Experimental Investigation of Engine Speed Transient Operation in a Light Duty RCCI Engine

Abstract

Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NO x and PM emissions while maintaining high thermal efficiency. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multi-cylinder engine over transient operating conditions using a high-bandwidth, transient capable engine test cell. Transient RCCI and CDC combustion and emissions results are compared over an up-speed change from 1,000 to 2,000 rev/min. and a down-speed change from 2,000 to 1,000 rev/min. at a constant 2.0 bar BMEP load.The engine experiments consisted of in-cylinder fuel blending with port fuel-injection (PFI) of gasoline and early-cycle, direct-injection (DI) of ultra-low sulfur diesel (ULSD) for the RCCI tests and the same ULSD for the CDC tests. At the selected engine load, a step speed change was commanded and both combustion modes were compared for performance and emissions using fast response HC, NO and PM instruments. Optimized intake conditions (i.e., intake pressure, temperature and exhaust gas recirculation (EGR)) were used to explore the robustness of RCCI using real-world operating conditions. It was found that the engine was able to operate in the RCCI combustion mode using production level engine hardware with significantly lower engine-out PM and NO x emissions than CDC over the specified transient engine operating conditions.

A detail simulation of reactivity controlled compression ignition combustion strategy in a heavy-duty diesel engine run on natural gas/diesel fuel

“…In this strategy, the power output demand could be controlled using a certain air and fuel at specified equivalence ratio (F) which, in turn, controls the thermodynamic conditions of gas composition inside the cylinder such as temperature and pressure. [8][9][10][11] The primary challenges in controlling the HCCI engine are the combustion initiation and the rate of heat release, especially when the engine operates at high loads. In another similar strategy, in order to coupling the fuel injection and the combustion, a premixed charge compression ignition strategy known as PCCI is introduced for improving the combination of air-fuel mixture, where fuel injection takes place prior to the compression stroke.…”

Effect of EGR and Fuel Injection Strategies on the Heavy-Duty Diesel Engine Emission Performance under Transient Operation

“…Diesel vehicles operate in transient conditions in most cases. The transient feature is the delay of boundary condition response compared to steady state [1][2][3][4], which leads to deterioration of fuel economy and pollutant emission [5][6][7][8]. In addition, in order to meet the requirements of increasingly stringent emissions regulations, many transient performances and optimization methods have been studied in recent years.…”

Use of Early Exhaust Valve Opening to Improve Combustion Efficiency and Catalyst Effectiveness in a Multi-Cylinder RCCI Engine System: A Simulation Study

“…These drawbacks occur due to low combustion efficiencies at low loads, which are, in turn, a consequence of low combustion temperatures that cause the oxidation rates of UHCs and CO to slow down [9,10]. Moreover, the combustion stability has also been found to deteriorate at low load [11].…”