A Water Reservoir Feeds a Turbine With a Flow Rate of 15

Supply Flow Rate

The water supply flow rate and pressure should be capable of maintaining water discharge at the design rate and duration for all systems designed to operated simultaneously.

From: Essentials of Oil and Gas Utilities , 2016

Thinning Films and Tribological Interfaces

Sergei B. Glavatskikh , in Tribology Series, 2000

4 CONCLUSIONS

The effects of step changes in bearing load, speed and oil supply flow rate on friction torque, collar, shaft and discharge oil temperatures have been experimentally investigated. The following principle results are obtained from the tests:

1.

The total transient period was quite long, 15   -   20   min, and depended on the parameter changed. The greatest change in temperatures (except T_c) took place during the first minute following step changes in speed and load. However, after a drop in oil supply flow the rate of collar temperature rise was much lower than that in cases with speed and load.

2.

Shaft temperature was far less sensitive to the increase in load than to variations in speed and oil flow. Collar temperatures varied in the radial direction and this variation increased with speed and load. A drop in oil flow also contributed to higher radial variation in collar temperatures.

3.

The rate of change of T_75% was always higher than that of T_25%. The greatest difference occurred after the drop in oil supply flow rate.

4.

A sharp change in friction torque followed a rapid change in operating conditions. The torque afterwards had a tendency to change gradually due to viscosity change. Such friction torque behaviour indicates that the thermal inertia of the collar tends to slow down the rate of oil film temperature change.

5.

Load redistribution between the pads occurred during a rapid loading. It resulted in unequal pad loading despite of the equalising system.

It is hoped that these data can be valuable to the bearing designers for predicting temperature rise and bearing behaviour in critical applications.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/S0167892200801285

Safety and firefighting equipment, part 1

Alireza Bahadori PhD , in Personnel Protection and Safety Equipment for the Oil and Gas Industries, 2015

9.13.2 Water supplies

It is of vital importance that water supplies be selected that provide water as free as possible from foreign materials.

●

Volume and pressure: The water-supply flow rate and pressure should be capable of maintaining water discharge at the design rate and duration for all systems designed to operated simultaneously. For water-supply distribution systems, an allowance for the flow rate of hose streams or other fire-protection water requirements should be made in determining the maximum demand. Sectional control shut-off valves should be located with particular care so that they will be accessible during an emergency case. When only a limited water source is available, sufficient water for a second operation should be provided so that the protection can be re-established without waiting for the supply to be replenished.

●

Sources: The water supply for water-spray systems should be from reliable fire-protection water supplies, such as:

Connections to waterworks systems

Gravity tanks (in special cases pressure tanks) or

Fire pumps with adequate water supply

●

Fire-department connection: One or more fire-department connections should be provided in all cases where water supply is marginal and/or where auxiliary or primary water supplies may be augmented by the response of suitable pumper apparatus responding to the emergency. Fire-department connections are valuable only when fire-department pumping capacities are equal to maximum demand-flow rate. Careful consideration should be given to such factors as the purpose of the system, reliability, and capacity and pressure of the water system. The possibility of serious exposure fires and similar local conditions should be considered. A pipeline strainer in the fire-department connection should be provided if indicated by 13.8.5. Where a fire-department connection is required, suitable suction provisions for the responding pumper apparatus should be provided.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128028148000092

All-air Systems

Roger Legg , in Air Conditioning System Design, 2017

Ventilation Rate

Consideration should be paid to the supply rate of fresh air if ventilation standards are to be maintained. It has already been shown that for most of the year a system designed for free cooling will operate on considerably more than the minimum percentage of outdoor air. However, as the total instantaneous heat gain reduces, the fresh air supply rate will also fall in proportion to the reduction in total supply flow rate. Then, if the air conditioned spaces remain fully occupied, the minimum ventilation requirements will not be met. One solution to this problem is to maintain, through the controller P ₁ acting on the dampers (as described above), the minimum flow rate at the fresh air intake. But even if this facility is incorporated into the system, ventilation rates may still be inadequate as is illustrated in the following example:

Example 6.7

Four zones in a building, air conditioned with a VAV 'system, have design flow rates as given in the table below. The total flow of 15   m³/s is based on an analysis of the total instantaneous cooling load of the building.

The zone ventilation rates are based on maximum occupancy; the total of these determines the minimum flow rate in the central plant of 1.9   m³/s, but the designer arbitrarily increases this to 2.25   m³/s to provide 15% of the total flow rate. Compare the ventilation rates of the four zones:

(a)

Ventilation flow rate as 15% of total supply flow rate

(b)

Ventilation flow rate maintained at design flow rate of 2.25   m³/s

Solution

With the system in use, the zone cooling loads are out of phase, and the zone flow rates are reduced as shown in the table, giving a total supply flow rate of 11.2  m³/s.

(a)

Ventilation flow rate as 15% of total

All zone supply rates include 15% fresh air. If the zones have the expected occupancy, then the ventilation air for zones 2 and 4 fall below the required level.

