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A numerical model is developed to predict the combustion processes in large-bore gas engines featuring prechamber ignition systems and being coupled with Computational Fluid Dynamics (CFD). The proposed combustion model is based on the simultaneous modeling of premixed and partially-premixed flames by an extended progress variable approach. By introducing an additional fuel scalar to track the externally injected fuel of the scavenged prechamber and depending on a gradient criteria of the fuel scalar, regions of locally premixed or partially-premixed state can be differentiated. The reaction rate for premixed combustion is described through a turbulent flame speed closure approach, whereas the partially-premixed combustion is described by a pre-tabulated flamelet chemistry approach. For the validation of the combustion model and its performance in the different flame propagation phases, that is, prechamber flame ignition and main-chamber flame propagation, experimental data of two large-bore gas engines with different operating conditions, prechamber configurations and engine geometries are taken into account. A good agreement of the simulations with the experimental results is shown for the variety of operating conditions and engine configurations. The developed combustion model is able to predict the combustion process in the prechamber as well as the ignition of the main chamber charge by means of the protruding flame jets through the prechamber nozzles. The prechamber ignition system accelerates the early flame phase and hence shortens the burning duration due to the deep-penetrating and turbulence-inducing flame jets in comparison to a conventional spark plug engine. [ABSTRACT FROM AUTHOR]

Oxygen additional system was examined for CO2 capture system in gas fueled engine. In this study, the effect of the oxygen supply on combustion was investigated to increase CO2 concentration of the exhaust gas. As the amount of supplied oxygen increased, the more EGR was required for the higher thermal efficiency. Exhaust temperature increased as the amount of supplied oxygen increased under same G/F condition. The supplied oxygen could increase the CO2 concentration and the temperature of the exhaust gas.

The potential for ammonia/hydrogen (NH 3 /H 2) blends as fuel in modern, turbocharged, gas engines is evaluated by comparing the combustion properties of these blends with those of methane. To ensure proper combustion phasing in existing spark-ignited (SI) engines, the laminar burning velocity (LBV) is used, while the ignition delay times (IDT) of the mixtures are compared to assess the risk of engine knock. The chemical mechanisms used for the computation of IDT and/or LBV of NH 3 /H 2 mixtures are selected from 8 chemical mechanisms based on their ability to predict experimental data. The application of a turbocharger is shown to "boost" the temperature in the cylinder after compression to values that admit the use of NH 3 /H 2 mixtures in natural-gas SI engines without increasing the compression ratio (CR). The analysis also identifies regions of temperature and H 2 fraction that increase the risk of knock. Using the conditions in a practical turbocharged SI engine as an example, 40–50% H 2 in NH 3 yields combustion phasing equivalent to that obtained with methane, while avoiding the risk of knock. Analysis of the IDT for the conditions in a high-pressure direct-injection natural-gas engine also shows that the use of a turbocharger in compression-ignition (diesel-type) engines strongly reduces the demands on CR for achieving the conditions necessary for reliable ignition of NH 3 /H 2 mixtures. Increasing the temperature by only a few tens of degrees above the conditions studied will yield an IDT for ∼20% H 2 in NH 3 that satisfies the ignitibility requirements for use in a turbocharged diesel engine. • Turbocharging facilitates the use of NH 3 /H 2 mixtures in gas engines. • The risk of engine knock limits the "boost" temperature and maximum H 2 fraction. • 40–50% H 2 in NH 3 mimics CH 4 combustion without knocking in the SI engine considered. • Modest preheating enables the use of NH 3 with 20% H 2 in a turbocharged CI engine. • The methodology used is readily applied to different fuels and engine conditions. [ABSTRACT FROM AUTHOR]

To limit global warming and meet international environmental targets, more environmentally benign technologies must be used in the residential market. Combined Heat and Power (CHP) at the micro-scale (<50 kWe) is seen as one of the best solutions that offers simultaneous generation of both electricity and heat with high overall efficiencies using environmentally friendly fuels (e.g., biofuel, hydrogen, syngas). In this study, four major micro-CHP prime movers (i.e. Micro-gas turbine, Gas engine, Stirling engine, and Fuel cell) have been evaluated in terms of their performance and the currently available technologies and products. The most suitable options for household applications were identified using Political, Economic, Social, Technological, Legal, and Environmental (PESTLE) risk analysis and a Multi-Criteria Decision Analysis (MCDA). Fuel cells display the best environmentally friendly properties despite their price and high start-up time. Gas engines (Reciprocating engines) have the most developed technology with the fastest start-up time and high efficiencies but have vibration and noise issues. Micro-gas turbine micro-CHPs are emerging into the market with relatively cheaper prices, lower maintenance, and good start-up time. Stirling engines are fuel flexible with reasonable prices and available products. Micro-CHP systems, particularly when running on biofuels and hydrogen, provide excellent energy solutions for the future net zero buildings. [ABSTRACT FROM AUTHOR]

PT. XYZ is a part of the largest oil and Gas Company in Indonesia, responsible for managing and developing oil and gas production activities in the East Java. The Central Processing Area serves as the facility for processing fluids produced from the East Java fields. The processed output consists of three phases: Gas, Oil, and Water. The operation of the Gas Engine G102-B TBG620 V16K running 24 hours a day to generate electricity at the central processing area of PT. XYZ requires regular maintenance, including scheduled preventive maintenance and unplanned or corrective maintenance. In the event of troubleshooting, such as a decrease in temperature in chamber 2B or a temperature sensor reading of 280 °C in that chamber, immediate corrective maintenance is necessary. Based on observations conducted in the power plant area, two possibilities causing the temperature decrease in that chamber were identified. The first possibility was the need for spark plug replacement, and the second was a malfunctioning temperature sensor resulting in incorrect readings. Therefore, the spark plug replacement was performed first, requiring a gas engine shutdown for approximately 2 hours for repairs. After the spark plug replacement, it was discovered that there was no change in the temperature reading in chamber 2B, which remained at 280 °C. Hence, the corrective maintenance performed did not have a significant impact because the issue was caused by a faulty temperature sensor. However, it was observed that there was a 1.16% increase in the generated power compared to before the corrective maintenance was conducted. The difference in power output could be attributed to variations in the quality of gas used in the combustion process of the gas engine. [ABSTRACT FROM AUTHOR]

