Differential pressure difference based altitude control of a stratospheric satellite

An autonomous altitude adjustment system for a stratospheric satellite(StratoSat)platform is proposed.This platform consists of a helium balloon,a ballonet,and a two-way blower.The helium balloon generates lift to balance the platform gravity.The two-way blower inflates and deflates the ballonet to regulate the buoyancy.Altitude adjustment is achieved by tracking the differential pressure difference(DPD),and a threshold switching strategy is used to achieve blower flow control.The vertical acceleration regulation ability is decided not only by the blower flow rate,but also by the designed margin of pressure difference(MPD).Pressure difference is a slow-varying variable compared with altitude,and it is adopted as the control variable.The response speed of the actuator to disturbance can be delayed,and the overshoot caused by the large inertia of the platform is inhibited.This method can maintain a high tracking accuracy and reduce the complexity of model calculation,thus improving the robustness of controller design.

Sand Production Prediction and Safe Differential Pressure Determination in a Deepwater Gas Field

Sand production is a critical issue during the development of offshore oil and gas fields.Certain gas fields(e.g.the AB gas field)have high porosity and high permeability,and with water at the bottom of the reservoir,the risk of sand production greatly increases at high differential pressures.Based on reservoir properties,geological conditions,production requirements,and well logging data,in this study an ultrasonic time difference method,a B index method,and a S index method are used together with a model of rock mass failure(accounting for water influx and pressure depletion)to qualitatively predict sand production.The results show that considered sample gas field has an overall high risk of sand production.The critical differential pressure(CDP)without water influx is in the range of 1.40 to 2.35 MPa,the CDP after water influx is from 0.60 to 1.41MPa.The CDP under pressure depletion is in the range of 1.20 to 1.92 MPa.The differential pressure charts of sand production are plotted,and the safe differential pressure windows with or without water influx are obtained.The model calculation results and the experimental results are consistent with the field production data,which indicates that the implemented prediction method could be taken as a reference for sand production prediction in similar deep water gas fields.

Analysis of Gas Flow Rate and Pressure Loss of Medical Mask Differential Pressure Tester

The objective of this study is to find a suitable method to overcome the pressure loss problem in the gas pipe during the gas exchange detection of medical masks.Based on the European Standards EN 14683,the parameters of a medical mask differential pressure tester were selected,subsequently two schemes of gas pipe layouts were designed,including four kinds of pipe diameter which are 4,5,6.5,and 8mm respectively.Lastly,the models of each scheme were established and imported into Fluent,and the relevant parameters were set for simulation.After data analysis,the results showed that among the four different pipe diameters,the pressure loss of 8mm diameter of the pipe was lower in both the schemes,additionally the pressure loss of the second scheme(the gas pipe was short and smooth)was lower under the same pipe diameter.At the flow rate of v=8L/min,the pressure loss from the inlet to the measurement point is less than 200Pa,and the estimated measurement error is less than 1.5%.In conclusion,shortening the length of the pipe,and increasing the diameter of the pipe can reduce the gas pressure loss,subsequently improve the measurement accuracy of the medical mask differential pressure tester.

Design of Na-K Alloy Differential Pressure Sensor with On-line Monitoring Function

Because the melting point of the alkalis is very high and the metal activity is strong, the common pressure sensor can＇t be used to measure pressure of liquid metal. In this paper, a differential transformer differential pressure sensor for measuring liquid alkalis pressure is designed, the working principle and specific design plan of the sensor are introduced, the standard current signal （ 4 -20 mA） or digital communication RS485 can be output according to the needs, and the functions of remote monitoring and data optimization can be realized through the LAN interface.

Differential pressure reset strategy based on reinforcement learning for chilled water systems

Air conditioning water systems account for a large proportion of building energy consumption.In a pressure-controlled water system,one of the key measures to save energy is to adjust the differential pressure setpoints during operation.Typically,such adjustments are based either on certain rules,which rely on operator experience,or on complicated models that are not easy to calibrate.In this paper,a data-driven control method based on reinforcement learning is proposed.The main idea is to construct an agent model that adapts to the researched problem.Instead of directly being told how to react,the agent must rely on its own experiences to learn.Compared with traditional control strategies,reinforcement learning control(RLC)exhibits more accurate and steady performances while maintaining indoor air temperature within a limited range.A case study shows that the RLC strategy is able to save substantial amounts of energy.