(b)

Ventilation flow rate maintained at design flow rate of 2.25   m³/s

The percentage of total flow rate is now $\left(2.25/11.2\right)\times 100=20\%\text{.}$ All zone supply rates include 20% fresh air. If the zones have design occupancy, then the ventilation air for zone 2 is now satisfactory, but zone 4 still falls below the required level.

System condition	Zone				Total flow rate
	1	2	3	4
At design load
Maximum supply flow rate	5.50	4.00	6.00	4.00	15.00
Minimum supply flow rate	0.55	0.40	0.60	0.40	2.25
At part load
Reduced supply flow rate	4.00	2.00	4.00	1.20	11.20
Ventilation rate—15%	0.60	0.30	0.60	0.18	1.68
Ventilation rate—20%	0.80	0.40	0.80	0.24	2.24

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780081011232000066

LOCAL VENTILATION

LARS OLANDER , ... XIANYUN WEN , in Industrial Ventilation Design Guidebook, 2001

Changing Flow Rates

The velocities outside the exhaust opening diminish proportionally to diminishing flow rate. However, the efficiency of the exhaust could diminish more rapidly due to the changed relationship between exhaust air velocity and contaminant velocity. Increased flow rate usually increases efficiency. A large increase could result in drafts that are uncomfortable for the workers. Air velocities that are too high could disturb the process and result in increased material losses.

The supply airflow rate should approximately equal the exhaust flow rate. A minor difference between supply and exhaust flow rates should not disturb the exhaust, since exhaust systems usually are operated with higher pressure differences than supply systems. If the exhaust flow rate is higher than the supply, it could result in lower efficiency due to lower exhaust flow rates and cross-drafts (see Disturbances ). If the exhaust flow rate is lower than the supply flow rate, there may be fewer problems with exhaust efficiency, but this could result in a supply airflow field different from the designed one and thus result in different kinds of disturbances.

Certain operations require that the workspace be at a lower pressure than surrounding workspaces, e.g., radioisotope laboratories. In these cases, the exhaust flow rate should exceed the supply flow rate, but this excess should be within 10%. The additional resistance resulting from this imbalance should be considered in the design of the exhaust system, specifically in the selection of exhaust fans.

Flow rate changes are sometimes used in the design of local exhaust systems. An example of this is the use of dampers, blastgates, or valves that are interlocked with the machinery of interest. When the tool is on, the damper is opened and air is exhausted from that hood. When the tool is off, the damper is closed and more exhaust air is available to other parts of the system. These kinds of systems diminish the cost for running the system but increase the cost for installation as well as periodic preventive maintenance. The supply system must be run parallel to the exhaust system, otherwise there will be little to gain by the changing flow rates and the exhaust could be less efficient than desired.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780122896767500138

ACTIVE SUSPENSION SYSTEM WITH HIGH-SPEED ON/OFF VALVE (APPLICATION OF PREVIEW CONTROL WITH ADAPTIVE DIGITAL FILTER)

Hironao YAMADA , Takayoshi MUTO , in Mechatronics for Safety, Security and Dependability in a New Era, 2007

CONSTITUTION OF THE ACTIVE SUSPENSION SYSTEM

The configuration of the new system proposed in this study is shown in Figure 1 . The pressure control valve, which is used in a conventional active suspension system, is replaced by two on/off valves (valves 1 and 2). The valves are of a high-speed solenoid type. In this system, the supply flow rate to the cylinder is controlled by either valve 1 or valve 2 according to the PWM-signal. The constitution of the on/off valve is illustrated in Figure 2.

Figure 1. The outline of the system used for the experiment

Figure 2. Structure of a high-speed ON/OFF valve

The poppet in the valve is actuated by the on/off input voltage applied to the solenoid and thus the flow rate through the valve is controlled in digital mode in accordance to a duty signal. In the following, the principle of the PWM method adopted in this study is demonstrated based on the experimental results shown in Figure 3.

Figure 3. PWM (Pulse-Width-Modulation)

In Figure 3, the signal u denotes the control input (=Duty) and the triangle waves are carrier waves. The input signal voltage to valves 1 and 2 is generated by comparing the control input u with the triangle carrier waves as shown in the figre.

Next, Figure 4 shows the valve characteristics between suspension cylinder speed and duty when the valves are driven by the duty signal. It is seen in Figure 4(a) that a dead zone exists in the vicinity of the origin because of the delay time of the valve. This kind of nonlinear characteristic, however, can easily be compensated into a linear one by adopting an appropriate compensation method. That is, in order to cancel the influence of the dead zone, we can impose a wider pulse width than the estimated Duty by the amount of the delay time. The results of compensation are shown in Figure 4 (b).

Figure 4. The Duty-velocity characteristics of an ON/OFF valve

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780080449630500680

Fire-fighting pump and water systems

Alireza Bahadori PhD , in Essentials of Oil and Gas Utilities, 2016

9.38 Water spray fixed systems for fire protection

Water spray is applicable for protection of specific hazards and equipment, and may be installed independently of or supplementary to other forms of fire protection systems or equipment.

9.38.1 Hazards

Water spray protection is acceptable for the protection of hazards involving:

•

gaseous, liquid flammable and toxic materials

•

electrical hazards such as transformers, oil switches, motors, cable trays, and cable runs

•

ordinary combustibles such as paper, wood, and textiles

•

certain hazardous solids.

