# Effects of Valve, Armature, and Armature Pin Guidance on Diesel Injector Performance
## 3 Results and Discussion
### Injector Function Results  
The measurements of sub-parts and the functional tests of injectors were finalized. The results of these injector function measurements, which correspond to the measurements of the sub-parts, are presented in Figure 11. Additionally, to align with the lower part tolerance analysis, tolerance values were also assessed at the pressure (\(P\)), spray (\(I\)), and backflow (\(G\)) measurement points. Figure 10: Fuel flow rates through (**a**) inner pipe and (**b**) intermediate pipe. Analysis of the graphs in Figure 11 shows that the injection quantities in groups 1, 2, 3, 4, 6, and 7 are closely clustered at each pressure point. As outlined in Table 1, in the first four groups, the clearance between the valve and armature varies, while the clearance between the armature and armature pin remains constant. Conversely, in the remaining three groups, the clearance between the valve and armature is constant, whereas the clearance between the armature and armature pin varies. The results depicted in Figure 11a suggest that the impact of the clearance between the armature and armature pin is more significant than that of the clearance between the valve and armature. Notably, the clearance in the fifth group is considerably high, causing the injector's injection quantity to fall out of tolerance. However, no significant difference is observed at \(minP\), as seen in Figure 11b. When \(minP\) and \(maxP\) are evaluated together, it is observed that the increase in pressure highlights the effect of the gap between the armature and armature pin. However, the increase in pressure does not significantly alter the effect of the clearance between the valve and armature. To gain further insight into this discrepancy, the backflow rates of injectors in the same groups are compared in Figure 12.  
Figure 11: Injection quantity rate (\(l\)) at (**a**) \(maxP\) and (**b**) \(minP\). Figure 12 reveals that the backflow rates in groups 1, 2, 3, and 4 are closely aligned. However, in the fifth group, characterized by a significantly high clearance between the armature and armature pin, the backflow rate surpasses the tolerance threshold, resulting in unintended injection quantities and inefficient combustion within the cylinder. Consequently, the engine's energy efficiency decreases while pollutant emissions increase. Similarly, in the sixth group, where the clearance is relatively high, the backflow rates approach the upper tolerance level. Conversely, the backflow rates remain within the tolerance limits in the seventh group, which has minimal clearance. In summary, the contrasting effects of clearance on backflow values are observed predominantly in the armature and armature pin, specifically within groups 5, 6, and 7. The flow rate between the armature and armature pin, as obtained from simulation results, closely mirrors the injector's backflow amount determined through physical measurements. However, the flow rate between the armature and valve varies depending on the injector's backflow amount, indicating that design changes between these components minimally impact backflow. Two primary factors contribute to the fuel movement that generates the low-pressure region: the clearance between the valve and armature and the clearance between the armature and armature pin. The backflow behavior illustrated in Figure 12 aligns with the spray flow behavior observed in Figure 11. A comprehensive examination of these figures reveals that the clearance between the valve and armature is significantly less impactful than that between the armature and armature pin. An important aspect supporting this observation is the continuous backflow between the armature and armature pin, regardless of the energizing time or armature lift. In contrast, the flow between the valve and armature only begins after the armature is lifted, which occurs during only one of the four engine strokes.