LEARN MORE ABOUT HYDRAULIC TECHNOLOGY IN HYDRAULIC SYSTEMS DESIGN WITH THIS COMPREHENSIVE RESOURCE
Hydraulic Fluid Power provides readers with an original approach to hydraulic technology education that focuses on the design of complete hydraulic systems. Accomplished authors and researchers Andrea Vacca and Germano Franzoni begin by describing the foundational principles of hydraulics and the basic physical components of hydraulics systems. They go on to walk readers through the most practical and useful system concepts for controlling hydraulic functions in modern, state-of-the-art systems.
Written in an approachable and accessible style, the book’s concepts are classified, analyzed, presented, and compared on a system level. The book also provides readers with the basic and advanced tools required to understand how hydraulic circuit design affects the operation of the equipment in which it’s found, focusing on the energy performance and control features of each design architecture. Readers will also learn how to choose the best design solution for any application.
Readers of Hydraulic Fluid Power will benefit from:- Approaching hydraulic fluid power concepts from an “outside-in” perspective, emphasizing a problem-solving orientation- Abundant numerical examples and end-of-chapter problems designed to aid the reader in learning and retaining the material- A balance between academic and practical content derived from the authors’ experience in both academia and industry- Strong coverage of the fundamentals of hydraulic systems, including the equations and properties of hydraulic fluids
Hydraulic Fluid Power is perfect for undergraduate and graduate students of mechanical, agricultural, and aerospace engineering, as well as engineers designing hydraulic components, mobile machineries, or industrial systems.
Table of Contents
PART I:Fundamental principles4
Objectives4
CHAPTER 1:Introduction to hydraulic control technology6
Historical perspective7
Fluid power symbology and its evolution12
Common ISO Symbols16
Problems25
CHAPTER 2:Hydraulic fluids28
Ideal vs. Actual hydraulic fluids28
Classification of hydraulic fluids31
Mineral oils (H)32
Fire resistant fluids (HF)33
Synthetic fluids (HS)34
Environmentally friendly fluids34
Water hydraulics34
Comparisons between hydraulic fluids35
Physical properties of hydraulic fluids36
Fluid compressibility: Bulk Modulus
Fluid density38
Fluid viscosity42
Viscosity as a function of temperature43
Viscosity as a function of pressure47
Entrained air, gas solubility and cavitation48
Entrained air48
Gas solubility48
Equivalent properties of liquid-air mixtures50
Contamination in hydraulic fluids57
Considerations on hydraulic filters59
Filter placement64
Considerations on hydraulic reservoirs68
Tank volume68
Basic design of a tank69
Problems71
CHAPTER 3:Fundamental Equations73
Pascal’s law73
Basic law of fluid statics74
Volumetric flow rate77
Conservation of mass80
Application to a hydraulic cylinder81
Bernoulli’s Equation84
Generalized Bernoulli’s equation85
Major losses calculation87
Minor losses89
Hydraulic resistance90
Stationary modeling of flow networks92
Momentum equation96
Flow forces100
Problems106
CHAPTER 4(*):Orifice Basics111
The orifice equation111
Fixed and variable orifices115
Power loss in orifices117
Parallel and series connection of orifices119
Functions of orifices in hydraulic systems123
Orifices in pressure and return lines123
Orifices in pilot lines126
Problems131
CHAPTER 5:Dynamic Analysis of Hydraulic Systems134
Pressure build-up Equation - hydraulic capacitance134
Fluid inertia Equation - hydraulic inductance140
Modeling flow network - dynamic considerations146
Validity of the lumped parameter approach151
Further considerations on the line impedance model152
Damping effect of hydraulic accumulators153
Problems156
References160
PART II:Main hydraulic components4
Objectives5
CHAPTER 6 (**):Hydrostatic pumps and motors6
Introduction6
The ideal case7
General operating principle9
ISO symbols13
Ideal equations14
The real case16
Losses in pumps and motors17
Fluid compressibility17
Internal and external leakage20
Friction21
Other types of losses23
Volumetric and hydro-mechanical efficiency24
Trends for volumetric and hydromechanical efficiencies28
Design types34
Swashplate type axial piston machines35
Bent axis type axial piston machines38
Radial piston machines39
Gear machines40
Vane type machines43
Problems46
CHAPTER 7(*):Hydraulic cylinders50
Classification50
Cylinder analysis52
Ideal vs. real cylinder55
Problems61
CHAPTER 8(*):Hydraulic control valves63
Spring basics64
Check and shuttle valves65
Check valve65
Pilot operated check valve66
Shuttle valve67
Pressure control valves68
Pressure relief valve68
Direct acting pressure relief valve68
Pilot operated pressure relief valve72
Pressure reducing valve75
Direct acting pressure reducing relieving valve75
Pilot operated pressure reducing valve77
Flow control valves80
Two-way flow control valve80
