78
as the reference
1
in this study. The test case simulations are performed using the rates of heat release predicted by the phenomenological model proposed in
Chapter 4 Figure 7.1. An outline of the engine model configuration and simulation program specifica-
tions are given in Table 7.1.
7.2 Simulations
In addition to cylinder pressure and temperature, standard engine characteristics, such as maximum pressure and temperature, maximum pressure location, and
exhaust temperature are used to compare engine process simulation results.
7.2.1 Cylinder Pressure and Temperature
As an initial indication of the practical applicability of the proposed ROHR model, Figure 7.2 shows both the measured and simulated cylinder pressures and ROHRs
left side, as well as the corresponding mean and burned gas temperatures right side for three representative operating conditions specifications are given in
Table 7.2.
1. Figure A.1 compares the measured and experimental cylinder pressures for six out of the 19 oper-
ating conditions used in this study, generally showing negligible variations with maximum devia- tions of less than 2 [bar] or 3.5 .
PROGRAM
GT-Suite™ 6.1
LAYOUT
Multi-cylinder turbocharged DI diesel engine incl. high-pressure EGR-path with inter-cooler
GAS EXCHANGE
1-D gas dynamics entire manifold exhaust
COMBUSTION
Input: measured simulated ROHR “burn rates” Two-zone temperature modeling heat transfer: Woschni
INJECTION
Experimental injection profiles
EMISSIONS
Built-in standard NO
x
and soot models Tab. 7.1
GT-Power Characteristics
c
m
[ms] BMEP
[bar] p
Inj
[bar] SOI
[°CA] EGR
[]
2 5.936
4.95 1400
356 23
5 5.936
4.89 700
350 15
8.699 8.79
1600 352
Tab. 7.2 Selected Operating Conditions Specifications c.f. Figure 7.2
79
From Figure 7.2 a, it can be seen that the discrepancy in peak rate of heat release values influences key process simulation outputs, such as cylinder pressure and
mean temperature errors: approx. 4 of the maximum values, whereas burned gas temperatures and other ROHR characteristics except the maximum rate of pressure
increase are much less affected. Regarding operating condition 5 Figure 7.2 b and 15 Figure 7.2 c, deviations between measured and simulated cylinder pres-
sures and temperatures are smaller than 1 of the maximum values, although the maximum ROHR values and the start of combustion can differ significantly e.g.
operating condition 15.
a
b
c
Fig. 7.2 Comparison of Cylinder Pressures and ROHRs left side, Burned
Gas and Mean Temperatures right side for Three Selected Heavy- Duty Diesel Operating Conditions; a 2, b 5, and c 15
R O
H R
[ °
C A
] 4
8 12
16 20
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
P re
ss u
re p
[b a
r] 10
20 30
40 50
60 70
80
Measurement Simulat ion
2
T e
m p
e ra
tu re
[K ]
500 1000
1500 2000
2500 3000
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
420
T
burn
T
mean
2
Measurement Simulat ion
P re
ss u
re p
[b a
r] 10
20 30
40 50
60 70
80
Measurement Simulat ion
R O
H R
[ °
C A
] 2
4 6
8 10
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
5
T e
m p
e ra
tu re
[K ]
500 1000
1500 2000
2500 3000
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
420
Measurement Simulat ion
T
burn
T
mean
5
R O
H R
[ °
C A
] 2
4 6
8 10
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
P re
ss u
re p
[b a
r]
30 40
50 60
70 80
90 100
110
Measurement Simulat ion
15
T e
m p
e ra
tu re
[K ]
500 1000
1500 2000
2500 3000
Crank Angle ϕ [° CA aTDC]
330 345
360 375
390 405
420
Measurement Simulation
T
burn
T
mean
15
