Semester

Fall

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Benjamin Shade

Abstract

Advanced combustion has progressively become a topic of interest as government regulations have stringently reduced the allowable limits of engine-out emissions from internal combustion engines. Advanced combustion can typically be classified as homogeneous charge compression ignition (HCCI) or premixed charge compression ignition (PCCI). In HCCI combustion, a well mixed fuel and air solution is spontaneously combusted, thus providing a homogeneous burn throughout the combustion process. By having an evenly distributed, homogeneous burn, fuel economy is not only significantly increased, but both oxides of nitrogen (NO x) and particulate matter (PM) can drastically be reduced from that of conventional combustion. HCCI has the ability to incorporate the low PM emissions of a spark ignited (SI) engine as well as the high thermal efficiency of a compression ignited (CI) engine. Similar to HCCI, PCCI offers low NO x and PM within a part load operating range with a quasi-homogenous fuel and air mixture. Other than identifying HCCI or PCCI as having very limited NOx and PM production, in-cylinder combustion techniques can also be utilized to characterize these forms of advanced combustion.;An experimental study was performed at West Virginia University (WVU) in an attempt to achieve HCCI or PCCI operation by implementing a number of engine control strategies using a range of fuels with varying fuel properties. The test engine, a GM 1.9L, was incorporated with an ECU controller capable of controlling engine operating parameters such as rail pressure, start of injection (SOI), fuel quantity injected and exhaust gas recirculation (EGR) valve position. Piezoelectric crystal pressure transducers were introduced into each cylinder via glow plug adapters and a custom WVU data acquisition system was used to evaluate in-cylinder combustion parameters. Testing was performed at a 2100 RPM, 53 N-m, steady-state set point using an engine dynamometer. By implementing high levels of EGR, NOx emissions were reduced nearly 90% due to lower cylinder pressures and increased ignition delay. PM emissions were also reduced by 15% within a specific EGR range due to increased mixing time available from a longer ignition delay as verified by in-cylinder pressure, heat release rate and mass fraction burned data. Fuel characteristics were compared at a single operating condition and at an optimized control strategy with increased thermal efficiency, for low NOx and PM emissions that were determined from a range of EGR, pilot injection, main injection, rail pressure and fuel split sweeps. The cetane number (CN) of the fuel was found to be the contributing factor affecting the combustion process compared to fuel properties such as aromatics and volatility while the net heat of combustion per unit volume effected the brake specific fuel consumption. Low CN fuels resulted in a PM reduction of 30% but showed a 50% increase in NOx emissions over the higher CN fuels at the same operating condition.

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