Gas Engine Generator Research Articles

On the Development of a Control System for a Small Bio-Methane Gas Engine Generator

In order to use the stable biomass resources that exist in rural areas, we have developed a small bio-methane gas engine generator that can be applied to various composition of bio-methane gas. Different from other conventional researches, we added auxiliary devices such as the surge tank, extra carburetor and ECU for our conventional gas engine generator, instead of alteration to the basic structure of the engine and the control method. Referred to the observation data such as the temperature, load and air-fuel ratio, we evaluated adaptability of auxiliary devices for various bio-methane compositions. The surge tank and extra carburetor are useful for getting more air and improve the mix for fuel-air. Along with various composition of bio-methane gas, the ECU could calculate the deviation of desired revolution and current revolution to adjust throttle valve angle by a PID controller, and realize the generator running stable.

A Study on Cooperative Voltage and Frequency Control Method Using Distributed Generations Considering Large Penetration of Renewable Energy Sources

SUMMARYIn order to solve energy and environmental issues, the introduction of photovoltaics (PVs) has been progressed in recent years. Due to the uncertain PV output fluctuation depending on the weather conditions, the proper frequency management becomes an important issue when a large amount of PVs are included in power systems. On the other hand, since the voltage increase in the end of feeder lines can be caused by the reverse power flow in distribution systems with PVs, it is needed to enhance the voltage controllability. When gas engine generators are included in distribution systems, they can contribute to both frequency and voltage control issues. However, the coordination between those control purposes will be another problem because the frequency and voltage controls have interactions each other. Hence, in this paper, we developed a distributed frequency control method taking into account the voltage constraint in distribution systems.

Increasing the application of gas engines to decrease China’s GHG emissions

This paper employs a review of the technical literature to estimate the potential decrease in greenhouse gas (GHG) emissions that could be achieved by increasing the application of gas engines in China in three sectors: urban public transport vehicle; shipping; and thermal power plants. China’s gas engine development strategies and three types of gas resource are discussed in the study, which indicates that gas engines could decrease GHG emissions by 520 megatonnes (Mt) of carbon dioxide equivalent (CO2e) by 2020. This would account for 9.7 % of the government’s target for decreasing GHG emissions and is dominated by methane recovery from the use of coal mine gas (CMG) and landfill gas (LFG) for power generation. In the public urban transport vehicle and shipping sectors the low price of natural gas and the increasing demand for the control of harmful emissions could spur the rapid uptake of gas engine vehicles. However, the development of CMG- and LFG-fuelled power plants has been limited by the unwillingness of local enterprises to invest in high-performance gas engine generators and the associated infrastructure. Therefore, further compulsory policies that promote CMG use and LFG recovery should be implemented. Moreover, strict regulations on limiting methane leakage during the production and distribution of gas fuels are urgently needed in China to prevent leakage causing GHG emissions and largely negating the climate benefits of fuel substitution. Strategies for increasing the application of gas engines, promoting gas resources and recovering methane in China are instrumental in global GHG mitigation strategies.

太陽光発電大量導入時の分散型電源を用いた電圧・周波数の協調制御手法の検討

SUMMARY In order to solve energy and environmental issues, the introduction of photovoltaics (PVs) has been progressed in recent years. Due to the uncertain PV output fluctuation depending on the weather conditions, the proper frequency management becomes an important issue when a large amount of PVs are included in power systems. On the other hand, since the voltage increase in the end of feeder lines can be caused by the reverse power flow in distribution systems with PVs, it is needed to enhance the voltage controllability. When gas engine generators are included in distribution systems, they can contribute to both frequency and voltage control issues. However, the coordination between those control purposes will be another problem because the frequency and voltage controls have interactions each other. Hence, in this paper, we developed a distributed frequency control method taking into account the voltage constraint in distribution systems.