Online differential pressure reset method with adaptive adjustment algorithm for variable chilled water flow control in central air-conditioning systems

Central air-conditioning systems predominantly operate under partial load conditions.The optimization of a differential pressure setpoint in the chilled water system of a central air-conditioning system leads to a more energy-efficient operation.Determining the differential pressure adjustment value based on the terminal user's real-time demand is one of the critical issues to be addressed during the optimal control process.Furthermore,the online application of the differential pressure setpoint optimization method needs to be considered,along with the stability of the system.This paper proposes a variable differential pressure reset method with an adaptive adjustment algorithm based on the Mamdani fuzzy model.The proposed method was compared with differential pressure reset methods with reference to the chilled water differential temperature,outdoor temperature,and linear model based on the adjustment algorithm.The energy-saving potential,temperature control effect,and avoidance of the most unfavorable thermodynamic loop effects of the four methods were investigated experimentally.The results indicated that,while satisfying the terminal user's energy supply demand and ensuring the avoidance of the most unfavorable thermodynamic loop,the proposed adaptive adjustment algorithm also decreased the differential pressure setpoint value by 25.1%—59.1%and achieved energy savings of 10.6%-45.0%.By monitoring the valve position and supply air temperature of each terminal user,the proposed method exhibited suitable online adaptability and could be flexibly applied to buildings with random load changes.

A triboelectric nanogenerator based on a spiral rotating shaft for efficient marine energy harvesting of the hydrostatic pressure differential

Equipment used in underwater sensing and exploration typically relies on cables or batteries for energy supply,resulting in a limited and inconvenient energy supply and marine environmental pollution that hinder the sustainable development of distributed ocean sensing networks.Here,we design a deep-sea differential-pressure triboelectric nanogenerator(DP-TENG)based on a spiral shaft drive using modified polymer materials to harness the hydrostatic pressure gradient energy at varying ocean depths to power underwater equipment.The spiral shaft structure converts a single compression into multiple rotations of the TENG rotor,achieving efficient conversion of differential pressure energy.The multi-pair electrode design enables the DP-TENG to generate a peak current of 61.7μA,the instantaneous current density can reach 0.69μA cm^(-2),and the output performance can be improved by optimizing the spiral angle of the shaft.The DP-TENG can charge a 33μF capacitor to 17.5 V within five working cycles.It can also power a digital calculator and light up 116 commercial power light-emitting diodes,demonstrating excellent output capability.With its simple structure,low production cost,and small form factor,the DP-TENG can be seamlessly integrated with underwater vehicles.The results hold broad prospects for underwater blue energy harvesting and are expected to contribute to the development of self-powered equipment toward emerging“smart ocean”and blue economy applications.

Electric power generation technology of natural gas pressure reduction:Insights from black box-gray box hierarchical exergy analysis and evaluation method

Based on the“three box”exergy analysis model,a black box-gray box hierarchical exergy analysis and evaluation method is put forward in this paper,which is applied to evaluate the power generation technology of differential pressure produced by natural gas expansion.By using the exergy analysis theory,the black box-gray box hierarchical exergy analysis models of three differential pressure power generation technologies are established respectively.Firstly,the“black box”analysis models of main energy consuming equipment are established,and then the“gray box”analysis model of the total system is established.Based on the calculation results of exergy analysis indexes,the weak energy consumption equipment in the whole power generation process is accurately located.Taking a gas field in southwest China as an example,the comprehensive energy consumption evaluation of the three power generation technologies is carried out,and the technology with the best energy consumption condition among the three technologies is determined.Finally,the rationalization improvement measures are put forward from improving the air tightness,replacing the deflector and reducing the flow loss.

An Analysis of the Static and Dynamic Behavior of the Hydraulic Compensation System of a Multichannel Valve

Electro-hydraulic proportional valve is the core control valve in many hydraulic systems used in agricultural and engineering machinery.To address the problem related to the large throttling losses and poor stability typically associated with these valves,here,the beneficial effects of a triangular groove structure on the related hydraulic response are studied.A mathematical model of the pressure compensation system based on the power-bond graph method is introduced,and the AMESim software is used to simulate its response.The results show that the triangular groove structure increases the jet angle and effectively compensates for the hydrodynamic force.The steady-state differential pressure at the valve port of the new pressure compensation structure was 0.65 MPa.Furthermore,experimental results show that the pressure difference at the main valve port is 0.73 MPa,and that the response time is less than 0.2 s.It is concluded that the new compensation structure has good pressure compensation response characteristics.

