Reducing pressure oscillation in high-load HCCI combustion via air injection before compression

2021 ◽  
pp. 146808742110317
Author(s):  
Yoshinari Kobayashi ◽  
Shota Nozaki ◽  
Hiroaki Hayashi ◽  
Tadayoshi Ihara ◽  
Shuhei Takahashi
Keyword(s):  
Waiting Time ◽  
Concentration Gradient ◽  
Pressure Rise ◽  
Pressure Oscillation ◽  
High Load ◽  
Air Injection ◽  
Reduced Pressure ◽  
Fuel Concentration ◽  
Hcci Combustion ◽  
Rapid Pressure

Pressure oscillation often occurs in high-load homogeneous charge compression ignition (HCCI) combustion, which is a challenge in the development of HCCI engines for automobiles. This work proposes a novel method of reducing the pressure oscillation in HCCI combustion at high loads. The proposed technique injects air into homogeneous mixtures before compression, thereby giving local fuel concentration gradient. The fuel concentration gradient is expected to suppress a rapid pressure rise, resulting in reduced pressure oscillation. High-load HCCI combustion was simulated via a rapid compression machine with a high compression ratio. Varying the period from air injection to compression, that is, the waiting time, controlled the magnitude of fuel concentration gradient. The pressure oscillation was quantified and evaluated via the knock intensity (KI) and the averaged pressure rise rate. For the short waiting time; in other words, when the local fuel concentration gradient was large, the KI was very lower than that for no air injection. The KI, however, increased with the waiting time to approach that for no air injection. The oscillation modes were also different with and without air injection according to a modal analysis. The in-cylinder temperature distribution was visualized via the infrared radiometry to better understand the effect of air injection. For no air injection, the temperature in the cylinder uniformly increased, and the whole mixtures were ignited instantaneously. With air injection and for the short waiting time, on the other hand, hot spots developed on the rim of the injected air where the specific heat ratio was higher and then gradually spread throughout the chamber. Therefore, retarded auto-ignition and subsequently slow spread would limit a rapid pressure rise, resulting in reduced pressure oscillation in HCCI combustion. In conclusion, the proposed technique is effective for reducing the pressure oscillation in high-load HCCI combustion only for the short waiting time.

Combustion Characteristics of HCCI in Motorcycle Engine

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Yuh-Yih Wu ◽  
Ching-Tzan Jang ◽  
Bo-Liang Chen
Keyword(s):  
Cylinder Head ◽  
Internal Combustion Engines ◽  
Peak Pressure ◽  
Pressure Rise ◽  
Combustion Characteristics ◽  
Hcci Combustion ◽  
Lower Maximum ◽  
Intake Air Heating ◽  
Gas Recirculation ◽  
Motorcycle Engine

Homogeneous charge compression ignition (HCCI) is recognized as an advanced combustion system for internal combustion engines that reduces fuel consumption and exhaust emissions. This work studied a 150 cc air-cooled, four-stroke motorcycle engine employing HCCI combustion. The compression ratio was increased from 10.5 to 12.4 by modifying the cylinder head. Kerosene fuel was used without intake air heating and operated at various excess air ratios (λ), engine speeds, and exhaust gas recirculation (EGR) rates. Combustion characteristics and emissions on the target engine were measured. It was found that keeping the cylinder head temperature at around 120–130°C is important for conducting a stable experiment. Two-stage ignition was observed from the heat release rate curve, which was calculated from cylinder pressure. Higher λ or EGR causes lower peak pressure, lower maximum rate of pressure rise (MRPR), and higher emission of CO. However, EGR is better than λ for decreasing the peak pressure and MRPR without deteriorating the engine output. Advancing the timing of peak pressure causes high peak pressure, and hence increases MRPR. The timing of peak pressure around 10–15 degree of crank angle after top dead center indicates a good appearance for low MRPR.

Development of a New Design Method for High Efficiency Swept Low Pressure Axial Fans With Small Hub/Tip Ratio

2014 ◽  
Author(s):  
Thore Bastian Lindemann ◽  
Jens Friedrichs ◽  
Udo Stark
Keyword(s):  
High Efficiency ◽  
Design Method ◽  
Tangential Velocity ◽  
Pressure Rise ◽  
Low Pressure ◽  
Aerodynamic Performance ◽  
Low Noise ◽  
Angle Distribution ◽  
Sweep Angle ◽  
Reduced Pressure

For a competitive low pressure axial fan design low noise emission is as important as high efficiency. In this paper a new design method for low pressure fans with a small hub to tip ratio including blade sweep is introduced and discussed based on experimental investigations. Basis is an empirical axial and tangential velocity distribution at the rotor outlet combined with a distinctive sweep angle distribution along the stacking line. Several fans were designed, built and tested in order to analyze the aerodynamic as well as the aeroacoustic behavior. For the aerodynamic performance particular attention was paid to compensate the influence of reduced pressure rise and efficiency due to increasing blade sweep. This was achieved by a method of increasing the blade chord depending on the local sweep angle which is based on single airfoil data. The tested fans without this compensation revealed a significant noise reduction effect of up to approx. 6 dB(A) for a tip sweep angle of 64° which was accompanied by an unsatisfactory effect of reduced overall aerodynamic performance. The second group of fans did not only confirm the method of the aerodynamic compensation by a nearly unchanged pressure rise and efficiency characteristic but also revealed an increased aeroacoustic benefit of in average 9.5 dB(A) compared to the unswept version. Beside the overall characteristics the individual differences between the designs are also discussed using results of wall pressure measurements which show some significant changes of the blade tip flow structure.

