• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.2
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• pp.49-58
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• 1994

A study on the performance of a Diesel engine with various intake gas compositions other than that of air are performed experimentally. In this study, the concentrations of each of oxygen, nitorgen, carbon dioxide, and argon are changed and their effects on the performance of the engine are investigated parametrically. The experiments are performed at constant engine speed condition, and main measured parameters are cylinder pressure, intake gas compositions, fuel consumption rate. Increase of oxygen concentration up to 24% improved the performance of the engine generally. The adverse effect was observed when the oxygen concentration was increased over 24%. Increase of carbon dioxide concentration degraded the performance of the engine, mainly due to the lower specific heat ratio of carbon dioxide. Adding argon gas to the intake gas improved the overall performance. Finally, it is found that two most influencing factors affecting the performance of the Diesel engine in this study of intake gas composition variation are ignition delay and specific heat ratio of the intake gas.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.1
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• pp.10-16
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• 2004

The Homogeneous Charge Compression Ignition (HCCI) engine has advantage for reducing the NOx and P.M. simultaneously. Therefore, HCCI engine is receiving attention as a low emission diesel engine concept. This study was carried out to investigate the characteristics of combustion and exhaust emission for operating conditions in a direct injection type of HCCI engines such as supercharged and naturally aspirated using diesel fuel and additive. From the experimental result, we found that cool flame was always appeared and also it was difficult to control combustion characteristics by changing the injection timing in HCCI. In addition, at the lean air-fuel ratio and high speed range, it was observed that charging air pressure, additive or increasing intake air temperature is effective to increase combustion performance and reduce exhaust emission. We concluded that chemical reaction by the increasing intake air temperature or additive without physical improvement has limitation for reduction of exhaust emission.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.4
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• pp.93-99
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• 1997

The re quest to develop the engines that are able to run without air or with very little oxygen condition is raised with the interest of ocean science or the mines. This research had already be gun before the world war II, but had been stagnant owing to the appearance of nuclear power. Recycle diesel engines have ability to run under the above mentioned condition the recycle diesel engine recirculates exhaust gases into intake port and consumes additional oxygen supplied by oxygen tank. Carbon dioxide is controlled by the absorber. The combustion and emission characteristics of recycle diesel engines are quite different with conventional one because the working fluids of recycle diesel engines consist of Ar, $CO_2$ and $O_2$ as well as $N_2$. Recycle diesel engine is therefore different with general diesel engine from the viewpoint of intake air composition. It is required to investigate the effect of intake composition in the combustion and emission to know recycle diesel engine. In this study, NOx concentration, smoke and cylinder pressure are measured with the variation of Ar and $CO_2$ Reduces show that the addition of Ar reduces NOx but increases smoke. Otherwise $CO_2$ reduces smoke and NOX simultaneously. Only $CO_2$ increases the ignition delay and both gases increase fuel consumption Ar addition is superior to $CO_2$ addition for the performance of recycle diesel engine system but $CO_2$ has the avantage with respect to emission.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.2
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• pp.91-96
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• 1994

Intake gases other than air, which is composed of oxygen, nitrogen, carbon dioxide, and argon, are used to study their effects on the performance of the diesel engine experimentally. The engine is operated at constant speed and fixed fuel injection timing, and cylinder pressure and heat release rate are measured at various intake gas compositions. The results show that increase of oxygen concentration improves the performance of the engine generally. The adverse effect is observed when the oxygen concentration is increased over the critical oxygen concentration of this test, mainly because of the over-shortened ignition delay. Increase of carbon dioxide concentration degardes the performance of the engine, mainly due to the lower specific heat ratio of carbon dioxide. Adding argon gas to the intake gas improves the overall performance. Finally, it is found that two most influencing factors affecting the performance of the diesel engine in this study are ignition delay and speific heat ratio of the intake gas.

• Journal of the Korean Society of Industry Convergence
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• v.18 no.4
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• pp.197-206
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• 2015

Recently the automobile engine has been developed in achieving the high performance, fuel economy, and emission reduction. In a conventional spark ignition engine the fuel and air are mixed together in the intake system, inducted through the intake valve into the cylinder, and then compressed. Under normal operating conditions, the combustion is initiated towards the end of the compression stroke at the spark plug by an electric discharge. Following inflammation, a flame develops and propagates through this premixed fuel-air mixture. Therefore the state of mixture is very important in the combustion and emission characteristics. In this study the combustion and emission characteristics were tested and analyzed with changing the mixture composition and engine operating parameters in order to improve the combustion and performance in engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.5
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• pp.15-21
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• 2003

The liquid phase LPG injection engine is a new technology to make good use of LPG as a clean energy. However, it is difficult to precisely control air/fuel ratio in the system because of variation of fuel composition, change of temperature and flash boiling injection mechanism. This study newly suggests an injector control logic for liquid phase LPG injection systems. This logic compensates a number of effects such as variations of density, stoichiometric air/fuel ratio, injection delay time, injection pressure, release pressure which is formed by flash boiling of fuel at nozzle exit. This logic can precisely control air/fuel ratio with only two parameters of intake air flow rate and injection pressure without considering fuel composition, fuel temperature.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1009-1015
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• 2011

In this study, in the high expansion cycle was conduced by variable valve timing system composition to close intake valve late, and in the intake air reduction on the low compression was solved by supercharging pressure. In this wise, by constituting Diesel-Atkinson cycle, this study looked into a possibility of thermal efficiency improvement. As a result, there was improvement in thermal efficiency and output in a whole range of closing timing from ABDC $40^{\circ}$ to ABDC $80^{\circ}$. However, after ABDC $70^{\circ}$ of closing timing, the thermal efficiency increase was getting smaller. As the result of the study, the optimum intake valve closing timing was about ABDC $70^{\circ}$, high loading territory of engine was more effective than low loading territory, and engine operation in middle loading territory was stable. At this time, brake thermal efficiency was 12.5% higher than ordinary engine on average.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.2
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• pp.185-193
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• 2005

