Abstract:Scaling three main lubricating interfaces (piston/cylinder interface, cylinder block/valve plate interface, and slipper/swash plate interface) of swash plate type axial piston machine while remaining the pump performance is a rewarding but challenging task. Instead of designing a new unit for the desired displacement, scaling a well-designed existing unit to the desired size requires much less computational and experimental cost. However, scaling all the components linearly is far from enough to remain the ori… Show more
“…According to Figures 5-7, by proportionally scaling the axial piston machine, the performance of the three lubricating interfaces does not match the pre-scaled one, which agrees with the result published before [27,28]. The reasons that were found through the analysis and demonstrated through the simulation are that:…”
Section: Findings and Scaling Guidessupporting
confidence: 70%
“…Together with a pump flow temperature prediction model [26], Shang and Ivantysynova proposed a concept for nonlinearly scaling a number of key design parameters in order to compensate for the performance loss due to the size variation; the concept is based on a full factory simulation study [27,28]. According to their research, nonlinearly scaled design parameters are able to bring the scaled pump and motor performance closer to the pre-scaled one.…”
Section: Introductionmentioning
confidence: 99%
“…For the piston/cylinder interface, use a lower normalized clearance for up-scaling, and use a higher normalized clearance for down-scaling [28]. For the cylinder block/valve plate interface, increase the sealing land area for up-scaling, and decrease the sealing land area for down-scaling [27].…”
In lieu of reliable scaling rules, hydraulic pump and motor manufacturers pay a high monetary and temporal price for attempting to expand their production lines by scaling their existing units to other sizes. The challenge is that the lubricating interfaces, which are the key elements in determining the performance of a positive displacement machine, are not easily scalable. This article includes an analysis of the size-dependence of these units with regard to the significant physical phenomena describing the behavior of their three most critical lubricating interfaces. These phenomena include the non-isothermal elastohydrodynamic effects in the fluid domain, and the heat transfer and thermal elastic deflection in the solid domain. The performance change due to size variation is found to be unavoidable and explained through fundamental physics. The results are demonstrated using a numerical fluid–structure–thermal interaction model over a wide range of unit sizes. Based on the findings, a guide to scaling swashplate-type axial piston machines such as to uphold their efficiency is proposed.
“…According to Figures 5-7, by proportionally scaling the axial piston machine, the performance of the three lubricating interfaces does not match the pre-scaled one, which agrees with the result published before [27,28]. The reasons that were found through the analysis and demonstrated through the simulation are that:…”
Section: Findings and Scaling Guidessupporting
confidence: 70%
“…Together with a pump flow temperature prediction model [26], Shang and Ivantysynova proposed a concept for nonlinearly scaling a number of key design parameters in order to compensate for the performance loss due to the size variation; the concept is based on a full factory simulation study [27,28]. According to their research, nonlinearly scaled design parameters are able to bring the scaled pump and motor performance closer to the pre-scaled one.…”
Section: Introductionmentioning
confidence: 99%
“…For the piston/cylinder interface, use a lower normalized clearance for up-scaling, and use a higher normalized clearance for down-scaling [28]. For the cylinder block/valve plate interface, increase the sealing land area for up-scaling, and decrease the sealing land area for down-scaling [27].…”
In lieu of reliable scaling rules, hydraulic pump and motor manufacturers pay a high monetary and temporal price for attempting to expand their production lines by scaling their existing units to other sizes. The challenge is that the lubricating interfaces, which are the key elements in determining the performance of a positive displacement machine, are not easily scalable. This article includes an analysis of the size-dependence of these units with regard to the significant physical phenomena describing the behavior of their three most critical lubricating interfaces. These phenomena include the non-isothermal elastohydrodynamic effects in the fluid domain, and the heat transfer and thermal elastic deflection in the solid domain. The performance change due to size variation is found to be unavoidable and explained through fundamental physics. The results are demonstrated using a numerical fluid–structure–thermal interaction model over a wide range of unit sizes. Based on the findings, a guide to scaling swashplate-type axial piston machines such as to uphold their efficiency is proposed.
“…Assessing the performance of surface shaping via physical testing is prohibitive for cost and time requirement reasons; the present work therefore prototypes virtually, simulating the behavior of the piston–cylinder lubricating interface using the multi-physics model developed at the Maha Fluid Power Research Center by Pelosi, 20 Mizell, 21 and Shang. 22 More information on this model and its validation is available in, 23,24,14,25,5,26 and an example of the design of water-lubricated piston–cylinder interfaces in a commercial APMSPD using the model, with physical testing, can be found in. 27 Since its outputs serve as performance markers in the design studies to follow, a brief overview of the model will be provided here, guided by Figure 5.Figure 5.Multi-physics lubricating interface model (image based on Ref.…”
Water’s low viscosity renders it a poor lubricant, but its green footprint, non-toxicity, inflammability, and low cost make it a desirable hydraulic fluid. Axial piston machines running on water are commercially available, but, especially the larger units, do not operate in the high-pressure regime ( ≥300 bar). The present work investigates micro surface shaping as a design solution for the critical piston–cylinder interfaces of these units, which are particularly hard-struck by the low viscosity of water in that the pistons are subject to a heavy side load, and these interfaces cannot be hydrostatically balanced. Through virtual prototyping, the effect of two surface shapes at a high-pressure operating condition is studied for the case of a 75 cc commercial unit: first, the concave bore profile, which gives the bore surfaces through which the pistons travel the lengthwise cross-section of a circular arc, and second, the barrel piston profile, which bestows this cross-section on the piston running surface instead. The design studies conducted show that, on account of the manner in which the pistons of these machines deform over the high-pressure stroke, the concave bore profile is most able to improve overall load support when its apex is in the middle of the guide length, or shifted toward the displacement chamber. Furthermore, the concave bore profile outperforms the barrel piston profile, largely because when the piston’s axial movement takes its apex into the displacement chamber, this surface shape is no longer able to enhance the piston-bore surface conformity at the end of the interface bordering the displacement chamber that is conducive to hydrodynamic pressure buildup in that region.
“…One limitation about the unit loss look-up table is the data may not be available for all the candidate units with different sizes considered in the study. A possible way to solve this problem is to use the linear scaling method to scale a known unit loss look-up table with respect to a certain unit size to a different unit size [31][32][33]. It introduced a linear scaling factor λ to scale the unit rotational speed, flowrate, and torque as shown in Equations ( 23)- (26).…”
This paper presents a novel method for designing and sizing high-efficient hydrostatic transmissions (HTs) for heavy duty propulsion applications such as agricultural and construction machinery. The proposed method consists in providing cost effective HT architectures that maximizes efficiency at the most frequent operating conditions of the transmission, as opposed to the traditional HT design methods based on the most demanding requirements of the system. The sizing method is based on a genetic optimization algorithm for calculating the optimal displacement of the main units of the HT to maximizes the efficiency in the most frequent operating conditions of the vehicle. A simulation model for HTs is built in MATLAB/Simulink® environment to test three different circuit alternatives for basic HTs. Considering a particular 250 kW heavy-duty application for which drive cycle data were available, this study shows great improvement in energy efficiency (14%) and power saving (20.1%) at frequent operating conditions while still achieving the corner power condition.
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