Lean-premixed gas combustion is an attractive option for meeting future emission standards toward considerably lower particulate matter and emissions while obtaining an efficiency comparable to diesel combustion. However, ignition processes still pose considerable challenges, with pre-ignition being a major issue. The pre-ignition phenomenon might result from the self-ignition of lube oil in hot zones, making it challenging to observe in real engines. To study single or sparsely separated lube oil droplets under engine-like conditions, the ‘‘Flex-OeCoS’’ experimental test facility was used. To be able to induce such pre-ignitions artificially a novel piezo droplet injector was developed and manufactured, which enabled the metering of minor amounts of lubricating oil or even the injection of single droplets. High-speed cameras and specially developed and partially automatable and adaptive evaluation algorithms were used to record and track the behavior of the injected droplet using overlaid schlieren and OH* chemiluminescence. During the measurement campaigns, relevant operating parameters were varied, and optical investigations were carried out with an ignitable mixture on the Flex-OeCoS test facility under engine-relevant operating conditions. Spontaneous ignition of the vaporized lubricating oil was observed, which subsequently led to ignition of the whole air-fuel mixture in the optical combustion chamber. This was especially evident for lean methane-air mixtures up to an air-fuel ratio of 2.0. With this approach, information could be gathered about the necessary internal engine conditions that lead to pre-ignition in lean mixtures and where their limits lie. [ABSTRACT FROM AUTHOR]

Renewable natural gas (RNG) is attractive for energy policy goals in the world. Therefore, a regional system is designed to explore RNG combustion for power generation in localities. This study investigates a direct injection (DI) engine fueled with hydrogen (H2) blended into the simulated renewable natural gas, which consists of 50% methane (CH4) and 50% carbon dioxide (CO2) in volume. In order to obtain higher efficiency, comparisons between DI and port fuel injection (PFI) of H2 addition were made. Then, the volume percentage of H2 was changed from 20% to 100% by keeping the volume ratio of CH4 and CO2 at 1:1. Finally, results of power output, brake mean effective pressure (BMEP), brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were discussed. Results showed that in contrast to PFI, H2 DI injection could increase efficiency by 4%. Additionally, H2 DI could retard the MBT ignition timing at 5 °CA. Compared with CH4/CH4 + CO2 combustion, under stoichiometric combustion, BMEP increases with H2 addition but BTE decreases significantly. However, by enlarging the excess air ratio (λ) to 1.24, both BMEP and BTE increase obviously with H2 addition. Moreover, when λ < 1.3, the MBT ignition timing should be advanced from −10 to 15 °CA top dead center (TDC). But the MBT ignition timing is fixed at −25 °CA TDC when λ is larger than 1.3. Furthermore, if efficiency is the priority, 30% H2 addition with λ at 1.24 (−15 °CA TDC) should be selected. If higher BMEP is preferred, 20% H2 addition with λ at 0.99 (−10 °CA TDC) should be selected. [ABSTRACT FROM AUTHOR]

This study attempted to identify the effect of optimized intake manifold geometry on the behaviors and emission level of hydrogen compressed natural gas (H2CNG) fueled engine. For this purpose, a commercial Hyundai Sonata spark ignition engine (SIE) is modified to operate with CNG and hydrogen blend. The optimal intake pipe length was predicted using an analytical acoustic method. A new intake manifold is designed and implemented utilizing natural supercharging managed by over-pressure waves acoustic propagation. Several tests are conducted on the engine using the new manifold with a speed range from 1000 to 5000 rpm. Based on various engine speeds, the variation of brake torque (BT), in-cylinder pressure, NOx and CO emissions investigated by using gasoline, CNG and hydrogen CNG blend (HCNG) fueled engines via external mixtures. The first finding of the study is that the novel geometry improves the in-cylinder pressure by 10% at 3500 rpm. However, high engine speeds show a reduction of 14% in NOx and 40% in HC while speeds below 2000 rpm reduce CO by 40%. The second finding is that the new optimized geometry serves to get rid of both the auto-ignition and the backfire for high ratio of hydrogen in the blend. [ABSTRACT FROM AUTHOR]

Trigeneration plants (TGP) desired for combined production of electricity, heat and refrigeration are highly flexible to follow current loading. But their highest efficiency might be possible only when heat production coincides with its consumption, which is generally impossible in traditional TGP with applying the absorption lithium-bromide chiller (ACh) converting the heat, released from combustion engine in the form of hot water, into refrigeration. Usually, the excessive heat of hot water, not consumed by ACh, is removed to the atmosphere through emergency radiator. However, the well-known methods of TGP efficiency assessment do not consider those heat losses and give the overestimated magnitudes of efficiency for conventional TGP with ACh. The application of booster ejector chiller (ECh), as an example, for utilization of the residual waste heat, remained from ACh and evaluated about 25%, has been proposed to produce supplementary refrigeration for cooling cyclic air of driving combustion engine to increase its electrical efficiency by 3-4 %. In the case of using the supplementary refrigeration for technological or other needs the heat efficiency of TGP will increase to about 0.43 against 0.37 for typical TGP with ACh as example. The new modified criteria to assess a real efficiency of conventional TGP, based on ACh, are proposed which enable to reveal the way of its improvement through minimizing the heat waste. Such combined twostage waste heat recovery system of TGP can be considered as the alternative to the use of back-up gas boiler to pick up the waste heat potential for conversion by ACh to meet increased refrigeration needs. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive technical and economic modeling of a trigeneraion system based on a gas engine named EF7 is presented. The innovation is presenting a differential model with high accuracy which considers the effects of spark timing in half-load and full-load modes on the system technical performance, including specific fuel consumption, and the economic performance of the system, including fuel cost savings, investment payback period, net present value and internal rate of return.From economic viewpoint, at half-load condition and optimal spark timing (18° CA BTDC), the system will reach profitability after 8 years. From technical viewpoint, at half-load condition, the spark timing should be more advanced (24° CA BTDC) and the overall specific fuel consumption is 103.24 gr/kWh.But, at full-load mode and optimum ignition timing (18° CA BTDC), the economic performance has improved and with 10% inflation rate, the system can reach profitability after 4 years. Also, after 7 and 10 years, the profit values are $42,300 and $80,500, respectively and internal rate of return values of 22 and 26%, respectively. Also, from technical viewpoint, at full-load condition and optimal spark timing (22° CA BTDC) the minimum amount of overall specific fuel consumption is 110.42 gr/kWh.

