Download chapter 6 experimental apparatus and procedures

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CHAPTER 6
EXPERIMENTAL APPARATUS AND PROCEDURES
6.1
INTRODUCTION
This chapter describes the about the experimental setup used for
conducting experiments, procedures, specification of the engine and the
measurement devices employed are clearly presented.
6.2
EXPERIMENTAL APPARATUS
6.2.1
Engine Test Setup
The schematic diagram of the experimental setup is shown in Fig.
6.1. It consists of single cylinder, four stroke diesel engines with data
acquisition system. It has eddy current dynamometer for loading. The setup is
provided with necessary instruments for combustion pressure and crank-angle
measurements. The Kistler piezoelectric air-cooled pressure transducer and
360 pulse count (ppr) crank angle encoder which measure the combustion
pressure and the corresponding crank angle, respectively, are mounted on the
engine cylinder head. The pressure transmitter type 6613CA contains a
piezoelectric sensor and an integrated charge amplifier. These signals are
interfaced to a computer through engine indicator for pressure-volume
diagrams. Provision is also made for interfacing airflow, fuel flow,
temperatures, and load measurement. The setup has a stand-alone panel box
consisting of two fuel tanks for multi-fuel test, manometer reading, fuel
measuring unit, transmitters for air and fuel flow measurements, process
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indicator, and engine indicator. Rota meters are provided for measurement of
engine cooling water and calorimeter cooling water. The setup enables the
study of diesel engine performances and combustion parameters. Lab viewbased engine performance analysis software package "Engine test expresses
V5.75" provides for online performance evaluation. A computerized cylinder
in line pressure measurement is provided to measure the combustion pressure
(Muralidharan and Vasudevan, 2011).
Figure 6.1 Schematic diagram of the experimental setup
6.2.2
Variable Compression Ratio
Conventional gasoline engines operate at fixed compression a ratio,
which is set low enough to prevent premature ignition of the fuel, or “knock,”
at high power levels under fast accelerations, high speeds, or heavy loads.
Most of the time, the gasoline engine operates at relatively low power levels
under slow accelerations, lower speed and light loads. If the compression
ratios are increased at low-power operation, gasoline engines could achieve
higher fuel efficiency (Kumaran et al. 2011).
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Figure 6.2 Compression ratios changing lever for VCR engine setup
Variable compression ratios are the technology to adjust internal
combustion engine cylinder head so that the volume of a cylinder is increased.
Figure 6.2 shows the compression ratio changing lever. In this setup the
compression ratios can be varied from 7:1 to 20:1 and the maximum cylinder
head varies from 0 to 21mm. This is done to increase fuel efficiency while
varying the loads. Higher loads require lower ratios be more efficient and
vice-versa. Variable compression ratio engines allow for the volume above
the piston at 'Top dead centre' to be changed. For automotive use, this needs
to be done dynamically in response to the load and driving demands. The
compression ratios are varied by changing the clearance volume. As the bore
and the head of the engine is raised and lowered, the clearance volume is
changed, resulting in the change in the compression ratios. As a result,
volumetric efficiency improves, which brings about better combustion.
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6.2.3
Engine Specification
The engine setup details and load ranges of VCR engine is given in
Table 6.1. Also, the specification of the variable compression ratio engine
shows this table.
Table 6.1, The specification of the variable compression ratio engine
Type
No. of strokes
Rated Power
Kirloskar, single cylinder, inline, vertical, water
cooling
Four
3.7 kW
Bore/Stroke
Rated RPM
Compression ratio
Injection timing
Type of ignition
80mm/110mm
1500
7:1 to 20:1
23 º before top dead center
Compression ignition
Method of loading
Eddy current dynamometer
Type
Load measurement method
Ranges
Power Mag
Strain gauge
0-50kgs
Cooling
Max. Speed
Air cooling
3000 rev.
/min.
Direct
Coupling type
Method of starting
Manual crank start
Injection opening
pressure
Method of water flow
measurement
200 bar (std.)
Combustion pressure
measurements
Type - Acrylic body rotameter
Ranges - 40-400 lph for engine cooling
10-100 lph for calorimeter cooling
Make - Kistler
Model - Piezoelectric
Range of pressure sensor - 0-100 bar
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6.3
MEASUREMENT DEVICES FOR ENGINE SETUP
The following measurement devices are used in the engine setup.
6.3.1
Air Flow Rate Measurement Method
Differential pressure sensor is used to measure the pressure
difference between the orifice plates. The differential pressure sensor gives a
proportional output with respect to the difference in pressure. The range of
this equipment is 0-99 m3/hr.
