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In order to effectively utilize woody biomass, which has a low abundance density, it is necessary to develop a power generation system that can convert it with high efficiency even with a small capacity as less than 2 MW. For electricity generation, it is reasonable to use a small reciprocating engine. In the case of a naturally aspirated spark ignition reciprocating engine (SIRE), the amount of aspirated gas in one cycle is determined almost entirely by the displacement. The thermal efficiency of the SIRE generally increases with the power. Therefore, to improve the thermal efficiency, it is effective to make the low heating value (LHV) of the fuel higher to increase the power of the naturally aspirated SIRE. In this paper, three methods are used to increase the LHV of the bio-syngas: 1) reducing the nitrogen density of the bio-syngas (upgrade bio-syngas), 2) adding hydrogen to the bio-syngas, and 3) adding methane to the bio-syngas. Using these fuels, 1) the conditions for high power, and 2) the costs assumed for each condition, are evaluated through experiments and estimates. The results showed that the upgrade bio-syngas, obtained by gasification with oxygen-enriched air, had the highest power and the best cost-effectiveness.

In order to exchange the wood biomass energy for electric power with small capacity and high efficiency, it is most effective to use a reciprocating engine operated with a wood gasifier. On the other hand, such a small-capacity system is often installed in urban areas. Therefore, strict emission regulation should be observed. Normally, as the low heating value (LHV) of bio-syngas is small, the engine should be operated with a stoichiometric mixture to achieve a maximum power density. However, the emission with a stoichiometric mixture contains much unburned CO. This means that a stoichiometric mixture operation shows low efficiency and can’t observe the regulations. In this report, a mechanism of the unburned CO is considered, and a method to reduce the unburned CO ratio is shown with experimental results. In the experiment, a commercial reciprocating engine (4-stroke, modified single cylinder) is used. The bio-syngas, a producer gas from a fixed bed gasifier, is produced by a self-made wood pellet gasifier (fixed bed, auto thermal down-draft). The bio-syngas flow rate is calculated with the nitrogen ratio between input air and bio-syngas. The LHV is adjusted with the city gas (as an alternative to methane) and hydrogen. The CO volume ratio of the exhaust from the engine is more than 3 v% when the excess air ratio of bio-syngas/air mixture is 1.3, as the LHV of bio-syngas is less than 5.0 MJ/m3-LHV. On the other hand, the CO volume ratio of the exhaust under operation of the mixture, the bio-syngas, and methane with more than 7.0 MJ/m3-LHV was less than 0.2 v%. The CO in the exhaust with low LHV fuel means that the combustion is not finished in the chamber. The unburned ratio could be predicted in consideration of the gap/clearance as crevice, the temperature boundary layer, and the quenching distance.

This study examined the tar characteristic of wood pellet using a downdraft gasifier system. The wood pellet was used as a feedstock with a variation of moisture content between 2 to 6 wt. %. Tar sample was taken using the JP 2009-40885 method. Gas chromatography mass spectrometry and gravimetric analysis were used to identify and to analyze the tar sample, respectively. The results show that an increase in moisture content slightly decreased the total concentration of tar formation on the nine tar compounds of the biomass. Additionally, the lowest moisture content produced the highest amount of light tar on tar classification. The amount of light tar indicates the ease of ignition in the gasifier. Therefore, this condition will minimize the failure-of-equipment problem because of no clogs in the gasifier equipment. The lowest moisture content had the lowest tar density, and this minimized the deposit of tar in the gasifier. Therefore, the lowest moisture content had low tar production in the biomass gasification process using wood pellets.

Two color ratio method was applied to measure temperature distributions of a luminous diffusion flame. A small blue butane diffusion flame, 3mm in flame diameter, was used. A small droplets array (300 droplets of 30um in diameter) was injected in the diffusion flame. The component was 85% hexadecane and 15% o-xylene to surrogate diesel oil. A color CMOS high speed camera of 4kpfs in flame speed and 16um/pix in spatial resolution was used to measure the flame shape and the temperature. The flame with the droplet array was luminous and the temperature was measured with optical two color ratio method (green and red). In the two color ratio method, a threshold of the red intensity should be defined. As the flame could be assumed as an axial symmetry, an Abel conversion was used. In the Abel conversion, thresholds of red/green intensities should be defined to form a sextic even polynomial. A thin sheath thermocouple (0.3mm in sheath diameter) was used to compare the two color ratio method results. As a result, the red intensity threshold for the two color method was reasonable and 40 in this experiment. In comparison with a KL value two color method, the two color ratio method could show lower temperature region.