The application of nanofluids to increase the heat transfer rate in heat exchangers of a proposed dual-loop RC–ORCheat recovery system (RC with water and ORC with R141b working fluids) is investigated here. The effects of adding nanoparticles into working fluids of a heat recovery system with two RC and ORC loops and its performance, has not been studied so far. Appropriate single-phase/two-phase heat transfer coefficients have been used for nanofluids in the system modeling by extracting their properties from available experimental data. Performance evaluation criterion (PEC) was also applied to assess and compare the performance of nanofluids in the proposed system. Optimization of the proposed system with exergy efficiency and payback period as objective functions for various nanofluids (working fluids mixed with four nanoparticles Al2O3, CuO, Cu, TiO2) with various volume fraction (0.5, 1, and 2%) which satisfied PEC > 1 provided a Pareto front. The selected optimum point from Pareto front by TOPSIS method showed that the proposed dual loop RC–ORC system with water/Cu nanofluid (with volume percent of 2% for the RC loop) and 141b/Cu nanofluid (with a volume percent of 0.5% for the ORC loop) had the most suitable performance (higher thermal and exergy efficiencies and lower payback period). Under these conditions, the thermal efficiency, the exergy efficiency, the turbine power output and the annual net profit of the proposed RC–ORC system increased by (4.4%), (17.2%), (15.4%) and (15.6%) respectively. [ABSTRACT FROM AUTHOR]

Transient modeling of an innovative dual-loop Rankin–organic Rankin (RC–ORC) heat recovery and power generation system integrated with a gas engine is performed here. The transient behavior of dual-loop cycles is not investigated so far, and hence the present work is an essential tool for predicting and controlling the performance of the RC–ORC dual-loop cycle during the start-up and the gas engine load change conditions. Transient energy conservation equations for heat exchangers are solved in discretized form. Quasi-dynamic equations are also considered for pumps, steam turbines, and expanders by the use of existing empirical relations. The model is developed in MATLAB software and validated using available data. Variations with time of operational parameters are presented and analyzed for both loops of RC and ORC. The results for the start-up period show a relatively sharp increase in parameters in time interval 500–1200 s. RC evaporator working fluid outlet temperature changes from 159 to 254 °C, RC net power output changes from 147 to 308 kW, and ORC net power output changes from 165 to 300 kW. Furthermore, RC and ORC working fluid mass flow rates changes from 0.25 to 0.50 kg s−1 and from 2.2 to 4.65 kg s−1 respectively. Moreover, results show that the turbine reached the steady state condition faster (1200 s) than that for evaporator (1750 s), RC loop reached steady state condition later than ORC loop (1750 s in comparison with 1300 s), and a single-loop ORC cycle reached steady state condition faster than RC–ORC dual-loop cycle (820 s in comparison with 1750 s). [ABSTRACT FROM AUTHOR]

Increasing the uniformity of the gas-air mixture in gas transport engines makes it possible to ensure more complete combustion of fuel, reduce its specific fuel consumption and exhaust gas toxicity. There are known ways to increase uniformity, but there is no generalization of their principles and applicability for various engines. The article analyzes the existing methods and identifies their shortcomings. A method has been developed to increase the uniformity of the gas-air mixture in gas transport engines by controlling the position of the gas fuel jet in the incoming air stream. The dependence for controlling the position of the gas jet in the air flow is described. The results of experiments performed by means of computer modeling with central and distributed gas supply with different gas and air pressures are analyzed. During the experiments, the coefficient of uniformity of the gas-air mixture was determined. Separately, the depth of penetration of the gas fuel jet into the incoming air stream is estimated. Based on the simulation results, the effectiveness of the method was justified. Purpose. Development of a method for increasing the uniformity of the gas-air mixture in internal combustion transport engines. Methodology. Modeling of the movement of a methane jet in an air stream by the finite element method was used in the work. Results. A method for increasing the uniformity of the gas-air mixture using the inlet pressure of the gas as the main variable parameter is formulated and justified. Practical implications. The obtained results should be used to improve the efficiency and environmental friendliness of gas transport engines.

