Cooling Strategies for Heated Cylinders Using Pulsating Airflow with Different Waveforms

Pulsate flow is an effective technique applied for cooling several engineering systems depending on their pulsate frequency. One very sound external flow pulsation application is heat transfer over heated bodies. In present work, an experimental design and numerical model of controlled pulsating flow according to generated pulsating frequency and wave shape around a heated cylinder were performed. The effects of pulsating frequency, amplitude, and mean velocity on the fluid flow and heat transfer characteristics over a heated cylinder were studied. The wave frequency varied from 2 to 12 Hz, and the amplitude varied from 0.2 to 0.8 m/s. Moreover, different waveforms were investigated to determine their effect on wall cooling. For constant wave frequency and amplitude, the most efficient wave in cooling was the sawtooth wave, with the average wall temperature after 30 s was 1.6 °C cooler than that of the forced convection case, followed by the triangular wave at 1.2 °C less. The heat transfer rate and the flow field were drastically influenced by the variations of these parameters. Optimization was conducted for each wave type to find the optimum wave frequency and amplitude. The optimizing showed that, the most efficient wave was the sawtooth with 12°C temperature reduction compared with that of the forced convection case, followed by the triangular. Furthermore, regression analysis was conducted to estimate the relationships between these variables and surface temperature. It was found that the wave amplitude had a greater role in cooling than that of the frequency

Pneumatic cylinder speed and force control using controlled pulsating flow

An application for accurate and low-cost force and velocity control of a pneumatic actuator, which can be used in any pneumatic circuit, is described in this paper. Control of a pneumatic cylinder is proposed via a pulsating flow technique. The technique uses on/off solenoid coils in the direction control valves in lieu of expensive servo controllers, such as proportional directional control valves. Pulsating air frequencies of 1.5, 3, and 4.5 Hz are applied by the designed circuit to investigate inlet constant pressures ranging from 1.72 to 5.17 × 105 Pa. The speed and force of a pneumatic cylinder rod are controlled using the generated pulsating flow and the results show success of idea of ​​controlling the speed and force of the pneumatic cylinder rod using the pulse flow technique. Empirical correlations suitable for later use in automatic control circuits are derived and are shown to exhibit an accuracy of up to ∼ 90–95.5% in predicting output force and velocity. It is also used to select the required frequency to obtain the speed and force required for the cylinder. To validate the pneumatic cylinder speed and force control using pulse flow technique, simulations are carried out using the Automation Studio program. The results show an improvement in control of the pneumatic cylinder mechanical performance and demonstrate that improvements are a function of the frequency of compressed air source pulses and pressure. An empirical correlation is also derived for predicting the cylinder rod speed and force at any source pressure and pulse frequency

Speed and torque control of pneumatic motors using controlled pulsating flow

Pneumatic motors have several advantages and have many robotics and automation applications. The importance of the study is that it is a cheap and possible way to apply it to the fixed displacement pneumatic motors with simple directional control valve used. The purpose of the addition to any traditional pneumatic motors is to change the fixed displacement pneumatic motor to be variable speed and torque compared to the expensive systems such as the proportional control valve in many industrial applications. The study also included validated simulations using the Automation Studio program to control the pneumatic motor’s speed and torque. In addition, the results showed remarkable success in controlling the pneumatic motor outputs depending on the frequency of the compressed air-source pulses and pressure. The pulsating air frequencies of 1.5, 3, and 4.5 Hz were considered at different inlet source pressure changes from 1.72, 3.45, and 5.17 bar. As the pulsating flow frequency of compressed air decreased from 4.5, 3, and 1.5 Hz, the motor pressure and torque decreased. Furthermore, empirical correlations related to frequency and pressure effect have been developed. The error is 6.3–9.5% in predicting the motor speed and torque outputs. The limitation of the proposed method in real-life applications is about a maximum of 7.5 bar. On the other hand, the frequency is limited to 9 Hz using a mechanical solenoid