9.38.2 Uses

In general, water spray may be used effectively for any one or a combination of the following purposes:

1.

extinguishment of fire

2.

control of burning

3.

exposure protection

4.

prevention of fire.

9.38.3 Limitations

There are limitations to the use of water spray, which should be recognized. Such limitations involve the nature of the equipment to be protected, the physical and chemical properties of the materials involved and the environment of the hazard.

Other standards also consider limitations to the application of water (slopover, frothing, electrical clearances, etc.)

9.38.4 Alarms

•

The location, purpose, and type of system should determine the alarm service to be provided.

•

An alarm, actuated independently of water flow, to indicate operation of the detection system should be provided on each automatically controlled system.

•

Electrical fittings and devices designed for use in hazardous locations should be used where required by the standard.

9.38.5 Flushing connections

A suitable flushing connection should be incorporated in the design of the system to facilitate routine flushing as required.

9.38.6 Water supplies

It is of vital importance that water supplies be selected which provide water as free as possible from foreign materials.

9.38.7 Volume and pressure

The water supply flow rate and pressure should be capable of maintaining water discharge at the design rate and duration for all systems designed to operated simultaneously.

For water supply distribution systems, an allowance for the flow rate of hose streams or other fire protection water requirements should be made in determining the maximum demand.

Sectional control shut-off valves should be located with particular care so that they will be accessible during an emergency case.

When only a limited water source is available, sufficient water for a second operation should be provided so that the protection can be reestablished without waiting for the supply to be replenished.

9.38.8 Sources

The water supply for water spray systems should be from reliable fire protection water supplies, such as:

•

connections to waterworks systems

•

gravity tanks (in special cases pressure tanks)

•

fire pumps with adequate water supply.

9.38.9 Fire department connection

One or more fire department connections should be provided in all cases where water supply is marginal and/or where auxiliary or primary water supplies may be augmented by the response of suitable pumper apparatus responding to the emergency. Fire department connections are valuable only when fire department pumping capacities equal maximum demand flow rate.

Careful consideration should be given to such factors as the purpose of the system, reliability, and capacity and pressure of the water system. The possibility of serious exposure fires and similar local conditions should be considered. A pipeline strainer in the fire department connection should be provided if indicated by 13.8.5. Where a fire department connection is required, suitable suction provisions for the responding pumper apparatus should be provided.

9.38.10 Workmanship

Water spray system design, layout, and installation should be entrusted to none but fully experienced and responsible parties. Water spray system installation is a specialized field of sprinkler system installation, which is a trade in itself.

Before a water spray system is installed or existing equipment remodeled, complete working plans, specifications, and hydraulic calculations should be prepared and made available to interested parties.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780128030882000092

Drilling

Viktor P. Astakhov , in Modern Machining Technology, 2011

2.8.2 Constraints on the drill penetration rate

As discussed above, the feed rate (which is called the penetration rate in drilling) is calculated as the product of the cutting feed (mm/rev or ipr), and the spindle rotational speed (rpm) (Eq.[2.6]). Therefore, this rate can be increased either by increasing the rotational speed or by increasing the cutting feed. There are some constraints on each of these ways which should be understood.

The major constraint on the rotational speed is the cutting temperature primarily at the drill corners as these have the highest linear (cutting) speed. The maximum allowable temperature is the sole property of the tool material (including its coating) while the maximum allowable rotational speed that causes this temperature is a function of many variables. Among them, the following are of prime importance:

▪

Work material. The stress and strain at fracture of the work material define the work spent on plastic deformation of this material in cutting, which is the greatest portion of the cutting energy and thus is the major contributor to the cutting temperature (Astakhov and Xiao, 2008).

▪

Tool design and geometry. This is because they define the state of stress in the deformation zone (the work of plastic deformation), chip formation and its sliding direction, as well as the sliding conditions on the tool margins and working conditions of the side cutting edges. Moreover, tool design and geometry define to a large extent the self-centering of the drill and thus affect the drill transverse vibration which is the prime cause of drill failure.

▪

Coolant. Coolant supply (flow rate) and access to the drill corners (drill flanks design) as well as the coolant composition, concentration, clearness, tramp oil, etc.

▪

Design and conditions of the drilling system. This includes drill holder (eccentricity), starting bushing (alignment), system rigidity and many others.

Unfortunately, the listed factors and their inter-correlations are not well understood in the practice of drill design and implementation where the rotational speed for a given tool material is selected based only upon the work material (type and hardness).

Compared to the drill rotational speed, there are many more constraints on the allowable cutting feed (feed per revolution). These constraints can be broadly divided into three categories: (1) constraints due to the quality requirements to machined holes (diametric, position, shape, location accuracies); (2) constraints due to the drill (buckling stability, excessive deformation, wear, breakage); and (3) constraints due to the machine (allowable axial force, power, structural rigidity). Although these listed categories relate to different phases of the drilling operation planning, they have a common basis. The force factors (drilling torque, axial force, and imbalanced forces) constitute this basis. Therefore, it is of importance to understand these force factors as drill geometry is one of the major contributors to their values.