6.3.2
Fuel Flow Rate Measurement Method
In the engine tests, fuel consumption is measured as a mass flow
per unit time and it is denoted by mf. The more useful parameter of fuel flow
measurement is specific fuel consumption. The fuel consumption is measured
by using optical sensors. The optical sensors are capable of detecting any
liquid and give an output in the form of signal. The system consists of two
burette fitted with two optical sensors, one at the high level and another at the
low level. As the liquid passes through the high level optical sensor, the
sensor gives a signal to the computer to start the time. Once the liquid reaches
the lower level optical sensor, the sensor gives a signal to the computer to
stop the time and refill the burette. The time taken in the consumption of fuel
for a fixed volume is calculated. Also, the range of fuel flow measurement
sensor is based on the engine specification.
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6.3.3
Speed Measurement Method
A non-contact PNP sensor is used to measure the engine rpm.
APNP sensor gives a pulse output for each revolution of the crankshaft. The
frequency of pulses is converted into voltage output and connected to the
computer. The range of speed measurement sensor is 0-9999 rpm.
6.3.4
Water Flow Measurement Method
Acrylic body rotameter is used to measure the water flow
measurement method. Here, two types of rotameter are used for engine
cooling and calorimeter cooling. The range of engine cooling is 40-400 lph
and the range of calorimeter cooling is 10-100 lph.
6.3.5
Torque or Load Measurement Method
The range of load measurement is 0-50 kg and method of loading is
eddy current dynamometer. Torque is measured using load cell transducer.
The transducer has a strain gauge base. The output of the load cell is
connected to the load cell transmitter. The output of the load cell transmitter is
connected to the UBS port through interface card.
6.3.6
Measurement of Temperature at Different Points
The temperature is measured at seven different points in the VCR
engine setup. All are ‘K’ type thermometers. The thermometer is placed at
different locations and temperature is measured, thus for calorimeter water
inlet and outlet temperature, the range of this temperature is 300 ºC. For
exhaust gas inlet and outlet temperature, the range of this temperature is
0-1500 ºC. For engine cooling water inlet and outlet temperature, the range of
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this temperature is 0-300 ºC. Ambient air temperature and range of the
temperature is 0-300 ºC. All the measured parameters from the sensor are
connected to the computer.
6.3.7
Cylinder Pressure Measurement
It consists of very precise and robust pressure sensor with an in-line
charge amplifier for combustion pressure measurement application. The
sensor will have almost an unlimited lifetime for combustion pressure
measurement application. Optimized piezoelectric sensor for continuous
cylinder pressure monitoring of engines sensor measurement is used. The
sensor is connected to the charge amplifier with a robust integrated high
temperature Viton cable. The good linearity and repeatable measurements are
recorded over a long period of time. The sealing takes place at the shoulder of
adapter that requires a flat and smooth machined sealing area. The charge
amplifier accepts a power supply between 7-32 VCD and has a range of 0-100
bar (40mV/ brand works with a time constant of 5 s).
6.3.8
Measurement of Crank Angle Encoder
The crank angle encoder contains a precision marker disk with a
trigger mark and 360 angle marks which are scanned by a transmission
photoelectric cell. The disk and the photoelectric cell are encased in a dustproof housing. It is powered by a 24 VDC power supply and supplies one
corresponding analog output between 0 and n dash; 360 degrees.
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Table 6.2, The details of crank angle encoder
Supply
24V DC (Regulated ± 15%)
Output
0 –8V
Resolution
2048 Steps (11-Bit)
Max Loop Resistance
Body
Machined Aluminum body with anodized
finish
Shaft
Mounting
6.3.9
Stainless steel (SS-304) of 10mm dia x 22mm
Length
Servo/Face is mounted with 3 screws of the
M4,
120 degrees apart on a PCD of 50,60mm dia
Measurement of Analog Input / Output
The data acquisition card has 14 external analog inputs. AIN0-
AIN3 are available on screw terminals and also on the DN37 connector. All
14 analog inputs are available on the DB37 connector. Each analog input can
be configured individually as unipolar or bipolar. Analog input resolution is
12 bits at maximum speed, increasing up to 16 bits at slower speeds (2.7 ms
conversion time)
Commands/response analog input reads typically take 1.2+ms
depending on number of channels and communication configurations.
Hardware timed input streaming has a maximum rate that varies with
resolution from 250 samples/s at 16 bit to 50+ K samples/s at 12 bits.
The data acquisition card has two analog outputs (DAC0 and
DAC1) that are available both are screw terminals and the DB37 connector.
Each analog output can be set to a voltage between 0 to 4.9 volts with 12 bits
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of resolution. The analog outputs are based on true voltage reference. The
analog outputs are updated in command/ response mode, with a typical update
time of 1.2-4.0 ms depending on communications configurations.
6.3.10
Measurement of Digital Input / Output
The data acquisition card has 23 input/output channels which can
be individually configured as input, output-high, or output low. Eight of these
lines, called flexible digital I/O (FIO) and can be software-configured as up to
6 times to two counters.
