# A Review of Road Design for Wind Farms in China
## 4 Research on Profile Design
\tag{13}\]  
In the above formula:  
\(a_{\text{Imax}}\)--The maximum gradient angle that can be overcome by the lowest gear;  
\(D_{\text{Imax}}\)--The maximum dynamic factor of the lowest gear;  
\(\lambda\)--The altitude load correction factor for the dynamic factor;  
\(f\)--Rolling resistance coefficient;  
\(i_{\text{max}}\)--Maximum climbing. Calculation of traction force on automobile drive shaft and resistance during driving  
1. Tractive force \[T=\frac{M_{\text{k}}}{r}=\frac{M\gamma\eta_{T}}{r}\] (14)  
\(T\)--Tractive force \((\text{N})\);  
\(M_{\text{k}}\)--Automobile driving wheel torque;  
\(M\)--Engine crankshaft torque \((\text{N}\cdot\text{m})\);  
\(\gamma\)--Overall gear ratio;  
\(\eta_{T}\)--Mechanical efficiency of the transmission system;  
\(r\)--Wheel working radius \((\text{m})\). 2. Air resistance \[R_{\text{W}}=\frac{1}{2}KA\rho v^{2}=\frac{KAV^{2}}{21.15}\] (15)  
\(R_{\text{W}}\)--air resistance \((N)\);  
\(K\)--Air drag coefficient;  
\(A\)--Vehicle windward area;  
\(\rho\)--Air density;  
\(v\)--Relative speed of the vehicle and air \((\text{m}/\text{s})\);  
\(V\)--Relative speed of the vehicle and air \((\text{km}/\text{h})\). \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Wind Farm Altitude/m**} & \multicolumn{2}{c}{**Maximum Gradient Angle \(\alpha_{\text{Imax}}/(^{\circ})\)**} & \multicolumn{2}{c}{**Maximum Climbing \(i_{\text{max}}\)/\%**} \\ \cline{2-7}  & **1500 kW** & **2000 kW** & **3000 kW** & **1500 kW** & **2000 kW** & **3000 kW** \\ \hline
0–500 & 8.749 & 5.537 & 3.31 & 15.4 & 9.7 & 5.8 \\
500–1000 & 8.054 & 5.037 & 2.943 & 14.2 & 8.8 & 5.1 \\
1000–1500 & 7.395 & 4.562 & 2.595 & 13.0 & 8.0 & 4.5 \\
1500–2000 & 6.768 & 4.111 & 2.264 & 11.9 & 7.2 & 4.0 \\
2000–2500 & 6.174 & 3.683 & 1.950 & 10.8 & 6.4 & 3.4 \\
2500–3000 & 5.611 & 3.276 & 1.651 & 9.8 & 5.7 & 2.9 \\ \hline \end{tabular}
\end{table} 
Table 3: Maximum climbing angle and maximum climbing value of typical vehicle models used by units of different levels. 3. Road resistance \[R_{R}=R_{f}+R_{i}=Gf\cos\alpha+G\sin\alpha=G(f\cos\alpha+\sin\alpha)\] (16) \(R_{R}\)--Road resistance \((N)\); \(R_{f}\)--Rolling resistance \((N)\); \(R_{i}\)--Slope resistance \((N)\); \(G\)--Total vehicle gravity \((N)\); \(f\)--Rolling resistance coefficient; \(\alpha\)--Slope angle of the wind farm road. (4) Inertial drag \[R_{I}=\delta\frac{G}{g}a\] (17) \(R_{I}\)--Inertial drag \((\mathrm{N})\); \(\delta\)--Inertial force coefficient; \(G\)--Total vehicle gravity \((\mathrm{N})\); \(g\)--Gravitational acceleration \((\mathrm{m}/\mathrm{s}^{2})\); \(a\)--Vehicle acceleration \((\mathrm{m}/\mathrm{s}^{2})\). For the fan transport road project, due to the super length of transport vehicles, in the design of the vertical section and for the sake of driving safety, the minimum radius and minimum length of the vertical curve at the gradient change of the road longitudinal slope should be emphatically considered. [PERSON] (2018) and others studied and obtained the calculation model of the minimum radius and length of the vertical curve in view of the problems caused by different vertical curve linearity during the vehicle driving process. It mainly ensures that the hanging part of the flailing tail of the blade will not scratch the ground. The calculation model of the concave vertical curve is shown in Formula (18). When designing the convex vertical curve, it mainly meets the rear elevation limit requirements of the semi-trailer and mitigates the impact. The determination of the length of the vertical curve mainly considers that the driving time is not too short and determines the applicable range of gradient. The calculation model of the convex vertical curve is shown in Formula (19). Finally, it is concluded that different design speeds and slope difference ranges use different vertical curve radii and minimum lengths, as shown in Table 4, which provides a reference for relevant design companies. \[\left\{