Week-4 : Basic Calibration of Single cylinder CI-Engine

Aim: Basic Calibration of Single cylinder CI-Engine

Objective :

Explore Tutorial No 1- CI final

1.Compare SI vs CI and list down differences (assignment no 2-SI)

2. Comments on the following parameters

• BSFC
• Exhaust Temperature
• A/F ratios

3.Change MFB 50 and observe impact on performance

Introduction

Difference between SI Engine and CI Engine

Sl No.	SI Engine	CI Engine
1.	SI engine is known as the Spark Ignition engine.	CI engine is known as the Combustion Ignition engine.
2.	The fuel used here is Gasoline or Petrol.	In the CI engine, the fuel used is Diesel.
3.	The compression ratio is 6 to 9.	The compression ratio is high around 15 to 20.
4.	This is light in weight because of the low pressure developed here.	This is heavy in weight because of the high pressure developed here.
5.	Low vibration and Noise here.	Here is more vibration and noise.
6.	SI engine works on the Otto cycle.	CI engine works on the Diesel cycle.
7.	The speed is higher in the SI engine.	The speed is low in the CI engine.
8.	Thermal efficiency is low or average.	Thermal efficiency is high.
9.	Air and fuel are used during the intake process	but here only air is used during the intake process.
10.	This is kind of cheaper in price.	This we get higher in price.
11.	This is also called a constant volume cycle.	This is called a constant pressure cycle.
12.	Petrol fuel has a high self-ignition temperature.	Diesel fuel has a self-ignition temperature but it’s low.
13.	Knocking takes place at the end of the combustion.	Knocking takes place at the beginning of the combustion.
14.	A homogenous mixture of fuel.	A heterogeneous mixture of fuel.
15.	Petrol fuel is used in aerospace and automobiles.	Diese fuel used in heavy vehicles such as lorries, buses, and trucks, more.
16.	SI engine fitted with carburetor and spark plug.	CI engine fitted with injection or fuel injected pump.
17.	Here ignition of air-fuel mixtures takes place by an electric spark produced by a spark plug.	But here air-fuel take place by injection of fuel into the hot compressed air.
18.	Temperature range here 250 to 300-degree celsius.	In CI engine Temperature 600 to 700 degree celsius.
19.	In the SI engine, Specific fuel consumption is more.	Here in the CI engine, the specific fuel consumption is less.

Brake-specific fuel consumption

(BSFC) is a measure of the fuel efficiency of any prime mover that burns fuel and produces rotational, or shaft power. It is typically used for comparing the efficiency of internal combustion engines with a shaft output. It is the rate of fuel consumption divided by the power produced.

Exhaust temperature

Diesel engine exhaust gases vary with speed and load. High loads and high speeds result in the highest temperatures. Generally, temperatures of 500–700°C (932–1293°F) are produced in the exhaust gases from diesel-cycle engines at 100% load to 200–300°C (392–572°F) with no load.

A/F ratio

Thermal engines use fuel and oxygen (from the air) to produce energy through combustion. To guarantee the combustion process, certain quantities of fuel and air need to be supplied in the combustion chamber. Complete combustion takes place when all the fuel is burned, in the exhaust gas there will be no quantities of unburned fuel. Air-fuel ratio (AF or AFR) is the ratio between the mass of air m_a and mass fuel m_f, used by the engine when running:

The inverse ratio is called fuel-air ratio (FA or FAR) and it’s calculated as:

The ideal (theoretical) air-fuel ratio, for complete combustion, is called the stoichiometric air-fuel ratio. For a gasoline (petrol) engine, the stoichiometric air-fuel ratio is around 14.7:1. This means that, in order to burn completely 1 kg of fuel, we need 14.7 kg of air. The combustion is possible even if the AFR is different than stoichiometric. For the combustion process to take place in a gasoline engine, the minimum AFR is around 6:1 and the maximum can go up to 20:1.

Engine model

BSFC : 221.3 g/kW-h

A/F RATIO : 19.18

EXHAUST TEMPERATURE : 1045 K

Case set up for MFB 50