Alternative energy sources have become a preferred energy production source with both clean energy production and wide usage area. In addition, the fact that alternative energy consumption is renewable gives confidence in the continuity of energy. Dairy farms have a great potential to use energy based on biomass from alternative energy sources. It is possible to obtain biogas energy by evaluating animal wastes in dairy farms and to use cooling, which includes the most important expense of the farm. In this example, numerical calculations and usage studies of a vapor compression milk cooling system were carried out using biogas energy obtained from animal wastes of a dairy farm. It maintains the model in hand, which uses the Java programming language for numerical calculations. With the measurements obtained from numerical calculations, a fermentor, consumption, storage and automation test system with a capacity of 2.5 m3 was established. Carbon dioxide, hydrogen sulfide, etc. in the biogas obtained from the system. The filtering processes of the gases were carried out and stored in a 10 m3 membrane. An internal combustion gas engine powered by stored biogas drove a 300-liter vapor-compression milk tank compressor with cooling. The biogas fueled milk cooling system provided 54.37% energy savings compared to the conventional milk cooling system. According to the experimental situation, TS EN 13732 limitation Turkish Standard and EN 13732 standard, raw feeding at 32 oC in each milking has the ability to cool down to +4 oC in a maximum of 2.5 hours. Colony count was made on the sample taken from the milk cooled to +4 oC and 2.1 x 104 colonies/ml log10 4.32 were determined. [ABSTRACT FROM AUTHOR]

Rising engine efficiency, increasingly stringent exhaust limits, and the use of synthetic and renewable fuels are all factors that demand a deeper knowledge of the combustion process. State-of-the-art investigations employ optical and laser-optical measurement techniques that rely on having optical access to the engine. In this paper, a new endoscopic system that provides full optical access to a high-speed large-bore engine is compared by thermodynamic experimentation to the equivalent all-metal engine. This comparison provides an insight into the altered combustion behavior resulting from modifying the engine to accommodate the optical elements. The successfully realized concept consists of two individually usable access points integrated in an engine with a bore of 170 mm and a stroke of 210 mm. The lateral endoscopic access is designed for full-load operating conditions and provides the best comparability to an all-metal engine. It is compared directly to the all-metal engine in the present investigations. Despite the changes in engine-out emissions from the optical engine, the experimental results display relatively equal combustion behavior in both setups. The lateral endoscopic access is then extended by adding a fisheye endoscope in place of one exhaust valve. This setup is compared to findings obtained with the endoscopic lateral access. The investigations reveal further deviations of the combustion process due to the more extensive modifications needed to fit the fisheye endoscope to the cylinder head. Nevertheless, the results display an overall good level of comparability of the combustion behaviors in these setups and, in turn, of the validity of further fundamental experiments based on the optical engine. [ABSTRACT FROM AUTHOR]

Increasing energy consumption, rapid population growth, and technological developments have increased the need for energy demand day by day. At the point of meeting this need, renewable energy is an important alternative resource that can replace rapidly exhaustible fossil fuels. There are many renewable energy sources such as sun, wind, hydrogen, geothermal, and biogas. Biogas, one of the most important renewable energy sources, is mainly used as fuel in combined heat-power (CHP) engines/gas engines and transformed into electrical energy. However, the efficiency of these engines is low owing to the fact that a considerable amount of the energy that enters with the combustion of biogas is thrown into the atmosphere as exhaust gas. In this context, the recovery of the waste heat of 26 gas engines with a temperature of 475–500 °C in the Silivri region of Istanbul and producing biogas from household wastes was studied. Calculate the waste heat values according to the exhaust gas flow, temperature, and pressure values to be taken from the chimney outlet of the gas engines in the facility. Subsequently, the determination of the parameters of the ORC (Organic Rankine Cycle) and the optimum consumption values of the equipment in the whole system in the loop as well as the optimum ORC mechanical power will help manage and optimize the electricity production.

This research/article aimed to analyze the influence of an after-treatment system (ATS) on emissions of a heavy-duty spark-ignition (HD-SI) engine fueled with liquified petroleum gas (LPG), in the context of current Euro VI emissions requirements. The ATS is composed by a three-way catalyst (TWC) in series with a diesel particle filter (DPF). Emissions testing were carried out on an engine test bench according to homologation procedures, performing both world harmonized stationary cycle (WHSC) and world harmonized transient cycle (WHTC), to study the effects of the engine operating parameters on pollutant emissions behavior and ATS performance during steady and dynamic states, respectively. Instruments used were a gas analyzer Horiba MEXA ONE to measure gaseous emissions, HORIBA OBS ONE PN to measure particle matter (PM) concentration, and spectrometer TSI EEPS 3090 to measure PM concentration and particle size distribution (PSD). The results showed some important aspects such as the effects of engine speed and load on pollutant emissions formation and ATS performance, the influence of the three-way catalyst (TWC) on particulate matter (PM) reduction due to the relationship between volatile unburned hydrocarbons (UHC) and the emergence of nucleation-mode particles, stressing that ATS implementation is mandatory to meet the current emissions requirements. [ABSTRACT FROM AUTHOR]

The study aims to clarify the influence of pre-chamber (PC) configurations on the combustion process in the main chamber (MC) of medium-speed spark-ignition gas engines equipped with an active PC. A constant volume combustion chamber was prepared to simulate the chamber configurations of the gas engines. A high-speed shadowgraph was applied to visualize the torch flame development and the combustion process in the MC. Experiments were done by changing the charged gas in the MC, the number, and the diameter of the PC orifices. Combustion was most accelerated when the PC orifice configuration was set appropriately so that the adjacent torch flames would combine with each other. It was also found that the unburned mixture in the PC, which ejected prior to the torch flame, supported the penetration of the torch flame.