Spray method is used for liquid vaporization. Especially in the internal combustion engine, ICE, the spray specifications are important to improve the efficiency and to reduce the emission amount. The main purpose of spray is vaporization but the necessary heat transfer amount is not enough at the cold-start of ICE. In the use of ethanol, an important alternative and sustainable fuel from biomass, this cold-start problem is much more serious because of the high latent heat and low heating value. The Local-contact Microwave-heating Injector, LMI, was designed and tested in this paper to solve the ethanol cold-start problem. The evaluation parameters of the LMI spray were droplet diameter distribution, Sauter Mean Diameter, SMD, and droplet velocity distribution. As a laser diffraction method (approximately 4mm spot-diameter He-Ne laser) was used to measure the droplet diameter distribution but could not measure other parameters, direct photographs with a high speed camera (512pix x 512pix, color, 12bit for each three colors, 30kfps, 87.7μm in spatial resolution) was used to measure the spray structure change and droplet velocity distribution. A threshold evaluation was important to distinguish the droplets in spray. A watershed method was used to divide exceptionally large droplets. As a result, the microwave heating can improve the atomization.

Tar is an undesirable product of biomass gasification. Tar analysis is a challenging task because it is a complex mixture. The objectives of this study are to identify and quantify the major tar compounds in raw producer gas and deposits from a 10 kW downdraft gasifier using cedar pellets. Gas chromatography-mass spectrometry (GC-MS) was used to analyze the 16 tar samples from raw producer gas under varying airflow rates and four tar samples from the deposit inside the suction pump after long-term operation. The results showed that tar in raw producer gas and tar deposits consisted of about 46 and 28 major chemical compounds, respectively. Tar in raw producer gas was found to contain three main groups of substances, including acids/ketones with 32.1 wt%, heterocyclics with 30.0 wt%, and light poly-aromatic hydrocarbons (light PAHs) with 31.8 wt%. Heterocyclic and light PAH compounds dominated in tar deposits and accounted for 58.6 wt% and 36.2 wt%, respectively. It was observed that the tar condensation problem was dominated by the components and the molecular weight of tar compositions instead of the tar concentration. These findings are useful for optimizing the gasification process and developing the gas cleaning system for a small downdraft gasifier. [ABSTRACT FROM AUTHOR]

Abstract  We conducted a retrospective review of the results of rotational acetabular osteotomy (RAO) procedures in 92 hips of 89 patients (81 females and eight males) with early-stage osteoarthritis. In this study, we discuss the indications for this surgery based on the preoperative congruency in abduction. The mean postoperative follow-up was 12.2 (7–19) years. The mean age at operation was 32.5 (13–54) years. Two hips with apparent technical failure were excluded. During follow-up, the osteoarthritic stage remained unchanged in 76 hips (good group) and progressed in 14 hips (poor group). Preoperative joint congruency in abduction was excellent in 20 hips, good in 62, and fair in eight. All eight hips with fair joint congruency showed progression to osteoarthritis at follow-up. Patients without good congruency in abduction may experience progression of osteoarthritis after RAO procedures even in early-stage osteoarthritis. [ABSTRACT FROM AUTHOR]

Abstract  α-Ionone, α-ionol, and their mixtures with phenolic volatiles act as potential male lures for the solanaceous fruit fly Bactrocera latifrons (Hendel). However, the attractiveness of these compounds is not as strong as that of other well-known tephritid male lures, such as methyl eugenol for Bactrocera dorsalis. Isophorone and isophorol, which have a partial skeletal structure of α-ionone/α-ionol (i.e., trimethylcyclohexene), were attractive to B. latifrons males, and their mixtures with α-ionol exhibited stronger activity than any of the individual compounds. We also tested 3-oxo-α-ionone, 3-oxo-α-ionol, 3-hydroxy-α-ionone, and 3-hydroxy-α-ionol, hybrid compounds between isophorone/isophorol and α-ionone/α-ionol. 3-Oxo-α-ionone and 3-oxo-α-ionol were active both as attractants and phagostimulants for males. The results suggest that the introduction of an oxygen atom at the 3-position of the α-ionone/α-ionol molecule optimizes the specific chemosensory responses in B. latifrons males. [ABSTRACT FROM AUTHOR]