Initial Results on a New Light-Duty 2.7L Opposed-Piston Gasoline Compression Ignition Multi-Cylinder Engine

2018 ◽  
Author(s):  
Ashwin Salvi ◽  
Reed Hanson ◽  
Rodrigo Zermeno ◽  
Gerhard Regner ◽  
Mark Sellnau ◽  
...  
Keyword(s):  
Pressure Rise ◽  
High Load ◽  
Combustion Stability ◽  
Residual Fraction ◽  
Compression Ignition ◽  
Cylinder Pressure ◽  
Peak Cylinder Pressure ◽  
Low Load ◽  
Initial Results ◽  
Load Conditions

Gasoline compression ignition (GCI) is a cost-effective approach to achieving diesel-like efficiencies with low emissions. Traditional challenges with GCI arise at low-load conditions due to low charge temperatures causing combustion instability and at high-load conditions due to peak cylinder pressure and noise limitations. The fundamental architecture of the two-stroke Achates Power Opposed-Piston Engine (OP Engine) enables GCI by decoupling piston motion from cylinder scavenging, allowing for flexible and independent control of cylinder residual fraction and temperature leading to improved low load combustion. In addition, the high peak cylinder pressure and noise challenges at high-load operation are mitigated by the lower BMEP operation and faster heat release for the same pressure rise rate of the OP Engine. These advantages further solidify the performance benefits of the OP Engine and demonstrate the near-term feasibility of advanced combustion technologies, enabled by the opposed-piston architecture. This paper presents initial results from a steady state testing on a brand new 2.7L OP GCI multi-cylinder engine. A part of the recipe for successful GCI operation calls for high compression ratio, leading to higher combustion stability at low-loads, higher efficiencies, and lower cycle HC+NOx emissions. In addition, initial results on catalyst light-off mode with GCI are also presented. The OP Engine’s architectural advantages enable faster and earlier catalyst light-off while producing low emissions, which further improves cycle emissions and fuel consumption over conventional engines.

HCCI Operability Limits: The Impact of Refinery Stream Gasoline Property Variation

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Joshua S. Lacey ◽  
Zoran S. Filipi ◽  
Sakthish R. Sathasivam ◽  
William J. Cannella ◽  
Peter A. Fuentes-Afflick
Keyword(s):  
Thermal Conditions ◽  
The United States ◽  
High Load ◽  
Fuel Properties ◽  
Research Octane Number ◽  
Property Variation ◽  
Hcci Combustion ◽  
Load Limit ◽  
Low Load ◽  
The Impact

Homogeneous charge compression ignition (HCCI) combustion is highly dependent on in-cylinder thermal conditions favorable to autoignition, for a given fuel. Fuels available at the pump can differ considerably in composition and autoignition chemistry; hence strategies intended to bring HCCI to market must account for the fuel variability. To this end, a test matrix consisting of eight gasoline fuels composed of blends made solely from refinery streams was investigated in an experimental, single cylinder HCCI engine. The base compositions were largely representative of gasoline one would expect to find across the United States, although some of the fuels had slightly lower average octane values than the ASTM minimum specification of 87. All fuels had 10% ethanol by volume included in the blend. The properties of the fuels were varied according to research octane number (RON), sensitivity (S=RON-MON) and the volumetric fractions of aromatics and olefins. For each fuel, a sweep of the fuelling was carried out at each speed from the level of instability to excessive ringing to determine the limits of HCCI operation. This was repeated for a range of speeds to determine the overall operability zone. The fuels were kept at a constant intake air temperature during these tests. The variation of fuel properties brought about changes in the overall operating range of each fuel, as some fuels had more favorable low load limits, whereas others enabled more benefit at the high load limit. The extent to which the combustion event changed from the low load limit to the high load limit was examined as well, to provide a relative criterion indicating the sensitivity of HCCI range to particular fuel properties.

New Downsized Diesel Engine Concept with HCCI Combustion at High Load Conditions

2015 ◽  
Author(s):  
Andrey Kuleshov ◽  
Alexey Kuleshov ◽  
Khamid Mahkamov ◽  
Timo Janhunen ◽  
Victor Akimov
Keyword(s):  
Diesel Engine ◽  
High Load ◽  
Hcci Combustion ◽  
Engine Concept ◽  
Load Conditions

Study on Combustion and Emission Characteristics of Acidic Oil Biodiesel

2014 ◽  
Vol 541-542 ◽  
pp. 982-988
Author(s):  
Jian Wu ◽  
Yang Hua ◽  
Zhan Cheng Wang ◽  
Li Li Zhu ◽  
Hong Ming Wang
Keyword(s):  
Diesel Engine ◽  
Load Condition ◽  
Pressure Rise ◽  
High Load ◽  
Emission Characteristics ◽  
Combustion Heat ◽  
Pressure Maximum ◽  
High Load Condition ◽  
Blended Fuel ◽  
Hc Emissions

In order to develop a new fuel alternative for the diesel engine, experiment of combustion and emission characteristics was carried on a high pressure common rail diesel engine fueled with diesel and acidic oil biodiesel blends, then the results were compared and analyzed. The results indicate that after adding acidic oil biodiesel, the ignition delay is prolonged, combustion pressure, maximum rate of pressure rise and maximum combustion temperature all increase. The maximum combustion heat release rate of blended fuel is higher than diesel at low and middle loads, and lower at high load condition. Compared with diesel, HC emissions of blends decrease dramatically with the increases of blending ratio. NOX emissions of blends are slightly higher than diesel. CO emissions of blends are almost the same as that of diesel. According to the results, acidic oil biodiesel has wide application prospects as an alternative fuel.

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