Integrated energy systems (IES) for combined power, heat and refrigeration supply achieved a wide application due to high flexibility in matching current loading. So as electricity is easily convertible into any other form of energy, gas engines are widely applied as driving engines characterized by high electrical and overall efficiency of about 45% and 90%, respectively. However, the highest thermal efficiency is achieved at full matching heat generated by the engine and heat transformed. This is often impossible in actual practice, especially if the heat is transformed into refrigeration by the most efficient and widespread absorption lithium-bromide chillers (ACh) and the heat not consumed by the ACh is removed from the atmosphere through an emergency radiator. The unused heat might be transformed by an ejector chiller (ECh) as the simplest and cheapest. So as the thermodynamic efficiency of any combustion engine is influenced essentially by the sucked air temperature, the excessive refrigeration produced by the ECh, is used for IES cooling to generate additional electricity and increase the electrical and overall efficiency of the engine. Such a redistribution of heat enables the enhancement of the efficiency of IES with an absorption-ejector chiller (AECh). The modified criteria for the comparative estimation of thermodynamic efficiency of innovative IESs with AEChs without overgenerated heat lost against a typical IES with an ACh and heat lost are proposed. In contrast to well-known electrical and heat efficiency, it considers the magnitude of heat loss and enables us to compare the heat efficiency of any version of transforming heat to refrigeration with an ideal basic version of IES based on a highly efficient ACh, transforming all the heat removed from the engine without heat loss. Some alternative scheme decisions for heat recovery systems have been developed based on monitoring data. They might be easily implemented into a typical IES with ACh. [ABSTRACT FROM AUTHOR]

This paper shows a practice to raise the reliability of an electric power system by the installation of distributed generation, taking gasified biomass as fuel. To calculate the reliability index, a probabilistic load flow was used. This index is determined as the fault probability of the system. The resolution of this probabilistic load flow combines the method of cumulants and Gram–Charlier expansion. To achieve the reliability index, simulating a number of contingencies is required; the greater the number of simulated contingencies, the higher the accuracy of the index obtained. This probabilistic technique uses the random variables as starting information, so the two generators and loads are simulated as random variables. The generators of this distributed generation are biomass-fueled gas engines, commonly found in Spain. The simulations carried out on the IEEE 14-bus Test System, including three biomass generators, show that the inclusion of this type of generation improves the overall reliability indices of the electrical system. [ABSTRACT FROM AUTHOR]

Significant improvements in the power density and efficiency of lean-burn large gas-engines with a prechamber and their high flexibility in meeting fluctuating power requirements illustrate the potential for using these engines in stationary power generation and in the transportation sector. Since these engines have comparatively low CO2 and NOx-emissions, they are seen as a promising solution to meet stricter emission standards. However, current combustion concepts for these engines must be enhanced to improve their performance and emission behavior; simulation methods play a major role in this process. It is critical to know and understand the fundamental processes and their relationships in the prechamber and main combustion chamber; conducting detailed analyses makes this possible. Zero-dimensional methods are suitable for these analyses. Due to their shorter calculation times, they allow extensive parameter variations to be investigated. Common methods in this area are limited to calculating performance and emission related values only in the main combustion chamber. Since a considerable share of NOx-emissions from high-performance lean-burn gas-engines arise in the prechamber, it is imperative to conduct a separate thermodynamic analysis of the prechamber and its interaction with the main combustion chamber. This paper presents a zero-dimensional method with which NOx-emissions from the prechamber can be calculated separately from the emissions of the main combustion chamber. To this end, it is necessary to conduct thermodynamic analyses of both the chambers and to consider their interaction. The measurement data for development and validation of this method is provided by tests on a single-cylinder engine with separate cylinder-pressure indication for both the chambers. Based on the results of the analyses, it can be determined to what extent each of the two systems is involved in the formation of nitrogen-oxides. With knowledge of the origin of NOx-emissions, measures may be enacted that reduce total NOx-emissions. [ABSTRACT FROM AUTHOR]

In the research, we have developed an operational concept based on new energy generation devices, which, in addition to providing heat and electricity, guarantees uninterrupted supply locally and the sale of system services off-site. Based on international experience in the sector, the overall business concept needs to be developed for successful pilot projects. The trends in the technical-economic and regulatory environment examined show that the direction of change, with uncertain outcomes today, is unanimous: they all support the market penetration and the continued profitability of small-scale power plant devices suitable for secondary regulation. An important task is to identify unique elements in the value propositions. The aim of the research is to identify which of the factors such as realized price differential, heat-side revenues, generation utilization, optimized plant operation, scaling, etc. have an impact on the investment, operation, as well as the overall business model and profitability, and to what extent. [ABSTRACT FROM AUTHOR]

The optimum size of the prime mover (PM) for combined cooling, heating and power (CCHP) systems is determined taking account of economics, environmental impacts, energy, and exergy. The optimum size of the PM greatly increases the justification of establishing a CCHP system. Optimum sizing of the PM is conducted here considering exergy efficiency, exergy destruction rate, total energy efficiency, overall fuel energy consumption, carbon release, carbon release decrease, equivalent uniform annual benefit, and payback duration. To determine the optimum size, an objective function is presented in which some of the aforementioned criteria are minimized and some others are maximized. To solve the problem arisen from this objective function, the improved pathfinder optimization algorithm is proposed. To prove its superior performance, it is compared to six other popular optimization algorithms used in CCHP optimization using six benchmark functions. After obtaining the optimum size of the PM, sensitivity analyses are conducted on all of the eight assessment sub-criteria versus the PM capacity, and the results are given in figures. In addition, their values are given with the optimum size of the PM. The results indicate that the studied CCHP with the optimum PM size yields exergy efficiency of 55.53%, exergy destruction rate of 48.34%, total energy efficiency of 68.79%, and overall fuel energy consumption of 209 kWh. Also, this system will produce 36.82kg of carbon per hour which is 23.46% lower than the initial separated generation system. Moreover, with the equivalent uniform annual benefit of 26376$, it will pay back in 3.21 years.