The present study composed a diesel-atkinson cycle of high expansion as a method of achieving high efficiency in diesel cycle engines. It also interpreted the cycle engine thermodynamically analysis to determine the possibility of the improvement of thermal efficiency and clarified the characteristics of several factors . According to the result of theoretical analysis, heat efficiency was highest when expansion-compression ratio Reど:1. In addition. diesel engines with high apparent compression ratio had higher expansion-compression ratio than otto engines and consequently their effect of high expansion was high. which in turn enhanced thermal efficiency. When the atkinson cycle was implemented in a real diesel engine by applying the miller cycle through the variation of the closing time of the intake valve, the effective compression ratio and the quantify of intake air decreased and as a result, the effect of high expansion was not observed. Accordingly. the atkinson cycle can be implemented when the quantity of intake air is compensated by supercharge and the effective compression ratio is maintained at its initial level through the reduction of the clearance volume. In this case. heat efficiency increased by $4.1\%$ at the same expansion-compression ratio when the apparent compression ratio was 20 and the fuel cut off ratio was 2. As explained above, when the atkinson cycle was used for diesel cycle. heat efficiency was improved. In order to realize high expansion through retarding the intake value closing time, the engine needs to be equipped with variable valve timing equipment, variable compression ratio equipment and supercharged Pressure equipment. Then a diesel-atkinson cycle engine is realized.

• Asian-Australasian Journal of Animal Sciences
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• v.25 no.10
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• pp.1364-1373
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• 2012

Four crossbred (75% Holstein Friesian) lactating dairy cows, with an average live weight of $418{\pm}5$ kg and $36{\pm}10$ d in milk were randomly assigned according to a $2{\times}2$ factorial arrangement in a $4{\times}4$ Latin square design to evaluate the effects of cassava hay (CH) and rice bran oil (RBO) on feed intake, nutrient digestibility, ruminal fermentation, milk yield, and milk composition. Factor A was non-supplementation or supplementation with CH in the concentrate. Factor B was supplementation with RBO at 0% or 4% in the concentrate mixture. The four dietary treatments were (T1) control (Concentrate with non-CH plus 0% RBO; C), (T2) Concentrate with CH plus 0% RBO (CH), (T3) Concentrate with non-CH plus 4% RBO (RBO), and (T4) Concentrate with CH plus 4% RBO (CHRBO). The cows were offered concentrate, at a ratio of concentrate to milk production of 1:2, and urea-lime treated rice straw was fed ad libitum. Urea-lime treated rice straw involved 2.5 g urea and 2.5 g $Ca(OH)_2$ (purchased as hydrated lime) in 100 ml water, the relevant volume of solution was sprayed onto a 100 g air-dry (91% DM) straw, and then covering the stack with a plastic sheet for a minimum of 10 d before feeding directly to animals. The CH based concentrate resulted in significantly higher roughage intake and total DM intake expressed as a percentage of BW (p<0.05). Ruminal pH, $NH_3$-N, BUN and total VFA did not differ among treatments, while RBO supplementation increased propionate, but decreased acetate concentration (p<0.05). Furthermore, the population of total ruminal bacteria was significantly lower on the RBO diet (p<0.05). In contrast, the total ruminal bacteria and cellulolytic bacteria on the CH diet were higher than on the other treatments. Supplementation with CH increased (p<0.05) F. succinogens and R. flavefaciens populations, whereas the populations of B. fibrisolvens and M. elsdenii were increased on the RBO diet. In addition, supplementation with CH and RBO had no effect on milk production and composition in dairy cows, while fatty acid composition of milk was influenced by RBO supplementation, and resulted in significantly lower (p<0.05) concentrations of both short-chain and medium-chain FA, and increased (p<0.05) the proportion of long-chain FA in milk fat, as well as significantly increased cis-9, trans-11 CLA and total CLA. In conclusion, RBO or CH exhibited specific effects on DMI, rumen fermentation, microbial population, milk yield and composition in lactating dairy cows, which were not interactions between CH and RBO in the diets. Feeding lactating dairy cows with RBO could improve fatty acid in milk fat by increasing cis-9, trans-11 CLA.

• Journal of The Korean Society of Grassland and Forage Science
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• v.44 no.2
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• pp.92-98
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• 2024

The objective of this study was to investigate the comparison of feeding a total mixed ration (TMR) containing imported alfalfa hay and TMR containing hot-air dried domestic alfalfa on rumination activity, milk production, and composition in lactating dairy cows. Ten Holstein dairy cows were divided into two groups: control (imported alfalfa hay + TMR) and treatment (hot-air dried domestic alfalfa + TMR) groups. The study was conducted over a total period of 18 days, including a 13-days adaptation period and a 5-days main experimental period. The results indicated no differences in total digestible nutrient and net energy intake between the imported and hot-air dried alfalfa. Body weight was not significantly different between the two groups (p>0.05), however, total feed intake and rumination time were significantly and tendentially higher in the treatment group compared with control group, respectively (p<0.001; p=0.075). Milk yield was not significantly different between the two groups (p>0.05), however, milk fat (kg) and lactose (%) concentration were significantly higher in the treatment group compared with control group (p=0.016; p=0.02). This study confirms that feeding TMR with hot-air dried domestic alfalfa results in no differences of feed intake, rumination activity, and milk productivity. Therefore, it is considered that hot-air dried domestic alfalfa can be used as a substitute for imported alfalfa on lactating dairy cows.