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Simulating a Complete Performance Map of an Ethanol-Fueled Boosted HCCI Engine

Lawrence Berkeley National Laboratory-Samveg Saxena
University of California-Alvaro Pinheiro, David Vuilleumier
Published 2015-04-14 by SAE International in United States
This paper follows a cycle-simulation method for creating an engine performance map for an ethanol fueled boosted HCCI engine using a 1-dimensional engine model. Based on experimentally determined limits, the study defined operating conditions for the engine and performed a limited parameter sweep to determine the best efficiency case for each condition. The map is created using a 6-Zone HCCI combustion model coupled with a detailed chemical kinetic reaction mechanism for ethanol, and validated against engine data collected from a 1.9L 4-Cylinder VW TDI engine modified to operate in HCCI mode. The engine was mapped between engine speeds of 900 and 3000 rpm, 1 and 3 bar intake pressure, and 0.2 and 0.4 equivalence ratio, resulting in loads between idle and 14.0 bar BMEP. Analysis of a number of trends for this specific engine map are presented, such as efficiency trends, effects of combustion phasing, intake temperature, engine load, engine speed, and operating strategy. The study found that, in general, delayed combustion timing, intermediate engine speed and high intake pressure yields optimal efficiency. Additionally, the…
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Quantifying the Flexibility for Electric Vehicles to Offer Demand Response to Reduce Grid Impacts without Compromising Individual Driver Mobility Needs

Lawrence Berkeley National Laboratory-Samveg Saxena, Jason MacDonald, Doug Black, Sila Kiliccote
Published 2015-04-14 by SAE International in United States
Electric vehicles (EVs) enable improved vehicle efficiency and zero emissions in population centers, however the large loads from EV charging can stress grid systems during periods of peak demand. We apply detailed physics-based models of EVs with data on how drivers use their cars to quantify the ability for EVs to reduce their charging during periods of peak demand, i.e. as in a demand response program. A managed charging controller is developed and applied within the vehicle-to-grid simulator (V2G-Sim) which charges vehicles during demand response (DR) events only if charging is required to satisfy anticipated mobility needs for a given driver over the next 24 hours.We find that up to 95% of EV charging loads can be removed during DR events without compromising the mobility needs of individual drivers. This value is found by comparing the charging loads of EVs using the managed charging controller against an uncontrolled charging case. Simulations are conducted with parametric sweeps of several important variables to understand the sensitivity of EV load reduction potential to these variables. For instance, demand…
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A Sequential Chemical Kinetics-CFD-Chemical Kinetics Methodology to Predict HCCI Combustion and Main Emissions

Lawrence Berkeley National Laboratory-Samveg Saxena
Lawrence Livermore National Lab-Salvador Aceves, Daniel Flowers
Published 2012-04-16 by SAE International in United States
This study presents the development of a new HCCI simulation methodology. The proposed method is based on the sequential coupling of CFD analysis prior to autoignition, followed by multi-zone chemical kinetics analysis of the combustion process during the closed valve period. The methodology is divided into three steps: 1) a 1-zone chemical kinetic model (Chemkin Pro) is used to determine either the intake conditions at IVC to achieve a desired ignition timing or the ignition timing corresponding with given IVC conditions, 2) the ignition timing and IVC conditions are used as input parameters in a CFD model (Fluent 6.3) to calculate the charge temperature profile and mass distribution prior to autoignition, and 3) the temperature profile and mass distribution are fed into a multi-zone chemical kinetic model (Chemkin Pro) to determine the main combustion characteristics.Different numbers of zones have been tested in the multi-zone step to determine the effectiveness of the general methodology. 40 zones are needed to achieve acceptable thermal stratification resolution to accurately predict peak heat release rates, peak pressures rise rates and…
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Characterization of Ion Signals under Ringing Conditions in an HCCI Engine

University of California at Berkeley-Samveg Saxena, Jyh-Yuan Chen, Robert W. Dibble
Published 2011-08-30 by SAE International in United States
The objective of this research is the characterization of ringing in HCCI engines based on in-cylinder ion signal measurements. A correlation is identified to quantify ringing intensity from ion signals by comparing ion and pressure signal characteristics under ringing conditions in an HCCI engine. The maximum ion rise rate (dIon/dtmax) is shown to be an excellent indicator of the maximum pressure rise rate (dP/dtmax), a factor which is very important to measure ringing intensity. The effects of changing bias voltage and ion sensing resistors are also explored for their effects upon the ion ringing intensity. The results show that the ion ringing intensity correlation is accurate at quantifying ringing across a range of HCCI engine operating conditions, including various equivalence ratios, combustion timings and intake pressures.
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Extending the Lean Stability Limits of Gasoline Using a Microwave-Assisted Spark Plug

Imagineering Inc.-Atsushi Nishiyama, Yuji Ikeda
Univ. of California-Berkeley-Anthony DeFilippo, Samveg Saxena, Vi Rapp, Robert Dibble, Jyh-Yuan Chen
Published 2011-04-12 by SAE International in United States
The extension of the lean stability limits of gasoline-air mixtures using a microwave-assisted spark plug has been investigated. Experiments are conducted on a 1200 RPM single-cylinder Waukesha Cooperative Fuel Research (CFR) engine at two compression ratios: 7:1 and 9:1; and four different levels of microwave energy input per cycle (prior to accounting for transmission losses): 0 mJ (spark only), 130 mJ, 900 mJ, and 1640 mJ. For various microwave energy inputs, the effects upon stability limits are explored by gradually moving from stoichiometric conditions to increasingly lean mixtures. The coefficient of variation (COVIMEP) of the indicated mean effective pressure (IMEP) is used as an indication of the stability limits.Specific characteristics of microwave-assisted ignition are identified. Microwave enhancement extends stability limits into increasingly lean regions, but slow and partial burning at the leanest mixtures curb efficiency gains. Microwave assistance decreases occurrence of misfire and partial-burn by increasing early heat release in very lean mixtures, but engine operation is unaffected at closer-to-stoichiometric conditions. Increasing microwave energy input can improve combustion characteristics as compared to low-energy microwave enhancement,…
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Maximizing Power Output in an Automotive Scale Multi-Cylinder Homogeneous Charge Compression Ignition (HCCI) Engine

Univ of California-Berkeley-Samveg Saxena, Jyh-Yuan Chen, Robert Dibble
Published 2011-04-12 by SAE International in United States
Experimental investigations were conducted on a multi-cylinder automotive scale HCCI engine in determining a strategy that yields high power output, sufficient for passenger vehicles. A 1.9L Volkswagen TDI, modified for HCCI operation, is used with a compression ratio of 17:1 and boost pressures between 1.0 and 2.0 bar absolute. Various equivalence ratios and combustion times are explored at 1800 RPM with commercial-grade gasoline. The effects of exhaust backpressure that would be caused by a turbocharger in production engines are also explored.The results reveal that the highest power output can be achieved with high boost pressures and high equivalence ratios, and highly delayed combustion timing for controlling ringing. The optimal power output conditions exist near the boundaries of ringing, peak in-cylinder pressure, misfire and controllability. The results of the highest power output condition are displayed for a single cylinder; however, similar trends were seen across all four cylinders of the HCCI engine. The maximum power output identified in this study exceeded 9 bar gross IMEP, and high indicated efficiency points (exceeding 40%) were also found. NOx…
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