Computer Simulation of Gasoline-Direct-Injected (Gdi) Extended Expansion Engine 2005-26-057

This paper deals mainly with computer simulation of processes of Gasoline Direct Injection (GDI) associated with Extended Expansion Engine (EEE) concept applied to a four-stroke, single-cylinder SI engine.

In the case of standard SI engines, part-load brake thermal efficiencies are low due to higher pumping losses. The pumping losses can be reduced by operating the engine always at full throttle as done in extended expansion engine. In extended expansion engine, higher Geometric Expansion Ratio (GER) compared to Effective Compression Ratio (ECR) is responsible for better performance at part loads. Usually, in this engine, by delaying inlet valve closure timing along with reduced clearance volume, extended expansion is achieved. Experimentally many researchers have proved that variable valve timing and variable compression ratio techniques adopted in SI engines, improves the part- load performance greatly.

Nowadays, load control in the SI engines is also done by Gasoline Direct Injection (GDI) of the fuel into the cylinder. In these engines, by electronic means, it is possible to meter the fuel accurately thereby improving the fuel economy to a great extent. Also, stratification is possible with GDI thereby overall lean mixtures can be used with high compression ratios, which further increase the thermal efficiency. The other advantage of the GDI concept is that it helps to reduce emissions, which is very much required for today's emission norms.

In this work, an attempt has been made to develop a computer program, which involves thermodynamic and phenomenological models for simulating the processes of the GDI associated with Extended Expansion Engine (hereafter called as GIEEE). Appropriate sub-models have been chosen and used for predicting heat transfer, friction and droplet evaporation, etc. Combustion model involves premixed and diffusion phases, which predicts mass burning rate, ignition delay and combustion duration, etc. Also, sub-models for calculating flame front area, flame speed, and chemical equilibrium composition of burned product species have been used. Exhaust emission models are also involved in the program to predict the unburned hydrocarbons, carbon monoxide and nitric oxide emissions.

Firstly, some of the results obtained by predictions using the computer code developed in this work have been validated with the available experimental results in the literature. It seems that the predicted results match reasonably well with the experimental values. Secondly, the computer code has been used for further parametric studies. Finally, it is concluded that the computer code developed in this work can be used with confidence for optimizing the parameters of GIEEE for the given configuration of the engine.