• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.992-995
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• 2011

A study on the performance design schemes of the supersonic air intakes applied to the supersonic air-breathing propulsion system(Ramjet/Scramjet) was conducted and for two kinds of air intakes, the preliminary configuration designs and the performance analysis models were established. For axisymmetric conical air intake and two dimensional rectangular air intake, the performance effects were assessed according to compression angles and shock wave numbers.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.70-76
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• 2012

Recently, because people are taking a great interest in the water supply system and the related facilities are getting larger, the surge suppression is very important problem. The waterhammer occurs when the pumps are started or stoped for operation or tripped due to the power failure. As the waterhammer problems as a result of the pump power failure were very serious, these situations were carefully investigated. Accordingly, we carried out both numerical simulations and field tests to confirm the safety of Juam intake pumping station in which had the in-line pumps. In this paper, it was reviewed that the water supply system has the reliability on the pressure surge, in case the air chambers were installed at both the inlet and the oulet of the in-line pumping station. From the numerical simulations, we found that negative pressure occurred at the inlet disappeared and high pressure occurred at the outlet reduced due to the air chambers. And these results of numerical simulations verified by the field tests. The field tests carried out in case of normal start, normal stop, one and two of pumps emergency stop. By results of simulations and field tests, we are sure that Juam intake pumping station in which have the air chambers is safe for the waterhammer. In addition, we suggested the operation methods of facilities for safe maintenance of the pumping station.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.11-16
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• 2006

The pressure fluctuation in the intake and exhaust pipe of 4 stroke-cycle diesel engine is caused by reciprocating motion of piston for suction of fresh air and exhaust of burned gas. this gas dynamic effect can be utilized for increase the volumetric efficiency. Many empirical studies have been carried out to investigate the effects of intake pulsating flow on the volumetric efficiency. However, when the gas dynamic effects are utilized for the variable speed engine to increase its performance, The speed range in which the maximum volumetric efficiency is limited and there occurs some difficulties in lay-out of intake system because it become too long. During induction process, as waves travel both directions, they are reflected and interacted each other and pressure waves are transmitted through it. Hence, the flow becomes more complex and unsteady flow. These pressure waves act upon intake pulsating flow and affects on the volumetric efficiency. In this paper the effects of pulsating flow of intake and exhaust pipes on volumetric efficiency were examined and evaluated. It was found that volumetric efficiency was affected by pulsating flow of intake and exhaust pipes.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.6
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• pp.76-86
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• 1994

Combustion of diesel engine depends on the mixing of air and evaporating fuel during ignition delay greatly. Variation of air-fuel mixing rate and ignition delay for engine operating condition causes difference of combustion, performance and exhaust emissions. This study is investigated in a turbocharged diesel engine of IDI swirl chamber type. In the results, As injection timing is advanced until $12.6^{\circ}$ BTC, ignition delay decreases. NOx concentration and smoke level in exhaust gas increases for advanced injection timing Ignition delay, combustion period, pressure rise rate and exhaust gas temperature are increased with increasing engine speed. And ignition delay at high load is more decreased than that at low load. Ignition delay and combustion period are decreased with increasing intake pressure. Power increases, temperature and CO, NOx concentration in exhaust gas decreases as intake pressure increases. With increasing load, ignition delay is decreased and combustion period, motoring pressure are increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.63-74
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• 1999

When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus , this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine dropkets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10m/s ∼30m/s. And fuel pressur ewas fixed to 300kPa, but air assist pressure was varied to 0∼25kPa for a vairable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.100-106
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• 2012

Ice accretion on the surface of aircraft in flight can adversely affect the safety of aircraft. In particular, it can cause degradation of critical aircraft performances such as maximum lift coefficient and total pressure recovery factor in engine air intake. In this study, computational prediction of ice accretion around a rotorcraft air intake is conducted in order to identify the impingement region with high droplet collection efficiency. Then the amount of ice accretion on the air intake, which is essential in determining the required power of ice protection system, is calculated. Finally, the effect of icing wind tunnel size is investigated in order to check the compatibility with the real in-flight test environment.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.649-656
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• 2004

Hypersonic wind tunnel test of the rectangular variable geometry intake is performed. For realization of a Precooled turbojet engine, development of a hypersonic ramjet engine is planned. To investigate performance of the intake of the hypersonic ramjet engine, wind tunnel test is done with freestream Mach number of 5.1. The total pressure recovery was 18 % with 12.9 % of ramp bleed. Several reasons for low total pressure recovery are shown. Supersonic internal compression is not enough. Then, the throat Mach number is high (M2.61) and total pressure losses at the terminal shock is large. Supersonic flow at the throat and position of the terminal shock is sensitive to a difference of the second ramp's throat height and the third ramp's throat height. Flow separations at the second ramp's trailing edge and the third ramp's leading edge are seen those could result in the trigger of unstart. The seal mechanism between the ramps and the sidewalls is important.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.480-485
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• 2008

In this study, two types of ramjet intake were designed for the flight condition of Mach number 2 and 5 and numerical analysis was performed. In order to widen the flight envelope range(Mach number $2{\sim}6$), movable intake concept was applied. The central body was designed so that the capture area ratio which is one of most important factors of ramjet intake design could be adjusted. And various types of cowl and movable insert part of shell were designed in order to control throat area which could increase total pressure recovery. The numerical results showed that the designed ramjet intake could be applied in various flights Mach number.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1921-1930
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• 1996

To design an optimum engine intake system, a flow model for the intake manifold was developed by the finite difference method. The flow in the intake manifold was one-dimensional, and the finite difference equations were derived from governing equations of flow, continuity, momentum and energy. The thermodynamic properties of the cylinder were found by the first law of thermodynamics, and the boundary conditions were formulated using steady flow model. By comparing the calculated results with experimental data, the appropriate boundary conditions and convergence limits for the flow model were established. From this model, the optimum manifold lengths at different engine operating conditions were investigated. The optimum manifold length became shorter when the engine speeds were increased. The effect of intake valve timings on inlet air mass was also studied by this model. Advancing intake valve opening decreased inlet air mass slightly, and the optimum intake valve closing was found. The difference in inlet air mass between cylinders was very small in this engine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.3
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• pp.13-20
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• 2009

Development of a dynamic engine model is essential to predict and analyze of dynamic characteristics from a natural gas engine. Reducing the harmful exhaust emissions can be accomplished by a precise air-fuel ratio control. In this paper, the dynamic engine model was proposed and included mixture formation and intake process because the dynamic characteristics can be affected by the mixture components such as an air and a gaseous fuel. The air mass flow, the partial pressure ratio, and the gas constant are changed by variations of the components in the mixture formation and intake process. The dynamic engine model is applied to the natural gas engine for validation test. Experimental results show that the dynamic engine model is effective to predict the dynamic characteristics of the natural gas engine.