• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1867-1875
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• 2003

In exhaust pipes of automotive engines, the pulsating pressure waves are composed of fundamental frequency and high order harmonics. The nonlinearities in the exhaust pipe is caused by their interactions. The error between prediction and measurement is induced by the nonlinearities. We can not explain this phenomenon using linear acoustics theory. So power spectrum, which is used in linear theory, is not useful. This paper is concerned with the development of useful engineering techniques to detect and analyze nonlinearity in exhaust pipe of automotive engines. The study of higher order statistics has been dominated by work on the bispectrum. The bispectrum can be viewed as a decomposition of the third moment (skewness) of a signal over frequency and as such is blind to symmetric nonlinearities. The phenomenon of quadratic phase coupling (QPC) can be analyzed by the bicoherence function. Finally the application of these techniques to data from actual exhaust pipe systems is performed.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.526-534
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• 2000

In this study, the characteristics of exhaust emissions in medium speed diesel engine under various operating conditions were investigated through experiments to derive the optimum conditions for minimizing the exhaust emissions, especially, nitrogen oxides. The 355 KW$\times$1200 rpm medium speed diesel engine was intensively examined to investigate the trend of exhaust emissions in case that the parameters affecting combustion conditions such as fuel injection timing, intake air temperature and pressure, engine speed and load were changed. The exhaust emissions for 9 sets of medium speed diesel engine were analyzed in addition. From this study, NOx level could be reduced by 30~50% through the adjustment of retarded fuel injection timing, lowered intake air temperature and increased charging air pressure.

• Journal of the Korean Institute of Gas
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• v.21 no.1
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• pp.80-86
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• 2017

In this paper, it is proposed to solve the problem of the harmful exhaust gas reduction device DPF. The exhaust gas is effectively guided through the control of the exhaust gas flow path which is separated in both directions. Through cross control of two DPF units, it helps to improve the purification and regeneration combustion characteristics of harmful emissions. It is possible to prevent an increase in internal pressure caused by deposition of particulate matter in the DPF. It is also an object of the present invention to provide an automobile harmful exhaust gas reduction device capable of solving the problem of lowering the output and lowering the fuel consumption.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.15-20
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• 2018

The objective of this study is to numerically investigate the thermal characteristics of an automobile exhaust-based heat exchanger for automotive thermoelectric power generation with various exhaust gas mass flow rates and temperatures. The heat exchanger for automotive thermoelectric power generation has a square-type pin installed inside, so the maximum amount of heat can be transferred to the thermoelectric element from the heat energy coming from the automobile exhaust gas. The exhaust gas mass flow rate changed from 0.01, to 0.02, to 0.03 kg/s, and the exhaust gas temperature changed from 400, to 450, to 500, to 550, to $600^{\circ}C$, respectively. A numerical simulation was conducted by using the commercial program ANSYS CFX v17.0. Consequently, the exhaust gas pressure difference between the inlet and the outlet of the heat exchanger is determined according to the flow rate of the exhaust gas. When the mass flow rate of the exhaust gas increased, the pressure difference between the inlet and the outlet of the heat exchanger increased, but the exhaust gas pressure difference between the inlet of the heat exchanger and the outlet did not vary with the exhaust gas temperature. Therefore, in order to obtain the maximum surface temperature from the heat exchanger, the exhaust gas mass flow rate should be lower, and the exhaust gas temperature should be higher.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.115-122
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• 2006

To evaluate the durability characteristics of in-direct injection diesel engine using BDF 20(a blend of 20% biodiesel fuel and 80% diesel fuel in volume), an IDI diesel engine used to commercial vehicle was operated on BDF 20 for 300 hours. Engine dynamometer testing was completed at regularly scheduled intervals to investigate the combustion characteristics, engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis. From the results, the combustion variations such as the combustion maximum pressure($P_{max}$) and the crank angle at which this maximum pressure occurs(${\Theta}_{Pmax}$) were not appeared during long-time dynamometer testing. Also, BSFC with BDF 20 resulted in lower than with diesel fuel. The peak pressure with BDF 20 was higher than that with diesel fuel due to the oxygen content in BDF. And, BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with a little increase of oxides of nitrogen than diesel fuel. It was concluded that there was no unusual deterioration of the engine, or any unusual change in exhaust emissions during the durability test of an IDI diesel engine using BDF 20.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.411-415
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• 2008

This paper presents on design factor considered in an altitude test cell facility to determine the best sizing to optimize exhaust diffuser pressure recovery and the exact cooling load required to be supplied under transient operation. Engine simulation was performed to analyse the exhaust gas temperature, exit mass flow rate, specific fuel consumption and exhaust velocity helpful in determining secondary mass air flow and the mixed air temperature entering the ejector. based on this, the amount of cooling load was deduced. It was found that improved pressure recovery reduces operational cost(air supply facility, cooling water).

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.479-485
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• 2019

As exhaust gas systems of ships become more complicated, it is necessary to calculate an accurate pressure loss at their design stage. If the dynamic loss coefficients of non-standard fittings mainly used in exhaust gas pipe (EGP) are well-documented, it would be possible to calculate precise pressure loss more readily than using the conventional method that analyzes the entire system. In the case of a ship's EGP, the flow rates and temperatures of exhaust gas are determined by engine specifications, and the range of the flow rate and temperature is limited according to operating conditions. In addition, as it is possible to define non-standard fittings frequently used in an EGP, a database can be easily constructed and effective. This paper illustrates effective parameters and analysis cases of several types of non-standard fittings mounted in ship EGPs. The analysis procedure proposed in this paper is verified using existing research results on HVAC fittings. The numerical procedure, which is minimally affected by manpower and grid, is established such that it can be applied at the industry level.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.970-972
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• 2011

The vacuum chamber pressure was investigated according to the second throat exhaust diffuser entrance diameter. The sizes of diffuser entrance were changed three cases, and each case was computed by using CFD. Also in order to relatively compare the vacuum chamber pressure the Euler equation was adopted. According to the results, as the size of diffuser entrance was increased it was observed that the vacuum chamber pressure was decreased.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.191-200
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• 1997

This paper discusses prediction of the sound pressure level produced by simple engine exhaust systems(plain pipe, plain expansion chamber pipe, plain expansion chamber with internally extended inlet and outlet pipe, perforated pipe enclosed in a plain expansion chamber) and a computer program has been developed which predicts the sound pressure level and the frequency spectrum. The program utilizes unsteady flow gas dynamic theory and acoustic theory to predict the pressure-time history in the exhaust system and the mass flow rate-time history at the open end of the system and the sound pressure levels(1/3 Octave band levels) and the frequency spectrum in semi-anechoic room. The predictions are compared with measured levels and show a high degree of correlation.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.421-426
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• 2000

A study on the combustion and exhaust emissions characteristics of diesel engine with various suction air humidity is performed experimentally. In this paper, suction air humidity is changed from RH 50% to RH 90%, the experiments are performed at engine speed 1800rpm, and main measured parameters are cylinder pressure, fuel consumption rate, CO, HC, NOx and Soot emissions etc. Increase of suction air humidity from RH 50% to RH 90% does not effect specific fuel consumption, decreases maximum pressure in cylinder, ratio of maximum pressure rise and net heat release, and delays ignition timing. Also, that increases CO and HC emissions, decreases NOx emissions, but does not constant in changing tendency on emission.