Analysis and Improvement of Water Leakage Fault of a Ground Radar Water Hinge_Hinge Knowledge

Abstract: This article provides a detailed analysis of the leakage issue in a ground radar water hinge. It identifies the location of the fault, determines the main cause of the fault, and proposes improvement measures. The effectiveness of these measures is then verified through mechanical simulation analysis and testing.

As radar technology systems continue to evolve, the demand for radar transmission power is increasing, particularly with the move towards larger arrays and big data. Traditional air cooling methods are no longer sufficient to meet the cooling requirements of these larger radars. Cooling the radar front is essential, even though modern ground radars are transitioning from mechanical scanning to phase scanning. However, mechanical azimuth rotation is still required. This rotation and the transmission of coolant between surface equipment is achieved through liquid rotary joints, also known as water hinges. The performance of the water hinge directly impacts the overall performance of the radar cooling system, making it crucial to ensure the reliability and longevity of the water hinge.

Fault Description: The leakage fault in the radar water hinge is characterized by an increase in leakage rate with longer continuous rotation time of the antenna. The maximum leakage rate reaches 150mL/h. Additionally, the leakage rate varies significantly when the antenna stops at different azimuth positions, with the highest leakage rate observed in the direction parallel to the vehicle body (approximately 150mL/h) and the lowest in the direction perpendicular to the vehicle body (around 10mL/h).

Fault Location and Cause Analysis: To pinpoint the location of the leakage fault, a fault tree analysis is conducted, taking into account the internal structure of the water hinge. The analysis rules out certain possibilities based on pre-installation pressure tests. It is determined that the fault lies in dynamic seal 1, which is caused by a connection issue between the water hinge and the collector ring during the assembly process. The wear of the toothed slip ring exceeds the compensation capability of the O-ring, leading to dynamic seal failure and liquid leakage.

Mechanism Analysis: Actual measurements reveal that the starting torque of the slip ring is 100N·m. A finite element model is created to simulate the water hinge's behavior under ideal conditions and unbalanced loads caused by the slip ring's torque and yaw angle. The analysis shows that the deflection of the inner shaft, particularly at the top, leads to compression rate variations among the dynamic seals. Dynamic seal 1 experiences the most severe wear and leakage due to the eccentric load caused by the connection between the water hinge and the diversion ring.

Improvement Measures: Based on the identified failure causes, the following improvements are proposed. Firstly, the structural form of the water hinge is changed from radial arrangement to axial arrangement, reducing its axial dimensions while keeping the original shape and interfaces unchanged. Secondly, the support method for the inner and outer rings of the water hinge is enhanced by using angular contact bearings with paired distribution at both ends. This improves the water hinge's anti-sway ability.

Mechanical Simulation Analysis: A new finite element model is created to analyze the behavior of the improved water hinge, including the newly added eccentricity elimination device. The analysis confirms that the addition of the eccentricity elimination device effectively eliminates the deflection caused by the connection between the diversion ring and the water hinge. This ensures that the inner shaft of the water hinge is no longer affected by eccentric loads, thus improving the life and reliability of the water hinge.

Verification Results: The improved water hinge undergoes standalone performance tests, pressure tests after integrated rotation combination with the diversion ring, whole machine installation tests, and extensive field tests. After 96 hours of copying tests and 1 year of field debugging tests, the improved water hinge demonstrates excellent performance with no failures.

By implementing structural improvements and adding an eccentricity elimination device, the deflection issue between the water hinge and the collector ring is effectively controlled. This ensures the longevity and reliability of the water hinge, reducing the risk of leakage. The mechanical simulation analysis and test verification confirm the effectiveness of these improvements.