An experimental investigation on hydrogen fuel injection in intake port and manifold with different EGR rates

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International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2010 International Energy & Environment Foundation. All rights reserved.

225

Figure 3. Schematic view of the experimental setup

Table 1. Hydrogen fuel injector specifications

Make Quantum technologies
Supply Voltage 8 – 16 Volts
Peak Current 4 Amps
Holding Current 1 Amp
Flow Capacity 0.8 g /s @ 483-552 kPa
Working Pressure 103 – 552 kPa
Durability >500 Million cycles
Dynamic range 12:1 Typical
Length 79.8 mm
Diameter (Max) 24.5 mm (Excl connector)
Resistance 2.05 +/-0.25Ω at 20°C
Inductance 3.98 +/- 0.3 mH at 1000Hz typical

The hydrogen from the flame trap was passed to the 2-way valve. One end of the two-way valve was
connected to the pipeline and it was kept away from the working area. This was done to remove the
excess hydrogen in the fuel line during the engine shutoff time. The other end of the two-way valve was
connected to a selector switch, which will permit the supply of hydrogen to either the port fuel injector or
the manifold injector. The port injector was placed in the engine head 13 mm above the intake valve and
the manifold injector was placed at a distance of 100 mm away from the engine head in the intake
manifold. A Quantum make gas injector was used. An electronic control unit (ECU) controlled the
injector opening timing and duration. An infrared detector was used to give the signal to the ECU for the
injector opening. Based on the preset timing and duration the injector was opened for injection and
closed after injection. The injection timing and injection duration was varied within the specified range
by using a knob. The power supply for opening the injector was 4A and for holding the armature to inject
the fuel was 1A. Figure 4 shows the peak and holding current of the hydrogen injector. Based on the
International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2010 International Energy & Environment Foundation. All rights reserved.

226
preset timing the hydrogen flow was taking place and the flow was controlled by using the pressure
regulator and also by using the digital mass flow controller. Figure 5 shows the hydrogen injector
positioning on the cylinder head. Table 2 shows the properties of hydrogen in comparison with diesel.


Figure 4. Peak and hold current for the hydrogen injector



Figure 5. Photographic view of the hydrogen injector position on the cylinder head

4. Instrumentation
The power output of the test engine was measured by an electrical dynamometer. The power capacity of
the dynamometer was 10 kW with a current rating of 43.5 amps. The exhaust gas emission was measured
by using a Qrotech five gas analyzer. The analyzer was capable of measuring carbon monoxide (CO),
carbon dioxide (CO
2
) and unburned hydrocarbon (HC) and oxides of nitrogen (NO
x
). The analyser uses
Non-Dispersive Infra Red (NDIR) principle for the measurement of CO, HC and CO
2
. Smoke emissions
were measured using a Bosch type smoke meter. 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 charge
output of the pressure transducer was amplified by using a kistler charge amplifier. The amplified signals
were correlated with the signal from Kistler crank angle encoder having an accuracy of 0.1 degree crank
angle and these data were stored on a personal computer for analysis. Table 3 gives the engine
specifications. Table 4 gives the instrumentation list. Figure 6 shows the circuit diagram for hydrogen
injector. Figure 7 shows the valve timing diagram for hydrogen operation.
Exhaust
valve
Inlet
valve
Hydrogen
injector
International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
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227
Table 2. Properties of hydrogen in comparison with diesel

Properties Hydrogen (H
2
) Diesel (C
10
H
22
)
Auto Ignition Temperature (K) 858 553
Flammability limits (Volume % in air) 4-75 0.7-5
Molecular Weight (g) 2.016 170
Density of NTP gas (g/cm
3
) 0.0838 0.86
Mass Ratio (kg of air/kg of fuel) 34.4 15.2
Flame Velocity (cm/s) 270 30
Specific gravity 0.091 0.83
Heat of Combustion (kJ/kg) 120.0 42.46
Octane Number (R) 130
Cetane Number 40-60
Boiling Point (K) 20.27 523-630