Drilling torque

The drilling torque is a function of the work material properties, drill diameter and geometry, and the drilling regime. Of these factors, the drill geometry and drilling regime can be varied to achieve optimal drill performance. As the cutting speed has a weak influence on the cutting force, it also has little influence on the drilling torque so that the cutting feed is the only factor to be considered.

While for modern production CNC machines the drilling torque is not a limiting factor as these machines are equipped with powerful motors to deliver high torques, for relatively small machines the drilling torque can be a constraint limited by the power of the drive motor. When the latter is the case, the feed per revolution is lowered or the hole is drilled in two consecutive drilling operations using first a smaller drill and then a drill to the required hole size.

The length of a drill imposes another important limitation. The problem is that the so-called angle of twist increases proportionally to the drill length under the same drilling torque. As known (Beer et al., 2006), this angle is calculated as

[2.20] ${\phi }_{\mathit{tw}}=\frac{M_{\mathit{dr}}{L_{\mathit{dr}}}_{-1}}{\mathit{JG}}$

where L _dr–1 is the length from the drill corner to the SECTION A–A (Figure 2.36), J is the polar moment of inertia of the drill cross-section, and G is the shear modulus of the drill (tool) material. In reality, however, length L _dr–2, considered in Figure 2.36 as the polar moment, is much smaller in the cross-section B–B.

When the angle of twist achieves a certain critical value (particular to the drill material and some other factors), the drill breaks. As follows from Eq.[2.20], there are two principal ways to prevent this from happening (for a given drill material). The first is to decrease the drilling torque that, in turn, reduces the penetration rate. Another way is to increase the polar moment of inertia of the drill cross-section. The latter is used in the practice of drill design.

The flutes are made so that the web thickness increases along the length of the drill from the tip to the shank as shown in Figure 2.37. This is because the angle of twist increases proportionally to the drill length. Normally, a relatively shallow web taper rate is used in a drill so that the flute depth along the length of the flute is as great as possible. This should provide the maximum amount of volume to convey chips, swarf, or sawdust back from the tip and out of the hole being drilled. The American Society of Mechanical Engineers (ASME B94.11   M-1993) and the Aerospace Industries Association of America, Inc. (NAS 907) Standards define the conventional web thickness taper rate as between 0.60   mm and 0.76   mm.

Figure 2.37. Web thickness increases from the tip towards the shank

For a 'conventional' drill, the major cutting edges (lips) contribute approximately 80%, minor cutting edges (margins) 10%, and chisel edge 10% to the total drilling torque defined by Eq. [2.16]. Optimizing the essential design parameters of the drill, one can achieve a reduction of the total drilling torque while the relative contribution of the drill components to this torque will be almost the same.

Axial force

According to Eq.[2.17], the resultant axial force in drilling shown in Figure 2.33 is the sum of the axial forces on the major cutting edges (lips), chisel edge, and due to friction on the margins. The latter is small compared to the first two terms so that the contribution of the major cutting edges (lips) and the chisel edge are considered. It is very important to realize that the axial force produced by the unit length of the cutting edge is not a linear function of the location radius of this unit length. Rather, the contributions of the portions of the cutting edge located closer to the drill center are much greater than the peripheral regions.

To illustrate this statement, Figure 2.38 shows the principle (Figure 2.38(a)) and results (Figure 2.38(b)) of a simple axial force test. A pre-drilled test specimen made of gray cast iron (HB 200) is placed on a table dynamometer. An HSS twist drill of 29.5   mm diameter was used. As the drill progressed in the pre-drilled hole (of d₁ diameter), the contributions of different portions of the cutting edge into the resultant axial force can be assessed. Subtracting the axial force measured when a drilled hole of 6   mm diameter from the resultant axial force measured when a solid specimen was drilled, one can obtain the contribution of the chisel edge into the resultant axial force. As can be seen in Figure 2.38(b), different portions of the cutting edge contribute differently to the total axial force. For a 'conventional' drill, the major cutting edges (lips) contribute approximately 30–40%, minor cutting edges (margins) 10%, and chisel edge 50–60% to the total axial force defined by Eq.[2.17]. Optimizing the essential design parameters of the drill, one not only can achieve a reduction of the resultant axial force but also can change substantially the relative contribution of the drill components to this force.

Figure 2.38. (a) Principle, and (b) results of a simple axial force test. Cutting speed v  =   59   m/min, feed f  =   0.32   mm/rev

A significant axial force in drilling restricts the penetration rate because:

▪

It affects the buckling stability of the drill. Compromising this stability causes a number of hole quality problems. It also significantly reduces tool life, causing excessive drill corner or even margin wear.

▪

Many machines used for drilling have insufficient thrust capacity that limits any increase in the penetration rate with standard drills.

