Katsuhide Hiraoka

Combustion characteristics of stoichiometric hydrogen and oxygen mixture in water

Abstract The authors have proposed a novel heat engine which is used as the power source for an undersea vessel. The engine is a kind of steam turbine, in which steam and water are directly heated by stoichiometric combustion of a hydrogen and oxygen mixture. This paper presents the characteristics of combustion in water at room temperature using a stoichiometric premix. The premix burned water using a single-hole-nozzle burner with a cylindrical hood, but some flame missing and flashback were observed. Combustion is not stable when the ratio of the length to inner diameter is less than 2.5. When the flame is observed, the combustion efficiency of the premix is almost 100% of the theoretical one in the range of equivalence ratio between 0.9 and 1.1. With an ion-current detector it is proved that the flame periodically enters the nozzle for an instant while the flame is observed.

Characteristics of stoichiometriC H2-O2 combustion in water with premixing and diffusion burners

Abstract The stoichiometric H 2 -O 2 combustion in liquid water and that in steam are to be used for generation of superheated steam, in turn to drive an internal combustion steam turbine. This concept was proposed by the authors (T. Kumakura et al., Int. J. Hydrogen Energy 17 , 887 (1992)). The purpose of this work is to investigate the fundamental characteristics of the stoichiometric H 2 -O 2 combustion in liquid water. Experiments both with a premixing and with a diffusion burner were carried out in a water tank under the atmospheric pressure. The temperature of the water was changed from room temperature to saturated temperature. In the water at the room temperature, the premixing burner obtained a high combustion efficiency (99.86%) at stoichiometry of the supplied gas, but showed occassional flashbacks. In contrast the diffusion burner maintained stable combustion, but the combustion efficiency was lowered. By using partially premixed gases, the efficiency was improved to the level of the premixing burner, while the flames were kept stable. The influence of the temperature of the water on the combustion characteristics is also presented.

Suppression of Combustion Noise and Combustion Oscillation by Thermo-Acoustic Active Control Using Secondary Flame

A feedback combustion control system based on the active noise control (ANC) principle was investigated with an experimental lean premixed dump combustor. In the control system, secondary diffusion flames were used as the sound source to attenuate pressure fluctuation in the combustion system. Piezo-valves with fast response were used to modulate the flow rate of the fuel for the secondary flames and to generate controlled sound by heat release oscillation. We investigated two kinds of controllers, that is, a time delay type controller and a model-based type one. In the experiment of the former, the dominant resonant mode of the combustion noise was suppressed more than 10dB in maximum. Clear periodicity of the suppression effect according to delay time indicates that the suppression is due to the acoustic interaction between the main flame and the secondary flames. In the model-based controller, robust control algorithms (mixed H2 /H∞ ) were used. In addition, the gain-scheduled control was implemented to tune in to the shift of the dominant mode of the combustion noise, which resulted from variation of equivalence ratio. This control system effectively suppressed the dominant mode by more than 25dB without increase in other modes.Copyright

Conceptual Design of Power Generation System Utilizing Heat from Exhaust Gases of Marine Diesel Engine

Exhaust gas economizers have been installed on a wide range of ships, for better fuel oil economy; since the oil crises of the 1970s. After the turn of the century, the pressure improve the fuel economy further, as well as to protect the environment markedly increased. The authors propose a concept for a power generation system, for domestic ships, to substantially improve fuel oil economy. Also, reduce SOx emissions by utilizing the rejected heat of exhaust gases from marine diesel engines. As a heat exchanging device, a circulating fluidized bed, here a mixture of the exhaust gas and fine, desulphurization solid particles circulate. This for reason of higher overall heat transfer coefficients and the quality to reduce sulphur-oxides emissions through a dry desulphurization process, in the fluidized bed. As an electric power plant, a radial steam turbine was integrated with a high speed dynamo, this selected because of a higher energy conversion rate. This technology is based on the micro gas turbine. A preliminary estimate indicates that an electric power of 80 to 100 kW will be recovered from the exhaust gases, and at the loading factor of 75 % for 1500kW-class marine diesel engines.

