HISTORY

It all started back in 1506 when no one else than Leonardo da Vinci described a compression

less engine-his description may not imply the idea was original with him or that is was

actually build. The same thing was done a century and a half later, in 1673 by Christian

Huygens. In 1794, Robert Street built a compression-less engine whose principle of operation

would dominate for nearly a century. English inventor Sir Samuel Morland used gunpowder

to drive water pumps in the 17th

century.

The first internal combustion engine to be applied industrially was patented by Samuel

Brown in 1823. It was based on what Hardenberg calls the Leonardo cycle, which, as this

name implies, was already out of date at that time. The Italians Eugenio Barsanti and Felice

Matteucci patented the first working, efficient internal combustion engine in 1854 in London

but did not get into production with it.

A steam engine is a device that converts the potential energy that exists as pressure in steam,

and converts that to mechanical force. Early examples were the steam locomotive trains,

and steamships that relied on these steam engines for movement. The Industrial

Revolution came about primarily because of the steam engine. The thirty seconds or so

required to develop pressure made steam less favoured for automobiles, which are generally

powered by internal combustion engines. The first practical steam engine was patented

by James Watt, a Scottish inventor, in 1769. Steam engines are of various types but most are

reciprocal piston or turbine devices.

TYPES OF CYCLES

1) Otto Cycle

Otto demonstrated the first true 4-stroke cycle in 1876 after giving up active management

of Otto & Langen and going back to an 1861 design of his own. Rather than relying on

the atmospheric imbalance to provide the power stroke, he instead turned the initial

explosion into the power stroke and used the flywheel to help maintain momentum and

return the piston down the cylinder. He replaced the rack and pinion with the connecting

rod and crank to improve efficiency and remove slack from the mechanical transfer of the

power from the piston to the flywheel. His design had four strokes to complete one entire

cycle.

First Stroke: Intake

A specific mass of air is sucked in the engine cylinder at constant pressure.

Second Stroke: Compression

It is an isentropic adiabatic process in which air fuel mixture (in case of petrol) is

compressed

Third Stroke: Power

This is divided into two processes.

Process 1: At constant Volume, heat is added to the engine cylinder when the piston is

at top dead centre.

Process 2: It is again an isentropic process in which expansion takes place when the

piston goes from top dead centre to bottom dead centre.

Fourth Stroke: Exhaust

In this process, heat is rejected out of the engine cylinder.

Nowadays the engines we are using that runs on petrol are all work on Otto cycle.

2) Diesel Cycle

The Diesel cycle is a compression ignition (rather than spark ignition) engine. Fuel is

sprayed into the cylinder at (high pressure) when the compression is complete, and

there is ignition without a spark. This cycle can operate with a higher compression

ratio than the Otto cycle because only air is compressed and there is no risk of auto-

ignition of the fuel. Although for a given compression ratio the Otto cycle has higher

efficiency, because the Diesel engine can be operated to higher compression ratio, the

engine can actually have higher efficiency than an Otto cycle when both are operated

at compression ratios that might be achieved in practice.

Process 1-2: isentropic compression

Process 2-3: Heat is added to the engine cylinder at constant pressure.

Process 3-4: isentropic expansion

Process 4-1: reversible constant volume cooling

3) Stirling Cycle

In Stirling cycle, Carnot cycle’s compression and expansion isentropic processes are

replaced by two constant-volume regeneration processes. During the regeneration

process heat is transferred to a thermal storage device (regenerator) during one part and is

transferred back to the working fluid in another part of the cycle. The regenerator can be a

wire or a ceramic mesh or any kind of porous plug with a high thermal mass (mass times

specific heat). The regenerator is assumed to be reversible heat transfer device.

Process 1-2: isothermal expansion heat addition from external source

Process 2-3: const. vol. heat transfer internal heat transfer from the gas to the

regenerator

Process 3-4: isothermal compression heat rejection to the external sink

Process 4-1: const. vol. heat transfer internal heat transfer from the regenerator to

the gas.

The Stirling cycle was invented by Robert Stirling in 1816. The execution of the Stirling

cycle requires innovative hardware. That is the main reason the Stirling cycle is not

common in practice.

Some important points:

Unlike internal combustion engines, a Stirling cycle does not exchange the working

gas in each cycle, the gas is permanent.

The heat is supplied outside the engine, so any heat source can be used, e.g.: coal, gas,

solar energy, nuclear power, etc.

The pressure changes are very smooth and its torque is uniform, it has no valves,

exhaust pipes, etc. Thus, Stirling cycle is quiet and has less maintenance points.

To achieve competitive efficiency, it needs to work on high pressures which cause

tremendous problems of sealing.

