Pumping Losses Research Articles

A Study on the Fuel Economy Potential of Parallel and Power Split Type Hybrid Electric Vehicles

What is the best number of gear steps for parallel type hybrid electric vehicles (HEVs) and what are the pros and cons of the power split type HEV compared to the parallel type have been interesting issues in the development of HEVs. In this study, a comparative analysis was performed to evaluate the fuel economy potential of a parallel HEV and a power split type HEV. First, the fuel economy potential of the parallel HEV was investigated for the number of gear steps. Four-speed, six-speed, and eight-speed automatic transmissions (ATs) and a continuously variable transmission (CVT) were selected, and their drivetrain losses were considered in the dynamic programming (DP). It was found from DP results that the power electronics system (PE) loss decreased because the magnitude of the motor load leveling power decreased as the number of gear steps increased. On the other hand, the drivetrain losses including the electric oil pump (EOP) loss increased with increasing gear step. The improvement rate from the 4-speed to the 6-speed was the greatest, while it decreased for the higher gear step. The fuel economy of the CVT HEV was rather low due to the large EOP loss in spite of the reduced PE loss. In addition, the powertrain characteristics of the parallel HEV were compared with the power split type HEV. In the power split type HEV, the PE loss was almost double compared to that of the parallel HEV because two large capacity motor-generators were used. However, the drivetrain loss and EOP loss of the power split type HEV were found to be much smaller due to its relatively simple architecture. It is expected that the power characteristics of the parallel and power split type HEVs obtained from the DP results can be used in the development of HEV systems.

Valve timing optimisation of a spark ignition engine with skip cycle strategy

Skip cycle strategy (SCS) is a stroke volume modulation method leading to reduction in pumping loss through deactivation of engine valves under part-load conditions. Although SCS achieves a significant fuel economy, it increases regulated pollutant emissions such as nitrogen oxide and unburned hydrocarbon in comparison to normal 4-cycle engine operation. This paper investigated normal cycle strategy, skip cycle strategy as well as combination of skip cycle strategy and variable valve timing strategy for a spark-ignition engine using one-dimensional numerical model. The skip cycle engine was modelled at several steady-state operation points and then optimised at best ignition timing providing maximum brake torque at each simulation case. The numerical results obtained for both normal cycle and skip cycle have been validated against the experimental data. After completing the validation of numerical results with engine test bench data for both normal and skip cycle operations, optimisation of intake and exhaust valve timing profiles have been carried out regarding advancing or retarding camshaft relatively to the crankshaft position. In case of SCS and variable valve timing application together, NOx concentration was reduced by 35.1%, 39.4%, 26.8% and HC emission was reduced by 54.9%, 49.3% and 47.4% on average for brake mean effective pressure load levels of 1, 2 and 3 bar respectively at all among engine speed ranges between 1200 and 1800 rpm compared to stand alone SCS strategy. Furthermore, no remarkable additional brake specific fuel consumption was observed for SCS plus variable valve timing strategy compared to stand alone SCS.

Localized plasmonic fields of nanoantennas enhance second harmonic generation from two-dimensional molybdenum disulfide

Abstract

Diesel air path control using pressure difference: Pumping loss and aging considerations

Pressure difference across the exhaust and intake manifolds ([Formula: see text] P) is a crucial variable to control the pumping loss and cylinder charge dilution through the exhaust gas recirculation in a diesel engine. This paper presents a novel architecture for controlling [Formula: see text] P and the engine-out NO x emissions, which increases the controller tolerance to engine components aging. The architecture has an internal control loop, designed as a two-input two-output controller, to coordinate the exhaust gas recirculation and variable geometry turbine valves. Using feedback from [Formula: see text] P and the estimated cylinder oxygen ratio [Formula: see text] cyl, the two-input two-output controller regulates the pumping loss and the engine NO x emissions. To reduce high turbo lag and its associated slow air–fuel ratio ([Formula: see text]) response, which are inherent features of a [Formula: see text] P-based control strategy, the two-input two-output linear quadratic controller is tuned such that [Formula: see text] is also regulated, but only during fast transients. An external loop is supplementing the core two-input two-output controller correcting the internal loop set points to reduce the effects of [Formula: see text] cyl estimation errors on NO x control and ensure [Formula: see text] stays above a minimum value, [Formula: see text] min, critical for smoke emissions. As a feature of the proposed control system, direct feedback from [Formula: see text] P increases pumping loss robustness to common degradation in diesel engines, namely, turbine efficiency and diesel particulate filter blockage due to ash deposit, compared to a conventional boost pressure–based controller. Also, it is shown that the input–output coupling structure of the proposed two-input two-output controller and use of the NO x feedback mitigate effects of exhaust gas recirculation fouling and associated exhaust gas recirculation valve saturation on increase in NO x emission.