Figure 6. Circuit diagram for hydrogen injector operation




Figure 7. Valve Timing Diagram for hydrogen injection

TDC - Top Dead Centre
BDC - Bottom Dead Centre
IVO - Inlet Valve Open
IVC - Inlet Valve Close
EVO - Exhaust Valve Open
EVC - Exhaust Valve Close
International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
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228
Table 3. Engine specifications

Make and Model Kirloskar, AV1 make
General 4-Stroke / Vertical
Type Compression Ignition
Number of Cylinder One
Bore 80 mm
Stroke 110 mm
Swept Volume 553 cc
Clearance Volume 36.87 cc
Compression Ratio 16.5: 1
Rated Output 3.7 kW @ 1500 rpm
Rated Speed 1500 rpm
Combustion Chamber Hemispherical Open
Type of Cooling Water Cooled

Table 4. Instrumentation list

S.No Instrument Purpose Make / Model
1 Electrical
Dynamometer
Measurement of power
output
Laurence Scott and elctromotor Ltd.,
Norwich and Manchester, UK,
Capacity-10kW, Current Rating-43
amps.

2 Exhaust Gas
Analyser
Measurement of HC, CO,
CO
2 ,
O
2
and NOx
QRO 401, Qrotech Corporation
Limited, Korea

3 Smoke meter Measurement of Smoke TI diesel tune, 114 smoke density
tester TI Tran service.

4 Pressure Transducer
and Charge Amplifier
Measurement of Cylinder
Pressure
Type 5015A, Kistler Instruments,
Switzerland.

5 Digital mass flow
controller
Measuring the H
2
flow DFC 46 mass flow controller
AALBORG, USA.

6 Hydrogen Leak
Detector
To identify the H
2
leakage Finch Mono II, Portable single gas
monitor, INIFITRON INC, Korea.

5. Estimation of uncertainty
All measurements of physical quantities are subject to uncertainties. Uncertainty analysis was needed to
prove the accuracy of the experiments. In order to have reasonable limits of uncertainty for a computed
value an expression was derived as follows:
Let `R’ be the computed result function of the independent measured variables x
1
, x
2
, x
3
, … x
n
, as per
the relation. R = f (x
1
, x
2
, x
n
) and let error limits for the measured variables or parameters be x
1
, ±
∆n
1
, x
2
± ∆n
2
, , x
a
± ∆x
a
and the error limits for the computed result be R ± ∆R
To get the realistic error limits for the computed result, the principle of root-mean square method was
used to get the magnitude of error given by Holman [19] as;
2/1
22
2
2
2
1
1

⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
∆
∂
∂
++
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
∆
∂
∂
+
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
∆
∂
∂
=∆
n
n
x
x
R
x
x
R
x
x
R
R
(1)

Using equation (1) the uncertainty in the computed values such as brake power, brake thermal efficiency
and fuel flow measurements were estimated. The measured values such as speed, fuel time, voltage and
International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2010 International Energy & Environment Foundation. All rights reserved.

229
current were estimated from their respective uncertainties based on the Gaussian distribution. The
uncertainties in the measured parameters, voltage (∆V) and current (∆I), estimated by the Gaussian
method, are ± 3 V and ± 0.14 A respectively. For fuel time (∆t
r
) and fuel volume (∆t), the uncertainties
are ± 0.2 sec and ± 0.1 sec respectively. For a Speed (N) of 1500 rpm, Voltage (V) of 230 volts, Current
(I) of 14 A, Fuel volume (fx) of 10 cc and brake power (BP) of 3.7 kW the uncertainty in brake power
calculation is;
kW
1000 x η
VI
BP
g
=

BP = f (V, I)
⎥
⎦
⎤
⎢
⎣
⎡
=−==
∂
∂
0.0163
)(0.86x1000
14
)(0.86x1000
I
V
BP

0.2674
)(0.86x1000
230
)(0.86x1000
V
I
BP
===
∂
∂
(2)
⎥
⎥
⎦
⎤
⎢
⎢
⎣
⎡
⎟
⎠
⎞
⎜
⎝
⎛
∂
∂
+
⎟
⎠
⎞
⎜
⎝
⎛
∂
∂
=
2
BP
2
BP
BP
x∆
I
x∆
V
∆ IV


()( )
⎥
⎦
⎤
⎢
⎣
⎡
+=
22
14.02674.030163.0 xx
= 0.185 kW

Therefore, the uncertainty in the brake power from equation (2) is ± 0.185 kW and the uncertainty limits
in the calculation of B.P are 3.6 ± 0.185 kW. Uncertainty in temperature measurement is:± 1 % (T > 150
°C), ± 2 % (150 °C < T < 250 °C), ± 3 % (T < 250 °C). The uncertainties of other operating parameters
are given in Table 5. Appendix 1 shows the mean and standard deviation calculations for 6 samples.

