• Title/Summary/Keyword: Variable air pressure

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Performance Analysis on the Variable Speed Scroll Compressor with Operating Conditions (가변속 스크롤 압축기의 운전조건의 변화에 따른 성능 해석)

  • 박홍희;박윤철;김용찬
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.12 no.7
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    • pp.649-658
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    • 2000
  • Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

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Fluid Dynamic Performance in a Hot-Water Heating System with a Variable-Flow-Rate Balancing Valve (가변유량 밸런싱밸브를 적용한 온수 난방시스템의 유체역학적 성능 평가)

  • Hur, Jurn;Lee, Suk- Jong;Sung, Jae-Yong;Lee, Myeong-Ho
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.8
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    • pp.577-584
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    • 2007
  • A variable-flow-rate balancing valve has been developed and optimized to apply to a distributor in a hot-water heating system. Fluid dynamic performance of the system was evaluated by comparing the results with the previous pressure difference control valve (PDCV) system. In view of the variations of pressure drop and flow rate according to the sequential closing of the control valves, the present system which is named "smart system distributor", is very stable without a certain flow rate concentration. The level of pressure drop variation is also low as compared with the previous system with a PDCV. In view of the occurrence of cavitation, the present system is quite superior to the previous system because the instantaneous pressures at all sections are much higher than the vapor pressure. On the other hand, the previous system has a possibility of cavitation when one or more control valves are closed.

A Study on Injection and Combustion of D.I. Diesel Engine with Electronic-hydraulic Fuel Injection System (전자유압식 분사계를 갖는 D.I. 디젤기관의 분사 및 연소에 관한 연구)

  • Kim, Hyun-Gu;Ra, Jin-Hong;Ahn, Soo-Kil
    • Journal of Fisheries and Marine Sciences Education
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    • v.9 no.1
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    • pp.83-97
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    • 1997
  • Diesel engine is widely used for ship and industry source of power because of its high thermal efficiency and reliability and durability. However it lead to air pollution due to exhaust gas, and it is important to develop diesel engine of lower air-pollution to decrease the hazardous exhaust gas emissions. As one of the ways, the study for practically using the high pressure of fuel injection and variable injection timing system is being processing. The high pressure injection, which is said to be an effective means for reducing both NOx and particulate emissions, and great improvements in combustion characteristics have been reported by many researchers. In this study, electronic-hydraulic fuel injection system and hydraulic fuel injector system have been applied to the D.I. test engine for high pressure injection and variable injection timing. The injection pressure and injection rate depending upon accumulator pressure were measured with strain gage and Bosch injection rate measuring system before fitting the system into test engine, and analyzed the characteristics of the injection system. The combustion characteristics with this injection system has been analyzed with data concerning heat release rate, pressure rising rate, ignition point, ignition delay and maximum pressure value.

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Numerical Simulation of Laminar Reacting Flows Using Unstructured Finite Volume Method With Adaptive Refinement

  • Kang, Sung-Mo;Kim, Hoo-Joong;Kim, Yong-Mo
    • Journal of the Korean Society of Combustion
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    • v.6 no.2
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    • pp.15-22
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    • 2001
  • A pressure-based, unstructured finite volume method has been applied to couple the chemical kinetics and fluid dynamics and to capture effectively and accurately the steep gradient flame field. The pressure-velocity coupling is handled by two methodologies including the pressure-correction algorithm and the projection scheme. A stiff, operator-split projection scheme for the detailed nonequilibrium chemistry has been employed to treat the stiff reaction source terms. The conservative form of the governing equations are integrated over a cell-centered control volume with collocated storage for all transport variables. Computations using detailed chemistry and variable transport properties were performed for two laminar reacting flows: a counterflow hydrogen-air diffusion flame and a lifted methane-air triple flame. Numerical results favorably agree with measurements in terms of the detailed flame structure.

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Design Study on a Variable Intake and a Variable Nozzle for Hypersonic Engines

  • Taguchi, Hideyuki;Futamura, Hisao;Shimodaira, Kazuo;Morimoto, Tetsuya;Kojima, Takayuki;Okai, Keiichi
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.03a
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    • pp.713-721
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    • 2004
  • Variable air intake and variable exhaust nozzle of hypersonic engines are designed and tested in this study. Dimensions for variable geometry air intake, ram combustor and variable geometry exhaust nozzle are defined based on the requirements of a pre-cooled turbojet engine. Hypersonic Ramjet Engine is designed as a scaled test bed for each component. Actuation forces of moving parts for variable intake and variable nozzle are reduced by balancing the other force in the opposite direction. A demonstrator engine which includes variable intake and variable nozzle is designed and the components are fabricated. Composite material with silicone carbide is applied for high temperature parts under oxidation environment such as leading edge of the variable intake and combustor liner. Internal cooling structure is adopted for both moving and static parts of the variable nozzle. Pressure recovery and mass capture ratio of the variable intake at Mach 5 is obtained by a hypersonic wind tunnel test. Flow characteristics of the variable nozzle are obtained by a low temperature flow test. Wall temperature and heat flux of the nozzle at Mach 3 is obtained by a firing test. As results, the intake and the nozzle are proved to be used at designed pressure and temperature environment.