Determination of the spin Hall effect and the spin diffusion length of Pt from self-consistent fitting of damping enhancement and inverse spin-orbit torque measurements

Understanding the evolution of spin-orbit torque (SOT) with increasing heavy-metal thickness in ferromagnet/normal metal (FM/NM) bilayers is critical for the development of magnetic memory based on SOT. However, several experiments have revealed an apparent discrepancy between damping enhancement and damping-like SOT regarding their dependence on NM thickness. Here, using linewidth and phase-resolved amplitude analysis of vector network analyzer ferromagnetic resonance (VNA-FMR) measurements, we simultaneously extract damping enhancement and both field-like and damping-like inverse SOT in Ni$_{80}$Fe$_{20}$/Pt bilayers as a function of Pt thickness. By enforcing an interpretation of the data which satisfies Onsager reciprocity, we find that both the damping enhancement and damping-like inverse SOT can be described by a single spin diffusion length ($\approx$ 4 nm), and that we can separate the spin pumping and spin memory loss (SML) contributions to the total damping. This analysis indicates that less than 40% of the angular momentum pumped by FMR through the Ni$_{80}$Fe$_{20}$/Pt interface is transported as spin current into the Pt. On account of the SML and corresponding reduction in total spin current available for spin-charge transduction in the Pt, we determine the Pt spin Hall conductivity ($\sigma_\mathrm{SH} = (2.36 \pm 0.04)\times10^6 \Omega^{-1} \mathrm{m}^{-1}$) and bulk spin Hall angle ($\theta_\mathrm{SH}=0.387 \pm0.008$) to be larger than commonly-cited values. These results suggest that Pt can be an extremely useful source of SOT if the FM/NM interface can be engineered to minimize SML. Lastly, we find that self-consistent fitting of the damping and SOT data is best achieved by a model with Elliott-Yafet spin relaxation and extrinsic inverse spin Hall effect, such that both the spin diffusion length and spin Hall conductivity are proportional to the Pt charge conductivity.

Decentralized Feedback Control of Pumping Losses and NOx Emissions in Diesel Engines

A novel decentralized control architecture is developed based on a feedback from the pressure difference across the engine which is responsible for the pumping losses and the exhaust gas recirculation (EGR) flow in diesel engines. The controller is supplemented with another feedback loop based on NOx emissions measurement. Aiming for simple design and tuning, the two control loops are designed and discussed: one manipulates the variable geometry turbine (VGT) actuator and the other manipulates the EGR valve. An experimentally validated mean-value diesel engine model is used to analyze the best pairing of actuators and set points. Emphasis is given to the robustness of this pairing based on gain changes across the entire operating region, since swapping the pairing needs to be avoided. The VGT loop is designed to achieve fast cylinder air charge increase in response to a rapid pedal tip-in by a feedforward term based on the real-time derivative of the desired boost pressure. The EGR loop relies on a feedback measurement from a NOx sensor and a real-time estimation of cylinder oxygen ratio, χcyl. The engine model is used for evaluating the designed controllers over the federal test procedure (FTP) for heavy duty (HD) vehicles. Results indicate that the control system meets all targets, namely fast air charge and χcyl control during torque transients, robust NOx control during steady-state operation, and controlled pumping losses in all conditions.

