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International Journal of Fluid Machinery and Systems DOI: http://dx.doi.org/10.5293/IJFMS.2019.13.1.136 Vol. 13, No. 1, January-March 2020 ISSN (Online): 1882-9554 Original Paper Modeling of the Manifold Configuration for Maximum Efficiency in a Hydraulic Machine Kesar M Kothari 1, R.Udayakumar1, Ram Karthikeyan1, Vishweshwar S1and Nikitha Raj2 1Department of Mechanical Engineering, Bits Pilani Dubai Campus Dubai, United Arab Emirates, [email protected], [email protected], [email protected], [email protected] 2Department of Electrical & Electronics Engineering, Bits Pilani Dubai Campus Dubai, United Arab Emirates, [email protected] Abstract Hydraulic manifolds are metal cuboids machined to realize the compact circuit layout within them. They are introduced in the hydraulic machines to fit the large and complex hydraulic system layouts in narrow spaces available in the machines. Therefore, designing of the manifold in fact is more oriented towards achieving minimum size and weight. But the use of manifold, may introduce high pressure losses in the system. Efficiency of the system decreases and temperature of the fluid increases with pressure drop. This present research work focuses on understanding the pressure losses in the most common channel connections used in the manifold to realize the hydraulic circuit and to understand the efficiency of the manifold at different flow values. To achieve these objectives, a real-time case study is considered, where a manifold for a cable pulling winch machine is modified to reduce the pressure drop and increase the efficiency of the machine. Simple channel models are considered and analyzed using semi empirical equations available in the literature and are compared with results obtained from Computational Fluid Dynamics (CFD) analysis. Various geometric bend models are drafted in Solid Works and then exported to do the CFD software to obtain the pressure drop with different flows. The values obtained from CFD and the characteristic of the valves from the manufacturer’s catalogue are used to create the manifold in Matlab Simulink to predict the performance of the manifold at different flows. Therefore, with these results, the overall hydraulic efficiency of the winch is determined. Keywords: CFD analysis; Efficiency; Hydraulics; Manifolds; Matlab Simulink; Pressure Drop; Solid Works 1. Introduction The science involving the generation of power by utilizing the mechanical properties of fluids encloses the principles of hydraulics. The applications of hydraulics are used to generate, control and transmit power using pressurized liquids. Hydraulic machinery or modern mobile hydraulic equipment use a typical hydraulic circuit in which the pressurized fluid is transferred from hydraulic pumps to different actuators (hydraulic motors and cylinders) through pipes, conduits, channels and valves. The extensive use of this mechanism in drive trains is mainly due to excellent power to weight ratio of the fluid power and large forces produced over a moderate distance. The purpose of the system may be to control the fluid flow or to control the fluid pressure. Hydraulic circuits, in mobile applications such as off-road applications, must fit in the narrow spaces available in the machines and guarantee functionality with acceptable efficiency. So, the hydraulic manifolds are used, which contains compact circuit layouts and can be fitted in a small space. A hydraulic manifold is a rectangular metal block machined to achieve minimum size, less weight and simplify the complex hydraulic circuit layout by logically interlinking the different elements of the internal mechanism of the winch hydraulics. The blocks are drilled through to create internal channels and oil circulation passages which are fitted with screwed cartridge valves. A general drawback for developing a manifold is its high-pressure loss and unwanted temperature rise when manufactured compactly. The efficiency of the hydraulic machine is reduced due to unwanted losses in a compact manifold as well as due to the losses experienced by the other components. So, the designing of the manifold with less pressure drop and good heat dissipation is extremely important. In the past, researches on the manifolds were mainly focused on minimum block size or less volume and mechanical strength. Received November 25 2018; revised January 19 2019; accepted for publication August 02 2019: Review conducted by Xuelin Tang. (Paper number O18052C) Corresponding author: R.Udayakumar, [email protected] 136 2. Literature Review Efficiency of a hydraulic system is the major concern in the industry. In the past, attempts were made to design the manifold blocks in an automated way [1]. The design was focused on fabricating the