The working fluid has to be an ideal gas. Helium or hydrogen is typically used

because of their high heat conductivity and low molecular masses which lead to faster

heat transfer.

4) Atkinson Cycle

Invented by British engineer James Atkinson, the Atkinson Cycle is one in which the

stroke of the piston can vary in length across the four cycles in a four-stroke internal

combustion engine. Typically, the length of the stroke during the power cycle is increased

to promote efficiency; however, because this can come at the expense of a shorter intake

stroke, there is some loss of power—for this reason, this type of engine design is best

suited for use in a hybrid system where the electric motor can compensate for these power

losses. The Atkinson cycle is designed to provide efficiency at the expense of power

density.

Its expansion ratio and compression ratio can be different because of its unique crankshaft

design.

Process 1-2: Isentropic or reversible adiabatic compression.

Process 2-3: Isochoric heating

Process 3-4 Isobaric heating

Process 4-5 Isentropic expansion

Process 5-6 Isochoric cooling

Process 6-1 Isobaric cooling

Atkinson cycle recently used in Ford Ecoboost Engine which we noticed at AUTOEXPO-

The Motor Show 2014 held at Greater Noida from 7th

Feb 2014-11th

Feb 2014.

5) Lenoir Cycle

The Lenoir cycle is approximated by the air-standard cycle shown in Fig. 3-20. The first

half of the first stroke was intake, with air-fuel entering the cylinder at atmospheric

pressure. At about halfway through the first stroke, the intake valve was closed and the

air-fuel mixture was ignited without any compression. Combustion raised the temperature

and pressure in the cylinder almost at constant volume in the slow-moving engine

(process 2-3). The second half of the first stroke then became the power or expansion

process 3-4. Near BDC, the exhaust valve opened and blowdown occurred (4-5). This

was followed by the exhaust stroke 5-1, completing the two-stroke cycle. There was

essentially no clearance volume.

6) Miller Cycle

The Miller cycle, named after R. H. Miller (1890-1967), is a modern modification of the

Atkinson cycle and has an expansion ratio greater than the compression ratio. This is

accomplished, however, in a much different way. Whereas an engine designed to operate

on the Atkinson cycle needed a complicated mechanical linkage system of some kind, a

Miller cycle engine uses unique valve timing to obtain the same desired results. Air intake

in a Miller cycle is unthrottled. The amount of air ingested into each cylinder is then

controlled by closing the intake valve at the proper time, long before BDC.

As the piston then continues towards BDC during the latter part of the intake stroke,

cylinder pressure is reduced along process 7-1. When the piston reaches BDC and starts

back towards TDC cylinder pressure is again increased during process 1-7. The resulting

cycle is 6-7-1-7-2-3-4-5-6. The work produced in the first part of the intake process 6-7 is

cancelled by part of the exhaust stroke 7-6, process 7-1 is cancelled by process 1-7, and

the net indicated work is the area within loop 7-2-3-4-5-7. There is essentially no pump

work. Subaru B5-TPH engine’s runs on the miller cycle.

These were some the heat engine cycles on which automobiles engine work.

TYPES OF ENGINE

Here comes a very basic topic as we engineers always start the topic engine by discussing

what the types of engine are or how the engines are classified.

Engines are Classified on various basis:

Classification Types

Number of strokes per cycle

2 stroke

4 Stoke

5 Stroke

6 Stroke

Type Of fuel Burned

Petrol

Diesel

Biodiesel(B10, B20, B100)

Hydrogen

LPG

CNG

M85(Blended form)

Method of ignition Spark ignition

Compression ignition

Firing order

(examples is only for 4 cylinder engine)

1-3-4-2 1-2-4-3 1-3-2-4 1-4-3-2 1-2-3-4

Reciprocating or rotary Reciprocating piston cylinder arrangement

Rotary type- Wankel engine

Number of cylinders

Single Cylinder

2 cylinder, 3 cylinder, 4 cylinder, 5 cylinder

6 cylinder, 8 cylinder, 10 cylinder,

12 cylinder, 16 cylinder, 18 cylinder

22 cylinder, 24 cylinder

Arrangements of cylinders

V type

Inline type

W type

H type

U type

X type

K type

Radial

Arrangement of valves and valve train

DOHC

SOHC

Overhead camshaft with bucket tappet

Overhead camshaft with rocker arm

Camshaft in block with pushrod

Type of cooling Air Cooled

Water Cooled

TYPES OF ENGINE FOR SPECIFIC VEHICLE

Vehicle Types of Engine

Single cylinder Twin

cylinder

Inline V

type

W type

Cars Hatchbacks •

Sedan • • •

SUV • •

Sports cars • • •

Convertible • •

Off roaders • • •

Coupe • •

Trucks Trailors • •

Semi trailors • •

Farm trucks •

Buses •

Motorcycles 3 wheelers • •

Moped •

Motorcycle with 2

wheelers

•

TYPES OF ANALYSIS USED

1) Combustion Analysis

Combustion analysis is very useful for getting physical and chemical conditions of the

cylinder. For implementing the analysis, we need to have a Combustion pressure sensor,

crank angle encoder and a power supply.