The first four FIO available are screw terminals and the DB37
connector. All 8 FIO and 3 MIO are available on the DB37 connector, and
8 EIO and 3 CIO are available on the DB37 connector.
The command/response reads/writes typically take 1.2 – 4.0 ms
depending on communication configurations. The digital inputs can also be
read in a hardware timed input stream where up to 16 inputs count as a single
stream channel.
6.4
EXHAUST GAS EMISSIONS MEASUREMENT SETUP
6.4.1
Measurements of Five Gas Analyzer
As shown in Fig. 6.3, A Multi-gas analyzer (NETEL make, NPM-
MGA-2 model) was used for measuring the exhaust gas emissions. The probe
of the analyzer is inserted into the exhaust pipe of the engine before taking the
measurements. After the engine is stabilized in working condition, the exhaust
emissions are measured. Using this analyzer, carbon-monoxide (CO),
hydrocarbon (HC), carbon-dioxide (CO2), nitrogen oxide (NOx) and oxygen
(O2) have been measured for different types of biodiesels, pre-heated palm oil
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blends and standard diesel for different compression ratios. The emission
results of all test fuels are within the acceptable limits. The various Indian
standards used for emission analysis are given in Table 6.3. Also, Table 6.4
shows the make, model, range, and resolution of the exhaust gas emissions.
Table 6.3 The various Indian standards used for emission analysis
Elements
Indian Standard
Carbon-dioxide
IS 13270:1992 (reaffirmed 1999)
Carbon-monoxide
IS 11293:1992
Hydrocarbon
---
Nitrogen oxides
IS 11255 – (PART 7) – 2005
Table 6.4
The make, model, range and resolution of the exhaust gas
emissions analyzer
Gas analyzer Make
NETEL
Gas analyzer Model
NPM-MGA-2
Emissions
Range
Resolution
CO
0-10 %
0.01%
CO2
0-20 %
0.1%
HC
0-2000 ppm
1 ppm
O2
0-25%
0.01%
NOx
0-10000 ppm
1 ppm
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Figure 6.3 Exhaust gas analyzer used in VCR engine
Figure 6.4 View for exhaust emission measurement
6.4.2
Measurement of Smoke
Also, the smoke emission from the test engine was measured in this
study. In order to measure smoke emission, an opacity type smoke meter was
used. The exhaust gas pipe from the test engine was connected to the smoke
meter and then smoke emission results were recorded. The smoke meter
specification is as shown in Table 6.5.
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Table 6.5 Smoke meter specifications
Model
MEXA-130S(Horiba Co., Ltd)
Measuring component
Smoke from diesel engine
Measuring principle
Opacity method
Measurement ranges
Opacity 0-100%
K value
0-10.00 1/m
Sampling method
Partial flow
Input/output
Digital
Power source
AC100 V 50/60 Hz
6.5
EXPERIMENTAL PROCEDURES
The variable compression ratio engine setup is shown in figure 6.5.
The engine is started by using diesel. The engine reaches the stable operating
conditions when applied with part- and full-load. To cool the engine socket,
water is used as cooling medium and the flow rate is maintained as 90 ml/s
and the cooling water temperature is stabilized at 40º C. The tests are
conducted at the rate of constant speed of 1500 rpm. In every test, all the
performance and combustion parameters are measured. From the initial
measurement, specific fuel consumption and brake thermal efficiency with
respect to compression ratios 17:1, 18:1, and 19:1 for different blends are
calculated and recorded. The combustion and emission levels are also
processed and stored in computers for further processing of the results. The
same procedure is repeated for all the tested fuels. Table 6.6 shows the
accuracy of the measurements and the uncertainty of the calculated results of
various parameters.
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Figure 6.5
Experimental setup for computerized variable compression
ratio engine test rig
Table 6.6
The accuracy of the measurements and the uncertainty of
the calculated results
Measurements
Accuracy
Engine speed
± 30 rpm
Temperatures
± 1ºC
Carbon-monoxide
± 0.03 %
Hydrocarbon
± 10 ppm
Carbon-dioxide
± 0.04%
Time
± 0.5%
Calculated results
Uncertainty
Power
± 2.2%
Specific fuel consumption
± 2.2%
Crank angle encoder
± 0.5º CA
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6.6
SUMMARY
The selected biodiesels and pre-heated oil is tested and the
following conclusions can be drawn
Engine test experiments were conducted on a DI diesel engine by
fueling these four kinds of methyl ester fuels, pre-heated palm oil and PBDF.
1.
The specifications of test engine, equipment and measurement
devices are discussed in this chapter. Also, the detailed
explanation of experimental procedure and, range and
accuracy of equipment are expressed.
2.
Also, the detailed specification of exhaust gas emission
analyzer and smoke meter are expressed in this chapter.