Municipal solid wastes (MSW) are, through the amount generated and energy content, one of the energy resources that can successfully contribute to covering energy consumption at local or regional level. The integration of this resource in modern energy systems can increase the penetration of renewable energy resources in energy supply. One of the most promising technologies for converting waste into energy is gasification. As conventional district heating and cooling systems require decarbonization, one solution is the use of waste gasification and solar energy conversion equipment. This paper analysis from an energetic and economic point of view the possibility of using the fuel produced by the gasification of refuse derived fuel (RDF) and solar thermal energy in a gas engine based combined cooling, heating and power generation (CCHP) system to be integrated into a district heating and cooling system. The proposed system can generate 27295685 Nm3/year of producer gas, 14.57 GWh/year of electricity, 32.11 GWh/year of heat and 1.55 GWh/year of chilled water with a solar thermal energy input of 1.15 GWh/year. The capital cost of the CCHP system can be recovered in 9.62 years when solar collector are not used and in 6.19 years when solar collectors are used. By using RDF and solar thermal energy are saved 3567778 Nm3 of natural gas in a year.

Introduction. This paper shows the results of a study of the frequency of maintenance of passenger cars in various operating conditions, and provides recommendations for replacing the engine oil of gasoline engines (category SN classification according to API) according to the actual engine operating time (moto-hours). The service book of passenger cars contains the regulations for car maintenance with a list of operations that must be performed. The oil change intervals specified in the Regulations on Maintenance and Repair of Rolling Stock of motor Transport and the factory instructions do not take into account the specifics of the operation of vehicles. Depending on the road and climatic conditions and the operating mode, the standard maintenance schedule can be adjusted, in particular, the frequency of engine oil changes. The scientific novelty of the work is to determine the intervals of car maintenance for specific operating conditions.Materials and methods. The paper presents an analysis of Russian and foreign car maintenance systems, in particular, the oil change intervals of gasoline engines in European countries, the United States and Japan.The results of operational and resource tests of motor oils of gasoline engines carried out by methods of measuring their physical and chemical properties are presented.Results. In this paper, based on the analysis of the problem, recommendations for changing oil in gasoline engines by motorcycle hours for the conditions of the Republic of Dagestan (RD) are developed.The use of external and built-in technical means for calculating the motor hours allows you to determine the recommended oil change interval.Discussion and conclusion. In this paper, on the basis of research on a certain number of vehicles operating in various (including difficult) conditions, recommendations are developed that allow you to determine the rules of car maintenance for various operating conditions.

This paper reports the results of studying the electronic control system designed for a gas internal combustion engine with spark ignition operated on liquefied petroleum gas. A new feature in the control system is the possibility to provide the most effective sequential type of gas fuel injection, in which fuel is injected in a sequence corresponding to the order of operation of the cylinders. The special feature of the designed control system is that a movable voltage distributor (ignition distributor) of the ignition system was modified to ensure sequential injection. The ignition distributor modification involves installing an additional setting disc with one integrated permanent magnet on its drive shaft and an additional Hall sensor on the body of the ignition distributor. This makes it possible to ensure that the electronic control unit receives a signal about the angular position of the camshaft, thereby enabling consistent fuel injection. The principle of operation of the gas engine control system provided by the electronic control unit has been described. The structure of the modified ignition distributor is shown. Tests of the gas engine with a new control system involving the designed electronic control unit Avenir Gaz 37 "B" and the software module "B2" were carried out. The tests confirmed the feasibility of the designed electronic control system, which implies consistent injection of gas fuel. In addition, idling tests have shown that the carbon monoxide and hydrocarbon content in exhaust engine gases is significantly lower than the maximum allowable for motors without catalysts. The control system designed could be used for converting the diesel vehicles in operation into gas engines. The use of this control system ensures their safe operation. [ABSTRACT FROM AUTHOR]

In thispaper,the results of modeling of the burning process in the piston engines whose working processis realizedon the basisof various conceptual approachesare presented: in diesel with direct injection of the fuel; in agas engine with spark ignition;and in atwo-fuel engine (in the gas-diesel),where the mixture of natural gas and air igniteswith the help of the fusedoseof the diesel fuel. The models of burning based on the different in-principle approachesare analyzedand used. Verification of the modelsis performedby a comparison of the results of modeling with the experimental diagrams. The specificvalues of the empirical coefficients, used inmodeling of the burning process in the engines under study,are determined. The practical recommendations on the choiceof the burning model depending on the working process conception are given.

Lean-burn gas engines equipped with an un-scavenged prechamber have proven to reduce nitrogen oxides (NOx) emissions and fuel consumption, while mitigating combustion cycle-to-cycle fluctuations and unburned hydrocarbon (UHC) emissions. However, the performance of a prechamber gas engine is largely dependent on the prechamber design, which has to be optimised for the particular main chamber geometry and the foreseen engine operating conditions. Optimisation of such complex engine components relies partly on computationally efficient simulation tools, such as quasi and zero-dimensional models, since extensive experimental investigations can be costly and time-consuming. This article presents a newly developed quasi-dimensional (Q-D) combustion model for un-scavenged prechamber gas engines, which is motivated by the need for reliable low order models to optimise the principle design parameters of the prechamber. Our fundamental aim is to enhance the predictability and robustness of the proposed model with the inclusion of the following: (i) Formal derivation of the combustion and flow submodels via reduction of the corresponding three-dimensional models. (ii) Individual validation of the various submodels. (iii) Combined use of numerical simulations and experiments for the model validation. The resulting model shows very good agreement with the numerical simulations and the experiments from two different engines with various prechamber geometries using a set of fixed calibration parameters. [ABSTRACT FROM AUTHOR]

This paper shows a practice to raise the reliability of an electric power system by the installation of distributed generation, taking gasified biomass as fuel. To calculate the reliability index, a probabilistic load flow was used. This index is determined as the fault probability of the system. The resolution of this probabilistic load flow combines the method of cumulants and Gram–Charlier expansion. To achieve the reliability index, simulating a number of contingencies is required; the greater the number of simulated contingencies, the higher the accuracy of the index obtained. This probabilistic technique uses the random variables as starting information, so the two generators and loads are simulated as random variables. The generators of this distributed generation are biomass-fueled gas engines, commonly found in Spain. The simulations carried out on the IEEE 14-bus Test System, including three biomass generators, show that the inclusion of this type of generation improves the overall reliability indices of the electrical system.