Fixed displacement pump circuit with a two-way flow control valve83
Three-way flow control valve87
Fixed displacement pump circuit with a three-way flow control valve89
Directional control valves95
Meter-in and meter-out configurations97
Neutral position100
Actuation methods103
Servovalves107
Characteristic of servovalves112
Servovalves vs. proportional valves123
Problems126
CHAPTER 9(*):Hydraulic Accumulators132
Accumulator Types132
Weight loaded accumulators132
Spring-loaded accumulators132
Gas-charged accumulators133
Piston-type accumulators133
Diaphragm-type accumulators134
Bladder-type accumulators135
Operation of gas charged accumulators137
Typical applications138
Energy accumulation138
Emergency supply140
Energy recuperation140
Hydraulic suspensions140
Pulsation dampening - shock attenuation141
Equations and sizing142
Accumulator as energy storage device142
Accumulator as dampening device145
Problems151
References154
PART 3:Actuator control concepts3
Objectives3
CHAPTER 10 (*):Basics of actuator control5
Control methods: speed, force and position control5
Resistive and overrunning loads7
Power flow depending on the load conditions9
Problems11
CHAPTER 11:General concepts for controlling a single actuator13
Supply and control Concepts13
Flow supply - primary control18
Flow supply - metering control19
Flow supply - secondary control21
Pressure supply - primary control21
Pressure supply - metering control23
Pressure supply - secondary control25
Additional remarks26
CHAPTER 12:Regeneration with single rod actuators27
Basic Concept of regeneration27
Actual implementation32
Directional control valve with external regeneration valves32
Directional control valve with regenerative extension position33
Solution with automated selection of the regeneration mode34
Problems36
References38
PART 4:Metering controls for a single actuator3
Objectives3
CHAPTER 13:Fundamentals of metering control5
Basic meter-in and meter-out control principles5
Meter-in control
Extension with resistive loads
Retraction with overrunning loads
Meter-out control10
Extension with resistive loads 14
Retraction with overrunning loads18
Remarks on meter-in and meter-out controls19
Actual metering control components36
Single spool proportional DCVs41
Independent metering control elements38
Usage of anti-cavitation valve for unloaded meter-out51
Problems49
CHAPTER 14:Load holding and counterbalance valves53
Load holding valves53
Pilot operated check valve61
Counterbalance valves60
Basic operating principle67
CBV architecture69
CBV detailed operation72
Effect of the pilot ratio and of the pressure setting83
Counterbalance valve with vented spring chambers85
Problems78
CHAPTER 15:Bleed-off and open center circuits80
Bleed-off circuit operation91
Energy analysis94
Basic open center system97
Operation98
Open center valve design101
Energy analysis102
Advanced open center control architectures106
Negative flow control106
Basic Schematic106
Operation107
Pump displacement setting mechanism110
Positive flow control114
Basic Schematic114
Operation115
Pump displacement setting mechanism115
Energy analysis for advanced open center architectures116
Problems118
CHAPTER 16:Load sensing systems109
Basic load sensing control concept121
LS system with fixed displacement pump122
Basic Schematic122
Operation123
Energy analysis125
Saturation conditions126
Load sensing valve127
LS system with variable displacement pump137
Basic Schematic137
Operation138
Energy analysis139
Saturation conditions140
Load sensing pump148
LS solution with independent metering valves157
Electronic load sensing (E-LS)159
Problems162
CHAPTER 17:Constant pressure systems150
Constant pressure system based on a variable displacement pump163
Basic schematic and operation163
Energy analysis166
Constant pressure system with unloader (CPU)167
Constant pressure system based on a fixed displacement pump170
Basic schematic and operation170
Application to hydraulic braking circuits173
Problems175
References
PART 5:Metering control of multiple actuators3
Objectives3
CHAPTER 18:Basics of multiple Actuator Systems5
Actuators in series and in parallel5
Series configuration6
Parallel configuration8
Elimination of the load interference in parallel actuators12
Solving load interference using compensators12
Solving load interference with a volumetric coupling13
Syncronization of parallel actuators through flow dividers15
Spool type flow divider15
Spool type flow divider-combiner16
Volumetric flow divider-combiner19
Linear flow divider-combiner24
Rotary flow divider-combiner25
Problems23
CHAPTER 19:Constant pressure systems for multiple actuators27
Basic concepts for a Multi-user constant pressure system27
Basic schematic35
Flow saturation36
Energy analysis37
Complete schematic of a multi-user constant pressure system29
Problems33
CHAPTER 20:Open center systems for multiple actuators35
Parallel open center systems36
Operation46
Energy analysis48
Flow saturation49
Considerations on the open center spool design49