smallest block possible using the complex machining. Designing hydraulic manifold blocks consisted of placing components and tapping holes on the block and placing oil circulation drillings according to the hydraulic schematic. The optimum result, i.e. a minimum block size, often implies to a rather complicated set of drillings to bring oil circulation between external ports of the components [2]. Nowadays fuel cost, fuel availability and the elimination of pollutants due to the burning of fuel are considered as a priority. So, designs are more focused on the efficiency of the system by reducing the losses in the system. Designing the manifold must focus on the decrease in pressure loss, evaluating heat generation and heat transfer in the system and also analyzing the flow through the passages. Wang J performed a consistent review of different methods to study the flow in manifolds where CFD with discrete and analytical models are analyzed. He even stated that a CFD model is suitable for optimizing the geometry of a manifold that may be too expensive from the point of view of time and computational effort [3]. Yang and Liu et al. studied the effects of different guide vane structures on tangential velocity distribution due to the Rankine vortex characteristics, and the corresponding impacts on the pressure drop[4]. Zhang and Zhou et al. researched numerically the influences of blade profile on velocity distribution, pressure distribution, and flow regulation pattern in the vicinity of an impeller of a centrifugal pump[5]. Heng Wang et al. presented two optimized designs of a commonly-used fluid distribution manifold having one entrance and six exits. Numerical simulations were carried out to optimize the dimensions and mechanisms of these proposed designs for the sake of enhancing the uniformity of fluid distribution amongst the exits and reducing the formation of dead zones inside the manifold cavities [6]. Missirlis D and Jones G.F on the other hand, studied the design parameters that can strongly affect the flow distribution and consequent heat transfer [7-8]. The main losses in the hydraulic systems come from pumps, motors and valves controlling the actuators. According to Lanke’s article the estimation of the impact of the U.S Fluid power industry resulted that the average efficiency of the hydraulic systems in the industrial applications is 50% and drops to 21% for mobile applications [9]. Even a little improvement in efficiency may have greater impact on fuel consumption. So, every component and every aspect of the hydraulic system should be considered carefully. Martinopoulos et al illustrated some examples for the application of CFD on manifolds which are helpful to analyze the flow inside solar collectors that are characterized by complex geometries thus allowing to identify critical regions that can compromise the efficiency [10]. Murrenhoff et al [11] describes the most recent energy-efficient hydraulic architectures for mobile applications. Changing the valve systems in which independent metering or digital valves can be used instead of the traditional ones. Moreover, pump- controlled systems which eliminate the directional valves and energy recovery systems which uses energy from braking or lowering of loads can recover hydraulic energy with accumulators and hydraulic motors. Empirical equations available in the literature are derived for simple bends and connections. These equations cannot be used for evaluating complex connections inside manifold. Internal channels may be present with multiple bends with different curvature values and different diameter sizes. For a singular particular case experiment, measurement of CFD analysis is the only resource to have correct estimation. Moreover, 2D and 3D CFD analysis have proven to be affordable when applied to study the flow through pipes as shown for example in [12]. Abe et al. in two research publications (Pressure drop of pipe flow in manifold block and Flow analysis in pipe of a manifold block respectively) used CFD analysis to analyze pressure drop through a complicated internal passage with multiple elbows for which empirical formulation could not be applied. Thus, it was proved that CFD was assessed to be an effective method to evaluate pressure drop even if a certain gap between the numerical and experimental results were evident [13-14]. Zhong L et al. performed an analysis on a rectangular asymmetric three-dimensional diffuser to assess the performance of a standard k-ε turbulence model for separated flows [15]. Song Z.A in the research and analysis of the resistance characteristic of combined flow channel confirmed the results obtained by applying CFD analysis to a hydraulic manifold with the bend geometries [16].

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