Seungmook Oh

Flame Propagation Characteristics in a Heavy Duty LPG Engine with Liquid Phase Port Injection

The authors would like to express thanks to the support of LG-Caltex Gas and SK Gas through Heavy duty LPG engine development in KIMM (Korea Institute of Machinery and Materials). The research was also supported by NRL (National Research Laboratory) scheme, Ministry of Science & Technology, Korea.

Mixture distribution and flame propagation in a heavy-duty liquid petroleum gas engine with liquid phase injection

Abstract Enhanced mixture preparation by liquid phase injection on to the port could promote the application of liquefied petroleum gas (LPG) in spark ignition (SI) engines. Mixture distribution and flame propagation of the liquid phase LPG injection (LPLI) engine with a large bore size were investigated in a single-cylinder optical engine which had optical accesses through both sides of the cylinder liner and bottom of the piston. LPG fuel distribution was visualized quantitively by the acetone planar laser-induced fluorescence (PLIF) method. In addition, a series of bottom-view images were taken by direct visualization using a high-speed camera. Flow conditions were varied with the shapes of intake port and piston geometries characterized by different swirl and squish flows. The effects of fuel injection timings were also studied to characterize the mixture preparation for open-valve injection and closed-valve injection. Stronger swirl with a swirl ratio of 3.4 and squish flow with a cylindrical piston bowl shape showed faster flame propagations under the open-valve injection condition with preferable mixture formation. On the contrary, closed-valve injection caused the undesirable mixture distribution of the mixture at the ignition, which led to a leaner mixture distribution near the spark plug.

Improvement of DME HCCI Engine Performance by Fuel Injection Strategies and EGR

The authors would like to express their appreciation for financial support from Combustion Engineering Research Center (CERC) in KAIST and the Korea Energy Management Corporation (KEMCO).

Effects of Stratified EGR on the Performance of a Liquid Phase LPG Injection Engine

The authors would like to thank the Korean Ministry of Science and Technology for funding this research through national research laboratory (NRL) scheme and engineering research center (ERC) program to CERC (Combustion Engineering Research Center).

Enhancing Low Temperature Combustion With Biodiesel Blending in a Diesel Engine at a Medium Load Condition

The present study investigated the effects of biodiesel blending under a wide range of intake oxygen concentration levels in a diesel engine. This study attempted to identify the lowest biodiesel blending rate that achieves acceptable levels of nitric oxides (NOx), soot, and coefficient of variation in the indicated mean effective pressure (COVIMEP). Biodiesel blending was to be minimized in order to reduce the fuel penalty associated with the biodiesels lower caloric value. Engine experiments were performed in a 1-liter single-cylinder diesel engine at an engine speed of 1400 rev/min under a medium load condition. The blend rate and intake oxygen concentration were varied independently of each other at a constant intake pressure of 200 kPa. The biodiesel blend rate varied from 0% (B000) to 100% biodiesel (B100) at a 20% increment. The intake oxygen level was adjusted from 8 to 19% by volume (vol %) in order to embrace both conventional and low-temperature combustion (LTC) operations. A fixed injection duration of 788 μs at a fuel rail pressure of 160 MPa exhibited a gross indicated mean effective pressure (IMEP) between 750 kPa and 910 kPa, depending on the intake oxygen concentration.The experimental results indicated that the intake oxygen level had to be below 10 vol% to achieve the indicated specific NOx (ISNOx) below 0.2g/kWhr with the B000 fuel. However, a substantial soot increase was exhibited at such a low intake oxygen level. Biodiesel blending reduced NOx until the blending rate reached 60% with reduced in-cylinder temperature due to lower total energy release. As a result, 60%-biodiesel blended diesel (B060) achieved NOx, soot, and COVIMEP of 0.2 g/kWhr, 0.37 filter smoke number (FSN), and 0.5, respectively, at an intake oxygen concentration of 14 vol%. The corresponding indicated thermal efficiency was 43.2%.Copyright

The Effects of Tumble Flow on Lean Burn Characteristics in a Four-Valve SI Engine

The authors would like to acknowledge the financial support provided for this project by the Korean Goverment, through the scheme of the National G7 Project. They would also like to Mr J.H. Lee for his contribution to the experiments

Combustion Characteristics of Stratified Mixture in Lean-Burn LPG Direct-Injection Engine With Spray-Guided Combustion System

Today, we are faced with the problems of global warming and fossil fuel depletion, and they have led to the enforcement of new emissions regulations. Direct-injection spark-ignition engines are a very promising technology that can comply with the new regulations. These engines offer the advantages of better fuel economy and lower emissions than conventional port-injection engines. The use of LPG as the fuel reduces carbon emissions because of its vaporization characteristics and the fact that it has lower carbon content than gasoline. An experimental study was carried out to investigate the combustion process and emission characteristics of a 2-liter spray-guided LPG direct-injection engine under lean operating conditions. The engine was operated at a constant speed of 2000 rpm under 0.2-MPa brake mean effective pressure, which corresponds to a common operation point of a passenger vehicle. Combustion stability, which is the most important component of engine performance, is closely related to the operation strategy and it significantly influences the degree of fuel consumption reduction. In order to achieve stable combustion with a stratified LPG mixture, an inter-injection spark ignition (ISI) strategy, which is an alternative control strategy to two-stage injection, was employed. The effects of the compression ratio on fuel economy were also assessed; due to the characteristics of the stratified LPG mixture, the fuel consumption did not reduce when the compression ratio was increased.© 2014 ASME

