Design and Output Performance Model of Turbodrill Blade Used in a Slim Borehole
Small-diameter turbodrills have great potential for use in slim boreholes because of their lower cost and higher efficiency when used in geothermal energy and other underground resource applications. Multistage hydraulic components consisting of stators and rotors are key aspects of turbodrills. This study aimed to develop a suitable blade that can be used under high temperature in granite formations. First, prediction models for single- and multi-stage blades were established based on Bernoulli’s Equation. The design requirement of the blade for high-temperature geothermal drilling in granite was proposed. A Φ89 blade was developed based on the dimensionless parameter method and Bezier curve; the parameters of the blade, including its radial size, symotric parameters, and blade profiles, were input into ANASYS and CFX to establish a calculation model of the single-stage blade. The optimization of the blade structure of the small-diameter turbodrill enabled a multistage turbodrill model to be established and the turbodrill’s overall output performance to be predicted. The results demonstrate that the design can meet the turbodrill’s performance requirements and that the multistage model can effectively improve the accuracy of the prediction.
Research on rotating speed measurement method of turbodrill based on tilt sensor
The rotating speed of turbodrill is a key parameter for adjusting the drilling process, which needs to be measured in real time. Based on this, a new rotating speed measurement method used in downhole turbodrill based on the tilt sensor is proposed in this paper. The basic principle is that a periodic signal will be generated by the tilt sensor along with the turbodrill, and then the rotating speed can be obtained by using fast Fourier transform to analyze the output data. Test results show that the measurement error is related to the inclination angle of the borehole, that is, this method cannot be used when the inclination angle is less than 0.4 degrees, while the measurement error is less than 3.5% when the inclination angle is more than 0.4 degrees, which meets the practical requirements. Compared with traditional methods, this method will not be interfered by mud, geological conditions and downhole vibration, and it is also a non-contact measurement method, which is very suitable for downhole environment.
A model for predicting heat transfer through gypsum‐board/wood‐stud walls exposed to fire
To facilitate the development of cost-effective and flexible design options there is a need to develop models to predict the fire resistance of wood-frame building assemblies. Such assemblies often derive much of their fire resistance from a protective membrane composed of gypsum board. A simple two-dimensional computer model is presented to predict heat transfer through gypsum-board/wood-stud walls exposed to fire. Input data for the thermophysical properties of gypsum board were measured exploying standard bench-scale tests. Input data for wood were selected from the literature. Small-and full-scale fire resistance tests were conducted on gypsum-board/wood-stud wall assemblies to provide data for the validation of the model. The model is shown to predict heat transfer through these walls rather well.