Electric-controlled pressure relief valve for enhanced safety in liquid-cooled lithium-ion battery packs

The liquid-cooled battery energy sto rage system(LCBESS) has gained significant attention due to its superior thermal management capacity.However,liquid-cooled battery pack(LCBP) usually has a high sealing level above IP65,which can trap flammable and explosive gases from battery thermal runaway and cause explosions.This poses serious safety risks and challenges for LCBESS.In this study,we tested overcharged battery inside a commercial LCBP and found that the conventionally mechanical pressure relief valve(PRV) on the LCBP had a delayed response and low-pressure relief efficiency.A realistic 20-foot model of an energy storage cabin was constructed using the Flacs finite element simulation software.Comparative studies were conducted to evaluate the pressure relief efficiency and the influence on neighboring battery packs in case of internal explosions,considering different sizes and installation positions of the PRV.Here,a newly developed electric-controlled PRV integrated with battery fault detection is introduced,capable of starting within 50 ms of the battery safety valve opening.Furthermore,the PRV was integrated with the battery management system and changed the battery charging and discharging strategy after the PRV was opened.Experimental tests confirmed the efficacy of this method in preventing explosions.This paper addresses the safety concerns associated with LCBPs and proposes an effective solution for explosion relief.

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.

Pneumatic resistance network analysis and dimension optimization of high pressure electronic pneumatic pressure reducing valve

The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.

Pressure Regulating Pressure of A New Pressure Regulating Valve with Spring

A new type of pressure regulating valve for agriculture irrigation, which used spring to regulate pressure was studied. Through the spring regulating pres-sure test, it concluded that for the pressure regulating valve with same spring mod-el, the outer pressure became smal er than the inlet pressure of the system and with the changes of inlet pressure, the outlet pressure remained almost the same, and that when inlet pressure was constant, the valve with smal er spring diameter had lower outlet pressure, indicating that the pressure regulating effect of the spring was more obvious with smal er diameter.

PRESSURE COMPENSATION METHOD OF UNDERWATER HYDRAULIC SYSTEM WITH HYDRAULIC POWER UNIT BEING UNDER ATMOSPHERIC CIRCUMSTANCE AND PRESSURE COMPENSATED VALVE

Based on the analysis of the-state-of-the-art of pressure compensation of underwater hydraulic systems （UHSs）, a new method of pressure compensation of UHSs, whose hydraulic power unit is in the atmospheric circumstance, is proposed. And a pilot-operated relief valve with pressure compensation is realized. The pressure compensation precision is guaranteed by direct detection. Its dynamic performance and stability are improved by a dynamic feedback. Theoretical study, simulation and experiment show that the pilot-operated relief valve with pressure compensation has a fine property of tracking underwater ambient pressure and meet the requirement of underwater ambient pressure compensation.

Pressure Control of a Large-scale Hydraulic Power Unit Using π Bridge Network

The steady state and dynamic characteristics of pressure output of a hydraulic power unit are important to the hydraulic system behavior.Because of the compact structure,the B-half bridge resistance network is widely used in the pilot controlled pressure relief valves.However the steady-state pressure error might be unacceptably big in those pressure control systems.A constant pressure power unit is typically assumed in analysis of steady state and dynamic behavior of hydraulic systems.The flow-pressure relationship seems to be much complex,in particular when big flow variation takes place.In this paper,the π bridge hydraulic resistance network pilot stage is designed in order to get better flow-pressure characteristics.Based on the similarity of electrical circuits,the main factors influencing flow-pressure characteristics are analyzed.Moreover,the optimum diameters of both constant hydraulic resistor and dynamic resistor are proposed.Flow-pressure characteristics are compared with different constant hydraulic resistors,dynamic resistor and spring stiffness by simulations and experiments.Results of simulations and experiments show that flow-pressure characteristics depend very little on the spring stiffness in whole flow range.Good controlled pressure characteristics can be achieved with suitable constant resistors.Overshoot can be reduced with the small diameter of the dynamic resistor.Flow-pressure characteristics of pressure relief valve can be improved with a π bridge pilot stage.The proposed pressure control method will provide some positive guidelines and be helpful to design a high performance hydraulic system with large flow.

SIMULATION AND EXPERIMENT OF BUBBLY FLOW INSIDE THROTTLING GROOVE

The relationship between pressure distribution and cavitation （noise） inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics（CFD） analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound nressure level accordingly.

Efficacy of selective laser trabeculoplasty following incisional glaucoma surgery

AIM： To evaluate the efficacy of selective laser trabeculoplasty（SLT） in glaucomatous eyes with previous incisional glaucoma surgery. METHODS： A retrospective cohort of eyes that underwent SLT at a single institution from 2013-2015 were followed for 1 y. Reduction in intraocular pressure（IOP） following SLT was evaluated in eyes with prior trabeculectomy with Ex Press mini shunt（Alcon, Ft Worth, TX, USA）, Ahmed valve（New World Medical, Cucamonga, CA, USA）, or combined phacoemulsification-trabeculectomy. A control group was included with eyes without prior surgery that underwent SLT. Success was defined as 〉20% drop in IOP from pre-SLT baseline. RESULTS： One-hundred and six eyes were included with 53 in both the prior glaucoma surgery（PGS） and no prior glaucoma surgery（NPGS） groups. Mean pre-SLT IOP was 19.2±4.3 and 20.6±6.0 mm Hg for PGS and NPGS groups, respectively（P=0.17）. Both groups produced statistically significant IOP reductions at 1 and 6 mo（P〈0.04）. At 6 mo, mean IOP reduction reached 7.3% and 10.8% for the PGS and NPGS groups, respectively（P=0.42）. Overall, 27.9% and 31.7% of eyes in PGS and NPGS groups met success criteria at 1 y（P=0.70）. In the PGS group, eyes with baseline IOP ≥21 mm Hg had IOP reductions of 18.1%（P〈0.001）, 16.7%（P〈0.01）, and 8.4%（P=0.31） compared to eyes with baseline IOP 〈21 mm Hg who had IOP reductions of 2.3%（P=0.39）, 3.4%（P=0.19）, and 1.1%（P=0.72） at 1, 6 mo, and 1 y, respectively. CONCLUSION： SLT is efficacious in eyes with prior incisional glaucoma surgery and results in similar IOP reductions compared to eyes without PGS. A larger IOP reduction is observed following SLT in eyes with higher pre-SLT IOP.

Numerical simulation and structure improvement of double throttling in a high parameter pressure reducing valve

In this paper, a new pressure reducing valve （PRV） with an orifice plate is proposed. The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV. A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure, outlet temperature, velocity, and superheat. A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss. The governing equations for internal flow numerical simulation are composed of the continuity, momentum, energy and k-e transport equations, based on isotropic eddy viscosity theory. Different valve plug displacement models were built to describe the double throttling process. Our analysis shows that the steam pressure drops twice and the degree of superheat increases. There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity. After modifying the structure, the numerical results show a better performance of steam flow.