• Journal of Energy Engineering
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• v.14 no.2 s.42
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• pp.73-81
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• 2005

An Experimental study was conducted to investigate the effective way for fuel consumption improvement in radiant tube burner heating system used in steel manufacturing process. To find effectiveness of increase of temperature and oxygen fraction of intake air on fuel consumption, the model radiant tube burner heating system with recuperator was designed to be able to adjust temperature and oxygen fraction of intake air, and was operated under various conditions with oxygen concentration in exhaust gas changed. The results show that burner chamber temperature was increased about $10\%$ of intake air temperature increase. so it was difficult to expect fuel consumption improvement. But only 1 or $2\%$ increase of oxygen fraction in intake air made a significant improvement in fuel consumption even though it made much NOx emissions also. Therefore, if NOx emissions is controlled under regulation with burner modification, it is expected that increase of oxygen fraction in Intake air is effective way to improve fuel consumption.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.76-88
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• 1995

The effects of exhaust gas recirculation(EGR) on the characteristics of NOx emissions and specific fuel consumption rate have been investigated using an eight-cylinder. four cycle. direct injection diesel engine operating at several loads and speeds. The theoretical NO formation concentration is calculated with the equivalence ratio as a parameter of flame temperature to study the effect of EGR on NOx emissions in the diesel combustion. The experiments in this study are conducted on the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. It is found that the specific fuel consumption rate is slightly increased with EGR rate. and NOx emissions are markedly reduced owing to the drop of the incoming oxygen concentratio and the increase of equivalence ratio as the EGR rate increases.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.6
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• pp.679-687
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• 2002

In this study, a cycle simulation using a two-zone model is carried out to investigate the effect of intake charging conditions such as oxygen concentration, temperature and pressure on NO emissions in a DI diesel engine. The model is validated against measurements in terms of cylinder pressure, torque, BSFC and NOx emissions with 2902 cc DI diesel engine. Calculated results can be summarized as follows. The oxygen concentration in the intake charge is decreased with increasing of EGR rate and equivalence ratio. As the intake oxygen concentration is reduced, the combustion pressure and the burned gas temperature decrease and, as a result, NO formation decreases. Also, the results show that as the intake pressure increases and the intake temperature decreases, NO emissions are effectively reduced.

• Tuberculosis and Respiratory Diseases
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• v.45 no.5
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• pp.1022-1030
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• 1998

Background : In volume-controlled ventilation, the use of inspiratory pause increases the inspiratory time and thus increases mean airway pressure and improves ventilation. But under the same I : E ratio, the effects of inspiratory pause on mean airway pressure and gas exchange are not certain. Moreover, the effects may be different according to the resistance of respiratory system. So we studied the effects of inspiratory pause on airway pressure and gas exchange under the same I : E ratio in volume-controlled ventilation. Methods: Airway pressure and arterial blood gases were evaluated in 12 patients under volume-controlled mechanical ventilation with and without inspiratory pause time 5%. The I : E ratio of 1 : 3, $FiO_2$, tidal volume, respiratory rate, and PEEP were kept constant. Results: $PaCO_2$ with inspiratory pause was lower than without inspiratory pause ($38.6{\pm}7.4$ mmHg vs. $41.0{\pm}7.7$ mmHg. p<0.01). P(A-a)$O_2$ was not different between ventilation with and without inspiratory pause $185.3{\pm}86.5$ mmHg vs. $184.9{\pm}84.9$ mmHg, p=0.766). Mean airway pressure with inspiratory pause was higher than without inspiratory pause ($9.7{\pm}4.0\;cmH_2O$ vs. $8.8{\pm}4.0\;cmH_2O$, p<0.01). The resistance of respiratory system inversely correlated with the pressure difference between plateau pressure with pause and peak inspiratory pressure without pause (r=-0.777, p<0.l), but positively correlated with the pressure difference between peak inspiratory pressure with pause and peak inspiratory pressure without pause (r=0.811, p<0.01). Thus the amount of increase in mean airway pressure with pause positively correlated with the resistance of respiratory system (r=0.681, p<0.05). However, the change of mean airway pressure did not correlated with the change of $PaCO_2$. Conclusion: In volume-controlled ventilation under the same I : E ratio of 1 : 3, inspiratory pause time of 5% increases mean airway pressure and improves ventilation. Although the higher resistance of respiratory system, the more increased mean airway pressure, the increase in mean airway pressure did not correlated with the change in $PaCO_2$.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.88-94
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• 2012