Comparison of Combustion Characteristics with Combustion Strategy and Excess Air Ratio Change in a Lean-burn LPG Direct Injection Engine

Abstract : Liquefied Petroleum Gas(LPG) has attracted attention as a alternative fuel. The lean-burn LPG direct injection engine is a promising technology because it has an advantage of lower harmful emissions. This study aims to investi-gate the effect of combustion strategy and excess air ratio on combustion and emission characteristics in lean-burn LPG direct injection engine. Fuel consumption and combustion stability were measured with change of the ignition timing and injection timing at various air/fuel ratio conditions. The lean combustion characteristics were evaluated as a func-tion of the excess air ratio with the single injection and multiple injection strategy. Furthermore, the feasibility of lean operation with stratified mixture was assessed when comparing the combustion and emission characteristics with premixed lean combustion. Key words : LPG direct injection(LPG 직접분사), Ultra lean combustion(초희박연소), Spray-guided type combustion system(분무유도방식 연소기구), Brake specific fuel consumption(연료소비율), Combustion stability(연소안정성)

Effect of Intake Pressure on Emissions and Performance in Low Temperature Combustion Operation of a Diesel Engine

One of the effective ways to reduce both NOx and PM at the same time in a diesel CI engine is to operate the engine in low temperature combustion (LTC) regimes. In general, two strategies are used to realize the LTC operation-dilution controlled LTC and late injection LTC - and in this study, the former approach was used. In the dilution controlled regime, LTC is achieved by supplying a large amount of EGR to the cylinder. The significant EGR gas increases the heat capacity of in-cylinder charge mixture while decreasing oxygen concentration of the charge, activating low temperature oxidation reaction and lowering PM and NO x emissions. However, use of high EGR levels also deteriorates combustion efficiency and engine power output. Therefore, it is widely considered to use increased intake pressure as a way to resolve this issue. In this study, the effects of intake pressure variations on performance and emission characteristics of a single cylinder diesel engine operated in LTC regimes were examined. LTC operation was achieved in less than 8% O 2 concentration and thus a simultaneous reduction of both PM and NOx emission was confirmed. As intake pressure increased, combustion efficiency was improved so that THC and CO emissions were decreased. A shift of the peak Soot location was also observed to lower O2 concentration while NOx levels were kept nearly zero. In addition, an elevation of intake pressure enhanced engine power output as well as indicated thermal efficiency in LTC regimes. All these results suggested that LTC operation range can be extended and emissions can be further reduced by adjusting intake pressure.

A Study on the Performance and Emissions Characteristics of a DI Compression Ignition Engine Operated With LPG and DTBP Blending Fuels

LPG (Liquefied Petroleum Gas) has been widely used as an alternative fuel for gasoline and diesel vehicles in light of clean fuel and diversity of energy resources. But conventional LPG vehicles using carburetors or MPI fuel injection systems can’t satisfy the emissions regulations and CO2 targets of the future. Therefore, it is essential to develop LPG engines of spark ignition or compression ignition type such that LPG fuel is directly injected into the combustion chamber under high pressure. A compression ignition engine using LPG is the ideal engine with many advantages of fuel economy, heat efficiency and low CO2 , even though it is difficult to develop due to the unique properties of LPG. This paper reports on numerical and experimental studies related to LPG fuel for a compression ignition engine. The numerical analysis is conducted to study the combustion chamber shape with CATIA and to analyze the spray and fluid behaviors with FLUENT for diesel and LPG (n-butane 100%) fuels. In one experimental study, a constant volume chamber is used to observe the spray formation for the chamber pressure 0 to 3MPa and to analyze the flame process, P-V diagram, heat release rate and emissions through the combustion of LPG fuel with the cetane additive DTBP (Di-tert-butyl peroxide) 5 to 15 wt% at 25MPa of fuel injection pressure. In engine bench tests, experiments were performed to find the optimum injection timing, lambda, COV and emissions for the LPG fuel with the cetane additive DTBP 5 to 15 wt% at 25MPa fuel injection pressure and 1500 rpm. The penetration distance of LPG (n-butane 100%) was shorter than that of diesel fuel and LPG was sensitive to the chamber pressure. The ignition delay was in inverse proportion to the ambient pressure linearly. In the engine bench tests, the optimum injection timing of the test engine to the LPG fuel with DTBP 15 wt% was about BTDC 12° CA at all loads and 1500 rpm. An increasing of DTBP blending ratio caused the promotion of flame and fast burn and this lead to reduce HC and CO emissions, on the other hand, to increase NOx and CO2 emissions.Copyright