Predicting the performance and exhaust NOX emissions of a spark-ignition engine generator fueled with methane based biogases containing various amounts of CO2

The effect of methane–CO2 blends with varying CO2 concentrations (corresponding to various biogas compositions) on combustion and emission characteristics were investigated numerically for a gas engine generator. CO2 variation in a methane-based biogas fuel produced effects similar to the CO2 effects of exhaust gas recirculation (EGR), decreasing the cylinder temperature, pressure, heat release rate, and flame speed. By design of experiment (DOE) analysis, the maximum brake torque (MBT) timing was calculated for various values of the spark timing and excess air ratio (EAR). As the EAR increased from 1.2 to 1.8 and the CO2 content decreased, the MBT timing was far advanced from top dead center (TDC). At 50% CO2 content, incomplete combustion phenomena were detected in the leaner region at EAR values above 1.6. In spite of the performance degradation of the engine itself, the addition of CO2 up to 50% in volumetric content improved the electrical generating efficiency by an average of 6.4%, with lower NOX formation.

Dynamic simulation of producer gas-engine operation

In the recent times, there has been a proliferation of a producer gas-engine-based power generation systems, particularly in market segments such as small enterprises and village electrification in countries such as India. The electrical load for such application is largely of inductive type, the major ones being water pumps, appliances and industrial loads. As the demand side load varies, the gas-engine generator is expected to match the demand within the shortest possible time and without large fluctuations in speed or frequency. Unlike a natural gas-fuelled engine, where fuel gas is available at the required pressure and flow rate at all times, the producer gas-engine is coupled to a biomass gasifier, and the fuel gas, i.e. producer gas, is generated on demand. Therefore, the gasifier and gas-engine form a coupled system with one mutually driving the other. The study of the coupled or integrated system becomes intriguing, particularly during transient conditions. But at the same time, the study of the coupled system is complicated, and therefore, to simplify the study, an attempt is made in this paper to model the gas-engine generator part along with the gas-fuelling system but without considering the upstream effects of the gasifier system. The behavior of the engine during steady-state and transient conditions is predicted by assuming producer gas to be available at the required pressure upstream of the engine. The results are validated against a few experimental results, and an attempt is made to explain the mismatch in a scientific manner. The need for an integrated model of the gasifier and gas-engine system has been brought out.

S084022 CO_2ハイドレートの生成・解離特性にもとづく分散電源システムに関する研究([S084-02]分散型エネルギーシステム(2))

A fluid mixture of gas and water, pressurized and cooled to a certain pressure and temperature, gas hydrate is produced. By heating the gas hydrate after the formation, extremely high pressure gas can be obtained by hydrate dissociation. This study aims the pressure obtained by dissociation of gas hydrate, drives a high-pressure gas engine generators as distributed power. Gas hydrate has a function of the energy storage capabilities and the working fluid. However, the actuator using the expansion properties dissociation of gas hydrate does not have any examples for previous discussion. This paper focuses on CO_2 hydrate. Then the expansive energy dissociation of CO_2 hydrate formation rate of hydrates storage capacity is investigated. As a result, it is proved an electric power corresponding to approximately 45% of the daily power consumption (4.5 kWh of generator outputs) of an individual house is stored, when 1 m^3 of water is used to generate CO_2 hydrate for 480 minutes.

Wood Pyrolysis in Pre-Vacuum Chamber

Climate change, global warming, and energy crisis are critical issues to be solved urgently in a global framework. Alternative energy and renewable energy technologies must be quickly developed to be substituted for fossil fuels like oil, gases, and coal. USA, UE, and Japan invested huge budgets to develop biomass renewable energy technology. Their target is to develop a commercial base large-scaled plant. On the other hand, in developing countries, especially in rural areas, people who can access electricity is still less than 70%, To decelerate or prevent global warming and improve electrification in rural areas, a new technology for wood pyrolysis, which requires low manufacturing cost and less maintenance, and of which gases are directly applicable to the gas engine generator, is developed in a laboratory scale. This paper reports the performance of this new plant and effects of several parameters on the performance. It is concluded that the new technology is quite feasible in rural areas, and upgrading of the plant is easily possible.

