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1. Is it necessary to verify the back pressure ratio of the sonic nozzle after the design is completed?
After the back pressure ratio of the sonic nozzle is designed, it must be verified The theoretical design of the necessity of verification is based on the simplified assumption of an ideal fluid at the end of the wheel. In practical applications, factors such as machining size errors, changes in pipe wall roughness, installation coaxiality deviations, and fluctuations in operating parameters may cause the actual back pressure ratio to deviate from the design value, making it impossible to ensure that the nozzle outlet reaches the expected supersonic flow state. If the sonic nozzle is used for gas flow measurement, industrial flow control and other scenarios, it must also comply with the requirements of the national metrological verification regulations, and its performance must be confirmed to meet the standards through verification. 2. Core content to be verified: Actual critical back pressure ratio: The pressure values upstream and downstream of the nozzle are collected by high-precision pressure sensors, and the actual pressure ratio is calculated to confirm whether it has reached the critical threshold of the design (i.e. $p2/p1 ≤ (2/(k+1)) ^ {k/(k-1)} $, where $k $is the specific heat ratio of the measured gas. Taking air as an example, the critical back pressure ratio is about 0.528). La Xun Qin ensures that the outlet airflow reaches the speed of sound. Consistency of flow characteristics: Verify whether the flow coefficient of the nozzle meets the design expectations within the designed back pressure ratio range, ensuring that the accuracy of flow measurement or control meets the requirements. • Flow
3. Mainstream verification method - laboratory calibration: Use authoritative equipment such as bell jar flow standard device and mass flow standard device to measure the flow parameters of the nozzle at the designed back pressure ratio, and compare them with the design indicators to complete the verification. -On site working condition testing: Collect upstream and downstream pressure data in actual usage scenarios, calculate the actual back pressure ratio, and combine it with the actual Changji flow data to confirm that the performance meets the design requirements. -CFD simulation verification: By simulating the actual machining error and flow field state under installation conditions through computational fluid dynamics, the actual back pressure ratio performance can be predicted in advance, and design details can be optimized. If the sonic nozzle is used in high-pressure, flammable, explosive, or toxic medium scenarios, the verification process must strictly follow safety operating procedures to prevent safety risks such as medium leakage and overpressure.
2. Product features of sonic nozzle calibration device
1. The nozzle structure is simple, sturdy, durable, easy to replicate and inspect, and the uncertainty of its outflow coefficient is ≤ 0.2%
2. The device structure is compact, with good repeatability and reliability.
.3、 The device is in operation and can freely combine multiple nozzles according to the flow rate, so the measurement range is wide. The l