Alternative Index for Compliance Verification of NOx Emission Value through On-board Nox Monitoring

The NOx Technical Code under the MARPOL 73/78 Convention ANNEX 6 specifies the NOx emission limits and has determined the direct measurement and monitoring method for the on-board NOx verification procedure. But the monitoring method might not have been established yet, since it is reported that some results of NOx emission values measured on board exceed the 15% allowance even in the case of engines with certification. Since there are several constraints in the measurements on board, the uncertainty is enhanced comparing to the measurements at a shop-test. In this report an alternative index is proposed to reduce the uncertainty and simplify the on-board measurement. The index is named as NOx 13 that is normalized with oxygen concentrations and contains the correction factor for humidity and temperature. The NOx emission value, NOx [g/kWh], is theoretically correlated to the NOx13 as in the following expression and the correlation is experimentally confirmed.NOx [g/kWh] = α1×α2× be [g/kWh] × N0x13 [ppm]α1, α2; constant, be [g/kWh] ; specific fuel consumption

Co2 Recovery from Diesel Engines in a Solar-Hydrogen-Methanol Energy System

Concept of solar-hydrogen-methanol energy system for the transportation sector in Japan is outlined. In the system, methanol is produced with CO2 recycled and H2 produced by electrolysis with photovoltaic power.Concerning CO2 recovery from the exhaust gas of a 10, 000 kW diesel engine to be used in the methanol energy system, the effects of CO2 recovery parameters such as gas and liquid flow rates, liquid concentration, and stripping temperature on the engine performance and the attainable CO2 recovery ratio are analyzed on the basis of a mass transfer calculation model for a packed column with aqueous monoethanolamine solution. Heat rejected from the engine is used for CO2 recovery, but reduction in the engine output power is not avoidable, which is mainly caused by the shortage in power of turbocharger and the supplemental supercharging power. Both the maximum attainable CO2 recovery ratio and the reduction in the engine output power depend on the ratio of the stripping steam feed rate to the flow rate of the exhaust gas.

Performance Analysis of Combustion Engine Systems With a Packed Column CO2 Separator Using Aqueous Monoethanolamine (MEA) Solution

Systems analysis is performed for a diesel engine of the 10,000 kW class with CO2 recovery equipment using aqueous monoethanolamine solution on the basis of a CO2 mass transfer calculation model for a packed column.The calculation model is based on the film theory, and gives calculation results in good accuracy, being compared with the experiments on CO2 absorption and on CO2 stripping.The net output power of the engine reduces in order to recover the CO2 in the exhaust gas of the engine, and reduction of the output power depends on the ratio of the gas-to-liquid feed rate ratio of the stripper to that of the absorber. The operating parameters such as the stripping temperature, the highest loading factor, and the MEA concentration of the solution have an influence on the maximum attainable CO2 recovery ratio. The maximum attainable CO2 recovery ratio depends on the allowable level of the output power reduction, and with reduction of 10% of the engine output power, 70% of CO2 in the exhaust gas is recovered.© 1997 ASME

Energy analysis and CO2 emission evaluation of a solar hydrogen energy system for the transportation system in Japan—I. Conceptual design of the system

Abstract A concept of a solar hydrogen energy system for transportation in Japan is proposed to replace all the fuel oil used by transportation, 69 Mm 3 yr −1 , with liquefied hydrogen (LH 2 ), 24.9 Tg yr −1 , in order to conserve petroleum and to reduce CO 2 emission into the atmosphere. The LH 2 is produced by way of electrolysis with solar photovoltaic cells on a large number of ocean rafts in the South Pacific Ocean. The LH 2 is transported to Japan by a fleet of LH 2 tankers and distributed to local end use stations. The types and number of required LH 2 facilities are estimated. The evaluation of the system in terms of energy investment and CO 2 emission is presented in the second part of the study.