1. Reactivity Controlled Compression Ignition for Simultaneous
Reduction of Emissions and Fuel Consumption in Diesel Engines
Brijesh P., Chowdhury A., Sreedhara S.
IC Engines and Combustion Laboratory
Indian Institute of Technology Bombay, India

2. Introduction
 Diesel engines are more popular over gasoline engines because of their higher
efficiencies
 Simultaneous reduction of NOx and PM becomes a major challenge
 Significant
reduction
in
NOx
and
PM
was
achieved
with
low temperature combustion (LTC) during our previous work*
 However, PM and CO for optimized LTC run are still higher than the limit
suggested in standards
 In this work, experimental study has been carried out to achieve Reactivity
Controlled Compression Ignition (RCCI) with liquefied petroleum gas (LPG)
 LPG fuel with low reactivity was introduced into the intake manifold while diesel
with high reactivity was injected into the cylinder
 Effects of LPG on engine performance and emissions have also been studied
Brijesh P., Chowdhury A., and Sreedhara S. “Effect of Ultra-Cooled EGR and Retarded Injection Timing on Low Temperature
Combustion in CI Engines.” SAE Technical Paper 2013-01-0321, 2013, doi:10.4271/2013-01-0321.
∗
2

3. Experimental Test Rig
 LPG was introduced into the intake manifold through LPG nozzle (24 holes, 2
mm dia. of each hole)
3

4. Testing Procedure
 All runs, as shown in table, were carried out by varying LPG percentage from 0 to
40% with a step size of 10
 LPG fuel consumption was described as an equivalent of diesel fuel energy
 LPG usage rate was calculated by using the Equation,
LPG (%) =
&
(m
&
mLPG × LCVLPG
LPG
&
× LCVLPG ) + ( mdiesel × LCVdiesel )
× 100
 Run 1 was carried out at an optimized set of input parameters for this engine
obtained through our previous work
Run no.
SOI, CAD aTDC
EGR, %
CR
1
−15
25
18
2
−10
25
18
3
−15
20
18
4
−15
25
16
4

5. Testing Procedure (Contd.)
 Composition and physical properties of LPG was measured by using Gas Chromatograph
with High Resolution Mass Spectrometer (GC-HRMS)
 CHNS elemental analyser was used to measure percentage of carbon, hydrogen,
nitrogen and sulphur in diesel
 Reaction rates of LPG and diesel were calculated by using single step global mechanism
of Westbrook and Dryer and found to be 5.53×108 and 7.91×108 gmol/cm3.s respectively
Measured property of diesel
Value
Specific gravity @ 15oC
0.823
Lower calorific value, MJ/kg
41.23
o
Measured property of LPG
Value
Density @ NTP, kg/m3
1.98
Lower calorific value, MJ/kg
46.48
Auto ignition temperature, oC
460
Viscosity @ 40 C, mm2/s
3.6
Ethane, vol.%
10.38
Auto ignition temperature , oC
210
Propene, vol.%
46.50
Butene, vol.%
21.27
i-Butane, vol.%
3.39
n-Butane, vol.%
17.31
i-Pentane, vol.%
0.24
n-Pentane, vol.%
0.91
Carbon, wt%
82.68
Hydrogen, wt%
13.83
Nitrogen, wt%
3.49
Sulphur, wt%
0
5

6. Effect of LPG on PM and NOx
Run no.
EGR, %
CR
1
−15
25
18
2
 Reduction in PM was observed with increased LPG percentage
SOI, CAD aTDC
−10
25
18
3
−15
20
18
4
−15
25
16
 Effect of LPG was observed significant in runs 1 and 3 compared to other runs
 Minor changes in NOx were found for all runs with lower flow rates of LPG
 However, NOx was reduced considerably with higher LPG percentage
 Runs 1 and 2 were found most favourable for improved NOx-PM trade-off
6

7. Effect of LPG on CO and HC
Run no.
EGR, %
CR
−15
25
18
2
 CO was reduced significantly with the introduction of LPG fuel
SOI, CAD aTDC
1
−10
25
18
3
−15
20
18
4
−15
25
16
 Considerable reduction in CO was achieved till LPG is around 10%
 Further reduction in CO was not observed with increasing percentage of LPG
 A fraction of LPG-air mixture might have been trapped in crevices during the
compression stroke
 As a result, higher HC was observed with higher amount of LPG
7

8. Effect of LPG on BTE
Run no.
SOI, CAD aTDC
EGR, %
CR
1
−15
25
18
2
−10
25
18
3
−15
20
18
4
−15
25
16
 BTE was reduced with increased LPG percentage
 Inducted LPG-air mixture traps in crevices during the compression stroke which in
turn reduces BTE
 Effect of LPG on HC and BTE was observed to be better for run 1. Hence, run 1 is
found optimal
 RCCI achieved with low LPG (∼10%) seems to be optimum for reduction of PM and
8

9. Effect of LPG on Combustion Parameters
Run no.
EGR, %
CR
1
 The combustion phasing of run 1 seems to be optimum for
SOI, CAD aTDC
−15
25
18
2
−10
25
18
3
−15
20
18
4
−15
25
16
reduction of NOx and PM without altering BTE
 The HRR traces of runs 2 and 3 are slightly shifted towards the compression stroke
while run 4 is shifted much towards the expansion stroke as compared with run 1
 Run 1 was chosen to study the effects of LPG on combustion parameters
9

10. Effect of LPG on Combustion Parameters (Contd.)
Run 1
SOI
EGR
25%
CR

-15
18
A reduction in premixed HRR peak and minor increase in ignition delays are
observed with increased LPG
 The presence of LPG slow down the chemical reaction rate during premixed
combustion
 Minor changes in ratio of premixed to diffusion combustion were observed with
increased rate of LPG
 As a result, wider and flatter HRR traces, improved LTC, were observed
10