소형 가스엔진 발전기의 배기가스 폐열을 이용한 바이오가스 개질 가능성에 관한 실험적 연구

This study has been carried out the experiment for the possibility of biogas reforming using waste heat. The source of this waste heat is the exhaust gas from a small-sized gas engine generator. For recovering the waste heat, Two-stage heat exchanger is manufactured. The two-stage heat exchanger is composed of a heat exchanger for the exhaust gas and a heat exchanger for the water. This two-stage heat exchanger is used for reforming the biogas by means of on-site hydrogen production at the small-sized gas engine generator. The two-stage heat exchanger is coupled with the biogas reformer which is a kind of catalytic reformer. To confirm a heat recovery efficiency of the two-stage heat exchanger, temperature differences of inlet and outlet locations are measured. Also, the variations of syngas concentrations with various biogas flow rates are investigated. As a result using manufactured two-stage heat exchanger, the biogas can be reformed from waste heat recovery. This experiment suggests that the exhaust gas heat exchanger is available for reforming the biogas.

F111001 要素技術とそのシステム化による省エネヘの貢献 : ターボチャージャ、ガスエンジン、リチウムイオン電池等に関して

The Rapid Growth in the emerging countries emphasizes the importance of saving energy resources. This presentation introduces recent technical trends for saving energy, purifying Air and supporting energy supply, in the "General Machinery" domain.Turbochargers improve emission and fuel consumption of the automobile, both diesel and gas engine type. The Natural Gas fueled engine generators become favorable because of the low-cost shale gas introduction. The Gas Engine Generators are also good for making the distributed generation network. The Lithium ion batteries are promising technology for the battery operated vehicles. It is also used as a key component in the Hybrid Power Train.

Experimental Study on the Effect of Gas Composition Variation on Engine Emissions

The pollutant emissions of a four-stroke spark ignition gas engine generator operating on biogas–LPG blends of varying excess air ratios and LPG concentrations were investigated in this paper. Experiments were carried out at a constant engine speed of 1400 rpm and a constant electric power output of 3.5 kW. The experimental results showed that NOx emissions were elevated at an excess air ratio of around 1.2 as the LPG concentration was increased. CO2 emissions decreased as the excess air ratio and LPG concentration increased, due to lean-burn conditions and LPG combustion. These results demonstrated that the addition of LPG to biogas enabled the effective generation of electricity using a gas engine generator through lean-burn combustion. The adding of LPG of 0%, 5%, and 10% in volume is interchangeable. Mixing inert gas such as N2 and CO2 in the end user side to increase the gas MN, thereby increasing its antiknock tendency, furthermore, the measures such as the installation of closed-loop control engine with oxygen sensor in the exhaust and adjust air-fuel ratio accurately and adjusting engine ignition timing, to adapt the changes in gas composition to ensure that the engine working conditions are not significantly affected, to meet the requirements of natural gas interchangeability.

A numerical study of a methane-fueled gas engine generator with addition of hydrogen using cycle simulation and DOE method

Conventional fossil fuels for combustion systems, such as gasoline and diesel, have a number of problems related to energy security and emissions. Alternative fuels, such as methane, hydrogen, and mixtures of these two gases, are being promoted as clean energy substitutes for primary fossil fuels. Natural gas (which consists mainly of methane) is one of the most promising of these fuels, providing lower cost, cleaner emissions and is direct applicable to existing combustion systems. However, the use of natural gas as fuel can adversely affect engine performance. Therefore, hydrogen is sometimes used as an additive, as its higher burning rate often leads to enhanced combustion. In this study, cycle simulation was used to numerically investigate the performance and emission characteristics of an engine employed primarily to power a generator, and fueled with methane and methane – hydrogen blends. Dominant parameters such as excess air ratio, spark timing, and volume percent of hydrogen content, were investigated as independent variables. The fundamental effect of hydrogen on methane combustion was investigated for a fixed excess air ratio of 1.2 and a spark timing of 14CA(Crank Angle) BTDC (Before Top Dead Center), with an accompanying reduction in ignition delay. By varying the excess air ratio, hydrogen was demonstrated to play an important role in extending the lean operating limit. The DOE (Design of Experiment) method was applied to study MBT (Maximum Brake Torque) spark timing for various excess air ratios and hydrogen contents. When MBT spark timing was employed, maximum brake torque could be achieved under leaner burning conditions by increasing the hydrogen content.

