Introduction: Compressed air is a versatile energy source used in various applications. However, pumping water with compressed air requires specific designs. Various designs have been proposed for pumping water using compressed air. Some of these designs include Air jet pumps, air-lift pumps, diaphragm pumps, and hydro-pneumatic pumps (discrete flow). The hydro-pneumatic pump is composed of a chamber with two unidirectional valves for intake and discharge, separated by a well. Additionally, it includes an internal tube connected from the top to the outlet unidirectional valve. As compressed air enters the chamber, it applies pressure on the water surface within the chamber, resulting in the closure of the intake valve and the opening of the outlet valve, facilitating the upward pumping of water through the internal tube. Studies have been carried out in the field of jet pumps and air-lift pumps. However, the notion of enhancing flow rate and efficiency by integrating the pumping mechanisms of these pumps gave rise to the original idea of developing a hybrid water pump with a compressed air driver. The primary goal was to approach the efficiency of a hydro-pneumatic pump and simplify the design, allowing water pumping without the need for sensors or control systems.

Materials and Methods: To assess the compressed air water pump and compare its performance with a hydro-pneumatic pump, a prototype with similar dimensions was constructed. By turning on or off and combining three compressed air nozzles within the pump structure, it was possible to operate the Combinatorial compressed air pump in four different modes. During field experiments, the performance, which included measuring input air pressure, flow rate, and water pumping height, was measured. Additionally, the efficiency of the Combinatorial compressed air pump was calculated under experimental conditions. Field experiments was conducted using a factorial design in randomized blocks. Treated variables included immersion depth (4 levels), inlet air pressure (6 levels), pump types and their working modes (5 levels). Discharge flow rates and water pumping height were measured across four replicates. at post processing, pumping efficiency calculated. Analysis of variance and post-hoc tests were conducted to analyze the significant effects of treatment variables and their interactions. to identify the best level for each treatment across different levels of other treatments, interaction slicing was employed. result was presented in charts and tables.

Results and Discussion: The variance analysis revealed a significant difference at the 1% confidence level among pump types, Immersion depth, input air pressure, and their interactions on water pump flow rate. Increasing submergence depth led to higher flow rates in the hydro-pneumatic pump, Combinatorial pneumatic pump, Bubble pump, Bubble & Airlift combined pump, and air-lift pump. Additionally, raising input air flow resulted in increased water pumping rates for all types of pumps.

The hydro-pneumatic pump exhibited higher flow rates compared to other pumps, attributed to its positive displacement structure. The flow rate in all pumps increased with higher input air pressure due to the increase in air flow.

The variance analysis on pump efficiency showed significant differences at the 1% confidence level in input air pressure levels, Immersion depth, pump type, and their interactions. With increased Immersion depth, pump efficiency rose in the following order: Combinatorial pneumatic pump, hydro-pneumatic pump, Bubble pump, Bubble & Airlift combined pump and air-lift pump, and air-lift pump. The Combinatorial pneumatic pump showed the most positive impact of Immersion depth on efficiency.

Immersion depth, inlet air pressure, and pump type significantly impacted discharge rate and pump efficiency. With increased immersion depth and air pressure, discharge and efficiency rose for all pump models and operating modes. The hydro-Pneumatic pump achieved higher efficiency and discharge due to its different structure. At 2m immersion depth, the best performance among all pump models and modes was observed: Airlift pump (10.3% efficiency), Bubble pump (20.8%), Bubble & Airlift Combined pump (19.3%), Pneumatic Combined Pump (27.1%), and Hydro-Pneumatic pump (25.2%).





Discussion: While the hydro-Pneumatic pump offered superior performance, the compressed air pump's simpler structure and lack of electronic control circuitry present advantages. Future research could explore optimizing the compressed air pump design for improved efficiency while maintaining its structural simplicity. Due to structural differences, the hydro-pneumatic pump exhibits significantly higher efficiency (approximately 54%). It was expected that this efficiency would be maintained with increasing pressure, but due to the limited immersion depth in the experiments and dimensional mismatch of the pump with high input air pressure, we observed a decrease in efficiency at higher pressures. This indicates that for each submergence depth and pump head, there is an optimal pressure that the pump dimensions should be designed to suit.