“Marine” Diesel Model Study on Different Engine Sizes

50 accuracy, the simulated overall combustion duration is only approximately 75 of the measured overall combustion duration e.g. 15: ϕ 90.sim = 72 [a.u.]. From an engineering point of view, the heavy-duty and marine diesel engine have well-known differences in the range of operating conditions speed, EGR rate, ..., in-cylinder flow field swirl, turbulence, ..., and injection system configurations, fuel properties, .... In order to account for this expert knowledge, an adjusted blind try model with a recalibrated empirical evaporation rate scaling factor β fuel prop- erties, as well as background c g and injection induced c Inj turbulence intensity scal- ing factors flow field and injection system configuration was developed, the results of which are shown in Figure 4.15 b. Other than the ϕ SOC characteristics already matched using the blind try model, the adjusted model is capable of predicting the ϕ 10 , ϕ 50 , and ϕ 90 characteristics as well. In order to visualize the differences between the three models or parameter sets employed optimized, blind try and adjusted, Figure 4.16 shows the comparison of the linear regression statistics c.f. Table A.7. While there are only small variations in correlation coefficients and regression slopes except for the blind try ϕ 90 regression slope, the variations in linear regression intercepts confirm the temporal offset delay of the ϕ 10 , ϕ 50 , and ϕ 90 characteristics for the blind try model. a b Fig. 4.14 Marine Diesel ROHR Model Calibration Verification: a Sequential Operating Conditions Plot, b “1-to-1” Scatter Plot a b Fig. 4.15 Marine Diesel Engine ROHR Model: a Blind Try, b Adjusted Verificat ion Calibrat ion N o rm a li z e d T im e 1 5 ϕ 9 = 1 [ a .u .] -20 20 40 60 80 100 120 140 Marine Operating Conditions [ -] 5 10 15 20 25 ϕ SOC Sim Meas ϕ 10 Sim Meas ϕ 50 Sim Meas ϕ 90 Sim Meas N o rm a li z e d T im e S im u la ti o n [ a .u .] -20 20 40 60 80 100 120 140 Normalized Time Measurement [ a. u. ] -20 20 40 60 80 100 120 140 Calibrat ion Verificat ion Start of Combust ion 10 Energy Release 50 Energy Release 90 Energy Release N o rm a li z e d T im e 1 5 ϕ 9 = 1 [ a .u .] -20 20 40 60 80 100 120 140 Marine Operating Conditions [ -] 5 10 15 20 25 ϕ SOC Sim Meas ϕ 10 Sim Meas ϕ 50 Sim Meas ϕ 90 Sim Meas ϕ SOC Sim Meas ϕ 10 Sim Meas ϕ 50 Sim Meas ϕ 90 Sim Meas N o rm a li z e d T im e 1 5 ϕ 9 = 1 [ a .u .] -20 20 40 60 80 100 120 140 Marine Operating Conditions [ -] 5 10 15 20 25 51 When comparing absolute measures of the marine diesel optimized model statis- tics with the heavy-duty Table 4.2 and automotive Table 4.3 optimized models, the quality of the marine diesel calibration even seems to be superior to the heavy- duty and automotive calibrations. This effect however is put into perspective by considering the limited range of the variations and the number of operating condi- tions employed marine diesel engine: 26 operating conditions without EGR varia- tions.