Study of a Power Generation System for Distributed Power Supplies that Utilizes the High-Pressure Dissociation Characteristics and the Small Difference in the Temperature of CO2 Hydrate

When the mixed fluid of gas and water is pressurized and cooled to a given pressure and temperature, the generation of a gas-hydrate occurs. By heating, a very high pressure is obtained from the dissociated gas from the gas-hydrate. The purpose of this study is to investigate the operation of a high-pressure gas engine generator for distributed power supplies using the high pressure obtained though the dissociation of a gas-hydrate. A gas-hydrate functions as a working fluid and as a form of energy storage. However, until now, an actuator that uses the dissociation inflation characteristics of a gas-hydrate has not been examined. Therefore, the generation rate of CO2 hydrate and the quantity to be stored from the dissociation expansion energy of CO2 hydrate were investigated. As a result, when 1 m3 of water was used to generate CO2 hydrate for 480 minutes, the result was that electric power corresponding to approximately 45% of the daily power consumption (4.5 kWh of generator outputs) of an individual house can be stored.

Generating efficiency and NO x emissions of a gas engine generator fueled with a biogas–hydrogen blend and using an exhaust gas recirculation system

This paper investigates the generating efficiency and NO x emissions of a gas engine generator with a low-pressure loop exhaust gas recirculation system, fueled by a model biogas. Experiments for improving the generating efficiency and reducing NO x emissions were conducted, utilizing optimum spark timings based on the maximum generating efficiencies with varying exhaust gas recirculation (EGR) rates. The test results show that both the NO x emissions and the generating efficiency generally decrease when the EGR rate is increased. Also, by utilizing optimum spark timings with varying EGR rates, the addition of hydrogen to the biogas increases the generating efficiency of the engine. In particular, the generating efficiency of the biogas–hydrogen test increased by about 1.5% in comparison with the model biogas test for the optimum spark timing at 15% EGR. Accordingly, comprehensive techniques, such as the use of a biogas–hydrogen fuel mixture and optimum spark timings with respect to EGR rates, should be employed to efficiently generate electricity with a biogas engine.

Power Hardware-in-the-loop Simulation of a Gas Engine Cogeneration System for Developing a Power Converter System

This research focuses on the development scheme of a power converter in a gas engine cogeneration system using a power hardware-in-the-loop simulation. A matrix converter is adopted to substitute a conventional ac/dc/ac converter and transfers three phase electricity to single phase electricity directly. To inevstigate the interaction between gas engine-generator unit and the proposed matrix converter, a power hardware-in-the-loop simulation is carried out, in which a piece of real matrix converter is installed in the simulation loop and interfaces with the numerical model of gas engine-generator unit. Numerical models of gas engine and generator are presented and verified by experiment. The configuration of the power hardware-in-the-loop simulation is described and results are also presented, through which the practical application of matrix converter is well demonstrated.

Generating efficiency and emissions of a spark-ignition gas engine generator fuelled with biogas–hydrogen blends

We investigated the generating efficiency and pollutant emissions of a four-stroke spark-ignition gas engine generator operating on biogas–hydrogen blends of varying excess air ratios and hydrogen concentrations. Experiments were carried out at a constant engine speed of 1200 rpm and a constant electric power output of 10 kW. The experimental results showed that the peak values of generating efficiency, maximum cylinder pressure, and NO x emissions were elevated at an excess air ratio of around 1.2 as the hydrogen concentration was increased. CO 2 emissions decreased as the excess air ratio and hydrogen concentration increased, due to lean-burn conditions and hydrogen combustion. An efficiency per NO x emissions ratio (EPN) was defined to consider the relationship between the generating efficiency and NO x emissions. A maximum EPN value of 0.7502 was obtained with a hydrogen concentration of 15%, for an excess air ratio of 2.0. At this EPN value, the NO x and CO 2 emissions were 39 ppm and 1678.32 g/kWh, respectively, and the generating efficiency was 29.26%. These results demonstrated that the addition of hydrogen to biogas enabled the effective generation of electricity using a gas engine generator through lean-burn combustion.