Effect of Charge Density on Spray Characteristics, Combustion Process, and Emissions of Heavy-Duty Diesel Engines

In-cylinder charge density at top dead center is an important parameter of diesel engines and is influenced by intake pressure, intake temperature, and compression ratio. The effects of charge density on fuel spray, combustion process, and emissions were investigated by using a constant volume bomb and a heavy-duty diesel engine. Spray development resistance increased with the increase of the charge density in the constant volume bomb. It was found that short spray penetration was accompanied by a large spray cone angle in the former stage with high charge density. However, the equivalence ratio was lowered and the degree of homogeneity of the mixture was increased in the later stage owing to the rapid interaction of fuel and gas at a high mixing rate. Combining the first law of thermodynamics and the second law of thermodynamics for analysis, as the charge density increased, the gross indicated thermal efficiency (ITEg) was improved. However, pumping loss had to be considered with higher charge density. Under this condition, the brake thermal efficiency (BTE) trend was increased initially and decreased subsequently. Under high-load operation (1200 r/min BMEP, 2.0 MPa), the minimum charge density value of 44.8 kg/m3 was found to be reasonable. This charge density was suitable for combustion and brought about minimum exhaust energy and trade-off emissions. Moreover, by analyzing two operation conditions in terms of the maximum BTE with the Miller and the conventional cycles, compression temperature and combustion temperature were reduced in the Miller cycle with the charge density 44.8 kg/m3. A high Cp/Cv could improve the cylinder exergy/power conversion process by its positive effect of increasing the specific heat ratio. Owing to the interaction between a high Cp/Cv and exergy loss to heat transfer, the condition with the minimal charge density could produce more piston work.

End Use Level Water and Energy Interactions: A Large Non-Residential Building Case Study

Within the European Union, buildings account for around 40% of the energy use and 36% of CO2 emissions, thus representing a significant challenge in the context of recent EU directives that require all new buildings to be nearly zero-energy by 2020. Reduced consumption of water, and hot water in particular, provides a significant opportunity to reduce energy consumption. While there have been numerous studies pertaining to the water-energy nexus of residential buildings, the complexity of water networks in larger buildings has meant that this area has been relatively unexplored. The paper presents a comprehensive investigation of the hot water use profile, associated energy use, on-site pumping energy use, carbon emissions, and solar energy harvesting potential in an Irish university building over periods before and after water conservation efforts. Total water-related energy consumption (including the heating and pumping losses) were analysed using the WHAM model and modified pumping energy expressions. The results revealed that water heating including losses contributed to as high as 30% of total building energy consumption, and stringent water conservation measures reduced the average hot water use rate by 8.5 m3/day. It was found that 10% of the total pumping energy was constituted by pump start-ups. Simulation results for solar harvesting potential in the study site found that around 60% of water heating energy demand could be met by solar energy in the new water demand scenario. The study results can act as a benchmark for similar buildings, and the model combination can be emulated in future studies.

Temporary and Permanent Viscosity Loss Correlated to Hydraulic System Performance

ABSTRACTStraight- and multigrade fluids were evaluated in a hydraulic dynamometer that incorporated a pressure-compensated axial piston pump and a fixed displacement axial piston motor. Pump, motor, pressure compensator, and directional control valve internal flow losses were determined under various conditions of pressure, speed, and temperature. Fluid samples were collected before and at various times during the dynamometer experiments, and viscosity measurements were performed to probe for correlations between viscosity, operating time, and system leakage flow losses. The low shear rate viscosities of the multigrade fluids decreased linearly throughout the duration of testing due to polymer degradation. However, system flow losses did not exhibit a statistically significant increase as the multigrade fluids sheared down. The fluids were also characterized by their permanent viscosity loss produced in sonic shear and tapered bearing tests and by their temporary shear thinning measured in an ultra-high-shear viscometer at several temperatures. The effects of these viscous properties were analyzed using an empirical model to identify which measures of viscosity were most correlated with flow loss. The results suggested that the relative contributions of temporary and permanent viscosity loss change as the fluid is used. Further, analysis of torque loss and input power revealed that input power and losses are more useful indicators of the effect of fluids on hydraulic system performance than pump efficiency.