Influence of the Hole Chamfer on the Characteristics of a Multi-hole Orifice Flowmeter

In order to analyze the influence of the hole chamfer on the metering performances of a Multi-hole Orifice Flowmeter and optimize the related orifice structure,a multi-hole orifice flowmeter with DN80 and throttle ratio of 0.45 was considered in the present study.The flow field characteristics were determined in the framework of a CFD technique.The results show that the multi-hole orifice flowmeter with filleting transition around the throttle orifice has higher accuracy in a wide range of the space of parameters,and is more suitable for accurate measurement of fluid in process control.

LIQUID-GAS TWO PHASE FLOW RATES METERING BY DUAL PRESSURE DIFFERENTIAL MEASUREMENTS

The measurement of the overall mass flow rates in a two phase, gas/liquid pipeline is considered on the basis of dual pressure differential measurements for a combined contraction/frictional pipe type of flow meter and a numerical model to predict overall mass flow rates from pressure differentials measured from this type of flow meter is presented. The experiments generally conform with the predictions of the flow rates prediction model. Whilst the practicability of such metering of two phase flows is clearly demonstrated, application of the method would require careful calibration to allow for the influence of nozzle coefficients, pipe Reynolds number and void fraction upon the one dimensional compressible flow equations through wall friction factor and interphase slip effects.

Micro-flow structure at regime transition from bubbling to turbulent fluidization in a fluidized bed

Gas-solid fluidized beds have found extensive utilization in frontline manufacturing,in particular as low-velocity beds.The fluidization status,the bubbling or turbulent flow regime and the transition in between,determine the system performance in practical applications.Though the convoluted hydrodynamics are quantitively evaluated through numerous data-processing methodologies,none of them alone can reflect all the critical information to identify the transition from the bubbling to the turbulent regime.Accordingly,this study was to exploit a coupling data processing methodology,in the combination of standard deviation,power spectrum density,probability density function,wavelet transform,and wavelet multiresolution method,to jointly explain the micro-flow structure at the regime transition from bubbling to turbulent fluidization.The transient differential pressure fluctuation was measured for the evaluation in a fluidized bed(0.267 m i.d.×2.5 m height)with FCC catalysts(d_(p)=65μm,ρ_(p)=1780kg/m^(3))at different superficial gas velocities(0.02–1.4 m/s).The results show that the onset of turbulent fluidization starts earlier in the top section of the bed than in the bottom section.The wavelet decomposition displays that the fluctuation of differential pressure mainly concentrates on the sub-signals with an intermediate frequency band.These sub-signals could be synthesized into three types of scales(micro-scale,meso-scale,and macro-scale),representing the multi-scale hydrodynamics in the fluidized bed.The micro-scale signal has the characteristic information of bubbling fluidization,and the characteristic information of turbulent fluidization is mainly represented by the meso-scale signal.This work provides a systematic comprehension of fluidization status assessment and serves as an impetus for more coupling analysis in this sector.

Distribution characteristics of holdups in a multi-stage bubble column using electrical resistance tomography

Based on the principle of chemical reaction engineering, the addition of perforated plates can improve the performance of conventional bubble column and decrease the backmixing behaviors. The distribution characteristics of gas holdup in a multi-stage bubble column embedded with five types of sieve plates and three types of tongue plates were studied using electrical resistance tomography （ERT）. The effects of superficial gas velocity and the geometric design of perforated plates on the gas holdup and its radial distribution above and below the plates of the bubble column were discussed. Experimental results show ERT is suitable as an online monitoring tool to provide useful information on the hydrodynamic param-eters of multi-stage bubble columns. With increasing superficial gas velocity, local gas holdup increases, and gas holdup below the plate increases with decrease of free area （%FA）, hole diameters or angle of tongue plates. ERT technique facilitates noninvasive and nonintrusive visualization of cross-sectional distribution of gas holdup in a bubble column.

Development of Test Method for Measuring Sintering Temperature of Mould Fluxes

Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands.Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting.An effective method of measuring the apparent sintering temperature has been developed in this study.The method is based on monitoring the formation of cavities caused by melting of samples.For monitoring,the differential pressure of an inert gas flow was measured through a set volume of sample（mould flux A）held in a furnace tube.The apparent sintering temperature was defined in this test to determine sintering process.The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures.The experimental results indicated that the apparent sintering temperature（AST）was a useful parameter to assess the threat of problems related to sinter.