One of the effective ways to reduce both $NO_x$ and PM at the same time in a diesel CI engine is to operate the engine in low temperature combustion (LTC) regimes. In general, two strategies are used to realize the LTC operation-dilution controlled LTC and late injection LTC - and in this study, the former approach was used. In the dilution controlled regime, LTC is achieved by supplying a large amount of EGR to the cylinder. The significant EGR gas increases the heat capacity of in-cylinder charge mixture while decreasing oxygen concentration of the charge, activating low temperature oxidation reaction and lowering PM and $NO_x$ emissions. However, use of high EGR levels also deteriorates combustion efficiency and engine power output. Therefore, it is widely considered to use increased intake pressure as a way to resolve this issue. In this study, the effects of intake pressure variations on performance and emission characteristics of a single cylinder diesel engine operated in LTC regimes were examined. LTC operation was achieved in less than 8% $O_2$ concentration and thus a simultaneous reduction of both PM and $NO_x$ emission was confirmed. As intake pressure increased, combustion efficiency was improved so that THC and CO emissions were decreased. A shift of the peak Soot location was also observed to lower $O_2$ concentration while $NO_x$ levels were kept nearly zero. In addition, an elevation of intake pressure enhanced engine power output as well as indicated thermal efficiency in LTC regimes. All these results suggested that LTC operation range can be extended and emissions can be further reduced by adjusting intake pressure.

• Tuberculosis and Respiratory Diseases
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• v.46 no.5
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• pp.662-673
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• 1999

Background : Pressure-controlled ventilation (PCV) is frequently used recently as the initial mode of mechanical ventilation in the patients with respiratory failure. Theoretically, because of its high initial inspiratory flow, pressure-controlled ventilation has lower peak inspiratory pressure and improved gas exchange than volume-controlled ventilation (VCV). But the data from previous studies showed controversial results about the gas exchange. Moreover, the comparison study between PCV and VCV with various inspiration : expiration time ratios (I : E ratios) is rare. So this study was performed to compare the respiratory mechanics and gas exchange between PCV and VCV with various I : E raitos. Methods : Nine patients receiving mechanical ventilation for respiratory failure were enrolled. They were ventilated by both PCV and VCV with various I : E ratios (1 : 2, 1 : 1.3 and 1.7 : 1). $FiO_2$, tidal volume, respiratory rate and external positive end-expiratory pressure (PEEP) were kept constant throughout the study. After 20 minutes of each ventilation mode, arterial blood gas, airway pressures, expired $CO_2$ were measured. Results : In both PCV and VCV, as the I : E ratio increased, the mean airway pressure was increased, and $PaCO_2$ and physiologic dead space fraction were decreased. But P(A-a)$O_2$ was not changed. In all three different I : E ratios, peak inspiratory pressure was lower during PCV, and mean airway pressure was higher during PCV. But $PaCO_2$ level, physiologic dead space fraction and P(A-a)$O_2$ were not different between PCV and VCV with three different I : E ratios. Conclusion : There was no difference in gas exchange between PCV and VCV under the same tidal volume, frequency and I : E ratio.

• Clinical and Experimental Pediatrics
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• v.45 no.5
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• pp.596-602
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• 2002

Purpose : The purpose of this study was to analyze the association of peripheral neutrophil count with the development of respiratory failure in preterm infants. Methods : A retrospective study was conducted from January 1993 to December 1999 on 44 preterm infants, who were admitted to the neonatal intensive care unit of St. Francisco hospital. Preterm infants(birth weight 500 to 1,350 gm) who had a complete blood count obtained within 2 hours after delivery. Patients in the lowest of neutrophil count(early neutropenia, < $1.0{\times}10^9/L$) were compared with patients in the remaining group. Results : Low neutrophil count were transient in early neutropenia group. The concentration the circulating neutrophil count rose from $0.85{\pm}0.11{\times}10^9/L$ at average of 2 hours after delivery to $5.3{\pm}2.7{\times}10^9/L$ at 24 hours after delivery in the early neutropenia group and from $3.6{\pm}1.6{\times}10^9/L$ to $5.8{\pm}3.2{\times}10^9/L$ in the non-neutropenia group during the same time period. Compare to the non-neutropenia group, the neutropenia group had a lower birth weight($1,046.50{\pm}180.76gm$ Vs $1,156.70{\pm}124.99gm$), a lower Apgar score(1 min : $3.41{\pm}1.18$ Vs $4.30{\pm}1.46$, 5 min : $5.41{\pm}0.87$ Vs $6.15{\pm}0.95$), and a higher incidence of bronchopulmonary dysplasia(27.27% Vs 7.0%). Patients who had early neutropenia were more likely to require mechanical ventilation, supplemental oxygen and hospital stay. Also, main effect factors for the two groups were birth weight(Odds ratio=5.457, 95% CI=1.551-27.525), initial peripheral blood white cells(odds ratio=8.308, 95% CI=2.054-52.699), and bronchopulmonary dysplasia(odds ratio=0.099, 95% CI=0.017-0.397). Conclusion : A low count of neutrophil in the systemic circulation of premature infants within 2 hours of birth is associated with more severe respiratory distress.

