Supercharged Homogeneous Charge Compression Ignition

Abstract

The Homogeneous Charge Compression Ignition (HCCI) is the third alternative for combustion in the reciprocating engine. Here, a homogeneous charge is used as in a spark ignited engine, but the charge is compressed to auto-ignition as in a diesel. The main difference compared with the Spark Ignition (SI) engine is the lack of flame propagation and hence the independence from turbulence. Compared with the diesel engine, HCCI has a homogeneous charge and hence no problems associated with soot and NO X formation. Earlier research on HCCI showed high efficiency and very low amounts of NO X , but HC and CO were higher than in SI mode. It was not possible to achieve high IMEP values with HCCI, the limit being 5 bar. Supercharging is one way to dramatically increase IMEP. The influence of supercharging on HCCI was therefore experimentally investigated. Three different fuels were used during the experiments: isooctane, ethanol and natural gas. Two different compression ratios were used, 17:1 and 19:1. The inlet pressure conditions were set to give 0, 1 or 2 bar of boost pressure. The highest attainable IMEP was 14 bar using natural gas as fuel at the lower compression ratio. The limit in achieving even higher IMEP was set by the high rate of combustion and a high peak pressure.Numerical calculations of the HCCI process have been performed for natural gas as fuel. The calculated ignition timings agreed well with the experimental findings. The numerical solution, is however, very sensitive to the composition of the natural gas.

Road Transportation Vehicles

“…[12][13][14][15][16][17] The most common clean-combustion techniques under consideration are homogeneous charge compression ignition (HCCI) and lowtemperature combustion (LTC); both involve modifications to the air-fuel mixture, ignition timing, air charge boost pressures, and percentage of exhaust gas recirculation (EGR) in the charge air. The goal of each of these technologies is to improve the engine thermal efficiency while minimizing unwanted exhaust compounds such as NO x and particulate matter (PM/soot).…”

A Review of Experimental and Simulation Studies on Controlled Auto-Ignition Combustion

“…Results from simulations of n-heptane and iso-octane with CAI combustion [29], cited in Figures 1 and 2, confirmed that both fuels ignited (main ignition) when air and fuel mixture reached a temperature of 1100K. Results from experimental studies on CAI combustion [1][2][3][4][5][6][7][8][9][10][11][12][13][30][31][32][33][34][35][36][37][38][39][40][41][42][43] proved the consistency of this temperature and its independence from fuel type. Figure 2.…”

“…As a result, high peak pressure accompanied with a high rate of heat release and knock related problems could occur if rich mixtures were used [33][34][35][40][41][42]. CO and HC emissions from CAI combustion could be higher than conventional CI [41] and SI [33] engines, too.…”

“…Air/fuel ratio -The strength of the air/fuel mixture has a direct effect upon CAI timing and its combustion heat release rate [31][32][33][34][35][36][37][38][39][40][41][42][43][44]46]. Enriching the mixture decreases the ratio of the specific heats (γ) and thus reduces the amount of disposable compression heating in the charge.…”

Low Cost, High Efficiency, Ultra Low Nox Arice Solution Using Hcci Combustion

“…This expression is obtained from the experimental results (Christensen et al 1998). The characteristics of the engine and the natural gas fuel used in the analysis are given in Table 5.…”