Back pressure effect on three-way catalyst light-off

The effect of back pressure on the light-off of a modern spark ignition engine three-way catalyst has been assessed by measuring the hydrocarbon conversion efficiency in a hot flow bench and in the cold-idle period in an engine. In the flow bench experiment, a small amount of propane/air mixture is used as a surrogate for the hydrocarbon mixture. The conversion efficiency is found to be only a function of temperature. The efficiency is independent of pressure, space velocity, and the equivalence ratio of the hydrocarbon mixture for λ ≥ 1. In the engine test, while the engine-out exhaust gas temperature is higher at a higher back pressure, there is little difference between the gas temperatures at the catalyst entrance for different back pressures at retarded spark timing. This observation is attributed to the larger amount of exhaust hydrocarbon conversion oxidation between the engine exit and the catalyst entrance with the lower back pressure. The heat release from this oxidation compensates for the lower engine-out exhaust temperature at the lower back pressure. The catalyst temperature increases modestly and light-off time shortens correspondingly at the higher back pressure. This observation is attributed solely to the increase in mass flow rate (and thus exhaust sensible enthalpy flow rate) of the engine needed to overcome the additional pumping loss due to the throttling of the exhaust. These results have been confirmed with a simple one-dimensional catalyst model.

PRODUCTIVE STRATA FLOODING ENERGY CONSUMPTION AT EXTRACTIVE ENTERPRISE AS A COMPLEX SYSTEM

Background The technological processes of the oil and gas industry are characterized by high energy intensity. Pumps are the prevailing technological electric drive equipment. The operation of the waterflooding system, along with the well equipment of mechanized oil production, determines mainly the efficiency of the development of oil and gas fields, the share of electricity for the operation of the waterflooding system at the late stage of development can reach 30 % of the total energy balance of the oil field. Aims and Objectives Study the questions of development of a hierarchy in the structure of consumption of electric energy in the system of maintaining pressure in productive reservoirs of deposits. Ranking the places of occurrence of energy costs in the waterflooding system, taking into account additional criteria will allow to optimize the flow of investments for the implementation of energy efficiency improvement measures. Methods The structure of the energy balance of the field is developed on the basis of data bases of technological parameters of exploitation of the oil field for 5 years. The multicriterial problem of vector optimization of the subsystem ranking has been formulated, a 4-dimensional space of particular features for 7 subsystems of the reservoir pressure maintenance system has been developed. At the preliminary stage of ranking the subsystems, a method of forming the Pareto set is used. The restriction of the Pareto set is realized by an additive convolution, the validity of which is proved by the homogeneity of particular characteristics. Results On the example of one of the deposits of the Republic of Sakha, the energy structure of the oil flooding system is developed. The shares of electric power consumption for overcoming the hydraulic resistance of all links in the system of ground and underground infrastructure and energy losses in pumps are determined. The systematization of the internal links of the subsystems determined the multi-level hierarchical appearance of the structure of the waterflooding system. A set of Pareto-optimal subsystems is formed on the basis of the 4-dimensional vector of particular features. As a result of the scalarization of the vector of quotients, the subsystems of the waterflooding system are ranked.

Improving the partial-load fuel economy of 4-cylinder SI engines by combining variable valve timing and cylinder-deactivation through double intake manifolds

The SI engines in passenger cars run in the partial-load conditions in the most time especially in the urban driving cycles; thus it is particularly important to improve the partial-load fuel economy. Cylinder deactivation (CDA) and variable valve timing (VVT) could be applied to improve the fuel economy in the middle to low load region. Current CDA technologies are realized by deactivating all intake and exhaust valves (CDAV) of the inactive cylinders with special mechanisms increasing system cost and complexity. An innovative CDA method is proposed for 4-cylinder SI engines through double intake manifolds (CDAM). A novel load control strategy combining the CDAM and VVT along with late intake valve closure (LIVC) has been investigated. The results show that the pumping loss decreases by 58.9–65.6% and 24.5–35.3%; and the fuel economy improves by 5.5–17.6% and 3.1–9.2% in the CDA mode at 2000 rpm and 4000 rpm, respectively. The fuel economy in the full-cylinder mode also improves by 0.68–2.95% because of the application of the double intake manifolds. The strategy is more effective in the low speed range and more suitable for the urban driving cycles. Although a less fuel economy improvement than the CDAV method, the CDAM method can be realized with less cost and complexity.