Therefore, the reduction of the resultant axial force is vitally important when one tries to increase the allowable penetration rate of the drill. As the chisel edge is the major contributor to this axial force, one should: (1) reduce the length of this edge; and (2) improve the geometry of this edge. These two objectives can be achieved simultaneously.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780857090997500022

High efficiency and low emission natural gas engines for heavy duty vehicles

M.E. Dunn , ... J. Saunders , in Internal Combustion Engines: Performance, Fuel Economy and Emissions: IMechE, London, 27–28 November 2013, 2013

3 EXAMPLE 1: DEVELOPMENT FOR THE AUSTRALIAN MARKET

3.1 Market requirements

The Australian heavy duty natural gas vehicle market is heavily driven by the desire for lower carbon emissions, high fuel efficiency and consumption of a locally produced and economic fuel. Useage patterns require more engine power than are typical for European or North American applications.

Development of the 15   L HD HPDI engine for the Australian market is presented here as an example of HPDI technology operating at high BMEP, without aftertreatment and with minimal levels of EGR. This is of particular interest as natural gas engine applications expand into larger engines for non-road, non-power generation applications.

The North American version of the 15   L HD HPDI engine was redeveloped to meet the needs of the Australian market, namely

1.

Revised exhaust emissions requirements (ADR 80/02)

2.

Increased torque (2780   Nm) and power (457   kW) output to suit the higher Gross Vehicle Mass (GVM)

3.

Greater on-board fuel storage to suit longer routes and higher duty cycle

4.

Harsher environmental conditions (ambient temperature, vibration, dust)

5.

Australian codes and standards for natural gas systems

Emissions requirements are specified under Australian Design Rule (ADR) 80 series. as shown in Figure 2. The initial engine variant was developed to meet ADR 80/02 requirements that were phased in from 2007. ADR 80/03 was phased in from 2010 and subsequent versions of the engine have been developed to meet this standard.

Figure 2. Australian and European NOx and PM emissions requirements compared to the Tier 4 non-road standard for engines >   560   kW

Figure 2 compares successive ADR 80 standards (NOx and PM emissions only) with other representative standards, including the Euro VI and EPA 2010 levels. The tier 4 non-road standard for non-generator set engines with output >   560   kW (applicable from 2015) is also shown. The alternative standard for ADR 80/02 is based on US EPA 2004 standard which regulated NOx+NMHC as a combined value. In the case of HPDI at this emissions level, the NOx level constitutes about 90% of the combined value and the figure is adjusted to reflect this.

At a high level, ADR 80/02 NOx emission requirements are somewhat similar to the full Tier 4 emissions standard for non-generator set engines >   560   kW. Note that the alternative standards, the Euro standards and Tier 4 standards apply differing test cycles and measurement procedures and so only provide a general comparison of the emissions level.

The European standards (adopted in ADR 80) for natural gas engines regulate NMHC and methane emissions whereas the ADR 80 alternative standards regulate only the NMHC components, as shown in Figure 3. Controlling methane emissions is still important for greenhouse gas emissions performance and is considered together with CO₂ emissions in the engine optimisation process.

Figure 3. Australian and European hydrocarbon and CO emissions requirements compared to Tier 4 non-road standard for engines >   560   kW

The HPDI combustion process has been previously shown to result in approximately 40% lower NOx emissions than combustion of diesel fuel for similar brake efficiency (1,3). Optimising the NOx emission levels to those similar to an equivalent diesel fueled engine creates an opportunity for fuel consumption and additional carbon emissions reductions. This overall strategy was selected for the Australian market.

3.2 Engine and fuel supply system modification

As indicated in Figure 2 and Figure 3, ADR 80/02 allows certification to EPA 2004 requirements as an alternative to Euro IV and this path was selected for the 15   L HD HPDI application to achieve commonality with the parent engine approach.

The ADR 80/02 version of the Cummins ISX engine (from which the 15   L HD HPDI is derived) was equipped with Exhaust Gas Recirculation (EGR) but without exhaust aftertreatment. Initial evaluation suggested that this platform would be sufficient to meet the emissions and performance requirements for HPDI in the Australian market. The alternative standard also provides potential to avoid an oxidation catalyst with attendant cost, vehicle packaging and efficiency benefits.

Engine performance targets were significantly higher than the equivalent generation North American product with a 17% increase in peak torque to 2780   Nm (23.4   bar BMEP) and a 32% increase in maximum power output to 457   kW (610   hp).

Engine cycle simulation coupled with in-house fuel system and combustion analysis (6) was used to evaluate the engine system modifications needed to meet the output, efficiency and operational range requirements, resulting in the following recommendations:

1.

Increased gas injection rate by re-optimisation of injector control parameters and enlarged injection nozzle

2.

Reduction in EGR rates across the engine map

3.

Adjustment of EGR system to reduce turbine inlet pressures

4.

Increased high pressure gas supply flow rate by increased LNG pump cycle rate

5.

Revised LNG pump control structure to permit installation of up to 4 tanks and pumps on each vehicle

3.3 Performance and efficiency

Even at the pressures used in the HPDI system, delivering the fuel rapidly enough can be a challenge, especially at high loads and speeds. To achieve the increase in performance up to 456   kW, higher flow rates were needed. In this case, the injector specification was revised, including a 15% increase in the nozzle flow rate and a 10% increase in valve lift. This was sufficient to meet the target as shown in Figure 4.

