chapter 3 experimental set-up, instrumentation and...

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CHAPTER 3

EXPERIMENTAL SET-UP, INSTRUMENTATION AND

TECHNIQUES

3.1 GENERAL

In this chapter, the experimental details and procedure to evaluate

the performance, emission and combustion parameters of a DI diesel engine

using WPO and DWPO adopting different techniques are discussed.

3.2 EXPERIMENTAL SET UP

In the present work, tests were conducted on a single cylinder, air-

cooled, four stroke, vertical, naturally aspirated, stationary, D.I diesel engine

with a displacement volume of 661.5 cc, compression ratio of 16.5:1,

developing 4.4 kW of power at 1500 rpm. The detailed technical

specifications of the engine are given in Appendix 1.

The test facility includes the following arrangements/ instruments/

analysers:

1. Test engine coupled to an alternator and an electrical loading

device.

2. Diesel flow measurement using a burette and stopwatch

arrangement.

3. Piezo-electric pressure pick up for in -cylinder pressure

measurement.

4. Thermocouples for the measurement of temperature of

exhaust gases, cooling water, EGR system and intake charge.

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5. Computer based digital data acquisition system for analysing

the pressure crank angle data and to obtain the heat release rate.

6. Smoke meter for measuring the exhaust smoke.

7. Exhaust gas analyser for measuring HC, CO, NOX, and CO2

emissions.

8. Exhaust Gas Recirculation unit.

9. Flow meter for maintaining EGR flow rates.

The engine was modified to operate with waste plastic oil by

changing the injection timing, provision for exhaust gas recirculation and for

supplying the fuel at different nozzle opening pressures. Figure 3.1 shows the

schematic diagram of the experimental set-up.

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13

9

8

1 2

7

6 5

4

10

12

11

3 15

1. Diesel engine 9. TDC position sensor

2. Electrical dynamometer 10. Charge amplifier

3. Dynamometer controls 11. TDC amplifier circuit

4. Air box 12. Analog /Digital converter card

5. U – Tube manometer 13. Computer

6. Fuel tank 14. Exhaust gas analyzer

7. Fuel measurement flask 15. AVL smoke meter

8. Pressure pickup

Figure 3.1 Schematic diagram of the experimental setup

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The photographic view of the experimental setup is shown in

Figure 3.2.

Figure 3.2 Photographic view of the experimental setup

3.3 DYNAMOMETER

An electrical swinging field dynamometer was used for measuring

the brake power of the engine. The electrical dynamometer consists of a

5 kVA AC alternator (220V, 1500rpm) mounted on the bearings and on the

rigid frame for the swinging field type loading. The output power was directly

obtained by measuring the reaction torque. Reaction force (torque) was

measured by using a strain gauge type load cell. A water rheostat was used to

dissipate the power generated. A panel board consisting of ammeter,

voltmeter, switches and fuse, load cell indicator, digital rpm readout etc,

was also provided. The specifications of the dynamometer are given in

Appendix 2.

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3.4 EMISSION MEASUREMENTS

3.4.1 HC, CO, CO2 Measurements

Carbon monoxide, carbon dioxide and hydrocarbon were measured

using a Qrotech (QRO-401) Non-Dispersive Infra Red (NDIR) exhaust gas

analyser. The analyser works on the principle of selective absorption of the

infrared energy of a particular wavelength peculiar to a certain gas, which will

be absorbed by that gas. The specifications of exhaust gas analyser are given

in Appendix 3.

3.4.2 Measurement of Smoke

Smoke emissions were measured using a standard BOSCH type

smoke meter. Gas samples were trapped on a filter paper for 30 seconds and

the filtered smoke was evaluated by using a photocell reflector, which gives a

smoke emission from 0 to 10. The value 0 indicates the absence of smoke and

10 indicates the full smoke. The value intermediate from 0 to 10 indicates the

proportionate concentration of smoke intensity. The specifications of smoke

meter are given in Appendix 4.

3.4.3 NOX Measurement

NO constitutes about 90 % of the total oxides of nitrogen. The

exhaust gas sample was passed through a glass bottle to remove the moisture

before it was analysed. The NOx emission was measured by using a Qrotech

exhaust gas analyser.

3.5 COMBUSTION CHAMBER PRESSURE

Engine cylinder pressure is the basic parameter, necessary for any

type of engine combustion analysis. Cylinder pressure changes with crank

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angle because of cylinder volume change, combustion, heat transfer to the

walls, flow in and out of the crevice regions and leakage. The combustion rate

information can be obtained from accurate pressure data.

3.5.1 Cylinder Pressure Measurement

The engine cylinder pressure was measured using a water-cooled

Kistler piezo electric pressure sensor, which has a sensitivity of 15.2 pC/bar.

The pressure transducer was located in a hole drilled through the cylinder

head into the combustion chamber. The sensing element consists of a metal

diaphragm, which deflects under pressure. This deflection was converted into

voltage, which is proportional to pressure. The charge output of the pressure

transducer is amplified by using a Kistler charge amplifier. The amplified

signals were correlated with the signal from crank angle encoder and the data

were stored on a personal computer for analysis. The specifications of

pressure transducer are given in Appendix 5. With the help of cylinder

pressure measurements, the heat release rate was determined as given in

Appendix 6.