Integrated energy systems (IES) for combined power, heat and refrigeration supply achieved a wide application due to high flexibility in matching current loading. So as electricity is easily convertible into any other form of energy, gas engines are widely applied as driving engines characterized by high electrical and overall efficiency of about 45% and 90%, respectively. However, the highest thermal efficiency is achieved at full matching heat generated by the engine and heat transformed. This is often impossible in actual practice, especially if the heat is transformed into refrigeration by the most efficient and widespread absorption lithium-bromide chillers (ACh) and the heat not consumed by the ACh is removed from the atmosphere through an emergency radiator. The unused heat might be transformed by an ejector chiller (ECh) as the simplest and cheapest. So as the thermodynamic efficiency of any combustion engine is influenced essentially by the sucked air temperature, the excessive refrigeration produced by the ECh, is used for IES cooling to generate additional electricity and increase the electrical and overall efficiency of the engine. Such a redistribution of heat enables the enhancement of the efficiency of IES with an absorption-ejector chiller (AECh). The modified criteria for the comparative estimation of thermodynamic efficiency of innovative IESs with AEChs without overgenerated heat lost against a typical IES with an ACh and heat lost are proposed. In contrast to well-known electrical and heat efficiency, it considers the magnitude of heat loss and enables us to compare the heat efficiency of any version of transforming heat to refrigeration with an ideal basic version of IES based on a highly efficient ACh, transforming all the heat removed from the engine without heat loss. Some alternative scheme decisions for heat recovery systems have been developed based on monitoring data. They might be easily implemented into a typical IES with ACh.

Shale gas reserves, which is globally accepted as unconventional gas resource, scattered around the world and can be used in order to meet the growing energy needs due to limited amounts of conventional resources. Since notable effort has to be put in order to investigate and drill shale gas resources the early decision has to be made carefully, especially considering the economic benefits. Several factors must be considered including the known technically recoverable shale gas amount at the selected region, current technology to drill the shale source and the amount of investment before the extraction of shale gas. In this study, global underground shale gas amount and recent discoveries as well as the potential shale gas areas in Turkey are presented. Benefits of using shale gas for electricity generation and common methods being used during shale gas extraction are studied along with gas and liquid flow mechanisms. At the end, general overview of separation and utilization of shale gas components is schematically presented. In the case study, the potential of electricity generation in the SE Anatolia region in Turkey is estimated with only using methane obtained from the shale gas purification process at the power generation step. According to the estimations, 3337.8 MW installed power may be generated for 50-55 years, at the appropriate gas engine by using 8.5 billion cubic meter shale gas annually. [ABSTRACT FROM AUTHOR]

An innovative dual-loop heat recovery and power generation system is proposed here to increase heat recovery from the gas engine (GE) exhaust and jacket cooling water and to augment the system power output and thermal efficiency. As this proposed dual-loop heat recovery system is not studied in existing references, for comparison purpose, 18 existing single- and dual-loop systems in the literature as well as one proposed dual-loop system with six working fluids in topping and six working fluids in bottoming loop (36 cases) are investigated here (54 cases in sum). These systems are modeled in energy, exergy and economic aspects and are optimized by selecting ten design variables and two objective functions (payback period and exergy efficiency) by the use of genetic algorithm. Results show that with water as working fluid for topping loop (Rankine cycle or RC loop) and R141b for bottoming loop (organic Rankine cycle or ORC loop), which are selected in modeling and optimization procedures, the proposed above RC–ORC system has advantages among 53 other studied single- and dual-loop cases. These advantages are higher power output, thermal efficiency, exergy efficiency, annual profit as well as lower investment cost per unit of power output ($ kW−1) and payback period. It is observed that the proposed configuration of RC–ORC (with water–R141b as working fluids), which is integrated with 2 MW gas engine (as an example) generated 617 kW power output with 24% thermal efficiency, 55% exergy efficiency, 1280 $ kW−1 investment cost per unit of power output and about 3-year payback period. Furthermore, the overall thermal efficiency of integrated system (GE–RC–ORC) was about 67%. Finally, RC–ORC power output, exergy efficiency, thermal efficiency and payback period are also obtained for 1, 2 and 3 MW gas engines at various partial loads. [ABSTRACT FROM AUTHOR]

An innovative modeling and optimizing of fire and water tube heat recovery steam generators (HRSG) for gas engine cogeneration plant are performed here. In modeling section, the equations of ɛ-NTU, LMTD and heat transfer coefficients for one-phase flow and two-phase flow are organized to form a nonlinear system of equations. Furthermore, in the next step, two pairs of objective functions (annual expenses—exergy destruction rate and annual expenses—thermal effectiveness) are selected for multi-objective optimization of HRSG by the use of genetic algorithm for one, two and three MW gas engine cogeneration plants. Results for a 2 MW gas engine (as an example) show that the fire tube HRSG total expenses are 50% lower than that for water tube HRSG. In this situation, for water and fire tube boilers, the effectiveness and cost are 0.9, 40,000 ($/year) and 0.9, 20,000 ($/year), respectively. Furthermore, the exergy destruction rates are close and equal to 1373.45 kW and 1366.2 kW for water tube and fire tube boilers, respectively. Moreover, for each gas engine, six equations with thirty constant coefficients are obtained to explain the behavior of HRSG outlet exhaust gas temperature, pinch temperature difference, steam generation mass flow rate, working pressure, thermal effectiveness and exergy destruction rate at partial load. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the constructions of oil pumps for an aircraft compression ignition engine. It is a two-stroke liquid-cooled engine with a power of 100 kW. The system has 3 cylinders and 6 opposed pistons. The paper estimates the required oil pump capacity to make the engine components well-lubricated. Next, automotive oil pumps for diesel engines are analyzed to select a correct pump for aircraft diesel engine applications. Three pump constructions of different constructions and dimensions of a rotor were selected. A measurement bench was designed and built to test these oil pumps in the range of pump shaft speeds from 0 to 4500 rpm and volumetric flow rate up to 150 l/min. The bench also enables stabilization of oil temperature at the required level within the range from 30 to 120oC. In addition, flow resistance through engine slide bearings was simulated by changing the position of a throttling valve at the pump output to regulate pressure in the range of 0–700 kPa. The obtained capacity characteristics of individual pumps versus on oil pressure and temperature allowed us to find an appropriate oil pump to make individual engine nodes well-lubricated.