Figure 4. Full load performance targets and test results

The inherent properties of the fuel and combustion approach provide for very high efficiency potential at the target emissions levels. The calibration parameters (fuel pressure, injection timing, VGT and EGR system settings) were selected over the speed and load range using design of experiments techniques. Optimization focused on engine efficiency, along with the regulated emissions to ensure compliance with ADR80/02. Figure 5 shows the brake thermal efficiency achieved. Values are greater than 40% for the majority of the map with large region at or above 44%.

Figure 5. Brake thermal efficiency versus torque and speed

3.4 Emissions results

Emissions certification was obtained at a 3^rd party facility capable of meeting the requirements of the Australian authority having jurisdiction. Tests were completed over the cold and hot FTP cycles (US Federal Register 40 CFR Part 86 Subpart N) and under the Supplemental Emissions Test (SET) using the Discrete Mode Cycle (DMC). The DMC is equivalent to the European Stationary Cycle (ESC) 13-mode test. Figure 6 shows the engine installed in the certification test cell.

Figure 6. Engine installed in transient test cell

The emissions results obtained are shown in Figure 7 and are comfortably within the ADR 80/02 alternative standard. The results indicate the potential to control particulate emissions to a low level without the need for aftertreatment, achieving a value of 0.03   g/kWh. The engine also achieved very similar SET cycle averaged brake thermal efficiency to the diesel baseline

Figure 7. Final emissions test results [note that values for NMHC are in units of 0.1   g/kWh and PM in units of 0.01   g/kWh]

Hydrocarbon emissions (NMHC and CH₄) were controlled by optimisation of the engine control parameters (injection timing, pilot quantity, pilot timing and EGR rate). Although not measured on the correct test cycle NMHC emissions values are consistent with Euro IV and V levels for natural gas engines and methane emissions are slightly higher than would be needed to meet Euro IV and V.

The diesel fuel contribution was also monitored over the test cycles; on an energy basis this was 7.0% over the FTP and 4.6% over the SET cycle. Extremely low diesel fuel contribution was not specifically targeted in this project, leaving potential further optimisation.

3.5 Tank-to-Wheel Life Cycle Assessment

Tailpipe emissions represent the vast majority of the emissons of GHGs from an HPDI natural gas engine. These are primarily in the form of CO₂ and CH₄; for HPDI, the tailpipe CO₂ includes the contributions from both diesel and natural gas combustion. For the assessment presented here, a global warming potential for methane of 25 is used, in accordance with the most recent recommendation from the Intergovernmental Panel on Climate Change (7). Nitrous oxide (N₂O) is not included in the analysis, in part due to a lack of reliable N2O data for the engine development work reported here, but also because at the very low levels N2O is produced by diesel and natural gas engines (< 0.027   g/kW-hr) it influences tailpipe GHG emissions by only approximately 1%. Beyond these tailpipe emissions, there are also other vehicle-level contributions to total GHG emissions that should be included in a full life-cycle analysis.

A tank-to-wheel, as opposed to well-to-wheel, analysis is used due to the large uncertainties and variations in upstream emissions at the time of writing. These variations are evident in natural gas fugitive emissions, with estimates ranging from 0.3 – 23   g CO₂/MJ_fuel (8) and the Environmental Protection Agency recently revising down their estimate of fugitive GHG emissions from natural gas development by 33% (equating to a change in well-to-tank leak rate of 2.3% to 1.4%) (9). Equally, variations in crude oil extraction emissions are considerable, both from the standpoint of geography, 6.2 – 30.5   g CO₂/MJ_fuel (10) and refinement technique, 4.0 - 17.5   g CO₂e/MJ_crude (11). A tank-to-wheel analysis avoids these upstream variations and enables an unobscured evaluation of diesel and HPDI natural gas engine technologies.

The nature of the HPDI fuel system requires that a small amount of gas may occasionally need to be vented during highly transient operation of the engine. This is a result of the dynamic behaviour of the fuel rail pressure control system, and is termed "dynamic venting". CH₄ emissions from dynamic venting were measured and added to the tailpipe emissions. Reduction in dynamic venting is an area of ongoing technological improvement for HPDI fuel systems.

The engine test-cell testing reported here also did not include the parasitic power required for the cryogenic LNG pump (the common rail diesel pump is included in the engine test cell results). Although it varies between duty cycles, research has indicated that the pump imposes a 1-2% fuel consumption penalty.

Combining tailpipe emissions with dynamic venting and hydraulic pump power provides an accurate reflection of the total tank-to-wheel emissions. A single net CO₂,_equivalent value can thus be calculated for each duty cycle. For the Australia ADR80/02 15   L HD HPDI engine, these show a reduction of 22.9% in CO_2eq emissions compared to the diesel baseline for both FTP and SET values, as shown in Figure 8. It is purely coincidence that the relative GHG emissions for both cycles are equivalent when reported to one decimal place.

