SPLIT CYCLE ENGINE

M.LOGANATHANMECHANICAL ENGG

ABSTRACT

Today’s engines operate at only 33% efficiency. This means that only 1/3 of the energy in each litre of fuel is used - the rest is lost through friction and heat. With over a billion engines currently in use worldwide, even small gains in efficiency will have huge impacts on the economy, dependency on foreign oil, and the environment.

INTRODUCTION

Despite immense efforts over the past century, engine efficiency has remained the same. The heart of the internal combustion engine is a piston moving up and down in a cylinder connected to a crankshaft. Its simplicity makes improving performance almost impossible. Small improvements have proven difficult and large improvements have been considered impossible. While the industry struggles for gains in the 1% range; the design of the Split-Cycle Technology pushes engine efficiency and performance to an entirely new level.

Contd…

The very concept of the split cycle gives way to certain in-built advantages:

1) The power stroke can be made longer than the compression stroke to over-expand the gas for increased thermal efficiency.

2) The compression piston diameter can be made larger than the power piston diameter to supercharge the gas for increased power.

3) The compression and power cylinders can be independently offset to almost any angle for increased mechanical efficiency.

Contd....

The unique combination of maintaining a pre-charged pressure in the gas passage and firing after top dead center in the power cylinder produces several additional advantages.

1) An extremely fast combustion rate, 2) A further increase in thermal

efficiency, and A significant reduction in nitrogen oxide (NOx) emissions.

The basic concept of the Split cycle Engine is to divide the four strokes of a standard engine over a paired combination of one compression cylinder and one power (or expansion) cylinder.

These two cylinders perform their respective functions once per crankshaft revolution.

THE BASICS

A common misconception is that twice as many cylinders are required. This is simply not accurate. Because this engine fires every revolution instead of every other revolution, the number of power strokes produced is equal to the power strokes produced by two of the conventional piston/cylinder designs.

. A four cylinder engine would still have four cylinders. There would simply be two sets of paired cylinders instead of four individual cylinders.

Contd…

In the configuration shown, an intake charge (Fig. 1) is drawn into the compression cylinder through typical poppet-style valves.

Intake and Compression

In this illustration, a check is used to prevent reverse flow from the crossover passage to the compression cylinder, and likewise a poppet-style valve (crossover valve) prevents reverse flow from the power cylinder to the crossover passage.

The check valve and crossover valve are timed to maintain pressure in the crossover passage at or above firing conditions during an entire four stroke cycle.

Intake Stroke

Combustion occurs (Fig. 3) soon after the intake charge enters the power cylinder from the crossover passage. This means that the start of combustion occurs after the power cylinder passes through its top dead center position (ATC).

Exhaust gases are than pumped out of the power cylinder through a poppet valve to start the cycle over again.

Power and Exhaust

Firing after Top Dead Center Is Counter-Intuitive to Engine Design;