11. Effect of LPG on Combustion Parameters (Contd.)
Run 1
SOI
-15
EGR
25%
CR
18
 Similar to the HRR traces, in-cylinder pressure traces of run 1 with LPG were also
shifted towards the expansion
 The combustion phases were shifted because of increasing lower reactivity LPG fuel
 Lower peak pressures were found with increasing LPG percentage, hence, reduction
in BTE was observed
11

12. Reduction of Emissions with RCCI
Operating run
(Inj. timing, CR, EGR, LPG)
BTE,
%
CO,
g/kW.hr
HC,
g/kW.hr
NOx,
g/kW.hr
PM,
g/kW.hr
Base run (−27, 18, 0 , 0)
26.61
0.68
0.30
19.43
0.58
Optimized LTC (−15, 18, 25, 0)
28.41
0.52
0.15
2.28
0.33
Optimized RCCI (−15, 18, 25, 10)
28.58
0.26
0.42
2.51
0.23
% Change (RCCI compared to
base)
7.40 (↑)
−61.76 (↓)
40.00 (↑)
% Change (RCCI compared to
LTC)
0.60 (↑)
−50.00 (↓) 180.00 (↑)
−87.10 (↓) −60.34 (↓)
10.10 (↓)
−30.30 (↓)
 RCCI with lower amount of LPG (10%) offers significant reduction in PM and CO with
the acceptable values of HC, BTE and NOx
12

13. Conclusions
 Reactivity controlled compression ignition (RCCI) achieved with low
LPG (∼10%) found to be optimum for further reduction of PM and CO
with the acceptable change in values of HC, NOx and BTE
 Reduction in premixed HRR peak and minor increase in ignition delays
were observed with increasing percentages of LPG
 Improved LTC, flatter and wider HRR traces, were achieved with
optimized RCCI
 Reduction in PM, CO and NOx emissions were observed with increased
LPG percentage
 HC was increased and BTE was decreased with increasing amount of
LPG
13

14. Thank You
14

15. Back Up
15

16. Results of Previous Study
 LTC, simultaneous reduction in NOx and PM, was achieved with the optimum operating
parameters
 Very low values of NOx and HC are achieved for the optimized run and are falling below
the limits stated in standards
 PM and CO for optimized run are still higher than the limit suggested in standards
Bharat State emission standards
16

17. Engine Specifications
Engine type
Four-stroke, water cooled, direct injection VCR engine
Make
Kirloskar Oil Engines Ltd.
Number of cylinders
1
Compression ratio
18:1 to 12:1
Cylinder bore × stroke
87.5 mm × 110 mm
Piston bowl shape
Hemisphere
Piston bowl diameter
52 mm
Maximum power
3.5 kW @ 1500 rpm
Inlet and exhaust valve diameter
34 mm
Inlet valve opens
−364.5 CAD aTDC
Inlet valve closes
−144.5 CAD aTDC
Exhaust valve opens
144.5 CAD aTDC
Exhaust valve closes
364.5 CAD aTDC
Connecting rod length
234 mm
Fuel injection pressure range
180 to 250 bar
Fuel injection timing variation
−27 to −7 CAD aTDC
Number of nozzle holes
3
Nozzle hole diameter
0.288 mm
Nozzle hole L/D ratio
2.78
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18. Specifications of Measuring Devices
Fuel line pressure
Instrument;
Make-Model
Dynamic pressure
transducer; PCB
piezotronics-111A22
Operating
range
Uncertainty
/Accuracy
Relative
error
0−345.5 bar
± 1%
± 1%
Engine speed
Encoder; Kubler-3700
0−6000 rpm
± 5 rpm
± 0.34 %
0−3.5 kg/hr
± 0.5 %
± 0.5 %
0−50 kg/hr
± 1%
± 1%
0−50 kg
± 0.075 kg
± 0.625 %
0−1200°C
± 1°C
± 0.34 %
0−5000 ppm
± 5%
± 5%
0−1000 ppm
± 5%
± 5%
HC
0−2000 ppm
± 5%
± 5%
CO
0−100000 ppm
± 5%
± 5%
−
± 5%
± 5%
Measured parameters
In-cylinder pressure
DP Transmitter;
Yokogawa-EJA110A
Air and EGR mass flow Pressure transmitter;
rate
Wika-SL1
Load cell; SensortronicsEngine load
60001
Intake and exhaust gas Thermocouple (k−type);
temperature
Radix-SS316
Fuel mass flow rate
NO
NO2
Particulate matters
Flue gas analyzer;
Kane-KM9106
MinivolTM TAS; Airmetrics
18

19. Heat release analysis
 The first law of Thermodynamics is applied to control volume,
δ Qhr = dU + δ W + δ Qht .............................................................(1)
Where, δQhr is the heat released by combustion and δQht is the heat transfer
with the chamber walls
 dU and δW can be calculated by using following equations:
dU = mcv dT
mdT =
dU =
1
( pdV + Vdp )
R
{Q pV = mRT }
cv
( pdV + Vdp ) and δ W = pdV ................................................................(2)
R
 Substituting equation (2) into equation (1) with an incremental angle basis:
dQhr dQht cv  dV
dp 
dV
−
= p
+V
÷+ p
dθ
dθ
R  dθ
dθ 
dθ
dQhr dQht
γ
dV
1
dp
−
=
p
+
V
dθ
dθ
γ − 1 dθ γ − 1 dθ
dQnet
γ
dV
1
dp
Net heat release,
=
p
+
V
dθ
γ − 1 dθ γ − 1 dθ
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