Table 5. Average uncertainties of some measured and calculated parameters

S.No Parameters Uncertainity, %
1 Speed 0.6
2 Temperature 0.3
3 Mass flow ratye of air 0.8
4 Mass flow rate of diesel 1.0
5 Mass flow rate of hydrogen 0.2
6 Oxides of nitrogen 0.6
7 Hydrocarbon 0.7
8 Smoke 0.9
9 Particulate matter 1.1

6. Combustion analysis
The details about combustion stages and events can be determined by analyzing the heat release rates as
determined from cylinder pressure measurements. Analysis of heat release can help to study the
combustion behaviour of the engine.
dQ
hr
= dU + dW + dQ
ht
(3)

Where dQ
hr
is the instantaneous heat release modeled as heat transfer to the working fluid, dU is the
change in internal energy of the working fluid, dW is the work done by the working fluid, and dQ
ht
is
the heat transmitted away from the

working fluid (to the combustion chamber walls)

Change in internal energy is given by;
dU = Cv/R (PdV+VdP)

(4)
Work done by the working fluid dW = pdV. Heat transfer rate to the wall is given by;
dQ
ht
/dt = h A (T
g
-T
w
) (5)

International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
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230
where R is the gas constant, T, P, V are the temperature, pressure and volume respectively, C
v
is the
specific heat at constant volume, h is the heat transfer coefficient, and T
w
is the temperature of the wall:
400 K.
θθγθγ
γ
d
dt
TwTghA
d
dp
V
d
dV
pdQ
sht
)(
1
1
1
−+
−
+
−
=

(6)

Where θ is the crank angle in degrees. γ is the ratio of specific heats of the fuel and air. A
s
is the area in

m
2
through which heat transfer from gas to combustion chamber walls take place. The pressure is
obtained from the cylinder pressure data at corresponding crank angle.

7. Results and discussions
In exhaust gas recirculation technique, part of the exhaust gases from the engine was cooled down to 30°
C and controlled by using a needle valve and admitted along with the intake air in the inlet manifold.
Figure 8 and 9 shows the variation of brake thermal efficiency for port and manifold injection for
different injection timings. Table 6 gives different injection timings used for hydrogen operation. The
optimized conditions in port injection was start of injection at 5º BGTDC, injection duration of 30º CA
with hydrogen flow of 7.5 litres/min while the optimized conditions in manifold injection was start of
injection at GTDC, injection duration of 30º CA with hydrogen flow of 7.5 litres/min (Table 7). The
optimized conditions were chosen based on the improvement in performance and reduction in emissions
which was mentioned in detail by the previous work done by the authors [20]. Values of Figure 8 and 9
are given in appendix 2. Table 9 shows the optimized injection timings for hydrogen operation. After
optimizing the injection timings the hydrogen flow optimization was done which is depicted in Figure 10
and 11. Since NO
X
emission was found to be higher in hydrogen operated engines compared to diesel
operation, exhaust gas recirculation technique was adopted for NO
X
reduction. The EGR flow rate was
varied in steps of 5 % from 5 to 25 % with the above optimized conditions in both port and manifold
injection. The engine was operated in the entire load spectrum from no load to full load at different EGR
flow rates to study the performance, combustion and emission characteristics of the engine along with
the combustion parameters such as peak pressure, heat release rate. Figure 12 and 13 shows the variation
of brake thermal efficiency with load for various EGR flows in port and manifold injection. The
optimized EGR flow percentage was found to be 20 % in both port and manifold injection. Table 10
shows the various EGR flow percentages used in port and manifold injection.