4.5 Advanced Fuels Survey

An advanced fuels survey is conducted to gain further information about the general applicability of the proposed ROHR model. The heavy-duty diesel engine is there- fore operated at various conditions using reference diesel fuel, two water-in-diesel fuel emulsions 13 and 21 water by mass and a diesel-butylal blend c.f. Table 4.4. Bertola et al. [11] provides further information on the specifications of the fuels used and their effects on engine-out emissions. To recalibrate the ROHR model parameters, the identical EA used for the heavy- duty engine Section 4.4.1 is applied using 20 calibration out of the 40 representa- tive operating conditions given in Table A.3. As both the calibration and verification subsets feature operating conditions with different fuels, two indices for referring the operating conditions are introduced; Arabic numerals to divide calibrationveri- fication, and Roman numerals to divide dieselemulsionsbutylal fuels. The resulting ROHR characteristics ϕ SOC , ϕ 10 , ϕ 50 , and ϕ 90 of this study are shown in calibrationverification order in Figure 4.17 a Arabic numerals, and are also plotted against the decreasing share in diesel fuel in Figure 4.17 c Roman numerals. Comparing the two figures, neither significant differences between cali- bration and verification model quality nor influences due to the type of fuel used a b Fig. 4.16 Marine Engine Comparison of Three Model Parameter Sets: a Pearson’s Correlation Coefficient Linear Regression Slope, b Linear Regression Intercept P e a rs o n s C o rr e la ti o n C o e ff ic ie n t r [ -] L in e a r R e g re ss io n S lo p e m [ -] 0. 5 0. 6 0. 7 0. 8

0. 9 1. 0

1. 1 1. 2 Optimized Blind Try Adj usted ϕ SOC r corr m reg ϕ 50 r corr m reg ϕ 10 r corr m reg ϕ 90 r corr m reg L in e a r R e g re ss io n I n te rc e p t b [ -] -3. 5 -3. 0 -2. 5 -2. 0 -1. 5 -1. 0 -0. 5 0. 0

0. 5 1. 0

1. 5

Optimized Blind Try Adj usted ϕ SOC b reg ϕ 50 b reg ϕ 10 b reg ϕ 90 b reg 52 e.g. diesel-butylal blend ϕ 90 are observed. To visualize the influence of the type of fuel on the deviations between measured and simulated characteristics, the absolute errors Δϕ = ϕ sim - ϕ meas are plotted against fuel type ranked operating conditions REFERENCE DIESEL EMULSION 13 EMULSION 21 BUTYLAL a 60 Lower Heating Value H u [MJkg] 43.14 37.98 34.96 38.25 Stoichiometric AF Ratio Λ st [kgkg] 14.64 12.98 12.38 12.57 Density ρ [kgm 3 ] 819 851 862 829 Water Content m H2O m tot [] 12.89 20.89 Oxygen Content m O2 m tot [] 10.15 15.36 11.98 Tab. 4.4 Advanced Fuels Properties a. Butylal - Acetal C 9 H 20 O 2 , high cetane number 73.7, oxygenate for diesel fuel a b c d Fig. 4.17 Heavy-Duty Advanced Fuels ROHR Model Characteristics: a CalibrationVerification Operating Conditions Plot, b “1-to-1” Scatter Plot, c Fuel Operating Conditions Plot, d Model Errors C ra n k A n g le ϕ [° C A a T D C ] 350 360 370 380 390 400 410 420 Heavy-Duty Advanced Fuels Operating Conditions [-] 5 10 15 20 25 30 35 40 Verificat ion Calibrat ion ϕ SOC Sim Meas ϕ 10 Sim Meas ϕ 50 Sim Meas ϕ 90 Sim Meas ϕ S im u la ti o n [° C A a T D C ] 350 360 370 380 390 400 410 420 ϕ Measurment [° CA aTDC] 350 360 370 380 390 400 410 420 Calibration Verification St art of Combustion 10 Energy Release 50 Energy Release 90 Energy Release C ra n k A n g le ϕ [° C A a T D C ] 350 360 370 380 390 400 410 420 Heavy-Duty Advanced Fuels Operating Conditions [-] V X XV XX XXV XXX XXXV XL B60 E21 E13 Diesel ϕ SOC Sim Meas ϕ 10 Sim Meas ϕ 50 Sim Meas ϕ 90 Sim Meas E rr o rs S im u la ti o n s- M e a su re m e n ts [ ° C A ] -10 -8 -6 -4 -2 2 4 6 8 10 Heavy-Duty Advanced Fuels Operating Conditions [-] V X XV XX XXV XXX XXXV XL B60 E21 E13 Diesel ϕ SOC ϕ 10 ϕ 50 ϕ 90