DYNAMICS MODEL AND SIMULATION OF FLAT VALVE SYSTEM OF INTERNAL COMBUSTION WATER PUMP

The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.

Causes of Odor in Kitchens,Bathrooms,and Toilets of Multi-story Residential Apartments with Natural Ventilation

The causes of an offensive odor in the kitchens,bathrooms,and toilets of residential apartments in multi-story buildings with natural ventilation in Tomsk,Russia,are discussed in this paper.This problem exists in other cities and countries.Wall electric fans can be installed in ventilation grills in kitchens,bathrooms,and toilets of apartments in multi-story residential buildings.Typically,these fans turn on with the light in the bathroom or toilet,so the problem is periodic.Forced airflow from a fan in one apartment disrupts the natural outflow of air in the ventilation system of a residential building designed and built according to building codes and regulations and can cause an unpleasant smell in neighboring apartments.In many cases,it is difficult to determine which apartments have fans and force the neighbors to remove them.Locally,on the scale of one apartment,the problem is solved by installing an air check valve in the ventilation grill,which will block the nuisance airflow from the ventilation system into the bathroom.Globally,the problem is solved by modification and subsequent compliance with building codes and regulations,the implementation of which is controlled by local authorities.

Fluid Pump Using a Bar-shaped Piezoelectric Transducer

There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump with check valve is desirable.However,adding check valves implies more complex structure and higher probability of valve blocking,etc.In order to solve the problem,effective driving and transport mechanics with compact construction and reliable service are being sought.In this paper,using the second-order longitudinal vibration mode of a bar-shaped piezoelectric vibrator for driving fluid,a piezoelectric pump is successfully made.The proposed piezoelectric pump consists of coaxial cylindrical shells and a bar-shaped piezoelectric vibrator,which has a disk part and a cone part.The lead zirconium titanate ceramic rings fixed in the vibrator are polarized along the thickness direction.When the second-order longitudinal vibration of the vibrator along its axis is excited,the disk part of the vibrator changes periodically the volume of the chamber and the cone part acts as a pin valve,driving the fluid from the inlet port to the outlet port.Finite elements analysis on the proposed pump model is carried out to verify its operation principle and design by the commercial FEM software ANSYS.Components of the piezoelectric pump were manufactured,assembled,and tested for flow rate and backpressure to validate the concepts of the proposed pump and confirm the simulation results of modal and harmonic analyses.The test results show that the performance of the proposed piezoelectric pump is about 910 mL/min in flow rate with a highest pressure level of 1.5 kPa under 400 V peak-to-peak voltage and 51.7 kHz operating frequency.It is confirmed that this bar-shaped piezoelectric transducer can be effectively applied in fluid transferring mechanism of pump through this research.

Experimental Investigation of the Water Impulse Force and Moment on the Disk of a Butterfly Check Valve

Butterfly check valves are widely used in water supply pipeline systems. Proper design of new valves requires accurate determination of the water impulse force and moment on the disk for transient flow conditions. The impulse moments were measured using pressure measurement and strain gauge measurements. Correlation was developed relating the impulse moment to the velocity and angle that were used to design a new type of valves.

Experimental study on airfoil flow separation control via an air-supplement plasma synthetic jet

An air-supplement plasma synthetic jet(PSJ)actuator increases the air supplemental volume in the recovery stage and improves the jet energy by attaching a check valve to the chamber of a conventional actuator.To explore the flow control effect and mechanism of the air-supplement actuator,via particle image velocimetry experiments in a low-speed wind tunnel,the flow field and boundary layer characteristics of a two-dimensional airfoil surface under different actuation states were compared for different attack angles and jet orifices.The experimental results show that,compared with the conventional actuation state,the jet energy of the air-supplement PSJ is higher and the indirect mixing effect of the counter-vortex sequence produced by the jet-mainstream interaction is stronger.Furthermore,the boundary layer mixing effect is better,which can further suppress flow separation and improve the critical flow separation attack angle.Moreover,increasing the jet momentum coefficient can enhance the flow control effect.The findings of this study could provide guidance for the flow control application of air-supplement PSJs.