## 2 Simulation Model
### Check the Accuracy of the 3D Model in AVL Fire  
To validate the combustion model of the 1 CH 12/13 engine established in AVL Fire, the in-cylinder pressure and the rate of heat release (RoHR) values were selected as the value basis for comparison with the those values in an experiment under the same conditions. The original piston bowl shape with \(D_{b}\) = 100 (mm) and \(T\) = 10 (mm) was used in experiments with the original engine. A schematic diagram of the experimental setup is shown in Figure 6. The devices are installed on the experiment engine and the measurement errors of the test equipment are shown in Table 7. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Mesh Parameters** & \(D_{b}\) **= 67 mm** & \(D_{b}\) **= 74 mm** & \(D_{b}\) **= 80 mm** & \(D_{b}\) **= 90 mm** & \(D_{b}\) **= 100 mm** \\ \hline Average cell size & 0.5 mm & 0.5 mm & 0.5 mm & 0.5 mm & 0.5 mm \\ \hline Number of faces & 47,395 & 47,004 & 31,747 & 27,885 & 29,135 \\ \hline Number of triangle faces & 0 & 0 & 0 & 0 & 0 \\ \hline Number of boundary faces & 885 & 913 & 719 & 679 & 679 \\ \hline Total number of cells & 540,220 & 551,564 & 378,036 & 353,316 & 363,452 \\ \hline \end{tabular}
\end{table} 
Table 6: Mesh parameters used for combustion model studies when the piston was at the bottom dead center (BDC). \begin{table}
\begin{tabular}{c c c c} \hline
**Measuring Devices** & **Name of Measuring Devices** & **Measurement Range** & **Measurement Error** \\ \hline Dynamometer & Electric dynamometer made in Germany, typ. GPFc 13 h & 0–6000 rpm & - \\ \hline Pressure in cylinder chamber & A Piezo sensor of MADI design is connected to the AVL A03 amplifier & 0–20 MPa & \(\pm\)5\% \\ \hline Crankshaft speed & Electronic tachometer & 50–9999 rpm & \(\pm\)0.2 rpm \\ \hline Effective torque & Elastically deformable beam with electrical resistance strain gauge & \\ \hline Fuel pressure in the rail & DMP 304—BD sensor & 0–400 MPa & \(\pm\)0.5\% \\ \hline Mass of fuel consumption per hour & mass fuel flow meter ART-2 & 10–99.99 kg/h & \(\pm\)0.3\% \\ \hline \end{tabular}
\end{table} 
Table 7: The devices on the experiment engine. Figure 5: Meshing in the calculated model in the case of 67 mm and 100 mm diameters: (**a**) \(D_{b}\) = 67 mm; (**b**) \(D_{b}\) = 100 mm. The simulation and experimental results were selected to compare the reliability of the model as follows. First, for the engine operating mode in which the engine speed reached 1400 rpm, the fuel injection pressure was 150 MPa at 23 deg. of crank angle BTDC, and the average effective pressure was limited to 0.9 MPa. With this mode, the maximum pressure value in the combustion chamber was 10.2 MPa and the maximum RoHC value was 48 J/deg. CA. When the injection pressure increased to 300 MPa, the fuel mass per cycle was 45 mg, the intake air pressure was 0.07 MPa, and a RoHR value of 225 J/degree was obtained. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Measuring Devices** & **Name of Measuring Devices** & **Measurement Range** & **Measurement Error** \\ \hline Volume of air per hour & Volumetric flowmeter RG 600-1 & 0–600 m\({}^{3}\)/h & \(\pm\)2\% \\ \hline \multirow{4}{*}{Intake pressure} & Pressure transducer NPP \"Elemer\" & & \\  & AIR-10N-DIV (model 1360) which & & \\  & was connected to the technological & 0–2.4 MPa & \(\pm\)0.5\% \\  & meter-regulator NPP \"Elemer\" & & \\  & IRT5320N & & \\ \hline \multirow{4}{*}{Intake temperature} & Thermal converter NPP \"Elemer\" & & \\  & TS-108 EL/1 which was connected & & \\  & to the technological meter-regulator & & \\  & NPP \"Elemer\" IRT5323N & & \\ \hline \multirow{2}{*}{NO\({}_{\text{x}}\) in exhaust gases} & Gas analyzer NPO \"Eco-Intech\" & 0–1000 rpm & \(\pm\)5\% \\  & Infralight-11P & & \\ \hline \multirow{2}{*}{Smoke of exhaust gases} & Opacimeter NPO \"Eco-Intech\" & & \\  & Infralight-11D & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: _Cont._  
Figure 6: Schematic diagram of the experimental setup.