• Tuberculosis and Respiratory Diseases
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• v.48 no.4
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• pp.487-499
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• 2000

Background : Acute lung injury is an hypoxic respiratory failure resulting from damage to the alveolar-capillary membrane, which can be developed by a variety of systemic inflammatory diseases. In this study the therapeutic effects of intra-tracheal pulmonary surfactant instillation was evaluated in the intratracheal endotoxin induced acute lung injury model of a rat. Methods : Twenty Sprague-Dawley rats were divided into 4 groups, and normal saline (2 ml/kg, for group 1) or LPS (5 mg/kg, for group 2, 3, and 4) was instilled into the trachea respectively. Either normal saline (2 ml/kg, for group 1 & 2, 30 min later) or bovine surfactant (15 mg/kg, 30 min later for group 3, 5 hr later for group 5) was instilled into the trachea. The therapeutic effect of intratracheal surfactant therapy was evaluated with one chamber body plethysmography (respiratory frequency, tidal volume and enhanced pause), ABGA, BAL fluid analysis (cell count with differential, protein concentration) and pathologic examination of the lung. Results : Intratracheal endotoxin instillation increased the respiration rate decreased the tidal volume and int creased the Penh in all group of rats. Intratracheal instillation of surfactant decreased Penh, increased arterial oxygen tension, decreased protein concentration of BAL fluid and decreased lung inflammation at both times of administration (30 minute and 5 hour after endotoxin instillation). Conclusion : Intratracheal instillation of surfactant can be a beneficial therapeutic modality as discovered in the acute lung injury model of rats induced by intratracheal LPS intillation. It deserves to be evaluated for treatment of human acute lung injury.

• Tuberculosis and Respiratory Diseases
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• v.42 no.4
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• pp.555-568
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• 1995

Background: It is most physiologic to measure the diffusing capacity of the lung by using oxygen, but it is so difficult to measure partial pressure of oxygen in the capillary blood of the lung that in clinical practice it is measured by using carbon monoxide, and single-breath diffusing capacity method is used most widely. However, since the process of withholding the breath for 10 seconds after inspiration to the total lung capacity is very hard to practice for patients who suffer from cough, dyspnea, etc, the intra-breath lung diffusing capacity method which requires a single exhalation of low-flow rate without such process was devised. In this study, we want to know whether or not there is any significant difference in the diffusing capacity of the lung measured by the single-breath and intra-breath methods, and if any, which factors have any influence. Methods: We chose randomly 73 persons without regarding specific disease, and after conducting 3 times the flow-volume curve test, we selected forced vital capacity(FVC), percent of predicted forced vital capacity, forced expiratory volume within 1 second($FEV_1$), percent of forced expiratory volume within 1 second, the ratio of forced expiratory volume within 1 second against forced vital capacity($FEV_1$/FVC) in test which the sum of FVC and $FEV_1$ is biggest. We measured the diffusing capacity of the lung 3 times in each of the single-breath and intra-breath methods at intervals of 5 minutes, and we evaluated which factors have any influence on the difference of the diffusing capacity of the lung between two methods[the mean values(ml/min/mmHg) of difference between two diffusing capacity measured by two methods] by means of the linear regression method, and obtained the following results: Results: 1) Intra-test reproducibility in the single-breath and intra-breath methods was excellent. 2) There was in general a good correlation between the diffusing capacity of the lung measured by a single-breath method and that measured by the intra-breath method, but there was a significant difference between values measured by both methods($1.01{\pm}0.35ml/min/mmHg$, p<0.01) 3) The difference between the diffusing capacity of the lung measured by both methods was not correlated to FVC, but was correlated to $FEV_1$, percent of $FEV_1$, $FEV_1$/FVC and the gradient of methane concentration which is an indicator of distribution of ventilation, and it was found as a result of the multiple regression test, that the effect of $FEV_1$/FVC was most strong(r=-0.4725, p<0.01) 4) In a graphic view of the difference of diffusing capacity measured by single-breath and intra-breath method and $FEV_1$/FVC, it was found that the former was divided into two groups in section where $FEV_1$/FVC is 50~60%, and that there was no significant difference between two methods in the section where $FEV_1$/FVC is equal or more than 60% ($0.05{\pm}0.24ml/min/mmHg$, p>0.1), but there was significant difference in the section, less than 60%($-4.5{\pm}0.34ml/min/mmHg$, p<0.01). 5. The diffusing capacity of the lung measured by the single-breath and intra-breath method was the same in value($24.3{\pm}0.68ml/min/mmHg$) within the normal range(2%/L) of the methane gas gradient, and there was no difference depending on the measuring method, but if the methane concentration gradients exceed 2%/L, the diffusing capacity of the lung measured by single-breath method became $15.0{\pm}0.44ml/min/mmHg$, and that measured by intra-breath method, $11.9{\pm}0.51ml/min/mmHg$, and there was a significant difference between them(p<0.01). Conclusion: Therefore, in case where $FEV_1$/FVC was less than 60%, the diffusing capacity of the lung measured by intra-breath method represented significantly lower value than that by single-breath method, and it was presumed to be caused largely by a defect of ventilation-distribution, but the possibility could not be excluded that the diffusing capacity of the lung might be overestimated in the single-breath method, or the actual reduction of the diffusing capacity of the lung appeared more sensitively in the intra-breath method.