Amirkabir Journal of Mechanical Engineering Amirkabir J. Mech. Eng., 52(8) (2020) 565-568 DOI: 10.22060/mej.2019.15770.6198 Modeling and Sliding Mode Control of Rotating Helical Pump B. Miripour Fard 1* , A. H. Sajjadinia 2 , F. Hashemi Nader 2 1 Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran. 2 Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran. ABSTRACT: Two-phase fluids transportation is very important in the industry. Rotating helical pump is a special form that can be used to transfer fluid-gas flows and also to generate pulsatile flows. The structure of this pump differs from conventional pumps and its geometry can be changed during operation. In this paper, while demonstrating a fabricated second version of the rotating helical pump, a dynamic analysis is performed for the first time and the governing equations are extracted based on the input control variables (rotational speed and tilt angle of the pump). In the dynamical analysis, a rotating control volume corresponding to a spiral tube is considered. In order to determine the values of the inputs corresponding to the desired outputs, we use the non-dimensional characteristic curves of the pump that was published in the previous study. Then the control is performed on the basis of two input variables to reach the desired pump head and flow rate. A sliding mode controller is implemented. The results include governing equations of the rotating helical pump that can be used in future studies. Moreover, the results show the success of the sliding mode method in control of the pump. Review History: Received: 2019/02/04 Revised: 2019/03/22 Accepted: 2019/04/14 Available Online: 2019/05/03 Keywords: Rotating helical pump Dynamic equation Sliding mode control 565 *Corresponding author’s email: bmf@guilan.ac.ir Copyrights for this article are retained by the author(s) with publishing rights granted to Amirkabir University Press. The content of this article is subject to the terms and conditions of the Creative Commons Attribution 4.0 International (CC-BY-NC 4.0) License. For more information, please visit https://mej.aut.ac.ir/article_3398.html. 1- Introduction There are generally two categories for pumps: displacement pumps and turbomachinery pumps. The positive displacement pumps are suitable when the amount of gas is too high in a very large mixture of multiphase flows. The turbomachinery pumps, are basically used for liquid transportation. The mentioned pumps have been made and used in the industry for a long time. The rotating helical pump, which is the subject of this paper, has a different structure. This pump has been first introduced by Mohseni et al. [1]. The first version of the pump was made and tested empirically, as well as its dimensionless performance characteristics. This pump has special capabilities in addition to the ability to transfer multiphase products which is very important in the industry. It can create pulsatile flow that has some applications in medicine [2] and this kind of flow is effective in increasing heat transfer [3]. Despite the high complexity, many pieces of research have been carried out on the two-phase flow inside the helical tubes. However, the focus of this paper is on the modeling and controlling of the rotating helical pump. In most applications, pumps operate under steady-state conditions. However, in some cases, it is necessary to control the flow rate and head. For example, when the fluid is pumped into (or from) a variable-height tank, the head should be controlled. Different methods are used to control a pump. For pumps with a fixed geometric structure, the pump speed is usually controlled by the Proportional–Integral–Derivative (PID) method [4]. PID method has many benefits and is easy to implement. However, it has also some drawbacks. For example, it is difficult to set up its parameters, and if some of the operating parameters of the system are changed online, PID control cannot be adapted [5]. As a result, methods such as optimal control [6] and sliding mode control [7] are used to control the pumps. The rotating helical pump has a variable structure that can affect the operation of the pump. The novelty of the present article is that, in addition to the construction of the second edition, for the first time, dynamic modeling and control are investigated for this variable structured pump. To this end, the dynamical equations governing the behavior of the pump are derived and, due to its nonlinearity, the sliding mode control method is used for control. 2- Methodology 2- 1- Dynamics of rotating the helical pump The pump of this paper, as shown in Fig. 1, is a rotating helical pump that is used to transport gas-liquid flows. The main structure of this pump consists of a solid cylinder, surrounded by a helical tube. It also passes through a cylinder of a shaft mounted on a bearing. This is a hollow shaft. Bearings are on the chassis. One side of the chassis is on the coupling of the transferring screw and on the other side it is hinged to the bottom of the base. The whole set is inside a reservoir containing a fluid such as water.