3.5.2 Charge Amplifier

The charge amplifier is used to convert the electrical charge output

of the pressure transducer into proportional voltage. It consists of an

operational amplifier with a feedback through a variable capacitor, which is

changed according to the range selected. This combination acts as an

integrator for the current inputs from the transducer and the integral of the

change variation appears as the output voltage. This voltage output is

proportional to the total charge at any instant. To ensure the accuracy of the

pressure measurement, the charge amplifier is allowed to warm up for four

hours before the measurements are taken. The specifications of charge

amplifier are given in Appendix 7.

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3.6 EXHAUST GAS RECIRCULATION SYSTEM

Exhaust gases from the engine were bypassed, regulated and cooled

by using a counter flow type heat exchanger in the EGR unit. The flow rate of

cooling water circulated through the EGR system was varied in such a way

that the cooled exhaust gas temperature was maintained around 30 C. The

cooled exhaust gas was allowed to pass through a filtering device to remove

the soot and particulate matter from the exhaust gas. The EGR flow rate was

determined by measuring the CO2 concentration in the exhaust gas.

ENGINEDYNAMO

METER

EXHAUST PIPE

HEAT

EXCHANGER

GAS

REGULATOREXHAUST

GAS IN

INLET

AIR

DIESEL

EXHAUST

GAS OUTCOOLANT

WATER IN

COOLANT

WATER OUT

Figure 3.3 Schematic diagram of the EGR unit

The EGR percentage was calculated from the ratio of CO2

concentration present in the intake manifold to the CO2 concentration present

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in the exhaust gas. The flow rate of EGR was increased until the necessary

CO2 concentration in the intake manifold was attained. The schematic

diagram and the photographic view of the EGR unit are shown in Figure 3.3

and 3.4 respectively.

Figure 3.4 Photographic view of the EGR unit

3.7 EXPERIMENTAL PROCEDURE

All the tests were conducted at the rated speed of 1500 rpm. All the

readings were taken only after the engine attained the stable condition. All the

instruments were periodically calibrated. The engine output was varied

insteps of 20% from no load to full load in the normal operation of the engine.

At each load, the fuel flow rate, exhaust gas temperature, emission of carbon

monoxide, hydrocarbon, oxides of nitrogen and smoke readings were

recorded. The pressure crank angle data for 100 consecutive cycles were also

recorded by using the data acquisition system and a personal computer. The

data were processed to get the average pressure crank angle variation.

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3.8 METHODOLOGY

The methodology adopted in the experimental work is given below,

Initial tests were conducted with diesel at the rated speed and

variable load conditions to compare the performance, emission

and combustion characteristics of the engine.

Tests were conducted with different blends of waste plastic oil

with diesel to study the effects of blending waste plastic oil on

the performance, emission and combustion characteristics of the

engine.

Tests were conducted with waste plastic oil only at different

retarded injection timings (20obTDC, 17

obTDC and 14

obTDC)

to study the performance, emission and combustion

characteristics of the engine.

Experiments were conducted with exhaust gas recirculation

(0%, 10 % and 20% on volume basis) with optimised injection

timing (17obTDC) using WPO to study the performance,

emission and combustion characteristics of the engine.

In the next phase, the engine was operated in WPO with

different nozzle opening pressure (200 bar, 210 bar and 220 bar)

with optimised injection timing (17obTDC) and optimised 20%

EGR to study the performance, emission and combustion


Tests were also conducted with DWPO to study the

performance, emission and combustion characteristics of the

engine.

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Experiments were conducted with retarded injection timing

(20obTDC, 17

obTDC and 14

obTDC) with 20% by volume

exhaust gas recirculation using DWPO to study the

performance, emission and combustion characteristics of the

engine.

Finally, the engine was operated with DWPO using different

nozzle opening pressure (200 bar, 210 bar and 220bar) with

optimised injection timing (17obTDC) and optimised 20% EGR

to study the performance, emission and combustion


The test matrix indicating all the experiments conducted is given in

Table 3.1.

Table 3.1 Test Matrix

Variables Fuel Requirement

Normal operation

Maintained constant load at 20%, 40%,

60%, 80% and 100% at the rated speed

of 1500 rpm

Diesel Baseline reading for

comparison

Normal operation with blends



of 1500 rpm

WPO

+

Diesel

Evaluation of performance,

emissions and combustion

parameters and selection of

an optimum blend

Normal operation with exhaust gas recirculation (EGR)



of 1500 rpm. EGR flow rate was varied

from 0% to 20% at optimised retarded

injection timing (17obTDC).

WPO Evaluation of performance,


parameters and optimisation

of EGR flow rate.

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Table 3.1 (Continued)

Variables Fuel Requirement

Normal operation with varied nozzle opening pressure



of 1500 rpm. Nozzle opening pressure

was varied from 200 bar to 220 bar at

optimised retarded injection timing (17o

bTDC) and 20% EGR.

WPO Evaluation of performance,



of nozzle opening pressure.

Normal operation with DWPO



of 1500 rpm.

DWPO+

Diesel

Evaluation of performance,


parameters.

Normal operation with exhaust gas recirulation (EGR)



of 1500 rpm. Injection timing was

retarded upto 14obTDC at optimised

EGR flow rate (20% EGR).

DWPO Optimisation of retarded

injection timing with EGR

flow rate. Evaluation of

performance, emissions and

combustion parameters.

Normal operation with varied nozzle opening pressure



of 1500 rpm. Nozzle opening pressure

was varied from 200 bar to 220 bar at

optimised retarded injection timing (17o

bTDC) and 20% EGR.

DWPO Evaluation of performance,



of nozzle opening pressure.

Error and uncertainty analysis were carried out for the measured

parameters and is given in Appendix 8.

chapter 3 experimental set-up, instrumentation and...

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