Geometric & Kinematic Models for An I.C. Engine

P M V SubbaraoProfessor

Mechanical Engineering Department

Creation of Infrastructure to Facilitate Thermodynamic Actions…..

Kinematics of Conventional I.C. Engine

Kinematics of Unconventional Piston Movement

Variable Piston Motion Kinematics

Free Piston Engine with Opposed Pistons

Free Piston Gas Generator

Free-Piston Engine With Linear Generator

p- v diagram for Free Piston Engine

The Dilemma of the Classical Engine KinematicsThe Dilemma of the Classical Engine Kinematics

1. High 1. High efficiencyefficiency requires requires highhigh expansion ratio expansion ratio

2. High 2. High powerpower densitydensity requires requires lowlow compression ratio compression ratio

BUT UNFORTUNATELYBUT UNFORTUNATELY

Expansion ratioExpansion ratio == Compression ratio

How can we change a

“BUT UNFORTUNATELY =“

into an

“AND FORTUNATELY ≠” ?

The Unreasonable Bias

A I R

CombustionProducts

Ignition

IntakeStroke

FUEL

Fuel/AirMixture

CompressionStroke

PowerStroke

ExhaustStroke

A General Physician to A Team of Specialists

• Why not add an additional degree of freedom?

Three times... “There is no reason to not try it!”

Why not allow different cylinders to Why not allow different cylinders to concentrate on different tasks?concentrate on different tasks?

Why not add an additional engine stroke?Why not add an additional engine stroke?

In 2000, a new engine is born ...

The software design...

The hardware manufacturing...

The New p-v Diagram

Six Stroke Engine

• Velozeta Six-stroke engine• German Charge pump• Crower six stroke engine • Griffin six stroke engine • Velozeta six-stroke engine• Bajulaz six stroke engine

Kinematics of Conventional I.C. Engine

Engine Cylinder Geometry

Bore/Stroke Ratio

Bore – to –Stroke Ratio

Geometry of Cylinder : A Primary Signature

• An engine is described as a square engine when it has equal bore and stroke dimensions, giving a bore/stroke value of exactly 1.

• By custom, engines that have a bore/stroke ratio of between 0.95 and 1.04 can be considered "square".

• An engine is described as under-square or long-stroke if its cylinders have a smaller bore than its stroke - giving a ratio value of less than 1.

• At a given engine speed, a longer stroke increases engine friction and increases stress on the crankshaft.

• The smaller bore also reduces the area available for valves in the cylinder head, requiring them to be smaller or fewer in number.

• These factors favor lower engine speeds, under-square engines are most often tuned to develop peak torque at relatively low speeds.

• An under-square engine will typically be more compact in the directions perpendicular to piston travel but larger in the direction parallel to piston travel.

• An engine is described as over-square or short-stroke if its cylinders have a greater bore diameter than its stroke length, giving a bore/stroke ratio greater than 1.

• An over-square engine allows for more and larger valves in the head of the cylinder, lower friction and lower crank stress.

• Due to the increased piston- and head surface area, the heat loss increases as the bore/stroke-ratio is increased excessively.

• These characteristics favor higher engine speeds, over-square engines are often tuned to develop peak torque at a relatively high speed.

• The reduced stroke length allows for a shorter cylinder and sometimes a shorter connecting rod, generally making over-square engines less tall but wider than under-square engines of similar engine displacement.