Combustion pressure sensor: The sensor is having unlimited life time for combustion

pressure measurement application. Optimized piezoelectric sensor for continuous cylinder

pressure monitoring of engines. The sensor is connected to the charge amplifier with a

robust integrated high temperature Viton cable. The good linearity and long term stability

ensures reliable and repeatable measurements over a long period of time. These sensors

measure the pressure inside the cylinder and can be installed by using spark plug, glow

plug.

Outcome of Combustion Analysis

Indicated power

P-V diagram and P-θ diagram

Calculate 5%,10%,50%,80%,90%,95%,99% mass fraction burnt angle

Estimated end of combustion Angle

Calculate heat release rate, heat release rate crank angle, pressure rise rate, pressure

rise rate crank angle, maximum pressure, maximum pressure crank angle

Calculate Start of combustion

Calculate total heat release

2) Performance Analysis

In performance analysis, we have to use lotus concept tool to play with the engine

performance parameters like torque, power and speed. As we are fabricating an off road

vehicle, our main concern will be the torque which should be as high as possible without

altering any other parameters. After having the result from the software simulator, we

need to use the optimizer tool to optimize the result keeping in mind that we have to get

the high torque below the redline rpm.

3) Thermal Analysis

Engine is made of many components of different materials and their properties. Any

material has its limit to sustain any type of force or pressure. In engine, while internal

combustion process, a high amount of temperature is produced inside the chamber which

also affects mostly all parts in terms of material property. So we need to do a thermal

analysis on these components like

Combustion chamber

Inlet and exhaust valves

inlet and exhaust manifold

Crankshaft

Gudgeon pin

Connecting rod and some other parts.

4) Stress Analysis

While engine in running condition, many of the parts or components suffer dynamic

forces and vibrations. These vibrations produce stresses on the components. So we need

to have the static as well as dynamic analysis of some specific components like

crankshaft, connecting rod, Gudgeon pin, cylinder, and some other parts. We all need to

have the fatigue analysis of the same.

PARAMETERS CONSIDERED IN DESIGNING OF ENGINE

1) Injection timing

It plays an important role in combustion process, if the injection is too early majority of

the combustion takes place in the compression stroke causing high compression work

and heat losses losing much of useful energy, if the injection is retarded then

majority of the combustion takes place in the expansion stroke causing a loss of

expansion, hence a correct injection timing is required to achieve MBT timing.

2) Injection pressure

The injector’s task is to inject fuel and mix with air. If the injection pressure is low, the

fuel droplets will be large and proper mixing is not feasible which results in improper

combustion resulting in high emissions, especially particulates.

3) Air-fuel ratio

The problem of air utilization arises when we try to increase the fuel quantity per cycle,

this air utilization problem results in excessive soot which cannot be burned before

exhaust. This black smoke or soot in the exhaust limits the air-fuel ratio. Therefore a

minimum of lambda 1.25 is maintained.

4) NOx emissions

As the emission regulations become more stringent, the need to reduce the NOx

emissions in an engine is inevitable. NOx is primarily formed because of the high

temperatures and presence of abundance of oxygen to oxidise the nitrogen during

combustion. The allowed engine-out NOx level for this particular engine model is 5

g/kWh. Furthermore the NOx emissions are reduced using a SCR.

5) Cylinder peak pressure

Since the engine is operated at higher BMEP the pressure in the cylinder increases and for

mechanical reasons the cylinder pressures are limited to 250 bars.

6) Exhaust temperature and pressure

The exhaust temperature and pressure are limited because of the design limitations. The

max permissible exhaust temperature and pressure are 953K and 5.5 bars respectively.

7) Turbine and compressor speeds(if equipped)

The turbine wheel and compressor wheel are not entitled to run faster than certain speeds

due to mechanical limitations. And from manufacturers data it is noted that a Titanium

85mm compressor wheel can run up to 124,000 rpm and using this relation, the speed

limit is chosen for the scaled diameter.

Engine Performance Parameters

Practical engine performances of interest are torque, power and specific fuel

consumption. Power and torque depend on an engine’s displaced volume.