Figure 8. Variation of brake thermal efficiency with brake power for different injection timings and
duration (Values are in Table 8) in port injection
International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
ISSN 2076-2895 (Print), ISSN 2076-2909 (Online) ©2010 International Energy & Environment Foundation. All rights reserved.

231
Table 6. Start of injection timings and injection duration for hydrogen operation in port and manifold
injection

Start of Injection Injection Duration
S.No.
Crank angle (Degrees) Time (ms) Crank angle (Degrees) Time (ms)
1
5° BGTDC
0.555 30 3.33
2
5° BGTDC
0.555 60 6.66
3
5° BGTDC
0.555 90 9.99
4 GTDC 1.110 30 3.33
5 GTDC 1.110 60 6.66
6 GTDC 1.110 90 9.99
7
5° AGTDC
1.665 30 3.33
8
5° AGTDC
1.665 60 6.66
9
5° AGTDC
1.665 90 9.99
10
10° AGTDC
2.220 30 3.33
11
10° AGTDC
2.220 60 6.66
12
10° AGTDC
2.220 90 9.99
13
15° AGTDC
2.775 30 3.33
14
15° AGTDC
2.775 60 6.66
15
15° AGTDC
2.775 90 9.99
16
20° AGTDC
3.330 30 3.33
17
20° AGTDC
3.330 60 6.66
18
20° AGTDC
3.330 90 9.99
19
25° AGTDC
3.885 30 3.33
20
25° AGTDC
3.885 60 6.66
21
25° AGTDC
3.885 90 9.99
22
23° BITDC
Diesel



Table 7. Optimized injection data for port and manifold injection

Injection Parameter Port Injection Manifold Injection
Start of injection of hydrogen
5° BGTDC
GTDC
Hydrogen injection duration
30° crank angle 30° crank angle
Hydrogen flow rate 7.5 litre/min 7.5 litre/min
Exhaust gas Recalculation 20 % EGR 20 % EGR

International Journal of Energy and Environment (IJEE), Volume 1, Issue 2, 2010, pp.221-248
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232


Figure 9. Variation of brake thermal efficiency with brake power for different injection timings and
duration (Values are in Table 8) in manifold injection






Figure 10. Variation of brake thermal efficiency with load for different hydrogen flow rate in port
injection
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233


Figure 11. Variation of brake thermal efficiency with load for different hydrogen flow rate in manifold
injection





Figure 12. Variation of brake thermal efficiency with load for different EGR flow rate in port injection
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234


Figure 13. Variation of brake thermal efficiency with load for different EGR flow rate in manifold
injection

Table 8. EGR flow percentages used in port and manifold injection

Port injection Manifold injection
S.No.
Optimized timings and
duration
EGR flow
percentage, (%)
Optimized timing and
duration
EGR flow
percentage, (%)
1
5º BGTDC, 30º CA,
7.5 litres/min
5
GTDC, 30º CA, 7.5
litres/min
5
2
5º BGTDC, 30º CA,
7.5 litres/min
10
GTDC, 30º CA, 7.5
litres/min
10
3
5º BGTDC, 30º CA,
7.5 litres/min
15
GTDC, 30º CA, 7.5
litres/min
15
4
5º BGTDC, 30º CA,
7.5 litres/min
20
GTDC, 30º CA, 7.5
litres/min
20
5
5º BGTDC, 30º CA,
7.5 litres/min
25
GTDC, 30º CA, 7.5
litres/min
25


7.1 Brake thermal efficiency
Hydrogen combustion exhibits a high cooling loss from the burning gas to the combustion chamber walls
compared to hydrocarbon combustion because of its higher burning velocity and shorter quenching
distance. These two characteristics have strong influence on the thermal efficiency of hydrogen-operated
engines. Indicated thermal efficiency of the engine is given by
( )
wugththi
φηηηη
−×××= 1
(7)

where
i
η
is the indicated thermal efficiency,
th
η
is the theoretical thermal efficiency,
gth
η
is the degree
of constant volume combustion,
u
η
is the combustion efficiency, and
w
φ
is the cooling loss ratio
The brake thermal efficiency for hydrogen combustion is