load conditions, the coil’s effective heat transfer area is reduced, which enables the coil surface temperature to be lower; hence the coil dehumidification performance can be improved. Actually, from our experimental study on a small-sized coil, we found that the adaptable coil shows an average 0.8% relative humidity reduction, while its water flow rate is more stable than a conventional coil. We also conducted detailed EnergyPlus simulations for a typical large-sized building in Singapore and found that the adaptable coil shows about 2.8% of relative humidity reduction and negligible overcooling reduction. Moreover, the adaptable coil shows better performance in reducing overcooling and space humidity, when the coil is heavily oversized and a large minimum airflow fraction is set. In summary, the adaptable coil does not show significant humidity and overcooling reduction advantages for a properly sized and well-operated air-conditioning system. Though with operational flexibility, the benefits of the adaptable coil are not as promising as expected; nevertheless, these results and conclusions may be valuable for future studies focusing on similar solutions for overcooling and high humidity issues.

Real Time Micro Gas Turbines Performance Assessment Tool: Comprehensive Transient Behavior Prediction With Computationally Effective Techniques

Abstract Conventional centralized power generation is increasingly transforming into a more distributed structure. The periodic power production that is created by the renewable production unit generates the need for small-scale heat and power units. One of the promising technologies which can assist flexible power grid is micro gas turbines (mGTs). Such engines are competent candidates for small-scale combined heat and power (CHP). mGTs, as compensators for demand fluctuations, are required to work on transient and part-load conditions, creating new research challenges. A complete characterization of their dynamic behavior through a real-time simulation tool is necessary to establish effective control systems. Moreover, the energy transition requires the conversion of conventional mGTs to more sophisticated high-efficient cycles with the addition of extra components (saturation unit, aftercooler, etc.). Consequently, a modular and computationally fast real-time tool offers an asset in the development of future cycles based on the mGT concept. This paper presents the development of a numerical in-house tool implemented in Python programing language for the performance prediction of the mGT. The fundamental target of our work is to achieve high fidelity of the simulated dynamic responses. The key benefit of this tool is the low complexity component modules. The model is validated with experimental results from the VUB T100 test rig. The code reproduces the experimental data well during steady-state and transient operations as the key cycle parameters present a deviation from the measurements within the range of 1.5%.

Investigation of Cylinder Deactivation (CDA) Application on a Naturally Aspirated Engine

Increasing oil prices and emission legislation have forced automotive company to investigate new methods and technologies to reduce the harmful effect produced from the motor vehicle, particularly CO2 (Carbon-Dioxide).A lot of studies and research have been put into in order to achieve a zero emission vehicle with the usage of electricity rather than fossil fuel, but the challenge to cost and environmental effect makes an IC engine is still being the predominant power plant for automobile in this century. One of the popular techniques among engine manufacturers to have a better engine efficiency is cylinder deactivation. Cylinder deactivation is a promising method to reduce the fuel consumption and emission by forced the engine to operate at higher load. However, the higher combustion pressure and extreme temperature at firing cylinders will result in higher NOx composition. This paper will investigate further the engine performance, fuel economy and emission by using one-dimensional (1-D) simulation tool. A standard 1.6 litre naturally aspirated four in-line cylinders, port fuel injection engine is modelled and correlated to the measured test data. The model is then simulated with cylinder deactivation mode by deactivating the intake and exhaust valves at cylinders no 2 and no 3 as well as fuel injection at various engine speeds at part load conditions to show improvements in fuel consumption, CO2 emissions, pumping losses and effects on CO and NOx emission. This correlated model is then used to investigate the application of EGR in order to reduce the emission level. Also, the effects on in-cylinder combustion as well as pumping losses are presented. The study shows that the application of EGR is very significant for engine with CDA mechanism to ensure the overall engine fuel consumption and emissions are reduced simultaneously.

Efficient modulation of the magnetocaloric refrigerator capacity

Magnetocaloric energy conversion devices (e.g., room air conditioners and household refrigerators) have the potential to significantly reduce the emissions associated with refrigerant leakage into the atmosphere but still have lower efficiencies compared to mature vapor compression systems. The efficiency of a magnetocaloric cooling device derives not only from its design characteristics (e.g., solid refrigerant, hydraulic system, and magnet system) and its operating temperature span but also from its modulating capability. Owing to the lack of experimental data regarding this topic, the advantage of modulating the cooling capacity (i.e., the part-load performance) of an active magnetic regenerator prototype is demonstrated experimentally for the first time. The capacity modulation is carried out by means of regulating both the cycle frequency of the device and the volumetric flow rate of the heat transfer fluid. At a 14 K temperature span and a 1.4 Hz frequency, the magnetocaloric refrigerator prototype using 3.8 kg of gadolinium provided a maximum cooling capacity of 452 W with an appreciable coefficient of performance of 3.2, which corresponds to a second-law efficiency of 15.5 %. At part-load operating conditions, the device can produce a cooling capacity of 245 W with an increased second-law efficiency of 29.7 %, or a coefficient of performance of 6.2, making it more competitive with traditional vapor compression systems. In future studies, the experimental data obtained may be implemented in a dynamic building energy model to quantify the energy-saving benefits of part-load operation by estimating the overall system efficiency during a typical cooling season.

Data-driven internet of things and cloud computing enabled hydropower plant monitoring system

Hydropower is one of the renewable energy sources that can play a crucial role to fulfil the global energy demand. However, the performance of the hydro turbine is severely affected by silt erosion and cavitation problems which causes a reduction in the overall efficiency of the plant. Various studies have been carried out and are available in the literature to investigate silt erosion and cavitation issues in hydro turbines. It has been reported that cavitation and silt erosion varies with the variation in discharge under part load and overload operating conditions of the machine. However, very few studies are available to predict the performance of the machine under variable operating conditions. Hence, there is a scope of study for monitoring the performance under these conditions in real-time, as it is difficult to predict the behavior of the machine using the existing models. In view of the above, an architecture of a data-driven IoT-based cloud computing-enabled hydropower plant monitoring system has been proposed under the present study. In order to develop this system, historical plant data has been collected and correlations are developed, which are validated with real-time data on the ThingSpeak cloud. It has been found that the developed model can accurately predict the condition of the hydro turbine with an R2-value of 0.9693 having a mean absolute percentage error (MAPE) of 0.67% at 0.89% of root mean square percentage error (RMSPE), and the power factor with an R2-value of 0.9503, having a MAPE of 0.798% at 0.91% of RMSPE.