Development of 6.6 kV/600 A superconducting fault current limiter using coated conductors

As one of the programs in the Ministry of Economy, Trade and Industry (METI) project regarding R&D on superconducting coated conductor, three-phase superconducting fault current limiter (SFCL) for 6.6 kV application was developed and successfully tested. The developed SFCL was mainly comprised three-phase set of current limiting coils installed in a sub-cooled nitrogen cryostat with a GM cryocooler, circuit breakers and a sequence circuit. The whole system was installed in a cubicle. Two tapes of coated conductor were wound in parallel in each coil to obtain the rated current of 72 A rms. After developing the whole SFCL system, short circuit experiments were implemented with a short circuit generator. In a three-line ground fault test, the SFCL successfully restricted the prospected short circuit current over 1.6 kA to about 800 A by the applied voltage of 6.6 kV. The SFCL was installed in a user field and connected with a gas engine generator, followed by a consecutive operation. In this program, 600 A class FCL coil, with which four coated conductor tapes were wound, was also developed. The coil showed sufficiently low AC loss at the rated current. With these results, the program attained the planned target of the fundamentals for the 6.6 kV/600 A SFCL.

An experimental study of the enhanced heating capacity of an electric heat pump (EHP) using the heat recovered from a gas engine generator

This paper is concerned with the effect of recovered heat on the heating capacity of an Electric Heat Pump (EHP), which is supplied with electric power and recovered heat from a gas engine generator system. Two methods of supplying recovery heat are examined: (i) to the refrigerant with the discharge line heat exchanger (HEX), and (ii) to the refrigerant of the evaporator with the sub-evaporator. Heating capacity, input power and coefficient of performance (COP) were investigated and compared for each heat recovery method. Conclusively, we found that the second method was most reasonable to recover wasted heat and increased system COP by 215%.

Study on the Polymer Membrane-Type Fuel Cell and Hybrid Hydrogenation Engine System Considering Improvement of Efficiency for Partial-Load Operation

Power demand patterns, such as for houses, fluctuate sharply. Therefore, if fuel cell cogeneration is installed in a house, partial-load operations with low efficiency frequently occur. On the other hand, if the hydrogen rate of hydrogenation gas-engine generation is increased at the time of low load, emission cleanup and brake thermal efficiency improve. So, in this paper, a hybrid cogeneration system that combines a hydrogenation gas engine and a solid polymer membrane-type fuel cell is proposed. So, operation of a fuel cell or a gas engine with the threshold value of load is investigated. In this paper, four systems were investigated by numerical analysis: independent hydrogenation gas-engine operation, solid polymer membrane-type fuel cell independent operation, that operates a fuel cell or a gas engine with the threshold value of load, and operation using a fuel cell to a base load. As a result, the operating method corresponding to a base load in polymer membrane-type fuel cell had the highest total efficiency. In this case, gas-engine generator (NEG) is operated corresponding to load fluctuation. Moreover, in the comparison results of carbon dioxide emissions, the hydrogenation operation of NEG achieved the best result.

Performance characterization of gas engine generator integrated with a liquid desiccant dehumidification system

Combined heat and power (CHP) involves on-site or near-site generation of electricity along with utilization of thermal energy available from the power generation process. CHP has the potential of providing a 30% improvement over conventional power plant efficiency and a CO 2 emissions reduction of 45% or more as compared to the US national average. In addition, an overall total system efficiency of 80% can be achieved because of the utilization of thermal energy that would be wasted if only the electric power were utilized, and because of the reduction of transmission, distribution, and energy conversion losses. The current research is being carried out in a four-story educational office building. This research focuses on the design, installation, and analysis of a modular CHP system consisting of a natural gas fired reciprocating engine generator with a liquid desiccant dehumidification system. The engine generator provides 75 kW of electric power to the building load bus while the combined waste heat from the exhaust gases and jacket water are used to regenerate the liquid desiccant. The liquid desiccant unit dehumidifies and cools the ventilation air to the building and supplies it to the mixed air section of the roof top unit. This paper discusses the various aspects involved in the design and installation of the system such as the heat recovery loop design and the electrical interconnection with the building load bus. Test results are also presented and the performance is compared to a traditional power plant with a conventional heating, ventilating, and air-conditioning system.