Figure 8. Relative tank-to-wheel GHG emissions compared to published diesel engine FTP data (13) and internally generated SET diesel baseline

The figure also provides a combined quantity using FTP and SET values weighted 30% and 70% respectively. The contributions of dynamic venting and tailpipe methane are compared to the tailpipe CO₂ for this combined case. Tailpipe CO₂ dominates, with tailpipe CH₄ contributing 3% and dynamically-vented CH₄ 1.3% to the CO_2,equivalent value for this combined cycle. This weighting is selected as being (on average) more representative of real-world conditions than either cycle alone for heavy duty on highway vehicles (12).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9781782421832500093

Efficiency achievement in water supply systems—A review

B. Coelho , A. Andrade-Campos , in Renewable and Sustainable Energy Reviews, 2014

4.2.3 Water demand prediction

An accurate estimation of water demand is an important requisite for the optimal operation and design of a WSS. The prediction of water demand allows better approximations between the water supply flow rate and the water consumption flow rate, providing more resource savings and, consequently, more cost savings [84].

Walski et al. define three basic water demand types [155]: (1) customer demand, the water required by the users in the system, (2) unaccounted-for water, related to water losses, unmetered services or other causes and (3) fire flow demand, the required system capacity to ensure protection during fire emergencies. Moreover, the authors refer that the process of establishing consumption rates requires studying of past and present usage trends and, sometimes, the projection of future ones [155].

The total water demand is characterised by time-varying (according to daily, weekly, seasonal and long-term scales), periodic and non-stationary series [6]. Current water consumptions are determined by a large number of industrial, commercial, public and domestic consumers [6]. Thus, the typical demand types are usually defined as [78]: (i) residential, (ii) commercial, (iii) industry, (iv) agriculture, (v) irrigation and (vi) leakages. Deviations caused by weather effects (temperature, humidity, wind, precipitation…), season effects (winter/summer) or even network effects (like pipe breaks) can be the reason of failure in some demand predictions [84].

Thus, for the water demand forecasting, socio-economic and climatic variables are usually needed [80]. While the climatic variables as air temperature or rainfall affects the short-term seasonal variations on demand, the socio-economic variables like water price, population or housing characteristics are responsible for long-term effects [80].

The most considered demand events are usually: (i) average day demand, (ii) maximum day demand, (iii) peak hour demand and (iv) maximum day of historical record [155].

Essentially during the peak periods, where higher demands are expected, re-evaluations of new demand profiles are usually more necessary [32].

For the development of a database, the water usage information can be collected by distinct forms [155]: (i) flow information, like the rate of production of a treatment system, (ii) volumetric information, provided, for example, by the client water consumption or (iii) hydraulic grade information, such as the level variation in a tank. All the information should be recorded into an accessible format in order to facilitate the process of data loading into a hydraulic model [155].

Typically, the most developed models provide 24-h patterns of demand prediction for a number of consumption points in each control area. The predictions are usually extrapolated from current water consumption and recorded data. A number of prediction strategies resorting to fuzzy logic and/or artificial neural networks have also been tested [87,80,36].

The advantage of forecasting models based on fuzzy logic or neural networks is to provide multiple points of data as long as enough historical data are available for training [87]. On the other hand, time series analysis, like auto-regressive models, do not require pre-training, but only provide a prediction of a few data points [87].

An et al. [6] proposed the use of a method called data mining (automated learn from observed data) for daily water demand prediction. The main objective of this work was to provide a technique for generating prediction rules from incomplete information. The authors used a database containing environmental and sociological information and the daily volume of distribution flow. Eighteen condition factors for water demand prediction (day of week, temperatures, humidity, etc.) were selected from the many existent. These factors were obtained from a monthly meteorological summary and the historical information about water consumption has been recorded by summing the daily distribution flows metered at the pumping stations.

A set of training samples (observed data) was used by An et al. [6] for the generation of each classification rule (rough-set method). The training samples consisted of more than 300 objects projected for each condition attribute. The process of rules generation was based on the set of condition attributes that did not provide any additional information to the system and needed to be removed (condition attributes reduction). Such probabilistic decision rules were then used for the water demand prediction.

The methodology of An et al. [6] simply describes the relationships between condition factors and decision variables. The accuracy of the prediction can even be improved through the collection of more data [6]. It also should be noticed that the process of rule generation must be performed for each distinct network since the influence of each condition factor may differ from case to case.

As demand forecasters using a single approach tend to produce high prediction errors, Lertpalangsunti et al. [87] proposed the Intelligent Forecasters Construction Set (IFCS), a tool that supports the use of distinct techniques for demand prediction such as fuzzy logic, neural networks, knowledge-based and case-based reasoning. This hybrid approach, applied first on an electrical system for power demand prediction, is based on individual modules (one for each approach) that are combined using adaptive filtering schemes. The modular structure provides the possibility of integration with other intelligent modules [87].

The IFCS tool was implemented on a real-time system that supports rule representation, providing easy interpretations for the users [87]. A data analysis and processing module is responsible for preparing the data for the forecaster modules.

The methodology of Lertpalangsunti et al. [87] was tested in the city of Regina for the daily water demand prediction. Comparing the use of multiple neural networks with linear regression and a case-based reasoning technique, the lower percentage of prediction error was obtained by the multiple neural networks approach. Days of a week and temperature demonstrated to have a major impact on customer demand. Furthermore, multiple neural networks that separate the data daily in a week generate better prediction results. Finally, the authors concluded that the use of multiple modules of predictors allows obtaining better results than using the single prediction models [87].

