Fire smoke machine: Where are the differences in performance testing between China and the United States?

1 Preface

At present, the mobile fire smoke exhauster used in China has different models and power, and can be selected according to the user's requirements when it is used. As the main performance parameters of the fire smoke exhauster, the amount of smoke exhausted is regarded as an important reference for selection and comparison of smoke exhausters. Due to the different test standards for the amount of smoke exhausted in different countries, the test equipment and test methods are different, which leads to differences in the amount of smoke exhausted under different test standards. The size of the differences has always been a concern in the industry. The author investigates and compares the status quo of American smoke machine standards and Chinese smoke machine standards.

2 standard status

2.1 American Standard

The United States fire smoke exhauster implements the AMCA (American Ventilation and Air Conditioning Association) standard ANSI/AMCA240 "Test Method for Positive Air Fume Exhauster Volume", and the test method for flue gas performance refers to ANSI/AMCA 210-07 "Radiator Rated Performance Qualification Of the standard plenum measurement method in the Experimental Test Method, but modified on the basis of the actual use of the fire smoke exhauster. The entrance of the smoke evacuation machine is the same as the diameter of the test fan fan. It was changed to an open standard size door, as shown in Figure 1.

The fire smoke exhauster test device and the test method are that the whole machine of the fire smoke exhauster is placed at a certain distance from the standard plenum for testing. The length and pitch angle of the distance are determined by the manufacturer, and generally the smoke exhauster is tested. The best placement. The fire smoke exhauster is relatively open to the plenum without any obstructions or ducts. The size of the opening of the plenum is based on the actual application of the scene to simulate two kinds of opening conditions: one is to open one door, and the other is to open two doors. The test results show that the amount of smoke discharged from two doors is greater than the amount of smoke from one door. Manufacturers can select one of the door opening conditions for testing according to their needs, and they can also choose to test both. This improvement compared to ANSI/AMCA 210, in addition to measuring the amount of air generated by the smoke evacuation engine, also includes the amount of air generated by the air around the suction, the measured air volume is much greater than the reference AMCA210, the use of conditions is more consistent with the smoke machine The actual conditions of use.

Figure 1 air chamber measuring device

The measurement method obtains the performance curve under different working conditions by adjusting the opening degree and rotation speed of the outlet fan, as shown in FIG. 2 . In FIG. 2, the x- axis represents the air volume, the y-axis represents the static pressure, and the final rated air volume is the measured value when the static pressure is zero. This method takes into account the actual vent cross-sectional area requirements, but when the static pressure is 0, the air volume is taken as the rated air flow, and it does not represent the actual air flow during the actual exhaust operation because the positive pressure generated by the actual test room air flow is not considered. .

Figure 2 air volume - static pressure curve

2.2 China Standard

In 2011, China promulgated and implemented the mandatory national standard GB27901-2011 "Mobile Fire Smoke Exhauster", in which the exhaust smoke performance test method completely refers to the national standard GB/T1236 "Standard Test Duct for Industrial Fans for Performance Test". The duct measurement method is implemented in the standard, and the standard GB/T1236 is equivalent to the international standard ISO5801-1997. The test device and method require that the fan blades of the smoke exhauster be removed, installed in a closed duct meeting the requirements of the standard, and the dynamic pressure and static pressure measured after rectification of the specified length be converted into air volume finally. Duct testing device is shown in Figure 3.

Figure 3 Duct tester

3 standard comparison

Comparison of 3.1 AMCA240 and GB27901 test methods

U.S. standards are conducted under standard plenum conditions and the rated smoke volume is the maximum value obtained in an ideal environment. The standard air flow measurement of China's standard smoke exhauster adopts the standard air duct measurement of industrial fans, which is inconsistent with the actual use of the smoke exhauster and is smaller than the actual amount of smoke exhausted. In order to compare the actual size of the smoke exhauster, two types of smoke exhausters with equivalent power in the exhaust hoods of China and the United States were selected for testing. A uniform test condition was established and the same calculation method was used to compare the actual amount of smoke exhausted. As shown in Figure 4. In Figure 4, the left side is the American-made smoke exhauster and the right side is the domestic smoke exhauster.

Figure 4 Test smoke machine prototype

(1) Test conditions. The test was conducted in a test room with a length of 5800 mm, a width of 6070 mm, and a height of 3500 mm. The smoke extractor was placed in the test room door for air supply and the room window was opened for smoke extraction, as shown in Figure 5. The size of the door is 0.9m wide and 2.0m high, and the window size is 1.14m wide and 1.45m high. Two-way probes were used to measure the dynamic pressure at the upper, middle and lower points of the smoke exhaust port (window). The measurement results are smoothed using the adjacent averaging method. The wind speed calculation is shown in formula (1).

Where: v is the wind speed, m; K is the correction factor, calibrated by wind tunnel test; Δp is dynamic pressure, Pa; ρ is air density, kg/m3.

The amount of smoke q is the product of the wind speed and the area of ​​the exhaust fumes. This method is closer to the actual conditions of use of the smoke evacuator.

(2) Compare the results. The measured amount of smoke under the same test conditions and measurement method is the actual amount of smoke exhausted. The measurement results show that the actual amount of smoke exhausted by the two tested fire smoke exhausters is basically the same, and the American standard smoke exhauster rated by the United States is used. The amount of smoke exhausted is 1.5 times of the actual amount of smoke exhausted, and the rated exhaust capacity of the domestic smoke exhauster using the Chinese standard is 0.5 times the actual amount of smoke exhausted. The comparison results are shown in Table 1.

Figure 5 test site map

Table 1 Comparison of test results

4 conclusions and recommendations

In China and the United States, the test standards for smoke exhausters are completely different. The United States standard is aimed at the specific use of smoke exhausters (placed in the entrance of test rooms), and a standard air chamber is established to measure the amount of smoke exhausted, but due to its measurement method is too ideal. The measured value is much higher than the actual smoke test value. The measurement of the air flow rate of the smoke exhauster in China adopts the standard air duct measurement method for industrial fans, which is inconsistent with the actual use of the smoke exhauster. It does not reflect the actual amount of smoke exhausted, and is much smaller than the actual amount of smoke exhausted. Therefore, the main performance parameters of the exhaust fume exhauster cannot measure and compare the performance of the exhaust hood. Therefore, it is recommended that China's relevant departments to develop fire smoke exhaust smoke testing standards as soon as possible, to unify the domestic and foreign smoke machine testing standards, while providing users with a real and reasonable amount of smoke data, convenient comparison of the advantages of smoke machine Poor, according to a reasonable and accurate performance parameters to develop effective smoke tactics.

This article is from "Fire Equipment Research" and is edited and edited by China Rescue Equipment Network.