• Title/Summary/Keyword: Recirculation system

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Investigation on the Turbulent Swirling Flow Field within the Combustion Chamber of a Gun-Type Gas Burner (Gun식 가스버너의 연소실내 난류 선회유동장 고찰)

  • Kim, Jang-Kweon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.9
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    • pp.666-673
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    • 2009
  • The turbulent swirling flow field characteristics of a gun-type gas burner with a combustion chamber were investigated under the cold flow condition. The velocities and turbulent quantities were measured by hot-wire anemometer system with an X-type probe. The turbulent swirling flow field in the edge of a jet seems to cause a recirculation flow from downstream to upstream due to the unbalance of static pressure between a main jet flow and a chamber wall. Moreover, because the recirculation flow seems to expand the main jet flow to the radial and to shorten it to the axial, the turbulent swirling flow field with a chamber increases a radial momentum but decreases an axial as compared with the case without a chamber from the range of about X/R=1.5. As a result, these phenomena can be seen through all mean velocities, turbulent kinetic energy and turbulent shear stresses. All physical quantities obtained around the slits, however, show the similar magnitude and profiles as the case without a chamber within the range of about X/R=1.0.

Corrosion Characteristics Improvement of Aluminium Tube for Diesel Engine Intercooler with LP-EGR(Low Pressure-Exhaust Gas Recirculation) (LP-EGR이 적용된 디젤 엔진 인터쿨러용 알루미늄 튜브의 내식성 향상)

  • Ahn, Joon;Ha, Seok;Kwak, Dong-Ho;Jung, Byung-Jun
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.6
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    • pp.140-145
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    • 2012
  • Recently, various after-treatment systems, such as LP-EGR(Low Pressure-Exhaust Gas Recirculation), SCR(Selective Catalytic Reduction) and LNT(Lean NOx Trap), were developed to obey the stringent emission regulations of diesel engine. There are many researches on LP-EGR system because it has advantages of NOx reduction and low fuel consumption. But, condensation water is generated in internal of intercooler tube and it contains various types of anion that cause the corrosion of aluminium tube. In this study, it is examined that the condensation water effects on corrosion of aluminium tube. And method for improvement of corrosion characteristics is investigated using the dipping and electrochemical test.

Expansion of Operating Range and Reduction of Engine out Emission in Low Temperature Diesel Combustion with Boosting (과급을 이용한 저온 디젤 연소의 운전영역 확장 및 배기 배출물 저감)

  • Shim, Eui-Joon;Han, Sang-Wook;Jang, Jin-Young;Park, Jung-Seo;Bae, Choong-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.5
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    • pp.31-38
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    • 2009
  • Supercharging system was adopted to investigate the influence of boost pressure on operating range and exhaust emissions by using a supercharger at low temperature diesel combustion (LTC) condition in a 5-cylinder 2.7 L direct injection diesel engine. The experimental parameters such as injection quantity, injection timing, injection pressure and exhaust gas recirculation (EGR) rate were varied to find maximum operating range in LTC condition. As a result of adopting increased boost pressure in LTC, wider operating range was achieved compared with naturally aspirated condition due to increased mixing intensity. Increased boost pressure resulted in lower hydrocarbon (HC) and carbon monoxide (CO) emissions due to increased swirl rate and mixing intensity, which induced complete combustion. Moreover, increased boost pressure in LTC resulted in much lower soot emissions compared with high speed direct injection (HSDI) condition.

