Layout analysis of compressed air and hydraulic energy storage systems for vehicles

The compressed air energy storage system has a better energy density, while the widely used hydraulic one is superior in power performance. Therefore, they are suitable for different hybrid vehicles, which require a comparative study on the performances and vehicle applicability of the broad pressure energy storage system layouts. In this paper, an integrated mathematical model of four basic pressure layouts is presented for characteristic analysis and applicability discussion. Results show that the open volume layout achieves the best power performance with the flow specific power of 13.92 MJ/m3, thus it is suitable for heavy hybrid trucks and mobile machinery. The open mass layout achieves the best energy performance with the energy density of 124.35 MJ/m3, which can be used in light new energy passenger vehicles. And the performance of the closed volume layout is close to the open volume layout with the flow specific power of 9.78 MJ/m3, so it could be applied to middle and light hybrid trucks. This research provides a basis for the hybrid method of pressure energy storage system layouts for vehicles, and could be applied in the design and research of non-electric hybrid vehicles in the near future.

Effect of Local Turbulent Structures on the Hot Jet in Transitional Flow

Turbulent parts localized in flow direction may arise in a pipe with transitional regime of the stable laminar Poiseuille flow. A key condition for occurrence of such structures is a pipe with rather long length relative to its diameter. Our paper presents numerical modelling of the hot air jet flowing from the long pipe into the cold open volume at Re=2426. The modelling was performed in OpenFOAM software on the basis of the large eddy simulation (LES) method. The WALE (Wall-adapting local eddy-viscosity) model was used for closure of Navier-Stokes equations on subgrid scales. We demonstrated that local turbulent structures have a weak effect on the hot jet at flowing into the cold open volume.

Squeezing Perforations Rigless – No Pumping or Injection Required

Squeezing perforated intervals is very common in oil and gas wells, either for isolation to produce from another zone or during P&A applications. Though cement is the common material used in this application, sometimes cement is not ideal. A few of these instances are: 1. The formation is too tight to inject a high viscosity fluid like cement. 2. The temperature of the wellbore exceeds the operating temperature of cement. 3. The "void" behind the casing is too large to fill with cement. 4. Remote locations where mobilizing a rig or coil tubing unit is difficult if not impossible. There is an alternative to cement for "squeezing" perforations that addresses all of these issues, bismuth alloys. Bismuth alloys have a viscosity similar to water and require no pumping or injection into the reservoir. With operating temperatures is up to 325°F, they are suitable for the majority of wells. Unlike cement, bismuth alloys solidify rapidly near the wellbore, isolating the perforations regardless of open volume behind the casing and they are deployed on wireline (rigless).