Opening areas39
Opening delay (valve timing)41
Load interference in open center systems41
Tandem and series open center systems47
Tandem configuration60
Series configuration63
Advanced open center circuit for multiple users: the case of excavators49
Problems52
CHAPTER 21:Load sensing systems for controlling multiple actuators53
Load sensing system without pressure compensation (LS)53
Basic circuit69
Energy analysis72
Valve implementation and extension to more actuators74
Load sensing pressure compensated systems (LSPC)61
LSPC with pre-compensated valve technology61
Basic circuit79
Energy analysis82
Valve implementation and architecture84
LSPC with post-compensated valve technology70
Basic circuit90
Energy analysis92
Valve implementation and architecture94
Flow saturation and flow sharing in LS systems79
Flow saturation with pre-compensated LSPC80
Flow saturation with post-compensated LSPC82
Pre vs. post compensated comparison84
Independent metering systems with load sensing88
Problems91
CHAPTER 22:Power steering and hydraulic systems with priority function102
Hydraulic power steering103
Classification of hydraulic power steering systems103
Hydrostatic power steering111
Hydrostatic steering unit description114
Types of hydrostatic steering units119
Priority valves121
Priority valve for a fixed displacement flow supply121
Priority valve for load sensing circuits128
Problems131
References
PART 6:Hydrostatic transmissions and hydrostatic actuators3
Objectives5
CHAPTER 23:Basics and classifications6
Hydrostatic transmissions and hydrostatic actuators6
Basic definitions6
Supply concepts used in HTs and HAs9
Primary units for hydrostatic transmissions and actuators10
Constant speed prime mover and variable displacement pump10
Variable speed prime mover and fixed displacement pump10
Variable speed prime mover and variable displacement pump11
Over-center variable displacement pump11
Typical applications12
CHAPTER 24:Hydrostatic transmissions15
Main parameters of a hydrostatic transmission15
Theoretical layouts19
Pump and motor with fixed displacement (PFMF)19
Variable displacement pump and fixed displacement motor (PVMF)20
Fixed displacement pump and variable displacement motor (PFMV)21
Variable displacement pump and variable displacement motor (PVMV)23
Variable displacement pump and dual displacement motor (PVM2)25
Open circuit hydrostatic transmissions29
Open-circuit HT with flow supply: basic circuit29
Open circuit HT with flow supply: common implementation31
Open circuit displacement regulator33
Open circuit HTs with pressure supply35
Closed circuit hydrostatic transmissions40
Charge circuit and filtration41
Cross-port relief valves45
Flushing circuit47
Closed circuit displacement regulators54
Electro-hydraulic displacement regulator for closed circuit pumps54
Automotive control for closed circuit pumps56
Conceptual schematic58
Actual implementation60
Electro-hydraulic displacement regulator for motors59
Automatic pressure regulator for motors60
Problems61
CHAPTER 25:Hydrostatic transmissions applied to vehicle propulsion67
Basic of vehicle transmission67
Classification for variable ratio transmission systems71
Power-split transmissions74
Planetary gear train76
Hydromechanical power split transmission78
Analysis of an output coupled hydromechanical power split transmission
Analysis of an input coupled hydromechanical power split transmission
Hybrid transmissions92
Series hybrids93
Parallel hybrids95
Series-parallel hybrids (or power split hybrids)97
Sizing hydrostatic transmissions for propel applications100
Step 1: Maximum tractive effort calculation101
Step 2: Fixed or variable displacement motor selection102
Step 3: Sizing of the motor (secondary unit)104
Step 4: Sizing of the pump (primary unit)105
Step 5: Check results106
Problems112
CHAPTER 26:Hydrostatic actuators113
Open circuit hydrostatic actuators113
Closed circuit hydrostatic actuators116
Cylinder extension117
Extension in pumping mode117
Extension in motoring mode118
Cylinder retraction120
Retraction in motoring mode121
Retraction in pumping mode122
Further considerations on the charge pump and the accumulator124
Final remarks on hydrostatic actuators127
CHAPTER 27:Secondary controlled hydrostatic transmissions129
Secondary control circuit with tachometric pump132
Secondary control circuit with tachometric pump and internal force feedback135
Secondary control circuit with electronic control137
Multiple actuators139
References
APPENDIX 1 - Prime movers and their interaction with the hydraulic circuit
Objectives
Corner power method and its limitations
Diesel engine and its interaction with a hydraulic pump
Diesel engine regulation
Engine stall
Overrunning loads
Fuel consumption
Electric prime movers
Brushed DC electric motors
DC hydraulic power units
Induction motors (or asynchronous motor)
Synchronous motor
Power limitation in hydraulic pumps
Torque limiting using fixed displacement pumps
Torque limiting using variable displacement pumps
References
