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Combustion Robustness Characterization of Gasoline and E85 for Startability in a Direct Injection Spark-Ignition Engine

GM Powertrain-Halim Santoso, Craig Marriott
Michigan Technological Univ-Vaibhav Kale, Jeremy Worm, Jeffrey Naber
Published 2012-04-16 by SAE International in United States
An experimental study and analysis was conducted to investigate cold start robustness of an ethanol flex-fuel spark ignition (SI) direct injection (DI) engine. Cold starting with ethanol fuel blends is a known challenge due to the fuel characteristics. The program was performed to investigate strategies to reduce the enrichment requirements for the first firing cycle during a cold start. In this study a single-cylinder SIDI research engine was used to investigate gasoline and E85 fuels which were tested with three piston configurations (CR11F, CR11B, CR15.5B - which includes changes in compression ratio and piston geometry), at three intake cam positions (95, 110, 125 °aTDC), and two fuel pressures (low: 0.4 MPa and high: 3.0 MPa) at 25°C±1°C engine and air temperature, for the first cycle of an engine start. The goal of this work was to simulate, test and investigate the engine's initial combustion cycle (1st fired cycle) including engine speed, manifold pressure, fuel pressure and ambient temperature (FTP testing temperature). The results revealed several trends with respect to hardware and fuel interactions: for gasoline,…
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Characteristics of HCCI Engine Operating in the Negative-Valve-Overlap Mode

Sloan Automotive Lab, MIT-Halim Santoso, Jeff Matthews, Wai Cheng
Published 2005-05-11 by SAE International in United States
Characteristics of un-throttled HCCI engine using negative valve overlap were examined under steady state and step-load change operations. The analysis employed a combined heat release analysis of the pressure data and a cycle simulation with a 1D gas exchange model to extract the residual fraction and the compression temperature from the experimental data. The residual gas fraction decreased with increase in engine load; the compression temperature decreased correspondingly. Substantial pumping loss attributed to the heat transfer in the re-compression process and the gas exchange friction was observed. At “optimum” setting of the combustion phasing, the GIMEP was not sensitive to the cycle-to-cycle combustion phasing variation. Large step high-to-low change in load was found to be stable. The reverse, however, had combustion failure in the first cycle due to unfavorable compression temperature and residual gas fraction.
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Load Control for an HCCI Engine

Sloan Automotive Laboratory, Massachusetts Institute of Technology-Jeff Matthews, Halim Santoso, Wai K. Cheng
Published 2005-04-11 by SAE International in United States
Homogeneous-Charge-Compression-Ignition (HCCI) engine operation in a vehicle drive cycle is a very dynamic process. In this paper, a controller is devised on the premise that the vehicle is operating under Drive-By-Wire so that the driver commands the engine torque output according to the perceived vehicle speed. Thus a load-following controller is appropriate. Such a controller was developed for a single cylinder engine with electromagnetic variable valve timing control (also known as Controlled-Auto-Ignition (CAI) operation). Under open-loop operation within the CAI regime, the results indicated that the engine response was bipolar in nature: (a) the engine either responded quasi-statically to the open-loop control, or (b) the CAI combustion failed. The latter happened in a load increase process in which the per-cycle increment was too high. Based on these results, a load following controller with a table-look-up feed-forward component and a feed-back component based on the cumulative difference between the targeted and measured output was developed. With the feed back feature, the engine was able to follow the commanded values of NIMEP and fuel equivalence ratio (Φ)…
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Managing SI/HCCI Dual-Mode Engine Operation

Sloan Automotive Laboratory, Massachusetts Institute of Technology-Halim Santoso, Jeff Matthews, Wai K. Cheng
Published 2005-04-11 by SAE International in United States
Gasoline HCCI engine has the potential of providing better fuel economy and emissions characteristics than the current SI engines. However, management of HCCI operation for a vehicle is a challenging task. In this paper, the issues of mode transitions between the Spark Ignition and HCCI regimes, and the dynamic nature of the load trajectory within the HCCI regime are considered. Then the phenomena encountered in these operations are illustrated by the data from a single-cylinder engine with electromagnetic-variable-valve timing control. Mode transitions from the SI to HCCI regime may be categorized as robust and non-robust. In a robust transition, every intended HCCI cycle is successful. In a non-robust transition, one or more intended HCCI cycles misfire, although the cycles progress to a satisfactory HCCI operating point in steady state. (The spark ignition was kept on so that the engine could recover from a misfired cycle.) Thus a stable HCCI point does not imply a robust transition from the corresponding SI operating point on the load/speed map. By carefully mapping the engine transition behavior, a smooth…
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Mixture Preparation and Hydrocarbon Emissions Behaviors in the First Cycle of SI Engine Cranking

Sloan Automotive Laboratory, Massachusetts Institute of Technology-Halim Santoso, Wai K. Cheng
Published 2002-10-21 by SAE International in United States
The mixture preparation and hydrocarbon (HC) emissions behaviors for a single-cylinder port-fuel-injection SI engine were examined in an engine/dynamometer set up that simulated the first cycle of cranking. The engine was motored continuously at a fixed low speed with the ignition on, and fuel was injected every 8 cycles. Unlike the real engine cranking process, the set up provided a well controlled and repeatable environment to study the cranking process. The parameters were the Engine Coolant Temperature (ECT), speed, and the fuel injection pulse width. The in-cylinder and exhaust HC were measured simultaneously with two Fast-response Flame Ionization Detectors. A large amount of injected fuel (an order of magnitude larger than the normal amount that would produce a stoichiometric mixture in a warm-up engine) was required to form a combustible mixture at low temperatures. That was because fuel delivery efficiency (the fraction of the injected fuel that constituted the combustible charge) decreased significantly with temperature, and that this efficiency also decreased with an increase in the injection amount. A thermodynamic model for mixture preparation based…
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