OPERATING VARIABLES THAT AFFECT SI ENGINE PERFORMANCE,

EFFICIENCY AND EMISSIONS

The major operating variables that affect spark ignition engine performance, efficiency

and emissions at any given load and speed are:

Spark timing

Variations in spark timing relative to top-center affect the pressure development in the SI

engine cylinder. If combustion starts too early in the cycle, the work transfer from the

piston to the gases in the cylinder at the end of the compression stroke is too large. If the

combustion starts too late, the peak cylinder pressure is reduced and the expansion stroke

work transfer from the gas to the piston decreases. There exists a particular spark timing

which gives maximum engine torque at fixed speed and mixture composition and flow

rate. It is referred to as MBT-maximum brake torque-timing. This torque also gives

maximum brake power and minimum brake specific fuel consumption.

Mixture Composition

The unburned mixture in the engine cylinder consists of fuel (normally vaporized), air,

and burned gases. The burned gas fraction is the residual gas plus any recycled exhaust

used for NO control. Mixture composition during combustion is most critical, since this

determines the development of the combustion process which governs the engine’s

operating characteristics. It is necessary to consider the effect of mixture composition

changes on engine operating and emissions characteristics in two regimes: 1) wide open

throttle (WOT) or full load and 2) part throttle or load. At WOT, the engine air flow is the

maximum that the engine will induct. Fuel flow can be varied, but air flow is set by the

engine design variables and speed. At part throttle, air flow, fuel flow, and EGR flow can

be varied.

Load and Speed

One common way to present the operating characteristics of an internal combustion

engine over its full load and speed range is to plot brake specific fuel consumption

contours on a graph of brake mean effective pressure versus engine speed. Operation of

the engine coupled to a dynamometer on a test stand, over its load and speed range,

generates the torque and fuel flow-rate data which such a performance map is derived.

Compression Ratio

In an actual engine other processes which influence engine performance and efficiency

vary with changes in compression ratio: namely combustion rate and stability, heat

transfer and friction. Over the load and speed range, the relative that these processes have

on power and efficiency varies also. while the geometric compression ratio is well

defined, the actual compression and expansion processes in engines depend on valve

timing details and the importance of flow through the valves while they are opening or

closing(which depends on engine speed). Of course our ability to increase the

compression ratio is limited by the octane quality of available fuels and knock.

DIFFERENT TYPES OF EFFICIENCIES

1) Combustion Efficiency

Combustion efficiency is defined to account for the fraction of fuel which burns. It

typically has values in the range 0.95 to 0.98 when an engine is operating properly.

Combustion Efficiency is defined as the amount of heat released during combustion over

the heating value of the fuel burned.

2) Thermal Efficiency

Efficiency indicates how well an energy conversion or transfer process is

accomplished. For thermal efficiency, the input, Qin, to the device is heat, or the heat-

content of a fuel that is consumed. The desired output is mechanical work, Wout or

heat, Qout, or possibly both. Because the input heat normally has a real financial cost, a

memorable, generic definition of thermal efficiency (n) is

n= Output/input

3) Volumetric Efficiency

Volumetric efficiency in the internal combustion engine design refers to the efficiency

with which the engine can move the charge into and out of the cylinders. More

specifically, volumetric efficiency is a ratio (or percentage) of the quantity of air that is

trapped by the cylinder during induction over the swept volume of the cylinder under

static conditions. Volumetric Efficiency can be improved in a number of ways, most

effectively this can be achieved by compressing the induction charge (forced induction)

or by aggressive cam phasing in Normally Aspirated engines as seen in racing

applications. In the case of forced induction Volumetric Efficiency can exceed 100%.

DESIGN PROCEDURE

Data required before starting the designing of the engine

Basic engine data like number of cylinder, arrangement of cylinder, Stroke to bore

ratio, type of heat transfer model using for the calculation.

Fuel and Fuel System data

Combustion and heat transfer data

Scavenging data

Ports and Valves data

Pipes and plenum data

Throttle data

Compressors/turbines and charge coolers data

Inlets and exits data

Connections data

Links data

Reflections data

Sensors and actuators data for valves timing

For doing analysis/simulation of the engine, we are using lotus engine simulation

software for single cylinder. It is freeware software available on the lotus website.

First we will do the Combustion analysis on combustion analysis tool in which we have

to play with the graphs between

rate of burn v/s crank angle,

mass fraction burn v/s crank angle,

pressure rise v/s crank angle(or volume),

cylinder pressure v/s crank angle(or volume)

Engine designer need to analyse a number of engine configurations and performance

characteristics, including:

Torque and power curves, airflow, volumetric efficiency, fuel consumption, emissions

Steady state or full transient analysis

Variable valve timing and lift

Acoustic analysis of intake and exhaust systems

Manifold and cylinder thermal analysis