Operation strategy of a Dual Fuel HCCI Engine with VGT

Författare

Carl Wilhelmsson
Per Tunestål
Bengt Johansson

Summary, in English

HCCI combustion is well known and much results regarding

its special properties have been published.

Publications comparing the performance of different

HCCI engines and comparing HCCI engines to conventional

engines have indicated special features of

HCCI engines regarding, among other things, emissions,

efficiency and special feedback-control requirements.

This paper attempts to contribute to the common

knowledge of HCCI engines by describing an operational

strategy suitable for a dual-fuel port-injected

Heavy Duty HCCI engine equipped with a variable geometry

turbo charger. Due to the special properties of

HCCI combustion a specific operational strategy has

to be adopted for the engine operation parameters (in

this case combustion phasing and boost pressure).

The low exhaust temperature of HCCI engines limits

the benefits of turbo charging and causes pumping

losses which means that “the more the merrier” principle

does not apply to intake pressure for HCCI engines.

It is desirable not to use more boost pressure

than necessary to avoid excessively rapid combustion

and/or emissions of NOx. It is also desirable to select

a correct combustion phasing which, like the boost

pressure, has a large influence on engine efficiency.

The optimization problem that emerges between the

need for boost pressure to avoid noise and emissions

and, at the same time, avoiding an extensive decrease

of efficiency because of pumping losses is the

topic of this paper. The experiments were carried out

on a 12 liter Heavy Duty Diesel engine converted to

pure HCCI operation. Individually injected natural gas

and n-Heptane with a nominal injection ratio of 85%

natural gas and the rest n-Heptane (based on heating

value) was used as fuel. The engine was under feedback combustion control during the experiments.

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