Session: 08-01: Poster Session

Paper Number: 149654

149654 - On the Importance of Combustion Phasing in Dual Fuel Rcci Combustion With a Variety of High and Low Reactivity Fuels 

Abstract: 

Reactivity Controlled Compression Ignition (RCCI) has been identified as a promising dual fuel combustion strategy due to its potential to improve engine performance while producing low engine-out NOx and soot emissions. The relative energy fractions of a high reactivity fuel (HRF such as diesel) and a low reactivity fuel (LRF such as natural gas, gasoline) are varied to achieve RCCI combustion. More recently, researchers have demonstrated excellent soot and NOx emissions reductions while using renewable alternative fuels like oxymethlene ethers (OMEs) as the HRF in RCCI combustion.

Combustion phasing, which is commonly defined as the location of the 50% of cumulative heat release (CA50), is well-known as an important parameter that affects engine performance and emissions. Combustion phasing can be impacted by engine operating parameters such as start of injection (SOI) of the HRF (which dictates in-cylinder stratification), in-cylinder pressure and temperature at SOI, and fuel properties, among others. Dual fuel combustion of multiple combinations of HRF and LRF were investigated on a heavy-duty single-cylinder research engine (SCRE) with a specific focus on the characterizing the importance (or lack thereof) of combustion phasing in dual fuel RCCI combustion. Among the fuel combinations, compressed city natural gas, bottled liquefied propane gas, and butanol were considered as LRFs while diesel and OMEs with methyl, propyl, and butyl groups were considered. The objectives of this study are to: (1) Identify if an “optimal” CA50 exists for dual fuel RCCI combustion, where high fuel conversion efficiencies and low emissions can be achieved, (2) characterize the impact of fuel stratification and LRF energy fraction on CA50 for the different HRF-LRF fuel combinations, and (3) quantify the sensitivity of engine performance and emissions to CA50 over the range of operating conditions and fuel combinations.

The experimental studies were performed at a constant engine speed of 1339 RPM, which was the B-speed of the engine, and at a low load of 5 bar IMEPg. At these low load conditions, RCCI combustion was compared for multiple fuel combinations at constant HRF energy substitution and constant HRF mass fractions. The SOI was varied from close-to-TDC injection to injection timings as early as 60 degrees BTDC. Indicated specific emissions values and indicated fuel conversion efficiencies at various SOIs were plotted vs. CA50 to examine the impact of CA50 under these vastly different levels of HRF stratification.

Presenting Author: Hariraja Thothadri The University of Alabama

Presenting Author Biography: Hariraja Thothadri is a graduate student at The University of Alabama. He is focused on reducing emissions and improving efficiency on heavy duty engines.

Authors:

Hariraja Thothadri The University of Alabama
Abinandhan Narayanan The University of Alabama
Yamini Baskara Babu The University of Alabama
Stephen Mundy The University of Alabama
Justin Gray The University of Alabama
Kalyan Srinivasan The University of Alabama
Sundar Krishnan The University of Alabama