100 MWe Oxyfuel Power Plant Boiler System Process Design and Operation Parameters Sensitivity Analysis (100 MWe급 순산소연소 발전소 보일러계통 공정설계 및 운전변수 민감도 예측)

  • Baek, Sehyun;Ko, SungHo
    • Journal of the Korean Society of Combustion
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    • v.18 no.4
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    • pp.1-11
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    • 2013
  • The oxy-fuel combustion is $CO_2$ capture technology that uses mixture of pure $O_2$ and recirculated exhaust as oxidizer. Currently some Oxy-fuel power plants demonstration project is underway in worldwide. Meanwhile research project for converting 125 MWe Young-Dong power plant to 100 MWe oxy-fuel power plants is progress. In this paper, 1 D process analytical approach was applied for conducting process design and operating parameters sensitivity analysis for oxy-fuel combustion of Young-Dong power plant. As a result, appropriate gas recirculation rates was 74.3% that in order to maintain normal rating superheater, reheater steam temperature and boiler heat transfer patterns. And boiler efficiency 85.0%, CPU inlet $CO_2$ mole concentration 71.34% was predicted for retrofitted boiler. The oxygen concentration in the secondary recycle gas is predicted as 27.1%. Meanwhile the oxygen concentration 22.4% and moisture concentration 5.3% predicted for primary recycle gas. As the primary and secondary gas recirculation increases, then heat absorption of the reheater is tends to increases whereas superheater side is decreased, and also the efficiency is tends to decrease, according to results of sensitivity analysis for operating parameters. In addition, the ambient air ingression have a tendency to lead to decline of efficiency for boiler as well as decline of $CO_2$ purity of CPU inlet.

Engineering Control of Mill Fire for High Volatile Sub-bituminous Coal (저급탄 미분기 화재발생 인자분석 연구)

  • Keel, Sang-In;Park, Ho-Young;Kim, Young-Joo;Youn, Sung-Hwan
    • Journal of the Korean Society of Combustion
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    • v.18 no.4
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    • pp.53-58
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    • 2013
  • Lots of Coal power plants (about 30) using bituminous coals are being run in Korea. The use of high volatile low grade sub-bituminous coal is increasingly extended because of imbalance between the worldwide coal supply and demand. Mill-fire has been an important issue since the use of such sub-bituminous coal. In existing coal plants of Korea, shutdown of coal and air supplies could be only a way, and an alternative has not been found in suppressing the mill fire. The inside fowfield in the mills has a highly fuel-rich, low temperature, and high velocity and non-reactive such that it could be a nonreactive system essentially. Nevertheless, occasional fire-occurrence could be attributed to the existence of an ignition source. However it has not been so far investigated in detail. The current work has a focus on suppressing the mile fire via some parametric experimental study such as effects of temperature, residence time, ignition source, and inert gas mixing. The results show that an small amount of $CO_2$- or $N_2$-mixing with air is very effective in suppressing fire formation even at high temperatures or flying sparks. The results suggest that exhaust gas recirculation into the mill should be an alternative to suppress mill fire.

Study on Fuel Consumption Improvement in SI Engine with EGR for Hybrid Electric Vehicle (하이브리드용 가솔린엔진의 EGR을 통한 연비향상에 관한 연구)

  • Park, Cheol-Woong;Choi, Young;Kim, Chang-Gi
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.2
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    • pp.128-135
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    • 2008
  • EGR(exhaust gas recirculation) is considered as a most effective method to reduce the NOx emissions. But high EGR tolerance is always pursued not only for its advantages of the pumping loss reduction and fuel economy benefit in Gasoline-Hybrid engine. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel efficiency, combustion stability, engine performance and exhaust emissions. With optimal EGR rates, the fuel consumption was improved by 4%. This improvement was achieved while a reduction in NOx emissions of 75% was accomplished. Increase of EGR gas temperature causes the charge air temperature to affect the knock phenomenon and moreover, the EGR valve lift changes for the same control signal.

