Stewart Gillies The University of Queensland MEASUREMENT OF AIRFLOW THROUGH REGULATORS AND REAL TIME INTEGRATED MONITORING Stewart Gillies The University of Queensland North American / Ninth U.S. Mine Ventilation Symposium, June 2002, Kingston Canada

Outline of Presentation Introduction Theory of Regulators Field Tests of Regulators UQEM Real Time Mine Ventilation System Trials of the UQEM System Conclusions North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

THEORY OF MINE REGULATORS An artificial resistance (in the form of shock loss) or a large thin plate installed in a fluid conduit with an orifice. When a difference in pressure exists between the two sides fluid flows as shown. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Mathematical Modelling of Regulators Irregularity in shape and symmetry and their positioning in roughly square or rectangular airways, Construction of the opening - louvres, sliding door, window or curtain or placement of drop boards, and Uncontrolled air leakage. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

C-Section (Drop Board Type) Regulator North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

An Example of Louvre Regulator North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Derivation of Regulator Equation Bernoulli’s equation can be applied to both sides of the orifice to calculate the velocity and hence the airflow quantity. A correction must be made for the contraction of the jet at the vena contracta. Velocity at the orifice is obtained with the following equation: North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Derivation of Regulator Equation (cont.) Airflow quantity through regulator is as follows. where Cc is the coefficient of contraction (Ac/Ar) Ar is orifice opening area N is the ratio of the orifice and airway cross sectional area, (Ar/A) Ps is the differential pressure across regulator  is air density North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

FIELD TESTS OF REGULATORS To verify airflow behaviour through a drop board regulator. Airflow quantity and pressure drop across the regulator were measured. Airflow quantity through the regulators can also be calculated in theory from pressure measurements. Results compared with measured values and the reasons for significant differences investigated. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Comparison of measured and predicted Q North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Reasons for the differences in Quantities Error during measurement: Small cross-sectional area No-symmetrical condition and shape Leakage occurs due to gaps or holes between boards, regulator frame and the airway walls. Airflow quantity can be expressed as follows to account for leakage. where Ql is the leakage quantity North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Airflow Paths in Regulator Regulators can be treated as a set of two parallel airways namely: Regulator opening and Leakage paths North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Resistance of Regulator The total resistance of regulator (Rt) can be modelled to consist of the regulator opening resistance (Ro) and the leakage path resistance (Rl). The regulator opening resistance (Ro) can be calculated from the derived formula Where A is the airway cross sectional area. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Resistance of Regulator When the regulator is in a fully closed condition, the air flows through the leakage path only with resistance Rl which can be empirically derived. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Measured and Predicted Airflow Quantity North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Regulator Resistance vs Opening Area North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

UQEM Regulator Characteristic Curves North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Plan of UQ Experimental Mine Showing locations of doors and sensors North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

VENTSIM – Real Time Simulations North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

VENTSIM - Remote Station Database Interface North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

VENTSIM - Airway Edit Interface Input of Remote Station Number North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

TRIALS OF THE UQEM SYSTEM Trial Scenarios: The inclined shaft door was open, and the regulator in 116’ level set on fully open. The inclined shaft door was open, and the regulator was set 1/5 open with 12 boards The inclined shaft door was open, and the regulator set on fully closed. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Schematic of UQEM Ventilation System North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Accuracy of Trial Results Ventsim monitoring system predicts changes with reasonable accuracy although some differences in quantities were larger than 10%. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Constraints of the System – Transition Time The transient period in UQEM is short and therefore is not of great significance in interpreting the network system. However, in large-scale mines, the period can be up to 10 minutes or more. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

Updating of Ventilation Simulation Models The trial demonstrated the importance and necessity of updating simulation models after changes. The three scenarios were examined for how the network reacted to the input of a real time fixed quantity in terms of maintenance of model accuracy without a change to the regulator/door R value Based on air quantity observations it is not necessary to make adjustment to the regulator/door R in the model as % error is no more than 5%. However when comparing the predicted pressure drops across regulators, significant need for adjustment was found. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

North American / Ninth US Mine Ventilation Symposium CONCLUSIONS Efforts to mathematically model some operating mine regulators have been described. Theoretical calculations to predict airflow quantity through regulators based on measured pressure drop are inadequate due to leakage, geometry etc. It is necessary to quantify the resistance of the leakage path based on regulator opening area and then recalculate the total resistance of the regulators. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada

North American / Ninth US Mine Ventilation Symposium CONCLUSIONS Cont. An investigation was undertaken as to whether the Real Time Airflow Monitoring system can accurately detect changes in a ventilation network and identify constraints. The system was able to detect changes and to predict the changes accurately. Limitations caused by transient period delays have been examined. It is important to update the simulation models based on real time data. North American / Ninth US Mine Ventilation Symposium June 2002, Kingston Canada