The work presented by Jain et al. [80] provides a model for short-term water demand forecasts through the use of climatic variables such as the total weekly rainfall and the weekly average maximum air temperature in addition to the past water demands. Distinct techniques to model the weekly water demand were developed for comparing: (i) 6 back propagation ANN models, (ii) 5 regression models (linear and nonlinear), and (iii) 2 time-series models. Both techniques were applied at the Indian Institute of Technology at Kanpur. Results demonstrated that models based on ANN consistently outperformed the other conventional techniques of regression and time-series analysis, presenting an average absolute error in forecasting of 2.41% [80]. The authors realised that the water demand process of the case study was mainly driven by the maximum air temperature and interrupted by occurrences of rainfall. Moreover, they noticed that the occurrence of rainfall was a more significant descriptive variable than the amount of rainfall [80].

The project of Barnett et al. [10] (already described in Section 4.2.2) is another example of the application of neural networks for water demand prediction taking into account factors such as historical consumption and online data including weather forecasts. The input variables considered for the prediction in this project included: air temperature, dew point, wind speed, humidity, day of week and flow. The output of the neural network was the flow at each hour. Forecast errors equal or inferior to 15% were considered acceptable. The experimental results of Barnett et al. [10] demonstrated that the daily forecast error was less than 10%; however, the hourly forecast errors reached 50%. The authors also indicated that short-term forecasts across 4–6   h horizon presented smaller errors.

Cutore et al. [35] present a technique for dealing with prediction uncertainties from a daily ANN predictor model. The authors applied the Shuffled Complex Evolution Metropolis (SCEM-UA) algorithm for calibrating (training) the parameters of the three-layer ANN. The input vector of the ANN consisted of climatic data, system data and some indexes characterising the day of prediction. The SCEM-UA trained ANN was applied in the real-case of Catania (Sicily, Italy) and compared with: (i) an ANN trained by a Bayesian learning algorithm, (ii) a regression model and (iii) an adaptive network based fuzzy interference system (ANFIS). The predictive performance of the SCEM-UA ANN model was similar to the Bayesian ANN model. Compared to the 3 techniques the SCEM-UA ANN model present the advantage of better fitting the observed data in some calibration periods of time, providing more accurate water prediction [36].

A model of linear regression was applied by Vasilio and Jorge [149] to predict the daily water consumption of the Apucarana system (Brazil). The prediction model used seasonal and climatic historical data. Results revealed demand prediction errors from 0.01% (around 1   m³) to 5.5% (almost 900   m³) [149], which are also adequate values.

Works dealing with water demand prediction are generally compared to works of power demand prediction. However, it has to be noticed that, due to the common and large existence of noise in the data for water demand, the associated prediction errors tend to be superior.

With respect to the consideration of water demand uncertainty in problems of design optimisation, Babayan et al. [9] verified that neglecting the demand uncertainty can imply serious under-design of the networks. Therefore, it should be important to verify the effect of this uncertainty also for operational optimisation problems.

Read full article

URL:

https://www.sciencedirect.com/science/article/pii/S1364032113006692

ESBWR passive safety system performance under loss of coolant accidents

Somboon Rassame , ... Mamoru Ishii , in Progress in Nuclear Energy, 2017

5.4 PCCS performance

The gas flow rate in a PCCS supply line and water flow rate in a PCCS drain line for four LOCA tests are illustrated in Figs. 10 and 11, respectively. In general, the PCCS function starts immediately after the rupture initiation. During the blowdown phase, the PCCS gas supply lines deliver a mixture of steam and non-condensable gas from the DW into the PCCS heat exchanger unit in the range of approximately 25–75 m³ /s. The gas supply flow rates are sharply dropped at the initial period of GDCS phase since steam leaks from the break are temporally stopped due to the GDCS operation. Subsequently, the PCCS gas supply flow is renewed after the RPV begins boiling again in the GDCS period and continues to decrease during the remainder of test periods.

Fig. 10. Gas flow rate in a PCCS supply line (PCCS performance).

Fig. 11. Water flow rate in a PCCS drain (PCCS performance).

It is found that the PCCS gas supply and water drain flow rates during the GDCS and long-term cooling period of the FWLB test are significant lower than those of other cases. This means that the heat removal capability of the PCCS in the FWLB tests is lower compared to other cases. Basically, the gas supply flow rate to the PCCS is governed by the different pressure between the DW and SP gas space which is relatively low in the FWLB test as shown in Fig. 12. Notably, the periodic oscillation of PCCS gas supply flow and water drain flow are observed with the similar frequency as occurred in the GDCS water drain flow.

Fig. 12. Different pressure between the DW and SP gas space (DW and SP performance).

Read full article

URL:

https://www.sciencedirect.com/science/article/pii/S0149197016302761

walkerthadely.blogspot.com

Source: https://www.sciencedirect.com/topics/engineering/supply-flow-rate

Share this post