A Study on Application of On/Off Type EGR and Optimal EGR Rate for Gasoline-Hybrid Engine (하이브리드용 가솔린 엔진에서 On/Off 방식 EGR적용 및 최적 EGR 율에 관한 연구)

  • Park, Cheol-Woong;Choi, Young;Kim, Chang-Gi
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.4
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    • pp.143-150
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    • 2008
  • EGR(exhaust gas recirculation) is an attractive means of improving the fuel economy of spark ignition engines, as it offers the benefits of charge dilution (lower pumping and cooling losses) while allowing stoichiometric fuelling to be retained for applications using the three-way catalysts. However, the occurrence of excessive cyclic variation with high EGR normally prevents substantial fuel economy improvements from being achieved in practice. Therefore, the optimum EGR rate in Gasoline-Hybrid engine should be carefully determined in order to achieve low fuel consumption and low exhaust emission. In this study, 2 liters gasoline engine with E-EGR system was used to investigate the effects of EGR on fuel economy, combustion stability, engine performance and exhaust emissions. EGR tolerance with load variation was found to be more sensitive than with rpm variation. With optimal EGR rates, the fuel consumption was improved by 5.5% while a combustion stability was guaranteed.

Numerical Evaluation of Flow Nature at the Downstream of a Ball Valve Used for Gas Pipelines with Valve Opening Rates (개도율에 따른 가스파이프라인용 볼 밸브 후류유동의 수치평가)

  • KIM, CHUL-KYU;LEE, SANG-MOON;JANG, CHOON-MAN
    • Journal of Hydrogen and New Energy
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    • v.29 no.4
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    • pp.370-377
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    • 2018
  • Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.

Performance Evaluation of Large Eddy Simulation for Recirculating and Swirling Flows (재순환 및 선회 유동에 대한 대와동모사(LES)의 성능검토)

  • Hwang Cheol-Hong;Lee Chang-Eon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.30 no.4 s.247
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    • pp.364-372
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    • 2006
  • The objective of this study is to evaluate the efficiency and the prediction accuracy of developed large eddy simulation (LES) program for complex turbulent flows, such as recirculating and swirling flows. To save the computational cost, a Beowulf cluster system consisting 16 processors was constructed. The flows in backward-facing step and dump combustor were examined as representative recirculating and swirling flows. Firstly, a direct numerical simulation (DNS) for laminar backward-facing step flows was previously conducted to validate the overall performance of program. Then LES was carried out for turbulent backward-facing step flows. The results of laminar flow showed a qualitative and quantitative agreement between simulations and experiments. The simulations of the turbulent flow also showed reasonable results. Secondly, LES results for non-swirling and swirling flows in a dump combustor were compared with the results of Reynolds-averaged Navier-Stokes (RANS) using standard $k-{\varepsilon}$ model. The results show that LES has a better performance in predicting the mean axial and azimuthal velocities, comer recirculation zone (CRZ) and center toroidal recirculation zone (CTRZ) than those of RANS. Finally, it was examined the capability of LES for the description of unsteady phenomena.

Study on Noise Generation Characteristics of Simulated EGR System for Compression Ignition Diesel Engine (압축착화 디젤엔진의 모사 EGR 시스템에 의한 소음 특성 변화 분석)

  • Park, B.;Yoon, S.;Park, S.;Park, J.
    • Journal of ILASS-Korea
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    • v.19 no.4
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    • pp.204-210
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    • 2014
  • Experimental study was conducted to investigate the effect of EGR(exhaust gas recirculation) on engine noise using single cylinder combustion ignition engine. Under constant engine rotary speed of 1200 RPM, 8 mg fuel quantity was injected with 15, 18 and 21% of oxygen ratio and 1400 bar of injection pressure. Using the in-cylinder pressure data acquired by a piezoelectric transducer, the engine performance parameters were calculated. Radiated engine noise measured for 10 seconds was analyzed using spectral characteristics and sound quality metrics such as loudness, sharpness, roughness. From the obtained engine performance parameters and sound quality metrics, effect of oxygen ratio of the premixed air, start of injection timing on frequency characteristic and sound quality metrics were analyzed. Correlation analysis was conducted between MPRR(maximum pressure rise rate), RI(ringing intensity) and sound quality metrics. RI was identified as the most important factor having influence on the sound quality metrics.