A Turbo Charged Dual Fuel HCCI Engine

Abstract

A 6-cylinder truck engine is modified for turbo charged dual fuel Homogeneous Charge Compression Ignition (HCCI) engine operation. Two different fuels, ethanol and n-heptane, are used to control the ignition timing. The objective of this study is to demonstrate high load operation of a full size HCCI engine and to discuss some of the typical constraints associated with HCCI operation. This study proves the possibility to achieve high loads, up to 16 bar Brake Mean Effective Pressure (BMEP), and ultra low NO X emissions, using turbo charging and dual fuel. Although the system shows great potential, it is obvious that the lack of inlet air pre heating is a drawback at low loads, where combustion efficiency suffers. At high loads, the low exhaust temperature provides little energy for turbo charging, thus causing pump losses higher than for a comparable diesel engine. Design of turbo charger therefore, is a key issue in order to achieve high loads in combination with high efficiency. In spite of these limitations, brake thermal efficiencies and power rating close to those of the original diesel engine are achieved with significant reduction in NO X emissions. The maximum efficiency is 41.2%, which is slightly lower than for the original diesel engine.

The Effect of Cooled EGR on Emissions and Performance of a Turbocharged HCCI Engine

“…Figure 1 shows a schematic of the engine system. Basically the same engine setup has been used in previous papers by the authors [25,26,28]. The main difference is the EGR system and the arrangement of heaters and CAC.…”

“…However, for a heavy-duty engine, turbo charging is a tempting way to improve power density. It has previously been shown by the authors [28] that turbo charging is an effective means of increasing the achievable load, but at the cost of high pumping losses. In this section temperature sweeps without EGR and with 45% EGR at 1600 rpm, 11 bar BMEP and about 0.9 bar boost are examined.…”

“…In earlier studies with the same engine, [25,26,28], combinations of n-heptane and gasoline or isooctane, have been used. In this study, combinations of n-heptane and ethanol are used because of the high octane rating of ethanol.…”

“…Combustion timing was maintained by using high fractions of n-heptane [28]. At these conditions combustion efficiency deteriorated to below 65%.…”

1-hexene autoignition control by prior reaction with ozone

“…One way to ensure that ignition takes place around TDC at varying engine operating conditions is to control the ignition quality of the fuel. This can be achieved by blending two fuels of varying ignition qualities [4], such as petrol and diesel fuel. The disadvantage of this approach is that an engine would require two fuels to operate, which would have to be kept in separate fuel tanks.…”