• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.167-176
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• 2014

The pyrovalves are widely used in aerospace industry for the opening and closing of flow channel due to the light-weight, high reliability and zero-leakage. In the United States, the loss of some spacecrafts using hydrazine as the propellent were proven by the blowby. Blowby is defined as the leakage of pyrovalve ignition combustion gas to the flow channel. Since then, the interference fit was applied for the sealing of piston to prevent the blowby. In this study, literature survey on pyrovalve technology is summarized mainly for AIAA papers. Common problems, improvement method, and performance comparisons of pyrovalves are also presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.4
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• pp.1-9
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• 2000

To understand the thermal characteristics around the piston ring gap ring gap positions and piston temperatures are measured simultaneously. The locations of piston ring gap are measured by the radio-tracer method and piston temperature are measured by a K-type thermocouple and scissors type linkage system. From these experiments following facts are clarified. Piston temperatures fluctuate according to the piston ring rotation. And the temperature fluctuation is mainly affected by top ring gap position irrelevant to the second ring fop position. If the top ring gap position increases and the temperature of top ring groove shows maximum value when top rin gap position coincide with temperature measuring point. The maximum amplitude of temperature fluctuation which is proportional to the blow by gas rate is around 12-15$^{\circ}C$.

• Journal of ILASS-Korea
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• v.25 no.4
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• pp.162-169
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• 2020

The worldwide focus on reducing the emissions, fuel and lubricant consumption in T-GDI engines is leading engineers to consider the crankcase ventilation and oil mist separation system as an important means of control. In today's passenger cars, the oil mist separation systems mainly use the inertia effect (e.g. labyrinth, cyclone etc.). Therefore, this study has investigated high efficiency cylinder head-integrated oil-mist separator by using a compact multi-impactor type oil mist separator system to ensure adequate oil mist separation performance. For this purpose, engine dynamometer testing with oil particle efficiency measurement equipment and 3D two-phase flow simulation have been performed for various engine operating conditions. Tests with an actual engine on a dynamometer showed oil aerosol particle size distributions varied depending on operating conditions. For instance, high rpm and load increases bot only blow-by gases but the amount of small size oil droplets. Submicron-sized particles (less than 0.5 ㎛) were also observed. It is also found that the impactor type separator is able to separate nearly no droplets of diameter lower than 3 ㎛. CFD results showed that the complex aerodynamics processes that lead to strong impingement and break-up can strip out large droplets and generate more small size droplets.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.19-24
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• 2004

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe but residual gas, is called 'Blow by gas', enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the crankcase isn't vented, this causes many bad effects such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So most automobiles are constituted with a PCV(Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new cases, engineers are designing it depending on their experiments than theoretical knowledges. Much efforts and times are needed for new development. This study will show quantitative results to increase the possibilities.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.66-73
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• 2005

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe. But residual gas 'Blowby gas' enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the blowby gas isn't vented, this causes many bad efffcts such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So most automobiles are constituted with a PCV(Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new cases, engineers are designing it depending on their experiments than theoretical knowledges. Much efforts and times are needed for new development. This study will show quantitative results to increase the possibilities for the optimal design.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.40-44
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• 2005

A great deal of exhaust gas inside a combustion room goes out through exhaust pipe but residual gas, is called "Blowby gas", enters the crankcase through a small gap between the piston and the cylinder wall. Here, if the crankcase isn't vented, this causes many bad effects such as lubricant oil contamination, corrosion by that and crankcase explosion by rising pressure. So, most automobiles are constituted with a PCV (Positive Crankcase Ventilation) system to prevent previous problems. PCV valve is the most important part in this ventilation system. When companies are manufacturing new engines, engineers are designing it depending on their experiments than theoretical knowledge. Mush efforts and times are needed for new development. This study will show quantitative results to increase the possibilities of reduction of developing time.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.68-74
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• 2006

In the development of new automobiles, the efforts to reduce environmental problems like air pollution have been risen. Blowby gas consists of about $20{\sim}35%$ of total amount of Hydrocarbon (HC), one of dangerous pollutants issuing from automobiles. A PCV valve is a very small component in an automotive engine but it is a very important part. Because that a PCV valve is used to control blowby gas and to recirculate it into a manifold automatically. Although it has very simple operating principle, designing a PCV valve is so difficult due to interaction between fluid and solid. In this study, our purpose is to develop a design program for a PCV valve and to verify its efficiency. Both Bernoulli equation and 4th order Runge-Kutta method were adopted to predict spool displacements and flow patterns. Comparing with experiments, it was found that both spool diameters and displacements were predicted well, however, flow rates showed a little differences because of the assumption of non viscous flow.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.223-227
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• 2005

A PCV valve is a part to control the flow rate of Blowby gas in a PCV system. A PCV system re-burns Blowby gas with fuel in a combustion chamber. Some gas enters to a crankcase room through the gap between piston ring and engine cylinder wall. This gas si called 'Blowby gas'. This gas causes many problems. In environmental view, Blowby gas includes about $25\~35\%$ hydrocarbon{HC) of total generated HC in an automobile. Hydrocarbon is a very harmful pollutant element in our life. In mechanical view, Blowby gas has some reaction with lubricant oil of crankcase room. Then, this causes lubricant oil contamination, crankcase corrosion and a decrease fo engine efficiency. Consequently, Blowby gas must be eliminated from a crankcase room. In this study, we simulated internal flow characteristics in a PCV valve according to spool dynamic behavior using local remeshing method And, we programmed our sub routine to simulate a spool dynamic motion. As results, spool dynamic behavior is periodically oscillated by the relationship between fluid force and elastic force of spring. And its magnitude is linearly increased by the differential pressure between inlet and outlet. Also, as spool is largely moved, flow area is suddenly decreased at orifice. For this reason, flow velocity is rapidly decreased by viscous effect.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.149-157
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• 2004

A Piston assembly is very important because it directly receives the energy generated during combustion process. Surely, the friction and lubrication of piston ring pack do an important role in the performance and fuel economy of an engine. in fact, the friction loss in piston ring pack is the biggest portion to the whole engine friction. Therefore, the improvement of lubrication quality and friction loss in piston ring pack will be directly related with the improvement in the performance and fuel economy of an engine. Meanwhile, the oil consumption and blow-by gas through piston-cylinder-ring crevices have to be controlled as less as possible. In these two aspects, the study on the optimized design of piston ring pack has to be carried out. In this study, for the efficient design of piston ring pack, it is focused to develop a basic computer program that predicts the inter-ring pressure, the motion of ring and the blow-by gas through a crevice volume model between adjacent rings, and the oil film thickness and the friction computed by lubrication theories.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.230-231
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• 2005

As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.