The Influence of Water and Mineral Oil On Mechanical Losses in the Displacement Pump for Offshore and Marine Applications

Abstract In this paper mechanical losses in a positive displacement pump supplied with water and mineral oil (two liquids having significantly different viscosity and lubricating properties) are described and compared. The experimental tests were conducted by using a prototype satellite pump of a special design. The design of the satellite pump is presented in the article. The pump features and a non-circular tooth working mechanism was developed to work with both water and mineral oil. The sources of mechanical losses in such pump are also characterized in this paper. On this basis, a mathematical model of the losses has been developed and presented. The results of the calculation of mechanical losses according to the model are compared with the results of the experiment. The experimental studies have shown that the mechanical losses in the water pump are even 2.8 times greater than those in the oil pump. It has been demonstrated that the mathematical model well describes the mechanical losses both in the water pump and the oil pump. It has been found that the results from the loaded pump simulation (at Δp=25MPa) differ from the results of the experiment by no more than 5% both for oil and water.

Top-Down and Bottom-Up Approaches for Water-Energy Balance in Portuguese Supply Systems

Water losses are responsible for increased energy consumption in water supply systems (WSS). The energy associated with water losses (EWL) is typically considered to be proportional to the water loss percentage obtained in water balances. However, this hypothesis is yet to be proved since flow does not vary linearly with headlosses in WSS. The aim of this paper is to validate the hypothesis, present real-life values for water-energy balance (WEB) components, and reference values for the key performance indicator that represents the ratio of total energy in excess (E3). This validation is achieved through the application of two approaches—top-down and bottom-up. The first approach requires minimum data, gives an overview of the main WEB components, and provides an effective diagnosis of energy inefficiencies through the calculation of E3 related to pumps, water losses, and networks. The second approach requires calibrated hydraulic models and provides a detailed assessment of the WEB components. Results allow the validation of the stated hypothesis as well as show that the most significant energy inefficiencies are associated with surplus energy, pumping, and water losses, each reaching up to 40% of total input energy. Less significant components are pipe friction and valve headlosses, each reaching up to 15% of total input energy.

Effect of intake swirl on combustion performance in an unthrottled spark ignition engine

A Fully Hydraulic Variable Valve System is described in this article which can achieve continuous variation in valve lift, duration, and timing. The system was installed in a four-cylinder port fuel injection spark ignition engine and achieved unthrottled load control through early intake valve closing. The in-cylinder pressure measured experimentally showed that pumping losses of the unthrottled spark ignition engine at 2000 r/min and 0.189 MPa brake mean effective pressure was reduced by 85.4% compared with the throttled spark ignition engine. However, its slow and unstable combustion reduced the indicated thermal efficiency. Compared with the throttled spark ignition engine, the amount of residual exhaust flowing back into the intake port was greatly reduced at the early stage of the intake process. Consequently, it negatively influenced fuel evaporation and fuel–air mixing processes in the intake port of the port fuel injection spark ignition engine and decreased the flow of in-cylinder gases, which resulted in a low combustion rate. A new centrosymmetric helical valve is proposed in this article to improve the fuel–air mixing and combustion rate of the unthrottled spark ignition engine. The experiments demonstrate that the helical valve can generate a strong intake swirl at small intake valve lift. It helps to increase combustion rate and lower cycle-to-cycle variation, which improves indicated thermal efficiency and fuel economy of the unthrottled spark ignition engine at low load.

Comparative study on the pumping losses between continuous variable valve lift (CVVL) engine and variable valve timing (VVT) engine

VVL and VVT are two common approaches to reduce engine pumping loss at part loads, however, the comparative study on their potentials and influence factors of pumping loss reduction is scarce. In this paper, the gas exchange processes of CVVL and VVT engines were investigated by bench testing. The mechanism and influence factors of pumping loss in the two types of engines were comparatively analyzed, the theoretic limitations of pumping loss in intake process were deduced and the suggestions to approach the theoretic minimum were proposed. The results show that the gross indicated mean effective pressure (IMEP) of engine is approximately proportional to cylinder pressure at bottom dead center (BDC) for both traditional throttle control strategy and early intake valve closing (EIVC) strategy. The difference of pumping losses between CVVL and VVT engines results from intake process. Due to the differences of intake modes, the CVVL engine has lower intake loss than VVT engine by nature. The pumping loss in intake process of CVVL engine is much closer to the theoretical minimum, and the BSFC of CVVL engine can be reduced by more than 20% at 2000 r/min and 2.3 bar IMEP by increasing the maximum lift of intake valve. All these have provided guidance for pumping loss reduction of gasoline engine.