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Flow and Combustion Characteristics according Control Strategy of Variable Valve Duration System for Compression Ignition Engine (압축착화기관용 가변밸브 듀레이션(VVD)시스템의 제어전략에 따른 유동 및 연소성능 해석)

  • Cho, Insu;Kim, Wootaek;Lee, Jinwook
    • Journal of ILASS-Korea
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    • v.25 no.2
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    • pp.45-50
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    • 2020
  • Recently, global warming and environmental pollution are becoming more important, and fuel economy is becoming important. Each automobile company is actively developing various new technologies to increase fuel efficiency. CVVD(Continuously Variable Valve Duration) system means a device that continuously changes the rotational speed of the camshaft to change the valve duration according to the state of the engine. In this paper, VVT(Variable Valve Timing) and CVVD were applied to a single-cylinder diesel engine, and the characteristics of intake and exhaust flow rate and in-cylinder pressure characteristics were analyzed by numerical analysis. In order to analyze the effect of CVVD on the actual engine operation, the study was performed by setting the valve control and injection pressure as variables in two sections of the engine operating region. As a result, In the case of applying CVVD, the positive overlap with the exhaust valve is maintained, thus it is possible to secure the flow smoothness of air and increase the volumetric efficiency by improving the flow rate. The section 2 condition showed the highest peak pressure, but the pressure rise rate was similar to that of the VVT 20 and CVCD 20 conditions up to 40 bar due to the occurrence of ignition delay.

Analysis of flow rate of variable displacement compressor ECV in automobile air conditioning control system (자동차 공조장치의 가변압축기 ECV 유량 분석)

  • Jeong, Yeong Jun;Cho, Haeng Muk
    • Journal of Energy Engineering
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    • v.22 no.4
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    • pp.394-398
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    • 2013
  • At present, using of electromagnetic control valve (ECV) in external variable displacement swash plate type compressor is a common issue. Solenoid operated ECV controls vehicle air conditioning system through a pulse width modulation (PWM) input signal that supplied from an external source. Different port pressure controls the swash plate movement inside the compressor at certain angles that finally determines the refrigerant flow rate to the vehicle compartment for passengers comfort. In this paper, crankcase pressure flow (Pc flow) is calculated with some ECV samples with corresponding to amount of variable supply of current ranges from 0.20Amp to 0.95Amp.

Fuzzy Control Algorithms for the Compressor and the Electronic Expansion Valve of a Multi-type Air-conditioning System using Multiple Input Variables (다입력변수를 사용한 멀티형 공조시스템 압축기와 전자팽창밸브의 퍼지 제어 알고리즘)

  • Han, Do-Young;Park, Kwan-Jun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.2
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    • pp.163-171
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    • 2006
  • In order to control multi-zone temperatures, a multi-type air-conditioning system may be used. In this study, control algorithms for the compressor and the electronic expansion valve of a multi-type air-conditioning system were developed by using fuzzy logics. The compressor control algorithm was composed of a compressor pressure setpoint algorithm, a compressor pressure setpoint reset algorithm, and a compressor frequency setpoint algorithm. The electronic expansion valve control algorithm was composed of an indoor temperature control algorithm, and a superheat control algorithm. These algorithms were applied to a multi-type air-conditioning system. Test showed good results for the control of a multi-type air-conditioning system.

Effect of Fiber Friction, Yarn Twist, and Splicing Air Pressure on Yarn Splicing Performance

  • Das A.;Ishtiaque S. M.;Parida Jyoti R.
    • Fibers and Polymers
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    • v.6 no.1
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    • pp.72-78
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    • 2005
  • The impact of fiber friction, yarn twist, and splicing air pressure on mechanical and structural properties of spliced portion have been reported in the present paper. The mechanical properties include the tensile and bending related properties and, in the structural properties, the diameter and packing density of the splices are studied. A three variable three level facto­rial design approach proposed by Box and Behnken has been used to design the experiment. The results indicate that there is a strong correlation between retained spliced strength (RSS) and retained splice elongation (RSE) with all the experimental variables. It has been observed that RSS increases with the increase in splice air pressure and after certain level it drops, whereas it consistently increases with the increase in yarn twist. The RSE increases with the increase in both fiber friction and yarn twist. It has also been observed that the yarn twist and splicing air pressure have significant influence on splice diameter, percent increase in diameter and retained packing coefficient, but the fiber friction has negligible influence on these parame­ters. Yarn twist and splicing air pressure has a strong correlation with splice flexural rigidity, where as poor correlation with retained flexural rigidity.

A numerical study on the aerodynamic characteristics of a variable geometry throttle valve(VGTV) system controlling air-flow rate (유량 제어장치인 가변스로틀밸브의 기하학적 형상변화에 따른 공기역학 특성분석 연구)

  • Cho, Hyun-Sung;Kim, Chul-Ho
    • Journal of Advanced Marine Engineering and Technology
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    • v.37 no.4
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    • pp.378-383
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    • 2013
  • A butterfly throttle valve has been used to control the brake power of an SI engine by controlling the mass flow-rate of intake air in the induction system. However, the valve has a serious effect on the volumetric efficiency of the engine due to the pressure resistance in the induction system. In this study, a new intake air controlling valve named "Variable Geometry Throttle Valve(VGTV)" is proposed to minimize the pressure resistance in the intake system of an SI engine. The design concept of VGTV is on the application of a venturi nozzle in the air flow path. Instead of change of the butterfly valve angle in the airflow field, the throat width of the VGTV valve is varied with the operating condition of an SI engine. In this numerical study, CFD(computational fluid dynamics) simulation technique was incorporated to have an aerodynamics performance analysis of the two air flow controlling systems; butterfly valve and VGTV and compared the results to know which system has lower pressure resistance in the air intake system. From the result, it was found that VGTV has lower pressure resistance than the butterfly valve. Especially VGTV is effective on the low and medium load operating condition of an SI engine. The averaged pressure resistance of VGTV is about 49.0% lower than the value of the conventional butterfly throttle valve.