Article presents the results of long-term testing of prototype of 64 kVA biogas cogeneration set (CHP – Combined Heat and Power), build with support of financial means from the MCP R&D program 1 2 1. Between others, the impact of fueling with biogas from the sewage treatment plant on the engine oil has been investigated. Used oil analyses unveiled adverse presence of silicon compounds, i.e. siloxanes, permissible level of which (according to MAN standard) was exceeded several times. In order to reduce these compounds, prototype biogas filter based on activated carbon has been developed. Based on initial calculations, overall efficiency of this cogeneration set is circa 70%. For the consumer needs, the entire installation is enclosed in a compact soundproof canopy. Besides environmental merits, the cogeneration set shows also economical advantages. If operating continuously, the gen-set CHP would produce electrical and heat power in an amount that its purchasing cost would be returned after about 12 months, under condition of having biogas.

Municipal solid waste (MSW) and charcoal can be used as a substitute fuel in a gas engine. In this work, performance of a downdraft gasifier and gas engine system operated on MSW briquette fuel was investigated. Experimental test was carried out on a 62 kW, four-cylinder, naturally aspirated engine coupled to a 20 kW dynamometer. The downdraft gasifier was used to generate producer gas from MSW briquettes and charcoal. The engine load was varied between 1.5-9.0 kW. Biomass consumption, producer gas production, cold gas efficiency, thermal efficiency of the gas engine, carbon monoxide (CO), hydrocarbon (HC) emissions and exhaust temperature were evaluated. The MSW briquette fuelled operation was compared against that with charcoal. It was found that, the use of MSW briquette led to lowering performance of the downdraft gasifier and gas engine system, in comparison with the use of charcoal. Maximum cold gas and thermal efficiencies obtained were 64.6% and 16% at 4.5 kW and 9 kW loading, respectively. The CO and HC emissions of the gas engine operated on MSW briquettes were higher than that on charcoal, while the exhaust temperatures were similar. ©2019. CBIORE-IJRED. All rights reserved

Searching for further reduction of fuel consumption simultaneously with the reduction of toxic compounds emission new systems for lean-mixture combustion for SI engines are being discussed by many manufacturers. Within the European GasOn-Project (Gas Only Internal Combustion Engines) the two-stage combustion and Turbulent Jet Ignition concept for CNG-fuelled high speed engine has been proposed and thoroughly investigated where the reduction of gas consumption and increasing of engine efficiency together with the reduction of emission, especially CO2 was expected. In the investigated cases the lean-burn combustion process was conducted with selection of the most effective pre-combustion chamber. The experimental investigations have been performed on single-cylinder AVL5804 research engine, which has been modified to SI and CNG fuelling. For the analysis of the thermodynamic, operational and emission indexes very advanced equipment has been applied. Based on the measuring results achieved for different pre-chamber config-urations the extended methodology of polioptimization by pre-chamber selection and the shape of main chamber in the piston crown for proposed combustion system has been described and discussed. The results of the three versions of the optimization methods have been comparatively summarized in conclusions.

The electric load demand on marine vessels is constantly changing during some operational modes, such as in harsh weather or complex operations. Therefore, diesel engines are typically used to handle these variations. Gas engines reduce the CO2 due to lower carbon content in LNG compared with diesel oil. However, they may not be able to handle the load variations of a marine power plant. There are multiple other energy sources with strict rate constraints, such as slow speed diesel engines and fuel cells. In such cases, a battery may be used to take care of the variations, while the generator set produces a slowly varying power. In this paper, a common power flow controller for the battery and the generator set is proposed. It utilizes the rotating inertia in the generator set as energy storage, in addition to a battery. This is done by allowing a small excursion in the speed of the generator set; the speed change will change the kinetic energy of the generator set and this is used analogously to energy storage. The controller is compared with a baseline controller based on virtual inertia and speed droop. A simulation study is included to demonstrate the performance of the control methods. The simulation study shows that the gas engine (with strict constraints) is not able to handle the given load series. Nonetheless, it can be used in combination with a battery to handle the variations. The power plant can handle a measured load series from an offshore vessel when either speed-droop control or model predictive control is used. However, the study indicates that by using MPC, the aging of the batteries and fuel rate variations can be reduced.

The creation of modern high-powered gas and gas-diesel engines is associated with the solution of two main tasks – the elimination of abnormal combustion and reduction of engine thermal factor. The paper discusses ways to reduce exhaust gas temperatures, methods to eliminate hot-tube ignition and detonation in single fuel gas engines. The ways of reducing exhaust gas temperatures, reducing the thermal factor of diesel injectors (pressure, duration of injection) and detonation issues in two-fuel gas-diesel engines are considered. The results of computational and experimental studies are presented. It is shown that due to the optimization of intake systems, fuel supply and control algorithms it is possible to significantly reduce the thermal stress of gas and gas-diesel engines, while ensuring the achievement of high values of the average effective cycle pressure up to 28 bar and the achievement of high volume power up to 43 kW/l.