Thermal Analysis of a Flux Pump With Simplified Conduction-Cooled Superconducting Magnet Model

A flux pump is one possible way to reduce the heat load of a superconducting magnet system by replacing mechanical connections with magnetic coupling. However, the heat loss of the flux pump should be analyzed so that it can be applied to conduction-cooled magnets because of the low temperature margin in conduction-cooled systems. In this paper, the simplified thermodynamic behavior of a linear-type flux pump system is investigated. The system is assumed to be cooled by a conduction cooling system. The heat generation of a linear-type flux pump is calculated based on the ac loss theory. The temperature stability of a thermal link for the flux pump system is analyzed with different design parameters. A design method is suggested for the thermal conductivity of the thermal link in a flux pump of conduction-cooled magnet by summarizing the results of the analysis.

Internal unsteady flow characteristics of centrifugal pump based on entropy generation rate and vibration energy

The transient fluid exciting force induced by unsteady flow in the centrifugal pump is the only exciting force that cannot be effectively eliminated. In order to explore the vibration problem caused by unsteady flow in the centrifugal pump, the steady and unsteady numerical calculations of the internal flow in a centrifugal pump with low specific speed were carried out under different flow rate conditions. With volute circumferential pressure pulsation test, the accuracy of numerical calculations was verified. At the same time, the vibration acceleration sensors were arranged in different positions of the pump body to complete the vibration characteristics experiment under different working conditions. Based on the numerical results, the amount and location of the internal flow loss of the centrifugal pump were predicted by the entropy generation rate method. According to the results of the vibration test, the vibration energy distribution of the centrifugal pump under different working conditions was obtained. In combination with the entropy generation rate and vibration energy distribution, the change rules of flow loss and the vibration energy with the flow condition of the pump were analyzed. By using the frequency-domain analysis method, the pressure pulsation, the unsteady radial fluid exciting force fluctuation and the vibration acceleration were compared and analyzed to study the change rules of the pressure pulsation, the unsteady fluid exciting force and the vibration characteristics with the flow rate. The results show that the internal flow loss is mainly concentrated in the impeller runner near the volute tongue under low flow condition and the internal flow loss under large flow rate condition is mainly concentrated in the volute channel near the pump outlet. The vibration induced by the unsteady flow in the centrifugal pump is mainly low-frequency vibration, which is very sensitive to the change of the flow rate. The vibration energy in the middle- and high-frequency ranges is almost not affected by the working condition. The internal flow loss and the low-frequency vibration energy change with the flow condition, showing similar change rules.

Optimization of Sine-Wave Clocking for High-Frequency AC-DC Conversion.

Wireless energy harvesting devices convert received AC energy into DC voltages suitable to power the back-end functionality of the devices. The low energy available to the devices require high AC-DC conversion efficiency in order for enough power to be delivered to the load. This paper presents a model to characterize loss through charge pump cells in wireless energy harvesting devices. The proposed model includes the time-domain effects of the input radio-frequency (RF) energy wave and provides additional insight into how clock and switch parameters along with architecture considerations can be used to improve the efficiency of AC-DC conversion. Results are verified using simulation in a 0.18-μm CMOS technology. We show the impact of threshold voltage on reverse conduction and the limitations on increasing transistor switch sizes to support high current loads. Design examples use the presented model to optimize design parameters to decrease loss in the charge pump. We compare the performance between sine-wave and square-wave clocked charge pumps to show the trade-off between charge pump loss and clock generation power consumption. Furthermore, the benefits of easily computing architectural changes is demonstrated using the proposed model showing how the calculated equivalent resistance can be used to determine the benefits of mixed-mode clocking.

Establishing a Relationship between Hydraulic Efficiency and Temperature Rise in Centrifugal Pumps: Experimental Study

AbstractHydraulic losses of a low specific speed centrifugal pump originate in the friction and turbulent dissipations in all components between the suction and discharge nozzles as well as fluid r...